Tuning Li-excess to optimize Ni/Li exchange and improve stability of structure in LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) cathode material for lithium-ion batteries

摘要

Ni/Li exchange is a detrimental effect on electrochemical performances for high-Ni cathode materials(LiNi_(x)Co_(y)Mn_(z)O_(2),x≥0.6).Adjusting Li-excess degree has been proved to be an effective way to optimize Ni/Li exchange in the materials.However,until now,how the Ni/Li exchange and thus the structural properties is affected by the Li-excess has not been understood and clearly elucidated in the literature.Herein,a feasible strategy is utilized to optimize Ni/Li exchange and the amount of anti-Li^(+)in LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) by mixing Ni_(0.8)Co_(0.1)Mn_(0.1)(OH)_(2) precursor with different amounts of lithium sources during lithiation.It was found that morphology and phase stability of the material can be tuned with moderate excessive lithium.With 10%Li-excess,LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) exhibits an initial discharge capacity of 211.5 mAh·g^(–1) at 0.1 C and maintains 93.3%of its initial capacity after 100 cycles at 1 C.Different technologies were used to characterize the materials and it shows that the formation of broader Li slab space,decreased anti-Ni^(2+)in Li layer,and gradient distribution of Ni3+in the surface is contributed to moderate Li-excess in the materials.Broader Li slab space facilitates diffusion of Li^(+),decreased antisite-Ni^(2+)and gradient distribution of Ni3+in materials surfaces optimizes the Ni/Li exchange.Based on these results,we thus believe that it is the moderate Li-excess in material that optimized the electrochemical performance of high-Ni cathode materials.