Department of Materials Science and Engineering, Stanford University, Stanford, CA, USA.
Department of Electrical Engineering, Stanford University, Stanford, CA, USA.
Nature. 2021 Dec;600(7890):659-663. doi: 10.1038/s41586-021-04168-w. Epub 2021 Dec 22.
The increasing demand for next-generation energy storage systems necessitates the development of high-performance lithium batteries. Unfortunately, current Li anodes exhibit rapid capacity decay and a short cycle life, owing to the continuous generation of solid electrolyte interface and isolated Li (i-Li). The formation of i-Li during the nonuniform dissolution of Li dendrites leads to a substantial capacity loss in lithium batteries under most testing conditions. Because i-Li loses electrical connection with the current collector, it has been considered electrochemically inactive or 'dead' in batteries. Contradicting this commonly accepted presumption, here we show that i-Li is highly responsive to battery operations, owing to its dynamic polarization to the electric field in the electrolyte. Simultaneous Li deposition and dissolution occurs on two ends of the i-Li, leading to its spatial progression toward the cathode (anode) during charge (discharge). Revealed by our simulation results, the progression rate of i-Li is mainly affected by its length, orientation and the applied current density. Moreover, we successfully demonstrate the recovery of i-Li in Cu-Li cells with >100% Coulombic efficiency and realize LiNiMnCoO (NMC)-Li full cells with extended cycle life.
由于下一代储能系统的需求不断增加，因此需要开发高性能的锂电池。不幸的是，由于固态电解质界面（SEI）和孤立锂（i-Li）的不断产生，目前的 Li 阳极表现出快速的容量衰减和较短的循环寿命。在锂枝晶不均匀溶解过程中形成的 i-Li，会导致在大多数测试条件下锂电池的容量损失。由于 i-Li 与集流器失去电连接，因此在电池中被认为是电化学惰性的或“死”的。与这一普遍接受的假设相反，我们在这里表明，由于其对电解质中电场的动态极化，i-Li 对电池的运行非常敏感。在 i-Li 的两端同时发生 Li 的沉积和溶解，导致其在充电（放电）期间向阴极（阳极）空间推进。我们的模拟结果表明，i-Li 的推进速度主要受其长度、取向和施加的电流密度的影响。此外，我们还成功地证明了在 Cu-Li 电池中恢复 i-Li 的可行性，实现了具有延长循环寿命的 LiNiMnCoO（NMC）-Li 全电池。
