A low-cost and eco-friendly network binder coupling stiffness and softness for high-performance Li-ion batteries

A Cellulose Reinforced Multifunctional Binder for High-Performance Silicon Anodes

Silicon (Si) has garnered significant interest as a potential anode material for next-generation lithium-ion batteries due to its high theoretical capacity. However, Si anodes suffer from substantial volume expansion during the charge and discharge processes, which severely undermines their cycling stability. To address this issue, developing novel binders has become an effective strategy to suppress the volume expansion of Si anodes. In this study, a multifunctional polymer binder (DCCS) was designed by the cross-linking of dialdehyde cellulose nanocrystal (DACNC) and carboxymethyl chitosan (CMCS), which forms a 3D network structure via Schiff-base bonds. The DCCS binder with abundant chemical and hydroxyl bonds shows strong adhesion between Si nanoparticles and current collectors, thus enhancing the mechanical properties of the electrode. Furthermore, the DACNC also served as the protecting buffer layer to release the inner stress and stabilize the solid electrolyte interface (SEI). At 4 A g-1, the resulting Si@25%DCCS electrode demonstrated a capacity of 1637 mAh g-1 after 500 cycles, with an average capacity fading rate of 0.07% per cycle. Therefore, this multifunctional binder is considered a promising binder for high-performance Si anodes.

A ductile and strong-affinity network binder coupling inorganic oligomers and biopolymers for high-loading lithium-sulfur batteries

Lithium sulfur (Li-S) batteries have become the predominant energy storage devices of the future. However, the reasons why Li-S batteries have not been widely commercialized include the shuttle effect of polysulfides and the volume expansion of sulfur active substances. In this study, a binder with a stretchable 3D reticular structure was induced using inorganic oligomers. Potassium tripolyphosphate (PTP) has been used to powerfully connect the tamarind seed gum (TSG) chain through robust intermolecular forces due to the strong electronegativity of P-O^- groups. With this binder, the volume expansion of sulfur active substances can be well restrained. In addition, a large amount of -OH groups in TSG and P-O^- bonds in PTP can also effectively adsorb polysulfides and inhibit the shuttle effect. Therefore, the S@TSG-PTP electrode shows an improved cycle performance. When the sulfur loading is as high as 4.29 mg cm^-2, the areal specific capacity can reach 3.37 mA h cm^-2 after 70 cycles. This study highlights a new way for the binder design of high-loading sulfur electrodes.

Progress of Binder Structures in Silicon-Based Anodes for Advanced Lithium-Ion Batteries: A Mini Review

Silicon (Si) has been counted as the most promising anode material for next-generation lithium-ion batteries, owing to its high theoretical specific capacity, safety, and high natural abundance. However, the commercial application of silicon anodes is hindered by its huge volume expansions, poor conductivity, and low coulombic efficiency. For the anode manufacture, binders play an important role of binding silicon materials, current collectors, and conductive agents, and the binder structure can significantly affect the mechanical durability, adhesion, ionic/electronic conductivities, and solid electrolyte interface (SEI) stability of the silicon anodes. Moreover, many cross-linked binders are effective in alleviating the volume expansions of silicon nanosized even microsized anodic materials along with maintaining the anode integrity and stable electrochemical performances. This mini review comprehensively summarizes various binders based on their structures, including the linear, branched, three-dimensional (3D) cross-linked, conductive polymer, and other hybrid binders. The mechanisms how various binder structures influence the performances of the silicon anodes, the limitations, and prospects of different hybrid binders are also discussed. This mini review can help in designing hybrid polymer binders and facilitating the practical application of silicon-based anodes with high electrochemical activity and long-term stability.