Revisit the Progress of Binders for a Silicon-Based Anode from the Perspective of Designed Binder Structure and Special Sized Silicon Nanoparticles

Achievements, challenges, and perspectives in the design of polymer binders for advanced lithium-ion batteries

Energy storage devices with high power and energy density are in demand owing to the rapidly growing population, and lithium-ion batteries (LIBs) are promising rechargeable energy storage devices. However, there are many issues associated with the development of electrode materials with a high theoretical capacity, which need to be addressed before their commercialization. Extensive research has focused on the modification and structural design of electrode materials, which are usually expensive and sophisticated. Besides, polymer binders are pivotal components for maintaining the structural integrity and stability of electrodes in LIBs. Polyvinylidene difluoride (PVDF) is a commercial binder with superior electrochemical stability, but its poor adhesion, insufficient mechanical properties, and low electronic and ionic conductivity hinder its wide application as a high-capacity electrode material. In this review, we highlight the recent progress in developing different polymeric materials (based on natural polymers and synthetic non-conductive and electronically conductive polymers) as binders for the anodes and cathodes in LIBs. The influence of the mechanical, adhesion, and self-healing properties as well as electronic and ionic conductivity of polymers on the capacity, capacity retention, rate performance and cycling life of batteries is discussed. Firstly, we analyze the failure mechanisms of binders based on the operation principle of lithium-ion batteries, introducing two models of "interface failure" and "degradation failure". More importantly, we propose several binder parameters applicable to most lithium-ion batteries and systematically consider and summarize the relationships between the chemical structure and properties of the binder at the molecular level. Subsequently, we select silicon and sulfur active electrode materials as examples to discuss the design principles of the binder from a molecular structure point of view. Finally, we present our perspectives on the development directions of binders for next-generation high-energy-density lithium-ion batteries. We hope that this review will guide researchers in the further design of novel efficient binders for lithium-ion batteries at the molecular level, especially for high energy density electrode materials.

Bio-Inspired Electrodes with Rational Spatiotemporal Management for Lithium-Ion Batteries

Lithium-ion batteries (LIBs) are currently the predominant energy storage power source. However, the urgent issues of enhancing electrochemical performance, prolonging lifetime, preventing thermal runaway-caused fires, and intelligent application are obstacles to their applications. Herein, bio-inspired electrodes owning spatiotemporal management of self-healing, fast ion transport, fire-extinguishing, thermoresponsive switching, recycling, and flexibility are overviewed comprehensively, showing great promising potentials in practical application due to the significantly enhanced durability and thermal safety of LIBs. Taking advantage of the self-healing core-shell structures, binders, capsules, or liquid metal alloys, these electrodes can maintain the mechanical integrity during the lithiation-delithiation cycling. After the incorporation of fire-extinguishing binders, current collectors, or capsules, flame retardants can be released spatiotemporally during thermal runaway to ensure safety. Thermoresponsive switching electrodes are also constructed though adding thermally responsive components, which can rapidly switch LIB off under abnormal conditions and resume their functions quickly when normal operating conditions return. Finally, the challenges of bio-inspired electrode designs are presented to optimize the spatiotemporal management of LIBs. It is anticipated that the proposed electrodes with spatiotemporal management will not only promote industrial application, but also strengthen the fundamental research of bionics in energy storage.

Enhancing the interfacial thermal conductance of Si/PVDF by strengthening atomic couplings

Thermal transport across inorganic/organic interfaces attracts interest from both academia and industry due to their wide applications in flexible electronics, etc. Here, the interfacial thermal conductance of inorganic/organic interfaces consisting of silicon and polyvinylidene fluoride is systematically investigated using molecular dynamics simulations. Interestingly, it is demonstrated that a modified silicon surface with hydroxyl groups can drastically enhance the conductance by 698%. These results are elucidated based on interfacial couplings and lattice dynamics insights. This study not only provides feasible strategies to effectively modulate the interfacial thermal conductance of inorganic/organic interfaces but also deepens the understanding of the fundamental physics underlying phonon transport across interfaces.

Application and Development of Silicon Anode Binders for Lithium-Ion Batteries

The use of silicon (Si) as a lithium-ion battery's (LIBs) anode active material has been a popular subject of research, due to its high theoretical specific capacity (4200 mAh g^-1). However, the volume of Si undergoes a huge expansion (300%) during the charging and discharging process of the battery, resulting in the destruction of the anode's structure and the rapid decay of the battery's energy density, which limits the practical application of Si as the anode active material. Lithium-ion batteries' capacity, lifespan, and safety can be increased through the efficient mitigation of Si volume expansion and the maintenance of the stability of the electrode's structure with the employment of polymer binders. The main degradation mechanism of Si-based anodes and the methods that have been reported to effectively solve the Si volume expansion problem firstly are introduced. Then, the review demonstrates the representative research work on the design and development of new Si-based anode binders to improve the cycling stability of Si-based anode structure from the perspective of binders, and finally concludes by summarizing and outlining the progress of this research direction.