直流电弧等离子体下共蒸发无定型TiO_(2)基纳米复合材料及储锂性能

Co-evaporation Synthesis in Arc Plasma of Amorphous TiO_(2)-based Nanocomposites with Stable Lithium Storage

零应变TiO_(2)由于结构稳定、安全无污染,以及循环过程中低的体积膨胀(≤4%),是一类极具潜力的锂电负极材料。但较低的理论比容量(335 mAh·g^(-1))和较小的锂离子扩散系数无法满足市场对高能量密度和快速充放电电池的需求,限制了其进一步的应用。本工作利用共蒸发混合原料(CuO+TiO_(2)粗粉)法,原位合成了核/壳型无定型二氧化钛(a.-TiO_(2))包覆的铜纳米粒子(Cu@a.-TiO_(2)NPs),通过后续热氧化处理将Cu核部分氧化为电化学活性的CuO中间包覆层,最终获得了Cu@CuO@a.-TiO_(2)纳米复合粒子(Cu@CuO@a.-TiO_(2)NCs)。结果表明,Cu@CuO@a.-TiO_(2)NCs电极的首周放电比容量为1936.1 mAh·g^(-1),200次循环后放电比容量保持在882.3 mAh·g^(-1),库伦效率为98.8%。无定型TiO_(2)壳层提供了快速的离子/电子渗透通道,促进锂离子扩散迁移,提高了电荷的传输效率;金属Cu核组元有利于提高电极整体电导率,氧化过程产生的空隙缓解了电化学活性CuO相的体积膨胀效应,从而提高了Cu@CuO@a.-TiO_(2)NCs电极整体的电化学性能。

TiO_(2)as an anode material for lithium ion batteries(LIBs)has received much attention due to its stable structure,safety and environmental benignity,as well as small volume expansion rate(≤4%)during cycling.However,the low theoretical specific capacity(335 mAh·g^(-1))and diffusion coefficient of lithium ions,which hinders its practical applications.According,the core-shell Cu@a.-TiO_(2)NPs are in situ synthesized by co-evaporation of the micron powder mixture of CuO and TiO_(2).The Cu core is oxidized into electrochemically active CuO phase that is used as the intermediate coating to obtain Cu@CuO@a.-TiO_(2)NCs.Testing results indicate that the Cu@CuO@a.-TiO_(2)NCs electrode delivers an initial discharge specific capacity of 1936.1 mAh·g^(-1).After 200 cycles,the discharge specific capacity can still maintain 882.3 mAh·g^(-1)with a coulombic efficiency of 98.8%.The amorphous TiO_(2)shell provides abundant active sites to promote the diffusion and migration of lithium ions,and thus improve the transfer efficiency of charge;metallic Cu can enhance conductivity of electrode,and the interspace generated by its oxidation can accommodate volume variation,which improves the electrochemical performances of Cu@CuO@a.-TiO_(2)NCs electrode.