CN116581249A - Dry-method positive plate, lithium ion battery and preparation method of dry-method positive plate - Google Patents

Dry-method positive plate, lithium ion battery and preparation method of dry-method positive plate Download PDF

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CN116581249A
CN116581249A CN202310847280.9A CN202310847280A CN116581249A CN 116581249 A CN116581249 A CN 116581249A CN 202310847280 A CN202310847280 A CN 202310847280A CN 116581249 A CN116581249 A CN 116581249A
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positive electrode
active material
electrode active
solid electrolyte
dry
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CN116581249B (en
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王明辉
宋赏
周柯
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Suzhou Qingtao New Energy S&T Co Ltd
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Suzhou Qingtao New Energy S&T Co Ltd
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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
    • H01M4/139—Processes of manufacture
    • H—ELECTRICITY
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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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    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0561—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of inorganic materials only
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    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/043—Processes of manufacture in general involving compressing or compaction
    • H01M4/0435—Rolling or calendering
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • 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
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
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    • 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
    • H01M4/139—Processes of manufacture
    • H01M4/1397—Processes of manufacture of electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H—ELECTRICITY
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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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    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
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    • 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 application discloses a dry-method positive plate, a lithium ion battery and a preparation method thereof, comprising the following steps: the first positive electrode active material layer is paved on the second positive electrode active material layer, an electrode film is formed through rolling, and the content of the binder in the first positive electrode active material layer is larger than that of the binder in the second positive electrode active material layer; compounding one side of a second positive electrode active material layer in the electrode film with a positive electrode current collector to obtain a pole piece to be treated; the first solid electrolyte layer is tiled on the second solid electrolyte layer, and the solid electrolyte layer is formed through rolling, wherein the content of the binder in the first solid electrolyte layer is larger than that of the binder in the second solid electrolyte layer; and carrying out dry-process compounding on one side of the first solid electrolyte layer in the solid electrolyte layers and one side of the electrode film of the electrode sheet to be treated to obtain the dry-process positive electrode sheet. The dry-method positive electrode plate, the lithium ion battery and the preparation method thereof provided by the application save cost, are safe and environment-friendly in preparation process, and avoid the use of solvents.

Description

Dry-method positive plate, lithium ion battery and preparation method of dry-method positive plate
Technical Field
The application relates to the technical field of batteries, in particular to a dry positive plate, a lithium ion battery and a preparation method thereof.
Background
The lithium ion battery is used as a green environment-friendly energy storage device, has the advantages of high working voltage, light weight, long cycle life, environmental friendliness and the like, and is widely applied to products such as mobile phones, computers, electric automobiles and the like. The lithium ion battery mainly comprises a battery pole piece, electrolyte, a diaphragm and the like, wherein the battery pole piece is the core of the lithium ion battery and directly determines the electrochemical performance and the safety of the battery.
The traditional lithium ion battery pole piece adopts a wet coating method, the method comprises the steps of dispersing active substances, conductive agents, binders and other materials in an organic solvent, stirring and dispersing the materials into uniform slurry, coating the slurry on a current collector by a coating machine, and drying the slurry by an oven to obtain the battery pole piece. A large amount of organic solvent is used in the preparation process of the slurry, and on one hand, the organic solvent has certain toxicity, so that the environment is polluted; on the other hand, the use of a large amount of organic solvent also significantly increases the production cost of lithium ion batteries.
Compared with a wet coating method, the dry method for preparing the battery pole piece can basically avoid the use of an organic solvent, not only solves the problem of environmental pollution in the battery manufacturing process, but also can effectively reduce the production cost of the lithium ion battery.
On the other hand, in order to improve the safety performance of the lithium ion battery, a solid electrolyte layer is generally disposed outside the active material layer, and the connection between the active material layer and the solid electrolyte layer is achieved by adhesion of an adhesive. However, since the active material layer prepared by the dry film forming method has low mechanical properties and the solid electrolyte layer has a small thickness of about tens of micrometers, the binding force between the positive electrode active material layer prepared by the dry film forming method and the solid electrolyte layer is weak; if the binder content is increased in order to increase the bonding strength between the two layers, the energy density of the prepared lithium ion battery may be low, thereby affecting the performance of the electrical performance of the lithium ion battery.
Therefore, how to prepare a positive electrode sheet for improving the energy density of a lithium ion battery by using a dry method is a problem to be solved by those skilled in the art.
Disclosure of Invention
The application provides a dry-method positive plate, a lithium ion battery and a preparation method thereof, which save cost, have safe and environment-friendly preparation process and avoid the use of solvents.
In order to solve one or more of the technical problems, the application adopts the following technical scheme:
in a first aspect, the application provides a method for preparing a dry-process positive electrode plate, which comprises the following steps:
Preparing a first positive electrode material into a first positive electrode active material layer by adopting a dry film forming method;
preparing a second positive electrode material into a second positive electrode active material layer by adopting a dry film forming method;
the first positive electrode active material layer is paved on the second positive electrode active material layer, an electrode film is formed through rolling, and the content of a binder in the first positive electrode active material layer is larger than that of the binder in the second positive electrode active material layer;
compounding one side of the second positive electrode active material layer in the electrode film with a positive electrode current collector to obtain a pole piece to be treated;
tiling a first solid electrolyte layer on a second solid electrolyte layer, and forming a solid electrolyte layer through rolling, wherein the content of a binding agent in the first solid electrolyte layer is larger than that in the second solid electrolyte layer;
and carrying out dry-process compounding on one side of the first solid electrolyte layer in the solid electrolyte layer and one side of the electrode film of the pole piece to be treated to obtain the dry-process positive pole piece.
Further, the first positive electrode active material layer contains a first positive electrode active material, and the first positive electrode active material is one or two of lithium iron phosphate and lithium manganese iron phosphate; the second positive electrode active material layer comprises a second positive electrode active material, and the molecular structural formula of the second positive electrode active material is as follows:
Li（Ni a Co b X c ）O 2 Wherein a+b+c=1 and a, b, c are all greater than 0, x is Mn or Al.
Further, in the dry positive electrode sheet, the thickness of the first positive electrode active material layer is 3 to 8% of the sum of the thicknesses of the first positive electrode active material layer and the second positive electrode active material layer.
Further, the thickness of the first solid electrolyte layer is 5-15% of the total thickness of the first solid electrolyte layer and the second solid electrolyte layer.
Further, the binder in the first positive electrode active material layer is the same as the binder in the second positive electrode active material layer.
Further, the binder in the first solid state electrolyte layer is the same as the binder in the second solid state electrolyte layer.
The mass fraction of the binder in the first positive electrode active material layer is 5-10wt%, and the mass fraction of the binder in the second positive electrode active material layer is 2-4wt%;
and/or the number of the groups of groups,
the mass fraction of the binder in the first solid electrolyte layer is 10-15wt%, and the mass fraction of the binder in the second solid electrolyte layer is 5-8wt%.
Further, the forming the first positive electrode material into the first positive electrode active material layer by a dry film forming method includes:
uniformly mixing a first positive electrode active material, a first conductive agent and a first binder by a dry method to obtain a first mixture, carrying out fiberizing treatment on the first mixture to obtain a first mixture, and carrying out heating calendaring treatment on the first mixture to obtain a first positive electrode active material layer;
And/or the number of the groups of groups,
the preparing of the second positive electrode material into the second positive electrode active material layer by the dry film forming method includes:
and uniformly mixing the second positive electrode active material, the second conductive agent and the second binder by a dry method to obtain a second mixture, carrying out fiberizing treatment on the second mixture to obtain a second mixture, and carrying out heating calendaring treatment on the second mixture to obtain a second positive electrode active material layer.
In a second aspect, the application also provides a dry-method positive electrode plate, which is prepared according to the preparation method of the dry-method positive electrode plate, and comprises a positive current collector, and a second positive active material layer, a first solid electrolyte layer and a second solid electrolyte layer which are sequentially arranged on at least one surface of the positive current collector.
Further, the second positive electrode active material layer, the first solid electrolyte layer and the second solid electrolyte layer are sequentially arranged on two sides of the positive electrode current collector.
In a third aspect, the application also provides a lithium ion battery, which comprises a dry positive electrode plate, a negative electrode plate, a diaphragm and electrolyte, wherein the dry positive electrode plate is the dry positive electrode plate.
According to the specific embodiment provided by the application, the application discloses the following technical effects:
the application provides a dry-method positive electrode plate, a lithium ion battery and a preparation method thereof. Because the content of the binder in the first positive electrode active material layer is greater than that in the second positive electrode active material layer, and the content of the binder in the first solid electrolyte layer is greater than that in the second solid electrolyte layer, a good bonding effect can be achieved between the first positive electrode active material layer and the first solid electrolyte layer, and the content of the binder in the second positive electrode active material layer and the second solid electrolyte layer is less, so that the energy density of the lithium ion battery can be remarkably improved.
Of course, it is not necessary for any one product to practice the application to achieve all of the advantages set forth above at the same time.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a flowchart of a method for preparing a dry positive electrode sheet according to an embodiment of the present application;
fig. 2 is a schematic structural diagram of a dry positive electrode sheet according to an embodiment of the present application;
fig. 3 is a schematic structural diagram of another dry positive electrode sheet according to an embodiment of the present application.
Detailed Description
The following description of the technical solutions in the embodiments of the present application will be clear and complete, and it is obvious that the described embodiments are only some embodiments of the present application, but not all embodiments. All other embodiments, which are derived by a person skilled in the art based on the embodiments of the application, fall within the scope of protection of the application.
As described in the background art, in the process of preparing the battery pole piece by adopting the dry method, the addition of an organic solvent is basically not needed, so that the problem of environmental pollution in the battery manufacturing process is solved, and the production cost of the lithium ion battery is effectively reduced. In order to improve the safety performance of lithium ion batteries, a solid electrolyte layer is generally disposed outside the active material layer, and the connection between the active material layer and the solid electrolyte layer is achieved by bonding with an adhesive. In order to improve the adhesion of the interface between the active material layer and the solid electrolyte layer, the content of the binder in the active material layer and the solid electrolyte layer is generally required to be increased, and too high a content of the binder can cause low energy density of the prepared lithium ion battery, thereby affecting the exertion of the electrical performance of the lithium ion battery.
In order to solve one or more of the problems, the application provides a dry positive electrode plate, a lithium ion battery and a preparation method thereof, wherein a first positive electrode active material layer with higher binder content is arranged outside a second positive electrode active material layer, a first solid electrolyte layer with higher binder content is arranged outside the second solid electrolyte layer, and the bonding of the second positive electrode active material layer and the second solid electrolyte layer is realized through the bonding of the first positive electrode active material layer and the first solid electrolyte layer, and the energy density of the lithium ion battery can be remarkably improved due to the fact that the binder content in the second positive electrode active material layer and the second solid electrolyte layer is less.
The following is an optional technical scheme of the present application, but not limiting the technical scheme provided by the present application, and the technical purpose and beneficial effects of the present application can be better achieved and achieved through the following optional technical scheme.
The application provides a preparation method of a dry-method positive electrode plate, which is shown in figure 1 and comprises the following steps:
s1: the first positive electrode material is formed into a first positive electrode active material layer by a dry film forming method.
Specifically, a first positive electrode active material, a first conductive agent and a first binder are uniformly mixed by a dry method to obtain a first mixture, the first mixture is subjected to a fiberization treatment to obtain a first mixture, and the first mixture is subjected to a heating calendaring treatment to obtain a first positive electrode active material layer.
In some embodiments, step S1 further comprises premixing, i.e., mixing the first positive electrode active material and the first conductive agent prior to mixing with the first binder. The first positive electrode active material and the first conductive agent should be premixed under a relatively low shearing force, and may be mixed in the presence of a solvent or dry mixed in the absence of a solvent. When mixing is performed in the presence of a solvent, the first positive electrode active material and the first conductive agent need to be dried to remove the solvent before mixing with the first binder.
It should be noted that the substantial absence of solvent in the present application means that the addition of ethanol or other liquid lubricant during the premixing process may help the active material and the conductive agent to be mixed more uniformly, and the use of solvent is not involved in the process of fiberizing the mixture and other processes that follow.
In a specific embodiment, the mixing process may be performed in a stirrer or ball milling may be performed under the protection of a protective gas. Specific mixing means include, but are not limited to, known mixing techniques such as ball milling, ultrasonic mixing, stirring mixing or acoustic mixing, and the user may select according to actual needs, which are not limited herein.
In some embodiments, the first binder comprises any one or a combination of at least two of Polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyethylene oxide (PEO), poly (vinylidene fluoride-hexafluoropropylene) (PVDF-HFP), polyacrylonitrile (PAN), polyvinyl alcohol (PVA), or polyacrylic acid (PAA).
The mass fraction of the first binder in the first positive electrode active material layer is 5 to 10wt%, more specifically, the mass fraction of the first binder in the first positive electrode active material layer may be 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, and specific point values among the above point values, which are limited in scope and for brevity, the present application is not exhaustive to list the specific point values included in the range.
In some embodiments, the step of fiberizing the first mixture to obtain a first mixture refers to breaking the first binder into fibers under the action of shear force, where the fiberizing of the first binder facilitates the preparation of the dry electrode and the improvement of the adhesive property. The crushing method according to the embodiment of the present application is not particularly limited, and any known crushing method can be applied to the present application without departing from the concept of the present application. As an embodiment, the crushing method includes, but is not limited to, one or more of jet milling or high-speed dispersion crushing, and when a plurality of crushing methods are used in combination, a tandem manner may be adopted.
In the embodiment of the present application, the first positive electrode active material layer is obtained by subjecting the first mixture to a heat rolling treatment, and the present application is not particularly limited to the rolling process, and any known rolling process can be used in the present application without departing from the concept of the present application. The rolling process can be arranged into multiple sections according to the requirement, for example, the rolling process comprises a first rolling process and a second rolling process, and a third rolling process and a fourth rolling process are arranged according to the requirement, and it is understood that the rolling processes of the sections can be directly connected or embedded into other working procedures according to the requirement.
The number of times of rolling is not particularly limited in the present application, and may be a number of times of rolling to a preset thickness of the first positive electrode active material layer. The temperature of the calendering process is 45-300 ℃, such as 45 ℃, 50 ℃, 60 ℃, 70 ℃, 80 ℃, 90 ℃, 100 ℃, 120 ℃, 135 ℃, 150 ℃, 165 ℃, 180 ℃, 200 ℃ or 300 ℃, and any range therebetween.
For the process of shaping the first positive electrode active material layer by calendering, the fibrillated first binder can be provided with higher adhesive properties by increasing the calendering temperature, which should be selected based on the filament binder softening but below the decomposition temperature of the first binder.
In one embodiment, the pressure of the heat calendering treatment is 100kPa to 800kPa, such as 100kPa, 150kPa, 200kPa, 250kPa, 300kPa, 400kPa, 500kPa, 600kPa, 650kPa, 700kPa, or 800kPa, or any range therebetween, preferably 200kPa to 600kPa.
Further, in the embodiment of the present application, the first positive electrode active material is a compound capable of reversibly intercalating and deintercalating lithium, and specifically, may include a lithium transition metal composite oxide containing lithium and at least one other transition metal selected from the group consisting of nickel, cobalt, manganese, and aluminum; preferably, the transition metal may be lithium, nickel, cobalt, manganese, or the like.
More specifically, the lithium transition metal composite oxide may be a lithium manganese-based oxide (e.g., liMnO 2 、LiMn 2 O 4 Etc.), lithium cobalt-based oxides (e.g. LiCoO 2 Etc.), lithium nickel-based oxides (e.g., liNiO 2 Etc.), lithium nickel manganese oxides (e.g., liNi1-yMnyO 2 (wherein 0<y<1)、LiMn 2-z Ni z O 4 (wherein 0<z<2) Etc.), lithium nickel cobalt-based oxides (e.g., liNi 1- y1 Co y1 O 2 (wherein 0<y1<1) Etc.), lithium manganese cobalt-based oxides (e.g., liCo 1-y2 Mn y2 O 2 (wherein 0<y2<1)、LiMn 2- z1 Co z1 O 4 (wherein 0<z1<2) Etc.), lithium nickel manganese cobalt-based oxides (e.g., li (Ni) p Co q Mn r1 )O 2 (wherein 0<p<1，0<q<1，0<r1<1, p+q+r1=1), or lithium nickel cobalt transition metal (M) oxide (e.g., li (Ni) p2 Co q2 Mn r3 A S2 )O 2 (wherein M is selected from the group consisting of Al, fe, V, cr, ti, ta, mg and Mo, p2, q2, r3 and s2 are each the atomic fraction of an independent element, and 0<p2<1、0<q2<1、0<r3<1、0<s2<1. p2+q2+r3+s2=1), etc.), and may contain any one of them or two or more of them. Of these, the lithium transition metal composite oxide may be LiCoO in terms of being capable of increasing the capacity and stability of the battery 2 、LiMnO 2 、LiNiO 2 Lithium nickel manganese cobalt oxide (e.g. Li (Ni) 0.6 Mn 0.2 Co 0.2 )O 2 、Li(Ni 0.5 Mn 0.3 Co 0.2 )O 2 、Li(Ni 0.7 Mn 0.15 Co 0.15 )O 2 Or Li (Ni) 0.8 Mn 0.1 Co 0.1 )O 2 Etc. or lithium nickel cobalt aluminum oxide (e.g., li (Ni 0.8 Co 0.15 Al 0.05 )O 2 Etc.), etc. When considering according to the pairThe lithium transition metal composite oxide may be Li (Ni 0.6 Mn 0.2 Co 0.2 )O 2 、Li(Ni 0.5 Mn 0.3 Co 0.2 )O 2 、Li(Ni 0.7 Mn 0.15 Co 0.15 )O 2 Or Li (Ni) 0.8 Mn 0.1 Co 0.1 )O 2 Etc., and any one or a mixture of two or more thereof may be used.
The first positive electrode conductive agent is mainly used to assist and improve conductivity in the secondary battery, and is not particularly limited as long as it has conductivity without causing chemical changes. Specifically, the first positive electrode conductive agent may include graphite, such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; conductive tubes, such as carbon nanotubes; metal powders such as fluorocarbon powder, aluminum powder, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxide; and polyphenylene derivatives, and may preferably contain carbon black in terms of improving conductivity.
The specific surface area of the first positive electrode conductive agent may be 80m 2 /g to 200m 2 /g, preferably 100m 2 /g to 150m 2 /g。
The above materials are merely illustrative examples of the first positive electrode material selected, and it is understood that any known positive electrode material including positive electrode active materials, positive electrode binders, positive electrode conductive agents, and other additives can be used in the present application without departing from the spirit of the present application.
S2: and preparing the second positive electrode material into a second positive electrode active material layer by adopting a dry film forming method.
Specifically, a second positive electrode active material, a second conductive agent and a second binder are uniformly mixed by a dry method to obtain a second mixture, the second mixture is subjected to fiberizing treatment to obtain a second mixture, and the second mixture is subjected to heating calendaring treatment to obtain a second positive electrode active material layer.
Wherein, regarding the second positive electrode active material, the second conductive agent, the second binder; dry mixing the second positive electrode active material, the second conductive agent and the second binder; carrying out a fiberizing treatment mode on the second mixture; the way of heating and calendaring the second mixture may refer to the relevant content in step S1, and will not be described here again.
The mass fraction of the second binder in the second positive electrode active material layer is 2 to 4wt%, more specifically, the mass fraction of the second binder in the second positive electrode active material layer may be 2wt%, 3wt%, 4wt%, and specific point values between the above point values, which are limited in space and for the sake of brevity, the present invention does not exhaustive list the specific point values included in the range.
S3: and paving the first positive electrode active material layer on the second positive electrode active material layer, and forming an electrode film through rolling, wherein the content of the binder in the first positive electrode active material layer is larger than that of the binder in the second positive electrode active material layer.
Specifically, the thickness of the first positive electrode active material layer is 5 to 30 μm, preferably, the thickness of the first positive electrode active material layer is 8 to 15 μm; more preferably, the thickness of the first positive electrode active material layer is 10 to 12 μm; more specifically, the thickness of the first positive electrode active material layer may be 5 μm, 15 μm, 20 μm, 25 μm, 30 μm, and specific point values between the above point values, and the present invention is not exhaustive of the specific point values included in the range, for the sake of brevity and conciseness. The thickness of the second positive electrode active material layer is 50 to 500 μm, preferably, the thickness of the second positive electrode active material layer is 100 to 300 μm; more preferably, the thickness of the second positive electrode active material layer is 150 to 250 μm; more specifically, the thickness of the second positive electrode active material layer may be 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, 500 μm and specific point values between the above point values, which are limited in space and for the sake of brevity, the present invention is not exhaustive. Since the second positive electrode active material layer has a relatively thick thickness but a relatively low binder content, and the first positive electrode active material layer has a relatively thin thickness but a relatively high binder content, the binder content in the electrode film is not high, and thus, in combination, the energy density of the lithium ion battery is not reduced in this range.
Further, the binder in the first positive electrode active material layer and the binder in the second positive electrode active material layer are the same, and the same binder has the same binding force, in which case the binding strength between the layers is achieved more easily by adjusting the content of the binder due to the same binder.
S4: and compounding one side of the second positive electrode active material layer in the electrode film with a positive electrode current collector to obtain a pole piece to be treated.
The mode of compounding the electrode film and the positive current collector is not limited in the embodiment of the invention, and the electrode film and the positive current collector can be compounded in a hot pressing mode.
Further, the first positive electrode active material layer contains a first positive electrode active material, and the first positive electrode active material is one or two of lithium iron phosphate and lithium manganese iron phosphate; the second positive electrode active material layer comprises a second positive electrode active material, and the molecular structural formula of the second positive electrode active material is as follows:
Li（Ni a Co b X c ）O 2 wherein a+b+c=1 and a, b, c are all greater than 0, x is Mn or Al.
According to the multi-layer positive electrode structure, the first positive electrode active material layer and the second positive electrode active material layer are made of the positive electrode active material, and the surface of the positive electrode active material is selected from lithium iron phosphate or lithium manganese iron phosphate with better safety and cycle performance, so that the safety performance of the battery is further improved.
In the embodiment of the present application, the positive electrode current collector is not particularly limited as long as it has conductivity without causing chemical changes in the battery. In particular, copper, stainless steel, aluminum, nickel, titanium, or a metal current collector surface-treated with carbon or other substances may be used.
The positive electrode current collector may generally have a thickness of 3 μm to 500 μm.
The positive electrode current collector may have fine irregularities formed on the surface thereof to improve the adhesion of the positive electrode active material. For example, positive electrode current collectors of various shapes such as films, sheets, foils, nets, porous bodies, foams and non-woven fabrics may be used.
In order to improve the bonding performance of the electrode film and the positive current collector, the positive current collector may be subjected to an activation treatment, such as a mechanical treatment or a chemical treatment, including but not limited to corona treatment, ultraviolet irradiation, plasma irradiation, chemical etching, electrochemical etching, direct current anodic oxidation, and other technical means.
S5: and flatly paving the first solid electrolyte layer on the second solid electrolyte layer, and rolling to form the solid electrolyte layer, wherein the content of the binding agent in the first solid electrolyte layer is larger than that in the second solid electrolyte layer.
The first solid electrolyte layer and the second solid electrolyte layer comprise solid electrolytes, and the solid electrolytes have better chemical inertness to electrolyte or liquid additives in the battery, so that the safety performance of the battery is greatly improved. The solid electrolyte herein may be a fast ion conductor or a metal oxide, wherein fast ion conductor is also known as a lithium ion conductive substance, which generally refers to a substance having a better ion conductive property. The fast ionic conductor in the present application comprises an inorganic solid state electrolyte, which may comprise one or more solid state electrolyte particles, preferably solid state electrolyte particles may comprise particles of one or more oxides, particles of sulfides, particles of halides, particles of borates, particles of nitrides or particles of hydrides.
As one embodiment, the first solid electrolyte layer and/or the second solid electrolyte layer consists of only a binder and a solid electrolyte.
As an embodiment, the oxide particles may comprise one or more garnet ceramics, LISICON-type oxides, NASICON-type oxides, and perovskite-type ceramics. For example, the one or more garnet ceramics may be selected from the group consisting of Group of people: li (Li) 6.5 La 3 Zr 1.75 Te 0.25 O 12 、Li 7 La 3 Zr 2 O 12 、Li 6.2 Ga 0.3 La 2.95 Rb 0.05 Zr 2 O 12 、Li 6.85 La 2.9 Ca 0.1 Zr 1.75 Nb 0.25 O 12 、Li 6.25 Al 0.25 La 3 Zr 2 O 12 、Li 6.75 La 3 Zr 1.75 Nb 0.25 O 12 、Li 6.75 La 3 Zr 1.75 Nb 0.25 O 12 And combinations thereof. The one or more LISICON-type oxides may be selected from the group comprising: li (Li) 14 Zn(GeO 4 ) 4 、Li 3+x (P 1−x Si x )O 4 (wherein 0<x<1）、Li 3+x Ge x V 1-x O 4 (wherein 0<x<1) And combinations thereof. One or more NASICON type oxides can be selected from LiMM ʹ (PO 4 ) 3 Definition, wherein M and M ʹ are independently selected from Al, ge, ti, sn, hf, zr and La. For example, in certain variations, the one or more NASICON-type oxides may be selected from the group consisting of: li (Li) 1+x Al x Ge 2-x (PO 4 ) 3 (LAGP) (wherein 0.ltoreq.x.ltoreq.2), li 1+x Al x Ti 2-x (PO 4 ) 3 (LATP) (where 0.ltoreq.x.ltoreq.2), li 1+x Y x Zr 2-x (PO 4 ) 3 (LYZP) (wherein 0.ltoreq.x.ltoreq.2), li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 、LiTi 2 (PO 4 ) 3 、LiGeTi(PO 4 ) 3 、LiGe 2 (PO 4 ) 3 、LiHf 2 (PO 4 ) 3 And combinations thereof. The one or more perovskite ceramics may be selected from the group comprising: li (Li) 3.3 La 0.53 TiO 3 、LiSr 1.65 Zr 1.3 Ta 1.7 O 9 、Li 2x-y Sr 1-x Ta y Zr 1-y O 3 (where x=0.75y and 0.60<y<0.75）、Li 3/8 Sr 7/16 Nb 3/4 Zr 1/4 O 3 、Li 3x La (2/3-x) TiO 3 (wherein 0<x<0.25 A) and combinations thereof. In one variation, the one or more oxide-based materials may have a weight of greater than or equal to about 10 -5 S/cm to less than or equal to about 10 -1 S/cm ionic conductivity.
In various aspects, the sulfide-based particles may include one or more sulfide-based materials selected from the group consisting of: li (Li) 2 S-P 2 S 5 、Li 2 S-P 2 S 5 -MS x (wherein M is Si, ge and Sn and 0.ltoreq.x.ltoreq.2), li 3.4 Si 0.4 P 0.6 S 4 、Li 10 GeP 2 S 11.7 O 0.3 、Li 9.6 P 3 S 12 、Li 7 P 3 S 11 、Li 9 P 3 S 9 O 3 、Li 10.35 Si 1.35 P 1.65 S 12 、Li 9.81 Sn 0.81 P 2.19 S 12 、Li 10 (Si 0.5 Ge 0.5 )P 2 S 12 、Li(Ge 0.5 Sn 0.5 )P 2 S 12 、Li(Si 0.5 Sn 0.5 )PsS 12 、Li 10 GeP 2 S 12 （LGPS）、Li 6 PS 5 X (wherein X is Cl, br or I), li 7 P 2 S 8 I、Li 10.35 Ge 1.35 P 1.65 S 12 、Li 3.25 Ge 0.25 P 0.75 S 4 、Li 10 SnP 2 S 12 、Li 10 SiP 2 S 12 、Li 9.54 Si 1.74 P 1.44 S 11.7 C l0.3 And combinations thereof. In one variation, the one or more sulfide-based materials may have a composition of greater than or equal to about 10 -7 An ion conductivity of from S/cm to less than or equal to about 1S/cm.
In various aspects, the halide-based particles may include a compound selected from the group consisting ofOne or more halide-based materials of the group: li (Li) 2 CdC l4 、Li 2 MgC l4 、Li 2 Cd I4 、Li 2 ZnI 4 、Li 3 OCl、LiI、Li 5 ZnI 4 、Li 3 OCl 1-x Br x (wherein 0<x<1) And combinations thereof. In one variation, the one or more halide-based materials may have a weight ratio of greater than or equal to about 10 -8 S/cm to less than or equal to about 10 -1 S/cm ionic conductivity.
In various aspects, the borate-based particles may include one or more borate-based materials selected from the group consisting of: li (Li) 2 B 4 O 7 、Li 2 O-(B 2 O 3 )-(P 2 O 5 ) And combinations thereof. In one variation, the one or more borate-based materials may have a weight ratio of greater than or equal to about 10 -7 S/cm to less than or equal to about 10 -2 S/cm ionic conductivity.
In various aspects, the nitride-based particles may include one or more nitride-based materials selected from the group consisting of: li (Li) 3 N、Li 7 PN 4 、LiSi 2 N 3 LiPON, and combinations thereof. In one variation, the one or more nitride-based materials may have a composition greater than or equal to about 10 -9 An ion conductivity of from S/cm to less than or equal to about 1S/cm.
In various aspects, the hydride-based particles can comprise one or more hydride-based materials of the group of: li (Li) 3 AlH 6 、LiBH 4 、LiBH 4 -LiX (wherein X is one of Cl, br and I), liNH 2 、Li 2 NH、LiBH 4 -LiNH 2 And combinations thereof. In one variation, the one or more hydride-based materials can have a composition of greater than or equal to about 10 -7 S/cm to less than or equal to about 10 -2 S/cm ionic conductivity.
In further variations, the solid electrolyte particles may be one or more metal oxide particles or compriseLithium compounds, including but not limited to Al 2 O 3 、SiO 2 、TiO 2 、LiNbO 3 、Li 4 Ti 5 O 4 、Li 3 PO 4 。
In one embodiment, the solid state electrolyte further includes a portion of a polymer solid state electrolyte, the polymer solid state electrolyte and the inorganic solid state electrolyte comprising a composite solid state electrolyte. In the embodiment of the application, the mass ratio of the inorganic solid electrolyte and the polymer solid electrolyte in the composite solid electrolyte is not particularly required, and a user can design according to actual needs. Wherein, the polymer solid electrolyte can be at least one of polyvinyl chloride (PVC), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA) and polyethylene oxide (PEO).
In another embodiment, the first and second solid state electrolyte layers further comprise a binder and a lithium salt.
The binder includes, but is not limited to, polyethylene glycol (PEO), poly (p-phenylene oxide) (PPO), poly (methyl methacrylate) (PMMA), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polyvinylidene fluoride co-hexafluoropropylene (PVDF-HFP), polyvinyl chloride (PVC), and combinations thereof, etc., and may be selected according to actual needs without departing from the inventive concept, and is not particularly limited herein.
The lithium salt comprises lithium hexafluorophosphateLiPF 6 ) Lithium perchlorate (LiClO) 4 ) Lithium tetrachloroaluminate (LiAlCl) 4 ) Lithium iodide (LiI), lithium bromide (LiBr), lithium thiocyanate (LiSCN), lithium tetrafluoroborate (LiBF) 4 ) Lithium difluorooxalato borate (LiBF) 2 （C 2 O 4 ) (LiODFB), lithium tetraphenylborate (LiB (C) 6 H 5 ） 4 ) Lithium bis (oxalato) borate (LiB (C) 2 O 4 ） 2 ) Lithium tetrafluorooxalate phosphate (LiPF) 4 （C 2 O 4 ) (LiFeP), lithium nitrate (LiNO) 3 ) Lithium hexafluoroarsenate (LiAsF) 6 ) Lithium triflate (LiCF) 3 SO 3 ) Lithium bis (trifluoromethanesulfonyl imide) (LITFSI) (LiN (CF) 3 SO 2 ） 2 ) Lithium bis (fluorosulfonyl imide) (LiN (FSO) 2 ） 2 ) (LIFSI) and combinations thereof. In certain variations, the lithium salt is selected from lithium hexafluorophosphateLiPF 6 ) Lithium bis (trifluoromethanesulfonyl imide) (LiTFSI) (LiN (CF) 3 SO 2 ） 2 ) Lithium bis (fluorosulfonyl imide) (LiN (FSO) 2 ） 2 ) (LiFSI), lithium fluoroalkylphosphonate (LiFAP), lithium phosphate (Li) 3 PO 4 ) And combinations thereof.
Further, the binder content in the first solid state electrolyte layer is greater than the binder content in the second solid state electrolyte layer. The mass fraction of the binder in the first solid electrolyte layer is 10 to 15wt%, more specifically, the mass fraction of the binder in the first solid electrolyte layer may be 10wt%, 11wt%, 12wt%, 13wt%, 14wt%, 15wt% and specific point values between the above point values, which are limited in length and for brevity, the present invention is not exhaustive list of specific point values included in the range. The mass fraction of the binder in the second solid electrolyte layer is 5-8wt%, more specifically, the mass fraction of the binder in the second solid electrolyte layer may be 5wt%, 6wt%, 7wt%, 8wt%, and specific point values between the above point values, which are limited in space and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the range. The thickness of the first solid electrolyte layer is 1 to 8 μm, preferably 3 to 8 μm; the thickness of the second solid electrolyte layer is 10 to 40 μm, more specifically, the thickness of the second solid electrolyte layer is 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, and specific point values between the above point values. The second solid electrolyte layer has a thicker thickness but lower binder content, and the first solid electrolyte layer has a thinner thickness but higher binder content, so that the effect of excessive internal resistance of the battery on the battery performance caused by excessive binder content is prevented, and better interface recombination between the solid electrolyte and the anode is realized.
S6: and carrying out dry-process compounding on one side of the first solid electrolyte layer in the solid electrolyte layer and one side of the electrode film of the pole piece to be treated to obtain the dry-process positive pole piece.
Specifically, the first solid electrolyte layer of the solid electrolyte layers and the first positive electrode active material layer of the electrode film are bonded, and the bonding effect between the first solid electrolyte layer and the first positive electrode active material layer is good because the binder content in the first solid electrolyte layer and the first positive electrode active material layer is high. The first solid electrolyte layer and the first positive electrode active material layer correspond to a glue layer that connects the electrode film and the solid electrolyte layer together.
In the finally prepared dry-process positive electrode sheet, the thickness of the first positive electrode active material layer is 3-8% of the sum of the thicknesses of the first positive electrode active material layer and the second positive electrode active material layer, and the thickness of the first solid electrolyte layer is 5-15% of the sum of the thicknesses of the first solid electrolyte layer and the second solid electrolyte layer. Since the second positive electrode active material layer has a relatively thick thickness but a relatively low binder content, the first positive electrode active material layer has a relatively thin thickness but a relatively high binder content, and the second solid electrolyte layer has a relatively thick thickness but a relatively low binder content, and the first solid electrolyte layer has a relatively thin thickness but a relatively high binder content, the binder content in the electrode film and the solid electrolyte layer is not high, and the energy density of the lithium ion battery is not reduced in this range.
In the embodiment of the application, the first positive electrode active material layer with higher binder content is arranged outside the second positive electrode active material layer, the first solid electrolyte layer with higher binder content is arranged outside the second solid electrolyte layer, the bonding strength between the electrode film and the solid electrolyte layer is improved through the bonding of the first positive electrode active material layer and the first solid electrolyte layer, and the energy density of the lithium ion battery can be remarkably improved due to the fact that the binder content in the second positive electrode active material layer and the second solid electrolyte layer is lower.
The application also provides a dry-method positive electrode plate, which is prepared by adopting the preparation method provided by any one example. The energy density of the lithium ion battery can be improved by applying the dry-method positive electrode plate to the lithium ion battery.
In a specific embodiment, as shown in fig. 2, the dry cathode sheet includes a cathode current collector 10, and a second cathode active material layer 11, a first cathode active material layer 12, a first solid electrolyte layer 13, and a second solid electrolyte layer 14 sequentially disposed on one side of the cathode current collector 10.
In another specific embodiment, as shown in fig. 3, in the dry positive electrode sheet, a second positive electrode active material layer 21, a first positive electrode active material layer 22, a first solid electrolyte layer 23, and a second solid electrolyte layer 24 are sequentially provided on both sides of a positive electrode current collector 20.
The application also provides a lithium ion battery corresponding to the dry positive electrode plate, which comprises the dry positive electrode plate, the negative electrode plate, the diaphragm and the electrolyte. The relevant content of the dry-method positive electrode sheet can be introduced by referring to the above description, and will not be repeated here.
The negative electrode plate comprises a negative electrode current collector and a negative electrode active material layer arranged on the surface of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode binder, a negative electrode active material and a negative electrode conductive agent.
The present application is not particularly limited as long as it has conductivity without causing chemical changes in the battery without departing from the inventive concept.
Optionally, the shape of the negative electrode current collector includes a foil shape, a plate shape, a mesh shape, or the like.
Optionally, the negative electrode current collector includes any one of simple substances of aluminum, copper, nickel or zinc.
Optionally, the negative electrode current collector includes any one of aluminum, copper, nickel, or zinc alloy.
The negative electrode binder is a high molecular compound for adhering a negative electrode active material to a negative electrode current collector, and has the main functions of binding and maintaining the negative electrode active material, enhancing the contact between the negative electrode active material and a negative electrode conductive agent and between the negative electrode active material and the negative electrode current collector, and better stabilizing the structure of a negative electrode plate. The negative electrode binder includes, but is not limited to, polytetrafluoroethylene (PTFE), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), nitrile-butadiene rubber (NBR), styrene-ethylene-butylene-styrene copolymer (SEBS), styrene-butadiene-styrene copolymer (SBS), lithium polyacrylate (LiPAA), sodium polyacrylate (NaPAA), sodium alginate, lithium alginate, etc., and the user may select according to actual needs, and is not particularly limited herein.
The kind of the negative electrode active material is not particularly limited in the present application, and any known negative electrode active material can be used in the present application without departing from the concept of the present application. In one embodiment, the anode active material comprises lithium metal and/or a lithium alloy, in other embodiments, the anode active material is a silicon-based anode active material comprising silicon, such as a silicon alloy, silicon oxide, or a combination thereof, which may also be mixed with graphite in some cases. In other embodiments, the anode active material may include a carbonaceous-based anode active material including one or more of graphite, graphene, carbon Nanotubes (CNTs), and combinations thereof. In further embodiments, the negative electrode active material includes one or more negative electrode active materials that accept lithium, such as lithium titanium oxide (Li 4 Ti 5 O 12 ) One or more transition metals (such as tin (Sn)), one or more metal oxides (such as vanadium oxide (V) 2 O 5 ) Tin oxide (SnO), titanium dioxide (TiO) 2 ) Titanium niobium oxide (Ti) x Nb y O z Where 0.ltoreq.x.ltoreq.2, 0.ltoreq.y.ltoreq.24, and 0.ltoreq.z.ltoreq.64), metal alloys (such as copper-tin alloys (Cu) 6 Sn 5 ) And one or more metal sulfides such as iron sulfide (FeS).
The negative electrode conductive agent may include a carbon-based material, powdered nickel or other metal particles, or a conductive polymer. The carbon-based material may include particles such as carbon black, graphite, super-P, acetylene black (such as KETCHENTM black or denktatm black), carbon fibers and single-walled carbon nanotubes (SWCNTs), graphene, and the like. Examples of the conductive polymer include polyaniline, polythiophene, polyacetylene, polypyrrole, poly (3, 4-ethylenedioxythiophene) polysulfstyrene, and the like.
The above materials are merely illustrative examples of the selected anode materials, and it is understood that any known anode materials including anode binders, anode active materials, anode conductive agents, and other additives can be used in the present application without departing from the spirit of the present application.
In order to prevent short circuits inside the battery, a separator is also required to be included in the lithium ion battery, and the separator is located between the positive electrode tab and the negative electrode tab to block the transmission of electrons inside the battery. The separator in the present application is any one of various separators used in lithium ion batteries, and includes a material having low resistance to ion migration of an electrolyte and good electrolyte holding ability. In the embodiment of the present application, the separator includes, but is not limited to, one or more of polypropylene, polyethylene, polyvinylidene fluoride, polyimide, and polyacrylonitrile, and the separator may be selected by a user according to actual needs, which is not specifically limited herein. It is to be noted here that when a solid electrolyte is employed, the solid electrolyte functions as a separator, and a conventional separator is not required.
In a specific embodiment, the membrane has a pore size of 0.01 μm to 15 μm and a thickness of 10 μm to 400 μm.
The electrolyte includes a liquid electrolyte and a solid electrolyte. The liquid electrolyte comprises a lithium salt and a nonaqueous solvent, the lithium salt comprising LiPF 6 、LiBF 4 、LiAsF 6 、LiClO 4 、LiB(C 6 H 5 ) 4 、LiCH 3 SO 3 、 LiCF 3 SO 3 、LiN(SO 2 CF 3 ) 2 、LiC (SO 2 CF 3 ) 3 、LiSiF 6 、LiBOB、LiBF 2 (C 2 O 4 ) One or more of these may be selected by the user according to actual needs, and are not particularly limited herein. In the embodiment of the application The lithium salt is preferably LiPF 6 Because of LiPF 6 Can have high ion conductivity and can improve cycle characteristics of the battery.
The nonaqueous solvent comprises one or more of a carbonate compound, a carboxylate compound and an ether compound. Further, the carbonate compound includes a chain carbonate compound, a cyclic carbonate compound, and a fluorocarbonate compound. Specifically, the chain carbonate compounds include, but are not limited to, diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), ethylmethyl carbonate (MEC), and the like; the cyclic carbonate compounds include, but are not limited to, ethylene Carbonate (EC), propylene Carbonate (PC), butylene Carbonate (BC), vinyl Ethylene Carbonate (VEC), and the like; the fluorocarbonate compounds include, but are not limited to, 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 the like.
The carboxylic acid ester compounds include, but are not limited to, methyl acetate, ethyl acetate, n-propyl acetate, t-butyl acetate, methyl propionate, ethyl propionate, gamma-butyrolactone, decalactone, valerolactone, mevalonic acid lactone, caprolactone, methyl formate, and the like.
The ether compounds include, but are not limited to, dibutyl ether, tetraglyme, diglyme, 1, 2-dimethoxyethane, 1, 2-diethoxyethane, ethoxymethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, and the like.
Further, the nonaqueous solvent may further include one or more of 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 ester.
In embodiments of the present application, the solid electrolyte includes, but is not limited to, a polymer solid electrolyte, an oxide solid electrolyte, a sulfide solid electrolyte, and the like.
Wherein the polymer solid electrolyte comprises at least one of polyvinyl chloride (PVC), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA) and polyethylene oxide (PEO).
The oxide solid electrolyte may include one or more garnet ceramics, LISICON-type oxides, NASICON-type oxides, and perovskite-type ceramics, among others. For example, the one or more garnet ceramics may be selected from the group consisting of: li (Li) 6.5 La 3 Zr 1.75 Te 0.25 O 12 、Li 7 La 3 Zr 2 O 12 、Li 6.2 Ga 0.3 La 2.95 Rb 0.05 Zr 2 O 12 、Li 6.85 La 2.9 Ca 0.1 Zr 1.75 Nb 0.25 O 12 、Li 6.25 Al 0.25 La 3 Zr 2 O 12 、Li 6.75 La 3 Zr 1.75 Nb 0.25 O 12 、Li 6.75 La 3 Zr 1.75 Nb 0.25 O 12 And combinations thereof. The one or more LISICON-type oxides may be selected from the group comprising: li (Li) 14 Zn(GeO 4 ) 4 、Li 3+x (P 1−x Si x )O 4 (wherein 0<x<1）、Li 3+x Ge x V 1-x O 4 (wherein 0<x<1) And combinations thereof. One or more NASICON type oxides can be selected from LiMM ʹ (PO 4 ) 3 Definition, wherein M and M ʹ are independently selected from Al, ge, ti, sn, hf, zr and La. For example, in certain variations, the one or more NASICON-type oxides may be selected from the group consisting of: li (Li) 1+x Al x Ge 2-x (PO 4 ) 3 (LAGP) (wherein 0.ltoreq.x.ltoreq.2), li 1+x Al x Ti 2-x (PO 4 ) 3 (LATP) (where 0.ltoreq.x.ltoreq.2), li 1+x Y x Zr 2-x (PO 4 ) 3 (LYZP) (wherein 0.ltoreq.x.ltoreq.2), li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 、LiTi 2 (PO 4 ) 3 、LiGeTi(PO 4 ) 3 、LiGe 2 (PO 4 ) 3 、LiHf 2 (PO 4 ) 3 And combinations thereof. The one or more perovskite ceramics may be selected from the group comprising: li (Li) 3.3 La 0.53 TiO 3 、LiSr 1.65 Zr 1.3 Ta 1.7 O 9 、Li 2x-y Sr 1-x Ta y Zr 1-y O 3 (wherein x=0.75 y and 0.60<y<0.75）、Li 3/8 Sr 7/16 Nb 3/4 Zr 1/4 O 3 、Li 3x La (2/3-x) TiO 3 (wherein 0<x<0.25 A) and combinations thereof.
Wherein the sulfide-based solid state electrolyte may include one or more sulfide-based materials selected from the group consisting of: li (Li) 2 S-P 2 S 5 、Li 2 S-P 2 S 5 -MS x (wherein M is Si, ge and Sn and 0.ltoreq.x.ltoreq.2), li 3.4 Si 0.4 P 0.6 S 4 、Li 10 GeP 2 S 11.7 O 0.3 、Li 9.6 P 3 S 12 、Li 7 P 3 S 11 、Li 9 P 3 S 9 O 3 、Li 10.35 Si 1.35 P 1.65 S 12 、Li 9.81 Sn 0.81 P 2.19 S 12 、Li 10 (Si 0.5 Ge 0.5 )P 2 S 12 、Li(Ge 0.5 Sn 0.5 )P 2 S 12 、Li(Si 0.5 Sn 0.5 )PsS 12 、Li 10 GeP 2 S 12 （LGPS）、Li 6 PS 5 X (wherein X is Cl, br or I), li 7 P 2 S 8 I、Li 10.35 Ge 1.35 P 1.65 S 12 、Li 3.25 Ge 0.25 P 0.75 S 4 、Li 10 SnP 2 S 12 、Li 10 SiP 2 S 12 、Li 9.54 Si 1.74 P 1.44 S 11.7 C l0.3 And combinations thereof.
Embodiments of the present invention will be described more specifically below by way of examples. However, embodiments of the present invention are not limited to these examples only.
Preparation of positive electrode active material layer:
a) Weighing an anode active substance, a conductive agent and a binder, and uniformly mixing in a stirrer;
b) C, carrying out fibrosis on the uniformly mixed powder in the step a;
c) And c, performing hot pressing treatment on the mixture obtained in the step b, wherein the hot pressing temperature is 150 ℃, the hot pressing pressure is 500kPa, and hot pressing is performed for a plurality of times to a specific thickness, so as to obtain the positive electrode active material layer.
Wherein the positive electrode active material layer includes a first positive electrode active material layer and a second positive electrode active material layer.
Preparation of solid electrolyte layer:
a) Weighing solid electrolyte material, placing the binder into a stirrer, and uniformly mixing;
b) C, carrying out fibrosis on the uniformly mixed powder in the step a;
c) And c, performing hot pressing treatment on the mixture obtained in the step b, wherein the hot pressing temperature is 130 ℃, the hot pressing pressure is 600kPa, and the solid electrolyte layer is obtained through repeated hot pressing to a specific thickness.
Wherein the solid electrolyte layer includes a first solid electrolyte layer and a second solid electrolyte layer.
Preparing a dry positive electrode plate:
a) Overlapping the prepared first positive electrode active material layer and the second positive electrode active material layer, and compositing the first positive electrode active material layer and the second positive electrode active material layer on a positive electrode current collector aluminum foil with the thickness of 10 mu m to obtain a positive electrode plate to be treated, wherein one side of the second positive electrode active material layer is attached to the positive electrode current collector;
b) And laminating the prepared first solid electrolyte layer and the second solid electrolyte layer, and laminating the laminated solid electrolyte layer and the positive electrode plate to be treated to form the dry-method positive electrode plate.
Preparing a negative electrode plate:
a) Weighing and uniformly mixing a negative electrode active material, a conductive agent and a binder, wherein the total mass ratio of the negative electrode active material to the binder to the conductive agent is 100wt%, and the negative electrode active material is graphite and the conductive agent is super-P; the binder is cmc+SBR; wherein the anode active material: conductive agent: the mass ratio of the binder is as follows: 95 wt.%: 2wt%:3wt%;
b) The mixture is subjected to fiberizing treatment, and is put into an air flow pulverizer to be subjected to air flow pulverization for 15min at the speed of 50 m/s;
c) Rolling the product by a four-roll rolling device, wherein the rolling temperature is 150 ℃, the rolling pressure is 600kPa, and the rolling speed is 1.0rpm, so as to obtain a negative electrode film;
d) And (3) carrying out hot-pressing compounding on the negative electrode film and a current collector copper foil with the thickness of 10 mu m to form a negative electrode plate.
Preparation of a lithium ion battery:
and stacking the prepared dry positive pole piece, the prepared dry negative pole piece and the prepared polypropylene diaphragm with the thickness of 25 mu m to form the battery cell.
The compositions of the dry cathode sheets prepared in examples 1 to 5 and comparative example 1 are shown in table 1.
TABLE 1
The respective composition thicknesses of the dry cathode sheets prepared in examples 1 to 5 and comparative example 1 are shown in table 2.
TABLE 2
Test methods and conditions
1. Method for testing cycle performance
1) Discharging at 0.33-1C to discharge end voltage at 20+ -5deg.C, and standing for 30min;
2) Charging at constant current of 0.33-1C to a final voltage, and standing for 30min;
3) Repeating the steps 1-2 for 100 times;
4) The ratio of the discharge capacity to the initial capacity was calculated. The charge-discharge cut-off voltage is 2.5-4.0V.
2. Method for testing peel strength
1) Firstly, cutting a dry-method positive electrode plate into a strip shape with the length of 170mm and the width of 20mm by using a flat paper cutter, and wiping a non-scale steel plate ruler clean by using dust-free paper without leaving dirt and dust;
2) Secondly, sticking double-sided adhesive tape with the width of 25mm on a steel plate ruler without graduation, wherein the length is 70mm, and the position is centered;
3) Then, sticking a test sample on a double-sided adhesive tape, enabling the end surfaces to be flush, and rolling the test sample back and forth on the surface of the dry-method positive electrode plate for 3 times by using a pressing wheel (2 kg) with the diameter of 84mm and the height of 45 mm;
4) And (3) turning over the free end of the dry positive pole piece in the experimental sample by 180 degrees, clamping the free end on an upper clamp of a tensile tester, clamping a non-scale steel plate ruler on a lower clamp, preparing a plurality of dry positive pole pieces with the width of 20mm under the conditions of 22-28 ℃ and humidity less than 25%, testing to obtain an average value of stretching 25-80 mm (total stretching distance 100 mm) at the stretching speed of 200mm/min, stripping the dry positive pole pieces, and reading the test result of the stripping strength of the pole piece coating when the current collector and the coating of the pole piece are completely separated.
The mechanical properties of the dry positive electrode sheets prepared in examples 1 to 5 and comparative example 1 and the battery performance test results of the lithium ion battery are shown in table 3.
TABLE 3 Table 3
1) As can be seen from the test results of examples 1 to 5 and comparative example 1, the present application provides a solid electrolyte layer and a positive electrode active material layer having a higher binder content between the positive electrode active material layer and the solid electrolyte layer, which has a beneficial effect on the improvement of the performance of the composite positive electrode film, and the adhesive strength of the electrode sheet is improved as the binder content in the transitional solid electrolyte film and the positive electrode film is improved, but the cycle performance of the battery composed of the electrode sheet is reduced when the binder content is too high; meanwhile, the transition layer adopts lithium iron phosphate with better cycle performance and safety performance, which is beneficial to improving the safety performance and cycle performance of the battery.
2) Compared with the technical scheme of directly attaching the solid electrolyte membrane and the positive electrode membrane, the positive electrode structure has better cycle performance and bonding strength.
The dry positive electrode plate, the lithium ion battery and the preparation method thereof provided by the application are described in detail, and specific examples are applied to illustrate the principle and the implementation mode of the application, and the description of the examples is only used for helping to understand the method and the core idea of the application; also, it is within the scope of the present application to be modified by those of ordinary skill in the art in light of the present teachings. In view of the foregoing, this description should not be construed as limiting the application.

Claims (10)

1. The preparation method of the dry-method positive electrode plate is characterized by comprising the following steps of:
preparing a first positive electrode material into a first positive electrode active material layer by adopting a dry film forming method;
preparing a second positive electrode material into a second positive electrode active material layer by adopting a dry film forming method;
the first positive electrode active material layer is paved on the second positive electrode active material layer, an electrode film is formed through rolling, and the content of a binder in the first positive electrode active material layer is larger than that of the binder in the second positive electrode active material layer;
Compounding one side of the second positive electrode active material layer in the electrode film with a positive electrode current collector to obtain a pole piece to be treated;
tiling a first solid electrolyte layer on a second solid electrolyte layer, and forming a solid electrolyte layer through rolling, wherein the content of a binding agent in the first solid electrolyte layer is larger than that in the second solid electrolyte layer;
and carrying out dry-process compounding on one side of the first solid electrolyte layer in the solid electrolyte layer and one side of the electrode film of the pole piece to be treated to obtain the dry-process positive pole piece.
2. The method for producing a dry positive electrode sheet according to claim 1, wherein in the dry positive electrode sheet, the thickness of the first positive electrode active material layer is 3 to 8% of the sum of the thicknesses of the first positive electrode active material layer and the second positive electrode active material layer.
3. The method for producing a dry positive electrode sheet according to claim 1, wherein in the dry positive electrode sheet, the thickness of the first solid electrolyte layer is 5 to 15% of the total of the thicknesses of the first solid electrolyte layer and the second solid electrolyte layer.
4. The method for producing a dry positive electrode sheet according to claim 1, wherein the binder in the first positive electrode active material layer and the binder in the second positive electrode active material layer are the same.
5. The method of manufacturing a dry positive electrode sheet according to claim 1, wherein the binder in the first solid electrolyte layer and the binder in the second solid electrolyte layer are the same.
6. The method for producing a dry positive electrode sheet according to claim 1, wherein the mass fraction of the binder in the first positive electrode active material layer is 5 to 10wt%, and the mass fraction of the binder in the second positive electrode active material layer is 2 to 4wt%;
and/or the number of the groups of groups,
the mass fraction of the binder in the first solid electrolyte layer is 10-15wt%, and the mass fraction of the binder in the second solid electrolyte layer is 5-8wt%.
7. The method of manufacturing a dry positive electrode sheet according to claim 1, wherein the manufacturing the first positive electrode material into the first positive electrode active material layer by a dry film forming method comprises:
uniformly mixing a first positive electrode active material, a first conductive agent and a first binder by a dry method to obtain a first mixture, carrying out fiberizing treatment on the first mixture to obtain a first mixture, and carrying out heating calendaring treatment on the first mixture to obtain a first positive electrode active material layer;
and/or the number of the groups of groups,
the preparing of the second positive electrode material into the second positive electrode active material layer by the dry film forming method includes:
And uniformly mixing the second positive electrode active material, the second conductive agent and the second binder by a dry method to obtain a second mixture, carrying out fiberizing treatment on the second mixture to obtain a second mixture, and carrying out heating calendaring treatment on the second mixture to obtain a second positive electrode active material layer.
8. A dry-process positive electrode sheet, characterized in that it is manufactured according to the manufacturing method of a dry-process positive electrode sheet according to any one of claims 1 to 7, and comprises a positive electrode current collector, and a second positive electrode active material layer, a first solid electrolyte layer, and a second solid electrolyte layer, which are sequentially provided on at least one side of the positive electrode current collector.
9. The dry positive electrode tab according to claim 8, wherein the second positive electrode active material layer, the first solid electrolyte layer, and the second solid electrolyte layer are sequentially provided on both sides of the positive electrode current collector.
10. A lithium ion battery, characterized in that the lithium ion battery comprises a dry positive electrode plate, a negative electrode plate, a diaphragm and an electrolyte, wherein the dry positive electrode plate is the dry positive electrode plate according to claim 8 or 9.
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Publication number Priority date Publication date Assignee Title
CN110112421A (en) * 2019-05-13 2019-08-09 浙江锋锂新能源科技有限公司 Non-contact mixed solid-liquid electrolyte lithium storage battery and preparation method thereof
CN212136623U (en) * 2020-04-09 2020-12-11 恒大新能源技术(深圳)有限公司 Battery cell structure and lithium ion battery
CN116057725A (en) * 2021-06-03 2023-05-02 株式会社Lg新能源 Positive electrode additive and positive electrode for lithium secondary battery comprising same
CN116404105A (en) * 2023-05-16 2023-07-07 安徽博石高科新材料股份有限公司 Dry electrode slice and preparation method and application thereof

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110112421A (en) * 2019-05-13 2019-08-09 浙江锋锂新能源科技有限公司 Non-contact mixed solid-liquid electrolyte lithium storage battery and preparation method thereof
CN212136623U (en) * 2020-04-09 2020-12-11 恒大新能源技术(深圳)有限公司 Battery cell structure and lithium ion battery
CN116057725A (en) * 2021-06-03 2023-05-02 株式会社Lg新能源 Positive electrode additive and positive electrode for lithium secondary battery comprising same
CN116404105A (en) * 2023-05-16 2023-07-07 安徽博石高科新材料股份有限公司 Dry electrode slice and preparation method and application thereof

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