A Cost-Effective Sulfide Solid Electrolyte Li7P3S7.5O3.5 with Low Density and Excellent Anode Compatibility.

The commercialization of all-solid-state Li batteries (ASSLBs) demands solid electrolytes with strong cost-competitiveness, low density (for enabling satisfactory energy densities), and decent anode compatibility (the need for cathode compatibility can be circumvented by the cathode coating techniques that are widely applied in sulfide-based ASSLBs). However, none of the reported oxide, sulfide, or chloride solid electrolytes meets these requirements simultaneously. Here, we design a Li7P3S7.5O3.5 (LPSO) solid electrolyte, which shows a combination of all the aforementioned characteristics. The synthesis of this material does not need the expensive Li2S, so the raw materials cost is only $14.42/kg, which, unlike most solid electrolytes, lies below the $50/kg threshold for commercialization. The density of LPSO is 1.70 g cm-3, considerably lower than those of the oxide (typically above 5 g cm-3) and chloride (around 2.5 g cm-3) solid electrolytes. Besides, LPSO also shows excellent anode compatibility. The Li|LPSO|Li cell cycles stably with a potential of ~50 mV under 0.1 mA cm-2 for over 4200 h at 25 °C, and the all-solid-state pouch cell with the Si anode shows a capacity retention of 89.29 % after 200 cycles under 88.6 mA g-1 at 60 °C.

Stable All-Solid-State Lithium Metal Batteries Enabled by Machine Learning Simulation Designed Halide Electrolytes.

Solid electrolytes (SEs) with superionic conductivity and interfacial stability are highly desirable for stable all-solid-state Li-metal batteries (ASSLMBs). Here, we employ neural network potential to simulate materials composed of Li, Zr/Hf, and Cl using stochastic surface walking method and identify two potential unique layered halide SEs, named Li2ZrCl6 and Li2HfCl6, for stable ASSLMBs. The predicted halide SEs possess high Li+ conductivity and outstanding compatibility with Li metal anodes. We synthesize these SEs and demonstrate their superior stability against Li metal anodes with a record performance of 4000 h of steady lithium plating/stripping. We further fabricate the prototype stable ASSLMBs using these halide SEs without any interfacial modifications, showing small internal cathode/SE resistance (19.48 Ω cm2), high average Coulombic efficiency (∼99.48%), good rate capability (63 mAh g-1 at 1.5 C), and unprecedented cycling stability (87% capacity retention for 70 cycles at 0.5 C).

Lead-Free Solid-State Organic-Inorganic Halide Perovskite Electrolyte for Lithium-Ion Conduction.

Exploring new solid electrolytes (SEs) for lithium-ion conduction is significant for the development of rechargeable all-solid-state lithium batteries. Here, a lead-free organic-inorganic halide perovskite, MASr0.8Li0.4Cl3 (MA = methylammonium, CH3NH3 in formula), is reported as a new SE for Li-ion conduction due to its highly symmetric crystal structure, inherent soft lattice, and good tolerance for composition tunability. Via density functional theory calculations, we demonstrate that the hybrid perovskite framework can allow fast Li-ion migration without the collapse of the crystal structure. The influence of the lithium content in MASr1-xLi2xCl3 (x = 0.1, 0.2, 0.3, or 0.4) on Li+ migration is systematically investigated. At the lithium content of x = 0.2, the MASr0.8Li0.4Cl3 achieves the room-temperature lithium ionic conductivity of 7.0 × 10-6 S cm-1 with a migration energy barrier of ∼0.47 eV. The lithium-tin alloy (Li-Sn) symmetric cell exhibits stable electrochemical lithium plating/stripping for nearly 100 cycles, indicating the alloy anode compatibility of the MASr0.8Li0.4Cl3 SE. This lead-free organic-inorganic halide perovskite SE will open a new avenue for exploring new SEs.

Composition Modulation of Ionic Liquid Hybrid Electrolyte for 5 V Lithium-Ion Batteries.

Electrolyte is a key component in high-voltage lithium-ion batteries (LIBs). Bis(trifluoromethanesulfonyl)imide-based ionic liquid (IL)/organic carbonate hybrid electrolytes have been a research focus owing to their excellent balance of safety and ionic conductivity. Nevertheless, corrosion of Al current collectors at high potentials usually happens for this kind of electrolyte. In this study, this long-standing problem is solved via the modulation of the IL/carbonate ratio and LiPF6 concentration in the hybrid electrolyte. The proposed electrolyte suppresses Al dissolution and electrolyte oxidation at 5 V (vs Li+/Li) and thus allows for ideal lithiation/delithiation performance of a high-voltage LiNi0.5Mn1.5O4 (LNMO) cathode even at 55 °C. The underlying mechanism is examined in this work. Excellent cycling stability (97% capacity retention) for an LNMO cathode after 300 cycles is achieved. This electrolyte shows good wettability toward a polyethylene separator and low flammability. In addition, satisfactory compatibility with both graphite and Si-based anodes is confirmed. The proposed electrolyte design strategies have great potential for applications in high-voltage LIBs.