Promoting All Key Parameters of LiFe_0.5Mn_0.5PO₄ Cathodes with Monovalent Ag⁺ Doping: A Smart Two-Birds-with-One-Stone Strategy

Olivine-type LiFe_1−xMn_xPO₄ (0 ≤ x < 1) is a high-energy cathode utilized in next-generation power sources. However, its poor electrical/ionic conductivity and Jahn–Teller distortions upon cycling limit its practical behaviors. To overcome these barriers, the use of monovalent Ag⁺ doping is confirmed to promote all key parameters (e.g., inherent electrical conductivity, cyclic lifespan, rate capability) of LiFe_0.5Mn_0.5PO₄ cathodes. Theoretical calculations predict that this monovalent doping can narrow its bandgap, help shift the density of states toward a higher energy, and raise the electronic state numbers near the Fermi level, guaranteeing the high intrinsic electrical conductivity of the cathode. Four-probe testing solidly confirms that its conductivity can be vastly enhanced by 155.6% after Ag⁺ doping. In addition, we prove that 1% Ag⁺ doping is an optimal/economical choice to promote these electrochemical behaviors. Also, in situ x-ray diffraction detections further confirm that our doping can reinforce the lattice structures and inhibit lattice distortions. The assembled cells can output discharge capacity greater than 153.5 mAh g⁻¹ at 0.1 C and achieve a capacity retention rate of 92.5% after 500 cycles, surpassing those of counterpart cases. Our work provides a smart two-birds-with-one-stone strategy to effectively elevate LiFe_0.5Mn_0.5PO₄ cathodes for practical use.