Simultaneous B/W dual coating on ultra-high nickel single crystal cathode material for lithium-ion batteries

The ultra-high nickel LiNixCoyMn1-x-yO2 (x > 0.9) cathode material is a prime candidate for powering next-generation electric vehicles. However, its inherent structural instability and complicated interface side-reactions limit its commercialization. Here, the LiNi0.92Co0.04Mn0.04O2 single-crystal cathode material with an average particle size of 1.69 μm is prepared via a simple temperature fluctuation method combined with B and W surface modification. As-formed surface Li–B–O and Li2WO4 lithium ion conductors can successfully enhance the discharge capacity of single crystal LiNi0.92Co0.04Mn0.04O2 from 219.9 to 226.5 mAh g−1 by facilitating lithium ion diffusion. At 4.5 V, the B and W surface modification significantly enhances the cycle retention from 71.8% to 87.1% at 1 C after 100 cycles due to the construction of a uniform boron-rich cathode/electrolyte interface (CEI) layer. The specific composition of the as-formed CEI film is clearly identified. The analysis results of B and W modifications show that the presence of boron-rich CEI and Li2WO4 coating layer protects the particles from electrolyte erosion under high voltage and enhances lithium-ion diffusion on the particle surface. Therefore, the chemical states of Ni within the particle for B- and W-modified samples are distributed more homogeneously after long cycling.