Suppressing Mn3+-induced Jahn-teller distortion in LiMnxFe1-xPO4 via synergistic Mg2+ and Ti4+ dopant toward robust battery performance

Innovatively proposed Mg 2+ & Ti 4+ co-doped to efficiently suppress Mn 3+ -induced Jahn-Teller distortion and stabilize LMFP's olivine framework. • In-situ characterizations combined with DFT calculations clarify the intrinsic mechanism of co-doped regulating LMFP's crystal/electronic structures. • Co-doped significantly boosts LMFP's electronic conductivity and capacitive contribution, realizing superior high-rate performance and structural reversibility. • Co-doped LMFP@C-MT reduces Mn dissolution by alleviating Jahn-Teller distortion, further enhancing the cathode's structural and electrochemical stability. LiMn x Fe 1-x PO 4 (LMFP) cathodes are considered promising candidates for next-generation lithium-ion (Li + ) batteries due to their high safety, low cost, environmental benignity, and relatively high energy density. However, they suffer from severe Jahn-Teller distortion and sluggish Li + kinetics, leading to poor structural stability and rate performance. Herein, a synergistic Mg 2+ and Ti 4+ co-doping strategy is proposed to concurrently regulate the crystal structure and electronic properties of LMFP. Structural and electrochemical analyses show that Mg 2+ and Ti 4+ effectively suppress Mn 3+ -induced Jahn-Teller distortion. This helps stabilize the olivine framework while causing a small shrinkage in the crystal lattice, thereby improving Li + diffusion capability. In situ XRD reveals that un-doped lithium manganese iron phosphate (LMFP@C) undergoes a distinct phase transition during the high-voltage plateau, as evidenced by peak splitting, whereas Mg 2+ and Ti 4+ co-doped lithium manganese iron phosphate (LMFP@C-MT) exhibits a continuous peak shift, indicative of a solid-solution reaction with improved structural reversibility. Density functional theory (DFT) calculations further demonstrate that Mg 2+ lowers the Li + migration energy barrier, while Ti 4+ stabilizes the Mn electronic structure near the Fermi level. This synergistic effect suppresses Jahn-Teller distortion, thereby enhancing both structural stability and electrochemical kinetics. This enables the LMFP@C-MT cathode to deliver a high initial capacity of 158.35 mAh g −1 at 0.2C, along with outstanding cycling stability, retaining 91.39% capacity after 500 cycles at 1C. This work both presents an effective structural modification strategy and supplies theoretical guidance for the development of high-performance LMFP-based cathode materials. The LMFP@C-MT synthesized by the high-temperature solid-state method suppresses the Jahn–Teller distortion induced by Mn 3+ and stabilizes the lattice. Combined with the ordered carbon coating, it enhances the charge transfer kinetics, thereby achieving excellent structural reversibility and electrochemical performance. Download: Download high-res image (196KB) Download: Download full-size image