摘要
Lithium(Li)metal anodes have the potential to stimulate the development of secondary batteries due to their high theoretical specific capacities and low redox potentials among all possible solid secondary anode compounds.However,the growth of Li dendrites during repeated Li stripping/plating processes leads to low coulombic efficiencies(CEs)and safety hazards,which significantly hinders their practical application.In this work,commercial Cu foil was modified in situ by Cu_(3)N nanowires(Cu_(3)N NWs/Cu)and used as the current collector for a Li anode.In addition to decreasing the true current density of the anode and alleviating the volume change during the cycles,Cu_(3)N reacted with Li during the initial cycle(3Li+Cu_(3)N→Li_(3)N+3Cu),which enabled the formation of a Li_(3)N-rich solid electrolyte interphase(SEI).This Li_(3)N-rich SEI with a high ionic conductivity not only boosted Li ion transport but also promoted the homogeneous deposition of Li via increased Li nucleation sites.The improvements in both mass transport and deposition dynamics restrained dendrite growth.As a result,the Cu_(3)N NWs/Cu anode had stable Li plating/stripping over 270 cycles with a high average CE of 98.6% at 1 mA cm^(-2),with Li capacities of 1 mA h cm^(-2).A long cycling lifespan of 430 cycles was achieved using a full cell with a high-load LiFePO_(4) cathode(mass loading:10 mg cm^(-2))and a Cu_(3)N NWs/Cu-Li anode(N/P=2.35),demonstrating the effectiveness and practicality of the Cu_(3)N NWs/Cu current collector in stabilizing the Li anode.
在二次电池的所有固态负极中,锂金属负极因其极高的理论比容量和极低的还原电位对促进二次电池的进一步发展具有很大的潜力.然而,锂负极在不断脱锂/嵌锂的过程中因锂枝晶的生长导致低库伦效率并存在安全隐患,严重阻碍了锂金属负极的实际应用.该研究通过化学方法在商业化的铜箔集流体表面原位修饰Cu_(3)N纳米线得到复合微结构型集流体(Cu_(3)N NWs/Cu).引入的Cu_(3)N纳米线具有三维结构,不仅可以增大集流体的比表面积、降低集流体表面的电流密度,还可以容纳锂负极在沉积/脱嵌过程中发生的体积变化.此外,在首次锂沉积的过程中,Cu_(3)N与锂金属反应生成Li_(3)N(3Li+Cu_(3)N→Li_(3)N+3Cu),可以促进稳定的富含Li_(3)N的固态电解质膜(SEI)形成.富含Li_(3)N的SEI既能增强锂离子的传输,又能给锂的沉积提供充足的形核位点,促进锂金属的均匀沉积,从而抑制了锂枝晶的生长.在锂沉积/剥离循环过程中,这种经过Cu_(3)N纳米线修饰的铜箔集流体在电流密度为1 mA cm^(-2),锂沉积量为1 mA h cm^(-2)的条件下可以稳定循环270圈,平均库伦效率为98.6%.将沉积锂金属后的Cu_(3)N NWs/Cu-Li复合负极与LiFePO_(4)正极(正极活性物质载量:10 mg cm^(-2);N/P=2.35)组装成全电池,该全电池能稳定循环430圈.研究表明经Cu_(3)N纳米线修饰的铜箔集流体在提高锂金属负极的循环稳定性方面具有良好的应用前景.
基金
supported by the National Natural Science Foundation of China(22075091)
the Natural Science Foundation of Hubei Province(2021CFA066)
the“Fundamental Research Funds for the Central Universities”(2021yjsCXCY026)。
