Enabling High-Voltage "Superconcentrated Ionogel-in-Ceramic" Hybrid Electrolyte with Ultrahigh Ionic Conductivity and Single Li+ -Ion Transference Number

Ultrathin Electrolyte Membranes With Reinforced Concrete Structure for Fast-Charging Solid-State Lithium Metal Batteries

Realizing solid-state lithium (Li) metal batteries with fast charging capability and desirable energy density remains a key challenge for emerging applications for drones and consumer electronics, which require solid electrolytes to maintain good ionic conductivity and mechanical integrity with fast reaction kinetics. Herein, an 8.4 µm ultrathin solid electrolyte membrane is manifested with a reinforced concrete structure and expedited ion hopping migration capability, enabling the solid-state battery with fast charging capability. The rapid multi-dimensional Li-ion transportation network is well-constructed based on nanosized ceramic conductor aggregation and polymer chain induction, which allows homogenized Li+ distribution on the interface with a continuous uniform and steady plating/stripping process, thereby enhancing interfacial stability and inhibiting dendrite growth. Attributed to its structural superiorities, the assembled solid-state lithium metal battery maintains an excellent capacity retention rate of 89.2% after 1300 cycles at 10 C. A 1.2 Ah pouch cell is fabricated with a high energy density of 415.2 Wh kg-1 and also capable of cycling at 5 C, showing great potential for the practical application of solid-state batteries for next-generation energy storage devices.

Supramolecular ionogels enable highly efficient electrochromism

Ionogels are a promising solution to improve the functionality of electrochromic devices (ECDs) by solving issues related to traditional liquid electrolytes, such as volatility, toxicity, and leakage. However, manufacturing ionogels is complicated as it often involves cross-linking polymerization or chemical sol-gel processes, requiring large amounts of inorganic or polymeric gelators. This results in low ionic conductivity and poor ECD performance. This study demonstrates the fabrication of highly conductive supramolecular ionogels by directly solidifying an ionic liquid (IL) using a low-molecular-weight gelator with a very low content (5 wt%). The resulting ionogel, DBS-G, exhibited self-healing properties, high optical transmittance (>86%), and high ionic conductivity (3.12 mS cm-1) comparable to the pure IL. When combined with a conjugated thiophene-based electrochromic polymer or by incorporating electrochromic viologen derivatives and ferrocene into the ionogel, the constructed five-or three-layer ECDs demonstrate electrochromic performance comparable to IL electrolyte and surpassing polymer gelator-based ionogels. They exhibit high optical contrast, rapid response, high coloring efficiency, good cycle stability, and can operate effectively in a broad temperature range from -25 °C to 80 °C. Furthermore, the adhesive properties of DBS-G facilitate the fabrication of flexible ECDs, which exhibit commendable electrochromic performance and cycle stability under bending conditions.

Host-Guest Inversion Engineering Induced Superionic Composite Solid Electrolytes for High-Rate Solid-State Alkali Metal Batteries

Composite solid electrolytes (CSEs) are promising for solid-state Li metal batteries but suffer from inferior room-temperature ionic conductivity due to sluggish ion transport and high cost due to expensive active ceramic fillers. Here, a host-guest inversion engineering strategy is proposed to develop superionic CSEs using cost-effective SiO2 nanoparticles as passive ceramic hosts and poly(vinylidene fluoride-hexafluoropropylene) (PVH) microspheres as polymer guests, forming an unprecedented "polymer guest-in-ceramic host" (i.e., PVH-in-SiO2) architecture differing from the traditional "ceramic guest-in-polymer host". The PVH-in-SiO2 exhibits excellent Li-salt dissociation, achieving high-concentration free Li+. Owing to the low diffusion energy barriers and high diffusion coefficient, the free Li+ is thermodynamically and kinetically favorable to migrate to and transport at the SiO2/PVH interfaces. Consequently, the PVH-in-SiO2 delivers an exceptional ionic conductivity of 1.32 × 10-3 S cm-1 at 25 °C (vs. typically 10-5-10-4 S cm-1 using high-cost active ceramics), achieved under an ultralow residual solvent content of 2.9 wt% (vs. 8-15 wt% in other CSEs). Additionally, PVH-in-SiO2 is electrochemically stable with Li anode and various cathodes. Therefore, the PVH-in-SiO2 demonstrates excellent high-rate cyclability in LiFePO4|Li full cells (92.9% capacity-retention at 3C after 300 cycles under 25 °C) and outstanding stability with high-mass-loading LiFePO4 (9.2 mg cm-1) and high-voltage NCM622 (147.1 mAh g-1). Furthermore, we verify the versatility of the host-guest inversion engineering strategy by fabricating Na-ion and K-ion-based PVH-in-SiO2 CSEs with similarly excellent promotions in ionic conductivity. Our strategy offers a simple, low-cost approach to fabricating superionic CSEs for large-scale application of solid-state Li metal batteries and beyond.

Three-Dimensionally Printed Ionogel-Coated Ceramic Electrolytes for Solid-State Lithium Batteries

Stereolithography three-dimensional (3D) printing technology enables the customization of ceramic-based solid electrolyte structures with desired electrochemical properties; however, formulating slurries that both are highly ceramic-loaded and have low viscosity for printing poses a challenge. Here, we propose an ionogel-coated ceramic approach to prepare a shear-thinning fast-ion conductor ceramic (Li6.5La3Zr1.5Ta0.5O12) slurry, which possesses both a high ceramic content of 50 wt % and a low viscosity of 1.53 Pa·s. Utilizing this slurry, 3D symmetric honeycomb briquette-like electrolyte films are printed, and solid-state lithium batteries are easily fabricated by filling the cathode and anode slurries into the respective symmetric honeycombs. The atomic-level interaction between ceramic/ionogel interfaces and the integrated electrode/electrolyte interface facilitates rapid Li+ transport across multiscale interphases in batteries. Additionally, the interactions of ceramic nanoparticles and ionic liquids with Li salt substantially increase the concentration of free Li+, both of which enhance the ionic conductivity and ensure stable Li+ transport efficiency. Solid-state lithium batteries can cycle stably 500 times without obvious degradation at 0.5 C and 50 °C. The strategy offers a feasible solution for printing customized solid-state ceramic-based electrolytes.

Self-Assembled Monolayer in Hybrid Quasi-Solid Electrolyte Enables Boosted Interface Stability and Ion Conduction

Complex interactions between the inorganic solid electrolyte (ISE) and the liquid electrolyte (LE) give rise to challenges of achieving durable interface stability in hybrid quasi-solid electrolytes (HQSE), and the influence on the involved ISE surface ionic conductivity also needs to be investigated. Here, 4-chlorobenzenesulfonic acid (CBSA) is utilized to establish a self-assembled monolayer (SAM) on the surface of Li6.4La3Zr1.4Ta0.6O12 (LLZTO), which is then incorporated into PEGDA-based in situ polymerized HQSE. The results show that the introduction of CBSA significantly improves the LLZTO/LE interface stability with the optimized solvation structure, resulting in a favorable ionic conductivity (1.19 mS⋅cm-1) and an increasing Li+ transference number (0.647). Mechanisms for the promotion of ionic conduction and interfacial stability of SAM-HQSE are unveiled through the density functional theory (DFT) combined with Raman spectra and 7Li solid-state nuclear-magnetic-resonance. There are no short-circuits in the Li|SAM-HQSE|Li cells after 1000 h. The LFP|SAM-HQSE|Li cells or LFP|SAM-HQSE|Graphite pouch cells respectively achieve the capacity retention of 91.2 % and 87.0 % with the 0.5.C-rate for 500 and 300 cycles. This facile and effective strategy proposed in this work make it accessible for constructing the stable surface micro-environments of LLZTO where boost and homogenize the Li+ conduction in a hybrid quasi-solid electrolyte system.

Designing Zwitterionic Bottlebrush Polymers to Enable Long-Cycling Quasi-Solid-State Lithium Metal Batteries

Ionogel polymer electrolyte (IPE), incorporating ionic liquid (IL) within a polymer matrix, presents a promising avenue for safe quasi-solid-state lithium metal batteries. However, sluggish Li+ kinetics, resulting from the formation of [Li(anion)n]-(n-1) clusters and the occupation of Li+ transport sites by organic cations, limit their practical applications. In this study, we have developed zwitterionic bottlebrush polymers-based IPE with promoted Li+ conduction by employing poly(sulfobetaine methacrylate)-grafted poly(vinylidene fluoride-co-chlorotrifluoroethylene) (PVC-g-PSBMA) bottlebrushes as matrices of IL. The grafted zwitterionic side chains greatly facilitate the dissociation of [Li(anion)n]-(n-1) clusters to produce more movable Li+. Moreover, the positively charged -NR4 + groups in zwitterionic side chains effectively restrain anions migration, while the negatively charged -SO3 - groups immobilize IL cations, preventing them from occupying Li+ hopping sites and reducing the energy barrier for Li+ migration. These synergistic effects contribute to a notable ionic conductivity (7.5×10-4 S cm-1) and Li+ transference number (0.62) of PVC-g-PSBMA IPE at 25 °C. As a result, PVC-g-PSBMA IPE enables ultralong-term (over 6500 h) reversible and stable Li plating/stripping in Li||Li symmetric cells. Remarkably, the assembled Li||LiFePO4 full batteries demonstrate unprecedented cycling stability of more than 2000 cycles with a superior capacity retention of 93.7 %.

Enhanced Interfacial Contact and Lithium-Ion Transport in Ionic Liquid Polymer Electrolyte via In-Situ Electrolyte-Cathode Integration

Solid polymer electrolytes (SPEs) have attracted much attention due to their excellent flexibility, strong interfacial adhesion, and good processibility. However, the poor interfacial contact between the separate solid polymer electrolytes and electrodes leads to large interfacial impedance and, thus, hinders Li transport. In this work, an ionic liquid-modified comb-like crosslinked network composite solid-state electrolyte with an integrated electrolyte/cathode structure is prepared by in situ ultraviolet (UV) photopolymerization. Combining the enhanced interfacial contact and the introduction of ionic liquid, a continuous and fast Li+ transport channel at the electrolyte-cathode interface is established, ultimately enhancing the overall performance of solid-state lithium batteries. The composite solid electrolytes (CSEs) exhibit an ionic conductivity of 0.44 mS cm-1 at 60 °C. LiFePO4//Li cells deliver a high discharge capacity (154 mAh g-1 at 0.5 C) and cycling stability (with a retention rate of more than 80% at 0.5 C after 200 cycles) at 60 °C.

Host-Guest Interactions of Metal-Organic Framework Enable Highly Conductive Quasi-Solid-State Electrolytes for Li-CO2 Batteries

High-energy lithium (Li)-based batteries, especially rechargeable Li-CO2 batteries with CO2 fixation capability and high energy density, are desirable for electrified transportation and other applications. However, the challenges of poor stability, low energy efficiency, and leakage of liquid electrolytes hinder the development of Li-CO2 batteries. Herein, a highly conductive and stable metal-organic framework-encapsulated ionic liquid (IL@MOF) electrolyte system is developed for quasi-solid-state Li-CO2 batteries. Benefiting from the host-guest interaction of MOFs with open micromesopores and internal IL, the optimized IL@MOF electrolytes exhibit a high ionic conductivity of 1.03 mS cm-1 and a high transference number of 0.80 at room temperature. The IL@MOF electrolytes also feature a wide electrochemical stability window (4.71 V versus Li+/Li) and a wide working temperature (-60 °C ∼ 150 °C). The IL@MOF electrolytes also enable Li+ and electrons transport in the carbon nanotubes-IL@MOF (CNT-IL@MOF) solid cathodes in quasi-solid-state Li-CO2 batteries, delivering a high specific capacity of 13,978 mAh g-1 (50 mA g-1), a long cycle life of 441 cycles (500 mA g-1 and 1000 mAh g-1), and a wide operation temperature of -60 to 150 °C. The proposed MOF-encapsulated IL electrolyte system presents a powerful strategy for developing high-energy and highly safe quasi-solid-state batteries.

Surface Coordination of Garnet Fillers Improves the Organic-Inorganic Interfacial Compatibility of Composite Solid Electrolyte

Composite solid electrolytes (CSEs) have become one of the most promising solid-state electrolytes due to their favorable safety and flexibility. However, the weak interaction between inorganic fillers and polymer matrix leads to poor organic-inorganic interfacial compatibility, which degrades the electrochemical performance of CSEs. Herein, it is demonstrated that Li6.4La3Zr1.4Ta0.6O12 (LLZTO) can be chemically bonded to the polymer matrix by surface coordination of the 1,2-dithiolane group of lipoic acid (LA) with metal atoms on the surface of LLZTO through a combination of experimental investigations and theoretical calculations. The surface coordination not only enhances the interfacial compatibility between LLZTO and the polymer matrix, but also facilitates rapid Li+ transport, which leads to the ionic conductivity of the prepared CSE (P-V-M@LLZTO) as high as 6.1 × 10-4 S cm-1 at 30 °C. The excellent interface compatibility ensures a stable cycle of Li/P-V-M@LLZTO/Li symmetrical cell for more than 3500 h. As a result, LiFePO4/P-V-M@LLZTO/Li cell delivers the discharge capacity of 161 mAh g-1 after 5 cycles with a capacity retention of 81% after 500 cycles at 0.5C under 30 °C. This work demonstrates that surface coordination is an effective strategy to solve the inherent interfacial incompatibility problem in CSEs.

High-Performance Solid-State Lithium Metal Batteries of Garnet/Polymer Composite Thin-Film Electrolyte with Domain-Limited Ion Transport Pathways

The integrated approach of interfacial engineering and composite electrolytes is crucial for the market application of Li metal batteries (LMBs). A 22 μm thin-film type polymer/Li6.4La3Zr1.4Ta0.6O12 (LLZTO) composite solid-state electrolyte (LPCE) was designed that combines fast ion conduction and stable interfacial evolution, enhancing lithium metal interface stability and cycling performance. The ether-based molecular coordination groups/clusters formed by triethylene glycol dimethyl ether (TGDE) and anions facilitated the movement of Li+ between the polymer chain segments. These specific coordination clusters significantly "constrained" the interaction between anions and Li+, inducing the anions to follow the clusters to the Li metal and preferentially participate in solid electrolyte interface (SEI) derivatization. The inorganic salt-rich gradient SEI modulates Li+ deposition and inhibits uncontrolled dendrite growth, achieving stable cycling of Li symmetric cell at 0.2 mA cm-2 for over 2000 h. Furthermore, the Li||NCM811 cell at a rate of 0.1 C exhibits an initial discharge capacity of 194.5 mAh g-1, maintaining a capacity retention rate of over 90% after 500 cycles. This work demonstrates the importance of domain-limited ion clusters in ion transport and interfacial evolution, providing a perspective for solid-state LMBs.

Molecular brush-based ultrathin polymer electrolytes with stable interfaces for high-voltage large-areal-capacity lithium metal batteries

Polymer electrolytes hold great promise for long-cycling lithium metal batteries, but their unsatisfactory ionic conductivities and unstable interfacial contacts with electrodes greatly limit their practical applications under high cut-off voltage and large areal capacity conditions. Herein, a super-structured multifunctional molecular brush, BC-g-P(CCMA-co-TFEMA) (BC = bacterial cellulose; CCMA = (2-oxo-1,3-dioxolan-4-yl) methyl methacrylate; TFEMA = 2,2,2-trifluoroethyl methacrylate), has been designed to develop an ultrathin polymer electrolyte with superior ionic conductivity and stable electrolyte/electrode interfaces. The cyclic carbonate group in CCMA can weaken the binding of solvents and anions with lithium ions, thereby enhancing ionic transport. Meanwhile, the fluorine-containing group in TFEMA is beneficial for simultaneously constructing LiF-rich electrolyte/anode and electrolyte/cathode interfaces with enhanced stability. Moreover, the robust BC backbone provides the polymer electrolyte with outstanding mechanical properties. With such polymer electrolytes, a remarkable capacity retention of 83% has been demonstrated for Li/LiFePO4 cells at 1C after 1000 cycles. Remarkably, the solid-state full cell with a high-loading LiNi0.8Mn0.1Co0.1O2 cathode delivers a high discharge specific capacity of 204 mA h g-1 for more than 400 cycles at a high cut-off voltage of 4.5 V. This work provides a novel design principle for advanced electrolytes of high-voltage and large-areal-capacity lithium metal batteries.

"Anions-in-Colloid" Hydrated Deep Eutectic Electrolyte for High Reversible Zinc Metal Anodes

Zn metal as a promising anode for aqueous batteries suffers from severe zinc dendrites, anion-related side reactions, hydrogen evolution reaction (HER) and narrow electrochemical stable window (ESW). Herein, an "anions-in-colloid" hydrated deep eutectic electrolyte consisting of Zn(ClO4)2 ⋅ 6H2O, β-cyclodextrin (β-CD), and H2O with mass ratio of 7 : 4.5 : 3 (ACDE-3) is designed to improve the stability of zinc anode. The ACDE-3 reconfigures the hydrogen-bond (HB) network and regulates the solvation shell. More importantly, the hydroxyl-rich β-cyclodextrins (β-CDs) in ACDE-3 self-assemble into micelles, in which the steric effect between adjacent β-CDs in micelles restricts the movement of anions. This unique "anions-in-colloid" structure enables the eutectic system with a high Zn2+ transference number (tZn 2+) of 0.84. Thus, ACDE-3 inhibits the formation of dendrite, prevents the anion-involved side reactions, suppresses the HER, and enlarges the ESW to 2.32 V. The Zn//Zn symmetric cell delivers a long lifespan of 900 hours at 0.5 mA cm-2, and the Zn//Cu half cells have a high average columbic efficiency (ACE) of 97.9 % at 0.5 mA cm-2 from cycle 15 to 200 with a uniform and compact zinc deposition. When matched with a poly(1,5-naphthalenediamine) (poly(1, 5-NAPD)) cathode, the full battery with a low negative/positive capacity (N/P) ratio of 2 can still cycle steadily for 200 cycles at a current density of 1.0 A g-1. Additionally, this electrolyte has been proven to be operative over a wide temperature range from -40 °C to 40 °C.

Multiple uniform lithium-ion transport channels in Li6.4La3Zr1.4Ta0.6O12/Ce(OH)3 modified polypropylene composite separator for high-performance lithium metal batteries

Lithium (Li) metal anodes (LMAs) are regarded as leading technology for advanced-generation batteries due to their high theoretical capacity and favorable redox potential. However, the practical integration of LMAs into high-energy rechargeable batteries is hindered by the challenge of Li dendrite growth. In this work, nanoparticles of Li6.4La3Zr1.4Ta0.6O12 (LLZTO) loaded with Ce(OH)3 (LLZTCO) were designed and synthesized by a hydrothermal method. A functional composite separator was crafted by coating one side of a polypropylene (PP) separator with a composite electrolyte comprised of polyvinylidene fluoride (PVDF) and LLZTCO. The synergistic interactions between PVDF and LLZTCO provide numerous rapid lithium-ion (Li+) channels, facilitating the efficient redistribution of disparate Li+ flux originating from the insulated PP separator. The composite separator demonstrated an ionic conductivity (σ) of 3.68 × 10-3 S cm-1, substantial Li+ transference number (t+) of 0.73, and a high electrochemical window of 4.8 V at 25℃. Furthermore, the Li/LLZTCO@PP/Li symmetric cells demonstrated stable cycling for over 2000 h without significant dendrite formation. The Li/LiFePO4 (LFP) cells assembled with LLZTCO@PP separators exhibited a capacity retention of 91.6 % after 400 cycles at 1C. This study offers a practical approach to fabricating composite separators with enhanced safety and superior electrochemical performance.

Molecule-Level Multiscale Design of Nonflammable Gel Polymer Electrolyte to Build Stable SEI/CEI for Lithium Metal Battery

The risk of flammability is an unavoidable issue for gel polymer electrolytes (GPEs). Usually, flame-retardant solvents are necessary to be used, but most of them would react with anode/cathode easily and cause serious interfacial instability, which is a big challenge for design and application of nonflammable GPEs. Here, a nonflammable GPE (SGPE) is developed by in situ polymerizing trifluoroethyl methacrylate (TFMA) monomers with flame-retardant triethyl phosphate (TEP) solvents and LiTFSI-LiDFOB dual lithium salts. TEP is strongly anchored to PTFMA matrix via polarity interaction between -P = O and -CH2CF3. It reduces free TEP molecules, which obviously mitigates interfacial reactions, and enhances flame-retardant performance of TEP surprisingly. Anchored TEP molecules are also inhibited in solvation of Li+, leading to anion-dominated solvation sheath, which creates inorganic-rich solid electrolyte interface/cathode electrolyte interface layers. Such coordination structure changes Li+ transport from sluggish vehicular to fast structural transport, raising ionic conductivity to 1.03 mS cm-1 and transfer number to 0.41 at 30 °C. The Li|SGPE|Li cell presents highly reversible Li stripping/plating performance for over 1000 h at 0.1 mA cm-2, and 4.2 V LiCoO2|SGPE|Li battery delivers high average specific capacity > 120 mAh g-1 over 200 cycles. This study paves a new way to make nonflammable GPE that is compatible with Li metal anode.

Challenges and Recent Progress on Solid-State Batteries and Electrolytes, using Qualitative Systematic Analysis. A Short Review

The rise in the energy demand, the need to decrease the use of fossil fuels, expanding investments in renewable energy and boosting the electric vehicle market, opens the door to new technologies in clean energy accumulators. Lithium-ion batteries are the most advanced technology in the market but have safety concerns due to the flammability of the electrolyte, which opens the door to innovations. One of these innovations is the solid-state batteries (SSB), which, by using solid electrolytes, do not have the flammable risk, bringing safety to users while reaching similar energy and power densities. This work presents a review about SSB, based on qualitative and exploratory research, using the Web of Science (WoS) platform. Keywords used to gather information from the database were "solid state batteries" and "electrolytes". Only publications from 2018 to 2023 were selected. The main research focus is to solve the challenges posed by the different physical-chemical phenomena of the SSB. This work focuses on the general comprehension of the SSB batteries, what are the factors that can affect it and the main solutions presented in the literature the last five years.

Retarding anion migration for alleviating concentration polarization towards stable polymer lithium-metal batteries

Traditional dual-ion lithium salts have been widely used in solid polymer lithium-metal batteries (LMBs). Nevertheless, concentration polarization caused by uncontrolled migration of free anions has severely caused the growth of lithium dendrites. Although single-ion conductor polymers (SICP) have been developed to reduce concentration polarization, the poor ionic conductivity caused by low carrier concentration limits their application. Herein, a dual-salt quasi-solid polymer electrolyte (QSPE), containing the SICP network as a salt and traditional dual-ion lithium salt, is designed for retarding the movement of free anions and simultaneously providing sufficient effective carriers to alleviate concentration polarization. The dual salt network of this designed QSPE is prepared through in-situ crosslinking copolymerization of SICP monomer, regular ionic conductor, crosslinker with the presence of the dual-ion lithium salt, delivering a high lithium-ion transference number (0.75) and satisfactory ionic conductivity (1.16 × 10-3 S cm-1 at 30 °C). Comprehensive characterizations combined with theoretical calculation demonstrate that polyanions from SICP exerts a potential repulsive effect on the transport of free anions to reduce concentration polarization inhibiting lithium dendrites. As a consequence, the Li||LiFePO4 cell achieves a long-cycle stability for 2000 cycles and a 90% capacity retention at 30 °C. This work provides a new perspective for reducing concentration polarization and simultaneously enabling enough lithium-ions migration for high-performance polymer LMBs.

Gel polymer electrolytes for rechargeable batteries toward wide-temperature applications

Rechargeable batteries, typically represented by lithium-ion batteries, have taken a huge leap in energy density over the last two decades. However, they still face material/chemical challenges in ensuring safety and long service life at temperatures beyond the optimum range, primarily due to the chemical/electrochemical instabilities of conventional liquid electrolytes against aggressive electrode reactions and temperature variation. In this regard, a gel polymer electrolyte (GPE) with its liquid components immobilized and stabilized by a solid matrix, capable of retaining almost all the advantageous natures of the liquid electrolytes and circumventing the interfacial issues that exist in the all-solid-state electrolytes, is of great significance to realize rechargeable batteries with extended working temperature range. We begin this review with the main challenges faced in the development of GPEs, based on extensive literature research and our practical experience. Then, a significant section is dedicated to the requirements and design principles of GPEs for wide-temperature applications, with special attention paid to the feasibility, cost, and environmental impact. Next, the research progress of GPEs is thoroughly reviewed according to the strategies applied. In the end, we outline some prospects of GPEs related to innovations in material sciences, advanced characterizations, artificial intelligence, and environmental impact analysis, hoping to spark new research activities that ultimately bring us a step closer to realizing wide-temperature rechargeable batteries.

Highly Ionic Conductive, Stretchable, and Tough Ionogel for Flexible Solid-State Supercapacitor

The increasing demand for wearable electronics calls for advanced energy storage solutions that integrate high  electrochemical performances and mechanical robustness. Ionogel is a promising candidate due to its stretchability combined with high ionic conductivity. However, simultaneously optimizing both the electrochemical and mechanical performance of ionogels remains a challenge. This paper reports a tough and highly ion-conductive ionogel through ion impregnation and solvent exchange. The fabricated ionogel consists of double interpenetrating networks of long polymer chains that provide high stretchability. The polymer chains are crosslinked by hydrogen bonds that induce large energy dissipation for enhanced toughness. The resultant ionogel possesses mechanical stretchability of 26, tensile strength of 1.34 MPa, and fracture toughness of 4175 J m-2. Meanwhile, due to the high ion concentrations and ion mobility in the gel, a high ionic conductivity of 3.18 S m-1 at room temperature is achieved. A supercapacitor of this ionogel sandwiched with porous fiber electrodes provides remarkable areal capacitance (615 mF cm-2 at 1 mA cm-2), energy density (341.7 µWh cm-2 at 1 mA cm-2), and power density (20 mW cm-2 at 10 mA cm-2), offering significant advantages in applications where high efficiency, compact size, and rapid energy delivery are crucial, such as flexible and wearable electronics.

Multifunctional Additive Enables a "5H" PEO Solid Electrolyte for High-Performance Lithium Metal Batteries

The solid-state battery with a lithium metal anode is a promising candidate for next-generation batteries with improved energy density and safety. However, the current polymer electrolytes still cannot fulfill the demands of solid-state batteries. In this work, we propose a "5H" poly(ethylene oxide) (PEO) electrolyte via introducing a multifunctional additive of tris(pentafluorophenyl)borane (TPFPB) for high-performance lithium metal batteries. The addition of TPFPB improves the ionic conductivity from 6.08 × 10-5 to 1.54 × 10-4 S cm-1 via reducing the crystallinity of the PEO electrolyte and enhances the lithium-ion transference number from 0.19 to 0.53 via anion trapping due to its Lewis acid nature. Furthermore, the fluorine and boron segments from TPFPB can optimize the composition of the solid-electrolyte interphase and cathode-electrolyte interphase, providing a high electrochemical stability window over 4.6 V of the PEO electrolyte along with significantly improved interface stability. At last, TPFPB can ensure improved safety through a self-extinguishing effect. As a result, the "5H" electrolyte enables the Li/Li symmetric cells to achieve a stable cycle over 2200 h at the current density of 0.2 mA cm-2 with a capacity of 0.2 mA h cm-2; the LiFePO4/Li full cells with a high LFP loading of 8 mg cm-2 exhibits decay-free capacity of 140 mA h g-1 (99% capacity retention) after 100 cycles; and the NCM811/Li cells exhibit a high capacity of 160 mA h g-1 after 50 cycles at 0.5 C. This work presents an innovative approach to utilizing a "5H" electrolyte for high-performance solid-state lithium batteries.

In Situ Constructing Robust and Highly Conductive Solid Electrolyte with Tailored Interfacial Chemistry for Durable Li Metal Batteries

Employing nanofiber framework for in situ polymerized solid-state lithium metal batteries (SSLMBs) is impeded by the insufficient Li+ transport properties and severe dendritic Li growth. Both critical issues originate from the shortage of Li+ conduction highways and nonuniform Li+ flux, as randomly-scattered nanofiber backbone is highly prone to slippage during battery assembly. Herein, a robust fabric of Li0.33La0.56Ce0.06Ti0.94O3-δ/polyacrylonitrile framework (p-LLCTO/PAN) with inbuilt Li+ transport channels and high interfacial Li+ flux is reported to manipulate the critical current density of SSLMBs. Upon the merits of defective LLCTO fillers, TFSI- confinement and linear alignment of Li+ conduction pathways are realized inside 1D p-LLCTO/PAN tunnels, enabling remarkable ionic conductivity of 1.21 mS cm-1 (26 °C) and tLi+ of 0.93 for in situ polymerized polyvinylene carbonate (PVC) electrolyte. Specifically, molecular reinforcement protocol on PAN framework further rearranges the Li+ highway distribution on Li metal and alters Li dendrite nucleation pattern, boosting a homogeneous Li deposition behavior with favorable SEI interface chemistry. Accordingly, excellent capacity retention of 76.7% over 1000 cycles at 2 C for Li||LiFePO4 battery and 76.2% over 500 cycles at 1 C for Li||LiNi0.5Co0.2Mn0.3O2 battery are delivered by p-LLCTO/PAN/PVC electrolyte, presenting feasible route in overcoming the bottleneck of dendrite penetration in in situ polymerized SSLMBs.

Computational approach inspired advancements of solid-state electrolytes for lithium secondary batteries: from first-principles to machine learning

The increasing demand for high-security, high-performance, and low-cost energy storage systems (EESs) driven by the adoption of renewable energy is gradually surpassing the capabilities of commercial lithium-ion batteries (LIBs). Solid-state electrolytes (SSEs), including inorganics, polymers, and composites, have emerged as promising candidates for next-generation all-solid-state batteries (ASSBs). ASSBs offer higher theoretical energy densities, improved safety, and extended cyclic stability, making them increasingly popular in academia and industry. However, the commercialization of ASSBs still faces significant challenges, such as unsatisfactory interfacial resistance and rapid dendrite growth. To overcome these problems, a thorough understanding of the complex chemical-electrochemical-mechanical interactions of SSE materials is essential. Recently, computational methods have played a vital role in revealing the fundamental mechanisms associated with SSEs and accelerating their development, ranging from atomistic first-principles calculations, molecular dynamic simulations, multiphysics modeling, to machine learning approaches. These methods enable the prediction of intrinsic properties and interfacial stability, investigation of material degradation, and exploration of topological design, among other factors. In this comprehensive review, we provide an overview of different numerical methods used in SSE research. We discuss the current state of knowledge in numerical auxiliary approaches, with a particular focus on machine learning-enabled methods, for the understanding of multiphysics-couplings of SSEs at various spatial and time scales. Additionally, we highlight insights and prospects for SSE advancements. This review serves as a valuable resource for researchers and industry professionals working with energy storage systems and computational modeling and offers perspectives on the future directions of SSE development.

Tunneling Interpenetrative Lithium Ion Conduction Channels in Polymer-in-Ceramic Composite Solid Electrolytes

Polymer-in-ceramic composite solid electrolytes (PIC-CSEs) provide important advantages over individual organic or inorganic solid electrolytes. In conventional PIC-CSEs, the ion conduction pathway is primarily confined to the ceramics, while the faster routes associated with the ceramic-polymer interface remain blocked. This challenge is associated with two key factors: (i) the difficulty in establishing extensive and uninterrupted ceramic-polymer interfaces due to ceramic aggregation; (ii) the ceramic-polymer interfaces are unresponsive to conducting ions because of their inherent incompatibility. Here, we propose a strategy by introducing polymer-compatible ionic liquids (PCILs) to mediate between ceramics and the polymer matrix. This mediation involves the polar groups of PCILs interacting with Li+ ions on the ceramic surfaces as well as the interactions between the polar components of PCILs and the polymer chains. This strategy addresses the ceramic aggregation issue, resulting in uniform PIC-CSEs. Simultaneously, it activates the ceramic-polymer interfaces by establishing interpenetrating channels that promote the efficient transport of Li+ ions across the ceramic phase, the ceramic-polymer interfaces, and the intervening pathways. Consequently, the obtained PIC-CSEs exhibit high ionic conductivity, exceptional flexibility, and robust mechanical strength. A PIC-CSE comprising poly(vinylidene fluoride) (PVDF) and 60 wt % PCIL-coated Li3Zr2Si2PO12 (LZSP) fillers showcasing an ionic conductivity of 0.83 mS cm-1, a superior Li+ ion transference number of 0.81, and an elongation of ∼300% at 25 °C could be produced on meter-scale. Its lithium metal pouch cells show high energy densities of 424.9 Wh kg-1 (excluding packing films) and puncture safety. This work paves the way for designing PIC-CSEs with commercial viability.

Improving the ionic conductivity of polymer electrolytes induced by ceramic nanowire fillers with abundant lithium vacancies

The addition of ceramic fillers is regarded as an effective strategy for enhancing the ionic conductivity of polymer electrolytes. However, particulate fillers typically fail to provide continuous conductive pathways and effective reinforcement. Herein, we report a ceramic nanowire filler with long-range interfacial conductivity and abundant lithium vacancies for a poly(ethylene oxide) (PEO)-based all-solid-state polymer electrolyte. LLZO nanowires (LLZO NWs) with a high aspect ratio are synthesized by combining sol-gel electrospinning and the multi-step process involving pre-oxidation, pre-sintering, and secondary sintering, resulting in a high tensile strength of the composite electrolyte (6.87 MPa). Notably, tantalum-aluminum co-substituted LLZO NWs (TALLZO NWs) release abundant lithium vacancies, further enhancing the Lewis acid-base properties, leading to a rapid ion migration speed (Li+ transfer number = 0.79) and significantly high ionic conductivity (3.80 × 10-4 S cm-1). Due to the synergistic effect of nanostructure modification and heteroatom co-doping, the assembled all-solid-state lithium-sulfur battery exhibits a high initial discharge capacity (776 mA h g-1 at 25 °C), remarkable rate capability, and excellent cycling performance (81% capacity retention after 200 cycles at 0.1C).

Beyond LiF: Tailoring Li2O-Dominated Solid Electrolyte Interphase for Stable Lithium Metal Batteries

The components and structures of the solid-electrolyte interphase (SEI) are critical for stable cycling of lithium metal batteries (LMBs). LiF has been widely studied as the dominant component of SEI, but Li2O, which has a much lower diffusion barrier for Li+, has rarely been investigated as the dominant component of SEI. The effect of Li2O-dominated SEI on electrochemical performance still remains elusive. Herein, an ultrastrong coordinated cosolvation diluent, 2,3-difluoroethoxybenzene (DFEB), is designed to modulate solvation structure and tailor Li2O-dominated SEI for stable LMBs. In the DFEB-based LHCE (DFEB-LHCE), DFEB intensively participates in the first solvation shell and synergizes with FSI- to tailor an Li2O-dominated inorganic-rich SEI which is different from the LiF-dominated SEI formed in conventional LHCE. Benefiting from this special SEI architecture, a high Coulombic efficiency (CE) of 99.58% in Li||Cu half cells, stable voltage profiles, and dense and uniform lithium deposition, as well as effective inhibition of Li dendrite formation in the symmetrical cell, are achieved. More importantly, the DFEB-LHCE can be matched with various cathodes such as LFP, NCM811, and S cathodes, and the Li||LFP full cell using DFEB-LHCE possesses 85% capacity retention after 650 stable cycles with 99.9% CE. Especially the 1.5 Ah practical lithium metal pouch cell achieves an excellent capacity retention of 89% after 250 cycles with a superb average CE of 99.93%. This work unravels the superiority of the Li2O-dominated SEI and the feasibility of tailoring SEI components through modulation of solvation structures.

A Fast Na-Ion Conduction Polymer Electrolyte via Triangular Synergy Strategy for Quasi-Solid-State Batteries

Polymer electrolytes provide a visible pathway for the construction of high-safety quasi-solid-state batteries due to their high interface compatibility and processability. Nevertheless, sluggish ion transfer at room temperature seriously limits their applications. Herein, a triangular synergy strategy is proposed to accelerate Na-ion conduction via the cooperation of polymer-salt, ionic liquid, and electron-rich additive. Especially, PVDF-HFP and NaTFSI salt acted as the framework to stably accommodate all the ingredients. An ionic liquid (Emim+ -FSI- ) softened the polymer chains through a weakening molecule force and offered additional liquid pathways for ion transport. Physicochemical characterizations and theoretical calculations demonstrated that electron-rich Nerolin with π-cation interaction facilitated the dissociation of NaTFSI and effectively restrained the competitive migration of large cations from EmimFSI, thus lowering the energy barrier for ion transport. The strategy resulted in a thin F-rich interphase dominated by NaTFSI salt's decomposition, enabling rapid Na+ transmission across the interface. These combined effects resulted in a polymer electrolyte with high ionic conductivity (1.37×10-3  S cm-1 ) and tNa+ (0.79) at 25 °C. The assembled cells delivered reliable rate capability and stability (200 cycles, 99.2 %, 0.5 C) with a good safety performance.

Composite Quasi-Solid-State Electrolytes with Organic-Inorganic Interface Engineering for Fast Ion Transport in Dendrite-Free Sodium Metal Batteries

Quasi-solid-state electrolytes (QSSE) are a promising candidate for addressing the limitations of liquid and solid electrolytes. However, different ion transport capacities between liquid solvents and polymers can cause localized heterogeneous distribution of Na+ fluxes. In addition, the continuous side reactions occurring at the interface between QSSE and sodium anode lead to uncontrollable dendrites growth. Herein, a novel strategy is designed to integrate the composite electrospun membrane of Na3 Zr2 Si2 PO12 and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) into QSSE, aiming to introduce new fast ion conducting channels at the organic-inorganic interface. The efficient ion transfer pathways can effectively promote the homogenization of ion migration, enabling composite QSSE to achieve an ultrahigh ionic conductivity of 4.1 mS cm-1 at room temperature, with a Na+ transference number as high as 0.54. Moreover, the PVDF-HFP is preferentially reduced upon contact with the sodium anode to form a "NaF-rich" solid electrolyte interphase, which effectively suppresses the growth of dendrites. The synergistic combination of multiple strategies can realize exceptional long-term cycling stability in both sodium symmetric batteries (≈700 h) and full batteries (2100 cycles). This study provides a new insight for constructing high performance and dendrite-free solid-state sodium metal batteries.

Mechanism of Bilayer Polymer-Based Electrolyte with Functional Molecules in Enhancing the Capacity and Cycling Stability of High-Voltage Lithium Batteries

Poly(ethylene oxide) (PEO)-based solid polymer electrolytes (SPEs) are favorable for all-solid-state lithium metal batteries (ASSLBs) to ensure safety and enhance energy density. However, their narrow work windows and unstable electrode/electrolyte interfaces hinder their practical application in high-voltage ASSLBs. Although introducing additives in SPEs has been proven to be effective to address the above issues, it could hardly optimize both cathode and anode interfaces by an individual additive. Herein, heterogeneously double-layer SPEs are constructed with two typical additives (LiPO2F2 and LiFSI), which are used to modify the LiNi0.6Co0.2Mn0.2O2 (NCM)-cathode/electrolyte interface (CEI) and lithium-anode/solid electrolyte interface (SEI), and further understand their respective mechanism in enhancing the capacity and cycling stability of ASSLBs. Specifically, LiPO2F2 not only leads to a uniform CEI layer to prevent the oxidation decomposition of PEO and LiTFSI but also ensures fast Li+ diffusion at high voltage (>3.9 V), improving the rate performances and life spans of the cells. The LiFSI contributes to a stable SEI layer with rich LiF, suppressing the growth of lithium dendrites and maximizing the specific capacity for ASSLBs. Integrating the advantages of the two functional molecules, the optimized ASSLB displays an excellent capacity of 141.4 mAh g-1 at 1C and an outstanding capacity retention of 81.6% after 400 cycles when using the NCM cathode, even reaching 154.2 mAh g-1 at 0.1 mA cm-2 with a high mass loading (6.4 mg cm-2). Additionally, the bilayer SPEs also match well with a LiFePO4 electrode with a high mass loading of 11.0 mg cm-2, displaying a high capacity of 155.7 mAh g-1 at 0.1 mA cm-2.

Monodispersed Sub-1 nm Inorganic Cluster Chains in Polymers for Solid Electrolytes with Enhanced Li-Ion Transport

The organic-inorganic interfaces can enhance Li+ transport in composite solid-state electrolytes (CSEs) due to the strong interface interactions. However, Li+ non-conductive areas in CSEs with inert fillers will hinder the construction of efficient Li+ transport channels. Herein, CSEs with fully active Li+ conductive networks are proposed to improve Li+ transport by composing sub-1 nm inorganic cluster chains and organic polymer chains. The inorganic cluster chains are monodispersed in polymer matrix by a brief mixed-solvent strategy, their sub-1 nm diameter and ultrafine dispersion state eliminate Li+ non-conductive areas in the interior of inert fillers and filler-agglomeration, respectively, providing rich surface areas for interface interactions. Therefore, the 3D networks connected by the monodispersed cluster chains finally construct homogeneous, large-scale, continuous Li+ fast transport channels. Furthermore, a conjecture about 1D oriented distribution of organic polymer chains along the inorganic cluster chains is proposed to optimize Li+ pathways. Consequently, the as-obtained CSEs possess high ionic conductivity at room temperature (0.52 mS cm-1 ), high Li+ transference number (0.62), and more mobile Li+ (50.7%). The assembled LiFePO4 /Li cell delivers excellent stability of 1000 cycles at 0.5 C and 700 cycles at 1 C. This research provides a new strategy for enhancing Li+ transport by efficient interfaces.

Solid Polymer Electrolytes with Dual Anion Synergy and Twofold Reinforcement Effect for All-Solid-State Lithium Batteries

Solid polymer electrolytes (SPEs) have emerged as a viable alternative to traditional organic liquid-based electrolytes for high energy density and safer lithium batteries. Poly(ethylene oxide) (PEO)-based SPEs are considered one of the mainstream SPE materials with excellent dissociation ability of lithium salts. However, the inferior ionic conductivity at room temperature and poor dimensional stability at high temperature limit their utilization. In this work, a semi-interpenetrating polymer network (semi-IPN) forming a precursor based on an ionic liquid (IL) monomer and linear PEO chains were introduced into an electrospun poly(acrylonitrile) (PAN) fibrous mat with subsequent thermal-initiated cross-linking. 1,4-Diazabicyclo [2.2.2] octane (DABCO) and 4-(chloromethyl) styrene were used to synthesize the styrenic-DABCO-based IL monomer with bis(trifluoromethane sulfonyl)imide (TFSI-) or bis(fluoromethane sulfonyl)imide (FSI-) as the anion, named as SDTFSI and SDFSI, respectively. Together, the FSI- and TFSI- anions demonstrate a synergistic effect in providing ion-conductive LiF and Li3N-rich inorganic SEI layer with enhanced lithium dendrite suppression ability. The twofold reinforcement effect is achieved collectively from the semi-IPN structure and the three-dimensional (3D) PAN network that help to construct highly efficient and uniform ion transport channels with excellent flexibility, further suppressing the lithium dendrite growth. The SPEs were dimensionally stable even at elevated temperatures of 150 °C. Moreover, the SPEs show an ionic conductivity of 4.4 × 10-4 S cm-1 at 25 °C and 1.81 × 10-3 S cm-1 at 55 °C and a lithium-ion transference number of 0.56. The favorable electrochemical performance of the SPEs was verified by operating LiFePO4/Li and NMC/Li cells.

Optimizing Li-ion Solvation in Gel Polymer Electrolytes to Stabilize Li-Metal Anode

Gel polymer electrolytes (GPEs) have potential as substitutes for liquid electrolytes in lithium-metal batteries (LMBs). Their semi-solid state also makes GPEs suitable for various applications, including wearables and flexible electronics. Here, we report the initiation of ring-opening polymerization of 1,3-dioxolane (DOL) by Lewis acid and the introduction of diluent 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE) to regulate electrolyte structure for a more stable interface. This diluent-blended GPE exhibits enhanced electrochemical stability and ion transport properties compared to a blank version without it. FTIR and NMR proved the effectiveness of monomer polymerization and further determined the molecular weight distribution of polymerization by gel permeation chromatography (GPC). Experimental and simulation results show that the addition of TTE enhances ion association and tends to distribute on the anode surface to construct a robust and low-impedance SEI. Thus, the polymer battery achieves 5 C charge-discharge at room temperature and 200 cycles at low temperature -20 °C. The study presents an effective approach for regulating solvation structures in GPEs, promoting advancements in the future design of GPE-based LMBs.

Engineering the Structural Uniformity of Gel Polymer Electrolytes via Pattern-Guided Alignment for Durable, Safe Solid-State Lithium Metal Batteries

Ultrathin and super-toughness gel polymer electrolytes (GPEs) are the key enabling technology for durable, safe, and high-energy density solid-state lithium metal batteries (SSLMBs) but extremely challenging. However, GPEs with limited uniformity and continuity exhibit an uneven Li+ flux distribution, leading to nonuniform deposition. Herein, a fiber patterning strategy for developing and engineering ultrathin (16 µm) fibrous GPEs with high ionic conductivity (≈0.4 mS cm-1 ) and superior mechanical toughness (≈613%) for durable and safe SSLMBs is proposed. The special patterned structure provides fast Li+ transport channels and tailoring solvation structure of traditional LiPF6 -based carbonate electrolyte, enabling rapid ionic transfer kinetics and uniform Li+ flux, and boosting stability against Li anodes, thus realizing ultralong Li plating/stripping in the symmetrical cell over 3000 h at 1.0 mA cm-2 , 1.0 mAh cm-2 . Moreover, the SSLMBs with high LiFePO4 loading of 10.58 mg cm-2 deliver ultralong stable cycling life over 1570 cycles at 1.0 C with 92.5% capacity retention and excellent rate capacity of 129.8 mAh g-1 at 5.0 C with a cut-off voltage of 4.2 V (100% depth-of-discharge). Patterned GPEs systems are powerful strategies for producing durable and safe SSLMBs.

Cellulose-Assisted Vertically Heterostructured PEO-Based Solid Electrolytes Mitigating Li-Succinonitrile Corrosion for Lithium Metal Batteries

In the field of solid-state lithium metal batteries (SSLMBs), constructing vertically heterostructured poly(ethylene oxide) (PEO)-based solid electrolytes is an effective method to realize their tight contact with cathodes and Li anodes at the same time. Succinonitrile (SN) has been widely used in PEO-based solid electrolytes to improve the interface contact with cathodes, enhance the ionic conductivities, and obtain a high electrochemical stability window of PEO, but its application is still hindered by its intrinsic instability to Li anodes, which results in corrosion and side interactions with lithium metal. Herein, the cellulose membrane (CM) is introduced creatively into the vertically heterostructured PEO-based solid electrolytes to match the PEO-SN solid electrolytes at the cathode side. With the advantage of the interaction between -OH groups of CM and -C≡N groups in SN, the movement of free SN molecules from cathodes to Li anodes is limited effectively, resulting in a stable and durable SEI layer. In specific, the Li||LiFePO₄ battery with the CM-assisted vertically heterostructured PEO-based solid electrolyte by in situ preparation delivers a discharge capacity of around 130 mAh g^-1 after 300 cycles and capacity retention of 95% after 500 cycles at 0.5 C. Our work provides a solution to construct PEO-based solid electrolytes feasible to match cathodes and Li anodes effectively by intimate contact with electrodes.

Solid electrolytes for solid-state Li/Na–metal batteries: inorganic, composite and polymeric materials

This feature article presents the electrolyte synthetic approaches, design strategies, and merging materials that may address the critical issues of solid electrolytes for solid-state Li/Na–metal batteries.