CN117832395A - Negative electrode plate, formation method of lithium ion battery and lithium ion battery - Google Patents
Negative electrode plate, formation method of lithium ion battery and lithium ion battery Download PDFInfo
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- CN117832395A CN117832395A CN202410100149.0A CN202410100149A CN117832395A CN 117832395 A CN117832395 A CN 117832395A CN 202410100149 A CN202410100149 A CN 202410100149A CN 117832395 A CN117832395 A CN 117832395A
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- formation
- ion battery
- lithium ion
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 64
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 64
- 238000000034 method Methods 0.000 title claims abstract description 33
- 229910003002 lithium salt Inorganic materials 0.000 claims abstract description 53
- -1 lithium salt compound Chemical class 0.000 claims abstract description 27
- 239000007773 negative electrode material Substances 0.000 claims abstract description 25
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Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
-
- 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
-
- 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
-
- 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
- H01M10/44—Methods for charging or discharging
- H01M10/446—Initial charging measures
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative electrodes
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- General Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- General Physics & Mathematics (AREA)
- Inorganic Chemistry (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- Physics & Mathematics (AREA)
- Secondary Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The application relates to a negative electrode plate, a formation method of a lithium ion battery and the lithium ion battery. The negative electrode plate comprises a negative electrode current collector, a negative electrode active material layer coated on the surface of the negative electrode current collector and an artificial SEI film layer positioned on the surface of the negative electrode active material layer; the artificial SEI film layer includes a lithium salt compound and a plasticizer. According to the scheme, the formation current and the formation temperature can be improved, the formation time is shortened, the effects of reducing cost and improving efficiency are achieved, meanwhile, the formation gas production rate can be effectively reduced, the risk of cell bulge leakage is reduced, and the deterioration of the formation current on the battery circulation performance is relieved.
Description
Technical Field
The application relates to the technical field of lithium ion batteries, in particular to a negative electrode plate, a formation method of a lithium ion battery and the lithium ion battery.
Background
The lithium ion battery is used as a clean and convenient energy source, plays a very important role in daily life of people, and more electrical equipment are required to be powered by the lithium ion battery.
The formation is an important step in the manufacture of lithium ion batteries, and is extremely critical to the performance of the lithium ion batteries. The main function of the formation is to form a layer of compact protective film on the surface of the negative electrode of the battery, thereby effectively preventing the co-intercalation of solvent molecules, avoiding the damage to the electrode material caused by the co-intercalation of the solvent molecules, and further improving the cycle performance and the service life of the battery.
In the formation process, the formation time can be shortened by a method of improving formation current, so that the effects of reducing cost and improving efficiency are achieved. However, when the formation current is increased, a large amount of gas is produced in the formation process, and the battery cell is at risk of bulge leakage.
Disclosure of Invention
In order to solve or partially solve the problems in the related art, the application provides a formation method of a negative electrode plate and a lithium ion battery and the lithium ion battery, which can improve formation current and formation temperature, shorten formation time, achieve the effects of cost reduction and synergy, effectively reduce formation gas yield, reduce the risk of battery cell swelling and leakage, and alleviate the deterioration of formation current promotion on battery cycle performance.
The first aspect of the application provides a negative electrode plate, which comprises a negative electrode current collector, a negative electrode active material layer coated on the surface of the negative electrode current collector and an artificial SEI film layer positioned on the surface of the negative electrode active material layer; the artificial SEI film layer includes a lithium salt compound and a plasticizer.
In some embodiments of the present application, the lithium salt compound comprises Li 4 SiO 4 、Li 2 SiO 3 、Li 3 N、LiAlH 4 、Li 2 One or more of S.
In some embodiments of the present application, the plasticizer comprises one or more of CMC, PVP, PAA, PMMA, PEO.
In some embodiments of the present application, the mass ratio of the lithium salt compound to the plasticizer is (80-90): (10-20).
In some embodiments of the present application, the artificial SEI film layer has a thickness of H in μm; wherein H is more than or equal to 10 and less than or equal to 100.
In some embodiments of the present application, the anode active material layer includes an anode active material selected from one of a si—c compound or a siom—c compound (m.ltoreq.2), a binder, and a conductive agent.
The second aspect of the present application provides a method for preparing a negative electrode sheet, including the following steps:
uniformly mixing a negative electrode active material, a binder and a conductive agent to obtain a negative electrode slurry, and coating the negative electrode slurry on the surface of a negative electrode current collector to form a negative electrode active material layer;
and uniformly mixing a lithium salt compound and a plasticizer to obtain artificial SEI film precursor slurry, and depositing the artificial SEI film precursor slurry on the surface of the negative electrode active material layer to form an artificial SEI film layer, so as to obtain the negative electrode plate.
A third aspect of the present application provides a formation method of a lithium ion battery, where the lithium ion battery includes a negative electrode tab according to the first aspect of the present application or a negative electrode tab manufactured by a manufacturing method according to the second aspect of the present application, where: forming the lithium ion battery by XC multiplying power charging current, wherein the range of X is more than or equal to 0.05 and less than or equal to 0.5; and/or forming the lithium ion battery at the formation temperature of T ℃, wherein the range of T is more than or equal to 45 and less than or equal to 70.
A fourth aspect of the present application provides a lithium ion battery, comprising a negative electrode sheet according to the first aspect of the present application or a negative electrode sheet prepared by a preparation method according to the second aspect of the present application, or a formation method according to the third aspect of the present application.
In some embodiments of the present application, the lithium ion battery further comprises an electrolyte, a separator, and a positive electrode sheet, wherein the negative electrode sheet, the separator, and the positive electrode sheet are sequentially stacked, wound, and then immersed in the electrolyte; the electrolyte comprises a solvent, a lithium salt and an additive, wherein the additive comprises fluoroethylene carbonate and a lithium salt additive, and the lithium salt additive comprises one or more of lithium bis (fluorosulfonyl) imide and lithium bis (trifluoromethylsulfonyl) imide.
In some embodiments of the present application, the fluoroethylene carbonate has a mass ratio of a.ltoreq.a.ltoreq.20 in the electrolyte.
In some embodiments of the present application, the mass ratio of the lithium salt additive in the electrolyte is b.ltoreq.b.ltoreq.5.
In some embodiments of the present application, the formation current of the lithium ion battery is XC multiplying power, the formation temperature is T ℃, the thickness of the artificial SEI film layer is H, and the unit is μm; wherein H/b is more than or equal to 2 and less than or equal to 100, H/(X X a) is more than or equal to 4 and less than or equal to 200,0.011, and b/T is more than or equal to 0.111.
The technical scheme that this application provided can include following beneficial effect:
the transmission capacity of lithium ions at an interface can be improved through the artificial SEI film layer in the negative electrode plate, and the low-temperature cycle performance of the battery is improved; the artificial SEI film layer can reduce the gas production caused by the decomposition of electrolyte in the lithium ion battery, reduce the risk of swelling and leakage of the battery core, relieve the deterioration of the cycle performance of the battery caused by the improvement of formation current, and reduce the interface impedance and improve the conductivity, so that the formation current can be obviously improved, the formation time is shortened, and the effects of reducing the cost and enhancing the efficiency are achieved.
Furthermore, the artificial SEI film layer in the negative electrode plate and fluoroethylene carbonate and lithium salt additive in the electrolyte are combined, so that the formation gas yield can be further reduced, the formation temperature and the formation current can be increased, and the formation time can be further shortened; and the degradation of the cycle performance of the battery caused by the formation current rise and the formation temperature rise can be effectively relieved, and the low-temperature cycle performance and the high Wen Qiantao cycle performance of the battery are improved.
Detailed Description
In order that the invention may be readily understood, the invention will be described in detail. Before the present invention is described in detail, it is to be understood that this invention is not limited to particular embodiments described. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.
The terminology used in the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. As used in this application and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any or all possible combinations of one or more of the associated listed items.
Where a range of values is provided, it is understood that each intervening value, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges, and are also encompassed within the invention, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the invention. In the description of the present application, the meaning of "plurality" is two or more, unless explicitly defined otherwise.
Unless defined otherwise, all terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Although any methods and materials equivalent to those described herein can also be used in the practice or testing of the present invention, the preferred methods and materials are now described.
In the formation process, the formation time can be shortened by a method of improving formation current, so that the effects of reducing cost and improving efficiency are achieved. However, when the formation current is increased, a large amount of gas is generated in the formation process, the battery cell has the risk of bulging and leakage, the SEI film stability on the surface of the negative electrode of the battery is poor, and the cycle performance of the battery cell is deteriorated.
Aiming at the problems, the embodiment of the application provides a formation method of a negative electrode plate and a lithium ion battery and the lithium ion battery, which can improve formation current and formation temperature, shorten formation time, achieve the effects of cost reduction and efficiency improvement, effectively reduce formation gas yield, reduce the risk of swelling and leakage of a battery core, and relieve the deterioration of the circulation performance of the battery caused by formation current improvement.
The negative electrode plate comprises a negative electrode current collector, a negative electrode active material layer coated on the surface of the negative electrode current collector and an artificial SEI film layer positioned on the surface of the negative electrode active material layer. The artificial SEI film layer on the surface of the negative electrode active material layer plays an isolating role, reduces direct contact between the negative electrode active material and electrolyte, further relieves decomposition of the electrolyte, reduces gas production, reduces interface impedance of the negative electrode, improves interface conductivity, improves transmission rate of lithium ions, and further improves low-temperature cycle performance and formation current of the battery.
Wherein the negative electrode current collector may be selected from a metal foil or a composite current collector, such as copper foil.
The negative electrode active material layer comprises a negative electrode active material, a binder and a conductive agent, wherein the negative electrode active material can be selected from natural graphite, artificial graphite, mesocarbon microbeads, hard carbon, soft carbon, silicon-carbon composite, li-Sn alloy, li-Sn-O alloy, sn, snO, snO 2 Or spinel structured lithiated TiO 2 -Li 4 Ti 5 O 12 One or more of Li-Al alloys; preferably a silicon-carbon composite, such as one of Si-C composite or Sium-C composite (m.ltoreq.2). The conductive agent may be selected from one or more of conductive carbon black (SP), acetylene black (ACET), ketjen black, carbon Dots (CDs), carbon Nanotubes (CNTs), graphene (GPE), carbon Nanofibers (CNF), superconducting carbon, which is not limited in this application. The binder may be selected from one or more of styrene-butadiene rubber (SBR), aqueous acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid (PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA), and polyvinyl butyral (PVB), which is not limited in this application.
The artificial SEI film layer may include a lithium salt compound and a plasticizer.
In some embodiments, the lithium salt compound comprises Li 4 SiO 4 、Li 2 SiO 3 、Li 3 N、LiAlH 4 、Li 2 One or more of S.
In some embodiments, the plasticizer comprises one or more of CMC, PVP, PAA, PMMA, PEO.
In some embodiments, the mass ratio of lithium salt compound to plasticizer is (80-90): (10-20).
In the embodiment of the application, the artificial SEI film layer formed by adopting the combination of the plasticizer and the lithium salt compound has good conductivity and low interface impedance, can effectively promote formation current, shortens formation time, and achieves the purposes of reducing cost and enhancing efficiency; meanwhile, the lithium salt compound can effectively improve the transmission capacity of lithium ions at an interface and improve the low-temperature cycle performance of the battery.
In some embodiments, the artificial SEI film layer has a thickness H in μm; wherein 10.ltoreq.H.ltoreq.100, for example 10 μm, 20 μm, 30 μm, 40 μm, 60 μm, 80 μm, 100 μm, etc., may be any value within the above-mentioned range. The thickness of the artificial SEI film layer is in the range, sodium ions can be rapidly transmitted at the interface, meanwhile, a stable negative electrode structure of a negative electrode plate can not be maintained, volume deterioration along with battery circulation is avoided, electrolyte consumption caused by side reaction of a negative electrode active substance rapidly exposed in electrolyte and the electrolyte is avoided, and the cycle performance and the battery capacity of the battery are improved.
The preparation method of the negative electrode plate comprises the following steps:
(1) And uniformly mixing the anode active material, the binder and the conductive agent to obtain anode slurry, coating the anode slurry on at least one side surface of the anode current collector to form an anode active material layer, and drying and cold pressing to obtain the first pole piece.
(2) And uniformly mixing the lithium salt compound and the plasticizer to obtain artificial SEI film precursor slurry, and depositing the artificial SEI film precursor slurry on the surface of the negative electrode active material layer of the first pole piece to form an artificial SEI film layer, so as to obtain the negative pole piece.
Firstly, uniformly dispersing a plasticizer in a solvent to obtain a precursor slurry solution, and uniformly dispersing a lithium salt compound in the precursor slurry solution to obtain an artificial SEI film precursor slurry; and then, continuously and uniformly depositing the artificial SEI film precursor slurry on the surface of the negative electrode active material layer under a non-vacuum condition by an atomic layer deposition technology, and drying to obtain the negative electrode plate.
According to the negative electrode plate, the atomic layer deposition technology is adopted to deposit and obtain the micron-sized artificial SEI film layer on the surface of the negative electrode active material layer, the artificial SEI film layer is utilized to isolate the negative electrode active material from electrolyte, consumption of active lithium is reduced, interface impedance of the negative electrode is reduced, and low-temperature cycle performance of the battery is improved.
The lithium ion battery comprises the negative electrode plate or the negative electrode plate manufactured by the method.
The lithium ion battery also comprises electrolyte, a separation film and a positive pole piece. The battery cell is prepared by sequentially laminating a negative electrode plate, a separation film and a positive electrode plate, then preparing a battery cell through a winding process or a lamination process, putting the battery cell into an aluminum plastic film which is formed by punching, baking the battery cell, injecting electrolyte into the baked and dried battery cell to enable the battery cell to be immersed in the electrolyte, and then carrying out the procedures of vacuum packaging, standing, formation and the like.
In some embodiments, the electrolyte includes a solvent, a lithium salt, and an additive.
Wherein the additive comprises an additive A and an additive B, the additive A is selected from fluoroethylene carbonate FEC, the additive B is selected from lithium salt additives, and the lithium salt additives can comprise one or more of lithium bis (fluorosulfonyl) imide and lithium bis (trifluoromethylsulfonyl) imide.
In the embodiment of the application, fluoroethylene carbonate FEC is used as a film forming additive, has good effect of improving the battery cycle performance, but when FEC is added into electrolyte, a large amount of gas is produced in the formation process, and the battery core also has the risk of swelling and leaking liquid, so that certain trouble is caused to production; the lithium hexafluorophosphate which is a common lithium salt in the electrolyte can be decomposed at high temperature to generate acidic byproducts, and the acidic byproducts can cause the electrolyte to decompose and produce gas during formation, so that the formation gas yield is increased. In the application, by utilizing the combined use of fluoroethylene carbonate and lithium salt additives such as lithium bis (fluorosulfonyl) imide and lithium bis (trifluoromethylsulfonyl) imide in the electrolyte, an SEI film with good stability and high density can be formed on the surface of a battery cathode, so that the high-temperature intermittent cycle performance of the battery is effectively improved; in addition, the use of lithium salt additives such as lithium bis (fluorosulfonyl) imide and lithium bis (trifluoromethylsulfonyl) imide can raise the decomposition temperature of the electrolyte, and the defect of high-temperature decomposition of lithium hexafluorophosphate can be overcome during high-temperature formation, so that the formation temperature can also be raised.
By using the combination of the additive in the electrolyte and the artificial SEI film layer in the negative electrode plate, the formation temperature and the formation current can be synergistically increased, the formation time is shortened, and the effects of cost reduction and synergy are achieved; meanwhile, the formation gas yield can be effectively reduced, the risk of cell bulge leakage is reduced, the low-temperature cycle performance and the high-temperature indirect cycle performance of the battery are improved, and the overall performance of the battery is improved.
It should be noted that, the high-temperature intermittent cycle performance is different from the high-temperature cycle performance, and the traditional high-temperature cycle improvement mode is to protect the dissolution of the cobalt in the positive electrode by the nitrile compound or form a stable SEI film; the high-temperature intermittent cycle performance needs a section of high-temperature rest process under full-power high voltage, which is equivalent to high-temperature cycle and full-power high-temperature storage, so that the stability of the SEI film on the negative electrode side affects the high-temperature intermittent cycle more remarkably. The lithium salt additive in the electrolyte is mainly used for improving the high-temperature standing stage, so that the electrolyte is not easy to decompose at high temperature, the formation temperature is further improved, and the high-temperature performance of the battery is improved.
In some embodiments, the fluoroethylene carbonate may have a mass ratio of a% to the electrolyte of 5.ltoreq.a.ltoreq.20, for example, 5%, 10%, 15%, 20%, etc., and may have any value within the above range. When the mass ratio of fluoroethylene carbonate is in the range, SEI film with high density and good stability can be rapidly formed on the surface of the negative electrode, and the cycle performance of the battery is improved.
In some embodiments, the mass ratio of the lithium salt additive in the electrolyte is b%, and b.ltoreq.0.05.ltoreq.5, for example, 0.05%, 0.5%, 1%, 2%, 3%, 4%, 5%, etc., and may be any value within the above range. When the mass ratio of the lithium salt additive is within the range, the lithium salt additive can be well matched with fluoroethylene carbonate to improve the defect that electrolyte is easy to decompose during high-temperature formation and improve the formation temperature and formation current.
In some embodiments, the lithium salt in the electrolyte may include lithium hexafluorophosphate (LiPF 6 ) Lithium difluorooxalato borate (LiODFB), lithium bisoxalato borate (LiBOB), lithium difluorodioxaato phosphate (LiDFOP), lithium tetrafluoroborate (LiBF) 4 ) Lithium bis (trifluoromethylsulfonyl) imide (LiTFSI), lithium bis (fluorosulfonyl) imide (LiFSI), lithium difluorophosphate (LiPO) 2 F 2 ) One or more of (a) and (b).
In some embodiments, the concentration of lithium salt in the electrolyte is 0.5 to 2mol/L.
In some embodiments, the solvent in the electrolyte includes one or more of Ethylene Carbonate (EC), propylene Carbonate (PC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), ethyl Propionate (EP), propyl Propionate (PP), ethyl fluoroacetate (DFEA), ethylene Fluorocarbonate (FEC), ethylmethyl Fluorocarbonate (FEMC), dimethyl Fluorocarbonate (FDMC), propylene Fluorocarbonate (FPC); two or more of the above organic solvents are preferable.
The electrolyte is one of the main materials of the lithium ion battery and is one of the important factors influencing the performance of the lithium ion battery. The solvent, the lithium salt and the additive are main components of the electrolyte, and have great influence on the performances of the battery, such as circulation, impedance, dynamics and the like. According to the embodiment of the application, through optimizing the composition of the electrolyte, the composition, the content and other parameters of the additive in the electrolyte are comprehensively designed, so that the parameters are met, the electrolyte and the negative electrode plate are matched in a synergistic way, the formation gas yield can be effectively reduced on the basis of meeting the requirements of improving the formation temperature and improving the formation current, the formation time is shortened, and the effects of reducing the cost and improving the efficiency are achieved; meanwhile, the transmission capacity of lithium ions at the interface is improved, and the low-temperature cycle performance and the high-temperature intermittent cycle performance of the battery are improved.
In some embodiments, the positive electrode tab includes a positive electrode current collector and a positive electrode active material layer coated on a surface of the positive electrode current collector. Wherein the positive current collector may be selected from a metal foil or a composite current collector, such as aluminum foil.
The positive electrode active material layer includes a positive electrode active material, a conductive agent, and a binder. Wherein the positive electrode active material is selected from lithium iron phosphate, lithium manganese iron phosphate, lithium cobaltate, ternary LiNi x Co y Mn z O 2 One or more of the materials, wherein: x+y+z=1, x is not less than y. The conductive agent may be one or more selected from superconducting carbon, acetylene black (ACET), carbon Black (CB), ketjen black, carbon Dots (CDs), carbon Nanotubes (CNTs), graphene (GPE), and Carbon Nanofibers (CNF), which are not limited in this application. The binder may be selected from one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluoroacrylate resin, which is not limited in this application.
In some embodiments, the separator may be arbitrarily selected from known porous structure separators having good chemical and mechanical stability. The material of the isolating film may be at least one selected from glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. When the separator is a multilayer composite film, the materials of the respective layers may be the same or different, and are not particularly limited.
In the formation method of the lithium ion battery in the embodiment of the present application, the lithium ion battery is formed by charging current with XC rate, and X is in a range of 0.05C or more and 0.5 or less, for example, 0.05C, 0.1C, 0.2C, 0.3C, 0.4C, 0.5C, or any value in the above range.
In the formation method of the lithium ion battery according to the embodiment of the present application, the lithium ion battery is formed at a formation temperature of T, where T is 45.ltoreq.t.ltoreq.70, for example, 45 ℃, 50 ℃, 55 ℃, 65 ℃, 70 ℃ and the like, and any value within the above range may be used.
According to the lithium ion battery disclosed by the embodiment of the application, as the formation temperature is increased, the formation gas yield is increased, the cohesiveness of the isolating film is enhanced, and the battery core of the lithium ion battery is tighter, namely the compactness between the negative pole piece and the positive pole piece is improved, so that the lithium ions are more smoothly transmitted in the battery; however, as the formation temperature is continuously increased, when the formation temperature is too high, the SEI film structure formed by the negative electrode of the battery cell becomes fluffy, the density is reduced, the stability of the interface film is reduced, and the cycle performance of the battery is deteriorated.
According to the formation method of the lithium ion battery, the formation temperature and the formation current can be improved, the formation time can be shortened, the production cost is reduced, and the cycle performance of the battery is improved. When the formation temperature is too low, the formation film forming speed is too slow, the diaphragm adhesion is poor, and the cycle performance is easy to deteriorate; when the formation temperature is too high, the SEI film is too fluffy, the energy consumption is increased, and the formation gas yield is increased sharply; when the formation current is lower, the formation time is longer, and the production cost is increased; when the formation current is higher, the formation gas yield increases dramatically, and the SEI film performance is unstable, deteriorating the cycle performance. Therefore, when the formation temperature is controlled to be less than or equal to 45 ℃ and less than or equal to 70 ℃ and the formation current is controlled to be less than or equal to 0.05 ℃ and less than or equal to 0.5 ℃ XC, the whole cycle performance of the battery can be improved on the premise of controlling the cost.
According to the lithium ion formation method, the relationship between the formation temperature, the formation current and fluoroethylene carbonate, the lithium salt additive and the artificial SEI film layer in the electrolyte is as follows: h/b is more than or equal to 2 and less than or equal to 100, H/(X. A) is more than or equal to 4 and less than or equal to 200,0.011, and b/T is more than or equal to 0.111.
According to the lithium ion battery, the formation temperature and the formation current can be adjusted according to the components of the electrolyte, the content of the additive and the thickness of the artificial SEI film layer in the negative electrode plate, so that good cooperation is formed between the battery formation step and the electrolyte as well as between the battery formation step and the negative electrode plate. When the relation between the electrolyte and the negative electrode plate in the lithium ion battery meets the conditions, the gas production rate can be effectively controlled under the conditions of improving the formation temperature and the formation current, the energy consumption is reduced, the production cost is reduced, and the effects of reducing the cost and enhancing the efficiency are achieved. In addition, the combination of the negative electrode plate and the electrolyte can form an SEI film with stable performance on the surface of the formed battery cell negative electrode, and improve the low-temperature cycle performance and the high-temperature intermittent cycle performance of the battery.
Embodiments of the present application also provide an electrical device or various energy storage systems using a battery as an energy storage element. The electric device comprises, but is not limited to, a mobile phone, a tablet, a computer, an electric toy, an electric tool, a battery car, an electric car, a ship, a spacecraft and the like.
In order that the invention may be more readily understood, the present application will be further described in detail in connection with the following examples which are provided for illustrative purposes only and are not limited in scope to the application. The starting materials or components used in the present application may be prepared by commercial or conventional methods unless specifically indicated.
Example 1
(1) Preparation of electrolyte
The ethylene carbonate EC, the diethyl carbonate DEC and the propylene carbonate PC are mixed in a mass ratio of 1:1:1 to obtain a solvent. Then based on the total mass of the electrolyte, the additive A (fluoroethylene carbonate) and the additive B (LiFSI) are respectively added in the mass percent and mixed, and then the lithium salt LiPF is added 6 And (5) uniformly mixing to obtain the electrolyte.
(2) Preparation of positive electrode plate
Lithium cobalt oxide (LiCoO) as a positive electrode active material 2 ) The conductive agent carbon nano tube CNT and the binder polyvinylidene fluoride PVDF are fully stirred and mixed in an N-methylpyrrolidone NMP solvent according to the mass ratio of 97:1.5:1.5, so that uniform anode slurry is formed; uniformly coating the positive electrode slurry on the surface of a positive electrode current collector; the positive pole piece meeting the winding requirement is manufactured through the procedures of drying, cold pressing, slitting, welding, rubberizing and the like.
(3) Preparation of negative electrode plate
The preparation method comprises the steps of fully stirring and mixing negative electrode active substances graphite, silicon, a conductive agent acetylene black, an adhesive styrene butadiene rubber SBR and a thickener sodium carboxymethylcellulose CMC in a mass ratio of 90:6:1.2:1.5:1.3 in a proper amount of deionized water solvent to form uniform negative electrode slurry; and uniformly coating the negative electrode slurry on each surface of a negative electrode current collector copper foil, and drying and cold pressing to obtain a first pole piece with the two side surfaces coated with the negative electrode active material layer.
Uniformly dispersing plasticizer CMC powder in a solvent to obtain a precursor slurry solution I, and uniformly dispersing lithium salt compound powder shown in table 1 in the precursor slurry solution I to obtain an artificial SEI film precursor slurry; and continuously and uniformly depositing the obtained artificial SEI film precursor slurry on the surface of the negative electrode active material layer of the first electrode plate under a non-vacuum condition by an atomic layer deposition technology, and drying to obtain the negative electrode plate meeting the winding requirement.
(4) Preparation of lithium ion batteries
PE porous polymer film is used as a separation film.
And sequentially stacking the positive electrode plate, the isolating film and the negative electrode plate, enabling the isolating film to be positioned between the positive electrode plate and the negative electrode plate, playing an isolating role, and winding the stacked electrode plate and the isolating film to obtain the bare cell. And (3) placing the bare cell in an aluminum plastic film formed by punching the shell to finish top side sealing. And injecting the electrolyte prepared by the method into the baked and dried battery cell, and performing vacuum packaging, standing and formation according to the formation current and formation temperature parameters in table 1 to complete the preparation of the lithium ion battery.
Examples 2 to 29 and comparative examples 1 to 4 were conducted in the same manner as in example 1, except for the differences shown in Table 1.
Table 1 lithium ion battery preparation parameters
The lithium ion batteries prepared in the above examples and comparative examples were subjected to the following performance tests.
Lithium ion battery performance test:
(1) -10 ℃ cycle test:
the lithium ion battery was charged to 4.55V at a constant current and constant voltage of 1C in an incubator at (-10+ -2) deg.C, the off current was 0.05C, and then 1C was set to 3V, and charge and discharge cycles were performed a plurality of times under the above conditions, and the capacity retention after 300 cycles of the battery was calculated, and the average value of the calculated capacity retention after each group of 5 batteries was recorded in Table 2.
Capacity retention (%) = corresponding cycle number discharge capacity (mAh)/discharge capacity for the third cycle (mAh) 100%
(2) Intermittent cycle test at 60 ℃):
placing the lithium ion battery at 60 ℃ for 1h, discharging to 3V at a constant current of 1C, and placing for 10min;1C constant current and constant voltage are charged to 4.55V, and the cut-off current is 0.05C; placing the lithium ion battery at a high temperature of 60 ℃ for 3 days; the cycle of the above steps is one week every three days. The capacity retention after 100 weeks of cycling was calculated, and the average of the calculated capacity retention after cycling for each group of 5 batteries was recorded in table 2.
Capacity retention (%) = corresponding cycle number discharge capacity (mAh)/discharge capacity for the third cycle (mAh) 100%
(3) And (3) testing formation gas production:
the thickness of the cells before and after formation was measured, and the formation thickness change rate (formation gas yield) of the cells was calculated, and the calculated formation thickness change rates of 5 cells each were averaged and recorded in table 2.
Formation gas yield (%) = (thickness after formation-thickness before formation)/(thickness before formation) ×100%
Table 2 test results
Comparison of the data of comparative examples 2 to 3 and comparative example 1 shows that when the lithium salt additive alone is added, the formation thickness change rate is reduced and the formation time is shortened when the lithium salt additive reaches 10%, that is, the formation gas production is reduced, but at the same time, the capacity retention rate is reduced after 300 weeks of-10 ℃ cycle, and the low temperature cycle performance is deteriorated mainly because the lithium salt additive has higher viscosity at low temperature, which results in difficult lithium ion transport, and thus deteriorates the low temperature cycle performance.
Comparison of the data of comparative example 4 and comparative example 1 shows that the formation thickness change rate is increased sharply with the increase of formation current, the capacity retention rate is greatly reduced after 300 weeks of-10 ℃ cycle, and the capacity retention rate is also greatly reduced after 100 weeks of 60 ℃ intermittent cycle, and the negative electrode plate and electrolyte of comparative example 4 are not beneficial to improving the cycle performance and reducing the formation gas yield.
Comparison of the data of examples 1-2 and comparative example 1 shows that the formation thickness change rate of the negative electrode plate, namely the negative electrode plate containing the artificial SEI film layer, is reduced, and the formation time is shortened, so that the artificial film coating is beneficial to reducing the formation gas yield of the battery and shortening the formation time.
The data in examples 1-29 show that the lithium salt additive and the artificial SEI film coating can play a better synergistic effect when being simultaneously present, and various comprehensive performances of the lithium ion battery are obviously improved.
From the data comparison of examples 3-6 and examples 12-18, the mutual relation exists between the artificial SEI film thickness and the lithium salt additive, when the relative ratio of the artificial SEI film is high, the high-temperature nesting circulation is obviously deteriorated, when the relative ratio is too low, the low-temperature circulation performance can not be effectively improved, and when the H/b is more than or equal to 2 and less than or equal to 100, the comprehensive performance is optimal; when the artificial SEI film content is higher, FEC reduction can be preferentially carried out, and the formation current can be increased due to low interface impedance, so that a certain proportion relation exists between the artificial SEI film and the FEC content and the formation current, when the artificial SEI film thickness is too low, the formation gas yield cannot be effectively reduced, when the artificial SEI film thickness is too high, the formation gas yield is not obviously improved, the high Wen Qiantao cycle performance is deteriorated, and when the comprehensive performance is 4-H/(X a) is less than or equal to 200, the comprehensive performance is optimal; the lithium salt additive can improve the decomposition of lithium hexafluorophosphate under high-temperature formation, the addition of the lithium salt additive can raise the formation temperature, the formation gas yield of the lithium salt additive cannot be effectively reduced when the content of the lithium salt additive is too low relative to the formation temperature, the formation gas yield is not obviously reduced when the content is too high, even the lithium salt additive is deteriorated, and the comprehensive performance is optimal when b/T is more than or equal to 0.011 and less than or equal to 0.111.
Further, from the data of examples 12 to 15, it was revealed that as the lithium salt additive was increased, the cycle performance of high Wen Qiantao was improved, the formation gas yield was decreased, and the formation time was shortened.
Further, from the data of examples 16 to 18, it was shown that the low temperature cycle performance was improved, the formation gas yield was reduced, and the formation time was shortened as the artificial SEI coating thickness was increased.
Comparison of the data of examples 7 to 9 and examples 21 to 24 shows that the improvement of the formation current leads to unstable deterioration of the circulating performance of the SEI film component, but the improvement of the formation current is not significant for the deterioration of the circulating performance when the requirements of 2.ltoreq.H/b.ltoreq.100, 4.ltoreq.H/(X.ltoreq.a). Ltoreq. 200,0.011.ltoreq.b/T.ltoreq.0.111 are satisfied, and 0.05.ltoreq.X.ltoreq.0.5, 45.ltoreq.T.ltoreq.70, 5.ltoreq.a.ltoreq.20, 0.5.ltoreq.b.ltoreq.5, 10.ltoreq.H.ltoreq.100 are satisfied at the same time.
The data from examples 25-29 show that lithium salt additives and artificial SEI films can also be used with other materials in the present application, and can also provide good synergy.
It should be noted that the above-described embodiments are only for explaining the present application, and do not constitute any limitation to the present application. The present application has been described with reference to exemplary embodiments, but it is understood that the words which have been used are words of description and illustration, rather than words of limitation. Modifications may be made to the present application as defined within the scope of the claims of the present application, and the present application may be modified without departing from the scope and spirit of the present application. Although the present application is described herein with reference to particular methods, materials and embodiments, the present application is not intended to be limited to the particular examples disclosed, but, on the contrary, the present application is to be extended to all other methods and applications having the same functionality.
Claims (10)
1. The negative electrode plate is characterized by comprising a negative electrode current collector, a negative electrode active material layer coated on the surface of the negative electrode current collector and an artificial SEI film layer positioned on the surface of the negative electrode active material layer; the artificial SEI film layer includes a lithium salt compound and a plasticizer.
2. The negative electrode tab of claim 1, wherein: the lithium salt compound comprises Li 4 SiO 4 、Li 2 SiO 3 、Li 3 N、LiAlH 4 、Li 2 One or more of S;
and/or the plasticizer comprises one or more of CMC, PVP, PAA, PMMA, PEO;
preferably, the mass ratio of the lithium salt compound to the plasticizer is (80-90): (10-20).
3. The negative electrode tab of claim 1, wherein: the thickness of the artificial SEI film layer is H, and the unit is mu m; wherein H is more than or equal to 10 and less than or equal to 100.
4. The negative electrode tab of claim 1, wherein: the anode active material layer includes an anode active material, a binder, and a conductive agent, wherein the anode active material is selected from one of Si-C composite or Sium-C composite (m.ltoreq.2).
5. The preparation method of the negative electrode plate is characterized by comprising the following steps:
uniformly mixing a negative electrode active material, a binder and a conductive agent to obtain a negative electrode slurry, and coating the negative electrode slurry on the surface of a negative electrode current collector to form a negative electrode active material layer;
and uniformly mixing a lithium salt compound and a plasticizer to obtain artificial SEI film precursor slurry, and depositing the artificial SEI film precursor slurry on the surface of the negative electrode active material layer to form an artificial SEI film layer, so as to obtain the negative electrode plate.
6. A formation method of a lithium ion battery, characterized in that the lithium ion battery comprises the negative electrode sheet according to any one of claims 1 to 4 or the negative electrode sheet manufactured by the manufacturing method according to claim 5, wherein:
forming the lithium ion battery by XC multiplying power charging current, wherein the range of X is more than or equal to 0.05 and less than or equal to 0.5;
and/or forming the lithium ion battery at the formation temperature of T ℃, wherein the range of T is more than or equal to 45 and less than or equal to 70.
7. A lithium ion battery comprising the negative electrode sheet according to any one of claims 1 to 4 or the negative electrode sheet produced by the production method according to claim 5, or the formation method according to claim 6.
8. The lithium ion battery of claim 7, wherein: the lithium ion battery also comprises electrolyte, an isolating film and a positive pole piece, wherein the negative pole piece, the isolating film and the positive pole piece are sequentially laminated and wound and then immersed in the electrolyte;
the electrolyte comprises a solvent, a lithium salt and an additive, wherein the additive comprises fluoroethylene carbonate and a lithium salt additive, and the lithium salt additive comprises one or more of lithium bis (fluorosulfonyl) imide and lithium bis (trifluoromethylsulfonyl) imide.
9. The lithium ion battery of claim 8, wherein:
the mass ratio of the fluoroethylene carbonate in the electrolyte is a percent, and a is more than or equal to 5 and less than or equal to 20;
and/or the mass ratio of the lithium salt additive in the electrolyte is b% and b is more than or equal to 0.05 and less than or equal to 5.
10. The lithium ion battery according to claim 9, wherein the formation current of the lithium ion battery is XC multiplying power, the formation temperature is T ℃, and the thickness of the artificial SEI film layer is H, in μm;
wherein H/b is more than or equal to 2 and less than or equal to 100, H/(X X a) is more than or equal to 4 and less than or equal to 200,0.011, and b/T is more than or equal to 0.111.
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