In Situ Construction of LiF-Li3N-Rich Interface Contributed to Fast Ion Diffusion in All-Solid-State Lithium-Sulfur Batteries

All-solid-state lithium-sulfur batteries (ASSLSBs) have attracted wide attention due to their ultrahigh theoretical energy density and the ability of completely avoiding the shuttle effect. However, the further development of ASSLSBs is limited by the poor kinetic properties of the solid electrode interface. It remains a great challenge to achieve good kinetic properties, by common strategies to substitute sulfur-transition metal and organosulfur composites for sulfur without reducing the specific capacity of ASSLSBs. In this study, a sulfur-(Ketjen Black)-(bistrifluoromethanesulfonimide lithium salt) (S-KB-LiTFSI) composite is constructed by introducing LiTFSI into the S-KB composite. The initial discharge capacity reaches up to 1483 mA h g-1, benefited from the improved ionic conductivity and diffusion kinetics of the S-KB-LiTFSI composite, where numerous LiF interphases with a Li3N component are in situ formed during cycling. Combined with DFT calculations, it is found that the migration barriers of LiF and Li3N are much smaller than that of the Li6PS5Cl solid electrolyte. The fast ionic conductors of LiF and Li3N not only enhance the Li+ transfer efficiency but also improve the interfacial stability. Therefore, the assembled ASSLSBs operate stably for 600 cycles at 200 mA g-1, and this study provides an effective strategy for the further development of ASSLSBs.

Exploring the Cathode Active Materials for Sulfide-Based All-Solid-State Lithium Batteries with High Energy Density

All-solid-state lithium batteries (ASSLBs) are considered promising alternatives to current lithium-ion batteries that employ liquid electrolytes due to their high energy density and enhanced safety. Among various types of solid electrolytes, sulfide-based electrolytes are being actively studied, because they exhibit high ionic conductivity and high ductility, which enable good interfacial contacts in solid electrolytes without sintering at high temperatures. To improve the energy density of the sulfide-based ASSLBs, it is essential to increase the loading of active material in the composite cathode. In this study, the Ni-rich LiNix Coy Mn1-x-y O2 (NCM) materials are explored with different Ni content, particle size, and crystalline form to probe suitable cathode active materials for high-performance ASSLBs with high energy density. The results reveal that single-crystalline LiNi0.82 Co0.10 Mn0.08 O2 material with a small particle size exhibits the best cycling performance in the ASSLB assembled with a high mass loaded cathode (active mass loading: 26 mg cm-2 , areal capacity: 5.0 mAh cm-2 ) in terms of discharge capacity, capacity retention, and rate capability.

Enhanced Electrochemical Stability and Extended Cycle Life in Sulfide-Based All-Solid-State Batteries: The Role of Li10 SnP2 S12 Coating on Ni-Rich NCM Cathode

Recently, sulfide-based all-solid-state batteries (ASSBs) have attracted great attention because of their excellent safety and high energy density. However, by-products formed from side-reactions between the oxide-based cathodes and sulfide-based solid electrolytes (SEs) increase the interfacial resistance and degrade the cell performance. Suppression of this interfacial resistance is thus critical. In this study, the extraordinarily high stability of the cathode/SE interface is discovered when a Li10 SnP2 S12 (LSnPS) is applied to a cathode buffer layer. The electrochemical properties of the cathode interface at high potential are improved by synthesizing a core-shell structure cathode using LSnPS. The synthesized LSnPS is uniformly coated on a Li2 ZrO3 -coated LiNi0.8 Co0.1 Mn0.1 O2 (LZO-NCM) surface using the cost-efficient mechano-fusion method. The ASSB with LSnPS-coated LZO-NCM as the cathode and Li6 PS5 Cl (argyrodite, LPSCl) as the SE exhibited a capacity of 192 mAh g-1 and excellent cycle retention of ≈75% after 500 charge/discharge cycles. In addition, the degradation mechanism at the cathode/SE interface is investigated. The results indicated that LSnPS stabilizes the interface between NCM and argyrodite, thereby inhibiting the decomposition of the SE. This technology is expected to contribute to the commercialization of cathode materials for sulfide-based ASSBs due to its enhanced cycle performance, low-cost material application, and eco-friendly process.

In Situ Construction of Elastic Solid-State Polymer Electrolyte with Fast Ionic Transport for Dendrite-Free Solid-State Lithium Metal Batteries

Solid-state lithium metal batteries (LMBs) have been extensively investigated owing to their safer and higher energy density. In this work, we prepared a novel elastic solid-state polymer electrolyte based on an in situ-formed elastomer polymer matrix with ion-conductive plasticizer crystal embedded with Li6.5La3Zr1.5Ta0.5O12 (LLZTO) nanoparticles, denoted as LZT/SN-SPE. The unique structure of LZT/SN-SPE shows excellent elasticity and flexibility, good electrochemical oxidation tolerance, high ionic conductivity, and high Li+ transference number. The role of LLZTO filler in suppressing the side reactions between succinonitrile (SN) and the lithium metal anode and propelling the Li+ diffusion kinetics can be affirmed. The Li symmetric cells with LZT/SN-SPE cycled stably over 1100 h under a current density of 5 mA cm-2, and Li||LiFePO4 cells realized an excellent rate (92.40 mAh g-1 at 5 C) and long-term cycling performance (98.6% retention after 420 cycles at 1 C). Hence, it can provide a promising strategy for achieving high energy density solid-state LMBs.

Polymeric Electronic Shielding Layer Enabling Superior Dendrite Suppression for All-Solid-State Lithium Batteries

LiBH4 is one of the most promising candidates for use in all-solid-state lithium batteries. However, the main challenges of LiBH4 are the poor Li-ion conductivity at room temperature, excessive dendrite formation, and the narrow voltage window, which hamper practical application. Herein, we fabricate a flexible polymeric electronic shielding layer on the particle surfaces of LiBH4. The electronic conductivity of the primary LiBH4 is reduced by 2 orders of magnitude, to 1.15 × 10-9 S cm-1 at 25 °C, due to the high electron affinity of the electronic shielding layer; this localizes the electrons around the BH4- anions, which eliminates electronic leakage from the anionic framework and leads to a 68-fold higher critical electrical bias for dendrite growth on the particle surfaces. Contrary to the previously reported work, the shielding layer also ensures fast Li-ion conduction due to the fast-rotational dynamics of the BH4- species and the high Li-ion (carrier) concentration on the particle surfaces. In addition, the flexibility of the layer guarantees its structural integrity during Li plating and stripping. Therefore, our LiBH4-based solid-state electrolyte exhibits a high critical current density (11.43 mA cm-2) and long cycling stability of 5000 h (5.70 mA cm-2) at 25 °C. More importantly, the electrolyte had a wide operational temperature window (-30-150 °C). We believe that our findings provide a perspective with which to avoid dendrite formation in hydride solid-state electrolytes and provide high-performance all-solid-state lithium batteries.

Li Dynamics in Mixed Ionic-Electronic Conducting Interlayer of All-Solid-State Li-metal Batteries

Lithium-metal (Li0) anodes potentially enable all-solid-state batteries with high energy density. However, it shows incompatibility with sulfide solid-state electrolytes (SEs). One strategy is introducing an interlayer, generally made of a mixed ionic-electronic conductor (MIEC). Yet, how Li behaves within MIEC remains unknown. Herein, we investigated the Li dynamics in a graphite interlayer, a typical MIEC, by using operando neutron imaging and Raman spectroscopy. This study revealed that intercalation-extrusion-dominated mechanochemical reactions during cell assembly transform the graphite into a Li-graphite interlayer consisting of SE, Li0, and graphite-intercalation compounds. During charging, Li+ preferentially deposited at the Li-graphite|SE interface. Upon further plating, Li0-dendrites formed, inducing short circuits and the reverse migration of Li0. Modeling indicates the interface has the lowest nucleation barrier, governing lithium transport paths. Our study elucidates intricate mechano-chemo-electrochemical processes in mixed conducting interlayers. The behavior of Li+ and Li0 in the interlayer is governed by multiple competing factors.

p-Phenylenediamine-Bridged Binder-Electrolyte-Unified Supramolecules for Versatile Lithium Secondary Batteries

The binder is an essential component in determining the structural integrity and ionic conductivity of Li-ion battery electrodes. However, conventional binders are not sufficiently conductive and durable to be used with solid-state electrolytes. In this study, a novel system is proposed for a Li secondary battery that combines the electrolyte and binder into a unified structure, which is achieved by employing para-phenylenediamine (pPD) moiety to create supramolecular bridges between the parent binders. Due to a partial crosslinking effect and charge-transferring structure of pPD, the proposed strategy improves both the ionic conductivity and mechanical properties by a factor of 6.4 (achieving a conductivity of 3.73 × 10-4 S cm-1 for poly(ethylene oxide)-pPD) and 4.4 (reaching a mechanical strength of 151.4 kPa for poly(acrylic acid)-pPD) compared to those of conventional parent binders. As a result, when the supramolecules of pPD are used as a binder in a pouch cell with a lean electrolyte loading of 2 µL mAh-1 , a capacity retention of 80.2% is achieved even after 300 cycles. Furthermore, when it is utilized as a solid-state electrolyte, an average Coulombic efficiency of 99.7% and capacity retention of 98.7% are attained under operations at 50 °C without external pressure or a pre-aging process.

Soft Carbon-Thiourea with Fast Bulk Diffusion Kinetics for Solid-State Lithium Metal Batteries

The development of all-solid-state lithium-metal batteries (ASSLMBs) is impeded by low coulomb efficiency, short lifetime, poor rate performance, and other problems caused by the rapid growth of lithium (Li) dendrites. Herein, a multiple-diffusion-channel N,S-doped soft carbon with expanded layer spacing is designed/developed by thiourea calcination for dendrite-free anodes. Since the enlarged layer spacing can improve Li+ transportation rate within the layers and N,S-doping can facilitate Li+ transport between the layers, the bulk phase diffusion (not just surface diffusion) kinetics can be improved, which in turn reduces the local current density, inhibits the growth of Li dendrites, and improves the rate performance. The resulting ASSLMB achieves record-high current density (15 mA cm-2 ), areal capacity (20 mAh cm-2 ), energy density (403 Wh kg-1 ), and ultra-long cycle life (13 000 cycles). >305 Wh kg-1 pouch cells are realized, representing one of the most critical breakthroughs for real-world application of ASSLMBs.

Synergistic Interfacial Optimization for High-Sulfur-Content All-Solid-State Lithium-Sulfur Batteries

Improving the sulfur content in the cathode is essential for achieving high-energy-density all-solid-state lithium-sulfur batteries (ASSLSBs). However, the complex multiinterfaces, akin to the short wooden planks that consist of the cask, severely limit the performance of ASSLSBs with high sulfur content. Since singular approaches fail to optimize these interfaces simultaneously, we propose a synergistic approach using a dual-doped sulfide solid electrolyte (Y2S3 and LiI) and an SbSn alloy sulfur host in this work. The incorporation of Y2S3 in the solid electrolyte serves to improve the electrolyte-electrolyte interfaces and enhance the ionic conductivity, while the inclusion of LiI helps stabilize the electrolyte-anode interface and suppress dendrite formation. Meanwhile, the SbSn alloy sulfur host facilitates the transfer of Li+ at the electrolyte-cathode interfaces. Consequently, the solid-solid interfaces are significantly improved, leading to impressive specific capacities in ASSLSBs with high sulfur content (>44% in the cathode composite) at room temperature (1163.5 mAh g-1) and at 60 °C (1408.7 mAh g-1) during the 50th cycle at 0.05C. This work presents a promising strategy for achieving practical high-performance ASSLSBs.

Possibility of High Ionic Conductivity and High Fracture Toughness in All-Dislocation-Ceramics

Based on the results of numerical calculations as well as those of some related experiments which are reviewed in the present paper, it is suggested that solid electrolytes filled with appropriate dislocations, which is called all-dislocation-ceramics, are expected to have considerably higher ionic conductivity and higher fracture toughness than those of normal solid electrolytes. Higher ionic conductivity is due to the huge ionic conductivity along dislocations where the formation energy of vacancies is considerably lower than that in the bulk solid. Furthermore, in all-dislocation- ceramics, dendrite formation could be avoided. Higher fracture toughness is due to enhanced emissions of dislocations from a crack tip by pre-existing dislocations, which causes shielding of a crack tip, energy dissipation due to plastic deformation and heating, and crack-tip blunting. All-dislocation-ceramics may be useful for all-solid-state batteries.

Evolution Process of the Interfacial Chemical Reaction in Ni-Rich Layered Cathodes for All-Solid-State Batteries

All-solid-state batteries (ASSBs) have attracted much attention in the fields of energy storage, electric vehicles, and portable electronic devices due to their safety and high energy density. Ni-rich layered ternary materials (LiNi1-y-zCoyMnzO2, 1 - y - z ≥ 0.7) are considered to be among the most promising candidates for cathode materials in ASSBs due to their unique advantages. Nevertheless, the interfacial chemical reaction between the ternary cathode (NCM) and solid-state electrolytes (SSEs) has become the main issue to limit the long-cycle stability of the cathode. Relative studies have shown that when NCM materials are in direct contact with sulfide-based SSEs, byproducts generated by the interfacial chemical reaction accumulate at the interface, resulting in increasing interfacial impedance. However, up to now, the formation mechanism of the NCM/SSE interfacial chemical reaction, as well as its properties and evolution process, still lacks detailed characterization. In this paper, batteries at different stages during the long-cycling process are characterized to reveal the dynamic evolution process of the chemical reaction from the cathode-electrolyte interface to the interior of the particle and to determine the chemical reaction effect on the irreversible degradation of the battery capacity. On this basis, a surface coating of LiNbO3 is adopted to establish a passivation protection layer at the cathode-electrolyte interface. The coated battery has been subjected to 2000 charge/discharge cycles at a rate of 1 C and achieved a capacity retention rate of up to 82%.

Interphase Stabilization of LiNi0.5 Mn1.5 O4 Cathode for 5 V-Class All-Solid-State Batteries

Employing high voltage cobalt-free spinel LiNi0.5 Mn1.5 O4 (LNMO) as a cathode is promising for high energy density and cost-effectiveness, but it has challenges in all-solid-state batteries (ASSBs). Here, it is revealed that the limitation of lithium argyrodite sulfide solid electrolyte (Li6 PS5 Cl) with the LNMO cathode is due to the intrinsic chemical incompatibility and poor oxidative stability. Through a careful analysis of the interphase of LNMO, it is elucidated that even the halide solid electrolyte (Li3 InCl6 ) with high oxidative stability can be decomposed to form resistive interphase layers with LNMO in ASSBs. Interestingly, with Fe-doping and a Li3 PO4 protective layer coating, LNMO with Li3 InCl6 displays stable cycle performance with a stabilized interphase at a high voltage (≈4.7 V) in ASSBs. The enhanced interfacial stability with the extended electrochemical stability window through doping and coating enables high electrochemical stability with LNMO in ASSBs. This work provides guidance for employing high-voltage cathodes in ASSBs and highlights the importance of stable interphases to enable stable cycling in ASSBs.

Additive-Derived Surface Modification of Cathodes in All-Solid-State Batteries: The Effect of Lithium Difluorophosphate- and Lithium Difluoro(oxalato)borate-Derived Coating Layers

Sulfide-based electrolytes, with their high conductivity and formability, enable the construction of high-performance, all-solid-state batteries (ASSBs). However, the instability of the cathode-sulfide electrolyte interface limits the commercialization of these ASSBs. Surface modification of cathodes using the coating technique has been explored as an efficient approach to stabilize these interfaces. In this study, the additives lithium difluorophosphate (LiDFP) and lithium difluoro(oxalato)borate (LiDFOB) are used to fabricate stable cathode coatings via heat treatment. The low melting points of LiDFP and LiDFOB enable the formation of thin and uniform coating layers by a low-temperature heat treatment. All-solid-state cells containing LiDFP- and LiDFOB-coated cathodes show electrochemical performances significantly better than those comprising uncoated cathodes. Among all of the as-prepared coated cathodes, LiDFP-coated cathodes fabricated using a slightly lower temperature than the phase-transition temperature of LiDFP (320 °C) show the best discharge capacity, rate capability, and cyclic performance. Furthermore, cells comprising LiDFP-coated cathodes showed significantly low impedance. X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy confirm the effectiveness of the LiDFP coating. LiDFP-coated cathodes minimized side-reactions during cycling, resulting in a significantly low cathode-surface degradation. Hence, this study highlights the efficiency of the proposed coating method and its potential to facilitate the commercialization of ASSBs. Overall, this study reports an effective technique to stabilize the cathode-electrolyte interface in sulfide-based ASSBs, which could expedite the practical implementation of these advanced energy-storage devices.

Experimental Corroboration of Lithium Orthothioborate Superionic Conductor by Systematic Elemental Manipulation

The Li superionic conductor Li3BS3 has been theoretically predicted as an ideal solid electrolyte (SE) due to its low Li+ migration energy barrier and high ionic conductivity. However, the experimentally synthesized Li3BS3 has a 104 times lower ionic conductivity. Herein, we investigate the effect of a series of cation and anion substitutions in Li3BS3 SE on its ionic conductivity, including Li3-xM0.05BS3 (M = Cu, Zn, Sn, P, W, x = 0.05, 0.1, 0.2, 0.25), Li3-yBS2.95X0.05 (X = O, Cl, Br, I, y = 0.05, 0.1) and Li2.75-xP0.05BS3-xClx (x = 0.05, 0.1, 0.15, 0.2, 0.4, 0.6). Amorphous ionic conductor Li2.55P0.05BS2.8Cl0.2 has a high ion conductivity of 0.52 mS cm-1 at room temperature with an activation energy of 0.41 eV. The electrochemical performance of all-solid-state batteries with Li2.55P0.05BS2.8Cl0.2 SEs show stable cycling with a discharge capacity retention of >97% after 200 cycles at 1C under 55 °C.

Low-Temperature In Situ Lithiation Construction of a Lithiophilic Particle-Selective Interlayer for Solid-State Lithium Metal Batteries

Unexpected interface resistance and lithium dendrite puncture hinder the application of garnet-type solid-state electrolytes in high-energy-density systems. Different from the previous high-temperature (>180 °C) molten lithium that promotes the alloying reaction between the coating layer and Li to enhance the interface contact, herein, we introduce liquid-metal-like SbCl3 to construct a three-dimensional Li+ directional-selection interlayer by in situ low-temperature lithiation (80 °C). An interlayer with a more negative interface energy composed of SbLi3 and LiCl exhibits a superior affinity with Li and LGLZO, which reduces the interface resistance and suppresses the growth of Li dendrites by an insulated electron. The introduction of the SbCl3 modification layer into Li/Li symmetric cells enables charge/discharge at a current density of 6.0 mA cm-2 and operation for more than 1000 h under 2.0 mA cm-2 at room temperature. The full cells with the LiFePO4 cathode exhibit a high residual capacity of 144.8 mAh g-1 at 0.5 C after 1000 cycles and excellent cycling stability with a retention ratio of 94.7% at 1 C after 600 cycles. The low-temperature lithiation method based on an energy-saving perspective should be applied to other types of solid-state electrolyte modification strategies.

Regulating Li-Ion Transport through Ultrathin Molecular Membrane to Enable High-Performance All-Solid-State-Battery

Solid-state lithium metal batteries with garnet-type electrolyte provide several advantages over conventional lithium-ion batteries, especially for safety and energy density. However, a few grand challenges such as the propagation of Li dendrites, poor interfacial contact between the solid electrolyte and the electrodes, and formation of lithium carbonate during ambient exposure over the solid-state electrolyte prevent the viability of such batteries. Herein, an ultrathin sub-nanometer porous carbon nanomembrane (CNM) is employed on the surface of solid-state electrolyte (SSE) that increases the adhesion of SSE with electrodes, prevents lithium carbonate formation over the surface, regulates the flow of Li-ions, and blocks any electronic leakage. The sub-nanometer scale pores in CNM allow rapid permeation of Li-ions across the electrode-electrolyte interface without the presence of any liquid medium. Additionally, CNM suppresses the propagation of Li dendrites by over sevenfold up to a current density of 0.7 mA cm-2 and enables the cycling of all-solid-state batteries at low stack pressure of 2 MPa using LiFePO4 cathode and Li metal anode. The CNM provides chemical stability to the solid electrolyte for over 4 weeks of ambient exposure with less than a 4% increase in surface impurities.

Nano Silicon Anode without Electrolyte Adding for Sulfide-Based All-Solid-State Lithium-Ion Batteries

All-solid-state lithium-ion batteries (ASSLBs) employing silicon (Si) anode and sulfide electrolyte attract much attention, since they can achieve both high energy density and safety. For large-scale application, sheet-type Si anode matching sulfide based ASSLBs is preferred. Here, a LiAlO2 layer coated Si (Si@LiAlO2 ) is reported for sheet-type electrode. This electrode employs conventional slurry coating methods without adding any sulfide electrolyte. The effect of LiAlO2 coating on the electrochemical performance and morphology evolution of Si electrode is investigated. Since the high mechanical strength and ionic conductivity of LiAlO2 layer can sufficiently relieve the huge expansion of Si and promote the Li+ diffusion, the electrochemical performance is significantly enhanced. The Si@LiAlO2 electrodes deliver high coulombic efficiency exceeding 80% and hold considerable specific capacity of 1205 mAh g-1 (150 cycles, 0.33 C). The Si@LiAlO2 | LiNi0.83 Co0.11 Mn0.06 O2 full-cells exhibit a high reversible capacity of 147 mAh g-1 (0.28 mA cm-2 ) and a considerable capacity retention of 80.2% (62 cycles, 2.8 mA cm-2 ). This work demonstrates promising practicability and provides a new route for the scalable preparation of Si electrode sheets for ASSLBs with extended lifespan.

Low-Cost Preparation of High-Performance Na-B-H-S Electrolyte for All-Solid-State Sodium-Ion Batteries

All-solid-state sodium-ion batteries have the potential to improve safety and mitigate the cost bottlenecks of the current lithium-ion battery system if a high-performance electrolyte with cost advantages can be easily synthesized. In this study, a one-step dehydrogenation-assisted strategy to synthesize the novel thio-borohydride (Na-B-H-S) electrolyte is proposed, in which both raw material cost and preparation temperature are significantly reduced. By using sodium borohydride (NaBH4 ) instead of B as a starting material, B atoms can be readily released from NaBH4 with much less energy and thus became more available to generate thio-borohydride. The synthesized Na-B-H-S (NaBH4 /Na-B-S) electrolyte exhibits excellent compatibility with current cathode materials, including FeF3 (1.0-4.5 V), Na3 V2 (PO4 )3 (2.0-4.0 V), and S (1.2-2.8 V). This novel Na-B-H-S electrolyte will take a place in mainstream electrolytes because of its advantages in preparation, cost, and compatibility with various cathode materials.

In-Situ-Generated Electron-Blocking LiH Enabling an Unprecedented Critical Current Density of Over 15 mA cm-2 for Solid-State Hydride Electrolytes

LiBH4 is a promising solid-state electrolyte (SE) due to its thermodynamic stability to Li. However, poor Li-ion conductivities at room temperature, low oxidative stabilities, and severe dendrite growth hamper its application. In this work, a partial dehydrogenation strategy is adopted to in situ generate an electronic blocking layer dispersed of LiH, addressing the above three issues simultaneously. The electrically insulated LiH reduces the electronic conductivity by two orders of magnitude, leading to a 32.0-times higher critical electrical bias for dendrite growth on the particle surfaces than that of the counterpart. Additionally, this layer not only promotes the Li-ion conductance by stimulating coordinated rotations of BH4 - and B12 H12 2- , contributing to a Li-ion conductivity of 1.38 × 10-3 S cm-1 at 25 °C, but also greatly enhances oxidation stability by localizing the electron density on BH4 - , extending its voltage window to 6.0 V. Consequently, this electrolyte exhibits an unprecedented critical current density (CCD) of 15.12 mA cm-2 at 25 °C, long-term Li plating and stripping stability for 2700 h, and a wide temperature window for dendrite inhibition from -30 to 150 °C. Its Li-LiCoO2 cell displays high reversibility within 3.0-5.0 V. It is believed that this work provides a clear direction for solid-state hydride electrolytes.

One Stone, Three Birds: An Air and Interface Stable Argyrodite Solid Electrolyte with Multifunctional Nanoshells

Li6 PS5 Cl (LPSC) solid electrolytes, based on Argyrodite, have shown potential for developing high energy density and safe all-solid-state lithium metal batteries. However, challenges such as interfacial reactions, uneven Li deposition, and air instability remain unresolved. To address these issues, a simple and effective approach is proposed to design and prepare a solid electrolyte with unique structural features: Li6 PS4 Cl0.75 -OF0.25 (LPSC-OF0.25 ) with protective LiF@Li2 O nanoshells and F and O-rich internal units. The LPSC-OF0.25 electrolyte exhibits high ionic conductivity and the capability of "killing three birds with one stone" by improving the moist air tolerance, as well as the interface compatibility between the anode or cathode and the solid electrolyte. The improved performance is attributed to the peculiar morphology and the self-generating and self-healing interface coupling capability. When coupled with bare LiCoO2 , the LPSC-OF0.25 electrolyte enables stable operation under high cutoff voltage (≈4.65 V vs Li/Li+ ), thick cathodes (25 mg cm-2 ), and large current density (800 cycles at 2 mA cm-2 ). This rationally designed solid electrolyte offers promising prospects for solid-state batteries with high energy and power density for future long-range electric vehicles and aircrafts.

Trimethylsilyl Compounds for the Interfacial Stabilization of Thiophosphate-Based Solid Electrolytes in All-Solid-State Batteries

Argyrodite-type Li6 PS5 Cl (LPSCl) has attracted much attention as a solid electrolyte for all-solid-state batteries (ASSBs) because of its high ionic conductivity and good mechanical flexibility. LPSCl, however, has challenges of translating research into practical applications, such as irreversible electrochemical degradation at the interface between LPSCl and cathode materials. Even for Li-ion batteries (LIBs), liquid electrolytes have the same issue as electrolyte decomposition due to interfacial instability. Nonetheless, current LIBs are successfully commercialized because functional electrolyte additives give rise to the formation of stable cathode-electrolyte interphase (CEI) and solid-electrolyte interphase (SEI) layers, leading to supplementing the interfacial stability between electrolyte and electrode. Herein, inspired by the role of electrolyte additives for LIBs, trimethylsilyl compounds are introduced as solid electrolyte additives for improving the interfacial stability between sulfide-based solid electrolytes and cathode materials. 2-(Trimethylsilyl)ethanethiol (TMS-SH), a solid electrolyte additive, is oxidatively decomposed during charge, forming a stable CEI layer. As a result, the CEI layer derived from TMS-SH suppresses the interfacial degradation between LPSCl and LiCoO2 , thereby leading to the excellent electrochemical performance of Li | LPSCl | LiCoO2 , such as superior cycle life over 2000 cycles (85.0% of capacity retention after 2000 cycles).

Anomalous Impact of Mechanochemical Treatment on the Na-ion Conductivity of Sodium Closo-Carbadodecaborate Probed by X-Ray Raman Scattering Spectroscopy

Solid-state sodium ion conductors are crucial for the next generation of all-solid-state sodium batteries with high capacity, low cost, and improved safety. Sodium closo-carbadodecaborate (NaCB11 H12 ) is an attractive Na-ion conductor owing to its high thermal, electrochemical, and interfacial stability. Mechanical milling has recently been shown to increase conductivity by five orders of magnitude at room temperature, making it appealing for application in all-solid-state sodium batteries. Intriguingly, milling longer than 2 h led to a significant decrease in conductivity. In this study, X-ray Raman scattering (XRS) spectroscopy is used to probe the origin of the anomalous impact of mechanical treatment on the ionic conductivity of NaCB11 H12 . The B, C, and Na K-edge XRS spectra are successfully measured for the first time, and ab initio calculations are employed to interpret the results. The experimental and computational results reveal that the decrease in ionic conductivity upon prolonged milling is due to the increased proximity of Na to the CB11 H12 cage, caused by severe distortion of the long-range structure. Overall, this work demonstrates how the XRS technique, allowing investigation of low Z elements such as C and B in the bulk, can be used to acquire valuable information on the electronic structure of solid electrolytes and battery materials in general.

Bilayer Zwitterionic Metal-Organic Framework for Selective All-Solid-State Superionic Conduction in Lithium Metal Batteries

Solid-state batteries (SSBs) hold immense potential for improved energy density and safety compared to traditional batteries. However, existing solid-state electrolytes (SSEs) face challenges in meeting the complex operational requirements of SSBs. This study introduces a novel approach to address this issue by developing a metal-organic framework (MOF) with customized bilayer zwitterionic nanochannels (MOF-BZN) as high-performance SSEs. The BZN consist of a rigid anionic MOF channel with chemically grafted soft multicationic oligomers (MCOs) on the pore wall. This design enables selective superionic conduction, with MCOs restricting the movement of anions while coulombic interaction between MCOs and anionic framework promoting the dissociation of Li+ . MOF-BZN exhibits remarkable Li+ conductivity (8.76 × 10-4 S cm-1 ), high Li+ transference number (0.75), and a wide electrochemical window of up to 4.9 V at 30 °C. Ultimately, the SSB utilizing flame retarded MOF-BZN achieves an impressive specific energy of 419.6 Wh kganode+cathode+electrolyte -1 under constrained conditions of high cathode loading (20.1 mg cm-2 ) and limited lithium metal source. The constructed bilayer zwitterionic MOFs present a pioneering strategy for developing advanced SSEs for highly efficient SSBs.

Development of an Electrophoretic Deposition Method for the In Situ Fabrication of Ultra-Thin Composite-Polymer Electrolytes for Solid-State Lithium-Metal Batteries

All-solid-state lithium-metal batteries offer higher energy density and safety than lithium-ion batteries, but their practical applications have been pushed back by the sluggish Li+ transport, unstable electrolyte/electrode interface, and/or difficult processing of their solid-state electrolytes. Li+ -conducting composite polymer electrolytes (CPEs) consisting of sub-micron particles of an oxide solid-state electrolyte (OSSE) dispersed in a solid, flexible polymer electrolyte (SPE) have shown promises to alleviate the low Li+ conductivity of SPE, and the high rigidity and large interfacial impedance of OSSEs. Solution casting has been by far the most widely used procedure for the preparation of CPEs in research laboratories; however, this method imposes several drawbacks including particle aggregation and settlement during a long-term solvent evaporation step, excessive use of organic solvents, slow production time, and mechanical issues associated with handling of ultra-thin films of CPEs (<50 µm). To address these challenges, an electrophoretic deposition (EPD) method is developed to in situ deposit ultra-thin CPEs on lithium-iron-phosphate (LFP) cathodes within just a few minutes. EPD-prepared CPEs have shown better electrochemical performance in the lithium-metal battery than those CPEs prepared by solution casting due to a better dispersion of OSSE within the SPE matrix and improved CPE contact with LFP cathodes.

High Cathode Loading and Low-Temperature Operating Garnet-Based All-Solid-State Lithium Batteries - Material/Process/Architecture Optimization and Understanding of Cell Failure

All-solid-state lithium batteries (ASSLBs) are prepared using garnet-type solid electrolytes by quick liquid phase sintering (Q-LPS) without applying high pressure during the sintering. The cathode layers are quickly sintered with a heating rate of 50-100 K min-1 and a dwell time of 10 min. The battery performance is dramatically improved by simultaneously optimizing materials, processes, and architectures, and the initial discharge capacity of the cell with a LiCoO2 -loading of 8.1 mg reaches 1 mAh cm-2 and 130 mAh g-1 at 25 °C. The all-solid-state cell exhibits capacity at a reduced temperature (10 °C) or a relatively high rate (0.1 C) compared to the previous reports. The Q-LPS would be suitable for large-scale manufacturing of ASSLBs. The multiphysics analyses indicate that the internal stress reaches 1 GPa during charge/discharge, which would induce several mechanical failures of the cells: broken electron networks, broken ion networks, separation of interfaces, and delamination of layers. The experimental results also support these failures.

A Thin Composite Polymer Electrolyte Functionalized by a Novel Antihydrolysis Additive to Enable All-Solid-State Lithium Battery with Excellent Rate and Cycle Performance

Composite solid-state electrolyte (CSE) incorporated with fluorine-containing functional additives usually endows the assembled cell with improved electrochemical performance by forming stable electrode/electrolyte interfaces. However, most of fluorine-containing additives are prone to hydrolysis, which is not suitable for the large-scale preparation of CSEs. In this work, an antihydrolysis and fluorine-containing additive of magnesium 2,3,4,5,6-pentafluorophenylacetate (MgPFPAA) is successfully synthesized and then used to regulate the properties of the electrode/electrolyte interfaces of the all-solid-state lithium batteries (ASSLBs). The antihydrolysis property of MgPFPAA facilitates the large-scale preparation of the ultrathin CSEs in atmospheric environment. Both theoretical calculations and experimental results indicate that MgPFPAA can effectively improve the composition and structure of the generated solid electrolyte interface film by providing rich F sources and Mg2+ , thus leading to a stable CSE/Li interface. Furthermore, an ultrathin PEO/PVDF-based CSE (≈30 µm) functionalized by this novel MgPFPAA additive enables the assembled LiFePO4 -based ASSLB with greatly enhanced electrochemical performances, with high discharge specific capacity of 93.7 mAh g-1 at 10 C and a high capacity retention of 74.9% after 1500 cycles at 5.0 C. Also, this MgPFPAA functionalized CSE can be compatible with the high-areal-capacity LiFePO4 and the high-voltage LiNi0.8 Co0.1 Mn0.1 O2 cathodes.

Recent Strategies for Lithium-Ion Conductivity Improvement in Li7La3Zr2O12 Solid Electrolytes

The development of solid electrolytes with high conductivity is one of the key factors in the creation of new power-generation sources. Lithium-ion solid electrolytes based on Li7La3Zr2O12 (LLZ) with a garnet structure are in great demand for all-solid-state battery production. Li7La3Zr2O12 has two structural modifications: tetragonal (I41/acd) and cubic (Ia3d). A doping strategy is proposed for the stabilization of highly conductive cubic Li7La3Zr2O12. The structure features, density, and microstructure of the ceramic membrane are caused by the doping strategy and synthesis method of the solid electrolyte. The influence of different dopants on the stabilization of the cubic phase and conductivity improvement of solid electrolytes based on Li7La3Zr2O12 is discussed in the presented review. For mono-doping, the highest values of lithium-ion conductivity (~10-3 S/cm at room temperature) are achieved for solid electrolytes with the partial substitution of Li+ by Ga3+, and Zr4+ by Te6+. Moreover, the positive effect of double elements doping on the Zr site in Li7La3Zr2O12 is established. There is an increase in the popularity of dual- and multi-doping on several Li7La3Zr2O12 sublattices. Such a strategy leads not only to lithium-ion conductivity improvement but also to the reduction of annealing temperature and the amount of some high-cost dopant. Al and Ga proved to be effective co-doping elements for the simultaneous substitution in Li/Zr and Li/La sublattices of Li7La3Zr2O12 for improving the lithium-ion conductivity of solid electrolytes.

Influence of Molecular Weight and Lithium Bis(trifluoromethanesulfonyl)imide on the Thermal Processability of Poly(ethylene oxide) for Solid-State Electrolytes

New energy systems such as all-solid-state battery (ASSB) technology are becoming increasingly important today. Recently, researchers have been investigating the transition from the lab-scale production of ASSB components to a larger scale. Poly(ethylene oxide) (PEO) is a promising candidate for the large-scale production of polymer-based solid electrolytes (SPEs) because it offers many processing options. Hence, in this work, the thermal processing route for a PEO-Lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) SPE in the ratio of 20:1 (EO:Li) is investigated using kneading experiments. Here, we clearly show the sensitivity of PEO during thermal processing, especially for high-molecular-weight PEO (Mw = 600,000 g mol-1). LiTFSI acts as a plasticizer for low-molecular-weight PEO (Mw = 100,000 g mol-1), while it amplifies the degradation of high-molecular-weight PEO. Further, LiTFSI affects the thermal properties of PEO and its crystallinity. This leads to a higher chain mobility in the polymer matrix, which improves the flowability. In addition, the spherulite size of the produced PEO electrolytes differs from the molecular weight. This work demonstrates that low-molecular-weight PEO is more suitable for thermal processing as a solid electrolyte due to the process stability. High-molecular-weight PEO, especially, is strongly influenced by the process settings and LiTFSI.

Design Strategies of Li-Si Alloy Anode for Mitigating Chemo-Mechanical Degradation in Sulfide-Based All-Solid-State Batteries

Composite anodes of Li3 PS4  glass+Li-Si alloy (Type 1) and Li3 N+LiF+Li-Si alloy (Type 2) are prepared for all-solid-state batteries with Li3 PS4 (LPS) glass electrolyte and sulfur/LPS glass/carbon composite cathode. Using a three-electrode system, the anode and cathode potentials are separated, and their polarization resistances are individually traced. Even under high-cutoff-voltage conditions (3.7 V), Type 1 and 2 cells are stably cycled without voltage noise for >200 cycles. Although cathode polarization resistance drastically increases after 3.7 V charge owing to LPS oxidation, LPS redox behavior is fairly reversible upon discharge-charge unlike the non-composite alloy anode cell. Time-of-flight secondary ion mass spectrometry analysis reveals that the enhanced cyclability is attributed to uniform Li-Si alloying throughout the composite anode, providing more pathways for lithium ions even when these ions are over-supplied via LPS oxidation. These results imply that LPS-based cells can be reversibly cycled with LPS redox even under high-cutoff voltages, as long as non-uniform alloying (lithium dendrite growth) is prevented. Type 1 and 2 cells exhibit similar performance and stability although reduction product is formed in Type 1. This work highlights the importance of alloy anode design to prevent chemo-mechanical failure when cycling the cell outside the electrochemical stability window.

Rationally Designed Solution-Processible Conductive Carbon Additive Coating for Sulfide-based All-Solid-State Batteries

Sulfide-based all-solid-state batteries (ASSBs) have emerged as promising candidates for next-generation energy storage systems owing to their superior safety and energy density. A conductive agent is necessarily added in the cathode composite of ASSBs to facilitate electron transport therein, but it causes the decomposition of the solid electrolyte and ultimately the shortening of lifetime. To resolve this dilemmatic situation, herein, we report a rationally designed solution-processible coating of zinc oxide (ZnO) onto vapor-grown carbon fiber as a conductive agent to reduce the contact between the carbon additive and the solid electrolyte and still maintain electron pathways to the active material. ASSBs with the carbon additive with an optimal coating of ZnO have markedly improved cycling performance and rate capability compared to those with the bare conductive agent, which can be attributed to hindering the decomposition of the solid electrolytes. The results highlight the usefulness of controlling the interparticle contacts in the composite cathodes in addressing the challenging interfacial degradation of sulfide-based ASSBs and improving their key electrochemical properties.

Interface Engineering of All-Solid-State Batteries Based on Inorganic Solid Electrolytes

All-solid-state batteries (ASSBs) based on inorganic solid electrolytes (SEs) are one of the most promising strategies for next-generation energy storage systems and electronic devices due to the higher energy density and intrinsic safety. However, the poor solid-solid contact and restricted chemical/electrochemical stability of inorganic SEs both in cathode and anode SE interfaces cause contact failure and the degeneration of SEs during prolonged charge-discharge processes. As a result, the increasing interface resistance significantly affects the coulombic efficiency and cycling performance of ASSBs. Herein, we present a fundamental understanding of physical contact and chemical/electrochemical features of ASSB interfaces based on mainstream inorganic SEs and summarize the recent work on interface modification. SE doping, optimizing morphology, introducing interlayer/coating layer, and utilizing compatible electrode materials are the key methods to prevent side reactions, which are discussed separately in cathode/anode-SE interface. We also highlight the constant extra stack pressure applied during ASSB cycling, which is important to the electrochemical performance. Finally, our perspectives on interface modification for practical high-performance ASSBs are put forward.

A Novel Time-Saving Synthesis Approach for Li-Argyrodite Superionic Conductor

The wet-chemical synthetic approach for Li-argyrodite superionic conductors for all-solid-state batteries (ASSBs) is promising as it saves time, energy, and cost, while achieving scalable production. However, it faces certain commercialization issues such as byproduct generation, nucleophilic attack of the solvent, and long processing times. In this study, a facile and time-saving microwave-assisted wet synthesis (MW-process) approach is proposed for Li₆ PS₅ Cl (LPSC), which is completed in 3 h at the precursor-synthesis stage. The LPSC crystal obtained from the MW-process presents various advantages such as fast-PS₄ ^3- generation, high solubility of LiCl, and low adverse effects from solvent molecules. These features help in achieving a high Li-ion conductivity (2.79 mS cm^-1 ) and low electric conductivity (1.85×10^-6 mS cm^-1 ). Furthermore, the LPSC crystal is stable when reacting with Li metal (2000 h at 0.1 mA cm^-2 ) and exhibits superior cyclability with LiNi_0.6 Co_0.2 Mn_0.2 (NCM622) (145.5 mA h g^-1 at 0.5 C, 200 cycles with 0.12% of capacity loss per cycle). The proposed synthetic approach presents new insights into wet-chemical engineering for sulfide-based solid-electrolytes (SEs), which is crucial for developing ASSBs from a commercial-scale perspective.

LiAlO2-Modified Li Negative Electrode with Li10GeP2S12 Electrolytes for Stable All-Solid-State Lithium Batteries

Lithium (Li) metal has an ultrahigh specific capacity in theory with an extremely negative potential (versus hydrogen), receiving extensive attention as a negative electrode material in batteries. However, the formation of Li dendrites and unstable interfaces due to the direct Li metal reaction with solid sulfide-based electrolytes hinders the application of lithium metal in all-solid-state batteries. In this work, we report the successful fabrication of a LiAlO₂ interfacial layer on a Li/Li₁₀GeP₂S₁₂ interface through magnetic sputtering. As LiAlO₂ can be a good Li⁺ ion conductor but an electronic insulator, the LiAlO₂ interface layer can effectively suppress Li dendrite growth and the severe interface reaction between Li and Li₁₀GeP₂S₁₂. The Li@LiAlO₂ 200 nm/Li₁₀GeP₂S₁₂/Li@LiAlO₂ 200 nm symmetric cell can remain stable for 3000 h at 0.1 mA cm^-2 under 0.1 mAh cm^-2. Moreover, unlike the rapid capacity decay of a cell with a pristine lithium negative electrode, the Li@LiAlO₂ 200 nm/Li₁₀GeP₂S₁₂/LiCoO₂@LiNbO₃ cell delivers a reversible capacity of 118 mAh g^-1 and a high energy efficiency of 96.6% after 50 cycles. Even at 1.0 C, the cell with the Li@LiAlO₂ 200 nm electrode can retain 95% of its initial capacity after 800 cycles.

Reactive Magnesium Nitride Additive: A Drop-in Solution for Lithium/Garnet Wetting in All-Solid-State Batteries

Garnet oxides such as Li6.4La3Zr1.4Ta0.6O12 (LLZTO) are promising solid electrolyte materials for all-solid-state lithium-metal batteries because of high ionic conductivity, low electronic leakage, and wide electrochemical stability window. While LLZTO has been frequently discussed to be stable against lithium metal anode, it is challenging to achieve and maintain good solid-on-solid wetting at the metal/ceramic interface in both processing and extended electrochemical cycling. Here we address the challenge by a powder-form magnesium nitride additive, which reacts with the lithium metal anode to produce well-dispersed lithium nitride. The in-situ formed lithium nitride promotes reactive wetting at the Li/LLZTO interface, which lowers interfacial resistance, increases critical current density (CCD), and improves cycling stability of the electrochemical cells. The additive recipe has been diversified to titanium nitride, zirconium nitride, tantalum nitride, and niobium nitride, thus supporting the general concept of reactive dispersion-plus-wetting. Such a design can be extended to other solid-state devices for better functioning and extended cycle life.

Progress and Prospects of Inorganic Solid-State Electrolyte-Based All-Solid-State Pouch Cells

All-solid-state batteries have piqued global research interest because of their unprecedented safety and high energy density. Significant advances have been made in achieving high room-temperature ionic conductivity and good air stability of solid-state electrolytes (SSEs), mitigating the challenges at the electrode-electrolyte interface, and developing feasible manufacturing processes. Along with the advances in fundamental study, all-solid-state pouch cells using inorganic SSEs have been widely demonstrated, revealing their immense potential for industrialization. This review provides an overview of inorganic all-solid-state pouch cells, focusing on ultrathin SSE membranes, sheet-type thick solid-state electrodes, and bipolar stacking. Moreover, several critical parameters directly influencing the energy density of all-solid-state Li-ion and lithium-sulfur pouch cells are outlined. Finally, perspectives on all-solid-state pouch cells are provided and specific metrics to meet certain energy density targets are specified. This review looks to facilitate the development of inorganic all-solid-state pouch cells with high energy density and excellent safety.

Electrophoretic Deposition and Characterization of Thin-Film Membranes Li7La3Zr2O12

In the presented study, films from tetragonal Li₇La₃Zr₂O₁₂ were obtained by electrophoretic deposition (EPD) for the first time. To obtain a continuous and homogeneous coating on Ni and Ti substrates, iodine was added to the Li₇La₃Zr₂O₁₂ suspension. The EPD regime was developed to carry out the stable process of deposition. The influence of annealing temperature on phase composition, microstructure, and conductivity of membranes obtained was studied. It was established that the phase transition from tetragonal to low-temperature cubic modification of solid electrolyte was observed after its heat treatment at 400 °C. This phase transition was also confirmed by high-temperature X-ray diffraction analysis of Li₇La₃Zr₂O₁₂ powder. Increasing the annealing temperature leads to the formation of additional phases in the form of fibers and their growth from 32 (dried film) to 104 μm (annealed at 500 °C). The formation of this phase occurred due to the chemical reaction of Li₇La₃Zr₂O₁₂ films obtained by electrophoretic deposition with air components during heat treatment. The total conductivity of Li₇La₃Zr₂O₁₂ films obtained has values of ~10^-10 and ~10^-7 S cm^-1 at 100 and 200 °C, respectively. The method of EPD can be used to obtain solid electrolyte membranes based on Li₇La₃Zr₂O₁₂ for all-solid-state batteries.

Stable Cycling with Intimate Contacts Enabled by Crystallinity-Controlled PTFE-Based Solvent-Free Cathodes in All-Solid-State Batteries

All-solid-state batteries (ASSBs) employing Li-metal anodes and inorganic solid electrolytes are attracting great attention due to high safety and energy density for next-generation energy storage devices. However, the volume change of cathode active materials can cause contact loss, resulting in charge carrier isolation, heterogeneous current distribution, and poor electrochemical properties in ASSBs. Here, a simple, yet effective, solvent-free electrode engineering approach with polytetrafluoroethylene (PTFE) as a binder for ASSBs is reported, enabling intimate contact and stable interfaces with the cathode. It is substantiated that the crystallinity of PTFE can be controlled depending on the heat history, and highly crystalline PTFE displays robust mechanical properties. High-nickel LiNi_{0 . 8} Mn_0.1 Co_0.1 O₂ cathode prepared with crystalline PTFE show improved cycle and rate performances in ASSBs. In addition, it is revealed that the intimate contact between cathode particles with a stable cathode electrolyte layer is maintained during cycling by postmortem studies. This simple engineering method can be applied to prepare cathodes with a variety of active materials and solid electrolytes in ASSBs.

Tailoring Conversion-Reaction-Induced Alloy Interlayer for Dendrite-Free Sulfide-Based All-Solid-State Lithium-Metal Battery

Utilization of lithium (Li) metal anodes in all-solid-state batteries employing sulfide solid electrolytes is hindered by diffusion-related dendrite growth at high rates of charge. Engineering ex-situ Li-intermetallic interlayers derived from a facile solution-based conversion-alloy reaction is attractive for bypassing the Li0 self-diffusion restriction. However, no correlation is established between the properties of conversion-reaction-induced (CRI) interlayers and the deposition behavior of Li0 in all-solid-state lithium-metal batteries (ASSLBs). Herein, using a control set of electrochemical characterization experiments with LixAgy as the interlayer in different battery chemistries, this work identifies that dendritic tolerance in ASSLBs is susceptible to the surface roughness and electronic conductivity of the CRI-alloy interlayer. This work thereby tailors the CRI-alloy interlayer from the typical mosaic structure to a hierarchical gradient structure by adjusting the pit corrosion kinetics from the (de)solvation mechanism to an adsorption model, yielding a smooth organic-rich outer layer and a composition-regulated inorganic-rich inner layer composed mainly of lithiophilic LixAgy and electron-insulating LiF. Ultimately, desirable roughness, conductivity, and diffusivity are integrated simultaneously into the tailored CRI-alloy interlayer, resulting in dendrite-free and dense Li deposition beneath the interlayer capable of improving battery cycling stability. This work provides a rational protocol for the CRI-alloy interlayer specialized for ASSLBs.

Universal Renaissance Strategy of Metal Fluoride in Secondary Ion Batteries Enabled by Liquid Metal Gallium

All-solid-state alkali ion batteries represent a future trend in battery technology, as well as provide an opportunity for low-cost metal fluoride electrode materials, if certain intrinsic problems can be resolved. In this work, a liquid metal activation strategy is proposed in which liquid Ga elements are generated in situ and doped into the LiF crystal structure by introducing a small amount of GaF₃ . Benefiting from these two Ga states of existence, in which the liquid metal Ga can continuously maintain conformable ion/electron-transport networks, while doped Ga in the LiF crystal structure catalyzes LiF splitting, the lithium-ion storage capacity of MnF₂ significantly increases by 87%. A similar effect can be obtained in FeF₃ , where the sodium-ion storage capacity is enhanced by 33%. This universal strategy with few restrictions can be used to realize a complete renaissance of metal fluorides, as well as offer an opportunity for the new application of liquid metals in the field of energy storage.

Synergistic Bimetallic CoCu-Codecorated Carbon Nanosheet Arrays as Integrated Bifunctional Cathodes for High-Performance Rechargeable/Flexible Zinc-Air Batteries

The unremitting exploration of well-architectured and high-efficiency oxygen electrocatalysts is promising to speed up the surface-mediated oxygen reduction/evolution reaction (ORR/OER) kinetics of rechargeable zinc-air batteries (ZABs). Herein, bimetallic CoCu-codecorated carbon nanosheet arrays (CoCu/N-CNS) are proposed as self-supported bifunctional oxygen catalysts. The integrated catalysts are in situ constructed via a simple sacrificial-templated strategy, imparting CoCu/N-CNS with 3D interconnected conductive pathways, abundant mesopores for electrolyte penetration and ion diffusion, as well as Cu-synergized Co-N_x /O reactive sites for improved catalytic activities. By incorporating a moderate amount of Cu into CoCu/N-CNS, the bifunctional activities can be further increased due to synergistic oxygen electrocatalysis. Consequently, the optimized CoCu/N-CNS realizes a low overall overpotential of 0.64 V for OER and ORR and leads to high-performance liquid ZABs with high gravimetric energy (879.7 Wh kg^-1 ), high peak power density (104.3 mW cm^-2 ), and remarkable cyclic stability upon 400 h/1000 cycles at 10 mA cm^-2 . More impressively, all-solid-state flexible ZABs assembled with the CoCu/N-CNS cathode exhibit superior rate performance and exceptional mechanical flexibility under arbitrary bending conditions. This CoCu/N-CNS monolith holds significant potential in advancing cation-modulated multimetallic electrocatalysts and multifunctional nanocatalysts.

Effect of Lithium Substitution Ratio of Polymeric Binders on Interfacial Conduction within All-Solid-State Battery Anodes

Problematic issues with electrically inert binders have been less serious in the conventional lithium-ion batteries by virtue of permeable liquid electrolytes (LEs) for ionic connection and/or carbonaceous additives for electronic connection in the electrodes. Contrary to electron-conductive binders used to maximize an active loading level, the development of ion-conductive binders has been lacking owing to the LE-filled electrode configuration. Herein, we represent a tactical strategy for improving the interfacial Li⁺ conduction in all-solid-state electrolyte-free graphite (EFG) electrodes where the solid electrolytes are entirely excluded, using lithium-substitution-modulated (LSM) binders. Finely tuning a lithium substitution ratio, a conductive LSM-carboxymethyl cellulose (CMC) binder is prepared from a controlled direct Na⁺/Li⁺ exchange reaction without a hazardous acid involvement. The EFG electrode employing LSM with a maximum degree of substitution of lithium (DS_Li) of ∼68% in our study shows a considerably higher rate capability of 1.05 mA h cm^-2 at 1 C and a capacity retention of ∼61.9% after 200 cycles at 0.5 C than those using sodium-CMC (Na-CMC) (0.78 mA h cm^-2, ∼49.5%) and LSM with ∼35% lithium substitution (0.93 mA h cm^-2, ∼55.4%). More importantly, the correlation between the phase transition near the bottom region of the EFG electrode and the state of charge (SOC) is systematically investigated, clarifying that the improvement of the interfacial conduction is proportional to the DS_Li of the CMC binders. Theoretical calculations combined with experimental results further verify that creating the continuous interface through abundant pathways for mobile ions using the Li⁺-conductive binder is the enhancement mechanism of the interfacial conduction in the EFG electrode, mitigating serious charge transfer resistance.

Effective transport network driven by tortuosity gradient enables high-electrochem-active solid-state batteries

Simultaneously achieving high electrochemical activity and high loading for solid-state batteries has been hindered by slow ion transport within solid electrodes, in particular with an increase in electrode thickness. Ion transport governed by 'point-to-point' diffusion inside a solid-state electrode is challenging, but still remains elusive. Herein, synchronized electrochemical analysis using X-ray tomography and ptychography reveals new insights into the nature of slow ion transport in solid-state electrodes. Thickness-dependent delithiation kinetics are spatially probed to identify that low-delithiation kinetics originate from the high tortuous and slow longitudinal transport pathways. By fabricating a tortuosity-gradient electrode to create an effective ion-percolation network, the tortuosity-gradient electrode architecture promotes fast charge transport, migrates the heterogeneous solid-state reaction, enhances electrochemical activity and extends cycle life in thick solid-state electrodes. These findings establish effective transport pathways as key design principles for realizing the promise of solid-state high-loading cathodes.

Beneficial Role of Inherently Formed Residual Lithium Compounds on the Surface of Ni-Rich Cathode Materials for All-Solid-State Batteries

This study validates the beneficial role of residual Li compounds on the surface of Ni-rich cathode materials (LiNi_xCo_yMn_zO₂, NCM). Residual Li compounds on Ni-rich NCM are naturally formed during the synthesis procedure, which degrades the initial Coulombic efficiency and generates slurry gelation during electrode fabrication in Li-ion batteries (LIBs) using liquid electrolytes. To solve this problem, washing pretreatment is usually introduced to remove residual Li compounds on the NCM surface. In contrast to LIBs, we found that residual Li compounds can serve as a functional layer that suppresses the interfacial side reactions of the NCM in all-solid-state batteries (ASSBs). The formation of resistive phosphate-based compounds from the undesirable side reaction during the initial charging step is suppressed by the residual Li compounds on the surface of the NCM, thereby reducing polarization growth in ASSBs and enhancing rate performances. The advantageous effects of the intrinsic residual Li compounds on the NCM surface suggest that the essential washing process of the NCM for the liquid-based LIB system should be reconsidered for ASSB systems.

Manipulating Charge-Transfer Kinetics of Lithium-Rich Layered Oxide Cathodes in Halide All-Solid-State Batteries

Employing lithium-rich layered oxide (LLO) as the cathode of all-solid-state batteries (ASSBs) is highly desired for realizing high energy density. However, the poor kinetics of LLO, caused by its low electronic conductivity and significant oxygen-redox-induced structural degradation, has impeded its application in ASSBs. Here, the charge transfer kinetics of LLO is enhanced by constructing high-efficiency electron transport networks within solid-state electrodes, which considerably minimizes electron transfer resistance. In addition, an infusion-plus-coating strategy is introduced to stabilize the lattice oxygen of LLO, successfully suppressing the interfacial oxidation of solid electrolyte (Li₃ InCl₆ ) and structural degradation of LLO. As a result, LLO-based ASSBs exhibit a high discharge capacity of 230.7 mAh g^-1 at 0.1 C and ultra-long cycle stability over 400 cycles. This work provides an in-depth understanding of the kinetics of LLO in solid-state electrodes, and affords a practically feasible strategy to obtain high-energy-density ASSBs.

Stable Anode-Free All-Solid-State Lithium Battery through Tuned Metal Wetting on the Copper Current Collector

A stable anode-free all-solid-state battery (AF-ASSB) with sulfide-based solid-electrolyte (SE) (argyrodite Li₆ PS₅ Cl) is achieved by tuning wetting of lithium metal on "empty" copper current-collector. Lithiophilic 1 µm Li₂ Te is synthesized by exposing the collector to tellurium vapor, followed by in situ Li activation during the first charge. The Li₂ Te significantly reduces the electrodeposition/electrodissolution overpotentials and improves Coulombic efficiency (CE). During continuous electrodeposition experiments using half-cells (1 mA cm^-2 ), the accumulated thickness of electrodeposited Li on Li₂ Te-Cu is more than 70 µm, which is the thickness of the Li foil counter-electrode. Full AF-ASSB with NMC811 cathode delivers an initial CE of 83% at 0.2C, with a cycling CE above 99%. Cryogenic focused ion beam (Cryo-FIB) sectioning demonstrates uniform electrodeposited metal microstructure, with no signs of voids or dendrites at the collector-SE interface. Electrodissolution is uniform and complete, with Li₂ Te remaining structurally stable and adherent. By contrast, an unmodified Cu current-collector promotes inhomogeneous Li electrodeposition/electrodissolution, electrochemically inactive "dead metal," dendrites that extend into SE, and thick non-uniform solid electrolyte interphase (SEI) interspersed with pores. Density functional theory (DFT) and mesoscale calculations provide complementary insight regarding nucleation-growth behavior. Unlike conventional liquid-electrolyte metal batteries, the role of current collector/support lithiophilicity has not been explored for emerging AF-ASSBs.

Lithium Superionic Conduction in BH4 -Substituted Thiophosphate Solid Electrolytes

Compared with conventional liquid electrolytes, solid electrolytes can better improve the safety properties and achieve high-energy-density Li-ion batteries. Sulfide-based solid electrolytes have attracted significant attention owing to their high ionic conductivities, which are comparable to those of their liquid counterparts. Among them, Li thiophosphates, including Li-argyrodites, are widely studied. In this study, Li thiophosphate solid electrolytes containing BH₄ ^- anions are prepared via a simple and fast milling method even without heat treatment. The synthesized materials exhibit a high ionic conductivity of up to 11 mS cm^-1 at 25 °C, which is much higher than reported values. To elucidate the mechanism behind, the thiophosphate local structure, whose effect on the ionic conductivity remains unclear to date, is investigated. Raman and solid-state NMR spectroscopies are performed to identify the thiophosphate local structure in the sulfide samples. Based on the analysis results, the ratios of the different thiophosphate units in the prepared electrolyte samples are determined. It is found that the thiophosphate local structure can be varied by changing the amount of LiBH₄ and the milling conditions, which significantly impact the ionic conductivity. The all-solid-state cell with the prepared solid electrolyte exhibits superior cycle and rate performances.

Green Synthesis for Battery Materials: A Case Study of Making Lithium Sulfide via Metathetic Precipitation

For some future clean-energy technologies (such as advanced batteries), the concept of green chemistry has not been exercised enough for their material synthesis. Herein, we report a waste-free method of synthesizing lithium sulfide (Li₂S), a critical material for both lithium-sulfur batteries and sulfide-electrolyte-based all-solid-state lithium batteries. The key novelty lies in directly precipitating crystalline Li₂S out of an organic solution after the metathetic reaction between a lithium salt and sodium sulfide. Compared with conventional methods, this method is advantageous in operating at ambient temperatures, releasing no hazardous wastes, and being economically more competitive. To collect the valuable byproduct out of the liquid phases, a "solventing-out crystallization" technique is employed by adding an antisolvent (AS) of low boiling point. The subsequent distillation of the new solution under vacuum evaporates off the AS rather than the high-boiling-point reaction solvent (RS), saving a lot of energy. Consequently, the separated AS and RS containing the unreacted lithium salt can be directly reused. For industrial production, the entire process may be operated continuously in a closed loop without discharging any wastes. Moreover, Li₂S cathodes and sulfide-electrolyte Li₆PS₅Cl derived from the synthesized Li₂S show impressive battery performance, displaying the great potential of this method for practical applications.

All-Solid-State Thin Film Lithium/Lithium-Ion Microbatteries for Powering the Internet of Things

As the world steps into the era of Internet of Things (IoT), numerous miniaturized electronic devices requiring autonomous micropower sources will be connected to the internet. All-solid-state thin-film lithium/lithium-ion microbatteries (TFBs) combining solid-state battery architecture and thin-film manufacturing are regarded as ideal on-chip power sources for IoT-enabled microelectronic devices. However, unlike commercialized lithium-ion batteries, TFBs are still in the immature state, and new advances in materials, manufacturing, and structure are required to improve their performance. In this review, the current status and existing challenges of TFBs for practical application in internet-connected devices for the IoT are discussed. Recent progress in thin-film deposition, electrode and electrolyte materials, interface modification, and 3D architecture design is comprehensively summarized and discussed, with emphasis on state-of-the-art strategies to improve the areal capacity and cycling stability of TFBs. Moreover, to be suitable power sources for IoT devices, the design of next-generation TFBs should consider multiple functionalities, including wide working temperature range, good flexibility, high transparency, and integration with energy-harvesting systems. Perspectives on designing practically accessible TFBs are provided, which may guide the future development of reliable power sources for IoT devices.

High-Entropy Microdomain Interlocking Polymer Electrolytes for Advanced All-Solid-State Battery Chemistries

All-solid-state polymer electrolytes (ASPEs) with excellent processivity are considered one of the most forward-looking materials for large-scale industrialization. However, the contradiction between improving the mechanical strength and accelerating the ionic migration of ASPEs has always been difficult to reconcile. Herein, a rational concept is raised of high-entropy microdomain interlocking ASPEs (HEMI-ASPEs), inspired by entropic elasticity well-known in polymer and biochemical sciences, by introducing newly designed multifunctional ABC miktoarm star terpolymers into polyethylene oxide for the first time. The tailor-made HEMI-ASPEs possess multifunctional polymer chains, which induce themselves to assemble into micro- and nanoscale dynamic interlocking networks with high topological structure entropy. HEMI-ASPEs achieve excellent toughness, considerable ionic conductivity, an appreciable lithium transference number (0.63), and desirable thermal stability (T_d  > 400 °C) for all-solid-state lithium metal batteries. The Li|HEMI-ASPE-Li|Li symmetrical cell shows a stable Li plating/stripping performance over 4000 h, and a LiFePO₄ |HEMI-ASPE-Li|Li full cell exhibits a high capacity retention (≈96%) after 300 cycles. This work contributes an innovative design concept introducing high-entropy supramolecular dynamic networks for ASPEs.

In Situ Formed LiI Interfacial Layer for All-Solid-State Lithium Batteries with Li6PS5Cl Solid Electrolyte Membranes

Sulfide-based solid electrolytes are considered ideal materials for all-solid-state Li metal batteries owing to their high ion conductivity and satisfactory mechanical stiffness. However, the interfacial reaction between the sulfide electrolyte membrane and Li anode severely limits the commercial application of such membranes. Herein, a lithium iodide (LiI) layer is synthesized at the Li metal-sulfide electrolyte membrane interface via chemical vapor deposition. The synthesized LiI layer exhibits satisfactory ionic conductivity and high interfacial energy, as confirmed via density functional theory calculations. Consequently, the LiI@Li/Li₆PS₅Cl membrane/LiI@Li symmetric cell can cycle for >150 h at 0.1 mA cm^-2. The as-prepared all-solid-state batteries exhibit a high discharge capacity of 107 mA h g^-1 and an excellent capacity retention of 76% after 800 cycles at 1 C. This work offers a simple and effective method to improve the interface between the Li anode and sulfide electrolyte membranes that facilitates the mass production and practical application of high-energy-density sulfide-based all-solid-state batteries.