In this work, we systematically analyze the defect chemistry and electrochemical restoration of degraded LFP through chemical relithiation strategies. By comparing structural data, electrochemical characterization results and defect quantification, we show that regeneration is primarily governed by the correction of Li-Fe antisite fraction (reduced from similar to 2 to 3% to below 1%), the replenishment of lithium vacancies and the suppression of Fe3+ accumulation. These processes reopen blocked [010] diffusion channels, increasing Li+ diffusion coefficients from similar to 10(-16) to 10(-13)-10(-12) cm(2) s(-1) and reducing charge-transfer electrode resistance from >300 Omega to 80% retention. Comparative evaluation of six representative relithiation strategies demonstrates that defect-correction efficacy follows the order: photocatalytic dopamine-assisted regeneration approximate to redox-mediator/organolithium relithiation > aqueous redox relithiation > non-aqueous liquid-phase relithiation > chelation-driven surface cleaning >> solid-state redox relithiation. These findings establish a direct link between defect suppression and electrochemical recovery offering quantitative benchmarks to guide the design of efficient and sustainable regeneration strategies for spent LFP cathodes.