This work demonstrates the design, synthesis, characterization, and study of the electrochemical performance of a novel binder for silicon (Si) anodes in lithium-ion batteries (LIBs). Polymeric binders with three different functional groups, namely, carboxylic acid (COOH), carboxylate (COO(-)), and hydroxyl (OH), in a single polymer backbone have been synthesized and characterized via (1)H NMR and FTIR spectroscopies. A systematic study that involved varying the ratio of the functional groups indicated that a material with an acid-to-alcohol molar ratio of 60:40 showed promise as an efficient binder with an initial columbic efficiency of 89%. This exceptional performance is attributed to the strong adhesion of the binder to the silicon surface and to cross-linking between carboxyl and hydroxyl functional groups, which minimize the disintegration of the Si anode structure during the large volume expansion of the lithiated Si nanoparticle. Polymers with multiple functional groups can serve as practical alternative binders for the Si anodes of LIBs, resulting in higher capacities with less capacity fade.

A facile and efficient way to impart compelling chemical functionality is the utilization of bio-related materials that are easily accessible from natural products. Here, inspired by anomalous physicochemical features and natural abundance of agarose, we demonstrate a new class of agarose-biofunctionalized, dual-electrospun heteronanofiber mats as a chemically active separator membrane for high-performance lithium-ion batteries. The agarose-enabled metal ion chelation effect of the separator membrane, in combination with its highly porous structure and superior electrolyte wettability, provides unprecedented improvement in cell performance far beyond those accessible with conventional battery separator membranes.

Nanocrystalline Si (c-Si) dispersed in amorphous Si (a-Si) encapsulating hard carbon (HC) has been synthesized as an anode material for fast chargeable lithium-ion batteries. The HC derived from natural polysaccharide was coated by a thin a-Si layer through chemical vapour deposition (CVD) using silane (SiH₄) as a precursor gas. The HC@c-Si@a-Si anodes showed an excellent cycle retention of 97.8% even after 200 cycles at a 1 C discharge/charge rate. Furthermore, a high capacity retention of ∼54% of its initial reversible capacity at 0.2 C rate was obtained at a high discharge/charge rate of 5 C. Moreover, the LiCoO₂/HC@c-Si@a-Si full-cell showed excellent rate capability and very stable long-term cycle. Even at a rate of 10 C discharge/charge, the capacity retention of the LiCoO₂/HC@c-Si@a-Si full-cell was 50.8% of its capacity at a rate of 1 C discharge/charge and showed a superior cycle retention of 80% after 160 cycles at a rate of 1 C discharge/charge.

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