Strontium Doping Promotes Low-Temperature Growth of Single-Crystalline Ni-Rich Cathodes with Enhanced Electrochemical Performance.

Abstract

Nickel-rich cathode materials have emerged as ideal candidates for electric vehicles due to their high energy density; however, polycrystalline materials are prone to microcrack formation and unavoidable side reactions with electrolytes during cycling, leading to structural instability and capacity degradation. Herein, an Sr-doped single-crystalline nickel-rich LiNi_0.88Co_0.05Mn_0.07O₂/Sr cathode material is synthesized, with Sr doping levels controlled at x = 0.3%, 0.5%, 1 mol%. The nickel-rich LiNi_0.88Co_0.05Mn_0.07O₂/Sr cathode features particle sizes of approximately 2 μm, at a relatively low temperature. It inhibits the microcrack formation, prevents electrolyte penetration into the particle interior, and reduce side reactions, thereby enhancing structural stability. This enables the cathode to deliver a high initial discharge capacity of 205.3 mAh g^-1at 0.1 C and 170.8 mAh g^-1 at 10 C, within the voltage range of 2.7 V-4.3 V, and an outstanding capacity retention of 96.61% at 1 C after 100 cycles. These improvements can be attributed to the Sr-doping, which reduces the single-crystal growth temperature, effectively mitigating Li⁺/Ni²⁺ cation mixing. Moreover, the incorporation of Sr expands the interlayer spacing, thereby facilitating Li⁺ diffusion. The doping strategy employed in this work provides a new insight for low-temperature single-crystal materials synthesis, significantly improving the electrochemical performance of nickel-rich cathode materials.