CN117317224A - Positive pole piece, battery and electric equipment - Google Patents
Positive pole piece, battery and electric equipment Download PDFInfo
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- CN117317224A CN117317224A CN202210703160.7A CN202210703160A CN117317224A CN 117317224 A CN117317224 A CN 117317224A CN 202210703160 A CN202210703160 A CN 202210703160A CN 117317224 A CN117317224 A CN 117317224A
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- positive electrode
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Classifications
-
- 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
-
- 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
- H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
-
- 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
- H01M4/136—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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
-
- 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
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The application provides a positive electrode plate, a battery and electric equipment, wherein the positive electrode plate comprises a positive electrode current collector and a positive electrode active material layer which is sequentially laminated on at least one side surface of the positive electrode current collector, and the positive electrode active material layer contains a bomb additive; the piezoelectric additive is three-dimensional graphene, and the three-dimensional graphene has a porous structure; wherein, after the positive electrode sheet is applied with a pressure greater than 0 and less than or equal to 5Mpa along the thickness direction thereof, the thickness rebound rate and the thickness compression rate of the positive electrode sheet are independently in the range of 2% -20%. After the elastic pressing additive is added into the positive electrode active material layer, the positive electrode plate has certain elastic pressing performance, the volume change rate of a battery cell using the positive electrode plate in the charge-discharge cycle process is small, and the cycle performance of the battery can be improved.
Description
Technical Field
The application relates to the technical field of batteries, in particular to a positive pole piece, a battery and electric equipment.
Background
In the charging process of the lithium ion battery, the volume of the negative electrode is generally gradually increased, the volume of the whole battery cell is also increased, and under the condition that the size of a bag body of the battery cell is fixed, the external pressure born by the battery cell from a shell can be gradually increased along with the progress of the charging process, so that the electrode polarization condition is easily increased, electrolyte is easily extruded from the battery cell and the like; in the discharging process, the volume of the negative electrode is gradually reduced, and the external pressure born by the battery cell is gradually reduced. It can be seen that the volume change rate of the battery cell during charge and discharge is large, which results in poor cycle performance of the battery.
Disclosure of Invention
In view of this, this application provides a positive pole piece and battery and consumer to reduce the volume change rate of battery electric core in cyclic process, improve the cycle performance of battery.
The first aspect of the application provides a positive electrode plate, which comprises a positive electrode current collector and a positive electrode active material layer arranged on at least one side surface of the positive electrode current collector, wherein the positive electrode active material layer contains a bomb additive, the bomb additive is three-dimensional graphene, and the three-dimensional graphene has a porous structure; wherein, after being applied with a pressure of more than 0 and less than or equal to 5Mpa in the thickness direction of the positive electrode sheet, the thickness rebound rate and the thickness compression rate of the positive electrode sheet are each independently in a range of 2% -20%.
The three-dimensional graphene is introduced into the positive electrode plate as a compression spring additive, so that the positive electrode plate has certain compression elasticity, the positive electrode plate can effectively reduce the volume change rate of the battery core in the charge-discharge cycle process, and the effect on a battery system with the volume expansion of the negative electrode in the charge process is particularly obvious, so that the cycle performance of the battery can be improved.
In some embodiments of the present application, the positive electrode active material layer includes a first positive electrode coating and a second positive electrode coating that are stacked, where the first positive electrode coating is close to the positive electrode current collector, and the first positive electrode coating and/or the second positive electrode coating contains the piezoelastic additive.
In some embodiments of the present application, the first positive electrode coating comprises LiFe 1-a Mn a PO 4 And an active material, wherein the second positive electrode coating comprises a layered transition metal oxide active material and the piezoelastic additive. The volume change rate of the positive electrode plate under pressure can be improved more obviously by adding the compression-ejection additive with compression-ejection characteristics into the ternary material layer with volume expansion in the charging process, and the layered transition metal oxide material layer and LiFe can be reduced 1-a Mn a PO 4 The volume expansion rate difference between the material layers avoids interlayer separation phenomenon, and improves the long circulation capacity of the pole piece.
In a second aspect, the present application provides a battery comprising a positive electrode sheet as described in the first aspect of the present application.
Due to the adoption of the positive pole piece, the volume fluctuation of the battery core of the battery in the charging and discharging process is small, and the cycle performance can be improved.
In a third aspect, the present application provides a powered device with a battery as described in the second aspect of the present application.
Drawings
Fig. 1 is a schematic structural diagram of a positive electrode sheet according to an embodiment of the present application.
Fig. 2 is another schematic structural diagram of the positive electrode sheet provided in the embodiment of the present application.
Fig. 3 is a cross-sectional scanning electron micrograph (a) and a surface electron micrograph (b) of the three-dimensional graphene used in example 1.
Fig. 4 is a graph showing cycle performance of a full cell prepared from the positive electrode tab of example 1 of the present application and a full cell prepared from the positive electrode tab of comparative example 1.
Detailed Description
The technical solutions of the embodiments of the present application will be described below with reference to the accompanying drawings.
Referring to fig. 1, an embodiment of the present application provides a positive electrode sheet 100, including a positive electrode current collector 10 and a positive electrode active material layer 20 disposed on at least one side surface of the positive electrode current collector 10, wherein the positive electrode active material layer 20 contains a bomb additive, and the bomb additive is three-dimensional graphene, and the three-dimensional graphene has a porous structure; and the thickness rebound rate and the thickness compression rate of the positive electrode plate 100 are respectively and independently in the range of 2% -20% by applying a pressure of more than 0 and less than or equal to 5Mpa to the positive electrode plate 100 along the thickness direction of the positive electrode plate.
The above pressure of greater than 0 and less than or equal to 5Mpa is a force that the positive electrode tab 100 may withstand during a battery charge-discharge cycle. The thickness rebound and compression data of the positive electrode sheet 100 indicate that the positive electrode sheet 100 has good compression resilience. Wherein, the thickness rebound rate and the thickness compression rate of the positive electrode plate can be equal or different. In some embodiments, the pressure may be 0.1-1Mpa.
Along with Li during battery charging + The volume of the whole battery cell is generally increased, the volume expansion of the battery cell is particularly obvious for a battery system (such as silicon materials and the like) with the large volume expansion of the negative electrode, under the condition that the size of a bag body of the battery cell is fixed (such as a cylindrical battery), the battery cell can bear larger external pressure from a battery shell along with the progress of a charging process, the pressure can be transmitted to a positive electrode plate, a part of volume space can be released due to the gradual volume contraction of a piezoelectric additive, the problem of the volume expansion of the whole battery cell caused by the expansion of the negative electrode can be relieved, and the volume expansion range of the whole battery cell in the charging process is reduced. And during the discharging process of the battery, along with Li + The positive electrode is embedded from the negative electrode, the volume of the negative electrode is contracted, the external pressure born by the battery cell is gradually reduced, the spring-pressing additive can gradually rebound, and the volume increased by rebound can compensate the volume contraction of the whole battery cell caused by the volume contraction of the negative electrode, so that the volume contraction rate of the battery cell in the discharging process is reduced. Therefore, the positive electrode plate with the elastic function can effectively reduce the volume change rate of the battery core in the charge-discharge cycle process, stabilize the distance between the surfaces of the positive electrode and the negative electrode of the battery, and improve the cycle performance of the battery.
Wherein, the thickness rebound rate and the thickness compression rate of the positive pole piece 100 are controlled to be respectively and independently in the range of 2% -20%, so that the structural stability of the positive pole piece can be improved, the volume change rate of the battery core in the charge-discharge cycle process is reduced, the distance between the positive electrode surface and the negative electrode surface of the battery is stabilized, and the cycle stability of the battery is improved. If the thickness rebound rate and the thickness compression rate of the positive electrode plate are lower than the ranges, the fact that the compression spring additive is insufficient to achieve the effect of well connecting two material layers together is not obvious in improvement of cycle performance; if the thickness rebound rate and the thickness compression rate are higher than the above ranges, the content of the bomb additive is too high or the structural stability of the bomb additive is poor, the relative content of active substances is low or the structural stability of the positive electrode plate is poor, the energy density and the multiplying power performance of the battery are reduced, and the circulation stability is reduced.
The method for testing the rebound performance of the positive pole piece comprises the following steps: applying a value X to the positive electrode plate along the thickness direction of the positive electrode plate 1 Pressure of Mpa, measuring positive electrode plate at X 1 Thickness H under pressure of Mpa 1 The method comprises the steps of carrying out a first treatment on the surface of the Then the pressure is removed, and after the thickness of the positive pole piece is stable, the thickness of the positive pole piece is measured and is recorded as H 2 The thickness rebound rate r= (H) of the positive electrode plate 2 -H 1 )/H 1 . The method for testing the compression performance of the positive electrode plate comprises the following steps: the initial thickness of the positive electrode plate is H along the thickness direction of the positive electrode plate 3 Applying a value X to the positive electrode sheet of (2) 2 Pressure of Mpa, measuring positive electrode plate at X 2 The thickness under pressure of Mpa is denoted as H 4 The thickness compression rate p= (H) of the positive electrode sheet 3 -H 4 )/H 3 . Accordingly, the above-mentioned "the positive electrode sheet 100 is applied with a pressure of more than 0 and less than or equal to 5Mpa in the thickness direction of the positive electrode sheet", the thickness rebound rate and the thickness compression rate of the positive electrode sheet 100 are each independently in the range of 2% -20% "is understood to be that the positive electrode sheet is applied with a pressure of more than 0 and less than or equal to 5Mpa in the thickness direction of the positive electrode sheet, and the thickness of the positive electrode sheet at the pressure of more than 0 and less than or equal to 5Mpa is measured as H 1 The method comprises the steps of carrying out a first treatment on the surface of the Then the pressure is removed, and after the thickness of the positive pole piece is stable, the positive pole piece is measuredThickness, denoted as H 2 The thickness rebound rate r= (H) of the positive electrode plate 2 -H 1 )/H 1 R is in the range of 2% -20%; the initial thickness of the positive electrode plate is H along the thickness direction of the positive electrode plate 3 Applying a pressure of more than 0 and less than or equal to 5Mpa to the positive electrode sheet, determining the thickness of the positive electrode sheet under the pressure of more than 0 and less than or equal to 5Mpa, and marking as H 4 The thickness compression rate p= (H) of the positive electrode sheet 3 -H 4 )/H 3 P is in the range of 2% -20%.
In the embodiment of the application, the porous structure of the three-dimensional graphene is formed by mutually overlapping graphene sheets. The maximum pore diameter of the porous structure is not more than 300nm, the maximum pore diameter refers to the pore diameter of the pore with the largest size in the porous structure, and the "pore diameter" can refer to the maximum width of each pore. Since the pore diameter of the largest pore is not more than 300nm, it is understood that the pore diameter of each pore of the porous structure is not more than 300nm. The smaller pore diameters of the holes are beneficial to ensuring that the three-dimensional graphene is not easy to collapse after being subjected to certain pressure, and is convenient to rebound. In some embodiments of the present application, the average pore size of the porous structure is 10-200nm, e.g., 15nm, 20nm, 25nm, 30nm, 40nm, 50nm, 60nm, 70nm, etc. The average pore size of the porous structure can be measured by N 2 Adsorption/desorption testing.
In the embodiment of the application, in the three-dimensional graphene, the breaking strength of the overlapping part of the mutually overlapped graphene sheets is 20-50N/m, which indicates that the three-dimensional graphene has high structural stability, and even at the overlapping part of the graphene sheets with weak strength, the mechanical strength is still high, so that the three-dimensional graphene is not easy to collapse in structure under certain external force, and can be repeatedly compressed and rebounded.
The parameter "the breaking strength of the overlapping joint of the mutually overlapping graphene sheets" can be obtained by performing nano indentation test on the overlapping joint by using an atomic force microscope (Atomic Force Microscope, AFM) on the three-dimensional graphene. The specific test method is as follows: fixing three-dimensional graphene on a silicon wafer with small holes on the surface, and applying pressure to the graphene sheets on the small holes by using a probe, wherein the position for applying the pressure is near the lap joint position of two adjacent graphene sheets. And recording the critical pressure capable of breaking the lap joint of the two graphene sheets, and obtaining the breaking strength of the lap joint between the graphene sheets.
In the embodiment of the present application, the lateral dimension of the graphene sheet constituting the three-dimensional graphene is in the nanometer scale, for example, 10 to 100nm, for example, 10nm, 15nm, 18nm, 20nm, 25nm, 30nm, 40nm, 50nm, 60nm, 80nm, 90nm, and the like, and preferably, the lateral dimension of the graphene sheet is 10nm to 30nm, and more preferably, 10nm to 20nm. The lateral dimension herein refers to the length, width, or the like of the graphene sheet, and can be known from an electron micrograph of three-dimensional graphene. The graphene sheets may be single-layer graphene and/or multi-layer graphene. The transverse dimension of the graphene sheets is controlled in the above range, mainly for controlling the pore size formed by overlapping between the graphene sheets and the pore volume of the three-dimensional graphene in a proper range, and the pore size and the pore volume of the three-dimensional graphene and the breaking strength of the overlapping part of the graphene sheets influence the compression retraction elasticity of the three-dimensional graphene material.
In the embodiment of the application, the average particle size of the three-dimensional graphene is 0.5-20 μm. The three-dimensional graphene with the average particle size in the range is suitable for being used in the positive electrode plate, on one hand, the three-dimensional graphene is ensured to be uniformly dispersed and uniformly distributed in the second positive electrode coating 22, and on the other hand, the three-dimensional graphene can be ensured to be matched with positive electrode active particles, and the second positive electrode coating 22 has uniform compression retraction elasticity through two modes of filling pores among active materials and uniformly dispersing. Specifically, the average particle diameter of the three-dimensional graphene is 0.6 μm, 1 μm, 5 μm, 8 μm, 10 μm, 15 μm, 20 μm, or the like.
In the embodiment of the application, the pore volume of the three-dimensional graphene is 1-10cm 3 Between/g. Wherein, the pore volume can be measured by adopting a nitrogen adsorption method to the three-dimensional graphene. The three-dimensional graphene with the pore volume in the range can have more small pores, has better compressibility, and can ensure better rebound resilience, namely has reciprocable compression-rebound resilience.
In this embodiment, the three-dimensional graphene may be equal in sizeAnd growing by an ion-assisted chemical vapor deposition (PECVD) method. An exemplary preparation method comprises the following steps: by reacting a carbon source (e.g. C 2 H 2 ) And H 2 Introducing the mixed gas into a deposition chamber heated to a certain temperature in plasma deposition equipment, starting a plasma generator to deposit and grow three-dimensional graphene materials on a substrate (such as Cu) placed in the deposition chamber by a PECVD method, introducing auxiliary gas (such as Ar, he and the like) after the growth of the three-dimensional graphene is finished to cool the deposition chamber to room temperature in an inert atmosphere, taking out the obtained sample from the deposition chamber, stripping the three-dimensional graphene materials from the substrate, and crushing the three-dimensional graphene materials to the required particle size. The PECVD process can generate plasmas with high energy density and large volume, and the carbon source C can be used 2 H 2 And decomposing into more carbon-containing reaction free radicals, thereby realizing the growth of the three-dimensional graphene. In some embodiments, C 2 H 2 The flow rate of the mixture is 20mL/min, H 2 The flow rate of the auxiliary gas Ar is 250mL/min, the deposition growth temperature can be 950 ℃, the flow rate of the auxiliary gas Ar is 200mL/min, and the working power of the plasma generator is 300W.
In this application, the positive electrode active material layer 20 disposed on the positive electrode current collector side may be a single coating layer, or a stacked structure of two or more coating layers. When the positive electrode active material layer 20 is a coating layer, the positive electrode active material contained therein may be one or more. When the positive electrode active material layer 20 is a superposition of multiple coating layers, at least one of the coating layers contains the above-described piezoelastic additive.
In some embodiments of the present application, referring to fig. 2, the positive electrode active material layer 20 includes a first positive electrode coating layer 21 and a second positive electrode coating layer 22 that are stacked, wherein the first positive electrode coating layer 21 is close to the positive electrode current collector 10, and wherein the first positive electrode coating layer 21 and/or the second positive electrode coating layer 22 contains the above-mentioned piezoelastic additive. At this time, the coating of the positive electrode plate 100 is in a double-layer structure, and any one or two positive electrode coatings of the positive electrode plate 100 contain a compression spring additive, so that the positive electrode plate 100 can be ensured to have better compression retraction elasticity.
When the first or second positive electrode coating layer contains the above-mentioned pressure bullet additive, the corresponding positive electrode coating layer may contain no conductive agent or a small amount of conductive agent. In this embodiment, the first positive electrode coating layer 21 may contain a binder in addition to the first positive electrode active material, and optionally a small amount of a conductive agent or no conductive agent. Similarly, the second positive electrode coating 22 contains a binder in addition to the second positive electrode active material, and optionally a small amount of or no conductive agent. For convenience of description/reference, the conductive agent and the binder that may be contained in the first positive electrode coating layer 21 may be referred to as "first conductive agent" and "first binder", respectively, and the conductive agent and the binder that may be contained in the second positive electrode coating layer 22 may be referred to as "second conductive agent" and "second binder", respectively.
In the present embodiment, the mass of the second binder in the second positive electrode coating layer 22 may be 0.1% to 10%, preferably 2% to 10% of the mass of the second positive electrode active material. Taking the example that the second positive electrode coating 22 contains the three-dimensional graphene, the amount of the piezoelastic additive contained in the layer is larger than the amount of the second conductive agent contained in the layer. Specifically, the mass of the second conductive agent may be 0% to 2%, preferably 0.1% to 1.5%, more preferably 0.1% to 1% of the mass of the second positive electrode active material. At this time, the use of the viscoelastic additive in an amount larger than that of the conductive agent can provide the second positive electrode coating 22 with good compression set resilience which is not provided by the normal positive electrode coating. Similarly, in the first positive electrode coating layer 21, the mass of the first binder may be 0.1% to 10%, preferably 2% to 10% of the mass of the first positive electrode active material. The mass of the first conductive agent contained in the first positive electrode coating layer 21 may be 0% to 2%, preferably 0.1% to 1.5%, more preferably 0.1% to 1% of the mass of the first positive electrode active material.
In some embodiments of the present application, the first positive electrode coating 21 comprises LiFe 1-a Mn a PO 4 An active material, wherein a is more than or equal to 0 and less than or equal to 1; the second positive electrode coating 22 comprises a layered transition metal oxide active material of lithium and the above-described piezoelastic additive. In some embodiments of the present application, 0.ltoreq.a.ltoreq.0.8, and/or the layered transition metal oxide active material of lithium is a ternary material, i.e., the above-described first positive electrode active material includes LiFe 1-a Mn a PO 4 And an active material, wherein the second positive electrode active material comprises a ternary active material.
Wherein, liFe 1-a Mn a PO 4 The material will shrink in volume during charging (e.g. LiFePO 4 The volume shrinkage rate in the charging process is about 7%), the volume of the lithium-containing layered transition metal oxide can be increased in the normal charging process, for example, the volume of the ternary material can be increased by about 6% in the normal charging process, the volume changes of the lithium-containing layered transition metal oxide and the ternary material are asynchronous and have opposite trend, and the double-layer interlayer separation is easy to occur in the long-term circulation process.
Since the volume of the battery cell is generally increased during the charging process, the gradually increased volume of the battery cell can lead to the battery cell bearing larger external pressure from the battery shell, when a certain amount of the bomb additive is added into the layered transition metal oxide layer (namely, the second positive electrode coating 22) positioned on the surface layer of the positive electrode plate, the bomb additive gradually undergoes volume shrinkage under larger external pressure, and a part of volume space can be released to the layered transition metal oxide with volume expansion, so that the volume expansion rate of the layered transition metal oxide-containing second positive electrode coating 22 during charging can be reduced, and the volume expansion rate of the layered transition metal oxide-containing second positive electrode coating 22 and the LiFe content of the battery can be reduced 1-a Mn a PO 4 The difference in volume change rate between the first positive electrode coatings 21 of material reduces the overall volume change amplitude of the cell upon charging. And during discharging of the battery contains LiFe 1-a Mn a PO 4 The volume of the first positive electrode coating 21 of the material is increased, the volume of the second positive electrode coating 22 containing the layered transition metal oxide is reduced during discharge, the volume of the negative electrode is contracted during discharge, the external pressure born by the battery core is gradually reduced, and the elastic pressing additive is gradually rebounded, so that the volume shrinkage rate of the second positive electrode coating 22 containing the layered transition metal oxide during discharge is reduced, and the volume change difference of the two positive electrode coatings of the positive electrode plate during discharge is reduced. Therefore, the presence of the extrusion additive can improve the volume change rate of each layer of the positive electrode sheet 100 under different pressures, thereby avoiding volume expansion of the two positive electrode coatings during long-term circulationThe difference in rate causes interlayer separation.
In addition, the coating is a double-layer structure of the positive electrode plate 100, and layered transition metal oxide (such as ternary material) with high energy density is arranged on the surface layer of the positive electrode plate 100 far away from the positive electrode current collector, so that the impedance of lithium ion conduction is small, the polarization resistance of the positive electrode plate in a high potential interval can be reduced, the electrochemical polarization of the positive electrode plate in discharge is reduced, and uniform charge and discharge are facilitated, and the cycle performance is improved. Secondly, the layered transition metal oxide (such as ternary material) is arranged on the surface layer of the positive electrode plate 100, so that the layered transition metal oxide particles with the same SOC (State of charge) state are arranged around the layered transition metal oxide particles, which is beneficial to homogenizing the surrounding environment of the layered transition metal oxide, realizing uniform discharge of the layered transition metal oxide particles, ensuring the structural stability and the material capacity exertion of the layered transition metal oxide, and stably exerting the cycle performance. Third, since the layered transition metal oxide (e.g., ternary material) generally has a particle size that is larger than LiFe 1- a Mn a PO 4 The material is large, the porosity in the layered transition metal oxide layer is obviously larger than that of LiFe 1-a Mn a PO 4 The material layer is such that the pore structure of the surface layer of the positive electrode plate 100 is relatively loose, the positive electrode plate is more easily immersed by electrolyte, the removal/insertion of Li+ of the layered transition metal oxide is smoother, the high capacity characteristic of the positive electrode plate is easily exhibited, and meanwhile, the layered transition metal oxide layer with relatively high porosity on the surface layer is opposite to the inner layer LiFe 1-a Mn a PO 4 The discharge effect of the material is small, the multiplying power performance of the inner layer material is facilitated to be exerted, and the integral positive pole piece can be guaranteed to exert high capacity.
In the embodiment of the application, the structural general formula of the ternary material is LiNi x Co y M z O 2 M is at least one metal element from subgroup III to main group V, x is more than or equal to 0.33 and less than or equal to 0.98,0<y<1，0<z<1, and x+y+z=1. For example, M is at least one of Mn, al, zr, ti, Y, sr and W, etc., and M is Mn or Al is more common. When the value of x is higher, the specific capacity of the ternary material is higher, the multiplying power performance is better, and the ternary material can be used for preparing the ternary materialThe metamaterials are called "high nickel ternary materials". Preferably, the value range of x is: x is more preferably 0.70.ltoreq.x.ltoreq.0.98, still more preferably 0.80.ltoreq.x.ltoreq.0.90, and still more preferably 0.83.ltoreq.x.ltoreq.0.88. Alternatively, y satisfies: y is more than or equal to 0.01 and less than or equal to 0.33, and z satisfies the following conditions: z is more than or equal to 0.01 and less than or equal to 0.33.
In the present application, when a=0, the general formula is LiFe 1-a Mn a PO 4 Specifically lithium iron phosphate; when a is more than 0, the material is specifically a lithium iron manganese phosphate material, wherein a is less than or equal to 0.8, which is beneficial to ensuring the structural stability of the lithium iron manganese phosphate material.
Generally, liFe 1-a Mn a PO 4 The particle size of the material is smaller than the layered transition metal oxide active material. Alternatively, the layered transition metal oxide active material has a particle size D50 of 3-15 μm, for example 3-10 μm. Optionally, the LiFe 1-a Mn a PO 4 The particle size D50 of the material is 0.8-1.8. Mu.m, for example 0.8-1.5. Mu.m. Further, the LiFe 1-a Mn a PO 4 The surface of the material is also provided with a carbon coating layer so as to improve the conductivity of the material; liFe 1-a Mn a PO 4 The material can contain doping elements to improve the rate performance.
The binder and the conductive agent in the first positive electrode coating layer 21 and the second positive electrode coating layer 22 are not particularly limited in this application, and conventional materials in the art may be used. The first binder and the second binder may be independently selected from one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), polyimide (PI), polyacrylic acid (PAA), polyacrylate, polyolefin (e.g., polyethylene, polypropylene, polystyrene, etc.), sodium carboxymethyl cellulose (CMC), sodium alginate, etc., but are not limited thereto. The first conductive agent and the second conductive agent may be independently selected from one or more of carbon black (e.g., acetylene black, ketjen black, suppler P, 350G carbon black, etc.), furnace black, mesophase carbon microspheres, carbon fibers, carbon nanotubes, graphene, etc., but are not limited thereto.
In the embodiment of the present application, the thickness of the first positive electrode coating layer 21 may be in the range of 10 μm to 150 μm,preferably 20-100 μm. The thickness of the second positive electrode coating layer 22 may be in the range of 5 μm to 50 μm, preferably 5 μm to 30 μm. In some embodiments, liFe is contained 1-a Mn a PO 4 The thickness of the first positive electrode coating layer 21 is greater than that of the second positive electrode coating layer 22 containing the ternary active material. At this time, the positive electrode sheet 100 can obtain pure LiFe having a specific surface density 1-a Mn a PO 4 The positive plate has higher capacity and can ensure LiFe 1-a Mn a PO 4 The performance of the material in the positive electrode plate 100 is not worse than that of pure LiFe 1-a Mn a PO 4 And the respective properties when the pole pieces of the pure layered transition metal oxide material are used.
In this application, the positive electrode current collector 10 may be various materials suitable for the current collector of the positive electrode tab 100, including but not limited to a metal simple substance foil, an alloy foil, a metallized polymer film, or the foregoing materials with carbon coated surfaces. The metal simple substance foil can be specifically aluminum foil, the alloy foil can be aluminum alloy foil, and the metal plated on the surface of the polymer film can be an aluminum simple substance layer or an aluminum alloy layer.
In some embodiments of the present application, the double-coated positive electrode sheet shown in fig. 2 may be prepared by the following method: coating the surface of the positive electrode current collector 10 with a material containing LiFe 1-a Mn a PO 4 And after the first positive electrode slurry of the active material and the second positive electrode slurry containing the ternary active material and the compression and ejection additive are dried and pressed, sequentially forming a first positive electrode coating 21 and a second positive electrode coating 22 which are stacked on the positive electrode current collector 10, and obtaining the positive electrode plate.
Wherein the first positive electrode slurry is dried to form a positive electrode containing LiFe 1-a Mn a PO 4 The first positive electrode coating 21 of the active material and the second positive electrode slurry are dried to form a second positive electrode coating 22 containing the ternary active material and the viscoelastic additive. The first positive electrode slurry may further include a first conductive agent and a first binder, and the second positive electrode slurry may further include a second conductive agent and a second binder. The types and the contents of the materials of the conductive agents and the binders are as described in the specification. This isIn addition, the solvent contained in the first and second positive electrode pastes may be independently selected from one or more of N-methylpyrrolidone (NMP), dimethylformamide (DMF), diethylformamide (DEF), water, an alcoholic solvent (e.g., ethanol, etc.), etc., and is more common with NMP. The content of the solvent is not particularly limited, and may satisfy fluidity and uniformity of slurry coating.
In the embodiment of the application, the first positive electrode slurry and the second slurry can be sequentially coated by adopting a coater with a double coating die head; the coating may be performed by using a coater having a single coating die, respectively, and the second positive electrode slurry may be coated after the first positive electrode slurry is dried to form a first positive electrode coating. The positive electrode current collector may be coated on one side or on both sides. In other words, a laminated structure of the first and second positive electrode coatings may be formed on one side surface of the positive electrode current collector, or a laminated structure of the first and second positive electrode coatings may be formed on both opposite side surfaces of the positive electrode current collector.
The surface density of the positive electrode plate is not limited, and the positive electrode plate can be designed according to a specific electrochemical system. In some embodiments, the first positive electrode slurry is formulated to provide a single-sided surface density of the first positive electrode coating of 100 to 200g/m 2 Coating the second positive electrode slurry to make the single-sided surface density of the second positive electrode coating reach 10-100g/m 2 Coating is performed. In this embodiment, in the preparation process of the positive electrode sheet, the pressure used for the above-mentioned pressing may be 50-200Mpa, for example 150Mpa.
In some embodiments of the present application, a buffer layer (not shown in fig. 2) containing the above-described piezoelastic additive and binder may also be provided between the first positive electrode coating 21 and the second positive electrode coating 22. The buffer layer also has compression retraction elastic energy, can play a role in connecting two anode coatings like a spring, weakens the volume change difference of the two anode coatings in the battery circulation process, avoids interlayer separation phenomenon of the two anode coatings, and can better promote the long circulation capacity of the anode pole piece.
The embodiment of the application also provides a battery, which comprises the positive electrode plate.
In this application embodiment, this battery still includes negative pole piece to and set up diaphragm and electrolyte between above-mentioned positive pole piece and the above-mentioned negative pole piece. The separator is used for separating the positive pole piece from the negative pole piece, so that the insulativity and the liquid-retaining property between the positive pole piece and the negative pole piece are maintained; the diaphragm, the positive pole piece and the negative pole piece together form a battery core of the battery, and the battery core is accommodated in the battery shell.
In some embodiments of the present application, the above battery may be assembled by: and sequentially stacking the positive electrode plate, the diaphragm and the negative electrode plate to prepare a battery core, accommodating the battery core in a battery shell, injecting electrolyte, and sealing the battery shell to prepare the battery. In other embodiments of the present application, the above-described battery may be assembled by: and sequentially stacking the positive electrode plate, the semi-solid electrolyte or the solid electrolyte and the negative electrode plate to prepare a battery core, accommodating the battery core in a battery shell, and sealing the battery shell to prepare the battery. When the semi-solid electrolyte or the solid electrolyte is used, the positive electrode plate and the negative electrode plate can contain the semi-solid electrolyte material or the solid electrolyte material.
The separator may be a common separator for a battery such as a polymer separator and a non-woven fabric, and includes, but is not limited to, a single-layer PP (polypropylene) film, a single-layer PE (polyethylene) film, a double-layer PP/PE, a double-layer PP/PP, and a three-layer PP/PE/PP. The electrolyte comprises electrolyte salt and an organic solvent, wherein the specific types and the compositions of the electrolyte salt and the organic solvent are conventional choices in the field of batteries, and the electrolyte salt and the organic solvent can be selected according to actual requirements. The solid electrolyte or the semi-solid electrolyte may be a sulfide electrolyte, an oxide electrolyte, a polymer electrolyte, or the like. The battery shell can be an aluminum plastic film, a copper plastic film, a steel plastic film or other packaging films, can also be an aluminum shell, a steel shell and the like, and can be specifically selected according to the type of the battery.
The embodiment of the application also provides electric equipment, which is provided with the battery. The electric equipment can be a vehicle, such as a car, a ship and the like, and can also be a 3C product. Due to the adoption of the battery, the battery of the electric equipment has strong endurance and high safety.
The technical solution of the present application will be further described with reference to a plurality of specific embodiments.
Example 1
A preparation method of a positive plate comprises the following steps:
(1) Mixing lithium iron phosphate with a binder PVDF and a conductive agent supplier P according to a ratio of 100:3:2, mixing the mixture in a solvent NMP in a mass ratio, and uniformly stirring to prepare first positive electrode slurry;
ternary active material NCM811 (structural formula is LiNi 0.8 Co 0.1 Mn 0.1 O 2 ) Mixing PVDF, a supplier P and three-dimensional graphene according to a ratio of 100:2:1: mixing the mixture in a solvent NMP according to the mass ratio of 5, and uniformly stirring to obtain second anode slurry;
(2) Taking aluminum foil as a positive electrode current collector, sequentially coating a first positive electrode slurry and a second positive electrode slurry on one side surface of the aluminum foil, and drying to form a double-coating with a first positive electrode coating and a second positive electrode coating which are arranged in a laminated manner, wherein the first positive electrode coating 21 is close to the aluminum foil and is formed by drying the first slurry, and the surface density is 165g/m 2 The method comprises the steps of carrying out a first treatment on the surface of the The second positive electrode coating 22 was dried from the second slurry and had an areal density of 18.85g/m 2 ；
Then, sequentially forming a first positive electrode coating and a second positive electrode coating which are stacked on the other side surface of the aluminum foil in the same manner to obtain a double-sided positive electrode plate; rolling the double-sided positive plate under the pressure of 150Mpa to obtain a standby positive plate; in the positive electrode sheet, the thickness of the single-sided first positive electrode coating layer 21 is 72 μm, and the thickness of the single-sided second positive electrode coating layer 22 is 6 μm.
Wherein, the mass ratio of the lithium iron phosphate to NCM811 in example 1 is: 165X 100/105:18.85×100/108=9. In addition, the three-dimensional graphene (see FIG. 3) used in example 1 comprises graphene sheets that are overlapped with each other and has a porous structure, and has an average particle diameter of 0.8 μm and a pore volume of 2.5cm 3 /g, the three-dimensional graphene has a flat porous structureThe average pore diameter is 12nm, and the plane spacing of the crystal face of the three-dimensional graphene (002) is 0.34nm; and carrying out nano indentation test by AFM (atomic force microscope), and measuring the breaking strength of the joint of the graphene sheets which are mutually overlapped in the three-dimensional graphene to be 40N/m.
The preparation method of the three-dimensional graphene used in example 1 is as follows: cu is taken as a substrate, and is placed in a deposition chamber of PECVD deposition equipment for vacuumizing and heating to reach the growth temperature of 950 ℃, and a carbon source C is introduced into the deposition chamber 2 H 2 And H 2 Of (C) (wherein, C 2 H 2 The flow rate of (C) is 20mL/min, H 2 The flow rate of the three-dimensional graphene is 250 mL/min), and a plasma generator of a deposition device is turned on to deposit and grow the three-dimensional graphene material on a substrate by a PECVD method, and after the growth of the three-dimensional graphene is finished, the plasma generator, a heating source and the C feeding are turned off 2 H 2 And H 2 Simultaneously, auxiliary gas Ar is introduced at a flow rate of 200mL/min to cool the deposition chamber to room temperature under an inert atmosphere, then a sample is taken out of the deposition chamber, the graphene material is peeled off from the substrate, and the graphene material is crushed to a required particle size, so that the three-dimensional graphene material required by the embodiment 1 is obtained.
Example 2
Example 2 differs from example 1 in that: in the second positive electrode slurry, the mixing mass ratio of NCM811 to PVDF, supplier P and three-dimensional graphene is 100:2:2:15; the surface density of the first positive electrode slurry according to the first positive electrode coating layer to be formed is 150g/m 2 Coating the mixture to obtain a second positive electrode slurry with an areal density of 50g/m according to the second positive electrode coating to be formed 2 Coating is performed.
The positive electrode sheet obtained in example 2 was designated as P2. Wherein the thickness of the single-sided first positive electrode coating layer 21 is 65 μm, and the thickness of the single-sided second positive electrode coating layer 22 is 15 μm.
Example 3
Example 3 differs from example 1 in that: in the second positive electrode slurry, the mixing mass ratio of NCM811 to PVDF, supplier P and three-dimensional graphene is 100:2:1:3.
example 4
Example 4 differs from example 1 in that: in the second positive electrode slurry, the mixing mass ratio of NCM811 to PVDF, supplier P and three-dimensional graphene is 100:2:1:20.
example 5
Example 5 differs from example 1 in that: the three-dimensional graphene used in example 5 had an average particle diameter of 3 μm and a pore volume of 3cm 3 And/g, wherein the average pore diameter of the porous structure in the three-dimensional graphene is 40nm; and carrying out nano indentation test by AFM (atomic force microscope), and measuring the breaking strength of the joint of the graphene sheets which are mutually overlapped in the three-dimensional graphene to be 30N/m.
Example 6
Example 6 differs from example 1 in that: lithium iron manganese phosphate (formula is LiFe) 0.25 Mn 0.75 PO 4 ) The lithium iron phosphate in example 1 was replaced.
Example 7
Example 7 differs from example 1 in that: the second positive electrode coating 22 does not contain three-dimensional graphene, and the first positive electrode coating 21 contains the three-dimensional graphene. Wherein, lithium iron phosphate, PVDF, suppler P and three-dimensional graphene are mixed according to a ratio of 100:3:2:5, mixing the materials according to the mass ratio, and preparing a first positive electrode slurry: NCM811 was combined with PVDF, and suppler P at 100:2: and mixing the materials according to the mass ratio of 1 to prepare second positive electrode slurry. In addition, the first positive electrode slurry had a single-sided area density of 30g/m according to the first positive electrode coating layer to be formed 2 Coating the mixture to obtain a second positive electrode slurry with an areal density of 125g/m according to the second positive electrode coating to be formed 2 Coating is performed.
Example 8
Ternary active material NCM811, binder PVDF, conductive agent supplier P and three-dimensional graphene are mixed according to a ratio of 100:2.9:1.9:8, mixing the mixture in NMP solvent, stirring to obtain positive electrode slurry with single-sided surface density of 200g/m 2 Coating is performed on opposite side surfaces of the aluminum foil.
To highlight the benefits of the present application, the present application is also provided with the following comparative examples 1-3.
Comparative example 1
Lithium iron phosphate material and ternary active material NCM811 is mixed according to the mass ratio of 90:10 to obtain a mixed positive electrode active material, and then the mixed positive electrode active material is mixed with PVDF and a supplier P according to the mass ratio of 100:3:3, mixing the mixture in a solvent NMP in a mass ratio, and uniformly stirring to obtain anode slurry; the positive electrode slurry is coated on the two opposite side surfaces of an aluminum foil, and the positive electrode plate D1 is obtained after drying and rolling, wherein the thickness of the positive electrode coating on one side surface of the positive electrode plate D1 is 65 mu m, and the single-sided surface density is 185g/m 2 。
Comparative example 2
Comparative example 2 differs from example 1 in that: the first positive electrode coating 21 and the second positive electrode coating 22 do not contain three-dimensional graphene. The proportion of the first positive electrode slurry is the same as that of example 1, and the mass ratio of NCM811 to PVDF to suppler P in the second positive electrode slurry is 100:2:1. in addition, the first positive electrode slurry had a single-sided area density of 165g/m in accordance with the first positive electrode coating layer to be formed 2 Coating, wherein the second positive electrode slurry has a single-sided area density of 18.5g/m according to the second positive electrode coating to be formed 2 Coating is performed.
Comparative example 3
Comparative example 3 differs from example 8 in that: the positive electrode active coating does not contain three-dimensional graphene.
Comparative example 4
Comparative example 4 differs from example 1 in that the ternary active material NCM811 was combined with PVDF, suppler P and three-dimensional graphene at 100:2:1:2 preparing a second positive electrode slurry.
Wherein, the thickness rebound rate and the thickness compression rate of the positive electrode sheet obtained in comparative example 4 are both less than 2% (see table 2 below for details).
In order to strongly support the beneficial effects brought by the technical scheme of the application, the positive pole piece in each example is prepared into a corresponding full battery according to the following method: (1) Mixing natural graphite, silicon oxide, a conductive agent and a binder according to a ratio of 95:5:1:3.5, mixing the materials in water to obtain negative electrode slurry; coating the negative electrode slurry on two side surfaces of a copper foil with the thickness of 8 mu m, baking to remove a solvent, forming a negative electrode active material layer on the copper foil, and rolling, slitting and die cutting to obtain a double-sided negative electrode plate; (2) And (3) sequentially laminating the positive electrode plate, the PE diaphragm and the negative electrode plate of each embodiment or the comparative embodiment to prepare a battery cell, and packaging the battery cell in an aluminum plastic film after liquid injection. And (3) performing high-temperature aging, formation, aging, capacity division and vacuum final sealing to obtain the full battery.
The resulting cell was then placed in a jig with a gap between the jig and the cell of 2% of the cell thickness. The position of the fixing clamp is unchanged, and a first charge-discharge capacity test and a cycle performance test are respectively carried out on the battery. It should be noted that since different batteries are required for the first charge-discharge specific capacity test and the capacity retention test, respectively, at least 2 full-cell spares should be prepared for each example or comparative example, respectively.
The test method of the first charge and discharge capacity comprises the following steps: charging all the batteries to 4.25V at constant current at 0.1C at 25 ℃, and charging the batteries to 0.05C at constant voltage of 4.25V; then discharging to 2.5V at 0.1C to obtain a first charge specific capacity and a first discharge specific capacity;
and (3) testing the cycle performance: at 25 ℃, each full cell was charged to 4.25V at 1C at first, then charged to 0.1C at 4.25V at constant voltage, then discharged to 2.5V at 1C, and so on 300 times; the first discharge capacity and the discharge capacity after 300 cycles were recorded, and the capacity retention = (discharge capacity after 300 cycles/first discharge capacity) after 300 cycles was 100%.
The results are summarized in Table 1 below, and the battery cycle performance curves of some examples are plotted in FIG. 4.
TABLE 1
As can be seen from table 1, when the battery cell is circulated in a space with a fixed volume, the battery prepared from the positive electrode sheet with compression-rebound characteristics according to the embodiment of the present application has excellent cycle performance.
The above full batteries subjected to the first charge and discharge capacity test were disassembled, and the positive electrode sheets of the full batteries were respectively subjected to the test of the pole sheet rebound performance and the compression performance, and the results are summarized in table 2 below.
The method for testing the rebound performance of each positive pole piece comprises the following steps: applying an X to each pole piece 1 Pressure of Mpa, measuring pole piece at X 1 Thickness H under pressure of Mpa 1 The method comprises the steps of carrying out a first treatment on the surface of the Then the pressure is removed, and after the thickness of the pole piece is stable, the thickness of the pole piece is measured and is recorded as H 2 The thickness rebound rate r= (H) of the pole piece 2 -H 1 )/H 1 . The method for testing the rebound performance of the positive pole piece comprises the following steps: for an initial thickness of H 3 Is applied to the pole piece with a value X 2 Pressure of Mpa, measuring pole piece at X 2 The thickness under pressure of Mpa is denoted as H 4 The thickness compression rate p= (H) of the pole piece 3 -H 4 )/H 3 . In the embodiment of the application, X 1 ＝0.5Mpa，X 2 ＝0.3Mpa。
TABLE 2
| Thickness rebound rate of pole piece | Thickness compression rate of pole piece | |
| Example 1 | 2.3％ | 2.2％ |
| Example 2 | 9.2％ | 9.1％ |
| Example 3 | 2.0％ | 2.0％ |
| Example 4 | 4.2％ | 4.1％ |
| Example 5 | 2.4％ | 2.3％ |
| Example 6 | 2.3％ | 2.2％ |
| Example 7 | 3.5％ | 3.4％ |
| Example 8 | 19.4％ | 19.3％ |
| Comparative example 1 | 0.1％ | 0％ |
| Comparative example 2 | 0.1％ | 0.1％ |
| Comparative example 3 | 0.1％ | 0％ |
| Comparative example 4 | 0.9％ | 0.8％ |
As can be known from table 2, when a proper amount of three-dimensional graphene is added into the positive electrode active material layer of each positive electrode sheet in the embodiment of the application, a certain compression-rebound characteristic is given to the positive electrode sheet, which is beneficial to improving the cycle performance of the battery when the battery circulates in a space with a fixed volume. In addition, the positive electrode plate (comparative example 1) with the positive electrode coating formed by directly mixing and coating the ternary material and the lithium iron phosphate has no compression and rebound performance, the ternary material layer and the lithium phosphate material layer are arranged in a layered manner, and after a proper amount of three-dimensional graphene is added into the ternary material layer (examples 1-5), the compression rebound performance of the positive electrode plate is more remarkable, so that the cycle performance of the battery is further improved. In addition, the compression-rebound resilience performance of the positive electrode sheet of the single-layer positive electrode active material layer was also more remarkable than that of the positive electrode sheet (comparative example 3) without the three-dimensional graphene added to the positive electrode active coating layer (example 8). In addition, the three-dimensional graphene is added to the ternary material layer of comparative example 4, but the addition amount is small, so that the thickness rebound rate and the thickness compression rate of the positive electrode sheet of comparative example 4 are both less than 2%, that is, the compression-rebound performance of the positive electrode sheet is not outstanding, and thus the cycle performance of the battery of comparative example 4 in a volume-fixed space is still significantly lower than that of example 1 (see table 1 above).
The above examples only represent a few embodiments of the present application, which are described in more detail and are not to be construed as limiting the scope of the present application. It should be noted that it would be apparent to those skilled in the art that various modifications and improvements could be made without departing from the spirit of the present application, which would be within the scope of the present application. Accordingly, the scope of protection of the present application is to be determined by the claims appended hereto.
Claims (12)
1. The positive electrode plate is characterized by comprising a positive electrode current collector and a positive electrode active material layer arranged on at least one side surface of the positive electrode current collector, wherein a bomb additive is contained in the positive electrode active material layer, the bomb additive is three-dimensional graphene, and the three-dimensional graphene has a porous structure; wherein, after being applied with a pressure of more than 0 and less than or equal to 5Mpa in the thickness direction of the positive electrode sheet, the thickness rebound rate and the thickness compression rate of the positive electrode sheet are each independently in a range of 2% -20%.
2. The positive electrode sheet according to claim 1, wherein the porous structure of the three-dimensional graphene has an average pore diameter of 10 to 200nm.
3. The positive electrode sheet according to claim 1 or 2, wherein in the three-dimensional graphene, the three-dimensional graphene includes graphene sheets that overlap each other, and a breaking strength at an overlap of the overlapping graphene sheets is 20 to 50N/m.
4. A positive electrode sheet as claimed in any one of claims 1 to 3, wherein the pore volume of the three-dimensional graphene is in the range of 1 to 10cm 3 Between/g.
5. A positive electrode sheet according to claim 3, wherein the graphene sheet has a lateral dimension of 10nm to 100nm, preferably 10nm to 30nm.
6. The positive electrode sheet according to any one of claims 1 to 5, wherein the positive electrode active material layer comprises a first positive electrode coating layer and a second positive electrode coating layer which are stacked, the first positive electrode coating layer being adjacent to the positive electrode current collector, wherein the first positive electrode coating layer and/or the second positive electrode coating layer contains the piezoelastic additive.
7. The positive electrode sheet of claim 6, wherein the first positive electrode coating comprises LiFe 1-a Mn a PO 4 An active material, a is more than or equal to 0 and less than or equal to 1; the second positive electrode coating comprises a layered transition metal oxide active material and the piezoelastic additive;
preferably, a is more than or equal to 0 and less than or equal to 0.8, and the layered transition metal oxide active material is a ternary material.
8. The positive electrode sheet of any one of claims 1-7, wherein the mass of the piezoelastic additive is 3% -50% of the mass of the layered transition metal oxide active material.
9. The positive electrode sheet of claim 7, wherein the first positive electrode coating has a thickness in the range of 10-150 μm and the second positive electrode coating has a thickness in the range of 5-50 μm.
10. The positive electrode sheet according to any one of claims 6 to 9, wherein a buffer layer containing the piezoelastic additive and the binder is further provided between the first positive electrode coating layer and the second positive electrode coating layer.
11. A battery comprising the positive electrode sheet according to any one of claims 1 to 10.
12. A powered device comprising the battery of claim 11.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210703160.7A CN117317224A (en) | 2022-06-21 | 2022-06-21 | Positive pole piece, battery and electric equipment |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202210703160.7A CN117317224A (en) | 2022-06-21 | 2022-06-21 | Positive pole piece, battery and electric equipment |
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| CN117317224A true CN117317224A (en) | 2023-12-29 |
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| CN202210703160.7A Pending CN117317224A (en) | 2022-06-21 | 2022-06-21 | Positive pole piece, battery and electric equipment |
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