Polydopamine Coated Lithium Lanthanum Titanate in Bilayer Membrane Electrolytes for Solid Lithium Batteries

The demand for solid lithium batteries with high energy density and safety boosts the development of solid-state electrolytes in which composite membrane electrolytes consisting of polymers and ceramic fillers are attractive. As the common ceramic filler, perovskite-structured Li_0.33La_0.557TiO₃ (LLTO) has great advantage on cost and environmental friendliness by using earth-abundant raw materials in the production. Nevertheless, the chemical instability of LLTO against Li-metal hinders its application. Herein, LLTO particles are coated by biodegradable polydopamine (PDA) layers and united with poly(vinylidene fluoride) (PVDF) to prepare composite electrolytes which perform superior stability against Li-metal. Besides, PVDF:LLTO membranes are assembled at cathode sides and show high voltage tolerance. The Li/Ni_0.6Mn_0.2Co_0.2O₂ cells with bilayer membrane electrolytes can deliver the specific capacity of 158.2 mAh g^-1 and maintain 83% capacity after 100 cycles at 0.1 C. Furthermore, based on the bilayer membranes with outstanding flexibility and stretchability, the cells can even survive under several extreme conditions, such as bending, twisting, crimping, and stretching. This study offers an environmentally friendly strategy to improve the stability of LLTO against Li and sheds light on the development of cost-effective solid electrolytes.