Lithium-ion batteries have been playing an increasingly important role in new energy sources due to their high energy density. The energy density of lithium-ion batteries exceeds 150 Wh/Kg, which is almost the highest energy density in known secondary batteries.

In order to further improve the performance of lithium-ion batteries, researchers are trying to find new electrode materials, electrolytes, and additives. One of the most important aspects is to find the most suitable binder for the electrodes used. The binder is a very important component of the positive and negative electrode materials of the lithium battery. It can closely bind the active material, the conductive agent and the current collector in the electrode material, and reinforce the active material and the conductive agent as well as the active material and the current collector. The electronic contact between them stabilizes the structure of the pole piece.

At present, the adhesives used in lithium-ion batteries are mainly organic fluoropolymers, and styrene butadiene rubber (SBR) and carboxymethyl cellulose (CMC), but their electrochemical stability and ionic conductivity are still not satisfied with charge and discharge. During the process, the volume change of the negative electrode active material such as nano-silicon material requires a binder.

At home and abroad, there have been advances in other adhesive systems such as modified cellulose materials, chitin derivatives, and alginates, but conventional electrode binders have low lithium ion conductivity and poor electrical conductivity, and are charged and discharged at a large rate. It is easy to cause battery polarization. In the existing power lithium ion battery system, performance is limited at high rate charge and discharge due to the use of a binder that does not have high ion conductivity. The search for a new type of high performance new binder is of great significance for further improving the performance of lithium batteries.

In recent years, the polymer functional film team led by Xue Lixin, a researcher at the Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, has made a series of progresses in lithium-ion battery binders, synthesizing a fluorosulfonimide-containing backbone and The fluorosulfonic acid side-chain ionic polymer, which has excellent electrochemical stability as a lithium battery binder pole piece, exhibits a smaller peak potential difference than a polar piece using a PVDF adhesive. It is shown that the internal delithiation/lithium intercalation redox reaction of the pole piece containing the conductive binder is more reversible and the polarization is smaller.

Lithium iron phosphate (LiFePO4) positive electrode sheet and lithium sheet containing an ion binder were assembled into a battery to evaluate the battery cycle performance, and it was found that the charge and discharge were stable. When the charge/discharge rate is increased to 4C, the discharge capacity of the LiFePO4 film containing PVDF binder is only 74mAh/g, and it shows a sharp decrease. The pole piece containing the conductive adhesive can maintain the discharge capacity at 100 mAh/g at 4C or 5C. It shows that the conductive adhesive is conducive to improve the discharge capacity and stability under high current charge and discharge, and is more suitable for power lithium batteries than ordinary non-ionic adhesives. This part of the work was published in J. Mater. Chem. A, 2013, 1, 15016 and J. Power Sources, 2014, 256, 28. At present, the team is carrying out pilot scale up production and industrial application of such adhesives.

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