Significance of homogeneous conductive network in layered oxide-based cathode for high-rate capability of electric vehicle batteries

Abstract

The trade-off between battery energy density and power performance is the core problem that puzzles the development of electric vehicles (EVs). Although intensive researches are performed to explore active materials with good dynamics, the heterogeneous reactivity has been identified as an important cause for inferior capability and early death, especially for electrodes characterized with high areal loading and high compacted density. Herein, the heterogeneity and its origination of layered oxide-based (LiNixCoyMn1-x-yO2, NCM) electrodes at high C-rate are investigated through operando X-ray diffraction and ex-situ time-of-flight secondary ion mass spectrometry probe. By introducing Li3V2(PO4)3@G composite as a mixed conductor additive, the heterogeneous reactivity intro-particles are successfully mitigated, enabling NCM electrodes with both high rate capability, high energy density and high cyclability. In detail, the capacity retention at 20C is increased by 2.3 times, and the capacity retention at 0.5C after 160 full cycles is increased by 1.6 times, without electrolyte additive or material modification. This study demonstrates the significance of the homogeneous electronic/ionic transportation network to the rate capability and lifetime of an electrode, and discloses the design strategy of multifunctional additives to enhance the power density of a battery by maximizing the utility of the active particles.