碳纳米管提升氧化亚硅负极稳定性的起源

Origin of enhanced stability of SiO anode via using carbon nanotubes

高容量的SiO (SO)合金基材料是最有希望的下一代锂离子电池负极之一.使用碳纳米管(CNTs)导电添加剂,虽然可以有效地解决SO较差的循环寿命这一难题,然而除了动力学因素之外,其它潜在的作用机理目前仍不明确.在本工作中,一系列的测试结果表明CNTs可以使电极在循环后依然维持完整的导电网络,确保均匀的电化学反应.CNTs也使得电极局部的体积膨胀得到了抑制,从而避免了固态电解质界面的不断生长,活性材料从集流体剥离,甚至析锂.得益于CNTs的上述作用, SO-CNTs负极在0.5 C (1 C=1600 mA g^(-1))下可以稳定循环200次,其容量保持率为96.2%. CNTs的作用机理也进一步地在商业化的SO/石墨复合负极(SO650-CNTs, 1 C=650 mA g^(-1))中得到了验证,SO650-CNTs在1 C下循环400次后容量保持率为80.6%.本工作为导电添加剂的作用机理提出了新的见解,并将有助于加速合金类负极的商业化进程.

High-capacity SiO(SO)-based alloys are among the most promising anodes for next-generation lithium-ion batteries(LIBs).Challenges of SO-based anodes,including sluggish kinetics and poor stability,have been effectively mitigated by using carbon nanotubes(CNTs)as conductive additives.However,the underlying mechanism,apart from kinetics,remains elusive.Herein,we find that CNTs can help to maintain complete conductive networks of electrodes after cycling,ensuring uniform lithiation reaction.The alleviated local extra-huge volume expansion of SO will further suppress continuous solid-state interphase growth,active material delamination from the current collector,and even lithium plating.Accordingly,pure SO anode with CNTs(SO-CNTs)can cycle stably with the capacity retention of 96.2%over 200 cycles at 0.5 C(1 C=1600 mA g^(-1)).The function of CNTs is further proved in practical SO/graphite(SO650-CNTs,1 C=650 mA g^(-1))anode with a high capacity retention of 80.6%over 400 cycles at 1 C.This work provides a new perspective on the functional mechanism of conductive additives,and will accelerate the commercialization of alloy anodes in the battery industry.