Stabilizing a Si Anode via an Inorganic Oligomer Binder Enabled by Robust Polar Interfacial Interactions

Stable Silicon Anodes Enabled by Innovative Biobased Binder with Cross-Linking Network in Lithium-Ion Batteries

Graphite anodes, with their capacity nearing the theoretical maximum of 372 mA h g-1, are increasingly being complemented by silicon-based materials, which offer a 10-fold higher capacity. Nevertheless, extreme volume expansion (>300%) of Si during cycling poses significant challenges to its practical deployment. Previous studies on the synthesis of binders are often intricate and not conducive to large-scale implementation. In this study, an innovative binder, denoted as HM, is developed by combining the macromolecular polysaccharide sodium hyaluronate with the small organic molecule malic acid without the need for any external triggers. A cross-linked network structure is formed in situ after heat treatment with silicon under vacuum conditions. The contact interface establishes a robust network structure through multiple macromolecular hydrogen bonds and chemical interactions. Consequently, the HM binder exhibits exceptional mechanical properties and efficiently lessens the volumetric change of silicon particles, thereby benefiting the generation of a stable solid electrolyte interphase. Electrochemical characterization demonstrates that the exceptional cycling stability of Si@HM electrodes can maintain a high capacity of 1949 mA h g-1 at 0.1 C and 1426 mA h g-1 at 0.5 C after 100 cycles. Furthermore, silicon anodes employing the HM binder demonstrate superior rate performance and reduced internal resistance compared to those of conventional binders, representing a significant advancement in performance. This research provides crucial perspectives for binder design and experimental evidence for the commercial utilization of silicon anodes within lithium-ion batteries.

Perspective on Lewis Acid-Base Interactions in Emerging Batteries

Lewis acid-base interactions are common in chemical processes presented in diverse applications, such as synthesis, catalysis, batteries, semiconductors, and solar cells. The Lewis acid-base interactions allow precise tuning of material properties from the molecular level to more aggregated and organized structures. This review will focus on the origin, development, and prospects of applying Lewis acid-base interactions for the materials design and mechanism understanding in the advancement of battery materials and chemistries. The covered topics relate to aqueous batteries, lithium-ion batteries, solid-state batteries, alkali metal-sulfur batteries, and alkali metal-oxygen batteries. In this review, the Lewis acid-base theories will be first introduced. Thereafter the application strategies for Lewis acid-base interactions in solid-state and liquid-based batteries will be introduced from the aspects of liquid electrolyte, solid polymer electrolyte, metal anodes, and high-capacity cathodes. The underlying mechanism is highlighted in regard to ion transport, electrochemical stability, mechanical property, reaction kinetics, dendrite growth, corrosion, and so on. Last but not least, perspectives on the future directions related to Lewis acid-base interactions for next-generation batteries are like to be shared.

Dual Dynamic Cross-Linked Epoxy Vitrimers Used for Strong, Detachable, and Reworkable Adhesives

Novel reprocessable thermosetting adhesives (RTAs), which combine high adhesive strength, reusability, disassembly, and recyclability features, have attracted increasing attention. However, developing RTAs with a rapidly adhesive rate while ensuring high adhesive strength and self-healing ability is still a significant challenge. Here, we prepared a novel vitrimer called DAx-DTSAy, which can be used as an RTA. First, by adjusting the ratio of rigid and flexible segments, maximum tensile strength reached 35.92 MPa. Second, the combined effect of dynamic hydroxyl ester bonds and dynamic disulfide bonds resulted in a rapid stress relaxation behavior, with a complete relaxation time 13.6 times shorter than a vitrimer only cross-linked with hydroxy ester bonds. This feature endowed its good self-healing and reprocessing capabilities. After self-healing at 180 °C, the maximum healing rate of mechanical properties was 91.8%. After three reprocesses, the maximum recovery rate of tensile strength was 120.2%. Furthermore, the combination of rigid and flexible segments and the synergistic effect of dual dynamic covalent bonds made DAx-DTSAy capable of use as a high-performance RTA. The lap shear strength of a DAx-DTSAy film on stainless steel reached 18.18 MPa after 15 min, with a recovery rate of 91.9% after 5 rebonding cycles. Additionally, DAx-DTSAy can be disassembled in chemical agents and exhibited better insulation properties compared to traditional epoxy resins. DAx-DTSAy can be employed as a novel high-performance adhesive in applications such as electronic devices and transportation, contributing to the development of thermosetting adhesives toward recyclability and sustainability.

Tuning the Electrode/Electrolyte Interface Enabled by a Trifunctional Inorganic Oligomer Electrolyte Additive for Highly Stable and High-Rate Zn Anodes

The practical application of aqueous Zn-ion batteries is still greatly hindered by the unstable Zn anode with severe Zn dendrites growth and side reactions. As it is accessible and economical, the exploitation of electrolyte additives is one of the most promising strategies to stabilize the Zn electrode/electrolyte interface. Herein, the penta-potassium triphosphate (KTPP) as a novel trifunctional electrolyte additive is introduced to tune the electrode/electrolyte interface. First, the KTPP additive can induce an ion-conducting and mechanically robust solid electrolyte interphase film to stabilize the Zn anode. Second, the KTPP can complex with Zn2+ ions to reconstitute the dissolution sheath structure of the Zn2+ ion. Finally, the K+ cations in KTPP adsorb on the tips of the Zn anode surface as a shielding film to regulate Zn2+ ion flux. As a result, Zn//Zn symmetric cells can achieve significantly prolonged cycling stability (e.g., from 1077 to 3800 h at 1 mA cm-2 /1 mAh cm-2 , from 256 to 2500 h at 2 mA cm-2 /2 mAh cm-2 ), and ultrahigh cumulative capacity of 6400/7200 mAh cm-2 at high current density (40/20 mA cm-2 ). A four-layer Zn-MnO2 pouch full cell with a high capacity of 9 mAh can be constructed, showing impressive practical application potential.

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.

Constructing practical micron silicon anodes via a homogeneous and robust network binder induced by a strong-affinity inorganic oligomer

Designing robust binders has been demonstrated to be an effective and facile strategy to stabilize Si anodes. However, the binders that performed well for Si nanoparticles are not applicable for low-cost and accessible Si micron-powders. Hence, a novel binder design strategy is still greatly required for practical micron-Si anodes. Herein, a robust water-based network binder (named as c-PTP-Alg) has been designed via coupling potassium tripolyphosphate (PTP) inorganic oligomer with alginic acid (Alg) organic macromolecule. Owing to the unique structure of PTP, a network with high mechanical resistance can be constructed in c-PTP-Alg binder via strong ion-dipole interactions. Moreover, the highly soluble and dispersed PTP inorganic oligomer in water prevents the organic macromolecule from aggregation. This induces a homogeneous texture in the c-PTP-Alg binder, which enables the polar groups in the composite binder to anchor micron-Si particles efficiently. Therefore, by simply applying the c-PTP-Alg binder, a significantly improved electrochemical performance of micron-Si anode with a high reversible capacity of 1599.9 mAh g^-1 after 100 cycles at 3000 mA g^-1 has been obtained. More specially, the high-energy-density Si||S-PAN full cells have also been constructed, showing the practical application prospect of the c-PTP-Alg binder.

Constructing three-dimensional N-doped carbon coating silicon/iron silicide nanoparticles cross-linked by carbon nanotubes as advanced anode materials for lithium-ion batteries

Silicon (Si), have been considered as promising anode material for lithium-ion batteries (LIBs), due to its high theoretical specific capacity of 4200 mAh g-1. However, the poor electrical conductivity and large volume change during lithiation/delithiation process, resulting in poor cycling stability, and seriously hindered the practical application in LIBs. Herein, a multiple Si/FexSiy@NC/CNTs composite is synthesized and investigated as advanced anode materials for LIBs via a simple one-step method. Such multiple Si/FexSiy@NC/CNTs composite has several merits including the FexSiy can not only accommodate the huge volume change of Si nanoparticles, but also enhance the conductivity upon discharge/charge process. Furthermore, the in-situ growth CNTs may help establish a long-range conductivity, and the Nitrogen-doped carbon (NC) layer can further improve the conductivity of Si, as well as inhibit the direct contract between electrolyte and Si during cycling process. Accordingly, the Si/FexSiy@NC/CNTs-1 exhibits excellent cycling stability (a high capacity of 994.4 mAh g-1 is maintained at 1.0 A g-1 after 600cycles) and outstanding rate capability (a suitable capacity of 441.7 mAh g-1 was obtained even at 5.0 A g-1). Moreover, the assembled full cell can achieve a capacity of 141.4 mAh g-1 after 65 cycles at 1.0C, exhibiting outstanding cycling stability. This work provides a prospective way for the commercial production of high-performance Si-based anode materials for LIBs.

Formulating a New Electrolyte: Synergy between Low-Polar and Non-polar Solvents in Tailoring the Solid Electrolyte Interface for the Silicon Anode

Currently, lithium-ion batteries (LIBs) are assembled with polar electrolytes; thus, resulting SEI layers are dominated with organics. Herein, a low-polarity electrolyte is formulated with a low-polarity solvent (tetraethyl silicate, TEOS) and a non-polar inert shielding co-solvent (cyclohexane, CYH); solvation behaviors of lithium salt are investigated. The use of such a low-polarity solvent is found to improve the fraction of anions in the solvation sheath of Li⁺, and the presence of the non-polar co-solvent further shields the reductive decomposition of the solvent on the anode. The resulting SEI layer is relatively rich in LiF and has a 3D cross-linked Si-O network as a skeleton from the decomposition of TEOS molecules, which is more robust to tolerate the damage from the volume expansion of silicon. A Si-nanoparticle-based anode in such a low-polarity electrolyte delivers a capacity as high as 1491 mAh g^-1 after 200 cycles, outperforming those in the commercial polar electrolytes.