CN117878383A - Battery cell, battery and electricity utilization device - Google Patents
Battery cell, battery and electricity utilization device Download PDFInfo
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- CN117878383A CN117878383A CN202410268465.9A CN202410268465A CN117878383A CN 117878383 A CN117878383 A CN 117878383A CN 202410268465 A CN202410268465 A CN 202410268465A CN 117878383 A CN117878383 A CN 117878383A
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- lithium
- film layer
- negative electrode
- battery cell
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- Secondary Cells (AREA)
Abstract
The application relates to a battery monomer, battery and power consumption device, the battery monomer includes electrode assembly and electrolyte, and electrode assembly includes positive pole piece, negative pole piece and barrier film, and the positive pole piece includes positive pole current collector and sets up in at least one side of positive pole current collector and containsA positive electrode film layer of a positive electrode active material including a lithium-containing material of an olivine structure; the negative electrode plate comprises a negative electrode current collector and a negative electrode film layer which is arranged on at least one side of the negative electrode current collector and contains a negative electrode active material, wherein the negative electrode active material contains a carbon material; the isolating film is arranged between the positive pole piece and the negative pole piece, wherein the thickness of the single-side positive pole film layer in the positive pole piece is H 1 The unit is mu m; the thickness of the single-side negative electrode film layer in the negative electrode plate is H 2 The unit is mu m; the thickness of the isolating film is H 3 The unit is mu m; the battery cell satisfies: h is 65 mu m or less 1 ≤90μm，138μm≤H 1 +H 2 +H 3 190 μm or less and 7 or less (H) 1 +H 2 )/H 3 ≤12。
Description
Technical Field
The application relates to a battery cell, a battery and an electric device.
Background
The battery cell has the characteristics of high capacity, long service life and the like, and is widely applied to electronic equipment such as mobile phones, notebook computers, battery cars, electric automobiles, electric airplanes, electric ships, electric toy automobiles, electric toy ships, electric toy airplanes, electric tools and the like. As the battery field has advanced greatly, higher demands are being made on the performance of the battery cells.
However, the current battery cells have poor fast charge performance.
Disclosure of Invention
The application provides a battery monomer, battery and power consumption device, can promote the free quick charge performance of battery.
In a first aspect, embodiments of the present application provide a battery cell, the battery cell including an electrode assembly and an electrolyte, the electrode assembly including a positive electrode sheet including a positive electrode, a negative electrode sheet including a positive electrode, and a separatorThe positive electrode current collector comprises a current collector and a positive electrode film layer which is arranged on at least one side of the positive electrode current collector and contains a positive electrode active material, wherein the positive electrode active material comprises a lithium-containing material with an olivine structure; the negative electrode plate comprises a negative electrode current collector and a negative electrode film layer which is arranged on at least one side of the negative electrode current collector and contains a negative electrode active material, wherein the negative electrode active material contains a carbon material; the isolating film is arranged between the positive pole piece and the negative pole piece, wherein the thickness of the single-side positive pole film layer in the positive pole piece is H 1 The unit is mu m; the thickness of the single-side negative electrode film layer in the negative electrode plate is H 2 The unit is mu m; the thickness of the isolating film is H 3 The unit is mu m; the battery cell satisfies: h is 65 mu m or less 1 ≤90μm，138μm≤H 1 +H 2 +H 3 190 μm or less and 7 or less (H) 1 +H 2 )/H 3 ≤12。
Thus, embodiments of the present application include the above positive electrode active material and negative electrode active material, in the above system, by adjusting 138 μm.ltoreq.H 1 +H 2 +H 3 190 μm or less and 7 or less (H) 1 +H 2 )/H 3 And less than or equal to 12, is favorable for shortening the transmission path of lithium ions, in particular to the solid-phase transmission path of lithium ions, and can effectively improve the quick charging performance of the battery monomer.
In some embodiments, 7.5.ltoreq.H 1 +H 2 )/H 3 And is less than or equal to 11.50. When the embodiment of the application meets the range, the lithium ion transmission path, especially the lithium ion solid phase transmission path, is further shortened, and the quick charging performance of the battery monomer can be effectively improved.
In some embodiments, the separator film is a porous polymer film, and the porous polymer film satisfies: 13 μm < H 3 < 20 μm; alternatively, 13.5 μm.ltoreq.H 3 And is less than or equal to 19.5 mu m. When the thickness of the isolation film is in the range, the thickness of the isolation film is not too thick, the transmission path of lithium ions in the liquid phase is relatively short, the transmission resistance of the lithium ions is relatively small, the transmission is more stable, the transmission rate can be accelerated, and the quick charging performance of the battery monomers is improved. And the thickness of the isolating film can not be too thin, so that the heat resistance and the circulation stability of the isolating film can be improved.
In some embodiments, the porous polymer film comprises at least one of a polypropylene film and a polyethylene film. Optionally, the porous polymer membrane is a polypropylene membrane or a polyethylene membrane; the material has excellent heat resistance, is not easy to burn through in the process of cyclic charge and discharge of the battery monomer, and can improve the cyclic stability of the battery monomer. And as the ceramic coating and the like are not arranged on the surface of the porous polymer film, the transmission barrier of lithium ions in the porous polymer film can be further reduced, the migration rate is further improved, and the rapid charging of the battery monomer is more facilitated.
In some embodiments, the separator has a porosity of 35% to 45%. When the porosity of the isolating film is in the range, the porosity is relatively high, so that the transmission barrier of lithium ions can be further reduced, the migration rate of the lithium ions can be improved, and the quick charging performance of the battery monomer can be further improved.
In some embodiments, the single-sided positive electrode film layer has a compacted density of 2.1g/cm 3 To 2.4g/cm 3 The compaction density of the single-side negative electrode film layer is 1.0g/cm 3 To 1.3g/cm 3 . The negative electrode film layer is matched with the positive electrode film layer, so that lithium ions separated from the positive electrode film layer can be quickly embedded into the negative electrode film layer, and the quick charging performance of the battery cell is further improved.
In some embodiments, the areal density of the single-sided positive electrode film layer is 0.26g/1540.25mm 2 To 0.29g/1540.25mm 2 The surface density of the single-side negative electrode film layer is 0.12g/1540.25mm 2 To 0.14g/1540.25mm 2 . The negative electrode film layer is matched with the positive electrode film layer, so that lithium ions separated from the positive electrode film layer can be quickly embedded into the negative electrode film layer, and the quick charging performance of the battery cell is further improved.
In some embodiments, 0.9.ltoreq.H 1 /H 2 Less than or equal to 1.3; and H is more than or equal to 60 mu m 2 And is less than or equal to 80 mu m. When the thickness of the negative electrode film layer and the thickness of the positive electrode film layer are regulated and controlled to meet the range, lithium ions released from the positive electrode film layer can be quickly embedded into the negative electrode film layer, and the quick charging performance of the battery is further improved.
In some embodiments, the electrolyte has a retention factor of 4.0g/Ah to 5.0g/Ah. When the liquid retention coefficient of the battery monomer is in the range, the electrolyte can have a good infiltration effect on the positive electrode plate and the negative electrode plate, and the migration rate of lithium ions in a liquid phase can be improved, so that the quick charging capability of the battery monomer is improved.
In some embodiments, the electrolyte comprises a lithium salt, the lithium salt comprising a first lithium salt and a second lithium salt, the first lithium salt comprising lithium hexafluorophosphate LiPF 6 And at least one of lithium bistrifluoromethylsulfonylimide LiTFSI, optionally lithium hexafluorophosphate LiPF 6 The mass percentage of the first lithium salt relative to the total mass of the electrolyte is less than or equal to 10 percent, and can be selected to be 5 to 10 percent; the second lithium salt comprises lithium tetrafluoroborate LiBF 4 Lithium difluorophosphate LiPO 2 F 2 The mass percentage of the second lithium salt relative to the total mass of the electrolyte is more than or equal to 1 percent.
Therefore, the viscosity of the first lithium salt is relatively high in the embodiment of the application, which is not beneficial to the rapid migration of lithium ions; the viscosity of the second lithium salt is relatively low, and the second lithium salt can form an SEI film rich in boron and/or fluorine elements on the surface of the anode active material, so that an SEI film interface can be effectively repaired, the impedance of a circulation process is reduced, and the circulation performance is improved; the second lithium salt can also relieve the decomposition of lithium hexafluorophosphate into hydrofluoric acid to a certain extent, can further relieve the side reaction between the hydrofluoric acid and the active material, and can give consideration to the improvement of the quick charging performance and the cycle performance of the battery monomer.
In some embodiments, the second lithium salt comprises lithium tetrafluoroborate LiBF 4 Lithium difluorophosphate LiPO 2 F 2 The method comprises the steps of carrying out a first treatment on the surface of the Alternatively, lithium tetrafluoroborate LiBF 4 The mass percentage content relative to the total mass of the electrolyte is 0.3 to 1.0 percent, and the lithium difluorophosphate LiPO 2 F 2 The mass percentage content relative to the total mass of the electrolyte is 0.3 to 3.5 percent; further alternatively, lithium tetrafluoroborate LiBF 4 The mass percentage content relative to the total mass of the electrolyte is 0.5 to 0.8 percent, and the lithium difluorophosphate LiPO 2 F 2 The mass percentage content relative to the total mass of the electrolyte is 0.3 to 1.5 percent.
In some embodiments, the lithium salt further includes a third lithium salt including at least one of a lithium fluoroborate salt and a lithium fluorophosphate salt, wherein the third lithium salt is 0.1% to 2.5% by mass relative to the total mass of the electrolyte. By adding the third lithium salt with the content, the viscosity of an electrolyte system can be reduced, the rapid migration of lithium ions in a liquid phase is facilitated, and the rapid charging performance of the battery monomer is improved.
In some embodiments, the lithium fluoroborate salt comprises at least one of lithium difluorooxalato borate, lipfub, and lithium bisoxalato borate, lipfub; and/or the lithium fluorophosphate includes at least one of lithium difluorophosphate LiDFOP and lithium tetrafluorooxalate phosphate LiTFOP.
In some embodiments, the electrolyte further comprises an organic solvent; the mass percentage content of the organic solvent relative to the total mass of the electrolyte is more than or equal to 45 percent; optionally 60% to 95%; and/or the organic solvent comprises at least one of ethylene carbonate EC and propylene carbonate PC. By adding the organic solvent with the content, the viscosity of an electrolyte system can be reduced, the rapid migration of lithium ions in a liquid phase is facilitated, and the rapid charging performance of a battery monomer is improved.
In some embodiments, the electrolyte further comprises an additive comprising at least one of fluoroethylene carbonate FEC and vinylene carbonate VC; alternatively, the mass percent of the additive is 0.5% to 2.5% based on the total mass of the electrolyte. When the mass percentage of the additive is in the range, the cycle life of the battery monomer can be effectively prolonged, and the standing storage impedance can be improved.
In some embodiments, the olivine structured lithium-containing material includes an olivine structured lithium iron phosphate-based material, and the carbon material includes graphite. The positive electrode active material, the negative electrode active material and the electrode assembly with proper thickness are matched for use, so that the quick charging performance of the battery cell can be further improved.
In some embodiments, the olivine structured lithium-containing material includes a material having the general formula Li x A y Me a M b P 1-c X c Q z A compound of (2), whichWherein x is more than or equal to 0 and less than or equal to 1.3, y is more than or equal to 0 and less than or equal to 1.3, and x+y is more than or equal to 0.9 and less than or equal to 1.3; a is more than or equal to 0.9 and less than or equal to 1.5, b is more than or equal to 0 and less than or equal to 0.5, and a+b is more than or equal to 0.9 and less than or equal to 1.5; c is more than or equal to 0 and less than or equal to 0.5; z is more than or equal to 3 and less than or equal to 5; a comprises at least one of Na, K and Mg; me includes at least one of Mn, fe, co, ni; m comprises at least one of B, mg, al, si, P, S, ca, sc, ti, V, cr, cu, zn, sr, Y, zr, nb, mo, cd, sn, sb, te, ba, ta, W, yb, la, ce; x comprises at least one of S, si, cl, B, C, N; q includes at least one of O, F.
In a second aspect, the present application also proposes a battery comprising a battery cell according to any of the embodiments of the first aspect of the present application.
In a third aspect, the present application further proposes an electrical device comprising a battery according to any one of the embodiments of the third aspect of the present application.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments of the present application will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present application, and that other drawings may be obtained according to the drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic diagram of an embodiment of a battery cell of the present application.
Fig. 2 is an exploded schematic view of an embodiment of the battery cell of fig. 1.
Fig. 3 is a schematic view of an embodiment of a battery module of the present application.
Fig. 4 is a schematic view of an embodiment of a battery pack of the present application.
Fig. 5 is an exploded schematic view of the embodiment of the battery pack shown in fig. 4.
Fig. 6 is a schematic diagram of an embodiment of an electrical device including a battery cell of the present application as a power source.
The figures are not necessarily to scale.
The reference numerals are explained as follows:
1. a battery pack; 2. an upper case; 3. a lower box body; 4. a battery module;
5. a battery cell; 51. a housing; 52. an electrode assembly;
53. a cover plate;
6. and (5) an electric device.
Detailed Description
Hereinafter, embodiments of a battery cell, a battery, and an electric device of the present application are specifically disclosed with reference to the drawings as appropriate. However, unnecessary detailed description may be omitted. For example, detailed descriptions of well-known matters may be omitted, and repeated descriptions of the actual same structure may be omitted. This is to avoid that the following description becomes unnecessarily lengthy, facilitating the understanding of those skilled in the art. Furthermore, the drawings and the following description are provided for a full understanding of the present application by those skilled in the art, and are not intended to limit the subject matter recited in the claims.
The "range" disclosed herein is defined in terms of lower and upper limits, with a given range being defined by the selection of a lower and an upper limit, the selected lower and upper limits defining the boundaries of the particular range. Ranges that are defined in this way can be inclusive or exclusive of the endpoints, and any combination can be made, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3,4 and 5 are listed, the following ranges are all contemplated: 1 to 3,1 to 4,1 to 5,2 to 3,2 to 4 and 2 to 5. In this application, unless otherwise indicated, the numerical ranges "a to b" represent a shorthand representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0 to 5" means that all real numbers between "0 to 5" have been listed throughout, and "0 to 5" is only a shorthand representation of a combination of these values. When a certain parameter is expressed as an integer of 2 or more, it is disclosed that the parameter is, for example, an integer of 2,3,4,5,6,7,8,9, 10, 11, 12 or the like.
All embodiments and alternative embodiments of the present application may be combined with each other to form new solutions, unless specifically stated otherwise.
All technical features and optional technical features of the present application may be combined with each other to form new technical solutions, unless specified otherwise.
All steps of the present application may be performed sequentially or randomly, preferably sequentially, unless otherwise indicated. For example, the method may include steps (a) and (b), and the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, mention may be made of a method further comprising step (c), meaning that step (c) may be added to the method in any order, e.g., a method may comprise steps (a), (b) and (c), may also comprise steps (a), (c) and (b), may also comprise steps (c), (a) and (b), etc.
The household energy storage product can locally store electricity for subsequent use; it is mainly charged and discharged by means of a rechargeable battery (cell). The requirements of users on the performance of household energy storage products, in particular to the requirements on the quick charge performance are increasingly improved.
In view of the above problems, embodiments of the present application propose a battery cell by adjusting 100 μm.ltoreq.H 1 +H 2 +H 3 Less than or equal to 150 mu m and less than or equal to 5 percent (H) 1 +H 2 )/H 3 Less than or equal to 8, is favorable for shortening the transmission path of lithium ions, in particular to the solid phase transmission path of lithium ions, and can effectively improve the quick charging performance of the battery monomer.
Next, the technical scheme of the embodiment of the present application will be described in detail.
Battery cell
Embodiments of the present application provide a battery cell in a first aspect.
The battery monomer comprises an electrode assembly and electrolyte, wherein the electrode assembly comprises a positive electrode plate, a negative electrode plate and an isolating film, the positive electrode plate comprises a positive electrode current collector and a positive electrode film layer which is arranged on at least one side of the positive electrode current collector and contains a positive electrode active material, and the positive electrode active material comprises a lithium-containing material with an olivine structure; the negative electrode plate comprises a negative electrode current collector and a negative electrode film layer which is arranged on at least one side of the negative electrode current collector and contains a negative electrode active material, wherein the negative electrode active material contains a carbon material; the isolating film is arranged between the positive pole piece and the negative pole piece,
wherein,
the thickness of the single-side positive electrode film layer in the positive electrode plate is H 1 The unit is mu m;
the thickness of the single-side negative electrode film layer in the negative electrode plate is H 2 The unit is mu m;
the thickness of the isolating film is H 3 The unit is mu m;
the battery cell satisfies: h is 138 mu m or less 1 +H 2 +H 3 190 μm or less and 7 or less (H) 1 +H 2 )/H 3 ≤12。
In the charging process of the battery monomer, lithium ions in the positive electrode film layer are separated from the positive electrode active material and migrate into the negative electrode active material of the negative electrode film layer through the electrolyte, the lithium ions are mainly transported in a solid phase in the positive electrode film layer and the negative electrode film layer, the lithium ions are transported in a liquid phase in the electrolyte, and the lithium ions can migrate to the negative electrode film layer through the isolating film in the liquid phase in-transport process. In the discharging process of the battery monomer, lithium ions in the negative electrode film layer are separated from the negative electrode active material and migrate into the positive electrode active material of the positive electrode film layer through the electrolyte, the lithium ions are mainly transported in a solid phase in the positive electrode film layer and the negative electrode film layer, the lithium ions are transported in a liquid phase in the electrolyte, and the lithium ions can migrate to the positive electrode film layer through the isolating film in the liquid phase in-transport process.
Total thickness H of positive electrode film layer, separator film and negative electrode film layer 1 +H 2 +H 3 Regarding the length of the lithium ion transmission path, as the total thickness of the positive electrode film layer, the isolating film and the negative electrode film layer is increased, the lithium ion transmission path is increased, and H is found by research 1 +H 2 +H 3 When the lithium ion battery is more than 190 mu m, the transmission path of lithium ions is too long, and the battery monomer cannot be charged rapidly. H 1 +H 2 +H 3 When the thickness is less than or equal to 190 mu m, the transmission path of lithium ions is not too long, and lithium ions can be quickly transferred from the positive electrode film layer to the negative electrode film layer, so that the battery cell can be quickly charged. However, with the decrease of the total thickness of the positive electrode film layer, the separator film and the negative electrode film layer, the positive electrode film layer and the negative electrode film layer may not meet the capacity requirement, and thus the regulation of H is required 1 +H 2 +H 3 ≥138μm。
However, the rapid migration of lithium ions is also affected by the distribution system of the thickness in the positive electrode film layer, the negative electrode film layer and the isolating film, and the thickness of the positive electrode film layer, the thickness of the negative electrode film layer and the thickness of the isolating film need to be comprehensively considered; considering that the solid phase transmission process of lithium ions mainly occurs in the positive electrode film layer and the negative electrode film layer, and the liquid phase transmission process mainly occurs in the isolating film, the total thickness of the positive electrode film layer and the negative electrode film layer has larger influence on the transmission path of lithium ions, and the resistance of solid phase transmission is usually larger, so the embodiment of the application can control the total thickness H of the positive electrode film layer and the negative electrode film layer 1 +H 2 And isolating membrane H 3 The ratio of (7) to (12) can enable lithium ions to rapidly migrate between the positive electrode film layer and the negative electrode film layer, and is favorable for improving the rapid charging performance of the battery cell.
In conclusion, the embodiment of the application adjusts H to be less than or equal to 138 mu m 1 +H 2 +H 3 190 μm or less and 7 or less (H) 1 +H 2 )/H 3 And less than or equal to 12, is favorable for shortening the transmission path of lithium ions, in particular to the solid-phase transmission path of lithium ions, and can effectively improve the quick charging performance of the battery monomer. Especially in thick coated pole pieces, H is smaller than or equal to 138 mu m by adjusting 1 +H 2 +H 3 190 μm or less and 7 or less (H) 1 +H 2 )/H 3 And less than or equal to 12, is favorable for shortening the transmission path of lithium ions, in particular to the solid-phase transmission path of lithium ions, and can effectively improve the quick charging performance of the battery monomer.
Illustratively H 1 +H 2 +H 3 It may be 138 μm, 139 μm, 140 μm, 141 μm, 142 μm, 143 μm, 144 μm, 145 μm, 146 μm, 147 μm, 148 μm, 149 μm, 150 μm, 155 μm, 160 μm, 165 μm, 170 μm, 175 μm, 180 μm, 185 μm, 190 μm or a range of any two values of the above.
7≤(H 1 +H 2 )/H 3 Not more than 12, canOptionally, 7.5.ltoreq.H 1 +H 2 )/H 3 ≤11.50。
Illustratively, (H) 1 +H 2 )/H 3 May be 7.0, 7.1, 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.2, 8.5, 8.8, 9.0, 9.2, 9.5, 9.8, 10.0, 10.2, 10.5, 10.8, 11.0, 11.2, 11.30, 11.5, 11.8, 12.0 or a range of any two of the above values.
In this embodiment, the thickness of the positive electrode film layer or the negative electrode film layer is a single-side thickness, taking the positive electrode film layer as an example, for example, the positive electrode film layers are disposed on two sides of the positive electrode current collector, and the thickness of the positive electrode film layer on one side of the positive electrode current collector is the thickness of the single side of the positive electrode film layer; or one of the two sides of the positive current collector is provided with a positive electrode film layer, and the thickness of the positive electrode film layer at the side is the thickness of the positive electrode film layer at the single side. Taking the negative electrode film layer as an example, for example, the negative electrode film layers are arranged on two sides of the negative electrode current collector, and the thickness of the negative electrode film layer on one side of the negative electrode current collector is the thickness of one side of the negative electrode film layer; or one of the two sides of the negative current collector is provided with a negative electrode film layer, the thickness of the negative electrode film layer on the side is the thickness of the negative electrode film layer on the single side.
The thickness of the positive electrode film layer is in the meaning known in the art, equipment and methods known in the art can be adopted for detection, the related detection method can refer to domestic and foreign detection standards, domestic and foreign enterprise standards and the like, and a person skilled in the art can adaptively change certain detection steps/instrument parameters and the like from the aspect of detection accuracy so as to obtain a more accurate detection result. One detection method may be used qualitatively or quantitatively, or several detection methods may be used in combination for qualitative or quantitative determination. For example, according to GB/T17359-2012 "quantitative analysis of microbeam analysis Spectrometry", the thickness of the positive electrode film layer can be obtained by performing ion polishing section elemental analysis on a positive electrode sheet containing no electrolyte as a sample. For another example, the average value is measured by a micrometer for a plurality of measurements: taking a positive pole piece (positive pole piece with positive pole film layers coated on two sides) without electrolyte, firstly testing the thickness of any 5 sites of the positive pole piece by using a micrometer, obtaining an average value H1, wiping the positive pole film layers clean, testing the thickness of any 5 sites of the residual current collector, and obtaining an average value H2, wherein the thickness of the single-layer positive pole film layer is (H2-H1)/2. The testing process of the negative electrode film layer is the testing process of the positive electrode film layer, and will not be described herein.
In this embodiment, the isolation film is in the meaning known in the art, and can be detected by using the apparatus and method known in the art, 10 isolation films are taken as test samples, the thickness of the 10 isolation films is measured by using a ten-thousandth ruler, and the average thickness of the 10 isolation films is calculated as the thickness of the isolation film. In the embodiment of the present application, a newly prepared separator may be taken as a sample, or a battery that has been discharged (discharged to a lower limit cutoff voltage such that the charged state of the battery is about 0% soc) may be reversely disassembled, the separator may be taken from the battery, and the separator may be dried and taken as a sample.
[ isolation Membrane ]
The battery cell includes a separator film, which may include a porous polymer film.
In some embodiments, the thickness H of the barrier film 3 The method meets the following conditions: 13 μm < H 3 < 20 μm; alternatively, 13.5 μm.ltoreq.H 3 And is less than or equal to 19.5 mu m. Alternatively, 15 μm.ltoreq.H 3 And is less than or equal to 18 mu m. When the thickness of the isolation film is in the range, the thickness of the isolation film is not too thick, the transmission path of lithium ions in the liquid phase is relatively short, the transmission resistance of the lithium ions is relatively small, the transmission is more stable, the transmission rate can be accelerated, and the quick charging performance of the battery monomers is improved. And the thickness of the isolating film can not be too thin, so that the heat resistance and the circulation stability of the isolating film can be improved.
Exemplary thickness H of the barrier film 3 Can be 13.1 μm, 13.2 μm, 13.3 μm, 13.4 μm, 13.5 μm, 13.6 μm, 13.7 μm, 13.8 μm, 13.9 μm, 14 μm, 14.1 μm, 14.2 μm, 14.3 μm, 14.4 μm, 14.5 μm, 14.6 μm, 14.7 μm, 14.8 μm, 14.9 μm, 15 μm, 15.1 μm, 15.2 μm, 15.3 μm, 15.4 μm, 15.5 μm, 15.6 μm, 15.7 μm, 15.8 μm, 15.9 μm, 16.0 μm, 16.1 μm, 16.2 μm, 16.3 μm, 16.4 μm, 16.5 μm, 16.6 μm, 16.7 μm, 16.8 μm, 16.9 μm, 17.9 μm, 17.0 μm, 17.17.5 μm, 17.3 μm, 17.5 μm, 17.6 μm, or the likem, 17.6 μm, 17.7 μm, 17.8 μm, 17.9 μm, 18.0 μm, 18.1 μm, 18.2 μm, 18.3 μm, 18.4 μm, 18.5 μm, 18.6 μm, 18.7 μm, 18.8 μm, 18.9 μm, 19.0 μm, 19.1 μm, 19.2 μm, 19.3 μm, 19.4 μm, 19.5 μm, 19.6 μm, 19.7 μm, 19.8 μm, 19.9 μm or a range of any two of the above values.
Specifically, the separator may be a porous polymer film, and the porous polymer film may be a single-layer film or a multilayer film, and in the case where the porous polymer film is a multilayer film, the multilayer film may be two layers, three layers, four layers or more layers, and the materials in the multilayer film may be the same or different.
In some embodiments, the porous polymer film may include at least one of a polypropylene film and a polyethylene film; when the porous polymer film is a multilayer film, the porous polymer film may be a polypropylene film and a polyethylene film laminated in the thickness direction of the porous polymer film; the porous polymer films may be of the same material, for example, a multilayer polypropylene film laminate, or a multilayer polyethylene film laminate. The material has excellent heat resistance, is not easy to burn through in the process of cyclic charge and discharge of the battery monomer, and can improve the cyclic stability of the battery monomer. And as the ceramic coating and the like are not arranged on the surface of the porous polymer film, the transmission barrier of lithium ions in the porous polymer film can be further reduced, the migration rate is further improved, and the rapid charging of the battery monomer is more facilitated.
In some embodiments, the porous polymer film is a polypropylene film or a polyethylene film, both of which are "bare films" meaning that the separator film consists of an organic base film, the surface of which is free of a coating. Compared with the isolating film with the organic/inorganic coating commonly used in the market at present, the bare film has smaller transmission resistance to lithium ions, and the same material, the transmission medium of the lithium ions in the isolating film is the same, so that the lithium ions are more stable in conduction and the speed is increased. Further, since the "bare film" does not include a heat-resistant layer, the thickness of the "bare film" is set to be not less than 13 μm and not more than 20 μm, and the above thickness range makes the mechanical strength and hardness of the bare film higher, and the "bare film" is not easily damaged or even burned out due to heat generation in the battery cell cycle process; and the thickness can not be too thick, so that the transmission rate of lithium ions in the 'bare film' can be improved.
In some embodiments, the separator has a porosity of 35% to 45%. When the porosity of the isolating film is in the range, the porosity is relatively high, so that the transmission barrier of lithium ions can be further reduced, the migration rate of the lithium ions can be improved, and the quick charging performance of the battery monomer can be further improved.
Illustratively, the separator may have a porosity of 35%, 35.5%, 36%, 36.5%, 37%, 37.5%, 38%, 38.5%, 39%, 39.5%, 40%, 40.5%, 41%, 41.5%, 42%, 42.5%, 43%, 43.5%, 44%, 44.5% or a range of any two of the foregoing values.
In the present embodiments, porosity refers to the percentage of the total volume of the barrier film that is occupied by the pore volume of the barrier film. The porosity can be tested according to the standard GB/T36363-2018 polyolefin separator for Battery cells. It should be noted that, the actual testing process may be a testing process slightly different from the standard according to the difference of the testing instruments, the testing error, and the testing effect on the porosity to be eliminated as much as possible, so as to obtain a more accurate testing value.
According to the embodiment of the application, the porosity of the isolation film can be adjusted through the selection of the material of the isolation film and the preparation process of the isolation film.
[ Positive electrode sheet ]
The battery cell comprises a positive electrode plate.
The positive electrode sheet includes a positive electrode current collector having two surfaces opposite in a thickness direction thereof, and a positive electrode film layer disposed on at least one side of the positive electrode current collector, for example, on either one or both of the two opposite surfaces of the positive electrode current collector.
In some embodiments, the single-sided positive electrode film layer has a compacted density of 2.1g/cm 3 To 2.4g/cm 3 For example, 2.10g/cm 3 、2.15g/cm 3 、2.20g/cm 3 、2.25g/cm 3 、2.30g/cm 3 、2.35g/cm 3 、2.4g/cm 3 Or a range of any two values recited above. When the compaction density of the positive electrode film layer meets the range, the porosity and the thickness of the positive electrode film layer can be considered under the condition of meeting certain gram capacity of the positive electrode plate, so that the migration rate and the migration path of lithium ions in the positive electrode film layer are considered, and the quick charging performance of the battery monomer is improved.
The compacted density of the single-side negative electrode film layer can be 1.0g/cm in combination with the compacted density of the positive electrode film layer 3 To 1.3g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the When the compaction density of the negative electrode film layer meets the range, the porosity and the thickness of the negative electrode film layer can be considered under the condition that a certain gram capacity of the negative electrode plate is met, so that the migration rate and the migration path of lithium ions in the negative electrode film layer are considered; and the negative electrode film layer is matched with the positive electrode film layer, so that lithium ions separated from the positive electrode film layer can be quickly embedded into the negative electrode film layer, and the quick charging performance of the battery cell is further improved.
In embodiments of the present application, the compacted density of the single-sided positive electrode film layer is within the meaning well known in the art and may be tested using methods known in the art. For example, a single-sided coated and cold-pressed positive electrode sheet (in the case of a double-sided coated positive electrode sheet, the positive electrode sheet on one side thereof may be wiped off first), and a small wafer with an area S1 is punched, and the weight thereof is referred to as M1. Then, the positive electrode film layer of the weighed positive electrode plate is wiped off, the weight of the positive electrode current collector is weighed and recorded as M0, and the surface density of the positive electrode film layer= (the weight M1 of the positive electrode plate-the weight M0 of the positive electrode current collector)/S1, and the compacted density of the positive electrode film layer = the surface density of the positive electrode film layer/the thickness of the positive electrode film layer. The process of testing the compacted density of the single-sided negative electrode film layer is, for example, the process of testing the compacted density of the single-sided positive electrode film layer, and will not be described in detail herein.
In some embodiments, the areal density of the single-sided positive electrode film layer is 0.26g/1540.25mm 2 To 0.29g/1540.25mm 2 For example, 0.260g/1540.25mm 2 、0.265g/1540.25mm 2 、0.270g/1540.25mm 2 、0.275g/1540.25mm 2 、0.280g/1540.25mm 2 、0.285g/1540.25mm 2 、0.290g/1540.25mm 2 Or any of the aboveTwo values. When the surface density of the positive electrode film layer meets the range, the porosity and the thickness of the positive electrode film layer can be considered under the condition that a certain gram capacity of the positive electrode plate is met, so that the migration rate and the migration path of lithium ions in the positive electrode film layer are considered, and the quick charging performance of the battery monomer is improved.
The surface density of the single-side negative electrode film layer is 0.12g/1540.25mm in combination with the surface density of the positive electrode film layer 2 To 0.14g/1540.25mm 2 The method comprises the steps of carrying out a first treatment on the surface of the When the surface density of the negative electrode film layer meets the range, the porosity and the thickness of the negative electrode film layer can be considered under the condition that a certain gram capacity of the negative electrode plate is met, so that the migration rate and the migration path of lithium ions in the negative electrode film layer are considered; and the negative electrode film layer is matched with the positive electrode film layer, so that lithium ions separated from the positive electrode film layer can be quickly embedded into the negative electrode film layer, and the quick charging performance of the battery cell is further improved.
In embodiments of the present application, the areal density of the single-sided positive electrode film layer is within the meaning well known in the art and can be tested using methods known in the art. Areal density = single-sided positive electrode film weight/single-sided positive electrode film area, where single-sided positive electrode film weight = (average weight of pole piece-average weight of current collector)/2, since both sides of the positive electrode current collector may have positive electrode film. Compacted density = areal density/average thickness of positive electrode film layer, wherein positive electrode film layer average thickness = (average thickness of pole piece-average thickness of current collector)/2, since both sides of positive electrode current collector have positive electrode film layers.
The "average" here may be an average value taken after 5 parallel tests.
In some embodiments, the thickness of the single-sided positive electrode film layer and the thickness of the single-sided negative electrode film layer satisfy: h is more than or equal to 0.9 1 /H 2 Less than or equal to 1.3, e.g., H 1 /H 2 May be 0.90, 0.91, 0.92, 0.93, 0.94, 0.95, 1, 1.05, 1.10, 1.15, 1.20, 1.25, 1.3 or a range of any two of the foregoing values. Because the migration rate of lithium ions in the anode active material in the anode film layer is different from that of the cathode active material in the cathode film layer, the thickness of the anode film layer and the cathode film layer are regulated and controlled according to the embodiment of the applicationWhen the thickness of the lithium ion battery meets the range, lithium ions released from the positive electrode film layer can be quickly embedded into the negative electrode film layer, and the quick charging performance of the battery cell is further improved.
In some embodiments, the thickness H of the single-sided positive electrode film layer 1 The method meets the following conditions: h is 65 mu m or less 1 And.ltoreq.90 μm, for example 65 μm, 68 μm, 70 μm, 72 μm, 75 μm, 78 μm, 80 μm, 82 μm, 85 μm, 88 μm, 90 μm or a range consisting of any two of the above values.
The positive electrode film layer is a thick coating film layer, the thickness of the single-side film layer is matched with the surface density of the film layer, so that lithium ions released from the positive electrode film layer can be quickly embedded into the negative electrode film layer, and the quick charging performance of the battery is further improved. The thickness of unilateral rete and the compaction density cooperation of rete can further make the lithium ion that deviate from by the anodal rete can be embedded into in the negative pole rete fast, further promotes the free quick charge performance of battery.
The positive electrode film layer includes a positive electrode active material including a lithium-containing material of an olivine structure.
The kinetics of the olivine structured lithium-containing materials are relatively poor, by being compatible with the thickness parameters of the electrode assembly (138 μm.ltoreq.H 1 +H 2 +H 3 190 μm or less and 7 or less (H) 1 +H 2 )/H 3 And less than or equal to 12), can lead lithium ions to migrate in the electrode assembly rapidly, and improves the dynamic performance, thereby improving the rapid charging capability.
In some embodiments, the olivine structured lithium-containing material includes a material having the general formula Li x A y Me a M b P 1-c X c Q z Wherein x is more than or equal to 0 and less than or equal to 1.3, y is more than or equal to 0 and less than or equal to 1.3, and x+y is more than or equal to 0.9 and less than or equal to 1.3; a is more than or equal to 0.9 and less than or equal to 1.5, b is more than or equal to 0 and less than or equal to 0.5, and a+b is more than or equal to 0.9 and less than or equal to 1.5; c is more than or equal to 0 and less than or equal to 0.5; z is more than or equal to 3 and less than or equal to 5; a comprises at least one of Na, K and Mg; me includes at least one of Mn, fe, co, ni; m comprises at least one of B, mg, al, si, P, S, ca, sc, ti, V, cr, cu, zn, sr, Y, zr, nb, mo, cd, sn, sb, te, ba, ta, W, yb, la, ce; x comprises S, si, cl,B. C, N; q includes at least one of O, F.
The battery cells may be charged and discharged with the release and consumption of active ions such as Li, and the molar contents of Li are different when the battery cells are discharged to different states. In the list of the positive electrode active materials in the embodiments of the present application, the molar content of Li is the initial state of the material, that is, the state before charging, and the molar content of Li may change after charge and discharge cycles when the positive electrode active material is applied to a battery system.
In the examples of the positive electrode active material according to the present embodiment, the molar content of oxygen O is only a theoretical state value, and the lattice oxygen release causes a change in the molar content of oxygen O, and in practice, the molar content of oxygen O may float.
The olivine-structured lithium-containing material may include at least one of a lithium iron phosphate-based material, a lithium manganese phosphate-based material, a lithium nickel phosphate-based material, and a lithium cobalt phosphate-based material. Alternatively, the olivine structured lithium-containing material may include an olivine structured lithium iron phosphate-based material having a better lattice stability and a better cycling stability.
In some embodiments, the lithium iron phosphate-based material includes an element M; the material is stable, and the cycle life of the battery system can be effectively prolonged. The M element can be arranged on the surface of the lithium iron phosphate material to play a role in coating, so that the structural stability of the lithium iron phosphate material is improved; or is positioned in the crystal phase of the lithium iron phosphate material to stabilize the lattice structure; it can also be located on the surface of the lithium iron phosphate material and in the crystal phase of the lithium iron phosphate material. When the lithium iron phosphate material is detected, the M element can be detected, namely, the lithium iron phosphate material is considered to comprise the M element.
The battery cells may be charged and discharged with the release and consumption of active ions such as Li, and the molar contents of Li are different when the battery cells are discharged to different states. In the list of the positive electrode active materials in the embodiments of the present application, the molar content of Li is the initial state of the material, that is, the state before charging, and the molar content of Li may change after charge and discharge cycles when the positive electrode active material is applied to a battery system.
In some embodiments, M comprises at least one of Mg, al, ti, V and Zn, optionally Al. The mass content of the M element relative to the total mass of the lithium iron phosphate material is 100ppm to 2000ppm; alternatively 300ppm to 500ppm. The lithium iron phosphate material contains the M element with the content, and the M element can at least form a local fast ion conductor phase in the lithium iron phosphate material, so that the transmission of lithium ions in the material is accelerated, and the cycle performance in a working state can be improved.
For example, the lithium iron phosphate material may include at least one of Mg, al, ti, V and Zn, and the M element may be disposed on the surface of the lithium iron phosphate material, so as to perform a coating function and improve structural stability of the lithium iron phosphate material; or is positioned in the crystal phase of the lithium iron phosphate material to stabilize the lattice structure; it can also be located on the surface of the lithium iron phosphate material and in the crystal phase of the lithium iron phosphate material.
Illustratively, the mass content of the M element may be 100ppm, 200ppm, 300ppm, 400ppm, 450ppm, 500ppm, 600ppm, 700ppm, 800ppm, 900ppm, 1000ppm, 1100ppm, 1200ppm, 1300ppm, 1400ppm, 1500ppm, 1600ppm, 1700ppm, 1800ppm, 1900ppm, 2000ppm, or a range of any two of the foregoing numerical compositions.
In some embodiments, the lithium iron phosphate-based material includes a core including lithium iron phosphate particles and a carbon coating disposed on at least a portion of an outer surface of the core; the electrolyte further includes an organic solvent including a first solvent having a viscosity of not more than 0.8 Pa-s.
The lithium iron phosphate material is subjected to coating modification through the carbon coating layer, so that the conductivity of the lithium iron phosphate material can be improved, and the cycle performance in a working state is improved; however, due to the dense coating of the carbon coating layer, the electrolyte may infiltrate poorly into the core of the lithium iron phosphate material, and DCR growth in a state of standing and storage may be deteriorated; the embodiment of the application is matched with a low-viscosity organic solvent system, so that the wettability of electrolyte to the lithium iron phosphate material can be improved, and the DCR growth in a standing storage state can be reduced.
In some embodiments, the mass content of the carbon coating layer is 1.0% to 1.5% based on the total mass of the lithium iron phosphate-based material; the mass content of the organic solvent is more than or equal to 45 percent based on the total mass of the electrolyte; optionally 60% to 91%. When the mass content of the carbon coating layer and the mass content of the organic solvent are in the above ranges, both improvement of the cycle performance of the battery cell in the operating state and DCR growth in the stationary storage state can be achieved.
Illustratively, the carbon coating may be 1%, 1.1%, 1.2%, 1.3%, 1.4,%, 1.5% or a range of any two values recited above; the organic solvent may be present in an amount of 30%, 31%, 32%, 33%, 34%, 35%, 36%, 36.4%, 37%, 38%, 39%, 40%, 40.4%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 50.4%, 51%, 52%, 52.5%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91% or in a range comprised of any two of the foregoing values.
In some embodiments, the olivine structured lithium-containing material includes first particles having a particle size greater than a predetermined particle size and second particles having a particle size less than or equal to the predetermined particle size. Illustratively, the lithium iron phosphate-based material includes a first particle and a second particle.
Alternatively, the preset particle diameter may be an average particle diameter of the olivine-structured lithium-containing material, the preset particle diameter being a constant value, for example, any one value of 0.7 μm to 1 μm, for example, 0.7 μm; the average particle size is in the meaning known in the art, and can be detected by using equipment and methods known in the art, for example, a freshly prepared positive electrode sheet can be taken, or a battery which has been discharged (discharged to a lower limit cut-off voltage so that the charged state of the battery is about 0% soc) is reversely disassembled, and the positive electrode sheet is obtained from the battery and dried; then scraping the positive electrode film layer in the positive electrode plate from the positive electrode current collector to be used as a test sample, adopting a scanning electron microscope SEM to observe an SEM (scanning electron microscope) graph, for example, randomly selecting 100 particles in the SEM graph, respectively measuring the particle sizes of the 100 particles, taking the longest diameter of the particles as the particle size, and then calculating the average value of the longest diameters as the preset particle size. In the embodiment of the present application, particles are classified into two types of particles of a size by adopting the concept of a preset particle diameter, large particles exceeding the preset particle diameter are used as the first particles, and small particles smaller than or equal to the preset particle diameter are used as the second particles.
The lithium iron phosphate material is obtained by mixing large particles and small particles, the particle size distribution is wider, the contact area between the particles is larger, and good electron and ion passages can be formed between the particles, so that the cycle performance of the battery monomer in the working state can be improved.
In some embodiments, the first particles comprise at least one of single particles and agglomerated particles formed by agglomeration of a plurality of single particles. Single particles refer to a single particle alone, and agglomerated particles refer to particles formed by agglomeration of two or more individual particles. The mixed use of single particles and agglomerated particles can also promote the contact area between particles, form better electron and ion passage between the particles, further improve the cycle performance under the battery monomer operating condition.
In some embodiments, the second particles each independently comprise at least one of a single particle and an agglomerated particle formed by agglomeration of a plurality of single particles.
In embodiments of the present application, the content of the element in the positive electrode active material is in the meaning well known in the art, and may be detected using equipment and methods well known in the art, for example, by inductively coupled plasma atomic emission spectrometry testing with reference to EPA 6010D-2014, and measuring using plasma atomic emission (ICP-OES, instrument model: thermo ICAP 7400). First, 0.4. 0.4 g of the positive electrode active material was weighed, and 10ml (50% strength) of aqua regia was added thereto. Then placed on a 180℃plate for 30min. After digestion on the plate, the volume was fixed to 100% mL and quantitative testing was performed using standard curve method.
In some embodiments, the lithium iron phosphate-based material has a mass content of 85% or more and less than 100% based on the total mass of the positive electrode film layer. For example, the mass content of the lithium iron phosphate material may be 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or a range of any two of the above values.
In some embodiments, the positive electrode film layer further optionally includes a positive electrode conductive agent. The present embodiment is not particularly limited in the kind of the positive electrode conductive agent, and the positive electrode conductive agent includes at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers, as an example. In some embodiments, the mass content of the positive electrode conductive agent is 5% or less based on the total mass of the positive electrode film layer.
In some embodiments, the positive electrode film layer further optionally includes a positive electrode binder. The embodiment of the present application is not particularly limited in kind of the positive electrode binder, and the positive electrode binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluoroacrylate-based resin, as an example. In some embodiments, the mass content of the positive electrode binder is 5% or less based on the total mass of the positive electrode film layer.
In some embodiments, the positive current collector may employ a metal foil or a composite current collector. As an example of the metal foil, aluminum foil may be used. The composite current collector may include a polymeric material base layer and a metal material layer formed on at least one surface of the polymeric material base layer. As an example, the metal material of the metal material layer may include at least one of aluminum, aluminum alloy, nickel alloy, titanium alloy, silver, and silver alloy. As an example, the polymeric material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and Polyethylene (PE).
The positive electrode film layer is usually formed by coating positive electrode slurry on a positive electrode current collector, drying and cold pressing. The positive electrode slurry is generally formed by dispersing a positive electrode active material, an optional conductive agent, an optional binder, and any other components in a solvent and stirring uniformly. The solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.
[ negative electrode sheet ]
The battery cell also comprises a negative pole piece.
In some embodiments, the negative electrode tab includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and including a negative electrode active material. For example, the anode current collector has two surfaces opposing in the own thickness direction, and the anode film layer is provided on either or both of the two opposing surfaces of the anode current collector.
In some embodiments, the compacted density of the single-sided negative electrode film layer may be 1.0g/cm 3 To 1.3g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the When the compaction density of the negative electrode film layer meets the range, the porosity and the thickness of the negative electrode film layer can be considered under the condition that a certain gram capacity of the negative electrode plate is met, so that the migration rate and the migration path of lithium ions in the negative electrode film layer are considered; and the negative electrode film layer is matched with the positive electrode film layer, so that lithium ions separated from the positive electrode film layer can be quickly embedded into the negative electrode film layer, and the quick charging performance of the battery cell is further improved.
In some embodiments, the areal density of the single-sided negative electrode film layer is 0.12g/1540.25mm 2 To 0.14g/1540.25mm 2 The method comprises the steps of carrying out a first treatment on the surface of the When the surface density of the negative electrode film layer meets the range, the porosity and the thickness of the negative electrode film layer can be considered under the condition that a certain gram capacity of the negative electrode plate is met, so that the migration rate and the migration path of lithium ions in the negative electrode film layer are considered; and the negative electrode film layer is matched with the positive electrode film layer, so that lithium ions separated from the positive electrode film layer can be quickly embedded into the negative electrode film layer, and the quick charging performance of the battery cell is further improved.
In some embodiments, the thickness of the single-sided negative electrode film layer, H 2 The method meets the following conditions: h is more than or equal to 60 mu m 2 80 μm, for example, 60 μm, 65 μm, 68 μm, 70 μm, 72 μm, 75 μm, 78 μm, 80 μm or a range of any two values mentioned above.
The negative electrode film layer is a thick coating film layer, and the thickness of the single-side film layer is matched with the surface density of the film layer, so that lithium ions released from the positive electrode film layer can be quickly embedded into the negative electrode film layer, and the quick charging performance of the battery is further improved. The thickness of unilateral rete and the compaction density cooperation of rete can further make the lithium ion that deviate from by the anodal rete can be embedded into in the negative pole rete fast, further promotes the free quick charge performance of battery.
In some embodiments, the negative electrode film layer includes a carbonaceous material of layered structure. Optionally, the carbonaceous material comprises graphite, for example comprising at least one of artificial graphite and natural graphite, optionally artificial graphite, the structural stability of which is relatively high. Lithium-containing material of olivine structure as positive electrode active material system, carbon material (graphite system) as negative electrode active material system, and the lithium-containing material of olivine structure was prepared by mixing with the thickness parameter (138 μm.ltoreq.H of the electrode assembly 1 +H 2 +H 3 190 μm or less and 7 or less (H) 1 +H 2 )/H 3 And less than or equal to 12), can lead lithium ions to migrate in the electrode assembly rapidly, and improves the dynamic performance, thereby improving the rapid charging capability.
The qualitative and quantitative properties of each substance or each element in the application can be detected by using proper equipment and methods known to those skilled in the art, the related detection methods can refer to domestic and foreign detection standards, domestic and foreign enterprise standards and the like, and those skilled in the art can adaptively change certain detection steps/instrument parameters and the like from the aspect of detection accuracy so as to obtain more accurate detection results. One detection method may be used qualitatively or quantitatively, or several detection methods may be used in combination for qualitative or quantitative determination.
For example, the graphite material in the present application can be subjected to an X-ray powder diffraction test and qualitative analysis on a negative electrode sheet or a negative electrode active material in combination with JIS/K0131-1996X ray diffraction analysis method general rule.
In some embodiments, the mass content of the artificial graphite is 85% or more and less than 100% based on the total mass of the negative electrode film layer. For example, the mass content of the artificial graphite may be 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99% or a range of any two of the above values.
In some embodiments, the volume distribution particle size D of the artificial graphite v 99 is 30 μm to 45 μm. The artificial graphite meeting the above range has relatively large particle size, small specific surface area and relatively small contact area with electrolyte, and can reduce side reaction and improve the cycle life in working state.
Illustratively, the volume distribution particle size D of the artificial graphite v 99 is 30 μm, 31 μm, 32 μm, 33 μm, 34 μm, 35 μm, 36 μm, 37 μm, 38 μm, 39 μm, 40 μm, 41 μm, 42 μm, 43 μm, 44 μm, 45 μm or a range of any two values of the above.
In embodiments of the present application, the volume distribution particle size D of the particles v 99 is the meaning known in the art, the volume distribution particle diameter D of the particles v 99 refers to the particle size corresponding to 99% of the volume distribution, and can be detected by using equipment and methods known in the art, for example, taking a freshly prepared negative electrode active material as a sample for detection, or fully placing fresh battery cells to a state of charge (SOC), disassembling a negative electrode plate, removing a negative electrode current collector to reserve a negative electrode film layer, immersing the negative electrode film layer in N-methylpyrrolidone (NMP), washing out a binder in the negative electrode film layer, reserving the negative electrode active material, drying the negative electrode active material, and then testing the volume distribution particle size D of particles by a Mastersizer 2000E type laser particle size analyzer according to test standard GB/T19077-2016 v 99. In this embodiment, the fresh battery cell may be a battery cell that has just been shipped (not subjected to charge-discharge cycle after formation), or a battery cell that is mounted on an electric device and has a cycle number of cycles of less than 10.
Volume distribution particle size D of artificial graphite v 99 is 30 μm to 45 μm; the electrolyte also comprises at least one of fluoroethylene carbonate FEC and vinylene carbonate VC; alternatively, the total mass content in fluoroethylene carbonate FEC and vinylene carbonate VC is 0.5% to 2.5% based on the total mass of the electrolyte. The fluoroethylene carbonate FEC and the vinylene carbonate VC are matched with the artificial graphite with large particle size, so that the improvement of the cycle life and the DCR increase under static storage are both facilitated.
In some embodiments, the negative electrode film layer further optionally includes a negative electrode conductive agent. The present embodiment is not particularly limited in kind of the anode conductive agent, and the anode conductive agent may include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers, as an example. In some embodiments, the mass content of the negative electrode conductive agent is 5% or less based on the total mass of the negative electrode film layer.
In some embodiments, the negative electrode film layer further optionally includes a negative electrode binder. The present embodiment is not particularly limited in kind to the negative electrode binder, and may include, as an example, at least one of styrene-butadiene rubber SBR, a water-soluble unsaturated resin SR-1B, an aqueous acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAs, polyacrylamide PAM, polyvinyl alcohol PVA, sodium alginate SA, and carboxymethyl chitosan CMCS).
In some embodiments, the negative electrode film layer may also optionally include other adjuvants. As an example, other adjuvants may include thickeners, such as sodium carboxymethyl cellulose CMC-Na, PTC thermistor materials, and the like. In some embodiments, the mass content of the other auxiliary agent is 2% or less based on the total mass of the anode film layer.
In some embodiments, the negative electrode current collector may employ a metal foil or a composite current collector. As an example of the metal foil, copper foil may be used. The composite current collector may include a polymeric material base layer and a metal material layer formed on at least one surface of the polymeric material base layer. As an example, the metallic material may include at least one of copper, copper alloy, nickel alloy, titanium alloy, silver, and silver alloy. As an example, the polymeric material base layer may include at least one of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, and polyethylene.
The negative electrode film layer is usually formed by coating a negative electrode slurry on a negative electrode current collector, drying and cold pressing. The negative electrode slurry is generally formed by dispersing a negative electrode active material, an optional conductive agent, an optional binder, and other optional auxiliaries in a solvent and stirring uniformly. The solvent may be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.
The negative electrode tab does not exclude other additional functional layers than the negative electrode film layer. For example, in some embodiments, the negative electrode tab of an embodiment of the present application further includes a conductive primer layer (e.g., composed of a conductive agent and a binder) disposed on a surface of the negative electrode current collector, sandwiched between the negative electrode current collector and the negative electrode film layer. In other embodiments, the negative electrode tab of the embodiments of the present application further includes a protective layer covering the surface of the negative electrode film layer.
[ electrolyte ]
In some embodiments, the electrolyte has a retention factor of 4.0g/Ah to 5.0g/Ah.
The electrolyte retention coefficient of the battery monomer can reflect the electrolyte retention capacity of the electrolyte, when the electrolyte retention coefficient of the battery monomer is in the range, the electrolyte can have a good infiltration effect on the positive electrode plate and the negative electrode plate, and the migration rate of lithium ions in a liquid phase can be improved, so that the quick charging capacity of the battery monomer is improved.
Illustratively, the retention factor of the battery may be 4.0g/Ah, 4.1g/Ah, 4.2g/Ah, 4.3g/Ah, 4.4g/Ah, 4.5g/Ah, 4.6g/Ah, 4.7g/Ah, 4.8g/Ah, 4.9g/Ah, 5.0g/Ah, or a range of any two of the above values.
In the embodiment of the application, the liquid retention coefficient of the battery monomer is in a meaning known in the art, and can be detected by adopting equipment and a method known in the art, for example, the battery monomer is charged to 3.6V at the temperature of 25 ℃ and then discharged to 2.5V at the temperature of 1C according to GB/T31486-2015, namely the electric performance requirement and test method of a power storage battery for an electric automobile, and the discharged capacity C is taken as a denominator; weighing the battery monomer as M0, then disassembling the positive pole piece, the negative pole piece, the isolating film and the electrolyte, wherein the free electrolyte exists in a shell/bag, and putting all the solid components into a 60 ℃ oven to bake for more than 4 hours (including but not only the positive pole piece, the negative pole piece, the isolating film, and further packaging Include other contributions M of disassembled cells 0 And then weigh M1 again for all components of the cell, where the weight difference between M0 and M1 is taken as the molecule. The retention factor is equal to the capacity C divided by the weight difference between M0 and M1.
In the present embodiment, the viscosity of the electrolyte and the properties of the solid electrolyte interface (Solid Electrolyte Interphase, SEI) film may be adjusted by adjusting at least one of the specific kinds and contents of components in the electrolyte.
[ lithium salt ]
In some embodiments, the electrolyte comprises a lithium salt, the lithium salt comprising a first lithium salt and a second lithium salt, the first lithium salt comprising lithium hexafluorophosphate LiPF 6 And at least one of lithium bistrifluoromethylsulfonylimide LiTFSI, optionally lithium hexafluorophosphate LiPF 6 The mass percentage of the first lithium salt relative to the total mass of the electrolyte is less than or equal to 10 percent, and can be selected to be 5 to 10 percent; the second lithium salt comprises lithium tetrafluoroborate LiBF 4 Lithium difluorophosphate LiPO 2 F 2 The mass percentage of the second lithium salt relative to the total mass of the electrolyte is more than or equal to 1 percent.
The lithium salt can provide active lithium ions for a battery system, and the viscosity of the first lithium salt is relatively high, so that the quick migration of the lithium ions is not facilitated; the viscosity of the second lithium salt is relatively low, and the second lithium salt can form an SEI film rich in boron and/or fluorine elements on the surface of the anode active material, so that an SEI film interface can be effectively repaired, the impedance of a circulation process is reduced, and the circulation performance is improved; the second lithium salt can also relieve the decomposition of lithium hexafluorophosphate into hydrofluoric acid to a certain extent, can further relieve the side reaction between the hydrofluoric acid and the active material, and can give consideration to the improvement of the quick charging performance and the cycle performance of the battery monomer.
Illustratively, the first lithium salt is present in an amount greater than 0% and less than or equal to 10% by mass, for example 0.05%, 0.06%, 0.08%, 0.1%, 0.15%, 0.18%, 0.2%, 0.22%, 0.25%, 0.28%, 0.3%, 0.32%, 0.35%, 0.38%, 0.4%, 0.42%, 0.45%, 0.48%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 0.95%, 0.98%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 1.91, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 0.8%, 1.2 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.2%, 3.5%, 3.6%, 3.8%, 4.0%, 4.2%, 4.5%, 4.6%, 4.8%, 5.0%, 5.2%, 5.5%, 5.6%, 5.8%, 6.0%, 6.2%, 6.5%, 6.8%, 7.0%, 7.2%, 7.5%, 7.8%, 8.0%, 8.2%, 8.5%, 8.8%, 9.0%, 9.2%, 9.5%, 9.8%, 10% or a range of any two of the above values.
Illustratively, the mass percent of the second lithium salt is greater than 0% and equal to or less than 5%, such as 0.05%, 0.06%, 0.08%, 0.1%, 0.15%, 0.18%, 0.2%, 0.22%, 0.25%, 0.28%, 0.3%, 0.32%, 0.35%, 0.38%, 0.4%, 0.42%, 0.45%, 0.48%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 0.95%, 0.98%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 1.91, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3.2%, 3.5%, 3.6%, 3.8%, 4.0%, 4.2.5%, 4.5%, 4.6%, 4.8%, 4.5%, 4.8%, or any two of the ranges described above.
In some embodiments, the second lithium salt comprises lithium tetrafluoroborate LiBF 4 Lithium difluorophosphate LiPO 2 F 2 . Through the cooperation of the two lithium salts, the SEI film rich in boron and fluorine can be formed on the surface of the anode active material, the SEI film interface can be effectively repaired, the impedance of the circulation process is reduced, and the circulation performance is improved.
In some embodiments, lithium tetrafluoroborate LiBF 4 The mass percentage content relative to the total mass of the electrolyte is 0.3 to 1.0 percent, and the lithium difluorophosphate LiPO 2 F 2 The mass percentage content relative to the total mass of the electrolyte is 0.3 to 3.5 percent. Through the matched use of the two lithium salts with the content, an SEI film rich in boron elements and fluorine elements can be formed on the surface of the anode active material, the SEI film interface can be effectively repaired, the impedance of the circulation process is reduced, and the circulation performance is improved; and the content of inorganic components in the formed SEI film is increased, the pore structure is increased, the rapid migration or removal of lithium ions from the anode active material is facilitated, and the rapid charging performance of the battery cell is further improved.
When the solubility of lithium difluorophosphate in the electrolyte is high, the content of the lithium difluorophosphate can be more than or equal to 3%.
In view of further reducing the resistance of the cycle process and improving the quick charge performance, alternatively, lithium tetrafluoroborate LiBF 4 The mass percentage content relative to the total mass of the electrolyte is 0.5 to 0.8 percent, and the lithium difluorophosphate LiPO 2 F 2 The mass percentage content relative to the total mass of the electrolyte is 0.3 to 1.5 percent.
Illustratively, lithium tetrafluoroborate LiBF 4 The mass percentage of (C) may be 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 0.95%, 0.98%, 1% or a range composed of any two of the above values.
Illustratively, lithium difluorophosphate LiPO 2 F 2 The mass percentage of (c) may be 0.3%, 0.32%, 0.35%, 0.38%, 0.4%, 0.42%, 0.45%, 0.48%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 0.95%, 0.98%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 1.95%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.2%, 3.5% or a range consisting of any two of the foregoing values.
In some embodiments, the lithium salt further includes a third lithium salt including at least one of a lithium fluoroborate salt and a lithium fluorophosphate salt, wherein the third lithium salt is 0.1% to 2.5% by mass relative to the total mass of the electrolyte.
Lithium fluoroborate in the third lithium salt and lithium tetrafluoroborate LiBF in the second lithium salt 4 The lithium fluorophosphate in the third lithium salt and the lithium difluorophosphate LiPO in the second lithium salt are different in kind 2 F 2 The species are different. By adding the third lithium salt with the content, the viscosity of an electrolyte system can be reduced, the rapid migration of lithium ions in a liquid phase is facilitated, and the rapid charging performance of the battery monomer is improved.
Illustratively, the third lithium salt may be 0.1%, 0.15%, 0.18%, 0.2%, 0.22%, 0.25%, 0.28%, 0.3%, 0.32%, 0.35%, 0.38%, 0.4%, 0.42%, 0.45%, 0.48%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 0.95%, 0.98%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 1.95%, 2.0%, 2.05%, 2.1%, 2.15%, 2.2%, 2.25%, 2.3%, 2.35%, 2.4%, 2.45%, 2.5% or a range of any two of the foregoing numerical compositions by mass.
In some embodiments, the lithium fluoroborate salt may include at least one of lithium difluoroborate LiDFOB and lithium bisoxalato borate LiBOB. Alternatively, the lithium fluoroborate salts may include lithium difluorooxalato borate LiDFOB and lithium bisoxalato borate LiBOB. The lithium fluoborate can also participate in forming an SEI film containing boron element, which is beneficial to improving the cycle performance.
In some embodiments, the lithium fluorophosphate may include at least one of lithium difluorophosphate LiDFOP and lithium tetrafluorooxalate phosphate LiTFOP. Alternatively, the lithium fluorophosphate salts may include lithium difluorophosphate LiDFOP and lithium tetrafluorooxalate phosphate LiTFOP. The fluorine-containing lithium phosphate can also participate in forming an SEI film containing fluorine elements, which is beneficial to improving the cycle performance.
[ organic solvent ]
In some embodiments, the electrolyte further comprises an organic solvent, the mass percent of the organic solvent relative to the total mass of the electrolyte being greater than or equal to 45%; optionally 60% to 91%. By adding the organic solvent with the content, the viscosity of an electrolyte system can be reduced, the rapid migration of lithium ions in a liquid phase is facilitated, and the rapid charging performance of a battery monomer is improved.
Illustratively, the mass percent of the organic solvent may be 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91% or a range of any two numerical compositions described above.
In some embodiments, the organic solvent may include at least one of ethylene carbonate EC and propylene carbonate PC. Alternatively, the organic solvent may include ethylene carbonate EC and propylene carbonate PC.
[ additive ]
In some embodiments, the electrolyte further includes an additive, which may include at least one of fluoroethylene carbonate FEC and vinylene carbonate VC; alternatively, the additives may include fluoroethylene carbonate FEC and vinylene carbonate VC. Fluoroethylene carbonate FEC can obviously reduce the standing storage impedance; vinylene carbonate VC can significantly improve cycle life; when the electrolyte and the electrolyte are added together, the cycle life of the battery cell can be prolonged and the standing storage impedance can be improved.
Alternatively, the mass percent of the additive is 0.5% to 2.5% based on the total mass of the electrolyte. When the mass percentage of the additive is in the range, the cycle life of the battery monomer can be effectively prolonged, and the standing storage impedance can be improved.
Illustratively, the additive may be present in an amount of 0.5%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2.0%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5% by mass or in a range of any two values recited above.
The qualitative and quantitative properties of each substance or each element in the application can be detected by using proper equipment and methods known to those skilled in the art, the related detection methods can refer to domestic and foreign detection standards, domestic and foreign enterprise standards and the like, and those skilled in the art can adaptively change certain detection steps/instrument parameters and the like from the aspect of detection accuracy so as to obtain more accurate detection results. One detection method may be used qualitatively or quantitatively, or several detection methods may be used in combination for qualitative or quantitative determination.
In the embodiment of the present application, the type and content of the inorganic component/lithium salt concentration in the electrolyte are the meanings known in the art, and can be detected by using the equipment and method known in the art, for example, the inorganic component/lithium salt concentration in the electrolyte can be qualitatively or quantitatively analyzed by the ion chromatography method with reference to the standard JY/T020-1996 general rule of ion chromatography method. In the embodiment of the present application, a freshly prepared electrolyte may be taken as a sample, or a battery that has been discharged (charged state of about 0% soc) may be reversely disassembled, and a free electrolyte obtained from the battery may be taken as a sample and detected by an ion chromatography method.
In the embodiments of the present application, the types and contents of the organic components in the electrolyte are in the meaning known in the art, and may be detected by using devices and methods known in the art, for example, qualitative and quantitative analysis of the organic components in the electrolyte may be performed by gas chromatography with reference to GB/T9722-2006 general rules for chemical gas chromatography. In the embodiment of the present application, a freshly prepared electrolyte may be taken as a sample, or a battery that has been discharged (discharged to a charged state of about 0% soc) may be reversely disassembled, and a free electrolyte obtained from the battery may be taken as a sample and detected by an ion chromatography method.
For another example, taking liquid-phase Nuclear Magnetic Resonance (NMR) to test the components of a certain additive in the electrolyte, taking lithium difluorophosphate and lithium hexafluorophosphate as examples, preparing 1 7ml glass bottle in a nitrogen glove box, adding 5ml nuclear magnetic reagent premix into the glass bottle, and standing at room temperature of 20-25 ℃ for 24 hours in the nitrogen glove box, so that the electrolyte in the pole piece and the isolating film is diffused into the nuclear magnetic premix, thereby obtaining a nuclear magnetic measurement sample. The nuclear magnetic premix comprises 100ml of deuterated acetonitrile and 3ml of trifluoromethyl benzene C 7 H 5 F 3 The above nuclear magnetic reagent premix is pre-dried with molecular sieve 4A in advance (100 ml of nuclear magnetic reagent premix is added with 15g of newly opened 4A molecular sieve and dried in a nitrogen glove box for more than 30 days at room temperature of 20-25 ℃). The 19F NMR measurement (nuclear magnetic resonance (NMR): bruker Avance 400 HD) was used.
In order to identify and quantify the individual species, the following settings were employed in terms of flip angle and scan time.
Fluorine spectrum test pulse sequence: 2gfhigqn.2;
delay time: 1 second;
number of scans: 16 times.
Based on trifluoromethylbenzene and LiPF in F-NMR 6 The relative content of the two substances is calculated by the integral intensity of the signal peaks, and the calculation method comprises the following steps:
PF 6 - relative content= (I) PF6 - ×M PF6 - /6)/(I CF3ph ×M CF3ph And/3), wherein I is the corresponding nuclear magnetic peak area,m is the corresponding relative molecular mass, and then the molar ratio relation of the hexafluorophosphate radical and lithium ions is used for calculating the content of lithium hexafluorophosphate in the electrolyte.
Based on trifluoromethyl benzene and PO in F-NMR 2 F 2 - The relative content of the two substances is calculated by the integral intensity of the signal peaks, and the calculation method comprises the following steps:
PO 2 F 2 - relative content= (I) PO2F2- ×M PO2F2- /2)/(I CF3ph ×M CF3ph And 3), wherein I is the corresponding nuclear magnetic peak area, M is the corresponding relative molecular mass, and then the molar ratio relation of the difluorophosphate radical and lithium ions is used for calculating the content of the lithium difluorophosphate in the electrolyte.
In some embodiments, various types of solutes or solvents in the electrolytes referred to herein include both substances that are actively added in preparing the electrolyte and substances that are derived from substances already present in some electrolyte(s) during storage or use, either during electrolyte preparation or during battery preparation from the electrolyte or from a battery containing the electrolyte.
In some embodiments, the positive electrode tab, the separator, and the negative electrode tab may be manufactured into an electrode assembly through a winding process and/or a lamination process.
In some embodiments, the battery cell may include an outer package. The outer package may be used to encapsulate the electrode assembly and electrolyte as described above.
In some embodiments, the exterior packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, or the like. The outer package of the battery cell may also be a pouch, such as a pouch-type pouch. The soft bag can be made of plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT) and polybutylene succinate (PBS).
The shape of the battery cell according to the embodiment of the present application is not particularly limited, and may be cylindrical, square, or any other shape. Fig. 1 shows a square-structured battery cell 5 as an example.
In some embodiments, as shown in fig. 2, the outer package may include a housing 51 and a cover 53. The housing 51 may include a bottom plate and a side plate coupled to the bottom plate, the bottom plate and the side plate enclosing to form a receiving chamber. The housing 51 has an opening communicating with the accommodation chamber, and the cover plate 53 is used to cover the opening to close the accommodation chamber. The positive electrode sheet, the negative electrode sheet, and the separator may be formed into the electrode assembly 52 through a winding process and/or a lamination process. The electrode assembly 52 is packaged in the receiving chamber. The electrolyte is impregnated in the electrode assembly 52. The number of the electrode assemblies 52 included in the battery cell 5 may be one or more, and may be adjusted according to the need.
Methods of preparing the battery cells of the embodiments of the present application are well known. In some embodiments, the positive electrode tab, separator, negative electrode tab, and electrolyte may be assembled to form a battery cell. As an example, the positive electrode sheet, the separator and the negative electrode sheet may be wound and/or laminated to form an electrode assembly, the electrode assembly is placed in an outer package, dried and then injected with an electrolyte, and the battery cell is obtained through vacuum packaging, standing, formation, shaping and other steps.
In some examples of embodiments of the present application, the battery cells according to embodiments of the present application may be assembled into a battery module, and the number of battery cells included in the battery module may be plural, and the specific number may be adjusted according to the application and capacity of the battery module.
Fig. 3 is a schematic diagram of an embodiment of a battery module 4 of the present application. As shown in fig. 3, in the battery module 4, a plurality of battery cells 5 may be arranged in order along the longitudinal direction of the battery module 4. Of course, the arrangement may be performed in any other way. The plurality of battery cells 5 may be further fixed by fasteners.
Alternatively, the battery module 4 may further include a housing having an accommodating space in which the plurality of battery cells 5 are accommodated.
In some embodiments, the battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be adjusted according to the application and capacity of the battery pack.
Fig. 4 is a schematic view of an embodiment of the battery pack 1 of the present application, and fig. 5 is an exploded schematic view of the embodiment of the battery pack 1 shown in fig. 4. As shown in fig. 4 and 5, a battery box and a plurality of battery modules 4 disposed in the battery box may be included in the battery pack 1. The battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 is used for covering the lower box body 3 and forms a closed space for accommodating the battery module 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.
Power utilization device
A second aspect of the embodiments provides an electrical device comprising at least one of the battery cells, battery modules, or battery packs of the embodiments. The battery cell, the battery module, or the battery pack may be used as a power source of the electric device, and may also be used as an energy storage unit of the electric device. The electric device may be, but is not limited to, a mobile device (e.g., a cellular phone, a notebook computer, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc.
The power utilization device can select a battery cell, a battery module or a battery pack according to the use requirement.
Fig. 6 is a schematic diagram of an embodiment of an electrical device 6 that includes a battery cell of the present application as a power source. The electric device 6 is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or the like. To meet the high power and high energy density requirements of the power consumer 6, a battery pack or battery module may be employed.
As another example, the power consumption device may be a mobile phone, a tablet computer, a notebook computer, or the like. The power utilization device is required to be light and thin, and a battery unit can be used as a power supply.
Examples
The following examples more particularly describe the disclosure of embodiments of the present application, which examples are intended as illustrative only, since numerous modifications and variations within the scope of the disclosure of embodiments of the present application will be apparent to those skilled in the art. Unless otherwise indicated, all parts, percentages and ratios reported in the examples below are on a mass basis, and all reagents used in the examples are commercially available or were obtained synthetically according to conventional methods and can be used directly without further treatment, as well as the instruments used in the examples.
Example 1
1. Preparation of positive electrode plate
The positive pole piece comprises a positive current collector aluminum foil and a positive pole film layer, wherein the positive pole film layer comprises a film layer formed by uniformly coating positive pole slurry (N-methylpyrrolidone NMP as a solvent) on the surface of the positive current collector aluminum foil, drying and cold pressing, and the positive pole film layer comprises the following components in percentage by weight of 97.5:1.4:1.1, a positive electrode active material, a conductive agent carbon black, and a binder polyvinylidene fluoride (PVDF).
The positive electrode active material comprises a lithium iron phosphate material, wherein the lithium iron phosphate material further comprises an aluminum Al element with the content of 400ppm, and further comprises a carbon coating layer with the mass content of 1.2% relative to the lithium iron phosphate material. The lithium iron phosphate-based material includes first particles and second particles. The first particles have a particle size of 1 μm or less and the second particles have a particle size of 1 μm or less.
The compaction density of the single-side positive electrode film layer is 2.2g/cm 3 The surface density is 0.28g/1540.25mm 2 。
2. Preparation of negative electrode plate
The negative electrode plate comprises a negative electrode current collector copper foil and a negative electrode film layer, wherein the negative electrode film layer comprises a film layer formed by uniformly coating negative electrode slurry (deionized water serving as a solvent) on the surface of the negative electrode current collector copper foil, drying and cold pressing, and the negative electrode film layer comprises the following components in percentage by weight: 1.8:1.2:0.8 of a negative electrode active material, a binder styrene-butadiene rubber (SBR), a thickener sodium carboxymethylcellulose (CMC-Na) and a conductive agent carbon black (Super P).
The negative electrode active material comprises artificial graphite having a volume distribution particle size D v 99 is 35 μm.
The compaction density of the single-side negative electrode film layer is 1.2g/cm 3 The surface density is 0.13g/1540.25mm 2 。
3. Isolation film
The isolating film is porous polypropylene PP film.
4. Preparation of electrolyte
The electrolyte comprises an organic solvent, lithium salt and an additive.
The lithium salt comprises a first lithium salt lithium hexafluorophosphate LiPF 6 (7%) and a second lithium salt and a third lithium salt, the second lithium salt comprising lithium tetrafluoroborate LiBF 4 (0.7%) and lithium difluorophosphate LiPO 2 F 2 (1%) and the third lithium salt comprises lithium difluorooxalato borate LiDFOB (2%). The mass content of each component in the lithium salt is calculated based on the total mass of the electrolyte.
The additive comprises fluoroethylene carbonate FEC (1%), and the mass content of the additive is calculated based on the total mass of the electrolyte.
The organic solvent comprises dimethyl carbonate DMC (40%), methyl ethyl carbonate EMC (20%), ethylene carbonate EC (30%) and propylene carbonate PC (10%), the mass content of each component in the organic solvent is calculated based on the total mass of the organic solvent, and the mass content of the organic solvent relative to the total mass of the electrolyte is 88.3%.
The electrolyte has a retention coefficient of 4.5g/Ah.
5. Preparation of a Battery
The lithium ion battery comprises an outer packaging shell, an electrode assembly and electrolyte, wherein the electrode assembly and the electrolyte are arranged in the outer packaging shell, the electrode assembly comprises a positive electrode plate, a negative electrode plate and an isolating film, the electrode assembly is a winding type electrode assembly, and the isolating film is arranged between the positive electrode plate and the negative electrode plate.
Comparative example 1 and comparative example 2
A lithium ion battery was fabricated by a method similar to example 1, except that comparative example 1 and comparative example 2 adjusted the total thickness of the positive electrode film layer, the negative electrode film layer, and the separator, unlike example 1.
Comparative example 3 and comparative example 4
A lithium ion battery was fabricated by a method similar to example 1, except that comparative example 3 and comparative example 4 adjusted the thickness of at least one of the positive electrode film layer, the negative electrode film layer, and the separator, unlike example 1.
Comparative example 5
A lithium ion battery was fabricated by a method similar to example 1, except that comparative example 5 was modified in the structure of a separator using a porous PP film layer having a thickness of 20 μm and a single-sided alumina ceramic coating layer having a thickness of 2.5 μm and a total thickness of 25 μm and an alumina ceramic coating layer disposed on both sides of the porous PP film layer.
Examples 2-1 to 2-6
A lithium ion battery was fabricated by a method similar to that of example 1, except that examples 2-1 to 2-6 were each modified in at least the total thickness H of the positive electrode film layer, the negative electrode film layer and the separator film 1 +H 2 +H 3 。
Examples 3-1 to 3-3
A lithium ion battery was fabricated by a method similar to example 1, except that examples 3-1 to 3-3 adjusted at least one of the material and the porosity of the separator, unlike example 1.
Wherein, the isolation film in the embodiment 3-1 adopts a polyethylene PE film.
The separator in examples 3-2 and 3-3 adjusted the porosity.
Examples 4-1 and 4-2
A lithium ion battery was fabricated by a method similar to example 1, except that examples 4-1 and 4-2 adjusted the compacted density of the positive electrode film layer, etc., unlike example 1.
Performance testing
1. And (3) testing the cycle performance of the lithium ion battery:
the lithium ion batteries prepared in examples and comparative examples were charged to 3.6V at 3C rate and discharged to 2.5V at 1C rate at 25C, and the cycle test was performed until the capacity retention rate of the lithium ion battery was recorded after 600 weeks of the cycle of the lithium ion battery.
2. Static storage DCR growth rate test of lithium ion battery:
the lithium ion batteries prepared in the examples and comparative examples were tested for initial dc internal resistance DCR0; when the lithium ion battery is tested for DCR1 after being stored for 300 days at 60 ℃, the DCR growth rate is [ (DCR 1-DCR 0)/DCR 0 ]. Times.100%.
The test conditions for DCR are as follows:
the lithium ion battery was charged to 3.6V at a rate of 0.33C at 25C, and then discharged to 2.5V at a rate of 0.33C. Charging for 30min with current of 0.5C multiplying power, and recording the voltage as U1; the discharge was performed at a rate of 4C for 30S, and the voltage at this time was recorded as U2, dcr= (U1-U2)/I of the lithium ion battery.
The DCR influences the charging performance, the charging performance is reflected by the DCR growth rate, and the larger the DCR growth rate is, the worse the charging performance is; the smaller the DCR growth rate, the better the charging performance.
Test results
The test results of comparative examples 1 to 5, examples 1 to 4-2 are shown in Table 1.
TABLE 1
In comparative example 2, the total thickness of the positive electrode film layer, the separator film and the negative electrode film layer is small, and the positive electrode film layer and the negative electrode film layer may not meet the capacity requirement; the total thickness of the positive electrode film layer, the separator film and the negative electrode film layer in comparative examples 1 and 5 is too large, and the transmission path of lithium ions is too long, so that rapid charging of the battery cells cannot be achieved. It can be seen from comparative examples 3 and 4 that the solid phase transmission path of lithium ions is increased when the total thickness of the positive electrode film layer and the negative electrode film layer is too thick; when the thickness of the isolating film is too thick, the liquid phase transmission path of lithium ions is increased, and the rapid transmission of the lithium ions is not facilitated.
Compared with comparative examples 1, 2 and 5, the total thickness of the positive electrode film layer, the isolation film and the negative electrode film layer is adjusted, so that the cycle performance of the battery cell can be improved, the solid-liquid phase transmission path of lithium ions can be adjusted, the lithium ion transmission path, especially the solid-phase transmission path of lithium ions, can be shortened on the basis of meeting the capacity requirement of the lithium ion battery, and the quick charging performance of the battery cell can be effectively improved. By adjusting at least one of the thickness and the porosity of the separator within a reasonable range, the rate of lithium ion transfer in the liquid phase can be adjusted, improving the rapid charging performance of the battery cell. Through adjusting the thickness, compaction density and the like of at least one of the positive electrode film layer and the negative electrode film layer in a reasonable range, the rate of lithium ion in solid phase transmission can be effectively adjusted, and the quick charging performance of the battery monomer is improved.
Examples 5-1 to 5-3
A lithium ion battery was fabricated by a method similar to example 1, except that examples 5-1 to 5-3 adjusted the mass percent of the first lithium salt, unlike example 1.
Examples 6-1 to 6-4
A lithium ion battery was fabricated by a method similar to example 1, except that examples 6-1 to 6-4 adjusted the mass percent of the second lithium salt, unlike example 1.
Examples 7-1 and 7-2
A lithium ion battery was fabricated by a method similar to example 1, except that examples 7-1 and 7-2 adjusted the kind of the third lithium salt, unlike example 1.
Example 8
A lithium ion battery was fabricated by a method similar to example 1, except that example 8 was modified in the kind and mass percentage of the additive, unlike example 1.
Examples 9-1 and 9-2
A lithium ion battery was fabricated by a method similar to example 1, except that examples 9-1 and 9-2 adjusted the retention factor of the electrolyte, unlike example 1.
Test results
The test results of example 1, example 5-1 to example 9-2 are shown in Table 2.
TABLE 2
The mass content of each component of the electrolyte in table 2 is calculated based on the total mass of the electrolyte.
Through the collocation use of the first lithium salt and the second lithium salt in the embodiments 5-1 to 6-4, an SEI film rich in boron and/or fluorine elements can be formed on the surface of the anode active material, the SEI film interface can be effectively repaired, the impedance of the circulation process is reduced, and the circulation performance is improved; the second lithium salt can also relieve the decomposition of lithium hexafluorophosphate into hydrofluoric acid to a certain extent, can further relieve the side reaction between the hydrofluoric acid and the active material, and can give consideration to the improvement of the quick charging performance and the cycle performance of the battery monomer. In the embodiment 7-1 and the embodiment 7-2, the viscosity of the electrolyte system can be reduced by further adding the third lithium salt, which is favorable for the rapid migration of lithium ions in a liquid phase and improves the rapid charging performance of the battery cell. Example 8 contains two additives, FEC and VC, which can reduce the rest storage resistance. The performance of the lithium ion battery can be further improved by further controlling the retention coefficient of the electrolyte in examples 9-1 and 9-2.
Although illustrative embodiments have been shown and described, it will be understood by those skilled in the art that the foregoing embodiments are not to be construed as limiting the application and that changes, substitutions and alterations of the embodiments may be made without departing from the spirit, principles and scope of the application.
Claims (25)
1. A battery cell comprising an electrode assembly and an electrolyte, the electrode assembly comprising:
the positive electrode plate comprises a positive electrode current collector and a positive electrode film layer which is arranged on at least one side of the positive electrode current collector and contains a positive electrode active material, wherein the positive electrode active material comprises a lithium-containing material with an olivine structure;
the negative electrode plate comprises a negative electrode current collector and a negative electrode film layer which is arranged on at least one side of the negative electrode current collector and contains a negative electrode active material, wherein the negative electrode active material contains a carbon material; and
the isolating film is arranged between the positive pole piece and the negative pole piece,
wherein,
the thickness of the positive electrode film layer at one side of the positive electrode plate is H 1 The unit is mu m;
the thickness of the negative electrode film layer at one side of the negative electrode plate is H 2 The unit is mu m;
the thickness of the isolating film is H 3 The unit is mu m;
the battery cell satisfies: h is 65 mu m or less 1 ≤90μm，138μm≤H 1 +H 2 +H 3 190 μm or less and 7 or less (H) 1 +H 2 )/H 3 ≤12。
2. The battery cell of claim 1, wherein 7.5 +. 1 +H 2 )/H 3 ≤11.50。
3. The battery cell of claim 1, wherein the separator film is a porous polymer film, and the porous polymer film satisfies: 13 μm < H 3 ＜20μm。
4. The battery cell of claim 3, wherein the porous polymer film satisfies: h is more than or equal to 13.5 mu m 3 ≤19.5μm。
5. The battery cell of claim 3, wherein the porous polymer film comprises at least one of a polypropylene film and a polyethylene film.
6. The battery cell of claim 5, wherein the porous polymer film is a polypropylene film; or the porous polymer film is a polyethylene film.
7. The battery cell of claim 1, wherein the separator has a porosity of 35% to 45%.
8. The battery cell of claim 1, wherein the battery cell comprises a plurality of cells,
the compaction density of the positive electrode film layer on one side is 2.1g/cm 3 To 2.4g/cm 3 The compaction density of the negative electrode film layer on one side is 1.0g/cm 3 To 1.3g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the And/or
The surface density of the positive electrode film layer on one side is 0.26g/1540.25mm 2 To 0.29g/1540.25mm 2 The surface density of the negative electrode film layer on one side is 0.12g/1540.25mm 2 To 0.14g/1540.25mm 2 。
9. The battery cell of claim 8, wherein 0.9 +.h 1 /H 2 Less than or equal to 1.3; and H is more than or equal to 60 mu m 2 ≤80μm。
10. The battery cell of claim 1, wherein the electrolyte has a retention factor of 4.0g/Ah to 5.0g/Ah.
11. The battery cell of claim 1, wherein the electrolyte comprises a lithium salt comprising:
a first lithium salt comprising lithium hexafluorophosphate LiPF 6 And at least one of lithium bistrifluoromethylsulfonyl imide LiTFSI, wherein the mass percentage content of the first lithium salt relative to the total mass of the electrolyte is less than or equal to 10%; and
a second lithium salt comprising lithium tetrafluoroborate LiBF 4 Lithium difluorophosphate LiPO 2 F 2 The mass percentage content of the second lithium salt relative to the total mass of the electrolyte is more than or equal to 1 percent.
12. The battery cell of claim 11, wherein the first lithium salt is lithium hexafluorophosphate LiPF 6 。
13. The battery cell according to claim 11, wherein the first lithium salt is present in an amount of 5 to 10% by mass relative to the total mass of the electrolyte.
14. The battery cell of claim 11, wherein the second lithium salt comprises lithium tetrafluoroborate LiBF 4 Lithium difluorophosphate LiPO 2 F 2 。
15. The battery cell of claim 14, wherein the lithium tetrafluoroborate LiBF 4 The mass percentage content relative to the total mass of the electrolyte is 0.3% to 1.0%; the lithium difluorophosphate LiPO 2 F 2 The mass percentage content relative to the total mass of the electrolyte is 0.3% to 3.5%.
16. The battery cell of claim 15, wherein the lithium tetrafluoroborate LiBF 4 The mass percentage content relative to the total mass of the electrolyte is 0.5 to 0.8 percent; the lithium difluorophosphate LiPO 2 F 2 The mass percentage content relative to the total mass of the electrolyte is 0.3% to 1.5%.
17. The battery cell of claim 11, wherein the lithium salt further comprises a third lithium salt comprising at least one of a lithium fluoroborate salt and a lithium fluorophosphate salt, wherein the third lithium salt is present in an amount of 0.1% to 2.5% by mass relative to the total mass of the electrolyte.
18. The battery cell of claim 17, wherein the battery cell comprises a plurality of cells,
the fluorine-containing lithium borate salt comprises at least one of lithium difluoro oxalate borate LiDFOB and lithium bis oxalate borate LiBOB; and/or
The lithium fluorophosphate includes at least one of lithium difluorophosphate LiDFOP and lithium tetrafluorooxalate phosphate LiTFOP.
19. The battery cell of claim 1, wherein the electrolyte further comprises an organic solvent;
the mass percentage content of the organic solvent relative to the total mass of the electrolyte is more than or equal to 45 percent; and/or
The organic solvent includes at least one of ethylene carbonate EC and propylene carbonate PC.
20. The battery cell of claim 1, wherein the electrolyte further comprises an additive comprising at least one of fluoroethylene carbonate FEC and vinylene carbonate VC.
21. The battery cell of claim 20, wherein the additive is present in an amount of 0.5% to 2.5% by mass based on the total mass of the electrolyte.
22. The battery cell of claim 1, wherein the olivine structured lithium-containing material comprises an olivine structured lithium iron phosphate-based material, and the carbon material comprises graphite.
23. The battery cell of claim 1, wherein the olivine structured lithium-containing material comprises a material having the general formula Li x A y Me a M b P 1-c X c Q z Wherein x is more than or equal to 0 and less than or equal to 1.3, y is more than or equal to 0 and less than or equal to 1.3, and x+y is more than or equal to 0.9 and less than or equal to 1.3; a is more than or equal to 0.9 and less than or equal to 1.5, b is more than or equal to 0 and less than or equal to 0.5, and a+b is more than or equal to 0.9 and less than or equal to 1.5; c is more than or equal to 0 and less than or equal to 0.5; z is more than or equal to 3 and less than or equal to 5; a comprises at least one of Na, K and Mg; me includes at least one of Mn, fe, co, ni; m comprises at least one of B, mg, al, si, P, S, ca, sc, ti, V, cr, cu, zn, sr, Y, zr, nb, mo, cd, sn, sb, te, ba, ta, W, yb, la, ce; x comprises at least one of S, si, cl, B, C, N; q includes at least one of O, F.
24. A battery comprising a cell according to any one of claims 1 to 23.
25. An electrical device comprising the battery of claim 24.
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