天然石墨负极的氧化改性

Oxidative modification of natural graphite for use as the anode of a lithium ion battery

针对天然石墨负极的脱嵌锂过程中体积效应和表面活性基团的不利影响,通过硫酸(98%)-双氧水(30%)(1∶1 v/v)氧化和900℃高温煅烧3 h处理制备石墨插层化合物中间体和适度膨胀的石墨样品以改善其倍率和循环寿命。结果表明,膨胀石墨样品石墨层剥离,平均晶粒尺寸从26.8 nm增大至35.2 nm;改性后的石墨样品其倍率性能和循环稳定性均得到明显改善,改性后第50周的容量保持率由45.7%提高到81.3%。

Natural graphite was modified by oxidation with a mixture of sulfuric acid （98％） and hydrogen peroxide （30％） with a volume ratio of 1 ∶ 1,followed by a heat treatment under argon at 900 ℃ for 3 h to overcome its disadvantages of the presence of active surface groups and volume changes produced by the intercalation/deintercalation of Li ions.Results showed that the graphitic layers of the expanded graphite were exfoliated and grain size increased from 26.8 to 35.2 nm after the modification.Constant current charging-discharging and cyclic voltammetry indicated that its high rate performance and cyclic stability were improved.The capacity retention ratio increased from 45.7％ for the natural graphite to 81.3％ for the modified one in the 50th cycle.