ABSTRACT
Lithium metal batteries (LMBs) are a promising candidate for next-generation energy storage devices. However, the high irreversibility and dead Li accumulation of the lithium metal anode caused by its fragile original solid electrolyte interface (SEI) seriously hinder the practical application of LMBs. Herein, a facile slurry-coating and one-step thermal fluorination reaction method is proposed to construct the 3D structural LiF-protected Li/G composite anode. The existence of a 3D LiF protection layer is convincingly confirmed and the function of the Li/G skeleton is discussed in detail. The 3D structural LiF protection layer results in superior electrochemical performance by improving the utilization of Li and suppressing the accumulation of dead Li in symmetric and full coin cells. Moreover, a 0.85 Ah pouch cell strictly following the parameters of the practical battery industry can work stably for 140 cycles with a gradual internal resistance increase. This novel Li/G composite anode indicates a promising strategy in lithium/carbon composite anodes for LMBs, and the facile thermal fluorination reaction method presented in this paper offers a new method for the construction of a 3D structural protection layer for lithium metal anodes.
ABSTRACT
The fragile electrolyte/Li interface is responsible for the long-lasting consumption of Li resources and fast failure of Li metal batteries. The polymer artificial interface with high mechanical flexibility is a promising candidate to maintain the stability of the electrolyte/Li interface; however, sluggish Li-ion transportation of the conventional polymer interface hinders the application. In this work, Li-functionalized graphene oxide (GO-ADP-Li3), which is synthesized by covalent grafting of adenosine 5'-diphosphate lithium on GO nanosheets, is used as a functional additive to improve the Li-ion conductivity of the polymer artificial interface based on PVDF-HFP/LiTFSI. The enhanced Li-ion conductivity is contributed by accelerated Li-ion hopping at the surface between polymer chains and functionalized GO as well as the reduced crystallization degree of PVDF-HFP by this novel additive. The use of this modified polymer as an artificial interface on Li foil enables highly reversible Li stripping/plating and a high capacity retention of 78.4% after 150 cycles for a 0.2 A h Li metal pouch cell (Li/NCM811, strictly following practical conditions). This Li-grafted strategy on GO sheets provides an alternative for designing a compatible electrolyte/Li interface for practical Li metal batteries.
ABSTRACT
Using a coating layer to modify the separator in a practical Li metal battery has attracted wide attention; however, its function on Li-ion diffusion and Li plating/stripping has not been systematically investigated. Herein, in situ electrochemical Raman characterization using modified coin cell configuration is employed to directly reveal the anion adsorption mechanism of the coating layer. The adsorption ability of the MOF-based coating layer on the commercial separator is able to preserve high concentration of anions near the electrolyte/Li interface, which generates high local Li-ion concentration that delays the drain of Li+ to uniform Li plating. The feasible and large-area fabrication of GO/ZIF-8-modified separator enables the assembly of pouch cell strictly following practical parameters. 0.4 Ah pouch cell (Li/NCM811) delivers stable capacity for over 100 cycles. The deep understanding of the mechanism of how a coating layer affects Li plating behavior is helpful for the designing and preparation of high-performance separators for Li metal batteries.
