Lithium Storage Characteristics and Possible Applications of Graphene Materials

Abstract

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. LiFePO 4 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.

Tin-based materials supported on nitrogen-doped reduced graphene oxide towards their application in lithium-ion batteries

“…5e, illustration of the SnS 2 molecular structure) could buffer the volume change and improve the cycling stability of the electrodes. 34,35 To investigate the effect of N-rGO on the electrochemical performance of the composites, we undertook electrical tests using different samples. According to the elemental analysis of EDS (Table S1 †), it can be seen that the amount of N-rGO was lower than 3 wt% in the three composites; therefore, the Snbased materials still acted as the major active electrode material in our experiments.…”

Graphene‐Based Materials for Lithium‐Ion Hybrid Supercapacitors

“…Graphene has high theoretical surface area and a porous structure, excellent electrical conductivity, high chemical and thermal stability, and high mechanical strength, which make it a competitive candidate for energy‐storage applications . However, the excellent properties of graphene are based on its nanoscale structure, and bulk graphene always suffer from aggregation and restacking, which result in a much lower SSA than the theoretical value.…”

All Graphene Lithium Ion Capacitor with High-Energy-Power Density Performance

“…图 2c 是 3DG 基负极半电池在 0.01～3.0 V 电压区 间内的充放电曲线. 可以看到, 与石墨的脱嵌锂曲线主 要在低电压区间不同, 在整个充放电区间内 3DG 都没 有明显的平台 [28] , 与 CV 图一致(图 S3b). 另外, 在 0.1 A/g 电流密度下, 3DG 基负极扣式半电池的容量可达 620 mAh/g, 显著大于石墨的理论容量, 首次放电容量 更是高达 1500 mAh/g.…”