Chemically Recovered Lithium Dendrites Enabled by Gradient-Distributed Liquid Metal Particles in Composite Polymer Electrolytes.

The increasing demand for high-energy-density rechargeable batteries has spurred significant advancements in lithium (Li) metal batteries employing solid polymer electrolytes. Extensive efforts have been devoted to tackling the crucial shorting problem in cycled polymer electrolytes via tuning the polymer chemistries and polymer-metal interfacial properties. However, the working principles of these designs mainly focus on physical/chemical suppression, instead of full recovery of the grown dendrites. Here, we propose an effective gradient design in polymer electrolytes by introducing Ga-based liquid metal (LM) particles with a depth-dependent content, enabling effective recovery of Li dendrites via spontaneous alloying reaction. Such an asymmetric electrolyte configuration is capable of fully chemically alloying the dendrites upon their puncturing into the LM-rich layer, while inhibiting electrical percolation at the LM-free layer, especially under mechanical pressure during cell assembly. Post-mortem analyses reveal the structural deformation of piercing dendrites into spherical Li-LM alloys, thereby preventing shorting even with extended cycles. Consequently, ultrastable cycling stabilities are achieved in both symmetric cells (>2000 h) and Li/LiFePO4 full cells (>400 cycles; average CE of 99.86%). These findings not only exploit dendrite recovery functionality by using LM-based gradient electrolytes but also highlight the potential of incorporating gradient designs in various battery systems.