A waterborne superLEphilic and thermostable separator based on natural clay nanorods for high-voltage lithium-ion batteries

Abstract Commercial separators for lithium-ion batteries still have shortcomings such as inferior electrolyte wettability, serious thermal shrinkage (polyolefin separators) and intrinsic brittleness (ceramic separators), which result in poor electrochemical performance and serious potential safety hazard. Here, a waterborne separator is fabricated by deposition and in situ crosslinking of a homogeneous aqueous suspension containing natural clay nanorods (attapulgite, ATP) and polyvinylalcohol (PVA) onto both the external and internal surfaces of the Celgard@2400 matrix. Different from conventional grafted or coated functional separators, the ATP-PVA/Celgard separator has a unique sandwiching/infusing structure. The separator features super-electrolyte-philicity with a liquid electrolyte contact angle of 0°, high Li+ conductivity (0.782 mS cm−1), excellent mechanical properties and high thermostability. Consequently, the 4.9 V Li/LiNi0.5Mn1.5O4 cell with the separator shows higher cycling stability (94.7% after 100 cycles), better rate performance and lower resistance than the cell with commercial ceramic separator. Moreover, the separator could improve performance of the Li/LiFePO4 cell and stable open circuit voltage at 160 °C. This work provides an avenue for the design of advanced separators for high-voltage lithium-ion batteries via an environmentally friendly method using natural nanomaterials.