Separator-driven synergistic suppression of Li dendrite for > 2600 cycles with simultaneous 10C rate capability

Lithium metal batteries (LMBs) offer the most compact energy storage but face challenges from dendrite growth, causing short-circuits and cycle instability. Current strategies, such as lithiophilicity, heat spreading on the Li metal surface, mechanical hardness on Li anode, and enhanced Li+ conductivity, address these issues separately lacking cohesive engineering. Here, a Si3N4-coated polyimide (PI) separator combines dendrite prevention features, resulting in the preservation of 62 % of the full capacity under 10C and the ability to withstand over 2600 and 1500Li | LiFePO4 full LMB cell cycles under 2C and 10C respectively without experiencing short-circuits. The cycle stability achieved using this separator surpasses even that of ultralong cyclable electrode materials and the targeted 1500 cycle lifespan of electric vehicles. It presents itself as a standard separator for both ultralong cyclability and high-rate capability, free from dendrite-led short-circuits. The Si3N4-coated PI separator can benefit other rechargeable batteries with dendrite-related limitations such as Li - air, Zn - ion, and Mg - ion batteries, enhancing not only their cycle stability but also improve their rate capability.