Improving the structural reversibility of LiNiO2 by incorporation of Cu, an electrochemical and in-situ XRD study

LiNiO2 is one of the most appealing cathode materials for lithium-ion batteries. However, during electrochemical cycling, irreversible phase transitions occur at high potentials leading to rapid capacity decay. Stopping irreversible structural changes has been achieved by several strategies such as cation doping, solid solution formation, protective coatings, and hybrid strategies. However, no definitive strategy has been envisaged to achieve 100% reversibility. In this work, the effect of incorporating Cu into LNO on the electrochemical performance and structural stability was evaluated by electrochemical and in situ XRD experiments. The structural properties indicate that this material has an ordered crystalline structure with a high degree of cationic ordering, where the presence of Cu3+ was confirmed by XPS. By in situ XRD, it was shown that the Cu-containing LiNiO2 phase is responsible of the charge retention, due to its structural stability during the insertion/deinsertion of Li ions. Furthermore, the presence of Cu, within the LiNiO2 crystalline structure, demonstrated a specific capacity retention of 95%, a high value compared to 45% observed in LiNiO2 after 10 cycles in a potential window of 3.0–4.3 V.