Battery monomer, preparation method of secondary battery, electrolyte and electric device

Abstract

The invention relates to the technical field of batteries, in particular to a battery monomer, a preparation method of a secondary battery, an electrolyte and an electric device. Each single battery comprises a positive pole piece, a negative pole piece and an electrolyte, at least partial structures of the positive pole piece and the negative pole piece are located in the electrolyte, the electrolyte comprises a metal ion complexing agent, and the metal ion complexing agent comprises an organic complexing agent and / or an inorganic complexing agent; the organic complexing agent comprises at least one of phenanthroline, a crown ether compound, oxalic acid, citric acid, tartaric acid, ethylenediamine tetraacetic acid and deferoxamine; and / or the inorganic complexing agent comprises at least one of sodium oxalate, sodium citrate, sodium tartrate and sodium ethylene diamine tetracetate. The metal ion complexing agent in the electrolyte can be combined with impurity metal ions in the electrolyte to form a stable complex, so that the risk that the impurity metal ions are separated out into dendritic metal foreign matters at an anode to pierce a diaphragm to cause self-discharge of the battery is reduced.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a battery cell, a method for preparing a secondary battery, an electrolyte, and an electrical device. Background Technology

[0002] Lithium-ion batteries, for example, have attracted much attention due to their high specific energy, long cycle life, low self-discharge, and good safety performance. Currently, lithium-ion batteries are used in all aspects of daily life, such as cameras, laptops, and electric vehicles.

[0003] With the rapid growth of portable electronic devices, electric vehicles, and other technologies, the demand for power batteries is also constantly increasing. Among these, the electrochemical performance of batteries is receiving increasing attention.

[0004] Battery self-discharge refers to the phenomenon where a battery's internal chemical energy is spontaneously converted into electrical energy and gradually lost when it is not connected to an external circuit. Self-discharge reduces the battery's usable capacity, causes voltage drop, and affects the normal use of equipment. Summary of the Invention

[0005] The main objective of this application is to provide a method for preparing a battery cell, a secondary battery, an electrolyte, and an electrical device, with the aim of reducing the risk of battery self-discharge.

[0006] To achieve the above objectives, this application proposes a battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein at least a portion of the structures of the positive and negative electrodes are located in the electrolyte, and the electrolyte comprises a metal ion complexing agent.

[0007] The metal ion complexing agent includes organic complexing agents and / or inorganic complexing agents;

[0008] The organic complexing agent includes at least one of o-phenanthroline, crown ether compounds, oxalic acid, citric acid, tartaric acid, ethylenediaminetetraacetic acid, and deferoxamine;

[0009] And / or, the inorganic complexing agent includes at least one of sodium oxalate, sodium citrate, sodium tartrate, and sodium ethylenediaminetetraacetate.

[0010] The metal ion complexing agent in the electrolyte of this application can combine with impurity metal ions in the electrolyte to form a stable complex, thereby reducing the risk of impurity metal ions precipitating as dendritic metal foreign matter at the anode and piercing the separator, leading to battery self-discharge.

[0011] It is understandable that a small amount of metallic impurities will inevitably be introduced during battery cell production. If these metallic impurities are located at the cathode, they will undergo electrochemical oxidation and dissolve into impurity metal ions (such as Fe) at a high potential. 2+ / Cr2+ / Cu 2 + The impurities then diffuse through the diaphragm to the anode surface, where they precipitate as dendritic metallic foreign matter at the low anode potential. Metal complexing agents can combine with impurity metal ions in the electrolyte to form stable complexes, rendering the impurity metal ions electrochemically inactive and thus reducing the risk of their precipitation on the anode surface.

[0012] The metal ion complexing agent in this application includes organic complexing agents and / or inorganic complexing agents. That is, the metal ion complexing agent includes an organic complexing agent, or the metal ion complexing agent includes an inorganic complexing agent, or the metal ion complexing agent includes both organic and inorganic complexing agents.

[0013] The organic complexing agent in this application includes at least one of o-phenanthroline, crown ether compounds, oxalic acid, citric acid, tartaric acid, ethylenediaminetetraacetic acid, and deferoxamine. That is, the organic complexing agent includes any one of the above, or a combination of multiple of the above.

[0014] The inorganic complexing agent in this application includes at least one of sodium oxalate, sodium citrate, sodium tartrate, and sodium ethylenediaminetetraacetate. That is, the inorganic complexing agent includes any one of the above, or a combination of multiple of the above.

[0015] Optionally, the mass percentage of the metal ion complexing agent to the total mass of the electrolyte is 0.01% to 1%.

[0016] In this application, the mass percentage of the metal ion complexing agent in the electrolyte of the battery meets the above-mentioned range. This effectively complexes impurity metal ions, reducing the risk of impurity metal ions depositing as dendritic metal foreign objects at the anode, piercing the separator and causing battery self-discharge. It is understood that the metal ion complexing agent in the electrolyte of the battery will be gradually consumed; that is, the amount of metal ion complexing agent gradually decreases throughout the entire process from battery manufacturing to battery use. For example, when the amount of metal ion complexing agent added is small, it may be completely consumed. The dissolution and precipitation of metal impurities in the battery is a long-term process. The long-term presence of metal ion complexing agent in the battery electrolyte is beneficial for the long-term effective complexation of impurity metal ions.

[0017] Optionally, the crown ether compound includes at least one of 18-crown ether-6, benzo-18-crown ether-6, dibenzo-18-crown ether-6, 12-crown ether-4, aza-12-crown ether-4, and 15-crown ether-5.

[0018] The crown ether compound in this application includes at least one of the above-mentioned compounds. That is, it includes any one of the above-mentioned compounds, or a combination of multiple of the above-mentioned compounds.

[0019] Optionally, the battery cell includes a positive electrode sheet, the positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, the thickness of the positive electrode film layer on one side being 0.01 mm to 0.07 mm.

[0020] It is understandable that when the thickness of the positive electrode film layer on the positive electrode current collector side is within this range, various impurity metals in the ionic state are more likely to migrate out of the positive electrode film layer and diffuse to the negative electrode (anode). That is, when the thickness of the positive electrode film layer is within this range, the path from the inside of the positive electrode film layer to the surface of the positive electrode film layer is short, which increases the risk of impurity ions dissolving and diffusing to the negative electrode, and then being reduced to metal foreign matter at the negative electrode to pierce the separator, leading to short-circuit discharge. This application adds a metal ion complexing agent to the electrolyte, which can solve the problem that batteries in this positive electrode film layer thickness range are prone to self-discharge.

[0021] Optionally, the power density of the battery cell is from 2000W / kg to 20000W / kg.

[0022] Generally, high-power batteries design lower coating weight on the positive electrode side. With reduced coating weight, the thickness of the positive electrode film becomes correspondingly thinner. Due to the thinner positive electrode film, impurity ions are more likely to dissolve and diffuse to the negative electrode, and then be reduced to metal foreign matter at the negative electrode, piercing the separator and causing short-circuit discharge. In other words, the power density of the battery in this application is within the above range, making it more prone to self-discharge problems. This application adds a metal ion complexing agent to the electrolyte, which can solve the problem of self-discharge problems in batteries with this power density.

[0023] Optionally, this application also provides a method for preparing a secondary battery, comprising: injecting an electrolyte into the secondary battery, wherein the electrolyte includes a metal ion complexing agent.

[0024] To enable the addition of metal ion complexing agents to the electrolyte of secondary batteries, these agents can be added to the electrolyte injected into the secondary battery. Specifically, the electrolyte, which includes a metal ion complexing agent, is injected inside the secondary battery. This inclusion of a metal ion complexing agent in the electrolyte, without altering the cell manufacturing process or affecting cell performance, can prevent self-discharge. The mechanism is that metal particles dissolved in the electrolyte at high potential are captured by the metal ion complexing agent and form stable complexes, preventing them from migrating to the anode and depositing as metal at low potential. This reduces the risk of metal foreign objects piercing the separator and causing battery self-discharge.

[0025] Optionally, the step of injecting electrolyte into the battery includes:

[0026] A first electrolyte is injected into the battery to obtain a first electrolyte-filled battery;

[0027] A second electrolyte is injected into the first electrolyte-filled battery to obtain a second electrolyte-filled battery.

[0028] The first electrolyte includes a metal ion complexing agent, and / or the second electrolyte includes a metal ion complexing agent.

[0029] It is understandable that multiple injections can be used during the process of injecting electrolyte into the battery. For example, at least two injections can be used. The electrolyte injected in the first injection may contain a metal ion complexing agent, or the electrolyte injected in the second injection may contain a metal ion complexing agent, or both the electrolyte injected in the first and second injections may contain a metal ion complexing agent.

[0030] For example, a first electrolyte can be injected into the battery to obtain a first electrolyte-filled battery, wherein the first electrolyte includes a metal ion complexing agent; a second electrolyte can be injected into the first electrolyte-filled battery to obtain a second electrolyte-filled battery, wherein the second electrolyte includes a metal ion complexing agent.

[0031] Optionally, the mass percentage of the metal ion complexing agent to the total mass of the electrolyte is 0.05% to 1%.

[0032] And / or, the metal ion complexing agent includes organic complexing agents and / or inorganic complexing agents.

[0033] It is understood that the electrolyte used for injection contains a metal ion complexing agent accounting for 0.05% to 1% of the total mass of the electrolyte.

[0034] Optionally, the mass percentage of the metal complexing agent in the first electrolyte to the total mass of the first electrolyte is w1, and the mass percentage of the metal complexing agent in the second electrolyte to the total mass of the second electrolyte is w2, wherein w1 < w2;

[0035] The mass of the first electrolyte is greater than the mass of the second electrolyte.

[0036] Generally, secondary batteries undergo a second electrolyte injection process during manufacturing. For example, in the production of lithium batteries, after the initial electrolyte injection, some air bubbles or incompletely wetted areas may remain inside the battery, which can affect its performance and lifespan. Therefore, a second electrolyte injection can further optimize the distribution of the electrolyte inside the battery, improving its electrochemical performance and stability.

[0037] Generally, during the second electrolyte injection, the amount of electrolyte injected in the first injection is greater than that in the second injection, with w1 < w2. This helps to reduce the viscosity of the electrolyte during the first injection. When the viscosity of the electrolyte is within a suitable range, it is beneficial for the electrolyte to penetrate into the battery.

[0038] Optionally, the mass percentage of the metal complexing agent in the first electrolyte relative to the total mass of the first electrolyte is w1, satisfying 0.05% ≤ w1 ≤ 0.1%.

[0039] And / or, the mass percentage of the metal complexing agent in the second electrolyte relative to the total mass of the second electrolyte is w2, satisfying 0.5% ≤ w2 ≤ 1%.

[0040] During multiple electrolyte injection processes, in the first injection, the mass percentage of the metal complexing agent in the first electrolyte relative to the total mass of the first electrolyte meets the aforementioned range. It is understood that adding a metal ion complexing agent to the electrolyte at a concentration within the aforementioned range, and maintaining an appropriate electrolyte viscosity, facilitates the electrolyte's penetration into the battery interior.

[0041] Optionally, this application also provides an electrolyte comprising a metal ion complexing agent.

[0042] The metal ion complexing agent includes organic complexing agents and / or inorganic complexing agents;

[0043] The organic complexing agent includes at least one of o-phenanthroline, crown ether compounds, oxalic acid, citric acid, tartaric acid, ethylenediaminetetraacetic acid, and deferoxamine;

[0044] And / or, the inorganic complexing agent includes at least one of sodium oxalate, sodium citrate, sodium tartrate, and sodium ethylenediaminetetraacetate.

[0045] It is understandable that the electrolyte contains a metal ion complexing agent. The metal complex can complex impurity metal ions. When this electrolyte is applied to a battery, it can combine with the impurity metal ions dissolved in the electrolyte to form a stable complex, reducing the risk of impurity metal ions precipitating as dendritic metal foreign objects at the anode and piercing the separator, thus causing the battery to self-discharge.

[0046] Optionally, the mass percentage of the metal ion complexing agent to the total mass of the electrolyte is 0.05% to 1%.

[0047] Optionally, this application also provides an electrical device, which includes the battery as described above.

[0048] The battery of this application includes a positive electrode, a negative electrode, and an electrolyte. At least a portion of the structure of the positive and negative electrodes is located in the electrolyte. The electrolyte includes a metal ion complexing agent, which includes organic and / or inorganic complexing agents. The organic complexing agent includes at least one of o-phenanthroline, crown ether compounds, oxalic acid, citric acid, tartaric acid, ethylenediaminetetraacetic acid, and deferoxamine, and / or the inorganic complexing agent includes at least one of sodium oxalate, sodium citrate, sodium tartrate, and sodium ethylenediaminetetraacetic acid. The metal ion complexing agent in the electrolyte of this application can combine with impurity metal ions in the electrolyte to form stable complexes, reducing the risk of impurity metal ions depositing as dendritic metal foreign matter at the anode, piercing the separator, and causing battery self-discharge. It is understood that a small amount of metal impurities will inevitably be introduced during cell production. If these metal impurities are located at the cathode, they will undergo electrochemical oxidation at high potential and dissolve into impurity metal ions (such as Fe). 2+ / Cr 2+ / Cu 2+ The impurity metal ions diffuse through the diaphragm to the anode surface and precipitate as dendritic metallic foreign matter at the low anode potential. Metal complexing agents can combine with impurity metal ions dissolved in the electrolyte to form stable complexes, rendering the impurity metal ions electrochemically inactive and thus reducing the risk of their precipitation on the anode surface. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0050] Figure 1 This is a schematic diagram illustrating the principle of the complexing agent in the electrolyte of this application inhibiting metal deposition;

[0051] Figure 2 This is a diagram showing the metal particle precipitation phenomenon at the anode interface in Comparative Example 1 and Example 1 of this application;

[0052] Figure 3 This is a schematic diagram of a battery cell according to one embodiment of this application;

[0053] Figure 4 yes Figure 3 An exploded view of a battery cell according to one embodiment of this application is shown.

[0054] Figure 5 This is a schematic diagram of a battery module according to one embodiment of this application;

[0055] Figure 6This is a schematic diagram of a battery pack according to one embodiment of this application;

[0056] Figure 7 yes Figure 6 An exploded view of a battery pack according to one embodiment of this application is shown;

[0057] Figure 8 This is a schematic diagram of an electrical device in which a single battery cell is used as a power source according to one embodiment of this application.

[0058] Explanation of icon numbers:

[0059] label name label name 1 battery pack 5 battery cell 2 Upper box 51 case 3 Lower box 52 Electrode assembly 4 Battery Module 53 cover plate 10 metal particles

[0060] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0061] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0062] The following detailed description, with appropriate reference to the accompanying drawings, discloses the battery cell, method for preparing the secondary battery, electrolyte, and electrical device of this application. However, unnecessary details may be omitted. For example, detailed descriptions of well-known facts and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0063] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0064] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0065] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0066] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0067] Battery self-discharge refers to the phenomenon where a battery's internal chemical energy is spontaneously converted into electrical energy and gradually lost when it is not connected to an external circuit. Self-discharge reduces the battery's usable capacity, causes voltage drop, and affects the normal use of equipment.

[0068] For example, precipitation-type physical self-discharge defects are caused by particles such as stainless steel, iron, and copper introduced during cathode powder production or battery manufacturing processes dissolving at high potential and diffusing to the anode, where they are reduced to metallic foreign objects that pierce the separator. Self-discharge phenomena caused by the above reasons may occur during battery use and are difficult to detect directly during battery manufacturing.

[0069] To reduce the risk of self-discharge in batteries, this application proposes a battery comprising a positive electrode, a negative electrode, and an electrolyte. At least a portion of the structures of the positive and negative electrodes are located in the electrolyte. The electrolyte comprises a metal ion complexing agent. The metal ion complexing agent comprises an organic complexing agent and / or an inorganic complexing agent. The organic complexing agent comprises at least one of o-phenanthroline, crown ether compounds, oxalic acid, citric acid, tartaric acid, ethylenediaminetetraacetic acid, and deferoxamine. And / or, the inorganic complexing agent comprises at least one of sodium oxalate, sodium citrate, sodium tartrate, and sodium ethylenediaminetetraacetic acid.

[0070] Metal ion complexing agents are compounds that bind with metal ions to form stable complexes, thereby rendering the metal ions electrochemically inactive. It is understood that metal ion complexing agents are selective, complexing with transition metal ions, such as divalent and trivalent transition metal ions, but not with alkali metal ions, such as monovalent lithium ions.

[0071] Organic complexing agents are a class of organic substances that can form stable complexes with metal ions.

[0072] Inorganic complexing agents are a class of inorganic substances that can form stable complexes with metal ions.

[0073] Crown ether compounds are a class of macrocyclic compounds containing multiple oxygen atoms. Their basic unit is ethoxylation (-CH2CH2O-), such as 15-crown ether-5, which has a cyclic structure containing five ether oxygen atoms.

[0074] To distinguish the types of metal ions, this application refers to metals that are not intended to be introduced into the battery system as impurity metals, and their ionic states as impurity metal ions.

[0075] The metal ion complexing agent in the electrolyte of this application can combine with impurity metal ions in the electrolyte to form a stable complex, thereby reducing the risk of impurity metal ions precipitating as dendritic metal foreign matter at the anode and piercing the separator, leading to battery self-discharge.

[0076] It is understandable that a small amount of metallic impurities will inevitably be introduced during battery cell production, such as... Figure 1 As shown, if these metallic impurities are located at the cathode, they will undergo electrochemical oxidation and dissolve into impurity metal ions (such as Fe) at a high potential. 2+ / Cr2+ / Cu 2+ The impurities then diffuse through the diaphragm to the anode surface, where they precipitate as dendritic metallic foreign matter at the low anode potential. Metal complexing agents can combine with impurity metal ions in the electrolyte to form stable complexes, rendering the impurity metal ions electrochemically inactive and thus reducing the risk of their precipitation on the anode surface.

[0077] The metal ion complexing agent in this application includes organic complexing agents and / or inorganic complexing agents. That is, the metal ion complexing agent includes an organic complexing agent, or the metal ion complexing agent includes an inorganic complexing agent, or the metal ion complexing agent includes both organic and inorganic complexing agents.

[0078] In one embodiment, the organic complexing agent in this application includes o-phenanthroline, crown ether compounds, oxalic acid, citric acid, tartaric acid, ethylenediaminetetraacetic acid, and deferoxamine (the chemical formula of deferoxamine is C...). 25 H 48 At least one of N6O8. That is, the organic complexing agent includes any one of the above, or the organic complexing agent includes a combination of the above.

[0079] In one embodiment, the inorganic complexing agent in this application includes at least one of sodium oxalate, sodium citrate, sodium tartrate, and sodium ethylenediaminetetraacetate. That is, the inorganic complexing agent includes any one of the above, or a combination of multiple of the above.

[0080] Detection method for metal ion complexing agents: The metal ion complexing agents in this application include organic and inorganic complexing agents. From the several metal ion complexing agents given, each compound contains an organic functional group. In the case where it is unknown whether the electrolyte contains a metal ion complexing agent, infrared spectroscopy can be used to determine the organic functional groups and chemical bonds of the compounds in the electrolyte, inferring possible components. Then, the analytical methods corresponding to the suspected components can be used to further analyze whether the component is included. It is understood that the analytical methods for possible components can refer to the existing disclosed methods.

[0081] For example, taking o-phenanthroline as an example, its structural formula is: When using infrared spectroscopy, the presence of CH bond vibration peaks and C=N bond vibration peaks in the benzene ring suggests the possible presence of o-phenanthroline. If the presence of o-phenanthroline is assumed, it can be detected using surface-enhanced Raman spectroscopy (e.g., the method in CN201210363302.6), or based on the interaction between o-phenanthroline and Fe. 2+ A red complex is formed, which has a maximum absorption peak at 510 nm, using Fe. 2+ The property of forming stable complexes with o-phenanthroline in solutions with pH 2–9 was used for qualitative and quantitative analysis by measuring absorbance with a spectrophotometer.

[0082] Similarly, crown ether compounds have a COC structure. If a COC bond vibration peak appears during infrared spectroscopy, it is inferred that a crown ether compound may be present. The electrolyte sample is then injected into a GC-MS / HPLC-MS system for analysis using gas chromatography-mass spectrometry or liquid chromatography-mass spectrometry to obtain a mass spectrum. The substances of each component are identified based on the mass spectra of the detected components and the corresponding spectral library search results. After confirming the specific crown ether component, standard solutions of different concentration gradients of the target crown ether substance are prepared. Using the electrolyte as the analyte, GC-MS / HPLC-MS is used to analyze both the standard solutions and the analyte. The mass of the target substance in the analyte is calculated based on the standard curve, thus obtaining the concentration of the target substance.

[0083] Similarly, infrared spectroscopy can be used to analyze inorganic complexes. For example, oxalate has a carboxylic acid bond vibration peak. If a carboxylic acid bond vibration peak appears when infrared spectroscopy is used, it can be inferred that oxalic acid or its salts may be present. Ion chromatography can be used to quantitatively analyze oxalic acid and its salts.

[0084] In one embodiment, the mass percentage of the metal ion complexing agent to the total mass of the electrolyte is 0.01% to 1%.

[0085] In this application, the mass percentage of the metal ion complexing agent in the electrolyte of the battery to the total mass of the electrolyte meets the above range, which can effectively complex impurity metal ions and reduce the risk of impurity metal ions precipitating as dendritic metal foreign objects at the anode and piercing the separator, leading to battery self-discharge.

[0086] It is understandable that the metal ion complexing agent in the electrolyte of the battery will be gradually consumed. That is, the amount of metal ion complexing agent gradually decreases throughout the entire process from battery manufacturing to battery use. For example, when the amount of metal ion complexing agent added is small, it may be completely consumed. The dissolution and precipitation of metal impurities in the battery is a long-term process. The long-term presence of metal ion complexing agent in the battery electrolyte is beneficial for the long-term effective complexation of impurity metal ions.

[0087] The values ​​in the range of 0.01% to 1% include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 0.01%, 0.02%, 0.05%, 0.07%, 0.1%, 0.3%, 0.5%, 0.7%, 0.9%, 1%, etc., as well as the range values ​​between any two of the above point values.

[0088] In one embodiment, the crown ether compound includes at least one of 18-crown ether-6, benzo-18-crown ether-6, dibenzo-18-crown ether-6, 12-crown ether-4, aza-12-crown ether-4, and 15-crown ether-5.

[0089] The crown ether compound in this application includes at least one of the above-mentioned compounds. That is, it includes any one of the above-mentioned compounds, or a combination of multiple of the above-mentioned compounds.

[0090] In one embodiment, the battery cell includes a positive electrode sheet, which includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, wherein the thickness of the positive electrode film layer on one side is 0.01 mm to 0.07 mm.

[0091] The positive electrode film layer refers to the active material layer located on one or both sides of the current collector in the positive electrode sheet. This active material layer includes the positive electrode active material. The thickness of the positive electrode film layer refers to the thickness of the active material layer on the current collector side. Its thickness can be measured by scanning electron microscopy (SEM). That is, by observing the cross-section of the film layer, the thickness of the film layer can be accurately measured. This is a commonly used microscopic detection method.

[0092] It is understandable that when the thickness of the positive electrode film layer on the positive electrode current collector side is within this range, various impurity metals in the ionic state are more likely to migrate out of the positive electrode film layer and diffuse to the negative electrode (anode). That is, when the thickness of the positive electrode film layer is within this range, the path from the inside of the positive electrode film layer to the surface of the positive electrode film layer is short, which increases the risk of impurity ions dissolving and diffusing to the negative electrode, and then being reduced to metal foreign matter at the negative electrode to pierce the separator, leading to short-circuit discharge. This application adds a metal ion complexing agent to the electrolyte, which can solve the problem that batteries in this positive electrode film layer thickness range are prone to self-discharge.

[0093] The values ​​in the range of 0.01mm to 0.07mm include the minimum and maximum values ​​of this range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 0.01mm, 0.02mm, 0.03mm, 0.04mm, 0.05mm, 0.06mm, 0.07mm, etc., as well as the range values ​​between any two of the above point values.

[0094] In one embodiment, the power density of the battery cell is from 2000 W / kg to 20000 W / kg.

[0095] Power density, calculated as follows: Power density = Power / Volume or Power / Mass. The units of power density are: if calculated by volume, typically watts per cubic meter (W / m³) or kilowatts per liter (kW / L); if calculated by mass, typically watts per kilogram (W / kg). Power density is a key indicator for evaluating the performance of energy systems; high power density means that equipment can provide more power in a smaller volume or with a lighter mass. Power density can be measured using the HPPC pulse charge / discharge test. The test conditions can be the nominal operating conditions of the secondary battery, including discharge rate, test temperature, test SOC, charging or discharging time, and protection voltage range. During the test, the charging or discharging voltage of the battery is recorded, and the power is calculated using the following formulas: Discharge power capability = Vmin × (VOCdis - Vmin) / Rdis; Charging power capability = Vmax × (Vmax - VOCcha) / Rcha; Rdis = -(Vt1 - Vt0) / (It1 - It0); Rcha = (Vt3 - Vt2) / (It3 - It2); Where: Vmax and Vmin are the charging or discharging cutoff voltages (V); VOCcha and VOCdis are the open-circuit voltages of the corresponding SOCs before charging or discharging (V), VOCdis ≠ VOCcha; Rcha and Rdis are the charging or discharging internal resistances of the corresponding SOCs (Ω); t0 and t2 are the times when discharging or charging begins (s); t1 and t3 are the times after 10 seconds of discharging or charging (s).

[0096] Generally, high-power batteries design lower coating weight on the positive electrode side. With reduced coating weight, the thickness of the positive electrode film becomes correspondingly thinner. Due to the thinner positive electrode film, impurity ions are more likely to dissolve and diffuse to the negative electrode, and then be reduced to metal foreign matter at the negative electrode, piercing the separator and causing short-circuit discharge. In other words, the power density of the battery in this application is within the above range, making it more prone to self-discharge problems. This application adds a metal ion complexing agent to the electrolyte, which can solve the problem of self-discharge problems in batteries with this power density.

[0097] The values ​​in the range of 2000W / kg to 20000W / kg include the minimum and maximum values ​​of this range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 2000W / kg, 3000W / kg, 5000W / kg, 8000W / kg, 10000W / kg, 15000W / kg, 20000W / kg, etc., as well as the range values ​​between any two of the above point values.

[0098] In one embodiment, this application also provides a method for preparing a secondary battery, comprising: injecting an electrolyte into the secondary battery, the electrolyte comprising a metal ion complexing agent.

[0099] To enable the addition of metal ion complexing agents to the electrolyte of secondary batteries, these agents can be added to the electrolyte injected into the secondary battery. Specifically, a secondary battery is prepared, and an electrolyte containing a metal ion complexing agent is injected inside. This electrolyte, without altering the cell manufacturing process or affecting cell performance, can prevent self-discharge. The mechanism is that metal particles dissolved in the electrolyte at high potential are captured by the metal ion complexing agent and form stable complexes, preventing them from migrating to the anode and depositing as metal at low potential. This reduces the risk of metal foreign objects piercing the separator and causing battery self-discharge.

[0100] In one embodiment, the step of injecting electrolyte into the battery includes: injecting a first electrolyte into the battery to obtain a first electrolyte-filled battery; injecting a second electrolyte into the first electrolyte-filled battery to obtain a second electrolyte-filled battery; the first electrolyte includes a metal ion complexing agent, and / or the second electrolyte includes a metal ion complexing agent.

[0101] It is understandable that multiple injections can be used during the process of injecting electrolyte into the battery. For example, at least two injections can be used. The electrolyte injected in the first injection may contain a metal ion complexing agent, or the electrolyte injected in the second injection may contain a metal ion complexing agent, or both the electrolyte injected in the first and second injections may contain a metal ion complexing agent.

[0102] For example, a first electrolyte can be injected into the battery to obtain a first electrolyte-filled battery, wherein the first electrolyte includes a metal ion complexing agent; a second electrolyte can be injected into the first electrolyte-filled battery to obtain a second electrolyte-filled battery, wherein the second electrolyte includes a metal ion complexing agent.

[0103] In one embodiment, the mass percentage of the metal ion complexing agent to the total mass of the electrolyte is 0.05% to 1%; and / or, the metal ion complexing agent includes organic complexing agents and / or inorganic complexing agents.

[0104] It is understood that the electrolyte used for injection contains a metal ion complexing agent accounting for 0.05% to 1% of the total mass of the electrolyte.

[0105] In one embodiment, the mass percentage of the metal complexing agent in the first electrolyte is w1, and the mass percentage of the metal complexing agent in the second electrolyte is w2, where w1 < w2; and / or, the mass of the first electrolyte is less than the mass of the second electrolyte.

[0106] Generally, secondary batteries undergo a second electrolyte injection process during manufacturing. For example, in the production of lithium batteries, after the initial electrolyte injection, some air bubbles or incompletely wetted areas may remain inside the battery, which can affect its performance and lifespan. Therefore, a second electrolyte injection can further optimize the distribution of the electrolyte inside the battery, improving its electrochemical performance and stability.

[0107] Generally, during the second electrolyte injection, the amount of electrolyte injected in the first injection is greater than that in the second injection, with w1 < w2. This helps to reduce the viscosity of the electrolyte during the first injection. When the viscosity of the electrolyte is within a suitable range, it is beneficial for the electrolyte to penetrate into the battery.

[0108] In one embodiment, the mass percentage of the metal complexing agent in the first electrolyte is w1, satisfying 0.05% ≤ w1 ≤ 0.1%; and / or, the mass percentage of the metal complexing agent in the second electrolyte is w2, satisfying 0.5% ≤ w2 ≤ 1%.

[0109] During multiple electrolyte injection processes, in the first injection, the mass percentage of the metal complexing agent in the first electrolyte relative to the total mass of the first electrolyte meets the aforementioned range. It is understood that adding a metal ion complexing agent to the electrolyte at a concentration within the aforementioned range, and maintaining an appropriate electrolyte viscosity, facilitates the electrolyte's penetration into the battery interior.

[0110] In the above 0.05%≤w1≤0.1%, the values ​​include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, etc., as well as the range values ​​between any two of the above point values.

[0111] In the above 0.5%≤w2≤1%, the values ​​include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the embodiments, and 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, etc., as well as the range values ​​between any two of the above point values.

[0112] In one embodiment, this application also provides an electrolyte comprising a metal ion complexing agent, which includes an organic complexing agent and / or an inorganic complexing agent; the organic complexing agent includes at least one selected from o-phenanthroline, crown ether compounds, oxalic acid, citric acid, tartaric acid, ethylenediaminetetraacetic acid, and deferoxamine; and / or, the inorganic complexing agent includes at least one selected from sodium oxalate, sodium citrate, sodium tartrate, and sodium ethylenediaminetetraacetic acid.

[0113] It is understandable that the electrolyte contains metal ion complexing agents. Metal complexes can complex impurity metal ions. When this electrolyte is applied to a battery, it can combine with the impurity metal ions in the electrolyte to form stable complexes, reducing the risk of impurity metal ions depositing as dendritic metal foreign objects at the anode, piercing the separator and causing battery self-discharge.

[0114] In one embodiment, the mass percentage of the metal ion complexing agent to the total mass of the electrolyte is 0.05% to 1%.

[0115] In one embodiment, this application also provides an electrical device, which includes a battery as described above.

[0116] In addition, the following description of the battery (cell battery, battery module, battery pack) and electrical device of this application will be made with appropriate reference to the accompanying drawings.

[0117] In one embodiment of this application, a battery cell is provided.

[0118] Typically, a battery cell includes a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor of ions between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through. The separator described above is the improved separator of this application.

[0119] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector.

[0120] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0121] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0122] In some embodiments, when the electrode assembly is a lithium-ion battery, the positive electrode active material may be a positive electrode active material known in the art for lithium-ion batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0123] During the charging and discharging process of a battery, Li undergoes insertion / extraction and consumption, resulting in varying molar Li content at different discharge states. In the examples of cathode materials in this application, the molar Li content refers to the initial state of the material, i.e., the state before feeding. When the cathode material is applied to the battery system, the molar Li content changes after charge-discharge cycles.

[0124] In the examples of cathode materials in this application, the molar content of O is only a theoretical value. Oxygen release from the crystal lattice will cause changes in the molar content of oxygen, and the actual molar content of O will fluctuate.

[0125] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0126] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0127] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0128] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0129] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0130] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0131] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0132] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0133] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0134] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0135] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0136] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not specify any particular type of electrolyte; it can be selected according to requirements.

[0137] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0138] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0139] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0140] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0141] In some embodiments, the outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell can also be a flexible package, such as a pouch. The material of the flexible package can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0142] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 3 The example shown is a square-structured battery cell 5.

[0143] In some implementations, refer to Figure 4 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in a single battery cell 5 may be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0144] In some implementations, individual battery cells can be assembled into a battery module. The number of individual battery cells contained in a battery module can be one or more, and the specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0145] Figure 5 This is battery module 4, used as an example. (See reference...) Figure 5 In battery module 4, multiple battery cells 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0146] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0147] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0148] Figure 6 and Figure 7 This is battery pack 1 as an example. (See reference...) Figure 6 and Figure 7 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0149] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0150] As an electrical device, you can choose individual battery cells, battery modules, or battery packs according to your usage requirements.

[0151] Figure 8 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of individual battery cells, a battery pack or battery module can be used.

[0152] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell as their power source.

[0153] Example

[0154] Example 1

[0155] Positive electrode sheet: Lithium iron phosphate, conductive carbon black, polyvinylidene fluoride, and surfactant (polyvinylpyrrolidone) are mixed in a mass ratio of 97.2%:0.7%:1.8%:0.3%, and then N-methylpyrrolidone solvent is added and stirred. The uniformly stirred slurry is coated on both sides of aluminum foil, and after cold pressing and cutting, the positive electrode sheet is obtained. Furthermore, impurity metal particles (Fe particles, particle size 5μm-25μm, accounting for 500 parts per million of the total mass of the positive electrode powder) are added to the formulation of the positive electrode sheet.

[0156] Negative electrode sheet: Artificial graphite, conductive carbon black, carboxymethyl cellulose (CMC), polystyrene rubber, and binder are mixed evenly in a mass ratio of 96.2:0.4:0.9:2:0.5. Deionized water is then added to the mixture for kneading and stirring. The uniformly stirred slurry is coated on both sides of copper foil and then cold-pressed and cut to obtain the negative electrode sheet.

[0157] Separator: A 7μm thick polyethylene membrane is used as the separator, with CCS (ceramic coating) and PCS (polymer coating) coatings on the surface.

[0158] Electrolyte:

[0159] The first electrolyte solution is prepared by solvents including ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1, and electrolyte salts including LiPF6:LiFSI (2:8) with a concentration of 1 mol / L.

[0160] The second electrolyte solution includes: solvents such as ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1; electrolyte salts such as LiPF6:LiFSI (2:8) with a concentration of 1 mol / L; and metal ion complexing agent such as o-phenanthroline with an addition percentage of 1%.

[0161] The metal ion complexing agent (o-phenanthroline) was dissolved in the second electrolyte solution at 25°C with stirring, and the addition ratio was 1%. The weight ratio of the first and second electrolyte solutions was 9:1. The formula for calculating the mass percentage of the metal ion complexing agent in the total electrolyte mass of the battery is: W = (w1×m1 + w2×m2) / (m1 + m2) × 100%, where w1 is the mass percentage of the metal ion complexing agent in the first electrolyte solution; m1 is the mass of the first electrolyte solution injected into the battery; w2 is the mass percentage of the metal ion complexing agent in the second electrolyte solution; and m2 is the mass of the second electrolyte solution injected into the battery. For example, when w1 = 0, w2 = 1%, and m1 / m2 = 9:1, then W = (0 × m1 + 0.01 × m2) / (m1 + m2) × 100% = 0.1%.

[0162] Test methods and procedures for metal ion complexing agents in electrolytes: When it is unknown whether a metal ion complexing agent is present in the electrolyte, infrared spectroscopy can be used to determine the organic functional groups and chemical bonds of the compounds in the electrolyte, inferring possible components. Then, the analytical methods for suspected components can be used for further analysis to determine whether the component is present and to perform quantitative analysis. For example, taking o-phenanthroline as an example, if a benzene ring CH bond vibration peak and a C=N bond vibration peak appear during infrared spectroscopy analysis, it is inferred that o-phenanthroline may be present. If the presence of o-phenanthroline is assumed, it can be detected by surface-enhanced Raman spectroscopy (e.g., the method in CN201210363302.6), or based on the interaction between o-phenanthroline and Fe... 2+ A red complex is formed, which has a maximum absorption peak at 510 nm, using Fe. 2+ The property of forming stable complexes with o-phenanthroline in solutions with pH 2–9 can be used for qualitative and quantitative analysis by measuring absorbance with a spectrophotometer. It is understood that, depending on the type of metal ion complexing agent added, existing detection methods can be used to detect the metal ion complexing agent in the electrolyte. For example, the test method for oxalic acid can refer to GB / T 1626-2008, using acid-base titration with phenolphthalein as an indicator and titration with a standard sodium hydroxide solution.

[0163] Assembly: The electrodes are arranged in the order of "separator-negative electrode-separator-positive electrode". One end of the positive electrode, negative electrode, and two separators is fixed to the discharge roller, and the other end is stacked together and fixed to the winding shaft. The winding shaft is rotated by a motor to wind the positive electrode, negative electrode, and two separators to obtain a wound battery (bare cell). The bare cell then undergoes Mylar (polyester film) coating, casing, welding, helium detection, primary electrolyte injection, wetting, formation, secondary electrolyte injection, sealing nail welding, high-temperature aging, settling, and capacity testing (charging and discharging the battery under full charge conditions) to obtain the finished hard-shell cell.

[0164] Example 2

[0165] Based on Example 1, during the first injection, the mass percentage w1 of the metal ion complexing agent was 0.1%; during the second injection, the mass percentage w2 of the metal ion complexing agent was 1%; and the total mass percentage W of the metal ion complexing agent in the electrolyte was 0.19%.

[0166] Example 3

[0167] Based on Example 1, during the first injection, the mass percentage w1 of the metal ion complexing agent was 1.1%; during the second injection, the mass percentage w2 of the metal ion complexing agent was 0%; and the total mass percentage W of the metal ion complexing agent in the electrolyte was 1%.

[0168] Example 4

[0169] Based on Example 1, during the first injection, the mass percentage w1 of the metal ion complexing agent was 0.056%; during the second injection, the mass percentage w2 of the metal ion complexing agent was 0; and the total mass percentage W of the metal ion complexing agent in the electrolyte was 0.05%.

[0170] Example 5

[0171] Based on Example 1, o-phenanthroline was replaced with oxalic acid. During the first injection, the mass percentage w1 of the metal ion complexing agent was 0.1%; during the second injection, the mass percentage w2 of the metal ion complexing agent was 0%; and the total mass percentage W of the metal ion complexing agent in the electrolyte was 0.09%.

[0172] Example 6

[0173] Based on Example 5, oxalic acid was replaced with sodium oxalate. During the first injection, the mass percentage w1 of the metal ion complexing agent was 0.1%; during the second injection, the mass percentage w2 of the metal ion complexing agent was 0; and the total mass percentage W of the metal ion complexing agent in the electrolyte was 0.09%.

[0174] Example 7

[0175] Based on Example 1, o-phenanthroline was adjusted to 15-crown ether-5. During the first injection, the mass percentage w1 of the metal ion complexing agent was 1%; during the second injection, the mass percentage w2 of the metal ion complexing agent was 0%; and the total mass percentage W of the metal ion complexing agent in the electrolyte was 0.9%.

[0176] Comparative Example 1

[0177] Based on Example 1, no metal ion complexing agent was added to the electrolyte during the injection process.

[0178] Long-term self-discharge test: The temperature was maintained at 25℃, and the charge and discharge settings were set after 70% SOC. The voltage drop ΔU was monitored during the 7-day storage period.

[0179] Table 1 List of Battery Storage Self-Discharge Tests

[0180]

[0181] As can be seen from Table 1, after adding a metal ion complexing agent to the battery electrolyte and storing the battery for a period of time, the battery in the example showed a significant inhibitory effect on self-discharge compared to the battery without the addition of a metal ion complexing agent.

[0182] Disassemble the batteries of Comparative Example 1 and Example 1, such as Figure 2As shown, observing the anode interface, it can be seen that the electrolyte in Comparative Example 1 is a normal electrolyte (without added metal ion complexing agent), and a large number of metal particles 10 appear at its anode interface. In contrast, the electrolyte in Example 1 contains added metal ion complexing agent, and the number of metal particles precipitated at its anode interface is significantly less than that in Comparative Example 1.

[0183] Adding metal ion complexing agents to the electrolyte can mitigate voltage drop and significantly reduce the amount of metal particles deposited. This indicates that the electrolyte contains metal ion complexing agents, which can combine with impurity metal ions in the electrolyte to form stable complexes, reducing the risk of impurity metal ions depositing as dendritic metal foreign objects at the anode, piercing the separator, and causing battery self-discharge.

[0184] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A battery cell, characterized in that, The battery cell includes a positive electrode, a negative electrode, and an electrolyte. At least a portion of the structures of the positive and negative electrodes are located in the electrolyte, which includes a metal ion complexing agent. The metal ion complexing agent includes organic complexing agents and / or inorganic complexing agents; The organic complexing agent includes at least one of o-phenanthroline, crown ether compounds, oxalic acid, citric acid, tartaric acid, ethylenediaminetetraacetic acid, and deferoxamine; And / or, the inorganic complexing agent includes at least one of sodium oxalate, sodium citrate, sodium tartrate, and sodium ethylenediaminetetraacetate.

2. The battery cell as described in claim 1, characterized in that, The mass percentage of the metal ion complexing agent to the total mass of the electrolyte is 0.01% to 1%.

3. The battery cell according to claim 1 or 2, wherein the crown ether compound comprises at least one of 18-crown ether-6, benzo-18-crown ether-6, dibenzo-18-crown ether-6, 12-crown ether-4, aza-12-crown ether-4, and 15-crown ether-5.

4. The battery cell according to any one of claims 1 to 3, characterized in that, The battery cell includes a positive electrode sheet, which includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, wherein the thickness of the positive electrode film layer on one side is 0.01 mm to 0.07 mm.

5. The battery cell according to any one of claims 1 to 4, characterized in that, The power density of the battery cell is between 2000W / kg and 20000W / kg.

6. A method for preparing a secondary battery, characterized in that, include: An electrolyte is injected into the secondary battery, the electrolyte comprising a metal ion complexing agent.

7. The method for preparing a secondary battery as described in claim 6, characterized in that, The step of injecting electrolyte into the secondary battery includes: A first electrolyte is injected into the battery to obtain a first electrolyte-filled battery; A second electrolyte is injected into the first electrolyte-filled battery to obtain a second electrolyte-filled battery. The first electrolyte includes the metal ion complexing agent, and / or the second electrolyte includes the metal ion complexing agent.

8. The method for preparing a secondary battery as described in claim 6 or 7, characterized in that, The mass percentage of the metal ion complexing agent to the total mass of the electrolyte is 0.05% to 1%. And / or, the metal ion complexing agent includes organic complexing agents and / or inorganic complexing agents.

9. The method for preparing a secondary battery as described in claim 7 or 8, characterized in that, The mass percentage of the metal complexing agent in the first electrolyte to the total mass of the first electrolyte is w1, and the mass percentage of the metal complexing agent in the second electrolyte to the total mass of the second electrolyte is w2, wherein w1 < w2; The mass of the first electrolyte is greater than the mass of the second electrolyte.

10. The method for preparing a secondary battery according to any one of claims 7 to 9, characterized in that, The mass percentage of the metal complexing agent in the first electrolyte relative to the total mass of the first electrolyte is w1, which satisfies 0.05% ≤ w1 ≤ 0.1%. And / or, the mass percentage of the metal complexing agent in the second electrolyte relative to the total mass of the second electrolyte is w2, satisfying 0.5% ≤ w2 ≤ 1%.

11. An electrolyte, characterized in that, The electrolyte includes a metal ion complexing agent. The metal ion complexing agent includes organic complexing agents and / or inorganic complexing agents; The organic complexing agent includes at least one of o-phenanthroline, crown ether compounds, oxalic acid, citric acid, tartaric acid, ethylenediaminetetraacetic acid, and deferoxamine; And / or, the inorganic complexing agent includes at least one of sodium oxalate, sodium citrate, sodium tartrate, and sodium ethylenediaminetetraacetate.

12. The electrolyte as described in claim 11, characterized in that, The mass percentage of the metal ion complexing agent to the total mass of the electrolyte is 0.05% to 1%.

13. An electrical appliance, characterized in that, The electrical device includes a battery cell as described in any one of claims 1 to 5.

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