Enhanced Electrochemical Performance and Safety of LiNi_0.88Co_0.1Al_0.02O₂ by a Negative Thermal Expansion Material of Orthorhombic Al₂(WO₄)₃

LiNi0.88Co0.1Al0.02O2 (NCA) is attractive for high-energy batteries, but phase transition and side reactions leave large volume change and thermal runaway. In order to address the drawbacks, orthorhombic Al2(WO4)3, a cheap anisotropic negative thermal expansion material, was synthesized and adopted to modify NCA, and its effects on the electrochemical performance and safety of NCA were investigated using multifarious techniques. Al2(WO4)3 can greatly improve the rate performance, cyclability at different temperatures, thermal stability, and interface behavior and intensify charge transfer as well as decline the deformation and side reactions of NCA. The discharge capacity of the NCA modified with 5 wt % Al2(WO4)3 reaches 170.0 mA h/g at 5.0 C and 25 °C. After 100 cycles, the values of this electrode at 1.0 C and 25 °C and at 3.0 C and 60 °C are 164.2 and 148.7 mA h/g, respectively, much higher than those of the pure NCA under the same conditions. Moreover, Al2(WO4)3 declines the byproducts and cation mixing and decreases the released heat, strain, and charge-transfer resistance after cycles of NCA about 37.1, 33.0, and 32.8%, respectively. The improvement mechanism is discussed. It opens an effective avenue for the applications of energy materials by simultaneously adjusting heat, structure, interface, and deformation.