Hierarchical Co3O4 Nanofiber-Carbon Sheet Skeleton with Superior Na/Li-Philic Property Enabling Highly Stable Alkali Metal Batteries
Hierarchical Co3O4 Nanofiber-Carbon Sheet Skeleton with Superior Na/Li-Philic Property Enabling Highly Stable Alkali Metal Batteries
复制标题
多级Co3O4纳米纤维-碳片骨架具有优异的亲Na/Li特性，可实现高度稳定的碱金属电池
DOI：
10.1002/adfm.201808847
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发表时间：
2019-05-09
影响因子：
19
通讯作者：
Lu, Yingying
中科院分区：
文献类型：
--
作者：
Li, Siyuan;Liu, Qilei;Lu, Yingying
碱金属负极中的枝晶行为和无限体积膨胀导致高能电池存在严重的安全隐患和使用寿命短的问题。构建具有优良的亲钠/亲锂性能的稳定宿主是实现商业化的前提。证明了金属氧化物(Co3O4、SnO2、CuO)与碱金属反应中的小Gibbs自由能变化是金属注入的关键。所制备的层次化Co3O4纳米纤维-碳片(CS)骨架对熔融的Li/Na具有更好的润湿性。3D碳片作为主要骨架，为快速电荷转移提供了足够的锂成核位置和足够的电解液/电极接触。通过COMSOL多物理模拟验证，Co/Li2O纳米纤维的二级骨架对沉积的Li提供了物理限制，并进一步将Li+通量重新分布在每根碳纤维上。由于均匀的沉积行为和近零的体积变化，改进的对称型Li/Li电池可以在20 mA cm(-2)的超高电流密度下工作120次以上。当与LiFePO4阴极配对时，Li/Co-CS电池表现出低极化，在2C循环200次后容量保持率为88.4%。采用NaClO4基电解液的Na/Co-CS对称电池的容量也得到了令人信服的改善。这些结果表明，在开发安全稳定的碱金属电池方面有了显著的进步。
Uncontrollable dendritic behavior and infinite volume expansion in alkali metal anode results in the severe safety hazards and short lifespan for high-energy batteries. Constructing a stable host with superior Na/Li-philic properties is a prerequisite for commercialization. Here, it is demonstrated that the small Gibbs free energy change in the reaction between metal oxide (Co3O4, SnO2, and CuO) and alkali metal is key for metal infusion. The as-prepared hierarchical Co3O4 nanofiber-carbon sheet (CS) skeleton shows improved wettability toward molten Li/Na. The 3D carbon sheet serves as a primary framework, offering adequate lithium nucleation sites and sufficient electrolyte/electrode contact for fast charge transfer. The secondary framework of Co/Li2O nanofibers provides physical confinement of deposited Li and further redistributes the Li+ flux on each carbon fiber, which is verified by COMSOL Multiphysics simulations. Due to the uniform deposition behavior and near-zero volume change, modified symmetrical Li/Li cells can operate under an ultrahigh current density of 20 mA cm(-2) for more than 120 cycles. When paired with LiFePO4 cathodes, the Li/Co-CS cell shows low polarization and 88.4% capacity retention after 200 cycles under 2 C. Convincing improvement can also be observed in Na/Co-CS symmetrical cells applying NaClO4-based electrolyte. These results illustrate a significant improvement in developing safe and stable alkali metal batteries.