Improved electrochemical performance of LiNi _0.8 Co _0.1 Mn _0.1 O ₂ modified with 4-vinylbenzeneboronic acid

Nickel-rich layered lithium transitional metal oxides are in high demand for lithium ion batteries with high specific energy density. However, the strong affinity of the material to water is undesirable for manipulation. Herein, we report an approach for modifying the surface of LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (NCM) with a layer of 4-vinylbenzeneboronic acid (4-VBBA) to alter the surface properties of NCM. The presence of a 4-VBBA layer can lead to the surface of NCM becoming less hydrophilic, while having comparable wettability of the electrolyte. Importantly, the electrochemical performance of NCM, modified with 4-VBBA (NCM@B), can be greatly improved, relative to that of pristine NCM. Although both of the materials can deliver high specific discharge capacity at 0.1 C (189 mA h g ⁻¹ for NCM and 190 mA h g ⁻¹ for NCM@B), NCM@B exhibits better rate capability and improves ability to cycle (85.9 mA h g ⁻¹ for NCM and 105.6 mA h g ⁻¹ for NCM@B at 2 C, capacity retention of 46.5% for NCM and 66.1% for NCM@B after 500 cycles). It is demonstrated that that less F-containing species, which may have great effect on the electrochemical performance of the electrode materials, are formed in the solid electrolyte interphase (SEI) film on the surface of NCM@B, probably due to the blockage of the residual water in the electrolyte by the 4-VBBA layer to the electrode surface. The strategy may be applicable to various metal oxide electrode materials sensitive to humidity.