Lithium/Boron Co-doped Micrometer SiO_x as Promising Anode Materials for High-Energy-Density Li-Ion Batteries

The carbon-coated silicon monoxide (SiOx@C) has been considered as one of the most promising high-capacity anodes for the next-generation high-energy-density lithium-ion batteries (LIBs). However, the relatively low initial Coulombic efficiency (ICE) and the still existing huge volume expansion during repeated lithiation/delithiation cycling remain the greatest challenges to its practical application. Here, we developed a lithium and boron (Li/B) co-doping strategy to efficiently enhance the ICE and alleviate the volume expansion or pulverization of SiOx@C anodes. The in situ generated Li silicates (LixSiOy) by Li doping will reduce the active Li loss during the initial cycling and enhance the ICE of SiOx@C anodes. Meanwhile, B doping works to promote the Li+ diffusion and strengthen the internal bonding networks within SiOx@C, enhancing its resistance to cracking and pulverization during cycling. As a result, the enhanced ICE (83.28%), suppressed volume expansion, and greatly improved cycling (85.4% capacity retention after 200 cycles) and rate performance could be achieved for the Li/B co-doped SiOx@C (Li/B-SiOx@C) anodes. Especially, the Li/B-SiOx@C and graphite composite anodes with a capacity of 531.5 mA h g–1 were demonstrated to show an ICE of 90.1% and superior cycling stability (90.1% capacity retention after 250 cycles), which is significant for the practical application of high-energy-density LIBs.