Thermal composite gluing diaphragm and preparation method thereof, naked battery cell and preparation method and application thereof

Abstract

The invention relates to a thermal composite gluing diaphragm and a preparation method thereof, a naked battery cell and a preparation method and application thereof, the thermal composite gluing diaphragm comprises a base film, at least one side surface of the base film is provided with an inorganic heat conduction layer, and the inorganic heat conduction layer comprises first inorganic particles and second inorganic particles comprising AlN; the thermal composite gluing diaphragm further comprises a heat conduction diaphragm gluing layer which comprises third inorganic particles. One side surface of the base film is provided with an inorganic heat-conducting layer, and the heat-conducting diaphragm gluing layer is located on one side surface, away from the base film, of the inorganic heat-conducting layer and located on one side surface, away from the inorganic heat-conducting layer, of the base film; or inorganic heat-conducting layers are arranged on the surfaces of the two sides of the base film, and the heat-conducting diaphragm gluing layer is located on the surfaces of the sides, away from the base film, of the inorganic heat-conducting layers. Aluminum nitride has a high heat conductivity coefficient, it can be guaranteed that internal heat is rapidly conducted in the hot pressing process of the battery cell, a good hot pressing effect is guaranteed, better and more uniform adhesive force exists between the pole piece and the diaphragm, and the obtained naked battery cell has lower internal resistance and better electrochemical performance.

Description

Technical Field

[0001] This invention relates to the field of diaphragm preparation technology, and in particular to a thermally composite coated diaphragm and its preparation method, a bare battery cell and its preparation method and application. Background Technology

[0002] In the electrode forming process of lithium-ion batteries, stacking and winding are the two core technical paths. The precise layer-by-layer stacking of the soft-pack stacking process eliminates the stress concentration problem in the corner areas during winding, resulting in a more uniform current distribution and lower internal resistance between the electrodes. Simultaneously, the flexibility of the aluminum-plastic film encapsulation and the adaptability of the stacking structure allow the battery to be precisely matched to the irregularly shaped cavities of 3C products and power batteries, and it is not prone to rigid deformation due to electrode expansion during cycling, making it fully suitable for high-power applications.

[0003] However, the bare cells of pouch-pack stacked batteries suffer from issues such as loose structure and electrode alignment deviations after stacking. Furthermore, during long-term cycling, the active materials on the electrodes undergo volume expansion, which can easily lead to electrode displacement, separator wrinkling, and even internal short circuits. To address these problems, existing technologies generally employ a process of coating the separator with adhesive and then hot-pressing to shape the bare cells. This process solidifies and shapes the bare cells while simultaneously using adhesive force to constrain electrode expansion and improve cycle stability. This is a core element in ensuring the yield and reliability of pouch-pack stacked batteries.

[0004] However, traditional coated separators have low heat transfer efficiency. After hot pressing, the external heat is much higher than the internal heat, resulting in a much stronger adhesion between the external electrodes and the internal electrodes, and the adhesion is uneven. Furthermore, traditional coated separators require higher temperatures, pressures, and times to achieve the desired bonding effect. Excessively high temperatures can cause the external PVDF to dissolve and clog the separator pores. Dissolved PVDF remaining in the electrolyte can also lead to poor sealing of the soft-pack. Conversely, excessively low temperatures will not achieve the desired bonding and shaping effects, thus easily affecting the electrochemical performance and yield of the battery.

[0005] Therefore, how to provide a thermally composite coated separator that can achieve better bonding at a suitable temperature, and thus enable it to have lower internal resistance and better electrochemical performance when used in bare battery cells, is a technical problem that urgently needs to be solved. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a thermally composite coated separator and its preparation method, a bare battery cell and its preparation method, and its applications. The thermally composite coated separator of this invention comprises a base film, an inorganic thermally conductive layer, and a thermally conductive separator coating layer. The inorganic thermally conductive layer includes first inorganic particles and second inorganic particles including AlN. Aluminum nitride has a high thermal conductivity, thus its high thermal conductivity ensures rapid heat conduction during the hot-pressing process of the battery cell, thereby ensuring a better hot-pressing effect. Combined with the superior adhesion of the thermally conductive separator coating layer itself, it enables better and more uniform adhesion between the electrode and the thermally composite coated separator, optimizing the electrode interface. While ensuring adhesion, it also reduces the thermal bonding temperature and shortens the thermal bonding time, effectively improving production efficiency. The resulting bare battery cell has lower internal resistance, higher hardness, and better electrochemical performance.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a thermally composite coated separator, the thermally composite coated separator comprising a base film, wherein an inorganic thermally conductive layer is disposed on at least one side surface of the base film, the inorganic thermally conductive layer comprising a first inorganic particle and a second inorganic particle, wherein the second inorganic particle comprises AlN;

[0009] The thermally composite coated diaphragm also includes a thermally conductive diaphragm coating layer, which includes third inorganic particles.

[0010] An inorganic thermally conductive layer is provided on one side surface of the base film, and the thermally conductive membrane coating layer is located on the side surface of the inorganic thermally conductive layer away from the base film and on the side surface of the base film away from the inorganic thermally conductive layer.

[0011] Alternatively, an inorganic thermally conductive layer is provided on both sides of the base film, and the thermally conductive membrane coating layer is located on the side of the inorganic thermally conductive layer away from the base film.

[0012] The thermally composite coated separator of this invention includes a base film, an inorganic thermally conductive layer, and a thermally conductive separator coating layer. The inorganic thermally conductive layer includes first inorganic particles and second inorganic particles including AlN. Aluminum nitride has a high thermal conductivity, so its high thermal conductivity can ensure rapid heat conduction during the hot pressing process of the battery cell, thereby ensuring a better hot pressing effect. Combined with the excellent adhesion of the thermally conductive separator coating layer itself, it can make the electrode and the thermally composite coated separator have better and more uniform adhesion, and the electrode interface is also optimized. While ensuring adhesion, it can also reduce the thermal bonding temperature and shorten the thermal bonding time, effectively improving production efficiency. The resulting bare battery cell has lower internal resistance, higher hardness, and better electrochemical performance.

[0013] The inorganic thermally conductive layer of this invention includes first inorganic particles and second inorganic particles including AlN. Mixing AlN with the first inorganic particles can ensure that AlN has a better dispersion effect, the slurry has a higher uniformity, and the coating effect is better. The thermally conductive membrane coating layer includes third inorganic particles, which can ensure that the thermally conductive membrane coating layer has a better coating effect, and at the same time can play a supporting role to avoid significant thermal shrinkage of the thermally conductive membrane coating layer.

[0014] As a preferred embodiment of the present invention, the first inorganic particles include at least one of alumina, boehmite, MgO, SiO2, BaSO4, or TiO2.

[0015] Preferably, the median particle size D50 of the first inorganic particles is 0.5μm-1.2μm, such as 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1.0μm, 1.1μm or 1.2μm.

[0016] Preferably, the median particle size D50 of the second inorganic particles is 0.7μm-1.5μm, such as 0.7μm, 0.8μm, 0.9μm, 1.0μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm or 1.5μm.

[0017] Preferably, the third inorganic particle includes at least one of AlN, alumina, boehmite, MgO, SiO2, BaSO4, or TiO2.

[0018] Preferably, the inorganic thermally conductive layer and the thermally conductive membrane coating layer each independently further include an adhesive.

[0019] Preferably, the adhesive comprises at least one of polyvinylidene fluoride, polyacrylic acid (PAA), polyacrylate (PA), polymethyl methacrylate (PMMA), or styrene-butadiene rubber (SBR).

[0020] As a preferred technical solution of the present invention, the thickness of the inorganic thermal conductive layer is 1.5μm-4μm, such as 1.5μm, 1.8μm, 2μm, 2.2μm, 2.5μm, 2.8μm, 3μm, 3.2μm, 3.5μm, 3.8μm or 4μm.

[0021] In this invention, the thickness of the inorganic thermally conductive layer is controlled to be between 1.5 μm and 4 μm, which enables the thermally composite coated diaphragm to have good thermal conductivity and safety performance. If the thickness of the inorganic thermally conductive layer is too thick, it will increase the internal resistance of the bare cell, reduce the power density, and increase the cost ratio of the diaphragm; if the thickness of the inorganic thermally conductive layer is too thin, the coating consistency will be poor, and the thermal conductivity effect will not be achieved.

[0022] It should be noted that the thickness of the inorganic thermal conductive layer in this invention is 1.5μm-4μm, which refers to the thickness of a single inorganic thermal conductive layer being 1.5μm-4μm.

[0023] Preferably, based on the total mass of the inorganic thermal conductive layer being 100wt%, the content of the first inorganic particles is 40wt%-70wt%, for example, 40wt%, 45wt%, 50wt%, 55wt%, 60wt%, 65wt%, or 70wt%.

[0024] Preferably, based on the total mass of the inorganic thermal conductive layer being 100wt%, the content of the second inorganic particles is 30wt%-60wt%, for example, 30wt%, 32wt%, 35wt%, 38wt%, 40wt%, 42wt%, 45wt%, 48wt%, 50wt%, 52wt%, 55wt%, 58wt%, or 60wt%.

[0025] In this invention, controlling the mass percentage of the second inorganic particles to be 30wt%-60wt% achieves better thermal conductivity, higher hot-pressing efficiency, and better adhesion of the electrode diaphragm. If the mass percentage of the second inorganic particles is too low, the improvement in thermal conductivity will be insignificant, failing to achieve the expected improvement effect; if the mass percentage of the second inorganic particles is too high, the particle dispersion will be poor, the membrane surface will be uneven, performance will decrease, and costs will be higher.

[0026] Preferably, based on the total mass of the inorganic thermally conductive layer as 100wt%, the content of the binder is 3wt%-5wt%, such as 3wt%, 3.2wt%, 3.5wt%, 3.8wt%, 4wt%, 4.2wt%, 4.5wt%, 4.8wt%, or 5wt%.

[0027] Preferably, the thickness of the thermally conductive membrane coating layer is 1μm-3μm, such as 1μm, 1.2μm, 1.5μm, 1.8μm, 2μm, 2.2μm, 2.5μm, 2.8μm or 3μm.

[0028] It should be noted that the thickness of the thermally conductive membrane coating layer in this invention is 1μm-3μm, which refers to the thickness of a single layer of thermally conductive membrane coating layer being 1μm-3μm.

[0029] Preferably, based on the total mass of the thermally conductive membrane coating layer as 100wt%, the content of the third inorganic particles is 5wt%-10wt%, such as 5wt%, 5.5wt%, 6wt%, 6.5wt%, 7wt%, 7.5wt%, 8wt%, 8.5wt%, 9wt%, 9.5wt%, or 10wt%.

[0030] In this invention, controlling the mass percentage of the third inorganic particles to be 5wt%-10wt% can achieve a more stable thermally conductive membrane coating layer and better adhesion. If the mass percentage of the third inorganic particles is too low, it will lead to a decrease in the stability of the thermally conductive membrane coating layer and will also be detrimental to coating during the preparation process; if the mass percentage of the third inorganic particles is too high, it will lead to a decrease in the adhesion between the thermally conductive membrane coating layer and the electrode.

[0031] Preferably, based on the total mass of the thermally conductive membrane coating layer as 100wt%, the content of the adhesive is 90wt%-95wt%, such as 90wt%, 91wt%, 92wt%, 93wt%, 94wt%, or 95wt%.

[0032] As a preferred technical solution of the present invention, the base film includes a wet-process PE base film or a dry-process PP base film.

[0033] Preferably, the molecular weight of the base film is 1 million to 3 million, such as 1 million, 1.2 million, 1.5 million, 1.8 million, 2 million, 2.2 million, 2.5 million, 2.8 million or 3 million.

[0034] In this invention, the molecular weight of the base film is controlled to be between 1 million and 3 million, which can improve the strength of the thermally composite coated diaphragm and enhance its processing and safety performance.

[0035] Preferably, the thickness of the base film is 7μm-20μm, such as 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm or 20μm.

[0036] Preferably, the porosity of the base membrane is 43%-60%, such as 43%, 45%, 48%, 50%, 52%, 55%, 58% or 60%.

[0037] In this invention, the porosity of the base film is controlled to be 43%-60%. High porosity can provide more transport channels for lithium ions. When applied to batteries, it can reduce the internal resistance of the battery during the charging and discharging process, which is beneficial to improving the electrochemical performance of the battery.

[0038] Preferably, the air permeability of the base membrane is ≤200s / 100mL, such as 200s / 100mL, 180s / 100mL, 150s / 100mL, 120s / 100mL, 100s / 100mL, 80s / 100mL, 50s / 100mL or 30s / 100mL, etc.

[0039] In a second aspect, the present invention also provides a method for preparing a thermally composite coated separator according to the first aspect, the method comprising the following steps:

[0040] A base film is provided, an inorganic thermally conductive layer is formed on one surface of the base film, and a thermally conductive membrane coating layer is formed on the surface of the inorganic thermally conductive layer away from the base film and on the surface of the base film away from the inorganic thermally conductive layer; or,

[0041] A base film is provided, an inorganic thermally conductive layer is prepared on both sides of the base film, and a thermally conductive membrane coating layer is prepared on the side of the inorganic thermally conductive layer away from the base film to obtain a thermally composite coated membrane.

[0042] The inorganic thermally conductive layer includes a first inorganic particle and a second inorganic particle, wherein the second inorganic particle includes AlN;

[0043] The thermally conductive membrane coating layer includes a third inorganic particle.

[0044] As a preferred technical solution of the present invention, the inorganic thermal conductive layer is obtained by coating with an inorganic thermal conductive layer slurry. The preparation method of the inorganic thermal conductive layer slurry includes the following steps: mixing and dispersing the first inorganic particles, the second inorganic particles, the binder and the first solvent to obtain the inorganic thermal conductive layer slurry.

[0045] Preferably, the coating method for the inorganic thermally conductive layer includes wire bar coating or gravure roller coating.

[0046] Preferably, the first solvent comprises water and / or an aqueous solution of sodium polyacrylate.

[0047] Preferably, the solid content of the inorganic thermally conductive layer slurry is 35%-45%, such as 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, or 45%.

[0048] It should be noted that the present invention does not impose specific requirements or special limitations on the mixing and dispersion methods and conditions, as long as the raw materials can be uniformly dispersed. Those skilled in the art can make adaptive selections and adjustments according to actual conditions.

[0049] As a preferred technical solution of the present invention, the thermally conductive membrane coating layer is obtained by coating with a thermally conductive membrane coating layer slurry. The preparation method of the thermally conductive membrane coating layer slurry includes the following steps: mixing and dispersing the third inorganic particles, the binder and the second solvent to obtain the thermally conductive membrane coating layer slurry.

[0050] Preferably, the coating method for the thermally conductive membrane coating layer includes roller coating or intermittent coating.

[0051] In this invention, the use of roller coating can improve the adhesion between the subsequent electrode and the thermally composite coated diaphragm, while the use of intermittent coating can allow the electrolyte to enter the interior of the thermally composite coated diaphragm more quickly.

[0052] Preferably, the second solvent includes at least one of acetone, N-methylpyrrolidone (NMP), or an aqueous solution of sodium polyacrylate.

[0053] Preferably, the solid content of the thermally conductive diaphragm coating slurry is 3%-10%, such as 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%.

[0054] It should be noted that the present invention does not impose specific requirements or special limitations on the mixing and dispersion methods and conditions, as long as the raw materials can be uniformly dispersed. Those skilled in the art can make adaptive selections and adjustments according to actual conditions.

[0055] Thirdly, the present invention also provides a bare battery cell, the bare battery cell comprising a thermally composite coated separator as described in the first aspect, or a thermally composite coated separator prepared by the preparation method described in the second aspect.

[0056] Preferably, the bare battery cell further includes a positive electrode, a negative electrode, and an electrolyte.

[0057] It should be noted that the present invention does not impose specific requirements or special limitations on the positive and negative active materials in the positive and negative electrode sheets. Commonly used positive and negative active materials in the art are applicable to the present invention, and those skilled in the art can make adaptive selections and adjustments according to actual conditions.

[0058] It should be noted that the present invention does not impose specific requirements or special limitations on the composition and content of the positive and negative active material layers in the positive and negative electrode sheets. Commonly used materials in the art are all suitable for the present invention, and those skilled in the art can make adaptive selections and adjustments according to actual conditions.

[0059] It should be noted that the present invention does not impose specific requirements or special limitations on the electrolyte. Commonly used electrolytes suitable for lithium batteries in the art are applicable to the present invention, and those skilled in the art can make adaptive selections and adjustments according to actual conditions.

[0060] Fourthly, the present invention also provides a method for preparing a bare battery cell according to the third aspect, the method comprising the following steps:

[0061] After stacking the positive electrode, negative electrode, and thermally coated separator, electrolyte is injected, and the cells are hot-pressed to obtain bare cells.

[0062] As a preferred technical solution of the present invention, the hot pressing temperature is 70℃-85℃, such as 70℃, 72℃, 75℃, 78℃, 80℃, 82℃ or 85℃.

[0063] Preferably, the hot pressing time is 15 min to 45 min, such as 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, or 45 min.

[0064] Preferably, the hot pressing pressure is 2000 kgf-4000 kgf, such as 2000 kgf, 2200 kgf, 2500 kgf, 2800 kgf, 3000 kgf, 3200 kgf, 3500 kgf, 3800 kgf or 4000 kgf.

[0065] Preferably, after the hot pressing is completed, a cold pressing step is also included.

[0066] Preferably, the temperature of the cold pressing is 20℃-30℃, such as 20℃, 22℃, 25℃, 28℃ or 30℃.

[0067] Preferably, the cold pressing time is 5 min to 15 min, such as 5 min, 8 min, 10 min, 12 min or 15 min.

[0068] Preferably, the pressure of the cold pressing is 2000 kgf-4000 kgf, such as 2000 kgf, 2200 kgf, 2500 kgf, 2800 kgf, 3000 kgf, 3200 kgf, 3500 kgf, 3800 kgf or 4000 kgf.

[0069] Preferably, the time interval between hot pressing and cold pressing is <15 min, for example, 15 min, 12 min, 10 min, 8 min, 5 min, 2 min or 1 min, etc.

[0070] Fifthly, the present invention also provides an application of bare cells, wherein the bare cells prepared according to the method described in the third aspect or the method described in the fourth aspect are applied to start-stop batteries.

[0071] Compared with the prior art, the present invention has at least the following beneficial effects:

[0072] 1) The thermally composite coated separator of the present invention includes a base film, an inorganic thermally conductive layer, and a thermally conductive separator coating layer. The inorganic thermally conductive layer includes first inorganic particles and second inorganic particles including AlN. Aluminum nitride has a high thermal conductivity, so its high thermal conductivity can ensure rapid heat conduction during the hot pressing process of the battery cell, thereby ensuring a better hot pressing effect. Combined with the superior adhesion of the thermally conductive separator coating layer itself, it can make the electrode and the thermally composite coated separator have better and more uniform adhesion. The electrode interface is also optimized. While ensuring adhesion, it can also reduce the thermal composite temperature and shorten the thermal composite time, effectively improving production efficiency. The resulting bare battery cell has lower internal resistance, higher hardness, and better electrochemical performance.

[0073] 2) The inorganic thermal conductive layer of the present invention includes first inorganic particles and second inorganic particles including AlN. Mixing AlN with the first inorganic particles can ensure that AlN has a better dispersion effect and the slurry has a higher degree of uniformity. The thermal conductive membrane coating layer includes third inorganic particles, which can ensure that the thermal conductive membrane coating layer has a better coating effect and at the same time play a supporting role in avoiding significant thermal shrinkage of the thermal conductive membrane coating layer. Attached Figure Description

[0074] Figure 1 This is a schematic diagram of the structure of the thermally composite coated diaphragm provided in Embodiment 1 of the present invention.

[0075] Figure 2 This is a schematic diagram of the structure of the thermally composite coated diaphragm provided in Embodiment 5 of the present invention.

[0076] Among them, 1-wet process PE base film; 2-first inorganic thermal conductive layer; 3-second inorganic thermal conductive layer; 4-first thermal conductive membrane coating layer; 5-second thermal conductive membrane coating layer. Detailed Implementation

[0077] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0078] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0079] Example 1

[0080] This embodiment provides a thermally laminated adhesive diaphragm. Figure 1This diagram illustrates the structure of the thermally composite coated separator provided in Embodiment 1 of the present invention. The thermally composite coated separator includes a wet-process PE base film 1 with a thickness of 9 μm. A first inorganic thermally conductive layer 2 with a thickness of 2 μm and a second inorganic thermally conductive layer 3 with a thickness of 2 μm are respectively disposed on both sides of the wet-process PE base film. A first thermally conductive separator coating layer 4 with a thickness of 1 μm is disposed on the side of the first inorganic thermally conductive layer away from the base film. A second inorganic thermally conductive layer 3 with a thickness of 1 μm is disposed on the side of the second inorganic thermally conductive layer away from the base film. The second thermally conductive membrane coating layer 5; wherein, the wet-process PE base film has a molecular weight of 1.5 million, a porosity of 50%, and an air permeability of 60s / 100mL; the first inorganic thermally conductive layer 2 and the second inorganic thermally conductive layer 3 both include 48wt% alumina (median particle size D50 of 1μm), 48wt% AlN (median particle size D50 of 1μm) and 4wt% polyacrylic acid; the first thermally conductive membrane coating layer 4 and the second thermally conductive membrane coating layer 5 both include 5wt% alumina and 95wt% polyvinylidene fluoride.

[0081] This embodiment provides a method for preparing the aforementioned thermally composite coated separator, the method comprising the following steps:

[0082] After mixing and dispersing alumina, AlN, PAA and water according to the above formula, an inorganic thermally conductive layer slurry (solid content of 40%) is obtained. After mixing and dispersing alumina, PVDF and acetone according to the above formula, a thermally conductive membrane coating slurry (solid content of 6%) is obtained. The inorganic thermally conductive layer slurry is coated onto both sides of a wet-process PE base film by gravure roller coating. After drying, a first inorganic thermally conductive layer and a second inorganic thermally conductive layer are formed. The thermally conductive membrane coating slurry is coated onto the surfaces of the first inorganic thermally conductive layer and the second inorganic thermally conductive layer by roller coating. After drying, a first thermally conductive membrane coating layer and a second thermally conductive membrane coating layer are formed, resulting in a thermally composite coated membrane.

[0083] This embodiment provides a bare battery cell, which uses the thermally composite coated separator provided in this embodiment, and also includes a lithium iron phosphate positive electrode, a graphite negative electrode, and a 1.0 mol / L LiPF6 solution as electrolyte (the solvent is EC, DMC and EMC in a volume ratio of 1:1:1).

[0084] This embodiment provides a method for preparing the bare battery cell, the method comprising the following steps:

[0085] After stacking lithium iron phosphate positive electrode, graphite negative electrode and thermally coated separator, electrolyte is injected. After hot pressing at 85℃ and 2500kgf for 30 minutes, after a 10-minute interval, it is cold pressed at 25℃ and 3000kgf for 10 minutes to obtain bare cell.

[0086] Example 2

[0087] This embodiment provides a thermally composite coated diaphragm. The difference between the thermally composite coated diaphragm and Embodiment 1 is that both the first thermally conductive diaphragm coating layer and the second thermally conductive diaphragm coating layer include 5 wt% AlN and 95 wt% polyvinylidene fluoride, while the remaining structure and parameters are consistent with Embodiment 1.

[0088] This embodiment provides a method for preparing the thermally composite coated diaphragm. The difference between this method and Example 1 is that AlN, PVDF and acetone are mixed and dispersed according to the above formula to obtain a thermally conductive diaphragm coating slurry (solid content of 6%). The remaining preparation methods and parameters are the same as in Example 1.

[0089] This embodiment provides a bare battery cell, which uses the thermally composite coated separator provided in this embodiment, and the rest of the structure is consistent with that of Embodiment 1.

[0090] This embodiment provides a method for preparing the bare battery cell, and the preparation method and parameters are consistent with those in Embodiment 1.

[0091] Example 3

[0092] This embodiment provides a thermally composite coated diaphragm, the structure and parameters of which are consistent with those of Embodiment 1.

[0093] This embodiment provides a method for preparing the thermally composite coated diaphragm, and the preparation method and parameters are consistent with those in Embodiment 1.

[0094] This embodiment provides a bare battery cell, which uses the thermally composite coated separator provided in this embodiment, and the rest of the structure is consistent with that of Embodiment 1.

[0095] This embodiment provides a method for preparing the bare battery cell. The difference between this method and that of Embodiment 1 is that the hot pressing time is 15 minutes, while the rest of the preparation method and parameters are the same as those of Embodiment 1.

[0096] Example 4

[0097] This embodiment provides a thermally composite coated diaphragm. The difference between the thermally composite coated diaphragm and Embodiment 1 is that both the first thermally conductive diaphragm coating layer and the second thermally conductive diaphragm coating layer include 5 wt% AlN and 95 wt% polyvinylidene fluoride, while the remaining structure and parameters are consistent with Embodiment 1.

[0098] This embodiment provides a method for preparing the thermally composite coated diaphragm. The difference between this method and Example 1 is that AlN, PVDF and acetone are mixed and dispersed according to the above formula to obtain a thermally conductive diaphragm coating slurry (solid content of 6%). The remaining preparation methods and parameters are the same as in Example 1.

[0099] This embodiment provides a bare battery cell, which uses the thermally composite coated separator provided in this embodiment, and the rest of the structure is consistent with that of Embodiment 1.

[0100] This embodiment provides a method for preparing the bare battery cell. The difference between this method and that of Embodiment 1 is that the hot pressing time is 15 minutes, while the rest of the preparation method and parameters are the same as those of Embodiment 1.

[0101] Example 5

[0102] This embodiment provides a thermally laminated adhesive diaphragm. Figure 2 A schematic diagram of the structure of the thermally composite coated diaphragm provided in Embodiment 5 of the present invention is shown. The thermally composite coated diaphragm includes a wet-process PE base film 1 with a thickness of 9 μm. A first inorganic thermally conductive layer 2 with a thickness of 2 μm is disposed on one side surface of the wet-process PE base film. A first thermally conductive diaphragm coating layer 4 with a thickness of 1 μm is disposed on the side surface of the first inorganic thermally conductive layer away from the base film. A second thermally conductive diaphragm coating layer 5 with a thickness of 1 μm is disposed on the side surface of the base film away from the first inorganic thermally conductive layer.

[0103] This embodiment provides a method for preparing the thermally composite coated diaphragm. The difference between this method and that of Embodiment 1 is that the coating step of the second inorganic thermally conductive layer is omitted, while the rest of the preparation methods and parameters remain the same as those of Embodiment 1.

[0104] This embodiment provides a bare battery cell, which uses the thermally composite coated separator provided in this embodiment, and the rest of the structure is consistent with that of Embodiment 1.

[0105] This embodiment provides a method for preparing the bare battery cell, and the preparation method and parameters are consistent with those in Embodiment 1.

[0106] Example 6

[0107] This embodiment provides a thermally composite coated separator, which includes a 20μm thick wet-process PE base film. A first inorganic thermally conductive layer with a thickness of 1.5μm and a second inorganic thermally conductive layer with a thickness of 1.5μm are respectively disposed on both sides of the wet-process PE base film. A first thermally conductive separator coating layer with a thickness of 3μm is disposed on the side of the first inorganic thermally conductive layer away from the base film, and a second thermally conductive separator coating layer with a thickness of 3μm is disposed on the side of the second inorganic thermally conductive layer away from the base film. The wet-process PE base film has a molecular weight of 1.5 million, a porosity of 60%, and an air permeability of 100s / 100mL. Both the first and second inorganic thermally conductive layers comprise 67wt% alumina, 30wt% AlN, and 3wt% polyacrylic acid. Both the first and second thermally conductive separator coating layers comprise 5wt% alumina and 95wt% polyvinylidene fluoride.

[0108] This embodiment provides a method for preparing the thermally composite coated diaphragm. The difference between this method and that of Embodiment 1 is that the amount of each raw material added is adjusted according to the adjustment of the component content of the thermally composite coated diaphragm. The rest of the preparation method and parameters are the same as those of Embodiment 1.

[0109] This embodiment provides a bare battery cell, which uses the thermally composite coated separator provided in this embodiment, and the rest of the structure is consistent with that of Embodiment 1.

[0110] This embodiment provides a method for preparing the bare battery cell, the method comprising the following steps:

[0111] After stacking lithium iron phosphate positive electrode, graphite negative electrode and thermally coated separator, electrolyte is injected. After hot pressing at 70℃ and 4000kgf for 45min, after a 10min interval, it is cold pressed at 25℃ and 3000kgf for 10min to obtain bare cell.

[0112] Example 7

[0113] This embodiment provides a thermally composite coated separator, which includes a 7μm thick wet-process PE base film. A first inorganic thermally conductive layer with a thickness of 4μm and a second inorganic thermally conductive layer with a thickness of 4μm are respectively disposed on both sides of the wet-process PE base film. A first thermally conductive separator coating layer with a thickness of 2μm is disposed on the side of the first inorganic thermally conductive layer away from the base film, and a second thermally conductive separator coating layer with a thickness of 2μm is disposed on the side of the second inorganic thermally conductive layer away from the base film. The wet-process PE base film has a molecular weight of 1.5 million, a porosity of 43%, and an air permeability of 85s / 100mL. Both the first and second inorganic thermally conductive layers comprise 40wt% alumina, 57wt% AlN, and 3wt% polyacrylic acid. Both the first and second thermally conductive separator coating layers comprise 10wt% alumina and 90wt% polyvinylidene fluoride.

[0114] This embodiment provides a method for preparing the thermally composite coated diaphragm. The difference between this method and that of Embodiment 1 is that the amount of each raw material added is adjusted according to the adjustment of the component content of the thermally composite coated diaphragm. The rest of the preparation method and parameters are the same as those of Embodiment 1.

[0115] This embodiment provides a bare battery cell, which uses the thermally composite coated separator provided in this embodiment, and the rest of the structure is consistent with that of Embodiment 1.

[0116] This embodiment provides a method for preparing the bare battery cell, the method comprising the following steps:

[0117] After stacking lithium iron phosphate positive electrode, graphite negative electrode and thermally coated separator, electrolyte is injected, and hot-pressed at 80℃ and 3000kgf for 20 minutes, followed by a 10-minute interval, cold-pressed at 25℃ and 3000kgf for 10 minutes to obtain bare cell.

[0118] Example 8

[0119] This embodiment provides a thermally composite coated diaphragm. The difference between the thermally composite coated diaphragm and Embodiment 1 is that the thickness of the first inorganic thermally conductive layer and the second inorganic thermally conductive layer is 5 μm, while the remaining structure and parameters are consistent with Embodiment 1.

[0120] This embodiment provides a method for preparing the thermally composite coated diaphragm. The difference between this method and that of Embodiment 1 is that the coating thickness is adjusted according to the above-mentioned thickness adjustment adaptability, while the rest of the preparation methods and parameters remain the same as those of Embodiment 1.

[0121] This embodiment provides a bare battery cell, which uses the thermally composite coated separator provided in this embodiment, and the rest of the structure is consistent with that of Embodiment 1.

[0122] This embodiment provides a method for preparing the bare battery cell, and the preparation method and parameters are consistent with those in Embodiment 1.

[0123] Example 9

[0124] This embodiment provides a thermally composite coated diaphragm. The difference between the thermally composite coated diaphragm and Embodiment 1 is that the thickness of the first inorganic thermally conductive layer and the second inorganic thermally conductive layer is 1 μm, while the remaining structure and parameters are consistent with Embodiment 1.

[0125] This embodiment provides a method for preparing the thermally composite coated diaphragm. The difference between this method and that of Embodiment 1 is that the coating thickness is adjusted according to the above-mentioned thickness adjustment adaptability, while the rest of the preparation methods and parameters remain the same as those of Embodiment 1.

[0126] This embodiment provides a bare battery cell, which uses the thermally composite coated separator provided in this embodiment, and the rest of the structure is consistent with that of Embodiment 1.

[0127] This embodiment provides a method for preparing the bare battery cell, and the preparation method and parameters are consistent with those in Embodiment 1.

[0128] Example 10

[0129] This embodiment provides a thermally composite coated diaphragm. The difference between the thermally composite coated diaphragm and that in Embodiment 1 is that both the first inorganic thermally conductive layer and the second inorganic thermally conductive layer include 32 wt% alumina, 65 wt% AlN and 3 wt% polyacrylic acid, while the remaining structure and parameters are consistent with those in Embodiment 1.

[0130] This embodiment provides a method for preparing the thermally composite coated diaphragm. The difference between this method and Example 1 is that the amount of raw materials added is adjusted according to the above-mentioned content adjustment adaptability, while the rest of the preparation method and parameters remain the same as in Example 1.

[0131] This embodiment provides a bare battery cell, which uses the thermally composite coated separator provided in this embodiment, and the rest of the structure is consistent with that of Embodiment 1.

[0132] This embodiment provides a method for preparing the bare battery cell, and the preparation method and parameters are consistent with those in Embodiment 1.

[0133] Example 11

[0134] This embodiment provides a thermally composite coated diaphragm. The difference between the thermally composite coated diaphragm and that in Embodiment 1 is that both the first inorganic thermally conductive layer and the second inorganic thermally conductive layer comprise 72 wt% alumina, 25 wt% AlN, and 3 wt% polyacrylic acid, while the remaining structure and parameters are consistent with those in Embodiment 1.

[0135] This embodiment provides a method for preparing the thermally composite coated diaphragm. The difference between this method and Example 1 is that the amount of raw materials added is adjusted according to the above-mentioned content adjustment adaptability, while the rest of the preparation method and parameters remain the same as in Example 1.

[0136] This embodiment provides a bare battery cell, which uses the thermally composite coated separator provided in this embodiment, and the rest of the structure is consistent with that of Embodiment 1.

[0137] This embodiment provides a method for preparing the bare battery cell, and the preparation method and parameters are consistent with those in Embodiment 1.

[0138] Example 12

[0139] This embodiment provides a thermally composite coated diaphragm. The difference between the thermally composite coated diaphragm and Embodiment 1 is that the first thermally conductive diaphragm coating layer and the second thermally conductive diaphragm coating layer both include 13 wt% alumina and 87 wt% polyvinylidene fluoride, while the remaining structure and parameters are consistent with Embodiment 1.

[0140] This embodiment provides a method for preparing the thermally composite coated diaphragm. The difference between this method and Example 1 is that the amount of raw materials added is adjusted according to the above-mentioned content adjustment adaptability, while the rest of the preparation method and parameters remain the same as in Example 1.

[0141] This embodiment provides a bare battery cell, which uses the thermally composite coated separator provided in this embodiment, and the rest of the structure is consistent with that of Embodiment 1.

[0142] This embodiment provides a method for preparing the bare battery cell, and the preparation method and parameters are consistent with those in Embodiment 1.

[0143] Example 13

[0144] This embodiment provides a thermally composite coated diaphragm. The difference between the thermally composite coated diaphragm and Embodiment 1 is that the first thermally conductive diaphragm coating layer and the second thermally conductive diaphragm coating layer both include 2 wt% alumina and 98 wt% polyvinylidene fluoride, while the remaining structure and parameters are consistent with Embodiment 1.

[0145] This embodiment provides a method for preparing the thermally composite coated diaphragm. The difference between this method and Example 1 is that the amount of raw materials added is adjusted according to the above-mentioned content adjustment adaptability, while the rest of the preparation method and parameters remain the same as in Example 1.

[0146] This embodiment provides a bare battery cell, which uses the thermally composite coated separator provided in this embodiment, and the rest of the structure is consistent with that of Embodiment 1.

[0147] This embodiment provides a method for preparing the bare battery cell, and the preparation method and parameters are consistent with those in Embodiment 1.

[0148] Comparative Example 1

[0149] This comparative example provides a thermally composite coated diaphragm. The difference between the thermally composite coated diaphragm and Example 1 is that the second inorganic thermally conductive layer is omitted, and the first inorganic thermally conductive layer omits AlN and only includes 96 wt% alumina and 4 wt% polyacrylic acid. The remaining structure and parameters are consistent with Example 1.

[0150] This comparative example provides a method for preparing the thermally composite coated diaphragm. The difference between this method and Example 1 is that, after mixing and dispersing alumina, PAA and water according to the above formula, an inorganic thermally conductive layer slurry (solid content of 40%) is obtained, and the preparation of the second inorganic thermally conductive layer is omitted. The remaining preparation methods and parameters are consistent with those of Example 1.

[0151] This comparative example provides a bare battery cell, which uses the thermally composite coated separator provided in this comparative example, and the rest of the structure is consistent with that of Example 1.

[0152] This comparative example provides a method for preparing the bare battery cell, and the preparation method and parameters are consistent with those in Example 1.

[0153] Comparative Example 2

[0154] This comparative example provides a thermally composite coated diaphragm. The difference between the thermally composite coated diaphragm and Example 1 is that AlN is omitted in both the first and second inorganic thermally conductive layers, and only 96 wt% alumina and 4 wt% polyacrylic acid are included. The remaining structure and parameters are consistent with those of Example 1.

[0155] This comparative example provides a method for preparing the thermally composite coated diaphragm. The difference between this method and Example 1 is that, after mixing and dispersing alumina, PAA and water according to the above formula, an inorganic thermally conductive slurry (solid content of 40%) is obtained. The remaining preparation methods and parameters are consistent with those of Example 1.

[0156] This comparative example provides a bare battery cell, which uses the thermally composite coated separator provided in this comparative example, and the rest of the structure is consistent with that of Example 1.

[0157] This comparative example provides a method for preparing the bare battery cell, and the preparation method and parameters are consistent with those in Example 1.

[0158] Comparative Example 3

[0159] This comparative example provides a thermally composite coated diaphragm. The difference between the thermally composite coated diaphragm and Example 1 is that the first and second inorganic thermally conductive layers omit alumina and only include 96 wt% AlN and 4 wt% polyacrylic acid. The remaining structure and parameters are consistent with Example 1.

[0160] This comparative example provides a method for preparing the thermally composite coated diaphragm. The difference between this method and Example 1 is that, after AlN, PAA and water are mixed and dispersed according to the above formula, an inorganic thermally conductive slurry (solid content of 40%) is obtained. The remaining preparation methods and parameters are consistent with those of Example 1.

[0161] This comparative example provides a bare battery cell, which uses the thermally composite coated separator provided in this comparative example, and the rest of the structure is consistent with that of Example 1.

[0162] This comparative example provides a method for preparing the bare battery cell, and the preparation method and parameters are consistent with those in Example 1.

[0163] Comparative Example 4

[0164] This comparative example provides a thermally composite coated diaphragm. The difference between the thermally composite coated diaphragm and Example 1 is that AlN is omitted in both the first and second inorganic thermally conductive layers, and only 96 wt% alumina and 4 wt% polyacrylic acid are included. The remaining structure and parameters are consistent with those of Example 1.

[0165] This comparative example provides a method for preparing the thermally composite coated diaphragm. The difference between this method and Example 1 is that, after mixing and dispersing alumina, PAA and water according to the above formula, an inorganic thermally conductive slurry (solid content of 40%) is obtained. The remaining preparation methods and parameters are consistent with those of Example 1.

[0166] This comparative example provides a bare battery cell, which uses the thermally composite coated separator provided in this comparative example, and the rest of the structure is consistent with that of Example 1.

[0167] This comparative example provides a method for preparing the bare battery cell. The difference between this method and Example 1 is that the hot pressing time is 15 minutes, while the rest of the preparation method and parameters are the same as in Example 1.

[0168] Comparative Example 5

[0169] This comparative example provides a thermally composite coated diaphragm. The difference between the thermally composite coated diaphragm and Example 1 is that the first inorganic thermally conductive layer and the second inorganic thermally conductive layer are omitted, while the remaining structure and parameters are consistent with Example 1.

[0170] This comparative example provides a method for preparing the thermally composite coated diaphragm. The difference between this method and Example 1 is that the preparation of the first inorganic thermally conductive layer and the second inorganic thermally conductive layer is omitted, while the remaining preparation methods and parameters are consistent with those of Example 1.

[0171] This comparative example provides a bare battery cell, which uses the thermally composite coated separator provided in this comparative example, and the rest of the structure is consistent with that of Example 1.

[0172] This comparative example provides a method for preparing the bare battery cell, and the preparation method and parameters are consistent with those in Example 1.

[0173] Comparative Example 6

[0174] This comparative example provides a thermally composite coated diaphragm. The difference between the thermally composite coated diaphragm and Example 1 is that the first thermally conductive diaphragm coating layer and the second thermally conductive diaphragm coating layer are omitted, while the remaining structure and parameters are consistent with Example 1.

[0175] This comparative example provides a method for preparing the thermally composite coated diaphragm. The difference between this method and Example 1 is that the preparation of the first thermally conductive diaphragm coating layer and the second thermally conductive diaphragm coating layer is omitted, while the remaining preparation methods and parameters are consistent with Example 1.

[0176] This comparative example provides a bare battery cell, which uses the thermally composite coated separator provided in this comparative example, and the rest of the structure is consistent with that of Example 1.

[0177] This comparative example provides a method for preparing the bare battery cell, and the preparation method and parameters are consistent with those in Example 1.

[0178] The bare cells provided in Examples 1-13 and Comparative Examples 1-6 were tested for hardness, capacity, room temperature DCR (DCR of 15C discharge for 10s), and electrochemical performance. The test voltage range was 2.2V-3.65V. The test results are shown in Table 1.

[0179] Table 1

[0180]

[0181] The test results show that:

[0182] (1) As can be seen from Examples 1 to 7, the thermal composite coating diaphragm of the present invention includes a base film, an inorganic thermally conductive layer and a thermally conductive diaphragm coating layer. The inorganic thermally conductive layer includes first inorganic particles and second inorganic particles including AlN. Aluminum nitride has a high thermal conductivity, so its high thermal conductivity can ensure that the internal heat is quickly conducted during the hot pressing process of the battery cell, thereby ensuring a better hot pressing effect. Combined with the superior adhesion of the thermally conductive diaphragm coating layer itself, it can make the electrode and the thermal composite coating diaphragm have a better and more uniform adhesion force, and the electrode interface is also optimized. While ensuring the adhesion force, it can also reduce the thermal composite temperature and shorten the thermal composite time, effectively improving the production efficiency. The resulting bare battery cell has lower internal resistance, higher hardness and better electrochemical performance. Specifically, the battery cell has high hardness, with a DCR of 1.48-1.60mΩ, a capacity retention rate of 34.36-35.57% at -40℃ and 0.2C discharge, a capacity retention rate of 94.58-96.69% at 25℃ and 20C discharge, and a capacity retention rate of 89.91-91.58% after 1000 cycles at 55℃ and 1C.

[0183] (2) As can be seen from Examples 1 and 8-9, the present invention can achieve good thermal conductivity and safety performance by adjusting the thickness of the inorganic thermal conductive layer to 1.5μm-4μm.

[0184] (3) As can be seen from Examples 1 and 10-11, the mass ratio of the second inorganic particles in this invention is adjusted to 30wt%-60wt%, which can achieve better heat conduction, higher hot pressing efficiency, and better adhesion of the electrode diaphragm.

[0185] (4) As can be seen from Examples 1 and 12-13, the mass ratio of the third inorganic particles in this invention is adjusted to 5wt%-10wt%, which can make the thermally conductive membrane coating layer more stable and the adhesion effect better.

[0186] (5) As can be seen from Example 1 and Comparative Examples 1-4, the inorganic thermally conductive layer of the present invention includes first inorganic particles and second inorganic particles including AlN. Aluminum nitride has a high thermal conductivity, so its high thermal conductivity can ensure rapid heat conduction during the hot pressing process of the battery cell, thereby ensuring a better hot pressing effect. This results in better and more uniform adhesion between the electrode and the thermally composited adhesive separator, and the electrode interface is also optimized. While ensuring adhesion, it can also reduce the thermal composite temperature and shorten the thermal composite time, effectively improving production efficiency. The resulting bare battery cell has lower internal resistance and better electrochemical performance. If the second inorganic particles including AlN are omitted, the overall performance improvement of the bare battery cell cannot be achieved.

[0187] (6) As can be seen from Example 1 and Comparative Examples 5-6, if the preparation of the inorganic thermal conductive layer or the preparation of the thermal conductive membrane coating layer is omitted in the present invention, the resulting membrane will be used in the bare cell, which will lead to a significant reduction in the overall performance of the bare cell.

[0188] In summary, the thermally composite coated separator of the present invention comprises a base film, an inorganic thermally conductive layer, and a thermally conductive separator coating layer. The inorganic thermally conductive layer includes first inorganic particles and second inorganic particles including AlN. Aluminum nitride has a high thermal conductivity, thus its high thermal conductivity can ensure rapid heat conduction during the hot pressing process of the battery cell, thereby ensuring a better hot pressing effect. Combined with the superior adhesion of the thermally conductive separator coating layer itself, it can achieve better and more uniform adhesion between the electrode and the thermally composite coated separator, and the electrode interface is also optimized. While ensuring adhesion, it can also reduce the thermal bonding temperature and shorten the thermal bonding time, effectively improving production efficiency. The resulting bare battery cell has lower internal resistance, higher hardness, and better electrochemical performance.

[0189] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A thermally laminated adhesive diaphragm, characterized in that, The thermally composite coated diaphragm includes a base film, and an inorganic thermally conductive layer is disposed on at least one side surface of the base film. The inorganic thermally conductive layer includes a first inorganic particle and a second inorganic particle, wherein the second inorganic particle includes AlN. The thermally composite coated diaphragm also includes a thermally conductive diaphragm coating layer, which includes third inorganic particles. An inorganic thermally conductive layer is provided on one side surface of the base film, and the thermally conductive membrane coating layer is located on the side surface of the inorganic thermally conductive layer away from the base film and on the side surface of the base film away from the inorganic thermally conductive layer. Alternatively, an inorganic thermally conductive layer is provided on both sides of the base film, and the thermally conductive membrane coating layer is located on the side of the inorganic thermally conductive layer away from the base film.

2. The thermally laminated adhesive diaphragm according to claim 1, characterized in that, The first inorganic particles include at least one of alumina, boehmite, MgO, SiO2, BaSO4, or TiO2; Preferably, the inorganic thermally conductive layer and the thermally conductive membrane coating layer each independently further include an adhesive.

3. The thermally laminated adhesive diaphragm according to claim 2, characterized in that, The thickness of the inorganic thermally conductive layer is 1.5μm-4μm; Preferably, based on a total mass of 100wt% for the inorganic thermally conductive layer, the content of the first inorganic particles is 40wt%-70wt%; Preferably, based on a total mass of 100wt% for the inorganic thermally conductive layer, the content of the second inorganic particles is 30wt%-60wt%; Preferably, based on a total mass of 100wt% for the inorganic thermally conductive layer, the binder content is 3wt%-5wt%; Preferably, the thickness of the thermally conductive membrane coating layer is 1μm-3μm; Preferably, based on a total mass of 100wt% for the thermally conductive membrane coating layer, the content of the third inorganic particles is 5wt%-10wt%; Preferably, the content of the adhesive is 90wt%-95wt%, based on the total mass of the thermally conductive membrane coating layer being 100wt%.

4. The thermally laminated adhesive diaphragm according to any one of claims 1-3, characterized in that, The base film includes wet-process PE base film or dry-process PP base film; Preferably, the porosity of the base membrane is 43%-60%.

5. A method for preparing a thermally composite coated diaphragm according to any one of claims 1-4, characterized in that, The preparation method includes the following steps: A base film is provided, an inorganic thermally conductive layer is formed on one surface of the base film, and a thermally conductive membrane coating layer is formed on the surface of the inorganic thermally conductive layer away from the base film and on the surface of the base film away from the inorganic thermally conductive layer; or, A base film is provided, an inorganic thermally conductive layer is prepared on both sides of the base film, and a thermally conductive membrane coating layer is prepared on the side of the inorganic thermally conductive layer away from the base film to obtain a thermally composite coated membrane. The inorganic thermally conductive layer includes a first inorganic particle and a second inorganic particle, wherein the second inorganic particle includes AlN; The thermally conductive membrane coating layer includes a third inorganic particle.

6. The preparation method according to claim 5, characterized in that, The inorganic thermal conductive layer is obtained by coating with an inorganic thermal conductive layer slurry. The preparation method of the inorganic thermal conductive layer slurry includes the following steps: mixing and dispersing the first inorganic particles, the second inorganic particles, the binder and the first solvent to obtain the inorganic thermal conductive layer slurry. Preferably, the thermally conductive membrane coating layer is obtained by coating with a thermally conductive membrane coating layer slurry, and the preparation method of the thermally conductive membrane coating layer slurry includes the following steps: mixing and dispersing the third inorganic particles, binder and second solvent to obtain the thermally conductive membrane coating layer slurry; Preferably, the coating method for the thermally conductive membrane coating layer includes roller coating or intermittent coating.

7. A bare battery cell, characterized in that, The bare cell includes the thermally composite coated separator as described in any one of claims 1-4, or the thermally composite coated separator prepared by the preparation method described in claim 5 or 6. Preferably, the bare battery cell further includes a positive electrode, a negative electrode, and an electrolyte.

8. A method for preparing a bare battery cell according to claim 7, characterized in that, The preparation method includes the following steps: After stacking the positive electrode, negative electrode, and thermally coated separator, electrolyte is injected, and the cells are hot-pressed to obtain bare cells.

9. The preparation method according to claim 8, characterized in that, The hot pressing temperature is 70℃-85℃; Preferably, the hot pressing time is 15 min to 45 min; Preferably, the pressure of the hot pressing is 2000 kgf-4000 kgf.

10. An application of a bare battery cell, characterized in that, The bare cell according to claim 7, or the bare cell prepared by the preparation method according to claim 8 or 9, is applied to a start-stop battery.

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