CN117832394A - Negative pole piece, lithium ion battery and device - Google Patents

Negative pole piece, lithium ion battery and device Download PDF

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Publication number
CN117832394A
CN117832394A CN202410070777.9A CN202410070777A CN117832394A CN 117832394 A CN117832394 A CN 117832394A CN 202410070777 A CN202410070777 A CN 202410070777A CN 117832394 A CN117832394 A CN 117832394A
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active material
material layer
anode active
negative electrode
anode
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喻磊
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Ningde Amperex Technology Ltd
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Ningde Amperex Technology Ltd
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Abstract

A negative electrode tab includes a negative electrode current collector and a negative electrode active material layer located on at least one surface of the negative electrode current collector. The negative electrode current collector is copper foil with a thickness of 1-4 μm. The anode active material layer includes a first anode active material layer and a second anode active material layer. The first anode active material layer includes a first anode active material, and the first anode active material layer has an OI value of 13 to 20. The second anode active material layer includes a second anode active material, and the second anode active material layer has an OI value of 5 to 10. The application also provides a lithium ion battery comprising the negative electrode plate and a device comprising the lithium ion battery. The thickness of the copper foil of the negative electrode plate is thinner, the ductility is poor, the negative electrode plate is enabled to expand less under the conditions of high compaction density and high coating weight by designing the negative electrode active material layer with a double-layer structure, the energy density is higher, and the problem of deformation does not exist.

Description

Negative pole piece, lithium ion battery and device
Technical Field
The application relates to the technical field of batteries, in particular to a negative electrode plate, a lithium ion battery comprising the negative electrode plate and a device comprising the lithium ion battery.
Background
Currently, as the energy density requirements of lithium ion batteries are higher, the negative electrode sheet tends to have a high compacted density and high coating weight design. However, such a limit design may cause a problem in that the ductility of the negative electrode tab is deteriorated to cause deformation of the battery. Therefore, how to avoid the deformation problem of the battery is a problem to be solved under the conditions of high compacted density and high coating weight of the negative electrode tab.
Disclosure of Invention
In view of this, the first aspect of the present application provides a negative electrode tab, comprising:
the negative electrode current collector is a copper foil, and the thickness of the copper foil is 1-4 mu m;
the negative electrode active material layer is positioned on at least one surface of the negative electrode current collector, and the negative electrode active material layer comprises:
a first anode active material layer located on a surface of the anode current collector, the first anode active material layer including a first anode active material, the first anode active material layer having an OI value of 13 to 20; and
the second anode active material layer is positioned on the surface, facing away from the anode current collector, of the first anode active material layer, the second anode active material layer comprises a second anode active material, the OI value of the second anode active material layer is 5-10, and the weight of the second anode active material layer is larger than that of the first anode active material layer;
the OI value of the first anode active material layer is the peak area ratio of 004 characteristic diffraction peaks to 110 characteristic diffraction peaks in an X-ray diffraction spectrogram of the first anode active material layer;
the OI value of the second anode active material layer is a peak area ratio of 004 characteristic diffraction peaks to 110 characteristic diffraction peaks in an X-ray diffraction spectrum of the first anode active material layer.
The copper foil of the negative electrode plate is thinner and poor in ductility, the first negative electrode active material layer on the lower layer is designed to have a larger OI value and is coated with a smaller weight, so that the expansion of the first negative electrode active material layer in the XY direction is small, and the first negative electrode active material layer is directly coated on the thin copper foil to ensure that the whole expansion is small, so that the deformation resistance is enhanced; meanwhile, the second anode active material layer on the upper layer adopts the OI value which is smaller and is coated with more weight, so that the depth of lithium intercalation in the thickness direction is ensured to be low, the expansion rate is smaller, and the energy density is higher. The design can ensure that the negative electrode plate has smaller expansion, higher energy density and no deformation problem under the conditions of high compaction density and high coating weight.
In some embodiments, the weight ratio of the first anode active material layer to the second anode active material layer is 0.11 to 0.35.
In some embodiments, the weight ratio of the first anode active material layer to the second anode active material layer is 0.20 to 0.32.
The first negative electrode active material layer of the lower layer has a relatively large OI value and thus needs to be coated with a relatively small amount of weight, so that the first negative electrode active material layer has a small extension in the XY direction, and the second negative electrode active material layer of the upper layer has a relatively small OI value and thus needs to be coated with a relatively large amount of weight, so that the depth of lithium intercalation in the thickness direction is ensured to be low.
In some embodiments, the negative electrode active material layer has a thickness of 90 μm to 130 μm.
The thickness of the second anode active material layer is 70% -90% of the thickness of the anode active material layer, and the thickness of the first anode active material layer is 10% -30% of the thickness of the anode active material layer.
In some embodiments, the first negative active material is graphite, the powder of which has an OI value of 3 to 8; the powder OI value of the graphite is the peak area ratio of 004 characteristic diffraction peaks to 110 characteristic diffraction peaks in an X-ray diffraction spectrogram of the powder of the graphite.
The OI value of the first anode active material layer is made to be 13 to 20 by controlling the OI value of the graphite powder of the first anode active material to be 3 to 8.
In some embodiments, the second negative active material is graphite, the powder of which has an OI value of 1 to 5; the powder OI value of the graphite is the peak area ratio of 004 characteristic diffraction peaks to 110 characteristic diffraction peaks in an X-ray diffraction spectrogram of the powder of the graphite.
The OI value of the graphite powder of the second anode active material is controlled to be 1 to 5, so that the OI value of the second anode active material layer is 5 to 10.
In some embodiments, the second anode active material layer has a coating weight of 100mg/1540.25mm 2 To 160mg/1540.25mm 2 。
In some embodiments, the first anode active material layer has a coating weight of 20mg/1540.25mm 2 To 50mg/1540.25mm 2 。
In some embodiments, the negative electrode active material layer has a compacted density of 1.47g/cm 3 To 1.60g/cm 3 。
The second aspect of the application provides a lithium ion battery, which comprises a positive electrode plate, a negative electrode plate and electrolyte, wherein the negative electrode plate is the negative electrode plate in the first aspect of the application.
A third aspect of the present application provides an apparatus comprising a lithium ion battery as described in the second aspect.
Drawings
Fig. 1 is a schematic cross-sectional view of a negative electrode tab according to an embodiment of the present application.
Description of main reference numerals:
negative electrode sheet 10
Negative electrode current collector 11
Negative electrode active material layer 13
First anode active material layer 131
Second anode active material layer 132
Detailed Description
The data range values recited in this application shall include the end values unless otherwise specified.
The application provides a negative pole piece and use lithium ion battery of this negative pole piece, this lithium ion include negative pole piece, anodal pole piece, electrolyte and set up the barrier film between anodal pole piece and negative pole piece. The embodiment of the application is mainly improved aiming at the negative electrode plate, and the negative electrode plate has high energy density and low expansion rate, so that the risk of expansion deformation of the battery is effectively reduced.
Referring to fig. 1, a negative electrode tab 10 of a lithium ion battery provided in an embodiment of the present application includes a negative electrode current collector 11 and a negative electrode active material layer 13 located on at least one surface of the negative electrode current collector 11. The negative electrode current collector 11 is a copper foil, and the copper foil is thin, with a thickness of 1 μm to 4 μm. The thinner copper foil is provided, so that the thickness of the negative electrode active material layer 13 can be correspondingly increased, and the energy density can be increased on the basis of maintaining the same integral negative electrode plate, however, the battery deformation problem is easily caused due to insufficient ductility of the thinner copper foil.
In this embodiment, the anode active material layer 13 is configured as a double-layer structure, and includes a stacked first anode active material layer 131 and a second anode active material layer 132, where the first anode active material layer 131 is located on the surface of the anode current collector 11, and the second anode active material layer 132 is located on the surface of the first anode active material layer 131 facing away from the anode current collector 11. That is, the first anode active material layer 131 is located between the second anode active material layer 132 and the anode current collector 11.
The first anode active material layer 131 includes a first anode active material, and the first anode active material layer 131 has an OI value of 13 to 20. The second anode active material layer 132 includes a second anode active material, and the second anode active material layer 132 has an OI value of 5 to 10. The OI value of the first anode active material layer 131 is a peak area ratio of 004 characteristic diffraction peaks to 110 characteristic diffraction peaks in the X-ray diffraction pattern of the first anode active material layer 131; the OI value of the second anode active material layer 132 is a peak area ratio of 004 characteristic diffraction peaks to 110 characteristic diffraction peaks in the X-ray diffraction pattern of the first anode active material layer 131.
The weight of the second anode active material layer 132 is greater than the weight of the first anode active material layer 131. In some embodiments, the weight ratio of the first anode active material layer 131 to the second anode active material layer 132 is 0.11 to 0.35. In some embodiments, the weight ratio of the first anode active material layer 131 to the second anode active material layer 132 is 0.20 to 0.32. In addition, the weight ratio of the first anode active material layer 131 to the second anode active material layer 132 may be equal to the ratio of the thicknesses of the first anode active material layer 131 to the second anode active material layer 132.
In some embodiments, the weight (or thickness) of the second anode active material layer 132 accounts for 70% -90% of the weight (or thickness) of the anode active material layer 13, and the weight (or thickness) of the first anode active material layer 131 accounts for 10% -30% of the weight (or thickness) of the anode active material layer 13.
The copper foil of the negative electrode plate 10 is thinner and smaller in ductility, and the first negative electrode active material layer 131 at the lower layer is designed to have a larger OI value and a smaller coating weight, so that the expansion of the first negative electrode active material layer 131 in the XY direction is small, and the first negative electrode active material layer 131 is directly coated on the thin copper foil to ensure that the whole expansion is small, so that the deformation resistance is enhanced; meanwhile, the second anode active material layer 132 on the upper layer adopts the OI value which is smaller and is coated with more weight, so that the depth of lithium intercalation in the thickness direction is ensured to be low, the expansion rate is smaller, and the energy density is higher. The design can ensure that the negative electrode plate 10 has smaller expansion and higher energy density under the conditions of high compaction density and high coating weight, and can effectively prevent the deformation problem.
The first negative electrode active material is graphite, and the OI value of graphite powder is 3 to 8; the powder OI value of the graphite is the peak area ratio of 004 characteristic diffraction peaks to 110 characteristic diffraction peaks in an X-ray diffraction spectrogram of the powder of the graphite.
The second negative electrode active material is graphite, and the OI value of the graphite powder is 1 to 5; the powder OI value of the graphite is the peak area ratio of 004 characteristic diffraction peaks to 110 characteristic diffraction peaks in an X-ray diffraction spectrogram of the powder of the graphite.
Controlling the OI value of the first anode active material layer to be 13 to 20 by controlling the OI value of the graphite powder of the first anode active material to be 3 to 8; the OI value of the second anode active material layer is controlled to be 5 to 10 by controlling the OI value of the graphite powder of the second anode active material to be 1 to 5.
The coating weight of the first anode active material layer 131 was 20mg/1540.25mm 2 To 50mg/1540.25mm 2 . The coating weight of the second anode active material layer 132 was 100mg/1540.25mm 2 To 160mg/1540.25mm 2 。
In some embodiments, the thickness of the anode active material layer 13 is 90 μm to 130 μm. The compacted density of the anode active material layer 13 was 1.47g/cm 3 To 1.60g/cm 3 . The thickness of the second anode active material layer 132 occupies the anode active material layer 13, the thickness of the first anode active material layer 131 accounts for 10% to 30% of the thickness of the anode active material layer 13.
The first anode active material layer 131 and the second anode active material layer 132 are mainly composed of anode active materials, and contain some conventional components.
In some embodiments, the first and second anode active material layers 131 and 132 further include a conductive agent to improve electrode conductivity. Any conductive material may be used as the conductive agent as long as it does not chemically change during production and use. Examples of conductive agents include, but are not limited to: carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, and the like; metal-based materials such as metal powders or metal fibers of copper, nickel, aluminum, silver, etc.; conductive polymers such as polyphenylene derivatives and the like; or mixtures thereof.
In some embodiments, the first and second anode active material layers 131 and 132 further include a binder. The binder may be various binder polymers such as polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, an ethyleneoxy-containing polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy, nylon, polyacrylic acid, poly (styrene-acrylate), and the like.
In some embodiments, the method of making the negative electrode tab 10 is well known in the art as a method of making a negative electrode that can be used in a lithium ion battery. Illustratively, the negative electrode tab 10 may be obtained by: (1) Mixing the first negative electrode active material, a conductive agent, a binder, and a solvent, and optionally adding a thickener to prepare a first negative electrode active material slurry; (2) Mixing a second anode active material, a conductive agent, a binder, and a solvent, and optionally adding a thickener to prepare a second anode active material slurry; (3) And sequentially coating the first anode active material slurry and the second anode active material slurry on a current collector, drying, and cold pressing to form an anode active material layer. In some embodiments, suitable solvents include, but are not limited to: water, N-methylpyrrolidone.
The application also provides a device comprising the lithium ion battery.
The use of the device of the present application is not particularly limited and it may be used in any electronic device known in the art. For example, the electronic device includes, but is not limited to, a notebook computer, a pen-input computer, a mobile computer, an electronic book player, a portable telephone, a portable facsimile machine, a portable copier, a portable printer, a headset, a video recorder, a liquid crystal television, a portable cleaner, a portable CD, a mini-compact disc, a transceiver, an electronic organizer, a calculator, a memory card, a portable audio recorder, a radio, a backup power supply, a motor, an automobile, a motorcycle, a power assisted bicycle, a lighting fixture, a toy, a game machine, a clock, an electric tool, a flash lamp, a camera, a household large-sized battery, a lithium ion capacitor, and the like. In addition, the lithium ion battery of the present application is applicable to an energy storage power station, a marine vehicle, and an air vehicle, in addition to the above-described electronic device. The air carrier comprises an air carrier within the atmosphere and an air carrier outside the atmosphere.
Positive electrode plate
The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. It is understood that the positive electrode active material layer mainly includes a positive electrode active material. The specific type of the positive electrode active material is not particularly limited, and may be selected according to the need.
In some embodiments, the positive electrode active material includes a compound that reversibly intercalates and deintercalates lithium ions (i.e., lithiated intercalation compound). In some embodiments, the positive electrode active material may include a lithium transition metal composite oxide. The lithium transition metal composite oxide contains lithium and at least one element selected from cobalt, manganese and nickel. In some embodiments, the positive electrode active material is selected from at least one of the following: lithium cobalt oxide (LiCoO) 2 ) Lithium nickel manganese cobalt ternary material (NCM), lithium manganate (LiMn) 2 O 4 ) Lithium nickel manganese (LiNi) 0.5 Mn 1.5 O 4 ) Lithium iron phosphate (LiFePO) 4 ) Nickel cobalt lithium manganate or lithium-rich manganese material.
In some embodiments, the positive electrode active material layer further comprises a binder, and optionally further comprises a conductive material. The binder may improve the bonding of the positive electrode active material particles to each other, and may improve the bonding of the positive electrode active material to the positive electrode current collector. In some embodiments, the binder includes, but is not limited to, polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethyleneoxy-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy, nylon, and the like.
In some embodiments, the positive electrode active material layer further includes a conductive material, thereby imparting conductivity to the electrode. The conductive material may include any conductive material as long as it does not cause a chemical change. Non-limiting examples of conductive materials include carbon-based materials (e.g., natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fibers, etc.), metal-based materials (e.g., metal powders, metal fibers, etc., including, for example, copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof.
In some embodiments, the positive electrode current collector is a metal, including, for example, but not limited to, aluminum foil.
In some embodiments, the structure of the positive electrode is a positive electrode structure that can be used in lithium ion batteries as known in the art.
In some embodiments, the method of preparing the positive electrode is known in the art as a method of preparing a positive electrode that can be used in a lithium ion battery. For example, the positive electrode can be obtained by: and mixing the active material, the conductive material, the binder and the positive electrode additive in a solvent to prepare positive electrode active material slurry, coating the positive electrode active material slurry on a current collector, drying, and cold pressing to form a positive electrode active material layer. In some embodiments, the solvent may include water, N-methylpyrrolidone, etc., but is not limited thereto.
Electrolyte solution
The electrolyte used in embodiments of the present application may be an electrolyte known in the art. The electrolyte can be divided into an aqueous electrolyte and a non-aqueous electrolyte, wherein a lithium ion battery employing the non-aqueous electrolyte can operate under a wider voltage window than the aqueous electrolyte, thereby achieving a higher energy density. In some embodiments, the nonaqueous electrolyte includes an organic solvent, an electrolyte, and an additive.
Electrolytes useful in the electrolytes of embodiments of the present application include, but are not limited to: inorganic lithium salts, e.g. LiClO 4 、LiAsF 6 、LiPF 6 、LiBF 4 、LiSbF 6 、LiSO 3 F、LiN(FSO 2 ) 2 Etc.; fluorine-containing organolithium salts, e.g. LiCF 3 SO 3 、LiN(FSO 2 )(CF 3 SO 2 )、LiN(CF 3 SO 2 ) 2 、LiN(C 2 F 5 SO 2 ) 2 Cyclic 1, 3-hexafluoropropane disulfonimide lithium, cyclic 1, 2-tetrafluoroethane disulfonimide lithium and LiPF 4 (CF 3 ) 2 、LiN(CF 3 SO 2 )(C4F 9 SO 2 )、LiC(CF 3 SO 2 ) 3 、LiPF 4 (CF 3 SO 2 ) 2 、LiPF 4 (C 2 F 5 ) 2 、LiPF 4 (C 2 F 5 SO 2 ) 2 、LiBF 2 (CF 3 ) 2 、LiBF 2 (C 2 F 5 ) 2 、LiBF 2 (CF 3 SO 2 ) 2 、LiBF 2 (C 2 F 5 SO 2 ) 2 The method comprises the steps of carrying out a first treatment on the surface of the Examples of the dicarboxylic acid-containing complex lithium salt include lithium bis (oxalato) borate, lithium difluorooxalato borate, lithium tris (oxalato) phosphate, lithium difluorobis (oxalato) phosphate, lithium tetrafluoro (oxalato) phosphate, and the like. In addition, the above electrolytes may be used alone or in combinationTwo or more kinds are used. For example, in some embodiments, the electrolyte includes LiPF 6 And LiBF 4 Is a combination of (a) and (b). In some embodiments, the electrolyte comprises LiPF 6 . In some embodiments, the mass percent of electrolyte is in the range of 8% to 15% based on the mass of the electrolyte.
Additives useful in the electrolytes of the present application may be additives known to those skilled in the art that can be used to enhance the electrochemical performance of a battery. In some embodiments, the additive includes, but is not limited to, at least one of a polynitrile compound, a sulfur-containing additive, fluoroethylene carbonate (FEC), 1, 3-Propane Sultone (PS), 1,4 butane sultone.
The organic solvent that may be used in the electrolyte of the present application may be any organic solvent known in the art. In some embodiments, the organic solvent includes, but is not limited to: carbonate compounds, ester-based compounds, ether-based compounds, ketone-based compounds, alcohol-based compounds, aprotic solvents, or combinations thereof. Examples of carbonate compounds include, but are not limited to, chain carbonate compounds, cyclic carbonate compounds, fluorocarbonate compounds, or combinations thereof.
In some embodiments the organic solvent comprises at least one of Ethylene Carbonate (EC), propylene Carbonate (PC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate, methyl acetate, or ethyl propionate.
The preparation method of the electrolyte in the embodiment of the application is not limited, and the electrolyte can be prepared in a conventional electrolyte mode. In some embodiments, the electrolytes of the present application may be prepared by mixing the components.
Isolation film
A separator is provided between the positive electrode and the negative electrode to prevent short circuit. The material and shape of the separator are not particularly limited and may be any of the techniques disclosed in the prior art. In some embodiments, the separator comprises a polymer or inorganic, etc., formed from a material that is stable to the electrolyte of the present application.
For example, in some embodiments, the release film includes a substrate layer. The substrate layer is a non-woven fabric, a membrane or a composite membrane with a porous structure. The material of the base material layer may be at least one selected from polyethylene, polypropylene, polyethylene terephthalate, and polyimide. Specifically, the material of the substrate layer may be selected from a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane.
The substrate layer is provided with a surface treatment layer on at least one surface thereof. The surface treatment layer may be a polymer layer, an inorganic layer, or a layer formed by mixing a polymer and an inorganic substance. Specifically, the inorganic layer includes inorganic particles and a binder. The inorganic particles may be selected from one or more of alumina, silica, magnesia, titania, hafnia, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconia, yttria, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. The binder can be selected from one or a combination of more of polyvinylidene fluoride, polymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene.
The technical scheme of the embodiment of the application is further described through specific embodiments.
Comparative example 1
The negative electrode slurry was prepared by adding artificial graphite (powder OI value 5) as a negative electrode active material, conductive carbon black (Super P) as a conductive agent, sodium carboxymethyl cellulose (racer 2200) as a thickener, and the above negative electrode binder as a negative electrode binder to water as a solvent at a weight ratio of 97.3% to 0.5% to 1.2% to 1.0%, using a ROSS double planetary mixer. Coating with extrusion coater at coating speed of 18m/min and coating weight of 160mg/1540.25cm 2 The above slurry negative electrode slurry was coated on the surface of a 4 μm copper foil as a current collector. Then baking in an oven until the pole piece is dried, and compacting to 1.55g/cm by cold pressing by using a cold press 3 And preparing the negative electrode plate. Coating layerIs 15 and has a thickness of 120. Mu.m.
Example 1
An artificial graphite having a powder OI value of 3.5 was added as a negative electrode active material, conductive carbon black (Super P) as a conductive agent, sodium carboxymethyl cellulose (macrogol 2200) as a thickener, SBR/styrene-acrylic emulsion as a negative electrode binder in a weight ratio of 97.3% to 0.5% to 1.2% to 1.0% to water as a solvent, and a slurry (upper layer) of the second negative electrode active material layer was prepared using a ROSS double planetary mixer. An artificial graphite having a powder OI value of 5.3 was added as a negative electrode active material, conductive carbon black (Super P) as a conductive agent, sodium carboxymethyl cellulose (macrogol 2200) as a thickener, SBR/styrene-acrylic emulsion as a negative electrode binder in a weight ratio of 97.3% to 0.5% to 1.2% to 1.0% to water as a solvent, and a slurry (lower layer) of the first negative electrode active material layer was prepared using a ROSS double planetary mixer. Coating by using an extrusion double-layer coater at a coating speed of 18m/min, and setting the coating weight of the second anode active material layer to 140mg/1540.25cm 2 The coating weight of the first negative electrode active material layer was set to 20mg/1540.25cm 2 The above two slurries were coated onto the surface of a 4 μm copper foil as a current collector, in which the slurry (lower layer) of the first negative electrode active material layer was directly coated on the surface of the copper foil. Then baking in an oven until the pole piece is dried, and compacting to 1.55g/cm by cold pressing by using a cold press 3 And preparing the negative electrode plate. The first negative electrode active material layer prepared after cold pressing had an OI value of 20 and the second negative electrode active material layer had an OI value of 10. The thickness of the first anode active material layer was 15 μm, and the thickness of the second anode active material layer was 105 μm.
And preparing a positive electrode plate, wherein the materials of the positive electrode active material layer comprise lithium cobaltate, conductive carbon black and polyvinylidene fluoride. Stirring lithium cobaltate, acetylene black, polyvinylidene fluoride and NMP solvent to prepare positive electrode slurry, coating the positive electrode slurry on the surface of 6 mu m aluminum foil serving as a positive electrode current collector, drying, and cold pressing to 4.15g/cm by using a cold press 3 And (5) preparing the positive pole piece.
A single-sided ceramic-coated and double-sided aqueous vinylidene fluoride-hexafluoropropylene copolymer was used as the separator.
Adopts a conventional electrolyte formula: 1mol/L of lithium hexafluorophosphate+ (ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl propionate, fluoroethylene carbonate and 1, 3-propane sultone) solvent to prepare an electrolyte.
And (3) welding the positive electrode plate and the negative electrode plate with the lugs, winding the positive electrode plate and the negative electrode plate with the diaphragm to form a battery core, packaging the battery core by adopting an aluminum plastic film, baking the battery core in a vacuum state for 24 hours to remove moisture, injecting the electrolyte, standing the battery at a high temperature, and forming and sorting the battery to obtain the square soft package lithium ion polymer battery with the thickness/width/height of 3.8mm, 64mm and 82mm respectively.
Comparative examples 2 to 5 and examples 2 to 8 lithium ion polymer batteries were prepared with reference to example 1.
In Table 1, the differences between comparative examples 1 to 5 and examples 1 to 7 are shown in Table 1 below, and other production process parameters such as a negative electrode sheet, a positive electrode sheet, a separator, an electrolyte, a battery, etc. are substantially the same, for example, the coating weight of the second negative electrode active material layer is 140mg/1540.25cm 2 The coating weight of the first negative electrode active material layer was 20mg/1540.25cm 2 The thickness of the first anode active material layer is 15 μm, the thickness of the second anode active material layer is 105 μm, and the compaction density of the anode piece is 1.55g/cm 3 。
TABLE 1
The measurement methods of the respective performance parameters of the examples and comparative examples are as follows.
(1) Collector thickness test
And using a ten-thousandth ruler to align the current collector, and rotating the ten-thousandth ruler to test the reading h2.
(2) Pole piece thickness test
And (3) using a ten-thousandth ruler, aligning the pole pieces, and rotating the ten-thousandth ruler to test the reading h1.
(3) Pole piece compaction test
The punched sheet has an area of 1540.25mm 2 Is used as the pole piece of a balanceThe weighing mass is m1; the punched sheet has an area of 1540.25mm 2 The current collector of (2) was weighed with a balance to a mass of m2, and the above thicknesses h1 and h2 were used to calculate the compaction pd= (m 1-m 2)/(h 1-h 2).
(4) Graphite powder OI value test
Taking graphite powder, obtaining diffraction peaks by XRD test, and calculating the peak intensity ratio of C004/C110 to obtain the OI value of the graphite powder.
(5) Pole piece OI value test
Taking a pole piece, testing by XRD to obtain diffraction peak, and calculating the peak intensity ratio of C004/C110 to obtain the pole piece OI value.
(6) Pole piece adhesive force
The method comprises the steps of sticking a double-sided adhesive tape on a steel plate, cutting a cold-pressed pole piece into a 20mm strip, sticking the strip on the double-sided adhesive tape, rolling the strip back and forth for 4 times by using a roller, clamping one end of a slurry pole piece strip on a tension machine clamp, starting a tension machine test, and completing the test to obtain a binding force value.
(7) Cohesive force of pole piece
The method comprises the steps of sticking a double-sided adhesive tape on a steel plate, cutting a cold-pressed pole piece into a 20mm strip, sticking the strip on the double-sided adhesive tape, centering and sticking special cohesive force adhesive paper for an anode on the pole piece, cutting a white paper strip with the width of 20mm and the length of 60mm, inserting the white paper into a gap between the pole piece and the green glue, overlapping the gap by about 15mm, rolling the strip back and forth for 4 times by using a roller, clamping the slurry white paper on a tension machine clamp, starting a tension machine test, and completing the test to obtain cohesive force values.
(8) Full charge XY elongation
Disassembling the battery, taking out the negative electrode plate, placing the empty foil area of the negative electrode plate on the X-ray, and testing the size reading of the empty foil area from the width direction of the electrode plate, wherein a1 is calculated; and (3) placing the fully charged pole piece with the active material layers coated on the two sides on the X-ray, testing the size reading of the current collector from the width direction of the pole piece, counting a2, and calculating (a 2-a 1)/a which is 100% to be the fully charged expansion rate. (9) MMC expansion rate of battery with 25 ℃ cycle fixed number (500 cls, for example)
Charging and discharging an initial battery for 1cls, and measuring the initial thickness of the battery to be H by using a micrometer 1 . The battery is charged and discharged for 500cls continuously, and the thickness of the battery is measured to be H by using a micrometer 2 . The retention rate of MMC with the thickness of 500cls after 25 ℃ cycle is (H) 1 -H 2 )/H 1 *100%. (10) Cell PPG expansion rate of 25 ℃ cycle fixed circle number (500 cls)
Charging and discharging 1cls of initial battery, and measuring initial thickness of battery to H by using flat plate thickness measuring instrument 1 . The charge and discharge were continued for 500cls, and the thickness of the battery was measured to be H using a flat plate thickness measuring instrument 2 . Its thickness retention rate of 500cls at 25℃cycle was (H) 1 -H 2 )/H 1 *100％。
As can be seen from table 1: compared with comparative examples 1 to 4, the negative electrode sheets of examples 1 to 7 had significantly lower battery MMC expansion rate and battery PPG expansion rate in the case of securing the adhesive force and cohesive force of the sheets, indicating that the expansion of the battery was smaller, the energy density was higher, and furthermore, the difference between the battery MMC expansion rate and the battery PPG expansion rate was smaller than 0.2% or 0.3%, indicating that the deformation of the battery was smaller. Remarks: the closer the battery MMC expansion ratio and the battery PPG expansion ratio are (the smaller the difference value is), the smaller the deformation of the battery is, and on the contrary, the larger the deformation of the battery is. (deformation of a battery refers to surface irregularities such as bulging of the battery surface, warping of both ends, protruding points on the surface, etc.).
In table 2, in each of examples 9 to 18, the OI values of the graphite powders in the first anode active material layer were 4.1, the OI values of the graphite powders in the second anode active material layer were 3, the OI values of the first anode active material layer were 15, the OI values of the first anode active material layer were 9, and the thickness of the copper foil was 3 μm; the difference is shown in the following table 2, and the proportion of each functional component of the two kinds of negative electrode slurry, the positive electrode plate, the diaphragm, the electrolyte, the battery and other preparation process parameters are the same.
TABLE 2
As can be seen from table 2: in examples 8 to 13, the weight ratio of the first anode active material layer to the second anode active material layer was adjusted within a reasonable range (0.11 to 0.33), the battery MMC expansion ratio and the battery PPG expansion ratio were not substantially affected, and the battery MMC expansion ratio and the battery PPG expansion ratio of examples 9 to 14 were substantially close, compared to comparative examples 1 to 5, indicating that the deformation of the battery was small.
As can be seen from table 2: in examples 14 to 17, the thickness of the anode active material layer (sum of thicknesses of the first and second anode active material layers) was adjusted without changing the battery MMC expansion ratio and the battery PPG expansion ratio, with the other parameters being the same (coating weight ratio of the first and second anode active material layers was 1:7).
The above embodiments are only for illustrating the technical solution of the present application and not for limiting, and although the present application has been described in detail with reference to the above preferred embodiments, it should be understood by those skilled in the art that the technical solution of the present application may be modified or substituted without departing from the spirit and scope of the technical solution of the present application.

Claims (11)

1. A negative electrode tab, comprising:
the negative electrode current collector is a copper foil, and the thickness of the copper foil is 1-4 mu m;
a negative electrode active material layer located on at least one surface of the negative electrode current collector, the negative electrode active material layer including:
a first anode active material layer located on a surface of the anode current collector, the first anode active material layer including a first anode active material, the first anode active material layer having an OI value of 13 to 20; and
the second anode active material layer is positioned on the surface, facing away from the anode current collector, of the first anode active material layer, the second anode active material layer comprises a second anode active material, the OI value of the second anode active material layer is 5-10, and the weight of the second anode active material layer is larger than that of the first anode active material layer;
the OI value of the first anode active material layer is the peak area ratio of 004 characteristic diffraction peaks to 110 characteristic diffraction peaks in an X-ray diffraction spectrogram of the first anode active material layer;
the OI value of the second anode active material layer is a peak area ratio of 004 characteristic diffraction peaks to 110 characteristic diffraction peaks in an X-ray diffraction spectrum of the first anode active material layer.
2. The anode electrode tab of claim 1, wherein a weight ratio of the first anode active material layer to the second anode active material layer is 0.11 to 0.35.
3. The anode electrode tab of claim 1, wherein a weight ratio of the first anode active material layer to the second anode active material layer is 0.20 to 0.32.
4. The anode electrode tab according to claim 1, wherein the anode active material layer has a thickness of 90 μm to 130 μm.
5. The negative electrode tab of claim 1, wherein the first negative electrode active material is graphite, the powder of the graphite having an OI value of 3 to 8;
the powder OI value of the graphite is the peak area ratio of 004 characteristic diffraction peaks to 110 characteristic diffraction peaks in an X-ray diffraction spectrogram of the powder of the graphite.
6. The negative electrode tab of claim 1, wherein the second negative electrode active material is graphite, the powder of the graphite having an OI value of 1 to 5;
the powder OI value of the graphite is the peak area ratio of 004 characteristic diffraction peaks to 110 characteristic diffraction peaks in an X-ray diffraction spectrogram of the powder of the graphite.
7. The anode electrode tab of claim 1, wherein the coating weight of the second anode active material layer is 100mg/1540.25mm 2 To 160mg/1540.25mm 2 。
8. The anode according to claim 1A sheet, characterized in that the coating weight of the first anode active material layer is 20mg/1540.25mm 2 To 50mg/1540.25mm 2 。
9. The anode electrode tab according to claim 1, wherein the compacted density of the anode active material layer is 1.47g/cm 3 To 1.60g/cm 3 。
10. A lithium ion battery comprising a positive electrode sheet, a negative electrode sheet and an electrolyte, wherein the negative electrode sheet is the negative electrode sheet according to any one of claims 1 to 9.
11. An apparatus comprising a lithium-ion battery according to claim 10.
CN202410070777.9A 2024-01-17 2024-01-17 Negative pole piece, lithium ion battery and device Pending CN117832394A (en)

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