石墨烯空心球的弹性缓冲效应助力高性能硅基锂离子电池

Enhanced performance of Si-based Li-ion batteries through elastic cushioning with hollow graphene shells

硅被认为是下一代锂离子电池极具潜力的负极材料.纳米硅的使用缓解了其在锂化时因体积变化引起的颗粒粉碎化.然而,团聚的硅颗粒间的相互挤压仍然会引起硅负极的迅速失效.为此,我们以弹性的石墨烯空心球为媒介在硅粒子之间引入机械缓冲空间,来灵活缓冲硅的体积变化,保持电极结构的稳定性.在锂化过程中,硅体积膨胀产生的应力通过压缩石墨烯空心球的内部空心得到了机械式的缓冲.除此之外,石墨烯空心球还减少了硅颗粒的局部团聚,有效地提高了整体电导率.基于这些优势,所设计的Si/GS电极在0.8 A g^(-1)的电流密度下循环200圈后性能仍维持在1200 mA hg^(-1)以上;在4 A g^(-1)的电流密度下,200次循环后仍可达到1025 mA h g^(-1).

Silicon(Si)is a promising anode material for next-generation Li-ion batteries.The nanometer-sized Si could alleviate the pulverization caused by large volume changes during deep cycling.However,compression between agglomerated Si particles causes Si cracking and electrode failure.Considering this,we engineered a mechanical cushioning space between Si particles via elastic hollow graphene shells(GSs)to flexibly buffer volume changes and maintain the stability of the electrode structure.The stress generated from the Si volume expansion during lithiation was mechanically buffered and gently released by compression of the hollow space of the GS.In this Si/GS composite electrode,GS also reduced the local agglomeration of Si particles and effectively improved the overall conductivity.Considering these advantages,the designed Si/GS electrode showed an enhanced cycling performance with more than 1200 mA h g^(-1) at 0.8 A g^(-1) and an excellent rate capability of 1025 mA h g^(-1) at 4 A g^(-1) after 200 cycles.