Electrolyte detecting and screening method

Abstract

The invention provides an electrolyte detecting and screening method which comprises the following steps: S1, thickly coating an electrode auxiliary material on an initial positive pole piece and an initial negative pole piece until the surface density of the pole pieces reaches a preset surface density to obtain a soft package battery; s2, after activation circulation is carried out on the soft package battery, the soft package battery is disassembled and cleaned, and a test pole piece is obtained; s3, applying pressure to the test pole piece, so that the test pole piece is in contact with the multiple to-be-detected electrolytes in sequence for infiltration, and multiple micro batteries with pressure are obtained; and S4, after the minicell is stable, heat effect testing is carried out on the minicell in sequence. According to the invention, the problem of micro short circuit of powder is overcome by thick coating of the electrode auxiliary material, and meanwhile, the test pole piece is pressurized to be in full contact with the electrolyte to be tested, so that the problem of non-uniform infiltration of the electrolyte is remarkably improved, and the key problem of influence on the test accuracy in the prior art is overcome; and the test result is more stable and accurate, so that the method has a wide application prospect in the industry.

Description

Technical Field

[0001] The invention relates to the technical field of batteries, and in particular to a method for detecting and screening an electrolyte. Background Art

[0002] In today's energy field, lithium-ion batteries are widely used in electric vehicles, electronic devices, energy storage systems and other fields due to their advantages such as high energy density and long cycle life. As the market's requirements for lithium-ion battery performance and safety continue to increase, the research and development of high-performance and high-safety lithium-ion batteries and their electrolytes has become a key task in the industry.

[0003] However, existing lithium-ion battery research technology has many problems in terms of safety and electrolyte research and development. On the one hand, traditional research methods consume a large amount of electrode materials and electrolytes. During the experiment, in order to obtain sufficient data for analysis and research, it is often necessary to prepare excessive amounts of materials for repeated testing. This not only greatly increases research costs and puts research and development work under great economic pressure, but also causes varying degrees of pollution to the environment during material production, use, and waste disposal, which is not in line with the concept of sustainable development.

[0004] On the other hand, when testing the safety of micro batteries, existing methods have obvious defects. In the process of assembling micro batteries and testing, uneven electrolyte infiltration often occurs. This is because the differences in the microstructure and surface properties of the electrode materials lead to inconsistent distribution of the electrolyte on the electrode surface, which affects the uniformity of the electrochemical reaction inside the battery. At the same time, powder micro short circuit problems also occur from time to time. This is mainly because the fine particles in the electrode material contact each other during assembly or testing, forming a local short circuit path, which interferes with the normal operation of the battery. Uneven electrolyte infiltration and powder micro short circuit problems seriously affect the accuracy of the test results, making it difficult for researchers to obtain real and reliable data to evaluate the safety of the battery and the performance of the electrolyte, thereby hindering the research and development of high-performance lithium-ion batteries and their electrolytes. Summary of the invention

[0005] To this end, the technical problem to be solved by the present invention is to overcome the problems of uneven electrolyte infiltration and powder micro-short circuit that exist in the prior art when testing the safety of micro batteries, and to provide an electrolyte detection and screening method.

[0006] In order to solve the above technical problems, the present invention provides an electrolyte detection and screening method, which includes: step S1, providing an initial positive electrode sheet and an initial negative electrode sheet, and thickly coating the electrode auxiliary material on the initial positive electrode sheet and the initial negative electrode sheet until the surfaces of the initial positive electrode sheet and the initial negative electrode sheet reach a preset surface density, thereby obtaining a soft-pack battery; step S2, after the soft-pack battery is activated and cycled, it is disassembled and cleaned to obtain a test positive electrode sheet and a test negative electrode sheet with a stable solid electrolyte interface formed on the surface; step S3, applying pressure to the test positive electrode sheet and the test negative electrode sheet so that they are fully contacted and infiltrated with a variety of electrolytes to be detected in turn, to obtain a variety of pressurized micro-batteries; step S4, after the micro-batteries are stable, the thermal effect tests of the various pressurized micro-batteries under different temperature conditions are performed in turn, and the screening process of the electrolyte safety is completed after comparing the thermal effects of different micro-batteries.

[0007] In one embodiment of the present invention, in step S3, a pressurized environment is provided for the test positive electrode plate and the test negative electrode plate by a sealed crucible and a pressure spring. The pressure spring is arranged inside the sealed crucible, one end of which is connected to the inner wall of the sealed crucible, and the other end is abutted against the test positive electrode plate and the test negative electrode plate to form the microbattery inside the sealed crucible.

[0008] In one embodiment of the present invention, the wire diameter of the pressure spring is 0.1-0.2 mm and the outer diameter is 1.2-2.5 mm.

[0009] In one embodiment of the present invention, in step S1, the initial positive electrode sheet, the initial negative electrode sheet and the electrode auxiliary material are mixed, and the electrode auxiliary material is thickly coated on the initial positive electrode sheet and the initial negative electrode sheet until the surface density of the initial positive electrode sheet and the initial negative electrode sheet is greater than 250 mg / cm 2 Afterwards, a soft pack battery is obtained.

[0010] In one embodiment of the present invention, in step S2, the soft-pack battery is activated at 0.04~0.06C to form the solid electrolyte interface on the surface of the test positive electrode plate and the test negative electrode plate, and then the soft-pack battery is subjected to multiple charge and discharge cycles at 0.30~0.40C, and is charged to the maximum cut-off voltage after the last cycle.

[0011] In one embodiment of the present invention, in step S2, after the soft-pack battery is activated and cycled, the soft-pack battery is disassembled in an inert environment, and then a solvent is used to clean the disassembled test positive electrode sheet and the test negative electrode sheet, and after cleaning, the test positive electrode sheet and the test negative electrode sheet are heated and cured in an inert environment, wherein the heating and curing temperature is 70-100°C, and the heating and curing time is 8-12 minutes.

[0012] In one embodiment of the present invention, before performing step S3, the test positive electrode sheet, the test negative electrode sheet and the separator are punched, and the test positive electrode sheet, the test negative electrode sheet and the separator are cut to a target size.

[0013] In one embodiment of the present invention, in step S3, any electrolyte to be tested is LiPF 6 , LiBF 4 、LiClO 4 、LiAsF 6 、LiCF 3 SO 3 One or more of the above, wherein the concentration of the electrolyte to be tested is 0.8~1.2mol / L.

[0014] In one embodiment of the present invention, in step S4, the micro-batteries assembled into various pressure-carrying batteries are left to stand for 8 to 12 hours, and then gradually heated from low to high within a preset temperature range using a differential scanning calorimeter to perform thermal effect tests at different temperatures, wherein the upper limit of the preset temperature range does not exceed 300°C; and the heating rate of the differential scanning calorimeter is 10°C / min.

[0015] In one embodiment of the present invention, in step S4, the microbattery thermal effect evaluation parameters include the temperature peak value of the microbattery during the temperature rise process and the thermal runaway temperature of the microbattery in a fully charged state.

[0016] In one embodiment of the present invention, the electrode auxiliary material includes a conductive agent and a binder, and the mass ratio of the binder to the conductive agent is 1:2-1:3.

[0017] The above technical solution of the present invention has the following advantages compared with the prior art: The electrolyte detection and screening method described in the present invention overcomes the problem of powder micro-short circuit by thickly coating the electrode auxiliary material, and at the same time pressurizes the test electrode to make it fully contact with the electrolyte to be tested, thereby significantly improving the problem of uneven electrolyte infiltration. Based on the above process, in terms of material use, the method of this application reduces the amount of electrode materials and electrolytes, avoids unnecessary waste, and truly saves reagents, thereby effectively reducing research costs. From an environmental protection perspective, reducing material use means reducing the negative impact of material production and waste treatment on the environment, which is in line with the concept of green environmental protection. In terms of test results, this application overcomes the key problems that affect test accuracy in the prior art, making the test results more stable and accurate, and providing reliable data support for the research and development of high-performance lithium-ion batteries and their electrolytes, thus having broad prospects for use in this industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to make the contents of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings.

[0019] Figure 1 is a process flow chart of the electrolyte detection and screening method in a preferred embodiment of the present invention; Figure 2 It is a schematic diagram of the structure of the sealing crucible and the pressure spring; Figure 3 yes Figure 1 Heat release curves of different microbatteries shown; Figure 4 This is the repeated heat release curve of a microbattery using electrolyte C as the electrolyte solution.

[0020] Description of the accompanying drawings in the specification: 100, sealing crucible; 200, pressure spring. DETAILED DESCRIPTION

[0021] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention. Embodiment 1

[0022] This embodiment provides an electrolyte detection and screening method, which is used to detect the thermal effects of different electrolytes to screen out the safest and most stable electrolyte, thereby achieving the purpose of improving product stability and safety of use, and specifically includes the following steps: Step S1, providing an initial positive electrode sheet and an initial negative electrode sheet, and thickly coating an electrode auxiliary material on the initial positive electrode sheet and the initial negative electrode sheet until the surfaces of the initial positive electrode sheet and the initial negative electrode sheet reach a preset surface density, thereby obtaining a soft-pack battery; Furthermore, the initial positive electrode sheet and the initial negative electrode sheet can be the core component structure of the soft pack battery. The thick coating can form a separation layer between the active material powders, improve the uniformity of the electrode coating, enhance the structural stability of the electrode, improve the conductive network, and reduce the porosity of the electrode coating. Based on these factors, the direct contact between the active material powders and the penetration of the electrolyte can be reduced, thereby reducing the risk of micro-short circuits. In addition, the thick coating helps to ensure that electrons are transmitted along the network formed by the conductive agent rather than through direct contact between the powders, so that the stability of the electrode and the safety of the battery can be maintained even during high-rate charge and discharge.

[0023] Furthermore, step S1 in this embodiment is specifically as follows: mixing the initial positive electrode sheet, the initial negative electrode sheet and the electrode auxiliary material, and thickly coating the electrode auxiliary material on the initial positive electrode sheet and the initial negative electrode sheet until the surface density of the initial positive electrode sheet and the initial negative electrode sheet is greater than 250 mg / cm 2 Afterwards, a soft pack battery is obtained.

[0024] Furthermore, the electrode auxiliary material in this embodiment includes a conductive agent and a binder, and the mass ratio of the binder to the conductive agent is 1:2.5. Among them, the binder can firmly bond the active material to the electrode; the conductive agent can increase the conductivity of the electrode material. The present invention does not limit the specific type of the conductive agent for bonding the electrode. In addition, the mass ratio of the binder to the conductive agent can also be adaptively adjusted according to actual use requirements.

[0025] Step S2, after the soft-pack battery is activated and cycled, it is disassembled and cleaned to obtain a test positive electrode sheet and a test negative electrode sheet with a stable solid electrolyte interface formed on the surface; in this embodiment, the small current activation can make the electrode material and the electrolyte inside the battery fully react to form a stable solid electrolyte interface (SEI) film, which helps to improve the performance and life of the battery, so that the battery reaches the best working state, thereby ensuring the accuracy of subsequent test data.

[0026] Specifically, in this embodiment, the soft pack battery is activated at 0.05C to form the solid electrolyte interface on the surface of the test positive electrode plate and the test negative electrode plate, and then the soft pack battery is subjected to multiple charge and discharge cycles at 0.33C, and is charged to the maximum cut-off voltage after the last cycle. The charging time of each cycle is 1 hour, the discharging time is 2 hours, and the maximum cut-off voltage is 4.2V.

[0027] Furthermore, in step S2, after the activation cycle of the soft-pack battery, the soft-pack battery is disassembled in an inert environment, and then the disassembled test positive electrode plate and the test negative electrode plate are cleaned with a solvent, and after cleaning, the test positive electrode plate and the test negative electrode plate are heated and cured in an inert environment, wherein the heating and curing temperature is 80°C and the heating and curing time is 10 minutes. Specifically, the soft-pack battery is disassembled in an inert environment to prevent the electrode material from reacting with oxygen, moisture, etc. in the air and being oxidized or deteriorated; the electrode plate is cleaned twice using carbonate dissolution to remove impurities remaining on the surface of the electrode plate, unreacted substances, and by-products generated during use, thereby ensuring the purity of the electrode plate; baking the electrode plate in an inert environment can further remove moisture and solvent residues on the electrode plate, providing dry electrode plates for subsequent experiments.

[0028] Furthermore, before performing step S3, the test positive electrode sheet, the test negative electrode sheet and the diaphragm are punched, and the test positive electrode sheet, the test negative electrode sheet and the diaphragm are cut to a target size, so that the test positive electrode sheet, the test negative electrode sheet and the diaphragm can meet the subsequent test size processing.

[0029] Specifically, the test positive electrode plate in this embodiment uses a 3mm puncher, the diaphragm uses a 5mm puncher, and the test negative electrode plate uses a 4mm puncher for punching and cutting. In different implementations, adaptive adjustments can be made according to actual usage requirements.

[0030] Step S3, applying pressure to the test positive electrode plate and the test negative electrode plate, so that they are in full contact and infiltration with the multiple electrolytes to be tested in turn, and obtaining multiple pressure-carrying micro batteries. Among them, the pressure spring 200 can provide a certain pressure on the electrode plate, so that the electrode plate and the diaphragm are in close contact, thereby reducing the internal resistance of the battery and improving the battery performance. Further, see Figure 2 As shown, in step S3, a pressurized environment is provided for the test positive electrode sheet and the test negative electrode sheet through a sealed crucible 100 and a pressure spring 200, wherein the pressure spring 200 is disposed inside the sealed crucible 100, one end of which is connected to the inner wall of the sealed crucible 100, and the other end of which is in contact with the test positive electrode sheet and the test negative electrode sheet, so as to form the microbattery inside the sealed crucible 100. Specifically, the wire diameter of the pressure spring 200 in this embodiment is 0.15 mm and the outer diameter is 2.0 mm.

[0031] Furthermore, in step S3 of this embodiment, the electrolyte to be tested is LiPF 6 , LiBF 4 and LiClO 4, the concentration of the electrolyte to be tested is 1.0 mol / L.

[0032] Step S4: After the micro-battery is stable, the thermal effect tests of various pressurized micro-batteries under different temperature conditions are carried out in turn, and the screening process of the safety of the electrolyte is completed after the thermal effects of different micro-batteries are compared. Furthermore, in step S4 of this embodiment, after the micro-batteries assembled into various pressurized micro-batteries are left to rest for 10 hours, the temperature is gradually increased from low to high within a preset temperature range by a differential scanning calorimeter to carry out thermal effect tests at different temperatures, wherein the upper limit of the preset temperature range does not exceed 300°C; the heating rate of the differential scanning calorimeter is 10°C / min.

[0033] Specifically, in step S4 of this embodiment, the microbattery thermal effect evaluation parameter includes the temperature peak value of the microbattery during the temperature rise process and the thermal runaway temperature of the microbattery in a fully charged state. Figure 3 As shown, in this embodiment, LiPF 6 The solution is defined as electrolyte A, and LiBF 4 The solution is defined as electrolyte B, LiClO 4 The solution is defined as the electrolyte C, which is composed of Figure 3 It can be seen that the electrolyte C in this embodiment has the lowest temperature peak and the lowest thermal runaway temperature, so the application safety of the electrolyte C is optimal. Based on this, the present embodiment makes the electrolyte C repeatedly release heat to prove that it has good charge and discharge repetition performance.

[0034] It should be noted that, in different embodiments, the electrolyte to be tested is LiPF 6 , LiBF 4 、LiClO 4 、LiAsF 6 、LiCF 3 SO 3 One or more of the above, the present invention does not impose any specific limitation on this. Embodiment 2

[0035] This embodiment provides another electrolyte detection and screening method, the main principle and operation process of which are the same as those of the first embodiment. Only some parameter settings in this embodiment are different from those in the first embodiment, specifically: in step S1, the electrode auxiliary material includes a conductive agent and a binder, and the mass ratio of the binder to the conductive agent is 1:2; in step S2, the soft-pack battery is activated at 0.04C to form the solid electrolyte interface on the surface of the test positive electrode plate and the test negative electrode plate, and then the soft-pack battery is charged and discharged for multiple cycles at 0.30C, and charged to the maximum cut-off voltage after the last cycle, the heating curing temperature is 70°C, and the heating curing time is 8min; in step S3, the electrolyte to be tested is LiPF 6 , LiBF 4 、LiClO 4 、LiAsF 6 、LiCF 3 SO 3 One of the above, the concentration of the electrolyte to be tested is 0.8 mol / L, the wire diameter of the pressure spring 200 is 0.1 mm, and the outer diameter is 1.2 mm; in step S4, the micro-batteries assembled into multiple pressure-carrying batteries are left to stand for 8 hours. Embodiment 3

[0036] This embodiment provides another electrolyte detection and screening method, which is specifically as follows: in step S1, the electrode auxiliary material includes a conductive agent and a binder, and the mass ratio of the binder to the conductive agent is 1:3; in step S2, the soft-pack battery is activated at 0.06C to form the solid electrolyte interface on the surface of the test positive electrode plate and the test negative electrode plate, and then the soft-pack battery is subjected to multiple charge and discharge cycles at 0.40C, and charged to the maximum cut-off voltage after the last cycle, the heating curing temperature is 100°C, and the heating curing time is 12min; in step S3, any of the electrolytes to be tested is LiPF 6 , LiBF 4 、LiClO 4 、LiAsF 6 、LiCF 3 SO 3 One or more of the above, the concentration of the electrolyte to be tested is 1.2 mol / L, the wire diameter of the pressure spring 200 is 0.2 mm and the outer diameter is 2.5 mm; in step S4, the micro-batteries assembled into multiple pressure-carrying batteries are left to stand for 12 hours.

[0037] In summary, the electrolyte detection and screening method described in the present invention overcomes the problem of powder micro-short circuit by thickly coating the electrode auxiliary material, and at the same time pressurizes the test electrode to make it fully contact with the electrolyte to be tested, thereby significantly improving the problem of uneven electrolyte infiltration. Based on the above process, in terms of material use, the method of this application reduces the amount of electrode materials and electrolytes, avoids unnecessary waste, and truly saves reagents, thereby effectively reducing research costs. From an environmental protection perspective, reducing material use means reducing the negative impact of material production and waste treatment processes on the environment, which is in line with the concept of green environmental protection. In terms of test results, this application overcomes the key problems that affect test accuracy in the prior art, making the test results more stable and accurate, and providing reliable data support for the research and development of high-performance lithium-ion batteries and their electrolytes, thus having broad prospects for use in this industry.

[0038] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A method for detecting and screening an electrolyte, characterized in that: include: Step S1, providing an initial positive electrode sheet and an initial negative electrode sheet, and thickly coating an electrode auxiliary material on the initial positive electrode sheet and the initial negative electrode sheet until the surfaces of the initial positive electrode sheet and the initial negative electrode sheet reach a preset surface density, thereby obtaining a soft-pack battery; Step S2, after the soft-pack battery is activated and cycled, it is disassembled and cleaned to obtain a test positive electrode sheet and a test negative electrode sheet with a stable solid electrolyte interface formed on the surface; Step S3, applying pressure to the test positive electrode sheet and the test negative electrode sheet, so that they are fully contacted and infiltrated with multiple electrolytes to be tested in turn, to obtain multiple pressurized micro batteries; Step S4: After the micro-battery is stable, thermal effect tests are performed on various pressurized micro-batteries under different temperature conditions in turn, and the screening process for the safety of the electrolyte is completed after comparing the thermal effects of different micro-batteries.

2. The electrolyte detection and screening method according to claim 1, characterized in that: In step S3, a pressurized environment is provided for the test positive electrode plate and the test negative electrode plate by a sealed crucible and a pressure spring. The pressure spring is arranged inside the sealed crucible, one end of which is connected to the inner wall of the sealed crucible, and the other end is abutted against the test positive electrode plate and the test negative electrode plate to form the microbattery inside the sealed crucible.

3. The electrolyte detection and screening method according to claim 2, characterized in that: The wire diameter of the pressure spring is 0.1-0.2 mm and the outer diameter is 1.2-2.5 mm.

4. The electrolyte detection and screening method according to claim 1, characterized in that: In step S1, the initial positive electrode sheet, the initial negative electrode sheet and the electrode auxiliary material are mixed, and the electrode auxiliary material is thickly coated on the initial positive electrode sheet and the initial negative electrode sheet until the surface density of the initial positive electrode sheet and the initial negative electrode sheet is greater than 250 mg / cm 2 Finally, a soft pack battery is obtained.

5. The electrolyte detection and screening method according to claim 1, characterized in that: In step S2, the soft-pack battery is activated at 0.04-0.06C to form the solid electrolyte interface on the surface of the test positive electrode plate and the test negative electrode plate, and then the soft-pack battery is subjected to multiple charge and discharge cycles at 0.30-0.40C, and is charged to the maximum cut-off voltage after the last cycle.

6. The electrolyte detection and screening method according to claim 1, characterized in that: In step S2, after the soft-pack battery is activated and cycled, the soft-pack battery is disassembled in an inert environment, and then a solvent is used to clean the disassembled test positive electrode sheet and the test negative electrode sheet. After cleaning, the test positive electrode sheet and the test negative electrode sheet are heated and cured in an inert environment, wherein the heating and curing temperature is 70-100°C, and the heating and curing time is 8-12 minutes.

7. The electrolyte detection and screening method according to claim 1, characterized in that: Before performing step S3, the test positive electrode sheet, the test negative electrode sheet and the separator are punched, and the test positive electrode sheet, the test negative electrode sheet and the separator are cut to a target size.

8. The electrolyte detection and screening method according to claim 1, characterized in that: In step S3, any electrolyte to be tested is one or more of LiPF6, LiBF4, LiClO4, LiAsF6, and LiCF3SO3, and the concentration of the electrolyte to be tested is 0.8~1.2 mol / L.

9. The electrolyte detection and screening method according to claim 1, characterized in that: In step S4, the assembled micro-batteries with various pressures are left to rest for 8 to 12 hours, and then gradually heated from low to high within a preset temperature range using a differential scanning calorimeter to conduct thermal effect tests at different temperatures, wherein the upper limit of the preset temperature range does not exceed 300°C; and the heating rate of the differential scanning calorimeter is 10°C / min.

10. The electrolyte detection and screening method according to claim 1, characterized in that: In step S4, the microbattery thermal effect evaluation parameters include the temperature peak value of the microbattery during the temperature rise process and the thermal runaway temperature of the microbattery in a fully charged state.

11. The electrolyte detection and screening method according to claim 1, characterized in that: The electrode auxiliary material includes a conductive agent and a binder, and the mass ratio of the binder to the conductive agent is 1:2-1:3.

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