Realizing ultrahigh-voltage performance of single-crystalline LiNi0.55Co0.15Mn0.3O2 cathode materials by simultaneous Zr-doping and B2O3-coating

Abstract

Improving the high-voltage stability of cathode materials is a new strategy to enhance the energy density of lithium-ion batteries (LIBs) in recent years. However, as a traditional cathode material, the low reversible capacity at high cut-off voltages (≥ 4.3 V) greatly restricts the application of LiCoO2. Herein, we have rationally synthesized a novel single-crystalline LiNi0.55Co0.15Mn0.3O2 cathode material (Z-NCM@B) by using the synergistic effect of Zr-doping and B2O3-coating. Excitedly, the modified Z-NCM@B cathode material shows improved high-voltage stability and excellent long-term cycling performance. Furthermore, it is revealed that the stronger ZrO bond formed by Zr4+ dopant can stabilize the crystal structure and promote the migration of Li+ in the cathode materials. Meanwhile, the uniform B2O3 coating layer effectively suppresses the material corrosion by electrolyte and reduces the loss of transition metal ions during the charge/discharge cycle process. As anticipated, the Z2-NCM@B2 || graphite pouch-type full cell exhibits an advanced capacity retention of 96.9% over 250 cycles at an operating voltage of 4.2 V, while the capacity retention of the pristine NCM is only 88%. Besides, the Z2-NCM@B2 coin-cell retains a discharge capacity of 145.2 mA h g−1 at 1 C with a satisfactory capacity retention of 79.2% after 100 cycles within a broad voltage range between 2.95 and 4.7 V, which is much superior than that for the pristine NCM (130.9 mA h g−1, 70.9%). This synergistic modification strategy offers a reference for the practical application of NCM cathode materials with high-voltage stability and long-term cycling performance in LIBs.