Effect of Cobalt Doping on Enhanced Lithium Storage Performance of Nanosilicon

Abstract High‐capacity silicon anodes are attracting more attention, owing to their high theoretical capacities and low working potentials. However, massive volume changes and low intrinsic electric conductivity remain substantial challenges that limit the practical applications of these anodes in lithium‐ion batteries (LIBs). In this study, cobalt‐doped silicon nanoparticles with different Co concentrations (0.1 %, 0.3 %, and 0.5 %) are prepared by using a simple low‐temperature annealing process and are studied as anodes for LIBs. Compared to pure silicon, the obtained 0.5 % cobalt‐doped silicon anode can serve as a promising anode and shows a high discharge capacity of 3409 mAh g −1 (97.2 % capacity retention vs. first reversible capacity) with 98.1 % coulombic efficiency after 40 cycles, at 200 mA g −1 . After a long 320 cycles, the electrode delivered 3029 mAh g −1 with 86.4 % capacity retention. This cobalt‐doped silicon anode also exhibits superior rate capability and a highly stable long cycle life at higher current densities as well as high mass loading. These remarkable enhancements in electrochemical properties indicate that cobalt doping yields increased conductivity, mitigates volume expansion, and provides shorter lithium transportation lengths across the silicon nanoparticles.