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

Abstract

Na₃V₂(PO4)₂F₃ (NVPF₃)|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 NVPF₃ 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 (─SO₃) and electron aggregation adjacent to C═C, PES is revealed to passivate anode by a novel preferential ─SO₃ adsorption and C═C induced reduction. Dense and inorganic-rich cathode/anode-electrolyte interfaces can be synchronously achieved. Consequently, the NVPF₃|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.