Integrated Ni and Li-Rich Layered Oxide Cathode Materials for High Voltage Cycling in Rechargeable Li-Ion Batteries

Although the Ni-rich oxide cathodes possess a high specific capacity above 180 mAh g⁻¹, they suffer from capacity fading upon cycling to above 4.3 V due to their high surface reactivity with the electrolyte, structural layered to rock-salt phase transformation and development of micro-cracks. Herewith, the Ni-rich oxide is integrated with those of Li and Mn-rich oxides and their electrochemical performance is evaluated in Li half-cells: LiNi_0.6Mn_0.2Co_0.2O₂ (NMC622), 0.5LiNi_0.6Mn_0.2Co_0.2O₂ ⋅ 0.5Li_1.2Ni_0.16Mn_0.56Co_0.08O₂ (NL5050), and 0.25 LiNi_0.6Mn_0.2Co_0.2O₂ ⋅ 0.75 Li_1.2Ni_0.16Mn_0.56Co_0.08O₂ (NL2575). Interestingly, the resultant integrated 0.5LiNi_0.6Mn_0.2Co_0.2O₂ ⋅ 0.5Li_1.2Ni_0.16Mn_0.56Co_0.08O₂ (NL5050) cathode with an equal molar concentration of Ni and Li-rich oxides exhibits a specific capacity of about 190 mAh g⁻¹ with a capacity retention of 83 % after 100 cycles at 0.1 C rate. On the other hand, the Ni-rich oxide alone although exhibits an initial high specific capacity of 200 mAh g⁻¹, it suffers from a low capacity retention of only 35 % after 100 cycles. Thus, this study clearly indicates the benefits of higher cycling stability that results from the integration of Ni-rich and Li-rich oxide cathodes. Hence, the current work promotes the high voltage cycling of oxides through the optimization of integrated oxide cathodes, which can provide high capacity and long cycle-life for Li-ion batteries.