CN113707869A - Battery cell and battery - Google Patents
Battery cell and battery Download PDFInfo
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- CN113707869A CN113707869A CN202111117637.5A CN202111117637A CN113707869A CN 113707869 A CN113707869 A CN 113707869A CN 202111117637 A CN202111117637 A CN 202111117637A CN 113707869 A CN113707869 A CN 113707869A
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- 238000000576 coating method Methods 0.000 claims abstract description 113
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Images
Classifications
-
- 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
- H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
-
- 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
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
- H01M4/366—Composites as layered products
-
- 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
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
- H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
-
- 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
- H01M4/64—Carriers or collectors
-
- 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
-
- 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
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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Composite Materials (AREA)
- Inorganic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
- Secondary Cells (AREA)
Abstract
The invention provides a battery core and a battery. The battery cell provided by the invention comprises: positive electrode piece, negative electrode piece and diaphragm, the diaphragm sets up positive electrode piece with between the negative electrode piece, positive electrode piece includes first mass flow body, first active substance layer, second active substance layer and first utmost point ear, first mass flow body includes first coating section and connects the first blank section of the at least one end of first coating section, adhere to on one face of first coating section first active substance layer with second active substance layer, second active substance layer with first active substance layer splices mutually adhere to on the another face of first coating section first active substance layer, first utmost point ear sets up first blank section. The invention provides a battery cell and a battery, which are used for at least solving the technical problem that lithium is easy to separate at a position close to a lug in a negative electrode plate of the battery cell and the battery.
Description
Technical Field
The invention relates to the technical field of batteries, in particular to a battery core and a battery.
Background
The lithium ion battery is used as a green and environment-friendly new energy source, particularly a winding type lithium ion battery, and becomes the mainstream of the current consumer batteries due to mature process and simple flow, and the factors such as quick charge and safety of the lithium ion battery are paid more and more attention by more people.
However, in the wound lithium ion battery, because the current density distribution is not uniform, the problem of lithium separation is easily caused at the position of the negative electrode plate of the battery cell close to the tab due to the overlarge current density, and the lithium separation occurs at the negative electrode plate during charging, so that the thickness of the position of local lithium separation is increased, and the application of the wound lithium ion battery in the fast charging field is limited.
Disclosure of Invention
The invention provides a battery cell and a battery, which are used for at least solving the technical problem that lithium is easy to separate at a position close to a lug in a negative electrode plate of the battery cell and the battery.
In order to achieve the above object, the present invention provides a battery cell and a battery. The battery cell provided by the invention comprises: the separator comprises a positive electrode plate, a negative electrode plate and a separator, wherein the separator is arranged between the positive electrode plate and the negative electrode plate to separate the positive electrode plate from the negative electrode plate, and the positive electrode plate, the negative electrode plate and the separator are wound together after being laminated;
the positive electrode plate comprises a first current collector, a first active substance layer, a second active substance layer and a first tab, wherein the first current collector comprises a first coating section and a first blank section connected to at least one end of the first coating section, the first active substance layer and the second active substance layer are attached to one surface of the first coating section, the second active substance layer is spliced with the first active substance layer, the first active substance layer is attached to the other surface of the first coating section, and the first tab is arranged at the first blank section;
negative electrode piece includes that the second collects the body, third active material layer and second utmost point ear, the second collects the body and includes second coating section and connection the blank section of second of the at least one end of second coating section, second coating section includes interconnect's single-sided coating section and two-sided coating section, one of them side coating on two positive and negative surfaces of single-sided coating section the third active material layer, two positive and negative surfaces of two-sided coating section are all coated the third active material layer, the second utmost point ear set up with the single-sided coating section meets on the blank section of second, the coating of single-sided coating section the third active material layer towards positive electrode piece the second active material layer.
In the battery cell provided by the invention, in the positive electrode sheet, a first active material layer and a second active material layer are attached to one surface of the first coating section, the first active material layer and the second active material layer have different components, so that the lithium ion separation speeds in the first active material layer and the second active material layer are different, in the negative electrode sheet, the third active material layer coated on the single-surface coating section faces to the second active material layer of the positive electrode sheet, the lithium ion separation speed of the second active material layer corresponding to the single-surface coating section is controlled, the current density around the second electrode tab can be controlled, the surface lithium transition deposition of the negative electrode sheet caused by the overlarge current around the second electrode tab is avoided, and the lithium separation speeds of the positive electrode sheet and the negative electrode sheet are balanced, therefore, the risk that lithium is easily separated from the position, close to the second tab, in the negative electrode plate is reduced, and the safety is improved.
In one possible embodiment, the coating length of the second active material layer in the length direction of the first current collector is 60% to 150% of the length of the one-side coated section. And enabling the second active material layer to have enough length corresponding to the length of one surface and the coating section, and ensuring that the lithium removal speed of the second active material layer corresponding to the coating section of one surface can be controlled.
In one possible embodiment, the coating length of the second active material layer in the longitudinal direction of the first current collector is 100% to 120% of the length of the single-sided coating section.
In one possible embodiment, the active material in the second active material layer includes lithium iron phosphate, and the mass percentage of the lithium iron phosphate in the active material in the second active material layer is 5% to 100%.
In one possible embodiment, the active material in the second active material layer further includes at least one of lithium cobaltate, lithium vanadate, lithium manganese phosphate, lithium cobalt phosphate, lithium titanate, lithium iron manganese phosphate, ternary nickel cobalt aluminum, ternary nickel cobalt manganese, quaternary nickel cobalt manganese aluminum, lithium manganate, lithium nickelate, and a lithium-rich manganese group.
In one possible embodiment, the active material in the first active material layer includes lithium cobaltate or nickel cobalt manganese ternary.
In one possible embodiment, the electrical conductivity of the first active material layer in the powder state is less than the electrical conductivity of the second active material layer in the powder state.
In one possible embodiment, the first active material layer and the second active material layer are applied to a thickness of 20 μm to 80 μm.
In one possible embodiment, the second active material layer and the first tab are respectively located on opposite sides of the first current collector.
In one possible embodiment, the first tab is located on an inner circle layer of the battery cell, and the second tab is located on the inner circle layer of the battery cell.
The invention also provides a battery, which comprises a shell, electrolyte and the battery core, wherein the battery core is arranged in the shell, and the battery core is soaked in the electrolyte.
According to the battery cell provided by the invention, the lithium iron phosphate ion diffusion capacity contained in the second active material layer is lower than that of lithium cobaltate and nickel cobalt manganese contained in the first active material layer, so that the lithium removal rate of the positive electrode plate is limited, and therefore, the surface lithium transition deposition caused by overlarge current density of the negative electrode plate is avoided, and lithium dendrite is avoided.
According to the battery provided by the invention, the battery core is adopted, so that the problems of surface lithium transition deposition and lithium precipitation of the negative electrode plate caused by overlarge current around the second electrode lug can be avoided, and the capacity retention rate of the battery is better.
In addition to the technical problems solved by the embodiments of the present invention, the technical features constituting the technical solutions, and the advantages brought by the technical features of the technical solutions, other technical problems that can be solved by the battery cell and the battery provided by the embodiments of the present invention, other technical features included in the technical solutions, and advantages brought by the technical features will be further described in detail in the detailed description.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a battery cell according to an embodiment of the present invention;
fig. 2 is a schematic front view of a positive electrode plate of a battery cell according to an embodiment of the present invention;
fig. 3 is a schematic top view of a positive electrode plate of a battery cell according to an embodiment of the present invention;
fig. 4 is a schematic bottom view of a positive electrode plate of a battery cell according to an embodiment of the present invention;
fig. 5 is a schematic view of a front view structure of a negative electrode plate of a battery cell according to an embodiment of the present invention;
fig. 6 is a schematic top view of a negative electrode plate of a battery cell according to an embodiment of the present invention;
fig. 7 is a schematic view of a bottom view structure of a negative electrode plate of a battery cell according to an embodiment of the present invention.
Description of reference numerals:
10-positive electrode sheet;
11-a first current collector;
12-a first coating section;
13-a first blank section;
14-a first active material layer;
15-a second active material layer;
16-a first tab;
20-a negative electrode plate;
21-a second current collector;
211-second blank segment;
22-a third active material layer;
24-a second coating section;
241-single-side coating section;
242-two-sided coating section;
25-a second tab;
30-a membrane.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In the battery cell, especially in the conventional winding type battery cell, a first tab is welded at one end of a positive electrode plate, a second tab is welded at one end of a negative electrode plate, the positions for welding the first tab and the second tab are generally in the battery cell, and when current flows in, the current can be unevenly distributed on the positive electrode plate and the negative electrode plate, wherein the current density near the position for welding the second tab is high, the de-intercalation speed of lithium ions at the position is higher, the quantity of de-intercalated lithium is also more, so that the position for welding the second tab on the negative electrode plate can be subjected to lithium precipitation when charging, the thickness of the position is increased, and safety risk is caused.
Therefore, the distribution of the current density in the cell is improved, which is helpful for improving the problem of lithium deposition at the position of the second lug welding on the negative electrode sheet. In a lithium ion battery, various reactions occur, including a solvation reaction and a desolvation reaction, wherein the solvation reaction is a solvation reaction in which lithium ions are released from a positive electrode sheet, and transfer of the lithium ions in an electrolyte; the desolvation reaction refers to desolvation reaction of lithium ions entering the negative electrode plate from the electrolyte. Increasing the lithium intercalation speed of the negative electrode sheet requires a great deal of cost, for example, using a negative electrode sheet with a faster lithium intercalation speed or a lower compaction density to reduce the probability of lithium accumulation on the surface of the negative electrode sheet, but this measure increases the cost and causes a large loss in energy density. For the positive electrode plate, the lithium separation of the negative electrode plate caused by high current density can be improved by reducing the lithium removal speed of the welding position of the first tab on the positive electrode plate.
Based on the above knowledge, the present invention provides a battery core and a battery, which can control the current density around the second tab by controlling the lithium ion detachment speed of the second active material layer in the positive electrode sheet corresponding to the negative electrode sheet, and avoid the surface lithium transition deposition of the negative electrode sheet caused by the excessive current around the second tab, so that the lithium detachment and insertion rates of the positive electrode sheet and the negative electrode sheet are balanced, thereby reducing the risk of lithium precipitation of the negative electrode sheet, and improving the safety. The second active material layer utilizes the characteristics of large powder resistivity, slower lithium removal speed and higher safety of the lithium iron phosphate, and the lithium iron phosphate is arranged at the position corresponding to the single-surface coating section of the negative electrode plate, so that the lithium removal speed of the single-surface coating section of the negative electrode plate is reduced, and the risk of lithium precipitation of the negative electrode plate is reduced.
The following describes a battery cell and a battery provided in an embodiment of the present invention with reference to the drawings.
Referring to fig. 1, the present invention provides a battery cell, including: the lithium ion battery comprises a positive electrode sheet 10, a negative electrode sheet 20 and a diaphragm 30, wherein the diaphragm 30 is arranged between the positive electrode sheet 10 and the negative electrode sheet 20 to isolate the positive electrode sheet 10 and the negative electrode sheet 20, the positive electrode sheet 10, the negative electrode sheet 20 and the diaphragm 30 are laminated and then wound together, and the diaphragm 30 has a microporous structure and can allow lithium ions to freely pass through but electrons cannot pass through.
Referring to fig. 1 and 2, the positive electrode sheet 10 includes a first current collector 11, a first active material layer 14, a second active material layer 15, and a first tab 16, the first current collector 11 includes a first coating section 12 and a first blank section 13 connected to at least one end of the first coating section 12, as shown in fig. 3 and 4, the first active material layer 14 and the second active material layer 15 are attached to one surface of the first coating section 12, the second active material layer 15 is joined to the first active material layer 14, the first active material layer 14 is attached to the other surface of the first coating section 12, and the first tab 16 is disposed on the first blank section 13.
Referring to fig. 5 and 6, the negative electrode sheet 20 includes a second current collector 21, a third active material layer 22, and a second tab 25, the second current collector 21 includes a second coating section 24 and a second blank section 211 connected to at least one end of the second coating section 24, the second coating section 24 includes a single-sided coating section 241 and a double-sided coating section 242 connected to each other, one of the front and back surfaces of the single-sided coating section 241 is coated with the third active material layer 22, both the front and back surfaces of the double-sided coating section 242 are coated with the third active material layer 22, the second tab 25 is disposed on the second blank section 211 connected to the single-sided coating section 241, and as shown in fig. 1 and 6, the third active material layer 22 coated by the single-sided coating section 241 faces the second active material layer 15 of the positive electrode sheet 10.
Referring to fig. 2 and 4, in a battery cell provided by the present invention, in a positive electrode sheet 10, a first active material layer 14 and a second active material layer 15 are attached to one surface of a first coating segment 12, and the first active material layer 14 and the second active material layer 15 have different compositions, so that the lithium ion desorption rates in the first active material layer 14 and the second active material layer 15 are different. Referring to fig. 5 and 6, in the negative electrode sheet 20, the third active material layer 22 coated by the single-side coating section 241 faces the second active material layer 15 of the positive electrode sheet 10, and the lithium ion separation speed of the second active material layer 15 corresponding to the single-side coating section 241 is controlled, so that the current density around the second tab 25 can be controlled, the surface lithium transition deposition of the negative electrode sheet 20 caused by the excessive current around the second tab 25 is avoided, the lithium separation and insertion rates of the positive electrode sheet 10 and the negative electrode sheet 20 are balanced, the risk that lithium is easily separated from the position close to the second tab 25 in the negative electrode sheet 20 is reduced, and the safety is improved.
In a possible implementation, as shown in fig. 2, the first current collector 11 may be a positive electrode current collector, for example, an aluminum foil, and has a sheet-like structure. Referring to fig. 5, the second current collector 21 may be a negative electrode current collector, for example, a copper foil, and has a sheet structure.
In one possible implementation, referring to fig. 1, the separator 30 may include a substrate and a coating layer, wherein the substrate may be a Polyethylene (PE) monolayer film, a polypropylene (PP) monolayer film, or a polypropylene-polyethylene-polypropylene three-layer composite film, and the coating layer may be at least one of porous silica, alumina, titania, and zirconia.
In one possible embodiment, as shown with reference to fig. 4 and 5, the coating length of the second active material layer 15 in the length direction of the first current collector 11 is 60% to 150% of the length of the single-sided coating section 241.
Referring to fig. 2, the longitudinal direction of the first current collector 11 is the direction indicated by the arrow X in fig. 2, and the coating length of the second active material layer 15 in the longitudinal direction of the first current collector 11 is L1; referring to fig. 5, the length of the single-coated segment 241 is the distance L2 between the second blank segment 211 and the double-coated segment 242 in fig. 5, so that L1 is 60% L2-150% L2.
In one possible embodiment, the coating length of the second active material layer 15 in the length direction of the first current collector 11 is 100% to 120% of the length of the single-sided coating section 241.
In one possible embodiment, the coating length of the second active material layer 15 in the longitudinal direction of the first current collector 11 is 60%, 70%, 80%, 90%, 100%, 110%, 120%, 130%, 140% or 150% of the length of the single-sided coating segment 241, for example, L1 ═ 60% L2, L1 ═ 70% L2, L1 ═ 90% L2, L1 ═ 100% L2, L1 ═ 110% L2, L1 ═ 120% L2, L1 ═ 130% L2, and L1 ═ 150% L2. In this way, the second active material layer 15 is made to have a sufficient length corresponding to the length of the one-side coating section 241, ensuring that control of the delithiation rate of the second active material layer 15 corresponding to the one-side coating section 241 can be achieved.
In one possible embodiment, the active material in the second active material layer 15 includes lithium iron phosphate, wherein the mass percentage of the lithium iron phosphate in the active material in the second active material layer 15 is 5% to 100%. When the addition amount of the lithium iron phosphate is more than 5%, the lithium precipitation effect is better improved. For example, the mass percentage of the lithium iron phosphate to the active material in the second active material layer 15 may be 5%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 100%, or the like.
Referring to fig. 2 and 4, a first active material layer 14 and a second active material layer 15 are attached to one surface of the first coating section 12, and the second active material layer 15 is adjacent to the first blank section 13 provided with the first tab 16, so that the intrinsic stability of lithium iron phosphate is good, which is beneficial to improving the surface oxidation capability of the position of the positive electrode sheet 10 coated with the second active material layer 15 due to over-delithiation, and has a certain improvement effect on over-charging. When the positive electrode plate 10 is charged and discharged rapidly, the second active material layer 15 is doped with lithium iron phosphate particles, so that the lithium extraction rate of the second active material layer 15 is smaller than that of the first active material layer 14, and the lithium extracted from the second active material layer 15 is inserted into the negative electrode plate 20 at a lower rate.
In one possible embodiment, the second active material layer 15 and the first tab 16 are respectively located on opposite sides of the first current collector 11. That is, the second active material layer 15 is coated on one surface of the first coating section 12 of the first current collector 11, the first tab 16 is disposed on the first blank section 13, and the first tab 16 is located on one surface of the first current collector 11 facing away from the second active material layer 15.
In one possible embodiment, the active material in the second active material layer 15 further includes at least one of lithium cobaltate, lithium vanadate, lithium manganese phosphate, lithium cobalt phosphate, lithium titanate, lithium iron manganese phosphate, ternary nickel cobalt aluminum, ternary nickel cobalt manganese, quaternary nickel cobalt manganese aluminum, lithium manganate, lithium nickelate, and lithium rich manganese base.
In one possible embodiment, the lithium iron phosphate may be present in the second active material layer 15 in the form of a single layer or in a mixture with other active materials in the second active material layer 15.
In one possible embodiment, the active material in the first active material layer 14 includes lithium cobaltate or nickel cobalt manganese ternary.
In one possible embodiment, the active material in the first active material layer 14 includes lithium cobaltate and nickel cobalt manganese ternary. The lithium removal speed of the lithium cobaltate and the nickel cobalt manganese ternary is high relative to that of lithium iron phosphate.
In the battery core provided by this embodiment, because the lithium iron phosphate is low in lithium removal speed, the lithium iron phosphate ion diffusion capacity contained in the second active material layer 15 is lower than that of the ternary lithium cobaltate and nickel cobalt manganese contained in the first active material layer 14, so that the positive electrode lithium removal rate of the positive electrode plate 10 is limited, and it is ensured that the negative electrode plate 20 does not generate lithium dendrite due to surface lithium transition deposition caused by excessive current density.
In one possible embodiment, the electrical conductivity of the first active material layer 14 in the powder state is less than the electrical conductivity of the second active material layer 15 in the powder state.
In one possible embodiment, as shown with reference to fig. 2, the first active material layer 14 and the second active material layer 15 are applied to a thickness of 20 μm to 80 μm.
In one possible embodiment, as shown with reference to fig. 2, the first active material layer 14 may be coated to a thickness of 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, or 80 μm.
In one possible embodiment, the second active material layer 15 may be coated to a thickness of 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, or 80 μm.
In one possible embodiment, the first active material layer 14 and the second active material layer 15 are applied in equal thickness. For example, the coating thickness of each of the first active material layer 14 and the second active material layer 15 is 50 μm.
The second active material layer 15 further includes a second conductive agent and a second binder. The second binder may be at least one of polyvinylidene fluoride (PVDF), polyacrylic acid (PAA), sodium polyacrylate (PAA-Na), lithium polyacrylate (PAA-Li), Polyamide (PA), Polytetrafluoroethylene (PTFE), Polyacrylonitrile (PAN), polyvinylpyrrolidone (PVP), sodium carboxymethylcellulose (CMC-Na), Styrene Butadiene Rubber (SBR), and Polymethacrylate (PMMA). The second conductive agent may be at least one of carbon black, acetylene black, carbon fiber, graphite, graphene, carbon nanotubes, ketjen black, an organic conductive polymer, and a metal conductive powder.
The first active material layer 14 further includes a first conductive agent and a first binder. The first conductive agent may be at least one of carbon black, acetylene black, carbon fiber, graphite, graphene, carbon nanotubes, ketjen black, an organic conductive polymer, and a metal conductive powder. The first binder can be at least one of polyvinylidene fluoride, polyacrylic acid, polyamide, polytetrafluoroethylene, sodium carboxymethylcellulose, styrene-butadiene rubber and polymethacrylate.
The third active material layer 22 includes a negative electrode active material, which may be at least one of artificial graphite, natural graphite, soft carbon, hard carbon, lithium titanate, silicon oxide, and a lithium sheet, a third binder, and a third conductive agent. The third adhesive may be at least one of polyvinylidene fluoride, polyacrylic acid, polyamide, polytetrafluoroethylene, sodium carboxymethylcellulose, styrene-butadiene rubber, and polymethacrylate. The third conductive agent may be at least one of carbon black, acetylene black, carbon fiber, graphite, graphene, carbon nanotubes, ketjen black, and an organic conductive polymer.
In one possible embodiment, referring to fig. 1, the first tab 16 is located at an inner circle layer of the cell, and the second tab 25 is located at an inner circle layer of the cell. It is easy to understand that, the positive electrode sheet 10, the negative electrode sheet 20, and the separator 30 are laminated and then wound together to form a winding structure with multiple winding layers, and the head of the positive electrode sheet 10 and the head of the negative electrode sheet 20 are used as inner winding layers of the battery cell; in the orthographic projection direction of the battery cell, the inner circle layer of the battery cell is close to the geometric center of the battery cell. It is easily understood that the first blank section 13 of the first tab 16 is provided as a head of the positive electrode sheet 10, and the second blank section 211 of the second tab 25 is provided as a head of the negative electrode sheet 20. The embodiment reduces the risk of lithium deposition at the position close to the second tab 25 in the negative electrode sheet 20, and reduces the risk of lithium deposition at the head of the battery cell.
In the battery cell provided in this embodiment, because the current density distribution around the first tab 16 and the second tab 25 is not uniform, the degree of lithium release from the position of the negative electrode sheet 20 close to the second tab 25 is higher than that in other regions, and meanwhile, because the negative electrode sheet 20 has the single-sided coating section 241 in the inner ring layer of the battery cell, the pressure applied to the single-sided coating section 241 during rolling is small, the peeling force between the third active material layer 22 coated by the single-sided coating section 241 and the second current collector 21 is low, and the electrical conductivity is worse than that in other positions, so that the phenomenon of lithium deposition is more likely to occur. In this embodiment, the position of the positive electrode sheet 10 opposite to the single-side coating section 241 is adjusted to be the second active material layer 15, so that the lithium desorption rates of the positive electrode sheet 10 and the negative electrode sheet 20 are balanced, and the risk of lithium precipitation of the positive electrode sheet 10 is reduced. In addition, the present embodiment can also improve the problem of occurrence of side reactions such as cell collapse and electrolyte oxidation caused by excessive delithiation of the positive electrode sheet 10 inside the cell.
The invention also provides a battery, which comprises a shell, electrolyte and the battery core, wherein the battery core is arranged in the shell, and the battery core is soaked in the electrolyte.
In one possible embodiment, the shell may be an aluminum plastic film shell.
The battery provided by the invention can be implemented in various ways, and five examples are listed below and are respectively specifically described:
example one
Referring to fig. 2 and 3, lithium cobaltate of 10um with a particle diameter of 50, lithium iron phosphate of 0.7um with a particle diameter of 50, polyvinylidene fluoride and carbon black were mixed in a ratio of 90: 7: 2: 1, and dispersing at a high speed to obtain a slurry of the second active material layer 15 with a mass solid content of 70%, wherein the slurry of the second active material layer 15 is uniformly coated on one surface of the first coating section 12 of the first current collector 11, which is close to the first blank section 13, and the coating thickness is 50 um. Then, heat drying is performed.
10um lithium cobaltate with a particle diameter of 50, polyvinylidene fluoride and carbon black were mixed in a 97: 2: 1, obtaining 70% of first active material layer 14 slurry after high-speed dispersion, uniformly coating the first active material layer 14 slurry on a position, which is not coated with the second active material layer 15 slurry, in the first coating section 12 of the positive electrode sheet 10, wherein the coating thickness is 50 micrometers, and then heating and drying. And rolling, slitting and welding the first tab 16 by weight of 70 tons, and sticking protective adhesive paper to manufacture the positive electrode plate 10.
Referring to fig. 5 and 7, the weight ratio of artificial graphite, styrene butadiene rubber as a binder, sodium carboxymethyl cellulose as a thickener and acetylene black as a conductive agent is selected to be 96: 1.5: 0.5: 1, adding deionized water as a solvent, dispersing at a high speed to obtain slurry of a third active material layer 22 with a mass solid content of 45%, uniformly coating the slurry of the third active material layer 22 on one surface of a single-side coating section 241 and two surfaces of a double-side coating section 242 of a second current collector 21 to a coating thickness of 55um, baking, rolling, slitting, welding a second lug 25, and sticking protective adhesive paper, and processing into a negative electrode plate 20.
And (3) production of the battery: winding a positive electrode plate 10, a negative electrode plate 20 and a diaphragm 30 which is arranged between the positive electrode plate 10 and the negative electrode plate 20 to obtain a battery core, wherein the diaphragm 30 can be a polypropylene film with the thickness of 8um, and after the battery core is arranged in a shell, diethyl carbonate (DEC), and/or zinc carbonate (Cu) are injected,Ethylene Carbonate (EC) and Ethyl Methyl Carbonate (EMC), wherein diethyl carbonate (DEC): ethylene Carbonate (EC): the mass ratio of Ethyl Methyl Carbonate (EMC) is 1: 1: 1, lithium hexafluorophosphate LiPF6And (3) the electrolyte with the concentration of 1mol/L (1M) is subjected to the working procedures of aging, formation, sorting and the like after the electrolyte is injected into the battery, and the production of the battery is completed.
Example two
Referring to fig. 2 and 3, lithium cobaltate of 10um with a particle diameter of 50, lithium iron phosphate of 0.7um with a particle diameter of 50, polyvinylidene fluoride and carbon black were mixed in a ratio of 80: 17: 2: 1, and dispersing at a high speed to obtain a slurry of the second active material layer 15 with a mass solid content of 70%, wherein the slurry of the second active material layer 15 is uniformly coated on one surface of the first coating section 12 of the first current collector 11, which is close to the first blank section 13, and the coating thickness is 50 um. Then, heat drying is performed.
10um lithium cobaltate with a particle diameter of 50, polyvinylidene fluoride and carbon black were mixed in a 97: 2: 1, obtaining 70% of first active material layer 14 slurry after high-speed dispersion, uniformly coating the first active material layer 14 slurry on a position, which is not coated with the second active material layer 15 slurry, in the first coating section 12 of the positive electrode sheet 10, wherein the coating thickness is 50 micrometers, and then heating and drying. And rolling, slitting and welding the first tab 16 by weight of 70 tons, and sticking protective adhesive paper to manufacture the positive electrode plate 10.
The negative electrode sheet 20 in example two is the same as the negative electrode sheet 20 in example one, and the production of the finished battery is the same.
EXAMPLE III
The difference from the first embodiment is that: the second active material layer 15 has different compositions of slurry, and lithium cobaltate of 10um having a particle diameter of 50, lithium iron phosphate of 0.7um having a particle diameter of 50, polyvinylidene fluoride, and carbon black were mixed in a ratio of 50: 47: 2: 1, dispersing at a high speed to obtain a slurry of the second active material layer 15 with a mass solid content of 70%, and uniformly coating the slurry of the second active material layer 15 on one surface of the first coating section 12 of the first current collector 11, wherein the coating thickness is 50um, and the position is close to the first blank section 13. Then, heat drying is performed.
10um lithium cobaltate with a particle diameter of 50, polyvinylidene fluoride and carbon black were mixed in a 97: 2: 1, obtaining 70% of first active material layer 14 slurry after high-speed dispersion, uniformly coating the first active material layer 14 slurry on a position, which is not coated with the second active material layer 15 slurry, in the first coating section 12 of the positive electrode sheet 10, wherein the coating thickness is 50 micrometers, and then heating and drying. And rolling, slitting and welding the first tab 16 by weight of 70 tons, and sticking protective adhesive paper to manufacture the positive electrode plate 10.
The negative electrode sheet 20 in example three is the same as the negative electrode sheet 20 in example one, and the production of the finished battery is the same.
Example four
The difference from the first embodiment is that: the second active material layer 15 has different compositions of the slurry, and lithium cobaltate of 10um having a particle diameter of 50, lithium iron phosphate of 0.7um having a particle diameter of 50, polyvinylidene fluoride, and carbon black were mixed in a ratio of 0: 97: 2: 1, dispersing at a high speed to obtain a slurry of the second active material layer 15 with a mass solid content of 70%, and uniformly coating the slurry of the second active material layer 15 on one surface of the first coating section 12 of the first current collector 11, wherein the coating thickness is 50um, and the position is close to the first blank section 13. Then, heat drying is performed.
10um lithium cobaltate with a particle diameter of 50, polyvinylidene fluoride and carbon black were mixed in a 97: 2: 1, obtaining 70% of first active material layer 14 slurry after high-speed dispersion, uniformly coating the first active material layer 14 slurry on a position, which is not coated with the second active material layer 15 slurry, in the first coating section 12 of the positive electrode sheet 10, wherein the coating thickness is 50 micrometers, and then heating and drying. And rolling, slitting and welding the first tab 16 by weight of 70 tons, and sticking protective adhesive paper to manufacture the positive electrode plate 10.
The negative electrode sheet 20 in example four is the same as the negative electrode sheet 20 in example one, and the production of the finished battery is the same.
EXAMPLE five
The difference from the first embodiment is that: the second active material layer 15 has different compositions of slurry, and lithium cobaltate of 10um having a particle diameter of 50, lithium iron phosphate of 0.7um having a particle diameter of 50, polyvinylidene fluoride, and carbon black were mixed in a ratio of 95: 2: 2: 1, dispersing at a high speed to obtain a slurry of the second active material layer 15 with a mass solid content of 70%, and uniformly coating the slurry of the second active material layer 15 on one surface of the first coating section 12 of the first current collector 11, wherein the coating thickness is 50um, and the position is close to the first blank section 13. Then, heat drying is performed.
10um lithium cobaltate with a particle diameter of 50, polyvinylidene fluoride and carbon black were mixed in a 97: 2: 1, obtaining 70% of first active material layer 14 slurry after high-speed dispersion, uniformly coating the first active material layer 14 slurry on a position, which is not coated with the second active material layer 15 slurry, in the first coating section 12 of the positive electrode sheet 10, wherein the coating thickness is 50 micrometers, and then heating and drying. And rolling, slitting and welding the first tab 16 by weight of 70 tons, and sticking protective adhesive paper to manufacture the positive electrode plate 10.
The negative electrode sheet 20 in example five is the same as the negative electrode sheet 20 in example one, and the production of the finished battery is the same.
In order to better illustrate the technical effects of the invention and verify that the invention can improve the problem of lithium precipitation of the negative electrode plate 20, the existing battery is taken as a comparative example and is compared with the batteries produced in the first to fifth examples in a test mode:
comparative example 1
10um lithium cobaltate with a particle diameter of 50, polyvinylidene fluoride and carbon black were mixed in a 97: 2: 1, obtaining 70% of first active material layer 14 slurry after high-speed dispersion, uniformly coating the first active material layer 14 slurry on the front and back surfaces of a first coating section 12 of a positive electrode sheet 10, wherein the coating thickness is 50 microns, and then heating and drying. And rolling, slitting and welding the first tab 16 by weight of 70 tons, and sticking protective adhesive paper to manufacture the positive electrode plate 10.
The negative electrode sheet 20 in the comparative example a was the same as the negative electrode sheet 20 in the example a, and the production of the finished battery was the same.
The batteries produced in examples one to five and the battery produced in comparative example were each tested at 10 ℃ at a charge/discharge rate of 1C/1C, and when full charge after 100T cycling, dissection was performed and whether lithium deposition occurred in the single-sided region of the negative electrode was examined. The results are shown in table 1 below:
| 0 ℃ cycle 100T | 0 ℃ circulation 100T capacity | |
| Example one | Inner ring layer of battery cell does not precipitate lithium | 93.45％ |
| Example two | Inner ring layer of battery cell does not precipitate lithium | 93.51％ |
| EXAMPLE III | Inner ring layer of battery cell does not precipitate lithium | 93.48％ |
| Example four | Inner ring layer of battery cell does not precipitate lithium | 93.56％ |
| EXAMPLE five | Inner ring layer of battery cellSlight precipitation of lithium | 92.50％ |
| Comparative example 1 | Inner ring chromatography lithium of battery cell | 91.22％ |
TABLE 1
As can be seen from the first to fifth embodiments and the first comparative example, by adding the second active material layer 15 and controlling the lithium iron phosphate added to the component of the second active material layer 15 in the positive electrode sheet 10 corresponding to the negative electrode sheet 20, the lithium ion desorption rate of the second active material layer 15 corresponding to the single-sided coating section 241 can be controlled, so as to control the current density around the second tab 25, avoid the problem of lithium precipitation caused by excessive current around the second tab 25 due to surface lithium transition deposition of the negative electrode sheet 20, facilitate the application of the battery in the fast charge field, and achieve better capacity retention rate of the battery.
It should be noted that the numerical values and numerical ranges referred to in this application are approximate values, and there may be some error due to the manufacturing process, and the error may be considered to be negligible by those skilled in the art.
In the description of the present invention, it is to be understood that the terms "center", "length", "width", "thickness", "top", "bottom", "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal", "inner", "outer", "axial", "circumferential", and the like, are used to indicate an orientation or positional relationship based on that shown in the drawings, merely to facilitate the description of the invention and to simplify the description, and do not indicate or imply that the position or element referred to must have a particular orientation, be of particular construction and operation, and thus, are not to be construed as limiting the invention.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integral; may be mechanically coupled, may be electrically coupled or may be in communication with each other; either directly or indirectly through intervening media, such as through internal communication or through an interaction between two elements. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In the present invention, unless otherwise expressly stated or limited, "above" or "below" a first feature means that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact with each other via another feature therebetween. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly under and obliquely below the second feature, or simply meaning that the first feature is at a lesser elevation than the second feature.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (11)
1. A battery cell, comprising: the battery comprises a positive electrode sheet (10), a negative electrode sheet (20) and a diaphragm (30), wherein the diaphragm (30) is arranged between the positive electrode sheet (10) and the negative electrode sheet (20) to isolate the positive electrode sheet (10) and the negative electrode sheet (20), and the positive electrode sheet (10), the negative electrode sheet (20) and the diaphragm (30) are laminated and then wound together;
the positive electrode plate (10) comprises a first current collector (11), a first active material layer (14), a second active material layer (15) and a first tab (16), wherein the first current collector (11) comprises a first coating section (12) and a first blank section (13) connected to at least one end of the first coating section (12), the first active material layer (14) and the second active material layer (15) are attached to one surface of the first coating section (12), the second active material layer (15) is spliced with the first active material layer (14), the first active material layer (14) is attached to the other surface of the first coating section (12), and the first tab (16) is arranged on the first blank section (13);
the negative electrode plate (20) comprises a second current collector (21), a third active material layer (22) and a second tab (25), the second current collector (21) comprises a second coating section (24) and a second blank section (211) connected to at least one end of the second coating section (24), the second coating section (24) comprises a single-sided coating section (241) and a double-sided coating section (242) which are connected with each other, one of the front and back surfaces of the single-coated segment (241) is coated with the third active material layer (22), the front surface and the back surface of the double-coated section (242) are coated with the third active material layer (22), the second tab (25) is arranged on the second blank section (211) connected with the single-coated section (241), the third active material layer (22) coated by the single-side coating section (241) faces the second active material layer (15) of the positive electrode sheet (10).
2. The cell of claim 1, wherein the coating length of the second active material layer (15) in the length direction of the first current collector (11) is 60-150% of the length of the single-coated section (241).
3. The electrical core of claim 2, wherein the coating length of the second active material layer (15) in the length direction of the first current collector (11) is 100-120% of the length of the single-coated section (241).
4. The battery cell of claim 1, wherein the active material in the second active material layer (15) comprises lithium iron phosphate, and the mass percentage of the lithium iron phosphate in the active material in the second active material layer (15) is 5% to 100%.
5. The electrical core according to claim 4, wherein the active material in the second active material layer (15) further comprises at least one of lithium cobaltate, lithium vanadate, lithium manganese phosphate, lithium cobalt phosphate, lithium titanate, lithium iron manganese phosphate, ternary nickel cobalt aluminum, ternary nickel cobalt manganese, quaternary nickel cobalt manganese aluminum, lithium manganate, lithium nickelate, lithium rich manganese base.
6. The electrical core according to claim 1, wherein the active material in the first active material layer (14) comprises lithium cobaltate or nickel cobalt manganese ternary.
7. The electrical core according to claim 1, characterized in that the electrical conductivity of the first active material layer (14) in the powder state is smaller than the electrical conductivity of the second active material layer (15) in the powder state.
8. The electrical core according to claim 1, characterized in that the first active material layer (14) and the second active material layer (15) are applied in a thickness of 20 μm to 80 μm.
9. The electrical core according to claim 1, wherein the second active material layer (15) and the first tab (16) are located on opposite sides of the first current collector (11).
10. The cell of any of claims 1 to 9, wherein the first tab (16) is located on an inner loop layer of the cell and the second tab (25) is located on an inner loop layer of the cell.
11. A battery comprising a housing, an electrolyte, and the cell of any of claims 1-10, the cell being disposed within the housing and the cell being immersed in the electrolyte.
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| CN202111117637.5A CN113707869A (en) | 2021-09-23 | 2021-09-23 | Battery cell and battery |
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| CN202111117637.5A CN113707869A (en) | 2021-09-23 | 2021-09-23 | Battery cell and battery |
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