Mechanical Pulverization of Co-Free Nickel-Rich Cathodes for Improved High-Voltage Cycling of Lithium-Ion Batteries

Nickel-rich cathode materials are quickly becoming the next commercial cathode for electric vehicles; however, their long-term cycle life retention and air stability remain a barrier to the use of these lower-cost, higher-energy density materials. Surface reactivity and mechanical degradation, especially at high voltages, remain two issues that impede these material's commercialization. While surface treatments have shown great promise in reducing surface reactivity, mechanical degradation or "cathode cracking" persists yet. In the present work, LiNi0.9Mn0.05Al0.05O2 (NMA) cathode materials are first pulverized into their primary particle constituents and then coated with lithium phosphate via solution-based chemistry with varying concentrations of phosphoric acid. The cathodes are characterized using energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, electrochemical impedance spectroscopy, and electrochemical cycling. After 100 cycles, the pulverized NMA cathodes coated using the lowest concentration of phosphoric acid show delayed voltage decay and double the discharge capacity compared to the pristine material in full cells during high-voltage cycling.