A solid-electrolyte-reinforced separator through single-step electrophoretic assembly for safe high-capacity lithium ion batteries
© 2019 Elsevier B.V. In rechargeable lithium ion batteries (LIBs), the separator undergoes stresses in repeated charge and discharge processes. Polyvinylidene fluoride (PVDF) gel separators own excellent thermal stability and electrolyte wettability, but their limited mechanical strength cannot sustain severe strains under the conditions of large Li ion fluxes, mechanical and thermal shocks of batteries. In this report, a solid-electrolyte-reinforced gel separator is prepared through a single-step electrophoretic deposition on a stable surfactant-free colloid of PVDF-HFP and Al-doped Li6.75La3Zr1.75Ta0.25O12 (LLZTO). The LLZTO/PVDF-HFP separator owns a 3D laminated structure, a mechanical strength of 28.6 MPa, a room-temperature ionic conductivity of 7.13 × 10−4 S cm−1 and improved thermal stability. With the LLZTO/PVDF-HFP separator, LiFePO4 LIBs deliver a threshold discharge capacity of 170 mAh g−1 at 0.1 C and stable cycling with nearly zero capacity decay over 100 cycles at 0.5 C.