CN114024034B - Battery with improved battery capacity - Google Patents
Battery with improved battery capacity Download PDFInfo
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- CN114024034B CN114024034B CN202111251998.9A CN202111251998A CN114024034B CN 114024034 B CN114024034 B CN 114024034B CN 202111251998 A CN202111251998 A CN 202111251998A CN 114024034 B CN114024034 B CN 114024034B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0566—Liquid materials
- H01M10/0569—Liquid materials characterised by the solvents
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0566—Liquid materials
- H01M10/0567—Liquid materials characterised by the additives
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/058—Construction or manufacture
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
- H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0025—Organic electrolyte
- H01M2300/0028—Organic electrolyte characterised by the solvent
- H01M2300/0037—Mixture of solvents
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
The invention discloses a battery, which comprises a positive plate, a negative plate, a diaphragm and a non-aqueous electrolyte; the diaphragm comprises a base material, heat-resistant layers and glue coating layers, wherein the heat-resistant layers are oppositely arranged on two sides of the base material, and the glue coating layers are arranged on the heat-resistant layers; the nonaqueous electrolyte comprises a nonaqueous organic solvent and an additive, wherein the nonaqueous organic solvent at least comprises ethyl propionate; the additives include fluoroethylene carbonate, ethylene carbonate and lithium difluorophosphate; the ratio of the mass percentage content of the ethyl propionate in the non-aqueous electrolyte to the mass percentage content of the hexafluoropropylene in the hexafluoropropylene-vinylidene fluoride copolymer in the adhesive of the adhesive layer is 0.2-60. According to the invention, through the synergistic effect of the diaphragm and the electrolyte, the battery prepared by combining the positive and negative electrode materials can effectively prolong the cycle life of the battery, reduce the cycle expansion of the battery and simultaneously give consideration to the low-temperature performance of the battery.
Description
Technical Field
The invention belongs to the technical field of batteries, and particularly relates to a battery.
Background
In recent years, lithium ion batteries have been widely used in smart phones, tablet computers, smart wearing, electric tools, electric vehicles, and other fields. With the wide application of lithium ion batteries, the demands of consumers on the service life and the application environment of the lithium ion batteries are continuously increased, so that the lithium ion batteries are required to have long cycle life while having high and low temperature performances.
At present, potential safety hazards exist in the use process of lithium ion batteries, for example, when the batteries are used for a long time, the problems of lithium precipitation, thickness expansion increase and the like occur in the batteries, and then serious safety accidents such as fire and even explosion are easily caused. Meanwhile, the battery is difficult to discharge when used at a low ambient temperature, and further, the use is influenced by automatic shutdown. The main reasons for the above problems are that the active material has an unstable structure at high temperature and high voltage, metal ions are easily dissolved out from the positive electrode and reduced and deposited on the surface of the negative electrode, and the electrolyte is catalyzed to be reduced and decomposed on the surface of the negative electrode, so that the SEI film structure of the negative electrode is damaged, the impedance of the negative electrode and the thickness of the battery are continuously increased, and the temperature of the battery is continuously increased to cause safety accidents; on the other hand, the battery resistance increases at low temperature, and the SEI film resistance greatly affects low-temperature discharge.
Under the current situation, the development of a high-voltage lithium ion battery with long cycle life and low expansion is urgently needed, for example, the cycle performance can be improved by adding a negative electrode film-forming agent into an electrolyte, but the use of the negative electrode film-forming agent can cause severe deterioration of the low-temperature performance of the battery. Therefore, the development of a high-voltage lithium ion battery with long cycle life and low expansion on the premise of not influencing the low-temperature performance of the battery is the current primary task.
Disclosure of Invention
The invention aims to solve the problems that the existing battery has potential safety hazard in the use process, the cycle life of the battery and the low-temperature performance cannot be considered simultaneously, and the like, and provides a battery which has the performances of high voltage, long cycle life and low expansion.
In order to achieve the purpose, the invention adopts the following technical scheme:
a battery includes a positive electrode sheet, a negative electrode sheet, a separator interposed between the positive electrode sheet and the negative electrode sheet, and a nonaqueous electrolytic solution;
the diaphragm comprises a base material, heat-resistant layers and glue coating layers, wherein the heat-resistant layers are oppositely arranged on two sides of the base material, and the glue coating layers are arranged on the heat-resistant layers; the glue coating layer comprises an adhesive, and the adhesive comprises hexafluoropropylene-vinylidene fluoride copolymer;
the nonaqueous electrolytic solution comprises a nonaqueous organic solvent and an additive, wherein the nonaqueous organic solvent at least comprises ethyl propionate; the additives include fluoroethylene carbonate, ethylene carbonate and lithium difluorophosphate;
the ratio of the mass percentage content of the ethyl propionate in the nonaqueous electrolyte solution to the mass percentage content of Hexafluoropropylene (HFP) in the hexafluoropropylene-vinylidene fluoride copolymer is 0.2-60.
According to the invention, the change rate of the adhesive force between the adhesive coating and the positive and negative electrodes is within 10% in 100 weeks before the battery is cycled.
According to the invention, the ratio of the mass percentage of the ethyl propionate in the nonaqueous electrolytic solution to the mass of the Hexafluoropropylene (HFP) in the hexafluoropropylene-vinylidene fluoride copolymer is 0.5-35, and the ratio is exemplarily 0.26, 0.5, 1, 2.4, 5.8, 9.2, 11.3, 13.7, 15, 20, 30, 35, 36.7, 40, 50, 60 or any one of the above two values in the range.
According to the invention, the hexafluoropropylene-vinylidene fluoride copolymer is, for example, a polyvinylidene fluoride (PVDF) -hexafluoropropylene copolymer.
According to the invention, the PVDF has a number average molecular weight of 50 to 200 ten thousand, illustratively 50, 60, 70, 80, 100, 200 ten thousand, or any point in the range of values of two of the above points.
According to the present invention, the mass ratio of HFP in the hexafluoropropylene-vinylidene fluoride copolymer is 1wt.% to 25wt.%, preferably 1.5 wt.% to 15 wt.%, illustratively 1wt.%, 1.5 wt.%, 2wt.%, 2.5 wt.%, 3 wt.%, 3.5 wt.%, 5wt.%, 6.5 wt.%, 9wt.%, 10 wt.%, 15 wt.%, 20 wt.%, 23 wt.%, 25wt.%, or any point within the foregoing range of values.
According to the invention, the addition amount of ethyl propionate in the nonaqueous organic solvent is 5-60 wt% of the total mass of the nonaqueous electrolyte, namely the mass percentage of ethyl propionate in the nonaqueous electrolyte is 5-60 wt%; preferably 10 to 40 wt.%, exemplary 5wt.%, 6 wt.%, 10 wt.%, 12 wt.%, 15 wt.%, 20 wt.%, 22 wt.%, 23 wt.%, 25wt.%, 30 wt.%, 34 wt.%, 35 wt.%, 38 wt.%, 40 wt.%, 48 wt.%, 50 wt.%, 55 wt.%, 60wt.%, or any point in the range of values consisting of two of the foregoing.
According to the present invention, the additives can be prepared by methods known in the art, or can be obtained after being purchased commercially.
According to the invention, in the nonaqueous electrolyte, the addition amount of the fluoroethylene carbonate is 6-25 wt.% of the total mass of the nonaqueous electrolyte; preferably 6 to 18 wt.%, exemplified by 6 wt.%, 10 wt.%, 15 wt.%, 18 wt.%, 20 wt.%, 25wt.% or any point within the range of values consisting of two of the foregoing.
According to the invention, the addition amount of the ethylene carbonate in the nonaqueous electrolytic solution is 0.01 to 2wt.%, illustratively 0.01 wt.%, 0.02 wt.%, 0.03 wt.%, 0.05 wt.%, 0.1 wt.%, 0.5 wt.%, 1wt.%, 2wt.% or any one of the above ranges of the two numerical values.
According to the invention, the lithium difluorophosphate is added in the nonaqueous electrolyte in an amount of 0.01-2% by weight, illustratively 0.01 wt.%, 0.02 wt.%, 0.03 wt.%, 0.05 wt.%, 0.1 wt.%, 0.5 wt.%, 1wt.%, 2wt.% or any one of the foregoing ranges of values.
According to the present invention, the additive may further include other additives, for example, the other additives may be at least one of tris (trimethylsilane) phosphite, tris (trimethylsilyl) borate, lithium bistrifluoromethanesulfonylimide, 1, 3-propanesultone, 1, 3-propenesulfonylimide, vinyl sulfite, vinyl sulfate, vinylene carbonate, lithium dioxalate borate, lithium difluorooxalate phosphate.
According to the invention, the other additive is added in an amount of 0-10wt% of the total mass of the nonaqueous electrolytic solution, and is exemplified by 0wt%, 1 wt%, 2 wt%, 5 wt%, 8 wt%, 10wt% or any one of the foregoing ranges of values.
According to the present invention, the non-aqueous organic solvent further includes at least one of Ethylene Carbonate (EC), Propylene Carbonate (PC), dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, Propyl Propionate (PP), and propyl acetate.
According to an exemplary embodiment of the present invention, the non-aqueous organic solvent includes Ethylene Carbonate (EC), Propylene Carbonate (PC) and Propyl Propionate (PP). Illustratively, the mass ratio of the Ethylene Carbonate (EC), the Propylene Carbonate (PC) and the Propyl Propionate (PP) is (1-2): 1:2, for example, 1.5:1: 2.
According to the present invention, the nonaqueous electrolytic solution further includes a lithium salt.
According to the invention, the lithium salt is selected from lithium bistrifluoromethylsulphonylimide, lithium bistrifluorosulphonylimide and lithium hexafluorophosphate (LiPF) 6 ) Preferably lithium hexafluorophosphate (LiPF) 6 )。
According to the invention, the addition amount of the lithium salt is 13-20 wt.%, exemplified by 13 wt.%, 14 wt.%, 15 wt.%, 16 wt.%, 17 wt.%, 18 wt.%, 19 wt.%, 20 wt.% or any one of the foregoing ranges of numerical values of the nonaqueous electrolytic solution.
According to the invention, the heat-resistant layer comprises a ceramic and a binder.
According to the invention, the ceramic in the heat resistant layer is 20-99 wt.%, exemplary 20 wt.%, 30 wt.%, 40 wt.%, 60wt.%, 80wt.%, 90 wt.%, 95 wt.%, 99wt.% or any point in the range of the aforementioned two numerical values.
According to the invention, the binder is present in the heat resistant layer in an amount of 1 to 80wt.%, exemplified by 1wt.%, 5wt.%, 10 wt.%, 20 wt.%, 30 wt.%, 50 wt.%, 60wt.%, 80wt.% or any one of the aforementioned ranges of values.
According to the invention, the ceramic is selected from one, two or more of alumina, boehmite, magnesia, boron nitride and magnesium hydroxide.
According to the invention, the binder in the heat-resistant layer is selected from one, two or more of polytetrafluoroethylene, polyvinylidene fluoride, hexafluoropropylene-vinylidene fluoride copolymer (such as polyvinylidene fluoride-hexafluoropropylene copolymer), polyimide, polyacrylonitrile and polymethyl methacrylate.
According to the invention, the thickness of the glue layer is between 0.5 μm and 2 μm, and is exemplary 0.5 μm, 1 μm, 2 μm.
According to the invention, the solvent used for the heat-resistant layer and the glue coating layer is at least one selected from acetone, tetrahydrofuran, dichloromethane, chloroform, dimethylformamide, N-methyl-2-pyrrolidone, cyclohexane, methanol, ethanol, isopropanol and water.
According to the invention, the battery is, for example, a lithium ion battery.
According to the present invention, the positive electrode sheet includes a positive electrode collector and a positive electrode active material layer coated on one or both surfaces of the positive electrode collector.
According to the present invention, the positive electrode active material layer includes a positive electrode active material, a conductive agent, and a binder.
According to an exemplary embodiment of the present invention, the mass ratio of the positive electrode active material, the conductive agent, and the binder is 97.6:1.4: 1.0.
According to the invention, the positive active material is selected from lithium cobaltate (LiCoO) 2 ) Or lithium cobaltate (LiCoO) which is doped and coated by two or more elements of Al, Mg, Mn, Cr, Ti and Zr 2 ) The chemical formula of the lithium cobaltate subjected to doping and coating treatment by two or more elements of Al, Mg, Mn, Cr, Ti and Zr is Li x Co 1-y1-y2-y3-y4 A y1 B y2 C y3 D y4 O 2 (ii) a X is more than or equal to 0.95 and less than or equal to 1.05, y1 is more than or equal to 0.01 and less than or equal to 0.1, y2 is more than or equal to 0.01 and less than or equal to 0.1, y3 is more than or equal to 0.1, y4 is more than or equal to 0 and less than or equal to 0.1, and A, B, C, D is selected from two or more elements of Al, Mg, Mn, Cr, Ti and Zr.
According to the present invention, the conductive agent in the positive electrode active material layer is selected from acetylene black.
According to the present invention, the binder in the positive electrode active material layer is selected from polyvinylidene fluoride (PVDF).
According to the present invention, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on one or both surfaces of the negative electrode current collector, the negative electrode active material layer including a negative electrode active material, a conductive agent, and a binder.
According to the present invention, the negative electrode active material is selected from graphite.
According to the invention, the negative electrode active material also optionally contains SiOx/C or Si/C, wherein 0< x < 2. For example, the negative electrode active material further contains 1 to 15 wt% SiOx/C or Si/C, illustratively 1 wt%, 2 wt%, 5 wt%, 8 wt%, 10wt%, 12 wt%, 15 wt%, or any point in the range of the two aforementioned values.
According to the present invention, the charge cut-off voltage of the battery is 4.45V or more.
The invention has the beneficial effects that:
(1) the invention provides a battery, which is prepared by the synergistic effect of a diaphragm and an electrolyte and the combination of a positive electrode material and a negative electrode material, and can effectively prolong the cycle life of the battery, reduce the cycle expansion of the battery and simultaneously give consideration to the low-temperature performance of the battery.
(2) The battery comprises a positive plate, a negative plate, a diaphragm arranged between the positive plate and the negative plate and a non-aqueous electrolyte. The ratio of the mass percentage of the ethyl propionate in the nonaqueous electrolyte to the mass percentage of HFP in the hexafluoropropylene-vinylidene fluoride copolymer is controlled to be 0.2-60, wherein: the ethyl propionate non-aqueous organic solvent has a strong swelling effect on PVDF in the diaphragm, and the swelling effect of the diaphragm can be enhanced through the synergistic effect of the ethyl propionate non-aqueous organic solvent and HFP. Based on the method, the content ratio of ethyl propionate to HFP is controlled, so that the bonding force between the diaphragm and the positive and negative plates can be improved, the change rate of the bonding force between the diaphragm glue coating layer and the positive and negative electrodes in 100 weeks before the battery cycle is ensured to be within 10%, the positive and negative electrodes of the battery can have better interfaces, the cycle expansion is reduced, the damage and the recombination of a CEI (cellulose-rich electrolyte interface) film are reduced, and the stability of a positive electrode material under high temperature and high voltage is improved; meanwhile, the ethyl propionate can also reduce the viscosity of the solvent so as to improve the wettability of the electrolyte and the ionic conductivity and further improve the low-temperature performance of the battery. In addition, the synergistic effect of the additives in the electrolyte formula enables the battery to have both long cycle and low temperature performance, wherein the fluoroethylene carbonate and the ethylene carbonate can form a thicker and stable composite SEI protective film on the surface of the negative electrode to prevent the electrolyte from being reduced and decomposed on the surface of the negative electrode, so that the heat release of side reactions is reduced, the cycle expansion is reduced, and the cycle life of the battery is prolonged; and lithium difluorophosphate can form an SEI film rich in inorganic components on the positive electrode and the negative electrode so as to reduce the impedance of the film and further improve the low-temperature performance of the battery.
Detailed Description
The present invention will be described in further detail with reference to specific examples. It is to be understood that the following examples are only illustrative and explanatory of the present invention and should not be construed as limiting the scope of the present invention. All the technologies realized based on the above-mentioned contents of the present invention are covered in the protection scope of the present invention.
The experimental methods used in the following examples are all conventional methods unless otherwise specified; reagents, materials and the like used in the following examples are commercially available unless otherwise specified.
Comparative examples 1 to 6 and examples 1 to 8
The lithium ion batteries of comparative examples 1 to 6 and examples 1 to 8 were manufactured according to the following manufacturing method, except for the selection of the separator and the electrolyte, and the specific differences are shown in table 1.
(1) Preparation of positive plate
LiCoO as positive electrode active material 2 Mixing polyvinylidene fluoride (PVDF) serving as a binder and acetylene black serving as a conductive agent according to the weight ratio of 97.6:1.4:1.0, adding N-methylpyrrolidone (NMP), and stirring under the action of a vacuum stirrer until a mixed system becomes uniform and flowable anode slurry; uniformly coating the anode slurry on an aluminum foil with the thickness of 11 mu m; baking the coated aluminum foil in 5 sections of baking ovens with different temperature gradients, drying the aluminum foil in a baking oven at 120 ℃ for 8 hours, and rolling and cutting to obtain the required positive plate.
(2) Preparation of cathode plate
Preparing a slurry from an artificial graphite negative electrode material with the mass ratio of 96.9%, a single-walled carbon nanotube (SWCNT) conductive agent with the mass ratio of 0.1%, a conductive carbon black (SP) conductive agent with the mass ratio of 0.8%, a sodium carboxymethylcellulose (CMC) binder with the mass ratio of 0.9% and a Styrene Butadiene Rubber (SBR) binder with the mass ratio of 1.3% by a wet process, coating the slurry on the surface of a negative current collector copper foil, drying (the temperature: 85 ℃, the time: 5h), rolling and die cutting to obtain a negative electrode sheet.
(3) Preparation of non-aqueous electrolyte
In a glove box filled with argon (moisture)<10ppm, oxygen content<1ppm), Ethylene Carbonate (EC), Propylene Carbonate (PC) and Propyl Propionate (PP) were mixed uniformly in a mass ratio of 1.5:1:2, and 14 wt.% of LiPF based on the total mass of the nonaqueous electrolyte was slowly added to the mixed solution 6 And 5-60 wt.% of ethyl propionate (the specific amount of ethyl propionate is shown in table 1) and additives (the specific amount and selection of additives are shown in table 1) based on the total mass of the nonaqueous electrolyte, and uniformly stirring to obtain the nonaqueous electrolyte.
(4) Preparation of the separator
The method comprises the steps of coating an aluminum oxide ceramic layer with the thickness of 2 mu m on each of two sides of a polyethylene base material with the thickness of 5 mu m, coating a glue coating layer with the thickness of 1 mu m on the surface of the ceramic coating layer, wherein the glue coating layer adopts polyvinylidene fluoride (PVDF) -hexafluoropropylene copolymer (HFP) as a bonding agent, and the specific content of hexafluoropropylene in the polyvinylidene fluoride (PVDF) -Hexafluoropropylene (HFP) copolymer in mass ratio is shown in table 1.
(5) Preparation of lithium ion battery
Winding the prepared positive plate, the diaphragm and the negative plate to obtain a bare cell without liquid injection; and (3) placing the bare cell in an outer packaging foil, injecting the prepared electrolyte into the dried bare cell, and performing vacuum packaging, standing, formation, shaping, sorting and other processes to obtain the required lithium ion battery.
TABLE 1 lithium ion batteries prepared in comparative examples 1 to 6 and examples 1 to 8
The cells obtained in the above comparative examples and examples were subjected to electrochemical performance tests, as described below:
25 ℃ cycling experiment: will be described in detailThe batteries obtained in the examples and the comparative examples are placed in an environment of (25 +/-2) DEG C and are kept stand for 2-3 hours, when the battery body reaches (25 +/-2) DEG C, the cut-off current of the battery is 0.05C according to 1C constant current charging, the battery is kept stand for 5 minutes after being fully charged, then the battery is discharged to the cut-off voltage of 3.0V according to 1C constant current, the highest discharge capacity of the previous 3 cycles is recorded as the initial capacity Q, and when the cycle times reach 1000 times, the last discharge capacity Q of the battery is recorded 1 (ii) a Recording the initial thickness T of the battery cell, and recording the thickness T when the battery cell is cycled for 1000 times 1 The results are reported in Table 2.
The calculation formula used therein is as follows: capacity retention (%) ═ Q 1 (ii)/Q × 100%; thickness change rate (%) - (T) 1 -T)/T×100％。
10 ℃ cycling experiment: placing the batteries obtained in the above examples and comparative examples in an environment of (10 +/-2) DEG C, standing for 2-3 hours, when the battery body reaches (10 +/-2) DEG C, keeping the cut-off current of the battery at 0.05C according to 0.7C constant current charging, standing for 5 minutes after the battery is fully charged, then discharging to the cut-off voltage of 3.0V at 0.5C constant current, and recording the highest discharge capacity of the previous 3 cycles as the initial capacity Q 2 When the circulation reaches 300 times, recording the last discharge capacity Q of the battery 3 (ii) a Recording cell initial thickness T 2 And the thickness of the solution after the cycle of selection and the cycle of 300 weeks is recorded as T 3 The results are reported in Table 2.
The calculation formula used therein is as follows: capacity retention (%) ═ Q 3 /Q 2 X is 100%; thickness change rate (%) - (T) 3 -T 2 )/T 2 ×100％。
Low-temperature discharge experiment: discharging the batteries obtained in the above examples and comparative examples to 3.0V at ambient temperature of 25 + -3 deg.C at 0.2C, and standing for 5 min; charging at 0.7C, changing into constant voltage charging when the battery terminal voltage reaches the charging limit voltage, stopping charging until the charging current is less than or equal to the cut-off current, discharging at 0.2C to 3.0V after laying aside for 5 minutes, and recording the discharge capacity as the normal temperature capacity Q 4 . Then the battery is charged at 0.7C, when the terminal voltage of the battery reaches the charging limiting voltage, the constant voltage charging is changed, and the charging is stopped until the charging current is less than or equal to the cut-off current; placing the fully charged battery at-10 +/-2 DEG CAfter standing for 4h, discharging with 0.4C current to cut-off voltage of 3.0V, and recording discharge capacity Q 5 The low-temperature discharge capacity retention rate was calculated and reported in table 2.
The calculation formula used therein is as follows: low-temperature discharge capacity retention (%) ═ Q 5 /Q 4 ×100％。
Thermal shock test at 130 ℃: the batteries obtained in the above examples and comparative examples were heated at an initial temperature of 25. + -. 3 ℃ by convection or a circulating hot air oven at a temperature change rate of 5. + -. 2 ℃/min, heated to 130. + -. 2 ℃ and held for 60min, and the test was terminated, and the results of the battery state were recorded as shown in Table 2.
The method for measuring the adhesive force between the diaphragm glue coating layer and the negative electrode comprises the following steps:
the batteries obtained in the above examples and comparative examples were left to stand at (25. + -. 2) ℃ for 2 to 3 hours, when the temperature of the battery body reaches (25 +/-2) DEG C, the battery is charged according to the constant current of 0.7C, the cut-off current is 0.05C, when the voltage of the battery terminal reaches the charging limiting voltage, changing constant voltage charging until the charging current is less than or equal to the cut-off current, stopping charging and standing for 5min, dissecting the fully charged battery, selecting a diaphragm and a negative electrode integral sample with the length of 30mm x 15mm in width along the direction of a tab, testing the diaphragm and the negative electrode at an included angle of 180 degrees on a universal stretching machine at the speed of 100mm/min and the test displacement of 50mm, and recording the test result as the bonding force N (unit N/m) between the diaphragm and the negative electrode, wherein the bonding force tested by a fresh battery is N1 (unit N/m), and the bonding force tested by a battery circulating for 100 weeks is N2 (unit N/m);
the calculation formula used therein is as follows:
the change rate (%) of the adhesive force between the separator coating layer and the negative electrode was (N1-N2)/N1 × 100%
TABLE 2 experimental test results of the batteries obtained in comparative examples 1 to 6 and examples 1 to 8
As can be seen from the results of table 2: according to the invention, the lithium ion battery prepared by the synergistic effect of the diaphragm and the electrolyte and combined use of the positive and negative electrode materials can effectively prolong the cycle life of the battery, reduce the cycle expansion of the battery and simultaneously give consideration to the low-temperature performance of the battery.
The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (24)
1. A battery, comprising a positive electrode sheet, a negative electrode sheet, a separator interposed between the positive electrode sheet and the negative electrode sheet, and a nonaqueous electrolytic solution;
the diaphragm comprises a base material, heat-resistant layers and glue coating layers, wherein the heat-resistant layers are oppositely arranged on two sides of the base material, and the glue coating layers are arranged on the heat-resistant layers; the glue coating layer comprises a bonding agent, and the bonding agent comprises hexafluoropropylene-vinylidene fluoride copolymer;
the nonaqueous electrolytic solution comprises a nonaqueous organic solvent and an additive, wherein the nonaqueous organic solvent at least comprises ethyl propionate; the additives include fluoroethylene carbonate, ethylene carbonate and lithium difluorophosphate;
the ratio of the mass percentage content of the ethyl propionate in the nonaqueous electrolyte to the mass percentage content of Hexafluoropropylene (HFP) in the hexafluoropropylene-vinylidene fluoride copolymer is 0.2-60;
the mass proportion of HFP in the hexafluoropropylene-vinylidene fluoride copolymer is 1wt.% to 25 wt.%;
the addition amount of the ethyl propionate is 5-60 wt% of the total mass of the nonaqueous electrolyte.
2. The battery as claimed in claim 1, wherein the ratio of the mass percentage of ethyl propionate in the nonaqueous electrolyte to the mass of HFP in the hexafluoropropylene/vinylidene fluoride copolymer is 0.5 to 35.
3. The battery according to claim 1 or 2, wherein the hexafluoropropylene-vinylidene fluoride copolymer is a polyvinylidene fluoride-hexafluoropropylene copolymer, and the polyvinylidene fluoride has a number average molecular weight of 50 to 200 ten thousand.
4. The battery according to claim 1, wherein the fluoroethylene carbonate is added in an amount of 6 to 25wt.% based on the total mass of the nonaqueous electrolyte solution.
5. The battery according to claim 1, wherein the addition amount of the ethylene carbonate is 0.01 to 2wt.% based on the total mass of the nonaqueous electrolyte solution.
6. The battery of claim 1, wherein the lithium difluorophosphate is added in an amount of 0.01 to 2wt.% based on the total mass of the electrolyte.
7. The battery of claim 1, wherein the additive further comprises other additives.
8. The cell of claim 7, wherein the other additive is at least one of tris (trimethylsilane) phosphite, tris (trimethylsilyl) borate, 1, 3-propanesultone, vinyl sulfite, vinyl sulfate, vinylene carbonate, lithium dioxalate borate, lithium difluorooxalato phosphate, and vinyl carbonate.
9. The battery according to claim 7, wherein the other additive is added in an amount of 0 to 10wt% based on the total mass of the electrolyte.
10. The battery of claim 1, wherein the non-aqueous organic solvent further comprises at least one of Ethylene Carbonate (EC), Propylene Carbonate (PC), dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, Propyl Propionate (PP), and propyl acetate.
11. The battery of claim 1, wherein the nonaqueous electrolyte further comprises a lithium salt.
12. The cell of claim 11, wherein the lithium salt is selected from the group consisting of lithium bistrifluoromethylsulfonyl imide, lithium bistrifluorosulfonimide, and lithium hexafluorophosphate (LiPF) 6 ) At least one of (1).
13. The battery according to claim 11, wherein the lithium salt is added in an amount of 13 to 20 wt.% based on the total mass of the nonaqueous electrolyte solution.
14. The battery of claim 1, wherein the heat resistant layer comprises a ceramic and a binder.
15. The battery according to claim 14, wherein the proportion of the ceramic in the heat-resistant layer is 20 to 99 wt.%.
16. The battery according to claim 14, wherein the binder is present in the heat-resistant layer in an amount of 1 to 80 wt.%.
17. The cell of claim 14, wherein the ceramic is selected from one, two or more of alumina, boehmite, magnesium oxide, boron nitride, and magnesium hydroxide.
18. The battery according to claim 14, wherein the binder in the heat-resistant layer is one, two or more selected from the group consisting of polytetrafluoroethylene, polyvinylidene fluoride, hexafluoropropylene-vinylidene fluoride copolymer, polyimide, polyacrylonitrile, and polymethyl methacrylate.
19. The battery according to claim 1, wherein the thickness of the rubber coating layer is 0.5-2 μm.
20. The battery according to claim 1, wherein the positive electrode sheet comprises a positive electrode collector and a positive electrode active material layer coated on one or both surfaces of the positive electrode collector, and the positive electrode active material layer comprises a positive electrode active material, a conductive agent, and a binder.
21. The cell of claim 20, wherein the positive active material is selected from the group consisting of lithium cobaltate or lithium cobaltate doped with two or more elements selected from the group consisting of Al, Mg, Mn, Cr, Ti and Zr, and the chemical formula of the lithium cobaltate doped with two or more elements selected from the group consisting of Al, Mg, Mn, Cr, Ti and Zr is Li x Co 1-y1-y2-y3-y4 A y1 B y2 C y3 D y4 O 2 (ii) a X is more than or equal to 0.95 and less than or equal to 1.05, y1 is more than or equal to 0.01 and less than or equal to 0.1, y2 is more than or equal to 0.01 and less than or equal to 0.1, y3 is more than or equal to 0.1, y4 is more than or equal to 0 and less than or equal to 0.1, and A, B, C, D is selected from two or more elements of Al, Mg, Mn, Cr, Ti and Zr.
22. The battery according to claim 1, wherein the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer coated on one or both surfaces of the negative electrode current collector, the negative electrode active material layer comprising a negative electrode active material, a conductive agent, and a binder.
23. The cell defined in claim 22, wherein the negative active material is selected from graphite.
24. The battery of claim 23, wherein the negative electrode active material further optionally comprises SiOx/C or Si/C, where 0< x < 2.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
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| CN202111251998.9A CN114024034B (en) | 2021-10-25 | 2021-10-25 | Battery with improved battery capacity |
| PCT/CN2022/127437 WO2023072095A1 (en) | 2021-10-25 | 2022-10-25 | Battery |
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| CN202111251998.9A CN114024034B (en) | 2021-10-25 | 2021-10-25 | Battery with improved battery capacity |
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| CN114024034B true CN114024034B (en) | 2022-08-30 |
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| WO2023072108A1 (en) * | 2021-10-25 | 2023-05-04 | 珠海冠宇电池股份有限公司 | Battery |
| CN114024034B (en) * | 2021-10-25 | 2022-08-30 | 珠海冠宇电池股份有限公司 | Battery with improved battery capacity |
| CN115172990A (en) * | 2022-07-08 | 2022-10-11 | 珠海冠宇电池股份有限公司 | Diaphragm and battery |
| CN115275524B (en) * | 2022-08-12 | 2023-11-28 | 珠海冠宇电池股份有限公司 | Battery diaphragm and battery |
| CN116231091B (en) * | 2023-05-08 | 2023-08-29 | 宁德时代新能源科技股份有限公司 | Electrolyte for lithium secondary battery, and electricity using device |
| CN117154187A (en) * | 2023-10-30 | 2023-12-01 | 宁德时代新能源科技股份有限公司 | Battery cell, battery and electricity utilization device |
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| WO2019093853A1 (en) * | 2017-11-13 | 2019-05-16 | 주식회사 엘지화학 | Non-aqueous electrolyte for lithium secondary battery and lithium secondary battery comprising same |
| CN112467209A (en) * | 2019-09-09 | 2021-03-09 | 珠海冠宇电池股份有限公司 | High-voltage lithium ion battery with high and low temperature performance |
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| CN101651234B (en) * | 2008-08-13 | 2012-10-17 | 比亚迪股份有限公司 | Lithium-ion secondary battery |
| CN110635133B (en) * | 2019-08-30 | 2021-08-06 | 东莞赣锋电子有限公司 | Quick-charging type lithium ion battery and preparation method thereof |
| CN112825370A (en) * | 2019-11-20 | 2021-05-21 | 珠海冠宇电池股份有限公司 | Non-aqueous electrolyte and lithium ion battery containing same |
| CN114024034B (en) * | 2021-10-25 | 2022-08-30 | 珠海冠宇电池股份有限公司 | Battery with improved battery capacity |
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| JPH10241691A (en) * | 1996-12-24 | 1998-09-11 | Hitachi Ltd | Battery |
| JP2001110443A (en) * | 1999-10-13 | 2001-04-20 | Matsushita Electric Ind Co Ltd | Nonaqueous electrolytic solution secondary battery |
| JP2011181354A (en) * | 2010-03-02 | 2011-09-15 | Sony Corp | Negative electrode and nonaqueous electrolyte battery |
| WO2019093853A1 (en) * | 2017-11-13 | 2019-05-16 | 주식회사 엘지화학 | Non-aqueous electrolyte for lithium secondary battery and lithium secondary battery comprising same |
| CN112467209A (en) * | 2019-09-09 | 2021-03-09 | 珠海冠宇电池股份有限公司 | High-voltage lithium ion battery with high and low temperature performance |
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| CN114024034A (en) | 2022-02-08 |
| WO2023072095A1 (en) | 2023-05-04 |
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