Functional Polymers as Artificial Solid Electrolyte Interfaces for Stabilizing Lithium Metal Anode.

The practical implementation of the lithium metal anode (LMA) has long been pursued due to its extremely high specific capacity and low electrochemical equilibrium potential. However, the unstable interfaces resulting from lithium ultrahigh reactivity have significantly hindered the use of LMA. This instability directly leads to dendrite growth behavior, dead lithium, low Coulombic efficiency, and even safety concerns. Therefore, artificial solid electrolyte interfaces (ASEI) with enhanced physicochemical and electrochemistry properties have been explored to stabilize LMA. Polymer materials, with their flexible structures and multiple functional groups, offer a promising way for structurally designing ASEIs to address the challenges faced by LMA. This Concept demonstrates an overview of polymer ASEIs with different functionalities, such as providing uniform lithium ion and single-ion transportation, inhibiting side reactions, possessing self-healing ability, and improving air stability. Furthermore, challenges and prospects for the future application of polymeric ASEIs in commercial lithium metal batteries (LMBs) are also discussed.

Stabilizing Lithium Metal Batteries by Synergistic Effect of High Ionic Transfer Separator and Lithium-Boron Composite Material Anode.

The development of lithium (Li) metal batteries (LMBs) has been limited by problems, such as severe dendrite growth, drastic interfacial reactions, and large volume change. Herein, an LMB (8AP@LiB) combining agraphene oxide-poly(ethylene oxide) (PEO) functionalized polypropylene separator (8AP) with a lithium-boron (LiB) anode is designed to overcome these problems. Raman results demonstrate that the PEO chain on 8AP can influence the Li+ solvation structure in the electrolyte, resulting in Li+ homogeneous diffusion and Li+ deposition barrier reduction. 8AP exhibits good ionic conductivity (4.9 × 10-4 S cm-1), a high Li+ migration number (0.88), and a significant electrolyte uptake (293%). The 3D LiB skeleton can significantly reduce the anode volume changes and local current density during the charging/discharging process. Therefore, 8AP@LiB effectively regulates the Li+ flux and promotes the uniform Li deposition without dendrites. The Li||Li symmetrical cells of 8AP@LiB exhibit a high electrochemical stability of up to 1000 h at 1 mA cm-2 and 5 mAh cm-2. Importantly, the Li||LiFePO4 full cells of 8AP@LiB achieve an impressive 2000 cycles at 2C, while maintaining a high-capacity retention of 86%. The synergistic effect of the functionalized separator and LiB anode might provide a direction for the development of high-performance LMBs.

Reactive Polymer as Artificial Solid Electrolyte Interface for Stable Lithium Metal Batteries.

Lithium (Li) metal anodes have the highest theoretical capacity and lowest electrochemical potential making them ideal for Li metal batteries (LMBs). However, Li dendrite formation on the anode impedes the proper discharge capacity and practical cycle life of LMBs, particularly in carbonate electrolytes. Herein, we developed a reactive alternative polymer named P(St-MaI) containing carboxylic acid and cyclic ether moieties which would in situ form artificial polymeric solid electrolyte interface (SEI) with Li. This SEI can accommodate volume changes and maintain good interfacial contact. The presence of carboxylic acid and cyclic ether pendant groups greatly contribute to the induction of uniform Li ion deposition. In addition, the presence of benzyl rings makes the polymer have a certain mechanical strength and plays a key role in inhibiting the growth of Li dendrites. As a result, the symmetric Li||Li cell with P(St-MaI)@Li layer can stably cycle for over 900 h under 1 mA cm-2 without polarization voltage increasing, while their Li||LiFePO4 full batteries maintain high capacity retention of 96 % after 930 cycles at 1C in carbonate electrolytes. The innovative strategy of artificial SEI is broadly applicable in designing new materials to inhibit Li dendrite growth on Li metal anodes.