Titanium-Polyoxometalate Crosslinked Metallo-Supramolecular Polymer as Artificial Interfacial Layer for Highly Persistent and Low-Temperature Tolerant Lithium Metal Batteries.

Abstract

The uncontrolled lithium (Li) dendrite growth and fragile native solid electrolyte interphase formation have severely hindered the practical development of Li metal batteries. Herein, a coordinatively cross-linked metallo-supramolecular polymer as anodic interfacial protective layer (MSP-IPL) is developed by utilizing titanium(IV)-polyoxometalates (Ti-POMs) as hexatopic linkers to bridge organic and inorganic moieties. The constructed MSP-IPL possesses high electrochemical stability, superior ion-transfer ability, and good air stability. Due to its high film formation uniformity and mechanical tenacity, the MSP-IPL can effectively avoid non-uniform Li deposition caused by the tip effect, thus inhibiting Li dendrite proliferation. The uniformly distributed Ti-POMs in polymer skeleton can efficiently bind with PF6- anions, thus increasing Li+ transference number and promoting homogeneous Li+ distribution. The re-processability and self-healing ability endowed by dynamic coordination bonds enable the MSP-IPL to accommodate electrode volume changes and maintain good interface contact. Consequently, high-loading Li||LiFePO4 and Li||LiNi0.8Co0.1Mn0.1O2 batteries based on MSP-IPL-coated Li anodes demonstrate impressive cyclability and extraordinary rate capability. Even at a low temperature of -20 °C, the MSP-IPL-coated Li||NCM811 batteries can still cycle stably for over 500 cycles (equivalent to 138 days) with a considerable capacity retention of 86.8%. This work presents a promising solution for developing practical low-temperature Li metal batteries.