CN116525835A - Composite current collector, positive plate and secondary battery - Google Patents
Composite current collector, positive plate and secondary battery Download PDFInfo
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- CN116525835A CN116525835A CN202310352184.7A CN202310352184A CN116525835A CN 116525835 A CN116525835 A CN 116525835A CN 202310352184 A CN202310352184 A CN 202310352184A CN 116525835 A CN116525835 A CN 116525835A
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/64—Carriers or collectors
- H01M4/66—Selection of materials
- H01M4/665—Composites
- H01M4/667—Composites in the form of layers, e.g. coatings
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- H—ELECTRICITY
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/64—Carriers or collectors
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- H01M4/664—Ceramic materials
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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- H—ELECTRICITY
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
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Abstract
The invention belongs to the technical field of secondary batteries, and particularly relates to a composite current collector which comprises a high polymer substrate layer, a bonding layer arranged on at least one surface of the high polymer substrate layer, a metal conductive layer arranged on one side of the bonding layer far away from the high polymer substrate layer, and a surface reinforcing layer arranged on one side of the metal conductive layer far away from the bonding layer; the surface enhancement layer comprises the following components in parts by weight: 65-110 parts of inorganic filler, 1-10 parts of binder and 0.2-2 parts of conductive agent. The composite current collector has higher strength, is not easy to wrinkle when being rolled, is firm in bonding between the substrate layer and the metal layer, is not easy to fall off, and is coated on the surface, so that burrs are shielded and coated during safety test, and the safety is good.
Description
Technical Field
The invention belongs to the technical field of secondary batteries, and particularly relates to a composite current collector, a positive plate and a secondary battery.
Background
The lithium ion battery has the advantages of high energy density, no memory effect, long cycle life, environmental friendliness and the like, and is widely applied to products such as 3C, electric automobiles, electric tools and the like. As the competition in the lithium battery industry is more and more intense, the requirement on the energy density of the lithium battery is also more and more high, and the adoption of the composite current collector is a mainstream method adopted by the industry for solving the problem. The common composite current collector is a typical sandwich structure, wherein a layer of high polymer material is arranged in the middle of the composite current collector, and a metal conductive layer is deposited on one side or two sides of the composite current collector in a vapor deposition mode. Taking 8 μm composite aluminum foil (1 μm+6μm+1μm, namely, the thickness of the aluminized layers on two sides is 1 μm, and the thickness of the polymer material is 6 μm) as an example, compared with 8 μm conventional aluminum foil, the weight can be reduced by 40%, the cell mass can be reduced by 1.2% (the aluminum foil in the cell accounts for 3%), and the mass energy density can be increased by 1.2%. In addition, the use of the composite current collector can also reduce the generation of section burrs when the pole piece is broken, so that the probability of short circuit of the battery core is reduced, and the safety performance of the battery is improved.
However, the conventional composite current collector has the following problems in the use process:
1. the ductility of the polymer layer in the composite current collector is very good, and the polymer layer is very easy to recover after rolling, so that very serious wrinkling is caused, especially under the condition of large compaction density, the subsequent winding process can not be performed, and the processability is poor;
2. the cross section of the composite current collector is not easy to generate burrs when the composite current collector is subjected to safety test, but the surface of the composite current collector is not protected, and the risk of short-circuit objects still exists;
3. the bonding force between the composite current collector and the active material is small, so that the separation of the metal conductive layer and the active material easily occurs in the circulation process, the internal resistance of the battery cell is increased, and the multiplying power and the circulation performance are deteriorated;
because the compatibility of the polymer film base material and the metal conductive layers on two sides is poor, the binding force is small, and the metal conductive layers are easy to fall off under the swelling action of electrolyte after rolling under the condition of high pressure density, so that the cycle performance of the battery core is reduced.
The existence of the problems limits the use of the composite current collector, and the problems are urgent to be solved when the composite current collector is applied in a large scale.
Disclosure of Invention
One of the objects of the present invention is: aiming at the defects of the prior art, the composite current collector is provided with higher strength, is not easy to wrinkle during rolling, is firmly bonded with a base material layer and a metal layer, is not easy to fall off, and is coated on the surface, so that burrs are shielded and coated during safety test, and the safety is good.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
a composite current collector comprises a high polymer substrate layer, a bonding layer arranged on at least one surface of the high polymer substrate layer, a metal conductive layer arranged on one side of the bonding layer away from the high polymer substrate layer, and a surface reinforcing layer arranged on one side of the metal conductive layer away from the bonding layer.
Wherein, the surface enhancement layer comprises the following components in parts by weight: 65-110 parts of inorganic filler, 1-10 parts of binder and 0.2-2 parts of conductive agent.
Wherein the surface density of the surface enhancement layer is 0.5-2 mg/cm 2 。
Wherein the inorganic filler has a compaction density of 1.0 to 3.5g/cm when tested at a pressure of 5 tons 3 。
Under the common regulation and control of the surface density and the compaction density, the surface enhancement layer with higher mechanical strength, thinner thickness and smaller influence on the energy density can be obtained, and the rolling wrinkling of the pole piece and the exposure of burrs generated by the section can be effectively improved.
Wherein the inorganic filler comprises a ceramic material. The ceramic material can further improve the safety performance of the battery cell.
Wherein the ceramic material comprises Al 2 O 3 、Al(OH) 3 、Mg(OH) 2 One or more of boehmite.
Wherein the inorganic filler also comprises lithium salt, and the mass ratio of the ceramic material to the lithium salt in the inorganic filler is 1:0.1-1:5. The ceramic material and the lithium salt are used simultaneously, so that the surface enhancement layer with the performance can be obtained, and the energy density and the electrical performance of the battery core can be improved while the safety performance of the battery core is improved.
More preferably, in the inorganic filler, the mass ratio of the ceramic material to the lithium salt is 1:2-1:3. At this time, the safety performance, energy density and electrical performance (storage, circulation, multiplying power, etc.) of the battery cell are better.
Preferably, the lithium salt comprises LiCoO 2 、LiNiO 2 、LiVO 2 、LiCrO 2 、LiMn 2 O 4 、LiCoMnO 4 、Li 2 NiMn 3 O 8 、LiNi 0.5 Mn 1.5 O 4 、LiCoPO 4 、LiMnPO 4 、LiFePO 4 、LiNiPO 4 、LiMn x Fe 1-x PO 4 (x＝0.4～0.9)、LiCoFSO 4 At least one of them. The addition of lithium salt can improve the energy density and electrical performance of the battery cell.
More preferably, the lithium salt comprises LiMnPO 4 、LiMn x Fe 1-x PO 4 (x＝0.4～0.9)、LiFePO 4 At least one of them. These lithium salts are readily available and have better safety properties or can better enhance the electrical properties of the cell.
Wherein the particle size Dv50 of the inorganic filler is 0.1-5 μm. The inorganic filler with the particle size range is beneficial to the buffer and support effect of the surface enhancement layer, and meanwhile, the processing performance of the material during coating is not affected.
Wherein the binder comprises one or more of polyvinylidene fluoride, styrene-butadiene rubber, sodium carboxymethyl cellulose, polyacrylic acid, polyvinyl alcohol, polyamide, polyethyleneimine and polyimide.
Wherein the conductive agent comprises one or more of acetylene black, conductive carbon black, artificial graphite, metal fiber, carbon nanotube and graphene.
Wherein the polymer substrate layer comprises one or more of polyethylene, polypropylene, polyethylene terephthalate, polyethylene naphthalate, poly-p-phenylene terephthalamide and polyimide, and the thickness of the polymer substrate layer is 1-20 mu m.
Wherein the bonding layer is a bonding layer containing nano aluminum oxide and/or nano silicon oxide. The nano aluminum oxide and the nano silicon oxide can obviously increase the roughness of the surface of the high polymer substrate, provide interfacial chemical bonding, obviously improve the bonding force between the high polymer substrate and the aluminum layer, ensure that the high polymer substrate layer and the metal conductive layer are firmly bonded and are not easy to fall off.
The second object of the present invention is: the positive plate has good multiplying power performance, safety performance and cycle performance.
The positive plate comprises a positive electrode active material coating and the composite current collector, wherein the positive electrode active material coating is arranged on one side of the surface enhancement layer, which is far away from the metal conductive layer.
The third object of the present invention is to: provided is a secondary battery having good rate performance, safety performance and cycle performance.
A secondary battery comprises the positive plate. The secondary battery comprises a positive plate, a negative plate, a separation film, electrolyte and a shell, wherein the separation film is used for separating the positive plate from the negative plate, and the shell is used for sealing and packaging the positive plate, the negative plate, the separation film and the electrolyte.
Compared with the prior art, the invention has the beneficial effects that: the composite current collector is provided with the surface enhancement layer, has good buffer supporting effect and cladding protection effect, can increase the overall strength of the pole piece, can limit the deformation of the high polymer substrate layer during rolling, thereby improving the wrinkling phenomenon, and can also clad the surface of the pole piece during safety test, so that the short circuit caused by the exposure of burrs generated by the section is avoided. The composite current collector is also provided with a bonding layer, so that the bonding force between the high polymer base material and the metal conductive layers at two sides can be increased, and the metal conductive layers are prevented from falling off easily under the conditions of rolling under high pressure and under the swelling action of electrolyte.
Drawings
Fig. 1 is a schematic structural view of a composite current collector of the present invention.
Fig. 2 is a comparative graph after rolling of a conventional pole piece of the prior art and a composite current collector of the present invention.
FIG. 3 is a graph comparing a conventional pole piece of the prior art with a composite current collector of the present invention after cycling (800 cls@25℃).
Wherein: 1. a composite current collector; 11. a polymer base material layer; 12. a bonding layer; 13. a metal conductive layer; 14. surface enhancement layer.
Detailed Description
The invention will be described in further detail with reference to the following detailed description and the accompanying drawings, but the embodiments of the invention are not limited thereto.
A composite current collector 1 comprises a polymer substrate layer 11, a bonding layer 12 arranged on at least one surface of the polymer substrate layer 11, a metal conductive layer 13 arranged on one side of the bonding layer 12 far away from the polymer substrate layer 11, and a surface reinforcing layer 14 arranged on one side of the metal conductive layer 13 far away from the bonding layer 12.
The surface enhancement layer 14 is arranged on the surface of the composite current collector 1, so that buffering and supporting can be provided for the pole piece, the wrinkling phenomenon of the pole piece of the composite current collector 1 after rolling is obviously improved, and the processing performance of the battery cell is improved. Meanwhile, the surface enhancement layer 14 can also cover the surface of the composite current collector 1, so that the risk of short circuit is reduced, the surface enhancement layer 14 also increases the binding force between the composite current collector 1 and active substances, the problem that the active layers fall off after long-term circulation of the battery cell is solved, the increase of internal resistance is slowed down, and the multiplying power and the circulation performance are improved; meanwhile, the bonding layer 12 is arranged between the high polymer substrate layer 11 and the metal conductive layer 13 in the composite current collector 1, so that the compatibility and the bonding force of the high polymer substrate layer 11 and the metal conductive layer 13 are increased, and the problem that the metal conductive layer 13 falls off after long-term circulation of a battery cell is relieved. The polymer substrate layer 11 is made of one or more materials selected from Polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), poly-paraphenylene terephthalamide (PPA) and Polyimide (PI), and the thickness of the polymer substrate layer 11 is 1-20 μm. Preferably, the thickness of the polymeric substrate layer 11 is 4 μm, 6 μm, 8 μm or 10 μm.
Wherein, the surface enhancement layer 14 comprises the following raw materials in parts by weight: 65-110 parts of inorganic filler, 1-10 parts of binder and 0.2-2 parts of conductive agent. The surface reinforcing layer 14 includes an inorganic filler capable of providing cushioning and support to the composite current collector 1, and improving wrinkling during pole piece rolling, thereby improving processability. The conductive agent can improve the conductivity of the surface enhanced layer 14 and reduce the resistance; the binder is capable of mixing the inorganic filler and the conductive agent with each other and firmly binding with the surface of the metal conductive layer 13. An appropriate amount and size of inorganic filler can be mixed in the binder to provide cushioning and support, so it is necessary to set the particle size of the inorganic filler to be in an appropriate range, otherwise it is difficult to function.
Preferably, when the surface enhancing layer 14 is applied by pulping, 50-200 parts by weight of solvent is added based on the above formulation of the surface enhancing layer 14 to adjust the solid content of the slurry, thereby realizing the application with different surface densities. In the subsequent cell manufacturing process, the solvent in the coating is evaporated. Preferably, the solvent may employ NMP.
Wherein the surface density of the surface reinforcing layer 14 is 0.5-2 mg/cm 2 . The surface enhancement layer 14 under the surface density can not generate a coating leakage phenomenon, can play an effective supporting and buffering role in the composite current collector 1, limit the deformation of the high polymer substrate layer 11 during rolling, improve pole piece wrinkling, and can also coat the surface of the pole piece during safety test, so that burrs generated by the section are prevented from being exposed to cause short circuit. If the surface density of the surface enhancement layer 14 is too small, it may cause coating leakage, while if the surface density is too large, it may cause the thickness of the surface enhancement layer 14 to be too thick, which affects the energy density and cycle performance of the battery cell. The surface enhancement layer 14 has a certain surface density, which can make the composite current collector 1 have good safetyPerformance and thinner thickness. Preferably, the surface enhancing layer 14 has a thickness of 3 to 12 μm.
Wherein the inorganic filler has a compaction density of 1.0 to 3.5g/cm when tested at a pressure of 5 tons 3 . Preferably, the inorganic filler has a compacted density of 1.0 to 3.3g/cm when tested at a pressure of 5 tons 3 . The compaction density of the inorganic filler may affect the coating thickness of the surface enhancing layer 14, and too small compaction density may result in too thick coating thickness, affecting the energy density and cycle performance, rate performance, and other electrical properties of the cell.
Wherein the inorganic filler comprises a ceramic material. The ceramic material can further improve the safety performance of the battery cell.
Preferably, the ceramic material comprises Al 2 O 3 、Al(OH) 3 、Mg(OH) 2 One or more of boehmite.
Preferably, the inorganic filler further comprises a lithium salt.
More preferably, in the inorganic filler, the mass ratio of the ceramic material to the lithium salt is 1:0.1-1:5. The use of both ceramic materials and lithium salts not only results in a surface enhancement layer 14 having the above properties, but also increases the energy density and electrical properties of the cell while improving the safety properties of the cell.
More preferably, in the inorganic filler, the mass ratio of the ceramic material to the lithium salt is 1:2-1:3. At this time, the safety performance, energy density and electrical performance (storage, circulation, multiplying power, etc.) of the battery cell are better.
Preferably, the lithium salt comprises LiCoO 2 、LiNiO 2 、LiVO 2 、LiCrO 2 、LiMn 2 O 4 、LiCoMnO 4 、Li 2 NiMn 3 O 8 、LiNi 0.5 Mn 1.5 O 4 、LiCoPO 4 、LiMnPO 4 、LiFePO 4 、LiNiPO 4 、LiMn x Fe 1-x PO 4 (x＝0.4～0.9)、LiCoFSO 4 At least one of them. The addition of lithium salt can improve the energy density and electrical performance of the battery cell.
More preferably, the lithium salt comprises LiMnPO 4 、LiMn x Fe 1-x PO 4 (x＝0.4～0.9)、LiFePO 4 At least one of them. These lithium salts are readily available and have better safety properties or can better enhance the electrical properties of the cell. The ceramic and lithium salt may be used in combination, such as boehmite and LiFePO 4 The mixed use can provide good supporting effect and reduce the material cost.
The inorganic filler has a compaction density of 1.0-3.5 g/cm when tested under a pressure of 5 tons 3 . The compaction density of the inorganic filler can affect the coating thickness of the surface enhancement layer 14, and too small compaction density can cause too thick coating thickness, reduce the energy density of the battery core, and too high compaction density is unfavorable for infiltration of the electrolyte in the later stage, and affects the cycle performance, the multiplying power performance and other electrical properties of the battery core.
Wherein the particle size of the inorganic filler is 0.1-5 mu m. The particle size of the inorganic filler is set to be a certain size, so that stirring and dispersion are not affected due to the fact that the particle size of the inorganic filler is too small, and the condition of coating missing due to the fact that the particle size is too large is avoided. The particle size range of the particles is selected to facilitate cushioning and support of the surface enhancing layer 14 without affecting processability. In addition, the introduction of the inorganic filler is favorable for heat conduction, and the safety performance of the battery cell is improved to a certain extent.
Wherein the binder comprises one or more of polyvinylidene fluoride, styrene-butadiene rubber, sodium carboxymethyl cellulose, polyacrylic acid, polyvinyl alcohol, polyamide, polyethyleneimine and polyimide. The binder binds the inorganic filler and the conductive agent together and uniformly mixes the inorganic filler and the conductive agent to form a whole with good cohesiveness. The binder content is too low, the cohesiveness is poor, the content is too high, the dispersion of other substances is not facilitated, and the development of the subsequent coating process is also not facilitated.
Wherein the conductive agent comprises one or more of acetylene black, conductive carbon black, artificial graphite, metal fiber, carbon nanotube and graphene. The conductive agent is advantageous in reducing the contact resistance between the surface-enhancing layer 14 and the composite current collector 1, and between the surface-enhancing layer 14 and the positive electrode active material layer. The conductive agent can adopt one or two different conductive agents, and the multiple conductive agents cooperate, so that good conductivity is obtained, and the consumption of the conductive agent is reduced.
Wherein the polymer substrate layer 11 comprises one or more of polyethylene, polypropylene, polyethylene terephthalate, polyethylene naphthalate, poly-p-phenylene terephthalamide and polyimide, and the thickness of the polymer substrate layer 11 is 1-20 μm. Preferably, the thickness of the polymer base material layer 11 is 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 14 μm, 16 μm, 18 μm, 20 μm.
Wherein the bonding layer 12 is a nano aluminum oxide (AlO) x ) And/or nano silicon oxide (SiO) x ) The thickness of the adhesive layer 12 is 50-100 nm. The bonding layer 12 can obviously increase the roughness of the surface of the polymer substrate, provide interfacial chemical bonding, promote the bonding force between the polymer substrate and the metal conductive layer 13, and alleviate the problem that the metal conductive layer 13 falls off after long-term circulation of the battery cell. Wherein the metal conductive layer 13 is evaporated on the nano adhesive layer 12 by vacuum evaporation, and the metal conductive layer 13 may be one or more of aluminum, copper, nickel, copper alloy, nickel alloy or aluminum alloy. Specifically, alO-containing x The adhesive layer 12 of (c) may be obtained by vacuum evaporation, including a cleaning process and a deposition process. The cleaning process is under high vacuum (< 133.3X10) -4 Pa), treating the surface of the polymer film substrate by using a radio frequency plasma system, introducing a certain polar group on the surface of the polymer film substrate while removing pollutants on the surface of the substrate, and increasing AlO x Adhesion of the layers. The deposition process is to heat aluminum wires with purity not lower than 99.5% to the surface of an evaporation boat at 1400-1600 deg.c while introducing oxygen at 0.1-10L/min to evaporate Al molecules and O 2 Under the action of microwave plasma system above the evaporation boat, the molecules form aluminum ions and oxygen ions, which react fully to deposit on the surface of the base material to obtain a layer of uniform nano AlO x A layer. Containing SiO x The adhesive layer 12 of (2) can be obtained by chemical vapor deposition, and the silicon source isLiquid hexamethyldisiloxane HMDSO, liquid tetramethyldisiloxane TMDSO, or gaseous silane SiH 4 Helium is used as carrier gas, oxygen is used as reaction gas, and the polymer film is deposited on the surface of the polymer film. In particular, by adopting an ion-body enhanced chemical vapor deposition (PECVE), the coating is more uniform, and the deposited silicon oxide is not easy to crack.
Before rolling, the long molecular chains of the polymer base material in the composite current collector 1 are in a natural curled state and intertwined, however, when rolling occurs, the molecular chains are forced to be oriented, and the molecular chains are straightened, so that the ductility of the composite current collector is far greater than that of a conventional metal foil. Taking conventional aluminum foil and composite aluminum foil as examples, the extensibility of conventional aluminum foil is 0.65% and the extensibility of composite aluminum foil is 1.10% when the compaction density is 4.10. After the rolling is finished, the forced orientation of the molecular chains disappears and returns, so that the pole piece is severely wrinkled, and the phenomenon is especially serious under the condition of high compaction density, and even the follow-up winding process cannot be performed. The inorganic filler in the surface reinforcing layer 14 can provide a certain buffering and supporting function, and weakens the forced orientation of the molecular chains of the polymer base material, so that the wrinkling phenomenon of the composite current collector 1 pole piece after rolling can be greatly relieved. As shown in FIG. 2, the two pole pieces each had a compacted density of 4.10g/cm 3 The appearance of the conventional aluminum foil pole piece which does not contain the surface enhancement layer 14 after rolling can be found to be very serious wrinkling, and the appearance of the composite aluminum foil pole piece which contains the surface enhancement layer 14 after rolling can be found to be very flat, so that the subsequent process is not influenced, and the processing performance of the composite current collector 1 battery is improved.
In addition, the introduction of the surface enhancement layer 14 can also improve the safety performance of the composite current collector 1 cell. In general, an internal short circuit occurs when a cell is mechanically abused, and the internal short circuit includes the following 4 types: positive electrode current collector vs. negative electrode active material; the positive electrode current collector is opposite to the negative electrode current collector; the negative electrode current collector is aligned with the positive electrode active material and the positive electrode active material is aligned with the negative electrode active material. The positive electrode current collector and the negative electrode active material are directly contacted, the most serious internal short circuit occurs, the temperature is rapidly increased, the electrolyte and the positive electrode active material are decomposed, the thermal runaway of the battery is extremely easy to induce, and the positive electrode current collector and the negative electrode active material are one of the most dangerous types of the 4 short circuits. For the battery core with the conventional aluminum foil as the positive current collector, the conventional aluminum foil is broken when a safety test is carried out, burrs are easily generated on the section of the conventional aluminum foil, and the conventional aluminum foil is contacted with a negative electrode material to generate a very serious short circuit. The composite aluminum foil is not easy to generate burrs on the section of the composite aluminum foil when the composite aluminum foil breaks due to the specific sandwich structure, but the surface of the composite aluminum foil is exposed, and the risk of short circuit still exists. And the surface reinforcing layer 14 can be firmly adhered to the surface of the composite aluminum foil, so that the occurrence probability of short circuit is greatly reduced. In addition, the surface enhancement layer 14 is coarser than the conductive metal layer, so that the binding force between the positive electrode active substance and the composite current collector 1 is increased after the surface enhancement layer is introduced, the problem that the positive electrode active layer falls off after the battery core circulates for a long time is solved, the increase of internal resistance is slowed down, and the multiplying power and the circulation performance are improved. As shown in fig. 3, (b) the introduction of the surface enhancing layer 14 significantly improved the shedding of the positive electrode active material of the electrode sheet after 800cls@25 ℃ (i.e., 25 ℃ for 800 cycles), whereas the positive electrode active material of the electrode sheet (a) without the surface enhancing layer 14 was shed after 800cls@25 ℃.
The positive plate comprises a positive electrode active material coating and the composite current collector, wherein the positive electrode active material coating is arranged on one side of the surface enhancement layer far away from the metal conductive layer.
The secondary battery comprises the positive plate. The secondary battery of the invention has excellent multiplying power, safety and circularity.
Specifically, a secondary battery may be a lithium ion battery, a sodium ion battery, a magnesium ion battery, a calcium ion battery, a potassium ion battery, or the like. Preferably, the following secondary battery takes a lithium ion battery as an example, the lithium ion battery comprises a positive electrode plate, a negative electrode plate, an isolating film, an electrolyte and a shell, the positive electrode plate comprises the composite current collector 1, the isolating film separates the positive electrode plate from the negative electrode plate, and the shell is used for installing the positive electrode plate, the negative electrode plate, the isolating film and the electrolyte.
The lithium ion battery also comprises electricityAnd the electrolyte comprises an organic solvent, electrolyte lithium salt and an additive. Wherein the electrolyte lithium salt can be LiPF used in high temperature electrolyte 6 And/or LiBOB; liBF used in the low-temperature electrolyte may be used 4 、LiBOB、LiPF 6 At least one of (a) and (b); liBF used in the overcharge-preventing electrolyte may also be used 4 、LiBOB、LiPF 6 At least one of LiTFSI; liClO may also be 4 、LiAsF 6 、LiCF 3 SO 3 、LiN(CF 3 SO 2 ) 2 At least one of them. And the organic solvent may be a cyclic carbonate, including PC, EC; chain carbonates are also possible, including DEC, DMC, or EMC; carboxylic esters, including PP, MA, EA, EP, and the like, are also contemplated. And additives include, but are not limited to, film forming additives, conductive additives, flame retardant additives, overcharge prevention additives, and control of H in electrolytes 2 At least one of an additive for O and HF content, an additive for improving low temperature performance, and a multifunctional additive.
The separator may be a variety of materials suitable for lithium ion battery separators in the art, and may be, for example, a combination of one or more of polyethylene, polypropylene, polyvinylidene fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester, natural fibers, and the like.
The shell is made of one of stainless steel and aluminum plastic films.
Example 1:
(1) Preparation of a positive plate:
providing a composite aluminum foil S1: the composite aluminum foil is provided by Selen Honghu aerospace science and technology Co., ltd, and is composed of PET base material, nanometer AlO deposited on two surfaces of PET base material x Layer (adhesive layer 12) and deposit on nano AlO x The layer surface is composed of a metal Al layer, the thickness of the PET base material is 6 mu m, and the thickness of the PET base material is nanometer AlO x The thickness of the layer was 50nm and the thickness of the metallic Al layer was 1. Mu.m.
Preparation of surface enhancement layer 14S 2: 93 parts by weight of an inorganic filler, 6 parts by weight of PVDF binder, 1 part by weight of a conductive agent and 150 parts by weight of NMP were dissolvedAnd (5) uniformly mixing the agents to prepare the slurry. The inorganic filler is Al 2 O 3 The particle size Dv50 was 0.8 μm and the compacted density measured at a pressure of 5 tons was 2.9g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the The conductive agent is a mixture formed by mixing conductive carbon black and carbon nano tubes in a mass ratio of 1:1. The slurry was applied to both surfaces of the composite aluminum foil obtained in S1 by gravure printing (gravure roll gauge: 90 mesh 73 μm), and the surface density of the single-sided coating was 1mg/cm 2 Simultaneously reserving a groove for welding the tab, and drying to obtain a composite aluminum foil with a surface reinforcing layer 14, wherein the thickness of the single-layer surface reinforcing layer 14 is 6 mu m;
positive electrode active material coating S3: the positive electrode active material, the conductive agent (a mixture of conductive carbon black and carbon nano tubes in a mass ratio of 6:5), the PVDF binder and NMP are uniformly mixed according to a mass ratio of 97.6:1.1:1.3:35 to prepare positive electrode slurry. Coating the positive electrode slurry on the surface of the surface enhancement layer 14, drying and rolling at 85 ℃, coating and drying the positive electrode slurry on the surface enhancement layer on the other side according to the method, and carrying out cold pressing treatment on the positive electrode sheet with the positive electrode active material layer coated on both sides; and then trimming and slitting are carried out to prepare the positive plate of the lithium ion battery, as shown in figure 1.
(2) Preparing a negative electrode sheet:
taking water as a solvent, and mixing graphite, a thickening agent and an SBR binder according to the mass ratio of 97.7:1.1:1.2, uniformly mixing to prepare a lithium ion battery negative electrode slurry with solid content of 50% and certain viscosity, coating the slurry on one surface of a copper foil current collector, drying and rolling at 80 ℃, and then coating and drying the negative electrode slurry on the other surface of the copper foil according to the method to obtain the negative electrode plate with both surfaces coated with active substances.
(3) Preparation of electrolyte:
lithium hexafluorophosphate (LiPF) 6 ) Dissolved in a mixed solvent of dimethyl carbonate (DMC), ethylene Carbonate (EC) and methyl ethyl carbonate (EMC) (the mass ratio of DMC, EC and EMC is 3:5:2) to obtain an electrolyte.
(4) Preparation of the battery:
and winding the prepared positive plate, negative plate and diaphragm into a battery core, wherein the capacity of the battery core is about 5Ah. The diaphragm is positioned between the adjacent positive plate and the negative plate, the positive electrode is welded in the reserved through groove by an aluminum tab, and the negative electrode is led out by a nickel tab in a spot welding manner; and then placing the battery core in an aluminum-plastic packaging bag, baking, injecting the electrolyte, and finally preparing the lithium ion battery through the procedures of packaging, formation, capacity division and the like.
Example 2
The difference from example 1 is that: the adhesive layer 12 of the composite aluminum foil is different, and the adhesive layer 12 of example 2 is nano SiO x The layer is also provided by Sedan Cheng, swiss and Tech.
The remainder is the same as in example 1 and will not be described again here.
Example 3
The difference from example 1 is that: the surface enhancing layer 14 has a different composition. The surface-enhancing layer 14 of example 3 was uniformly mixed with 110 parts by weight of an inorganic filler, 10 parts by weight of a PVDF binder, 2 parts by weight of a conductive agent, and 180 parts by weight of an NMP solvent to prepare a slurry. The surface density of the slurry single-side coating is 1mg/cm 2 The inorganic filler and the conductive agent used were the same as in example 1.
The remainder is the same as in example 1 and will not be described again here.
Example 4
The difference from example 1 is that: the surface enhancing layer 14 has a different composition. The surface-enhancing layer 14 of example 3 was uniformly mixed with 65 parts by weight of an inorganic filler, 1 part by weight of a PVDF binder, 0.2 part by weight of a conductive agent, and 110 parts by weight of an NMP solvent to prepare a slurry. The surface density of the slurry single-side coating is 1mg/cm 2 The inorganic filler and the conductive agent used were the same as in example 1.
The remainder is the same as in example 1 and will not be described again here.
Example 5
The difference from example 1 is that: the surface-enhanced layers 14 have different areal densities, specifically, the solid content of the slurry is adjusted by adjusting the solvent dosage, so that the regulation and control of the areal density are realized.
The surface enhancing layer 14 of example 5 was prepared by: 93 parts by weight of inorganic filler and 6 parts by weight of PVDF binder1 part by weight of a conductive agent and 200 parts by weight of an NMP solvent were uniformly mixed to prepare a slurry. The inorganic filler and the conductive agent used were the same as in example 1. Coating the slurry on the two surfaces of the composite aluminum foil obtained in the step S1 in a gravure printing mode, wherein the surface density of single-side coating is 0.5mg/cm 2 。
The remainder is the same as in example 1 and will not be described again here.
Example 6
The difference from example 1 is that: the areal density of the surface enhancing layer 14 was 2mg/cm 2 Specifically, the solid content of the slurry is adjusted by adjusting the dosage of the solvent, so that the regulation and control of the surface density are realized.
The surface enhancing layer 14 of example 6 was prepared by: 93 parts by weight of an inorganic filler, 6 parts by weight of a PVDF binder, 1 part by weight of a conductive agent and 50 parts by weight of an NMP solvent were uniformly mixed to prepare a slurry. The inorganic filler and the conductive agent used were the same as in example 1. Coating the slurry on the two surfaces of the composite aluminum foil obtained in the step S1 in a gravure printing mode, wherein the surface density of single-side coating is 2mg/cm 2 。
Example 7
The difference from example 1 is that: the inorganic filler in the surface-enhancing layer 14 had a compacted density of 1.0g/cm when tested at a pressure of 5 tons 3 。
The remainder is the same as in example 1 and will not be described again here.
Example 8
The difference from example 1 is that: the inorganic filler in the surface-enhancing layer 14 had a compacted density of 3.3g/cm when tested at a pressure of 5 tons 3 。
The remainder is the same as in example 1 and will not be described again here.
Example 9
The difference from example 1 is that: the inorganic filler in the surface-enhancing layer 14 had a compacted density of 3.5g/cm when tested at a pressure of 5 tons 3 。
The remainder is the same as in example 1 and will not be described again here.
Example 10
The difference from example 1 is that: the inorganic filler species in the surface enhancing layer 14 are different.
The inorganic filler of example 10 is Al 2 O 3 And LiFePO 4 Is a mixture of (a) and (b); wherein LiFePO 4 Has a particle size Dv50 of 0.9 μm and a compacted density of 2.5g/cm measured at a pressure of 5 tons 3 ；Al 2 O 3 And LiFePO 4 The mass ratio of (2) is 1:0.1.
The remainder is the same as in example 1 and will not be described again here.
Example 11
The difference from example 1 is that: the inorganic filler species in the surface enhancing layer 14 are different.
The inorganic filler of example 11 is Al 2 O 3 And LiFePO 4 Is a mixture of (a) and (b); wherein LiFePO 4 Has a particle size Dv50 of 0.9 μm and a compacted density of 2.5g/cm measured at a pressure of 5 tons 3 The method comprises the steps of carrying out a first treatment on the surface of the And Al is 2 O 3 And LiFePO 4 The mass ratio of (2) is 1:2.
The remainder is the same as in example 1 and will not be described again here.
Example 12
The difference from example 1 is that: the inorganic filler species in the surface enhancing layer 14 are different.
The inorganic filler of example 12 is Al 2 O 3 And LiFePO 4 Is a mixture of (a) and (b); wherein LiFePO 4 Particle diameter D of particles v50 0.9 μm, a compaction density of 2.5g/cm measured at a pressure of 5 tons 3 The method comprises the steps of carrying out a first treatment on the surface of the And Al is 2 O 3 And LiFePO 4 The mass ratio of (2) is 1:3.
The remainder is the same as in example 1 and will not be described again here.
Example 13
The difference from example 1 is that: the inorganic filler species in the surface enhancing layer 14 are different.
The inorganic filler of example 13 is Al 2 O 3 And LiFePO 4 Is a mixture of (a) and (b); wherein LiFePO 4 Particle diameter D of particles v50 0.9 μm, a compaction density of 5 tons under pressure of2.5g/cm 3 The method comprises the steps of carrying out a first treatment on the surface of the And Al is 2 O 3 And LiFePO 4 The mass ratio of (2) is 1:5.
The remainder is the same as in example 1 and will not be described again here.
Comparative example 1
The difference from example 1 is that: the surface-enhanced layers 14 have different areal densities, specifically, the solid content of the slurry is adjusted by adjusting the solvent dosage, so that the regulation and control of the areal density are realized.
The surface enhancing layer 14 of comparative example 1 was prepared by: 93 parts by weight of an inorganic filler, 6 parts by weight of a PVDF binder, 1 part by weight of a conductive agent and 500 parts by weight of an NMP solvent were uniformly mixed to prepare a slurry. The inorganic filler and the conductive agent used were the same as in example 1. Coating the slurry on the two surfaces of the composite aluminum foil obtained in the step S1 in a gravure printing mode, wherein the surface density of single-side coating is 0.1mg/cm 2 。
The remainder is the same as in example 1 and will not be described again here.
Comparative example 2
The only difference from example 1 is that: the surface-enhanced layers 14 have different areal densities, specifically, the solid content of the slurry is adjusted by adjusting the solvent dosage, so that the regulation and control of the areal density are realized.
The surface enhancing layer 14 of comparative example 2 was prepared by: 93 parts by weight of an inorganic filler, 6 parts by weight of a PVDF binder, 1 part by weight of a conductive agent and 25 parts by weight of an NMP solvent were uniformly mixed to prepare a slurry. The inorganic filler and the conductive agent used were the same as in example 1. Coating the slurry on the two surfaces of the composite aluminum foil obtained in the step S1 in a gravure printing mode, wherein the surface density of single-side coating is 2.5mg/cm 2 。
Comparative example 3
The difference from example 1 is that: the inorganic filler in the surface-enhancing layer 14 had a compacted density of 0.8g/cm when tested at a pressure of 5 tons 3 。
The remainder is the same as in example 1 and will not be described again here.
Comparative example 4
The difference from example 1 is that: the positive electrode sheet does not include the surface enhancing layer 14.
The remainder is the same as in example 1 and will not be described again here.
Comparative example 5
The difference from example 1 is that: the positive plate does not contain a bonding layer 12, namely nanometer AlO x A layer.
The remainder is the same as in example 1 and will not be described again here.
To verify the effect of the introduction of the surface enhancing layer 14 on the performance of the cell of the composite current collector 1, the rate performance, needling, single-side extrusion, heavy impact and cycle performance of the cell were tested.
The multiplying power performance testing method comprises the following steps: according to the method specified in GB31241-2014 safety requirements of lithium ion batteries and battery packs for portable electronic products, a battery core is charged to 4.45V at a constant current and constant voltage of 0.7C, the cut-off rate is 0.02C, then discharged to 3.0C at 2.0C, and the discharge capacity is recorded.
The safety performance testing method comprises the following steps: under the condition that the ambient temperature is 25+/-2 ℃, discharging the battery core to 3.0V at a constant current of 0.5C, then charging to 4.45V at a constant current and constant voltage of 1.5C, and performing needling, unilateral extrusion and heavy object impact test according to a method prescribed in GB31241-2014 safety requirements of lithium ion batteries and battery packs for portable electronic products, wherein the battery is free from fire and explosion.
The method for testing the cycle performance comprises the following steps: and discharging the battery cell to 3.0V at a constant current of 0.2 under the condition that the ambient temperature is 25+/-2 ℃, then charging to 4.45V at a constant current and constant voltage of 1.5C, recording the battery cell at a cut-off rate of 0.05C, and recording the voltage, the internal resistance, the capacity and the thickness (600 gPPG for thickness measurement) of the battery cell when the battery cell is fully charged for the first time. The circulation process is as follows: discharging to 3V at constant current of 0.2C; charging to 4.25V at a constant current of 1.5C; charging to 4.45V at a constant current of 1.2C; charging to 4.48V with constant current and constant voltage of 0.8C, and stopping multiplying power of 0.19C; charging to 4.45V with constant current and constant voltage of 2A, and cutting-off multiplying power of 0.05C; discharge to 3V at a constant current of 1.0C. After the above steps are completed for 1 cycle and 49 times, the recovery of the small current is carried out according to the following system: discharging to 3V at constant current of 0.2C; charging to 4.25V at a constant current of 1.5C; charging to 4.45V at a constant current of 1.2C; charging to 4.48V with constant current and constant voltage of 0.8C, and stopping multiplying power of 0.19C; charging to 4.45V with constant current and constant voltage of 2A, and cutting-off multiplying power of 0.05C; discharge to 3V at 0.2C constant current. The full charge core voltage, internal resistance, thickness (600 gpg for thickness measurement) were recorded every 50 weeks.
The secondary batteries obtained in examples 1 to 13 and comparative examples 1 to 5 were tested, and the test results are shown in table 1 below.
As can be seen from the test results of table 1 above for example 1 and comparative example 4, after the surface reinforcing layer 14 was introduced, the composite current collector 1 was free from wrinkling, and the passing rate of the needling, single-side extrusion and weight impact tests were all 100%, and both the multiplying power and the cycle performance were improved. As is clear from examples 1, 2 and 5, the introduction of nano aluminum oxide and nano silicon oxide can improve the cycle performance of the cell, and comparative example 5 causes the cycle performance of the cell to be reduced due to the lack of the adhesive layer 12; and the test proves that the adhesive force of the comparative example 5 is also obviously reduced, and the conductive metal layer is easy to fall off under the soaking of the electrolyte. Comparison of examples 1, 3 and 4 shows that the technical effects of the present invention can be achieved within the formulation of the surface enhancing layer 14 of the present invention; the test results of examples 1, examples 5 to 6 and comparative examples 1 to 2 show that too small a coating surface density of the surface enhanced layer 14 deteriorates the safety performance of the battery cell, and too low a coating surface density of the surface enhanced layer 14 makes it impossible to perform the buffer supporting function well, resulting in wrinkling of the pole piece, and too large a coating surface density of the surface enhanced layer 14 also results in a decrease in the electrical performance of the battery cell. From the test results of example 1, examples 7 to 9 and comparative example 3, it is understood that too low a compaction density of the inorganic filler in the surface-enhanced layer 14 may deteriorate the rate and cycle performance of the battery cell. From the above analysis we can conclude that: by introducing the surface enhancement layer 14 with certain surface density on the surface of the conventional current collector, the processing performance of the battery cell is improved, the wrinkling problem of the composite current collector 1 during pole piece rolling is solved, and the multiplying power, safety and cycle performance of the battery cell are improved. The introduction of nano aluminum oxide or silicon oxide on the surface of the polymer film substrate can slow down the problem of falling of the metal conducting layer 13 after long-term circulation of the battery cell, and improve the circulation performance.
Variations and modifications of the above embodiments will occur to those skilled in the art to which the invention pertains from the foregoing disclosure and teachings. Therefore, the present invention is not limited to the above-described embodiments, but is intended to be capable of modification, substitution or variation in light thereof, which will be apparent to those skilled in the art in light of the present teachings. In addition, although specific terms are used in the present specification, these terms are for convenience of description only and do not limit the present invention in any way.
Claims (10)
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| CN117382274A (en) * | 2023-10-20 | 2024-01-12 | 江阴纳力新材料科技有限公司 | An air composite copper current collector and its preparation method |
| CN119056877A (en) * | 2024-09-25 | 2024-12-03 | 艾姆西艾(宿迁)电池技术有限公司 | Rolling shaping equipment for manufacturing composite current collector with anti-bias effect |
| WO2025107774A1 (en) * | 2023-11-24 | 2025-05-30 | 宁德时代新能源科技股份有限公司 | Composite current collector, electrode sheet, secondary battery, and electric apparatus |
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| CN110676460A (en) * | 2018-12-29 | 2020-01-10 | 宁德时代新能源科技股份有限公司 | Electrode plate and electrochemical device |
| CN114583100A (en) * | 2021-12-23 | 2022-06-03 | 惠州锂威新能源科技有限公司 | Positive plate, preparation method thereof and lithium ion battery |
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| CN107154499A (en) * | 2017-04-14 | 2017-09-12 | 深圳鑫智美科技有限公司 | A kind of lithium battery containing new current collector and preparation method thereof |
| CN110676460A (en) * | 2018-12-29 | 2020-01-10 | 宁德时代新能源科技股份有限公司 | Electrode plate and electrochemical device |
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| CN117382274A (en) * | 2023-10-20 | 2024-01-12 | 江阴纳力新材料科技有限公司 | An air composite copper current collector and its preparation method |
| WO2025107774A1 (en) * | 2023-11-24 | 2025-05-30 | 宁德时代新能源科技股份有限公司 | Composite current collector, electrode sheet, secondary battery, and electric apparatus |
| CN119056877A (en) * | 2024-09-25 | 2024-12-03 | 艾姆西艾(宿迁)电池技术有限公司 | Rolling shaping equipment for manufacturing composite current collector with anti-bias effect |
| CN119056877B (en) * | 2024-09-25 | 2025-04-18 | 艾姆西艾(宿迁)电池技术有限公司 | Rolling shaping equipment for manufacturing composite current collector with anti-bias effect |
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