Enhanced elevated-temperature performance of LiMn2O4 cathodes in lithium-ion batteries via a multifunctional electrolyte additive

Abstract

LiMn2O4 is a promising cathode material for lithium-ion batteries (LIBs) due to its low cost, environmental friendliness, and high voltage operation. However, its electrochemical performance deteriorates at elevated temperatures, primarily by reason of the structural degradation during cycling and proliferation of adverse reactions at the electrode/electrolyte interface. One of the main reasons is that the hydrolysis and decomposition of the LiPF6 at high temperatures produces HF, which leads to corrosion at the electrode/electrolyte interface and accelerates manganese dissolution. In this work, we report a multifunctional silane-based electrolyte additive, trimethoxyphenylsilane (TMPS), to solve these problems. Theoretical calculations and experimental results both demonstrate that TMPS can eliminate HF, stabilize PF5, and inhibit LiPF6 hydrolysis, thereby mitigating transition metal leaching. Additionally, TMPS improves the stability between cathode and electrolyte by constructing a highly stable and homogeneous cathode-electrolyte interfacial. The LiMn2O4//Li cell using the electrolyte containing 1 wt% TMPS retains 95.5 % and 83.7 % of its capacity after 500 cycles at 25 °C and 60 °C, respectively. Moreover, 18650-type cylindrical cells with this electrolyte also exhibit enhanced electrochemical performance at elevated temperatures. It demonstrates that TMPS is a promising multifunctional additive for manganese-based cathodes in LIBs.