Self-Healing Binder for High-Voltage Batteries

Fluorine-Free Cycloaliphatic Epoxy-Based Siloxane Nanohybrid Binder with High Polar Hydroxyl Group Content Enabling LiFePO4-Type Battery with High Electrochemical Performance and Stability

LiFePO4-type (LFP) batteries have attracted significant attention in most battery manufacturing industries due to their long lifespan, high-temperature safety, and low cost of raw materials. However, as an active material, LFP still suffers from several intrinsic drawbacks, including poor conductivity, a low Li+ diffusion coefficient, low capacity, and a lack of electrochemical stability, primarily due to conventional fluorine-based binders. Here, we report a simple yet effective approach to developing a fluorine-free binder based on a robust cycloaliphatic epoxy-based siloxane nanohybrid material (CES) to achieve high electrochemical stability in LFP batteries. The high content of silanol moieties in CES induces a strong affinity for the active material and conductive agent, significantly improving rheological (thixotropy) and mechanical (adhesion and cohesion) properties, which enable the formation of a uniformly coated electrode. As a result, we achieved superior electrochemical performance and stability in CES-applied electrodes compared to those with conventional fluorine-based binders. We investigate the reasons behind the contribution of CES to the electrochemical stability of LFP batteries through various analyses. The high thermal and oxidation stability of CES effectively prevents degradation of LFP-based active materials. Our binder development strategy offers a significant breakthrough in replacing conventional fluorine-based binders, advancing the development of high-performance and stable secondary batteries.

Sapiential battery systems: beyond traditional electrochemical energy

As indispensable energy-storage technology in modern society, batteries play a crucial role in diverse fields of 3C products, electric vehicles, and electrochemical energy storage. However, with the growing demand for future electrochemical energy devices, lithium-ion batteries as an existing advanced battery system face a series of significant challenges, such as time-consuming manual material screening, safety concerns, performance degradation, non-access in the off-grid state, poor environmental adaptability, and pollution from waste batteries. Accordingly, incorporating the characteristics of sapiential life into batteries to construct sapiential systems is one of the most engaging tactics to tackle the above issues. In this review, we introduce the concept of sapiential battery systems and provide a comprehensive overview of their core sapiential features, including materials genomics, non-destructive testing, self-healing, self-sustaining capabilities, temperature adaptation, and degradability, which endow batteries with higher performance and more functions. Moreover, the possible future research directions on sapiential battery systems are deeply discussed. This review aims to offer insights for designing beyond traditional electrochemical energy, meeting broader application scenarios such as ultra-long-endurance electric vehicles, wide-temperature energy storage, space exploration, and wearable electronic devices.

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.

Towards Efficient Polymeric Binders for Transition Metal Oxides-based Li-ion Battery Cathodes

Transition metal oxide cathodes (TMOCs) such as LiNi0.8Mn0.1Co0.1O2 and LiMn1.5Ni0.5O4 have been widely employed in Li-ion batteries (LIBs) owing to superior operating voltages, high reversible capacities and relatively low cost. Nevertheless, despite significant advancements in practical application, TMOC-based LIBs face great challenges such as transition metal dissolution and volume expansion during cycling, which jeopardizes the future advance of high-voltage TMOCs. As a critical component of cathode, polymeric binder acts as a crucial part in maintaining the mechanical and ion/electron conductive integrity between active particles, carbon additives, and the aluminum collector, hence minimizing cathode pulverization during battery cycling. Moreover, Polymeric binder with specialized functions is thought to offer a new solution to enhancing the electrochemical stability of the TMOCs. Therefore, this review aims at providing a comprehensive summary of the ideal requirements, design strategies and recent progress of polymeric binders for TMOCs. Future design perspectives and promising research technologies for advanced binders for high-voltage TMOCs are introduced.