Improved High Voltage Performance of Li-ion Conducting Coated Ni-rich NMC Cathode Materials for Rechargeable Li Battery

Recently, in lithium batteries, high-capacity Ni-rich cathode materials (LiNi0.8Mn0.1Co0.1O2) have gained tremendous attention. However, they also suffer from serious capacity degradation upon cycling, particularly at high voltage. To solve this problem, two strategies are proposed. The first one is the surface modification on the NMC811 cathode material with Li-ion-conducting Li3PO4. The second is the use of IL-based gel polymer electrolytes in Li metal batteries. Li3PO4 coating not only maintains the structure stability of the cathode but also suppresses the side reaction at the electrode–electrolyte interface. It also improves the Li+ ion conduction in the cathode material. Furthermore, in order to avoid the sensitivity of the cathode material toward H2O, CO2, and HF attack and solubility of transition metal ions in the electrolyte and enhance the cyclic performance of the Li battery, an IL-based gel polymer electrolyte is used. Mechanical stability of the polymer electrolyte can help suppress the lithium dendrite growth and overcome the issues of low electrochemical stability, leakage, and corrosion in liquid electrolytes. Electrochemical performance of the Li3PO4-coated NMC cathode material with the gel polymer electrolyte is tested at higher and lower upper cutoff voltages. Li batteries show a high discharge capacity of ∼182 mA h/g and an energy density of 606 mW h g–1 at C/10 current rate with almost stable cyclic stability up to 300 cycles. These tremendous features of polymer-based batteries with a surface-modified cathode material highlight its promising application in next-generation Li batteries.