Ptc ceramic safety coating, pole piece and lithium battery

Abstract

The application belongs to the technical field of lithium batteries, and particularly relates to a PTC ceramic safety coating, a pole piece and a lithium battery. The PTC ceramic safety coating comprises PTC ceramic powder, a conductive additive, a binder and a solvent, wherein the PTC ceramic powder is a perovskite oxide material, the chemical general formula of which is ABO3, the A site is doped with one or more of Sr, Ca, Ba and Pb, and the B site is substituted with one or more of Ti, Mn and Fe. A self-repairing PTC ceramic composite coating with temperature response characteristics is constructed on the surface of the positive or negative pole piece, so that the battery can inhibit large current discharge and further temperature rise when the temperature abnormally rises, effectively inhibit thermal runaway, significantly improve the safety of the lithium battery under extreme working conditions, and ensure the self-repairing of the pole piece coating after the abnormal temperature rise of the battery, and restore the normal use state of the battery.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery technology, and particularly relates to a PTC ceramic safety coating, electrode, and lithium battery. Background Technology

[0002] Battery thermal runaway is one of the most serious safety failure modes of lithium batteries. It is usually caused by factors such as internal short circuit, overcharging, external short circuit, mechanical extrusion, high temperature environment or manufacturing defects. Once triggered, it will rapidly release a large amount of heat energy, leading to serious consequences such as fire and explosion.

[0003] Currently, the main technical approaches to improve the safety of lithium batteries include: (1) adding flame retardants (such as organophosphorus compounds and fluorinated esters) to the electrolyte. However, the introduction of flame retardants often leads to a decrease in the ionic conductivity of the electrolyte and a narrowing of the electrochemical window, affecting the rate performance and cycle life of the battery. (2) using ceramic-coated separators to enhance thermal dimensional stability. However, although ceramic separators can delay thermal shrinkage, they cannot fundamentally cut off the electrochemical reaction chain. (3) optimizing the battery management system (BMS) for real-time monitoring and cut-off protection of voltage, temperature, and current, as well as using mechanical protection structures such as high-strength casings or pressure relief valves. However, the BMS system relies on external signal responses and has risks such as detection delays and sensor failures. Mechanical structures are also difficult to cope with the chain reaction of rapid internal temperature rise.

[0004] Since the electrode is the core site of electrochemical reactions, directly constructing a thermally responsive protective layer at this location allows for the shortest path to sense temperature changes and respond rapidly, achieving "source control." Therefore, it is necessary to develop a high-safety coating that can be effectively applied to the surface of lithium-ion battery electrodes, while also possessing good electrochemical compatibility, high safety response sensitivity, and long-term cycle stability. Summary of the Invention

[0005] In view of this, this application provides a PTC ceramic safety coating, electrode, and lithium battery. By constructing a self-healing PTC ceramic composite coating with temperature-responsive characteristics on the surface of the positive or negative electrode, the battery can suppress high-current discharge and further temperature rise during abnormal temperature rises, thereby blocking the chain reaction process of thermal runaway, effectively suppressing thermal runaway, significantly improving the safety of lithium batteries under extreme conditions, and ensuring the self-repair of the electrode coating after abnormal temperature rise, restoring the battery to its normal operating state.

[0006] To achieve the above objectives, this application adopts the following solution: The first aspect of this application provides a PTC ceramic safety coating, comprising PTC ceramic powder, conductive additives, binders, inorganic fast ion conductor fillers, and solvents, wherein the PTC ceramic powder is a perovskite oxide material with the general chemical formula ABO3, the A site being one or more doped from Sr, Ca, Ba, and Pb, and the B site being one or more substituted from Ti, Mn, and Fe.

[0007] Furthermore, the ABO3 is BaTiO3.

[0008] Furthermore, the PTC ceramic powder is strontium (Sr). 2+ Doped BaTiO3, the chemical formula of which is Ba 1-x Sr x TiO3, where 0 < x < 0.5.

[0009] Furthermore, x = 0.2, and the chemical formula is Ba. 0.8 Sr 0.2 TiO3, using barium titanate (BaTiO3) as the raw material, for Ba 2+ The A-site doped alkaline earth metal ion Strontium Sr 2+ The barium-strontium doping ratio was 0.8:0.2. High-purity Ba powder with a narrow particle size distribution was prepared via solid-state reaction, followed by calcination, ball milling, and classification. 0.8 Sr 0.2 TiO3 has a particle size of 100 nm to 1 μm.

[0010] It should be noted that: by performing A-site doping, the Curie temperature of barium titanate (BaTiO3) is adjusted, that is, by replacing some barium ions (BaTiO3) with other alkaline earth metal ions with similar ionic radii. 2+ ), such as strontium (Sr) 2+ ), calcium (Ca 2+ ), lead (Pb) 2+ Elements such as ).

[0011] This application utilizes Sr doping... 2+ And adjust Sr 2+ The doping ratio is designed for a Curie temperature range of 90℃ to 120℃, with a barium-strontium ratio of 0.8:0.2. Lower doping levels have limited effect on material performance regulation and cannot achieve the desired wide-temperature range application; excessive dopant will form impurities, compromising material purity, leading to a sharp increase in dielectric loss and a decrease in insulation performance. The barium-strontium doping ratio used in this application can trigger a rapid increase in resistance during the initial stage of abnormal battery temperature rise (such as the initial stage of a short circuit or localized overheating), achieving rapid current limiting. Control of particle size ensures consistent coating performance.

[0012] Furthermore, the conductive additive is one or more of carbon nanotubes, graphene, and conductive carbon black; The adhesive is a thermally reversible polymer adhesive containing Diels-Alder reversible bonds; The solvent is one or a mixture of N-methylpyrrolidone (NMP) and deionized water; The inorganic fast ion conductor filler is LLZTO, LATP, or LPSCl.

[0013] It should be noted that the addition of conductive additives is used to maintain the conductive network of the coating at room temperature, ensuring efficient electron transport between the electrode and the coating, while also assisting in the construction of a three-dimensional conductive framework to improve the mechanical strength of the coating. Surface-modified carbon nanotubes or graphene oxide are preferred to enhance the interfacial adhesion with the ceramic powder.

[0014] Inorganic fast ion conductor fillers are used to improve the lithium-ion conductivity in the coating, reduce the electrode / electrolyte interface impedance, and prevent lithium-ion diffusion from being hindered by the coating, thereby ensuring the high-rate performance of the battery. These fillers are preferably nano-sized particles, uniformly dispersed in the slurry, and do not damage the thermal response characteristics of the PTC material.

[0015] Furthermore, the preparation method of the thermally reversible polymer binder is as follows: First, 2,5-furandiethanol and bismaleimide are dissolved in anhydrous dimethylformamide (DMF). Then, the mixture is stirred and reacted at 60°C for 24 hours under nitrogen protection to form a furan-maleimide Diels-Alder adduct. Finally, after the reaction is completed, the product is precipitated in deionized water, filtered, washed, and vacuum dried at 60°C for 24 hours to obtain the thermally reversible polymer binder.

[0016] Furthermore, the PTC ceramic powder accounts for 50% to 80% of the mass, the conductive additive accounts for 5% to 10% of the mass, the binder accounts for 10% to 25% of the mass, and the inorganic fast ion conductor filler accounts for 2% to 8% of the mass.

[0017] Furthermore, the thickness of the PTC ceramic safety coating is 10–30 μm, preferably 12–16 μm.

[0018] It should be noted that this application requires control over the thickness of the safety coating after drying. If it is too thin, the protective effect will be insufficient; if it is too thick, it will increase internal resistance and affect energy density.

[0019] The second aspect of this application provides an electrode sheet, including a positive electrode sheet and a negative electrode sheet, wherein the surfaces of the positive electrode sheet and / or the negative electrode sheet are coated with a PTC ceramic safety coating as described in any one of claims 1-8. The PTC ceramic safety coating is uniformly applied to the surface of the active material layer of the positive electrode sheet or the negative electrode sheet by scraping, spraying, screen printing or slot extrusion coating, and then dried at a low temperature of 60-80°C for 6-12 hours and cold-pressed at a pressure of 5-15 MPa to form a dense, uniform and strongly adhesive safety coating. The positive electrode active material is one or more of NCM, NCA, LFP, and LCO; The active material of the negative electrode is one or more of graphite, mesophase carbon microspheres, silicon-carbon composite materials, and metallic lithium.

[0020] It should be noted that the PTC ceramic safety coating process of this application can be carried out on the basis of existing electrode preparation production lines, and has strong compatibility.

[0021] A third aspect of this application provides a lithium battery, including the electrode sheets described above. The lithium battery is assembled into an electrode assembly through cutting and winding processes, followed by casing, liquid injection, and formation processes.

[0022] Compared with the prior art, the beneficial effects of this application are: This application introduces PTC ceramic material as a functional coating component onto the surface of the active layer of lithium battery electrodes. This triggers a rapid increase in resistance at the initial stage of abnormal temperature rise (such as the initial stage of a short circuit or localized overheating), achieving rapid current limiting and realizing "temperature-triggered" self-limiting current protection, overcoming the limitations of traditional passive protection. The coating acts directly on the electrode reaction interface, resulting in the shortest sensing and response path and the highest protection efficiency, enabling precise suppression of localized hotspots. Specifically: In this application, Sr is used as an equivalent ion dopant element in BaTiO3-based PTC ceramics, which can lower the Curie temperature of PTC ceramic materials from 120℃ to around 110℃, or even lower, such as 60-120℃. Combined with the thermally reversible DA-bonded polymer binder of this application, the reverse reaction temperature can also be designed in the range of 80-120℃.

[0023] This application quantitatively designs Sr doping to set both the Curie temperature of the PTC ceramic coating and the reaction temperature of the DA bond polymer binder at 110±5℃. Utilizing this overlapping temperature window, the two functional materials achieve synergistic response within a specific overheating temperature range. The Curie temperature Tc of the PTC material and the reversible decrosslinking temperature Tc of the DA bond are related. DA They substantially overlap or have a specified temperature difference range (e.g., |Tc-T) DA(≤10℃) This allows both devices to trigger their respective response functions simultaneously or sequentially when the temperature exceeds the thermal runaway warning threshold. This achieves long-term overheat protection and long-term cycle stability of the battery. Attached Figure Description

[0024] Figure 1 Ba prepared for this application 0.8 Sr 0.2 A comparison of the temperature-resistivity characteristic curves of TiO3 and traditional BaTiO3 ceramic materials. Figure 2 This is a comparison diagram of Example 3 of this application and the comparative example of a 5mm needle puncture test; Figure 3 Examples 1-3 of this application and the comparative example are the capacity retention rates during 1C room temperature cycling. Detailed Implementation

[0025] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0026] The embodiments of this application take the coating of a safety coating on the surface of the active material of the negative electrode as an example.

[0027] In this application, Sr is doped into BaTiO3, and the product is Ba. 1-x Sr x The preparation method of TiO3 is as follows: Raw materials: Barium carbonate (BaCO3, analytical grade), strontium carbonate (SrCO3, analytical grade), titanium dioxide (TiO2, analytical grade). Proportion calculation: Target value x = 0.2 (i.e., Ba... 0.8 Sr 0.2 TiO3), accurately weigh the raw materials according to the stoichiometric ratio.

[0028] Using the traditional solid-state reaction method: S1. Ball Milling and Mixing: Place the weighed raw materials, anhydrous ethanol, and zirconium oxide grinding balls into a ball mill jar. Ball mill for 24 hours at a speed of 400 r / min to ensure uniform mixing of the raw materials.

[0029] S2. Pre-calcination (solid-phase synthesis): Dry the ball-milled slurry and sieve it. Pre-calcine at 1150℃ for 3 hours. This step causes a solid-phase reaction in the raw materials to form a barium strontium titanate solid solution.

[0030] S3. Secondary ball milling and granulation: The pre-calcined powder is ball milled again for 12 hours to refine the particles. An appropriate amount of polyvinyl alcohol (PVA) binder is added, and the granules are sieved (80-120 mesh).

[0031] S4. Pressing and molding: The granulated powder is pressed into round or square green sheets under a pressure of 20 MPa. The sheets are held at 550℃ for 2 hours to remove PVA. Then, they are sintered in air at 1400℃ for 3 hours.

[0032] For product Ba 0.8 Sr 0.2 The resistance-temperature characteristics of TiO3 were tested to verify the Curie temperature. A temperature-controlled powder resistivity meter was used to dynamically observe and record the change in powder resistivity with temperature during programmed heating. The specific operating steps are as follows: An appropriate amount of strontium-doped PTC powder to be tested is poured into a dedicated insulating mold of the instrument. At room temperature or high temperature, a constant and controllable pressure is applied to the powder in the mold using a pressure rod to expel air between particles and form a stable packing state. Under continuous pressure, the resistivity (ρ) of the powder is read using the instrument's measurement system. The instrument automatically records multi-dimensional data such as resistivity, pressure, and temperature, and plots curves in real time. Thus, its temperature-resistivity characteristic curve is obtained, as shown below. Figure 1 As shown.

[0033] Test results show: Figure 1 As shown, the PTC ceramic material obtained by doping with Sr has a Curie temperature that is about 10°C lower than that of conventional BaTiO3 ceramic material. This makes it more sensitive to resistance response when the lithium battery is abnormally heated, and the safe response temperature is increased by 10°C. Before the thermal runaway temperature occurs, the resistance is significantly improved, thereby cutting off the large current and improving battery safety.

[0034] The method for synthesizing the thermally reversible polymer binder containing Diels-Alder reversible bonds in this application comprises the following steps: First, 2,5-furandiethanol (10 mmol, 1.28 g) and bismaleimide (10 mmol, 2.96 g) were dissolved in 50 mL of anhydrous dimethylformamide (DMF); Then, under nitrogen protection, the mixture was stirred at 60°C for 24 hours to form a furan-maleimide Diels-Alder adduct. Finally, after the reaction is complete, the product is precipitated in deionized water, filtered, washed, and vacuum dried at 60°C for 24 hours to obtain a thermally reversible polymer binder.

[0035] It should be noted that the thermally reversible polymer binder of this application maintains an intact cross-linked network and structural stability at lower temperatures (<110°C); when the temperature exceeds approximately 110°C, the Diels-Alder bonds undergo reversible breakage, the polymer network disintegrates, and the bound conductive filler is released; when the temperature drops below 110°C, the Diels-Alder bonds reform, the polymer network recovers, and the conductive filler rearranges to form conductive pathways.

[0036] Example 1 Take 60g of BaTiO3 ceramic powder, add 5g of sp conductive particles, 15g of CMC / SBR (mass ratio 1:1) binder, add 2g of LLZTO, add deionized water to a solid content of 30%, and sand mill for 6 hours to obtain a uniformly dispersed slurry. Spray the slurry onto the surface of a graphite + 10% silicon-carbon negative electrode sheet. After drying, the coating thickness is 15μm, and the double-sided coating thickness is 30μm. Dry at 70℃ for 8 hours to remove solvent and avoid bubbles and cracks. Cold press the coated electrode sheet at 10 MPa to form a dense, uniform, and strongly adherent safety coating. The treated electrode sheet undergoes laser cutting, winding, and assembly processes, and is assembled with a 9-series ternary positive electrode sheet to form a 58Ah square lithium-ion battery (LP2714897) for safety and electrical performance testing.

[0037] Example 2 Weigh 60g of Ba prepared in this invention 0.8 Sr 0.2 TiO3 powder was mixed with 5g of sp conductive agent, 15g of CMC / SBR (mass ratio 1:1) binder, and 2g of LLZTO. Deionized water was added to bring the solid content to 30%. The mixture was then milled and dispersed for 6 hours to obtain a uniformly dispersed slurry. The slurry was sprayed onto the surface of a graphite + 10% silicon-carbon negative electrode. After drying, the coating thickness was 15μm, with a double-sided coating thickness of 30μm. The electrode was dried at 70℃ for 8 hours, and then cold-pressed at 10 MPa. The same battery model as in Example 1 was assembled, with a rated capacity of 58Ah.

[0038] Example 3 Based on Example 2, 15g of the thermally reversible polymer binder prepared according to this invention was added to replace the CMC / SBR binder in Example 2, along with 5g of sp conductive carbon black. All other conditions remained the same as in Example 2. This was used to compare and study the performance impact of the thermally reversible polymer binder. The same battery model as in Example 2 was assembled, with a rated capacity of 58Ah.

[0039] Comparative Example The same type of lithium battery without any coating was used, with the other electrode preparation, cell structure, and assembly process completely consistent with the example. The positive electrode was a ternary nine-series positive electrode, and the negative electrode was the same graphite + 10% silicon-carbon negative electrode as in Example 2. It was assembled with a rated capacity of 63Ah.

[0040] Performance testing: (1) Multiple thermal cycle stability test: The negative electrode sheets prepared in Examples 1 and 3 were subjected to three thermal cycle tests: each cycle was room temperature → 120℃ (held for 30 minutes) → cooled to room temperature (held for 2 hours). The resistivity of the battery was measured after each cycle. The test results are shown in Table 1 below: The test results show that even after three thermal cycles, the coating can still maintain a conductive working state (resistivity not exceeding 4×10). -2 (Ω·cm), significantly better than the irreversible failure mode of conventional PTC coatings.

[0041] Table 1. Resistivity test results after three thermal cycles in Examples 1 and 3.

[0042] (2) Needle Penetration Test: The core of the needle penetration test is to simulate an internal short circuit in the battery. During the test, a 5mm steel needle is inserted into the fully charged battery at a set speed, forcibly piercing the positive and negative terminals and causing an internal short circuit. This process generates a large amount of heat instantly, which can easily trigger the battery's "thermal runaway," thereby testing the battery's stability and safety under the most severe conditions. Before the needle penetration test, the battery is charged at a constant current of 0.5C to 4.25V, and then charged at a constant voltage of 4.25V to 0.05C. A 5mm steel needle is used, perpendicular to the direction of the electrode sheet, and pierced towards the center of the large surface. In the comparative example, the highest temperature reached 658.3℃ during the needle penetration, and an instantaneous fire and explosion occurred, resulting in thermal runaway, and the test was deemed unsuccessful. In Example 3, after the steel needle was inserted, the highest temperature on the battery surface reached 154.9℃, the voltage dropped to 0V, and no obvious fire occurred, thus the test was deemed successful. The test results are as follows: Figure 2 As shown.

[0043] (3) Overcharge test: The overcharge test of ternary lithium batteries is the core means of assessing their safety. It is mainly used to observe the battery's reaction under conditions exceeding the rated charging conditions (such as excessively high voltage or continuous charging), forcing the battery into an overcharged state, thereby triggering a series of dangerous chemical reactions inside. Internal short circuits and continuous side reactions will generate huge amounts of heat, causing the temperature to rise sharply. If the heat cannot be dissipated in time, it will trigger a chain reaction, eventually leading to the battery catching fire or exploding.

[0044] This application conducted overcharge tests on the batteries of Examples 1-3 and the comparative example at 2.0C with a cutoff condition of 150% SOC. The test results are shown in Table 2 below: Table 2 shows the overcharge test results for the examples and comparative examples.

[0045] As can be seen from Table 2, in Example 3, no fire or explosion occurred under 150% SOC overcharge conditions, and the highest temperature was 125.0℃. This indicates that the Sr-doped PTC ceramic material coating and the thermally reversible polymer binder effectively cut off the current in time and reversibly fractured the thermally reversible DA bond polymer three-dimensional network under overheating conditions. When the overheating temperature was relieved, the DA bond polymer three-dimensional network self-recovered, realizing the coating in a low-resistance conductive state.

[0046] (4) Cyclic testing: Constant current 1.0C charge-discharge was performed at 45℃, with a test voltage range of 3.0-4.2V. After 795 cycles, the capacity retention rates of Example 1 and Example 2 were 79.95% and 80.38%, respectively. The capacity retention rate of Example 3 was 0.15% lower than that of the comparative example, indicating that the coating with added self-healing binder improved the effect on long-cycle performance and had a smaller impact on cycle life compared to the uncoated battery. Figure 3 The figures shown are the capacity retention rates of Examples 1-3 and the comparative example at 1C room temperature cycling.

[0047] In summary: The safety coating of this application uses Sr-doped PTC ceramic material and thermally reversible DA bond polymer binder to achieve three synergistic functions under overheating conditions: (1) Electrically interrupting the current and blocking the spread of thermal runaway. Electrically, the resistance increases dramatically (completed by the PTC coating). The PTC ceramic coating exhibits a low-resistance conduction state below the Curie point, allowing normal charging and discharging current to pass through; when the temperature reaches the Curie point, the resistance jumps sharply by 3 to 8 orders of magnitude, instantly interrupting the current path and blocking the spread of thermal runaway from an electrical perspective. (2) Reversible fracture of the DA bond polymer three-dimensional network. The DA bond binder undergoes decrosslinking reaction simultaneously in the same temperature range, and the polymer three-dimensional network fractures reversibly, giving the coating fluidity to absorb and disperse microcracks caused by thermal stress and volume expansion. (3) Local heat absorption during DA bond fracture. The chemical heat absorption process accompanying DA bond fracture (heat absorption capacity can reach 500~800 J / g) can effectively absorb local heat, forming an "electric-thermal" dual-mode cooling with the resistance jump of the PTC layer.

[0048] Self-recovering after thermal triggering: Under extreme overheating conditions, the low-temperature Sr-doped PTC ceramic coating achieves millisecond-level electronic pathway interruption (self-melting). When the temperature drops or the external heat source is removed, and the temperature returns to a safe range, the DA bonds can recover the polymer's three-dimensional network structure through a reversible recrosslinking reaction. Simultaneously, the resistance of the PTC coating decreases synchronously with the temperature reduction to a low-resistance conducting state. The PTC coating continuously provides long-term overheat protection throughout its lifespan, and its self-healing capability extends the electrode's service life, exhibiting a dual gain of cycle life and safety redundancy.

[0049] The foregoing has shown and described the preferred embodiments of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, the embodiments should be regarded as exemplary and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of the equivalents of the claims be included within the invention.

[0050] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A PTC ceramic safety coating, characterized in that, The product comprises PTC ceramic powder, conductive additives, binders, inorganic fast ion conductor fillers, and solvents. The PTC ceramic powder is a perovskite oxide material with the general chemical formula ABO3. The A-site is doped with one or more of Sr, Ca, Ba, and Pb, and the B-site is substituted with one or more of Ti, Mn, and Fe.

2. The PTC ceramic safety coating according to claim 1, characterized in that, The ABO3 is BaTiO3.

3. The PTC ceramic safety coating according to claim 2, characterized in that, The PTC ceramic powder is strontium (Sr). 2+ Doped BaTiO3, the chemical formula of which is Ba 1-x Sr x TiO3, where 0 < x < 0.

5.

4. The PTC ceramic safety coating according to claim 3, characterized in that, The x=0.2, and the chemical formula is Ba. 0.8 Sr 0.2 TiO3 was obtained by the following method: using barium titanate (BaTiO3) as the raw material, Ba... 2+ The A-site doped alkaline earth metal ion Strontium Sr 2+ The barium-strontium doping ratio was 0.8:0.

2. High-purity Ba powder with a narrow particle size distribution was prepared via solid-state reaction, followed by calcination, ball milling, and classification. 0.8 Sr 0.2 TiO3 has a particle size of 100 nm to 1 μm.

5. The PTC ceramic safety coating according to claim 1, characterized in that, The conductive additive is one or more of carbon nanotubes, graphene, and conductive carbon black. The adhesive is a thermally reversible polymer adhesive containing Diels-Alder reversible bonds; The solvent is one or a mixture of N-methylpyrrolidone (NMP) and deionized water; The inorganic fast ion conductor filler is LLZTO, LATP, or LPSCl.

6. The PTC ceramic safety coating according to claim 5, characterized in that, The preparation method of the thermally reversible polymer binder is as follows: First, 2,5-furandiethanol and bismaleimide are dissolved in anhydrous dimethylformamide (DMF). Then, under nitrogen protection, the mixture is stirred and reacted at 60°C for 24 hours to form a furan-maleimide Diels-Alder adduct. Finally, after the reaction is completed, the product is precipitated in deionized water, filtered, washed, and vacuum dried at 60°C for 24 hours to obtain the thermally reversible polymer binder.

7. The PTC ceramic safety coating according to claim 4, characterized in that, The PTC ceramic powder accounts for 50% to 80% of the total mass, the conductive additive accounts for 5% to 10% of the total mass, the binder accounts for 10% to 25% of the total mass, and the inorganic fast ion conductor filler accounts for 2% to 8% of the total mass.

8. The PTC ceramic safety coating according to claim 1, characterized in that, The thickness of the PTC ceramic safety coating is 10–30 μm, preferably 12–16 μm.

9. An electrode, comprising a positive electrode and a negative electrode, characterized in that, The positive electrode and / or negative electrode are coated with a PTC ceramic safety coating as described in any one of claims 1-8. The PTC ceramic safety coating is uniformly applied to the surface of the active material layer of the positive electrode or negative electrode by scraping, spraying, screen printing or slot extrusion coating. After drying at a low temperature of 60-80°C for 6-12 hours and cold pressing at a pressure of 5-15 MPa, a dense, uniform and strongly adherent safety coating is formed. The positive electrode active material is one or more of NCM, NCA, LFP, and LCO; The active material of the negative electrode is one or more of graphite, mesophase carbon microspheres, silicon-carbon composite materials, and metallic lithium.

10. A lithium battery, characterized in that, Including the electrode sheet as described in claim 9, the lithium battery is assembled into an electrode assembly through cutting and winding processes, followed by casing, liquid injection, and formation processes.

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