<p>Enhancing the lithium-ion diffusion and electronic conductivity of olivine-type LiMn_0.8Fe_0.2PO₄ cathode materials via solid-state synthesis is crucial for industrial application. In this study, a combination of high-energy grinding and solid-state synthesis was employed to systematically investigate the influence mechanisms of conventional grinding, single-stage high-energy grinding, and two-stage high-energy grinding regarding the electrochemical properties of LiMn_0.8Fe_0.2PO₄. Electrochemical characterization revealed that the Mn²⁺/Mn³⁺ redox pair contributed 72.99%, 77.31%, and 77.89% to the charge specific capacity under conventional grinding, single-stage high-energy grinding, and two-stage high-energy grinding, respectively. Correspondingly, the contribution rates to the discharge specific capacity were 55.44%, 75.48%, and 74.29%, with the corresponding specific capacity values being 39.37&#xa0;mAh/g, 84.85&#xa0;mAh/g, and 107.57&#xa0;mAh/g, respectively. These results demonstrate that the high-energy grinding process significantly enhances the electrochemical activity of the Mn²⁺/Mn³⁺ redox pair. Mechanistic analysis further indicated that two-stage high-energy grinding effectively reduces particle size, thereby improving lithium-ion diffusion kinetics and forming a uniform and continuous carbon conductive network that enhances electronic conductivity. This enables the discharge capacity of the Mn²⁺/Mn³⁺ redox pair in LiMn_0.8Fe_0.2PO₄ to be fully exploited. Overall, this work provides valuable theoretical insights into the controllable solid synthesis and performance optimization of phosphate-based cathode materials.</p> Graphical abstract