摘要
由于石墨烯材料独特的性质,其在锂离子电池材料方面显示出潜在的应用前景.深入理解石墨烯材料的储锂行为,对于其在储能领域的应用具有极为重要的意义.石墨烯材料作为负极材料具有与低温软炭材料类似的充放电特征.无序度或比表面积高的热还原石墨烯材料具有相对更高的可逆储锂容量.石墨烯材料中大量的微孔缺陷能够提高可逆储锂容量,但同时也会造成电压滞后及容量衰减.石墨烯材料作为锂电池正极材料,其电化学性能主要来源于表面含氧官能团与锂离子在高电位下的可逆氧化还原反应,且不可逆容量较低.利用石墨烯负极高容量与石墨烯正极高倍率放电的特性,可以设计出具有高能量密度的锂离子电容器和高比容量的石墨烯复合锂电池正极材料.
Graphene materials are materials with a flat mono/few layer of carbon atoms tightly packed to a two-dimensional honeycomb lattice. Graphene materials are expected to be applied in lithium ion batteries due to their unique structural, mechanical and electrical properties. As an anode material, the charge/discharge characteristics of graphene materials is similar to those of low-temperature soft carbon materials, such as high capacity, low initial efficiency and large voltage hysteresis. Although attractive results have been achieved for graphene as anode materials for LIBs, detailed lithium storage mechanisms are still not clear. The effects of the following several structural parameters including disorder degree, surface area, micropores, interlayer spacing, C/O ratio and layer number on the lithium storage properties are discussed. Thermally reduced graphene materials with a highly disordered structure and high surface area has exceptionally high reversible capacity. Micropores in graphene materials have a great impact on their electrochemical performance. Although these micropores can provide additional sites for increased reversible lithium storage, it can also results in severe capacity fading and voltage hysteresis. Oxygen functional groups and larger interlayer spacing may provide higher reversible capacity of graphene, but the micropores and defect-based reversible storage may be the main contribution. Effect of layer number on lithium storage mechanisms of graphene and the conclusion are still in debate. Graphene with rich oxygen functional groups is a promising cathode material with high capacity and rate performance for lithium storage. High specific capacity of graphene cathode is mainly ascribed to lithiation reaction of oxygen functional groups, such as epoxide and carbonyl groups. Lithiation of oxygen functional groups still requires further study for a full understanding. Based on the lithium storage characteristics of graphene anode and cathode, lithium ion capacitors with high energy density and graphene composite cathode materials for lithium ion batteries may be designed and developed in the future. Graphene based lithium ion capacitors facilitate the reversible lithium storage, which significantly improves the energy density of lithium ion capacitors compared to those of conventional systems based on activated carbon. LiFePO4 modified with graphene layers has reached 208 mAh/g in specific capacity. The excess capacity is attributed to the reversible reduction-oxidation reaction between the lithium ions of the electrolyte and the exfoliated graphene flakes.
出处
《化学学报》
SCIE
CAS
CSCD
北大核心
2014年第3期333-344,共12页
Acta Chimica Sinica
基金
国家自然科学基金(Nos.51172242,51221264)
中国科学院战略性先导科技专项(No.XDA01020304)资助~~
关键词
石墨烯
储锂机制
正极材料
负极材料
锂离子电池
graphene
lithium storage mechanism
cathode material
anode material
lithium ion battery
作者简介
闻雷，2004年在东北大学获得博士学位，2004至2006年在北京大学化学与分子工程学院做博士后研究，出站后就职于中国科学院金属研究所，研究领域为石墨烯和碳纳米管等新型炭材料在储能材料及器件中的应用．
E—mail：fli@imr．ac．cn李峰，2001年中国科学院金属所获得博士学位，随后在中国科学院金属研究所从事电化学能量储存与转换用碳基纳米材料及相关器件的制备和应用研究．在高性能超级电容器、锂硫电池和锂离子电池用碳基纳米电极材料、柔性电极材料及新型储能器件的设计等方面取得了多项创新性成果，并实现部分成果的转化．现已在国际刊物Angew．Chemie，Energy＆Environmental Science，Adv．Mater．，Adv．Funct．Mater．，ACS Nano等杂志发表论文160余篇，引用超过6000次．
