Thermally Stable Polymer-Rich Solid Electrolyte Interphase for Safe Lithium Metal Pouch Cells

Removing α-H in Carboxylate-Based Electrolytes for Stable Lithium Metal Batteries

Although carboxylate esters greatly improve the cold weather performance of graphite-based lithium-ion batteries utilized in arctic expeditions, the underlying cause of the incompatibility between carboxylates and lithium (Li) anodes has not been sufficiently explained, resulting in the greatly restricted usage of carboxylate in lithium metal batteries (LMBs). Herein, we reveal the serious parasitic reactions between carboxylate α-H atoms and Li metal are the culprits that render carboxylate-based ineffectiveness for LMBs. By replacing all α-H atoms with fluorine atoms and methyl groups, we successfully construct inert carboxylates and find the ions/molecules distribution in electric-double-layer (EDL) can be manipulated at a molecular-level. The unique structure ensuring more anions are positioned closer to the Li surface in the EDL of the inert carboxylate-based electrolyte, the morphology of the deposited Li is significantly regulated and the chemical corrosion gets effectively inhibited, as a consequence of remarkable extending lifespan of carboxylate-based LMBs with routine salt concentration and few additives. More generally, using carboxylates lacking α-H atoms offer a realistic approach to increase the variety of solvents that can be used in LMBs electrolytes.

Stabilizing Residual Monomers within In Situ Polymerized Electrolytes for High-Voltage Lithium Metal Batteries

Poly(1,3-dioxolane) (PDOL)-based electrolyte has gained wide attention due to its high compatibility with the lithium metal anode, intimate contact with electrodes, and high ionic conductivity. However, its application in high-voltage batteries is limited because the residual DOL monomers are prone to oxidation at high voltage. Here, we report that LiDFOB-initiated in situ polymerization stabilizes these residual monomers, thus overcoming the oxidation-related limitations of PDOL-based electrolytes. This approach promotes the formation of a thermodynamically stable Li+-DOL-DFOB- solvation structure and DOL-PDOL clusters, reducing the oxidative decomposition of the residual DOL monomers and extending the electrochemical stability window up to 5.0 V vs Li+/Li. It also enhances ionic conductivity (4.39 mS cm-1), and facilitates the formation of a uniform, F-rich cathode-electrolyte interphase. Electrochemical tests and computational simulations reveal that the reduced Li+-PDOL interactions in the designed PDOL promote higher ionic mobility and electrochemical stability. Consequently, Li||LiCoO2 cells using the designed PDOL exhibit remarkable cycling performance, maintaining 80% capacity retention over 760 cycles at a cut-off voltage of 4.35 V. These findings establish PDOL as a transformative electrolyte for high-voltage lithium metal batteries.

Double-Weak Coordination Electrolyte Enables 5 V and High Temperature Lithium Metal Batteries

Layered oxide cathodes offer high specific capacity and operating voltage, whereas constructing a stable interface to maintain the stable operation of high-voltage cathodes under high charge state and elevated temperature remains challenging. Herein, a double-weak coordination strategy which triggers by single solvent and dilute is designed. The solvent tris(2,2,2-trifluoroethyl) phosphate (TFEP) exhibits weak lithium coordination due to the partial fluorination of the alkyl chain, while the dilute ethoxy(pentafluoro)cyclo triphosphazene (PFPN) is involved in the inner solvation structure by weak lithium-TFEP coordination and its mild lithium affinity. This double-weak coordination increases the local anion concentration within the solvation structure, reduces the desolvation barrier of Li+, optimizes the desolvation and leads to a robust, hybrid organic-inorganic interface. Specifically, the DWCE electrolyte shows remarkable improvements in cycling stability under 60 °C for 4.7 V Li(50 µm)||NMC811 (1.84 mAh cm-2) cell, 4.8  and 5.0 V Li(50 µm)||LRMO (1.75 mAh cm-2) cells. Meanwhile, 5.2 Ah Li||LRMO pouch cell using DWCE achieves a high energy density of 495 Wh kg-1 and DWCE-based Ah-level pouch cell also presents significantly enhanced safety under thermal runaway condition. This work provides a novel but universal double-weak coordination policy initiated by solvent and diluent for high energy density lithium metal batteries.

Chemically Patterning Lithiophilic Interphase to Harmonize Spatial Electrons and Thermal Catalysis Dynamics for Safe Lithium Metal Batteries

Lithium metal batteries have garnered significant attention as promising energy storage solutions. However, their performance is often compromised by the risks associated with highly active metallic lithium, unrestricted electrode expansion, and excessive dendrites growth. Here we introduce an advanced lithiophilic anode substrate designed by chemically patterning technology for multiple security enhancements. The innovative lithiophilic array harmonizes spatial Li+ to prepare compact and reversible electrodes. The composite electrodes feature an enhanced C-F component in the solid-electrolyte interface, which protects the deposited lithium metal from unwanted side reactions, thereby stabilizing electrochemical cycling. Notably, the thermal safety can be revealed through the substrate's excellent catalytic ability to convert smoke and toxic gases during extreme thermal runaway. This work demonstrates a novel approach to integrating battery cycling stability with thermal safety, paving the way for more reliable and secure energy storage systems.

Data-Knowledge-Dual-Driven Electrolyte Design for Fast-Charging Lithium Ion Batteries

Electric vehicles (EVs) starve for minutes-level fast-charging lithium-ion batteries (LIBs), while the heat gathering at high-rate charging and torridity conditions has detrimental effects on electrolytes, triggering rapid battery degradation and even safety hazards. However, the current research on high-temperature fast-charging (HTFC) electrolytes is very lacking. We revolutionized the conventional paradigm of developing HTFC electrolytes integrating with high-throughput calculation, machine-learning techniques, and experimental verifications to establish a data-knowledge-dual-driven approach. Ethyl trimethylacetate was efficiently screened out based on the approach and enabled batteries to work under high temperatures with distinctly restricted side reactions. A stable and highly safe fast-charging (15-min charging to 80% capacity) cycling without Li plating was achieved over 4100 cycles at 45 °C based on 181 Wh kg-1 pouch cells, demonstrating the state-of-the-art in this field.

Enhancement of Dendrite-Free Lithium Metal Anode Performance through LiF-Rich Protective Layer for Lithium Metal Batteries

Lithium metal batteries represent a cutting-edge class of energy storage devices, yet the high surface diffusion energy barrier of lithium metal prompts preferential Li+ accumulation and deposition, fostering the growth of lithium dendrites. To address this challenge, a straightforward solvent-based approach is employed to create a LiF-rich protective layer on the lithium anode. The uniform LiF interface facilitates the transport of Li+ and effectively induces the uniform plating and stripping of lithium while inhibiting the formation of dendrites. Notably, the symmetric battery incorporating a lithium anode modified with appropriate LiF demonstrates substantially enhanced cycling performance. Importantly, the full cell matched with LiFePO4 displays an initial capacity of 146.3 mAh g-1 and a capacity retention rate of 92.7% after 300 cycles. Its practical application has also been verified in symmetric batteries and full batteries for PEO solid-state batteries. This work underscores the potential of the LiF protective layer to boost the dendrite-free lithium metal anode.

Catalysis-Induced Highly-Stable Interface on Porous Silicon for High-Rate Lithium-Ion Batteries

Silicon stands as a key anode material in lithium-ion battery ascribing to its high energy density. Nevertheless, the poor rate performance and limited cycling life remain unresolved through conventional approaches that involve carbon composites or nanostructures, primarily due to the un-controllable effects arising from the substantial formation of a solid electrolyte interphase (SEI) during the cycling. Here, an ultra-thin and homogeneous Ti doping alumina oxide catalytic interface is meticulously applied on the porous Si through a synergistic etching and hydrolysis process. This defect-rich oxide interface promotes a selective adsorption of fluoroethylene carbonate, leading to a catalytic reaction that can be aptly described as "molecular concentration-in situ conversion". The resultant inorganic-rich SEI layer is electrochemical stable and favors ion-transport, particularly at high-rate cycling and high temperature. The robustly shielded porous Si, with a large surface area, achieves a high initial Coulombic efficiency of 84.7% and delivers exceptional high-rate performance at 25 A g-1 (692 mAh g-1) and a high Coulombic efficiency of 99.7% over 1000 cycles. The robust SEI constructed through a precious catalytic layer promises significant advantages for the fast development of silicon-based anode in fast-charging batteries.

Monofluorinated Phosphate with Unique P-F Bond for Nonflammable and Long-Life Lithium-Ion Batteries

Lithium-ion batteries (LIBs) with conventional carbonate-based electrolytes suffer from safety concerns in large-scale applications. Phosphates feature high flame retardancy but are incompatible with graphite anode due to their inability to form a passivated solid electrolyte interphase (SEI). Herein, we report a monofluorinated co-solvent, diethyl fluoridophosphate (DEFP), featuring a unique P-F bond that allows a trade-off between safety and electrochemical performance in LIBs. The P-F bond in DEFP weakens ion-dipole interactions with Li+ ions, lowering the desolvation barrier, and simultaneously reduces the lowest unoccupied molecular orbital (LUMO) of DEFP, promoting the formation of a robust and inorganic-rich SEI. Additionally, DEFP exhibits improved thermal stability due to both robust SEI and the inherent flame-retardant properties of the P-F bond. Consequently, the optimized DEFP-based electrolyte exhibits improved cyclability and rate capacity in LiNi0.8Co0.1Mn0.1O2||graphite full cells compared with triethyl phosphate-based electrolytes and commercial carbonate electrolytes. Even at a low E/C ratio of 3.45 g Ah-1, the 1.16 Ah NCM811||Gr pouch cells achieve a high capacity retention of 94.2 % after 200 cycles. This work provides a promising approach to decouple phosphate safety and graphite compatibility, paving the way for safer and high-performance lithium-ion batteries.

Temperature-Responsive Formation Cycling Enabling LiF-Rich Cathode-Electrolyte Interphase

Formation of LiF-rich cathode-electrolyte interphase is highly desirable for wide-temperature battery, but its application is hindered by the unwanted side reactions associated with conventional method of introducing fluorinated additives. Here, we developed an additive-free strategy to produce LiF-rich cathode electrolyte interphase (CEI) by low-temperature formation cycling. Using LiNi0.33Mn0.33Co0.33O2 as a model cathode, the atomic ratio of LiF in the CEI formed at -5 °C is about 17.7 %, enhanced by ~550 % compared to CEI formed at 25 °C (2.7 %). The underlying mechanism is uncovered by both experiments and theoretic simulation, indicating that the decomposition of LiPF6 to LiF is transformed into spontaneous and exothermic on positively charged cathode surface and lowering the temperature shift chemical equilibrium towards the formation of LiF-rich CEI. Superior to conventional fluorinated additives, this approach is free from unwanted side reactions, imparting batteries with both high-temperature (60 °C) cyclability and low-temperature rate performance (capacity enhanced by 100 % at 3 C at -20 °C). This low-temperature formation cycling to construct LiF-rich CEI is extended to various cathode systems, such as LiNi0.8Mn0.1Co0.1O2, LiCoO2, LiMn2O4, demonstrating the versatility and potential impact of our strategy in advancing the performance and stability of wide-temperature batteries and beyond.

Intrinsically Safe Lithium Metal Batteries Enabled by Thermo-Electrochemical Compatible In Situ Polymerized Solid-State Electrolytes

In situ polymerized solid-state electrolytes have attracted much attention due to high Li-ion conductivity, conformal interface contact, and low interface resistance, but are plagued by lithium dendrite, interface degradation, and inferior thermal stability, which thereby leads to limited lifespan and severe safety hazards for high-energy lithium metal batteries (LMBs). Herein, an in situ polymerized electrolyte is proposed by copolymerization of 1,3-dioxolane with 1,3,5-tri glycidyl isocyanurate (TGIC) as a cross-linking agent, which realizes a synergy of battery thermal safety and interface compatibility with Li anode. Functional TGIC enhances the electrolyte polymeric level. The unique carbon-formation mechanism facilitates flame retardancy and eliminates the battery fire risk. In the meantime, TGIC-derived inorganic-rich interphase inhibits interface side reactions and promotes uniform Li plating. Intrinsically safe LMBs with nonflammability and outstanding electrochemical performances under extreme temperatures (130 °C) are achieved. This functional polymer design shows a promising prospect for the development of safe LMBs.

Understanding the Coupling Mechanism of Intercalation and Conversion Hybrid Storage in Lithium-Graphite Anode

Anodes with high capacity and long lifespan play an important role in the advanced batteries. However, none of the existing anodes can meet these two requirements simultaneously. Lithium (Li)-graphite composite anode presents great potential in balancing these two requirements. Herein, the working mechanism of Li-graphite composite anode is comprehensively investigated. The capacity decay features of the composite anode are different from those of Li ion intercalation in Li ion batteries and Li metal deposition in Li metal batteries. An intercalation and conversion hybrid storage mechanism are proposed by analyzing the capacity decay ratios in the composite anode with different initial specific capacities. The capacity decay models can be divided into four stages including Capacity Retention Stage, Relatively Independent Operation Stage, Intercalation & Conversion Coupling Stage, Pure Li Intercalation Stage. When the specific capacity is between 340 and 450 mAh g-1, its capacity decay ratio is between that of pure intercalation and conversion model. These results intensify the comprehensive understandings on the working principles in Li-graphite composite anode and present novel insights in the design of high-capacity and long-lifespan anode materials for the next-generation batteries.

Carboxymethyl chitosan composited poly(ethylene oxide) electrolyte with high ion conductivity and interfacial stability for lithium metal batteries

Low ionic conductivity and poor interface stability of poly(ethylene oxide) (PEO) restrict the practical application as polymeric electrolyte films to prepare solid-state lithium (Li) metal batteries. In this work, biomass-based carboxymethyl chitosan (CMCS) is designed and developed as organic fillers into PEO matrix to form composite electrolytes (PEO@CMCS). Carboxymethyl groups of CMCS fillers can promote the decomposition of Lithium bis(trifluoromethane sulfonimide) (LiTFSI) to generate more lithium fluoride (LiF) at CMCS/PEO interface, which not only forms ionic conductive network to promote the rapid transfer of Li+ but also effectively enhances the interface stability between polymeric electrolyte and Li metal. The enrichment of carboxyl, hydroxyl, and amidogen functional groups within CMCS fillers can form hydrogen bonds with ethylene oxide (EO) chains to improve the tensile properties of PEO-based electrolyte. In addition, the high hardness of CMCS additives can also strengthen mechanical properties of PEO-based electrolyte to resist penetration of Li dendrites. LiLi symmetric batteries can achieve stable cycle for 2500 h and lithium iron phosphate full batteries can maintain 135.5 mAh g-1 after 400 cycles. This work provides a strategy for the enhancement of ion conductivity and interface stability of PEO-based electrolyte, as well as realizes the resource utilization of biomass-based CMCS.

Rational Design of F-Modified Polyester Electrolytes for Sustainable All-Solid-State Lithium Metal Batteries

Solid polymer electrolytes (SPEs) are one of the most practical candidates for solid-state batteries owing to their high flexibility and low production cost, but their application is limited by low Li+ conductivity and a narrow electrochemical window. To improve performance, it is necessary to reveal the structure-property relationship of SPEs. Here, 23 fluorinated linear polyesters were prepared by editing the coordination units, flexible linkage segments, and interface passivating groups. Besides the traditionally demonstrated coordinating capability and flexibility of polymer chains, the molecular asymmetry and resulting interchain aggregation are observed critical for Li+ conductivity. By tailoring the molecular asymmetry and coordination ability of polyesters, the Li+ conductivity can be raised by 10 times. Among these polyesters, solvent-free poly(pentanediol adipate) delivers the highest room-temperature Li+ conductivity of 0.59 × 10-4 S cm-1. The chelating coordination of oxalate and Li+ leads to an electron delocalization of alkoxy oxygen, enhancing the antioxidation capability of SPEs. To lower the cost, high-value LiTFSI in SPEs is recycled at 90%, and polyesters can be regenerated at 86%. This work elucidates the structure-property relationship of polyester-based SPEs, displays the design principles of SPEs, and provides a way for the development of sustainable solid-state batteries.

Designing an Air-Stable Interphase on Lithium Metal Anode to Improve Cycling Performance

The application of rechargeable lithium metal batteries is challenged by intractable issues of uncontrollable Li dendrite growth that result in poor cycle life and safety risks. In this work, an air-stable interphase is developed to protect the lithium metal anode (LMA) via a facile solution-based approach. The Ag-embedded fluoride-rich interphase not only creates abundant lithiophilic sites for homogenizing Li nucleation and growth but also resists severe air erosion to protect the LMA beneath and enable decent cycling stability. As a result, the Ag-F-rich interphase enables flat Li deposition on LMA, which is clearly observed in the operando Li plating experiments. Paired with a LiFePO4 cathode (11.8 mg cm-2), the Ag-F-rich interphase-modified LMA enables 300 stable cycles at 0.5 C, delivering a capacity retention ratio as high as 91.4%. Even after being exposed to air for 1 h, the modified LMA still runs smoothly for over 120 cycles with ignorable capacity decay, exhibiting great air stability. This work proves the concept of functionalizing the interphase on the LMA to enable good cycling performance even under severe air erosion.

N-Rich Bilayer Solid Electrolyte Interphase toward Highly Reversible Lithium Metal Batteries

Continuous lithium (Li)/electrolyte interfacial reactions and uncontrollable Li dendrites severely hamper the application of paradigmatic Li metal batteries (LMBs). Aiming to address the above-mentioned crucial issues, N-rich polymer-inorganic bilayers at the Li/electrolyte interface are designed via nitrate-rich electrolytes, achieving high-energy-density and long-lifespan LMBs. The inner layer of Li3N favors rapid and uniform Li+ deposition, while the outer layer of N-containing flexible polymers facilitates uniform Li+ distribution at the interlayer and accommodates volume changes during cycling. The synergistic effect of N-rich polymer-inorganic bilayers promotes the formation of dense uniform spherical nuclei morphology instead of dendrites, thus significantly improving the plating-stripping reversibility of LMBs. Attributed to the unique interphase, the Li|Li cell can stably run for over 1000 h at 1.0 mA cm-2 with an even deposition morphology, which is monitored and proven by in situ optical microscopy. Moreover, the assembled Li|S cell displays a high capacity of 697.6 mA h g-1 for over 150 cycles and a 99% Coulombic efficiency. This work paves the way for designing high-energy and long-lifespan LMBs.

Mechanically and Thermally Stable Cathode Electrolyte Interphase Enables High-temperature, High-voltage Li||LiCoO2 Batteries

The development of high-energy-density Li||LiCoO2 batteries is severely limited by the instability of cathode electrolyte interphase (CEI) at high voltage and high temperature. Here we propose a mechanically and thermally stable CEI by electrolyte designing for achieving the exceptional performance of Li||LiCoO2 batteries at 4.6 V and 70 °C. 2,4,6-tris(3,4,5-trifluorophenyl)boroxin (TTFPB) as the additive could preferentially enter into the first shell structure of PF6 - solvation and be decomposed on LiCoO2 surface at low oxidation potential to generate a LiBx Oy -rich/LiF-rich CEI. The LiBx Oy surface layer effectively maintained the integrity of CEI and provided excellent mechanical and thermal stability while abundant LiF in CEI further improved the thermal stability and homogeneity of CEI. Such CEI drastically alleviated the crack and regeneration of CEI and irreversible phase transformation of the cathode. As expected, the Li||LiCoO2 batteries with the tailored CEI achieved 91.9 % and 74.0 % capacity retention after 200 and 150 cycles at 4.6 and 4.7 V, respectively. Moreover, such batteries also delivered an unprecedented high-temperature performance with 73.6 % capacity retention after 100 cycles at 70 °C and 4.6 V.

Electrochemically and Thermally Stable Inorganics-Rich Solid Electrolyte Interphase for Robust Lithium Metal Batteries

Severe dendrite growth and high-level activity of the lithium metal anode lead to a short life span and poor safety, seriously hindering the practical applications of lithium metal batteries. With a trisalt electrolyte design, an F-/N-containing inorganics-rich solid electrolyte interphase on a lithium anode is constructed, which is electrochemically and thermally stable over long-term cycles and safety abuse conditions. As a result, its Coulombic efficiency can be maintained over 98.98% for 400 cycles. An 85.0% capacity can be retained for coin-type full cells with a 3.14 mAh cm-2 LiNi0.5 Co0.2 Mn0.3 O2 cathode after 200 cycles and 1.0 Ah pouch-type full cells with a 4.0 mAh cm-2 cathode after 72 cycles. During the thermal runaway tests of a cycled 1.0 Ah pouch cell, the onset and triggering temperatures were increased from 70.8 °C and 117.4 °C to 100.6 °C and 153.1 °C, respectively, indicating a greatly enhanced safety performance. This work gives novel insights into electrolyte and interface design, potentially paving the way for high-energy-density, long-life-span, and thermally safe lithium metal batteries.

Synergistically Stabilizing Thin Li Metal through the Formation of a Stable and Highly Conductive Solid Electrolyte Interface and Silver-Lithium Alloy

In this study, a stable solid electrolyte interface (SEI) and a Ag-Li alloy were formed through a simple slurry coating of silver (Ag) nanoparticles and Li nitrate (LiNO3) on a Li metal surface (AgLN-coated Li). The Ag-Li alloy has a high Li diffusion coefficient, which allowed the inward transfer of Li atoms, thus allowing Li to be deposited below the alloy. Moreover, the highly conductive SEI enabled the fast diffusion of Li ions corresponding to the alloy. This inward transfer resulted in dendrite suppression and improved the Coulombic efficiency (CE). The AgLN-coated Li exhibited an initial capacity retention >81% and CE > 99.7 ± 0.2% over 500 cycles at a discharge capacity of 2.3 mA h cm-2.

Long-Life Quasi-Solid-State Anode-Free Batteries Enabled by Li Compensation Coupled Interface Engineering

Initially, anode-free Li metal batteries present a promising power source that merges the high production feasibility of Li-ion batteries with the superb energy capabilities of Li-metal batteries. However, their application confronts formidable challenges of extremely short lifespan due to the inadequacy of zero-Li-excess cell configuration against irreversible Li loss. A Li compensation coupled interface engineering strategy is reported for realizing long-life quasi-solid-state anode-free batteries. The Li2 S is utilized as a sacrificial Li supplement to effectively counterbalance irreversible Li loss without damage to cell chemistry. Meanwhile, it demonstrates remarkable efficacy in establishing a robust yet slender inorganic-organic hybrid solid-state interphase for inhibiting cell degradation by dead and dendritic Li. This strategy enables quasi-solid-state anode-free batteries with a long lifespan of 500 cycles. The Ah-scale quasi-solid-state pouch cells, featuring a high-loading LiFePO4 cathode and lean gel polymer electrolyte, exhibit a high specific energy of 300 Wh kgcell -1 . This achievement translates into an improvement of 46% in gravimetric energy and 94% in volumetric energy compared to LiFePO4 ||graphite batteries while outperforming LiFePO4 ||Li-metal batteries by 22-47% in volumetric energy. Such quasi-solid-state anode-free cells also demonstrate good safety, showcasing remarkable resistance against nail penetration in ambient air without failure, smoke, or fire accidents.

A hybrid polymer protective layer with uniform Li+ flux and self-adaption enabling dendrite-free Li metal anodes

Lithium (Li) metal is considered as an ideal negative electrode material for next-generation secondary batteries; however, the hideous dendrite growth and parasitic reactions hinder the practical applications of Li metal batteries. Herein, a hybrid polymer film composed of polyvinyl alcohol (PVA) and polyacrylic acid (PAA) is adopted as an artificial protective layer to inhibit the dendritic formation and side reactions in Li metal anodes. PVA with large quantities of polar functional groups can induce even distribution of Li ions (Li+). Alternatively, PAA can in situ react with Li metal to form highly elastic and ionic conducting lithium polyacrylic acid (LiPAA), thereby enabling tight contact and flexible self-adaption with Li metal anodes. Therefore, such a rationally designed functional composite layer, with good binding ability and relatively high Li+ conductivity, as well as excellent capability of homogenizing Li+ flow, accordingly enables Li metal anodes to reveal dendrite-free plating/stripping behaviours and minimum volume variation. As a result, the PVA-PAA modified Li metal anode delivered stable cycling for 700 and 250 h, respectively, at current densities of 1 and 3 mA cm-2 under an areal capacity of 1 mA h cm-2, in a carbonate ester-based electrolyte without any additive, exhibiting boosted cycling and rate performances. The Li anode with a functional PVA-PAA hybrid interlayer can maintain the dense and smooth texture without dendrite formation after long cycles. The full cell of Li|LiFeO4 with our modified Li anode and a cathode with a high areal capacity of 2.45 mA h cm-2 delivers, change to achieved a long-term lifespan of 180 cycles at 1.0 C, with a capacity retention of 96.7%. This work demonstrates a simple and effective strategy of designing multi-functional artificial protective layers, targeting dendrite-free Li anodes.

In Situ Construction Channels of Lithium-Ion Fast Transport and Uniform Deposition to Ensure Safe High-Performance Solid Batteries

Solid-state lithium-ion batteries (SLIBs) are the promising development direction for future power sources because of their high energy density and reliable safety. To optimize the ionic conductivity at room temperature (RT) and charge/discharge performance to obtain reusable polymer electrolytes (PEs), polyvinylidene fluoride (PVDF), and poly(vinylidene fluoride-hexafluoro propylene) (P(VDF-HFP)) copolymer combined with polymerized methyl methacrylate (MMA) monomers are used as substrates to prepare PE (LiTFSI/OMMT/PVDF/P(VDF-HFP)/PMMA [LOPPM]). LOPPM has interconnected lithium-ion 3D network channels. The organic-modified montmorillonite (OMMT) is rich in the Lewis acid centers, which promoted lithium salt dissociation. LOPPM PE possessed high ionic conductivity of 1.1 × 10-3 S cm-1 and a lithium-ion transference number of 0.54. The capacity retention of the battery remained 100% after 100 cycles at RT and 0.5 C. The initial capacity of one with the second-recycled LOPPM PE is 123.9 mAh g-1 . This work offered a feasible pathway for developing high-performance and reusable LIBs.

Nitrogen Ion Implantation-Modified Cu Substrate for Stable Lithium Metal Anode

As the only commercialized negative current collector, copper (Cu) foil possesses insurmountable applicational advantages as a lithium metal anode (LMA) substrate. However, the successful usage of Cu foil is limited by the poor Li affinity and crystal face variation, which will lead to severe lithium dendrite growth and poor cyclability. Herein, an industrial-popular ion implantation technique is first adopted for Cu surface modification. With the high-energy implantations of N+ plasma, the unique N-rich transition interface can be formed, among which the lithiophilic CuxNy with extended crystal domains can have uniform Cu crystal faces and offer benefit for Li nucleation/deposition; besides, the induced Li3N-rich SEI with high ionic conductivity can support Li-ion transport kinetics, suppress Li dendrite growth, and mitigate the side reaction to improve LMA stability. Consequently, a uniform Li nucleation/deposition is achieved, with obviously enhanced cycling stability and rate capability for the full cells. This technological maturity ion implantation method can be readily extended to any non/metallic ion species, or joint implantation of bi/multiple ions, and other substrates, demonstrating a possible route to surmount the metal anode challenges.

Outstanding Electrochemical Performance of Ni-Rich Concentration-Gradient Cathode Material LiNi0.9Co0.083Mn0.017O2 for Lithium-Ion Batteries

The full-concentrationgradient LiNi_0.9Co_0.083Mn_0.017O₂ (CG-LNCM), consisting of core Ni-rich LiNi_0.93Co_0.07O₂, transition zone LiNi_1-x-yCo_xMn_yO_2, and outmost shell LiNi_1/3Co_1/3Mn_1/3O₂ was prepared by a facile co-precipitation method and high-temperature calcination. CG-LNCM was then investigated with an X-ray diffractometer, ascanning electron microscope, a transmission electron microscope, and electrochemical measurements. The results demonstrate that CG-LNCM has a lower cation mixing of Li⁺ and Ni²⁺ and larger Li⁺ diffusion coefficients than concentration-constant LiNi_0.9Co_0.083Mn_0.017O₂ (CC-LNCM). CG-LNCM presents a higher capacity and a better rate of capability and cyclability than CC-LNCM. CG-LNCM and CC-LNCM show initial discharge capacities of 221.2 and 212.5 mAh g^-1 at 0.2C (40 mA g^-1) with corresponding residual discharge capacities of 177.3 and 156.1 mAh g^-1 after 80 cycles, respectively. Even at high current rates of 2C and 5C, CG-LNCM exhibits high discharge capacities of 165.1 and 149.1 mAh g^-1 after 100 cycles, respectively, while the residual discharge capacities of CC-LNCM are as low as 148.8 and 117.9 mAh g^-1 at 2C and 5C after 100 cycles, respectively. The significantly improved electrochemical performance of CG-LNCM is attributed to its concentration-gradient microstructure and the composition distribution of concentration-gradient LiNi_0.9Co_0.083Mn_0.017O₂. The special concentration-gradient design and the facile synthesis are favorable for massive manufacturing of high-performance Ni-rich ternary cathode materials for lithium-ion batteries.

Tuning Li Nucleation by a Hybrid Lithiophilic Protective Layer for High-Performance Lithium Metal Batteries

Lithium (Li) metal has been recognized as the most promising anode material for next-generation rechargeable batteries. However, the practical application of Li anodes is hampered by the growth of Li dendrites. To address this issue, a robust and uniform Sb-based hybrid lithiophilic protective layer is designed and built by a facile in situ surface reaction approach. As evidenced theoretically and experimentally, the as-prepared hybrid protective layer provides outstanding wettability and fast charge-transfer kinetics. Moreover, the lithiophilic Sb embedded in the protective layer provides a rich site for Li nucleation, which effectively reduces the overpotential and induces uniform Li deposition. Consequently, the symmetric cell exhibits a long lifespan of over 1600 h at 1 mA cm^-2 and 1 mAh cm^-2 with a low voltage polarization. Furthermore, excellent cycling stability is also obtained in Li-S full cells (60% capacity retention in 800 cycles at 1 C) and Li||LFP full cells (74% capacity retention in 500 cycles at 5 C). This work proposed a facile but efficient strategy to stabilize the Li metal anode.