Sulfur anion doping and surface modification with LiNiPO4 of a Li[Co0.1Ni0.15Li0.2Mn0.55]O2 cathode material for Li-ion batteries

A simple combustion method was used to prepared Li[Co0.1Ni0.15Li0.2Mn0.55]O2 and Li[Co0.1Ni0.15Li0.2Mn0.55]S0.03O1.97. Surface coating was carried out using the sol–gel method with Li[Co0.1Ni0.15Li0.2Mn0.55]O2, Li[Co0.1Ni0.15Li0.2Mn0.55]S0.03O1.97, and LiNiPO4. The physical properties of the synthesized materials were measured using X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Electrochemical performance was assessed by measuring parameters such as charge and discharge capacity, cycle performance, rate capability, electrochemical impedance spectroscopy (EIS), and differential scanning calorimetry (DSC). Sulfur-doped cathode material conferred improved cycle performance compared with that of Li[Co0.1Ni0.15Li0.2Mn0.55]O2 and had a low capacity decrease after 50 cycles. The LiNiPO4 coated materials have an enhancement of rate capability for discharge at 0.1 C to 5 C-rate. In addition, the 5 wt.% LiNiPO4-coated Li[Co0.1Ni0.15Li0.2Mn0.55]S0.03O1.97 cathode material had improved cycle performance, rate capability, EIS test results, and DSC results compared with those of the other samples. The rate capability and cycle performance of the Li[Co0.1Ni0.15Li0.2Mn0.55]O2 cathode material for lithium ion batteries were enhanced through the stabilization of the cathode surface with a LiNiPO4 coating and sulfur doping. The 5.0 wt.% LiNiPO4-coated LCNLMSO had capacity retentions of 75, 48 and 14% at the 1, 2 and 5 C-rates, respectively, and also had capacity retention of 85% after 50 cycles compared to 75% for LCNLMO at 0.2 C-rate.

► Sulfur doped materials were prepared by simple combustion method.
► Surface coating was carried out using the sol-gel method with LiNiPO4.
► The rate capability and cycle performance of the cathode materials were enhanced.