Boron improved electrochemical performance of LiNi_0.8Co_0.1Mn_0.1O₂ by enhancing the crystal growth with increased lattice ordering

Boron-modified Li(Ni_0.8Co_0.1Mn_0.1)_1−xB_xO₂ cathode materials(NCM811) were successfully prepared by a nano-milling assisted solid-state approach. X-ray diffraction investigations showed that the materials are solid solutions with a layered structure. SEM observations implied that the doped B ions promoted the growth of the target crystal with well-developed facets since it will form liquid phase at lower temperature. The intensity ratio of I(003)/I(104) raised with the increase in Boron doping concentration, until a maximum value of 1.453 was observed at x = 0.01. Further Rietveld refinements revealed that boron ions occupy the crystal lattice in the transition metal slab which helps to promote the lattice ordering by decreasing the Li/Ni ionic mixing. Such B promoted NCM811 cathode materials were confirmed to have an improved diffusion coefficient with a reduced interfacial resistance by subsequent CV and EIS measurements. From the electrochemical test, those B modified NCM811 cathode materials presented enhanced electrochemical performance. Among the synthesized samples, Li(Ni_0.8Co_0.1Mn_0.1)_0.99B_0.01O₂ exhibited the best specific capacity, with 194.7 mAh g⁻¹ and 166.8 mAh g⁻¹ at 0.1C and 5C respectively. The capacity retention at 0.5C was also confirmed as 98.2% after 100 cycles. Such improvement can be explained by the reduced Li/Ni ionic mixing, the increased Li ionic diffusion and the reduced interfacial resistance caused by the promoted growth of the B doped NCM811 crystals. Compared to those NCM811 materials reported elsewhere, the material obtained by this approach showed high potential for future application.