CN-121123288-B - Composite current collector and lithium battery

CN121123288BCN 121123288 BCN121123288 BCN 121123288BCN-121123288-B

Abstract

The invention relates to a composite current collector and a lithium battery, wherein the composite current collector comprises an organic polymer layer and a conductive layer which are stacked, wherein spherical crystals are included in the organic polymer layer, the maximum width of each spherical crystal is 2-20 mu m, the spherical crystals with the maximum width of 3-7 mu m are first spherical crystals, and the number of the first spherical crystals accounts for more than or equal to 40% of the number of all the spherical crystals in a slicing state. By precisely controlling the size of the spherulites and the number proportion of the first spherulites, the mechanical strength and the heat resistance of the composite current collector can be effectively improved. The proper spherulitic size distribution can avoid local thermal stress concentration, reduce the risk of thermal deformation of the organic polymer layer when the battery heats, further enhance the safety performance of the battery, ensure the stable combination of the conductive layer and the organic polymer layer, ensure smooth current conduction and ensure the working reliability.

Inventors

TANG CHUNMING
LIANG XIANFA
ZHOU JIANGANG
QIU GUOCHAO

Assignees

哲创(中山)新材料有限公司

Dates

Publication Date: 20260508
Application Date: 20250915

Claims (6)

1. The composite current collector is characterized by comprising an organic polymer layer and a conductive layer which are stacked, wherein spherical crystals are included in the organic polymer layer, the maximum width of each spherical crystal is 2-20 mu m, the spherical crystals with the maximum width of 3-7 mu m are first spherical crystals, the number of the first spherical crystals accounts for more than or equal to 40% of the number of all spherical crystals, the spherical crystals with the maximum width of 7-12 mu m in the organic polymer layer are second spherical crystals, and the number of the second spherical crystals accounts for more than or equal to 35% of the number of all spherical crystals; The organic polymer layer further comprises platelets, the maximum width of the platelets is 50 nm-1.2 mu m, the maximum thickness of the platelets is 5-30 nm, the maximum width of the platelets is 100 nm-0.5 mu m, the number of the first platelets accounts for 25-40% of the number of the platelets, and the crystallinity of the organic polymer layer is 40% -75%.
2. The composite current collector of claim 1 wherein the standard deviation of the crystalline region distribution of the organic polymer layer is 5% or less of the mean crystallinity.
3. The composite current collector of claim 1 wherein said organic polymer layer has an X-ray diffraction half-peak width between 0.5 ° and 2 °.
4. The composite current collector of claim 1, wherein the ratio of crystallinity to enthalpy of fusion of the organic polymer layer is 0.8 to 1.2.
5. The composite current collector of claim 1, wherein the ratio of the maximum length to the maximum thickness of the platelets in the sliced state ranges from 5 to 11.
6. A lithium battery comprising the composite current collector of any one of claims 1-5.

Description

Composite current collector and lithium battery Technical Field The invention relates to the field of lithium battery materials, in particular to a composite current collector and a lithium battery. Background The current collector is an indispensable component in the lithium ion battery, and has the main functions of bearing electrode active substances and conducting electricity, so that the current collector can collect and output current generated by electrochemical reaction, reduce the internal resistance of the battery and improve the coulomb efficiency and the cycling stability. Common current collector materials include aluminum foil for positive electrode and copper foil for negative electrode, and in recent years, the occurrence of composite current collectors can improve the energy density of the battery and reduce the cost by replacing the conventional metal foil with a lightweight base film. In the conventional composite current collector, the problem that the organic polymer is not heat-resistant is prominent. When the battery heats in the charge and discharge process, the organic polymer is easy to generate thermal deformation and even fail, so that internal short circuit of the battery is caused, thermal runaway is caused, and the safety performance of the battery is seriously threatened. This problem limits the widespread use of lithium batteries in fields such as electric vehicles, energy storage systems, etc. where the safety requirements are extremely high. Therefore, the development of the technical scheme capable of effectively improving the heat resistance of the composite current collector and enhancing the safety of the battery has important practical significance and urgency. Disclosure of Invention Based on the above, it is necessary to provide a composite current collector and a lithium battery, which can effectively improve the heat resistance of the composite current collector and enhance the working safety of the lithium battery. The composite current collector comprises an organic polymer layer and a conductive layer which are stacked, wherein spherical crystals are included in the organic polymer layer, the maximum width of each spherical crystal is 2-20 mu m, the spherical crystals with the maximum width of 3-7 mu m are first spherical crystals, and the number of the first spherical crystals is more than or equal to 40% of the number of all the spherical crystals in a slicing state. The composite current collector is composed of laminated organic polymer layers and conductive layers, and spherulites in the organic polymer layers show specific size distribution in a sliced state. The maximum width of the spherulites is limited to 2-20 μm, and the spherulites in the range can form stable interaction with the molecular chains of the organic polymer. Wherein, the first spherulites with the maximum width of 3-7 μm account for more than or equal to 40%, and the spherulites with the size can enhance the intertwining and the restraint among molecular chains and improve the structural stability of the organic polymer layer. When the composite current collector is used in a lithium battery, the mechanical strength and the heat resistance of the composite current collector can be effectively improved by precisely controlling the size of the spherulites and the number ratio of the first spherulites. The proper spherulitic size distribution can avoid local thermal stress concentration, reduce the risk of thermal deformation of the organic polymer layer when the battery heats, further enhance the safety performance of the battery, ensure the stable combination of the conductive layer and the organic polymer layer, ensure smooth current conduction and ensure the working reliability. In one embodiment, the spherulites with the maximum width of 7-12 μm in the organic polymer layer are second spherulites, and the number of the second spherulites is more than or equal to 35% of the number of all the spherulites. In one embodiment, the crystallinity of the organic polymer layer is 40% -75%. In one embodiment, the standard deviation of the distribution of the crystalline regions of the organic polymer layer is less than or equal to 5% of the average crystallinity. In one embodiment, the organic polymer layer has an X-ray diffraction half-peak width between 0.5 ° and 2 °. In one embodiment, the ratio of the crystallinity to the melting enthalpy of the organic polymer layer is 0.8-1.2. In one embodiment, the organic polymer layer further includes platelets, in a sliced state, the maximum width of the platelets is 50nm to 1.2 μm, the maximum thickness is 5 to 30nm, the platelets with the maximum width of 100nm to 0.5 μm are first platelets, and the number of the first platelets accounts for 25 to 40% of the number of all the platelets. In one embodiment, the total thickness of all the platelets is 5-15% of the total thickness of the organic polymer layer. In one embodiment, the ratio of the maximum