Dual-ion battery and electric device

Abstract

The invention provides a dual-ion battery and an electric device. The dual-ion battery comprises an electrolyte and a positive pole piece, the electrolyte comprises lithium tetrafluoroborate, the positive pole piece comprises an artificial graphite positive active material, and the graphitization degree of the artificial graphite positive active material is 70%-90%. The dual-ion battery has excellent cycle performance and long service life.

Description

Technical Field

[0001] The present application relates to the technical field of electrochemical batteries, and in particular to a dual-ion battery and an electrical device. Background Art

[0002] Dual-ion batteries (DIBs) have become a research focus in recent years due to their high operating voltage, high charge cutoff voltage, high material availability, low cost, good safety, fast charging, and applicability for large-scale energy storage. However, their poor cycling performance has limited their further application. Summary of the Invention

[0003] The present application is made in view of the above-mentioned problems, and its purpose is to provide a dual-ion battery, aiming to effectively improve the cycle stability of the dual-ion battery, improve the cycle performance of the battery, and extend the service life of the battery.

[0004] A first aspect of the present application provides a dual-ion battery, which includes an electrolyte and a positive electrode plate. The electrolyte contains lithium tetrafluoroborate, and the positive electrode plate includes an artificial graphite positive electrode active material. The degree of graphitization of the artificial graphite positive electrode active material is 70%-90%.

[0005] During the cycle of the dual-ion battery, the anions in the electrolyte will continuously undergo the process of intercalation / deintercalation of the positive electrode graphite. The process of anion intercalation / deintercalation of the positive electrode graphite will affect the cycle performance of the battery. The main factors affecting the process of anion intercalation / deintercalation of the positive electrode graphite are the radius of the anion and the interlayer spacing of the positive electrode graphite. The present application uses tetrafluoroborate anions in combination with artificial graphite with a graphitization degree of 70%-90%, which can increase the speed and stability of anion intercalation / deintercalation of the positive electrode graphite, reduce the impedance of the positive electrode sheet during the cycle, and improve the cycle performance of the battery.

[0006] In any embodiment, the degree of graphitization of the artificial graphite positive electrode active material is 80%-85%.

[0007] In any embodiment, the Raman spectrum of the artificial graphite positive active material is 1575 cm -1 to 1600cm -1 The peak area A G and 1255cm -1 to 1355cm -1 The peak area A D Ratio A G / A D It is 0.7-1.

[0008] Controlling the AG / AD of the artificial graphite positive electrode active material within a suitable range, on the one hand, a small AG / AD means the material has a high degree of defect or disorder, and the material has relatively more storage active sites, which improves the specific capacity of the material. At the same time, the material has a high degree of defect, which is beneficial to improving the rate performance of the material. On the other hand, the material has an AG / AD within a suitable range to avoid side reactions between the electrolyte and the positive electrode sheet caused by an excessive number of defects, which affects the kinetic performance and cycle performance of the battery.

[0009] In any embodiment, the artificial graphite positive active material includes mesopores, and the pore diameter of the mesopores is 13 nm to 20 nm.

[0010] In any embodiment, the pore size of the mesopore is 15 nm-17 nm.

[0011] The mesopores in artificial graphite positive electrode active materials provide space for anions to expand and contract, shortening the bulk transmission path of anions, which is beneficial to increasing the density of active sites such as end face and basal surface defects in the material, making it easier for anions to enter the graphite interlayer to complete the electrode reaction, improving the battery's kinetic performance and improving the battery's cycle performance.

[0012] In any embodiment, the artificial graphite positive active material satisfies at least one of the following:

[0013] (1) The volume distribution particle size Dv50 of the artificial graphite positive electrode active material is 10 μm-30 μm;

[0014] (2) The specific surface area of ​​the artificial graphite positive electrode active material is 140m 2 / g-160m 2 / g.

[0015] By controlling the volume distribution particle size Dv50 of the artificial graphite positive electrode active material within an appropriate range, the artificial graphite positive electrode active material has a high surface area, the diffusion path of the anion is short and the embedding rate is too fast, and the battery has high capacity and high rate performance, which is beneficial to improving the battery's cycle capacity retention rate. At the same time, it is beneficial to improve the artificial graphite positive electrode active material has high structural stability, which is beneficial to improving the cycle stability of the positive electrode, improving the cycle stability of the battery, and extending the battery life.

[0016] Controlling the specific surface area of ​​the artificial graphite positive electrode active material within an appropriate range is beneficial to increasing the active sites on the surface of the artificial graphite positive electrode active material, shortening the ion diffusion path, improving the diffusion kinetics of ions, and improving the rate performance of the battery. At the same time, it is beneficial to reduce the side reactions between the artificial graphite positive electrode active material and the electrolyte, reduce the impedance of the positive electrode sheet during the cycle, and improve the cycle performance of the dual-ion battery.

[0017] In any embodiment, the molar solubility of the lithium tetrafluoroborate is 1.5 mol / L-4 mol / L.

[0018] High concentrations of lithium tetrafluoroborate help alleviate the collapse of the ordered graphite structure caused by solvent co-intercalation during the intercalation / deintercalation process of anions, thereby improving the structural stability of the positive electrode graphite during the cycle and enhancing the battery's cycling performance. High concentrations of lithium salts also reduce the likelihood of side reactions between the electrolyte and the positive electrode, as well as between materials with high defectivity and the electrolyte, thereby improving the battery's kinetic and cycling performance.

[0019] In any embodiment, the electrolyte includes a solvent, the solvent includes ethyl methyl carbonate and a sulfone compound, and the sulfone compound includes one or more of sulfolane, 3-methylsulfolane, and methyl ethyl sulfone.

[0020] The solvents of ethyl methyl carbonate and sulfolane, 3-methylsulfolane or methyl ethyl sulfone in the electrolyte can reduce and weaken the solvation effect of anions and the existing steric hindrance effect, reduce the embedding potential of anions, slow down the co-embedding effect of anions and solvents, improve the structural stability of the positive electrode during the cycle, improve the cycle stability of the battery, improve the cycle performance of the battery, and extend the service life of the battery. At the same time, the electrolyte containing ethyl methyl carbonate and sulfolane, 3-methylsulfolane or methyl ethyl sulfone can reduce the possibility of side reactions between the electrolyte and the positive electrode sheet, reduce the possibility of the positive electrode sheet impedance continuously increasing during the cycle, and improve the kinetic performance of the battery.

[0021] In any embodiment, the volume ratio of the ethyl methyl carbonate to the sulfone compound is 4:6-7:3.

[0022] In any embodiment, the volume ratio of the ethyl methyl carbonate to the sulfone compound is 5:5-6:4.

[0023] Controlling the volume ratio of ethyl methyl carbonate to sulfone compounds in the solvent within an appropriate range can reduce the solvation effect of the anion, which is beneficial to slowing down the co-embedding effect of the anion and the solvent, improving the structural stability of the positive electrode during the cycle, and improving the cycle stability of the battery.

[0024] In any embodiment, the dual-ion battery includes a negative electrode plate, the negative electrode plate includes a graphite negative electrode active material, and the Raman spectrum of the graphite negative electrode active material is 1575 cm -1 to 1600cm -1 The peak area A G and 1255cm -1 to 1355cm -1 The peak area A D Ratio AG / A D It is 0.1-0.5.

[0025] In any embodiment, the Raman spectrum of the graphite negative electrode active material is 1575 cm -1 to 1600cm -1 The peak area A G and 1255cm -1 to 1355cm -1 The peak area A D Ratio A G / A D It is 0.2-0.4.

[0026] Controlling the A of graphite anode active materials G / A D In the appropriate range, on the one hand, the small A G / A D The material has a high degree of defect or disorder, and the material has relatively more storage active sites, which improves the specific capacity of the material. At the same time, the material has a high degree of defect, which is beneficial to improve the rate performance of the material. On the other hand, the material has an A in a suitable range. G / A D , reducing the possibility of side reactions between materials with high defectivity and the electrolyte, and improving the cycle performance of the battery.

[0027] In any embodiment, the graphite negative electrode active material comprises micropores, and the pore diameter of the micropores is 0.1 nm to 0.7 nm.

[0028] In any embodiment, the pore size of the micropores is 0.3 nm to 0.5 nm.

[0029] The microporous structure provides space for the graphite material to expand and contract during the charge and discharge process, greatly suppressing the electrode damage caused by volume expansion during repeated charge and discharge, improving the structural stability of the negative electrode and the cycle performance of the battery. At the same time, the microporous structure also helps to enhance the transmission performance of ions and electrons, improving the battery's rate performance.

[0030] In any embodiment, the graphite negative electrode active material contains doping elements, and the doping elements include one or more of boron, phosphorus, nitrogen, and sulfur.

[0031] Doping elements can effectively adjust the electronic structure of carbon atoms in graphite negative electrode active materials, enhance the electron cloud distribution of carbon atoms, improve the transmission dynamics of lithium ions, improve the rate performance of materials, and improve the rate performance and cycle performance of batteries.

[0032] In any embodiment, the graphite negative electrode active material satisfies at least one of the following:

[0033] (1) The specific surface area of ​​the graphite negative electrode active material is 800m 2 / g-1000m 2 / g;

[0034] (2) The volume distribution particle size Dv50 of the graphite negative electrode active material is 5 μm-10 μm.

[0035] Controlling the specific surface area of ​​the graphite negative electrode active material within an appropriate range is beneficial to increasing the active sites on the surface of the graphite negative electrode active material, shortening the ion diffusion path, improving the diffusion kinetics of ions, and improving the rate performance and cycle performance of the battery. At the same time, it is beneficial to reduce the side reactions between the graphite negative electrode active material and the electrolyte, and improve the cycle performance of the dual-ion battery.

[0036] By controlling the volume distribution particle size Dv50 of the graphite negative electrode active material within an appropriate range, the graphite negative electrode active material has a high surface area, the diffusion path of cations is short and the embedding rate is too fast, the battery has high capacity and high rate performance, which is beneficial to improving the battery's cycle capacity retention rate. At the same time, the appropriate volume distribution particle size Dv50 is beneficial to improving the high structural stability of the graphite negative electrode active material, which is beneficial to improving the cycle stability of the positive electrode, improving the cycle stability of the battery, and extending the battery life.

[0037] A second aspect of the present application provides an electrical device comprising the dual-ion battery described in the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 is a schematic diagram of a dual-ion battery according to one embodiment of the present application;

[0039] Figure 2 yes Figure 1 An exploded view of a dual-ion battery according to an embodiment of the present application is shown;

[0040] Figure 3 is a schematic diagram of a battery module according to one embodiment of the present application;

[0041] Figure 4 is a schematic diagram of a battery pack according to one embodiment of the present application;

[0042] Figure 5 yes Figure 4 An exploded view of a battery pack according to an embodiment of the present application is shown;

[0043] Figure 6 Schematic diagram of an electrical device using a dual-ion battery according to one embodiment of the present application as a power source.

[0044] Reference numerals:

[0045] 1. Battery pack; 2. Upper box; 3. Lower box; 4. Battery module; 5. Dual-ion battery; 5. Casing; 5. Electrode assembly; 5. Cover. DETAILED DESCRIPTION

[0046] The following detailed description of the embodiments of the dual-ion battery and electrical device disclosed herein is described in detail, with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repeated descriptions of substantially identical structures may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0047] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0048] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0049] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0050] Unless otherwise specified, all steps of the present 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 may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0051] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0052] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0053] Dual-ion batteries have become a hot research area in recent years due to their good sustainability, long cycle life, high energy density, and low cost. Dual-graphite batteries are a common structure in dual-ion batteries. During the charging process, anions in the electrolyte intercalate into the positive electrode graphite, while cations simultaneously intercalate into the negative electrode graphite. During the discharge process, anions and cations deintercalate from the positive and negative electrode graphite back into the electrolyte. The radius of the anion and the interlayer spacing of the positive electrode graphite affect the process of anion intercalation / deintercalation into the positive electrode graphite, thereby affecting the battery's cycle performance. How to select the right anion to match the right positive electrode graphite, thereby increasing the speed and stability of the anion intercalation / deintercalation process into the positive electrode graphite, and improving the cycle performance of dual-ion batteries is an urgent problem to be solved in this field.

[0054] [Dual-ion battery]

[0055] Based on this, the present application proposes a dual-ion battery, which includes an electrolyte and a positive electrode plate. The electrolyte includes lithium tetrafluoroborate, and the positive electrode plate includes an artificial graphite positive electrode active material. The degree of graphitization of the artificial graphite positive electrode active material is 70%-90%.

[0056] In some embodiments, the degree of graphitization of the artificial graphite positive electrode active material is 70%-90%. In some embodiments, the degree of graphitization of the artificial graphite positive electrode active material can be 70%, 75%, 80%, 85%, 90%, or a value in a range consisting of any two of the above points.

[0057] The degree of graphitization measures the extent to which a carbon material has undergone structural rearrangement from amorphous carbon to a crystal structure approaching perfect graphite. The degree of graphitization can be used to measure the relative size of the interlayer spacing of graphite: the higher the degree of graphitization, the smaller the interlayer spacing, and the smaller the degree of graphitization, the larger the interlayer spacing.

[0058] The degree of graphitization of the artificial graphite positive electrode active material is tested using instruments and methods known in the art. For example, an X-ray diffractometer (such as a Bruker D8 Discover) can be used for testing. The test can refer to JISK 0131-1996 and JB / T 4220-2011. The average interlayer spacing d002 of the C(002) plane in the material's crystal structure is obtained. The degree of graphitization is then calculated using the formula g = (0.344 - d002) / (0.344 - 0.3354) × 100%. In the above formula, d002 is the average interlayer spacing of the C(002) plane in the material's crystal structure, expressed in nanometers (nm).

[0059] As mentioned above, the main factors in the process of anion intercalation / deintercalation of positive electrode graphite are the radius of the anion and the interlayer spacing of the positive electrode graphite. In the prior art, it is often believed that the smaller the radius of the anion, the smaller the graphitization degree of the positive electrode graphite (i.e., the larger the interlayer spacing of the positive electrode graphite), which may be more conducive to improving the speed of anion intercalation / deintercalation and the cycle stability of the positive electrode graphite, and the more conducive to the cycle performance of the battery. However, the applicant found that when the anion is selected as tetrafluorophosphate with a small radius, when the graphitization degree of the positive electrode graphite material is 70%-90%, the speed of anion intercalation / deintercalation can be increased, the cycle stability of the battery can be improved, and the cycle performance of the battery can be significantly improved. In addition, the applicant's research found that an electrolyte containing lithium tetrafluoroborate combined with an artificial graphite positive electrode active material with a graphitization degree of 70%-90% can effectively suppress the increase in the impedance of the positive electrode sheet during the cycle, improve the kinetic performance of the battery, and improve the cycle performance of the battery.

[0060] In addition, natural graphite has relatively curved graphite layers or closed edges, which will affect the process of anion intercalation in the positive electrode graphite. However, the present application uses artificial graphite, which reduces the impact of curved graphite layers or closed edges on the anion intercalation in the positive electrode graphite, thereby helping to increase the speed of anion intercalation / deintercalation, and helping to improve the cycle performance of the battery.

[0061] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer located on at least one side of the positive electrode current collector.

[0062] In some embodiments, the cathode material layer includes an artificial graphite cathode active material.

[0063] In some embodiments, the degree of graphitization of the artificial graphite positive electrode active material is 80%-85%. In some embodiments, the degree of graphitization of the artificial graphite positive electrode active material can be 80%, 81%, 82%, 83%, 84%, 85%, or a value in a range consisting of any two of the above points.

[0064] The graphitization degree of the artificial graphite positive electrode active material is within an appropriate range, which is beneficial to further improve the cycle capacity retention rate of the dual-ion battery and extend the service life of the battery.

[0065] In any embodiment, the Raman spectrum of the artificial graphite positive active material is 1575 cm -1 to 1600cm -1 The peak area A G and 1255cm -1 to 1355cm -1 The peak area A D Ratio A G / A D It is 0.7-1.0.

[0066] In some embodiments, the Raman spectrum of the artificial graphite positive active material is 1575 cm -1 to 1600cm -1 The peak area A G and 1255cm -1 to 1355cm -1 The peak area A D Ratio A G / A D The value may be 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, or a value in a range consisting of any two of the above values.

[0067] In this paper, the term "1575 cm in Raman spectroscopy" -1 to 1600cm -1 The peak area A G and 1255cm -1 to 1355cm -1 The peak area A D Ratio A G / A D " can be used to characterize the degree of defects in materials, A G / A D The smaller the value, the more defects the material has.

[0068] The Raman spectrum of artificial graphite positive active material at 1575 cm -1 to 1600cm -1 The peak area A G and 1255cm -1 to 1355cm -1 The peak area A D Ratio A G / A D Any known method in the art can be used. For example, an InVia Qontor (Reflex) laser microscope Raman spectrometer is used for testing, wherein a solid laser with a wavelength of 523 nm is used as a light source, 100 points are sampled in an area of ​​100 μm × 100 μm, and the peak at 1575 cm is calculated for each point. -1 to 1600cm -1 The peak area A of the characteristic peak G and 1255cm -1 to 1355cm -1 The peak area A of the characteristic peak D A G / A D The ratio of , take 100 points A G / A D The median value of 1575 cm in the Raman spectrum of artificial graphite positive active material -1 to 1600cm -1 The peak area A G and 1255cm -1 to 1355cm -1 The peak area A D Ratio A G / A D .

[0069] Controlling the A of artificial graphite positive electrode active materials G / A D In the appropriate range, on the one hand, the small A G / A D The material has a high degree of defect or disorder, and the material has relatively more storage active sites, which improves the specific capacity of the material. At the same time, the material has a high degree of defect, which is beneficial to improve the rate performance of the material. On the other hand, the material has an A in a suitable range. G / A D , reducing the possibility of side reactions between materials with high defectivity and the electrolyte, affecting the battery's kinetics and cycle performance.

[0070] In some embodiments, the artificial graphite positive active material includes mesopores, and the pore diameter of the mesopores is 13 nm to 20 nm.

[0071] In some embodiments, the pore size of the mesopores may be 13 nm, 15 nm, 17 nm, 19 nm, 20 nm, or a value within a range consisting of any two of the above values.

[0072] In this article, the term "mesopore" refers to pores with a pore size of 2 nm to 50 nm.

[0073] The pore size of the mesopores of the artificial graphite positive electrode active material can be measured using instruments and methods known in the art. As an example, a certain amount of the artificial graphite positive electrode active material prepared above is taken as a sample. First, the sample tube containing the material is degassed under vacuum at 200°C for more than 4 hours. Then, N2 is used as the gas probe molecule and the gas adsorption / desorption amount is tested in a liquid nitrogen (77.4K) environment. Based on the test results, the BET method is used to calculate the specific surface area of ​​the sample, and the micropore pore size distribution is analyzed by the HK algorithm, and the mesopore pore size distribution is analyzed by the BJH algorithm.

[0074] The mesopores in the artificial graphite positive electrode active material provide space for anions to expand and contract, shortening the bulk transport path of anions, which is beneficial for increasing the density of active sites such as end face and basal plane defects in the material, making it easier for anions to enter the graphite interlayers to complete electrode reactions, thereby improving the battery's kinetic performance and cycle performance. At the same time, the pore size of the mesopores in the artificial graphite positive electrode active material is within a suitable range, providing sufficient space for anions to expand and contract, and the bulk transport path of anions is relatively short, which is beneficial for improving the battery's kinetic performance and cycle performance, while also helping to reduce the impact of side reactions between the artificial graphite positive electrode active material and the electrolyte on cycle performance. Furthermore, the pore size of the mesopores in the artificial graphite positive electrode active material is within a suitable range, which is beneficial for improving the structural stability of the positive electrode active material, improving the cycle stability of the positive electrode, and improving the cycle performance of the battery.

[0075] In some embodiments, the pore size of the mesopore is 15 nm to 17 nm. In some embodiments, the pore size of the mesopore can be selected as 15 nm, 16 nm, 17 nm, or a value in a range consisting of any two of the above points.

[0076] The pore size of the mesopores of the artificial graphite positive electrode active material is within a suitable range, which is beneficial to further improve the cycle capacity retention rate of the dual-ion battery.

[0077] In some embodiments, the volume distribution particle size Dv50 of the artificial graphite positive electrode active material is 10 μm-30 μm. In some embodiments, the volume distribution particle size Dv50 of the artificial graphite positive electrode active material can be selected as 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, or a value in a range consisting of any two of the above points.

[0078] The volume distribution particle size Dv50 of artificial graphite positive electrode active materials is well known in the art and represents the particle size corresponding to 50% of the cumulative volume distribution percentage of the material. It can be measured using instruments and methods known in the art. For example, it can be conveniently measured using a laser particle size analyzer, referring to the particle size distribution laser diffraction method described in GB / T 19077-2016. The testing instrument can be a Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd. in the UK.

[0079] Controlling the volume distribution particle size Dv50 of the artificial graphite positive electrode active material within a suitable range, the artificial graphite positive electrode active material has a high surface area, the diffusion path of the anion is short and the embedding rate is too fast, the battery has high capacity and high rate performance, which is beneficial to improving the battery's cycle capacity retention rate. At the same time, the volume distribution particle size Dv50 of the material is within a suitable range, which is beneficial to improving the cycle structure stability of the artificial graphite positive electrode active material, improving the cycle stability of the positive electrode, improving the cycle stability of the battery, and extending the battery life.

[0080] In some embodiments, the volume distribution particle size Dv50 of the artificial graphite positive electrode active material is 15 μm-20 μm. In some embodiments, the volume distribution particle size Dv50 of the artificial graphite positive electrode active material can be selected as 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, or a value in a range consisting of any two of the above points.

[0081] Controlling the volume distribution particle size Dv50 of the artificial graphite positive electrode active material within an appropriate range is beneficial to further improving the cycle capacity retention rate of the dual-ion battery.

[0082] In some embodiments, the specific surface area of ​​the artificial graphite positive active material is 140 m 2 / g-160m 2 In some embodiments, the specific surface area of ​​the artificial graphite positive active material can be 140m 2 / g、145m 2 / g, 150m 2 / g、155m 2 / g, 160m 2 / g, or a value within the range consisting of any two of the above points.

[0083] In this application, the specific surface area of ​​the artificial graphite positive electrode active material can be measured using methods known in the art. As an example, the specific surface area of ​​the artificial graphite positive electrode active material can be measured using the nitrogen adsorption specific surface area analysis method according to GB / T 19587-2017 and calculated using the BET (Brunauer Emmett Teller) method. The testing instrument can be a Tri-Star 3020 specific surface area pore size analyzer from Micromeritics, USA.

[0084] Controlling the specific surface area of ​​the artificial graphite positive electrode active material within an appropriate range is beneficial to increasing the active sites on the surface of the artificial graphite positive electrode active material, shortening the ion diffusion path, improving the diffusion kinetics of ions, and improving the rate performance of the battery. At the same time, it is beneficial to reduce the side reactions between the artificial graphite positive electrode active material and the electrolyte, and improve the cycle performance of the dual-ion battery.

[0085] In some embodiments, a method for preparing an artificial graphite positive electrode active material includes: pyrolyzing an organic ligand and an iron source to obtain the artificial graphite positive electrode active material.

[0086] In some embodiments, the organic ligand comprises one or more of L-glutamic acid and 2-methylimidazole.

[0087] In some embodiments, the iron source includes ferric chloride, which is added to the system in the form of ferric chloride hexahydrate.

[0088] In some embodiments, the molar ratio of the organic ligand to ferric chloride is 1:3-2:1. In some embodiments, the molar ratio of the organic ligand to ferric chloride is 1:3, 1:2, 1:1, 2:1, or a value in a range consisting of any two of the above.

[0089] In some embodiments, the preparation method specifically comprises:

[0090] The organic ligand and ferric chloride are added into a pyrolysis treatment device for heat treatment to obtain an artificial graphite positive electrode active material.

[0091] In some embodiments, the heat treatment device refers to any device capable of performing pyrolysis treatment, including but not limited to Acheson furnace, box furnace, inner series furnace, continuous graphitization, electric calcining furnace, medium frequency furnace, tubular furnace and the like, which can be selected according to actual conditions.

[0092] In some embodiments, the heat treatment atmosphere is an inert atmosphere, which may be a nitrogen or argon atmosphere.

[0093] In some embodiments, the heating rate of the pyrolysis treatment device is 3°C / min-10°C / min. In some embodiments, the heating rate of the pyrolysis treatment device can be 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min.

[0094] / min, or a value within the range consisting of any two of the above points.

[0095] In some embodiments, the pyrolysis temperature of the pyrolysis treatment is 1000°C-1400°C. In some embodiments, the pyrolysis temperature of the pyrolysis treatment can be selected from 1000°C, 1100°C-1200°C, 1300°C, 1400°C, or a value within a range consisting of any two of the foregoing values. In some embodiments, the holding time of the pyrolysis treatment is 1 hour-3 hours. In some embodiments, the holding time of the pyrolysis treatment can be selected from 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, or a value within a range consisting of any two of the foregoing values.

[0096] In some embodiments, the positive electrode current collector has two opposite surfaces in its thickness direction, and the positive electrode material layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0097] In some embodiments, the positive electrode 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 material base and a metal layer formed on at least one surface of the polymer material base. 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 material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0098] In some embodiments, the positive electrode plate may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0099] In some embodiments, the positive electrode plate may further include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0100] In some embodiments, the positive electrode sheet can be prepared by the following method: the above-mentioned artificial graphite positive electrode active material, binder, conductive agent or other components and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0101] In some embodiments, the molar solubility of lithium tetrafluoroborate is 1.5 mol / L-4 mol / L. In some embodiments, the molar solubility of lithium tetrafluoroborate can be 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, or a value in a range consisting of any two of the above points.

[0102] High concentrations of lithium tetrafluoroborate help alleviate the collapse of the ordered graphite structure caused by the co-intercalation of solvents during the intercalation / deintercalation process of anions, thereby improving the structural stability of the positive electrode graphite during the cycle and enhancing the battery's cycling performance. At the same time, high concentrations of lithium salts can reduce the possibility of side reactions between the electrolyte and the positive electrode, reducing the possibility of the positive electrode impedance increasing during the cycle, and improving the battery's kinetic performance.

[0103] In some embodiments, the electrolyte includes a solvent, and the solvent includes ethyl methyl carbonate and a sulfone compound, and the sulfone compound includes one or more of sulfolane, 3-methylsulfolane, and methyl ethyl sulfone.

[0104] Solvation refers to the interaction between the solvent molecules in the electrolyte and the anions or cations. After the lithium salt is dissolved in the solvent, the solvent molecules will gather around the lithium ions or anions. The aggregates formed by the lithium ions or anions and the solvent molecules are called solvation structures.

[0105] Due to the solvation effect, the anion will form a solvation structure with the solvent molecules. When the anion is inserted into the positive electrode, the incomplete desolvation process will cause the anion and part of the solvent to be co-embedded in the positive electrode, causing a dramatic volume expansion of the positive electrode, affecting the structural stability of the positive electrode, and also reducing the oxidative stability of the electrolyte.

[0106] The solvent of the electrolyte of the present application is ethyl methyl carbonate and sulfolane, 3-methylsulfolane or methyl ethyl sulfone, which can reduce the solvation effect of the anion and the steric hindrance effect, reduce the embedding potential of the anion, slow down the irreversible expansion of the positive electrode volume caused by the co-embedding of the anion and the solvent, improve the structural stability of the positive electrode during the cycle, improve the cycle stability of the positive electrode plate, improve the cycle performance of the battery, and extend the service life of the battery. At the same time, ethyl methyl carbonate and sulfone solvents as solvents for the electrolyte have excellent antioxidant properties, significantly improve the antioxidant capacity of the electrolyte, and are beneficial to improving the cycle performance of the battery. At the same time, the electrolyte contains ethyl methyl carbonate and sulfolane, 3-methylsulfolane or methyl ethyl sulfone at the same time, which can reduce the possibility of side reactions between the electrolyte and the positive electrode plate, reduce the possibility of the positive electrode plate impedance increasing continuously during the cycle, and improve the kinetic performance of the battery. In addition, the viscosity of ethyl methyl carbonate and sulfolane, 3-methylsulfolane or methyl ethyl sulfone is low, which is beneficial to increase the solubility of the lithium salt, improve the conductivity of the electrolyte, and improve the rate performance of the battery. Furthermore, the electrolyte's enhanced antioxidant capacity helps raise the secondary battery's charge cutoff voltage and improve its energy density. Furthermore, the electrolyte contains a solvent composed of ethyl methyl carbonate and a sulfone compound, along with lithium tetrafluoroborate, a lithium salt. This combination helps form a stable and dense SEI inorganic component, enhancing the stability of the electrolyte-negative electrode interface and improving the battery's cycling performance and safety.

[0107] In some embodiments, the volume ratio of ethyl methyl carbonate to sulfone compound is 4:6-7:3. In some embodiments, the volume ratio of ethyl methyl carbonate to sulfolane can be 4:6, 5:6, 6:6, 7:6, 7:5, 7:4, 7:3 or any range consisting of the above two points.

[0108] Controlling the volume ratio of ethyl methyl carbonate to sulfone compounds within an appropriate range helps to further reduce the solvation effect between the anion and the solvent, slow down the volume expansion caused by the solvation structure formed by the anion and the solvent during the embedding process of the positive electrode, improve the structural stability of the positive electrode during the cycle, improve the cycle stability of the battery, and extend the service life of the battery.

[0109] In some embodiments, the volume ratio of ethyl methyl carbonate to sulfone compound is 5:5-6:4. In some embodiments, the volume ratio of ethyl methyl carbonate to sulfolane can be 5:5, 7:6, 6:5 or any range consisting of the above two points.

[0110] Controlling the volume ratio of ethyl methyl carbonate to sulfone compounds within an appropriate range is beneficial to further improving the cycle capacity retention rate of the dual-ion battery and extending the service life of the battery.

[0111] In some embodiments, the electrolyte may further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0112] In some embodiments, a dual-ion battery includes a negative electrode sheet comprising a graphite negative electrode active material.

[0113] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode material layer located on at least one side of the negative electrode current collector.

[0114] In some embodiments, the Raman spectrum of the graphite negative electrode active material is 1575 cm -1 to 1600cm -1 The peak area A G and 1255cm -1 to 1355cm -1 The peak area A D Ratio A G / A D It is 0.1-0.5.

[0115] In some embodiments, the Raman spectrum of the graphite negative electrode active material is 1575 cm -1 to 1600cm -1 The peak area A G and 1255cm -1 to 1355cm -1 The peak area A D Ratio A G / A D The value can be selected as 0.1, 0.2, 0.3, 0.4, 0.5, or a value in a range consisting of any two of the above points.

[0116] The Raman spectrum of graphite anode active material is 1575 cm -1 to 1600cm -1 The peak area A G and 1255cm -1 to 1355cm -1 The peak area A D Ratio A G / A D Any known method in the art can be used. For example, an InVia Qontor (Reflex) laser microscope Raman spectrometer is used for testing, wherein a solid laser with a wavelength of 523 nm is used as a light source, 100 points are sampled in an area of ​​100 μm × 100 μm, and the peak at 1575 cm is calculated for each point. -1 to 1600cm -1The peak area A of the characteristic peak G and 1255cm -1 to 1355cm -1 The peak area A of the characteristic peak D A G / A D The ratio of , take 100 points A G / A D The median value of 1575 cm in the Raman spectrum of graphite anode active material -1 to 1600cm -1 The peak area A G and 1255cm -1 to 1355cm -1 The peak area A D Ratio A G / A D .

[0117] The Raman spectrum of graphite anode active material is 1575 cm -1 to 1600cm -1 The peak area and 1255cm -1 to 1355cm -1 The peak area A D Ratio A G / A D It can characterize the ratio of the crystalline region to the defective region or disordered region of the material, A G / A D The smaller the value, the greater the proportion of defective or disordered regions in the graphite negative electrode active material. High defect or disordered regions can increase the deintercalation and insertion channels of lithium ions and increase the deintercalation and insertion speed of lithium ions, thereby improving the rate performance of the graphite negative electrode active material. At the same time, high defect or disorder means that the material has relatively more storage active sites, which increases the material's specific capacity and improves the battery's cycle capacity retention rate.

[0118] A of graphite negative electrode active material G / A D Within a suitable range, high defect or disorder degree can improve the rate performance and specific capacity of the material, improve the cycle performance of the battery, and also avoid A G / A D If the size is too small, the material defect or disorder will be too high, which will lead to excessive side reactions between the material and the electrolyte, resulting in irreversible capacity loss and affecting the battery's cycle performance.

[0119] In some embodiments, the Raman spectrum of the graphite negative electrode active material is 1575 cm -1 to 1600cm -1 The peak area A G and 1255cm -1 to 1355cm-1 The peak area A D Ratio A G / A D It is 0.2-0.4.

[0120] In some embodiments, the Raman spectrum of the graphite negative electrode active material is 1575 cm -1 to 1600cm -1 The peak area A G and 1255cm -1 to 1355cm -1 The peak area A D Ratio A G / A D The value can be selected as 0.1, 0.2, 0.3, 0.4, 0.5, or a value in a range consisting of any two of the above points.

[0121] In some embodiments, the graphite negative electrode active material comprises micropores, and the pore size of the micropores is 0.1 nm to 0.7 nm. In some embodiments, the pore size of the micropores can be selected from 0.1 nm, 0.3 nm, 0.5 nm, 0.7 nm, or a value in a range consisting of any two of the above points.

[0122] As used herein, the term "micropore" refers to a pore with a pore diameter of 2 nm or less.

[0123] The method and equipment for testing the pore size of the micropores of the graphite negative electrode active material refer to the method and equipment for testing the pore size of the mesopores of the artificial graphite positive electrode active material.

[0124] The microporous structure provides space for the graphite material to expand and contract during the charge and discharge process, which greatly suppresses the electrode damage process caused by volume expansion during repeated charge and discharge, improves the structural stability of the negative electrode plate, and improves the cycle performance of the battery. At the same time, the microporous structure is also conducive to improving the transmission performance of ions and electrons, improving the rate performance of the battery. At the same time, the pore size of the micropores of the graphite negative electrode active material is within an appropriate range, which can provide space for the graphite material to expand and contract during the charge and discharge process, and improve the cycle stability of the material. At the same time, the appropriate micropore size is conducive to the insertion / extraction of lithium ions during the cycle process, which is conducive to improving the battery's kinetic performance and cycle performance, and is also conducive to reducing the impact of the side reactions between the graphite negative electrode active material and the electrolyte on the cycle performance, thereby improving the cycle stability of the battery.

[0125] In some embodiments, the pore size of the micropore is 0.3 nm to 0.5 nm. In some embodiments, the pore size of the micropore can be selected from 0.3 nm, 0.4 nm, 0.5 nm, or a value in a range consisting of any two of the above points.

[0126] The pore size of the micropores of the graphite negative electrode active material is within an appropriate range, which is beneficial to further improve the cycle capacity retention rate of the dual-ion battery.

[0127] In some embodiments, the graphite negative electrode active material contains doping elements, and the doping elements include one or more of boron, phosphorus, nitrogen, and sulfur.

[0128] Doping elements can effectively adjust the electronic structure of carbon atoms in graphite negative electrode active materials, enhance the electron cloud distribution of carbon atoms, improve the transmission dynamics of lithium ions, improve the rate performance of materials, and improve the rate performance and cycle performance of batteries.

[0129] In some embodiments, the specific surface area of ​​the graphite negative electrode active material is 800 m 2 / g-1000m 2 In some embodiments, the specific surface area of ​​the graphite negative electrode active material can be 800m 2 / g、850m 2 / g、900m 2 / g、950m 2 / g、1000m 2 / g, or a value within the range consisting of any two of the above points.

[0130] The test method and equipment for the specific surface area of ​​the graphite negative electrode active material refer to the test method and equipment for the specific surface area of ​​the artificial graphite positive electrode active material mentioned above.

[0131] Controlling the specific surface area of ​​the graphite negative electrode active material within an appropriate range is beneficial to increasing the active sites on the surface of the graphite negative electrode active material, shortening the ion diffusion path, improving the diffusion kinetics of ions, and improving the rate performance and cycle performance of the battery. At the same time, it is beneficial to reduce the side reactions between the graphite negative electrode active material and the electrolyte, and improve the cycle performance of the dual-ion battery.

[0132] In some embodiments, the specific surface area of ​​the graphite negative electrode active material is 850 m 2 / g-900m 2 In some embodiments, the specific surface area of ​​the graphite negative electrode active material can be 850m 2 / g、860m 2 / g、870m 2 / g、880m 2 / g、890m 2 / g、900m 2 / g, or a value within the range consisting of any two of the above points.

[0133] Controlling the specific surface area of ​​the graphite negative electrode active material within an appropriate range can further improve the cycle performance of the dual-ion battery and extend the battery life.

[0134] In some embodiments, the volume distribution particle size Dv50 of the graphite negative electrode active material is 5 μm-10 μm. In some embodiments, the volume distribution particle size Dv50 of the graphite negative electrode active material can be selected as 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, or a value in a range consisting of any two of the above points.

[0135] The test method and equipment for the volume distribution particle size Dv50 of the graphite negative electrode active material refer to the test method and equipment for the volume distribution particle size Dv50 of the above-mentioned artificial graphite positive electrode active material.

[0136] Controlling the volume distribution particle size Dv50 of the graphite negative electrode active material within a suitable range, the graphite negative electrode active material has a high surface area, the diffusion path of lithium ions is short and the embedding rate is too fast, the battery has high capacity and high rate performance, which is beneficial to improving the battery's cycle capacity retention rate. At the same time, the volume distribution particle size Dv50 of the material is within a suitable range, which is beneficial to improving the cycle structure stability of the graphite negative electrode active material, improving the cycle stability of the positive electrode, improving the cycle stability of the battery, and extending the battery life.

[0137] In some embodiments, the volume distribution particle size Dv50 of the graphite negative electrode active material is 7 μm-9 μm. In some embodiments, the volume distribution particle size Dv50 of the graphite negative electrode active material can be selected as 7 μm, 8 μm, 9 μm, or a value in a range consisting of any two of the above points.

[0138] Controlling the volume distribution particle size Dv50 of the graphite negative electrode active material within an appropriate range can further improve the cycle capacity retention rate of the dual-ion battery and improve the cycle performance of the battery.

[0139] In some embodiments, the preparation method of the graphite negative electrode active material is: pyrolysis treatment of the organic ligand, the iron source and the doping source to obtain the graphite negative electrode active material.

[0140] In some embodiments, the organic ligand comprises one or more of L-glutamic acid and 2-methylimidazole.

[0141] In some embodiments, the iron source comprises ferric chloride, which is added to the system in the form of ferric chloride hexahydrate.

[0142] In some embodiments, the doping source includes one or more of a boron source, a sulfur source, a nitrogen source, and a phosphorus source.

[0143] In some embodiments, the molar ratio of the organic ligand, ferric chloride, and dopant source is 1:2:0.1 to 1:2:0.5. In some embodiments, the molar ratio of the organic ligand, ferric chloride, and dopant source can be 1:2:0.1, 1:2:0.2, 1:2:0.3, 1:2:0.4, 1:2:0.5, or a value within a range consisting of any two of the above.

[0144] In some embodiments, the preparation method specifically comprises:

[0145] The organic ligand, ferric chloride and a doping source are added into a pyrolysis treatment device for heat treatment to obtain a graphite negative electrode active material.

[0146] In some embodiments, the heat treatment device refers to any device capable of performing pyrolysis treatment, including but not limited to Acheson furnace, box furnace, inner series furnace, continuous graphitization, electric calcining furnace, medium frequency furnace, tubular furnace and the like, which can be selected according to actual conditions.

[0147] In some embodiments, the heat treatment atmosphere is an inert atmosphere, which may be a nitrogen or argon atmosphere.

[0148] In some embodiments, the heating rate of the pyrolysis treatment device is 3°C / min-10°C / min. In some embodiments, the heating rate of the pyrolysis treatment device can be selected from 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min, or a value in a range formed by any two of the above points.

[0149] In some embodiments, the pyrolysis temperature of the pyrolysis treatment is 1000-1400° C. In some embodiments, the pyrolysis temperature of the pyrolysis treatment can be selected from 1000° C., 1100-1200° C., 1300° C., 1400° C., or a value in a range consisting of any two of the above points.

[0150] In some embodiments, the holding time of the pyrolysis treatment is 1 hour to 3 hours. In some embodiments, the holding time of the pyrolysis treatment can be selected from 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, or a value in a range consisting of any two of the above points.

[0151] In some embodiments, the negative electrode current collector has two opposite surfaces in its thickness direction, and the negative electrode material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0152] 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 base layer and a metal layer formed on at least one surface of the polymer base material. 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 base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0153] In some embodiments, the negative electrode material layer may further include a binder. The binder may include 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).

[0154] In some embodiments, the negative electrode material layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0155] In some embodiments, the negative electrode material layer may optionally further include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0156] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as graphite negative electrode active material, conductive agent, binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0157] [Isolation film]

[0158] In some embodiments, the dual-ion battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0159] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0160] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0161] In some embodiments, the dual-ion battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0162] In some embodiments, the outer packaging of the dual-ion battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the dual-ion battery can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0163] The present application has no particular restrictions on the shape of the dual-ion battery, which can be cylindrical, square or any other shape. For example, Figure 1 A dual-ion battery 5 having a square structure is used as an example.

[0164] In some embodiments, reference Figure 2 The outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the dual-ion battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0165] In some embodiments, dual-ion batteries can be assembled into a battery module. The number of dual-ion batteries contained in the battery module can be one or more. The specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0166] Figure 3 4 is an example of a battery module. Figure 3 In the battery module 4, the plurality of dual-ion batteries 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other manner. The plurality of dual-ion batteries 5 can further be fixed by fasteners.

[0167] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of dual-ion batteries 5 are received in the receiving space.

[0168] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0169] Figure 4 and Figure 5 The battery pack 1 is used as an example. Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner in the battery box.

[0170] In addition, the present application also provides an electrical device, which includes at least one of the dual-ion battery, battery module, or battery pack provided in the present application. The dual-ion battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as 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., but is not limited thereto.

[0171] As an electrical device, a dual-ion battery, a battery module or a battery pack can be selected according to its usage requirements.

[0172] Figure 6 This is an example of an electric device. This device is 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 the dual-ion battery, a battery pack or battery module can be used.

[0173] As another example, the device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be light and thin, and may use dual ions as a power source.

[0174] Example

[0175] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0176] 1. Preparation method

[0177] Example 1

[0178] 1) Preparation of electrolyte

[0179] Lithium tetrafluoroborate (LiBF4) is dissolved in a mixed solvent containing ethyl methyl carbonate (EMC) and sulfolane to obtain an electrolyte, wherein the concentration of LiBF4 is 2 mol / L and the volume ratio of ethyl methyl carbonate to sulfolane in the mixed solvent is 5:5.

[0180] 2) Preparation of positive electrode sheet

[0181] L-glutamic acid and ferric chloride hexahydrate were dissolved in deionized water at a molar ratio of 1:2. The water was removed using a rotary evaporator and then dried in an oven. The dried sample was placed in a tube furnace and pyrolyzed at 1200°C for 1 hour at a heating rate of 5°C / min in an Ar atmosphere. The pyrolyzed sample was then acid-washed with 6 mol / L hydrochloric acid for 24 hours to remove iron particles. Finally, the sample was washed with deionized water until neutral to obtain artificial graphite cathode active material A1.

[0182] Artificial graphite positive electrode active material A1 was mixed with conductive carbon black and polyvinylidene fluoride binder in a mass ratio of 80%:10%:10%, and an appropriate amount of N-methylpyrrolidone solvent was added and stirred thoroughly to prepare a positive electrode slurry. The positive electrode slurry was evenly coated on an aluminum sheet and vacuum dried at 70°C for 24 hours to obtain a positive electrode sheet.

[0183] 3) Preparation of negative electrode sheet

[0184] The natural graphite material B1 was mixed with conductive carbon black and styrene-butadiene rubber binder in a mass ratio of 80%:10%:10%, and then an appropriate amount of deionized water solvent was added and stirred thoroughly to prepare a negative electrode slurry. The negative electrode slurry was evenly coated on a copper sheet and vacuum dried at 70°C for 24 hours to obtain a negative electrode sheet. The Raman spectrum of the natural graphite material B1 at 1575 cm -1 to 1600cm -1 The peak area A G and 1255cm -1 to 1355cm -1 The peak area A D Ratio A G / A D is 4.0.

[0185] 4) Isolation film

[0186] Polyethylene is used as the separator.

[0187] 6) Preparation of batteries

[0188] The positive electrode sheet, the separator, and the negative electrode sheet are stacked in order and wound to obtain a battery cell. The battery cell is placed in an outer package, and the above-mentioned electrolyte is added. After packaging, standing, formation, aging and other processes, a dual-ion battery is obtained.

[0189] Examples 2-4

[0190] Compared with Example 1, Examples 2-4 adjusted the graphitization degree of the artificial graphite positive active material by adjusting the molar ratio of L-glutamic acid to ferric chloride hexahydrate, the heating rate, and the pyrolysis temperature. The specific adjustment parameters are shown in Table 1.

[0191] Examples 5-8

[0192] Compared with Example 1, Examples 5-8 adjusted the solvent in the electrolyte, as shown in Table 2 for details.

[0193] Example 9

[0194] Compared with Example 3, the natural graphite B1 is replaced with a graphite negative electrode active material B2. The preparation method of the graphite negative electrode active material B2 is as follows:

[0195] Boric acid, L-glutamic acid, and ferric chloride hexahydrate were mixed in a 0.2:1:2 molar ratio and dissolved in deionized water. The mixture was then removed by rotary evaporation and dried in an oven. The dried sample was then pyrolyzed in a tube furnace at 1200°C for 1 hour at a heating rate of 5°C / min in an Ar atmosphere. The pyrolyzed sample was then acid-washed with 6 mol / L hydrochloric acid for 24 hours to remove iron particles. Finally, the sample was washed with deionized water until neutral to obtain graphite anode active material B2.

[0196] Examples 10-13

[0197] Compared with Example 9, Examples 10-13 adjusted the molar ratio of boric acid to L-glutamic acid and ferric chloride hexahydrate to adjust the A of the graphite negative electrode active material. G / A D , see Table 1 for specific adjustment parameters.

[0198] Comparative Example 1

[0199] Compared with Example 1, the type of lithium salt and solvent in the electrolyte was adjusted. See Table 2 for specific parameters.

[0200] Comparative Example 2

[0201] Compared with Example 1, the artificial graphite positive electrode active material A1 is replaced by natural graphite NA, wherein the degree of graphitization of the natural graphite NA is 90%.

[0202] Comparative Examples 3-4

[0203] Compared with Example 1, Comparative Examples 3-4 adjusted the graphitization degree of the artificial graphite positive electrode active material by adjusting the molar ratio of L-glutamic acid to ferric chloride hexahydrate, the heating rate, and the pyrolysis temperature. The specific adjustment parameters are shown in Table 1.

[0204] 2. Test Method

[0205] 1. Cycle performance

[0206] The dual-ion batteries prepared in each example and comparative example were charged at 25°C at a constant current rate of 0.5C to a charge cutoff voltage of 5V. They were then charged at a constant voltage to a current of ≤0.05C, allowed to rest for 5 minutes, and then discharged at a constant current rate of 0.33C to a discharge cutoff voltage of 3V, allowed to rest for 5 minutes. This constituted one charge-discharge cycle. The batteries were subjected to cyclic charge-discharge testing using this method, and the capacity retention of the dual-ion batteries after 50 cycles was determined.

[0207] 2. Impedance of the positive electrode after 50 cycles of battery

[0208] The dual-ion batteries prepared in each embodiment and comparative example were charged at a constant current rate of 0.5C to a charge cut-off voltage of 5V at 25°C, then charged at a constant voltage to a current of ≤0.05C, allowed to stand for 5 minutes, and then discharged at a constant current rate of 0.33C to a discharge cut-off voltage of 3V, allowed to stand for 5 minutes. This constituted one charge and discharge cycle. The battery was subjected to a charge and discharge test for 50 cycles according to this method. The battery after 50 cycles was disassembled to obtain the positive electrode sheet. The positive electrode sheet was cleaned with an organic solvent and tested for electrochemical impedance spectroscopy (EIS) using an electrochemical workstation at 25°C to obtain the impedance of the positive electrode sheet. The frequency of the perturbed alternating current during the impedance test was 300kHz to 0.2Hz, and the amplitude was ±5mV.

[0209] 3. Analysis of test results of various embodiments and comparative examples

[0210] The dual-ion batteries of the embodiments and comparative examples were prepared according to the above method, and various parameters were measured. The results are shown in the table below.

[0211] Table 1

[0212]

[0213] Table 2

[0214]

[0215]

[0216] As can be seen from the above table, the dual-ion batteries provided in Examples 1-13 of the present application include an electrolyte and a positive electrode plate. The electrolytes all contain lithium tetrafluoroborate, and the positive electrode plates include an artificial graphite positive electrode active material, and the degree of graphitization of the artificial graphite positive electrode active material is 70%-90%. As can be seen from the comparison of Examples 1-13 with Comparative Examples 1-4, the electrolyte containing lithium tetrafluoroborate and the artificial graphite positive electrode active material with a degree of graphitization of 70%-90% can reduce the impedance of the positive electrode plate after 50 cycles of the dual-ion battery, improve the battery's cycle capacity retention rate, and extend the battery's service life.

[0217] From the comparison between Examples 1 and 3 and Examples 2 and 4, it can be seen that controlling the graphitization degree of the artificial graphite positive electrode active material to 80%-85% is beneficial to further reduce the impedance of the positive electrode sheet after 50 cycles of the dual-ion battery, improve the cycle capacity retention rate of the dual-ion battery, and extend the service life of the battery.

[0218] From Examples 1-4, it can be seen that the Raman spectrum of the artificial graphite positive active material is 1575 cm -1 to 1600cm -1 The peak area A G and 1255cm -1 to 1355cm -1 The peak area A D Ratio A G / A D The impedance of the positive electrode sheet is 0.7-1.0 after 50 cycles of battery, and the battery has excellent cycle performance.

[0219] From the comparison between Examples 1, 6-8 and Example 5, it can be seen that the solvent contains ethyl methyl carbonate and sulfone solvents such as cyclopentane or methyl ethyl sulfone, which can further improve the cycle capacity retention rate of the battery and improve the cycle performance of the battery.

[0220] From the comparison between Examples 9-13 and Example 3, it can be seen that the Raman spectrum of the graphite negative electrode active material at 1575 cm -1 to 1600cm -1 The peak area AG and 1255 cm -1 to 1355cm -1 The peak area AD ratio AG / AD is 0.1-0.5, which improves the cycle capacity retention rate of the battery and extends the battery life. From the comparison of Examples 9-11 and Examples 12-13, it can be seen that controlling the AG / AD of the graphite negative electrode active material to 0.2-0.4 can further improve the cycle capacity retention rate of the dual-ion battery and improve the battery's cycle performance.

[0221] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A dual-ion battery, characterized in that: The invention comprises an electrolyte and a positive electrode plate, wherein the electrolyte contains lithium tetrafluoroborate, and the positive electrode plate contains an artificial graphite positive electrode active material, and the graphitization degree of the artificial graphite positive electrode active material is 70%-90%.

2. The dual-ion battery according to claim 1, characterized in that: The degree of graphitization of the artificial graphite positive electrode active material is 80%-85%.

3. The dual-ion battery according to claim 1 or 2, characterized in that: The Raman spectrum of the artificial graphite positive active material is 1575 cm -1 to 1600cm -1 The peak area A G and 1255cm -1 to 1355cm -1 The peak area A D Ratio A G / A D It is 0.7-1.

0.

4. The dual-ion battery according to any one of claims 1 to 3, characterized in that The artificial graphite positive electrode active material includes mesopores, and the pore diameter of the mesopores is 13 nm to 20 nm.

5. The dual-ion battery according to claim 4, characterized in that The pore diameter of the mesopores is 15 nm to 17 nm.

6. The dual-ion battery according to any one of claims 1 to 5, characterized in that The artificial graphite positive electrode active material satisfies at least one of the following: (1) The volume distribution particle size Dv50 of the artificial graphite positive electrode active material is 10 μm-30 μm; (2) The specific surface area of ​​the artificial graphite positive electrode active material is 140m 2 / g-160m 2 / g.

7. The dual-ion battery according to any one of claims 1 to 6, characterized in that The molar solubility of the lithium tetrafluoroborate is 1.5 mol / L-4 mol / L.

8. The dual-ion battery according to any one of claims 1 to 7, characterized in that The electrolyte includes a solvent, wherein the solvent contains ethyl methyl carbonate and a sulfone compound, and the sulfone compound includes one or more of sulfolane, 3-methylsulfolane, and methyl ethyl sulfone.

9. The dual-ion battery according to claim 8, characterized in that The volume ratio of the ethyl methyl carbonate to the sulfone compound is 4:6-7:

3.

10. The dual-ion battery according to claim 8, characterized in that The volume ratio of the ethyl methyl carbonate to the sulfone compound is 5:5-6:

4.

11. The dual-ion battery according to any one of claims 1 to 10, characterized in that The dual-ion battery includes a negative electrode plate, the negative electrode plate includes a graphite negative electrode active material, and the graphite negative electrode active material has a Raman spectrum of 1575 cm -1 to 1600cm -1 The peak area A G and 1255cm -1 to 1355cm -1 The peak area A D Ratio A G / A D It is 0.1-0.

5.

12. The dual-ion battery according to claim 11, characterized in that The Raman spectrum of the graphite negative electrode active material is 1575 cm -1 to 1600cm -1 The peak area A G and 1255cm -1 to 1355cm -1 The peak area A D Ratio A G / A D It is 0.2-0.

4.

13. The dual-ion battery according to claim 11 or 12, characterized in that: The graphite negative electrode active material contains micropores, and the pore diameter of the micropores is 0.1 nm-0.7 nm.

14. The dual-ion battery according to claim 13, characterized in that The pore diameter of the micropores is 0.3 nm to 0.5 nm.

15. The dual-ion battery according to any one of claims 11 to 14, characterized in that The graphite negative electrode active material contains doping elements, and the doping elements include one or more of boron, phosphorus, nitrogen, and sulfur.

16. The dual-ion battery according to any one of claims 11 to 15, characterized in that The graphite negative electrode active material satisfies at least one of the following: (1) The specific surface area of ​​the graphite negative electrode active material is 800m 2 / g-1000m 2 / g; (2) The volume distribution particle size Dv50 of the graphite negative electrode active material is 5 μm-10 μm.

17. An electrical device, characterized in that: A dual-ion battery comprising the dual-ion battery according to any one of claims 1 to 16.

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