Borate-Water-Based 3D-Slime Interface Quasi-Solid Electrolytes for Li-ion Batteries

The development of solid-state batteries (SSBs) that do not use hazardous materials as electrolytes and are not flammable is progressing rapidly, however the production of sulfide-based SSBs requires strict low-dew-point control due to their high reactivity with atmospheric moisture and the concern of generating hydrogen sulfide, and several issues remain in terms of the cost and recyclability. Thus, low-cost facile materials and low-CO₂-emission processes are necessary. With regard to oxide-type SSBs, which are attracting attention for their safety, there are issues with manufacturing suitability, as high-temperature sintering of oxide solid electrolyte particles is required. A new quasi-solid-state (QSS) electrolyte with 3D-ionic conduction and adhesive interfaces by combining amorphous Li₂B₄O₇ and water (3D-Slime Interface Solid Electrolyte: 3D-SLISE) is synthesized without stringent dew point control and sintering. Electrode and electrolyte slurries containing 3D-SLISE are applied to current-collecting foils in air, naturally dried, and used to construct battery laminates. 3D-SLISE-QSSBs (LiCoO₂ cathode/3D-SLISE with 7 wt.% bound-water/Li₄Ti₅O₁₂ or TiNb₂O₇ anodes) maintain several hundred cycles of charge/discharge as a 2.35 V lithium-ion battery. The 3D-SLISE-QSSB technology can promote the use of safe and low-cost batteries, eliminate the need for a dry room during manufacturing, and enable direct recycling of active materials.