Unsaturated Organic Sulfonate‐Based Electrolyte Reinforced Interface for Stable Na3V2(PO4)2F3|HC Full‐batteries with Long Duration at 4.1 V

Abstract Na 3 V 2 (PO4) 2 F 3 (NVPF 3 )|hard carbon (HC) full‐battery has the advantage of high‐specific‐energy due to a high voltage range (2.0–4.3 V). However, the stability is limited by parasitic oxidation/reduction of intrinsically electrochemically‐unstable electrolytes at the cathode/anode. In this work, a class of electrolytes amicable for both cathode and anode are designed, which composites dual ─C≡N‐containing additives (e.g., Succinonitrile, SN) with unsaturated organic sulfonates (e.g., prop‐1‐ene‐1,3‐sultone, PES). SN can effectively elevate the high‐voltage endurance of electrolytes on the NVPF 3 cathode for a long duration at 4.2 V versus Na/Na + , while triggering serious electrolyte reduction at the anode. After introducing unsaturated organic sulfonates like PES with SN, the electrolyte is resistant to reduction while preserving the oxidation‐alleviation effect induced by SN. Profiting from the interfacial enriched negative end of dipole molecule (─SO 3 ) and electron aggregation adjacent to C═C, PES is revealed to passivate anode by a novel preferential ─SO 3 adsorption and C═C induced reduction. Dense and inorganic‐rich cathode/anode‐electrolyte interfaces can be synchronously achieved. Consequently, the NVPF 3 |HC full‐battery can achieve an energy density of >150 Wh kg −1 and capacity retention of 86.67% after 1000 cycles @1 C with long duration at 4.1 V that outperforms all the homologous works, showing a bright prospect for practical application.