Effect of Zr doping and Li2O-2B2O3 layer on the structural electrochemical properties of LiNi0.5Co0.2Mn0.3O2 cathode material: experiments and first-principle calculations

In order to enhance the electrochemical performance of LiNi0.5Co0.2Mn0.3O2 (NCM), an in situ doping with zirconium (Zr) by wet grind-solid state method then coating with Li2O-2B2O3 (LBO) by crystal phase selection method is successfully developed. At the same time, based on the density functional theory (DFT) with the generalized gradient approximation (GGA), use of the first-principle calculation method theoretically proved the experimental results. The XRD results of experimental and the calculated both revealed the lattice parameters become larger after Zr doped. The thickness of the LBO layer uniformly deposited on the surface of the Zr-doped sample is 5 nm, which can scavenge and neutralize HF erosion. Particularly, the Zr-doped and LBO-coated NCM sample exhibited excellent cycling performance with 90.5% capacity retention after 100 cycles at 1 C, which are apparently higher than 76.97% of NCM. The initial discharge capacity of double optimized sample was 170.4 mAh g−1 at 1 C which is higher than 157.1 mAh g−1 of NCM. Zr and LBO layers can effectively reduce the energy of the system and the band gap. Obtained results were consistent with the experimental results. Therefore, co-modification method plays an import role to optimize the material from the structure to the surface and hence greatly improved the battery performance.