2D Zn(Bim)OAc MOF functionalized polyacrylonitrile composite separator for Li⁺ redistribution to achieve dendrite-free lithium metal batteries

The dendrite formation and growth during Li plating/stripping process, as well as the reduced coulomb efficiency, result in a shortened cycle life of lithium metal batterie (LMB), restricting its commercial application. 2D Zn(Bim)OAc MOF functionalized polyacrylonitrile (Zn(Bim)OAc-PAN) composite separator with regulating Li⁺ flux and increasing Li⁺ migration number was successfully prepared by electrospinning combined with vacuum filtration technology. The introduction of Zn(Bim)OAc nanosheets can fix the anion, improve the ionic conductivity (2.13 mS/cm) and Li⁺ migration number (0.67). Meanwhile, the pores on Zn(Bim)OAc nanosheets and the nanofluid channels between the stacked nanosheets synergistically construct a micro/nano pore structure, reducing the pore size, resulting in uniform Li⁺ flux distribution and promoting uniform Li⁺ deposition on the lithium metal surface. Therefore, as-prepared Zn(Bim)OAc-PAN separator assembled Li|LiFePO₄ cells can also exhibit higher initial capacity (146.6 mA·h/g) and better cycle stability (96.3% capacity retention after 300 cycles) at 2 C. Besides, as-prepared Zn(Bim)OAc-PAN separator based Li|Li achieves a stable cycle up to 1000 h under 1 mA/cm², and there was no obvious lithium dendrite growth on the Li anode surface after cycling. The reported approach provides a feasible strategy to improve the LMB performance by regulating the Li⁺ flux through separators.