Ion Flux Regulation through PTFE Nanospheres Impregnated in Glass Fiber Separators for Long-Lived Lithium and Sodium Metal Batteries

摘要

Practical implementation of alkali metal batteries currently still facesformidable challenges because of the dendrite growth upon continuouscharge/discharge processes and the associated unstable solid–electrolyteinterphase. Herein, it is reported that dendrites can be fundamentallymitigated in lithium and sodium metal batteries by regulating the Li+ andNa~+ flux using a glass fiber (GF) separator impregnated withpolytetrafluoroethylene nanospheres (PTFE-NSs), which results inhomogeneous deposition of Li and Na during charging. The COMSOLMultiphysics simulations reveal that the introduction of negatively chargedPTFE-NSs into the GF separator enhances the local electric field near theanode, thereby boosting the transfer of cations. It is demonstrated that Li//Liand Na//Na symmetric cells utilising a PTFE-GF separator show outstandingcycle stability of 1245 and 2750 h, respectively, at 0.5 mA cm~（?2）. Moreover, theLi//LiFePO_4 and Na//Na_3V_2(PO_4)_2F_3 full cells exhibit remarkably improvedcapacity retention when cycled at 1 C, in the presence of a PTFE-GF separator.The nuclear magnetic resonance spectroscopy studies suggest that theimpregnation of PTFE-NSs into GF helps “liberate” more Li+ and Na+ andchanges the coordination interaction between ions and solvents, contributingto the enhanced electrochemical performance.