Carboxymethylated tamarind polysaccharide gum as a green binder for silicon-based lithium-ion battery anodes

Binders pave the way for silicon (Si)-based lithium-ion batteries (LIBs) by alleviating excessive expansion of Si and offer an intriguingly high theoretical specific capacity (4200 mAh g(-1)), even with small amounts of additive. Here, we report a novel aqueous binder, carboxymethylated tamarind polysaccharide gum (1-CMT), created by modifying a low-cost, abundant, and non-toxic natural polysaccharide (tamarind kernel powder) under mild conditions. The Si@1-CMT electrode has a satisfactory specific capacity of 3626.7 mAh g(-1) as well as a coulombic efficiency of 90.96% at the initial cycle; the Si mass loading is approximately 0.75 mg cm-2. A specific capacity of 1176 mAh g(-1) is retained after 200 cycles at a strict current density of 2000 mA g-1; the corresponding value for a Si@CMC electrode is only 697 mAh g(-1). The 1-CMT electrode has a specific capacity greater than 1600 mAh g(-1) even under a current density of 4000 mA g(-1). The unique branched chain structure and substantial number of free polar functional groups explain the outstanding electrochemical properties. Hence, 1-CMT acts as a premium binder in a Si-based anode that can be used to create high-performance batteries.