A Novel Ternary Li‐Rich Li ₄ Fe _0.5 Mn _0.5 V(PO ₄ ) ₃ Cathode for Ultra‐High‐Capacity Li‐Ion Batteries with Potential Far Beyond LFP via Multi‐Electron Reaction

Abstract LiFePO ₄ (LFP) has successfully realized large‐scale applications due to excellent stability. However, the low potential and insufficiently high specific capacity lead to lower energy density, so it becomes imperative to find new cathodes with high potential and high specific capacity. Herein, a novel ternary lithium‐rich Li ₄ Fe _0.5 Mn _0.5 V(PO ₄ ) ₃ (FMV) cathode is designed, which combines the high specific capacity of V, high potential of Mn and high stability of Fe. Multiple electron transfer by activation of multiple redox pairs of Fe ²⁺ /Fe ³⁺ , Mn ²⁺ /Mn ³⁺ , and V ³⁺ /V ⁴⁺ /V ⁵⁺ at 2.0–4.5 V, demonstrated through the XPS results. The obtained Li ₄ Fe _0.5 Mn _0.5 V(PO ₄ ) ₃ /C cathode, charging/discharging at 2.0–4.5 V, can deliver a specific capacity of ≈163.3 mAh g ⁻¹ at 0.1C, and a capacity retention of 94.2% after 500 cycles at 5C. The reversibility and stability of the structure upon the charging/discharging process are revealed by ex‐situ XRD. In addition, the redox reaction of V ²⁺ /V ³⁺ can be activated by charging/discharging within 1.5–4.5 V, proving through the XPS of the electrodes at 2.0 and 1.5 V, so that it can deliver an amazing reversible specific capacity of ≈220 mAh g ⁻¹ at 0.1 C, with a capacity retention of 91.1% after 200 cycles at 1C (≈170 mAh g ⁻¹ ), providing new perspectives for high‐performance Li‐ion batteries.