Fusion Bonding Technique for Solvent-Free Fabrication of All-Solid-State Battery with Ultrathin Sulfide Electrolyte.

For preparing next-generation sulfide all-solid-state batteries (ASSBs), the solvent-free manufacturing process has huge potential for the advantages of economic, thick electrode, and avoidance of organic solvents. However, the dominating solvent-free process is based on the fibrillation of polytetrafluoroethylene, suffering from poor mechanical property and electrochemical instability. Herein, a continuously solvent-free paradigm of fusion bonding technique is developed. A percolation network of thermoplastic polyamide (TPA) binder with low viscosity in viscous state is constructed with Li6PS5Cl (LPSC) by thermocompression (≤5 MPa), facilitating the formation of ultrathin LPSC film (≤25 µm). This composite sulfide film (CSF) exhibits excellent mechanical properties, ionic conductivity (2.1 mS cm-1), and unique stress-dissipation to promote interface stabilization. Thick LiNi0.83Co0.11Mn0.06O2 cathode can be prepared by this solvent-free method and tightly adhered to CSF by interfacial fusion of TPA for integrated battery. This integrated ASSB shows high-energy-density feasibility (>2.5 mAh cm-2 after 1400 cycles of 9200 h and run for more than 10 000 h), and energy density of 390 Wh kg-1 and 1020 Wh L-1. More specially, high-voltage bipolar cell (≥8.5 V) and bulk-type pouch cell (326 Wh kg-1) are facilely assembled with good cycling performance. This work inspires commercialization of ASSBs by a solvent-free method and provides beneficial guiding for stable batteries.

Self-organized hetero-nanodomains actuating super Li+ conduction in glass ceramics.

Easy-to-manufacture Li2S-P2S5 glass ceramics are the key to large-scale all-solid-state lithium batteries from an industrial point of view, while their commercialization is greatly hampered by the low room temperature Li+ conductivity, especially due to the lack of solutions. Herein, we propose a nanocrystallization strategy to fabricate super Li+-conductive glass ceramics. Through regulating the nucleation energy, the crystallites within glass ceramics can self-organize into hetero-nanodomains during the solid-state reaction. Cryogenic transmission electron microscope and electron holography directly demonstrate the numerous closely spaced grain boundaries with enriched charge carriers, which actuate superior Li+-conduction as confirmed by variable-temperature solid-state nuclear magnetic resonance. Glass ceramics with a record Li+ conductivity of 13.2 mS cm-1 are prepared. The high Li+ conductivity ensures stable operation of a 220 µm thick LiNi0.6Mn0.2Co0.2O2 composite cathode (8 mAh cm-2), with which the all-solid-state lithium battery reaches a high energy density of 420 Wh kg-1 by cell mass and 834 Wh L-1 by cell volume at room temperature. These findings bring about powerful new degrees of freedom for engineering super ionic conductors.

Aluminium ion doping mechanism of lithium thiophosphate based solid electrolytes revealed with solid-state NMR.

We investigate the impact of Al incorporation on the structure and dynamics of Al-doped lithium thiophosphates (Li3-3xAlxPS4) based on ß-Li3PS4. 27Al and 6Li magic-angle spinning NMR spectra confirm that Al3+ ions occupy octahedral sites in the structure. Quantitative analyses of 27Al NMR spectra show that the maximum Al incorporation is x = 0.06 in Li3-3xAlxPS4. The ionic conductivity of ß-Li3PS4 is enhanced by over a factor 3 due to Al incorporation. Further increase of the Al doping level leads to the formation of a more complicated material consisting of multiple crystalline and distorted phases as indicated by 31P NMR spectra and powder X-ray diffraction. Consequently, novel Li ion diffusion pathways develop leading to a very high ionic conductivity at room temperature. NMR relaxometry shows that the activation barrier for long-range Li ion diffusion in ß-Li3PS4 hardly changes upon Al incorporation, but the onset temperature for motional narrowing comes down significantly due to Al doping. The activation barrier in the subsequently formed multiphase material decreases significantly, however, indicating a different more efficient Li ion conduction pathway.

Percolated Sulfide in Salt-Concentrated Polymer Matrices Extricating High-Voltage All-Solid-State Lithium-metal Batteries.

All-solid-state lithium-metal batteries (ASLMBs) are considered to be remarkably promising energy storage devices owing to their high safety and energy density. However, the limitations of current solid electrolytes in oxidation stability and ion transport properties have emerged as fundamental barriers in practical applications. Herein, a novel solid electrolyte is presented by in situ polymerization of salt-concentrated poly(ethylene glycol) diglycidyl ether (PEGDE) implanted with a three-dimensional porous L10 GeP2 S12 skeleton to mitigate these issues. The poly(PEGDE) endows more oxygen atoms to coordinate with Li+ , significantly lowering its highest occupied molecular orbital level. As a consequence, the electro-oxidation resistance of poly(PEGDE) exceeds 4.7 V versus Li+ /Li. Simultaneously, the three-dimensonal porous L10 GeP2 S12 skeleton provides a percolated pathway for rapid Li+ migration, ensuring a sufficient ionic conductivity of 7.7 × 10-4 S cm-1 at room temperature. As the bottlenecks are well solved, 4.5 V LiNi0.8 Mn0.1 Co0.1 O2 -based ASLMBs present fantastic cycle performance over 200 cycles with an average Coulombic efficiency exceeding 99.6% at room temperature.

In Situ Polymerization Permeated Three-Dimensional Li+-Percolated Porous Oxide Ceramic Framework Boosting All Solid-State Lithium Metal Battery.

Solid-state lithium battery promises highly safe electrochemical energy storage. Conductivity of solid electrolyte and compatibility of electrolyte/electrode interface are two keys to dominate the electrochemical performance of all solid-state battery. By in situ polymerizing poly(ethylene glycol) methyl ether acrylate within self-supported three-dimensional porous Li1.3Al0.3Ti1.7(PO4)3 framework, the as-assembled solid-state battery employing 4.5 V LiNi0.8Mn0.1Co0.1O2 cathode and Li metal anode demonstrates a high Coulombic efficiency exceeding 99% at room temperature. Solid-state nuclear magnetic resonance results reveal that Li+ migrates fast along the continuous Li1.3Al0.3Ti1.7(PO4)3 phase and Li1.3Al0.3Ti1.7(PO4)3/polymer interfacial phase to generate a fantastic conductivity of 2.0 × 10-4 S cm-1 at room temperature, which is 56 times higher than that of pristine poly(ethylene glycol) methyl ether acrylate. Meanwhile, the in situ polymerized poly(ethylene glycol) methyl ether acrylate can not only integrate the loose interfacial contact but also protect Li1.3Al0.3Ti1.7(PO4)3 from being reduced by lithium metal. As a consequence of the compatible solid-solid contact, the interfacial resistance decreases significantly by a factor of 40 times, resolving the notorious interfacial issue effectively. The integrated strategy proposed by this work can thereby guide both the preparation of highly conductive solid electrolyte and compatible interface design to boost practical high energy density all solid-state lithium metal battery.

Leakage-Proof Electrolyte Chemistry for a High-Performance Lithium-Sulfur Battery.

Electrolyte leakage is a severe safety concern in lithium batteries. With highly volatile 1,2-dimethoxyethane as solvent, the leakage related hazards are more pronounced in lithium-sulfur (Li-S) batteries. To address this concern, a leakage-proof electrolyte is delicately designed through functionalizing the commercial electrolyte by Li6 PS5 Cl-grafted poly(ethyl cyanoacrylate), which can interact readily with the aluminum-plastic packing through hydrogen bond to immobilize the electrolyte. The moisture from ambient can also catalyze a further polymerization of the macromolecules to seal the leaking points and thereby to solve the leakage issue, endowing Li-S batteries superior safety even in an artificial cut pouch cell. With a bare S loading of 4.9 mg cm-2 , the battery can deliver good endurance owing to the suppressed polysulfide shuttle by its polar groups. This work enlightens the design of leakage-proof electrolyte and makes a milestone for high performance Li-S batteries.

Zinc anode-compatible in-situ solid electrolyte interphase via cation solvation modulation.

The surface chemistry of solid electrolyte interphase is one of the critical factors that govern the cycling life of rechargeable batteries. However, this chemistry is less explored for zinc anodes, owing to their relatively high redox potential and limited choices in electrolyte. Here, we report the observation of a zinc fluoride-rich organic/inorganic hybrid solid electrolyte interphase on zinc anode, based on an acetamide-Zn(TFSI)2 eutectic electrolyte. A combination of experimental and modeling investigations reveals that the presence of anion-complexing zinc species with markedly lowered decomposition energies contributes to the in situ formation of an interphase. The as-protected anode enables reversible (~100% Coulombic efficiency) and dendrite-free zinc plating/stripping even at high areal capacities (>2.5 mAh cm‒2), endowed by the fast ion migration coupled with high mechanical strength of the protective interphase. With this interphasial design the assembled zinc batteries exhibit excellent cycling stability with negligible capacity loss at both low and high rates.

Integrated Interface Strategy toward Room Temperature Solid-State Lithium Batteries.

Solid-state lithium batteries have drawn wide attention to address the safety issues of power batteries. However, the development of solid-state lithium batteries is substantially limited by the poor electrochemical performances originating from the rigid interface between solid electrodes and solid-state electrolytes. In this work, a composite of poly(vinyl carbonate) and Li10SnP2S12 solid-state electrolyte is fabricated successfully via in situ polymerization to improve the rigid interface issues. The composite electrolyte presents a considerable room temperature conductivity of 0.2 mS cm-1, an electrochemical window exceeding 4.5 V, and a Li+ transport number of 0.6. It is demonstrated that solid-state lithium metal battery of LiFe0.2Mn0.8PO4 (LFMP)/composite electrolyte/Li can deliver a high capacity of 130 mA h g-1 with considerable capacity retention of 88% and Coulombic efficiency of exceeding 99% after 140 cycles at the rate of 0.5 C at room temperature. The superior electrochemical performance can be ascribed to the good compatibility of the composite electrolyte with Li metal and the integrated compatible interface between solid electrodes and the composite electrolyte engineered by in situ polymerization, which leads to a significant interfacial impedance decrease from 1292 to 213 Ω cm2 in solid-state Li-Li symmetrical cells. This work provides vital reference for improving the interface compatibility for room temperature solid-state lithium batteries.

An insight into intrinsic interfacial properties between Li metals and Li10GeP2S12 solid electrolytes.

Density functional theory simulations and experimental studies were performed to investigate the interfacial properties, including lithium ion migration kinetics, between lithium metal anode and solid electrolyte Li10GeP2S12(LGPS). The LGPS[001] plane was chosen as the studied surface because the easiest Li+ migration pathway is along this direction. The electronic structure of the surface states indicated that the electrochemical stability was reduced at both the PS4- and GeS4-teminated surfaces. For the interface cases, the equilibrium interfacial structures of lithium metal against the PS4-terminated LGPS[001] surface (Li/PS4-LGPS) and the GeS4-terminated LGPS[001] surface (Li/GeS4-LGPS) were revealed based on the structural relaxation and adhesion energy analysis. Solid electrolyte interphases were expected to be formed at both Li/PS4-LGPS and Li/GeS4-LGPS interfaces, resulting in an unstable state of interface and large interfacial resistance, which was verified by the EIS results of the Li/LGPS/Li cell. In addition, the simulations of the migration kinetics show that the energy barriers for Li+ crossing the Li/GeS4-LGPS interface were relatively low compared with the Li/PS4-LGPS interface. This may contribute to the formation of Ge-rich phases at the Li/LGPS interface, which can tune the interfacial structures to improve the ionic conductivity for future all-solid-state batteries. This work will offer a thorough understanding of the Li/LGPS interface, including local structures, electronic states and Li+ diffusion behaviors in all-solid-state batteries.