三维石墨烯包封石墨的储锂性能研究

Modification of Three-Dimensional Graphene Wrapped Graphite on Lithium Storage Performance

石墨由于价格低廉、电压平台稳定以及质量比容量高[372(mA·h)/g]等优势,在锂离子电池领域已被广泛应用,但其存在振实密度较低和循环稳定性较差等不足。利用石墨和氧化石墨烯进行水热反应获得水凝胶,通过石墨烯的毛细收缩和静电自组装原理,获得具有致密结构的石墨烯包封石墨复合块体(石墨@石墨烯),使粉末石墨的振实密度从1.2 g/cm^(3)提高到1.7 g/cm^(3)。与石墨相比,石墨烯构筑的致密三维导电网络结构具有更优异的电化学循环稳定性和倍率性能。在0.01~2.00 V测试电压区间,石墨在0.5 A/g倍率下,经过100圈循环后放电比容量仅保持在227.4(mA·h)/g,容量保持率仅为64.1%;而石墨@石墨烯复合材料的容量保持在353.9(mA·h)/g,维持了98%的高容量保持率。证明石墨烯包封石墨可以有效提高石墨的振实密度以及长循环稳定性。

Graphite has been widely used in the field of lithium-ion batteries(LIBs)because of its low price,stable voltage platform,and high specific capacity[372(mA·h)/g)].However,it suffers from the issues of low tap density and poor cycle stability.In this work,a graphene wrapped graphite(Graphite@graphene)compact monolith with dense structure was obtained by a hydrothermal method based on the principle of capillary shrinkage and electrostatic self-assembly of graphene.After graphene wrapping,the tap density of graphite powders increased from 1.2 g/cm^(3)to 1.7 g/cm^(3).More importantly,the three-dimensional(3D)dense conductive network structure constructed by graphene endowed the Graphite@graphene monolith material with better electrochemical cycle stability and rate performance than that of pristine graphite.In the test voltage range of 0.01-2.00 V,the Graphite@graphene monolith presented an initial discharge capacity of 353.9(mA·h)/g and maintained a high capacity retention rate of 98%after 100 cycles at 0.5 A/g.While the pristine graphite anode only kept at 227.4(m A·h)/g with 64.1%capacity retention.It proved that the 3D graphene wrapped graphite structure can effectively improve the tap density and electrochemical properties of pristine graphite anode.