CN111864275B - Battery cell, preparation method thereof and lithium ion battery - Google Patents
Battery cell, preparation method thereof and lithium ion battery Download PDFInfo
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- CN111864275B CN111864275B CN201910343250.8A CN201910343250A CN111864275B CN 111864275 B CN111864275 B CN 111864275B CN 201910343250 A CN201910343250 A CN 201910343250A CN 111864275 B CN111864275 B CN 111864275B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/058—Construction or manufacture
- H01M10/0585—Construction or manufacture of accumulators having only flat construction elements, i.e. flat positive electrodes, flat negative electrodes and flat separators
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Abstract
The invention provides a battery cell, a preparation method thereof and a lithium ion battery, wherein the battery cell comprises a composite layer, a supporting layer and a second electrode plate; the composite layer comprises a first diaphragm, a first electrode plate and a second diaphragm which are contacted in sequence; the supporting layers are arranged on the upper surface and the lower surface of the composite layer or on the upper surface and the lower surface of the second electrode plate; the composite layer is connected with the second electrode plate through the supporting layer; one of the first electrode plate and the second electrode plate is a positive electrode plate, and the other is a negative electrode plate; the supporting layer comprises a plurality of supporting units; a gap exists between two adjacent supporting units. The supporting layer in the battery core enables a certain gap to be formed between the composite layer and the second electrode plate, and electrolyte can flow and infiltrate favorably during electrolyte injection of the battery core; the supporting layer has certain solubility in the electrolyte, and after the battery cell is fully soaked, the supporting layer is partially dissolved, so that the gap between the composite layer and the second electrode plate is reduced, and the internal resistance of the lithium ion battery and the cyclicity of the battery cell cannot be obviously increased.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a battery cell, a preparation method of the battery cell and a lithium ion battery.
Background
The lithium ion battery has the advantages of high energy density, long service life, low self-discharge rate, light weight and the like, and is one of important energy storage devices. With the continuous development of scientific technology, the requirements on the performance of the lithium ion battery are higher and higher, and particularly the desire for the lithium ion power battery with high energy density, high safety and long cycle life is more and more prominent.
Currently, there are many methods for improving energy density and safety of lithium ion batteries, such as developing mixed solid-liquid (composite of electrolyte and solid electrolyte) lithium ion batteries, and increasing the thickness of an active material coating layer or the compaction density of an electrode plate to improve the space occupation ratio of the active material. However, the above method can improve the energy density and safety of the battery and also negatively affect the performance of the battery. The electrolyte viscosity of the mixed solid-liquid lithium ion battery is high, so that the resistance to lithium ion migration is increased, and the wettability of a pole piece is poor; the thick pole piece or the high compaction density pole piece increases the contact distance between the active substance at the bottom layer and the electrolyte, prolongs the migration path of lithium ions, and causes the electrolyte to be difficult to soak and absorb. Whether the lithium ion battery is a mixed solid-liquid lithium ion battery or a thick pole piece or a high-compaction lithium ion battery, the poor wettability of the pole piece can increase the internal resistance of the battery, cause abnormal capacity exertion, poor rate capability, fast capacity attenuation, serious lithium precipitation and the like.
Aiming at the existing thick pole piece or high-compaction density pole piece, the technical personnel in the field adopt the following method to improve the infiltration of the electrolyte so as to improve the migration speed of lithium ions. For example, the pole piece structures disclosed in chinese patent application nos. CN200580027135.6 and CN2012191956.5 and the manufacturing methods thereof all improve the wettability of the electrolyte in the pole piece and reduce the concentration polarization from the viewpoint of increasing the porosity of the pole piece in the thickness direction; for example, the pole piece manufacturing method disclosed in the chinese patent application with application number CN102969483A adopts a multi-layered coating method of low solid content slurry to prepare thick coating pole pieces with different porosity gradients.
However, in the above existing improvement methods, the wettability of the electrolyte is improved, and at the same time, different negative effects such as increase of an electron transmission path, complex multilayer coating process and the like are caused, and no good solution is provided for the wettability problem of the mixed solid-liquid lithium ion battery.
Disclosure of Invention
In view of the above, the present invention provides a battery cell, a method for manufacturing the battery cell, and a lithium ion battery, where the battery prepared from the battery cell has good wettability.
The invention provides a battery cell which comprises a composite layer, a supporting layer and a second electrode plate;
the composite layer comprises a first diaphragm, a first electrode plate and a second diaphragm which are contacted in sequence;
the supporting layers are arranged on the upper surface and the lower surface of the composite layer or on the upper surface and the lower surface of the second electrode plate; the composite layer is connected with the second electrode plate through a supporting layer;
one of the first electrode plate and the second electrode plate is a positive electrode plate, and the other one is a negative electrode plate;
the supporting layer comprises a plurality of supporting units; a gap exists between two adjacent supporting units.
Preferably, the height of each supporting unit is greater than 0 and equal to or less than 1 cm.
Preferably, the area of each supporting unit in contact with the composite layer accounts for 0.0000001-40% of the upper surface area or the lower surface area of the composite layer;
or the contact area of each supporting unit and the second electrode plate accounts for 0.0000001-40% of the upper surface area or the lower surface area of the second electrode plate.
Preferably, the plurality of supporting units are arranged at the edges of the upper and lower surfaces of the second electrode sheet;
the plurality of supporting units are arranged at the edges of the upper surface and the lower surface of the composite layer.
The material of the supporting unit comprises solid organic matters which can be dissolved in electrolyte;
preferably, the solid organic substance is selected from one or more of fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, methylethyl carbonate, ethylene carbonate, 1, 3-propane sultone, 1, 4-butanediol sulfate, N' -sulfuryl diimidazole, methylene methanedisulfonate, butylene sulfite, propylene sulfate, dimethyl sulfite, vinylene carbonate, vinyl sulfate, ethylene carbonate, vinyl sulfite, polyacrylates, polyethers, polycarbonates, polycarboxylates, polyacetates, polysulfates, or a copolymer of two or more of the above polymer monomers.
Preferably, the first and second membranes are independently selected from a substrate membrane, a coated membrane, or a solid electrolyte membrane;
the base material diaphragm is selected from a polyolefin diaphragm, a cellulose diaphragm or non-woven fabric;
the coating diaphragm is prepared by coating glue on the surface of the substrate diaphragm.
Preferably, the first electrode sheet comprises a first current collector and a first coating disposed on the first current collector;
the second electrode plate comprises a second current collector and a second coating arranged on the second current collector;
the thickness of the first coating and the second coating is 5-400 mu m;
the second coating layer and the first coating layer both comprise an active material, a conductive agent and a binder.
The invention provides a preparation method of the battery cell in the technical scheme, which comprises the following steps:
a) sequentially compounding the first diaphragm, the first electrode plate and the second diaphragm to obtain a composite layer;
b1) arranging support layers on the upper surface and the lower surface of the second electrode plate, then sequentially stacking and packaging the support layers and the composite layer, and baking to obtain a battery cell;
or b2) arranging support layers on the upper and lower surfaces of the composite layer, then stacking and packaging the support layers and the second electrode sheet in sequence, and baking to obtain the battery cell.
Preferably, the first diaphragm, the first electrode plate and the second diaphragm are compounded in a cross-linking compounding mode, a hot-pressing compounding mode or an electrostatic compounding mode;
the support layer is arranged in a manner selected from spray coating, transfer coating, extrusion coating, blade coating, heat attachment, dip solvent attachment or 3D printing.
The invention provides a lithium ion battery, which is prepared by injecting liquid into a battery cell, standing, dissolving a supporting unit, forming, aging and grading;
the support unit is dissolved by one or more selected from the group consisting of standing, heating and pressurizing;
at least one substance A in the substances after the support units are dissolved is enriched on the plane where the original support layer is located, and the concentration of the substance A is gradually reduced along the direction from the original support layer to the current collector;
the battery cell is the battery cell in the technical scheme or the battery cell prepared by the preparation method in the technical scheme.
The invention provides a battery cell which comprises a composite layer, a supporting layer and a second electrode plate; the composite layer comprises a first diaphragm, a first electrode plate and a second diaphragm which are contacted in sequence; the supporting layers are arranged on the upper surface and the lower surface of the composite layer or on the upper surface and the lower surface of the second electrode plate; the composite layer is connected with the second electrode plate through a supporting layer; one of the first electrode plate and the second electrode plate is a positive electrode plate, and the other one is a negative electrode plate; the supporting layer comprises a plurality of supporting units; a gap exists between two adjacent supporting units. According to the battery cell provided by the invention, the supporting layer is arranged between the composite layer and the second electrode plate, so that a certain gap is formed between the composite layer and the second electrode plate, and the flowing and infiltration of electrolyte are facilitated when the battery cell is injected with liquid; the supporting layer has certain solubility in the electrolyte, and after the battery cell is fully soaked, the supporting layer is partially dissolved, so that the gap between the composite layer and the second electrode plate is reduced, and the internal resistance of the lithium ion battery is not obviously increased, and the cyclicity of the battery cell is not reduced. The experimental results show that: the resistance of the prepared lithium ion battery is 2.1-3.4 m omega; the first-week capacity exertion rate is 96.4-98.4%; the first-week efficiency is 75.8-87.8%; the capacity retention rate of 50-week circulation is 94.1-98.2%.
Drawings
FIG. 1 is a schematic structural view of a first electrode sheet-separator composite layer according to the present invention;
FIG. 2 is a schematic structural diagram of a supporting layer disposed on a second electrode sheet according to an embodiment of the present invention;
fig. 3 shows the results of wettability tests of the lithium ion batteries prepared in example 1 of the present invention and comparative example.
Detailed Description
The invention provides a battery cell which comprises a composite layer, a supporting layer and a second electrode plate;
the composite layer comprises a first diaphragm, a first electrode plate and a second diaphragm which are contacted in sequence;
the supporting layers are arranged on the upper surface and the lower surface of the composite layer or on the upper surface and the lower surface of the second electrode plate; the composite layer is connected with the second electrode plate through a supporting layer;
one of the first electrode plate and the second electrode plate is a positive electrode plate, and the other one is a negative electrode plate;
the supporting layer comprises a plurality of supporting units; a gap exists between two adjacent supporting units.
According to the battery cell, the supporting layer is arranged between the composite layer and the second electrode plate, so that a certain gap is formed between the composite layer and the second electrode plate, and the flowing and soaking of electrolyte are facilitated when the battery cell is injected with liquid; the supporting layer has certain solubility in the electrolyte, and after the battery cell is fully soaked, the supporting layer is partially dissolved, so that the gap between the composite layer and the second electrode plate is reduced, and the internal resistance of the lithium ion battery cannot be obviously increased. The experimental results show that: the resistance of the prepared lithium ion battery is 2.1-3.4 m omega;
the battery core provided by the invention can obviously improve the wettability problem of batteries with mixed solid-liquid lithium ion batteries, thick pole pieces (the thickness of the coating on the pole pieces is more than 200 microns), high-compaction pole pieces and layer-stacked thick battery core structures.
Fig. 1 is a schematic structural diagram of a composite layer according to the present invention, in which a battery cell provided by the present invention includes a first electrode sheet-separator composite layer; the composite layer comprises a first diaphragm, a first electrode plate and a second diaphragm which are contacted in sequence; the second membrane is in contact with the support layer. In the present invention, the first separator and the second separator are independently preferably selected from a substrate separator, a coated separator, or a solid electrolyte membrane; the base material diaphragm is selected from a polyolefin diaphragm, a cellulose diaphragm or non-woven fabric; the coating diaphragm is prepared by coating glue on the surface of the substrate diaphragm. The specifically selected membranes of the first membrane and the second membrane may be the same or different. In a specific embodiment, the substrate of the separator is PE or PP; the coating on the separator was PVDF.
In the present invention, the first electrode sheet includes a first current collector and a first coating layer disposed on the first current collector. The first current collector is preferably selected from aluminum foil or copper foil; the first coating layer preferably includes an active material, a conductive agent, and a binder; the first coating preferably further comprises an electrolyte; the electrolyte is preferably selected from one or more of a polymer electrolyte, an oxide electrolyte and a sulfide electrolyte. The thickness of the first coating is preferably 5-400 μm. In a particular embodiment of the invention, the conductive agent is selected from Super-P; the binder is polyvinylidene fluoride (PVDF) and sodium carboxymethylcelluloseOne or more of (CMC) and Styrene Butadiene Rubber (SBR); the polymer electrolyte is selected from one or more of Polymethylmethacrylate (PMMA), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), Polyacrylonitrile (PAN) and polyvinylidene fluoride (PVDF). The active substance is preferably selected from graphite, SOC-450A, SOC-600A, NCA or NCM. In a specific embodiment, the surface capacity of the active material on the positive pole piece is 4.2-6 mAh/cm2(ii) a The surface capacity of the active material on the negative pole piece is 4.41-6.3 mAh/cm2。
The battery cell provided by the invention comprises a supporting layer; the supporting layer comprises a plurality of supporting units; a gap exists between every two adjacent supporting units; i.e., do not overlap and do not touch each other. In the present invention, the thickness of the support layer is preferably greater than 0 and not greater than 1cm, and more preferably 2 to 500 μm. In a particular embodiment, the thickness of the support layer is in particular 30 μm, 50 μm, 100 μm, 150 μm, 200 μm or 300 μm.
In the invention, the area of each supporting unit contacting with the composite layer preferably accounts for 0.0000001-40% of the upper surface area or the lower surface area of the composite layer; more preferably 0.001 to 0.1%;
or the contact area of each supporting unit and the second electrode plate accounts for 0.0000001-40%, more preferably 0.001-0.1% of the upper surface area or the lower surface area of the second electrode plate. In a specific embodiment of the invention, the area of each of the support layer elements accounts for 0.04% or 0.05% of the single surface area of the second electrode.
In the present invention, the plurality of supporting units may be disposed at any position of the upper and lower surfaces of the second electrode sheet, preferably at the edges of the upper and lower surfaces of the second electrode sheet, and more preferably at the edges of the opposite sides of the electrode sheet; the plurality of supporting units are preferably uniformly distributed at opposite side edges of the electrode sheet. In a specific embodiment, the support layer is preferably provided with 8 support units, and is provided on both sides of the opposite long sides of the electrode sheet, 4 on each side.
Or a plurality of supporting units may be provided at any position of the upper and lower surfaces of the composite layer, preferably at the edges of the upper and lower surfaces of the composite layer.
The material of the supporting unit comprises solid organic matters which can be dissolved in electrolyte;
preferably, the solid organic substance is selected from one or more of fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, methylethyl carbonate, Ethylene Carbonate (EC), 1, 3-propane sultone, 1, 4-butanediol sulfate, N' -thiodiimidazole, methylene methanedisulfonate, butylene sulfite, propylene sulfate, dimethyl sulfite, vinylene carbonate, vinyl sulfate, ethylene carbonate, vinyl sulfite, polyacrylates, polyethers, polycarbonates, polycarboxylates, polyacetates, polysulfates, or a copolymer of two or more of the above polymer monomers. The polyacrylate is selected from PMMA; the polycarbonate is selected from PPC; the polycarboxylate is selected from PCL; the polyacetate is selected from PVAc. In a specific embodiment, the material of the support layer is PMMA, PVAc, PPC, PCL or a mixture of PMMC and EC at a mass ratio of 1: 1.
In the present invention, the support layer is disposed between the composite layer and the second electrode sheet in a manner selected from one or more of spray coating, transfer coating, extrusion coating, blade coating, heat attaching, dip solvent attaching, and 3D printing. In a specific embodiment, the support layer is disposed in a solvent dipping attachment manner.
The battery cell provided by the invention comprises a second electrode plate; the composite layer is connected with the second electrode plate through a supporting layer; one of the first electrode plate and the second electrode plate is a positive electrode plate, and the other is a negative electrode plate. The second electrode plate comprises a second current collector and a second coating arranged on the second current collector; the second coating layer includes an active material, a conductive agent, and a binder. The second coating preferably further comprises an electrolyte; the electrolyte is preferably selected from one or more of a polymer electrolyte, an oxide electrolyte and a sulfide electrolyte. The thickness of the second coating is preferably 5-400 μm. In the specific embodiment of the invention, when the second electrode plate is a negative electrode plate, the active substance in the second coating is graphite, SOC-600A, SOC-450A, the conductive agent is Super-P and/or CNT, and the binder is a mixture of CMC and SBR; the electrolyte is preferably a polymer electrolyte, more preferably one or more selected from PVDF, PAN, and PVDF-HFP; the mass content of the polymer electrolyte is preferably 0 to 50%, more preferably 0 to 6%, and in specific embodiments, the mass content of the polymer electrolyte is 0, 4%, 5%, or 6%.
The invention provides a preparation method of the battery cell in the technical scheme, which comprises the following steps:
a) sequentially compounding the first diaphragm, the first electrode plate and the second diaphragm to obtain a composite layer;
b1) arranging support layers on the upper surface and the lower surface of the second electrode plate, then sequentially stacking and packaging the support layers and the composite layer, and baking to obtain a battery cell;
or b2) arranging support layers on the upper and lower surfaces of the composite layer, then stacking and packaging the support layers and the second electrode sheet in sequence, and baking to obtain the battery cell.
The first diaphragm, the first electrode plate and the second diaphragm are sequentially compounded to obtain the compound layer. In the present invention, the first separator, the first electrode sheet, and the second separator are preferably cross-linked, hot-pressed, or electrostatically compounded. When the first diaphragm and the second diaphragm are selected from the base material diaphragms, the compounding mode is cross-linking or electrostatic compounding; when the first diaphragm and the second diaphragm are selected from coating diaphragms or solid electrolyte membranes, the compounding mode is hot-pressing compounding, cross-linking compounding or electrostatic compounding. The process for compounding the first diaphragm, the first electrode plate and the second diaphragm eliminates bubbles of the diaphragm and the first electrode plate, avoids the problems of dislocation of the pole piece and the diaphragm, corrugation of the diaphragm and the like, and has the advantages that the burrs of the single electrode plate are too much, the compounded composite layer is integrally flat, and the burrs of the electrode plates are reduced. In a specific embodiment, the first diaphragm, the first electrode plate and the second diaphragm are compounded in a hot-press compounding mode and a cross-linking compounding mode; the hot-pressing compounding temperature is 40-100 ℃, specifically 60 ℃, 70 ℃ or 90 ℃; the pressure of the hot-pressing compounding is preferably 50-1000 KPa, specifically 200KPa, 500KPa or 800 KPa.
According to the invention, the supporting layers can be arranged on the upper surface and the lower surface of the second electrode plate, and then the supporting layers and the composite layer are sequentially stacked, packaged and baked to obtain the battery cell. The battery core can also be obtained by arranging the supporting layers on the upper and lower surfaces of the composite layer, then sequentially stacking and packaging the supporting layers and the second electrode plate, and baking the supporting layers and the second electrode plate.
The invention provides a lithium ion battery, which is prepared by injecting liquid into a battery cell, standing, dissolving a supporting unit, forming, aging and grading;
the support unit is dissolved by one or more selected from the group consisting of standing, heating and pressurizing;
the battery cell is the battery cell in the technical scheme or the battery cell prepared by the preparation method in the technical scheme.
In the invention, the electrolyte adopted by the liquid injection is a sea electrolyte; the Yangrong electrolyte is purchased from Shandonghai Rong New Material GmbH.
In the present invention, the means for dissolving the support unit is selected from one or more of standing, heating and pressurizing. After the support unit is dissolved, the thickness of the support unit is reduced after the support unit is dissolved, so that the internal resistance of the battery is reduced, the dissolved substance A is enriched on the plane where the original support layer is located, and the concentration of the substance A is gradually reduced along the direction away from the original support layer to the current collector.
In the invention, as the aperture ratio of the compacted positive and negative pole pieces is smaller and the viscosity of the electrolyte is large, the diffusion of the substance A in the gradient direction from the original supporting layer to the current collector is slower, so that the concentration of at least one substance A is gradually reduced along the direction from the supporting layer to the current collector, and even the substance A does not exist near the current collector.
In order to further illustrate the present invention, the following will describe a battery cell, a method for manufacturing the battery cell, and a lithium ion battery in detail with reference to the following examples, which should not be construed as limiting the scope of the present invention.
Preparatory examples
Preparing a positive pole piece:
as shown in table 1, the main material of the positive electrode, the superconducting carbon (Super-P), the binder, and the polymer electrolyte were added to the solvent NMP according to the data listed in table 1, and mixed and stirred uniformly, with the solvent accounting for 65% of the total slurry, to obtain a positive electrode slurry with a certain fluidity; then, the positive electrode slurry is addedCoating on aluminum foil with surface capacity of X mAh/cm2And performing air-blast drying, and then performing cold pressing treatment by using a roller press, wherein the obtained positive pole pieces are named as C1, C2, C3 and C4 respectively.
TABLE 1 Material parameters of Positive Pole pieces
Preparation of negative pole piece
As shown in table 2, the negative electrode main material, the Super-conductive carbon (Super-P), the binder and the polymer electrolyte are added into the solvent deionized water according to the data listed in table 2, and the mixture is uniformly mixed and stirred, wherein the solvent accounts for 45% of the total slurry, and the negative electrode slurry with certain fluidity is obtained; then, the negative electrode slurry was coated on a copper foil with a surface capacity of Y1.05 × m ah/cm2And performing air-blast drying, and then performing cold pressing treatment by using a roller press, wherein the obtained negative pole pieces are named as A1, A2, A3 and A4 respectively.
TABLE 2 Material parameters of negative electrode sheet
The membranes used in the present invention are shown in table 3:
TABLE 3 separators used in examples 1 to 6
Examples 1 to 6
The invention performs cell preparation according to table 4: the size of the pole piece is as follows: the positive electrode is 107mm by 83mm, the negative electrode is 109mm by 85mm, and the number of layers is 10 for the positive electrode and 11 for the negative electrode.
TABLE 4 preparation parameters of cells
Fig. 2 is a schematic structural diagram of a supporting layer arranged on a second electrode sheet in the embodiment of the present invention, wherein 4 supporting units are arranged on each side of a long side of the electrode sheet; the support layer is arranged in a manner of dipping in a solvent for attachment.
Among them, in examples 1 to 3,
stacking the first diaphragm, the first electrode pole piece and the second diaphragm from top to bottom in sequence to form a sandwich structure, and compounding to obtain a composite layer;
fixing a solid organic matter with a certain thickness on the surface of the second electrode plate to form a supporting layer; stacking and packaging the second electrode pole piece and the composite unit in sequence after the support layer is formed, and baking to obtain a dry battery cell;
injecting a hairong electrolyte into the dry battery core, standing, dissolving a supporting unit, forming, aging and grading to obtain a lithium ion battery;
the support unit is dissolved by one or more selected from the group consisting of standing, heating and pressurizing; the dissolved substance A is enriched on the plane of the original support layer, and the concentration of the substance A is gradually reduced along the direction from the original support layer to the current collector.
Among them, in examples 4 to 6,
stacking the first diaphragm, the first electrode pole piece and the second diaphragm from top to bottom in sequence to form a sandwich structure, and compounding to obtain a composite layer;
fixing a solid organic matter with a certain thickness on the surface of the composite layer to form a supporting layer; stacking and packaging the first electrode plate-diaphragm composite layer and the second electrode plate which form the supporting layer in sequence, and baking to obtain a dry battery cell;
injecting a hairong electrolyte into the dry battery core, standing, dissolving a supporting unit, forming, aging and grading to obtain a lithium ion battery;
the support unit is dissolved by one or more selected from the group consisting of standing, heating and pressurizing; the dissolved substance A is enriched on the plane of the original support layer, and the concentration of the substance A is gradually reduced along the direction from the original support layer to the current collector.
Comparative example
And (3) carrying out lamination, baking, liquid injection and formation on the positive pole piece C1, the negative pole piece A1 and the diaphragm S1 to obtain the lithium ion battery without compounding and rubberizing.
The invention carries out the wettability test on the lithium ion batteries prepared in the embodiment 1 and the comparative example, the dry electric core prepared in the comparative example and the embodiment 1 is injected with liquid, vacuumized, packaged, then kept stand for 8 hours, disassembled and observed the wettability of the pole piece and the dissolution of the adhesive pasted in the embodiment 1.
The test result is shown in fig. 3, where a in fig. 3 is a comparative positive electrode sheet, a white area is an unwetted area, and the rest is an infiltrated area, b is a comparative negative electrode sheet, a white area is an unwetted area, and the rest is an infiltrated area, c is the positive electrode sheet of example 1, and d is the negative electrode sheet of example 1; therefore, after the lithium ion battery prepared by the battery core provided by the invention is disassembled, a large area of the positive pole piece and the negative pole piece close to the middle part is not soaked, and the pole pieces are completely soaked after the lithium ion battery prepared by the battery core provided by the invention is disassembled, and the pole pieces are completely dissolved in the second electrode piece or the supporting layer fixed by the composite layer. The invention can greatly improve the wettability of the battery.
The lithium ion batteries prepared in examples 1 to 6 and comparative examples are tested for resistance, first-cycle capacity exertion rate, first-cycle efficiency and 50-cycle capacity retention rate, and the results are shown in table 5, wherein table 5 shows the resistance, the first-cycle capacity exertion rate, the first-cycle efficiency and the 50-cycle capacity retention rate of the lithium ion batteries prepared in examples 1 to 6 and comparative examples; the test results are shown in table 5: the test voltage range is 2.75-4.2V, and the charge-discharge current is as follows: 0.5C/0.5C;
TABLE 5 test results of resistance, first-cycle capacity exertion rate, first-cycle efficiency and 50-cycle capacity retention rate of lithium ion batteries prepared in inventive examples 1-6 and comparative example
As can be seen from table 5, the resistance of the comparative example battery was 7.3m Ω, the capacity exertion rate was only 72.9%, the first-cycle efficiency was low, only 65.3%, and the battery cyclicity was poor; the lithium ion battery prepared by the battery core provided by the invention has good wettability, so that the resistance of the battery can be obviously reduced, and the resistance of the battery is 2.1-3.4 m omega; the battery capacity is exerted, and the capacity exertion rate is more than 96.4 percent; the capacity retention rate after 50 weeks of circulation is more than 94.1 percent, while the capacity retention rate after 50 weeks of circulation of the comparative example is only 58.4 percent, which shows that the invention can obviously improve the cyclicity of the battery.
The invention provides a battery cell which comprises a composite layer, a supporting layer and a second electrode plate; the composite layer comprises a first diaphragm, a first electrode plate and a second diaphragm which are contacted in sequence; the supporting layers are arranged on the upper surface and the lower surface of the composite layer or on the upper surface and the lower surface of the second electrode plate; the composite layer is connected with the second electrode plate through a supporting layer; one of the first electrode plate and the second electrode plate is a positive electrode plate, and the other one is a negative electrode plate; the supporting layer comprises a plurality of supporting units; a gap exists between two adjacent supporting units. According to the battery cell provided by the invention, the supporting layer is arranged between the composite layer and the second electrode plate, so that a certain gap is formed between the composite layer and the second electrode plate, and the flowing and infiltration of electrolyte are facilitated when the battery cell is injected with liquid; the supporting layer has certain solubility in the electrolyte, and after the battery cell is fully soaked, the supporting layer is partially dissolved, so that the gap between the composite layer and the second electrode plate is reduced, and the internal resistance of the lithium ion battery cannot be obviously increased. The experimental results show that: the lithium ion battery prepared from the battery core provided by the invention has good wettability, so that the internal resistance of the battery can be obviously reduced, the capacity of the battery is exerted, and the performance of the battery is improved.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (9)
1. A battery cell comprises a composite layer, a supporting layer and a second electrode plate;
the composite layer comprises a first diaphragm, a first electrode plate and a second diaphragm which are contacted in sequence;
the supporting layers are arranged on the upper surface and the lower surface of the composite layer or on the upper surface and the lower surface of the second electrode plate; the composite layer is connected with the second electrode plate through a supporting layer;
one of the first electrode plate and the second electrode plate is a positive electrode plate, and the other one is a negative electrode plate;
the supporting layer comprises a plurality of supporting units; a gap exists between every two adjacent supporting units;
the material of the supporting unit comprises solid organic matters which can be dissolved in electrolyte; the solid organic matter is selected from one or more of fluoroethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, 1, 3-propane sultone, 1, 4-butanediol sulfate, N' -sulfuryl diimidazole, methylene methane disulfonate, butylene sulfite, propylene sulfate, dimethyl sulfite, vinylene carbonate, ethylene sulfate, ethylene carbonate, ethylene sulfite, polycarbonates and polysulfates, or a copolymer of two or more of the above polymer monomers.
2. The cell of claim 1, wherein the height of each support unit is greater than 0 and less than or equal to 1 cm.
3. The battery cell of claim 1, wherein the area of each support unit in contact with the composite layer accounts for 0.0000001-40% of the upper surface area or the lower surface area of the composite layer;
or the contact area of each supporting unit and the second electrode plate accounts for 0.0000001-40% of the upper surface area or the lower surface area of the second electrode plate.
4. The battery cell of claim 1, wherein the plurality of support units are arranged at edges of upper and lower surfaces of the second electrode sheet;
or a plurality of supporting units are arranged at the edges of the upper surface and the lower surface of the composite layer.
5. The cell of claim 1, wherein the first and second membranes are independently selected from a substrate membrane, a coated membrane, or a solid electrolyte membrane;
the base material diaphragm is selected from a polyolefin diaphragm, a cellulose diaphragm or non-woven fabric;
the coating diaphragm is prepared by coating glue on the surface of the substrate diaphragm.
6. The cell of claim 1, wherein the first electrode sheet comprises a first current collector and a first coating disposed on the first current collector;
the second electrode plate comprises a second current collector and a second coating arranged on the second current collector;
the thickness of the first coating and the thickness of the second coating are both 5-400 mu m;
the second coating layer and the first coating layer both comprise an active material, a conductive agent and a binder.
7. A preparation method of the battery cell of any one of claims 1 to 6, comprising the following steps:
a) sequentially compounding the first diaphragm, the first electrode plate and the second diaphragm to obtain a composite layer;
b1) arranging support layers on the upper surface and the lower surface of the second electrode plate, then sequentially stacking and packaging the support layers and the composite layer, and baking to obtain a battery cell;
or b2) arranging support layers on the upper and lower surfaces of the composite layer, then stacking and packaging the support layers and the second electrode sheet in sequence, and baking to obtain the battery cell.
8. The production method according to claim 7, wherein the first separator, the first electrode sheet, and the second separator are compounded in a cross-linked compounding, a hot-press compounding, or an electrostatic compounding;
the support layer is arranged in a manner selected from spray coating, transfer coating, extrusion coating, blade coating, heat attachment, dip solvent attachment or 3D printing.
9. A lithium ion battery is prepared by injecting liquid into a battery cell, standing, dissolving a supporting unit, forming, aging and grading;
the support unit is dissolved by one or more selected from the group consisting of standing, heating and pressurizing;
at least one solid organic matter in the substances dissolved by the supporting unit is enriched on the plane where the original supporting layer is located, and the concentration of the solid organic matter is gradually reduced along the direction away from the original supporting layer to the current collector;
the battery cell is prepared by the battery cell of any one of claims 1 to 6 or the preparation method of any one of claims 7 to 8.
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| CN112652808B (en) * | 2021-01-11 | 2022-07-29 | 天津市捷威动力工业有限公司 | Lithium ion battery core and lithium ion battery |
| CN113131096A (en) * | 2021-03-04 | 2021-07-16 | 深圳市璞厉科技有限公司 | Method for compounding pole piece and diaphragm of lithium ion battery and lithium ion battery |
| CN113300051A (en) * | 2021-03-04 | 2021-08-24 | 深圳市璞厉科技有限公司 | Method for compounding pole piece and diaphragm of lithium ion battery and lithium ion battery |
| CN113611912B (en) * | 2021-06-15 | 2023-07-07 | 万向一二三股份公司 | Lamination structure of electrode assembly, preparation method and electrochemical device |
| CN114552130A (en) * | 2021-09-13 | 2022-05-27 | 万向一二三股份公司 | Pole piece structure for improving lithium ion battery thermal compounding process infiltration |
| CN114464951A (en) * | 2022-01-26 | 2022-05-10 | 珠海冠宇电池股份有限公司 | Diaphragm containing fulcrum and battery containing diaphragm |
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