Positive electrode active material, positive electrode plate, lithium ion battery and electronic equipment

Abstract

The invention relates to a positive active material, a positive pole piece, a lithium ion battery and electronic equipment, and relates to the technical field of lithium ion batteries. The positive electrode active material comprises a first effective component, the first effective component comprises a positive electrode additive, and the mass of the positive electrode additive accounts for 0.01-0.12% of the total mass of the first effective component. By adding the positive electrode additive into the first effective component of the positive electrode active material, the flexibility of the positive electrode plate can be improved, so that the compaction density of the positive electrode plate is improved, and the energy density of the battery is further improved; moreover, the addition of the positive electrode additive can reduce the impedance of the positive electrode plate, thereby improving the charging speed of the battery.

Description

Technical Field

[0001] This disclosure relates to the field of lithium-ion battery technology, and more particularly to a positive electrode active material, a positive electrode sheet, a lithium-ion battery, and an electronic device. Background Technology

[0002] With the fast pace of life, there is an increasing demand for faster mobile phone charging and longer battery life. However, lithium-ion batteries experience a significant capacity loss during fast charging, and this problem becomes even more pronounced at low temperatures. Currently, the voltage of lithium-ion batteries has been increased to over 4.5V, approaching the limit of lithium cobalt oxide. As the charging voltage increases, battery performance declines significantly. Summary of the Invention

[0003] To overcome the problems existing in related technologies, this disclosure provides a positive electrode active material, a positive electrode sheet, a lithium-ion battery, and an electronic device.

[0004] According to a first aspect of the present disclosure, a positive electrode active material is provided, the positive electrode active material comprising a first effective component, the first effective component comprising a positive electrode additive, the positive electrode additive comprising 0.01-0.12% of the total mass of the first effective component.

[0005] In some embodiments of this disclosure, the cathode additive comprises a saturated alkyl chain containing an amino group.

[0006] In some embodiments of this disclosure, the grafting rate of the amino groups is 0.1-2%.

[0007] In some embodiments of this disclosure, the number of carbon atoms in the saturated alkyl chain containing the amino group is 5-20.

[0008] In some embodiments of this disclosure, the number average molecular weight of the saturated alkyl chain containing an amino group is 1000-5000.

[0009] In some embodiments of this disclosure, the boiling point of the saturated alkyl chain containing an amino group is less than or equal to 200°C.

[0010] In some embodiments of this disclosure, the saturated alkyl chain containing an amino group includes at least one of aminopentane, diaminopentane, aminoheptane, diaminoheptane, triaminoheptane, and aminoisoheptane.

[0011] In some embodiments of this disclosure, the first effective component further includes components with the following mass percentages:

[0012] The first active material is 93.49-98.99%;

[0013] First conductive agent: 0.5-3.2%;

[0014] The first adhesive is 0.5-3.3%.

[0015] In some embodiments of this disclosure, the first active material includes at least one of lithium cobalt oxide, lithium manganese oxide, nickel-cobalt-manganese ternary materials, and lithium iron phosphate.

[0016] The first conductive agent includes at least two of conductive carbon black, Ketjen black, carbon nanotubes, and graphene;

[0017] The first adhesive includes at least one of polyvinylidene fluoride, polytetrafluoroethylene, polypropylene, polyacrylic acid, polyacrylate, polyacrylonitrile, sodium carboxymethyl cellulose, styrene-butadiene rubber, and polyurethane.

[0018] In some embodiments of this disclosure, the solid content of the positive electrode active material is 70.3 wt% to 78.8 wt%.

[0019] In some embodiments of this disclosure, the viscosity of the positive electrode active material is 3000 mPa·s-8000 mPa·s.

[0020] In some embodiments of this disclosure, the positive electrode additive includes a silane coupling agent containing double or triple bonds.

[0021] In some embodiments of this disclosure, the silane coupling agent includes at least one of vinylmethoxysilane coupling agent, propenylmethoxysilane coupling agent, butenylmethoxysilane coupling agent, ethynylmethoxysilane coupling agent, propynylmethoxysilane coupling agent, and butynylmethoxysilane coupling agent.

[0022] In some embodiments of this disclosure, the positive electrode active material further includes a first solvent, which includes at least one of N-methylpyrrolidone, N-butylpyrrolidone, and propylene carbonate.

[0023] According to a second aspect of the present disclosure, a positive electrode sheet is provided, the positive electrode sheet including a positive current collector and a first active material layer disposed on at least one side of the positive current collector, the first active material layer including any of the positive active materials described above.

[0024] In some embodiments of this disclosure, the positive electrode sheet has a first thickness H1 when fully charged, and a second thickness H2 after being stored at 130°C for 1 hour.

[0025] The first thickness H1 and the second thickness H2 satisfy the following relationship:

[0026] 1.2≤H2 / H1≤4.9.

[0027] In some embodiments of this disclosure, the first thickness is 50-150 μm;

[0028] The second thickness is 100-250 μm.

[0029] In some embodiments of this disclosure, the first active material layer and the positive electrode current collector have a first adhesive force F1 when cold-pressed, and the first active material layer and the positive electrode current collector have a second adhesive force F2 when stored at 130°C for 1 hour.

[0030] The first adhesive force F1 and the second adhesive force F2 satisfy the following relationship:

[0031] 10%F1≤F2≤25%F1.

[0032] In some embodiments of this disclosure, the positive electrode further includes a second active material layer, which is disposed on the side of the first active material layer away from the positive current collector.

[0033] The second active material layer includes an active material.

[0034] In some embodiments of this disclosure, the active material includes a second effective component, the second effective component includes a second active material, and the mass of the second active material accounts for 96.8-99.0% of the total mass of the second effective component.

[0035] In some embodiments of this disclosure, the first active material of the first effective component has a first bulk density a1, and the second active material has a second bulk density a2;

[0036] The first g / cm volumetric weight a1 and the second g / cm volumetric weight a2 satisfy the following relationship:

[0037] 4.8≤a2 / a1≤21.3.

[0038] In some embodiments of this disclosure, the first gram bulk density is 180-200 mAh / g;

[0039] The second gram has a bulk density of 200-240 mAh / g.

[0040] In some embodiments of this disclosure, the compaction density of the first active material layer is 4.0-4.5 g / cc;

[0041] The compaction density of the second active material layer is 3.90-4.45 g / cc.

[0042] In some embodiments of this disclosure, the first weight m1 per unit volume of the first active material layer and the second weight m2 per unit volume of the first active material layer satisfy the following relationship:

[0043] 0.9≤m1 / m2≤4.1.

[0044] In some embodiments of this disclosure, m1 is 10.2-22.4 mg / cc;

[0045] The m2 is 2.8-11.5 mg / cc.

[0046] In some embodiments of this disclosure, the second active material includes at least one of lithium cobalt oxide, lithium nickel manganese oxide, and lithium manganese-based materials.

[0047] In some embodiments of this disclosure, the active material further includes a second solvent, the second solvent including at least one of N-methylpyrrolidone, N-butylpyrrolidone, and propylene carbonate.

[0048] According to a third aspect of the present disclosure, a lithium-ion battery is provided, including a negative electrode, an electrolyte, and a positive electrode as described above.

[0049] In some embodiments of this disclosure, the electrolyte comprises a carboxylic acid ester, wherein the mass of the carboxylic acid ester accounts for 5-50% of the total mass of the electrolyte.

[0050] In some embodiments of this disclosure, the electrolyte further includes at least one of linear esters, cyclic esters, ether compounds, and nitrile compounds; the viscosity of the electrolyte is less than or equal to 1 cp.

[0051] According to a fourth aspect of the present disclosure, an electronic device is provided, including a lithium-ion battery as described above.

[0052] The technical solutions provided by the embodiments of this disclosure may include the following beneficial effects:

[0053] This disclosure discloses that by adding a positive electrode additive to the first effective component of the positive electrode active material, the flexibility of the positive electrode sheet can be improved, thereby increasing the compaction density of the positive electrode sheet and thus improving the energy density of the battery; furthermore, the addition of the positive electrode additive can also reduce the impedance of the positive electrode sheet, thereby improving the charging speed of the battery.

[0054] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this disclosure. Attached Figure Description

[0055] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0056] Figure 1 This is a schematic diagram of the layer structure of a positive electrode sheet according to an exemplary embodiment.

[0057] Figure 2 This is a schematic diagram of the layer structure of a positive electrode sheet according to an exemplary embodiment.

[0058] Figure 3 This is a schematic diagram of the layer structure of a positive electrode sheet according to an exemplary embodiment. Detailed Implementation

[0059] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0060] In related technologies, adding a certain proportion of conductive carbon black to the positive electrode or using a high-conductivity electrolyte can improve the battery's high-rate charge and discharge performance. However, when the content of conductive carbon black increases, the specific capacity of the positive electrode will decrease, leading to a decrease in the battery's energy density and range. On the other hand, when the amount of high-conductivity electrolyte added increases, it will lead to an increase in the risk of electrode side reactions and gas expansion, causing problems such as battery aging.

[0061] To address the aforementioned technical problems, this disclosure provides a positive electrode active material comprising a first effective component, which includes a positive electrode additive, wherein the mass of the positive electrode additive accounts for 0.01-0.12% of the total mass of the first effective component. The addition of the positive electrode additive to the first effective component of this disclosure can improve the flexibility of the positive electrode sheet, thereby increasing the compaction density of the positive electrode sheet and thus improving the energy density of the battery. Furthermore, the addition of the positive electrode additive can also reduce the impedance of the positive electrode sheet, thereby improving the charging speed of the battery.

[0062] An exemplary embodiment of this disclosure provides a positive electrode active material, the positive electrode active material comprising a first effective component, the first effective component comprising a positive electrode additive, the mass of the positive electrode additive accounting for 0.01-0.12% of the total mass of the first effective component.

[0063] In this embodiment, by adding a positive electrode additive to the first effective component of the positive electrode active material, the flexibility of the positive electrode sheet can be improved, thereby increasing the compaction density of the positive electrode sheet and thus improving the energy density of the battery. Furthermore, the addition of the positive electrode additive can also reduce the impedance of the positive electrode sheet, thereby improving the charging speed of the battery. Exemplarily, the mass of the positive electrode additive accounts for 0.01%, 0.05%, 0.08%, 0.10%, and 0.12% of the total mass of the first effective component. The mass percentage of the positive electrode additive in the total mass of the first effective component can also be any ratio among the exemplary mass percentages; for example, the mass percentage of the positive electrode additive in the total mass of the first effective component can also be any ratio between 0.05% and 0.10%.

[0064] In one exemplary embodiment, the positive electrode additive comprises a saturated alkyl chain containing an amino group.

[0065] In this embodiment, the positive electrode additive includes a saturated alkyl chain containing an amino group. By introducing the amino group, hydrogen bonds can be formed with the groups in the positive electrode active material. Through the strong force of the hydrogen bond, the interaction between the components in the positive electrode active material (such as the first active material, the first conductive agent, and the first binder) can be enhanced, thereby improving the flexibility of the positive electrode sheet, increasing the compaction density of the positive electrode sheet, and thus improving the energy density of the battery. Furthermore, the addition of the positive electrode additive can also improve the compatibility between the electrolyte and the positive electrode sheet, enhance the ionic conductivity of the electrolyte, and thus reduce the interfacial impedance. In addition, the saturated alkyl chain containing the amino group can also improve the ionic conductivity of the electrolyte, thereby reducing the impedance of the positive electrode sheet and thus improving the charging speed of the battery.

[0066] In one exemplary embodiment, the grafting rate of the amino groups is 0.1-2%.

[0067] In this embodiment, by controlling the grafting rate of amino groups, the battery can maintain better overall performance. For example, the grafting rate of amino groups can be 0.1%, 0.5%, 1.0%, 1.4%, 1.8%, or 2.0%. The grafting rate of amino groups can also be any value between the exemplary grafting rates; for example, the grafting rate of amino groups can be any value between 1.0% and 1.8%.

[0068] In one exemplary embodiment, the number of carbon atoms in the saturated alkyl chain containing the amino group is 5-20.

[0069] In this embodiment, by controlling the number of carbon atoms in the saturated alkyl chain containing the amino group to be between 5 and 20, the battery can maintain better overall performance. Exemplarily, the number of carbon atoms in the saturated alkyl chain containing the amino group can be 5, 7, 10, 15, or 20. The number of carbon atoms in the saturated alkyl chain containing the amino group can also be any value between the exemplary values; for example, the number of carbon atoms in the saturated alkyl chain containing the amino group can also be any value between 5 and 10.

[0070] In one exemplary embodiment, the number average molecular weight of the saturated alkyl chain containing an amino group is 1000-5000.

[0071] In this embodiment, the number-average molecular weight of the saturated alkyl chain containing the amino group is 1000-5000, which allows the battery to maintain better overall performance. Exemplarily, the number-average molecular weight of the saturated alkyl chain containing the amino group can be 1000, 2000, 3500, 4000, or 5000. The number-average molecular weight of the saturated alkyl chain containing the amino group can be any value between the exemplary number-average molecular weights; for example, the number-average molecular weight of the saturated alkyl chain containing the amino group can also be any value between 2000 and 4000.

[0072] In one exemplary embodiment, the boiling point of the saturated alkyl chain containing an amino group is less than or equal to 200°C.

[0073] In this embodiment, when the boiling point of the saturated alkyl chain containing an amino group is less than or equal to 200°C, the battery can maintain better overall performance. Exemplarily, the boiling points of the saturated alkyl chain containing an amino group are 90°C, 104°C, 154°C, 180°C, 200°C, etc. The boiling point of the saturated alkyl chain containing an amino group can also be any value within the exemplary mass percentage range; for example, the boiling point of the saturated alkyl chain containing an amino group can also be any value between 104°C and 180°C.

[0074] In one exemplary embodiment, the saturated alkyl chain containing an amino group includes at least one of aminopentane, diaminopentane, aminoheptane, diaminoheptane, triaminoheptane, and aminoisoheptane.

[0075] In this embodiment, the saturated alkyl chain containing an amino group can be selected from one of aminopentane, diaminopentane, aminoheptane, diaminoheptane, triaminoheptane, and aminoisoheptane, or several of them can be selected and compounded. For example, the saturated alkyl chain containing an amino group includes aminopentane and diaminopentane in a mass ratio of 1:1, or the saturated alkyl chain containing an amino group includes aminopentane, diaminopentane, and aminoheptane in a mass ratio of 1:2:3.

[0076] In one exemplary embodiment, the first effective component further includes components in the following mass percentages:

[0077] The first active material is 93.49-98.99%;

[0078] First conductive agent: 0.5-3.2%;

[0079] The first adhesive is 0.5-3.3%.

[0080] In this embodiment, by controlling the first active material, the first conductive agent, and the first binder within the above-mentioned ranges, the battery can maintain better overall performance.

[0081] For example, in one embodiment, the first effective component comprises components in the following mass percentages:

[0082]

[0083] In another embodiment, the first effective component comprises the following components by mass percentage:

[0084]

[0085] In another embodiment, the first effective component comprises the following components by mass percentage:

[0086]

[0087] In another embodiment, the first effective component comprises the following components by mass percentage:

[0088]

[0089]

[0090] In an exemplary embodiment, the first active material includes at least one of lithium cobalt oxide, lithium manganese oxide, nickel-cobalt-manganese ternary materials, and lithium iron phosphate.

[0091] The addition of a first active material enables energy storage and release. In this embodiment, the first active material can be selected from lithium cobalt oxide, lithium manganese oxide, nickel-cobalt-manganese ternary materials, and lithium iron phosphate, or a combination of several of them. For example, the first active material includes lithium cobalt oxide and lithium manganese oxide in a mass ratio of 1:1.3-3.5; or, the first active material includes lithium cobalt oxide, lithium manganese oxide, and lithium iron phosphate in a mass ratio of 1:1.5-2.4:2.7-4.5.

[0092] In one exemplary embodiment, the first conductive agent includes at least two of conductive carbon black, Ketjen black, carbon nanotubes, and graphene.

[0093] The first conductive agent can form a conductive network between the first active material and the positive electrode current collector 1 to improve the conductivity of the positive electrode sheet. In this embodiment, the first conductive agent can be a combination of several of conductive carbon black, Ketjen black, carbon nanotubes, and graphene. For example, the first conductive agent includes conductive carbon black and carbon nanotubes in a mass ratio of 1:1.5-3.4; or, the first conductive agent includes conductive carbon black, carbon nanotubes, and graphene in a mass ratio of 1:2.3-4.0:4.5-5.8.

[0094] In one exemplary embodiment, the first adhesive includes at least one selected from polyvinylidene fluoride, polytetrafluoroethylene, polypropylene, polyacrylic acid, polyacrylate, polyacrylonitrile, sodium carboxymethyl cellulose, styrene-butadiene rubber, and polyurethane.

[0095] The first adhesive is used to adhere the first active material and the first conductive agent to the positive electrode current collector 1 to ensure the integrity of the positive electrode structure and to enhance the transmission efficiency between the first active material, the first conductive agent, and the positive electrode current collector 1. In this embodiment, the first adhesive can be selected from one of polyvinylidene fluoride, polytetrafluoroethylene, polypropylene, polyacrylic acid, polyacrylate, polyacrylonitrile, sodium carboxymethyl cellulose, styrene-butadiene rubber, and polyurethane, or several of them can be selected and compounded. For example, the first adhesive includes polytetrafluoroethylene and polypropylene in a mass ratio of 1:1.2-3.6, or the first adhesive includes polytetrafluoroethylene, polyacrylate, and sodium carboxymethyl cellulose in a mass ratio of 1:1.4-2.4:2.5-4.5.

[0096] In one exemplary embodiment, the solid content of the positive electrode active material is 70.3 wt% to 78.8 wt%.

[0097] The solid content of the positive electrode active material has a significant impact on battery performance. In this embodiment, by controlling the solid content of the positive electrode active material between 70.3 wt% and 78.8 wt%, the uniformity and smoothness of the positive electrode active material coating can be improved, thereby enhancing the battery's conductivity, charge-discharge performance, electrode structural integrity, and battery safety. Exemplarily, the solid content of the positive electrode active material is 70.3 wt%, 72.5 wt%, 75.1 wt%, and 78.8 wt%. The solid content of the positive electrode active material can also be any average particle size within the exemplary solid content range; for example, the solid content of the positive electrode active material can also be any solid content between 72.5 and 75.1 wt%.

[0098] In one exemplary embodiment, the viscosity of the positive electrode active material is 3000 mPa·s-8000 mPa·s.

[0099] In this embodiment, by controlling the viscosity of the positive electrode active material within the range of 3000 mPa·s to 8000 mPa·s, the continuity and uniformity of the coating can be ensured. Furthermore, this helps to improve the migration speed of lithium ions in the battery, thereby enhancing the battery's rate performance, charge / discharge efficiency, energy density, and safety. Exemplarily, the viscosity of the positive electrode active material is 3000 mPa·s, 4000 mPa·s, 6000 mPa·s, or 8000 mPa·s. The viscosity of the positive electrode active material can also be any viscosity within the exemplary range; for example, the viscosity of the positive electrode active material can also be 4000-6000 mPa·s.

[0100] In one exemplary embodiment, the positive electrode additive includes a silane coupling agent containing double or triple bonds.

[0101] In this embodiment, a silane coupling agent containing double or triple bonds can form stable silicon-oxygen bonds with the groups in the positive electrode active material to enhance the structural stability of the positive electrode sheet. This is beneficial for maintaining the integrity of the material during battery charging and discharging, and for improving the safety performance and cycle stability of the battery at high temperatures.

[0102] In an exemplary embodiment, the silane coupling agent includes at least one of vinylmethoxysilane coupling agent, propenylmethoxysilane coupling agent, butenylmethoxysilane coupling agent, ethynylmethoxysilane coupling agent, propynylmethoxysilane coupling agent, and butynylmethoxysilane coupling agent.

[0103] In this embodiment, the silane coupling agent can be selected from one of vinylmethoxysilane coupling agents, propylenemethoxysilane coupling agents, butenylmethoxysilane coupling agents, ethynylmethoxysilane coupling agents, propynylmethoxysilane coupling agents, and butynylmethoxysilane coupling agents, or several of them can be selected and compounded. For example, the silane coupling agent includes vinylmethoxysilane coupling agent and propylenemethoxysilane coupling agent in a mass ratio of 1:3.4-5.6, or the silane coupling agent includes vinylmethoxysilane coupling agent, ethynylmethoxysilane coupling agent, and propynylmethoxysilane coupling agent in a mass ratio of 1:2.6-3.5:3.8-4.5.

[0104] In one exemplary embodiment, the first active material further includes a first solvent, which includes at least one of N-methylpyrrolidone, N-butylpyrrolidone, and propylene carbonate.

[0105] The first effective component contains the main functional ingredients, and the first solvent can dissolve or disperse the first effective component. In this way, the positive electrode active material can be made into a slurry for use. The positive electrode active material is coated on the positive electrode current collector 1 in the form of a slurry so as to form a uniform coating on the positive electrode current collector 1.

[0106] In this embodiment, the first solvent can be selected from one of N-methylpyrrolidone, N-butylpyrrolidone, and propylene carbonate, or several of them can be selected and compounded. For example, the first solvent includes N-methylpyrrolidone and N-butylpyrrolidone in a mass ratio of 1:2.0-3.5.

[0107] like Figure 1 As shown, an exemplary embodiment of this disclosure provides a positive electrode sheet, which includes a positive current collector 1 and a first active material layer 2 disposed on at least one side of the positive current collector 1. The first active material layer 2 includes the positive active material as described above.

[0108] In this embodiment, by setting a first active material layer 2 on the positive electrode current collector 1, the flexibility of the positive electrode sheet can be improved, thereby increasing the compaction density of the positive electrode sheet and thus improving the energy density of the battery; furthermore, the addition of positive electrode additives can also reduce the impedance of the positive electrode sheet, thereby improving the charging speed of the battery.

[0109] Among them, such as Figure 1 As shown, the first active material layer 2 can be disposed only on one side of the positive electrode current collector 1; it can be understood that, as Figure 2 As shown, the first active material layer 2 can also be disposed on both sides of the positive electrode current collector 1, and can be selected according to actual needs. There are no particular limitations on the material of the positive electrode current collector 1, and it can be a positive electrode current collector 1 known in the art, such as aluminum foil, aluminum alloy foil, and composite current collectors.

[0110] The positive electrode active material can be deposited on the positive electrode current collector 1 by roll coating or extrusion to form a first active material layer 2. Exemplarily, the positive electrode sheet can be prepared by: coating the positive electrode active material onto both sides of the positive electrode current collector 1 to form the first active material layer 2; and cold pressing to form the positive electrode sheet. The cold pressing (roll pressing) temperature can be, for example, 20-30°C, and the rolling pressure can be 20-40T.

[0111] In an exemplary embodiment, the positive electrode sheet has a first thickness H1 when fully charged, and a second thickness H2 after being stored at 130°C for 1 hour.

[0112] The first thickness H1 and the second thickness H2 satisfy the following relationship:

[0113] 1.2≤H2 / H1≤4.9.

[0114] In this embodiment, by controlling the ratio of the second thickness H2 to the first thickness H1, the battery can maintain better overall performance. For example, the H2 / H1 ratio can be 1.2, 2.4, 3.5, 4.2, or 4.9. The H2 / H1 ratio can also be any ratio between these examples, such as any ratio between 2.4 and 3.5.

[0115] In one exemplary embodiment, the first thickness is 50-150 μm; the second thickness is 100-250 μm.

[0116] In this embodiment, the first thickness can be 50μm, 70μm, 90μm, 120μm, or 150μm; the second thickness can be 100μm, 140μm, 180μm, 210μm, or 250μm. The first thickness and the second thickness can also be any thickness between the exemplary thickness values, for example, the first thickness can be any thickness between 70μm and 90μm, and the second thickness can be any thickness between 140μm and 210μm.

[0117] In an exemplary embodiment, the first active material layer 2 and the positive electrode current collector 1 have a first adhesive force F1 when cold-pressed, and the first active material layer 2 and the positive electrode current collector 1 have a second adhesive force F2 when stored at 130°C for 1 hour.

[0118] The first adhesive force F1 and the second adhesive force F2 satisfy the following relationship:

[0119] 10%F1≤F2≤25%F1.

[0120] In this embodiment, by controlling the relationship between the first adhesive force F1 and the second adhesive force F2, the battery can maintain better overall performance. Here, 10%F1≤F2≤25%F1 can also be expressed as the ratio of F2 / F1 being 10%-25%. For example, the ratio of F2 / F1 is 10%, 15%, 18%, 22%, or 25%. The ratio of F2 / F1 can also be any ratio between these exemplary values; for example, the ratio of F2 / F1 can be any ratio between 15% and 22%.

[0121] like Figure 3 As shown, in an exemplary embodiment, the positive electrode further includes a second active material layer 3, which is disposed on the side of the first active material layer 1 away from the positive current collector; the second active material layer 3 includes an active material material.

[0122] In this embodiment, by setting a double active layer on the positive electrode, the energy density and cycle performance of the battery are improved. Specifically, cyclic voltammetry testing showed that the second active material layer 3 exhibited no phase transition peak in the 4.5–4.9V range, indicating that it is beneficial for improving the battery's high-voltage tolerance.

[0123] In an exemplary embodiment, the active material includes a second effective component, which includes a second active material, wherein the mass of the second active material accounts for 96.8-99.0% of the total mass of the second effective component.

[0124] In this embodiment, by controlling the mass percentage of the second active material to be between 96.8% and 99.0%, the energy density of the battery can be increased, and the charge-discharge efficiency and cycle stability of the battery can be improved. For example, the mass percentage of the second active material is 96.8%, 97.2%, 98.1%, or 99.0% of the total mass of the second effective component. The mass percentage of the first active material to the total mass of the second effective component can also be any of the exemplary ratios; for example, the mass percentage of the first active material to the total mass of the second effective component can be any ratio between 97.2% and 98.1%.

[0125] To enable the second active material layer 3 to possess conductivity and adhesion, the active material may further include a second conductive agent and a second adhesive. The types of the second conductive agent and the second adhesive are not limited, as long as they achieve the purpose of this disclosure. For example, the second conductive agent in the second active material layer 3 can be the same type as the first conductive agent, and the type of the second adhesive can be the same type as the first adhesive. The mass of the second conductive agent accounts for 0.3-1.4% of the total mass of the second effective component, and the mass of the second adhesive accounts for 0.7-1.8% of the total mass of the second effective component.

[0126] In an exemplary embodiment, the first active material of the first effective component has a first bulk density a1, and the second active material has a second bulk density a2;

[0127] The first gram volumetric weight a1 and the second gram volumetric weight a2 satisfy the following relationship:

[0128] 4.8≤a2 / a1≤21.3.

[0129] In this embodiment, the second gram capacity a2 is much larger than the first gram capacity a1, which is beneficial for improving the energy density and cycle performance of the battery. For example, the ratio of a2 / a1 can be 4.8, 8.7, 13.4, 16.9, 19.2, or 21.3. The ratio of a2 / a1 can also be any ratio among the exemplary ratios; for example, the ratio of a2 / a1 can be any ratio between 13.4 and 19.2.

[0130] In one exemplary embodiment, the first gram capacity is 180-200 mAh / g; the second gram capacity is 200-240 mAh / g.

[0131] In this embodiment, the first gram capacity can be, for example, 180 mAh / g, 193 mAh / g, 196 mAh / g, or 200 mAh / g; the second gram capacity can be, for example, 200 mAh / g, 213 mAh / g, 226 mAh / g, 232 mAh / g, or 240 mAh / g. The first and second gram capacities can also be any gram capacity between the exemplary values; for example, the first gram capacity can be any gram capacity between 193 and 196 mAh / g, and the second gram capacity can be any gram capacity between 213 and 232 mAh / g.

[0132] In an exemplary embodiment, the compaction density of the first active material layer 2 is 4.0-4.5 g / cc; and the compaction density of the second active material layer 3 is 3.90-4.45 g / cc.

[0133] Compacted density, also known as lamination density, refers to the mass contained within a unit volume. By controlling the compacted density of the first active layer 2 and the second active layer 3, the energy density, charge-discharge performance, and cycle stability of the battery can be improved. For example, the compacted density of the first active material layer 2 is 4.0 g / cc, 4.2 g / cc, 4.4 g / cc, and 4.5 g / cc; the compacted density of the second active material layer 3 is 3.90 g / cc, 3.98 g / cc, 4.11 g / cc, 4.25 g / cc, 4.33 g / cc, and 4.45 g / cc. The compacted density of the first active material layer 2 and the compacted density of the second active material layer 3 can also be any g / cc within the exemplary compacted density range. For example, the first compacted density can be any compacted density between 4.2 and 4.4 g / cc, and the second compacted density can be any compacted density between 4.11 and 4.33 g / cc.

[0134] In an exemplary embodiment, the first weight m1 per unit volume of the first active material layer 2 and the second weight m2 per unit volume of the first active material layer 3 satisfy the following relationship:

[0135] 0.9≤m1 / m2≤4.1.

[0136] In this embodiment, by controlling the ratio of the first weight m1 to the second weight m2, the battery can maintain better overall performance. For example, the ratio of m1 / m2 can be 0.9, 1.3, 2.5, 3.6, or 4.1. The ratio of m1 / m2 can also be any ratio between these examples; for instance, the ratio of m1 / m2 can be any ratio between 2.5 and 3.6.

[0137] In an exemplary embodiment, m1 is 10.2-22.4 mg / cc; m2 is 2.8-11.5 mg / cc.

[0138] In this embodiment, m1 can be, for example, 10.2 mg / cc, 13.2 mg / cc, 16.1 mg / cc, 19.6 mg / cc, or 22.4 mg / cc; m2 can be, for example, 2.8 mg / cc, 3.2 mg / cc, 5.1 mg / cc, 9.5 mg / cc, or 11.5 mg / cc. m1 and m2 can also be any weight between the exemplary weight values. For example, m1 can be any weight between 16.1 and 19.6 mg / cc, and the second weight can be any weight between 5.1 and 9.5 mg / cc.

[0139] In one exemplary embodiment, the second active material includes at least one of lithium cobalt oxide, lithium nickel manganese oxide, and lithium manganese-based materials.

[0140] In this embodiment, lithium-rich cobalt oxide, lithium-rich nickel manganese oxide, and lithium-rich manganese-based materials have the advantages of high specific capacity and high energy density, which can effectively improve the battery's range performance. The second active material can be one of lithium-rich cobalt oxide, lithium-rich nickel manganese oxide, or lithium-rich manganese-based materials, or a combination of several of them. For example, the second active material includes lithium-rich cobalt oxide and lithium-rich nickel manganese oxide in a 1:1 mass ratio.

[0141] In one exemplary embodiment, the active material further includes a second solvent, which includes at least one of N-methylpyrrolidone, N-butylpyrrolidone, and propylene carbonate.

[0142] In this embodiment, the second solvent can be the same as or different from the first solvent, and can be selected according to actual needs. For example, the second solvent can be one of N-methylpyrrolidone, N-butylpyrrolidone, and propylene carbonate, or several of them can be selected and compounded. For example, the second solvent includes N-methylpyrrolidone and N-butylpyrrolidone in a mass ratio of 1:2.

[0143] An exemplary embodiment of this disclosure provides a lithium-ion battery, including a negative electrode, an electrolyte, and a positive electrode as described above.

[0144] The positive electrode in this embodiment can be the same as the positive electrode in the above embodiment. The resistance of the positive electrode after cold pressing is not higher than 1Ω / m, and the resistance after full charging is not higher than 0.8Ω / m.

[0145] In this embodiment, the negative electrode sheet and electrolyte are not particularly limited, as long as they can achieve the purpose of this disclosure. For example, the negative electrode sheet can be formed by coating with a negative electrode active material, such as graphite or silicon.

[0146] Lithium-ion batteries may also include a separator, separating the positive and negative electrode sheets to prevent internal short circuits. The positive and negative electrode sheets and the separator are wound or stacked to form a bare cell, which is then processed through liquid injection / formation / molding to create a finished lithium-ion battery. The fully charged voltage of a lithium-ion battery is not less than 4.5V.

[0147] The material of the separator is not particularly limited, as long as it can achieve the purpose of this disclosure; for example, the separator can be a polyolefin separator, a polyester separator, a polyamide separator, etc.; the polyolefin separator can be a polyethylene resin separator or a polypropylene resin separator; the polyester separator can be a polyethylene terephthalate separator; the polyamide separator can be a nylon 6 separator or a nylon 66 separator.

[0148] In one exemplary embodiment, the electrolyte includes a carboxylic acid ester, the mass of which accounts for 5-50% of the total mass of the electrolyte.

[0149] In this embodiment, by controlling the mass ratio of carboxylic acid esters to 5-50% and ensuring that the content of carboxylic acid esters in the electrolyte is not higher than 50%, it is beneficial to increase the charging speed and reduce the temperature rise during battery charging, thereby preventing thermal runaway during charging.

[0150] In one exemplary embodiment, the electrolyte further includes at least one of linear esters, cyclic esters, ether compounds, and nitrile compounds; the electrolyte viscosity is less than or equal to 1 cp.

[0151] In this embodiment, the electrolyte is compounded using the above-mentioned components, and the viscosity of the electrolyte is controlled at 1 cp, which can improve the ion migration rate, reduce the battery resistance, and improve the overall performance of the battery.

[0152] Among them, the carboxylic acid ester can be one or more of methyl formate, methyl acetate, ethyl acetate, methyl propionate, and ethyl propionate, and its amount can be 10-30%; the linear ester can be one or more of dimethyl carbonate (DMC), diethyl carbonate (DEC), and dipropyl carbonate (DPC), and its amount can be 20-50%; the cyclic ester can be one or more of ethylene carbonate (EC), propylene carbonate (PC), and butyl carbonate (BC), and its amount can be 3-10%; the ether compound can be one or more of dibutyl ether, diethylene glycol dimethyl ether, and ethoxymethoxyethane, and its amount can be 5-15%; the nitrile compound can be, for example, acrylonitrile, and its amount can be 0.5-5%.

[0153] An exemplary embodiment of this disclosure provides an electronic device including the lithium-ion battery described above. The electronic device may be, for example, a mobile phone, a laptop computer, a tablet computer, or a wearable device.

[0154] To more clearly explain the technical solution of this disclosure, specific embodiments of the positive electrode are provided, and the beneficial effects of selecting the above-mentioned ranges of parameters are illustrated by specific experimental data through specific embodiments.

[0155] Example

[0156] It should be noted that, unless otherwise specified, the raw materials used in the following embodiments are all commercially available.

[0157] The cathode current collector is aluminum; the cathode additive (a saturated alkyl chain containing an amino group) is aminopentane; the cathode additive (silane coupling agent) is vinyl methoxysilane coupling agent; the first active material is lithium cobalt oxide; the first and second conductive agents both include conductive carbon black and graphene in a mass ratio of 1:1; the first and second binders are both styrene-butadiene rubber; the first and second solvents are both N-methylpyrrolidone; and the second active material is lithium-rich cobalt oxide.

[0158] Example 1: A positive electrode sheet is prepared by the following method:

[0159] (1) Mix 93.49% of the first active material, 3.2% of the first conductive agent, 33.3% of the first binder and 0.01% of the positive electrode additive aminopentane to obtain the first effective component.

[0160] (2) The first effective component is mixed with the first solvent to obtain the positive electrode active material. The solid content of the positive electrode active material is 73.4 wt%, and the viscosity is 4000 mPa·s.

[0161] (3) The positive electrode active material is coated on both sides of the positive electrode current collector to form a first active material layer on both sides of the positive electrode current collector, thereby obtaining the electrode intermediate.

[0162] (4) The electrode intermediate is cold-pressed to obtain the positive electrode.

[0163] To more clearly explain the technical solution of this disclosure, this disclosure also provides examples 2-6 of the positive electrode sheet, wherein the setting parameters of examples 2-6 are shown in Table 1.

[0164] Table 1 shows specific embodiments of the positive electrode sheet in this disclosure. It should be noted that, except for the parameters listed in Table 1, the other parameters of embodiments 2-6 are basically the same as those of embodiment 1.

[0165] Table 1. Setting parameters for the positive electrode plates in Examples 1-6

[0166]

[0167] Example 7: A positive electrode sheet is prepared by the following method:

[0168] (1) Mix 93.49% of the first active material, 3.2% of the first conductive agent, 3.3% of the first binder and 0.01% of the positive electrode additive vinyl methoxysilane coupling agent to obtain the first effective component.

[0169] (2) The first effective component is mixed with the first solvent to obtain the positive electrode active material. The solid content of the positive electrode active material is 73.4 wt%, and the viscosity is 4000 mPa·s.

[0170] (3) The positive electrode active material is coated on both sides of the positive electrode current collector to form a first active material layer on both sides of the positive electrode current collector, thereby obtaining the electrode intermediate.

[0171] (4) The electrode intermediate is cold-pressed to obtain the positive electrode.

[0172] The positive electrode sheet has a first thickness H1 when fully charged, which is 100 μm; the positive electrode sheet has a second thickness H2 after being stored at 130℃ for 1 hour, which is 120 μm; H2 / H1=1.2.

[0173] To more clearly explain the technical solution of this disclosure, this disclosure also provides examples 8-12 of positive electrode plates, wherein the setting parameters of examples 8-12 are shown in Table 2.

[0174] Table 2 shows specific embodiments of the positive electrode sheet in this disclosure. It should be noted that, except for the parameters listed in Table 2, the other parameters of embodiments 8-12 are basically the same as those of embodiment 7.

[0175] Table 2. Setting parameters for the positive electrode sheet in Examples 7-12

[0176]

[0177] Example 13: A positive electrode sheet is prepared by the following method:

[0178] (1) 93.49% of the first active material, 3.2% of the first conductive agent, 3.3% of the first binder and 0.01% of the positive electrode additive aminopentane are mixed to obtain the first effective component. The first effective component is mixed with the first solvent to obtain the positive electrode active material.

[0179] (2) Mix 96.8% of the second active material, 1.6% of the first conductive agent, and 1.6% of the first binder to obtain the second effective component. Mix the second effective component with the second solvent to obtain the active material.

[0180] (3) The positive electrode active material is coated on both sides of the positive electrode current collector to form a first active material layer on both sides of the positive electrode current collector; the active material is coated on the side of the first active material layer away from the positive electrode current collector to form a second active material layer on the first active material layer, thereby obtaining the electrode intermediate.

[0181] (4) The electrode intermediate is cold-pressed to obtain the positive electrode.

[0182] The first active material layer has a first gram capacity a1 of 140-200 mAh / g; the second active material layer has a second gram capacity a2 of 200-240 mAh / g; and the ratio of a2 / a1 is 1-1.7.

[0183] The compaction density of the first active material layer is 4.0 g / cc; the compaction density of the second active material layer is 4.45 g / cc.

[0184] The first weight m1 per unit volume of the first active substance layer is 10.2 mg / cc; the second weight m2 per unit volume of the second active substance layer is 2.8 mg / cc; the ratio of m1 / m2 is 3.6.

[0185] To more clearly explain the technical solution of this disclosure, this disclosure also provides examples 14-18 of the positive electrode sheet, wherein the setting parameters of examples 14-18 are shown in Table 3.

[0186] Table 3 shows specific embodiments of the positive electrode sheet in this disclosure. It should be noted that, except for the parameters listed in Table 3, the other parameters of embodiments 14-18 are basically the same as those of embodiment 13.

[0187] Table 3. Setting parameters for the positive electrode in Examples 13-18

[0188]

[0189] Application examples

[0190] The negative electrode sheet, separator, and positive electrode sheet prepared in each embodiment are wound or stacked to form a bare cell, which is then injected with liquid / formed / shaped to form a finished lithium-ion battery.

[0191] The electrolyte contains 27.0% carboxylic acid ester (methyl formate), 48.5% linear ester (dimethyl carbonate), 8.5% cyclic ester (ethylene carbonate), 12.4% ether (dibutyl ether), and 3.6% nitrile (acrylonitrile). The electrolyte viscosity is 0.05 cp.

[0192] Performance testing

[0193] The performance of the positive electrode sheet in the embodiment and the lithium-ion battery in the application example were tested respectively, and the test results are recorded in Table 4.

[0194] Application Examples 1-18 correspond to Examples 1-18, respectively.

[0195] The first adhesive force F1 is the adhesive force between the first active material layer and the positive electrode current collector during cold pressing;

[0196] The second adhesive force F2 is the adhesive force between the first active material layer and the positive electrode current collector when stored at 130°C for 1 hour.

[0197] Table 4 Performance Test Table of Battery and Positive Electrode in Application Examples

[0198]

[0199] Table 4 (continued) Performance test table of battery and positive electrode in application examples

[0200]

[0201] As can be seen from the data in Table 4, the lithium-ion battery prepared using the positive electrode sheet disclosed herein has a resistance ≤30mΩ and a voltage ≥4.50V, indicating that the battery has good overall performance.

[0202] Other embodiments of this disclosure will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This disclosure is intended to cover any variations, uses, or adaptations of this disclosure that follow the general principles of this disclosure and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this disclosure are indicated by the claims.

[0203] It should be understood that this disclosure is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this disclosure is limited only by the appended claims.

Claims

1. A positive electrode active material, characterized in that, The positive electrode active material includes a first effective component, which includes a positive electrode additive, wherein the mass of the positive electrode additive accounts for 0.01-0.12% of the total mass of the first effective component.

2. The positive electrode active material according to claim 1, characterized in that, The cathode additive comprises a saturated alkyl chain containing an amino group.

3. The positive electrode active material according to claim 2, characterized in that, The grafting rate of the amino groups is 0.1-2%; and, or The saturated alkyl chain containing the amino group has 5-20 carbon atoms; and, or The number average molecular weight of the saturated alkyl chain containing the amino group is 1000-5000; and, or The boiling point of the saturated alkyl chain containing an amino group is less than or equal to 200°C.

4. The positive electrode active material according to claim 2, characterized in that, The saturated alkyl chain containing an amino group includes at least one of aminopentane, diaminopentane, aminoheptane, diaminoheptane, triaminoheptane, and aminoisoheptane.

5. The positive electrode active material according to any one of claims 2-4, characterized in that, The first effective component also includes the following components by mass percentage: The first active material is 93.49-98.99%; First conductive agent 0.6-3.2%; First adhesive: 0.5-3.4%.

6. The positive electrode active material according to claim 1, characterized in that, The positive electrode additive includes silane coupling agents containing double or triple bonds.

7. The positive electrode active material according to claim 6, characterized in that, The silane coupling agent includes at least one of vinylmethoxysilane coupling agent, propenylmethoxysilane coupling agent, butenylmethoxysilane coupling agent, ethynylmethoxysilane coupling agent, propynylmethoxysilane coupling agent, and butynylmethoxysilane coupling agent.

8. A positive electrode sheet, characterized in that, The positive electrode sheet includes a positive current collector and a first active material layer disposed on at least one side of the positive current collector, wherein the first active material layer includes the positive active material as described in any one of claims 1-7.

9. The positive electrode sheet according to claim 8, characterized in that, When the positive electrode is fully charged, it has a first thickness H1, and after being stored at 130°C for 1 hour, it has a second thickness H2. The first thickness H1 and the second thickness H2 satisfy the following relationship: 1.2≤H2 / H1≤4.

9.

10. The positive electrode sheet according to claim 8, characterized in that, The first active material layer and the positive electrode current collector have a first adhesive force F1 when cold-pressed, and the first active material layer and the positive electrode current collector have a second adhesive force F2 when stored at 130°C for 1 hour. The first adhesive force F1 and the second adhesive force F2 satisfy the following relationship: 10%F1≤F2≤25%F1.

11. The positive electrode sheet according to claim 8, characterized in that, The positive electrode sheet further includes a second active material layer, which is disposed on the side of the first active material layer away from the positive current collector. The second active material layer includes an active material.

12. The positive electrode sheet according to claim 11, characterized in that, The active material includes a second effective component, which includes a second active material, wherein the mass of the second active material accounts for 96.8-99.0% of the total mass of the second effective component.

13. The positive electrode sheet according to claim 12, characterized in that, The first active material of the first effective component has a first bulk density a1, and the second active material has a second bulk density a2; The first g / cm volumetric weight a1 and the second g / cm volumetric weight a2 satisfy the following relationship: 4.8≤a2 / a1≤21.

3.

14. The positive electrode sheet according to claim 13, characterized in that, The first gram has a bulk density of 180-200mAh / g; The second gram has a bulk density of 200-240 mAh / g.

15. The positive electrode sheet according to claim 11, characterized in that, The compaction density of the first active material layer is 4.0-4.5 g / cc; The compaction density of the second active material layer is 3.90-4.45 g / cc.

16. The positive electrode sheet according to claim 11, characterized in that, The first weight m1 per unit volume of the first active material layer and the second weight m2 per unit volume of the first active material layer satisfy the following relationship: 0.9≤m1 / m2≤4.

1.

17. The positive electrode sheet according to claim 16, characterized in that, The m1 concentration is 10.2-22.4 mg / cc; The m2 is 2.8-11.5 mg / cc.

18. A lithium-ion battery, characterized in that, It includes a negative electrode, an electrolyte, and a positive electrode as described in any one of claims 8-17.

19. The lithium-ion battery according to claim 18, characterized in that, The electrolyte includes a carboxylic acid ester, and the mass of the carboxylic acid ester accounts for 5-50% of the total mass of the electrolyte.

20. An electronic device, characterized in that, Including the lithium-ion battery as described in any one of claims 18-19.

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