Ultrafast Charging and Stable Cycling Dual-Ion Batteries Enabled via an Artificial Cathode–Electrolyte Interface

Low-cost and environment-friendly dual-ion batteries (DIBs) with fast-charging characteristics facilitate the development of high-power energy storage devices. However, the incompatibility between the cathode and electrolyte at high voltage results in low Coulombic efficiency (CE) and short lifespan. Here, the addition of ≈0.5 wt% lithium difluoro(oxalate) borate salt into the electrolyte forms a robust and durable cathode–electrolyte interface (CEI) in situ on the graphite surface, which enables remarkable cycling of the graphite||Li battery with 87.5% capacity retention after 4000 cycles at 5 C and ultrafast rate capability with 88.8% capacity retention under 40 C (4 A g⁻¹), delivering high-power of 0.4–18.8 kW kg⁻¹ at energy densities of 422.7–318.8 Wh kg⁻¹. Taking advantage of this robust CEI, a graphite||graphite full battery demonstrates high reversible capacities of 97.6, 92.8, 88.7, and 85.4 mAh (g cathode)⁻¹ at current rates of 10, 20, 30, and 40 C, respectively. The full battery also shows a long cycling life of over 6500 cycles with 92.4% capacity retention and an average CE of ≈99.4% at 1 A g⁻¹, which is superior to other dual-graphite (carbon) batteries in the literature. This work offers an effective interface-stabilizing strategy on protecting graphite cathodes and a promising approach for developing DIBs with high-power capability.