CN-121983582-A - Thermal response current collector, preparation method thereof and battery pole piece

Abstract

The invention discloses a thermally responsive current collector, a preparation method thereof and a battery pole piece, belonging to the technical field of lithium battery current collectors, namely, the high-melting point polymer is taken as a polymer matrix together and is fused and blended with the conductive filler to form a thermally responsive layer by film drawing, so that the thermally responsive current collector is constructed. By taking the two polymers as the matrix, the relationship among room temperature resistance, resistance temperature and PTC intensity is balanced, and the prepared reversible thermal response layer has higher resistance state at high temperature and in a wide temperature range, so that the temperature of NTC is improved. The battery using the reversible thermal response layer as a current collector can be effectively turned off at a high temperature in a wide temperature range, thereby avoiding thermal runaway. In addition, the polymer and the conductive filler are all raw materials which are commercialized and can be produced in large quantities, namely the reversible thermal response layer can be produced in large quantities, so the cost is low.

Inventors

• XU HENGHUI
• ZHAO JIE
• CUI YANMING
• LIN JIU
• YANG LIN
• YU SHENGDONG
• HUANG YUNHUI

Assignees

• 华中科技大学
• 江西赣锋锂电科技股份有限公司

Dates

Publication Date

20260505

Application Date

20260205

Claims (10)

1. 1. The thermal response current collector is characterized by comprising a thermal response layer formed by taking a first polymer and a second polymer as matrixes, taking conductive filler as a conductive phase, carrying out melt blending and film drawing; The melting point of the first polymer is 60-120 ℃, the melting point of the second polymer is 80-150 ℃, the half-width of DSC melting peaks of the first polymer and the second polymer are both more than or equal to 2.5 ℃, the ending temperature of the DSC melting peak of the first polymer is more than or equal to the starting temperature of the DSC melting peak of the second polymer, and the difference between the peak temperatures of the DSC melting peak of the first polymer and the DSC melting peak of the second polymer is 10-50 ℃; the mass ratio of the first polymer to the second polymer is 0.5-10:1.
2. 2. The thermally responsive current collector of claim 1, wherein the thermally responsive layer has an initial temperature response interval of 70 ℃ to 130 ℃.
3. 3. The thermally responsive current collector of claim 1, wherein the mass ratio of the matrix to the conductive filler is 1:0.1-0.5.
4. 4. The thermally responsive current collector of claim 1, wherein the thermally responsive current collector is formed of thermally responsive layers or is composited of thermally responsive layers and electrically conductive layers disposed between adjacent thermally responsive layers by alternating layers of electrically conductive layers.
5. 5. The thermally responsive current collector of claim 1, wherein said thermally responsive layer has a thickness of 1 μm to 30 μm.
6. 6. The thermally responsive current collector of claim 1, wherein said first polymer is selected from at least one of low density polyethylene, polypropylene, polyolefin-based elastomers, ethylene-vinyl acetate copolymers, polyurethane elastomers, thermoplastic elastomers, and polyester materials; the second polymer is at least one selected from polyethylene, low-density linear polyethylene, high-density polyethylene, ultra-high-density polyethylene, polyvinyl chloride, copolyamide elastomer and phosphorus-containing flame-retardant copolyester, and the conductive filler is at least one selected from conductive carbon, conductive metal, conductive ceramic and conductive polymer.
7. 7. A method of preparing a thermally responsive current collector as claimed in claim 4 comprising the steps of: first melting and blending the first polymer and the second polymer according to the mass ratio of 0.5-10:1, adding conductive filler to perform second melting and blending to obtain PTC master batch, and drawing a film to form a thermal response layer to obtain a thermal response current collector; Or the first polymer and the second polymer are subjected to first melt blending according to the mass ratio of 0.5-10:1, then conductive filler is added for second melt blending, PTC master batch is obtained, film drawing is carried out, a thermal response layer is formed, and the two thermal response layers are respectively compounded on the upper surface and the lower surface of the conductive layer, so that the thermal response current collector is obtained.
8. 8. The method of claim 7, wherein the first melt blending temperature is 100 ℃ to 150 ℃ and the second melt blending temperature is 120 ℃ to 180 ℃.
9. 9. The method of claim 7, wherein the compounding is hot pressing at 100 ℃ to 160 ℃.
10. 10. A battery pole piece, which is characterized in that the battery pole piece is obtained by coating a battery anode or cathode material on the surface of the thermally-responsive current collector of any one of claims 1-6.

Description

Thermal response current collector, preparation method thereof and battery pole piece Technical Field The invention relates to the technical field of lithium battery current collectors, in particular to a thermally-responsive current collector, a preparation method thereof and a battery pole piece. Background The lithium battery is easy to cause thermal anomaly under high-temperature environment or abnormal working condition, so that thermal runaway of the battery can be induced, even chain type thermal spread reaction occurs in the battery pack, and the life safety of a user is seriously endangered. Currently, batteries are mainly subjected to safety protection in a passive manner by detecting temperature through a BMS system and the like. In order to further improve the safety performance of the battery, it is necessary to actively block the thermal runaway of the battery from the source by optimizing the internal components of the battery. The current collector is used as a main component of the battery and mainly used for conducting electricity and supporting anode and cathode materials. However, the current collector does not participate in the electrochemical reaction inside the battery, and does not contribute to the energy density of the battery, but is one of the main influencing factors of the internal short circuit of the battery. By specially designing the current collector to impart functionality thereto, the intrinsic safety performance of the battery current collector can be achieved. The reversible thermal response layer is designed on the surface or inside of the current collector, so that electrons can be conducted at the normal working condition temperature of the battery through the reversible thermal response layer, the reversible thermal response layer becomes an electronic insulator when the temperature rises to block the battery from continuously discharging, and the reversible thermal response layer is converted into an electronic conductor when the temperature recovers the normal working condition temperature of the battery to recover the battery performance. Currently, the reversible thermal response layer in the prior art is mainly implemented using PTC (positive temperature coefficient) materials. In battery safety protection, a Positive Temperature Coefficient (PTC) material realizes current limiting and turn-off of a circuit by rapidly rising resistance when the temperature is too high. However, many PTC materials, such as a conductive composite material with high PTC strength having an isolated-double percolation structure disclosed in the patent application publication No. CN109762277a, are converted into a Negative Temperature Coefficient (NTC) effect after the temperature exceeds the melting point, i.e., the resistance decreases instead with the increase of the temperature, which causes that it is not possible to maintain a high resistance state in a high temperature range, and thus it is difficult to continuously and effectively turn off the circuit in a wide temperature range. In addition, the high temperature significantly increases the ionic conductivity inside the battery and aggravates side reactions, so that thermal runaway of the battery is more likely to occur. In order to effectively inhibit the NTC effect of the PTC material at high temperature, in the prior art, an invention patent application with publication number of CN117186629A discloses an irradiation nylon 12/carbon black PTC composite material and a preparation method thereof, wherein a stable three-dimensional network structure is formed inside the PTC material mainly through radiation crosslinking so as to inhibit disordered rearrangement of a high polymer chain above a melting point, thereby preventing the resistivity from decreasing along with the temperature rise and achieving the purpose of inhibiting the NTC effect. Another patent application of the invention with publication number CN118085478a discloses a PTC film material based on a solution method and a preparation method thereof, which is to design special conductive particles with a composite core-shell structure or surface coating layer, so that the special conductive particles can stably maintain a dispersion state and form a firmer conductive network at high temperature, thereby still limiting particle aggregation and migration after the polymer matrix is melted, and effectively inhibiting the occurrence of NTC effect. However, the above-described manner of suppressing the NTC effect adds additional cost. Disclosure of Invention The invention provides a thermal response current collector, a preparation method thereof and a battery pole piece, which effectively solve the technical problems that the battery cannot be turned off in a wide temperature range due to the NTC effect of the traditional PTC material, so that thermal runaway is caused, and the cost of the traditional method for inhibiting the NTC effect is high. The first object of