Electrode, secondary battery, and electric device

Abstract

An electric device, the electric device comprising a secondary battery, and the secondary battery comprising an electrode. The electrode comprises a lithium supplementation layer. The lithium supplementation layer comprises a lithium supplementation agent and a conductive agent. The ratio of the sum of the surface areas of the conductive agent in the lithium supplementation layer to the sum of the surface areas of the lithium supplementation agent in the lithium supplementation layer is (0.5-5):1.

Description

Electrode, secondary battery and electrical equipment

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office of China on December 28, 2023, with application number 202311852256.0 and titled “Electrode, Secondary Battery and Electrical Equipment,” the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The present application relates to the field of battery technology, and in particular to electrodes, secondary batteries, and electrical equipment. Background Art

[0004] With the increasing popularity of new energy technologies, the market is placing higher demands on the energy density of lithium secondary batteries. To address this issue, the industry is opting for lithium replenishment. Lithium replenishers release active lithium ions during the initial charge to compensate for irreversible lithium loss and extend the battery's cycle life. Related technologies optimize the replenishment effect by providing a separate lithium replenishment layer within the electrode. However, existing lithium replenishment layers often exhibit poor conductivity, impacting the battery's rate performance.

[0005] Public content

[0006] In view of this, an embodiment of the present application provides an electrode, in which the sum of the surface areas of the lithium replenishing agent and the conductive agent in the lithium replenishing layer meet certain conditions, so that the lithium replenishing layer can achieve a good lithium replenishing effect while also having good conductivity.

[0007] In a first aspect, an embodiment of the present application provides an electrode, comprising a lithium replenishing layer; the lithium replenishing layer comprises a lithium replenishing agent and a conductive agent, and the ratio of the sum of the surface areas of the conductive agent in the lithium replenishing layer to the sum of the surface areas of the lithium replenishing agent in the lithium replenishing layer is (0.5-5):1.

[0008] By controlling the ratio of the sum of the surface areas of the conductive agent to the sum of the surface areas of the lithium replenisher within the range of (0.5-5):1, a conductive network can be constructed within the lithium replenisher layer, enhancing the electronic conductivity of the lithium replenisher layer and, in turn, improving the rate performance of the battery. Furthermore, the uniformity of the lithium replenisher layer can be improved, which helps to increase the mechanical strength of the lithium replenisher layer, thereby making it less likely to delaminate or peel from the electrode active material during the battery's charge and discharge cycles, thus benefiting the battery's cycle stability. Based on the inherent effects of the lithium replenisher, it can provide the battery with additional active lithium ions, compensating for the battery's irreversible active ion loss, increasing the battery's energy density, and extending the battery's cycle life.

[0009] In some embodiments, the ratio of the sum of the surface areas of the conductive agents to the sum of the surface areas of the lithium supplementing agents is (0.8-3):1.

[0010] In some embodiments, in the lithium replenishing layer, the mass percentage of the lithium replenishing agent is 40%-80%, and the mass percentage of the conductive agent is 1.5%-15%.

[0011] In some embodiments, in the lithium replenishing layer, the mass ratio of the conductive agent to the lithium replenishing agent is in the range of 1:(3-50).

[0012] Furthermore, the lithium replenishing layer further comprises a binder and a dispersant. In the lithium replenishing layer, the mass percentage of the binder is 2%-15%, and the mass percentage of the dispersant is 0.3%-10%.

[0013] In some embodiments, the D50 of the lithium supplement is in the range of 1 μm-15 μm.

[0014] In some embodiments, the conductive agent has at least one dimension less than or equal to 200 nm.

[0015] In some embodiments, the lithium replenishing layer satisfies the following conditions: the material of the lithium replenishing layer is dispersed in a solvent to obtain a slurry, and the slurry satisfies the following conditions: the room temperature viscosity change rate within 72 hours does not exceed 23%, and / or the backscattered light change rate of the slurry within 72 hours is less than 10%; wherein the solvent is selected from at least one of water, N-methylpyrrolidone, N,N-dimethylformamide, ethanol, isopropanol, acetone, tetrahydrofuran, dimethylformamide, toluene or n-hexane.

[0016] In some embodiments, the lithium supplement layer satisfies at least one of the following: (1) A slurry with a solid content of 10% is obtained by dispersing the material of the lithium supplement layer in a solvent, and the room temperature viscosity of the slurry is in the range of 150 mPa·s - 400 mPa·s; (2) A slurry with a solid content of 16% is obtained by dispersing the material of the lithium supplement layer in a solvent, and the room temperature viscosity of the slurry is in the range of 200 mPa·s - 500 mPa·s; (3) A slurry with a solid content of 20% is obtained by dispersing the material of the lithium supplement layer in a solvent, and the room temperature viscosity of the slurry is in the range of 300 mPa·s - 650 mPa·s; (4) A slurry with a solid content of 25% is obtained by dispersing the material of the lithium supplement layer in a solvent, and the room temperature viscosity of the slurry is in the range of 400 mPa·s - 1000 mPa·s; (5) A slurry with a solid content of 30% is obtained by dispersing the material of the lithium supplement layer in a solvent, and the room temperature viscosity of the slurry is in the range of 480 mPa·s - 1500 mPa·s; wherein, the solvent is selected from at least one of water, N-methylpyrrolidone, N,N-dimethylformamide, ethanol, isopropanol, acetone, tetrahydrofuran, dimethylformamide, toluene or n-hexane.

[0017] In some embodiments, the electrode further includes a current collector and an electrode material layer, and the lithium supplement layer, the electrode material layer and the current collector are stacked.

[0018] In some embodiments, the thickness of the lithium supplement layer is 1 μm - 15 μm, and the thickness of the electrode material layer is 40 μm - 120 μm.

[0019] In some embodiments, the electrode is a positive electrode.

[0020] In some embodiments, the lithium supplement agent includes Li x A y and at least one of metal oxides of lithium; wherein, x > 0, 0 < y ≤ 3, and element A includes at least one of C, N, O, P and S; the metal oxides of lithium include Li2M 1 O2, Li2M 2 O3, Li5Fe a M 3 1-a O4, Li6Mn b M 4 <, 1-b O4 and Li5M 5 O4; wherein, M 1 includes at least one of Ni, Mn, Cu, Fe, Cr and Mo; M 2 includes at least one of Ni, Mn, Fe, Mo, Zr, Si, Cu, Cr and Ru; M 3Including at least one of Al, Nb, Co, Mn, Ni, Mo, Ru and Cr, 0≤a≤1; M 4 Including at least one of Ni, Fe, Cu and Ru, 0≤b≤1; M 5 Contains at least one of Ni, Mn, Fe, Mo, Zr, Si, Cu and Cr; optionally, the Li x A y Including at least one of Li3N, Li2C2, Li2S, Li2O, Li2CO3, Li2C2O4 and Li3P.

[0021] In some embodiments, the conductive agent includes at least one of porous carbon, acetylene black, carbon nanotubes, carbon black, Ketjen black, graphene, and Mxenes.

[0022] A second aspect of the present application provides a secondary battery, comprising the electrode provided in the embodiments of the present application.

[0023] Due to the use of the electrode of the embodiment of the present application, the secondary battery can have a higher energy density, a longer cycle life and better rate performance.

[0024] In some embodiments, in the lithium replenishing layer after the delithiation of the electrode lithium replenishing agent, the mass percentage of the residue after the delithiation of the lithium replenishing agent is 40%-93%, and the mass percentage of the conductive agent is 5%-30%.

[0025] A third aspect of the present application provides an electrical device, comprising the secondary battery provided in the second aspect of the present application.

[0026] Since the secondary battery provided in the embodiment of the present application is used to power the electrical equipment, the electrical equipment has a strong endurance and can also have a certain fast charging performance, and has strong market competitiveness. DETAILED DESCRIPTION

[0027] An embodiment of the present application provides an electrode, including a lithium replenishing layer, the lithium replenishing layer including a lithium replenishing agent and a conductive agent, and the ratio of the sum of the surface areas of the conductive agent in the lithium replenishing layer to the sum of the surface areas of the lithium replenishing agent in the lithium replenishing layer is (0.5-5):1.

[0028] The ratio of the sum of the surface areas of all the conductive agents in the lithium replenishing layer to the sum of the surface areas of all the lithium replenishing agents in the lithium replenishing layer is controlled within the range of (0.5-5):1, so that the lithium replenishing agent and the conductive agent are in direct contact with each other and have sufficient contact area, and the surface of the lithium replenishing agent particles is coated with a sufficient amount of conductive agent to electrically connect the adjacent lithium replenishing agents, thereby forming a conductive network in the lithium replenishing layer, improving the electronic conductivity of the lithium replenishing layer, and thus improving the rate performance of the battery. In addition, controlling the surface area ratio of the two within the above range can improve the uniformity of the lithium replenishing layer, which is conducive to enhancing the mechanical strength of the lithium replenishing layer, thereby making it difficult to be peeled off, and not easy to be delaminated or peeled off from the electrode active material during the charge and discharge cycle of the battery, which is conducive to the cycle stability of the battery. Based on the inherent effect of the lithium replenishing agent, it can also provide additional active lithium ions for the battery, make up for the irreversible active ion loss of the battery, improve the energy density of the battery, and extend the cycle life of the battery.

[0029] Therefore, the electrode can be used to provide a battery with higher energy density, better rate performance and longer cycle life.

[0030] In the embodiment of the present application, a scanning laser particle size analyzer and a specific surface area analyzer can be used in combination to test the sum of the surface areas of the conductive agent and the lithium supplement agent, and further measure the ratio of the sum of the surface areas of the two. Specifically, the test process includes: taking a unit mass m (g) of lithium supplement layer material and placing it in a solvent to remove the binder that may be present in the lithium supplement layer, washing and drying the obtained solid and weighing the mass m1 of the solid, measuring the gas adsorption curve of the solid in a gas adsorption-desorption instrument, and calculating the specific surface area A (m2) of the unit mass of the lithium supplement layer material in combination with the BET model. 2 / g), then the total surface area of ​​the material of this part of the lithium replenishment layer is S=m1*A, the unit is m 2 The above solid in a laser particle size analyzer, to obtain a particle size distribution curve of the lithium supplement agent, which was integrated to obtain the surface area of ​​the lithium supplement agent S1 m 2 , then the sum of the surface areas of the conductive agents is S2=S-S1, and the ratio of the sum of the surface areas of the conductive agents to the sum of the surface areas of the lithium supplement is S2 / S1. It should also be noted that the above-mentioned solvents include but are not limited to at least one of N-methylpyrrolidone, N,N-dimethylformamide, ethanol, isopropanol, acetone, tetrahydrofuran, dimethylformamide, toluene or n-hexane, and those skilled in the art can choose according to actual conditions. The test conditions of the above-mentioned gas adsorption and desorption instrument are: during the test, the degassing time is maintained at ≥30min and the degassing temperature is ≥100°C, and the gas adsorption and desorption curve of the above-mentioned solid is obtained, and A is further obtained. In addition, the laser particle size analyzer will simultaneously measure the particle size distribution curves of the lithium supplement and the conductive agent, but the peaks of the particle size distribution curves of the lithium supplement and the conductive agent can be clearly distinguished. Generally, the particle size of the conductive agent will be significantly smaller than that of the lithium supplement.

[0031] In some embodiments of the present application, the electrode further comprises a current collector and an electrode material layer, and the lithium replenishing layer, the electrode material layer, and the current collector are stacked. In the embodiments of the present application, the current collector may be provided with stacked electrode material layers and lithium replenishing layers on both opposite sides of the current collector; or the current collector may be provided with stacked electrode material layers and lithium replenishing layers on one side, and the other side may be the electrode material layer, but the present invention is not limited thereto. In the embodiments of the present application, the lithium replenishing layer may be provided between the current collector and the electrode material layer, or the electrode material layer may be provided between the lithium replenishing layer and the current collector; or even the lithium replenishing layer and the electrode material layer may be alternately stacked, but the present invention is not limited thereto.

[0032] In the embodiments of the present application, the ratio of the sum of the surface areas of the conductive agent in the lithium replenishing layer to the sum of the surface areas of the lithium replenishing agent can be 0.5:1, 0.8:1, 1:1, 1.2:1, 1.5:1, 1.8:1, 2:1, 2.2:1, 2.5:1, 2.8:1, 3:1, 3.2:1, 3.5:1, 3.8:1, 4:1, 4.2:1, 4.5:1, 4.8:1, 5:1, etc. If the above ratio is too large or too small, it is not conducive to the adsorption and coating of the conductive agent on the surface of the lithium replenishing agent, making it impossible for the conductive agent to fully exert its conductive bridging effect on the lithium replenishing agent, thereby failing to build a conductive network in the lithium replenishing layer and failing to improve the electronic conductivity performance of the lithium replenishing layer.

[0033] In some embodiments of the present application, the ratio of the sum of the surface areas of the conductive agent in the lithium replenishing layer to the sum of the surface areas of the lithium replenishing agent in the lithium replenishing layer is (0.8-3): 1. For example, the ratio of the sum of the surface areas of the conductive agent in the lithium replenishing layer to the sum of the surface areas of the lithium replenishing agent in the lithium replenishing layer may be, but is not limited to, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3:1, etc. Further controlling the surface area ratio of the two within the above range will help improve the dispersion and adsorption of the conductive agent on the surface of the lithium supplement, further promoting the conductive agent's coating of the lithium supplement particles, reducing internal defects in the conductive network, and thus further improving the electronic conductivity of the lithium supplement layer. This characteristic can be reflected in the rate performance of the final battery. In addition, it can further improve the dispersion characteristics of the conductive agent and the lithium supplement, which also helps to further enhance the mechanical strength of the lithium supplement layer and the cycle stability of the battery.

[0034] In some embodiments of the present application, the D50 of the lithium supplement agent is within the range of 1 μm to 15 μm. In the present application, D50 refers to the particle size corresponding to when the cumulative particle size distribution percentage of the sample reaches 50%. Exemplarily, the D50 of the lithium supplement agent can be 1.0 μm, 2.0 μm, 5.0 μm, 8.0 μm, 10.0 μm, 12.0 μm, 15.0 μm, etc. Controlling the particle size of the lithium supplement agent within the above range is beneficial for the extraction of lithium ions, the regulation of the density (or porosity) of the lithium supplement layer, and can also ensure good mechanical strength of the lithium supplement layer. More importantly, it is beneficial for the coating of the conductive agent, thereby forming a more complete conductive network in the lithium supplement layer. In addition, considering that after delithiation, the lithium supplement agent will have a smaller particle size due to delithiation or cracking. Controlling the lithium supplement agent within the above range, the particle size of the residue after delithiation of the lithium supplement agent changes little, reducing the risk of voids in the lithium supplement layer affecting ion conduction and electron conduction, and further better reducing the conductivity after delithiation of the lithium supplement layer, which is beneficial for the rate performance of the battery. In the embodiments of the present application, the D50 of the lithium supplement agent can be measured by a laser particle size analyzer.

[0035] In some embodiments of the present application, the mass percentage content of the lithium supplement agent in the lithium supplement layer is 40% - 80%. Exemplarily, the mass percentage content of the lithium supplement agent in the lithium supplement layer can be 40%, 42%, 45%, 48%, 50%, 52%, 55%, 58%, 60%, 62%, 65%, 68%, 70%, 72%, 75%, 78%, etc. A suitable content of the lithium supplement agent can ensure the lithium supplement effect, and can also reserve enough share for other components (such as the conductive agent), making the lithium supplement layer have both good conductivity and mechanical strength, and controlling the ratio of the surface areas of the two in the lithium supplement layer within a suitable range.

[0036] In some embodiments of the present application, the lithium supplement agent includes but is not limited to at least one Li x A y and / or a metal oxide of lithium; wherein, x > 0, 0 < y ≤ 3, and element A includes at least one of C, N, O, P, and S; the metal oxide of lithium includes Li2M 1 O2, Li2M 2 O3, Li5Fe a M 3 1-a O4, Li6Mn b M 4 1-b O4, and Li5M 5 O4, and at least one of them. Wherein, M 1 includes at least one of Ni, Mn, Cu, Fe, Cr, and Mo; M 2 includes at least one of Ni, Mn, Fe, Mo, Zr, Si, Cu, Cr, and Ru; M 3Including at least one of Al, Nb, Co, Mn, Ni, Mo, Ru and Cr, 0≤a≤1; M 4 Including at least one of Ni, Fe, Cu and Ru, 0≤b≤1; M 5 Contains at least one of Ni, Mn, Fe, Mo, Zr, Si, Cu and Cr. x A y It can be but is not limited to Li3N, Li2C2, Li2S, Li2O, Li2CO3, Li2C2O4, Li3P, etc. The lithium supplement includes but is not limited to a mixture of the above substances.

[0037] In some specific embodiments, when the lithium replenishing layer is provided between the current collector and the electrode material layer, the lithium replenishing agent is selected from the above-mentioned lithium metal oxides. Further, in some specific embodiments, the above-mentioned lithium replenishing agent is selected from Li2M 1 O2、Li2M 2 O3、Li5Fe a M 3 1-a O4 and Li5M 5 At least one of O4. In this way, the residue after the lithium supplement is removed is the same as Li2M 1 O2、Li2M 2 O3、Li5Fe a M 3 1-a O4 and Li5M 5 O4 corresponding to M 1 、M 2 、M 3 、M 4 Oxides of metal elements are electrochemically inert. When combined with a conductive agent, they can form a conductive but non-lithium-intercalating electrochemically inert layer between the current collector and the electrode material layer. This can improve the safety performance of the battery and avoid hindering the transfer of lithium ions during the charge and discharge cycle, thereby improving the rate performance of the battery.

[0038] In some embodiments of the present application, the size of at least one dimension of the conductive agent is less than or equal to 200 nm. Exemplarily, the size of at least one dimension of the conductive agent can be 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 120 nm, 150 nm, 180 nm, 190 nm, etc. In this way, it is more conducive to the construction of the conductive network in the lithium replenishing layer, reducing the internal defects of the conductive network, and ensuring that the lithium replenishing layer maintains a low conductivity before and after delithiation. In the embodiment of the present application, the size of the conductive agent can be observed under a scanning electron microscope (SEM).

[0039] In some embodiments of the present application, the conductive agent includes but is not limited to porous carbon, acetylene black, carbon nanotubes, carbon black (e.g., Super P), Ketjen black, graphene, and MXenes. Among them, porous carbon includes but is not limited to at least one of nanoporous carbon and ordered porous carbon. In some specific embodiments, the conductive agent is selected from at least one of porous carbon having at least one dimension less than or equal to 200 nm, Super P, acetylene black, carbon nanotubes, carbon black, Ketjen black, graphene, and MXenes.

[0040] In some embodiments of the present application, the weight percentage of the conductive agent in the lithium replenishing layer is 1.5%-15%. For example, the weight percentage of the conductive agent in the lithium replenishing layer can be 1.5%, 2.0%, 3.0%, 5.0%, 8.0%, 10.0%, 11.0%, 12.0%, 13.0%, 14.0%, 14.5%, etc. An appropriate conductive agent content ensures good conductivity of the lithium replenishing layer and sufficient contact with the lithium replenishing agent, thereby establishing an optimal conductive network in the lithium replenishing layer.

[0041] In some embodiments of the present application, in the lithium replenishing layer, the mass ratio of the conductive agent to the lithium replenishing agent is in the range of 1: (3-50). In some specific embodiments, in the lithium replenishing layer, the mass ratio of the conductive agent to the lithium replenishing agent is in the range of 1: (5-20). When the sum of the surface areas of the conductive agent and the sum of the surface areas of the lithium replenishing agent are certain, the mass ratio of the two is controlled within the above range, and the surface area (or particle size) of the particles of the two needs to be controlled within a suitable range. In this way, the lithium replenishing agent particles can be more fully wrapped by the conductive agent and have good uniformity, so that the lithium replenishing layer can achieve an ideal lithium replenishing effect while taking into account better conductive properties, which is more conducive to the overall performance of the battery. Illustratively, the mass ratio of the conductive agent to the lithium supplement agent can be, but is not limited to, 1:3, 1:5, 1:8, 1:10, 1:12, 1:15, 1:18, 1:20, 1:22, 1:25, 1:28, 1:30, 1:32, 1:35, 1:38, 1:40, 1:42, 1:45, 1:48, 1:50, etc.

[0042] In some embodiments of the present application, the lithium replenishing layer also includes a binder. In some specific embodiments, the mass percentage of the binder in the lithium replenishing layer is 2%-15%. Exemplarily, the mass percentage of the binder in the lithium replenishing layer can be 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, etc. A suitable binder can ensure good structural stability of the lithium replenishing layer. It can be understood that in the commonly used embodiments in the field, the lithium replenishing layer is obtained by coating the lithium replenishing slurry on the surface of the current collector and / or electrode material layer, and an appropriate amount of binder is also conducive to the formation of the lithium replenishing layer.

[0043] In some embodiments of the present application, the binder includes but is not limited to at least one of polyvinylidene fluoride, polyvinyl alcohol, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylonitrile, polyacrylic acid, sodium alginate and styrene-butadiene rubber.

[0044] In some embodiments of the present application, the lithium replenishing layer also includes a dispersant. In some specific embodiments, the mass percentage of the dispersant in the lithium replenishing layer is 0.3%-10%. Exemplarily, the mass percentage of the dispersant in the lithium replenishing layer can be 0.3%, 0.5%, 1.0%, 2.0%, 5.0%, 8.0%, 10.0%, etc. An appropriate amount of dispersant helps to disperse the conductive agent and is more conducive to the construction of a conductive network in the lithium replenishing layer. In some specific embodiments, the mass of the dispersant is 5%-60% of the mass of the conductive agent. Exemplarily, the mass of the dispersant is 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, etc. of the mass of the conductive agent.

[0045] In some embodiments of the present application, the above-mentioned dispersant includes but is not limited to at least one of polyvinylpyrrolidone (abbreviated as PVP), sodium dodecyl sulfate (abbreviated as SDS), perfluoroalkyl ether alcohol amine salt, perfluoroalkyl ether quaternary ammonium salt, hexadecyltrimethylammonium bromide (abbreviated as CTAB), dodecyltrimethylammonium bromide and dodecylpyridinium bromide.

[0046] In some embodiments of the present application, the lithium replenishing layer includes 40%-80% by weight of a lithium replenishing agent, 1.5%-15% by weight of a conductive agent, 2%-15% by weight of a binder, and 0.3%-10% by weight of a dispersant.

[0047] It can be understood that, similar to the electrode material layer, the lithium replenishing layer can also be prepared by a wet method. In other words, the lithium replenishing layer can be obtained by coating the lithium replenishing slurry on the surface of the current collector and / or the electrode material layer, and then drying it. In order to improve the uniformity of the lithium replenishing layer, the thickness and porosity are adjusted to be within a more suitable range, and the characteristics of the lithium replenishing slurry can be further controlled within a suitable range. Since the lithium replenishing layer is obtained by drying the lithium replenishing slurry, then, by scraping a certain amount of the lithium replenishing layer and dispersing it in a solvent, the original lithium replenishing slurry can be restored. Specifically, the material scraped from the lithium replenishing layer is dispersed in a solvent to prepare slurries with different solid contents, which are tested using a rheometer at a shear rate of 50 / s at 25°C to test the viscosity of each slurry. The room temperature viscosity of the slurry with a solid content of 10% is within the range of 150mPa·s-400mPa·s; the room temperature viscosity of the slurry with a solid content of 16% is within the range of 200mPa·s-500mPa·s; the room temperature viscosity of the slurry with a solid content of 20% is within the range of 300mPa·s-650mPa·s; the room temperature viscosity of the slurry with a solid content of 25% is within the range of 400mPa·s-1000mPa·s; the room temperature viscosity of the slurry with a solid content of 30% is within the range of 480mPa·s-1500mPa·s. In the embodiment of the present application, the above-mentioned solvent can be at least one of water, N-methylpyrrolidone, N,N-dimethylformamide, ethanol, isopropanol, acetone, tetrahydrofuran, dimethylformamide, toluene or n-hexane.

[0048] For example, the material of the lithium replenishing layer is dispersed in a solvent to obtain a slurry, and the room temperature viscosity of the slurry with a solid content of 10% may be, but is not limited to, 150mPa·s, 180mPa·s, 200mPa·s, 250mPa·s, 300mPa·s, 350mPa·s, 380mPa·s, and 400mPa·s; the room temperature viscosity of the slurry with a solid content of 16% may be, but is not limited to, 200mPa·s, 250mPa·s, 300mPa·s, 350mPa·s, 400mPa·s, 450mPa·s, and 500mPa·s; the room temperature viscosity of the slurry with a solid content of 20% may be, but is not limited to, 300mPa·s, 350mPa·s, 400mPa·s, 450mPa·s, 500mPa·s, 550mPa·s, and 600mPa·s. The room temperature viscosity of the slurry with a solid content of 25% may be, but is not limited to, 400mPa·s, 450mPa·s, 500mPa·s, 550mPa·s, 600mPa·s, 650mPa·s, 700mPa·s, 750mPa·s, 800mPa·s, 850mPa·s, 900mPa·s, 950mPa·s, 10 00mPa·s; the room temperature viscosity of the slurry with a solid content of 30% can be but is not limited to 480mPa·s, 500mPa·s, 600mPa·s, 700mPa·s, 800mPa·s, 900mPa·s, 1000mPa·s, 1100mPa·s, 1200mPa·s, 1300mPa·s, 1400mPa·s, and 1500mPa·s.

[0049] In some embodiments of the present application, the room temperature viscosity change rate of the slurry within 72 hours does not exceed 23%, and the backscattered light change rate is less than 10%. That is, within 72 hours after the lithium-supplemented slurry is prepared, its room temperature viscosity change rate does not exceed 23%, and the backscattered light change rate is less than 10%. For example, when the lithium-supplemented slurry is prepared, its viscosity is A0, and its backscattered light intensity measured by a multiple light scattering instrument is B0; when the lithium-supplemented slurry is placed at room temperature for 72 hours, its viscosity is A1, and its backscattered light intensity measured by a multiple light scattering instrument is B1. Room temperature viscosity change rate = (A0-A1) / A0. Backscattered light change rate = (B0-B1) / B0. Exemplarily, the room temperature viscosity change rate of the slurry within 72 hours can be 1%, 2%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 21%, 22%, etc. For example, the backscattered light change rate of the slurry within 72 hours can be 0.1%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, 9.5%, etc. This illustrates the composition of the lithium replenishing layer of the embodiment of the present application. When it exists in the form of a slurry, it can remain stable for a long time, is not easy to settle, is more conducive to preparation, and reduces production costs.

[0050] It should be noted that the "room temperature" in the examples of the present application refers to the ambient temperature when the slurry is prepared. In the examples of the present application, in most cases, the room temperature is 25±2°C.

[0051] In some embodiments of the present application, the thickness of the lithium replenishing layer is 1 μm-15 μm. Specifically, when the lithium replenishing layer is provided on both opposing surfaces of the electrode, the thickness of each lithium replenishing layer is 1 μm-15 μm. For example, the thickness of the lithium replenishing layer can be 1 μm, 2 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, etc. Controlling the thickness of the lithium replenishing layer within the above range is conducive to controlling the lithium replenishment amount of the electrode within an appropriate range.

[0052] In some embodiments of the present application, the porosity of the lithium replenishment layer is in the range of 18%-40%. In this way, in a liquid secondary battery using an electrolyte, it is beneficial for the infiltration of the electrolyte, making the transmission of active lithium ions smoother (that is, it is beneficial for the performance of the lithium replenishment agent), and the impedance of the lithium replenishment layer can be controlled within an appropriate range. For example, the porosity of the lithium replenishment layer can be 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, etc.

[0053] In some embodiments of the present application, the thickness of the electrode material layer is 40μm-120μm. Specifically, when the electrode material layer is provided on both sides of the electrode, the thickness of the single electrode material layer is 40μm-120μm. Exemplarily, the thickness of the electrode material layer can be 40μm, 50μm, 60μm, 70μm, 80μm, 90μm, 100μm, 110μm, 120μm, etc. Taking into account the thickness of the lithium replenishing layer and the use of the electrode, controlling the thickness of the electrode material within the above range is beneficial to the performance of the lithium replenishing agent and the battery performance, especially to the volume energy density of the battery.

[0054] It can be understood that the electrode material layer includes electrode materials. In some embodiments of the present application, in the electrode, the mass ratio of the lithium supplement agent to the electrode material is (0.8-10):100. Exemplarily, the mass ratio of the lithium supplement agent to the electrode material can be 0.8:100, 1:100, 1:50, 3:100, 1:25, 1:20, 3:50, 7:100, 2:25, 9:100, etc. Controlling the ratio of the two within the above range is beneficial to the final battery performance, and those skilled in the art can make a selection according to actual needs.

[0055] In some embodiments of the present application, the electrode is a positive electrode; and the electrode material layer includes a positive electrode material.

[0056] In the embodiment of the present application, the positive electrode material layer includes a positive electrode material, a binder, and a conductive agent. The positive electrode material, binder, and conductive agent can be selected from any materials known in the art, and those skilled in the art can select them according to application requirements.

[0057] In the embodiments of the present application, the current collector of the positive electrode can be any current collector for the positive electrode of a lithium secondary battery known in the art, and the present application does not impose any limitation thereto.

[0058] The present invention also provides a secondary battery comprising the electrodes provided in the present invention. The secondary battery can be either a liquid battery or a solid-state battery. Due to the use of the electrodes provided in the present invention, the secondary battery can achieve high energy density, long cycle life, and good rate performance.

[0059] In some embodiments of the present application, the secondary battery includes a positive electrode, a negative electrode plate, and a separator and electrolyte disposed between the positive and negative electrode plates. In the embodiments of the present application, the negative electrode plate is any negative electrode plate known in the art, and the present application does not impose any limitation thereto.

[0060] It is understandable that the lithium replenisher will be fully or partially delithiated during the formation process of the battery. In the subsequent charge and discharge cycle process, the original lithium replenisher is converted into the residue of the lithium replenisher, and the lithium replenisher layer is correspondingly converted into a material layer including the residue of the lithium replenisher and the conductive agent. Although the lithium replenisher has been decomposed, in view of the special design of the embodiment of the present application, the structure of the lithium replenisher layer will not change significantly before / after delithiation, and in the lithium replenisher layer after delithiation, the ratio of the sum of the surface areas of the conductive agent and the sum of the surface areas of the lithium replenisher residues still satisfies (0.5-5):1, and the conductive agent can still form a conductive network in the above-mentioned material layer, ensuring that the lithium replenisher layer after delithiation can still transmit electrons faster, so that the battery has better rate performance. Correspondingly, in some specific embodiments, in the electrodes of the secondary battery, the ratio of the sum of the surface areas of the conductive agent and the sum of the surface areas of the lithium replenisher residues is in the range of (0.8-3):1. In some embodiments of the present application, in the lithium replenishing layer after delithiation, the weight percentage of the residual lithium replenishing agent is 40%-93%, and the weight percentage of the conductive agent is 5%-30%. For example, the weight percentage of the residual lithium replenishing agent can be 40%, 42%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, 92%, 93%, etc. For example, the weight percentage of the conductive agent can be 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, etc.

[0061] In the embodiment of the present application, the method for determining the ratio of the surface area of ​​the lithium replenishing agent residue and the conductive agent in the lithium replenishing layer after delithiation is the same as the test method for the ratio of the sum of the surface areas of the conductive agent in the lithium replenishing layer to the sum of the surface areas of the lithium replenishing agent in the previous text.

[0062] The present invention also provides an electrical device including the secondary battery provided in the present invention. Since the electrical device is powered by the secondary battery provided in the present invention, the electrical device has a long battery life and can also have a certain fast charging performance, making it highly competitive in the market.

[0063] In some embodiments of the present application, the above-mentioned electrical equipment includes but is not limited to 3C electronic equipment, power vehicles, etc. Power vehicles include but are not limited to new energy vehicles, power-assisted bicycles, etc.

[0064] The technical solution of this application is further illustrated below with multiple embodiments.

[0065] Example 1

[0066] The positive electrode includes a current collector (specifically aluminum foil) and a lithium replenishing layer and a positive electrode material layer stacked sequentially on the current collector surface. The lithium replenishing layer has a single layer thickness of 3 μm, and the positive electrode material layer has a single layer thickness of 88 μm.

[0067] The lithium-replenishing layer comprises 75.5 wt.% of a lithium-replenishing agent (specifically Li₅FeO₄), 4.2 wt.% of a conductive agent (specifically acetylene black), 14.5 wt.% of a binder (specifically polyvinylidene fluoride), and 5.8 wt.% of a dispersant (specifically PVP). The acetylene black has a particle size distribution of 25 nm to 125 nm, the D50 of the lithium-replenishing agent is 5 μm, and the ratio of the sum of the surface areas of the conductive agent to the sum of the surface areas of the lithium-replenishing agent is 2.0. The residue left after the lithium-replenishing agent is removed accounts for 67.95% of the mass of the lithium-replenishing layer after delithiation.

[0068] The preparation method of the positive electrode comprises:

[0069] (1) Preparation of conductive paste: Weigh a conductive agent (specifically acetylene black) and a dispersant (specifically PVP), dissolve them in a solvent, and mill them in a ball mill to prepare a conductive agent mother solution with a mass fraction of 20 wt%.

[0070] (2) Preparation of adhesive solution: Weigh the adhesive (specifically polyvinylidene fluoride) and sprinkle it into the solvent several times, stirring for 5 minutes each time until the addition is complete, to prepare an adhesive solution with a mass fraction of 10 wt%.

[0071] (3) Preparation of conductive adhesive: According to the proportion of the conductive agent, binder and dispersant in the lithium replenishing layer, a certain amount of the conductive paste of step (1) and the binder adhesive of step (2) are measured and stirred for 20 to 60 minutes to obtain the conductive adhesive.

[0072] (4) Preparation of lithium replenishing slurry: According to the proportion of lithium replenishing agent, conductive agent, binder and dispersant in the lithium replenishing layer, a certain amount of lithium replenishing agent is weighed and added to the conductive glue prepared in step (3) and stirred.

[0073] Example 2

[0074] The only difference from Example 1 is that the particle size D50 of the lithium supplement agent is 10 μm, and the ratio of the sum of the surface areas of the conductive agent to the sum of the surface areas of the lithium supplement agent is 2.8.

[0075] Example 3

[0076] The only difference from Example 1 is that the particle size D50 of the lithium supplement agent is 4 μm, and the ratio of the sum of the surface areas of the conductive agent to the sum of the surface areas of the lithium supplement agent is 1.5.

[0077] Example 4

[0078] The only difference from Example 1 is that the D50 of the lithium supplement agent is 3 μm, and the ratio of the sum of the surface areas of the conductive agent to the sum of the surface areas of the lithium supplement agent is 1.2.

[0079] Example 5

[0080] The difference from Example 1 is that the conductive agent is replaced by graphite with a particle size distribution of 220 nm-300 nm, and the ratio of the sum of the surface areas of the conductive agents to the sum of the surface areas of the lithium supplementing agents is 0.6.

[0081] Example 6

[0082] The difference from Example 1 is that the lithium replenishing layer comprises 95.3 wt.% of a lithium replenishing agent, 1.2 wt.% of a conductive agent, 2.5 wt.% of a binder, and 1 wt.% of a dispersant. The ratio of the total surface area of ​​the conductive agent to the total surface area of ​​the lithium replenishing agent is 0.5. The residue after the lithium replenishing agent is removed accounts for 85.77% of the mass of the lithium replenishing layer after delithiation.

[0083] Example 7

[0084] The difference from Example 1 is that the thickness of the lithium replenishing layer is 16 μm, and the thickness of the positive electrode material layer is 125 μm.

[0085] Example 8

[0086] The difference from Example 2 is that the mass content of the lithium replenisher is 78.1%, the mass content of the conductive agent is 1.6%, the ratio of the total surface area of ​​the conductive agent to the total surface area of ​​the lithium replenisher is 0.8, and the mass of the residue after the lithium replenisher is removed accounts for 70.29% of the lithium replenisher layer after delithiation.

[0087] Example 9

[0088] The only difference from Example 1 is that in the lithium replenishing layer, the particle size of acetylene black is distributed in the range of 120-200 nm, the particle size D50 of the lithium replenishing agent is 1.0 μm, and the surface area ratio of the conductive agent to the lithium replenishing agent is 0.6.

[0089] In order to highlight the beneficial effects of the embodiments of the present application, the following comparative examples are provided.

[0090] Comparative Example 1

[0091] The only difference from Example 1 is that the lithium replenishing layer is replaced by a conductive layer with a thickness of 3 μm, and the conductive layer includes a conductive agent, a binder and a dispersant in a mass ratio of 1:2:0.8.

[0092] Comparative Example 2

[0093] The only difference from Example 1 is that in the lithium replenishing layer, the particle size of acetylene black is distributed in the range of 20-40 nm, the particle size D50 of the lithium replenishing agent is 20 μm, and the surface area ratio of the conductive agent to the lithium replenishing agent is 14.

[0094] Comparative Example 3

[0095] The only difference from Example 1 is that the particle size D50 of the lithium supplement agent is 5 μm, the particle size distribution of the conductive agent is 220-500 nm, and the ratio of the total surface area of ​​the conductive agent to the total surface area of ​​the lithium supplement agent is 0.4.

[0096] Performance Testing

[0097] (1) The lithium-replenishing layer material from each positive electrode was scraped and dispersed in N-methylpyrrolidone to prepare a slurry with a solid content of 10%. The viscosity of each slurry was tested using a rheometer at a shear rate of 50 / s at 25°C. The solid content of the slurry was tested using the loss on drying method. A portion of the slurry was dried at 160°C until the dry weight remained constant, then weighed and the solid content was calculated.

[0098] (2) Test of the change rate of backlight scattered light: measured using a multiple light scattering instrument.

[0099] (3) Peel strength test of positive electrode: Using a universal tensile testing machine, each positive electrode was cut into strips with a width of 40 mm and a length of 150 to 200 mm. The peeling angle was set at 180° and the peel strength test was performed.

[0100] (4) Electrochemical performance test:

[0101] Preparation of test cells: The positive electrodes of the above-mentioned embodiments and comparative values ​​were assembled with negative electrode sheets to form test cells. The negative electrode sheets included a current collector (specifically copper foil) and a negative electrode material layer disposed on the surface of the current collector. The negative electrode material layer consisted of graphite, a conductive agent, and a binder in a mass ratio of 95:3:2. The electrolyte was a 1.2 mol / L lithium hexafluorophosphate organic solution, in which the solvent was an EC:DMC:EMC solution in a mass ratio of 1:1:1. After formation, test cells of the embodiments and comparative values ​​were obtained. The formation process was as follows: charging at 0.05C for 3 hours, standing for 10 minutes, and then charging at 0.2C to 3.8V.

[0102] In the present application, the residue after delithiation refers to the residue of the lithium supplement agent after the battery undergoes the above-mentioned formation process.

[0103] Rate performance test: The discharge capacity in grams of each battery was tested at different rates, such as 0.5C and 3C, as a function of cycle number at 25°C, with a voltage range of 2.5V-3.8V. When calculating the capacity in grams, the ratio of the discharge capacity at a certain current density to the mass of the positive electrode active material can be used as the discharge capacity in grams at that current density. Table 1 summarizes the ratio of the first-cycle discharge capacity at 3C to the first-cycle discharge capacity at 0.5C (3C / 0.5C) for each battery.

[0104] Cycle life: The battery was tested at 25±1°C under a charge-discharge cycle rate of 0.33C charge and 0.5C discharge. The procedure was as follows: 10 minutes of idling, followed by 0.5C constant current charge to 3.8V, constant voltage charge to 0.05C cutoff, 10 minutes of idling, and 0.5C constant power discharge to 2.5V. This cycle was repeated. The number of cycles required for a capacity retention rate of 80% was the battery's cycle life.

[0105] Energy density: Furthermore, each battery was charged and discharged at the aforementioned 0.1C constant current to generate a charge-discharge curve. The discharge curve was integrated and divided by the initial discharge capacity to obtain the average voltage of each battery, i.e., the charge-discharge voltage platform. The gravimetric energy density of each battery was then calculated using the formula: Gravimetric energy density = fractional capacity × average voltage platform / battery weight.

[0106] The results are summarized in Table 1.

[0107] Table 1

[0108] It can be seen from the data in Table 1 that the electrodes provided in the examples of the present application can effectively improve the comprehensive electrochemical performance of the final battery.

[0109] The above is an exemplary embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made thereto without departing from the principles of the present application. These improvements and modifications are also considered to be within the scope of protection of the present application.

Claims

1. An electrode, characterized in that, It includes a lithium supplement layer; Among them, the lithium supplement layer includes a lithium supplement agent and a conductive agent, and the ratio of the sum of the surface areas of the conductive agent in the lithium supplement layer to the sum of the surface areas of the lithium supplement agent in the lithium supplement layer is (0.5 - 5):

1.

2. The electrode according to claim 1, wherein The ratio of the sum of the surface areas of the conductive agent to the sum of the surface areas of the lithium supplement agent is (0.8 - 3):

1.

3. The electrode according to claim 1 or 2, characterized in that, In the lithium supplement layer, the mass percentage content of the lithium supplement agent is 40% - 80%, and the mass percentage content of the conductive agent is 1.5% - 15%.

4. The electrode according to any one of claims 1 to 3, characterized in that In the lithium supplement layer, the mass ratio of the conductive agent to the lithium supplement agent is in the range of 1:(3 - 50).

5. The electrode according to any one of claims 1-4, characterized in that, The lithium supplement layer further includes a binder and a dispersant. In the lithium supplement layer, the mass percentage content of the binder is 2% - 15%, and the mass percentage content of the dispersant is 0.3% - 10%.

6. The electrode according to any one of claims 1-5, characterized in that The D50 of the lithium supplement agent is in the range of 1μm - 15μm.

7. The electrode according to any one of claims 1-6, characterized in that, At least one dimension of the conductive agent is less than or equal to 200nm.

8. The electrode according to any one of claims 1-7, characterized in that, The lithium supplement layer satisfies: taking the material of the lithium supplement layer and dispersing it in a solvent to obtain a slurry, and the slurry satisfies: The room temperature viscosity change rate within 72h does not exceed 23%; and / or The backscattered light change rate of the slurry within 72h is less than 10%; where the solvent is selected from at least one of water, N-methylpyrrolidone, N,N-dimethylformamide, ethanol, isopropanol, acetone, tetrahydrofuran, dimethylformamide, toluene or n-hexane.

9. The electrode according to any one of claims 1-8, characterized in that, The lithium supplement layer satisfies at least one of the following: (1) Taking the material of the lithium supplement layer and dispersing it in a solvent to obtain a slurry with a solid content of 10%, and the room temperature viscosity of the slurry is in the range of 150mPa·s - 400mPa·s; (2) Taking the material of the lithium supplement layer and dispersing it in a solvent to obtain a slurry with a solid content of 16%, and the room temperature viscosity of the slurry is in the range of 200mPa·s - 500mPa·s; (3) Taking the material of the lithium supplement layer and dispersing it in a solvent to obtain a slurry with a solid content of 20%, and the room temperature viscosity of the slurry is in the range of 300mPa·s - 650mPa·s; (4) Taking the material of the lithium supplement layer and dispersing it in a solvent to obtain a slurry with a solid content of 25%, and the room temperature viscosity of the slurry is in the range of 400mPa·s - 1000mPa·s; (5) Taking the material of the lithium supplement layer and dispersing it in a solvent to obtain a slurry with a solid content of 30%, and the room temperature viscosity of the slurry is in the range of 480mPa·s - 1500mPa·s; Where the solvent is selected from at least one of water, N-methylpyrrolidone, N,N-dimethylformamide, ethanol, isopropanol, acetone, tetrahydrofuran, dimethylformamide, toluene or n-hexane.

10. The electrode according to any one of claims 1-9, characterized in that, The electrode further includes a current collector and an electrode material layer, and the lithium supplement layer, the electrode material layer and the current collector are stacked.

11. The electrode according to claim 10, wherein The thickness of the lithium supplement layer is 1μm - 15μm, and the thickness of the electrode material layer is 40μm - 120μm.

12. The electrode according to any one of claims 1-11, characterized in that, The electrode is a positive electrode.

13. The electrode according to any one of claims 1-12, characterized in that, The lithium supplement includes Li x A y and at least one of metal oxides of lithium; wherein, x > 0, 0 < y ≤ 3, and element A includes at least one of C, N, O, P, and S; the metal oxides of lithium include Li2M 1 O2, Li2M 2 O3, Li5Fe a M 3 1-a O4, Li6Mn b M 4 1-b O4, and Li5M 5 O4; wherein, M 1 includes at least one of Ni, Mn, Cu, Fe, Cr, and Mo; M 2 includes at least one of Ni, Mn, Fe, Mo, Zr, Si, Cu, Cr, and Ru; M 3 includes at least one of Al, Nb, Co, Mn, Ni, Mo, Ru, and Cr, 0 ≤ a ≤ 1; M 4 includes at least one of Ni, Fe, Cu, and Ru, 0 ≤ b ≤ 1; M 5 contains at least one of Ni, Mn, Fe, Mo, Zr, Si, Cu, and Cr; Optionally, the Li x A y comprises at least one of Li3N, Li2C2, Li2S, Li2O, Li2CO3, Li2C2O4 and Li3P.

14. The electrode according to any one of claims 1-13, characterized in that, The conductive agent includes at least one of porous carbon, acetylene black, carbon nanotubes, carbon black, Ketjen black, graphene and Mxenes.

15. A secondary battery, characterized in that, Comprising the electrode according to any one of claims 1-14.

16. The secondary battery according to claim 15, wherein In the lithium supplement layer after delithiation of the lithium supplement agent of the electrode, the mass percentage of the residue after delithiation of the lithium supplement agent is 40%-93%, and the mass percentage of the conductive agent is 5%-30%.

17. An electrical device, characterized in that, The electrical device comprises the secondary battery according to claim 15 or 16.

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