Binder used for lithium ion battery anode, lithium ion battery anode using the same and preparation method thereof

Abstract

The invention provides a binder used for a lithium ion battery anode. The binder is an aromatic polymer containing a lithium fluorosulfonate side group, or an aromatic polymer containing a lithium fluorosulfimide side group, or a mixture of the two. The binder has strong binding power, and powder does not fall off. Ethanol and water are adopted as the solvent, and organic solvent consumption is reduced, thereby reducing harm to the environment. The side chain unit contains the -SO3Li or -SO2N<->Li<+>SO2- structure, so that lithium ions can be effectively dissociated so as to supplement lithium ions to the lithium ion battery anode, thus not only improving the utilization rate of lithium ions, but also indirectly enhancing the battery capacity. Experiments prove that the lithium ion battery taking the binder as the anode binder has stable electrochemical performance, and cannot be degraded along with the charge-discharge cycle of the battery, thereby effectively prolonging the service life of the battery.

Description

Technical field [0001] The invention belongs to the technical field of lithium ion batteries, and specifically relates to a binder for lithium ion battery positive electrodes, a lithium ion battery positive electrode using the binder and a preparation method thereof. Background technique [0002] Due to the advantages of high power density, low self-discharge rate, no memory effect and stable discharge voltage, lithium-ion batteries have gradually replaced traditional lead-acid batteries and cadmium-nickel batteries, becoming the main choice for power batteries. Power batteries have high requirements in terms of high-power output performance and safety, so they pose a major challenge to lithium-ion batteries. [0003] The binder is an important part of the positive and negative electrodes of lithium ion batteries, and is a polymer compound used to adhere the electrode active material to the current collector. Its main function is to bond and maintain the electrode active material,...

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Problems solved by technology

However, PVDF also has disadvantages in lithium-ion battery applications. For example, when the internal temperature of the battery rises, PVDF will interact with metal lithium and lithium carbide (Li x C 6 ) to react, therefore, the reaction of PVDF becomes one of the main sources of heat release of lithium-ion batteries; and, PVDF can be swelled by non-aqueous liquid electrolyte, resulting in a change in the structure of the pole piece, so that the adhesion of the electrode material to the current collector changes. poor, resulting in an increase in the contact resistance between electrode materials, and the need to strictly control the moisture in the environment, resulting in increased process costs; at the same time, a large amount of organic solvents are required, which pollutes the environment and poses a greater hazard to the health of operators , does not conform to the development trend of green industry

However, the bonding force of SBR is weak. As the battery charge-discharge cycle proceeds, the C=C in SBR will continue to degrade and make it gradually invalid, which will further cause the active material of the pole piece to fall off, resulting in a decrease in capacity and affecting battery life; and Due to the limitation of the chemical properties of its material components, SBR water-based binder can only be used as a binder for lithium-ion battery negative electrode materials.

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