Lithium-ion　batteries　are　pivotal　in　energy　storage,　yet　their　performance　is　often　limited　by　cathode　materials.　Here,　we　employ　density　functional　theory　(DFT)　calculations　to　investigate　the　synergistic　effects　of　Ni-N　codoping　on　LiMn0.5Fe0.5PO4　(LMFP),　a　promising　olivine-type　cathode　material.　Our　results　demonstrate　that　Ni-N　co-doping　significantly　enhances　the　thermodynamic　stability,　electrochemical　performance,　and　mechanical　properties　of　LMFP.　The　doped　system　exhibits　a　negative　formation　energy　(-0.28　eV),　confirming　its　thermodynamic　stability.　Notably,　co-doping　reduces　the　volume　change　rate　during　lithium　deintercalation　from　5.82　%　to　4.42　%,　improving　cycling　stability.　Furthermore,　the　average　delithiation　voltage　increases　from　3.66　V　to　3.90　V,　enhancing　energy　density.Electronic　structure　analysis　reveals　a　dramatic　reduction　in　bandgap　(from　3.44　eV　to　0.70　eV),　facilitating　electron　transition,　thus　improving　conductivity.　Additionally,　the　Li-ion　diffusion　coefficient　increases　by　three　orders　of　magnitude　(from　5.24　x　10-11　cm2/s　to　3.20　x　10-　8　cm2/s),　indicating　superior　rate　capability.　Mechanical　property　calculations　show　that　Ni-N　co-doping　enhances　strength,　stiffness,　and　plasticity　while　reducing　anisotropy,　thereby　suppressing　microcrack　formation.　This　study　provides　fundamental　insights　into　the　atomic-scale　mechanisms　governing　the　performance　enhancement　of　Ni-N　co-doped　LMFP,　offering　a　viable　strategy　for　designing　high-performance　cathode　materials　for　nextgeneration　lithium-ion　batteries.