Promoting uniform lithium deposition with Janus gel polymer electrolytes enabling stable lithium metal batteries

Lithium metal batteries (LMBs) are desirable candidates owing to their high-energy advantage for next-generation batteries. However, the practical application of LMBs continues to be constrained by thorny safety issues with the formation and growth of Li dendrites. Herein, the ZIF-67 MOFs are in situ coupled onto a single face of 3D porous nanofiber to fabricate an asymmetric Janus membrane, harnessing their anion adsorption capabilities to promote the uniform deposition of Li ions. In addition, the poly(ethylene glycol) diacrylate and trifluoromethyl methacrylate are introduced into nanofiber skeleton to form Janus@GPE, which preferentially reacts with Li metal to form a LiF-rich stable SEI layer to inhibit Li dendrite growth. Importantly, the synergistic effect of the MOFs and stable solid electrolyte interphase (SEI) layer results in superior cycling performance, achieving a remarkable 2500 h cycling at 1 mA cm⁻² in the Li/Janus@GPE/Li configuration. In addition, the Janus@GPE electrolyte has a certain flame retardant, which can self-extinguish within 3 s, improving the safety performance of the batteries. Consequently, the Li/Janus@GPE/LFP flexible pouch cell exhibits favorable cycling stability (the capacity retention rate of 45 cycles is 91.8% at 0.1 C). This work provides new insights and strategies to improve the safety and practical utility of LMBs.