Summary
The LiNiO2 (LNO) positive electrode material is one of the most promising high‐voltage alternatives for the layered oxide materials such as LiCoO2 (LCO). However, the poor cyclability still limits widespread commercialization of LNO, whereas crack formation is one of the main issues leading to its premature aging. In this study, a series of Al‐doped LNO (LiNi1−xAlxO2, x = 0, 0.02, 0.04, 0.06) positive electrode materials are synthetized via a simple sol‐gel method. Overall, this study aims at providing new insights of the sol‐gel method and Al‐doped strategy for LNO positive electrode materials. The synthesis is found to readily yield in small nanosized crystals, which alleviate the cracking issue. Besides, the optimized Al‐doping amount (2 at%) in LNO decreases cation mixing and primary particle size resulting in improved layered structure stability attributed to more reversible H2‐H3 phase transitions. As a result, the assembled lithium ion batteries equipped with LiNi0.98Al0.02O2 can smoothly run for 400 cycles with a relatively high capacity retention of 81% at 100 mA g−1 charging‐discharging and a wide operating voltage window of 2.5‐4.5 V.
LiNiO2 (LNO) is one of the most potential alternatives to LiCoO2 in Li ion batteries (LIBs). However, it still suffers from poor cyclability. Meanwhile, the recycling processes of LIBs are widely investigated to enable effective recycling for the growing amounts of LIB waste. Cu is one of the dominating impurities in LIB recycling fractions. In this work, LNO and 0.2 mol% Cu-doped LNO are studied. Cu-doping is demonstrated to stabilize the LNO lattice structure, reduce cation mixing and improve the reversibility of phase transitions during electrochemical processes. Consequently, the rate capability of LNO is improved by Cu-doping, especially at high C-rates. The Cu-doped LNO shows much higher capacity retention of 85% than that of 66% for the undoped LNO at the current density of 100 mA·g−1 after 100 cycles in a voltage window of 2.5–4.5 V. Our results show that a possible Cu contamination in the Ni fraction of the LIB material recovery process can be used to enhance the electrochemical properties of newly synthetized Ni-based positive electrode materials.
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