Battery cell and single cell

Abstract

The application provides a battery cell and a single battery. The battery cell comprises a positive electrode sheet, a transfer diaphragm and a negative electrode sheet, the transfer diaphragm is arranged between the positive electrode sheet and the negative electrode sheet; the transfer diaphragm comprises an isolation layer, the isolation layer comprises first ceramic particles, second ceramic particles and a first water-based adhesive, the first ceramic particles and the second ceramic particles are dispersed and mixed, the water-based adhesive is used for bonding the first ceramic particles and the second ceramic particles, in the isolation layer, the particle size of the first ceramic particles is smaller than the particle size of the second ceramic particles; the mass ratio M1 / M2 of the first ceramic particles and the second ceramic particles ranges from 0.1 to 0.7.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a battery cell and a single battery cell. Background Technology

[0002] The stacked battery cells in related technologies include multiple layers of positive electrode sheets, separators, and multiple layers of negative electrode sheets. The positive and negative electrode sheets are stacked alternately, with a separator between adjacent positive and negative electrode sheets. The separators are stacked using a Z-shaped stacking process (i.e., the separator layers of the cell are bent in a Z-shape). This process results in low stacking efficiency and low production capacity. While some related technologies use integrated cutting and stacking machines, the efficiency matching between cutting and stacking in these machines is poor, and the technology is not yet mature in industrial applications, leading to low stacking efficiency. In addition, in related technologies, the diaphragm slurry is directly coated onto the surface of the positive or negative electrode sheet. However, the surface of the positive or negative electrode sheet is uneven and has pores. After the diaphragm slurry is coated on the surface and dries, it is very easy to produce defects such as pinholes, which increases the risk of short circuit in the battery cell. Furthermore, the solvent of the diaphragm slurry can easily penetrate into the pores of the positive and negative electrode sheets, and it is difficult to completely remove it even after long-term baking, making it easy for the positive and negative electrode sheets to shed powder. Summary of the Invention

[0003] This application provides a battery cell whose transfer separator has good liquid retention and wettability. When applied to a single battery cell, it can better improve the cycle capacity retention rate and rate performance of the single battery cell.

[0004] In a first aspect, embodiments of this application provide a battery cell, the battery cell comprising a positive electrode, a transfer separator, and a negative electrode, wherein the transfer separator is disposed between the positive electrode and the negative electrode; the transfer separator comprises: An isolation layer comprising first ceramic particles, second ceramic particles, and a first water-based adhesive, wherein the first ceramic particles and the second ceramic particles are dispersed and mixed, and the water-based adhesive is used to bond the first ceramic particles and the second ceramic particles together. In the isolation layer, the particle size of the first ceramic particles is smaller than that of the second ceramic particles. The mass ratio M1 / M2 of the first ceramic particles to the second ceramic particles is in the range of 0.1 ≤ M1 / M2 ≤ 0.7.

[0005] Furthermore, the isolation layer satisfies at least one of the following conditions: The D501 of the first ceramic particle is in the range of 50nm ≤ D501 ≤ 500nm, where D501 is the particle size value corresponding to when the cumulative volumetric particle size distribution of the first ceramic particle reaches 50%; and The range of D502 for the second ceramic particle is 500nm≤D502≤2000nm, where D502 is the particle size value corresponding to the cumulative volumetric particle size distribution of the second ceramic particle reaching 50%.

[0006] Furthermore, the loose density of the mixture of the first ceramic particles and the second ceramic particles is ρ1, and the tap density of the mixture of the first ceramic particles and the second ceramic particles is ρ2, then 1≤ρ2 / ρ1≤1.4.

[0007] Furthermore, the loose density ρ1 of the mixture of the first ceramic particles and the second ceramic particles is in the range of 0.3 g / cm³ ≤ ρ1 ≤ 1.0 g / cm³; the tap density ρ2 of the mixture of the first ceramic particles and the second ceramic particles is in the range of 0.4 g / cm³ ≤ ρ2 ≤ 1.2 g / cm³.

[0008] Furthermore, the transfer diaphragm also includes an adhesive layer disposed on the surface of the diaphragm, the adhesive layer comprising a second water-based adhesive, and the coverage S of the adhesive layer on the surface of the diaphragm toward the adhesive layer being in the range of 10% ≤ S ≤ 30%.

[0009] Furthermore, the transfer diaphragm also includes non-aqueous adhesive particles, which are dispersed in at least one of the isolation layer and the adhesive layer. The mass of the first ceramic particle in the isolation layer is M1, the mass of the second ceramic particle is M2, and the mass of the non-aqueous adhesive particles in the transfer diaphragm is M3. Then, 0.3×(M1+M2)≤M3≤0.5×(M1+M2).

[0010] Furthermore, the D503 of the non-aqueous binder particles is in the range of 1μm≤D503≤8μm, where D503 is the particle size value corresponding to the cumulative volumetric particle size distribution of the non-aqueous binder particles reaching 50%.

[0011] Furthermore, the transfer diaphragm satisfies at least one of the following conditions: The porosity P of the transfer membrane is in the range of 40% ≤ P ≤ 65%; and The thickness d1 of the isolation layer is in the range of 5μm≤d1≤25μm.

[0012] Furthermore, the transfer diaphragm also includes non-aqueous binder particles, which are dispersed in the isolation layer; the number distribution density of non-aqueous binder particles on the contact surface between the isolation layer and the positive electrode or between the isolation layer and the negative electrode is in the range of 12 particles / (115μm×85μm) to 20 particles / (115μm×85μm).

[0013] Furthermore, the transfer diaphragm further includes an adhesive layer disposed on the surface of the separator layer; the transfer diaphragm also includes non-aqueous binder particles, which are dispersed in the adhesive layer or in the separator layer and the adhesive layer; the number distribution density of non-aqueous binder particles on the contact surface between the adhesive layer and the positive electrode sheet or between the adhesive layer and the negative electrode sheet ranges from 12 particles / (115μm×85μm) to 20 particles / (115μm×85μm).

[0014] Secondly, embodiments of this application also provide a single-cell battery, the single-cell battery comprising: A housing having a receiving cavity open at one end; The battery cell described in this application embodiment is disposed within the receiving cavity; An electrolyte, wherein the electrolyte is disposed within the receiving cavity, and the battery cell is at least partially immersed in the electrolyte; and An end cap assembly, comprising a top cover and an electrode post, wherein the top cover is used to close the opening of the receiving cavity and connect to the housing, the electrode post passes through the top cover and is partially exposed, and the electrode post is electrically connected to the battery cell.

[0015] Furthermore, the electrolyte wettability K of the transfer membrane of the battery cell is in the range of 20mm≤K≤70mm, wherein the electrolyte wettability K of the transfer membrane refers to the diffusion length of the electrolyte on the transfer membrane after 1 minute when 0.5mL of electrolyte is dropped onto the transfer membrane with a size of 5mm×200mm.

[0016] The battery cell in this application includes a positive electrode, a transfer separator, and a negative electrode. The transfer separator can be transferred and bonded to the surface of the positive or negative electrode by a transfer method. When the transfer separator is applied to a laminated battery cell, the transfer separator can be transferred to the surface of the positive or negative electrode first, and then the positive and negative electrode are cut, stacked, and assembled into a laminated battery cell, which can greatly improve the stacking efficiency of the battery cell, by more than 50%. In addition, compared with the scheme of directly coating the separator slurry onto the surface of the positive or negative electrode, the transfer separator of this application is transferred to the surface of the positive or negative electrode by a transfer method. Since there is no solvent, the adhesive will not block the surface pores of the positive or negative electrode and can play a good insulating role. Furthermore, the transfer separator includes an isolation layer comprising first ceramic particles, second ceramic particles, and a first aqueous binder. The first and second ceramic particles are dispersed and mixed, and the aqueous binder is used to bond the first and second ceramic particles together. In the isolation layer, the particle size of the first ceramic particles is smaller than that of the second ceramic particles. The mass ratio M1 / M2 of the first ceramic particles to the second ceramic particles is in the range of 0.1 ≤ M1 / M2 ≤ 0.7. By designing the size and mass ratio of the first and second ceramic particles, the transfer separator can have a more suitable pore size and porosity, resulting in strong capillary action and good liquid retention and wettability. When applied to single-cell batteries, this can better improve the cycle capacity retention and rate performance of the single-cell batteries. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of an energy storage system according to an embodiment of this application.

[0019] Figure 2 This is a schematic diagram of the structure of an energy storage system according to another embodiment of this application.

[0020] Figure 3 This is a schematic diagram of the structure of an energy storage system according to another embodiment of this application.

[0021] Figure 4 This is a schematic diagram of the structure of an electrical system according to an embodiment of this application.

[0022] Figure 5 This is a schematic diagram of the structure of an energy storage device according to an embodiment of this application.

[0023] Figure 6 This is a schematic diagram of the structure of a single battery cell according to an embodiment of this application.

[0024] Figure 7 For the application of an embodiment of the single cell battery Figure 6 A schematic diagram of the cross-sectional structure along the AA direction.

[0025] Figure 8 This is a cross-sectional view of a transfer diaphragm according to one embodiment of the application.

[0026] Figure 9 A cross-sectional view of the transfer diaphragm according to yet another embodiment of the application.

[0027] Figure 10 This is a cross-sectional view of a transfer diaphragm assembly according to an embodiment of the application.

[0028] Figure 11 A cross-sectional view of a transfer diaphragm assembly according to yet another embodiment of the application.

[0029] Figure 12 This is a schematic flowchart illustrating a method for preparing a battery cell according to one embodiment of the application.

[0030] Figure 13 This is a schematic flowchart illustrating a method for preparing a transfer membrane assembly according to one embodiment of the application.

[0031] Figure 14 This is a schematic flowchart illustrating a method for preparing a transfer membrane assembly according to yet another embodiment of the application.

[0032] Explanation of reference numerals in the attached figures: 100-Energy storage system, 110-First power conversion device, 120-First user load, 130-Second user load, 140-High voltage cable, 150-Second power conversion device, 160-Photovoltaic-energy storage-charging station, 170-Automobile, 200-Energy storage device, 100'-Power system, 110'-Power equipment, 300-Single battery cell, 310-Casing, 311-Receiving cavity, 320-Battery cell, 321-Positive electrode, 322-Negative electrode, 330-End cap assembly, 331-Top cover, 332-Electrode post, 400-Transfer diaphragm, 410-Separation layer, 420-Adhesive layer, 500-Transfer diaphragm assembly, 510-Release film. Detailed Implementation

[0033] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present application.

[0034] The terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0035] The technical solutions in the embodiments of this application will now be described with reference to the accompanying drawings.

[0036] It should be noted that, for ease of explanation, the same reference numerals denote the same components in the embodiments of this application, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments.

[0037] Because the energy we need is highly time- and space-dependent, in order to utilize energy rationally and improve energy efficiency, it is necessary to store one form of energy in the same way or by converting it into another, and then release it in a specific energy form based on future application needs. Currently, the main way to generate green electricity is to develop green energy sources such as photovoltaics and wind power to replace fossil fuels.

[0038] Currently, the generation of green electricity generally relies on solar, wind, and hydropower. However, wind and solar power are generally characterized by strong intermittency and large fluctuations, which can cause grid instability, insufficient power during peak demand periods, and excessive power during off-peak periods. Unstable voltage can also damage the power grid. Therefore, insufficient electricity demand or insufficient grid capacity may lead to the problem of "wind and solar curtailment." Solving these problems requires energy storage. This involves converting electrical energy into other forms of energy through physical or chemical means and storing it. When needed, this energy can be converted back into electrical energy and released. Simply put, energy storage is like a large "power bank," storing electrical energy when solar and wind power are abundant and releasing the stored electricity when needed.

[0039] Taking electrochemical energy storage as an example, this solution provides an energy storage device for use in energy storage systems. The energy storage device is equipped with a set of chemical batteries, which mainly use the chemical elements in the batteries as energy storage media. The charging and discharging process is accompanied by the chemical reaction or change of the energy storage media. Simply put, the electrical energy generated by wind and solar energy is stored in the chemical batteries. When the use of external electrical energy reaches its peak, the stored electricity is released for use, or transferred to places with a shortage of electricity for use.

[0040] Current energy storage applications are quite widespread, including generation-side energy storage, grid-side energy storage, and consumption-side energy storage. The corresponding types of energy storage devices include: (1) Large-scale energy storage power stations (composed of multiple prefabricated energy storage modules) applied to wind power and photovoltaic power stations can help renewable energy power generation meet grid connection requirements and improve the utilization rate of renewable energy. As a high-quality active / reactive power regulation power source on the power supply side, the energy storage power station realizes the load matching of power in time and space, enhances the renewable energy absorption capacity, reduces instantaneous power changes, reduces the impact on the power grid, improves the problem of new energy power generation absorption, and is of great significance in power grid system backup, alleviating peak load power supply pressure and peak regulation and frequency regulation. (2) The energy storage prefabricated cabin applied on the grid side mainly functions as peak regulation, frequency regulation and grid congestion relief. In terms of peak regulation, it can realize peak shaving and valley filling of electricity load, that is, charging the energy storage battery when the electricity load is low and releasing the stored electricity during the peak electricity load period, thereby achieving a balance between power production and consumption. (3) Small energy storage cabinets applied to the electricity consumption side mainly function as self-consumption of electricity, peak-valley price arbitrage, capacity cost management, and improvement of power supply reliability. Depending on the application scenario, electricity consumption side energy storage can be divided into industrial and commercial energy storage cabinets, household energy storage devices, energy storage charging piles, etc., which are generally used in conjunction with distributed photovoltaics. Industrial and commercial users can use energy storage for peak-valley price arbitrage and capacity cost management. In the electricity market implementing peak-valley pricing, by charging the energy storage system when the electricity price is low and discharging the energy storage system when the electricity price is high, peak-valley price arbitrage can be achieved, reducing electricity costs. In addition, industrial enterprises subject to two-part tariffs can use energy storage systems to store energy during off-peak hours and discharge during peak loads, thereby reducing peak power and the maximum demand declared, achieving the goal of reducing capacity costs. Household photovoltaics with energy storage can improve the level of self-consumption of electricity. Due to high electricity prices and poor power supply stability, the demand for household photovoltaic installations is driven. Given that photovoltaic power generation occurs during the day, while user load is generally higher at night, configuring energy storage can better utilize photovoltaic power, improve self-consumption levels, and reduce electricity costs. Furthermore, energy storage is needed in areas such as communication base stations and data centers for backup power.

[0041] In some embodiments, see Figure 1 , Figure 1 This is a schematic diagram of the structure of an energy storage system 100 according to an embodiment of this application. Figure 1 The embodiments are illustrated using a home energy storage scenario in user-side energy storage as an example. The energy storage device 200 of this application is not limited to the home energy storage scenario.

[0042] This application provides an energy storage system 100, which includes a first power conversion device 110 (photovoltaic panel), a first user load 120 (household lighting fixture), a second user load 130 (e.g., household appliances such as air conditioners), and an energy storage device 200. The energy storage device 200 is a small energy storage box that can be wall-mounted on an outdoor wall. However, the energy storage device 200 is not limited to wall mounting and can also be placed in a user's residence in other ways. Specifically, the photovoltaic panel can convert solar energy into electrical energy during periods of low electricity prices, and the energy storage device 200 stores this electrical energy and supplies it to lighting fixtures and household appliances during peak electricity prices, or provides power during power outages / power interruptions.

[0043] In some embodiments, see Figure 2 , Figure 2 This is a schematic diagram of the structure of an energy storage system 100 according to another embodiment of this application, and this application Figure 2 The embodiments are illustrated using a shared energy storage scenario on the generation / distribution side as an example. The energy storage device 200 of this application is not limited to its generation / distribution side energy storage scenario.

[0044] This application provides an energy storage system 100, which includes: a high-voltage cable 140, a first power conversion device 110, a second power conversion device 150, and an energy storage device 200 provided in this application. In some embodiments of the power generation scenario, the second power conversion device 150 can be a wind power conversion device. Since the electricity generated by wind power conversion is volatile, random, and intermittent, the unstable electricity output by the wind power conversion device can be stored in the energy storage device 200 through grid connection. The energy storage device 200 is connected to the high-voltage cable 140 and outputs smooth electricity to the power consumption side of the distribution network, realizing peak shaving and frequency regulation, and stable grid operation; or, wind power conversion... The power conversion device is always connected to the high-voltage cable 140. Under normal power generation conditions, the power output of the wind power conversion device is supplied to the power consumption side of the distribution network through the high-voltage cable 140. When the current power load is low and the wind power conversion device generates excess power, the excess power is first stored in the energy storage device 200 to reduce wind and solar curtailment rates and improve the problem of new energy power generation consumption. When the power load is high, the power grid issues an instruction to transmit the power stored in the energy storage device 200 together with the high-voltage cable 140 in grid-connected mode to supply power to the power consumption side. This provides the power grid with various services such as peak shaving, frequency regulation, and backup, giving full play to the peak shaving role of the power grid, promoting peak shaving and valley filling, and alleviating the power supply pressure of the power grid.

[0045] In some embodiments on the distribution network side, the first power conversion device 110 can be a photovoltaic panel, and the energy storage device 200 is connected to the high-voltage cable 140 and installed downstream of the high-voltage cable 140 between the user load and the photovoltaic power conversion device. The electrical energy output by the photovoltaic power conversion device is stored in the energy storage device 200, which can respond in a timely manner to act as a backup power source when the power grid / distribution network fails; or, it can provide power supply support to alleviate line congestion when the high-voltage cable 140 transmission line is blocked, and to delay the economic pressure caused by the expansion of the power grid / distribution capacity when the power grid is planned to be expanded.

[0046] In some embodiments, see Figure 3 , Figure 3 This is a schematic diagram of the structure of an energy storage system 100 according to another embodiment of this application, and this application Figure 3 The embodiments are illustrated using an industrial and commercial energy storage scenario as an example. The energy storage device 200 of this application is not limited to industrial and commercial energy storage scenarios.

[0047] This application provides an energy storage system 100, which includes: an energy storage device 200, a high-voltage cable 140, a factory equipped with a first power conversion device 110, a photovoltaic-energy storage-charging station 160, and a vehicle 170. In some embodiments of industrial and commercial scenarios, the first power conversion device 110 can be a photovoltaic panel, which converts solar energy into electrical energy and stores it in the energy storage device 200 in the factory. In the event of a power grid failure, the energy storage device 200 provides power to ensure the safe and stable operation of the factory without interruption. Alternatively, when the factory's power load is high, the power grid issues an instruction to transmit the electricity stored in the energy storage device 200 in conjunction with the high-voltage cable 140 in a grid-connected mode to supply the factory with electricity, providing various services such as peak shaving / frequency regulation and backup for the power grid operation. In addition, the first power conversion device 110 can also convert solar energy into electrical energy and store it in the energy storage device 200 of the photovoltaic-energy storage-charging station 160, which can directly charge the vehicle 170, making it fast and convenient.

[0048] Optionally, the first power conversion device 110 may include, but is not limited to, a photovoltaic panel, and the second power conversion device 150 may include, but is not limited to, a wind power conversion device. The first power conversion device 110 and the second power conversion device 150 can convert at least one of solar energy, light energy, wind energy, thermal energy, tidal energy, biomass energy, and mechanical energy into electrical energy.

[0049] Figure 4 This is a schematic diagram of the structure of an electrical system 100' according to an embodiment of this application.

[0050] Please see Figure 4 This application embodiment also provides an electrical system 100', which includes an electrical device 110' and an energy storage device 200. The energy storage device 200 is electrically connected to the electrical device 110' and is used to supply power to the energy storage device 200.

[0051] Optionally, the electrical equipment 110' can be, but is not limited to, at least one of the following: power grid, base station, household appliances (such as air conditioner, refrigerator, washing machine, etc.).

[0052] Optionally, the electrical equipment 110' and the energy storage device 200 can be electrically connected via a high-voltage cable 140.

[0053] Please see Figure 5 , Figure 5 This is a schematic diagram of the structure of an energy storage device 200 according to an embodiment of this application.

[0054] Optionally, the energy storage device 200 includes one or more individual battery cells 300.

[0055] The term "multiple" refers to two or more, such as, but not limited to, 2, 5, 10, 30, 50, 100, 200, 300, 400, 800, 1000, etc.

[0056] It should be noted that the number of individual battery cells 300 included in the energy storage device 200 can be determined based on the rated capacity of the individual battery cells 300 and the rated capacity that the energy storage device 200 is to achieve.

[0057] Optionally, the energy storage device 200 can be used, but is not limited to, energy storage power stations, hydropower / thermal / wind power generation systems, solar power generation systems, mobile power systems, smart home systems, or temporary power supply systems, and is also applied in multiple fields such as data centers, military equipment, aerospace, charging piles, and electric vehicles.

[0058] Optionally, the energy storage device 200 may include, but is not limited to, battery integrated systems comprising a single battery cell 300, or battery modules, battery packs, battery clusters, power banks, energy storage cabinets / prefabricated energy storage containers, etc., composed of single battery cells 300. In other words, when the energy storage device 200 includes a single battery cell 300, the energy storage device 200 may exist in the form of a single battery cell 300. When the energy storage device 200 includes multiple single battery cells 300, the multiple single battery cells 300 may be stacked, arranged, assembled, etc., to form battery integrated systems such as battery modules, battery packs, battery clusters, power banks, energy storage cabinets / energy storage containers, etc.; that is, the energy storage device 200 exists in the form of battery integrated systems such as battery modules, battery packs, battery clusters, power banks, energy storage cabinets / energy storage containers, etc. The actual application form of the energy storage device 200 provided in this application embodiment may be, but is not limited to, the listed products, and may also be other application forms. This application embodiment does not strictly limit the application form of the energy storage device 200. In the embodiments of this application, the energy storage device 200 is illustrated by taking a multi-cell battery (i.e., multiple single cells 300) as an example.

[0059] Optionally, the single cell 300 can be, but is not limited to, at least one of cylindrical, square, prismatic, or other shaped cells.

[0060] Optionally, the single cell 300 can be a rechargeable battery, which refers to a single cell 300 that can be recharged after discharge to activate the active materials and continue to be used. The single cell 300 can be a lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, sodium metal battery, lithium-sulfur battery, magnesium-ion battery, nickel-metal hydride battery, nickel-cadmium battery, lead-acid battery, etc., and this application does not specifically limit it.

[0061] Understandably, the 300 single cell can be, but is not limited to, sodium batteries, lithium batteries, magnesium batteries, nickel-hydrogen batteries, nickel-cadmium batteries, lead-acid batteries, etc.

[0062] Figure 6 This is a schematic diagram of the structure of a single cell battery 300 according to an embodiment of this application. Figure 7 For an embodiment of the application, a single cell 300 is applied for. Figure 6 A schematic diagram of the cross-sectional structure along the AA direction.

[0063] Please see Figure 6 and Figure 7 This application also provides a single-cell battery 300, which includes: a housing 310, a cell 320, an electrolyte, and an end cap assembly 330. The housing 310 has a receiving cavity 311 with one end open; the cell 320 is disposed in the receiving cavity 311; the electrolyte is disposed in the receiving cavity 311, and the cell 320 is at least partially immersed in the electrolyte; the end cap assembly 330 includes a top cover 331 and an electrode post 332, the top cover 331 is used to close the opening of the receiving cavity 311 and connect to the housing 310, the electrode post 332 passes through the top cover 331 and is partially exposed, and the electrode post 332 is electrically connected to the cell 320.

[0064] Optionally, the electrode post 332 includes a positive post and a negative post spaced apart, the positive post and the negative post respectively pass through the top cover 331 and are partially exposed, and the positive post and the negative post are respectively electrically connected to the battery cell 320.

[0065] The stacked battery cells in related technologies include multiple layers of positive electrode sheets, separators, and multiple layers of negative electrode sheets. The positive and negative electrode sheets are stacked alternately, with a separator between adjacent positive and negative electrode sheets. The separators are stacked using a Z-shaped stacking process (i.e., the separator layers of the cell are bent in a Z-shape). This process results in low stacking efficiency and low production capacity. While some related technologies use integrated cutting and stacking machines, the efficiency matching between cutting and stacking in these machines is poor, and the technology is not yet mature in industrial applications, leading to low stacking efficiency. In addition, in related technologies, the diaphragm slurry is directly coated onto the surface of the positive or negative electrode sheet. However, the surface of the positive or negative electrode sheet is uneven and has pores. After the diaphragm slurry is coated on the surface and dries, it is very easy to produce defects such as pinholes, which increases the risk of short circuits in the battery cell. Furthermore, the solvent of the diaphragm slurry is usually water, which can easily seep into the pores of the positive and negative electrode sheets. It is difficult to completely remove the water even after long-term baking, making it easy for the positive and negative electrode sheets to shed powder.

[0066] Please see again Figure 7This application embodiment also provides a battery cell 320, which includes a positive electrode 321, a transfer diaphragm 400 and a negative electrode 322, wherein the transfer diaphragm 400 is disposed between the positive electrode 321 and the negative electrode 322.

[0067] Optionally, the battery cell 320 can be a wound battery cell 320 or a stacked battery cell 320. When the battery cell 320 is a wound battery cell 320, the transfer diaphragm 400, the negative electrode 322, the transfer diaphragm 400, and the positive electrode 321 are stacked in sequence and then wound to form the wound battery cell 320. When the battery cell 320 is a stacked battery cell 320, the positive electrode 321, the transfer diaphragm 400, and the negative electrode 322 are all multi-layered, and the positive electrode 321 and the negative electrode 322 are stacked alternately in sequence, with a transfer diaphragm 400 between adjacent positive electrode 321 and negative electrode 322. It should be noted that during the preparation of the battery cell 320, the transfer membrane 400 can be transferred to one side of the positive electrode 321 or the negative electrode 322, so that the transfer membrane 400 adheres to the positive electrode 321 or the negative electrode 322.

[0068] Figure 8 This is a cross-sectional view of a transfer diaphragm 400 according to an embodiment of the application.

[0069] Please see Figure 8 This application embodiment also provides a transfer diaphragm 400, which includes: an isolation layer 410, the isolation layer 410 including first ceramic particles (not shown), second ceramic particles (not shown) and a first water-based adhesive, the first ceramic particles and the second ceramic particles being dispersed and mixed, the water-based adhesive being used to bond the first ceramic particles and the second ceramic particles, in the isolation layer 410, the particle size of the first ceramic particles being smaller than the particle size of the second ceramic particles; the mass ratio M1 / M2 of the first ceramic particles to the second ceramic particles being in the range of: 0.1≤M1 / M2≤0.7.

[0070] It should be noted that the first ceramic particles, the second ceramic particles, and the first aqueous binder are dispersed and mixed, and then bonded together by the first aqueous binder to form a porous membrane structure. During the preparation of the transfer separator 400, a release film is required as a substrate. When the transfer separator 400 is transferred to the surface of the positive electrode 321 or the negative electrode 322, the release film is removed.

[0071] It should be noted that the isolation layer 410 allows ions to pass through, that is, the isolation layer 410 has ion-conducting properties. However, the isolation layer 410 has insulating properties, that is, it does not have electronic properties, so as to insulate the positive electrode 321 from the negative electrode 322.

[0072] It should be noted that "water-based adhesives" refer to binders or adhesives that are soluble in water.

[0073] Specifically, the mass ratio M1 / M2 of the first ceramic particles to the second ceramic particles can be, but is not limited to, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, etc. If the mass ratio M1 / M2 of the first ceramic particles to the second ceramic particles is too small, the proportion of the first ceramic particles in the separator layer 410 will be too low, and the proportion of the second ceramic particles will be too high. This will increase the porosity and porosity of the separator layer 410, reduce the heat resistance of the transfer membrane 400, and when the transfer membrane 400 is applied to the single cell 300, the self-discharge effect of the single cell 300 will increase, and the probability of short circuit will increase. If the mass ratio M1 / M2 of the first ceramic particles to the second ceramic particles is too large, the proportion of the first ceramic particles in the separator 410 will be too high and the proportion of the second ceramic particles will be too low. This will reduce the porosity and pore size of the separator 410, thereby reducing its liquid retention and electrolyte wettability, and consequently reducing the long-cycle capacity retention and rate performance of the single cell 300. Furthermore, the excessively high proportion of the first ceramic particles makes it difficult to disperse the first and second ceramic particles during the preparation of the separator 410, making them prone to agglomeration.

[0074] The transfer separator 400 of this application embodiment can be transferred and bonded to the surface of the positive electrode 321 or the negative electrode 322 by transfer. When the transfer separator 400 is applied to the laminated cell 320, the transfer separator 400 can be transferred to the surface of the positive electrode 321 or the negative electrode 322 first, and then the positive electrode 321 and the negative electrode 322 can be cut, laminated and assembled into the laminated cell 320, which can greatly improve the lamination efficiency of the cell 320, and the lamination efficiency can be increased by more than 50%. In addition, compared with the scheme of directly coating the separator slurry onto the surface of the positive electrode 321 or the negative electrode 322, the transfer separator 400 of this application is transferred to the surface of the positive electrode 321 or the negative electrode 322 by transfer. Since there is no solvent, the adhesive will not block the surface pores of the positive electrode 321 or the negative electrode 322, and it can play a good insulating role. Furthermore, the transfer separator 400 includes an isolation layer 410, which comprises first ceramic particles, second ceramic particles, and a first aqueous adhesive. The first ceramic particles and the second ceramic particles are dispersed and mixed, and the aqueous adhesive is used to bond the first ceramic particles and the second ceramic particles. In the isolation layer 410, the particle size of the first ceramic particles is smaller than that of the second ceramic particles; the mass ratio M1 / M2 of the first ceramic particles to the second ceramic particles is in the range of 0.1 ≤ M1 / M2 ≤ 0.7. By designing the size and mass ratio of the first ceramic particles and the second ceramic particles, the transfer separator 400 can have a more suitable pore size and porosity, resulting in strong capillary action and good liquid retention and wettability. When applied to a single cell 300, it can better improve the cycle capacity retention rate and rate performance of the single cell 300.

[0075] In some embodiments, the D501 of the first ceramic particle is in the range of 50nm≤D501≤500nm, where D501 is the particle size value corresponding to the cumulative volumetric particle size distribution of the first ceramic particle reaching 50%.

[0076] Specifically, the D501 of the first ceramic particle can be, but is not limited to, 50nm, 80nm, 100nm, 130nm, 150nm, 180nm, 200nm, 230nm, 250nm, 280nm, 300nm, 330nm, 350nm, 380nm, 400nm, 430nm, 450nm, 480nm, 500nm, etc.

[0077] In this embodiment, if the D501 of the first ceramic particles is too small, the first ceramic particles will be difficult to disperse during the preparation of the separator 410, and will easily agglomerate. In addition, if the porosity of the separator 410 is too small, the liquid retention will be reduced, the wettability will be worse, and the capacity retention rate of the single cell 300 during long cycles will be reduced. If the D501 of the first ceramic particles is too large, the particle size of the first ceramic particles will be too close to that of the second ceramic particles, which will increase the porosity of the separator 410, reduce the heat resistance of the separator 410, enhance the self-discharge effect of the single cell 300, and increase the probability of short circuit.

[0078] Furthermore, the D501 of the first ceramic particles is in the range of 250nm≤D501≤400nm. This allows the separator 410 to have high liquid retention and wettability, as well as high heat resistance. When applied to a single cell 300, the single cell 300 has a high long-cycle capacity retention rate and rate performance, is not prone to self-discharge, and reduces the probability of short circuit in the single cell 300.

[0079] In some embodiments, the D502 of the second ceramic particle is in the range of 500nm≤D502≤2000nm, where D502 is the particle size value corresponding to the cumulative volumetric particle size distribution of the second ceramic particle reaching 50%.

[0080] Specifically, the D502 of the second ceramic particle can be, but is not limited to, 500nm, 600nm, 700nm, 800nm, 850nm, 900nm, 950nm, 1000nm, 1050nm, 1100nm, 1150nm, 1200nm, 1300nm, 1400nm, 1500nm, 1600nm, 1700nm, 1800nm, 1900nm, 2000nm, etc.

[0081] In this embodiment, if the D502 of the second ceramic particles is too small, the porosity of the separator 410 will be too small, resulting in reduced liquid retention, poor wettability, and decreased capacity retention during long-cycle operation of the single cell 300. If the D502 of the second ceramic particles is too large, the porosity of the separator 410 will increase, reducing its heat resistance, enhancing the self-discharge effect of the single cell 300, and increasing the probability of short circuit.

[0082] Furthermore, the D502 of the second ceramic particles is in the range of 800nm ​​≤ D502 ≤ 1300nm. This allows the separator layer 410 to have high liquid retention and wettability while also having high heat resistance. When applied to a single cell 300, the single cell 300 has a high long-cycle capacity retention rate and rate performance, is less prone to self-discharge, and reduces the probability of short circuits in the single cell 300.

[0083] In some embodiments, the loose density of the mixture of the first ceramic particles and the second ceramic particles is ρ1, and the tap density of the mixture of the first ceramic particles and the second ceramic particles is ρ2, then 1≤ρ2 / ρ1≤1.4.

[0084] "Loose packing density" refers to the mass of powder per unit volume when the container is naturally filled.

[0085] "Tap density" is the mass per unit volume of powder after it has been vibrated under specified conditions in a vibrating container.

[0086] Understandably, the ratio of tap density to loose density ρ2 / ρ1 after the first ceramic particles and the second ceramic particles are mixed ranges from 1 to 1.4.

[0087] It should be noted that the ratio of the tap density to the loose density after the first ceramic particles and the second ceramic particles are mixed is also called the Hausner ratio H, and 1≤H=ρ2 / ρ1≤1.4.

[0088] Specifically, ρ2 / ρ1 can be, but is not limited to, 1, 1.03, 1.05, 1.08, 1.1, 1.13, 1.15, 1.18, 1.2, 1.23, 1.25, 1.28, 1.3, 1.33, 1.35, 1.38, 1.4, etc.

[0089] In this embodiment, if ρ2 / ρ1 is too large, the tap density after mixing the first ceramic particles and the second ceramic particles will be too large, the compactness of the isolation layer 410 will be too high, the porosity and porosity of the isolation layer 410 will be too small, the liquid retention will be reduced, the wettability will be worse, and the capacity retention rate of the single cell 300 during long cycles will be reduced.

[0090] In some embodiments, the loose density ρ1 of the mixture of the first ceramic particles and the second ceramic particles is in the range of 0.3 g / cm³ ≤ ρ1 ≤ 1.0 g / cm³.

[0091] Specifically, the loose packing density ρ1 of the mixture of the first ceramic particles and the second ceramic particles can be, but is not limited to, 0.3 g / cm³, 0.4 g / cm³, 0.5 g / cm³, 0.6 g / cm³, 0.7 g / cm³, 0.8 g / cm³, 0.9 g / cm³, 1.0 g / cm³, etc. This allows the separator layer 410 to have a more appropriate pore size and porosity, and the separator layer 410 has higher liquid retention and wettability, thereby improving the long-cycle capacity retention rate and rate performance of the single cell 300.

[0092] In some embodiments, the tap density ρ2 of the mixture of the first ceramic particles and the second ceramic particles is in the range of 0.4 g / cm³ ≤ ρ2 ≤ 1.2 g / cm³.

[0093] Specifically, the tap density ρ2 of the mixture of the first ceramic particles and the second ceramic particles can be, but is not limited to, 0.4 g / cm³, 0.5 g / cm³, 0.6 g / cm³, 0.7 g / cm³, 0.8 g / cm³, 0.9 g / cm³, 1.0 g / cm³, 1.1 g / cm³, 1.2 g / cm³, etc. This allows the separator layer 410 to have a more appropriate pore size and porosity, and the separator layer 410 has higher liquid retention and wettability, thereby improving the long-cycle capacity retention rate and rate performance of the single cell 300.

[0094] The test of the tapped density and loose density of the mixture of the first and second ceramic particles in this application can be carried out with reference to the standard GB / T 6609.25-2023 Chemical Analysis Methods and Physical Property Determination Methods for Alumina Part 25: Determination of Loose and Tapped Densities. Weigh 50g of powder, measure the volume change before and after tapping, and then calculate the loose and tapped densities of the mixture. Then calculate the Hausner ratio (H), which is the ratio of tapped density to loose density, to evaluate the powder flowability.

[0095] Figure 9 A cross-sectional view of the transfer diaphragm 400 according to another embodiment of the application.

[0096] Please see Figure 9 In some embodiments, the transfer diaphragm 400 further includes an adhesive layer 420 disposed on the surface of the isolation layer 410, the adhesive layer 420 including a second water-based adhesive, and the coverage S of the adhesive layer 420 on the surface of the isolation layer 410 facing the adhesive layer 420 being in the range of 10% ≤ S ≤ 30%.

[0097] Understandably, in some embodiments, the transfer diaphragm 400 includes only the isolation layer 410, while in other embodiments, the transfer diaphragm 400 includes the isolation layer 410 and the adhesive layer 420 stacked together.

[0098] Optionally, the adhesive layer 420 can be formed on the surface of the isolation layer 410 by means of roller coating, dot coating, spraying, etc.

[0099] Specifically, the coverage S of the adhesive layer 420 on the surface of the isolation layer 410 facing the adhesive layer 420 can be, but is not limited to, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, etc.

[0100] In this embodiment, the adhesive layer 420 is used to improve the adhesion of the transfer separator 400, so that the transfer separator 400 can be better transferred to the positive electrode 321 or the negative electrode 322, thereby improving the integrity and efficiency of the transfer of the transfer separator 400. If the coverage S of the adhesive layer 420 on the surface of the separator 410 facing the adhesive layer 420 is too small, the improvement of the adhesion of the transfer separator 400 will be limited. If the coverage S of the adhesive layer 420 on the surface of the separator 410 facing the adhesive layer 420 is too large, the adhesive layer 420 will easily block the pores of the separator 410, reduce the ion transport efficiency of the transfer separator 400, and reduce the rate performance of the single cell 300.

[0101] In some embodiments, the transfer diaphragm 400 further includes non-aqueous adhesive particles dispersed in at least one of the release layer 410 and the adhesive layer 420.

[0102] Optionally, if the mass of the first ceramic particle in the isolation layer 410 is M1, the mass of the second ceramic particle is M2, and the mass of the non-aqueous binder particle in the transfer diaphragm 400 is M3, then 0.3×(M1+M2)≤M3≤0.5×(M1+M2).

[0103] "Non-aqueous adhesives" refer to adhesives or binders that are insoluble in water.

[0104] It should be noted that the non-aqueous binder particles remain dispersed and exist in particulate form in water.

[0105] For example, non-aqueous adhesive particles are dispersed in the isolation layer 410, meaning the non-aqueous adhesive particles are one component of the isolation layer 410, which includes first ceramic particles, second ceramic particles, a non-aqueous adhesive, and a first aqueous adhesive. Also for example, non-aqueous adhesive particles are dispersed in the adhesive layer 420, meaning the non-aqueous adhesive particles are one component of the adhesive layer 420, which includes a non-aqueous adhesive and a second aqueous adhesive. Still for example, both the isolation layer 410 and the adhesive layer 420 include a non-aqueous adhesive.

[0106] Understandably, 0.3 ≤ M3 / (M1 + M2) ≤ 0.5.

[0107] Specifically, M3 can be, but is not limited to, 0.3×(M1+M2), 0.33×(M1+M2), 0.35×(M1+M2), 0.38×(M1+M2), 0.4×(M1+M2), 0.43×(M1+M2), 0.45×(M1+M2), 0.48×(M1+M2), 0.5×(M1+M2), etc.

[0108] In this embodiment, by adding a non-aqueous binder to at least one of the isolation layer 410 and the adhesive layer 420, the bonding force between the transfer diaphragm 400 and the positive electrode 321 or negative electrode 322 can be better improved when the transfer diaphragm 400 is transferred to the positive electrode 321 or negative electrode 322 by molding or rolling (such as room temperature molding or rolling or hot pressing), thereby improving the integrity and efficiency of the transfer of the transfer diaphragm 400. In this embodiment, if the mass of the non-aqueous binder particles in the transfer diaphragm 400 is too small, the improvement in the adhesion of the transfer diaphragm 400 will be limited; if the mass of the non-aqueous binder particles in the transfer diaphragm 400 is too large, when the non-aqueous binder is dispersed in the isolation layer 410, the viscosity of the isolation slurry is too high during the preparation of the isolation layer 410, which is prone to agglomeration and is not conducive to the dispersion of the first ceramic particles, the second ceramic particles and the non-aqueous binder.

[0109] In some embodiments, the mass fraction of the non-aqueous binder particles in the transfer diaphragm ranges from 16% to 35%. Specifically, the mass fraction of the non-aqueous binder particles in the transfer diaphragm can be, but is not limited to, 16%, 18%, 20%, 23%, 25%, 28%, 30%, 33%, 35%, etc. If the mass fraction of the non-aqueous binder particles in the transfer diaphragm is too low, the improvement in the adhesion of the transfer diaphragm will be limited; if the mass fraction of the non-aqueous binder particles in the transfer diaphragm is too high, when the non-aqueous binder is dispersed in the isolation layer, the viscosity of the isolation slurry will be too high during the preparation of the isolation layer, which is prone to agglomeration and is not conducive to the dispersion of the first ceramic particles, the second ceramic particles, and the non-aqueous binder.

[0110] In some embodiments, the D503 of the non-aqueous binder particles is in the range of 1 μm ≤ D503 ≤ 8 μm, where D503 is the particle size value corresponding to the cumulative volumetric particle size distribution of the non-aqueous binder particles reaching 50%.

[0111] Specifically, the D503 of the non-aqueous binder particles can be, but is not limited to, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, etc.

[0112] In this embodiment, if the D503 of the non-aqueous binder particles is too small, it increases the difficulty of preparing the non-aqueous binder particles; if the D503 of the non-aqueous binder particles is too large, after the transfer membrane 400 is transferred to the positive electrode 321 or the negative electrode 322, the compression ratio of the non-aqueous binder particles is too large, and the area covered by the non-aqueous binder particles on the surface of the transfer membrane 400 after compression is large, which can easily block the pores of the transfer membrane 400 and reduce the ion transport rate of the transfer membrane 400.

[0113] In some embodiments, the porosity P of the transfer membrane 400 is in the range of 40% ≤ P ≤ 65%. Specifically, the porosity P of the transfer membrane 400 can be, but is not limited to, 40%, 43%, 45%, 48%, 50%, 53%, 55%, 58%, 60%, 63%, 65%, etc. If the porosity of the transfer membrane 400 is too low, its liquid retention and wettability are reduced. If the porosity of the transfer membrane 400 is too high, the self-discharge effect of the single cell 300 is increased, increasing the probability of short circuit in the single cell 300; in addition, the heat resistance of the transfer membrane 400 is reduced, the adhesive strength of the transfer membrane 400 is reduced, and it is prone to cracking.

[0114] Furthermore, the porosity P of the transfer membrane 400 is in the range of 50% ≤ P ≤ 65%. This allows the transfer membrane 400 to have high liquid retention and wettability, and the single cell 300 to have a low self-discharge effect, reducing the probability of short circuit in the single cell 300.

[0115] In some embodiments, the thickness d of the transfer separator 400 ranges from 5μm ≤ d ≤ 25μm. Specifically, the thickness d of the transfer separator 400 can be, but is not limited to, 5μm, 8μm, 10μm, 12μm, 14μm, 16μm, 18μm, 20μm, 22μm, 24μm, 25μm, etc. It should be noted that when the transfer separator 400 is transferred to the surface of the positive electrode 321 or the negative electrode 322, it is compressed during molding or rolling, thus reducing the overall thickness of the transfer separator 400. If the thickness d of the transfer separator 400 is too thin, the insulation of the transfer separator 400 will decrease. When the transfer separator 400 is applied to a single cell 300, the self-discharge effect will be more pronounced, and micro-short circuits will easily form; in addition, the mechanical properties will decrease, and cracking will easily occur. If the thickness d of the transfer separator 400 is too thick, it increases the ion transport path of the single cell 300 and reduces the kinetic performance of the single cell 300.

[0116] Optionally, the thickness d1 of the separator 410 is in the range of 5μm ≤ d1 ≤ 25μm. Specifically, the thickness d1 of the separator 410 can be, but is not limited to, 5μm, 8μm, 10μm, 12μm, 14μm, 16μm, 18μm, 20μm, 22μm, 24μm, 25μm, etc. If the thickness d of the separator 410 is too thin, the insulation of the separator 410 will be reduced, and when the transfer separator 400 is applied to the single cell 300, the self-discharge effect will be more obvious, and micro-short circuits will easily form; in addition, the mechanical properties will be reduced, and cracking will easily occur. If the thickness d of the separator 410 is too thick, the ion transport path of the single cell 300 will be increased, and the kinetic performance of the single cell 300 will be reduced.

[0117] Optionally, the thickness d2 of the adhesive layer 420 is in the range of 2μm≤d2≤6μm. Specifically, the thickness d2 of the adhesive layer 420 can be, but is not limited to, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, etc. If the thickness d2 of the adhesive layer 420 is too thin, the improvement in the adhesion of the transfer separator 400 will be limited; if the thickness d2 of the adhesive layer 420 is too thick, after the transfer separator 400 is transferred to the surface of the positive electrode 321 or the negative electrode 322, the adhesive layer 420 will be compressed, and the area covering the separator layer 410 will be too large. The adhesive layer 420 will easily block the pores of the separator layer 410, reducing the ion transport efficiency of the transfer separator 400 and reducing the rate performance of the single cell 300.

[0118] Optionally, the first ceramic particles include at least one of alumina, boehmite, lithium titanium aluminum phosphate, lithium garnet oxide, zirconium oxide, silicon dioxide, barium titanate, etc.

[0119] Optionally, the second ceramic particles include at least one of alumina, boehmite, lithium titanium aluminum phosphate, lithium garnet oxide, zirconium oxide, silicon dioxide, barium titanate, etc.

[0120] Optionally, the material of the first ceramic particle and the material of the second ceramic particle can be the same or different.

[0121] Optionally, the first water-based adhesive may include, but is not limited to, at least one of polyacrylic acid (PAA), acrylate, etc.

[0122] Optionally, the mass fraction of the first aqueous adhesive in the isolation layer 410 ranges from 3% to 15%. Specifically, the mass fraction of the first aqueous adhesive in the isolation layer 410 can be, but is not limited to, 3%, 5%, 6%, 8%, 10%, 12%, 14%, 15%, etc.

[0123] Optionally, the second water-based adhesive may include, but is not limited to, at least one of polyacrylic acid (PAA), acrylate, etc.

[0124] Optionally, the material of the first water-based adhesive and the material of the second water-based adhesive may be the same or different.

[0125] Optionally, the non-aqueous binder particles may be, but are not limited to, at least one of polymethyl methacrylate (PMMA) particles and polyvinylidene fluoride (PVDF) particles.

[0126] In some embodiments, the transfer diaphragm 400 further includes non-aqueous binder particles, which are dispersed in the isolation layer 410; the number distribution density of adhesive dots formed by the non-aqueous binder particles on the contact surface between the isolation layer 410 and the positive electrode 321 or between the isolation layer 410 and the negative electrode 322 ranges from 12 dots / (115μm×85μm) to 20 dots / (115μm×85μm).

[0127] It should be noted that during the preparation of the transfer membrane 400, some of the non-aqueous binder particles on its surface will protrude from the surface of the transfer membrane 400. These non-aqueous binder particles will melt and form adhesive dots when the transfer membrane 400 is transferred to the surface of the positive electrode 321 or the negative electrode 322, thus bonding the transfer membrane 400 to the positive electrode 321 or the transfer membrane 400 to the negative electrode 322. When the transfer membrane 400 only includes the separator layer 410, some of the non-aqueous binder particles protrude from one surface of the separator layer 410.

[0128] Specifically, the number distribution density of adhesive dots formed by non-aqueous binder particles on the contact surface between the isolation layer 410 and the positive electrode 321 or between the isolation layer 410 and the negative electrode 322 can be, but is not limited to, 12 / (115μm×85μm), 13 / (115μm×85μm), 14 / (115μm×85μm), 15 / (115μm×85μm), 16 / (115μm×85μm), 17 / (115μm×85μm), 18 / (115μm×85μm), 19 / (115μm×85μm), 20 / (115μm×85μm), etc.

[0129] In this embodiment, if the density of adhesive dots formed by non-aqueous adhesive particles on the contact surface between the isolation layer 410 and the positive electrode 321 or between the isolation layer 410 and the negative electrode 322 is too low, the adhesion between the isolation layer 410 and the positive electrode 321 or between the isolation layer 410 and the negative electrode 322 will be too low, or the cohesion of the transfer diaphragm 400 will be too low, and the transfer diaphragm 400 will be prone to cracking during the transfer process, resulting in unqualified adhesion between the isolation layer 410 and the positive electrode 321 or between the isolation layer 410 and the negative electrode 322. If the density of adhesive dots formed by non-aqueous binder particles on the contact surface between the separator 410 and the positive electrode 321 or the separator 410 and the negative electrode 322 is too high, the adhesion between the separator 410 and the positive electrode 321 or the separator 410 and the negative electrode 322 will be too high. During the charge-discharge cycle, there is a risk of separation between the positive active layer of the positive electrode 321 and the positive current collector or between the negative active layer of the negative electrode 322 and the negative current collector, which reduces the energy efficiency and cycle capacity retention of the single cell 300. In addition, if the adhesion between the transfer separator 400 and the positive electrode 321 or the negative electrode 322 is too strong, the proportion of non-aqueous binder particles in the transfer separator 400 will be too high, and the tortuosity inside the transfer separator 400 will be too large, affecting the ion transport efficiency and energy efficiency.

[0130] Please see again Figure 9 In some embodiments, the transfer diaphragm 400 further includes an adhesive layer 420 disposed on the surface of the isolation layer 410; the transfer diaphragm 400 also includes non-aqueous adhesive particles, which are dispersed in the adhesive layer 420 or in the isolation layer 410 and the adhesive layer 420; the number distribution density of adhesive dots formed by the non-aqueous adhesive particles on the contact surface between the adhesive layer 420 and the positive electrode 321 or between the adhesive layer 420 and the negative electrode 322 ranges from 12 dots / (115μm×85μm) to 20 dots / (115μm×85μm).

[0131] It should be noted that when the transfer diaphragm 400 includes a separation layer 410 and an adhesive layer 420 stacked together, the non-aqueous adhesive particles protrude from the adhesive layer 420 away from the surface of the separation layer 410.

[0132] Understandably, in this embodiment, the adhesive layer 420 includes non-aqueous adhesive particles, and the release layer 410 may include non-aqueous adhesive particles or may not include non-aqueous adhesive particles.

[0133] Specifically, the number distribution density of adhesive dots formed by non-aqueous adhesive particles on the contact surface between the adhesive layer 420 and the positive electrode 321 or between the adhesive layer 420 and the negative electrode 322 can be, but is not limited to, 12 / (115μm×85μm), 13 / (115μm×85μm), 14 / (115μm×85μm), 15 / (115μm×85μm), 16 / (115μm×85μm), 17 / (115μm×85μm), 18 / (115μm×85μm), 19 / (115μm×85μm), 20 / (115μm×85μm), etc.

[0134] In this embodiment, if the density of adhesive dots formed by non-aqueous adhesive particles on the contact surface between the adhesive layer 420 and the positive electrode 321 or the adhesive layer 420 and the negative electrode 322 is too low, the adhesion between the adhesive layer 420 and the positive electrode 321 or the adhesive layer 420 and the negative electrode 322 will be too low, or the cohesion of the transfer diaphragm 400 will be too low, and the transfer diaphragm 400 will be prone to cracking during the transfer process, resulting in unqualified adhesion between the adhesive layer 420 and the positive electrode 321 or the adhesive layer 420 and the negative electrode 322. If the density of adhesive dots formed by non-aqueous binder particles on the contact surface between the adhesive layer 420 and the positive electrode 321 or the adhesive layer 420 and the negative electrode 322 is too high, there is a risk of separation between the positive active layer of the positive electrode 321 and the positive current collector or the negative active layer of the negative electrode 322 and the negative current collector during the charge-discharge cycle of the cell 320, which reduces the energy efficiency and cycle capacity retention of the single cell 300. In addition, if the bonding between the transfer separator 400 and the positive electrode 321 or the negative electrode 322 is too strong, the proportion of non-aqueous binder particles in the transfer separator 400 will be too high, and the tortuosity inside the transfer separator 400 will be too large, affecting the ion transport efficiency and energy efficiency.

[0135] Optionally, the isolation layer 410 further includes a first dispersant. Optionally, the first dispersant may be, but is not limited to, polyvinyl alcohol (PVA). Optionally, the mass fraction of the first dispersant in the isolation layer 410 ranges from 0.5% to 2%, specifically, it may be, but is not limited to, 0.5%, 0.8%, 1.0%, 1.3%, 1.5%, 1.8%, 2%, etc. If the mass fraction of the first dispersant in the isolation layer 410 is too low, the first dispersant cannot sufficiently cover the surface of the non-aqueous binder particles in the isolation layer 410, resulting in the inability to effectively reduce the adsorption and aggregation forces between the non-aqueous binder particles, thus failing to achieve a good dispersion effect. If the mass fraction of the first dispersant in the isolation layer 410 is too high, the interaction forces between the first dispersants are too large, which may cause the non-aqueous binder particles to agglomerate and lose the dispersion effect; in some cases, excessive first dispersant may make the particles easily agglomerate, which is not conducive to obtaining bead-like particles; in addition, excessive first dispersant may also have an adverse effect on the performance of the isolation layer 410 and increase the cost of the transfer diaphragm 400.

[0136] Optionally, the adhesive layer 420 further includes a second dispersant. Optionally, the second dispersant may be, but is not limited to, polyvinyl alcohol (PVA). Optionally, the mass fraction of the second dispersant in the adhesive layer 420 ranges from 0.5% to 2%, specifically, it may be, but is not limited to, 0.5%, 0.8%, 1.0%, 1.3%, 1.5%, 1.8%, 2%, etc. If the mass fraction of the second dispersant in the adhesive layer 420 is too low, the second dispersant cannot sufficiently cover the surface of the non-aqueous adhesive particles in the adhesive layer 420, resulting in the inability to effectively reduce the adsorption and aggregation forces between the non-aqueous adhesive particles, thereby failing to achieve a good dispersion effect. If the mass fraction of the second dispersant in the adhesive layer 420 is too high, the interaction force between the second dispersants will be too large, which may cause the non-aqueous binder particles to agglomerate and lose the dispersion effect. In some cases, excessive second dispersant may make the particles easy to stick together, which is not conducive to obtaining bead-shaped particles. In addition, excessive second dispersant may also have an adverse effect on the performance of the adhesive layer 420 and increase the cost of the transfer diaphragm 400.

[0137] Figure 10 This is a cross-sectional view of a transfer diaphragm assembly 500 according to an embodiment of the application. Figure 11 A cross-sectional view of a transfer diaphragm assembly 500 according to yet another embodiment of the application.

[0138] Please see Figure 10 and Figure 11This application embodiment also provides a transfer diaphragm assembly 500, which includes: a release film 510 and the transfer diaphragm 400 described in this application embodiment, wherein the isolation layer 410 of the transfer diaphragm 400 is formed on the surface of the release film 510.

[0139] It should be noted that the release membrane 510 and the transfer diaphragm 400 are stacked together. The release membrane 510 is used to support the transfer diaphragm 400. When the transfer diaphragm 400 is transferred onto the positive electrode 321 or the negative electrode 322, the release membrane 510 is removed.

[0140] Optionally, the thickness of the release film 510 ranges from 40 μm to 60 μm. Specifically, the thickness of the release film 510 can be, but is not limited to, 40 μm, 43 μm, 45 μm, 48 μm, 50 μm, 53 μm, 55 μm, 58 μm, 60 μm, etc.

[0141] Optionally, the release film 510 may be made of at least one of the following materials: polypropylene (PP), polytetrafluoroethylene (PTFE), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyurethane (PU).

[0142] It should be noted that when the transfer diaphragm 400 includes only the release layer 410, the release film 510 and the release layer 410 are stacked together. When the transfer diaphragm 400 includes the release layer 410 and the adhesive layer 420, the release film 510, the release layer 410 and the adhesive layer 420 are stacked sequentially.

[0143] The transfer diaphragm assembly 500 of this application can transfer and adhere the transfer diaphragm 400 to the surface of the positive electrode 321 or negative electrode 322 via transfer. When the transfer diaphragm 400 is applied to the laminated cell 320, the transfer diaphragm 400 can be transferred to the surface of the positive electrode 321 or negative electrode 322 first, and then the positive electrode 321 and negative electrode 322 can be cut, laminated, and assembled into the laminated cell 320. This can greatly improve the lamination efficiency of the cell 320, which can be increased by more than 50%. In addition, compared with the scheme of directly coating the diaphragm slurry onto the surface of the positive electrode 321 or negative electrode 322, the transfer diaphragm 400 of this application is transferred to the surface of the positive electrode 321 or negative electrode 322 via transfer, which will not block the surface pores of the positive electrode 321 or negative electrode 322, and can play a good insulating role. Furthermore, the transfer separator 400 includes an isolation layer 410, which comprises first ceramic particles, second ceramic particles, and a first aqueous adhesive. The first ceramic particles and the second ceramic particles are dispersed and mixed, and the aqueous adhesive is used to bond the first ceramic particles and the second ceramic particles. In the isolation layer 410, the particle size of the first ceramic particles is smaller than that of the second ceramic particles; the mass ratio M1 / M2 of the first ceramic particles to the second ceramic particles is in the range of 0.1 ≤ M1 / M2 ≤ 0.7. By designing the size and mass ratio of the first ceramic particles and the second ceramic particles, the transfer separator 400 can have a more suitable pore size and porosity, resulting in strong capillary action and good liquid retention and wettability. When applied to a single cell 300, it can better improve the cycle capacity retention rate and rate performance of the single cell 300.

[0144] In some embodiments, the average peel strength Q between the release film 510 and the separator 410 ranges from 1 N / m ≤ Q ≤ 8 N / m. Specifically, the average peel strength Q between the release film 510 and the separator 410 can be, but is not limited to, 1 N / m, 2 N / m, 3 N / m, 4 N / m, 5 N / m, 6 N / m, 7 N / m, 8 N / m, etc. If the average peel strength Q between the release film 510 and the separator 410 is too low, the separator 410 is not easily formed on the surface of the release film 510; if the average peel strength Q between the release film 510 and the separator 410 is too high, when the transfer separator 400 is to be transferred to the surface of the positive electrode 321 or the negative electrode 322, the transfer separator 400 is prone to incomplete transfer, or even difficult transfer to the surface of the positive electrode 321 or the negative electrode 322.

[0145] In some embodiments, the release film 510 has a wetting factor Ra / D, and the range of the wetting factor Ra / D of the release film 510 is 0.1 ≤ Ra / D ≤ 2.5, where Ra is the surface roughness of the release film 510 and D is the surface tension coefficient of the release film 510. Specifically, the wetting factor Ra / D of the release film 510 can be, but is not limited to, 0.1, 0.3, 0.5, 0.8, 1.0, 1.3, 1.5, 1.8, 2.0, 2.3, 2.5, etc. If the wetting factor Ra / D of the release film 510 is too small, the isolation slurry formed by the raw material components of the isolation layer 410 cannot be fully spread on the release film 510, and the formed isolation layer 410 is prone to defects such as shrinkage cavities, bubbles, and pinholes. If the wetting factor Ra / D of the release film 510 is too large, the isolation slurry formed by the raw material components of the isolation layer 410 will easily flow, resulting in uneven distribution and thickness of solid particles (such as the first ceramic particles and the second ceramic particles, or the first ceramic particles, the second ceramic particles and non-aqueous binder particles) in the isolation slurry.

[0146] In some embodiments, the electrolyte wettability K of the transfer membrane 400 of the battery cell 320 is in the range of 20mm≤K≤70mm, wherein the electrolyte wettability K of the transfer membrane 400 refers to the diffusion length of the electrolyte on the transfer membrane 400 after 1 minute when 0.5mL of electrolyte is dropped onto the transfer membrane 400 with a size of 5mm×200mm.

[0147] Specifically, the electrolyte wettability K of the transfer membrane 400 of the battery cell 320 can be, but is not limited to, 20mm, 30mm, 40mm, 50mm, 60mm, 70mm, etc. In this embodiment, if the electrolyte wettability K of the transfer membrane 400 of the battery cell 320 is too small, the battery cell 320 will not be sufficiently wetted, and purple spots and lithium plating will easily occur during charging and discharging. The larger the electrolyte wettability K of the transfer membrane 400 of the battery cell 320, the better. However, if the electrolyte wettability K of the transfer membrane 400 of the battery cell 320 is too large, it will be difficult to achieve.

[0148] In some embodiments, the coverage of non-aqueous adhesive particles on the surface of the transfer diaphragm 400 away from the release membrane 510 ranges from 1% to 4%.

[0149] It should be noted that the coverage rate of non-aqueous adhesive particles on the surface of the transfer diaphragm 400 away from the release membrane 510 refers to the ratio of the area occupied by non-aqueous adhesive particles M3 on the surface of the transfer diaphragm 400 away from the release membrane 510 to the area of ​​the surface of the transfer diaphragm 400. In short, it is the coverage rate of non-aqueous adhesive particles on the surface of the transfer diaphragm 400.

[0150] It should be noted that the coverage of non-aqueous binder particles on the surface of the transfer diaphragm 400 away from the release membrane 510 is not only related to the mass fraction of non-aqueous binder particles in the transfer diaphragm 400, but also to the degree of dispersion of the non-aqueous binder particles.

[0151] Specifically, the coverage of non-aqueous adhesive particles on the surface of the transfer diaphragm 400 away from the release membrane 510 can be, but is not limited to, 1%, 1.3%, 1.5%, 1.8%, 2%, 2.3%, 2.5%, 2.8%, 3%, 3.3%, 3.5%, 3.8%, 4%, etc.

[0152] In this embodiment, if the coverage rate of non-aqueous binder particles on the surface of the transfer separator 400 away from the release membrane 510 is too low, it indicates that the amount of non-aqueous binder added to the transfer separator 400 is too small, resulting in reduced adhesion between the transfer separator 400 and the positive or negative electrode, and weak cohesion of the transfer separator 400, making it prone to cracking during the transfer process. If the coverage rate of non-aqueous binder particles on the surface of the transfer separator 400 away from the release membrane 510 is too high, it indicates that the amount of non-aqueous binder added to the transfer separator 400 is too large, resulting in excessive adhesion between the transfer separator 400 and the positive or negative electrode, and an excessive proportion of non-aqueous binder particles inside the transfer separator 400, which can easily cause excessive tortuosity inside the transfer separator 400, affecting ion transport efficiency and the energy efficiency of the single cell 300.

[0153] Figure 12 This is a schematic flowchart of a method for preparing a battery cell 320 according to an embodiment of the application.

[0154] Please see Figure 12 This application also provides a method for preparing a battery cell 320, the method comprising: S601, a transfer diaphragm assembly 500 is provided, along with a positive electrode 321 and a negative electrode 322. The transfer diaphragm assembly 500 includes a release membrane 510 and a transfer diaphragm 400 stacked together. The transfer diaphragm 400 includes an isolation layer 410 disposed on the surface of the transfer diaphragm 400. The isolation layer 410 includes first ceramic particles, second ceramic particles, and a first aqueous adhesive. The first ceramic particles and the second ceramic particles are dispersed and mixed. The aqueous adhesive is used to bond the first ceramic particles and the second ceramic particles. In the isolation layer 410, the particle size of the first ceramic particles is smaller than the particle size of the second ceramic particles. The mass ratio M1 / M2 of the first ceramic particles to the second ceramic particles is in the range of 0.1 ≤ M1 / M2 ≤ 0.7. S602, the transfer diaphragm 400 on the transfer diaphragm assembly 500 is transferred to at least one of the positive electrode 321 and the negative electrode 322 by molding or rolling, and the release film 510 is removed; and Optionally, molding can be, but is not limited to, at least one of hot pressing and room temperature molding. Optionally, rolling can be, but is not limited to, at least one of hot rolling and room temperature rolling. It should be noted that when the rolling process is used to transfer the transfer diaphragm 400, the transfer of the transfer diaphragm 400 can be integrated with the rolling process of the positive electrode 321 or the negative electrode 322. That is, the transfer of the transfer diaphragm 400 is performed simultaneously with the rolling process of the positive electrode 321 or the negative electrode 322.

[0155] S603, at least one of the positive electrode 321 and the negative electrode 322 having a transfer membrane 400 are stacked, such that the transfer membrane 400 is located between the positive electrode 321 and the negative electrode 322.

[0156] In one example, the positive electrode 321 has a transfer membrane 400 transferred on both opposite surfaces. The positive electrode 321 with transfer membrane 400 on both sides and the negative electrode 322 are stacked. When both the positive electrode 321 and the negative electrode 322 are multilayered, the positive electrode 321 with transfer membrane 400 on both sides and the negative electrode 322 are stacked alternately.

[0157] In another example, if both opposite surfaces of the negative electrode 322 are printed with a transfer membrane 400, then the negative electrode 322 with transfer membranes 400 on both sides and the positive electrode 321 are stacked together; when both the positive electrode 321 and the negative electrode 322 are multilayered, the negative electrode 322 with transfer membranes 400 on both sides and the positive electrode 321 are stacked alternately in sequence.

[0158] In another example, a transfer separator 400 is transferred onto one surface of the positive electrode 321, and a separator is transferred onto one surface of the negative electrode 322. The positive electrode 321 with a transfer separator 400 on one side and the positive electrode 321 with a transfer separator 400 on one side are stacked together, and a transfer separator 400 is placed between the positive electrode 321 and the negative electrode 322. When both the positive electrode 321 and the negative electrode 322 are multilayered, the negative electrode 322 with a transfer separator 400 on one side and the positive electrode 321 with a transfer separator 400 on one side are stacked alternately.

[0159] The method for preparing the battery cell 320 in this application embodiment involves transferring the transfer membrane 400 to at least one of the positive electrode 321 and the negative electrode 322 by molding or roll transfer, and then stacking the positive electrode 321 and the negative electrode 322 having the transfer membrane 400, such that the transfer membrane 400 is located between the positive electrode 321 and the negative electrode 322. The transfer separator 400 can be transferred and adhered to the surface of the positive electrode 321 or the negative electrode 322 by transfer. When the transfer separator 400 is applied to the laminated cell 320, the transfer separator 400 can be transferred to the surface of the positive electrode 321 or the negative electrode 322 first, and then the positive electrode 321 and the negative electrode 322 can be cut, laminated and assembled into the laminated cell 320, which can greatly improve the lamination efficiency of the cell 320, which can be increased by more than 50%. In addition, compared with the scheme of directly coating the separator slurry onto the surface of the positive electrode 321 or the negative electrode 322, the transfer separator 400 of this application is transferred to the surface of the positive electrode 321 or the negative electrode 322 by transfer, which will not block the surface pores of the positive electrode 321 or the negative electrode 322, and can play a good insulating role. Furthermore, the transfer separator 400 includes an isolation layer 410, which comprises first ceramic particles, second ceramic particles, and a first aqueous adhesive. The first ceramic particles and the second ceramic particles are dispersed and mixed, and the aqueous adhesive is used to bond the first ceramic particles and the second ceramic particles. In the isolation layer 410, the particle size of the first ceramic particles is smaller than that of the second ceramic particles; the mass ratio M1 / M2 of the first ceramic particles to the second ceramic particles is in the range of 0.1 ≤ M1 / M2 ≤ 0.7. By designing the size and mass ratio of the first ceramic particles and the second ceramic particles, the transfer separator 400 can have a more suitable pore size and porosity, resulting in strong capillary action and good liquid retention and wettability. When applied to a single cell 300, it can better improve the cycle capacity retention rate and rate performance of the single cell 300.

[0160] Figure 13 This is a schematic flowchart illustrating the preparation method of a transfer diaphragm assembly 500 according to an embodiment of the application.

[0161] Please see Figure 13 In some embodiments, in S601, providing the transfer diaphragm assembly 500 includes: S6011, Weigh the raw material components of the isolation layer 410, disperse the raw material components of the isolation layer 410 in water to obtain the isolation slurry; and In one example, the raw material components of the isolation layer 410 include first ceramic particles, second ceramic particles, and a first water-based adhesive. In another example, the raw material components of the isolation layer 410 include first ceramic particles, second ceramic particles, non-water-based adhesive particles, and a first water-based adhesive.

[0162] Optionally, the raw material components for the isolation layer 410 are weighed according to the specified ratio, and each raw material component is sequentially placed into deionized water for stirring and dispersion (e.g., stirring speed ranges from 500 rpm / 15 min to 2500 rpm / 15 min, specifically including but not limited to 500 rpm / 15 min, 1000 rpm / 15 min, 1500 rpm / 15 min, 2000 rpm / 15 min, 2500 rpm / 15 min, etc.) to obtain the isolation slurry. Heating can be performed during stirring (e.g., heating to 35°C to 45°C, specifically including but not limited to 35°C, 38°C, 40°C, 43°C, 45°C, etc.) to accelerate the dissolution of the first water-based binder.

[0163] S6012, a release film 510 is provided, and the isolation slurry is coated on the surface of the release film 510 and dried to obtain a release film 510 / isolation layer 410 stacked together.

[0164] Optionally, the release slurry can be applied to the surface of the release film 510 by gravure roller coating and dried and rolled up in an oven at 70°C to 80°C (e.g., but not limited to 70°C, 73°C, 75°C, 78°C, 80°C, etc.).

[0165] Understandably, in this embodiment, the transfer diaphragm assembly 500 includes a release film 510 / isolation layer 410 stacked together.

[0166] Figure 14 This is a schematic flowchart of a method for preparing a transfer diaphragm assembly 500 according to another embodiment of the application.

[0167] Please see Figure 14 In other embodiments, in S601, providing the transfer diaphragm assembly 500 includes: S6011, Weigh the raw material components of the isolation layer 410, disperse the raw material components of the isolation layer 410 in water to obtain the isolation slurry; S6012, a release film 510 is provided, and the release slurry is coated onto the surface of the release film 510 and dried to obtain a laminated release film 510 / release layer 410; and For a detailed description of other aspects of S6011 and S6012, please refer to the description of the corresponding parts of the above embodiments, which will not be repeated here.

[0168] S6013, an aqueous solution of a second water-based adhesive is coated on the surface of the release film 510 away from the release layer 410, and dried to form an adhesive layer 420, thus obtaining a release film 510 / release layer 410 / adhesive layer 420 stacked together.

[0169] Optionally, the second water-based adhesive is dissolved in water to obtain an adhesive slurry, which is then coated onto the surface of the release film 510 away from the release layer 410 and dried and wound up in an oven at 70°C to 80°C (e.g., but not limited to 70°C, 73°C, 75°C, 78°C, 80°C, etc.).

[0170] Understandably, in this embodiment, the transfer diaphragm assembly 500 includes a release film 510, a release layer 410, and an adhesive layer 420 stacked together.

[0171] In some embodiments, S602, the step of transferring the transfer diaphragm 400 on the transfer diaphragm assembly 500 to at least one of the positive electrode 321 and the negative electrode 322 by molding or rolling, and removing the release film 510, includes: The transfer membrane assembly 500 is stacked on the positive electrode 321 or the negative electrode 322, with the transfer membrane 400 positioned between the release film 510 and the positive electrode 321 or the negative electrode 322. Hot pressing is performed at a temperature of 65°C to 110°C, a transfer speed of 10 m / min to 80 m / min, and a pressure of 2 MPa to 6 MPa to transfer the transfer membrane 400 to at least one of the positive electrode 321 and the negative electrode 322, and the release film 510 is removed.

[0172] Specifically, the hot-pressing temperature can be, but is not limited to, 65℃, 70℃, 80℃, 90℃, 100℃, 110℃, etc. If the hot-pressing temperature is too low, the adhesion of the transfer diaphragm 400 will be too low, reducing the integrity of the transfer; in addition, the transfer diaphragm 400 is prone to uneven heating, and there may be areas of missed transfer. If the hot-pressing temperature is too high, the non-aqueous adhesive particles are prone to melting, thereby clogging the pores of the isolation layer 410 and reducing the ion transport rate of the transfer isolation layer.

[0173] Specifically, the transfer speed can be, but is not limited to, 10 m / min, 20 m / min, 30 m / min, 40 m / min, 50 m / min, 60 m / min, 70 m / min, 80 m / min, etc. If the transfer speed is too low, the production efficiency of cell 320 will be reduced. If the transfer speed is too high, the transfer integrity of the transfer separator 400 will be deteriorated.

[0174] Specifically, the hot-pressing pressure can be, but is not limited to, 2 MPa, 3 MPa, 4 MPa, 5 MPa, 6 MPa, etc. If the hot-pressing pressure is too low, the bonding strength between the transfer diaphragm 400 and the positive electrode 321 or negative electrode 322 will be reduced. If the hot-pressing pressure is too high, the compression ratio of the non-aqueous adhesive particles and / or the adhesive layer 420 will be too high, resulting in excessive compaction, which may clog the pores of the transfer diaphragm 400 and reduce the ion transport rate of the transfer diaphragm 400.

[0175] The following specific embodiments further describe the transfer separator 400, transfer separator assembly 500, battery cell 320, and single battery cell 300 of this application. It should be noted that in the following embodiments of this application, the single battery cell 300 is described using a lithium-ion battery as an example, and should not be construed as a limitation on the single battery cell 300 and transfer separator 400 of this application.

[0176] Examples 1 to 19, Comparative Examples 1 to 10 The single-cell battery 300 of each embodiment and comparative example is prepared by the following steps: (1) Preparation of positive electrode 321: The positive active material lithium iron phosphate (LiFePO4), conductive carbon black (Super-P) and binder PVDF are mixed in a mass ratio of 97:1:2; then N-methylpyrrolidone (NMP) is added as a solvent and stirred evenly to obtain a positive electrode slurry with a solid content of 60wt%. The positive electrode slurry is then uniformly coated on one surface of a positive current collector aluminum foil with a thickness of 11μm and dried at 85℃. The above steps are repeated on the other surface of the positive electrode 321. After rolling, a positive electrode 321 with a positive active layer coated on both sides is obtained, and the single-sided thickness of the positive active layer is 90μm.

[0177] (2) Preparation of negative electrode sheet 322: The negative electrode active materials artificial graphite, conductive carbon black (Super-P), sodium carboxymethyl cellulose (CMC-Na), and styrene-butadiene rubber (SBR) were mixed in a mass ratio of 97:1:1.5:0.5, deionized water was added, and the mixture was stirred evenly to obtain a negative electrode slurry with a solid content of 55wt%. The negative electrode slurry was then uniformly coated on one surface of a negative electrode current collector copper foil with a thickness of 6μm and dried at 105℃. The above steps were repeated on the other surface of the negative electrode sheet 322. After rolling, a negative electrode sheet 322 with a negative electrode material layer coated on both sides was obtained, and the single-sided thickness of the negative electrode active layer was 70μm.

[0178] (3) Preparation of electrolyte: Ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 1:1:1, dissolved, and stirred thoroughly. The mixture was then placed at 5°C or lower for 12 hours. Lithium hexafluorophosphate (LiPF6) was then added and mixed thoroughly to obtain the electrolyte. The molar concentration of LiPF6 in the electrolyte was 1.0 mol / L.

[0179] (4) Preparation of transfer membrane assembly 500: ① Preparation of isolation slurry: Weigh the first ceramic particles (alumina), the second ceramic particles (alumina), the non-aqueous binder particles (PMMA), polyacrylic acid (PAA, the first water-based binder), and polyvinyl alcohol (PVA, the first dispersant, wherein the mass ratio of PAA to PVA is 4:1) according to the preset mass ratio; add deionized water as solvent in the stirrer, then add the weighed PAA, stir evenly at 1000 rpm / 15 min, then add PVA, stir evenly at 1000 rpm / 15 min, control the temperature at about 40℃, and control the pH value at about 7; then add the first ceramic particles and the second ceramic particles that have been mixed, stir evenly at 2500 rpm / 60 min, then add the non-aqueous binder particles, stir evenly at 1000 rpm / 15 min, and then slowly stir at 500 rpm / 15 min to eliminate bubbles, and obtain the isolation slurry. ② Preparation of the transfer diaphragm assembly 500: The release slurry is roller-coated onto one side of the release film 510 (50μm thick PET) using a gravure roller coating machine. After drying in a 75℃ oven, the release slurry forms a release layer 410, and the film is then wound up to obtain the transfer diaphragm assembly 500. The performance parameters of the release layer 410 are shown in Tables 1 and 2 below.

[0180] (5) Transfer of the transfer membrane 400: The transfer membrane assembly 500 is stacked with the positive electrode 321, and the transfer membrane 400 (isolation layer 410) is located between the positive electrode 321 and the release film 510. A layer of transfer membrane 400 is transferred to the two opposite surfaces of the positive electrode 321 by hot rolling process. The temperature of hot rolling is 80℃, the transfer speed of the transfer membrane 400 is 40m / min, and the pressure of hot rolling is 4MPa.

[0181] (6) Assembly of lithium-ion battery (single cell 300): The positive electrode 321 and negative electrode 322 with double-sided transfer separators 400 prepared above are arranged in sequence, with the transfer separator 400 positioned between the positive and negative electrodes to provide isolation. The cells are then stacked to obtain bare cell 320. The bare cell 320 is pressed at room temperature, with the unit area pressure controlled at 4.8 MPa and the holding time at 40 s. The bare cell 320 is then placed in an aluminum-plastic film, vacuum dried, and injected with electrolyte. After vacuum sealing, settling, and formation processes, a lithium-ion battery is obtained.

[0182] It should be noted that the transfer diaphragm 400 in Examples 1 to 19 and Comparative Examples 8 only includes the isolation layer 410.

[0183] Example 20 The difference between this embodiment and Embodiment 3 is that the non-aqueous binder particles in this embodiment are polyvinylidene fluoride (PVDF) particles.

[0184] Examples 21, 22, Comparative Examples 11 and 12 The difference between the embodiments and comparative examples and Example 1 lies in that the mass fraction of non-aqueous binder particles in the isolation slurry is kept constant, while the mass fraction of PVA in the isolation slurry and the stirring rate are adjusted to regulate the coverage of non-aqueous binder particles on the surface of the isolation layer 410 away from the release membrane 510. Within a certain range of addition, increasing the content of PVA dispersant can improve the dispersion uniformity of non-aqueous binder particles and increase the number of non-aqueous binder particles on the surface of the obtained transfer membrane 400; conversely, it will reduce the number of non-aqueous binder particles on the surface of the obtained transfer membrane 400. Furthermore, in the addition of non-aqueous binder particles to the isolation slurry, decreasing the stirring rate will reduce the dispersion uniformity of the non-aqueous binder particles and decrease the number of non-aqueous binder particles on the surface of the obtained transfer membrane 400; conversely, increasing the stirring rate will increase the number of non-aqueous binder particles on the surface of the obtained transfer membrane 400. The performance parameters of the transfer membrane 400 of each embodiment and comparative example are shown in Table 4 below.

[0185] The following performance tests were performed on the transfer separator 400 and lithium-ion batteries of each embodiment and comparative example. The test results are shown in Tables 1 to 3 below: (1) Coverage of non-aqueous adhesive particles on the surface of the transfer diaphragm 400 away from the release membrane 510: Measurement method: The surface of the transfer diaphragm 400 away from the release film 510 was identified and calculated using a specialized adhesive dot coverage testing device. Five random photos were taken and the average value was taken. The measurement area was 60mm × 40mm. The identification and calculation principle was based on the color difference between the non-aqueous adhesive particles and the substrate under an optical microscope. The total area of ​​the adhesive dots was identified and calculated by surface scanning. The coverage was then calculated using the total area of ​​the non-aqueous adhesive particles and the area of ​​the measurement size.

[0186] (2) Quantity fraction density test of the intersection points formed by non-aqueous binder particles on the contact surface between the transfer diaphragm 400 and the positive electrode sheet: The transfer membrane 400 was transferred onto the positive electrode sheet. Ten regions were selected for sample preparation using CP cross-section polishing technology. The cross-sectional micromorphology of the ten regions was photographed using a scanning electron microscope (SEM) at a magnification of 1000x. At the contact interface between the transfer membrane 400 and the positive electrode sheet, the number of non-aqueous binder particles M3 per 115μm × 85μm area was measured and calculated.

[0187] (3) Adhesion evaluation of transfer diaphragm 400-electrode (e.g., transfer diaphragm 400 and positive electrode, or transfer diaphragm 400 and negative electrode): The peel strength of the transfer diaphragm 400-electrode was tested according to the standard GB / T 2792-2014 Test Method for Peel Strength of Adhesive Tape. The sample size was 20mm × 100mm. 3M tape was used to adhere the transfer diaphragm 400 side. The sample was fixed in the middle of the tensile testing machine's clamps. The tensile testing machine was then used to peel the transfer diaphragm 400 from the electrode at a speed of 50mm / min along a 180° direction. The test distance was up to 80mm. The structure of the peeled interface layer was observed and determined: it was the transfer diaphragm 400, the transfer diaphragm 400-electrode, the electrode coating, or the electrode coating-current collector foil. If multiple interface layer structures were included, the grade was determined according to the structure with the largest area. The judgment criteria are shown in the table below:

[0188] (4) Laser particle size test: The first ceramic particles, the second ceramic particles and the non-aqueous binder particles were tested according to the standard GB / T 19077-2024 Particle size distribution by laser diffraction. The Better size 2600 laser particle size analyzer system was used, and the average value of D50 was taken after 3 tests.

[0189] (5) Peel strength test: The peel strength of release film 510-transfer diaphragm 400 was tested according to the standard GB / T 2792-2014 Test method for peel strength of adhesive tape. After pressing, the sample size was cut to 20mm×100mm and fixed in the middle of the clamp of the tensile testing machine. Then the tensile testing machine peeled the transfer diaphragm 400 from the release film 510 along the 180° direction at a speed of 50mm / min. The test distance was 80mm. Five tests were conducted and the average value was taken. The adhesive force was the average value of the peel strength.

[0190] (6) Thickness and porosity test of the transfer membrane 400 after transfer to the positive electrode 321: The cross-sectional microstructure of the positive electrode 321 with the transfer membrane 400 after transfer was photographed. The thickness of the transfer membrane 400 was measured 5 times and the average value was taken as the thickness of the transfer membrane 400. Porosity of the transfer membrane 400: The theoretical mass of the transfer membrane 400 was calculated using the thickness of the transfer membrane 400 and the theoretical density of the first ceramic powder and the second ceramic powder. The actual mass of the transfer membrane 400 was weighed and the porosity of the transfer membrane 400 was calculated. The average value was taken for 5 tests.

[0191] (7) Electrolyte wettability test of the transfer membrane 400 after transfer: Take the positive electrode 321 with the transfer membrane 400 (or the negative electrode 322 with the transfer membrane 400) for electrolyte wettability test. Cut the sample size to 5mm×200mm. Observe the diffusion distance of 0.5mL electrolyte in the 200mm length direction within 1min. Take the average value after 5 tests.

[0192] (8) Rate performance test: The single cell 300 was subjected to charge-discharge cycle tests at current densities of 0.33C, 0.5C, 1C, and 2C, respectively, with a voltage range of 2.45V to 3.7V. The energy efficiency at different rates was calculated. Energy efficiency refers to the ratio of the actual output energy to the input energy during the charge-discharge process. The higher this ratio, the better the energy conversion efficiency of the single cell 300 and the less energy loss.

[0193] (9) Room temperature cycle capacity retention rate and low temperature cycle capacity retention rate test: 0.5P was subjected to cycle charge-discharge tests at 25℃ and -10℃, respectively, for 300 cycles, with a voltage range of 2.45~3.7V. Capacity retention rate refers to the percentage of the remaining discharge capacity of a single cell 300 after a certain number of charge-discharge cycles or a period of aging, relative to its initial discharge capacity. Capacity retention rate = (current discharge capacity / initial discharge capacity) × 100%. It directly reflects the lifespan and the degree of capacity decay of the single cell 300. The higher the capacity retention rate, the better the health status of the single cell 300 and the longer its lifespan.

[0194] Table 1 Performance parameters of the isolation layer 410 in each embodiment and comparative example

[0195] Table 2 Performance parameters of the isolation layer 410 in each embodiment and comparative example

[0196] Table 3: Performance data of lithium-ion batteries in each embodiment and comparative example

[0197] Table 4: Performance parameters of transfer separator 400 and lithium-ion battery in some embodiments and comparative examples

[0198] The test results of Examples 1, 15, 17, 19, Comparative Example 9, and Comparative Example 10 show that as the mass fraction of non-aqueous binder particles in the transfer separator 400 increases, the coverage of non-aqueous binder particles on the surface of the transfer separator 400 gradually increases, the number distribution density of adhesive dots formed by non-aqueous binder particles on the contact surface between the transfer separator 400 and the positive electrode 321 gradually increases, the 1C energy efficiency of the single cell 300 first gradually increases and then gradually decreases; the capacity retention of the single cell 300 at 25°C with 0.5P for 300 cycles first gradually increases and then gradually decreases. Furthermore, as the mass fraction of non-aqueous binder particles in the transfer separator 400 increases, the adhesion between the transfer separator 400 and the positive electrode 321 gradually increases. When the number distribution density of adhesive dots formed by non-aqueous binder particles on the contact surface between the transfer separator 400 and the positive electrode 321 is too small (as in Comparative Example 9), the cohesion of the transfer separator 400 is low, the weak point is inside the transfer separator 400, and the adhesion between the transfer separator 400 and the positive electrode 321 is unqualified. When the number distribution density of adhesive dots formed by non-aqueous binder particles on the contact surface between the transfer separator 400 and the positive electrode 321 is too large (as in Comparative Example 10), the adhesion between the transfer separator 400 and the positive electrode 321 is too large. During the charge and discharge cycle, there is a risk that the positive active layer of the positive electrode 321 will separate from the positive current collector, reducing the energy efficiency and cycle capacity retention rate of the single cell 300.

[0199] The test results from Examples 1, 21, 22, Comparative Example 11, and Comparative Example 12 show that when the mass fraction of non-aqueous binder particles in the transfer separator 400 remains constant, the coverage rate of non-aqueous binder particles on the surface of the transfer separator 400 is adjusted. As the coverage rate of non-aqueous binder particles on the surface of the transfer separator 400 increases, the number distribution density of adhesive dots formed by non-aqueous binder particles on the contact surface between the transfer separator 400 and the positive electrode 321 gradually increases. The 1C energy efficiency of the single cell 300 first gradually increases and then gradually decreases; the capacity retention of the single cell 300 at 25°C with 0.5P for 300 cycles first gradually increases and then gradually decreases. Furthermore, as the coverage of non-aqueous binder particles on the surface of the transfer separator 400 increases, the adhesion between the transfer separator 400 and the positive electrode 321 gradually increases. When the number distribution density of adhesive dots formed by non-aqueous binder particles on the contact surface between the transfer separator 400 and the positive electrode 321 is too small (as in Comparative Example 11), the cohesion of the transfer separator 400 is low, the weak point is inside the transfer separator 400, and the adhesion between the transfer separator 400 and the positive electrode 321 is unqualified. When the number distribution density of adhesive dots formed by non-aqueous binder particles on the contact surface between the transfer separator 400 and the positive electrode 321 is too large (as in Comparative Example 12), the adhesion between the transfer separator 400 and the positive electrode 321 is too large. During the charge and discharge cycle of the cell 320, there is a risk of separation between the positive active layer of the positive electrode 321 and the positive current collector, which reduces the energy efficiency and cycle capacity retention rate of the single cell 300.

[0200] As shown in Tables 1 to 3, the test results of Examples 1 to 5 and Comparative Examples 1 to 5 reveal that as the mass ratio (M1 / M2) of the first ceramic particles to the second ceramic particles in the separator 410 increases, the porosity of the transfer membrane 400 (separator layer 410) gradually decreases, the electrolyte wettability of the transfer membrane 400 gradually decreases, and the average peel strength between the release film 510 and the transfer membrane 400 gradually increases. Furthermore, as the mass ratio (M1 / M2) of the first ceramic particles to the second ceramic particles in the separator 410 increases, the energy efficiency of the lithium-ion battery at different rates first increases and then decreases; the capacity retention rate after 300 cycles at room temperature (25°C) and after 300 cycles at low temperature (-10°C) also first increases and then decreases.

[0201] The test results of Examples 3, 6 to 10, and Comparative Example 6 show that as the D501 of the first ceramic particles increases, the porosity and electrolyte wettability of the transfer separator 400 both show an increasing trend, but the overall increase is not significant; the average peel strength between the release film 510 and the transfer separator 400 first increases and then decreases. Furthermore, as the D501 of the first ceramic particles increases, the energy efficiency of the lithium-ion battery at different rates first increases and then decreases; the capacity retention rate after 300 cycles at room temperature (25°C) and after 300 cycles at low temperature (-10°C) also first increases and then decreases.

[0202] The test results of Examples 3, 11 to 14, Comparative Examples 7 and 8 show that, with the increase of the D502 of the second ceramic particles, the porosity and electrolyte wettability of the transfer separator 400 first increase and then decrease; the average peel strength between the release film 510 and the transfer separator 400 first increases and then decreases. Furthermore, with the increase of the D502 of the second ceramic particles, the energy efficiency of the lithium-ion battery at different rates first increases and then decreases; the capacity retention rate after 300 cycles at room temperature (25°C) and after 300 cycles at low temperature (-10°C) also first increases and then decreases.

[0203] The test results of Examples 3, 15 to 19 show that as the mass fraction of the non-aqueous binder in the separator layer 410 increases, the porosity and electrolyte wettability of the transfer membrane 400 do not change significantly, while the average peel strength between the release membrane 510 and the transfer membrane 400 gradually increases. Furthermore, as the mass fraction of the non-aqueous binder in the separator layer 410 increases, the energy efficiency of the lithium-ion battery decreases at different rates; the capacity retention rate after 300 cycles at room temperature (25°C) and after 300 cycles at low temperature (-10°C) also decreases.

[0204] As can be seen from the test structures of Examples 3 and 20, changing the type of non-aqueous binder can make the transfer membrane 400 of this application have better liquid retention and wettability, and the lithium-ion battery has better cycle capacity retention and rate performance.

[0205] In this application, the terms "embodiment" and "implementation" mean that a specific feature, structure, or characteristic described in connection with an embodiment can be included in at least one embodiment of this application. The appearance of these phrases in various locations throughout the specification does not necessarily refer to the same embodiment, nor are they independent or alternative embodiments mutually exclusive with other embodiments. Those skilled in the art will understand, explicitly and implicitly, that the embodiments described in this application can be combined with other embodiments. Furthermore, it should be understood that the features, structures, or characteristics described in the various embodiments of this application can be arbitrarily combined to form another embodiment that does not depart from the spirit and scope of the technical solution of this application, provided there is no contradiction between them.

[0206] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. Although this application has been described in detail with reference to the above preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions to the technical solutions of this application should not depart from the spirit and scope of the technical solutions of this application.

Claims

1. A battery cell, characterized in that, The battery cell includes a positive electrode, a transfer separator, and a negative electrode, wherein the transfer separator is disposed between the positive electrode and the negative electrode; the transfer separator comprises: An isolation layer comprising first ceramic particles, second ceramic particles, and a first water-based adhesive, wherein the first ceramic particles and the second ceramic particles are dispersed and mixed, and the water-based adhesive is used to bond the first ceramic particles and the second ceramic particles together. In the isolation layer, the particle size of the first ceramic particles is smaller than that of the second ceramic particles. The mass ratio M1 / M2 of the first ceramic particles to the second ceramic particles is in the range of 0.1 ≤ M1 / M2 ≤ 0.

7.

2. The battery cell according to claim 1, characterized in that, The isolation layer satisfies at least one of the following conditions: The D501 of the first ceramic particle is in the range of 50nm ≤ D501 ≤ 500nm, where D501 is the particle size value corresponding to when the cumulative volumetric particle size distribution of the first ceramic particle reaches 50%; and The range of D502 for the second ceramic particle is 500nm≤D502≤2000nm, where D502 is the particle size value corresponding to the cumulative volumetric particle size distribution of the second ceramic particle reaching 50%.

3. The battery cell according to claim 1, characterized in that, The loose density of the mixture of the first ceramic particles and the second ceramic particles is ρ1, and the tap density of the mixture of the first ceramic particles and the second ceramic particles is ρ2. Then 1≤ρ2 / ρ1≤1.

4.

4. The battery cell according to claim 3, characterized in that, The loose density ρ1 of the mixture of the first ceramic particles and the second ceramic particles is in the range of 0.3 g / cm³ ≤ ρ1 ≤ 1.0 g / cm³; the tap density ρ2 of the mixture of the first ceramic particles and the second ceramic particles is in the range of 0.4 g / cm³ ≤ ρ2 ≤ 1.2 g / cm³.

5. The battery cell according to claim 1, characterized in that, The transfer diaphragm further includes an adhesive layer disposed on the surface of the diaphragm, the adhesive layer comprising a second water-based adhesive, and the coverage S of the adhesive layer on the surface of the diaphragm toward the adhesive layer being in the range of 10% ≤ S ≤ 30%.

6. The battery cell according to claim 5, characterized in that, The transfer diaphragm also includes non-aqueous binder particles, which are dispersed in at least one of the isolation layer and the adhesive layer. The mass of the first ceramic particle in the isolation layer is M1, the mass of the second ceramic particle is M2, and the mass of the non-aqueous binder particles in the transfer diaphragm is M3. Then, 0.3×(M1+M2)≤M3≤0.5×(M1+M2).

7. The battery cell according to claim 6, characterized in that, The D503 of the non-aqueous binder particles is in the range of 1μm≤D503≤8μm, where D503 is the particle size value corresponding to the cumulative volume particle size distribution of the non-aqueous binder particles reaching 50%.

8. The battery cell according to any one of claims 1-7, characterized in that, The transfer diaphragm satisfies at least one of the following conditions: The porosity P of the transfer membrane is in the range of 40% ≤ P ≤ 65%; and The thickness d1 of the isolation layer is in the range of 5μm≤d1≤25μm.

9. The battery cell according to any one of claims 1-7, characterized in that, The transfer diaphragm also includes non-aqueous binder particles, which are dispersed in the separator layer; the number distribution density of adhesive dots formed by the non-aqueous binder particles on the contact surface between the separator layer and the positive electrode sheet or between the separator layer and the negative electrode sheet ranges from 12 dots / (115μm×85μm) to 20 dots / (115μm×85μm).

10. The battery cell according to any one of claims 1-7, characterized in that, The transfer diaphragm further includes an adhesive layer disposed on the surface of the separator layer; the transfer diaphragm further includes non-aqueous binder particles, which are dispersed in the adhesive layer or in the separator layer and the adhesive layer; the number distribution density of adhesive dots formed by the non-aqueous binder particles on the contact surface between the adhesive layer and the positive electrode sheet or between the adhesive layer and the negative electrode sheet ranges from 12 dots / (115μm×85μm) to 20 dots / (115μm×85μm).

11. A single-cell battery, characterized in that, The single battery cell includes: A housing having a receiving cavity open at one end; The battery cell according to any one of claims 1-10, wherein the battery cell is disposed within the receiving cavity; An electrolyte, wherein the electrolyte is disposed within the receiving cavity, and the battery cell is at least partially immersed in the electrolyte; and An end cap assembly, comprising a top cover and an electrode post, wherein the top cover is used to close the opening of the receiving cavity and connect to the housing, the electrode post passes through the top cover and is partially exposed, and the electrode post is electrically connected to the battery cell.

12. The single-cell battery according to claim 11, characterized in that, The electrolyte wettability K of the transfer membrane of the battery cell is in the range of 20mm≤K≤70mm. The electrolyte wettability K of the transfer membrane refers to the diffusion length of the electrolyte on the transfer membrane after 1 minute when 0.5mL of electrolyte is dropped onto the transfer membrane with a size of 5mm×200mm.

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