Excellent cycling performance of high-nickel single-crystal cathode material by a well-tailored binary molten-salt method

Abstract

Nickel-rich LiNixCoyMnzO2 (x + y + z = 1) cathode materials have been extensively studied due to their improved energy density and reduced cost in comparison to conventional layered oxides (LiCoO2) and perovskite-type compounds (LiFePO4). However, the further commercialization of polycrystalline nickel-rich layered cathodes are severely hampered by entrenched particle microcracking that evolves mainly from the randomly oriented grain boundaries in the primary particles. Herein, an environmental-friendly LiOH⋅H2O/Li2CO3 binary molten-salt method is introduced to synthesize single-crystal LiNi0.88Co0.09Mn0.03O2 with good crystallinity and dispersion, and the possible growth mechanism of the particles is inferred. The sample prepared at a lithium ratio of 1.7 (SC1.7) shows a lower degree of cation mixing and larger lithium layer spacing compared to control polycrystalline sample (PC), and the residual alkali is effectively removed from the surface of single crystal particles. These features enable SC1.7 to maintain robust structural stability during cycling, with the cycle retention at 1C rate and a voltage of 4.5 V to be 86.73% after 100 cycles. The desirable performance is rationally derived from the significant inhibition of microcracks in particles, and reduction of parasitic reactions. The unique binary molten-salt strategy provides a new avenue for the design of high-performance high-nickel cathode materials in lithium-ion batteries.