Battery cell, battery, battery pack, electric device, quality control method of battery cell

Abstract

The application provides an electrode, a battery, a battery pack, a power consumption device and a quality control method of the electrode. The electrode comprises a positive electrode sheet, a negative electrode sheet, a diaphragm, an electrolyte and a packaging assembly. The positive electrode sheet and the negative electrode sheet are stacked, and the diaphragm is between the positive electrode sheet and the negative electrode sheet. The electrolyte comprises an active metal salt. The positive electrode sheet, the negative electrode sheet and the diaphragm are in a cavity formed by the packaging assembly. The electrode satisfies: wherein is the molar concentration of the active metal salt in the electrolyte, and the unit is mol / L; and = V2 / V1, wherein V2 is the remaining space volume inside the electrode after the electrolyte is soaked into the electrode, and the unit is ml; and V1 is the remaining space volume inside the electrode after the electrolyte is removed from the electrode, and the unit is ml. The electrode provided by the application has high cycle performance and high rate performance.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a quality control method for battery cells, batteries, battery packs, electrical devices, and battery cells. Background Technology

[0002] Secondary batteries, as energy storage devices, are widely used in new energy vehicles, energy storage systems, consumer electronics (such as mobile phones and laptops), and aerospace due to their ability to be repeatedly charged and discharged. In practical applications, users are placing higher demands on the cycle performance and rate performance of batteries.

[0003] As the medium for active metal ion transport and the regulator of the interface film (SEI / CEI), the electrolyte's design parameters (such as active metal salt concentration and injection volume) directly affect the battery cell's performance. Currently, there is a significant contradiction in the synergistic optimization of electrolyte active metal salt concentration and injection volume: while high concentrations of active metal salts can improve interfacial stability, they also increase electrolyte viscosity and reduce ionic conductivity; although increasing the injection volume can improve electrolyte wetting to some extent, the electrolyte still cannot wet the pores formed by surface tension, capillary action, liquid sealing, etc., which increases the amount of "dead volume" electrolyte (i.e., less effective injection volume of electrolyte), thus reducing battery rate performance and cycle performance.

[0004] Therefore, it is urgent to solve the contradiction between the concentration of active metal salts in the electrolyte and the effective amount of electrolyte injected in secondary batteries, so as to improve the lifespan and rate performance of the battery cells. Summary of the Invention

[0005] This invention provides a quality control method for battery cells, batteries, battery packs, electrical devices, and battery cells. The battery cells of this invention can improve the contradiction between the concentration of active metal salts in the electrolyte and the effective electrolyte volume in secondary batteries, and have a longer cycle life and rate performance.

[0006] This invention provides a battery cell, including a positive electrode, a negative electrode, a separator, an electrolyte, and a packaging assembly;

[0007] The positive electrode and the negative electrode are stacked together, and the separator is located between the positive electrode and the negative electrode.

[0008] The electrolyte comprises an active metal salt;

[0009] The positive electrode, negative electrode, and separator are located in the cavity formed by the encapsulation assembly;

[0010] The battery cell meets the following requirements: ;

[0011] in, The molar concentration of the active metal salt in the electrolyte is expressed in mol / L.

[0012] =V2 / V1, where V2 is the remaining volume of the battery cell after the electrolyte has soaked the battery cell, in ml; and V1 is the remaining volume of the battery cell after the electrolyte has been removed, in ml.

[0013] Some embodiments of the present invention, .

[0014] In some embodiments of the present invention, 0.65≤ ≤1.4.

[0015] Some embodiments of the present invention, ≤0.45.

[0016] In some embodiments of the present invention, the active metal salt includes a lithium salt, preferably one or more of lithium fluoride, lithium perchlorate, lithium hexafluorophosphate, lithium bis(oxalato)borate, lithium bis(fluorosulfonyl)imide, lithium trifluoromethanesulfonate, and lithium tetrafluoroborate.

[0017] In some embodiments of the present invention, the electrolyte further includes additives, preferably including at least one of vinylene carbonate and fluoroethylene carbonate.

[0018] This invention also provides a battery, including the cell described above.

[0019] This invention also provides a battery pack, including the cells described above, or at least two batteries as described above.

[0020] This invention also provides an electrical device, including the battery described above, or the battery pack described above.

[0021] This invention also includes a quality control method for a battery cell, comprising the following steps: the battery cell includes a positive electrode, a negative electrode, a separator, an electrolyte, and a packaging assembly;

[0022] The positive electrode and the negative electrode are stacked together, and the separator is located between the positive electrode and the negative electrode.

[0023] The electrolyte comprises an active metal salt;

[0024] The positive electrode, negative electrode, and separator are located in the cavity formed by the encapsulation assembly;

[0025] The current parameter λ of the battery cell is detected;

[0026] Determine whether λ satisfies 1.35 ≤ λ ≤ 5.3;

[0027] Wherein, λ is calculated according to the following formula:

[0028] λ= ;

[0029] in, The molar concentration of the active metal salt in the electrolyte is expressed in mol / L.

[0030] =V2 / V1, where V2 is the remaining volume of the battery cell after the electrolyte has soaked into the cell, in ml; and V1 is the remaining volume of the battery cell after the electrolyte has been removed, in ml.

[0031] In some embodiments of the present invention, the quality control method for the battery cell further includes: if λ does not satisfy 1.35≤λ≤5.3, the method includes adjusting the molar concentration of the active metal salt in the electrolyte and / or performing a pressure treatment on the battery cell until the λ of the battery cell satisfies 1.35≤λ≤5.3.

[0032] This invention provides a quality control method for battery cells, batteries, battery packs, electrical devices, and battery cells, wherein the battery cells are controlled by... It can effectively improve the contradiction between the concentration of active metal salts in the electrolyte and the effective injection volume, and has a long cycle life and rate performance. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0034] In existing technologies, electrolyte design and effective electrolyte filling volume control have the following limitations: High-concentration active metal salts can form a dense interfacial film, but they significantly increase electrolyte viscosity, leading to increased ion transport resistance, higher cell internal resistance, and ultimately, decreased battery cycle performance. While low-concentration active metal salts can reduce viscosity, insufficient Li⁺ concentration results in an excessively high solvent ratio, poor SEI / CEI film stability, and exacerbated side reactions, accelerating battery capacity decay and deteriorating rate performance. Furthermore, insufficient effective electrolyte filling volume (i.e., electrolyte not filling electrode pores) leads to inadequate electrolyte wetting, reduced utilization of active materials, longer lithium-ion transport paths, increased cell internal resistance, and shortened battery cycle life.

[0035] Therefore, it is urgent to improve the balance between the concentration of active metal salts in the electrolyte and the effective amount of electrolyte injected into the battery cell, so as to improve the cycle life and rate performance of the battery.

[0036] Based on this, embodiments of the present invention provide a battery cell, including a positive electrode, a negative electrode, a separator, an electrolyte, and an encapsulation assembly; the positive and negative electrode are stacked, and the separator is located between the positive and negative electrode; the electrolyte includes an active metal salt; the positive electrode, negative electrode, and separator are located in a cavity formed by the encapsulation assembly; the battery cell satisfies: ;in, This represents the molar concentration of the active metal salt in the electrolyte, expressed in mol / L. =V2 / V1, where V2 is the remaining internal volume of the battery cell after the electrolyte is soaked in the battery cell, in ml; and V1 is the remaining internal volume of the battery cell after the electrolyte is removed from the battery cell, in ml.

[0037] The battery cell of this invention balances the contradiction between the concentration of active metal salts in the electrolyte and the effective amount of electrolyte injected, so that the battery has both high cycle life and rate performance.

[0038] The inventors analyzed that the reason why the battery cell of the present invention can improve the cycle life of the battery is that when the battery cell of the present invention meets the above conditions, by precisely controlling the effective amount of electrolyte injection, the electrolyte can be fully wetted by the electrode material. Under the premise of ensuring the stability of the interface film and the ionic conductivity, the concentration range of active metal salts in the electrolyte can be precisely controlled. This can suppress side reactions and maintain the low viscosity and high ion transport efficiency of the electrolyte. Therefore, the rate performance and cycle life of the battery can be taken into account.

[0039] In this embodiment of the invention, in order to balance the cycle performance and rate performance of the battery, the cycle life of the battery needs to meet the following requirements: when the battery capacity drops to 90% at 60°C, the number of cycles should be ≥600; at the same time, the rate performance of the battery at 3C / 1C should be ≥95.5%, so that the battery can achieve both good cycle performance and rate performance.

[0040] The embodiments of the present invention can use conventional testing methods and instruments in the art to determine the molar concentration of active metal salts in the electrolyte, The values ​​are tested. For example, the molar concentration c (unit: mol / L) of the active metal salt in the electrolyte can be determined by ion chromatography (IC). The value can be tested using the inert gas injection method. In detail, The value is the effective electrolyte injection ratio, which can be tested by V2 / V1. When the ratio of V2 / V1 is small, there is less "dead volume" in the battery. At this time, the electrolyte can fully penetrate into each component in the battery, that is, it can fully fill the pores of the electrodes, so that the effective electrolyte injection volume of the battery is basically filled with electrolyte, and the effective electrolyte injection volume in the battery is increased.

[0041] In this embodiment of the invention, the molar concentration c of the active metal salt in the electrolyte can be tested using the following method: After the battery is fully discharged, it is disassembled and the cell is separated. The cell is disassembled using ceramic tweezers in an inert atmosphere glove box (Ar environment, H2O and O2 concentrations are both below 0.01 ppm). 1) If the battery contains residual electrolyte, 30 μL of electrolyte is pipetted and diluted to 6 ml with acetonitrile (dilution factor D). After filtration, the sample is tested. The sample is placed in the injector of an ion chromatograph (IC) for analysis. The cations in the sample undergo ion exchange with the sulfonic acid groups on the stationary phase in the chromatographic column and are eluted sequentially at different retention times under the hydrogen ion elution system. Based on the characteristic elution time and peak area of ​​the active metal ions, the concentration C of the active metal salt in the electrolyte is quantitatively calculated. 测 (Unit: mg / L), the molar concentration of the active metal salt in the electrolyte before dilution can be calculated as C. 实际 =D×C 测 / 1000 / M (M is the molar mass of the active metal salt). (2) If there is no residual electrolyte in the battery, cut the positive / negative electrode (15 mm in diameter) with a sampler and put it into a centrifuge tube. Add 4 ml of acetonitrile to the centrifuge tube and soak for 24 h. Then, follow the procedure in step 1 to perform IC testing and calculate the molar concentration C of the active metal salt. In fact, 100 μL of residual electrolyte between the positive / negative electrode and the separator is taken by pipette and transferred to a test tube containing 900 μL of acetonitrile. After thorough shaking and dilution, add 2 mL of ultrapure water, mix evenly and let stand to separate the layers. Take the lower aqueous phase and filter it through a filter membrane as the sample to be tested. Place the obtained sample to be tested in the injector of the ion chromatograph (IC) for analysis. The cations in the sample undergo ion exchange with the sulfonic acid groups on the stationary phase in the chromatographic column and are eluted sequentially according to different retention times under the hydrogen ion elution system. Based on the characteristic elution time and peak area of ​​the active metal ions, the molar concentration c of the active metal salt in the electrolyte (that is, the above C) is quantitatively calculated. 测 ).

[0042] In this embodiment of the invention, parameters The method for determining V2 / V1 is as follows: where V2 is the remaining internal volume of the battery cell after the electrolyte has been absorbed (unit: mL), and V1 is the remaining internal volume of the battery cell after the electrolyte has been removed (unit: mL). First, in an environment with a dew point ≤ -40℃, V2 is determined using the inert gas injection method: the rubber plug of the battery cell to be tested is removed, a matching PTFE interface is attached, and a PTFE two-way valve is connected to control the gas flow; the battery cell is placed in a steel casing fixture to prevent deformation under pressure; then, the interface is connected via a gas pipe to an argon cylinder equipped with a pressure reducing valve and a gas flow meter (which can record cumulative flow and system pressure); the pressure reducing valve is adjusted to stabilize the output pressure at 0.4 MPa, and after the gas flow meter is zeroed, the ambient atmospheric pressure P0 and temperature T are recorded. The two-way valve is then opened to begin gas injection; during the injection process, the valve is closed at fixed pressure intervals, and the corresponding system pressure P and cumulative injected gas volume V are recorded; based on the ideal gas law, the relationship between P and V is established, yielding:

[0043]

[0044] The gas constant R = 8.314 J / (mol·K), at room temperature T = 298.15 K, V m =25.053 L / mol. The cavity value approaches a constant under higher internal pressure, which is the actual cavity volume V. 空腔 (That is, V2).

[0045] Subsequently, the same cell was dried to determine V1: At a dew point of -40°C, the electrolyte injection hole was opened using needle-nose pliers and tweezers, and as much free electrolyte as possible was poured out. The cell was then filled with dimethyl carbonate (DMC) that had been dried using molecular sieves (to remove moisture), soaked for 10–16 hours, and then poured out completely. This cleaning step was repeated three times to fully replace any residual electrolyte in the electrodes. The treated cell was then baked in a vacuum drying oven at 105°C for 48 hours, followed by cooling at room temperature (25°C) for 8 hours to obtain a completely dry cell. The remaining cavity volume of this dry cell was determined using the same inert gas injection method as described above, and denoted as V1. Finally, the volume was calculated... =V2 / V1.

[0046] In this embodiment of the invention, in order to ensure that the electrolyte fully wets the battery cell, the battery cell can be placed for 2-3 days after electrolyte injection, or the inside of the battery cell can be subjected to pressure treatment to allow the electrolyte to wet the inside of the battery cell.

[0047] In some embodiments of the present invention, This approach helps to further balance the contradiction between the concentration of active metal salts in the electrolyte and the effective amount of electrolyte injected, thereby better improving the rate performance and cycle life of the battery.

[0048] In some embodiments of the present invention, 0.65 ≤ A value ≤1.4 is more conducive to improving ionic conductivity, reducing electrolyte viscosity, and promoting the formation of a stable interfacial film, thereby better balancing the battery's high cycle life and rate performance. For example, the value of c can be 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.4, or any combination thereof.

[0049] In some embodiments, A concentration ≤0.45 is more conducive to optimizing the utilization efficiency of the internal space of the battery cell. While ensuring sufficient electrolyte wetting of the positive and negative electrode materials and the separator, it increases the proportion of active metal ions per unit volume, thereby better balancing the battery's rate performance and cycle stability. For example, The value can be, for example, 0.03, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, or a range of any two of these. Preferably, 0.03 ≤ A value of ≤0.45 can better balance the rate performance and cycle stability of the battery.

[0050] In some embodiments of the present invention, the active metal salt includes lithium salt, preferably one or more of lithium fluoride, lithium perchlorate, lithium hexafluorophosphate, lithium bis(oxalato)borate, lithium bis(fluorosulfonyl)imide, lithium trifluoromethanesulfonate, and lithium tetrafluoroborate, which is beneficial to further improve the rate performance and cycle performance of the battery.

[0051] In some embodiments of the present invention, the electrolyte further includes additives, preferably including at least one of vinylene carbonate and fluoroethylene carbonate, which is more conducive to forming a dense interface film with better ion conductivity on the surfaces of the negative and positive electrodes, better promoting the reversible insertion and extraction of lithium ions, further improving the stability of the electrode / electrolyte interface, and thus further enhancing the cycle life of the battery.

[0052] The embodiments of the present invention can test the types and contents of active metal salts and additives in the electrolyte using conventional testing methods and instruments in the art. For example, the above-described method can be used to test them using an ion chromatograph (IC).

[0053] The battery cell in this embodiment of the invention can be a laminated battery cell, that is, the battery cell is formed by alternating layers of positive electrode, separator and negative electrode; or, the battery cell can also be a wound battery cell, that is, the battery cell is formed by stacking positive electrode, separator and negative electrode and then winding them.

[0054] In this embodiment of the invention, conventional housing materials (encapsulation components) in the art can be used to encapsulate the battery cell. The encapsulation components include, for example, flexible packaging materials such as aluminum-plastic film, but are not limited thereto.

[0055] Specifically, the positive electrode sheet includes a positive current collector and a positive active material layer located on at least one side surface of the positive current collector. Specifically, the positive active material layer can be provided on one side surface in the thickness direction of the positive current collector, or positive active material layers can be provided on both opposite sides surface in the thickness direction of the positive current collector.

[0056] The positive electrode active material layer includes a positive electrode active material, a positive electrode conductive agent, and a positive electrode binder. In the positive electrode active material layer, the mass percentage of the positive electrode active material can be 70% to 99%, for example, 70%, 75%, 80%, 85%, 90%, 93%, 95%, 97%, 99%, or any combination thereof. The mass fraction of the positive electrode conductive agent can be 0.5% to 15%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 8%, 10%, 13%, 15%, or any combination thereof. The mass fraction of the positive electrode binder can be 0.5% to 15%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 8%, 10%, 13%, 15%, or any combination thereof.

[0057] In some embodiments, the battery is a lithium-ion battery, and the positive electrode active material includes, but is not limited to, LiCoO2, LiNiO2, and LiCo. x Ni 1-x O2 (0≤x≤1), LiCo x Ni 1-x-y Al y O2 (0≤x≤1, 0≤y≤1), LiMn2O4, LiFe x Mn y M z O4 (M is one or more of Al, Mg, Ga, Cr, Co, Ni, Cu, Zn or Mo, 0≤x≤1, 0≤y≤1, 0≤z≤1, x+y+z=1), Li 1＋ x L 1－y－z M y N zO2 (L, M, N are one or more of Li, Co, Mn, Ni, Fe, Al, Mg, Ga, Ti, Cr, Cu, Zn, Mo, F, I, S, B, -0.1≤x≤0.2, 0≤y≤1, 0≤z≤1, 0≤y+z≤1), LiFePO4, Li3V2(PO4)3, Li3V3(PO4)3, LiVPO4F, Li2CuO2, Li5FeO4, and metal sulfides and oxides (such as TiS2, V2S3, FeS, FeS2, LiMS) x (M is at least one of the transition metal elements such as Ti, Fe, Ni, Cu, Mo, etc., 1≤x≤2.5), TiO2, Cr3O8, V2O5, MnO2, etc.

[0058] In this embodiment of the invention, the positive electrode conductive agent in the positive electrode active material layer can be a conventional conductive material in the art. For example, the positive electrode conductive agent in the positive electrode active material layer may include one or more of conductive carbon black, conductive graphite, carbon nanotubes (CNTs), carbon fibers, graphene, acetylene black, and Ketjen black.

[0059] In this embodiment of the invention, the positive electrode binder in the positive electrode active material layer can be a conventional binder in the art. For example, the positive electrode binder in the positive electrode active material layer may include one or more of the following: polyvinylidene fluoride (PVDF), polyvinylidene fluoride, polyvinyl fluoride, polyethylene, polypropylene, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, etc.

[0060] The embodiments of the present invention may employ conventional positive current collectors in the art, for example, positive current collectors may include aluminum foil.

[0061] In this embodiment of the invention, the positive electrode sheet can be prepared by conventional methods in the art, such as by coating. Specifically, the components used to form the positive electrode active material layer, such as the positive electrode conductive agent and the positive electrode binder, can be dispersed in a solvent, such as N-methylpyrrolidone (NMP), to prepare a positive electrode slurry. This slurry is then coated onto the surface of the positive electrode current collector, and after drying, rolling, and other processes, the positive electrode sheet is obtained. The coating, drying, and rolling processes involved are conventional operations for preparing positive electrode sheets using the coating method, and are not particularly limited thereto.

[0062] In practice, a slurry containing positive electrode active material can be prepared at a temperature of 20~45℃; conventional coating equipment in the field, such as continuous coating equipment, can be used to coat the slurry containing positive electrode active material onto the surface of the positive electrode current collector.

[0063] Specifically, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer located on at least one side surface of the negative electrode current collector. Specifically, the negative electrode active material layer can be provided on one side surface of the negative electrode current collector, or negative electrode active material layers can be provided on both opposite sides of the negative electrode current collector in the thickness direction.

[0064] Specifically, the negative electrode active material layer may include a negative electrode active material, a negative electrode conductive agent, and a negative electrode binder, all of which can be conventional materials in the art. For example, the negative electrode active material may include graphite, and the negative electrode conductive agent may include one or more of conductive carbon black, carbon nanotubes (CNT), acetylene black, graphene, Ketjen black, and carbon fiber; the negative electrode binder may include one or more of sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamide-imide, polyvinyl alcohol, and sodium polyacrylate.

[0065] The embodiments of the present invention may employ conventional negative electrode current collectors in the art, for example, negative electrode current collectors include copper foil.

[0066] In this embodiment of the invention, the negative electrode sheet can be prepared by conventional methods in the art, such as by coating. Specifically, the components used to form the negative electrode active material layer, negative electrode conductive agent, negative electrode binder, etc., can be dispersed in a solvent, such as water, to prepare a negative electrode slurry. This slurry is then coated onto the surface of the negative electrode current collector, and after drying, rolling, and other processes, the negative electrode sheet is obtained. The coating, drying, and rolling processes involved are conventional operations for preparing negative electrode sheets using the coating method, and are not particularly limited thereto.

[0067] In practice, a slurry containing negative electrode active material can be prepared at a temperature of 20℃~45℃; conventional coating equipment in the field, such as continuous coating equipment, can be used to coat the slurry containing negative electrode active material onto the surface of the negative electrode current collector.

[0068] In this embodiment of the invention, the separator is used to separate the positive electrode and the negative electrode to prevent the positive electrode and the negative electrode from coming into contact and short-circuiting.

[0069] The electrolyte in this embodiment of the invention can be a conventional electrolyte in the art. For example, the electrolyte is a non-aqueous electrolyte, which may specifically include organic solvents, additives and electrolyte salts. Organic solvents include one or more of ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC) and propylene carbonate (PC). Additives are as described above, for example, they may include fluoroethylene carbonate (FEC) or vinylene carbonate (VC). Electrolyte salts may include lithium salts (if it is a lithium-ion battery), such as lithium hexafluorophosphate (LiPF6), but are not limited thereto.

[0070] This invention also provides a method for preparing the above-mentioned battery cell, comprising the following steps:

[0071] A positive electrode and a negative electrode are stacked together, with a separator positioned between them to obtain a cell precursor. This cell precursor is then placed within a cavity formed by an encapsulation assembly, and an electrolyte is injected to obtain the cell. The cell satisfies the following requirements: ;

[0072] in, This represents the molar concentration of the active metal salt in the electrolyte, expressed in mol / L.

[0073] =V2 / V1, where V2 is the remaining internal volume of the battery cell after the electrolyte is soaked in the battery cell, in ml; and V1 is the remaining internal volume of the battery cell after the electrolyte is removed from the battery cell, in ml.

[0074] In this embodiment of the invention, components such as positive electrode, separator and negative electrode can be assembled into a battery using conventional methods in the art. For example, positive electrode, separator and negative electrode can be stacked alternately to obtain a stacked cell precursor (or wound into a wound cell precursor); then the cell precursor is placed in a housing (encapsulation assembly), and after conventional processes such as electrolyte injection (i.e., injection of electrolyte) and encapsulation, a cell is obtained.

[0075] The present invention provides a battery cell with high cycle life and rate performance through the above-described battery cell preparation method.

[0076] Embodiments of the present invention can control the molar concentration of active metal salts in the electrolyte to achieve the desired effect. In addition, after the battery cell is filled with electrolyte, it can also be subjected to pressure treatment. The value is controlled.

[0077] This invention also provides a battery comprising the aforementioned battery cell. The battery of this invention has advantages corresponding to the aforementioned battery cell, which will not be elaborated here.

[0078] This invention also provides a battery pack, including the above-described battery cells, or at least two of the above-described batteries. The battery pack has advantages corresponding to the above-described battery cells, which will not be elaborated further.

[0079] Generally, a battery pack includes multiple batteries as individual cells, which are connected to form the battery pack. These batteries can be electrically connected using methods conventional in the art, such as series connection, parallel connection, or a combination of these connection methods, without any particular limitation.

[0080] This invention also provides an electrical device including the battery described above. This electrical device has advantages corresponding to the battery cells described above, which will not be elaborated further.

[0081] The electrical equipment used in the embodiments of the present invention can be conventional electrical equipment in the art, such as power equipment (e.g., electric vehicles, electric cars), electronic equipment (e.g., mobile phones, tablets, laptops, digital cameras, etc.), wearable devices (e.g., watches, bracelets, VR glasses, etc.), energy storage power stations, etc., and there are no particular limitations on this.

[0082] This invention also provides a quality control method for a battery cell, comprising the following steps: the battery cell includes a positive electrode, a negative electrode, a separator, an electrolyte, and a packaging assembly;

[0083] The positive and negative electrode plates are stacked together, and the separator is located between the positive and negative electrode plates;

[0084] The electrolyte includes active metal salts;

[0085] The positive electrode, negative electrode, and separator are located in the cavity formed by the encapsulation component;

[0086] The current parameter λ of the battery cell is detected;

[0087] Determine whether λ satisfies 1.35 ≤ λ ≤ 5.3;

[0088] Wherein, λ is calculated according to the following formula:

[0089] λ= ;

[0090] in, This represents the molar concentration of the active metal salt in the electrolyte, expressed in mol / L.

[0091] =V2 / V1, where V2 is the remaining volume of the cell after the electrolyte has been applied, in ml; and V1 is the remaining volume of the cell after the electrolyte has been removed, in ml.

[0092] The present invention, through the above-described quality control method, can control the quality of the battery cell during the cell manufacturing stage, which is more conducive to achieving the desired concentration of active metal salts in the electrolyte. and The synergistic optimization of the cells ensures that they maintain both high cycle stability and good rate performance during subsequent use.

[0093] In the quality control method described above in the embodiments of the present invention, Value and The value test has been described above and will not be repeated here.

[0094] In some embodiments of the present invention, the quality control method for the battery cell further includes steps such as adjusting the molar concentration of the active metal salt in the electrolyte and / or performing a pressure treatment on the battery cell until the λ of the battery cell satisfies 1.35≤λ≤5.3, which is beneficial for obtaining a battery cell with better rate performance and cycle life. Furthermore, the λ of the battery cell can also be adjusted by ultrasound. The embodiments of the present invention do not impose special limitations on the power, time, etc., of the ultrasound, and can be selected according to actual conditions.

[0095] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0096] Example 1

[0097] The battery cell in this embodiment is prepared by the following method:

[0098] 1) The positive electrode active material (specifically LFP) was mixed with conductive carbon black and PVDF at a weight ratio of 96%:2%:2%, and dispersed to obtain a positive electrode slurry. This slurry was then coated onto an aluminum foil positive electrode current collector, with a positive electrode areal density of 4.12 g / cm³. 3 The positive electrode sheet is prepared by rolling.

[0099] 2) The negative electrode active materials, artificial graphite, styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose, and conductive carbon black, are mixed in a weight ratio of 94%:3%:2%:1%. The mixture is dispersed in water and then mixed using a double planetary mixer to obtain a negative electrode slurry. This slurry is coated onto a copper negative electrode current collector, followed by rolling and drying to obtain a negative electrode sheet.

[0100] 3) Assemble the positive electrode, negative electrode, and separator (specifically, a PP separator) into a lithium-ion battery, and inject a non-aqueous electrolyte (electrolyte injection). After electrolyte injection, place the lithium-ion battery for 3 days. The electrolyte is prepared as follows: ethylene carbonate (EC): dimethyl carbonate (DMC): ethyl methyl carbonate (EMC) = 1:1:1; additives (ethyleneene carbonate) VC and fluoroethylene carbonate (FEC) account for 4 wt% (VC:FEC at a mass ratio of 1:1); the lithium salt is lithium hexafluorophosphate (LiPF6). The concentration of lithium salt (also the active metal salt) in this electrolyte is... It is 0.65 mol / L.

[0101] The electrolyte injection volume (actual injection volume) of the battery cell in this embodiment of the invention is 157.5g, the total weight of the battery cell is 882.5g, the thickness of the battery cell is 3.1cm, the width is 9.1cm, the length is 14.5cm, and the designed capacity is 45.6Ah.

[0102] The differences between Examples 2-14, Comparative Examples 1-2 and Example 1 are the electrolyte injection volume, the total weight of the battery cell, and the concentration of lithium salt in the electrolyte. The parameters differ, as detailed in Table 1. The battery cells in the above embodiments and comparative examples... Value, V2, V1, The values ​​are shown in Table 1. Furthermore, in Example 9 of this invention, the lithium salt is lithium hexafluorophosphate:lithium bisfluorosulfonylimide electrolyte prepared at a molar ratio of 9:1.

[0103]

[0104] Test case

[0105] (a) Cell physical property testing

[0106] Test of molar concentration c of active metal salt in electrolyte: After the battery was fully discharged, it was disassembled and the cell was separated. In an inert atmosphere glove box (Ar environment, H2O and O2 concentrations were both below 0.01 ppm), the cell was disassembled using ceramic tweezers. 100 μL of residual electrolyte between the positive and negative electrodes and the separator was aspirated by pipette and transferred to a test tube containing 900 μL of acetonitrile. After thorough shaking and dilution, 2 mL of ultrapure water was added, mixed evenly, and allowed to stand for separation. The lower aqueous phase was filtered through a filter membrane and used as the sample to be tested. The obtained sample to be tested was placed in the injector of an ion chromatograph (IC) for analysis. The cations in the sample underwent ion exchange with the sulfonic acid groups on the stationary phase in the chromatographic column and were eluted sequentially at different retention times under the hydrogen ion elution system. Based on the characteristic elution time and peak area of ​​the active metal ions, the molar concentration c of the active metal salt in the electrolyte was quantitatively calculated.

[0107] The determination methods for V1, V2, and V2 are as follows: Under an environment with a dew point ≤ -40℃, V2 is determined using the inert gas injection method: Remove the rubber plug from the injection hole of the battery cell to be tested, attach a PTFE interface matching the battery cell, and connect a PTFE two-way valve to control the gas flow; place the battery cell in a steel casing fixture to prevent deformation under pressure; then connect the interface to an argon cylinder equipped with a pressure reducing valve and a gas flow meter (which can record cumulative flow and system pressure) via a gas pipe; adjust the pressure reducing valve to stabilize the output pressure at 0.4 MPa, and after the gas flow meter returns to zero, record the ambient atmospheric pressure P0 and temperature T, then open the two-way valve to begin gas injection; during the gas injection process, close the valve at fixed pressure intervals, and record the corresponding system pressure P and cumulative injected gas volume V; establish the relationship between P and V based on the ideal gas law, obtaining:

[0108]

[0109] The gas constant R = 8.314 J / (mol·K), at room temperature T = 298.15 K, V m =25.053 L / mol. The cavity value approaches a constant under higher internal pressure, which is the actual cavity volume V. 空腔 (That is, V2).

[0110] Subsequently, the same cell was dried to determine V1: At a dew point of -40°C, the electrolyte injection hole was opened using needle-nose pliers and tweezers, and as much free electrolyte as possible was poured out. The cell was then filled with dimethyl carbonate (DMC) that had been dried using molecular sieves (to remove moisture), soaked for 10–16 hours, and then poured out completely. This cleaning step was repeated three times to fully replace any residual electrolyte in the electrodes. The treated cell was then baked in a vacuum drying oven at 105°C for 48 hours, followed by cooling at room temperature (25°C) for 8 hours to obtain a completely dry cell. The remaining cavity volume of this dry cell was determined using the same inert gas injection method as described above, and denoted as V1. Finally, the volume was calculated... =V2 / V1. The test results are shown in Table 1.

[0111] (II) Electrochemical performance testing of battery cells

[0112] Cell cycle performance test method: After completing the above capacity calibration, the battery was placed in a 60℃ constant temperature environment and charged at a constant current of 1C to 3.8V, then left to stand for 30 minutes. It was then discharged at a constant current of 1C to 2.0V, followed by a 30-minute stand, constituting one complete cycle. This charge-discharge cycle was repeated until the battery's discharge capacity decreased to 90% of the initial calibrated capacity C. The number of cycles was recorded to evaluate the battery's cycle stability under high temperature conditions. The test results are shown in Table 2.

[0113] Cell rate performance testing method: Under 25℃ conditions, the battery is charged and discharged three times within the range of 2.0 V–3.8 V at a rate of 0.33C. The discharge capacity of the third discharge is taken as the calibrated capacity C. Subsequently, the battery is charged to 3.8 V at a constant current of 0.33C, allowed to stand for 30 minutes, and then discharged to 2.0 V at a constant current of 1C. The discharge capacity Q is recorded. 1C With average discharge voltage V 1C Calculate the 1C discharge energy W 1C =V 1C ×Q 1C Then, it was charged again at 0.33C to 3.8V, left to stand for 30 minutes, and then discharged at a constant current of 3C to 2.0V. The discharge capacity Q was recorded. 3C With average discharge voltage V 3C Calculate the 3C discharge energy W 3C =V 3C ×Q 3C ; ultimately, the ratio W 3C / W 1C The 3C / 1C energy ratio is used to characterize the battery's energy retention capability under high-rate discharge conditions. The test results are shown in Table 2.

[0114] In this embodiment of the invention, in order to balance the cycle performance and rate performance of the battery, the cycle life of the battery needs to meet the following requirements: when the battery capacity drops to 90% at 60°C, the number of cycles should be ≥600; at the same time, the rate performance of the battery at 3C / 1C should be ≥95.5%, so that the battery can achieve both good cycle performance and rate performance.

[0115]

[0116] As shown in Table 2, the embodiments of the present invention control the battery cell to satisfy: This is beneficial for balancing the improvement of battery cycle performance and rate performance.

[0117] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A battery cell, characterized in that, Includes positive electrode, negative electrode, separator, electrolyte, and encapsulation components; The positive electrode and the negative electrode are stacked together, and the separator is located between the positive electrode and the negative electrode. The electrolyte comprises an active metal salt; The positive electrode, negative electrode, and separator are located in the cavity formed by the encapsulation assembly; The battery cell meets the following requirements: ; in, The molar concentration of the active metal salt in the electrolyte is expressed in mol / L. =V2 / V1, where V2 is the remaining volume of the battery cell after the electrolyte has soaked the battery cell, in ml; and V1 is the remaining volume of the battery cell after the electrolyte has been removed, in ml.

2. The battery cell according to claim 1, characterized in that, 。 3. The battery cell according to claim 1 or 2, characterized in that, 0.65≤ ≤1.4。 4. The battery cell according to any one of claims 1-3, characterized in that, ≤0.45。 5. The battery cell according to any one of claims 1-4, characterized in that, The active metal salt includes lithium salt, preferably one or more of lithium fluoride, lithium perchlorate, lithium hexafluorophosphate, lithium bis(oxalato)borate, lithium bis(fluorosulfonyl)imide, lithium trifluoromethanesulfonate, and lithium tetrafluoroborate.

6. The battery cell according to any one of claims 1-4, characterized in that, The electrolyte also includes additives, preferably including at least one of vinylene carbonate and fluoroethylene carbonate.

7. A battery, characterized in that, Includes the battery cell described in any one of claims 1-6.

8. A battery pack, characterized in that, Includes the battery cell according to any one of claims 1-6, or at least two batteries according to claims 7.

9. An electrical appliance, characterized in that, Includes the battery as described in claim 7, or the battery pack as described in claim 8.

10. A quality control method for battery cells, characterized in that, The battery cell includes the following steps: a positive electrode, a negative electrode, a separator, an electrolyte, and a packaging assembly. The positive electrode and the negative electrode are stacked together, and the separator is located between the positive electrode and the negative electrode. The electrolyte comprises an active metal salt; The positive electrode, negative electrode, and separator are located in the cavity formed by the encapsulation assembly; The current parameter λ of the battery cell is detected; Determine whether λ satisfies 1.35 ≤ λ ≤ 5.3; Wherein, λ is calculated according to the following formula: λ= ; in, The molar concentration of the active metal salt in the electrolyte is expressed in mol / L. =V2 / V1, where V2 is the remaining volume of the battery cell after the electrolyte has soaked into the cell, in ml; and V1 is the remaining volume of the battery cell after the electrolyte has been removed, in ml.

11. The quality control method for battery cells according to claim 10, characterized in that, Also includes: The condition that λ does not satisfy 1.35≤λ≤5.3 includes steps of adjusting the molar concentration of the active metal salt in the electrolyte and / or performing pressure treatment on the battery cell until the λ of the battery cell satisfies 1.35≤λ≤5.3.

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