CN-121565793-B - Safety coating for battery electrode plate and electrode plate

Abstract

The application provides a safety coating for a battery electrode plate and the electrode plate, and belongs to the technical field of new energy batteries. The safety coating is of a composite layer structure and comprises a blocking layer, a thermal melting insulating layer and a thermal melting insulating layer, wherein the blocking layer is arranged on a current collector, the impedance of the blocking layer is increased in a step mode along with the increase of potential difference at the position, the thermal melting insulating layer is arranged on the blocking layer, the impedance of the thermal melting insulating layer is increased in a step mode along with the increase of temperature, and the blocking layer and the thermal melting insulating layer are in a synergistic effect in function to provide a bidirectional response mechanism of voltage and temperature. The application is used for the safety coating of the battery electrode plate, can ensure the stability and the performance of the battery during the normal operation of the battery through the synergistic effect of the blocking layer and the thermal fusion insulating layer, quickly responds and forms an effective insulating barrier when the battery has faults such as internal short circuit and the like, cuts off current, avoids the occurrence of safety accidents such as thermal runaway and the like of the battery, and provides reliable safety guarantee for the use of the battery.

Inventors

• CHEN BAOHUI
• WANG JIANGFENG
• LI BO
• LIU JINGJU
• Chen kuo
• LIU JIARUI
• CHEN LUOJIA
• XIE LINJIN
• GUO XIAOHAN

Assignees

• 湖南防灾科技有限公司
• 国网湖南省电力有限公司防灾减灾中心
• 湖南省湘电试研技术有限公司

Dates

Publication Date

20260505

Application Date

20260122

Claims (7)

1. 1. A safety coating for a battery electrode sheet, characterized in that the safety coating is of a composite layer structure comprising a barrier layer and a thermal fusion insulating layer: The barrier layer is arranged on the current collector, comprises a functional material with a semiconductor characteristic, wherein the fermi level of the functional material is matched with that of the current collector so as to form ohmic contact when the battery works normally, the impedance of the barrier layer is increased in a step mode along with the increase of the potential difference at the position, the step-type increase is triggered based on the electrochemical dedoping characteristic of the functional material with the semiconductor characteristic, and the conductivity of the functional material is reduced by several orders of magnitude when the increase of the potential difference at the position leads to the rapid electrochemical dedoping of the functional material; the functional material with semiconductor characteristics is selected from at least one of polyaniline, polypyrrole, poly (3, 4-ethylenedioxythiophene) and derivatives thereof, and composite materials thereof; The thermal melting insulating layer is arranged on the barrier layer, and the impedance of the thermal melting insulating layer is increased in a step-like manner along with the temperature increase, and comprises a self-melting polymer matrix, a conductive medium with a preset melting point dispersed in the self-melting polymer matrix, and heat-resistant insulating particles dispersed in the self-melting polymer matrix, wherein the melting point of the conductive medium is higher than the glass transition temperature of the self-melting polymer matrix and lower than or equal to the melting point of the self-melting polymer matrix; the heat-melting insulating layer is configured to soften a self-melting polymer matrix when the temperature rises to a softening zone, and a conductive medium dispersed in the self-melting polymer matrix is extruded and gathered to form a temporary conductive path, so that the resistance of the coating is reduced to accelerate local heating; wherein the barrier layer and the thermally fused insulating layer functionally cooperate to provide a bi-directional response mechanism to voltage and temperature.
2. 2. The safety coating for battery electrode tabs according to claim 1, wherein the conductive medium having a preset melting point is a metal or alloy powder selected from at least one of indium, tin, bismuth, gallium and alloys thereof.
3. 3. The safety coating for battery electrode tabs according to claim 1, wherein the thermally fused insulating layer comprises, by mass, 20% -50% of a self-fused polymer matrix, 15% -25% of a conductive medium, 30% -50% of insulating particles, 2% -5% of a binder, and 1% -5% of a processing aid.
4. 4. The safety coating for battery electrode tabs according to claim 1, characterized in that the thickness T 1 of the barrier layer is 50: 50 nm-500: 500 nm; And/or, the thickness T 2 >10×T 1 of the thermally fused insulation layer.
5. 5. A method for preparing a safety coating for preparing the battery electrode sheet according to any one of claims 1 to 4, comprising the steps of: preparing a barrier layer slurry, coating the barrier layer slurry on a current collector, and forming a barrier layer through a first drying procedure; preparing a thermal melting insulating layer slurry, coating the slurry on the barrier layer, and forming a thermal melting insulating layer through a second drying procedure; wherein the highest temperature of the second drying procedure is less than the self-fluxing polymer matrix in the thermally fluxing insulation layer and less than the melting point of the conductive medium.
6. 6. The method of claim 5, wherein the second drying procedure is temperature programmed drying comprising at least one soak period in the range of 80 ℃ to 110 ℃.
7. 7. An electrode sheet comprising a current collector and an active material layer, characterized in that the safety coating according to any one of claims 1-4 is provided between the current collector and the active material layer.

Description

Safety coating for battery electrode plate and electrode plate Technical Field The application relates to the technical field of new energy batteries, in particular to a safety coating for a battery electrode plate and the electrode plate. Background The new energy sources such as wind power, photovoltaic and the like have the problems of large volatility and strong randomness, and large-scale energy storage needs to be configured. The secondary battery energy storage system such as the lithium ion battery and the sodium ion battery has the advantages of high energy density, high conversion efficiency, short construction period, convenience in installation and the like, is suitable for large-scale energy storage, and has wide application prospect. In long-term operation, secondary batteries such as lithium ion batteries and sodium ion batteries are easy to cause thermal runaway of the batteries due to internal and external faults and the like, release a large amount of heat and explosive gas, and cause ignition and explosion. In recent years, domestic and foreign battery energy storage the system has a plurality of fire and explosion accidents. The safety problem of the lithium ion battery and sodium ion battery energy storage system is a technical problem which needs to be solved in the energy storage field. At present, in the manufacturing process of the positive plate, a certain positive temperature coefficient PTC (Positive Temperature Coefficient) material safety coating is coated on the positive current collector, so that the safety of the battery is improved. When the temperature of the battery increases, the resistance of the PTC material increases, thereby causing the resistance of the entire electrode active material layer to become large, and having a safety effect of breaking power and preventing the electrochemical reaction from proceeding. Patent CN106229474A discloses a multifunctional coating of a lithium ion battery, which comprises the following components, by weight, 100 parts of a conductive agent, 20-5000 parts of ceramic material particles, and 10-500 parts of a binder. The patent CN107437622A discloses an electrode and a preparation method thereof, wherein an electrode coating is arranged between a current collector and an active material layer and comprises a polymer matrix and a conductive agent, wherein the polymer matrix is selected from one or more of low-density polyethylene, high-density polyethylene, epoxy resin, polyvinylidene fluoride, ethylene-ethyl acrylate copolymer, ethylene-vinyl acetate copolymer, polybutene, cellulose acetate and polyamide, and the conductive agent is selected from one or more of thorn spherical Ni powder, thorn spherical Cu powder, thorn spherical Al powder and thorn spherical tungsten carbide. When the PTC material in the prior art does not work, the resistance is larger, the energy conversion efficiency and other performances of the battery can be obviously reduced, the heat of the battery is increased, and the thermal runaway risk of the battery is induced. Therefore, there is a need to develop a coating layer which has a small resistance when the battery is normally operated, does not affect the safe operation of the battery, and can rapidly respond when a fault occurs in the battery, thereby improving the safety of the battery. Disclosure of Invention The present application has been made in view of the above-described problems, and an object thereof is to provide a safety coating layer for a battery electrode sheet and an electrode sheet. The first aspect of the present application provides a safety coating for a battery electrode sheet, the safety coating having a composite layer structure, comprising: the blocking layer is arranged on the current collector, and the impedance of the blocking layer is increased in a step-type manner along with the increase of the potential difference at the position; The thermal melting insulating layer is arranged on the barrier layer, and the impedance of the thermal melting insulating layer is increased in a step-like manner along with the temperature increase; wherein the barrier layer and the thermally fused insulating layer functionally cooperate to provide a bi-directional response mechanism to voltage and temperature. Further, the barrier layer includes a functional material having a semiconductor characteristic, and the fermi level of the functional material is matched with that of the current collector to form an ohmic contact when the battery is normally operated. Further, the functional material having semiconductor characteristics is selected from at least one of polyaniline, polypyrrole, poly (3, 4-ethylenedioxythiophene) and derivatives thereof, and composite materials thereof. Further, the thermally fused insulating layer includes: self-melting the polymer matrix; a conductive medium having a predetermined melting point dispersed in the self-fluxing polymer matrix; Heat resistant insulating part