CN116885103A - Graphite anode and preparation method and application thereof - Google Patents
Graphite anode and preparation method and application thereof Download PDFInfo
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- CN116885103A CN116885103A CN202311157525.1A CN202311157525A CN116885103A CN 116885103 A CN116885103 A CN 116885103A CN 202311157525 A CN202311157525 A CN 202311157525A CN 116885103 A CN116885103 A CN 116885103A
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 93
- 239000010439 graphite Substances 0.000 title claims abstract description 93
- 229910002804 graphite Inorganic materials 0.000 title claims abstract description 93
- 238000002360 preparation method Methods 0.000 title abstract description 13
- 230000000149 penetrating effect Effects 0.000 claims abstract description 25
- 238000000034 method Methods 0.000 claims abstract description 15
- 239000011149 active material Substances 0.000 claims abstract description 13
- 239000011248 coating agent Substances 0.000 claims description 11
- 238000000576 coating method Methods 0.000 claims description 11
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 6
- 229910001416 lithium ion Inorganic materials 0.000 claims description 6
- 229910001415 sodium ion Inorganic materials 0.000 claims description 3
- FKNQFGJONOIPTF-UHFFFAOYSA-N Sodium cation Chemical compound [Na+] FKNQFGJONOIPTF-UHFFFAOYSA-N 0.000 claims description 2
- 230000009977 dual effect Effects 0.000 claims description 2
- 239000011148 porous material Substances 0.000 abstract description 10
- 239000010410 layer Substances 0.000 description 67
- 230000000052 comparative effect Effects 0.000 description 19
- 239000007788 liquid Substances 0.000 description 12
- 230000014759 maintenance of location Effects 0.000 description 10
- 239000000463 material Substances 0.000 description 9
- 239000002245 particle Substances 0.000 description 9
- 239000003792 electrolyte Substances 0.000 description 8
- 238000012360 testing method Methods 0.000 description 7
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 6
- 229910052744 lithium Inorganic materials 0.000 description 6
- 239000011230 binding agent Substances 0.000 description 5
- 239000000654 additive Substances 0.000 description 4
- 230000000996 additive effect Effects 0.000 description 4
- 239000003795 chemical substances by application Substances 0.000 description 4
- 238000005553 drilling Methods 0.000 description 4
- 238000001035 drying Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 239000002562 thickening agent Substances 0.000 description 4
- 238000005056 compaction Methods 0.000 description 3
- 239000006258 conductive agent Substances 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 238000002347 injection Methods 0.000 description 3
- 239000007924 injection Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 239000002002 slurry Substances 0.000 description 3
- 101150058243 Lipf gene Proteins 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000006182 cathode active material Substances 0.000 description 2
- 230000008595 infiltration Effects 0.000 description 2
- 238000001764 infiltration Methods 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 239000002346 layers by function Substances 0.000 description 2
- 239000004973 liquid crystal related substance Substances 0.000 description 2
- 229910003002 lithium salt Inorganic materials 0.000 description 2
- 159000000002 lithium salts Chemical class 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 230000001502 supplementing effect Effects 0.000 description 2
- 238000010998 test method Methods 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- 239000013543 active substance Substances 0.000 description 1
- 238000007605 air drying Methods 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000012938 design process Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000007607 die coating method Methods 0.000 description 1
- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical compound [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 description 1
- 238000010894 electron beam technology Methods 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 238000010884 ion-beam technique Methods 0.000 description 1
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000004080 punching Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 159000000000 sodium salts Chemical class 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 238000001291 vacuum drying Methods 0.000 description 1
- 238000009777 vacuum freeze-drying Methods 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
- H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative electrodes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention discloses a graphite anode and a preparation method and application thereof, and belongs to the technical field of secondary batteries. The graphite anode provided by the invention comprises a current collector, a first active layer and a second active layer which are sequentially overlapped; the surface density of the graphite anode is CW mg/mm 2 The method comprises the steps of carrying out a first treatment on the surface of the The active material of the first active layer comprises graphite a, and the active material of the second active layer comprises graphite B; d of graphite B B D of 90 < graphite A A 90; starting from the second active layer, the graphite anode is provided with deep H non-penetrating pores, and: d when CW is less than or equal to 0.095 B 90≤H≤D A 90+1.3×D A 90; when CW > 0.095, D B 90+0.5×D A 90≤H＜D B 90+0.95×D A 90. The graphite anode provided by the invention can effectively improve the quick charge capability and can obviously prolong the cycle life. The invention also provides a preparation method and application of the graphite cathode.
Description
Technical Field
The invention relates to the technical field of secondary batteries, in particular to a graphite anode and a preparation method and application thereof.
Background
As the battery weight and the demand for fast charging increase, how to balance the problems of high energy density and fast charging has become the focus of industry attention. The double-coating structure is formed by matching high-rate and low-rate graphite, so that the charging capacity of the system can be improved without sacrificing the energy density, and the charging efficiency is improved. However, the double-layer coating is disadvantageous in maintaining long-term cycle stability due to its poor liquid retention ability caused by higher compaction density than conventional coating. When the lithium ion battery is circulated to the middle and later stages, corner cut-off phenomenon caused by the lack of electrolyte can occur, so that the problem of lithium precipitation occurs in advance, and the cycle life of the battery is shortened. In the related art, the purpose of continuously flowing electrolyte in the later period of circulation is achieved by using a diaphragm with high porosity, reducing the compaction density of an anode, increasing the liquid injection amount and the like. However, these methods have various disadvantages, such as deterioration of the safety performance of the battery cell due to the high porosity of the separator; reducing the anode compaction density sacrifices the battery energy density, covering up the advantages of the bilayer coating technique; increasing the liquid injection amount can lead to risks such as liquid expansion of the battery, thickness exceeding the specification, poor appearance and the like.
In view of the above, there is a strong need to provide an anode that can meet the requirements of rapid charging and has good cycle performance.
Disclosure of Invention
The present invention aims to solve at least one of the technical problems existing in the prior art. Therefore, the invention provides the graphite anode which can effectively improve the quick charge capability and can remarkably prolong the cycle life.
The invention also provides a preparation method of the graphite anode.
The invention also provides a secondary battery comprising the graphite anode.
According to an embodiment of the first aspect of the present invention, there is provided a graphite anode including a current collector, a first active layer, and a second active layer, which are sequentially stacked; the surface density of the graphite anode is CW mg/mm 2 ；
The active material of the first active layer comprises graphite A, and the active material of the second active layer comprises graphite B;
d of the graphite B B D of 90 < graphite A A 90；
Starting from the second active layer, the graphite anode is provided with deep H non-penetrating holes, and:
d when CW is less than or equal to 0.095 B 90≤H≤D B 90+1.3×D A 90；
When CW > 0.095, D B 90+0.5×D A 90≤H＜D B 90+0.95×D A 90。
The graphite anode provided by the embodiment of the invention has at least the following beneficial effects:
(1) The non-penetrating holes are arranged in the graphite anode, so that the liquid retention amount of the battery cell comprising the graphite anode can be improved; also, because one of the main causes of the decline in the cycle performance of the secondary battery is that the active electrolyte is consumed; therefore, the graphite anode provided by the invention can obviously improve the cycle performance through the structural design.
Furthermore, the existence of the non-penetrating holes can also reduce the path length of active ions (lithium ions or sodium ions) in the charge and discharge process to a certain extent, thereby improving the multiplying power/quick charge performance.
Generally, the deeper the depth of the non-penetrating hole, the higher the liquid retention amount, and the better and more pronounced the improvement in cycle performance.
However, if the limit is exceeded, the current collector may be damaged, conductivity may be reduced, or burrs may be generated, on the one hand, and the strength of the graphite anode may be reduced, on the other hand; eventually, breakage occurs when the graphite anode forms a cell, which reduces the yield of products, or causes degradation of safety of a secondary battery including the graphite anode.
Therefore, the invention is provided with the non-penetrating holes, wherein double-layer coating and the particle size of the active material in each layer provide accurate guide for the size of H, and the invention can accurately obtain H meeting the design by combining with the CW value, and the H can also obviously improve the cycle performance and the rate capability (quick charge performance) on the basis of ensuring the safety and the product yield of the secondary battery comprising the graphite anode; and the time and cost waste caused by multiple tests on the depth of the non-penetrating hole are avoided.
(2) The invention can fully exert the advantages of energy density by arranging the first active layer and the second active layer in sequence:
the graphite anode designed by the invention is improved on the basis of the traditional thick electrode, and the traditional thick electrode is difficult to simultaneously meet higher energy density and charging capability (high-rate charging and the like), and has the problems of large polarization, difficult electrolyte infiltration and the like. The non-penetrating hole and the double-layer structure are cooperated, so that the problems are obviously relieved:
in general, small particle size graphite has good rate capability (short path of active ions), and large particle size material has more advantages in compacted density (large particle gaps are easy to fill completely, and space utilization is high). The second active layer can increase the rate of lithium ions passing through a solid-liquid interface, prevent lithium precipitation, and the pore structure also improves the infiltration effect of the electrolyte; the first active layer increases energy density. If there is only the first active layer, its charge rate, charge speed and charge duration are limited due to the limited charge capacity.
In summary, the invention can simultaneously improve the energy density, the multiplying power performance and the cycle performance of the graphite anode by designing the double-layer active layer and limiting the relation between the particle size and the perforation depth of the active substance in the double-layer active layer. In the design process, the active material is only limited by the particle size, but not limited by special types such as fast charge (lattice spacing), and the application range of the graphite anode to the active material graphite is improved.
According to some embodiments of the invention, the distance between adjacent non-penetrating holes is 1-10 mm. Wherein the distance is the length of the central connecting line of two adjacent non-penetrating holes. The distance is 1.5-2 mm. For example, it may be about 1.8. Mu.m.
In practical production, the pore size of the non-penetrating pores is limited by the equipment conditions. Therefore, the pore diameter of the non-penetrating pore is not strictly limited as long as no powder falls off, and it is desirable that the smaller the size is, the better.
According to some embodiments of the invention, the thickness ratio of the second active layer to the first active layer is 1:1-4. The ratio has a certain correlation with the area density ratio of the second active layer and the first active layer.
According to some embodiments of the invention, the thickness ratio of the second active layer to the first active layer is 1:1.4-3.8. For example, it may be about 1:1.5, 1:2, 1:2.1, 1:2.2, 1:2.3 or 1:3.75.
According to some embodiments of the invention, the first active layer further comprises a binder and a thickener. Wherein the binder comprises SBR. The thickener comprises CMC. The first active layer further includes an additive. The additive comprises at least one of a lithium supplementing agent, a conductive agent, a tackifier and a surface modifying agent. In the first active layer, the proportion of each component is not strictly limited, and in actual production, the proportion can be adjusted according to the requirements on the performance and the cost of the graphite anode and the types of materials actually available.
According to some embodiments of the invention, the second active layer further comprises a binder and a thickener. Wherein the binder comprises SBR. The thickener comprises CMC. The second active layer further includes an additive. The additive comprises at least one of a lithium supplementing agent, a conductive agent, a tackifier and a surface modifying agent. In the second active layer, the proportion of each component is not strictly limited, and in actual production, the proportion can be adjusted according to the requirements on the performance and the cost of the graphite anode and the types of materials actually available.
According to some embodiments of the invention, the D A 50 is 10-13 μm. For example, it may be about 11 μm or 12. Mu.m.
Wherein D is A 50 represents D of graphite A V 50. Like reference numerals are used herein to explain the present invention unless otherwise specifically indicated.
According to some embodiments of the invention, the D A The value range of 90 is 18-25 μm. For example, the particle size may be 19 to 21. Mu.m. And more particularly about 20 μm.
According to some embodiments of the invention, the compacted density of the graphite A is 1.65-1.80 g/cm 3 。
According to some embodiments of the invention, the thickness of the first active layer is 20-40 μm. For example, it may be about 23 μm, 24 μm, 26 μm, 27 μm, 28 μm, 30 μm, 31 μm, 33 μm or 34 μm.
According to some embodiments of the invention, the D B 50 is 6-11 μm. For example, it may be about 8 μm, 9 μm or 10 μm.
According to some embodiments of the invention, the D B The value range of 90 is 12-20 μm. For example, it may be about 14 μm, 15 μm or 18 μm.
According to some embodiments of the invention, D of the graphite B B 50 < D of graphite A A 50。
According to some embodiments of the invention, the compacted density of graphite B is 1.51.70 g/cm 3 . For example, it may be about 1.7. 1.7 g/cm 3 。
According to an embodiment of the second aspect of the present invention, there is provided a method for preparing the graphite anode, the method comprising: and after the first active layer and the second active layer are sequentially arranged on the surface of the current collector, the non-penetrating holes are arranged.
The preparation method provided by the invention has at least the following beneficial effects:
the preparation method provided by the invention is simple and easy to realize, and the mathematical relationship among the surface density, the particle size and the depth also provides accurate guidance for the preparation method, so that the difficulty of the preparation method is further reduced; and the large-scale industrial application is more convenient.
According to some embodiments of the invention, the first active layer and the second active layer are disposed by: dual die head coating was used. Therefore, no obvious limit exists between the first active layer and the second active layer, and fusion between the two layers is promoted; and double-layer coating is performed at the same time, only primary drying is needed, and the flow is saved.
According to some embodiments of the invention, the method of disposing the first and second active layers further comprises drying after the twin-die coating. The method of drying is not strictly limited, and any method can be industrially used as long as the removal of the solvent can be achieved, for example, air drying, vacuum drying, freeze drying, and the like.
According to some embodiments of the invention, the non-penetrating holes are arranged in a manner including at least one of laser drilling, electron beam drilling, ion beam drilling, and nanoimprinting.
According to an embodiment of the third aspect of the present invention, there is provided a secondary battery including the graphite anode.
Since the secondary battery includes all the technical solutions of the graphite anode adopting the above embodiments, it has at least all the advantageous effects brought by the technical solutions of the above embodiments. I.e. has a high energy density, fast charge performance and cycle performance.
According to some embodiments of the invention, the secondary battery includes at least one of a lithium ion secondary battery and a sodium ion secondary battery.
According to some embodiments of the invention, when the secondary battery is a lithium ion secondary battery, the secondary battery further comprises a cathode. The cathode is prepared from raw materials including a cathode active material, a conductive agent and a binder. The cathode active material includes at least one of lithium cobaltate, ternary cathode material, lithium manganate and lithium iron phosphate.
According to some embodiments of the invention, the secondary battery further comprises a separator. The diaphragm is a modified diaphragm or an unmodified diaphragm. The material of the non-modified diaphragm comprises at least one of PP or PE. If two materials are present, the membrane may be a blend of two materials or a superposition of sub-layers formed from each material. The modified diaphragm comprises the non-modified diaphragm and a functional layer arranged on at least one surface of the non-modified diaphragm. The functional layer includes at least one of a ceramic layer and a polymer coating layer.
According to some embodiments of the invention, the secondary battery further comprises an electrolyte. The electrolyte solutionIncluding active salts. The active salt includes at least one of a sodium salt and a lithium salt. The lithium salt comprises LiPF 6 。
The areal density in the present invention refers to the areal density of the graphite anode as a whole, unless otherwise specified; in the coating of the graphite anode, the graphite accounts for 80.0% -99.9%. For example, the content may be 95 to 98%.
The term "about" as used herein, unless otherwise specified, means that the tolerance is within + -2%, for example, about 100 is actually 100 + -2%. Times.100.
Unless otherwise specified, the term "between … …" in the present invention includes the present number, for example "between 2 and 3" includes the end values of 2 and 3.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Drawings
The foregoing and/or additional aspects and advantages of the invention will become apparent and may be better understood from the following description of embodiments taken in conjunction with the accompanying drawings in which:
fig. 1 is a schematic structural diagram of a graphite anode provided in embodiment 1 of the present invention.
Reference numerals:
current collector 100;
a first active layer 210, graphite a 211; a second active layer 220, graphite B221;
non-penetrating aperture 300.
Detailed Description
The conception and the technical effects produced by the present invention will be clearly and completely described in conjunction with the embodiments below to fully understand the objects, features and effects of the present invention. It is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments, and that other embodiments obtained by those skilled in the art without inventive effort are within the scope of the present invention based on the embodiments of the present invention.
Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative only and are not to be construed as limiting the invention.
In the description of the present invention, the descriptions of the terms "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
Preparation method example
The example provides a preparation method of a graphite anode, which comprises the following specific steps:
after the first active layer 210 and the second active layer 220 are sequentially disposed on the surface of the current collector 100, the non-penetrating pores 300 are disposed using a laser drilling method. Wherein, the liquid crystal display device comprises a liquid crystal display device,
the first active layer 210 and the second active layer 220 are disposed by the following methods: and (3) respectively stirring to prepare slurries of the first active layer 210 and the second active layer 220, sequentially flowing out the slurries of the first active layer 210 and the second active layer 220 from a die head, coating the slurries on a current collector to form a double-layer active layer, and drying the double-layer active layer.
Unless otherwise specified, graphite anodes in the embodiments were prepared by the preparation method of this example.
Example 1
Referring to fig. 1, this example provides a graphite anode, specifically including a stack arrangement:
a current collector 100 made of copper;
a first active layer 210, the active material in the first active layer 210 being graphite a 211; wherein graphite a 211 accounts for 97.7% of the mass of the first active layer 210.
A second active layer 220, the active material in the second active layer 220 being graphite B221; wherein graphite B221 accounts for 97.7% of the mass of the second active layer 220.
The graphite anode is provided with a non-penetrating hole 300 having a depth H. The area of the graphite anode where the non-penetrating pores 300 were provided was the length of the graphite anode minus 10mm. Whereby non-perforated areas may be left to maintain mechanical strength and the like.
Parameters of graphite a and graphite B, the interval between non-penetrating pores 300 on the graphite anode, and the like are shown in table 1. Examples 2 to 5 and comparative examples 1 to 2 provide graphite anodes, respectively, and the specific difference from example 1 is that:
some of the parameters are different and the specific parameters are shown in table 1.
Table 1 parameters of graphite anodes of examples 1 to 5 and comparative examples 1 to 2
Comparative examples 1 to 5 provided a graphite anode, respectively, differing from examples 1 to 5 in that:
the comparative example does not include a non-penetrating hole, and for example, comparative example 1 does not include a non-penetrating hole as compared with example 1.
Application example
The present example provides a secondary battery, specifically employing the graphite anode provided in examples 1 to 5, comparative examples 1 to 5 or comparative examples 1 to 2;
the cathode is: lithium cobaltate, available from basquoia, model LC9000E;
the diaphragm is: PP separator.
The density of the electrolyte is 1.2g/ml, and the composition is as follows: liPF (LiPF) 6 Wherein the solvent is EC: dmc=3:7 (volume ratio).
The design capacity is 5Ah, and the N/P value is: 1.03-1.065: 1, the actual value will float within the above range due to instrument errors and test errors, but will not substantially affect the electrochemical performance of the resulting cell.
Test case
The present example examined the amount of increase in the amount of liquid held in the corresponding example, and the number of cycles of increase in cycle life, as compared with the comparative example. The test results are shown in Table 2. The method for testing the liquid retention amount increment comprises the following steps: weighing the injected battery cell and the two sealed battery cells, wherein the liquid retention amount is equal to the weight after injection, the weight after two seals and the weight of the air bag; increased retention = example retention-control retention. The cycle life test method comprises the following steps: the control, examples and comparative examples were synchronously tested using a maximum current of 1 to 4.5c for charge and discharge, a charge voltage of 4.50 to 4.56v, and a discharge cut-off voltage of 2.8 to 3.0v, and the cycle number was recorded and calculated for the increase in cycle number of the example (e.g., example 1) compared to the corresponding comparative example (e.g., comparative example 1) with the discharge capacity retention rate of 80% as the cycle life end node. Wherein, in order to fully compare the performance improvement generated after the display hole structure and the double-layer structure are cooperated, each embodiment and the corresponding comparative example adopt the same charge-discharge mechanism; however, since the graphite anode designed in each example/comparative example is different (active material type, coating thickness, etc.), different specific embodiments need to use different test conditions (extreme test conditions, the charge and discharge conditions may be the same in practical application) to reflect the improvement of the performance; the test methods of the different examples/comparative examples are as follows (CC is constant current charge, CV is constant voltage charge; DC is constant current discharge):
example 1: 4.5C CC 4.20V CV to 4.0C, 4.0C CC to 4.25V CV to 3.0C,3.0C CC 4.35V CV 2.0C,2.0C CC to 4.50V CV 0.02C, standing for 5min at normal temperature, and then 1.5C DC 3.5V,0.7C DC 3.0V;
example 2: 4.0C CC 4.30V CV to 3.5C, 3.5C CC to 4.40V CV to 2.0C,2.0C CC 4.50V CV 1.5C,1.5C CC to 4.53V CV 0.1C, standing for 5min at normal temperature, and then 1.5C DC 3.5V,0.7C DC 3.0V;
example 3: 3.5C CC 4.30V CV to 2.5C, 2.5C CC to 4.35V CV to 2.0C,2.0C CC 4.45V CV 1.5C,1.5C CC to 4.50V CV 1.2C,1.2C CC to 4.53V CV 0.1C, standing for 5min at normal temperature, and then 1.5C DC 3.5V,0.7C DC 3.0V;
example 4: 3.0C CC 4.20V CV to 2.5C, 2.5C CC to 4.35V CV to 2.0C,2.0C CC 4.45V CV 1.5C,1.5C CC to 4.50V CV 1.2C,1.2C CC to 4.53V CV 0.05C, standing for 5min at normal temperature, and then 1.5C DC 3.5V,0.7C DC 3.0V;
example 5: 2.5C CC 4.25V CV to 2.0C,2.0C CC to 4.35V CV to 1.5C,1.5C CC to 4.50V CV 0.02C, standing for 5min at normal temperature, and then 1.5C DC 3.5V,0.7C DC 3.0V;
comparative example 1: 2.5C CC 4.25V CV to 2.0C,2.0C CC to 4.35V CV to 1.5C,1.5C CC to 4.50V CV 0.02C, standing for 5min at normal temperature, and then 1.5C DC 3.5V,0.7C DC 3.0V;
comparative example 2: at normal temperature, 2.5C CC 4.25V CV to 2.0C,2.0C CC to 4.35V CV to 1.5C,1.5C CC to 4.50V CV 0.02C, left for 5min, then 1.5C DC 3.5V,0.7C DC 3.0V.
Table 2 performance results for examples, comparative examples and comparative examples
In table 2, the increase in the liquid retention amount, the number of cycles, etc. in comparative examples 1 and 2 is based on example 5.
The results show that the graphite anode provided by the invention has the advantages that compared with a graphite anode without a pore structure, the graphite anode provided by the invention has the advantages that the liquid retention amount and the cycle life are obviously increased, and particularly, the cycle number can be increased by at least 30 weeks, even up to about 100 weeks; according to the invention, the double-layer active layer is designed, and the depth of the non-penetrating type hole is limited by the particle size of the active material in the double-layer active layer, so that the damage to the current collector in the punching process is obviously avoided, and the safety performance and the product yield of the secondary battery comprising the graphite anode are improved.
The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of one of ordinary skill in the art without departing from the spirit of the present invention. Furthermore, embodiments of the invention and features of the embodiments may be combined with each other without conflict.
Claims (10)
1. The graphite anode is characterized by comprising a current collector, a first active layer and a second active layer which are sequentially overlapped; the surface density of the graphite anode is CW mg/mm 2 ；
The active material of the first active layer comprises graphite A, and the active material of the second active layer comprises graphite B;
d of the graphite B B D of 90 < graphite A A 90；
Starting from the second active layer, the graphite anode is provided with deep H non-penetrating holes, and:
d when CW is less than or equal to 0.095 B 90≤H≤D B 90+1.3×D A 90；
When CW > 0.095, D B 90+0.5×D A 90≤H＜D B 90+0.95×D A 90。
2. The graphite anode according to claim 1, wherein a distance between adjacent non-penetrating holes is 1 to 10mm.
3. The graphite anode of claim 1, wherein the second active layer and the first active layer have a thickness ratio of 1:1-4.
4. The graphite anode according to claim 1, wherein D of graphite B B 50 < D of graphite A A 50。
5. The graphite anode according to claim 1, wherein the compacted density of graphite a is 1.65-1.80 g/cm 3 。
6. The graphite anode according to claim 1, wherein the compacted density of the graphite B is 1.5 to 1.70 g/cm 3 。
7. A method for preparing a graphite anode as claimed in any one of claims 1 to 6, comprising: and after the first active layer and the second active layer are sequentially arranged on the surface of the current collector, the non-penetrating holes are arranged.
8. The method of claim 7, wherein the first and second active layers are disposed by: dual die head coating was used.
9. A secondary battery comprising the graphite anode according to any one of claims 1 to 6.
10. The secondary battery according to claim 9, wherein the secondary battery comprises at least one of a lithium ion secondary battery and a sodium ion secondary battery.
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