An in situ thermal cross-linking binder for silicon-based lithium ion battery

Novel strategies for constructing highly efficient silicon/carbon anodes: Chemical prelithiation and electrolyte post-treatment

Chemical prelithiation is an effective method to compensate for the loss of active lithium due to the formation of solid electrolyte interface, effectively addressing the issue of low initial coulombic efficiency (ICE) in silicon/carbon (Si/C) materials. Herein, the Si/C anode is prelithiated in a 1 M lithium-phenanthrene/2-methyltetrahydrofuran (Li-Phe/2-MTHF) solution in our work, and the prelithiated Si/C anode is followed by post-treatment with commercial electrolytes containing lithium difluorobis(oxalato)phosphate (LiDFBOP). The PSi/C-L0.5, originated from the reaction between residual Li-Phe/2-MTHF and the commercial electrolyte containing 0.5 wt% LiDFBOP, possesses the artificial SEI film, which not only contains a proper amount of LiF but also is rich in Li2C2O4 and Li3P. Among them, LiF and Li2C2O4 ensures the stability of the SEI film. Simultaneously, the synergistic effect of Li3P and LiF improves its Li+ transport kinetics. Therefore, the ICE of PSi/C-L0.5 reaches 92.50 %, and almost no drop in capacity occurs after 100 cycles at 0.5 A/g. Furthermore, the capacity stays steady at about 270 mAh/g through nearly 500 cycles at 1 A/g, achieving an impressive capacity retention rate of 97.8 %, significantly outperforming un-treated Si/C. This study offers new directions for constructing SEI films with stable structures and high Li+ kinetics transport.

Cooperation of covalent bonds and coordinative bonds stabilizing the Si-binder-Cu interfaces for extending lifespan of silicon anodes

Binders provide a straightforward and efficient strategy to mitigate the significant challenge of volume expansion in silicon anodes for lithium-ion batteries. To improve the cycle life of silicon anodes, a cross-linked binder carboxymethyl cellulose-phytic acid-pyrrole (CMC-DP) is designed and synthesized using carboxymethyl cellulose, phytic acid, and pyrrole. The numerous hydroxyl groups in phytic acid provide abundant binding sites for the formation of hydrogen and ester bonds. The formation of hydrogen bonds and covalent bonds enhances the mechanical properties of the adhesive. The amino groups in the binder form NSiO covalent bonds with silicon particles, while the hydroxyl and carboxyl groups form (COO)2Cu and (OH)2Cu coordination bonds with the copper foil, enhancing interfacial adhesion. When the CMC-DP10 (10 µL pyrrole) binder is applied to silicon nanoparticles (∼30 nm), the specific capacity of the electrode can be maintained at around 1700 mAh/g after 500, whereas the CMC binder achieves only ∼100 mAh/g under the same conditions. This work demonstrates that the CMC-DP binder exhibits strong adhesion to both silicon nanoparticles and copper foil.

Controllable Synthesis of Hollow Dodecahedral Si@C Core-Shell Structures for Ultrastable Lithium-Ion Batteries

Silicon (Si) has attracted considerable attention as a promising alternative to graphite in lithium-ion batteries (LIBs) because of its high theoretical capacity and voltage. However, the durability and cycling stability of Si-based composites have emerged as major obstacles to their widespread adoption as LIBs anode materials. To tackle these challenges, a hollow core-shell dodecahedra structure of a Si-based composite (HD-Si@C) is developed through a novel double-layer in situ growth approach. This innovative design ensures that the nano-sized Si particles are evenly distributed within a hollow carbon shell, effectively addressing issues like Si fragmentation, volume expansion, and detachment from the carbon layer during cycles. The HD-Si@C composite demonstrates remarkable structural integrity as a LIBs anode, resulting in exceptional electrochemical performance and promising practical applications, as evidenced by tests in pouch-type full cells. Notably, the composite shows outstanding cycling stability, retaining 85% of its initial capacity (713 mAh g-1) even after 3000 cycles at a high current rate of 5000 mA g-1. Additionally, the material achieves a gravimetric energy density of 369 W h kg-1, showcasing its potential for efficient energy storage solutions. This research signifies a significant step toward realizing the practical utilization of Si-based materials in the next generation of LIBs.

Poly(Acrylic Acid)-Based Polymer Binders for High-Performance Lithium-Ion Batteries: From Structure to Properties

Poly(acrylic acid) (PAA) and its derivatives have emerged as promising candidates for enhancing the electrochemical performance of lithium-ion batteries (LIBs) as binder materials. Recent research has focused on evaluating their ability to improve adhesion with silicon (Si) particles and facilitate ion transport while maintaining electrode integrity. Various strategies, including mixing modifications and copolymerization methods, are highlighted and the structural and physicochemical properties of these binders are examined. Additionally, the interaction mechanisms between PAA-based binders and active materials and their impact on key electrochemical properties such as initial Coulombic efficiency (ICE) and cycle stability are discussed. The findings underscore the efficacy of tailored PAA-based binders in enhancing the electrochemical properties of LIBs, offering insights into the design principles and practical implications for advanced battery materials. These advancements hold promise for developing high-performance lithium batteries capable of meeting future energy storage demands.

Cross-linking γ-Polyglutamic Acid as a Multifunctional Binder for High-Performance SiOx Anode in Lithium-Ion Batteries

SiOx is a highly promising anode material for realizing high-capacity lithium-ion batteries owing to its high theoretical capacity. However, the large volume change during cycling limits its practical application. The development of a binder has been demonstrated as one of the most economical and efficient strategies for enhancing the SiOx anode's electrochemical performance. In this work, a multifunctional binder (T-PGA) is fabricated by cross-linking γ-polyglutamic acid (PGA) and tannic acid (TA) for SiOx anodes. The introduction of TA into PGA helps to buffer the volume changes of the SiOx anodes, facilitate diffusion of Li+, and construct stable SEI layers. Benefiting from this proposed binder, the SiOx anode maintains a reversible capacity of 973.0 mAh g-1 after 500 cycles at 500 mA g-1 and the full cell, pairing with LiNi0.5Co0.2Mn0.3O2 cathode, delivers a reversible capacity of 133 mA h g-1 (73.2% retention) after 100 cycles. This study offers valuable insights into advanced binders that are used in high-performance Li-ion batteries.

Cross-Linkable Binders for Si Anodes in High-Energy-Density Lithium-Ion Batteries

Although silicon (Si) has a high theoretical capacity, the large volume expansion during lithiation has greatly hindered its application in high-energy-density lithium-ion batteries (LIBs). Among the strategies for improving the performance of Si anode, the role of binders should not be underestimated. Here, a novel strategy for designing a cross-linkable binder for Si anode has been proposed. The binder with hydroxyl and nitrile groups can be in situ covalently cross-linked through the amide group in the batteries. The cross-linked binder (c-POAH) shows high elasticity and strong adhesion to Si particles and the current collector. Si||Li half coin cells using the c-POAH binder have excellent cycle performance and the capacity retention ratio is 67.1% after 100 cycles at 0.2 C. Scanning electronic microscopy images show that the c-POAH binder can contribute to suppressing the pulverization of the Si anode. Moreover, the investigation with X-ray photoelectronic spectrum demonstrates that the decomposition of the liquid electrolyte on Si anode has been mitigated and the c-POAH binder can promote the formation of a more stable SEI film. Our strategy of endowing the binder with good elasticity through in situ cross-linking has opened up a new route for developing binders, which will definitely promote the application of Si anodes in high-energy-density LIBs.

Steric molecular combing effect enables Self-Healing binder for silicon anodes in Lithium-Ion batteries

Silicon is a promising anode material for lithium-ion batteries with its superior capacity. However, the volume change of the silicon anode seriously affects the electrode integrity and cycle stability. The waterborne guar gum (GG) binder has been regarded as one of the most promising binders for Si anodes. Here, a unique steric molecular combing approach based on guar gum, glycerol, and citric acid is proposed to develop a self-healing binder GGC, which would boost the structural stability of electrode materials. The GGC binder is mainly designed to weaken van der Waals' forces between polymers through the plasticizing effect of glycerol, combing and straightening the guar molecular chain of GG, and exposing the guar hydroxyl sites of GG and the carboxyl groups of citric acid. The condensation reaction between the hydroxyl sites of GG and the carboxyl groups of citric acid forms stronger hydrogen bonds, which can help achieve self-healing effect to cope with the severe volume expansion effect of silicone-based materials. Silicon electrode lithium-ion batteries prepared with GGC binders exhibit outstanding electrochemical performance, with a discharge capacity of up to 1579 mAh/g for 1200 cycles at 1 A/g, providing a high capacity retention rate of 96%. This paper demostrates the great potential of GGC binders in realizing electrochemical performance enhancement of silicon anode.