The Electrolyte Additive Effects on Commercialized Ni-Rich LiNi<sub><i>x</i></sub>Co<i><sub>y</sub></i>Mn<i>z</i>O<sub>2</sub> (<i>x</i> + <i>y</i> + <i>z</i> = 1) Based Lithium-Ion Pouch Batteries at High Temperature
Chengyun Wang, Qianqian Hu, Junnan Hao, Xijun Xu, Liuzhang Ouyang, Weizhen Fan, Jianshan Ye, Jiangwen Liu, Jin Li, Ao Mei, Min Zhu
Abstract
The commercialized lithium-ion pouch cells with an Ni-rich cathode material feature high energy density and are favored in the automotive market; however, they still suffer from rapid capacity loss and poor cyclability due to the unstable solid electrolyte interphase (SEI) at the anode surface under a high temperature. Here, an effective electrolyte additive of tripropargyl phosphate (TPP) is studied to improve the high-temperature performance of the Ni-rich cathode-based pouch cells. Resulting from the electrochemical reductions of TPP, a TPP-originated and phosphorus-rich SEI layer formed on the surface of a graphite anode, which directly avoids the graphite plates from being exposed in the electrolyte and suppresses the repeated consumption of cyclable Li+. After the storage for 15 days under 60 °C, an initial discharge capacity of 147.9 mAh g–1 can be achieved for the LiNi0.6Co0.2Mn0.2O2/graphite cell containing 1.0 wt % TPP, much higher than the value (132.2 mAh g–1) of the TPP-free cell. Meanwhile, the cycling performance at a high temperature for the LiNi0.8Co0.1Mn0.1O2/graphite cell is also significantly improved by introducing 1.0 wt % TPP into the electrolyte. Such an outstanding electrochemical performance and the solid evidences strongly confirmed that the stabilized anode surface film induced by the TPP addition plays a crucial role in enhancing the performance of commercialized cells.