Enhanced Capacity and Cyclability of Si@NiSi2 Nanocomposite Anodes Fabricated by Facile Electroless Ni Plating

Although silicon (Si) has been proposed as the most promising anode material in lithium-ion batteries due to their high capacity (similar to 4000 mA h g-1), the poor cyclability resulting from the strain-induced pulverization caused by the severe volume change during charge/discharge hinders the industrial applications. Here, Si nanoparticles were conformally coated with either Ni, NiO, or NiSi2 to suppress the tremendous volume change of Si, hence leading to prolonging the cycle life of the Si anode to a different degree. Both Si@Ni and Si@NiO nanocomposites were synthesized by one-step self-reducing (SR) electroless nickel plating without/with heat treatment, respectively, whereas Si@NiSi2 nanocomposites were obtained by a two-step (SR + electroless nickel deposition, EN) process, followed by heat treatment. Among all these three nanocomposite anodes, Si@NiSi2 prepared by 5 min of SR, 30 min of EN, and 400 degrees C annealing in sequence achieved the highest capacity of similar to 1390 mA h g-1 and the best capacity retention of similar to 86.6% with a Coulombic efficiency of 99% over 70 cycles. For comparison, the capacity retention of the Si@Ni and Si@NiO electrode over 70 cycles is estimated to be similar to 67 and 75%, respectively. These results suggest that NiSi2 could be a promising protective coating layer to effectively buffer the volume change of Si and promote the battery life.