Self-Adaptive 3D Skeleton with Charge Dissipation Capability for Practical Li Metal Pouch Cells

Abstract

Increased concentration polarization and cell resistance due to aggregation of “dead Li” is one of the main factors that cause capacity decay during cycling of practical lithium metal batteries. Effective strategies that are able to accommodate dynamic volume expansion of “dead Li” is required to solve the above problem. Herein, a compressible 3D skeleton (polyaniline modified melamine foam) is introduced to modify lithium metal anode to self-adapt the volume expansion. Meanwhile, moderate conductivity of this 3D skeleton can induce the “bottom-up” deposition manner of Li and provide electron pathways to exploit the inactive Li in “dead Li”. More importantly, the COMSOL simulations show that the 3D skeleton can effectively dissipate electrons accumulated on the tips of dendritic Li when unwanted Li dendrites contact the 3D skeleton to achieve low local current density. As a result, a Li/Cu cells using this 3D skeleton on the Cu side show long-term stability within 100 cycles under 3.8 mAh/cm2, and Li symmetrical cells using 3D skeleton modified Li foils achieve stable cycling for 2750 h under 5.0 mAh/cm2. The feasible fabrication process enables us to fabricate 0.6 Ah 3D skeleton modified Li/NCM811 pouch cells, which deliver capacity retention of 85% after 80 cycles under practical test protocols.