Zhao Bing, Li Bobo, Wang Zhixuan, Xu Chuxiong, Liu Xiaoyu, Yi Jin, Jiang Yong, Li Wenxian, Li Ying, Zhang Jiujun
School of Environmental and Chemical Engineering, Shanghai University, Shanghai 200444, China.
Institute for Sustainable Energy/College of Sciences, Shanghai University, Shanghai 200444, China.
ACS Appl Mater Interfaces. 2020 Apr 29;12(17):19530-19538. doi: 10.1021/acsami.0c02153. Epub 2020 Apr 16.
The nonuniform nucleation of lithium (Li) leads to dendritic behavior and formation of dead Li, which seriously hinders the practical application of Li metal batteries. Here, atomic layer deposition (ALD) is used to deposit uniform and conformal ZnO coating (at a low content of 5.96%) on carbon fibers to form a free-standing framework Li host material without uncontrollable dendrites. Compared with the liquid deposition process, the ALD method can achieve homogeneous and conformal ZnO coating and excellent lithiophilicity of the carbon fiber, guiding molten Li infusion into the carbon fiber skeleton to obtain the Li/C composite electrode with a flat surface, thereby minimizing the effective current density. More importantly, the converted LiZn alloy will serve as uniform and numerous nucleation sites for Li and guide synchronous growth of the Li metal along carbon fibers, displaying a dendrite-free morphology after large-current and long-term deposition/dissolution cycling. Therefore, the ALD ZnO-modified carbon fiber/Li exhibits significantly better cycle and rate performances than the liquid deposition ZnO-modified carbon fiber/Li composite anode. The electrodes display an ultralong lifespan up to 400 cycles at 3.0 mA/cm, as well as a high rate performance (with a deposition overpotential of 338 mV at 25.0 mA/cm) at a high Li deposition areal capacity of 5.0 mA h cm.
锂（Li）的非均匀成核会导致枝晶行为并形成死锂，这严重阻碍了锂金属电池的实际应用。在此，采用原子层沉积（ALD）在碳纤维上沉积均匀且保形的ZnO涂层（含量低至5.96%），以形成无不可控枝晶的独立框架锂主体材料。与液相沉积工艺相比，ALD方法能够实现均匀且保形的ZnO涂层以及碳纤维优异的亲锂性，引导熔融锂注入碳纤维骨架，从而获得表面平整的Li/C复合电极，进而使有效电流密度最小化。更重要的是，转化后的LiZn合金将作为锂均匀且众多的成核位点，并引导锂金属沿碳纤维同步生长，在大电流和长期沉积/溶解循环后呈现无枝晶形态。因此，ALD ZnO改性的碳纤维/Li比液相沉积ZnO改性的碳纤维/Li复合负极表现出明显更好的循环和倍率性能。这些电极在3.0 mA/cm下具有长达400次循环的超长寿命，以及在5.0 mA h cm的高锂沉积面积容量下的高倍率性能（在25.0 mA/cm下沉积过电位为338 mV）。
