Dual strategy of Na⁺ doping and biomass-derived carbon coating from wheat starch carbon for high-performance LiMnPO₄ cathodes

Abstract In this work, a dual modification strategy was explored to produce LiMnPO 4 based cathode materials through Na + doping and in situ carbon coating derived from wheat starch, a sustainable biomass resource. The use of wheat starch carbon as a green carbon precursor is a key feature of this work. Three samples were synthesised via the sol gel route: pristine LiMnPO 4 , biomass wheat starch carbon coated LiMnPO 4 and Na + doped (Li 0.97 Na 0.03 MnPO 4 ) with the same carbon coating. X-ray diffraction (XRD) confirmed an orthorhombic Pnmb structure for all prepared samples, which significantly denotes the modification by neither carbon nor Na + doping altered the fundamental phase of LiMnPO 4 cathode materials. The Na + doped, carbon-coated sample achieved an initial discharge capacity of 152.4 mAh g −1 and retained 95% of its capacity after 50 cycles, compared to 127.8 mAh g −1 for the pristine sample. The intermediate sample with carbon coating alone delivered 142.75 mAh g −1 in the first cycle, demonstrating notable enhancement due to the biomass carbon layer. Na + substitution improved lithium-ion diffusion, while the in situ carbon coating enhanced electronic conductivity and reduced crystallite size. These results highlight the potential of combining Na + doping with biomass-derived carbon coatings to produce high-performance, eco-friendly cathode materials for lithium-ion battery applications.