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. A robust and durable cathode‐electrolyte interface layer is constructed on the graphite surface in situ with a lithium difluoro(oxalate) borate salt additive, enabling the graphite||graphite full battery to give a superb power capability up to 50 C and a long cycling life over 6500 cycles with 92.4% capacity retention and an average Coulombic efficiency of ≈99.4%.