Construction of Co 1-x S Nanoparticles Embedding in N-Doped Amorphous Carbon@Graphene with Enhanced Li-Ion Storage.

Cobalt sulfide is deemed a promising anode material, owing to its high theoretical capacity (630 mAh g ^-1 ). Due to its low conductivity, fast energy decay, and the huge volume change during the lithiation process limits its practical application. In this work, a simple and large-scale method are developed to prepare Co _1-x S nanoparticles embedding in N-doped carbon/graphene (CSCG). At a current density of 0.2 C, the reversible discharge capacity of CSCG maintains 937 mAh g ^-1 after 200 cycles. The discharge capacity of CSCG maintains at 596 mAh g ^-1 after 500 cycles at the high current density of 2.0 C. The excellent performance of CSCG is due to its unique structural features. The addition of rGO buffered volume changes while preventing Co _1-x S from crushing/aggregating during the cycle, resulting in multiplier charge-discharge and long cycle life. The N-doped carbon provides a simple and easy way to achieve excellent performance in practical applications. Combined with density functional theory calculation, the presence of Co-vacancies(Co _1-x ) increases more active site. Moreover, N-doping carbon is beneficial to the improve adsorption energy. This work presents a simple and effective structural engineering strategy and also provides a new idea to improve the performance of Li-ion batteries.
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