Superior Low-Temperature All-Solid-State Battery Enabled by High-Ionic-Conductivity and Low-Energy-Barrier Interface.

All-solid-state batteries (ASSBs) working at room and mild temperature have demonstrated inspiring performances over recent years. However, the kinetic attributes of the interface applicable to the subzero temperatures are still unidentified, restricting the low-temperature interface design and operation. Herein, a host of cathode interfaces are constructed and investigated to unlock the critical interface features required for cryogenic temperatures. The unstable interface between LiNi0.90Co0.05Mn0.05O2 (Ni90) and Li6PS5Cl (LPSC) sulfide solid electrolyte (SE) results in unfavorable cathode-electrolyte interphase (CEI) and sluggish lithium-ion transport across the CEI. After inserting a Li2ZrO3 (LZO) coating layer, the activation energy of the Ni90@LZO/sulfide SE interface can be reduced from 60.19 kJ mol-1 to 41.39 kJ mol-1 owing to the suppressed interfacial reactions. Through replacing the LPSC SE and LZO coating layer by the Li3InCl6 (LIC) halide SE, both a highly stable interface and low activation energy (25.79 kJ mol-1) can be achieved, thus realizing an improved capacity retention (26.9%) at -30 °C for the Ni90/LIC/LPSC/Li-In ASSB. Moreover, theoretical evaluation clarifies that cathode/SE interfaces with high ionic conductivity and low energy barrier are favorable to the Li+ conduction through the interphase and the Li+ transfer across the cathode/interphase interface. These critical understandings may provide guidance for low-temperature interface design in ASSBs.

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

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

Experimental Corroboration of Lithium Orthothioborate Superionic Conductor by Systematic Elemental Manipulation.

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

Stable Interface between Sulfide Solid Electrolyte and Room-Temperature Liquid Lithium Anode.

Sulfide solid electrolytes (SEs) are considered to be some of the most promising SEs for commercialization due to their high ionic conductivity, good mechanical ductility, and good interfacial contact with electrodes. The Ohmic resistance of solid-state batteries assembled with sulfide SEs is significantly reduced, but the problem of high interfacial impedance due to poor interfacial chemical/electrochemical stability between sulfide SEs and the electrodes is serious. Therefore, the formation and evolution of the electrode/sulfide SE interface during battery assembly and cycling have a crucial impact on the performance of the battery, which is one of the key issues to be solved in battery commercialization. Herein, a variety of compatible interface protective layers, including PEO and ß-Li3PS4/S, are obtained between sulfide SEs and ether-based room-temperature liquid lithium anodes for long-term stable cycling of >1000 h. Such a technical method for stabilizing the solid-liquid interface between a sulfide SE and an organic liquid lithium anode successfully solves the key problem of interfacial side reactions, making this battery configuration safe and stable for long-cycle operation.

Thermal Stability between Sulfide Solid Electrolytes and Oxide Cathode.

In pursuit of high-energy/power density, lithium-ion batteries suffer from increasing safety risks that need to be urgently solved. These safety problems promisingly might be solved by replacing liquid electrolytes (LEs) with inorganic solid electrolytes (SEs), because of their high thermal stability and nonflammability. However, thermal stability studies on sulfide SEs have been rarely reported, due to their extremely high reactivity, strong corrosiveness, instability to air, toxic gas release, etc. To fill this gap, thermal stability performances of sulfide SEs are verified from the perspectives of essential combustion elements in this work. Simple and effective experimental devices/approaches have been developed to systematically study the thermodynamic and kinetic properties of thermal stability between typical sulfide SEs (Li3PS4, Li7P3S11, Li6PS5Cl, LSPSCl, Li4SnS4) and oxide cathode Li1-xCoO2 with different delithiation states. Practical improved methods are realized to block the thermochemical interfacial reaction for enhanced thermal stability between sulfide SEs and oxide cathodes.