A high performance lithium-selenium battery using a microporous carbon confined selenium cathode and compatible electrolyte
The rechargeable lithium-selenium (Li-Se) battery is a promising electrochemical system with higher energy density than traditional Li ion batteries. Nevertheless, the dissolution of high-order lithium selenides and the shuttle effect in electrolytes lead to a low Se utilization, inferior capacity and cycling performance. This study proposes a combination of nanostructured Se cathode materials and compatible carbonate electrolytes for promoting the performance of the Li-Se battery. The Se/MC composite nanoparticles (~35 nm) with a moderate Se content (≈51.4 wt%) were prepared by embedding Se into a metal-organic framework derived microporous carbon. The resulting Se/MC cathode exhibits significantly high rate capability and cycling stability in LiDFOB/EC-DMC-FEC electrolyte. It delivers a capacity of 511 mA h g-1Se after 1000 cycles at 5 C, with inappreciable capacity decay of 0.012% per cycle. Even at a very high rate of 20 C, a large capacity of 569 mA h g-1Se can be obtained, corresponding to a decrease of only 5.6% compared to that at 0.5 C. The impressive high rate performance is attributed to the co-effect of selenium confined in ultra-small microporous carbon particles and excellent compatibility of the electrolyte with both Li anode and selenium composite cathode.