CN115425175A - Thick electrode and preparation method and application thereof - Google Patents

Thick electrode and preparation method and application thereof Download PDF

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Publication number
CN115425175A
CN115425175A CN202211166472.5A CN202211166472A CN115425175A CN 115425175 A CN115425175 A CN 115425175A CN 202211166472 A CN202211166472 A CN 202211166472A CN 115425175 A CN115425175 A CN 115425175A
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electrode
current collector
electrode layer
electrostatic spinning
particle
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牛浩
冀亚娟
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Eve Energy Co Ltd
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Eve Energy Co Ltd
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Abstract

The invention provides a thick electrode and a preparation method and application thereof. The thick electrode comprises a current collector and at least two electrode layers positioned on the surface of the current collector, wherein an electrostatic spinning layer is also arranged between the electrode layers, active substances in the electrode layers close to the surface of the current collector are large-particle-size active substances, and active substances in the electrode layers far away from the surface of the current collector are small-particle-size active substances. According to the invention, at least two electrode layers are designed to improve the loading capacity and thickness of the electrode, the particle size collocation of the main materials of each active material layer is optimized, the specific capacity and the energy density of the battery are increased, and meanwhile, the connection between the electrode layers is realized through the electrostatic spinning layer, so that the porosity gradient distribution along the direction vertical to the electrode is realized, a high-efficiency ion diffusion conduction channel and electron transmission conduction are constructed, good ion diffusion and conduction are obtained, the polarization in the charging and discharging process is reduced, and the high energy density and the power performance of the battery are ensured.

Description

Thick electrode and preparation method and application thereof
Technical Field
The invention belongs to the technical field of lithium ion batteries, particularly relates to a thick electrode and a preparation method and application thereof, and particularly relates to a thick positive electrode and a preparation method and application thereof.
Background
The development planning of the power battery is clarified according to 'Chinese manufacturing 2025': in 2020, the energy density of the battery reaches 300Wh/kg; in 2025, the energy density of the battery reaches 400Wh/kg; in 2030, the energy density of the battery reaches 500Wh/kg. The traditional preparation method of the lithium ion battery is difficult to meet the requirement of the energy density in the future. Therefore, increasing the energy density of the battery is an important direction for future development. Based on the working principle and the structural composition of the lithium ion battery, the method for increasing the loading capacity and the thickness of the electrode active substance on the current collector and reducing the content of the inactive substance in the electrode is the most convenient and effective way for improving the energy density of the lithium ion battery.
However, the high-loading electrode causes uneven distribution of current along the thickness direction, and the concentration of lithium ions is also seriously different between the upper surface and the lower surface, which causes serious polarization, reduces the utilization rate of active materials, and is accompanied with the problems of lithium precipitation on the surface of the negative electrode, structural damage of the positive electrode and the like in the charging process. In addition, as the energy density is increased, the diffusion conduction kinetics of lithium ions are severely limited, so that the power performance of the electrode cannot be maintained. The key of the design of the high-capacity electrode is to ensure that the energy density of the battery is improved, solve the problem of conduction dynamics of ionic electrons in the electrode and ensure the power performance of the electrode
CN102324493A discloses a thick electrode with good electrochemical performance, which is characterized in that an electrode diaphragm and a current collector are compositely dried and rolled in a slurry coating mode, then slurry is coated on the surface of the dried electrode diaphragm for the second time, and the thick electrode is prepared by drying and rolling again, so that the electrode diaphragms at different positions have different conductivities and porosities by controlling the rolling pressure intensity twice, and the problem of difficult transmission of electrons and ions in the thick electrode plate is solved. However, the electrode diaphragm, the current collector and the electrode diaphragm are compounded by adopting a slurry coating mode, and wet slurry is coated on the surface of the dried electrode diaphragm, so that the phenomenon that the dried material is dissolved out again is avoided, and the electronic conductance and the pore distribution of the electrode are influenced.
CN110010900a discloses a thick electrode with good electrochemical performance, which is manufactured by laminating two electrode films with different porosities and laminating a composite electrode film on a carbon-coated aluminum foil, and is formed by laminating two dry electrode films. However, the invention is manufactured by pressing two electrode films with different porosities and then pressing a composite electrode film on a carbon-coated aluminum foil, and because the composite electrode film is formed by pressing two dry electrode films, an interface for bonding the two electrode films is inevitably arranged in the electrode film, and the electrode film interface is easy to delaminate and fall off due to the change of internal stress of the electrode in the charging and discharging processes of the battery, so that the cycle performance of the battery is influenced, and the cost is higher.
CN112670443A discloses a method for preparing a thick electrode, which adopts a method of adding pore-forming agents with different concentrations into slurry to prepare active layers of different layers, and utilizes high-temperature drying to make the gas generated by the decomposition of the pore-forming agents perform porosity adjustment. However, in the document, the electrode is prepared by using the added pore-forming agent and a pyrolysis pore-forming method, the non-conductive pore-forming agent is easily remained in the coating, the internal resistance of the battery is increased, closed pores are easily generated in the pyrolysis pore-forming process to reduce the porosity of the pole piece, the size of the pores cannot be controlled, the tortuosity of the pore channel is easily increased, and the improvement of the energy density of the battery is not facilitated.
Therefore, how to simultaneously ensure the high energy density and the dynamic performance of the thick electrode battery is a technical problem to be solved urgently.
Disclosure of Invention
In view of the shortcomings of the prior art, the invention aims to provide a thick electrode and a preparation method and application thereof. According to the invention, at least two electrode layers are designed to improve the loading capacity and thickness of the electrode, the particle size collocation of the main materials of each active material layer is optimized, the specific capacity and the energy density of the battery are increased, and meanwhile, the connection between the electrode layers is realized through the electrostatic spinning layer, so that the porosity gradient distribution along the direction vertical to the electrode is realized, a high-efficiency ion diffusion conduction channel and electron transmission conduction are constructed, good ion diffusion and conduction are obtained, the polarization in the charging and discharging process is reduced, and the high energy density and the power performance of the battery are ensured.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a thick electrode, which includes a current collector and at least two electrode layers located on the surface of the current collector, wherein an electrostatic spinning layer is further disposed between the electrode layers, active materials in the electrode layers close to the surface of the current collector are large-particle-size active materials, and active materials in the electrode layers far away from the surface of the current collector are small-particle-size active materials.
The at least two electrode layers are positioned on the same side of the current collector, and the current collector can be provided with at least two electrode layers on both sides or only one side.
The invention improves the loading capacity and thickness of the electrode by designing at least two electrode layers, optimizes the particle size collocation of main materials of active substances of each layer, increases the specific capacity and energy density of the battery, realizes the connection between the electrode layers through the electrostatic spinning layer, ensures the gradient distribution of the porosity along the direction vertical to the electrode, constructs a high-efficiency ion diffusion conduction channel and electron transmission conduction, obtains good ion diffusion and conduction, reduces the polarization in the charging and discharging process, and ensures the high energy density and power performance of the battery.
In the invention, a continuous ion channel is formed between the electrode layer and the electrostatic spinning layer, so that the redox reaction kinetics can be greatly improved, a gradient pore structure vertical to the electrode direction can be formed, and the rapid infiltration of electrolyte and the extraction/insertion of lithium ions in rapid charge and discharge are ensured.
In the invention, the electrostatic spinning layer plays a role in improving the electron conductivity between the electrode layers, and if the electrostatic spinning layer is not arranged between the electrode layers, the transfer of electrons between the electrode layers can be seriously influenced.
According to the invention, through the matching of the sizes and the particle diameters, the design of a gradient electrode is realized, the rate charging performance of a pole piece and the exertion of capacity under high rate are improved, if the particle diameters of active substances in different electrode layers are kept consistent, the performance under high rate is deteriorated, and if the active substances close to a current collector are small-particle-diameter active substances, and the active substances far away from the current collector are large-particle-diameter active substances, the rapid de-intercalation of lithium ions can not be realized.
Preferably, the electrospun layer comprises nanofibers and a binder.
Preferably, the electrospun layer further comprises a conductive agent.
In the invention, the conductive agent is added into the electrostatic spinning layer, so that the electronic conductivity of the electrostatic spinning layer can be further improved.
Preferably, the nanofibers comprise any one of polyacrylonitrile, polymethylmethacrylate, or carbon fibers or a combination of at least two thereof.
Preferably, the nanofibers are carbon fibers.
According to the invention, when the electrostatic spinning layer is made of carbon fibers, a 3D continuous electronic network/ion channel can be formed with the electrode layer, and active particles are embedded into the 3D framework structure, so that the redox reaction kinetics can be greatly improved, and a gradient pore structure perpendicular to the electrode direction can be formed, so that the rapid infiltration of electrolyte and the extraction and extraction of lithium ions in the rapid charging and discharging process are ensured.
Preferably, the electrode layer near the surface of the current collector comprises a conductive agent and a binder.
Preferably, the electrode layer close to the surface of the current collector further comprises a polymer electrolyte.
In the invention, by adding the polymer electrolyte, active substance particles can be coated by a cross-linked network formed by the conductive agent and the organic polymer electrolyte, so that a rapid ion/electron channel is provided, gaps among active materials can be filled to form compact particle particles, and the compound electrolyte can promote the penetration of electrolyte due to good wettability and solubility, thereby improving the electrochemical performance of the electrode.
Preferably, the mass ratio of the polymer electrolyte is 0.3 to 1%, for example, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or the like, based on 100% of the electrode layer near the surface of the current collector.
Preferably, the polymer electrolyte comprises any one of polyethylene oxide, polyacrylonitrile, polymethyl methacrylate, polypropylene oxide or polyvinylidene chloride or a combination of at least two thereof.
Preferably, the electrode layer away from the surface of the current collector comprises a conductive agent and a binder.
The conductive agent and the binder in the invention are selected by conventional techniques, namely common substances in the electrode preparation process, and the invention is applicable to the conductive agent, for example, the conductive agent can be one or a mixture of several of carbon black, conductive graphite, carbon fiber, graphene and carbon nano tube, and the binder can be one or a mixture of two of PVDF and PAA.
Preferably, the large-particle-size active material and the small-particle-size active material each independently include any one of lithium cobaltate, lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium manganese oxide, or lithium nickel manganese oxide, or a combination of at least two thereof.
The thick electrode of the present invention is suitable for a positive electrode.
Preferably, the D50 of the large particle size active material is 7.5 to 30 μm, for example 7.5 μm, 8 μm, 10 μm, 13 μm, 15 μm, 18 μm, 20 μm, 23 μm, 25 μm, 28 μm or 30 μm.
Preferably, the D50 of the small particle size active material is 0.5 to 10 μm, such as 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, or 10 μm, and the like.
In a second aspect, the present invention provides a method for preparing a thick electrode according to the first aspect, the method comprising the steps of:
(1) Coating the first electrode layer slurry on the surface of a current collector to obtain an electrode layer close to the surface of the current collector;
(2) Obtaining an electrostatic spinning layer on the electrode layer close to the surface of the current collector by electrostatic spinning of the electrostatic spinning slurry;
(3) Coating the second electrode layer slurry on the surface of the electrostatic spinning layer to obtain the thick electrode;
wherein the active material in the electrode layer near the surface of the current collector is a large-particle-diameter active material, and the active material in the electrode layer far from the surface of the current collector is a small-particle-diameter active material.
The invention improves the loading capacity and thickness of the electrode by adopting different processes to prepare at least two electrode layers, optimizes the particle size collocation of the main materials of each active material layer, increases the specific capacity and energy density of the battery, obtains the electrostatic spinning layer between the electrode layers by the electrostatic spinning technology, ensures the gradient distribution of the porosity along the direction vertical to the electrode, constructs an efficient ion diffusion conduction channel and electron transmission, obtains good ion diffusion and conduction, reduces the polarization in the charging and discharging process, and ensures the high energy density and power performance of the battery.
Preferably, the first electrode layer slurry of step (1) includes a large-particle-size active material, a binder, a conductive agent, and an organic solvent.
Preferably, the first electrode layer slurry of step (1) further comprises a polymer electrolyte.
Preferably, after the coating in the step (1), drying is carried out.
In the invention, the dried slurry is in a semi-dry state, so that the slurry is better fused with the electrostatic spinning layer, the interface contact area is large, and the resistance is small.
According to the invention, by adding the polymer electrolyte and the organic solvent into the first electrode layer slurry, active substance particles can be coated by a cross-linked network formed by the conductive agent and the organic polymer electrolyte along with the evaporation of the organic solvent in the drying process, so that a fast ion/electron channel is provided, gaps among the active substances can be filled to form compact particle particles, and the organic compound electrolyte promotes the penetration of electrolyte due to good wettability and solubility of the organic compound electrolyte, so that the electrochemical performance of the electrode is improved.
Preferably, the electrospinning slurry of step (2) comprises nanofibers, an organic solvent and a binder.
Preferably, the electrostatic spinning slurry of step (2) further comprises a conductive agent.
Preferably, after the electrostatic spinning in the step (2), drying is performed.
In the present invention, the drying of the electrostatic spinning layer is also in a semi-dry state.
Preferably, the coating method in step (3) is electrostatic spraying.
According to the invention, through electrostatic spinning and electrostatic spraying technologies, a continuous electron network/ion channel can be formed, the redox reaction kinetics can be greatly improved when active particles are embedded into a framework, and a gradient pore structure perpendicular to the electrode direction can be formed, so that the rapid infiltration of electrolyte and the extraction/insertion of lithium ions in rapid charging and discharging can be ensured.
And different coatings adopt different preparation methods, so that the utilization rate of active substances can be effectively increased, the internal polarization of the battery is reduced, and the energy density and the rate capability of the battery are improved.
Preferably, the second electrode paste of step (3) includes a small-particle-size active material, a conductive agent, a binder, and an organic solvent.
In the invention, the organic solvent comprises one or a mixture of N-methylpyrrolidone (NMP), propylene Carbonate (PC), ethylene Carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC) and Ethyl Methyl Carbonate (EMC).
Preferably, after the coating in the step (3) is finished, drying and rolling are sequentially performed.
In a third aspect, the present invention also provides a lithium ion battery comprising the thick electrode according to the first aspect.
Compared with the prior art, the invention has the following beneficial effects:
(1) According to the invention, at least two electrode layers are designed to improve the loading capacity and thickness of the electrode, the particle size collocation of the main materials of each active material layer is optimized, the specific capacity and the energy density of the battery are increased, and meanwhile, the connection between the electrode layers is realized through the electrostatic spinning layer, so that the porosity gradient distribution along the direction vertical to the electrode is realized, a high-efficiency ion diffusion conduction channel and electron transmission conduction are constructed, good ion diffusion and conduction are obtained, the polarization in the charging and discharging process is reduced, and the high energy density and the power performance of the battery are ensured. When the battery adopts the thick electrode provided by the invention, the polymer electrolyte is added into the electrode layer close to the current collector, the conductive agent is added into the electrostatic spinning layer, and meanwhile, when the second electrode layer is prepared by adopting a spraying method, the energy density can reach more than 230wh/kg, the first effect under 0.2C can reach more than 93 percent, the rate performance of 5C/0.2C can reach more than 85 percent, the capacity retention rate after 1C cycle for 1000 weeks can reach more than 90 percent, and when a lithium iron phosphate anode material is selected, the capacity retention rate after 1C cycle for 1000 weeks can reach more than 95 percent.
(2) In the preparation process, different coatings adopt different preparation methods, the utilization rate of active materials can be effectively increased, the internal polarization of the battery is reduced, the energy density and the rate capability of the battery are improved, a continuous electron network/ion channel can be formed by combining electrostatic spinning and electrostatic spraying technologies, the redox reaction kinetics can be greatly improved by embedding active particles into a framework, a gradient pore structure vertical to the direction of an electrode can be formed, and the rapid infiltration of electrolyte and the extraction/insertion of lithium ions in rapid charging and discharging are ensured.
Drawings
Fig. 1 is a schematic structural diagram of a thick electrode provided in example 1.
The electrode comprises a current collector 1, a first electrode layer 2, an electrostatic spinning layer 3 and a second electrode layer 4.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitation of the present invention.
Example 1
The embodiment provides a thick electrode, as shown in fig. 1, the thick electrode includes a current collector 1 and two electrode layers located on the surface (double surfaces) of the current collector 1, wherein an electrostatic spinning layer 3 is further disposed between the electrode layers, an active material in the electrode layer (first electrode layer 2) close to the surface of the current collector 1 is large-particle-size lithium iron phosphate (D50 is 7.5 μm), and an active material in the electrode layer (second electrode layer 4) far away from the surface of the current collector 1 is small-particle-size lithium iron phosphate (D50 is 0.6 μm).
The electrostatic spinning layer is composed of carbon fibers, conductive carbon black and polyvinylidene fluoride (mass ratio is 40.
The preparation method of the thick electrode comprises the following steps:
(1) Respectively preparing first electrode layer slurry, electrostatic spinning slurry and second electrode layer slurry;
the preparation method of the first electrode layer slurry comprises the following steps: mixing polyethylene oxide, large-particle-size lithium iron phosphate, conductive carbon black and polyvinylidene fluoride according to a mass ratio of 0.5;
the preparation method of the electrostatic spinning slurry comprises the following steps: mixing carbon fibers, conductive carbon black and polyvinylidene fluoride according to a mass ratio of 40;
the preparation method of the second electrode layer slurry comprises the following steps: mixing the small-particle-size lithium iron phosphate, the conductive carbon black and the polyvinylidene fluoride according to a mass ratio of 97.0;
(2) Coating (brushing) the first electrode layer slurry on the surface of an aluminum foil, and drying at low temperature to keep the pole piece in a semi-dry state to obtain a first pole piece;
(3) Spraying the electrostatic spinning slurry through electrostatic spinning, uniformly coating the electrostatic spinning slurry on the surface of the electrode layer of the first pole piece prepared in the step (2), and drying at a low temperature to keep a semi-dry state to obtain a second pole piece;
(4) And (4) spraying and coating the second electrode layer slurry on the surface of the electrostatic spinning layer of the second pole piece prepared in the step (3) through electrostatic spraying, and drying, rolling and die cutting to obtain the thick electrode.
Example 2
The embodiment provides a thick electrode, which includes a current collector and two electrode layers located on the surface (double surfaces) of the current collector, wherein an electrostatic spinning layer is further arranged between the electrode layers, an active material in the electrode layer (first electrode layer) close to the surface of the current collector is large-particle-size NCM811 (D50 is 11.0 μm), and an active material in the electrode layer (second electrode layer) far from the surface of the current collector is small-particle-size NCM811 (D50 is 4.0 μm).
Wherein, the first electrode layer comprises polyvinylidene chloride, large particle size NCM811, conductive graphite and polyvinylidene fluoride (mass ratio is 0.8, 96.5.
The preparation method of the thick electrode comprises the following steps:
(1) Respectively preparing first electrode layer slurry, electrostatic spinning slurry and second electrode layer slurry;
the preparation method of the first electrode layer slurry comprises the following steps: mixing polyvinylidene chloride, large-particle-size NCM811, conductive graphite and polyvinylidene fluoride in a mass ratio of 0.8;
the preparation method of the electrostatic spinning slurry comprises the following steps: mixing polyacrylonitrile, conductive graphite and polyvinylidene fluoride according to the mass ratio of 38;
the preparation method of the second electrode layer slurry comprises the following steps: mixing the small-particle-size NCM811, the conductive graphite and the polyvinylidene fluoride according to a mass ratio of 96.5;
(2) Coating (brushing) the first electrode layer slurry on the surface of an aluminum foil, and drying at low temperature to keep a pole piece in a semi-dry state to obtain a first pole piece;
(3) Spraying the electrostatic spinning slurry through electrostatic spinning, uniformly coating the electrostatic spinning slurry on the surface of the electrode layer of the first pole piece prepared in the step (2), and drying at a low temperature to keep a semi-dry state to obtain a second pole piece;
(4) And (3) spraying and coating the second electrode layer slurry on the surface of the electrostatic spinning layer of the second pole piece prepared in the step (3) through electrostatic spraying, and drying, rolling and die cutting to obtain the thick electrode.
Example 3
The difference between this example and example 1 is that, in this example, polyethylene oxide is not added to the first electrode layer, and the mass ratio in the first electrode layer is adjusted to 97.
The remaining preparation methods and parameters were in accordance with example 1.
Example 4
The difference between the present example and example 1 is that no conductive carbon black is added to the electrospun layer in the present example, and the mass ratio is adjusted to be 1.0.
The remaining preparation methods and parameters were in accordance with example 1.
Example 5
The present example is different from example 1 in that the coating method in step (4) of the present example is a brush coating method.
The remaining preparation methods and parameters were in accordance with example 1.
Comparative example 1
The comparative example is different from example 1 in that no electrostatic spinning layer is provided in the thick electrode of the comparative example, and the preparation method does not carry out preparation and treatment of electrostatic spinning slurry.
The remaining preparation methods and parameters were in accordance with example 1.
Comparative example 2
The comparative example is different from example 1 in that the active materials in the first electrode layer and the second electrode layer of the comparative example are both large-particle-size lithium iron phosphate.
The remaining preparation methods and parameters were in accordance with example 1.
Comparative example 3
The difference between the comparative example and the example 1 is that the active materials in the first electrode layer and the second electrode layer of the comparative example are both small-particle-size lithium iron phosphate.
The remaining preparation methods and parameters were in accordance with example 1.
Comparative example 4
The comparative example is different from the example 1 in that the first electrode layer of the comparative example is small-particle-size lithium iron phosphate, and the second electrode layer of the comparative example is large-particle-size lithium iron phosphate.
The remaining preparation methods and parameters were in accordance with example 1.
The electrodes provided in examples 1 to 5 and comparative examples 1 to 4 were used as positive electrodes, and artificial graphite was used as a negative electrode, and batteries were assembled to perform electrochemical performance tests under conditions of a first charge-discharge cycle at 0.2C and a rate performance test at 5.0C, and a charge-discharge cycle at 1.0C/1.0C for 1000 weeks, and the results of the capacity retention tests are shown in table 1.
Figure BDA0003861598820000111
Figure BDA0003861598820000121
From the data results of examples 1 and 3, it is understood that the addition of the polymer electrolyte further improves the lithium ion diffusion capability and improves the rate capability and cycle performance of the battery.
From the data results of example 1 and example 4, it can be seen that the addition of the conductive agent in the electrospinning is beneficial to the conduction of electrons between different electrode layers, and the rate capability and the cycle performance can be improved.
From the data results of example 1 and example 5, it can be seen that the preparation of coatings using different coating methods can better achieve high energy density designs.
From the data results of example 1 and comparative example 1, it is clear that without adding an electrostatic spinning layer, high-speed passage of electrons and lithium ions between different electrode layers cannot be achieved, rate capability is poor, and cycle performance is deteriorated.
As can be seen from the data results of example 1 and comparative examples 2 and 3, the incorporation of active materials having the same particle size in the electrode layer leads to a decrease in the rate capability of the battery.
From the data results of example 1 and comparative example 4, it is understood that the electrode layer close to the current collector has a small particle size, and the electrode layer far away from the current collector has a large particle size, which affects the performance of the battery rate doubling performance.
In conclusion, the invention improves the loading capacity and thickness of the electrode by designing at least two electrode layers, optimizes the particle size collocation of the main materials of each active material layer, increases the specific capacity and energy density of the battery, realizes the connection between the electrode layers through the electrostatic spinning layer, ensures the gradient distribution of the porosity along the direction vertical to the electrode, constructs a high-efficiency ion diffusion conduction channel and electron transmission conduction, obtains good ion diffusion and conduction, reduces the polarization in the charging and discharging process, and ensures the high energy density and power performance of the battery; in the preparation process, different coating layers adopt different preparation methods, the utilization rate of active materials can be effectively increased, the internal polarization of the battery is reduced, the energy density and the rate capability of the battery are improved, a continuous electron network/ion channel can be formed by combining electrostatic spinning and electrostatic spraying technologies, the redox reaction kinetics can be greatly improved by embedding active particles into a framework structure, a gradient pore structure vertical to the direction of an electrode can be formed, and the rapid infiltration of electrolyte and the detachment/insertion of lithium ions in rapid charging and discharging are ensured. When the battery adopts the thick electrode provided by the invention, the polymer electrolyte is added into the electrode layer close to the current collector, the conductive agent is added into the electrostatic spinning layer, and meanwhile, when the second electrode layer is prepared by adopting a spraying method, the energy density can reach more than 230wh/kg, the first effect under 0.2C can reach more than 93 percent, the rate performance of 5C/0.2C can reach more than 85 percent, and the capacity retention rate after 1C cycle for 1000 weeks can reach more than 90 percent.
The applicant states that the present invention is illustrated by the above examples of the process of the present invention, but the present invention is not limited to the above process steps, i.e. it is not meant that the present invention must rely on the above process steps to be carried out. It will be apparent to those skilled in the art that any modification of the present invention, equivalent substitutions of selected materials and additions of auxiliary components, selection of specific modes and the like, which are within the scope and disclosure of the present invention, are contemplated by the present invention.

Claims (10)

1. The thick electrode is characterized by comprising a current collector and at least two electrode layers positioned on the surface of the current collector, wherein an electrostatic spinning layer is also arranged between the electrode layers, active substances in the electrode layers close to the surface of the current collector are large-particle-size active substances, and active substances in the electrode layers far away from the surface of the current collector are small-particle-size active substances.
2. The thick electrode of claim 1, wherein the electrospun layer comprises nanofibers and a binder;
preferably, the electrospun layer further comprises a conductive agent;
preferably, the nanofibers comprise any one of polyacrylonitrile, polymethylmethacrylate, or carbon fibers or a combination of at least two thereof.
3. The thick electrode of claim 1 or 2, wherein the electrode layer near the surface of the current collector comprises a conductive agent and a binder;
preferably, the electrode layer close to the surface of the current collector further comprises a polymer electrolyte;
preferably, the mass of the polymer electrolyte accounts for 0.3-1% of 100% of the electrode layer close to the surface of the current collector;
preferably, the polymer electrolyte comprises any one of polyethylene oxide, polyacrylonitrile, polymethyl methacrylate, polypropylene oxide or polyvinylidene chloride or a combination of at least two thereof.
4. The thick electrode of any one of claims 1-3, wherein the electrode layer away from the surface of the current collector comprises a conductive agent and a binder.
5. The thick electrode of any one of claims 1-4, wherein the large and small particle size active materials each independently comprise any one or a combination of at least two of lithium cobaltate, lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium manganese oxide, or lithium nickel manganese oxide;
preferably, the D50 of the large particle size active material is 7.5 to 30.0 μm;
preferably, the D50 of the small particle size active material is 0.5 to 10.0 μm.
6. A method of manufacturing a thick electrode according to any of claims 1 to 5, comprising the steps of:
(1) Coating the first electrode layer slurry on the surface of a current collector to obtain an electrode layer close to the surface of the current collector;
(2) Obtaining an electrostatic spinning layer on the electrode layer close to the surface of the current collector by electrostatic spinning of the electrostatic spinning slurry;
(3) Coating the second electrode layer slurry on the surface of the electrostatic spinning layer to obtain the thick electrode;
wherein the active material in the electrode layer close to the surface of the current collector is a large-particle-diameter active material, and the active material in the electrode layer far from the surface of the current collector is a small-particle-diameter active material.
7. The method for preparing a thick electrode according to claim 6, wherein the first electrode layer slurry of step (1) comprises a large-particle-size active material, a binder, a conductive agent, and an organic solvent;
preferably, the first electrode layer slurry of step (1) further comprises a polymer electrolyte;
preferably, after the coating in the step (1), drying is carried out.
8. The method for preparing a thick electrode according to claim 6 or 7, wherein the electrospinning slurry of the step (2) comprises nanofibers, an organic solvent and a binder;
preferably, the electrostatic spinning slurry of step (2) further comprises a conductive agent;
preferably, after the electrostatic spinning in the step (2), drying is performed.
9. The method for preparing a thick electrode according to any one of claims 6 to 8, wherein the coating method in the step (3) is an electrostatic spraying method;
preferably, the second electrode paste of step (3) includes a small-particle-size active material, a conductive agent, a binder, and an organic solvent;
preferably, after the coating in the step (3) is finished, drying and rolling are sequentially performed.
10. A lithium ion battery comprising a thick electrode according to any one of claims 1 to 5.
CN202211166472.5A 2022-09-23 2022-09-23 Thick electrode and preparation method and application thereof Pending CN115425175A (en)

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