The Electrolyte Additive Effects on Commercialized Ni-Rich LiNi_xCo_yMnzO₂ (x + y + z = 1) Based Lithium-Ion Pouch Batteries at High Temperature

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.