Ionic transport regulation separator co-functionalized by conductive nanoparticles and nonconductive nanorods for high performance lithium battery

Abstract

Endowing the separator with the ionic transport regulation capacity is one of the most effective approaches to tackle the lithium dendrite problem and enhance the battery performance. Based on the mechanism of promoting lithium ions to homogenously deposit, we develop a functionalized separator (PAW) that can simultaneously immobilize the anions and lessen cation solvation, by facilely blade-coating a polyolefin separator with a mixture of nonconductive attapulgite (ATP) nanorods and conductive tungsten trioxide (WO₃) spherical nanoparticles. The composite separator has a higher porosity for electrolyte filling than the pure separator, and its electrolyte wettability and thermal stability are significantly improved by combining the advantages of the two inorganic nanoparticles. More importantly, the hybrid coating is able to modulate ionic transport, allowing lithium ions to rapidly pass through by adsorbing anions on the hydroxyl group of ATP and reducing the desolvation of lithium ions that primarily originates from the oxygen vacancies of WO₃. Meanwhile, the uniform dispersion of conductive particles permits a consistent current distribution, which, in conjunction with controlled ionic transport, helps to prevent dendrite formation in the lithium anode. Consequently, the Li//Li cell assembled with the functional separator presents highly stable Li plating/stripping cycles for 800 h at 2 mA cm⁻², and the Li//LiFePO₄ cell displays excellent cycle stability with a capacity retention of 74 % after 1000 cycles at 5C, suggesting the potential of the functional separator as a competitive candidate for lithium batteries.