Developing sustainable carboxymethyl cellulose lithium binders using agro-forestry biomass for high-performance LiFePO cathode.

Biomass-derived carboxymethyl cellulose lithium (CMCLi) was synthesized from poplar wood (PW) and corn stover (CS) as sustainable binders for lithium-ion batteries. The raw materials were pretreated with green deep eutectic solvents (DESs) to remove lignin and hemicellulose, followed by bleaching to purify the cellulose. The purified cellulose was subsequently subjected to alkaline swelling, alkalization, and etherification to produce CMC-Li binders. Results revealed that CMC-Li binders derived from neutral choline chloride (ChCl)/ethylene glycol (EG) (1:4) pretreatment (CMC-Li-PW(EG) and CMC-Li-CS(EG)) exhibited higher molecular weight and a more uniform molecular weight distribution, leading to improved force distribution between the binder and conductive agents. The cathodes of LiFePO (LFP) batteries fabricated with these binders displayed smoother surfaces, uniform particle distribution, and minimal agglomeration or voids, resulting in enhanced Young's modulus and adhesion strength compared to traditional polyvinylidene fluoride (PVDF) binders. Moreover, LFP batteries utilizing CMC-Li binders demonstrated low charge impedance, superior cyclic voltammetry performance, high initial charge-discharge capacities (175/174 mAh/g for CMC-Li-PW(EG) and 173/172 mAh/g for CMC-Li-CS(EG)), high initial Coulombic efficiency (>98 %), low capacity loss (4.2 % after 200 cycles), and excellent rate capability. These findings highlight the potential of biomass-derived CMC-Li binders as high-performance, eco-friendly alternatives for next-generation LIBs.