Tri-functionalized Li2B4O7 coated LiNi0.5Co0.2Mn0.3O2 for boosted performance lithium-ion batteries

Building stable interfacial structure is regarded as an effective strategy to enhance structure stability and facilitate Li+ migration. Herein, LiNi0.5Co0.2Mn0.3O2 (NCM523) cathode materials are surface-modified with amorphous Li2B4O7 (LBO) Li+-conductor with high relative permittivity. Comparing to pristine NCM, surface-modified electrodes exhibit a significant improvement in capacity retention and rate capability, delivering a reversible capacity of 163.4 mAh·g−1 and 87.6 % capacity retention over 100 cycles at 1 C. Besides the protection from HF-attack, enlarged crystal lattice volume by boron-doping and Li+-conductor characteristic of Li2B4O7 is beneficial for Li+-ion diffusion in NCM523 and reduces charge transfer resistance. In addition, the reduced work function induced by Li2B4O7-coating is helpful for the suppression of the electrolyte oxidation, the enhanced rate capability and improved cyclic stability in terms of interfacial stability. Moreover, dielectric polarization field induced by high-permittivity Li2B4O7 at NCM523-Li2B4O7-electrolyte triple-phase interface would synergistically facilitate Li-ion migration across electric double-layer. Our work would provide a new insight into the enhanced performance of cathode material surface-modified by Li+-conductor with large relative permittivity.