液态金属三维导电网络连通的SiOx负极研究

随着各领域对电池能量密度的需求不断提高，锂离子电池中传统的石墨负极因比容量低越来越难以满足需求。比容量大的硅基负极，则因为在嵌锂过程中体积膨胀太大而无法使用。而硅氧材料由于低于纯硅的膨胀效应，更具有实现电池长循环，高负载的潜力。为了加快硅氧基动力电池的产业化和提升其电化学性能，深入研究硅氧基负极存在的关键问题和应对策略尤为重要。

将液态金属引入硅氧基负极可以显著改善硅氧材料带来的膨胀效果，稳定SEI结构。本论文采用Ga:Sn为9:1比例的液态金属原料引入到SiO_x材料中，经过优化两者的混合比例，利用简单的超声分散技术，制备了液态金属与SiO_x的复合粉末。并将复合活性物质制备成电极，其电池表现出优异的电化学性能。

制备出的不同液态金属比例的复合电极中，液态金属占比为50%表现出最佳的电池性能。复合电极在0.4 mg cm^-2负载时，在0.5 C倍率电流下循环200圈和300圈容量保持率分别达到了83.19%和63.27%，在1 C倍率电流下循环200圈和300圈的容量保持率分别达到了96.50%和76.65%。此性能明显优于纯硅氧材料与添加了10%导电剂的硅氧材料。另外通过倍率性能测试表明，复合电极在高倍率电流情况下依旧能发挥出稳定容量，其容量回复率达到了100.06%。最后对复合电极进行了循环伏安测试与交流阻抗测试，显示出复合电极稳定的可逆性。

本文将循环不同圈数的复合电极进行电池拆解，用SEM与TEM表征了电极中的复合粉末结构变化。发现纳米级液态金属液滴在循环过程中可自发形成三维导电网络，后续还对复合电极进行了原位XRD测试，显示了复合电极材料在循环过程中材料成分的原位变化。揭示了液态金属在电极中的作用机理，为硅氧复合负极的设计、制备、应用提供了理论指导与实践基础。

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