The development of sustainable energy has been attracting much attention andurgently need to solve, and higher energy density battery system has become aresearch hotspot nowadays.Lithium ion batteries (LIBs) is a practical secondary battery system for commercial application based on the existing lithium secondary battery. While, this system is confronted with the problems of complicated preparation technology, environmental unfriendly and low energy density. Therefore, how to solve the above problems is becoming an important research topic.
Researchers have made substantial efforts in researching and developing active materials, separators and electrolytesto enhance the energy density. However, little attentionhas been paid to develop novel LIB auxiliary materials, such as thebinder. In fact, the binder plays an important role in a LIB as it bindsthe active materials onto the current collector,as well asthe performance of the electrode and even the entire lithium ion battery (internal resistance, capacity, cycle life, specific energy, etc.). An ideal bindershould be of low cost, strong bonding, high physical and electrochemical stability in the electrolyte.
The binders used in LIBs are generally made of high molecular polymers, which can be divided into two categories: organic solvent-based binders and aqueous binders. Poly(vinylidenefluoride) (PVDF), an organic solvent-based binder material, has been commercially and extensively used as a LIB cathode binder even though this polymer possesses unfavorable characteristics in LiFePO4due to its non-conductive defect and large volume change during Li+insertion/extraction process, as well as its negative effect on the environment and high cost.To address these issues,the development of water-soluble binders has become a new growing area of LIB technology.
However, this kind of binder is mainly distributed in point-type or line-type, and solidified the powers in 1Dor 2Ddirections. Therefore, the lack of long-distance connection between the powers in the electrode will lead to powder particles fall off the collector during charging and discharging process, reducing low utilization of active materials.If long range connections can be established between the binder and the powers, solidifying the electrode powers in the 3D direction, it will improve the adhesion of binders to reduce the amount of adhesives, enhancing the energy density of LIBs.
In this study, a unique 3Dhierarchical water-based polymerbinder was produced fromthe esteryl-enriched/cyano-enrichedmonomers and introducing a sulfo-anion into them. The walnutkernel shape 3Dhierarchical structure was induced by the latexself-assembly through the interaction between the hydrophilicsegment and the hydrophobic blocks in conjunction with theelectrostatic repulsion of the sulfonate groups and steric hindranceof large side groups; in turns ensuring constant adhesion andelectrical connections even when the electrode integrity wasdamaged during the charge-discharge cycling process.The related work was recently published online in Electrochimica Acta, the TOP journal of energy and fuel synthesis. The impact factor was 5.116, and the school of chemical engineering of Guizhou institute of technology was the first signatories.
This work is supported by National Natural Science Foundation of China (No. 51603049, 21766005), Natural Science Foundation of Guizhou Province (Grant No.  2059,  2069).
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Xianguo Ma, Shuliang Zou, Anjiang Tang, Lijun Chen, Zhenghua Deng, Bruno G. Pollet, Shan Ji,Three-dimensional hierarchical walnut kernel shape conducting polymer as water soluble binder for lithium-ion battery;Electrochimica Acta 269 (2018) 571-579; DOI:10.1016/j.electacta.2018.03.031. https://www.sciencedirect.com/science/article/pii/S001346861830519X