In situ inorganic conductive network formation in high-voltage single-crystal Ni-rich cathodes

Single-crystal Ni-rich cathodes suffer from side reactions with the electrolyte and slow Li-ion transport during high-voltage cycling. Herein, a Li1.4Y0.4Ti1.6(PO4)(3) coating is applied to facilitate the Li-ion transport and improve the cycling life of the cell. High nickel content in LiNixCoyMnzO2 (NCM, x >= 0.8, x + y + z = 1) layered cathode material allows high specific energy density in lithium-ion batteries (LIBs). However, Ni-rich NCM cathodes suffer from performance degradation, mechanical and structural instability upon prolonged cell cycling. Although the use of single-crystal Ni-rich NCM can mitigate these drawbacks, the ion-diffusion in large single-crystal particles hamper its rate capability. Herein, we report a strategy to construct an in situ Li1.4Y0.4Ti1.6(PO4)(3) (LYTP) ion/electron conductive network which interconnects single-crystal LiNi0.88Co0.09Mn0.03O2 (SC-NCM88) particles. The LYTP network facilitates the lithium-ion transport between SC-NCM88 particles, mitigates mechanical instability and prevents detrimental crystalline phase transformation. When used in combination with a Li metal anode, the LYTP-containing SC-NCM88-based cathode enables a coin cell capacity of 130 mAh g(-1) after 500 cycles at 5 C rate in the 2.75-4.4 V range at 25 degrees C. Tests in Li-ion pouch cell configuration (i.e., graphite used as negative electrode active material) demonstrate capacity retention of 85% after 1000 cycles at 0.5 C in the 2.75-4.4 V range at 25 degrees C for the LYTP-containing SC-NCM88-based positive electrode.

Automated summary

Single-crystal Ni-rich cathodes face issues such as performance degradation and structural instability during cycling. Despite the benefits of using single-crystal Ni-rich cathodes, ion diffusion limitations in large single-crystal particles impact rate capability. The application of an in situ Li1.4Y0.4Ti1.6(PO4)(3) conductive network helps improve lithium-ion transport and cycling life in high-nickel content cathodes.