Conductive agent, electrode, lithium ion battery, and electric device

Abstract

A conductive agent, comprising mesopores and micropores, the pore diameter of the mesopores being 2-50 nm, and the pore diameter of the micropores being less than 2 nm. The conductive agent is used for a lithium ion battery; the conductive agent comprises the micropores and the mesopores; the micropores and the mesopores provide a storage area for an electrolyte; when the swelling force of a battery cell is increased, the electrolyte is infiltrated into a pore channel; and when the swelling force is reduced, the electrolyte flows out of the pore channel.

Description

Conductive agents, electrodes, lithium-ion batteries and electrical equipment

[0001] This application claims priority to Chinese patent application No. 202410383180.X filed on March 29, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0002] The present disclosure relates to the field of battery technology, and in particular to a conductive agent, an electrode, a lithium-ion battery, and an electrical device. Background Art

[0003] Lithium-ion batteries are secondary batteries composed of electrode materials. They operate primarily through the reciprocating movement of lithium ions between the positive and negative electrodes. During the charge and discharge process, lithium ions are inserted and removed between the two electrodes. This insertion and removal of lithium ions causes the volume of the material to cyclically contract and expand during charge and discharge, resulting in a cyclic increase and decrease in the expansion force of the battery cell. This expansion force causes the electrolyte between the electrodes to be periodically squeezed out and drawn in.

[0004] Summary of the Invention

[0005] In response to the problems existing in the related art, some embodiments of the present disclosure provide a conductive agent, an electrode, a lithium-ion battery, and an electrical device.

[0006] In order to solve the above problems, some embodiments of the present disclosure provide the following solutions.

[0007] In a first aspect, some embodiments of the present disclosure provide a conductive agent, comprising mesopores and micropores, wherein the pore diameter of the mesopores is 2 nm to 50 nm, and the pore diameter of the micropores is less than 2 nm.

[0008] In some embodiments, the ratio of the total volume of mesopores to the total volume of micropores is 30% to 60%: 40% to 70%.

[0009] In some embodiments, the conductive agent includes at least one of carbon black, conductive graphite, activated carbon, and a metal conductive agent.

[0010] In some embodiments, the specific surface area of ​​the conductive agent is 200m 2 / g~2000m 2 / g.

[0011] In some embodiments, the specific surface area of ​​the conductive agent is 400 m 2 / g~1000m 2 / g.

[0012] In a second aspect, some embodiments of the present disclosure provide an electrode, comprising an active material layer, wherein the active material layer comprises a first conductive agent, and the first conductive agent is the conductive agent described in the first aspect.

[0013] In some embodiments, the electrode further includes a current collector, the active material layer includes a first active material layer and a second active material layer, the first active material layer is disposed on the current collector, the second active material layer is disposed on the first active material layer, and the first active material layer includes a first conductive agent.

[0014] In some embodiments, the first active material layer is a rectangular parallelepiped, and the current collector is a rectangular parallelepiped. The first active material layer and the current collector satisfy at least one of the following conditions: the length of the first active material layer accounts for 60% to 90% of the length of the current collector, or the width of the first active material layer accounts for 60% to 100% of the width of the current collector.

[0015] In some embodiments, the current collector satisfies at least one of the following conditions: the first active material layer is not provided at both ends of the current collector in the length direction, or the first active material layer is not provided at both ends of the current collector in the width direction.

[0016] In some embodiments, the second active material layer is disposed in an area of ​​the current collector where the first active material layer is not disposed.

[0017] In some embodiments, in the thickness direction of the electrode, the thickness H1 of the first active material layer accounts for 5% to 80% of the thickness H of the active material layer.

[0018] In some embodiments, the first active material layer further includes a first active material and a first binder; and the second active material layer includes a second active material, a second conductive agent, and a second binder.

[0019] In some embodiments, the first active material and the second active material are the same or different; the first binder and the second binder are the same or different; and the second conductive agent and the first conductive agent are the same or different.

[0020] In some embodiments, the electrode is a positive electrode or a negative electrode.

[0021] In a third aspect, some embodiments of the present disclosure provide a lithium-ion battery comprising the electrode described in the second aspect.

[0022] In a fourth aspect, some embodiments of the present disclosure provide an electrical device comprising the lithium-ion battery described in the third aspect.

[0023] The conductive agent provided in some embodiments of the present disclosure has the following technical effects: the conductive agent is used for lithium-ion batteries, and the conductive agent includes micropores and mesopores. The micropores and mesopores provide a storage area for the electrolyte. When the expansion force of the battery cell increases, the electrolyte infiltrates into the pores, and when the expansion force decreases, it flows out of the pores, thereby increasing the liquid retention capacity of the electrode and reducing the migration path of the electrolyte; the mesopores provide channels for the electrolyte to diffuse rapidly into the micropores. The mesopores have a large pore size, which promotes the migration of the electrolyte into the micropores when the expansion force of the battery cell increases, thereby preventing the electrolyte inside the active material layer from being squeezed out of the electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or related technologies, the following briefly introduces the drawings required for use in the embodiments or related technical descriptions. Obviously, the drawings described below are only some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0025] The structures, proportions, sizes, etc. depicted in the drawings of this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with this technology. They are not intended to limit the conditions under which the present disclosure can be implemented, and therefore have no substantive technical significance. Any structural modifications, changes in proportional relationships, or adjustments in size, without affecting the effects and objectives that can be achieved by the present disclosure, should still fall within the scope of the technical contents disclosed in the present disclosure.

[0026] The above and / or additional aspects and advantages of the present disclosure will become apparent and readily understood from the description of some embodiments in conjunction with the following drawings, in which:

[0027] FIG1 is a schematic structural diagram of electrodes according to some embodiments of the present disclosure;

[0028] FIG2 is another schematic structural diagram of electrodes according to some embodiments of the present disclosure.

[0029] Figure markings: A: first active material layer; B: second active material layer; C: current collector; A1: length of the first active material layer; A2: width of the first active material layer; C1: length of the current collector; C2: width of the current collector; H: thickness of the active material layer; H1: thickness of the first active material layer; X: length direction of the electrode; Y: width direction of the electrode; Z: thickness direction of the electrode. DETAILED DESCRIPTION

[0030] In order to make the technical problems, technical solutions and beneficial effects solved by the present disclosure more clearly understood, some embodiments of the present disclosure are further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the embodiments described herein are only used to explain the present disclosure and are not intended to limit the present disclosure.

[0031] The release and insertion of lithium ions from the electrode material causes the material's volume to periodically shrink and expand during the charge and discharge process, resulting in a periodic increase or decrease in the cell's expansion force. This expansion force periodically squeezes out and draws in the electrolyte between the electrodes. As the cell expands, the electrolyte is squeezed out, resulting in higher impedance in the electrode dressing area near the bottom layer of the foil. Furthermore, due to electrolyte consumption, the electrolyte can no longer penetrate properly, resulting in a lean area. This can lead to a series of problems, including lithium deposition, capacity decay, and cell heat generation.

[0032] In a first aspect, some embodiments of the present disclosure provide a conductive agent comprising mesopores and micropores, wherein the pore diameter of the mesopores is 2 nm to 50 nm, and the pore diameter of the micropores is less than 2 nm.

[0033] In some embodiments, the conductive agent includes mesopores and micropores. The combination of mesopores and micropores can not only store more electrolyte, but also because the pore size of the mesopores is larger, it can promote the migration of electrolyte into the pores when the battery cell expands, reducing the amount of electrolyte migrating out of the electrode, thereby increasing the liquid absorption capacity of the electrode and improving the liquid retention capacity of the electrode.

[0034] In some embodiments, mesopores refer to pores with a pore diameter of 2 nm to 50 nm, and micropores refer to pores with a pore diameter less than 2 nm. The pore diameter measurement method can refer to GB / T 10722-2003.

[0035] The present disclosure does not limit the method of forming mesopores and micropores. Mesopores and micropores can be formed in situ during the synthesis of the conductive agent, or through secondary pore formation using CO2 (carbon dioxide), KOH (potassium hydroxide) and other methods that can form mesopores and micropores.

[0036] The conductive agent provided in some embodiments of the present disclosure has the following effects: the conductive agent is used in lithium-ion batteries, and the conductive agent includes micropores and mesopores. The micropores and mesopores provide a storage area for the electrolyte. When the expansion force of the battery cell increases, the electrolyte infiltrates into the pores. When the expansion force decreases, the electrolyte flows out of the pores, thereby increasing the liquid retention capacity of the electrode and reducing the migration path of the electrolyte; the mesopores provide channels for the electrolyte to diffuse rapidly into the micropores. The mesopores have a large pore size, which promotes the migration of the electrolyte into the micropores when the expansion force of the battery cell increases, thereby preventing the electrolyte inside the active material layer from being squeezed out of the electrode.

[0037] In some embodiments, the ratio of the total volume of mesopores to the total volume of micropores is 30% to 60%: 40% to 70%.

[0038] In some embodiments, the total mesopore volume and the total micropore volume can be obtained by nitrogen adsorption tester testing, and the mesopore volume and micropore volume in the conductive agent are defined as the total pore volume, and then the percentage of mesopores and micropores in the total pore volume is calculated respectively. For example, the test method can refer to GB / T 10722-2003.

[0039] In some embodiments, the ratio of the total volume of mesopores to the total volume of micropores is 30% to 60%: 40% to 70%.

[0040] For example, the ratio of mesopore volume to micropore volume can include, but is not limited to, 30%:70%, 40%:60%, 50%:50%, and 60%:40%. A larger ratio of mesopore volume to micropore volume results in a greater proportion of mesopore volume, faster electrolyte diffusion, and greater electrolyte adsorption capacity of the electrode. A smaller ratio of mesopore volume to micropore volume results in a greater proportion of micropore volume, higher battery energy density, and better cell performance.

[0041] When the mesopore volume and micropore volume are in the range of 30% to 60% and 40% to 70%, the more the electrolyte adsorption in the electrode is, the faster the diffusion rate is, and the better the electrochemical performance of the battery cell is.

[0042] In some embodiments, the conductive agent includes at least one of carbon black, conductive graphite, a metal conductive agent, and activated carbon.

[0043] In some embodiments, carbon black, conductive graphite, metal conductive agent, and activated carbon can all be used to form pores, and the conductive agent includes at least one of carbon black, conductive graphite, metal conductive agent, and activated carbon having mesopores and micropores.

[0044] In some embodiments, the specific surface area of ​​the conductive agent is 200 m 2 / g~2000m 2 / g.

[0045] In some embodiments, the specific surface area of ​​the conductive agent can be measured by a BET specific surface area test method. For example, the test method can refer to GB / T 10722-2003.

[0046] In some embodiments, the specific surface area of ​​the conductive agent may include but is not limited to 200 m 2 / g、500m 2 / g、800m 2 / g, 1000m 2 / g、1200m 2 / g、1500m 2 / g、1700m 2 / g、2000m 2 / g. The smaller the specific surface area of ​​the conductive agent, the fewer the number of micropores and mesopores, the higher the energy density of the battery cell and the better the performance of the battery; the larger the specific surface area of ​​the conductive agent, the more mesopores and micropores there are, providing an appropriate amount of pore volume for the electrolyte and increasing the liquid absorption of the electrode. The specific surface area of ​​the conductive agent is 200m 2 / g~2000m 2 / g range, while improving the electrode liquid retention capacity, the energy density of the battery cell is guaranteed.

[0047] In some embodiments, the specific surface area of ​​the conductive agent is 400 m 2 / g~1000m 2 / g.

[0048] In some embodiments, the specific surface area of ​​the conductive agent may be, but is not limited to, 400 m 2 / g、500m 2 / g、600m 2 / g、700m 2 / g、800m 2 / g、900m 2 / g、1000m 2 / g. The specific surface area of ​​the conductive agent is within this range, which can better improve the liquid retention of the electrode and the performance of the battery cell.

[0049] In a second aspect, some embodiments of the present disclosure provide an electrode, the electrode comprising an active material layer, the active material layer comprising a first conductive agent, and the first conductive agent is the conductive agent described in the embodiment of the first aspect of the present disclosure.

[0050] In some embodiments, the first conductive agent has mesopores and micropores, the pore diameter of the mesopores is 2nm to 50nm, and the pore diameter of the micropores is less than 2nm; through the mutual cooperation of the mesopores and micropores, a storage area for the electrolyte is provided, and when the expansion force of the battery cell increases, the electrolyte infiltrates into the pores, and when the expansion force decreases, it flows out of the pores, thereby reducing the migration path of the electrolyte. The active material layer includes the first conductive agent, which can increase the electrolyte retention capacity of the active material layer, thereby improving the electrochemical performance of the battery.

[0051] In some embodiments, the electrode further includes a current collector, the active material layer includes a first active material layer and a second active material layer, the first active material layer is disposed on the current collector, the second active material layer is disposed on the first active material layer, and the first active material layer includes a first conductive agent.

[0052] In some embodiments, as shown in FIG. 1 and FIG. 2 , the first active material layer A is disposed on the current collector C, the second active material layer B is disposed on the first active material layer A, and the first active material layer A includes a conductive agent having mesopores and micropores.

[0053] It is understandable that as the battery cycles, the side of the electrode's active material layer close to the current collector (i.e., the first active material layer) is most likely to experience liquid starvation, which can cause problems such as lithium deposition in the electrode, heat generation in the battery cell, and battery capacity attenuation. The first active material layer A includes a conductive agent with mesopores and micropores in order to improve the position most prone to liquid starvation. The second active material layer B uses a common conductive agent, which can improve the performance of the battery cell while avoiding the problem of a significant decrease in battery energy density due to increased electrode porosity.

[0054] In some embodiments, the first active material layer A is disposed on one side or both sides of the current collector C in the thickness direction.

[0055] When the first active material layer A is disposed on one side of the current collector C in the thickness direction, one side of the current collector C is the first active material layer A and the second active material layer B, and the other side of the current collector C is only the second active material layer B.

[0056] When the first active material layer A is disposed on both sides of the current collector C, the second active material layer B is disposed on the first active material layer A.

[0057] In some embodiments, the first active material layer A is a rectangular parallelepiped, the current collector C is a rectangular parallelepiped, and the first active material layer A and the current collector C satisfy at least one of the following:

[0058] The length A1 of the first active material layer A accounts for 60% to 90% of the length C1 of the current collector C; or, the width A2 of the first active material layer A accounts for 60% to 100% of the width C2 of the current collector C.

[0059] In some embodiments, the first active material layer A satisfies at least one of the following:

[0060] The length A1 of the first active material layer A accounts for 60% to 90% of the length C1 of the current collector C; or, the width A2 of the first active material layer A accounts for 60% to 100% of the width C2 of the current collector C.

[0061] For example, the ratio of the length A1 of the first active material layer A to the length C1 of the current collector C may include, but is not limited to, 60%, 70%, 80%, or 90%.

[0062] For example, the ratio of the width A2 of the first active material layer A to the width C2 of the current collector C may include, but is not limited to, 60%, 70%, 80%, 90%, or 100%.

[0063] It can be understood that limiting the length A1 and width A2 of the first active material layer A can further improve the liquid absorption and liquid retention capabilities of the battery cell, improve the battery cell performance, and ensure the energy density of the battery cell.

[0064] In some embodiments, the current collector satisfies at least one of the following conditions: no first active material layer is provided at both ends of the current collector in the length direction; or no first active material layer is provided at both ends of the current collector in the width direction.

[0065] For ease of understanding, please refer to Figure 1 and Figure 2, and define the length direction of the electrode as the X direction, the width direction of the electrode as the Y direction, and the thickness direction of the electrode as the Z direction. The X direction, Y direction, and Z direction are perpendicular to each other.

[0066] In some embodiments, the first active material layer A is not provided at both ends of the current collector C in the length direction, i.e., the X direction, which means that in the length direction, i.e., the X direction, the first active material layer A is provided in the middle position of the current collector, and the middle position of the current collector C is more prone to liquid starvation than the two side areas of the current collector C. In this way, the first active material layer A is provided in the area most prone to liquid starvation, and the first active material layer A includes a first conductive agent, which further improves the liquid absorption and retention capacity of the first active material layer A, thereby further improving the battery performance.

[0067] In some embodiments, the first active material layer A is not provided at both ends of the current collector C in the width direction, i.e., the Y direction, which means that the first active material layer A is provided in the middle position of the current collector in the width direction, i.e., the Y direction, and the middle position of the current collector C is more prone to liquid poverty than the two side areas of the current collector C. In this way, the first active material layer A is provided in the area most prone to liquid poverty, and the first active material layer A includes a first conductive agent, which further improves the liquid absorption and retention capacity of the first active material layer A, thereby further improving the battery performance.

[0068] In some embodiments, a second active material layer is disposed in an area of ​​the current collector where the first active material layer is not disposed.

[0069] In some embodiments, a second active material layer B is provided in regions on both sides of the current collector C in at least one of the length or width directions where the first active material layer A is not provided. The thickness of the second active material layer B in this region is equal to the sum of the thicknesses of the first active material layer A and the second active material layer B on the first active material layer A. Providing the first active material layer A and the second active material layer B can further improve the energy density of the battery.

[0070] In some embodiments, in the thickness direction of the electrode, the thickness H1 of the first active material layer accounts for 5% to 80% of the thickness H of the active material layer.

[0071] In some embodiments, please refer to Figure 1. In the thickness direction of the electrode, i.e., the Z direction, the thickness H1 of the first active material layer A accounts for 5% to 80% of the thickness H of the active material layer, which means that on one side of the electrode, in the thickness direction of the electrode, i.e., the Z direction, the thickness H1 of the first active material layer A accounts for 5% to 80% of the total thickness H of the active material layer.

[0072] For example, the thickness H1 of the first active material layer A may account for, but is not limited to, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, or 80% of the total thickness H of the active material layer.

[0073] It can be understood that when the thickness H1 of the first active material layer A is within this range, the electrode energy density can be ensured while the electrode liquid retention capacity is increased, thereby improving the cycle performance of the battery.

[0074] In some embodiments, the first active material layer A further includes a first active material and a first binder; and the second active material layer B includes a second active material, a second conductive agent, and a second binder.

[0075] In some embodiments, the first active material and the second active material are the same or different; the first binder and the second binder are the same or different; and the second conductive agent and the first conductive agent are the same or different.

[0076] In some embodiments, the electrode comprises a positive electrode or a negative electrode.

[0077] In some embodiments of the present disclosure, when the electrode is a positive electrode, the first active material and the second active material independently include: phosphate systems such as lithium iron phosphate, lithium manganese iron phosphate, layered materials such as lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium-rich manganese-based materials, and spinel materials such as lithium manganese oxide; the second conductive agent includes: carbon black, carbon nanotubes, graphene, conductive graphite, etc.; the first binder and the second binder independently include: polyvinylidene fluoride, acrylic acid, polyurethane, epoxy resin, etc.

[0078] When the electrode is a negative electrode, the first active material and the second active material independently include: graphite, silicon carbon, silicon oxide, etc.; the second conductive agent includes: carbon black, carbon nanotubes, graphene, conductive graphite, etc.; the first binder and the second binder independently include: polyvinylidene fluoride, sodium carboxymethyl cellulose, styrene-butadiene latex, polyacrylic acid, etc.

[0079] In some embodiments, the electrode can be either a positive electrode or a negative electrode. When the electrode is a positive electrode, the active material, conductive agent, and binder are commonly used for positive electrodes; when the electrode is a negative electrode, the active material, conductive agent, and binder are commonly used for negative electrodes. The positive electrode active material, positive electrode conductive agent, positive electrode binder, negative electrode active material, negative electrode conductive agent, and negative electrode binder are all related technologies and will not be described in detail here.

[0080] In a third aspect, some embodiments of the present disclosure provide a lithium-ion battery comprising the electrode described in the embodiment of the second aspect above.

[0081] In some embodiments, a lithium-ion battery comprising the aforementioned electrodes refers to a lithium-ion battery comprising at least one of the aforementioned positive or negative electrodes. The inclusion of the electrodes provided by some embodiments of the present disclosure improves the electrochemical performance of the battery.

[0082] The lithium-ion battery further includes a separator and an electrolyte, and the separator and the electrolyte include the separator and the electrolyte used in the related art.

[0083] In a fourth aspect, some embodiments of the present disclosure provide an electrical device comprising the lithium-ion battery described in the embodiment of the third aspect.

[0084] Electrically powered devices include, but are not limited to, mobile phones, laptops, tablets, cameras, televisions, radios, wearable devices (such as smart watches, smart bracelets, stereo headphones, Bluetooth headsets), backup power supplies, new energy vehicles, power tools, and large household batteries. Because these electrical devices utilize the aforementioned lithium-ion batteries, the cycling performance of these electrical devices is improved.

[0085] Some embodiments of the present disclosure are described in further detail below.

[0086] Example 1

[0087] This embodiment is used to illustrate the conductive agent, electrode, lithium-ion battery and electrical equipment in some embodiments of the present disclosure, and includes the following steps:

[0088] Preparation of positive electrode:

[0089] ① Add 95% by mass of positive electrode active material (such as lithium iron phosphate), 2% of conductive agent (such as carbon black with mesopores and micropores), and 3% of binder (such as polyvinylidene fluoride) to a solvent (such as N-methylpyrrolidone) and stir and mix them evenly to obtain a positive electrode coating slurry; for example, the mesopore volume: micropore volume = 60%: 40%, and the specific surface area of ​​carbon black is 1000m 2 / g.

[0090] ② The above-mentioned positive electrode coating slurry is coated on the entire current collector (such as aluminum foil), and the positive electrode sheet is obtained after rolling, die cutting and baking. The double-sided density of the coating is 440g / m 2 The thickness H of the active material layer on one side is 80 μm, the length of the positive electrode sheet is 546 mm, and the width of the positive electrode sheet is 94 mm.

[0091] Preparation of negative electrode:

[0092] ① Add 94.5% by mass of a negative electrode active material (such as graphite), 1% of a conductive agent (such as carbon black (model: Cabot conductive carbon black LITX300)), and 4.5% of a binder (such as 1.5% of sodium carboxymethyl cellulose and 3% of styrene-butadiene latex) to a solvent (such as deionized water) and stir and mix them evenly to obtain a negative electrode coating slurry;

[0093] ② Apply the negative electrode coating slurry on the entire current collector (such as copper foil) with a double-sided density of 200g / m 2 After rolling, die-cutting and baking, the negative electrode sheet is obtained. The single-side thickness H of the active material layer is 64um, the length of the negative electrode sheet is 550mm, and the width of the negative electrode sheet is 98mm.

[0094] Preparation of lithium-ion batteries:

[0095] The positive electrode prepared in (1) and the negative electrode prepared in (2) are assembled with a separator, and then welded, shelled, liquid-filled, formed, and capacity-divided to obtain a lithium-ion battery.

[0096] Example 2

[0097] The difference between Example 2 and Example 1 lies in the difference in the positive and negative electrode conductive agents, and the rest is the same as Example 1.

[0098] Preparation of the positive electrode: The conductive agent carbon black is carbon black (the same as the carbon black used for the negative electrode in Example 1).

[0099] Preparation of the negative electrode: The conductive agent carbon black is carbon black with mesopores and micropores (the same as the carbon black used for the positive electrode in Example 1).

[0100] Example 3

[0101] The difference between Example 3 and Example 1 lies in the difference in the negative electrode conductive agent, and the rest is the same as Example 1.

[0102] (2) Preparation of negative electrode: The conductive agent carbon black is carbon black with mesopores and micropores (the same as the carbon black used for the positive electrode in Example 1).

[0103] Example 4

[0104] Preparation of positive electrode:

[0105] ① Positive electrode first active material layer: 95% by mass of a positive electrode active material (such as lithium iron phosphate), 2% of a conductive agent (such as carbon black with mesopores and micropores (the same as the carbon black used for the positive electrode in Example 1)), and 3% of a binder (such as polyvinylidene fluoride) are added to a solvent (such as N-methylpyrrolidone) and stirred and mixed to obtain a positive electrode first active material layer slurry; the mesopore volume: micropore volume = 60%: 40%, and the specific surface area of ​​the carbon black is 1000m 2 / g.

[0106] ② Positive electrode second active material layer: 95% by mass of a positive electrode active material (such as lithium iron phosphate), 2% of a conductive agent (such as carbon black (the same as the carbon black used for the negative electrode in Example 1)), and 3% of a binder (such as polyvinylidene fluoride) are added to a solvent (such as N-methylpyrrolidone) and stirred and mixed to obtain a positive electrode second active material layer slurry;

[0107] ③ The first active material layer of the positive electrode is coated on the middle area of ​​the current collector (such as aluminum foil), and the second active material layer of the positive electrode is coated on the first active material layer of the positive electrode and the area of ​​the current collector not coated with the first active material layer. After rolling, die cutting and baking, the positive electrode sheet is obtained. The double-sided surface density of the coating is 440g / m 2 The length A1 of the first active material layer of the positive electrode is 328mm, the width A2 is 94mm, the thickness H1 of the first active material layer is 40um, the single-side thickness H of the active material layer is 80um, the length of the positive electrode sheet is 546mm, and the width of the positive electrode sheet is 94mm.

[0108] Preparation of negative electrode:

[0109] The preparation of the negative electrode is the same as that in Example 1.

[0110] Preparation of lithium-ion batteries:

[0111] The positive electrode prepared in (1) and the negative electrode prepared in (2) are assembled with a separator, and then welded, shelled, liquid-filled, formed, and capacity-divided to obtain a lithium-ion battery.

[0112] Example 5

[0113] Preparation of positive electrode:

[0114] The preparation of the positive electrode is the same as that in Example 2.

[0115] Preparation of negative electrode:

[0116] ① Negative electrode first active material layer: 94.5% of a negative electrode active material (such as graphite), 1% of a conductive agent (such as carbon black with mesopores and micropores (the same as the carbon black used for the positive electrode in Example 1)), and 4.5% of a binder (such as 1.5% of sodium carboxymethyl cellulose and 3% of styrene-butadiene latex) are added to a solvent (such as deionized water) and stirred and mixed to obtain a negative electrode first active material layer slurry; the mesopore volume: micropore volume = 60%: 40%, and the specific surface area of ​​the carbon black is 1000m 2 / g.

[0117] ② Negative electrode second active material layer: 94.5% by mass of a negative electrode active material (such as graphite), 1% of a conductive agent (such as carbon black (the same as the carbon black used for the negative electrode in Example 1)), and 4.5% of a binder (such as 1.5% of sodium carboxymethyl cellulose and 3% of styrene-butadiene latex) are added to a solvent (such as deionized water) and stirred and mixed to obtain a negative electrode second active material layer slurry;

[0118] ③ The first active material layer of the negative electrode is coated on the middle area of ​​the current collector (such as copper foil), and the second active material layer of the negative electrode is coated on the first active material layer of the negative electrode and the area of ​​the current collector not coated with the first active material layer. After rolling, die cutting and baking, the negative electrode sheet is obtained. The double-sided surface density of the coating is 200g / m 2 The length A1 of the first active material layer of the negative electrode is 330mm, the width A2 is 98mm, the thickness H1 of the first active material layer is 32um, the thickness H of the single active material layer is 64um, the length of the negative electrode sheet is 550mm, and the width of the negative electrode sheet is 98mm.

[0119] Preparation of lithium-ion batteries:

[0120] The positive electrode prepared in (1) and the negative electrode prepared in (2) are assembled with a separator, and then welded, shelled, liquid-filled, formed, and capacity-divided to obtain a lithium-ion battery.

[0121] Example 6

[0122] Preparation of positive electrode:

[0123] The preparation of the positive electrode is the same as that in Example 4.

[0124] Preparation of negative electrode:

[0125] The preparation of the negative electrode is the same as that in Example 5.

[0126] Preparation of lithium-ion batteries:

[0127] The positive electrode prepared in (1) and the negative electrode prepared in (2) are assembled with a separator, and then welded, shelled, liquid-filled, formed, and capacity-divided to obtain a lithium-ion battery.

[0128] Comparative Example 1

[0129] Preparation of positive electrode:

[0130] The preparation of the positive electrode is the same as that in Example 2.

[0131] Preparation of negative electrode:

[0132] The preparation of the negative electrode is the same as that in Example 1.

[0133] Preparation of lithium-ion batteries:

[0134] The positive electrode prepared in (1) and the negative electrode prepared in (2) are assembled with a separator, and then welded, shelled, liquid-filled, formed, and capacity-divided to obtain a lithium-ion battery.

[0135] Capacity retention test:

[0136] Capacity retention rate after 50 cycles: Charge the battery according to the strategy shown in Table 1 and let it sit for 30 minutes; then discharge it at a current of 0.33C to a discharge termination voltage of 2.0V and let it sit for 30 minutes; repeat the above two steps a total of 50 times, record the first discharge capacity as the battery discharge capacity C1, and the discharge capacity of the 50th cycle as C50; 50-cycle capacity retention rate (%) = (C50 / C1) × 100%.

[0137] Capacity retention rate after 100 cycles: Charge the battery according to the strategy shown in Table 1 and let it sit for 30 minutes; then discharge it at a current of 0.33C to a discharge end voltage of 2.0V and let it sit for 30 minutes; repeat the above two steps a total of 100 times, record the first discharge capacity as the battery discharge capacity C1, and the discharge capacity of the 100th cycle as C100; 100-cycle capacity retention rate (%) = (C100 / C1) × 100%.

[0138] Capacity retention rate after 150 cycles: Charge the battery according to the strategy shown in Table 1 and let it sit for 30 minutes; then discharge it at a current of 0.33C to a discharge termination voltage of 2.0V and let it sit for 30 minutes; repeat the above two steps a total of 150 times, record the first discharge capacity as the battery discharge capacity C1, and the discharge capacity of the 150th cycle as C150; 150-cycle capacity retention rate (%) = (C150 / C1) × 100%.

[0139] Capacity retention rate after 200 cycles: Charge the battery according to the strategy shown in Table 1 and let it sit for 30 minutes; then discharge it at a current of 0.33C to a discharge end voltage of 2.0V and let it sit for 30 minutes; repeat the above two steps a total of 200 times, record the first discharge capacity as the battery discharge capacity C1, and the discharge capacity of the 200th cycle as C200; 200-cycle capacity retention rate (%) = (C200 / C1) × 100%.

[0140] Table 1 Charging strategies for capacity retention test of various embodiments and comparative examples

[0141] Energy density test method:

[0142] Charge the battery to 3.8V at 0.33C current and let it sit for 30 minutes; then discharge it to the discharge end voltage of 2.0V at 0.33C current and let it sit for 30 minutes; repeat the above two steps for a total of 3 times, record the third discharge energy, and calculate the energy density per unit area of ​​the battery cell (ECU).

[0143] Table 2 Performance test results of various embodiments and comparative examples

[0144] In summary, from the data of Examples 1 to 6 and Comparative Example 1, by providing micropores and mesopores on the first conductive agent, and through the mutual cooperation between the micropores and mesopores, the capacity retention rate of the battery can be effectively improved and the battery performance can be enhanced without significantly affecting the energy density of the battery cell.

[0145] From the data of Examples 1 to 3 and Examples 4 to 6, it can be seen that the double-layer coating has a higher energy density than the single-layer coating, and the single-layer coating has a better capacity retention rate than the double-layer coating.

[0146] The above description is only a preferred embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present disclosure should be included in the scope of protection of the present disclosure.

Claims

1. A conductive agent comprising: Mesopores and micropores, the pore diameter of the mesopores is 2nm to 50nm, and the pore diameter of the micropores is less than 2nm.

2. The conductive agent according to claim 1, wherein The ratio of the total volume of the mesopores to the total volume of the micropores is 30% to 60%: 40% to 70%.

3. The conductive agent according to claim 1 or 2, wherein The conductive agent includes at least one of carbon black, conductive graphite, activated carbon, and a metal conductive agent.

4. The conductive agent according to any one of claims 1 to 3, wherein The specific surface area of ​​the conductive agent is 200m 2 / g~2000m 2 / g. The conductive agent according to claim 4 , wherein The specific surface area of ​​the conductive agent is 400m 2 / g~1000m 2 / g.

6. An electrode comprising: The active material layer includes a first conductive agent, wherein the first conductive agent is the conductive agent according to any one of claims 1 to 5.

7. The electrode according to claim 6 further includes a current collector, the active material layer includes a first active material layer and a second active material layer, the first active material layer is arranged on the current collector, the second active material layer is arranged on the first active material layer, and the first active material layer includes the first conductive agent.

8. The electrode according to claim 7, wherein The first active material layer is a rectangular parallelepiped, and the current collector is a rectangular parallelepiped; the first active material layer and the current collector satisfy at least one of the following conditions: The length of the first active material layer accounts for 60% to 90% of the length of the current collector; or, The width of the first active material layer accounts for 60% to 100% of the width of the current collector.

9. The electrode according to claim 8, wherein The current collector satisfies at least one of the following: The first active material layer is not provided at both ends of the current collector in the length direction; or, The first active material layer is not provided at both ends of the current collector in the width direction.

10. The electrode according to claim 8 or 9, wherein The second active material layer is disposed in an area of ​​the current collector where the first active material layer is not disposed.

11. The electrode according to claim 7, wherein In the thickness direction of the electrode, the thickness H1 of the first active material layer accounts for 5% to 80% of the thickness H of the active material layer.

12. The electrode according to claim 7, wherein The first active material layer further includes a first active material and a first binder; the second active material layer includes a second active material, a second conductive agent, and a second binder.

13. The electrode according to claim 12, wherein The first active material and the second active material are the same or different; the first binder and the second binder are the same or different; and the second conductive agent and the first conductive agent are the same or different.

14. The electrode according to claim 6, wherein The electrode is a positive electrode or a negative electrode.

15. A lithium ion battery comprising the electrode according to any one of claims 6 to 14.

16. An electrical device comprising the lithium-ion battery according to claim 15.

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