CN118202483A - Electrochemical device and electronic device including the same - Google Patents

Electrochemical device and electronic device including the same Download PDF

Info

Publication number
CN118202483A
CN118202483A CN202180031462.8A CN202180031462A CN118202483A CN 118202483 A CN118202483 A CN 118202483A CN 202180031462 A CN202180031462 A CN 202180031462A CN 118202483 A CN118202483 A CN 118202483A
Authority
CN
China
Prior art keywords
functional layer
electrochemical device
current collector
lithium
adhesive
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN202180031462.8A
Other languages
Chinese (zh)
Inventor
李志愿
李娅洁
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Dongguan Amperex Technology Ltd
Original Assignee
Dongguan Amperex Technology Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Dongguan Amperex Technology Ltd filed Critical Dongguan Amperex Technology Ltd
Publication of CN118202483A publication Critical patent/CN118202483A/en
Pending legal-status Critical Current

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Secondary Cells (AREA)
  • Battery Electrode And Active Subsutance (AREA)
  • Connection Of Batteries Or Terminals (AREA)

Abstract

The present application relates to an electrochemical device and an electronic device including the same. The electrochemical device provided by the application comprises a positive electrode, wherein the positive electrode comprises a current collector, an active material layer, a first functional layer positioned between the current collector and the active material layer and a second functional layer positioned between the first functional layer and the active material layer, the adhesion force between the current collector and the first functional layer is F1, the adhesion force between the first functional layer and the second functional layer is F2, and the adhesion force between the second functional layer and the active material layer is F3, so that the following conditions are satisfied: f1 > F2, F3 > F2. The electrochemical device provided by the application can improve the safety performance of the mechanical abuse.

Description

Electrochemical device and electronic device including the same Technical Field
The present application relates to the field of energy storage technologies, and in particular, to an electrochemical device and an electronic device including the same.
Background
The lithium ion battery has the advantages of high energy density, high power, long cycle life and the like, and is widely applied to electric automobiles and consumer electronic products. However, in the use process of the lithium ion battery, the lithium ion battery may be abused by extrusion, impact, needling and other machines, so that the battery is short-circuited, and the safety performance risk is very high. Therefore, the safety problem of the lithium ion battery limits the application scene of the lithium ion battery to a certain extent.
In the prior art, a coating layer is coated on the surface of a positive current collector, so that the contact resistance between the positive current collector and a negative electrode and between the positive current collector and the negative current collector is increased, and the heat release of a short circuit is reduced, but the adhesion between the existing coating layer and the positive active material layer is strong (as shown in fig. 2), so that the positive current collector is limited in protection, the coating layer is driven to be stripped when the positive active material layer is stripped in the impact and penetrating nail test of a battery, the positive current collector is in an exposed state actually, and the negative active material layer or the negative current collector is very easy to be in direct contact with the positive current collector, so that the short circuit is caused, and a large amount of heat release is generated.
Disclosure of Invention
In view of the shortcomings existing in the prior art, the application provides an electrochemical device, wherein a double-layer coating is arranged between a current collector and an active material layer of an anode, and a strong bonding interface and a weak bonding interface are combined, so that the protection of the current collector is increased during mechanical abuse, and the mechanical safety performance of the electrochemical device is obviously improved. The application also relates to an electronic device comprising such an electrochemical device.
In a first aspect, the present application provides an electrochemical device comprising a positive electrode including a current collector, an active material layer, a first functional layer located between the current collector and the active material layer, and a second functional layer located between the first functional layer and the active material layer, wherein an adhesive force between the current collector and the first functional layer is F1, an adhesive force between the first functional layer and the second functional layer is F2, and an adhesive force between the second functional layer and the active material layer is F3, satisfying: f1 > F2, F3 > F2.
In the application, a first functional layer and a second functional layer are sequentially arranged between a positive electrode current collector and an active material layer, so that three bonding interfaces of strong and weak bonding are generated in the positive electrode, wherein a strong bonding interface is formed between the current collector and the first functional layer, and a weak bonding interface is formed between the first functional layer and the second functional layer. In the mechanical abuse process, the interface is easily stripped from the weak bonding interface of the second functional layer and the first functional layer, so that the integrity of the first functional layer on the surface of the positive electrode current collector is ensured, the positive electrode current collector is prevented from being in direct contact with the negative electrode active material layer or the negative electrode current collector, and the short circuit risk is reduced. The arrangement of the first functional layer and the second functional layer can better protect the current collector, can avoid the direct contact of the positive current collector and the negative electrode or the negative current collector (such as copper foil), and reduces the short-circuit heat release, thereby further improving the safety performance of the electrochemical device. In addition, the adhesion between the second functional layer and the active material layer is higher than the adhesion between the first functional layer and the second functional layer, and the risk of occurrence of film detachment when the electrochemical device is used for a long time can be reduced.
According to some embodiments of the application, 25.ltoreq.F1/F2.ltoreq.100. The F1/F2 has a value within the range, so that a strong bonding interface between the positive electrode current collector and the first functional layer and a weak bonding interface between the first functional layer and the second functional layer can be realized, the protection of the first functional layer on the positive electrode current collector is facilitated to be enhanced, the interface is easily peeled from the weak bonding interface in the mechanical abuse process, the damage to the first functional layer is reduced, and the safety performance of the electrochemical device is further improved. If F1/F2 is less than 25, the protection of the first functional layer to the positive current collector is limited, and if F1/F2 is more than 100, F2 is too small, which is unfavorable for keeping the pole piece structure stable in the long-cycle process of the electrochemical device. In some embodiments of the application, the value of F1/F2 may be 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100 and any value therebetween.
According to some embodiments of the application, F3/F2 is ≡1.5. The value of F3/F2 is within the range, so that the electrochemical device can be ensured to have excellent cycling performance while the mechanical safety performance of the electrochemical device is realized. If F3/F2 is less than 1.5, two weak adhesion interfaces exist in the positive electrode, namely, a weak adhesion interface between the first functional layer and the second functional layer and a weak adhesion interface between the second functional layer and the active material layer, and the more the weak adhesion interfaces are in a long cycle process of the electrochemical device, the higher the risk of demolding is, so that the cycle performance is deteriorated. In some embodiments of the application, the value of F3/F2 may be 1.5, 2, 2.5, 3,4,5,6, 7, 8, 9, 10 and any value therebetween.
According to some embodiments of the application, 200N/m.ltoreq.F1.ltoreq.400N/m. The value range of F1 is in the range, so that a strong bonding interface between the positive current collector and the first functional layer can be realized, the risk of damaging the first functional layer is reduced, the protection of the positive current collector is further enhanced, the probability of direct contact between the positive current collector and the negative electrode plate or the negative electrode current collector (such as copper foil) is reduced, and the mechanical safety performance of the electrochemical device is improved. If F1 is less than 200N/m, the first functional layer has a limited protective ability against the electrochemical device, and if F1 is more than 400N/m, the first functional layer has less influence on the safety performance of the electrochemical device. In some embodiments of the application, the value of F1 may be 200N/m, 220N/m, 240N/m, 260N/m, 280N/m, 300N/m, 320N/m, 340N/m, 360N/m, 380N/m, 400N/m, and any value therebetween.
According to some embodiments of the application, 4N/m.ltoreq.F2.ltoreq.8N/m. The value of F2 is in the range, so that a weak bonding interface between the first functional layer and the second functional layer can be realized, and the mechanical safety performance of the electrochemical device is improved and the cycle performance of the electrochemical device is ensured. If F2>8N/m, the adhesion between the second functional layer and the first functional layer is too strong, and peeling of the second functional layer during mechanical abuse may damage the integrity of the first functional layer, thereby affecting the mechanical safety performance of the electrochemical device. If F2<4N/m, the adhesion between the first functional layer and the second functional layer in the positive electrode is too low, in which case it is difficult for the electrochemical device to maintain close bonding of the multi-layered structure of the electrode sheet during cycling, and the probability of occurrence of cyclic stripping is high, thus affecting the cycling performance of the electrochemical device. In some embodiments of the application, the value of F2 may be 4N/m, 4.5N/m, 5N/m, 5.5N/m, 6N/m, 6.5N/m, 7N/m, 7.5N/m, 8N/m, and any value therebetween.
According to some embodiments of the application, the first functional layer has a thickness of 2 μm to 8 μm. If the thickness of the first functional layer is less than 2 μm, the protection effect of the first functional layer on the positive electrode current collector is weak, which is not beneficial to the improvement of the mechanical safety performance of the electrochemical device. As the thickness of the first functional layer increases, the degree of protection of the positive electrode current collector increases; however, too high a thickness may lose energy density, and thus the control of the thickness of the first functional layer within the above-described range is advantageous in improving mechanical safety performance of the electrochemical device. In some embodiments of the application, the thickness of the first functional layer is 2 μm, 2.5 μm, 3 μm, 3.5 μm,4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, and any value in between.
According to some embodiments of the application, the second functional layer has a thickness of 0.1 μm to 0.3 μm. The thickness of the second functional layer within this range enables the electrochemical device to achieve good mechanical safety performance. On the one hand, if the thickness of the second functional layer is too large, the bonding force between the second functional layer and the first functional layer is too large, so that the weak bonding interface between the first functional layer and the second functional layer is not easy to form; on the other hand, the increase of the thickness of the second functional layer lengthens the electron path from the active material layer to the positive electrode current collector in the positive electrode, which is unfavorable for the rate performance of the electrochemical device; in addition, the second functional layer has an excessively large thickness, which is also disadvantageous for the improvement of the energy density of the electrochemical device. If the thickness of the second functional layer is too small, the adhesion between the first functional layer and the second functional layer is too low, and there is a risk of demolding during the preparation and use of the electrochemical device. In some embodiments of the application, the thickness of the first functional layer is 0.1 μm, 0.12 μm, 0.14 μm, 0.16 μm, 0.18 μm, 0.2 μm, 0.22 μm, 0.24 μm, 0.26 μm, 0.28 μm, 0.3 μm, and any value in between.
According to some embodiments of the application, the first functional layer includes a first adhesive, a first conductive agent, and a first filler.
According to some embodiments of the application, the first adhesive comprises at least one of polyacrylic acid, polyvinyl alcohol, polyacrylonitrile, polyacrylamide, carboxymethyl cellulose, polyimide, styrene butadiene rubber, or polyurethane. The first adhesive contains a large number of polar groups such as carboxyl, cyano or amino, when the polar groups are contacted with the current collector, the current collector easily loses electrons, the polar groups easily obtain electrons, electrons are easily transferred from the current collector to the polar groups in the adhesive, contact potential is generated on two sides of an interface, and electrostatic attraction is generated by forming a double-electric layer, so that the adhesive effect is achieved, and the first functional layer and the current collector have strong adhesive effect, so that a strong adhesive interface is realized.
According to some embodiments of the application, the first binder is 5% to 40% by weight, the first conductive agent is 3% to 10% by weight, and the first filler is 50% to 92% by weight, based on the total weight of the first functional layer.
According to some embodiments of the application, the weight percentage of the first binder is 5% to 40%, for example, may be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40% or any value therebetween, based on the total weight of the first functional layer. The content of the first adhesive is increased, and the adhesive force F1 between the first functional layer and the positive electrode current collector is increased, so that the mechanical safety performance of the electrochemical device is improved; however, the weight percentage of the first binder is not preferably higher than 40%, which may result in too low a filler content, in which case it is difficult to ensure coverage of the filler on the positive electrode current collector, there is a risk of missing coating, so that protection of the first functional layer on the positive electrode current collector is weakened, and there is a risk of deteriorating mechanical safety performance.
According to some embodiments of the application, the weight percentage of the first conductive agent is 3% to 10%, for example, may be 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or any value therebetween, based on the total weight of the first functional layer. The weight percentage of the first conductive agent is within this range, and it is possible to achieve that the rate performance of the electrochemical device is not affected and excellent mechanical safety performance is ensured. If the weight percentage of the first conductive agent is less than 3%, the content of the conductive agent in the first functional layer is too small, the electronic resistance is increased, the influence on the electronic path in the positive electrode is large, and the improvement of the rate performance of the electrochemical device is not facilitated. If the weight percentage of the first conductive agent is greater than 10%, the electronic conductivity of the first functional layer is too strong, and the resistance of the first functional layer is too small, so that even if the positive current collector can be protected from being in direct contact with the negative electrode plate or the negative electrode current collector, the low resistance of the first functional layer is still not beneficial to the improvement of the safety performance of the electrochemical device.
According to some embodiments of the application, the weight percentage of the first filler is 50% to 92%, for example, may be 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 92% or any value therebetween, based on the total weight of the first functional layer. If the weight percentage of the first filler is less than 50%, the low filler content in the first functional layer is difficult to ensure high coverage of the first functional layer on the positive electrode current collector, and there is a risk of missing coating, so that the protection of the first functional layer on the positive electrode current collector is weakened, and there is a risk of deteriorating mechanical properties. If the weight percentage of the first filler is more than 92%, the content of the adhesive in the first functional layer is too small to ensure the strong adhesive effect between the positive electrode current collector and the first functional layer; the decrease in the content of the conductive agent increases the resistance of the first functional layer, which is detrimental to the rate performance of the electrochemical device.
According to some embodiments of the application, the second functional layer includes a second adhesive, a second conductive agent, and a second filler.
According to some embodiments of the application, the second binder comprises at least one of polyvinylidene fluoride or polytetrafluoroethylene. The second adhesive contains less polar groups, so that the adhesive force between the first functional layer and the second functional layer is low, and a weak adhesive interface is realized.
According to some embodiments of the application, the weight percentage of the second binder is 5% to 40%, the weight percentage of the second conductive agent is 3% to 10%, and the weight percentage of the second filler is 50% to 92% based on the total weight of the second functional layer.
According to some embodiments of the application, the weight percentage of the second binder is 5% to 40%, for example, may be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40% or any value therebetween, based on the total weight of the second functional layer. The control of the content of the second binder within the above-described range is advantageous in increasing the safety performance of the electrochemical device. If the content of the second adhesive is more than 40%, the adhesive force between the first functional layer and the second functional layer is too large, so that a weak adhesive interface is difficult to realize, and the mechanical safety performance of the electrochemical device is not facilitated; if the content of the second adhesive is less than 5%, the adhesive force between the first functional layer and the second functional layer is too small, and the positive electrode has a demolding risk in the circulating and cold pressing processes.
According to some embodiments of the application, the weight percentage of the second conductive agent is 3% to 10%, for example, may be 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or any value therebetween, based on the total weight of the second functional layer. If the weight percentage of the second conductive agent is less than 3%, the content of the second conductive agent is too small, the electronic resistance is increased, the influence on the electronic path in the positive electrode plate is large, and the improvement of the multiplying power performance of the battery cell is not facilitated. If the weight percentage of the second conductive agent is more than 10%, the filler content in the second functional layer is too small, which may affect the coverage of the first functional layer by the second functional layer.
According to some embodiments of the application, the weight percentage of the second filler is 50% to 92%, for example, may be 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 92% or any value therebetween, based on the total weight of the second functional layer. If the weight percentage of the second filler is less than 50%, the low filler content in the second functional layer is difficult to ensure high coverage of the first functional layer, there is a risk of missing coating, weak adhesion interfaces between the first functional layer and the second functional layer are unfavorable, and there is a risk of deteriorating mechanical properties. If the weight percentage of the second filler is more than 92%, the content of the adhesive in the second functional layer is too small, so that proper adhesion between the second functional layer and the active material layer is difficult to ensure, the risk of stripping the pole piece exists, and the cycle performance of the electrochemical device is affected; the reduction of the content of the conductive agent increases the resistance of the second functional layer, which is disadvantageous for the rate performance of the electrochemical device.
According to some embodiments of the application, the first filler and the second filler each independently comprise at least one of lithium iron phosphate, silica, titania, alumina, boehmite, magnesia, zirconia, titania, silicon carbide, boron carbide, barium carbonate, potassium titanate, barium sulfate, vanadium trioxide, polyetheretherketone powder, polyamide powder, or cellulose powder.
According to some embodiments of the application, the first conductive agent and the second conductive agent each independently include at least one of conductive carbon black, acetylene black, graphite, graphene, carbon nanotubes, carbon fibers, aluminum powder, nickel powder, or gold powder.
According to some embodiments of the application, the active material layer comprises at least one of lithium cobaltate, lithium nickel manganese aluminate, lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium iron silicate, lithium vanadium silicate, lithium cobalt silicate, lithium manganese silicate, spinel type lithium manganate, spinel type lithium nickel manganate, or lithium titanate.
According to some embodiments of the application, the current collector in the positive electrode is aluminum foil.
According to some embodiments of the application, the method of preparing the positive electrode comprises the steps of:
S1: coating slurry comprising a first adhesive, a first conductive agent and a first filler on the surface of a current collector, and drying to obtain the current collector coated with the first functional layer;
S2: coating slurry comprising a second adhesive, a second conductive agent and a second filler on the first functional layer, and drying to obtain a current collector coated with the first functional layer and the second functional layer;
s3: and coating an active material layer on the second functional layer, drying and cold pressing to obtain the positive electrode.
In a second aspect, the present application provides an electronic device comprising the electrochemical device of the first aspect of the application.
The electrochemical device can better protect the positive current collector, thereby avoiding the direct contact of the positive current collector and the negative electrode or the negative current collector and reducing the heat release of short circuit. The electrochemical device has higher mechanical safety performance.
Drawings
Fig. 1 shows a schematic structure of a positive electrode of an electrochemical device according to an embodiment of the present application, wherein 1 is a current collector, 2 is a first functional layer, 3 is a second functional layer, and 4 is an active material layer.
Fig. 2 is a schematic diagram showing the mechanism of interfacial delamination during mechanical abuse of the positive electrode in an electrochemical device according to the prior art, wherein 5 is a current collector, 6 is a conventional coating, and 7 is an active material layer.
Fig. 3 is a schematic view showing an action mechanism of interfacial peeling during mechanical abuse of a positive electrode in an electrochemical device according to an embodiment of the present application, wherein 1 is a current collector, 2 is a first functional layer, 3 is a second functional layer, 4 is an active material layer, an interface between 1 and 2 is a strong adhesive interface, and an interface between 2 and 3 is a weak adhesive interface.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be clearly and completely described below with reference to the embodiments, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments. The related embodiments described herein are of illustrative nature and are intended to provide a basic understanding of the application. The embodiments of the present application should not be construed as limiting the application.
For simplicity, only a few numerical ranges are specifically disclosed herein. However, any lower limit may be combined with any upper limit to form a range not explicitly recited; and any lower limit may be combined with any other lower limit to form a range not explicitly recited, and any upper limit may be combined with any other upper limit to form a range not explicitly recited. Furthermore, each separately disclosed point or individual value may itself be combined as a lower limit or upper limit with any other point or individual value or with other lower limit or upper limit to form a range not explicitly recited.
In the description herein, unless otherwise indicated, "above", "below" includes this number.
Unless otherwise indicated, terms used in the present application have well-known meanings commonly understood by those skilled in the art. Unless otherwise indicated, the numerical values of the parameters set forth in the present application may be measured by various measurement methods commonly used in the art (e.g., may be tested according to the methods set forth in the examples of the present application).
The list of items to which the term "at least one of," "at least one of," or other similar terms are connected may mean any combination of the listed items. For example, if items a and B are listed, the phrase "at least one of a and B" means only a; only B; or A and B. In another example, if items A, B and C are listed, the phrase "at least one of A, B and C" means only a; or only B; only C; a and B (excluding C); a and C (excluding B); b and C (excluding A); or A, B and C. Item a may comprise a single component or multiple components. Item B may comprise a single component or multiple components. Item C may comprise a single component or multiple components.
1. Electrochemical device
In a first aspect, the present application provides an electrochemical device comprising a positive electrode including a current collector, an active material layer, a first functional layer located between the current collector and the active material layer, and a second functional layer located between the first functional layer and the active material layer, wherein an adhesive force between the current collector and the first functional layer is F1, an adhesive force between the first functional layer and the second functional layer is F2, and an adhesive force between the second functional layer and the active material layer is F3, satisfying: f1 > F2, F3 > F2.
In the application, a first functional layer and a second functional layer are sequentially arranged between a positive electrode current collector and an active material layer, so that three bonding interfaces of strong and weak bonding are generated in the positive electrode, wherein a strong bonding interface is formed between the current collector and the first functional layer, and a weak bonding interface is formed between the first functional layer and the second functional layer. In the mechanical abuse process, the interface is easily stripped from the weak bonding interface of the second functional layer and the first functional layer, so that the integrity of the first functional layer on the surface of the positive electrode current collector is ensured, the positive electrode current collector is prevented from being in direct contact with the negative electrode active material layer or the negative electrode current collector, and the short circuit risk is reduced. The arrangement of the first functional layer and the second functional layer can better protect the current collector, can avoid the direct contact of the positive current collector and the negative electrode or the negative current collector (such as copper foil), and reduces the short-circuit heat release, thereby further improving the safety performance of the electrochemical device. In addition, the adhesion between the second functional layer and the active material layer is higher than the adhesion between the first functional layer and the second functional layer, and the risk of occurrence of film detachment when the electrochemical device is used for a long time can be reduced.
According to some embodiments of the application, 25.ltoreq.F1/F2.ltoreq.100. The F1/F2 has a value within the range, so that a strong bonding interface between the positive electrode current collector and the first functional layer and a weak bonding interface between the first functional layer and the second functional layer can be realized, the protection of the first functional layer on the positive electrode current collector is enhanced, the interface is easily peeled from the weak bonding interface in the mechanical abuse process, the damage to the first functional layer is reduced, and the safety performance of the electrochemical device is further improved. If F1/F2 is less than 25, the protection of the first functional layer to the positive current collector is limited, and if F1/F2 is more than 100, F2 is too small, which is unfavorable for keeping the pole piece structure stable in the long-cycle process of the electrochemical device. In some embodiments of the application, the value of F1/F2 may be 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100 and any value therebetween.
According to some embodiments of the application, F3/F2 is ≡1.5. The value of F3/F2 is within the range, so that the electrochemical device can be ensured to have excellent cycling performance while the mechanical safety performance of the electrochemical device is realized. If F3/F2 is less than 1.5, two weak adhesion interfaces exist in the positive electrode, namely, a weak adhesion interface between the first functional layer and the second functional layer and a weak adhesion interface between the second functional layer and the active material layer, and the more the weak adhesion interfaces are in a long cycle process of the electrochemical device, the higher the risk of demolding is, so that the cycle performance is deteriorated. In some embodiments of the application, the value of F3/F2 may be 1.5, 2, 2.5, 3,4,5,6, 7, 8, 9, 10 and any value therebetween.
According to some embodiments of the application, 200N/m.ltoreq.F1.ltoreq.400N/m. The value range of F1 is in the range, so that a strong bonding interface between the positive current collector and the first functional layer can be realized, the risk of damaging the first functional layer is reduced, the protection of the positive current collector is further enhanced, the probability of direct contact between the positive current collector and the negative electrode plate or the negative electrode current collector (such as copper foil) is reduced, and the mechanical safety performance of the electrochemical device is improved. If F1 is less than 200N/m, the first functional layer has a limited protective ability against the electrochemical device, and if F1 is more than 400N/m, the first functional layer has less influence on the safety performance of the electrochemical device. In some embodiments of the application, the value of F1 may be 200N/m, 220N/m, 240N/m, 260N/m, 280N/m, 300N/m, 320N/m, 340N/m, 360N/m, 380N/m, 400N/m, and any value therebetween.
According to some embodiments of the application, 4N/m.ltoreq.F2.ltoreq.8N/m. The value of F2 is in the range, so that a weak bonding interface between the first functional layer and the second functional layer can be realized, and the mechanical safety performance of the electrochemical device is improved and the cycle performance of the electrochemical device is ensured. If F2>8N/m, the adhesion between the second functional layer and the first functional layer is too strong, and peeling of the second functional layer during mechanical abuse may damage the integrity of the first functional layer, thereby affecting the mechanical safety performance of the electrochemical device. If F2<4N/m, the adhesion between the first functional layer and the second functional layer in the positive electrode is too low, in which case it is difficult for the electrochemical device to maintain close bonding of the multi-layered structure of the electrode sheet during cycling, and the probability of occurrence of cyclic stripping is high, thus affecting the cycling performance of the electrochemical device. In some embodiments of the application, the value of F2 may be 4N/m, 4.5N/m, 5N/m, 5.5N/m, 6N/m, 6.5N/m, 7N/m, 7.5N/m, 8N/m, and any value therebetween.
According to some embodiments of the application, the first functional layer has a thickness of 2 μm to 8 μm. If the thickness of the first functional layer is less than 2 μm, the protection effect of the first functional layer on the positive electrode current collector is weak, which is not beneficial to the improvement of the mechanical safety performance of the electrochemical device. As the thickness of the first functional layer increases, the degree of protection of the positive electrode current collector increases; however, too high a thickness may lose energy density, and thus the control of the thickness of the first functional layer within the above-described range is advantageous in improving mechanical safety performance of the electrochemical device. In some embodiments of the present application, the thickness of the first functional layer is 2 μm, 2.5 μm, 3 μm, 3.5 μm,4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, and any value in between.
According to some embodiments of the application, the second functional layer has a thickness of 0.1 μm to 0.3 μm. The thickness of the second functional layer within this range enables the electrochemical device to achieve good mechanical safety performance. On the one hand, if the thickness of the second functional layer is too large, the bonding force between the second functional layer and the first functional layer is too large, so that the weak bonding interface between the first functional layer and the second functional layer is not easy to form; on the other hand, the increase of the thickness of the second functional layer lengthens the electron path from the active material layer to the positive electrode current collector in the positive electrode, which is unfavorable for the rate performance of the electrochemical device; in addition, the second functional layer has an excessively large thickness, which is also disadvantageous for the improvement of the energy density of the electrochemical device. If the thickness of the second functional layer is too small, the adhesion between the first functional layer and the second functional layer is too low, and there is a risk of demolding during the preparation and use of the electrochemical device. In some embodiments of the application, the thickness of the first functional layer is 0.1 μm, 0.12 μm, 0.14 μm, 0.16 μm, 0.18 μm, 0.2 μm, 0.22 μm, 0.24 μm, 0.26 μm, 0.28 μm, 0.3 μm, and any value in between.
According to some embodiments of the application, the first functional layer includes a first adhesive, a first conductive agent, and a first filler.
According to some embodiments of the application, the first adhesive comprises at least one of polyacrylic acid, polyvinyl alcohol, polyacrylonitrile, polyacrylamide, carboxymethyl cellulose, polyimide, styrene butadiene rubber, or polyurethane. The first adhesive contains a large number of polar groups such as carboxyl, cyano or amino, when the polar groups are contacted with the current collector, the current collector easily loses electrons, the polar groups easily obtain electrons, electrons are easily transferred from the current collector to the polar groups in the adhesive, contact potential is generated on two sides of an interface, an electric double layer is formed to generate electrostatic attraction, the adhesive effect is achieved, and the first functional layer and the current collector have strong adhesive effect, so that a strong adhesive interface is achieved.
According to some embodiments of the application, the first binder is 5% to 40% by weight, the first conductive agent is 3% to 10% by weight, and the first filler is 50% to 92% by weight, based on the total weight of the first functional layer.
According to some embodiments of the application, the weight percentage of the first binder is 5% to 40%, for example, may be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40% or any value therebetween, based on the total weight of the first functional layer. The content of the first adhesive is increased, and the adhesive force F1 between the first functional layer and the positive electrode current collector is increased, so that the mechanical safety performance of the electrochemical device is improved; however, the weight percentage of the first binder is not preferably higher than 40%, which may result in too low a filler content, in which case it is difficult to ensure coverage of the filler on the positive electrode current collector, there is a risk of missing coating, so that protection of the first functional layer on the positive electrode current collector is weakened, and there is a risk of deteriorating mechanical safety performance.
According to some embodiments of the application, the weight percentage of the first conductive agent is 3% to 10%, for example, may be 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or any value therebetween, based on the total weight of the first functional layer. The weight percentage of the first conductive agent is within this range, and it is possible to achieve that the rate performance of the electrochemical device is not affected and excellent mechanical safety performance is ensured. If the weight percentage of the first conductive agent is less than 3%, the content of the conductive agent in the first functional layer is too small, the electronic resistance is increased, the influence on the electronic path in the positive electrode is large, and the improvement of the rate performance of the electrochemical device is not facilitated. If the weight percentage of the first conductive agent is greater than 10%, the electronic conductivity of the first functional layer is too strong, and the resistance of the first functional layer is too small, so that even if the positive current collector can be protected from being in direct contact with the negative electrode plate or the negative electrode current collector, the low resistance of the first functional layer is still not beneficial to the improvement of the safety performance of the electrochemical device.
According to some embodiments of the application, the weight percentage of the first filler is 50% to 92%, for example, may be 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 92% or any value therebetween, based on the total weight of the first functional layer. If the weight percentage of the first filler is less than 50%, the low filler content in the first functional layer is difficult to ensure high coverage of the first functional layer on the positive electrode current collector, and there is a risk of missing coating, so that the protection of the first functional layer on the positive electrode current collector is weakened, and there is a risk of deteriorating mechanical properties. If the weight percentage of the first filler is more than 92%, the content of the adhesive in the first functional layer is too small to ensure the strong adhesive effect between the positive electrode current collector and the first functional layer; the decrease in the content of the conductive agent increases the resistance of the first functional layer, which is detrimental to the rate performance of the electrochemical device.
According to some embodiments of the application, the second functional layer includes a second adhesive, a second conductive agent, and a second filler.
According to some embodiments of the application, the second binder comprises at least one of polyvinylidene fluoride or polytetrafluoroethylene. The second adhesive contains less polar groups, so that the adhesive force between the first functional layer and the second functional layer is low, and a weak adhesive interface is realized.
According to some embodiments of the application, the weight percentage of the second binder is 5% to 40%, the weight percentage of the second conductive agent is 3% to 10%, and the weight percentage of the second filler is 50% to 92% based on the total weight of the second functional layer.
According to some embodiments of the application, the weight percentage of the second binder is 5% to 40%, for example, may be 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40% or any value therebetween, based on the total weight of the second functional layer. The control of the content of the second binder within the above-described range is advantageous in increasing the safety performance of the electrochemical device. If the content of the second adhesive is more than 40%, the adhesive force between the first functional layer and the second functional layer is too large, so that a weak adhesive interface is difficult to realize, and the mechanical safety performance of the electrochemical device is not facilitated; if the content of the second adhesive is less than 5%, the adhesive force between the first functional layer and the second functional layer is too small, and the positive electrode has a demolding risk in the circulating and cold pressing processes.
According to some embodiments of the application, the weight percentage of the second conductive agent is 3% to 10%, for example, may be 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or any value therebetween, based on the total weight of the second functional layer. If the weight percentage of the second conductive agent is less than 3%, the content of the second conductive agent is too small, the electronic resistance is increased, the influence on the electronic path in the positive electrode plate is large, and the improvement of the multiplying power performance of the battery cell is not facilitated. If the weight percentage of the second conductive agent is more than 10%, the filler content in the second functional layer is too small, which may affect the coverage of the first functional layer by the second functional layer.
According to some embodiments of the application, the weight percentage of the second filler is 50% to 92%, for example, may be 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 92% or any value therebetween, based on the total weight of the second functional layer. If the weight percentage of the second filler is less than 50%, the low filler content in the second functional layer is difficult to ensure high coverage of the first functional layer, there is a risk of missing coating, weak adhesion interfaces between the first functional layer and the second functional layer are unfavorable, and there is a risk of deteriorating mechanical properties. If the weight percentage of the second filler is more than 92%, the content of the adhesive in the second functional layer is too small, so that proper adhesion between the second functional layer and the active material layer is difficult to ensure, the risk of stripping the pole piece exists, and the cycle performance of the electrochemical device is affected; the reduction of the content of the conductive agent increases the resistance of the second functional layer, which is disadvantageous for the rate performance of the electrochemical device.
According to some embodiments of the application, the first filler and the second filler each independently comprise at least one of lithium iron phosphate, silica, titania, alumina, boehmite, magnesia, zirconia, titania, silicon carbide, boron carbide, barium carbonate, potassium titanate, barium sulfate, vanadium trioxide, polyetheretherketone powder, polyamide powder, or cellulose powder.
According to some embodiments of the application, the first conductive agent and the second conductive agent each independently include at least one of conductive carbon black, acetylene black, graphite, graphene, carbon nanotubes, carbon fibers, aluminum powder, nickel powder, or gold powder.
According to some embodiments of the application, the active material layer comprises at least one of lithium cobaltate, lithium nickel manganese aluminate, lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium iron silicate, lithium vanadium silicate, lithium cobalt silicate, lithium manganese silicate, spinel type lithium manganate, spinel type lithium nickel manganate, or lithium titanate.
According to some embodiments of the application, the current collector in the positive electrode is aluminum foil.
According to some embodiments of the application, the method of preparing the positive electrode comprises the steps of:
S1: coating slurry comprising a first adhesive, a first conductive agent and a first filler on the surface of a current collector, and drying to obtain the current collector coated with the first functional layer;
S2: coating slurry comprising a second adhesive, a second conductive agent and a second filler on the first functional layer, and drying to obtain a current collector coated with the first functional layer and the second functional layer;
s3: and coating an active material layer on the second functional layer, drying and cold pressing to obtain the positive electrode.
In some embodiments, the electrochemical device of the present application includes any device in which an electrochemical reaction occurs, and specific examples thereof include a primary battery or a secondary battery. In particular, the electrochemical device is a lithium secondary battery, including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.
The positive electrode of the application can be used for electrochemical devices with different structures, such as wound lithium ion batteries, and is particularly applied to lithium ion structures such as lamination structures, multi-tab structures and the like. The positive electrode can also be used in different types of lithium ion batteries, such as soft-pack lithium ion batteries, and particularly applied to lithium ion batteries such as square aluminum shell batteries, cylindrical aluminum shell batteries and the like.
According to some embodiments of the application, the electrochemical device of the application further comprises a negative electrode, a separator, and an electrolyte.
1. Negative electrode
The materials, constitution, and manufacturing method of the anode used in the electrochemical device of the present application may include any of the techniques disclosed in the prior art.
According to some embodiments of the present application, a negative electrode includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector.
According to some embodiments of the present application, the anode active material layer includes an anode active material, which may include a material that reversibly intercalates/deintercalates lithium ions, lithium metal alloy, a material capable of doping/deintercalating lithium, or a transition metal oxide, such as Si, siO x (0 < x < 2), or the like. The material that reversibly intercalates/deintercalates lithium ions may be a carbon material. The carbon material may be any carbon-based anode active material commonly used in lithium ion rechargeable electrochemical devices. Examples of carbon materials include crystalline carbon, amorphous carbon, and combinations thereof. The crystalline carbon may be amorphous, plate-shaped, platelet-shaped, spherical or fibrous natural graphite or artificial graphite. Amorphous carbon may be soft carbon, hard carbon, mesophase pitch carbonized product, fired coke, and the like. Both low crystalline carbon and high crystalline carbon may be used as the carbon material. As the low crystalline carbon material, soft carbon and hard carbon may be generally included. As the high crystalline carbon material, natural graphite, crystalline graphite, pyrolytic carbon, mesophase pitch-based carbon fibers, mesophase carbon microbeads, mesophase pitch, and Gao Wenduan burnt carbon (such as petroleum or coke derived from coal tar pitch) may be generally included.
According to some embodiments of the present application, the negative electrode active material layer includes a binder, and the binder may include various binder polymers such as vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, an ethyleneoxy-containing polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylic (esterified) styrene-butadiene rubber, epoxy resin, nylon, and the like, but is not limited thereto.
According to some embodiments of the application, the anode active material layer further includes a conductive material to improve electrode conductivity. Any conductive material may be used as the conductive material as long as it does not cause chemical change. Examples of conductive materials include: 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 including copper, nickel, aluminum, silver, and the like; conductive polymers such as polyphenylene derivatives and the like; or mixtures thereof. The negative electrode current collector may be copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, or a combination thereof.
2. Isolation film
The material and shape of the separator used in the electrochemical device of the present application 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, the release film may include a substrate layer and a surface treatment layer. The substrate layer is a non-woven fabric, a film or a composite film with a porous structure, and the material of the substrate layer is at least one selected from polyethylene, polypropylene, polyethylene terephthalate and polyimide. Specifically, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric or a polypropylene-polyethylene-polypropylene porous composite membrane can be selected.
The surface treatment layer is provided on at least one surface of the base material layer, and the surface treatment layer may be a polymer layer or an inorganic layer, or may be a layer formed by mixing a polymer and an inorganic substance.
The inorganic layer includes inorganic particles and a binder, the inorganic particles being at least one selected from the group consisting of aluminum oxide, silicon oxide, magnesium oxide, titanium oxide, hafnium oxide, tin oxide, cerium oxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, and barium sulfate. The adhesive is at least one selected from polyvinylidene fluoride, copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, polyacrylate, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyethylene alkoxy, polymethyl methacrylate, polytetrafluoroethylene and polyhexafluoropropylene.
The polymer layer contains a polymer, and the material of the polymer is at least one selected from polyamide, polyacrylonitrile, acrylic polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl alkoxy, polyvinylidene fluoride and poly (vinylidene fluoride-hexafluoropropylene).
3. Electrolyte solution
The constitution of the electrolyte used in the electrochemical device of the present application and the method of manufacturing the same may include any of the techniques disclosed in the prior art.
In some embodiments, the electrolyte in the electrochemical device of the present application includes a lithium salt and a nonaqueous solvent.
In some embodiments of the application, the lithium salt is selected from one or more of LiPF 6、LiBF 4、LiAsF 6、LiClO 4、LiB(C 6H 5) 4、LiCH 3SO 3、LiCF 3SO 3、LiN(SO 2CF 3) 2、LiC(SO 2CF 3) 3、LiSiF 6、LiBOB and lithium difluoroborate. For example, liPF 6 may be selected as the lithium salt because it can give high ionic conductivity and improve cycle characteristics.
The nonaqueous solvent may be a carbonate compound, a carboxylate compound, an ether compound, other organic solvents, or a combination thereof.
The carbonate compound may be a chain carbonate compound, a cyclic carbonate compound, a fluorocarbonate compound, or a combination thereof.
Examples of such chain carbonate compounds are dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), ethylmethyl carbonate (MEC), and combinations thereof. Examples of cyclic carbonate compounds are Ethylene Carbonate (EC), propylene Carbonate (PC), butylene Carbonate (BC), vinyl Ethylene Carbonate (VEC) and combinations thereof. Examples of fluorocarbonate compounds are fluoroethylene carbonate (FEC), 1, 2-difluoroethylene carbonate, 1, 2-trifluoroethylene carbonate, 1, 2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1, 2-difluoro-1-methylethylene carbonate, 1, 2-trifluoro-2-methylethylene carbonate, trifluoromethyl ethylene carbonate, and combinations thereof.
Examples of the above carboxylic acid ester compounds are methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, gamma-butyrolactone, decalactone, valerolactone, mevalonic acid lactone, caprolactone, and combinations thereof.
Examples of the above ether compounds are dibutyl ether, tetraglyme, diglyme, 1, 2-dimethoxyethane, 1, 2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and combinations thereof.
Examples of such other organic solvents are dimethyl sulfoxide, 1, 2-dioxolane, sulfolane, methyl sulfolane, 1, 3-dimethyl-2-imidazolidinone, N-methyl-2-pyrrolidone, formamide, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, and phosphoric acid esters and combinations thereof.
2. Electronic device
The present application further provides an electronic device comprising the electrochemical device of the present application.
The electronic device or apparatus of the present application is not particularly limited. In some embodiments, the electronic device of the present application 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 notepad, a calculator, a memory card, a portable audio recorder, a radio, a backup power source, 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, or a household large battery, etc.
The application is further illustrated by the following examples. It is to be understood that these examples are illustrative of the present application and are not intended to limit the scope of the present application.
Test method
1. Thickness test
Samples 40cm long and 20cm wide (current collector (aluminum foil) +first functional layer+second functional layer) were taken, flatness was ensured without wrinkling, 12 different position thicknesses in this size range were tested using a Mitutoyo ten-thousandth ruler, and the average value D2 was taken. The second functional layer was peeled off and the average thickness D1 at 12 points was measured in the same manner. The first functional layer was continuously peeled off, and the average thickness D0 of 12 points was measured by the same method. The thickness of the first functional layer is: d1-D0, the thickness of the second functional layer is: D2-D1.
2. Adhesive force test
A steel plate with the width of 5cm and the length of 15cm is taken, and double faced adhesive tape with the length of 5cm and the width of 2cm is attached along the length direction. The sample (current collector (aluminum foil) +first functional layer+second functional layer+active material layer) was cut into strips 2cm wide and 15cm long, and attached to a double-sided tape along the length direction, ensuring complete coverage of the double-sided tape, and rolled for 15s using a pressure of 3 kg. Using an Instron3365 universal tester, selecting a stretching clamp to perform 180 DEG peeling test, fixing a steel plate by the lower clamp, fixing a sample by the upper clamp, stretching at a speed of 10mm/min, peeling length of 50mm, taking a force calculation average value of 10mm to 50mm as peeling force, and taking a peeling force average value of F2' by testing 12 sample bars. The adhesion force f2=50×f2' between the second functional layer and the active material layer. The same method was used to test a current collector (aluminum foil) +a first functional layer+a second functional layer to obtain a peeling force F1', and the adhesion force f1=50×f1' between the first functional layer and the second functional layer. The same method was used to test the current collector (aluminum foil) +the first functional layer to obtain a peeling force F0', and the adhesion force f0=50×f0' between the current collector and the first functional layer.
3. Impact testing
The cell with SOC 0% was run at 1.5 CC to 100% SOC, CV to 0.05C at 25 ℃. And drawing diagonal lines on the surface of the battery cell, wherein the intersection point is a geometric center. Round bars with a diameter of phi 15.8 + -0.1 mm and a length of at least 6cm were placed in the geometric center and perpendicular to the current collector. A9.1.+ -. 0.1Kg weight was used, 61.+ -. 2.5cm from the intersection of the round bar and the sample, and the vertical free fall was achieved. The cell does not fire or explode and passes the test.
4. Penetration test
The battery with SOC 0% was run at 1.5 CC to 100% SOC, CV to 0.05C at 25 ℃. And drawing diagonal lines on the surface of the battery, wherein the intersection point is a geometric center. The steel nails with the diameter of 4mm are used, the puncture speed is 30mm/s, the position of the penetrating nails is in the geometric center of the battery, the test is carried out for 3min, and the battery does not fire or explode and passes the test.
Examples and comparative examples
1. Preparation of positive electrode plate
Referring to fig. 1, the positive electrode sheet includes a current collector 1, a first functional layer 2, a second functional layer 3, and an active material layer 4, and is prepared as follows:
S1: respectively coating slurry comprising a first adhesive, a first conductive agent and a first filler shown in table 1 on the surface of a current collector 1, and drying to obtain a first functional layer 2 on the surface of the current collector 1;
S2: coating slurry comprising a second adhesive, a second conductive agent and a second filler shown in table 1 on the surface of the first functional layer 2, and drying to obtain a second functional layer 3 on the surface of the first functional layer 1;
s3: coating a positive electrode active material layer 4 on the surface of the second functional layer 3, drying and cold pressing to obtain a positive electrode plate;
Wherein the current collector 1 is aluminum foil, and the active material layer is lithium cobaltate; the specific first adhesive, first conductive agent, first filler, second adhesive, second conductive agent and second filler compositions in each example and comparative example are shown in table 1 below.
The positive electrode active material lithium cobaltate, acetylene black and polyvinylidene fluoride (PVDF) are mixed according to the mass ratio of 94:3:3, then adding N-methyl pyrrolidone (NMP) as a solvent, preparing slurry with the solid content of 75%, and uniformly stirring. And uniformly coating the slurry on two sides of the aluminum foil, drying at 110 ℃, and cold pressing to obtain the double-sided pole piece with the anode active material layer thickness of 130 mu m. And cutting the positive electrode plate into a specification of 74mm multiplied by 867mm, and welding the tab for later use.
2. Preparation of negative electrode plate
Artificial graphite, acetylene black, styrene-butadiene rubber and sodium carboxymethyl cellulose serving as anode active materials are prepared according to a mass ratio of 96:1:1.5:1.5, adding deionized water as a solvent, preparing into slurry with the solid content of 70%, and uniformly stirring. And uniformly coating the slurry on two sides of the copper foil, drying at 110 ℃, and cold pressing to obtain the double-sided pole piece with the thickness of the negative electrode active material layer of 150 mu m. Cutting the negative electrode plate into specifications of 74mm multiplied by 867mm, and welding the electrode lugs for later use.
3. Preparation of a separation film: PE isolation film
4. Preparation of electrolyte
The organic solvent of the electrolyte is Ethylene Carbonate (EC), propylene Carbonate (PC), diethyl carbonate (DEC) and ethyl propionate epoxy resin (EP), and the mass ratio of EC to PC to DEC to EP=3:1 to 3:3, and the solute is lithium hexafluorophosphate (LiPF 6),LiPF 6 concentration is 1mol/L.
5. Preparation of a lithium ion battery: and sequentially stacking the positive electrode plate, the isolating film and the negative electrode plate, so that the isolating film is positioned between the positive electrode and the negative electrode to play a role in isolation. And winding to obtain the bare cell. And placing the bare cell in an outer package, vacuum drying, injecting electrolyte, and packaging. The lithium ion battery is obtained through the technological processes of formation, degassing, trimming and the like.
In table 1, examples 1 to 9 show the effect of the kind and content of the first binder in the first functional layer on the performance of the lithium ion battery produced. According to the embodiments 1 to 5, the first adhesive has more polar groups, so that a strong bonding interface is formed between the first functional layer and the aluminum foil, and the second adhesive PVDF has no polar groups, so that a weak bonding interface is formed between the first functional layer and the second functional layer, so that when the machine is abused, the interface is easily peeled off from the weak bonding interface between the second functional layer and the first functional layer, the integrity of the first functional layer on the surface of the positive electrode current collector is ensured, the positive electrode current collector is prevented from being directly contacted with the negative electrode active material layer or the negative electrode current collector, the short circuit risk is reduced, the short circuit heat release is reduced, the battery has high impact test passing rate and penetrating nail test passing rate, and the safety performance of the battery is improved. As can be seen from examples 1 and 6 to 9, the content of the first adhesive increases, and the adhesion force F1 between the first functional layer and the aluminum foil increases, which is beneficial to improving the safety performance of the battery; however, the content of the first adhesive is not preferably higher than 40%, otherwise, the content of the filler is reduced, the coverage of the filler on the aluminum foil is difficult to ensure, the risk of missing coating exists, the protection of the first functional layer on the aluminum foil is weakened, and the risk of deteriorating the mechanical safety performance exists.
In table 1, examples 1 and 10 to 15 show the effect of the kind of the first conductive agent and the kind of the first filler in the first functional layer on the performance of the prepared lithium ion battery. As can be seen from examples 1 and 10 to 15, the kind of the first conductive agent has little influence on the adhesion force F1 between the first functional layer and the aluminum foil, and the kind of the first filler has no significant influence on the adhesion force F1 between the first functional layer and the aluminum foil, but both are very high, and the safety performance of the battery is also good.
In table 1, examples 1 and 16 to 19 show the effect of the thickness of the first functional layer on the performance of the prepared lithium ion battery. As can be seen from examples 1 and 16 to 19, the thickness of the first functional layer increases, and the degree of protection of the aluminum foil increases; however, too high a thickness would lose energy density, and therefore it is necessary to control the thickness of the first functional layer within a reasonable range.
In table 1, examples 1 and 20 to 25 show the effect of the kind and content of the second binder in the second functional layer on the performance of the prepared lithium ion battery. According to the embodiment 1, the embodiment 20 and the embodiment 21, the second adhesive is free of polar groups, so that a weak adhesion interface is formed between the first functional layer and the second functional layer, the first adhesive polyacrylic acid has more polar groups, so that a strong adhesion interface is formed between the first functional layer and the aluminum foil, and therefore when the battery is in mechanical abuse, the interface is easily peeled off from the weak adhesion interface between the second functional layer and the first functional layer, the integrity of the first functional layer on the surface of the positive electrode current collector is ensured, the positive electrode current collector is prevented from being directly contacted with the negative electrode active material layer or the negative electrode current collector, the short circuit risk is reduced, the short circuit heat release is reduced, the battery has high impact test passing rate and penetrating nail test passing rate, and the safety performance of the battery is improved. As can be seen from examples 1 and 22 to 25, when the content of the second adhesive is increased, the adhesive force F2 between the first functional layer and the second functional layer is increased, so that it is difficult to realize a weak adhesive interface, which is not beneficial to the mechanical safety performance of the battery; however, the second adhesive should not be too low, otherwise the adhesion force F2 between the first functional layer and the second functional layer is too small, and there is a risk of demolding during processing and use.
In table 1, examples 1 and 26 to 28 show the effect of the second filler in the second functional layer on the performance of the prepared lithium ion battery. As can be seen from examples 1 and 26 to 28, the kind of the second filler has no significant effect on the adhesion force F2 between the first functional layer and the second functional layer, and the safety performance of the battery is also good.
In table 1, examples 1 and 29 to 30 show the effect of the thickness of the second functional layer on the performance of the prepared lithium ion battery. As can be seen from examples 1 and 29 to 30, the thickness of the second functional layer increases, and the adhesion force between the second functional layer and the first functional layer is too large, which is not beneficial to the formation of a weak adhesion interface between the first functional layer and the second functional layer, and is not beneficial to the safety performance of the battery; however, if the thickness of the second functional layer is too small, the adhesion force F2 between the first functional layer and the second functional layer is too low, and there is a risk of demolding during the battery preparation and use, so that the thickness of the second functional layer needs to be controlled within a reasonable range.
In table 1, in the positive electrode sheet used in comparative example 1, no coating was performed between the aluminum foil and the active material layer, and the results showed that it failed the impact test and the nail penetration test; in the positive electrode sheet adopted in comparative example 2, only the first functional layer is coated between the aluminum foil and the active material layer, and the results show that the impact test passing rate and the penetrating nail test passing rate are low, and the safety performance is poor. In the positive electrode sheet adopted in comparative example 3, more polar groups are contained in the adhesive of the first functional layer and the second functional layer, so that strong adhesive interfaces are formed between the first functional layer and the aluminum foil, between the first functional layer and the second functional layer and between the second functional layer and the active material layer, and when the mechanical abuse occurs, the results show that the impact test passing rate and the penetrating nail test passing rate are low, and the safety performance is poor. In the positive electrode sheet adopted in comparative example 4, no polar group was contained in the adhesive of the first functional layer and the second functional layer, so that weak adhesion interfaces were formed between the first functional layer and the aluminum foil, between the first functional layer and the second functional layer, and between the second functional layer and the active material layer, and the results showed that the adhesive could not pass the impact test and the nail penetration test. In the positive electrode sheet adopted in comparative example 5, no polar group is in the adhesive of the first functional layer, so that a weak adhesion interface is formed between the first functional layer and the aluminum foil, and more polar groups are in the adhesive of the second functional layer, so that a strong adhesion interface is formed between the first functional layer and the second functional layer, and the result shows that the adhesive cannot pass the impact test and the penetrating nail test.
Although illustrative embodiments have been shown and described, it will be understood by those skilled in the art that the foregoing embodiments are not to be construed as limiting the application, and that changes, substitutions and alterations may be made herein without departing from the spirit, principles and scope of the application.

Claims (11)

  1. An electrochemical device comprising a positive electrode comprising a current collector, an active material layer, a first functional layer located between the current collector and the active material layer, and a second functional layer located between the first functional layer and the active material layer, wherein an adhesion force between the current collector and the first functional layer is F1, an adhesion force between the first functional layer and the second functional layer is F2, and an adhesion force between the second functional layer and the active material layer is F3, satisfying: f1 > F2, F3 > F2.
  2. The electrochemical device according to claim 1, wherein 25.ltoreq.f1/f2.ltoreq.100.
  3. The electrochemical device according to claim 1, wherein F3/F2 is 1.5 or more.
  4. The electrochemical device according to claim 1, wherein 200N/m.ltoreq.f1.ltoreq.400N/m, 4N/m.ltoreq.f2.ltoreq.8n/m.
  5. The electrochemical device according to claim 1, wherein the first functional layer has a thickness of 2 μm to 8 μm and the second functional layer has a thickness of 0.1 μm to 0.3 μm.
  6. The electrochemical device of claim 1, wherein the first functional layer comprises a first adhesive, a first conductive agent, and a first filler, and/or the second functional layer comprises a second adhesive, a second conductive agent, and a second filler.
  7. The electrochemical device of claim 6, wherein the first adhesive comprises at least one of polyacrylic acid, polyvinyl alcohol, polyacrylonitrile, polyacrylamide, carboxymethyl cellulose, polyimide, styrene-butadiene rubber, or polyurethane; and/or the second binder comprises at least one of polyvinylidene fluoride or polytetrafluoroethylene.
  8. The electrochemical device of claim 6, wherein at least one of conditions (a) to (d) is satisfied:
    (a) Based on the total weight of the first functional layer, the weight percentage of the first adhesive is 5-40%, the weight percentage of the first conductive agent is 3-10%, and the weight percentage of the first filler is 50-92%;
    (b) Based on the total weight of the second functional layer, the weight percentage of the second adhesive is 5-40%, the weight percentage of the second conductive agent is 3-10%, and the weight percentage of the second filler is 50-92%;
    (c) The first filler and the second filler each independently comprise at least one of lithium iron phosphate, silica, titania, alumina, boehmite, magnesia, zirconia, titania, silicon carbide, boron carbide, barium carbonate, potassium titanate, barium sulfate, vanadium trioxide, polyetheretherketone powder, polyamide powder, or cellulose powder;
    (d) The first conductive agent and the second conductive agent each independently include at least one of conductive carbon black, acetylene black, graphite, graphene, carbon nanotubes, carbon fibers, aluminum powder, nickel powder, or gold powder.
  9. The electrochemical device of claim 1, wherein the active material layer comprises at least one of lithium cobaltate, lithium nickel manganese aluminate, lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, lithium manganese phosphate, lithium iron silicate, lithium vanadium silicate, lithium cobalt silicate, lithium manganese silicate, spinel type lithium manganate, spinel type lithium nickel manganate, or lithium titanate.
  10. The electrochemical device of claim 1, wherein the current collector is aluminum foil.
  11. An electronic device comprising the electrochemical device of any one of claims 1-10.
CN202180031462.8A 2021-11-22 2021-11-22 Electrochemical device and electronic device including the same Pending CN118202483A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/CN2021/132074 WO2023087301A1 (en) 2021-11-22 2021-11-22 Electrochemical apparatus and electronic device containing said electrochemical apparatus

Publications (1)

Publication Number Publication Date
CN118202483A true CN118202483A (en) 2024-06-14

Family

ID=86396100

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202180031462.8A Pending CN118202483A (en) 2021-11-22 2021-11-22 Electrochemical device and electronic device including the same

Country Status (2)

Country Link
CN (1) CN118202483A (en)
WO (1) WO2023087301A1 (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117117205B (en) * 2023-10-25 2024-04-02 宁德时代新能源科技股份有限公司 Composite negative current collector, negative pole piece, winding structure battery core and secondary battery
CN117133927B (en) * 2023-10-25 2024-04-02 宁德时代新能源科技股份有限公司 Composite positive current collector, positive pole piece, winding structure battery core and power utilization device

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103633285B (en) * 2007-10-26 2017-07-07 赛昂能源有限公司 For the primer of battery electrode
CN105703010B (en) * 2014-11-28 2018-01-12 宁德时代新能源科技股份有限公司 Electrode slice and electrochemical energy storage device
CN106816575A (en) * 2015-11-30 2017-06-09 宁德新能源科技有限公司 Positive plate and lithium ion battery
JP6798393B2 (en) * 2017-03-31 2020-12-09 トヨタ自動車株式会社 Non-aqueous electrolyte secondary battery
CN112599722A (en) * 2020-12-14 2021-04-02 珠海冠宇电池股份有限公司 Positive plate and lithium ion battery comprising same
CN112582580A (en) * 2020-12-14 2021-03-30 珠海冠宇电池股份有限公司 Positive plate and lithium ion battery comprising same

Also Published As

Publication number Publication date
WO2023087301A1 (en) 2023-05-25

Similar Documents

Publication Publication Date Title
CN111326711A (en) Electrode pole piece, electrochemical device and electronic device comprising same
CN113394375B (en) Electrochemical device and electronic device
CN113097431B (en) Electrochemical device and electronic device
CN113366673B (en) Electrochemical device and electronic device
CN211879509U (en) Electrode pole piece, electrochemical device and electronic device comprising same
CN113066961B (en) Negative electrode sheet, electrochemical device, and electronic device
KR20230093520A (en) Electrochemical devices, electronic devices, and methods for manufacturing electrochemical devices
CN113078288B (en) Electrochemical device and electronic device
WO2022041194A1 (en) Electrode plate, electrochemical apparatus, and electronic apparatus
WO2023087301A1 (en) Electrochemical apparatus and electronic device containing said electrochemical apparatus
CN114583098A (en) Electrochemical device, method for manufacturing the same, and electronic device
CN115398667A (en) Electrode, method of manufacturing the same, electrochemical device, and electronic device
CN113421999B (en) Electrochemical device and electronic device
JP2023514835A (en) Electrode piece, electrochemical device and electronic device containing same
CN113078287B (en) Electrochemical device and electronic device
CN112802990B (en) Pole piece, electrochemical device and electronic device
CN113363417A (en) Electrochemical device and electronic device
CN113097474A (en) Electrochemical device and electronic device
KR20230093521A (en) Electrochemical and Electronic Devices
CN114122312A (en) Pole piece, electrochemical device and electronic device
CN113097426B (en) Electrochemical device and electronic device
CN116111037B (en) Electrochemical device and electronic device
CN113692654B (en) Pole piece, electrochemical device and electronic device
EP4089781A1 (en) Electrochemical device and electronic device
CN116964854A (en) Electrochemical device and electronic device

Legal Events

Date Code Title Description
PB01 Publication