An electrode sheet, a method of manufacturing the same, a secondary battery, and an electric device

Abstract

The application provides a pole piece and a preparation method thereof, a secondary battery and an electric device. The pole piece comprises a current collector and an active material layer arranged on at least one side of the current collector, wherein the active material layer comprises an active material, carbon nanotubes and a ceramic material, the carbon nanotubes are arranged around the outer periphery of the active material, the ceramic material is dispersed on the surface of the carbon nanotubes, and the surface of the active material is dispersed with the ceramic material. By adding the ceramic material which can inhibit the high-nickel positive active and manganese elution reaction in the active material layer, the application can improve the gas production and cycle instability of the battery under high-temperature and high-voltage conditions, and the carbon nanotubes can well disperse the ceramic material and make the inhibition effect of the ceramic material well play.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a pole piece, a preparation method thereof, a secondary battery and an electric device. BACKGROUND

[0002] Lithium ion secondary batteries have become one of the most widely used energy storage devices due to their high voltage, high specific energy and long cycle life. However, the battery often produces some gas during use, especially at high temperature and high voltage, which causes the battery life to accelerate and some safety problems.

[0003] The gas production problem caused by the positive electrode mainly consists of two aspects. On the one hand, high-nickel positive electrode materials have strong reactivity, and oxygen is released during the charging and discharging process, and gas is produced by the side reaction with the electrolyte during the charging process. The particle crushing in the rolling process of the battery can intensify the occurrence of this chemical reaction, especially during the battery cycle process, as the number of cycles increases, the gas production will increase significantly. On the other hand, the cycle stability of lithium ion batteries at high voltage will be greatly reduced, especially at high temperature of 55℃, there are problems such as manganese dissolution, and as the decomposition of electrolyte increases, more manganese ions are dissolved, resulting in rapid decline of electrochemical cycle performance.

[0004] The gas production of the negative electrode mainly comes from two aspects. On the one hand, the formation of the solid electrolyte interface (SEI) film on the interface between the negative electrode and the electrolyte solid-liquid phase, the formation of the SEI film will continuously consume lithium salt and organic solvent in the electrolyte during the first charge and cycle process, accompanied by gas production of the electrolyte; on the other hand, the dissolution of manganese ions in the solvent, the dissolved manganese in the battery cycle process will react with the electrolyte to produce gas.

[0005] In order to improve the electrochemical performance of lithium ion batteries at high temperature, the active material is usually doped or coated. However, the doping method in the prior art has a complex process and high energy consumption, which limits its popularization and application. The method of coating the modified pole piece has problems such as process and coating uniformity. Therefore, a new scheme is needed to improve the gas production and cycle instability of the battery at high temperature and high voltage. SUMMARY

[0006] The present application provides a pole piece, a preparation method thereof, a secondary battery and an electric device, which solves the problem of poor gas production and cycle stability of the battery at high temperature and high voltage.

[0007] According to the pole piece in the first embodiment of the present application, the pole piece comprises a current collector and an active material layer arranged on at least one side of the current collector, the active material layer comprises an active material, carbon nanotubes and a ceramic material, the carbon nanotubes are arranged around the outer periphery of the active material, and the ceramic material is dispersed on the surface of the carbon nanotubes.

[0008] Optionally, in other embodiments of the present application, the ceramic material and the active material are in a granular form, the particle size of the ceramic material can be 0.05-0.6 times the particle size of the active material, and the particle size of the ceramic material can also be 0.1-0.55 times, 0.2-0.5 times, 0.3-0.4 times or 0.35-0.4 times the particle size of the active material.

[0009] Optionally, in other embodiments of the present application, the D50 of the active material can be 1-10 μm, or 2-8 μm, 3-7 μm or 5-6 μm.

[0010] Optionally, in other embodiments of the present application, the D50 of the ceramic material can be 0.05-6 μm, or 0.4-5 μm, 1-3 μm or 2-2.5 μm.

[0011] Optionally, in other embodiments of the present application, the pole piece further comprises a binder, the binder disperses the ceramic material, and the binder and the carbon nanotubes are bonded to crosslink the ceramic material on the carbon nanotubes.

[0012] Optionally, in other embodiments of the present application, the ceramic material comprises at least one of Al(OH)3, Al2O3, Mg(OH)2, H3BO3, Ca(OH)2 or TiO2.

[0013] Optionally, in other embodiments of the present application, the length of the carbon nanotubes can be 1-40 μm, or the length of the carbon nanotubes can also be 5-35 μm, 10-30 μm, 15-25 μm or 17-20 μm.

[0014] Optionally, in other embodiments of the present application, the diameter of the carbon nanotubes can be 0.2-10 nm, or the diameter of the carbon nanotubes 12 can also be 1-9 nm, 2-8 nm, 3-7 nm or 5-6 nm.

[0015] Optionally, in other embodiments of the present application, the active material layer further comprises a conductive agent, and the mass ratio of the active material, the conductive agent, the carbon nanotubes, the binder and the ceramic material is (90-98):(0.2-2):(0.2-2):(1-5):(0.2-1); or the mass ratio can also be (93-96):(0.5-1.5):(0.5-1):(2-4):(0.5-0.8).

[0016] According to the preparation method of the pole piece of the second embodiment of the present application, the method comprises:

[0017] The ceramic material and the carbon nanotube are added, stirred and dispersed, so that the ceramic material is crosslinked on the carbon nanotube;

[0018] The active material and the conductive agent are added, stirred and dispersed, the ceramic material is crosslinked with the carbon nanotube and dispersed on the surface of the active material, the active material, the carbon nanotube and the ceramic material jointly constitute a crosslinked network, and the slurry is obtained;

[0019] The slurry is coated on the current collector, and the pole piece is obtained after drying and rolling.

[0020] Optionally, in other embodiments of the present application, before the step of adding the ceramic material and the carbon nanotube, stirring and dispersing, so that the ceramic material is crosslinked on the carbon nanotube, the method comprises the steps of:

[0021] The adhesive is provided, the adhesive is mixed with the ceramic material first, and the ceramic material is dispersed in the adhesive by stirring.

[0022] According to the secondary battery of the third embodiment of the present application, the secondary battery comprises a positive pole piece, a negative pole piece, a separator and an electrolyte, the positive pole piece comprises a positive current collector and a positive active material layer arranged on at least one side of the positive current collector, the positive active material layer comprises a positive active material, a carbon nanotube and a ceramic material, the carbon nanotube is crosslinked with the positive active material and surrounds the outer periphery of the positive active material, the ceramic material is crosslinked with the carbon nanotube and dispersed on the surface of the positive active material, and the positive active material, the carbon nanotube and the ceramic material jointly constitute a crosslinked network.

[0023] Optionally, in other embodiments of the present application, the positive active material comprises a ternary material, and the ternary material comprises at least one of a nickel-cobalt-manganese ternary material or a nickel-cobalt-aluminum ternary material.

[0024] Optionally, in other embodiments of the present application, the negative pole piece comprises a negative current collector and a negative active material layer arranged on at least one side of the negative current collector, the negative active material layer comprises a negative active material, a carbon nanotube and a ceramic material, the carbon nanotube is crosslinked with the negative active material and surrounds the outer periphery of the negative active material, the ceramic material is crosslinked with the carbon nanotube and dispersed on the surface of the negative active material, and the negative active material, the carbon nanotube and the ceramic material jointly constitute a crosslinked network.

[0025] Optionally, in other embodiments of the present application, the negative active material comprises one or more of a graphite material, a silicon-carbon material or a silicon-oxygen material.

[0026] According to the electric equipment of the fourth embodiment of the present application, the electric equipment comprises a secondary battery, and the secondary battery serves as a power supply of the electric equipment.

[0027] According to the pole piece provided by the embodiment of the present application, at least the following technical effects are achieved:

[0028] The active material layer in the pole piece of the present application comprises active material, ceramic material and carbon nanotubes, the carbon nanotubes are crosslinked with the active material and surround the outer periphery of the active material, the ceramic material is crosslinked with the carbon nanotubes and dispersed on the surface of the active material, the active material, the carbon nanotubes and the ceramic material together form a crosslinked network, by increasing the ceramic material which inhibits the high-nickel positive active and manganese elution reaction in the active material layer, and the crosslinked network formed by the carbon nanotubes protects the SEI film, the gas production and cycle instability of the battery under high temperature and high voltage conditions can be improved.

[0029] The long strip-shaped carbon nanotubes, the conductive agent and the ceramic material are attached to the surface of the active material under the action of the adhesive, and the long strip-shaped carbon nanotubes are attached with the conductive agent and the ceramic material under the action of the adhesive, the carbon nanotubes are attached to the surface of the active material and play a conductive crosslinking role, which plays an important role in improving the conductive capacity of the pole piece. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0031] Figure 1 is a schematic diagram of the pole piece provided by the embodiment of the present application;

[0032] Figure 2 is a scanning electron microscope (SEM) diagram of the positive pole piece provided by the embodiment of the present application;

[0033] Figure 3 is a scanning electron microscope (SEM) diagram of the negative pole piece provided by the embodiment of the present application;

[0034] Figure 4 is a flowchart of the preparation method of the pole piece provided by the embodiment of the present application;

[0035] Figure 5 is a schematic diagram of the secondary battery provided by the embodiment of the present application.

[0036] The marks in the figure respectively represent: 1-active material layer, 11-active material, 12-carbon nanotube, 13-ceramic material, 2-current collector, 3-secondary battery, 31-positive pole piece, 32-negative pole piece, 33-separator, 34-electrolyte. DETAILED DESCRIPTION

[0037] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the scope of protection of the present application. In addition, it should be understood that the specific implementation described herein is only used to illustrate and explain the present application, and is not used to limit the present application. In the present application, the orientation words such as "upper", "lower", "left", "right" generally refer to the upper, lower, left and right of the device in the actual use or working state, and specifically refer to the direction of the drawing plane in the drawings.

[0038] The first embodiment of the present application provides a pole piece and a preparation method thereof, a secondary battery and an electric device. The following are described in detail respectively. It should be noted that the description order of the following embodiments is not limited as the preferred order of the embodiments.

[0039] The embodiment of the present application provides a pole piece, which comprises a current collector and an active material layer arranged on at least one side of the current collector, the active material layer comprising an active material, carbon nanotubes and a ceramic material, the carbon nanotubes surrounding the outer periphery of the active material, and the ceramic material being dispersed on the surface of the carbon nanotubes and the surface of the active material. The present application adds ceramic material which inhibits high-nickel positive active and manganese dissolution reaction in the active material layer, thereby inhibiting the generation of gas at the positive electrode; the cross-linked network formed by the carbon nanotubes protects the SEI film, and the ceramic particles can inhibit the reaction of the electrolyte at the negative electrode interface and manganese ions, thereby inhibiting the dissolution of manganese ions and reducing the generation of gas at the negative electrode.

[0040] Please refer to Figure 1 , the pole piece 1 comprises a current collector 2 and an active material layer 1 arranged on both sides of the current collector 2, and the active material layer 1 comprises an active material 11, carbon nanotubes 12 and a ceramic material 13. The active material 11 and the ceramic material 13 are in the form of particles, the carbon nanotubes 12 are in the form of long strips, the carbon nanotubes 12 can be cross-linked with multiple active materials 11 and surround the outer periphery of the active material 11, and the carbon nanotubes 12 can be cross-linked with multiple ceramic material 13 particles at the same time, so that the carbon nanotubes 12 and the ceramic material 13 can be closely dispersed on the surface of the active material 11 particles to form a cross-linked network structure. The ceramic material 13 is dispersed on the surface of the carbon nanotubes 12, and based on the spatial three-dimensional structure of the long strip winding of the carbon nanotubes 12, the carbon nanotubes 12 can be well dispersed, improving the uniformity of the dispersion, and when the carbon nanotubes 12 surround the outer periphery of the active material 11, a cross-linked network structure is formed.

[0041] In some embodiments of the present application, the pole piece 1 further comprises a binder which disperses the ceramic material 13 and which binds the carbon nanotubes 12 to crosslink the ceramic material 13 on the carbon nanotubes 12. The binder not only serves as a base material for dispersing the ceramic material 13, so that the ceramic particles can be uniformly dispersed, but also provides a binding effect to adhere the dispersed ceramic material 13 to the carbon nanotubes 12.

[0042] Specifically, for the positive electrode binder, a high molecular resin material can be used. The high molecular resin material includes at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyimide (PI), polyamide (PA), polyvinyl alcohol (PVA), or other high molecular resin materials. Strict control of moisture during the preparation of the positive electrode pole piece helps to inhibit the occurrence of side reactions in the whole life cycle of the battery, so PVDF which is soluble in an organic dispersant is preferably used as the binder. For the negative electrode binder, a water-soluble binder can be used, including at least one of carboxymethyl cellulose (CMC), polyacrylic acid (PAA), lithium polyacrylate (PAALi), and styrene butadiene rubber (SBR), or other materials.

[0043] In some embodiments of the present application, the ceramic material 13 is an inorganic ceramic material, including at least one of Al(OH)3, Al2O3, Mg(OH)2, H3BO3, Ca(OH)2, and TiO2. The addition of Mg, Al oxides or hydroxides, etc. can inhibit the harmful structural phase transition of the ternary positive electrode material at high voltage charging and discharging, i.e. the irreversible phase transition of the ternary layered structure to the spinel structure. The addition of Ti oxide can stabilize the surface of the active material 11 at high charging voltage, and improve the electrochemical performance of the lithium ion battery. Since a small amount of Ti ions cannot be completely combined into the crystal lattice of the positive electrode active material, but are enriched on the surface of the positive electrode active material particles, the segregation of Ti ions at the grain boundaries and surface of the positive electrode active material changes the microstructure of the positive electrode active material particles, which is beneficial to the overall diffusion of lithium and uniform distribution of internal strain in the positive electrode active material particles, and on the other hand, inhibits the oxidation activity of oxygen ions on the surface of the positive electrode active material at high voltage, thereby slowing down the side reaction between the positive electrode active material and the organic electrolyte at high voltage, stabilizing the surface of the positive electrode active material, and inhibiting gas production. Boron doping can inhibit the activity of high-nickel ternary materials, ensuring that the lithium ion battery has stable electrochemical capacity under high temperature and high voltage conditions.

[0044] In some embodiments of the present application, the ceramic material 13 is a granular material, and the active material 11 is also a granular material. The particle size of the ceramic material 13 can be 0.05-0.6 times the particle size of the active material 11. Alternatively, the particle size of the ceramic material 13 can be 0.1-0.55 times, 0.2-0.5 times, 0.3-0.4 times, or 0.35-0.4 times the particle size of the active material 11. Alternatively, the particle size of the ceramic material 13 can be 0.08 times, 0.11 times, 0.15 times, 0.2 times, 0.25 times, 0.4 times, 0.45 times, or 0.56 times the particle size of the active material 11. The addition of ceramic material 13 of smaller size can be dispersed by cross-linking with CNTs during stirring, and finally form a cross-linked network with the active material 11 to form a good adhesion effect. The ceramic material 13 is chemically inert, and can play the inert properties of the ceramic material 13 while exerting the high capacity of the ternary positive electrode, reduce the chemical reaction activity inside the battery during the charge and discharge cycle, inhibit the gas production of the lithium ion battery under high voltage and high temperature, and improve the electrochemical stability of the lithium ion battery.

[0045] In some embodiments of the present application, the D50 of the active material 11 can be 1-10 μm, and alternatively, the D50 of the active material 11 can be 2-8 μm, 3-7 μm, or 5-6 μm. Alternatively, the D50 of the active material 11 can be 1.5 μm, 2.5 μm, 3.5 μm, 4 μm, 4.5 μm, 5.5 μm, 7.5 μm, or 9 μm. The D50 of the ceramic material 13 can be 0.05-6 μm, and alternatively, the D50 of the ceramic material 13 can be 0.4-5 μm, 1-3 μm, or 2-2.5 μm. Alternatively, the D50 of the ceramic material 13 can be 0.08 μm, 0.1 μm, 0.2 μm, 0.3 μm, 0.5 μm, 0.8 μm, 1.5 μm, 3.5 μm, 4 μm, or 5.5 μm. The D50 is the particle size corresponding to the cumulative particle size distribution percentage of 50% of the sample.

[0046] In some embodiments of the present application, the length of the carbon nanotube 12 can be 1-40 μm, optionally, the length of the carbon nanotube 12 can also be 5-35 μm, 10-30 μm, 15-25 μm or 17-20 μm. Optionally, the length of the carbon nanotube can be 2 μm, 3 μm, 8 μm, 13 μm, 16 μm, 18 μm, 22 μm, 28 μm or 35 μm. The diameter of the carbon nanotube 12 can be 0.2-10 nm, optionally, the diameter of the carbon nanotube 12 can also be 1-9 nm, 2-8 nm, 3-7 nm or 5-6 nm. Optionally, the diameter of the carbon nanotube 12 can be 0.5 nm, 1.5 nm, 2.5 nm, 3.5 nm, 4 nm, 5.5 nm, 7.5 nm or 8.5 nm. Specifically, the carbon nanotube 12 can be a single-walled carbon nanotube or a multi-walled carbon nanotube.

[0047] In some embodiments of the present application, the thickness of the current collector 2 can be 8-12 μm, optionally, the thickness of the current collector 2 can also be 8.5-11.5 μm, 9-11 μm or 9.5-10.5 μm. Optionally, the thickness of the current collector 2 can also be 8.3 μm, 8.6 μm, 9.2 μm, 9.8 μm or 10 μm.

[0048] In some embodiments of the present application, the thickness of the active material layer 1 can be 20-200 μm. Optionally, the thickness of the active material layer 1 can also be 30-180 μm, 40-160 μm, 50-150 μm, 80-130 μm or 100-120 μm. Optionally, the thickness of the active material layer 1 can be 25 μm, 35 μm, 45 μm, 55 μm, 60 μm, 70 μm, 90 μm, 110 μm, 140 μm, 170 μm or 190 μm. Preferably, the thickness of the active material layer 1 is 40-160 μm. When the thickness of the active material layer 1 is within this range, the battery has good high-current rate cycling performance, high energy density and high single cell capacity. When the thickness of the active material layer 1 is too low, the energy density of the battery is low; when the thickness of the active material layer 1 is too high, the rate and cycle can be poor, so a suitable coating thickness of the active material layer 1 is needed.

[0049] In some embodiments of the present application, the active material layer 1 further comprises a conductive agent, and the mass ratio of the active material 11, the conductive agent, the carbon nanotube 12, the binder and the ceramic material 13 is (90-98):(0.2-2):(0.2-2):(1-5):(0.2-1); or (93-96):(0.5-1.5):(0.5-1):(2-4):(0.5-0.8); or (94-95):(0.6-1.3):(0.7-0.9):(3-3.5):(0.6-0.7). Alternatively, the mass ratio of the active material 11, the conductive agent, the carbon nanotube 12, the binder and the ceramic material 13 can be 94:0.3:1.8:3:0.9; 95.5:0.4:0.3:3.1:0.7; 96:0.5:1:2:0.5; or 97:0.6:0.4:1.1:0.9.

[0050] Specifically, the conductive agent can be graphite, such as natural graphite, artificial graphite super p, carbon black, Ketjen black, carbon nanotube fiber, graphene, etc., which is an excellent electronic conductor that does not produce chemical changes in the charge and discharge voltage window range of the positive and negative active materials.

[0051] Referring to Figure 4 The second embodiment of the present application provides a preparation method of the pole piece, comprising the following steps:

[0052] S1, adding the ceramic material 13 and the carbon nanotube 12, stirring and dispersing, so that the ceramic material 13 is crosslinked on the carbon nanotube 12;

[0053] S2, adding the active material 11 and the conductive agent, stirring and dispersing, the ceramic material 13 is crosslinked with the carbon nanotube 12 and dispersed on the surface of the active material 11, the active material 11, the carbon nanotube 12 and the ceramic material 13 together form a crosslinked network, to obtain a slurry;

[0054] S3, coating the slurry on the current collector 2, drying and rolling to obtain the pole piece.

[0055] In some embodiments of the present application, before step S1, a pre-step is included:

[0056] Providing a binder, mixing the binder with the ceramic material 13 first, stirring and dispersing the ceramic material 13 in the binder. The present application introduces the role of the carbon nanotube 12, mixes the ceramic material 13 with the binder slurry first, then mixes the binder slurry uniformly dispersed with the ceramic material 13 with the CNT, which plays a crosslinking role, and finally is attached to the surface of the active material 11.

[0057] In the pre-step, the mass ratio of the binder and the ceramic material is (2-4) : (0.5-0.8). The stirring condition is not particularly limited, and the uniform dispersion of the materials can be achieved. For example, the stirring is performed at a self-rotation speed of 800-1000 rpm and a revolution speed of 15-20 rpm at room temperature, and the stirring time is 10-50 min.

[0058] In step S1, the stirring condition is not particularly limited, and the uniform dispersion of the materials can be achieved. For example, the stirring is performed at a self-rotation speed of 500-1000 rpm and a revolution speed of 10-20 rpm at room temperature, and the stirring time is 10-40 min.

[0059] In step S2, the mass ratio of the active material and the conductive agent is (90-98) : (0.2-2). The stirring condition is not particularly limited, and the uniform dispersion of the materials can be achieved. For example, the stirring is performed at a self-rotation speed of 600-1500 rpm and a revolution speed of 10-25 rpm at room temperature, and the stirring time is 30-100 min.

[0060] It should be noted that the mass ratio of the active material, the conductive agent, the carbon nanotube, the binder and the ceramic material in the present embodiment is the same as that provided in the first embodiment, and will not be described herein.

[0061] It can be understood that in step S3, the slurry coating can be performed in various known manners, such as doctor blade coating, roll coating, transfer coating and extrusion coating. As for the formation of the active material layer 1, it can be single-sided continuous coating, double-sided continuous coating, single-sided intermittent coating or double-sided intermittent coating, and will not be described herein.

[0062] It can be understood that after the drying treatment of the lithium ion battery pole piece, a rolling treatment is further required to enhance the adhesion strength of the active material layer 1 to the substrate, so as to prevent peeling in the electrolyte soaking and subsequent use. At the same time, after the rolling, the porosity among the active material 11, the conductive agent and the binder in the active material layer 1 can be reduced, so that the cell volume can be compressed, the cell energy density can be improved, the resistance of the battery can be reduced, and the performance of the lithium ion battery can be improved.

[0063] Please refer to the accompanying Figure 5The application also provides a secondary battery 3, comprising a positive electrode sheet 31, a negative electrode sheet 32, a separator 33 and an electrolyte 34. The positive electrode sheet 31 comprises a positive electrode current collector and a positive electrode active material layer arranged on at least one side of the positive electrode current collector. The positive electrode active material layer comprises a positive electrode active material, carbon nanotubes 12 and ceramic material 13. The carbon nanotubes 12 are crosslinked with the positive electrode active material and surround the outer periphery of the positive electrode active material. The ceramic material 13 is crosslinked with the carbon nanotubes 12 and dispersed on the surface of the positive electrode active material. The positive electrode active material, carbon nanotubes 12 and ceramic material 13 together form a crosslinked network. As shown in FIG. 1, the positive electrode active material layer 1 is arranged on the positive electrode current collector 2. The positive electrode active material layer 1 comprises a positive electrode active material, carbon nanotubes 12 and ceramic material 13. The carbon nanotubes 12 are crosslinked with the positive electrode active material and surround the outer periphery of the positive electrode active material. The ceramic material 13 is crosslinked with the carbon nanotubes 12 and dispersed on the surface of the positive electrode active material. The positive electrode active material, carbon nanotubes 12 and ceramic material 13 together form a crosslinked network. Figure 2 As shown in FIG. 1, the positive electrode active material layer 1 is arranged on the positive electrode current collector 2. The positive electrode active material layer 1 comprises a positive electrode active material, carbon nanotubes 12 and ceramic material 13. The carbon nanotubes 12 are crosslinked with the positive electrode active material and surround the outer periphery of the positive electrode active material. The ceramic material 13 is crosslinked with the carbon nanotubes 12 and dispersed on the surface of the positive electrode active material. The positive electrode active material, carbon nanotubes 12 and ceramic material 13 together form a crosslinked network.

[0064] In some embodiments of the application, the positive electrode active material can be any high-voltage positive electrode ternary material, which includes at least one of nickel-cobalt-manganese ternary material or nickel-cobalt-aluminum ternary material. The content of the ternary material Ni can be 50%-98%. For example, the positive electrode active material can be Ni 80 Co 10 Mn 10 , Ni 70 Co 10 Mn 20 or Ni 90-98 Co 1-8 Mn 1-8 , etc. The positive electrode sheet of the application preferably uses a high-voltage ternary positive electrode, which has higher specific energy.

[0065] In some embodiments of the application, the negative electrode sheet 32 comprises a negative electrode current collector and a negative electrode active material layer arranged on at least one side of the negative electrode current collector. The negative electrode active material layer comprises a negative electrode active material, carbon nanotubes 12 and ceramic material 13. The carbon nanotubes 12 are crosslinked with the negative electrode active material and surround the outer periphery of the negative electrode active material. The ceramic material 13 is crosslinked with the carbon nanotubes 12 and dispersed on the surface of the negative electrode active material. The negative electrode active material, carbon nanotubes 12 and ceramic material 13 together form a crosslinked network, as shown in FIG. 2. Figure 3 As shown in FIG. 2, the negative electrode active material layer 1 is arranged on the negative electrode current collector 2. The negative electrode active material layer 1 comprises a negative electrode active material, carbon nanotubes 12 and ceramic material 13. The carbon nanotubes 12 are crosslinked with the negative electrode active material and surround the outer periphery of the negative electrode active material. The ceramic material 13 is crosslinked with the carbon nanotubes 12 and dispersed on the surface of the negative electrode active material. The negative electrode active material, carbon nanotubes 12 and ceramic material 13 together form a crosslinked network.

[0066] In some embodiments of the application, the negative electrode active material can be at least one of graphite negative electrode, silicon-carbon negative electrode and silicon-oxygen negative electrode material.

[0067] It can be understood that the active material layer 1 is a functional layer formed by coating the current collector 2 with a positive electrode material slurry or a negative electrode material slurry. The positive electrode material slurry or the negative electrode material slurry is prepared according to different formulations. The active material layer 1 can be formed by continuous coating on one side, continuous coating on both sides, intermittent coating on one side, or intermittent coating on both sides, which will not be described here.

[0068] Specifically, the type of positive electrode current collector is not particularly limited, and it can be any known material suitable for use as a positive electrode current collector. Examples of the positive electrode current collector can include, but are not limited to, metal materials such as aluminum, stainless steel, nickel plating, titanium, tantalum, etc.; and carbon materials such as carbon cloth, carbon paper, etc. In some embodiments, the positive electrode current collector is a metal material. In some embodiments, the positive electrode current collector is aluminum. The form of the positive electrode current collector is not particularly limited. In some embodiments, the positive electrode current collector is a metal foil. In some embodiments, the metal foil is a mesh.

[0069] Specifically, the negative electrode current collector includes, but is not limited to, metal foils, metal cylinders, metal rolls, metal plates, metal films, metal plate meshes, punched metals, foamed metals, etc. In some embodiments, the negative electrode current collector is a metal foil. In some embodiments, the negative electrode current collector is a copper foil.

[0070] The embodiments of the present application also provide a power consuming device, which includes the secondary battery 3 as a power supply for the power consuming device.

[0071] The power consuming device of the present application is, but is not limited to, a backup power supply, an electric motor, an electric vehicle, an electric motorcycle, a power-assisted bicycle, a bicycle, an electric tool, a household large storage battery, etc.

[0072] The following will be described in conjunction with specific embodiments.

[0073] Embodiment 1,

[0074] The embodiments provide a preparation method of the battery, which includes the following steps:

[0075] 1) The active material 11 (high-voltage ternary positive electrode Ni 90 Co2Mn8), the conductive agent (conductive carbon black), the CNT, the binder (PVDF), and the ceramic material 13 (Mg(OH)2) are prepared according to the mass ratio of 96:0.5:1:2:0.5, and the D50 of the ceramic material 13 is 0.5 μm;

[0076] 2) First, the binder slurry PVDF and the ceramic material 13 are added to a stirring tank in proportion, and are stirred and dispersed with NMP as a solvent, and are stirred for 30 min at room temperature;

[0077] 3) The CNT is added into the stirring tank according to the above ratio, and secondary stirring dispersion is carried out, and stirring is carried out at room temperature for 30 min;

[0078] 4) The active material and the conductive agent are added into the stirring tank according to the ratio, and third stirring dispersion is carried out, and stirring is carried out at room temperature for 100 min, the solid content is controlled to be 68-75%, and coating is carried out through a double-layer 150-mesh screen;

[0079] 5) The sieved slurry is single-sidedly coated and dried, and then the second side is coated and dried, the drying temperature is 90°C, and the positive electrode sheet 31 is obtained through rolling, and the active material layer 1 has a thickness of 80 μm;

[0080] 6) Preparation of the negative electrode sheet 32: the active material 11 (artificial graphite), the conductive agent (super conductive carbon black Super P) and the binder (sodium carboxymethyl cellulose CMC) are weighed and stirred according to the mass ratio of 96:1:3, water is used as the solvent, the solid content is controlled to be 40-60%, stirring dispersion is carried out, coating is carried out after sieving through a double-layer 150-mesh screen, drying is carried out at a drying temperature of 75°C, and then the negative electrode sheet 32 is obtained through rolling.

[0081] 7) Battery assembly: after the positive electrode sheet 31 and the negative electrode sheet 32 are cut, the positive electrode sheet 31 and the negative electrode sheet 32 are separated by the separator 33, and then the positive electrode sheet 31 and the negative electrode sheet 32 are wound together and are placed in an aluminum plastic film, water in the electrode sheets is removed after drying, and then liquid injection is carried out in a drying room, and then the battery is obtained through heat sealing.

[0082] Example 2,

[0083] The remaining steps are the same as those in Example 1, except that the ceramic material 13 is replaced by Al(OH)3 of the same mass.

[0084] Example 3,

[0085] The remaining steps are the same as those in Example 1, except that the ceramic material 13 is replaced by B3HO3 of the same mass.

[0086] Example 4,

[0087] The remaining steps are the same as those in Example 1, except that the ceramic material 13 is replaced by TiO2 of the same mass.

[0088] Example 5,

[0089] The remaining steps are the same as those in Example 1, except that the ceramic material 13 is replaced by Ca(OH)2 of the same mass.

[0090] Example 6,

[0091] The remaining steps are the same as those in Example 1, except that the ceramic material 13 is replaced by V2O5 of the same mass.

[0092] Example 7,

[0093] The remaining steps are the same as in Example 1, except that the ceramic material 13 is replaced by an equal mass mixture of Al(OH)3and Mg(OH)2, with a mass ratio of 1:1 in the mixture.

[0094] Example 8,

[0095] The remaining steps are the same as in Example 1, except that the ceramic material 13 is replaced by an equal mass mixture of Mg(OH)2, H3BO3and TiO2, with a mass ratio of 1:1:1 in the mixture.

[0096] Example 9,

[0097] The remaining steps are the same as in Example 1, except that in the preparation of the negative electrode sheet 32, the negative electrode slurry formulation is: active material 11 (graphite), conductive agent (carbon black), carbon nanotube 12 CNT, binder PAA, ceramic material 13 (equal mass mixture of Mg(OH)2, H3BO3and TiO2), and the above materials are prepared into the negative electrode sheet 32 by the same process as the positive electrode sheet 31 with a mass ratio of 96:0.4:0.3:3:0.3.

[0098] Example 10,

[0099] The remaining steps are the same as in Example 7, except that the proportion of the mixed ceramic material 13 Al(OH)3and Mg(OH)2is reduced from 0.5% to 0.2%, and the mass ratio of Al(OH)3and Mg(OH)2remains 1:1.

[0100] Example 11,

[0101] The remaining steps are the same as in Example 7, except that the proportion of the mixed ceramic material 13 Al(OH)3and Mg(OH)2is increased from 0.5% to 1%, and the mass ratio of Al(OH)3and Mg(OH)2remains 1:1.

[0102] Example 12,

[0103] The remaining steps are the same as in Example 1, except that the D50 of the ceramic material 13 is 0.08 μm.

[0104] Example 13,

[0105] The remaining steps are the same as in Example 1, except that the D50 of the ceramic material 13 is 0.8 μm.

[0106] Example 14,

[0107] The remaining steps are the same as in Example 1, except that the D50 of the ceramic material 13 is 2 μm.

[0108] Example 15,

[0109] The remaining steps are the same as Example 1, except that the thickness of the active material layer 1 is 20 μm.

[0110] Example 16,

[0111] The remaining steps are the same as Example 1, except that the thickness of the active material layer 1 is 120 μm.

[0112] Example 17,

[0113] The remaining steps are the same as Example 1, except that the thickness of the active material layer 1 is 220 μm.

[0114] Comparative Example 1,

[0115] The remaining steps are the same as Example 1, except that the ceramic material 13 is not added, and the positive electrode slurry formulation is: active material (high-voltage ternary positive electrode Ni 90 Co2Mn8), conductive agent (conductive carbon black), CNT slurry, binder (PVDF), the above materials are processed in the same way as Example 1 to obtain the positive electrode sheet 31 in a mass ratio of 96.5:0.5:1:2.

[0116] The batteries in Examples 1-17 and Comparative Example 1 were tested for performance, and the test method is as follows:

[0117] After the formation and capacity steps, the discharge capacity and initial efficiency of the battery were obtained, and the initial volume V0 of the battery was measured by the drainage method. Then the battery was fully charged and transferred to an oven at 80°C for storage for 120 days, and then the battery volume V1 was measured again. The battery volume expansion rate was calculated according to the following formula.

[0118] Volume expansion rate = (V1-V0) / V0

[0119] The test results are shown in the following table:

[0120] Table 1

[0121]

[0122] As can be seen from Table 1, the volume expansion rate of Examples 1-17 is significantly lower than that of Comparative Example 1. The addition of ceramic material 13 in the active material layer 1 of Examples 1-17 indicates that the volume expansion caused by gas production in the battery is greatly inhibited by the addition of ceramic material 13.

[0123] Comparing Example 10, 11 and Example 7, it can be seen that the discharge capacity and initial efficiency of Example 11 are lower. The addition of more ceramic material 13 in Example 11 indicates that the increase in the amount of doped ceramic material 13 does not significantly increase the gas production inhibition effect, but rather inhibits the performance of the material capacity and initial efficiency.

[0124] Comparing example 8 and 9, it can be concluded that the negative electrode sheet doped with ceramic material 13 has a certain effect on inhibiting gas production, but the effect is not as obvious as that of the positive electrode sheet.

[0125] Comparing examples 1-8, it can be concluded that doping different inorganic ceramic compound particles has different effects on inhibiting gas production. Doping B has a relatively obvious effect on inhibiting gas production, and doping Mg, B and Ti has a very obvious effect on inhibiting gas production, and ensures the play of battery gram capacity and initial efficiency.

[0126] Comparing examples 15-17, it can be seen that the volume expansion rate of example 17 is relatively high, and the thickness of the active material layer 1 of example 17 exceeds the range of the present application, which indicates that when the thickness of the active material layer 1 is within the range of the present application, there is a better effect on inhibiting gas production.

[0127] The present application provides an electrode sheet and a preparation method thereof, a secondary battery and an electric device, which utilizes the cross-linked network formed by the carbon nanotube 12 and the stable electrochemical capacity of the ceramic material 13 under high-voltage charging and discharging conditions to improve the gas production and cycle instability of the lithium ion secondary battery under high-temperature and high-voltage conditions.

[0128] The above describes in detail the electrode sheet and the preparation method thereof, the secondary battery and the electric device provided by the present application. The principles and implementation modes of the present application are described by applying specific examples in this paper. The above example is only used to help understand the method of the present application and its core idea; at the same time, for those skilled in the art, according to the idea of the present application, the specific implementation mode and application range will be changed; in summary, the content of the present application should not be understood as a limitation.

Claims

1. An electrode sheet, characterized in that, The device includes a current collector, an adhesive, and an active material layer disposed on at least one side of the current collector. The active material layer comprises an active material, carbon nanotubes, and a ceramic material. The carbon nanotubes surround the outer periphery of the active material, and the ceramic material is dispersed on the surface of the carbon nanotubes. The active material, the carbon nanotubes, and the ceramic material together form a cross-linked network. The ceramic material and the active material are in particulate form. The particle size of the ceramic material is 0.05 to 0.6 times the particle size of the active material, and the D50 of the active material is 1 to 10 μm. The length of the carbon nanotubes is 1 to 40 μm, and the diameter of the carbon nanotubes is 0.2 to 10 nm. The adhesive disperses the ceramic material, and the adhesive bonds the carbon nanotubes to crosslink the ceramic material onto the carbon nanotubes; The electrode is used in a secondary battery where the positive electrode active material is a ternary material, and the Ni content in the ternary material is 50% to 98%.

2. The electrode sheet according to claim 1, characterized in that, The ceramic material includes at least one of Al(OH)3, Al2O3, Mg(OH)2, H3BO3, Ca(OH)2, or TiO2.

3. The electrode sheet according to claim 2, characterized in that, The active material layer further includes a conductive agent, and the mass ratio of the active material, the conductive agent, the carbon nanotube, the binder and the ceramic material is (90-98):(0.2-2):(0.2-2):(1-5):(0.2-1).

4. A method for preparing an electrode sheet as described in any one of claims 1 to 3, characterized in that, include: Add ceramic material and carbon nanotubes, stir and disperse, so that the ceramic material crosslinks on the carbon nanotubes; Add active material and conductive agent, stir and disperse. The ceramic material crosslinks with the carbon nanotubes and is dispersed on the surface of the active material. The active material, the carbon nanotubes and the ceramic material together form a crosslinked network to obtain a slurry. The slurry is coated onto the current collector, dried, and rolled to obtain the electrode sheet.

5. The method for preparing the electrode according to claim 4, characterized in that, include: Before performing the step of adding ceramic material and carbon nanotubes, stirring and dispersing, so that the ceramic material crosslinks onto the carbon nanotubes, the following steps are included: An adhesive is provided, which is first mixed with the ceramic material, stirred, and the ceramic material is dispersed in the adhesive.

6. A secondary battery, characterized in that, It includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode is an electrode as described in any one of claims 1 to 3, or an electrode prepared by the preparation method described in claim 4 or 5.

7. The secondary battery according to claim 6, characterized in that, The negative electrode sheet includes a negative current collector and a negative active material layer disposed on at least one side of the negative current collector. The negative active material layer includes a negative active material, carbon nanotubes, and ceramic materials. The carbon nanotubes are cross-linked with the negative active material and surround the outer periphery of the negative active material. The ceramic materials are cross-linked with the carbon nanotubes and dispersed on the surface of the negative active material. The negative active material, the carbon nanotubes, and the ceramic materials together form a cross-linked network.

8. The secondary battery according to claim 7, characterized in that, The negative electrode active material includes one or more of graphite materials, silicon-carbon materials, or silicon-oxygen materials.

9. An electrical appliance, characterized in that, The device includes a secondary battery as described in any one of claims 6 to 8, wherein the secondary battery serves as the power supply for the electrical equipment.

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