科研之友
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摘要
We report on the formation of composite silicon-based multiphase nanopowders as promising active-anode materials for highenergy-density, high-capacity-retention lithium-ion batteries. Simple synthetic routes have been developed for the preparation of core-shell Si and p-doped SiNi composite particles attached to carbon nanotubes. The particles were characterized by a variety of analytical and electrochemical methods. Environmental scanning-electron-microscopy and transmission-electron-microscopy images and electron-energy-loss-spectroscopy maps indicated formation of nanoparticles wrapped by carbon nanotubes and coated by nanometer-thick amorphous carbon. It was found that nickel diffuses to the bulk of silicon and forms either nickel-rich or nickel-depleted composite entities. The presence of boron in the synthesized composite powder has been detected by time-of-flight secondary-ion mass spectroscopy (TOFSIMS). Li/LiPE6 EC:DEC/Si-C-MWCNT cells with anodes composed of about 80% coreshell Si-C composite (36% Si in the anode) ran for more than 1000 cycles with a degradation rate of 0.07'k/cycle (beginning from cycle 25). The SiNi/MWCNT composite anode revealed a remarkably higher capacity-retention rate at initial cycles and higher C-rate capability. Li/SiNi/MVVCNT cells ran for about 250 cycles demonstrating a reversible capacity of about 620 mAh/g(Si) at 120 mu A/cm(2) and cycle 210, and 800 mu Ah/gsi at 50 mu A/cm(2) at cycle 240.
- 出版日期2015
