Pre-lithiation assembly, positive electrode, secondary battery and electrical device

Abstract

Provided are a pre-lithiation assembly, and a corresponding positive electrode, secondary battery and electrical device. The pre-lithiation assembly comprises a current collector and a pre-lithiation layer arranged on the surface of at least one side of the current collector; after delithiation of the pre-lithiation layer, the room temperature resistivity of the pre-lithiation assembly is 2 Ω·m-2000 Ω·m. The pre-lithiation assembly not only has a pre-lithiation effect, but also can maintain a lower resistivity after delithiation of the pre-lithiation layer, thus improving the energy density of batteries while ensuring the rate capability of the batteries.

Description

Lithium replenishment components, positive electrodes, secondary batteries and electrical equipment

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on December 28, 2023, with application number 202311862222X and application name “Lithium Supplement Component, Positive Electrode, Secondary Battery and Electrical Equipment”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of battery technology, and in particular to lithium supplement components, positive electrodes, secondary batteries and electrical equipment. Background Art

[0003] Lithium replenishment technology is an effective means to effectively increase battery energy density while improving battery cycle life and storage performance. Positive electrode lithium replenishment is favored due to its advantages such as stability, low price, and easy synthesis. If the positive electrode lithium replenisher is directly mixed into the positive electrode material layer, the positive electrode lithium replenisher will have residues after releasing active lithium ions, affecting ion transmission, or the lithium replenisher will produce gas during decomposition, affecting the structural stability of the active material layer, which is not conducive to the subsequent battery performance. If an independent lithium replenishment layer is set in the positive electrode, the resistivity of the positive electrode lithium replenisher is still high after delithiation, which will affect the electron transfer rate of the current path in the battery, thereby being detrimental to the battery's rate performance. In addition, the resistivity of the lithium replenisher layer after delithiation is high, so it is necessary to coat a conductive carbon layer on the current collector surface to improve the electrical conductivity of the electrode, which not only increases the cost but also affects the energy density of the battery. Summary of the Invention

[0004] In view of this, the embodiments of the present application provide a lithium replenishing component, a positive electrode, a secondary battery and an electrical device, which not only have a lithium replenishing effect, but also can maintain a low resistivity after the lithium replenishing layer is delithiated, thereby improving the battery energy density while taking into account the battery rate performance.

[0005] In a first aspect, the present application discloses a lithium replenishment component, comprising a current collector and a lithium replenishment layer disposed on at least one surface of the current collector; after the lithium replenishment layer is delithiated, the room temperature resistivity of the lithium replenishment component is 2Ω·m-2000Ω·m.

[0006] In a second aspect, the present application discloses a positive electrode, comprising the lithium replenishing component disclosed in the first aspect of the present application and a positive electrode material layer, wherein the positive electrode material layer is provided on a surface of the lithium replenishing layer facing away from the current collector.

[0007] In a third aspect, the present application discloses a secondary battery, comprising the positive electrode disclosed in the second aspect of the present application.

[0008] In a fourth aspect, the present application discloses an electrical device, including the secondary battery disclosed in the third aspect of the present application.

[0009] Combined with the above technical solutions, the lithium-supplementing assembly of the present application maintains good electronic conductivity after delithiation and also facilitates ion transport, thereby enabling the electrode to fully demonstrate its performance during the battery's charge and discharge cycles, especially its rate performance. Furthermore, the lithium-supplementing layer in the lithium-supplementing assembly has a lithium-supplementing effect, which can improve the battery's energy density and cycle life. DETAILED DESCRIPTION

[0010] An embodiment of the present application provides a lithium replenishment component, comprising a current collector and a lithium replenishment layer disposed on at least one surface of the current collector; after the lithium replenishment layer is delithiated, the room temperature resistivity of the lithium replenishment component is 2Ω·m-2000Ω·m.

[0011] The lithium replenishment component provided in the embodiment of the present application has a resistivity that can still be controlled within the range of 2Ω·m-2000Ω·m after the lithium replenishment layer is delithiated. It has good electronic conductivity and can support the electrode to fully exert its performance during the battery charge and discharge cycle. The lithium replenishment layer in the above lithium replenishment component has a lithium replenishment effect and can improve the energy density and cycle performance of the battery; after delithiation, it can also serve as a conductive layer. Compared with the battery using a pole piece with a lithium replenishment layer in the prior art, it can not only improve the rate performance, but also eliminate the need to set an additional conductive layer on the current collector surface (for example, instead of a carbon-coated foil), which is more conducive to improving the energy density of the battery. It can also make the resistivity of the final pole piece sufficiently low, reduce the internal resistance of the battery, and facilitate the performance of the battery.

[0012] In the embodiments of the present application, the lithium replenishment layer can be provided on a single surface of the current collector, or on two opposite surfaces of the current collector. In the embodiments of the present application, the lithium replenishment component can be used in a positive electrode. In the embodiments of the present application, the current collector in the lithium replenishment component can be any known current collector for lithium-ion batteries in the art. When used in a positive electrode, a current collector suitable for lithium secondary battery positive electrodes, such as aluminum foil, can be selected.

[0013] In the embodiments of the present application, room temperature refers to the ambient temperature when the resistivity is tested. In more cases, room temperature in the embodiments of the present application refers to 25±2°C.

[0014] In the embodiment of the present application, the room temperature resistivity of the lithium replenishing component after delithiation is measured by a two-electrode method. Specifically, the positive electrode and the negative electrode including the lithium replenishing component are assembled into a battery, wherein the negative electrode includes a current collector (specifically copper foil) and a negative electrode material layer arranged on the surface of the current collector, the negative electrode material layer is composed of graphite, a conductive agent and a binder with a mass ratio of 95:3:2, and the electrolyte is an organic solution of lithium hexafluorophosphate with a concentration of 1.2 mol / L, wherein the solvent is EC:DMC:EMC with a mass ratio of 1:1:1:. The battery is formed, and the formation process includes: charging at 0.05C for 3h, standing for 10min, and then charging at 0.2C to 3.8V. After formation, the battery is discharged to an SOC of 0, the positive electrode is disassembled, and the positive electrode is placed in a solvent dimethyl carbonate (DMC) and soaked for 10min-20min, and the positive electrode material is removed (for example, when the positive electrode includes a lithium replenishing component and a positive electrode material layer, the positive electrode material layer is removed) to obtain a lithium replenishing component after delithiation. The resistivity of the lithium-supplemented component after delithiation is tested: the lithium-supplemented component after delithiation is placed between two upper and lower electrodes (the two surfaces of the lithium-supplemented component in the thickness direction after delithiation are directly opposite the two electrodes). After applying a pressure of 25 MPa to the electrodes, a certain current is applied. The voltage across the electrodes is measured to calculate the resistance of the sample. The lithium content of the lithium-supplemented agent in the lithium-supplemented layer is 10-25% of the lithium content of the original lithium-supplemented agent. The room temperature resistivity of the lithium-supplemented component after delithiation is obtained. In this application, the specific method for delithiation of the lithium-supplemented layer can also be carried out with reference to the above steps for obtaining the lithium-supplemented component after delithiation.

[0015] In the embodiment of the present application, after the lithium replenishing layer is delithiated, the room temperature resistivity of the lithium replenishing component (that is, the lithium replenishing component after delithiation) can be 2Ω·m, 5Ω·m, 10Ω·m, 15Ω·m, 20Ω·m, 25Ω·m, 30Ω·m, 50Ω·m, 100Ω·m, 200Ω·m, 300Ω·m, 500Ω·m, 1000Ω·m, 1100Ω·m, 1200Ω·m, 1300Ω·m, 1400Ω·m, 1500Ω·m, 1800Ω·m, 2000Ω·m, etc. It can be understood that if the above resistivity is too high, it will affect the performance of the battery. At this time, the corresponding room temperature resistivity of the lithium replenishing component (that is, the lithium replenishing component before delithiation) is 1Ω·cm-500Ω·cm.

[0016] In some embodiments of the present application, after the lithium replenishment layer is delithiated, the room temperature resistivity of the lithium replenishment component (that is, the lithium replenishment component after delithiation) is 2Ω·m-1000Ω·m. For example, the room temperature resistivity of the lithium replenishment component after delithiation can be 2Ω·m, 10Ω·m, 100Ω·m, 200Ω·m, 300Ω·m, 400Ω·m, 500Ω·m, 600Ω·m, 700Ω·m, 800Ω·m, 900Ω·m, etc. In this way, it is more conducive to the rate performance of the battery. Correspondingly, the room temperature resistivity of the lithium replenishment component (that is, the lithium replenishment component before delithiation) is 1Ω·cm-300Ω·cm. Illustratively, the room temperature resistivity of the lithium-supplemented component before delithiation may be 5Ω·cm, 10Ω·cm, 20Ω·cm, 50Ω·cm, 100Ω·cm, 150Ω·cm, 200Ω·cm, 220Ω·cm, 250Ω·cm, 260Ω·cm, 280Ω·cm, 300Ω·cm, etc.

[0017] In some specific embodiments of the present application, after the lithium replenishment layer is delithiated, the room temperature resistivity of the lithium replenishment component (i.e., the lithium replenishment component after delithiation) is 5Ω·m-800Ω·m. For example, the room temperature resistivity of the lithium replenishment component after delithiation can be 5Ω·cm, 10Ω·cm, 20Ω·cm, 50Ω·cm, 100Ω·cm, 150Ω·cm, 250Ω·cm, 350Ω·cm, 450Ω·cm, 550Ω·cm, 650Ω·cm, 750Ω·cm, etc. Correspondingly, the room temperature resistivity of the lithium replenishment component (i.e., the lithium replenishment component before delithiation) is 2Ω·cm-200Ω·cm. Illustratively, the room temperature resistivity of the lithium-supplemented component before delithiation can be 2Ω·cm, 5Ω·cm, 10Ω·cm, 15Ω·cm, 25Ω·cm, 35Ω·cm, 55Ω·cm, 75Ω·cm, 95Ω·cm, 105Ω·cm, 115Ω·cm, 125Ω·cm, 135Ω·cm, 145Ω·cm, 155Ω·cm, 165Ω·cm, 175Ω·cm, 185Ω·cm, 195Ω·cm, etc.

[0018] In some embodiments of the present application, the thickness of the lithium replenishing layer is 3μm-20μm. For example, the thickness of the lithium replenishing layer can be 3μm, 4μm, 5μm, 8μm, 10μm, 12μm, 15μm, 18μm, 20μm, etc. Controlling the thickness of the lithium replenishing layer within the above range is conducive to ensuring a high energy density of the battery, and can control the path of electrons in the current collector and the positive electrode material layer within a more appropriate range, which is beneficial to the electron transmission efficiency of the internal current path of the battery. In addition, it can also make the mechanical strength of the lithium replenishing component higher. The thickness of the lithium replenishing layer here refers to the state before delithiation.

[0019] In some embodiments of the present application, the thickness of the current collector is 7 μm - 20 μm. Exemplarily, the thickness of the current collector can be 7 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, etc. Thus, it has a certain mechanical strength to carry the lithium supplement layer by itself, and can also control the weight of the final lithium supplement component within a relatively small range, thereby facilitating the structural stability and energy density of the battery. According to the actual application scenario, the thickness of the lithium supplement layer and the current collector can be the same or different.

[0020] In some embodiments of the present application, the lithium supplement layer includes a lithium supplement agent and a conductive agent. Based on the total mass of the lithium supplement layer, the mass content of the lithium supplement agent is 50% - 90%, and the mass content of the conductive agent is 1% - 40%. Exemplarily, the mass percentage content of the lithium supplement agent in the lithium supplement layer can be 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, etc. Exemplarily, the mass content of the conductive agent in the lithium supplement layer is 1%, 2%, 5%, 8%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, etc. The content of each component here refers to the state before delithiation. Controlling the content of the lithium supplement agent and the conductive agent in the lithium supplement layer within the above ranges is beneficial to controlling the resistivity of the lithium supplement component before and after delithiation within a relatively small range, optimizing the lithium supplement effect, and further improving the energy density of the battery.

[0021] In some embodiments of the present application, the D50 particle size of the lithium supplement agent in the lithium supplement layer is within the range of 0.5 μm - 20 μm. Exemplarily, the particle size of the lithium supplement agent can be 0.5 μm, 1.0 μm, 2.0 μm, 5.0 μm, 8.0 μm, 10.0 μm, 12.0 μm, 15.0 μm, 16 μm, 17 μm, 18 μm, 19 μm, etc. The D50 particle size of the lithium supplement agent here refers to the state before delithiation. Controlling the particle size of the lithium supplement agent within the above range is beneficial for the extraction of lithium ions, can ensure good mechanical strength of the lithium supplement layer, is also beneficial for the coating of the conductive agent, and reduces the resistivity of the lithium supplement component. In addition, considering that after delithiation, the lithium supplement agent will have a smaller particle size due to delithiation or rupture, controlling within the above range, the particle size of the residue of the lithium supplement agent after delithiation changes little, reducing the risk of voids in the lithium supplement layer affecting electron conduction, and thus can better reduce the resistivity of the lithium supplement layer after delithiation, which is beneficial to the rate performance of the battery. In the present application, D50 refers to the particle size corresponding to when the cumulative particle size distribution percentage of the sample reaches 50%.

[0022] 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 Li2M1 O2、Li2M 2 O3、Li5Fe a M 3 1-a O4、Li6Mn b M 4 1-b O4 and Li5M 5 At least one of O4; wherein, M 1 Including but not limited to at least one of Ni, Mn, Cu, Fe, Cr and Mo; M 2 Including but not limited to at least one of Ni, Mn, Fe, Mo, Zr, Si, Cu, Cr and Ru; M 3 Including at least one of Al, Nb, Co, Mn, Ni, Mo, Ru and Cr, 0≤a≤1; M 4 Including but not limited to at least one of Ni, Fe, Cu and Ru, 0≤b≤1; M 5 Including but not limited to 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.

[0023] In some specific embodiments, the lithium supplement agent is selected from the above-mentioned lithium metal oxides; further, in some specific embodiments, the above-mentioned lithium supplement 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. The lithium replenisher does not generate additional gas during the delithiation process (battery formation process), thereby maintaining the original structure of the lithium replenishment layer (no vacancies), further reducing the resistivity of the lithium replenishment component after delithiation, and also helping to maintain the structural stability of the electrode. Furthermore, the residue after delithiation still has a certain degree of activity, which facilitates the transport of active ions (lithium ions) in the battery.

[0024] In some embodiments of the present application, the conductive agent has at least one dimension less than or equal to 200 nm. For example, the conductive agent may have at least one dimension of 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. This facilitates coating of the conductive agent on the surface of the lithium supplementation agent particles, thereby further reducing the resistivity of the lithium supplementation component before and after delithiation.

[0025] 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; wherein the 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.

[0026] In some embodiments of the present application, the lithium replenishment layer further includes a binder; the binder has a mass percentage of 1%-20% in the lithium replenishment layer. For example, the mass percentage of the binder in the lithium replenishment 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%, 15.0%, 16.0%, 17.0%, 18.0%, 19.0%, etc. The binder not only maintains the structural stability of the lithium replenishment layer, but also, when the lithium replenishment component is applied to the electrode, an appropriate amount of binder in the lithium replenishment layer can enhance the bonding strength between the active material layer (e.g., the positive electrode material layer) and the current collector, further ensuring improvements in battery rate performance and cycle life.

[0027] 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. These binders exhibit strong adhesion, which not only enhances the structural stability of the lithium-replenishing layer itself but also improves the structural stability of the final electrode.

[0028] In some embodiments of the present application, the lithium replenishing layer includes a lithium replenishing agent, a conductive agent and a binder. Based on the total mass of the lithium replenishing layer, the mass content of the lithium replenishing agent is 50%-90%, the mass content of the conductive agent is 1%-40%; and the mass content of the binder is 1%-20%.

[0029] In some embodiments of the present application, the lithium-supplementing material layer further includes a dispersant. An appropriate amount of dispersant facilitates the dispersion of the conductive agent, further contributing to reducing the resistivity of the lithium-supplementing component before and after delithiation. In some specific embodiments, the mass of the dispersant is 5%-60% of the mass of the conductive agent. For example, 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.

[0030] 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.

[0031] In some embodiments of the present application, 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 (0.1-10):1. In some specific 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 (0.5-5):1. Further, in some specific examples, 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. Illustratively, the ratio of the sum of the surface areas of the conductive agent to the sum of the surface areas of the lithium supplementing agent can be 0.1:1, 0.5:1, 0.8:1, 1.0:1, 1.2:1, 1.5:1, 1.8:1, 2.0:1, 2.5:1, 2.8:1, 3.0:1, 3.2:1, 3.5:1, 3.8:1, 4.0:1, 4.2:1, 4.5:1, 4.8:1, 5.0:1, 6.0:1, 8.0:1, 9.0:1, and the like. Controlling the surface area ratio of the two within the above range is conducive to improving the dispersion and adsorption of the conductive agent on the surface of the lithium supplement agent, further promoting the coating of the lithium supplement agent particles by the conductive agent, thereby further reducing the resistivity of the lithium supplement layer before / after delithiation; at the same time, further improving the dispersion characteristics of the conductive agent and the lithium supplement agent is also conducive to further improving the mechanical strength of the lithium supplement layer before / after delithiation, which is beneficial to the cycle stability of the battery.

[0032] 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 measure 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 method includes: taking a unit mass mg of the 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 Am of the lithium supplement layer material per unit mass 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 and S1m 2 , then, the sum of the surface areas of the conductive agents S2 = S-S1, then, the ratio of the sum of the surface areas of the conductive agents to the sum of the surface areas of the lithium supplement agents is S2 / S1.

[0033] It should also be noted that the above-mentioned solvent includes but is 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 select the solvent according to actual conditions. The test conditions of the above-mentioned gas adsorption and desorption instrument are as follows: the degassing time is maintained at ≥30 minutes and the degassing temperature is maintained at ≥100°C during the test process, 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 agent and the conductive agent. However, the peaks of the particle size distribution curves of the lithium supplement agent and the conductive agent can be clearly distinguished. Generally, the particle size of the conductive agent is significantly smaller than that of the lithium supplement agent.

[0034] The embodiment of the present application also provides a positive electrode, comprising a positive electrode material layer and a lithium replenishing component provided in the embodiment of the present application; the positive electrode material layer is provided on the surface of the lithium replenishing layer facing away from the current collector. The inert layer formed after the lithium replenishing layer is delithiated will not hinder the transfer of lithium ions in the positive electrode during the charge and discharge process. Due to the lithium replenishing component provided in the embodiment of the present application, the positive electrode has a lithium replenishing layer, which can improve the energy density of the battery, and can maintain a low resistivity, which is beneficial to reducing the internal resistance of the battery and promoting the performance of the battery. In addition, the above-mentioned lithium replenishing component can also improve the peel strength of the positive electrode, which is beneficial to the structural stability of the positive electrode.

[0035] In the embodiments of the present application, a lithium replenishing layer may be provided on one surface of the current collector. In this case, a positive electrode material layer may be provided on the surface of the lithium replenishing layer facing away from the current collector, and a positive electrode material layer may also be provided on the opposite surface of the current collector. Alternatively, lithium replenishing layers may be provided on both opposite surfaces of the current collector, and positive electrode material layers may be provided on both surfaces of the lithium replenishing layers.

[0036] In some embodiments of the present application, in the lithium replenishment component of the positive electrode, the thickness of the current collector is 7μm-20μm; the thickness of the lithium replenishment layer is 1μm-15μm. In other embodiments, when the positive electrode is rolled, the thickness of the current collector is 7μm-20μm; the thickness of the lithium replenishment layer is 1μm-11μm. For example, after rolling, the thickness of the lithium replenishment layer can be 1μm, 2μm, 5μm, 8μm, 10μm, etc. The thickness of the lithium replenishment layer here refers to the state after delithiation. It should also be noted that in the embodiments of the present application, in the positive electrode after rolling, there is no obvious difference in the thickness of the lithium replenishment layer before and after delithiation.

[0037] In some embodiments of the present application, the room temperature resistivity of the positive electrode is 1Ω·m-100Ω·m. Exemplarily, the room temperature resistivity of the positive electrode can be 1Ω·m, 5Ω·m, 10Ω·m, 15Ω·m, 20Ω·m, 25Ω·m, 30Ω·m, 50Ω·m, 60Ω·m, 70Ω·m, 80Ω·m, 90Ω·m, 100Ω·m, etc. In the embodiments of the present application, the room temperature resistivity of the positive electrode refers to the resistivity of the positive electrode as a whole after the lithium replenishment layer is delithiated, including the resistivity of the current collector, the lithium replenishment layer after delithiation, and the positive electrode material layer. The specific test method is similar to the room temperature resistivity test method of the lithium replenishment component after delithiation, the only difference being that the positive electrode material layer does not need to be removed. In the embodiments of the present application, the room temperature resistivity of the positive electrode is measured using a two-electrode method.

[0038] In some embodiments of the present application, the mass ratio of the lithium supplement agent to the positive electrode active material in the positive electrode is (0.2-10):100. For example, the mass ratio of the lithium supplement agent to the positive electrode active material can be 0.2:100, 0.5:100, 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 ultimate performance of the battery, and those skilled in the art can select the ratio according to actual needs.

[0039] It is understood that the lithium supplement agent will completely or partially delithiate during the battery formation process. During subsequent charge and discharge cycles, the original lithium supplement agent is converted into a lithium supplement agent residue (the lithium supplement agent after delithiation), and the lithium supplement layer is correspondingly converted into a material layer including the lithium supplement agent residue and the conductive agent. After obtaining the battery, the lithium supplement component can be disassembled from the battery, and the lithium supplement agent residue can be separated from the positive electrode active material by cleaning the lithium supplement component materials, and then the mass ratio of the lithium supplement agent residue to the positive electrode active material is measured. The measured mass ratio of the lithium supplement agent residue to the positive electrode active material is the mass ratio of the lithium supplement agent to the positive electrode active material ((0.2-10):100)).

[0040] The present application also provides a secondary battery comprising the positive electrode provided in the present application. The secondary battery can be a liquid battery having an electrolyte or a solid-state battery. By utilizing the positive electrode provided in the present application, the secondary battery can have a high energy density, a long cycle life, and good rate performance.

[0041] 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.

[0042] It is understood that the lithium supplement agent will completely or partially delithiate during the battery formation process. During subsequent charge and discharge cycles, the original lithium supplement agent is converted into lithium supplement agent residue, and the lithium supplement layer is correspondingly converted into a material layer including the lithium supplement agent residue and the conductive agent. In some embodiments, the lithium supplement layer is also correspondingly converted into a material layer including the lithium supplement agent residue, the conductive agent, and the binder.

[0043] It is understandable that the particle size of the lithium supplement agent will change accordingly after delithiation. Accordingly, in some embodiments, the particle size D50 of the residue of the lithium supplement agent after delithiation is in the range of 0.4μm-18μm. Exemplarily, the particle size D50 of the residue of the lithium supplement agent after delithiation can be 0.4μm, 0.5μm, 1.0μm, 2.0μm, 5.0μm, 8.0μm, 10.0μm, 12.0μm, 15.0μm, 16μm, 17μm, 18μm, etc.

[0044] 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.

[0045] In some embodiments of the present application, the above-mentioned electrical equipment includes but is not limited to 3C electronic equipment, power vehicles, energy storage systems, etc. Power vehicles include but are not limited to new energy vehicles, power-assisted bicycles, etc.

[0046] The technical solution of this application is further illustrated below with multiple embodiments.

[0047] Example 1

[0048] A lithium replenishment component comprises a current collector and a lithium replenishment layer disposed on the surface of the current collector. The current collector is a 15μm-thick aluminum foil, the lithium replenishment layer is 10μm thick, and the lithium replenishment layer comprises 75wt.% of a lithium replenishment agent (specifically Li2NiO2), 20wt.% of a conductive agent (specifically Super P), and 5wt.% of a binder (specifically polyvinylidene fluoride). The conductive agent surface area is: lithium replenishment agent surface area = 3 (i.e., the ratio of the sum of the conductive agent surface area to the sum of the lithium replenishment agent surface area is 3:1). The D50 particle size of the lithium replenishment agent is 3.0μm, and the particle size of the conductive agent is 30-120nm.

[0049] A positive electrode slurry is applied to the surface of the lithium-ion battery assembly (i.e., the surface of the lithium-ion battery layer facing away from the current collector) to form a positive electrode material layer. The positive electrode material layer comprises a positive electrode active material (specifically, lithium iron phosphate), a binder (specifically, PVDF), and a conductive agent (specifically, super-P) in a mass ratio of 100:3:2. The lithium-ion battery assembly with the positive electrode material layer is then roll-pressed. After rolling, the lithium-ion battery layer has a thickness of 5μm.

[0050] After delithiation, the room-temperature resistivity of the lithium supplement component was 10 Ω·cm, and the mass ratio of the residual lithium supplement (i.e., the delithiation-free lithium supplement) to the positive electrode active material was 1:20. The particle size D50 of the residual lithium supplement after delithiation was 2.5 μm.

[0051] Example 2

[0052] The difference from Example 1 is that the lithium replenishing layer comprises 90 wt.% of a lithium replenishing agent (specifically Li₂NiO₂), 1 wt.% of a conductive agent (specifically Super P), and 9 wt.% of a binder. The mass ratio of the lithium replenishing agent to the positive electrode active material after delithiation is 1:16.7. The D50 particle size of the lithium replenishing agent is 3 μm, and the particle size of the conductive agent is 30 to 120 nm.

[0053] Conductive agent surface area: lithium supplement agent surface area = 1. The room temperature resistivity of the lithium supplement agent assembly after delithiation is 100 Ω·cm. The mass ratio of the lithium supplement agent residue after delithiation to the positive electrode active material is 1:16.7. The particle size D50 of the lithium supplement agent residue after delithiation is 2.5 μm.

[0054] Example 3

[0055] The difference from Example 1 is that the lithium replenishing layer includes 79wt.% of lithium replenishing agent (specifically Li2NiO2), 1wt.% of conductive agent (specifically Super P) and 20wt.% of binder, the D50 particle size of the lithium replenishing agent is 8μm, and the particle size of the conductive agent is 30-120nm.

[0056] Conductive agent surface area: lithium supplement surface area = 0.8. The room temperature resistivity of the lithium supplement component after delithiation is 500 Ω·cm. The mass ratio of the lithium supplement residue after delithiation to the positive electrode active material is 1:19. The particle size D50 of the lithium supplement residue after delithiation is 7.2 μm.

[0057] Example 4

[0058] The difference from Example 1 is that the lithium replenishing layer includes 90 wt.% of a lithium replenishing agent (specifically Li2NiO2), 1 wt.% of a conductive agent (specifically Super P), and 9 wt.% of a binder. The D50 particle size of the lithium replenishing agent is 0.5 μm, and the particle size of the conductive agent is 30 to 120 nm.

[0059] Conductive agent surface area: lithium supplement agent surface area = 1.5. The room temperature resistivity of the lithium supplement assembly after delithiation is 200 Ω·cm. The mass ratio of the lithium supplement agent residue after delithiation to the positive electrode active material is 1:16.7. The particle size of the lithium supplement agent residue after delithiation is 0.45 μm.

[0060] Example 5

[0061] The difference from Example 1 is that the conductive agent is replaced with graphite with a particle size of 220 nm to 300 nm. The room temperature resistivity of the lithium-supplemented component after delithiation is 150 Ω·cm.

[0062] Example 6

[0063] The differences from Example 1 are as follows: the conductive agent particle size is 30-120 nm, the D50 of the lithium replenisher is 20 μm, the conductive agent surface area:lithium replenisher surface area ratio is 8:1, and the room temperature resistivity of the lithium replenisher component after delithiation is 4 Ω·cm. The particle size of the residual lithium replenisher after delithiation is 18 μm.

[0064] Example 7

[0065] The differences from Example 1 are as follows: the D50 particle size of the lithium replenisher is 1 μm, the particle size of the conductive agent is 20-100 nm, and the surface area ratio of the conductive agent to the lithium replenisher is 10:1. The room temperature resistivity of the lithium replenisher component after delithiation is 3 Ω·cm. The particle size of the residual lithium replenisher after delithiation is 0.9 μm.

[0066] Example 8

[0067] The difference from Example 1 is that the D50 particle size of the lithium replenisher is 3 μm, the particle size of the conductive agent is 20-100 nm, the ratio of the surface area of ​​the conductive agent to the surface area of ​​the lithium replenisher is 2:1, and the room temperature resistivity of the lithium replenisher component after delithiation is 5 Ω·cm.

[0068] Example 9

[0069] The differences from Example 1 are as follows: before rolling, the thickness of the lithium-supplementing layer was 30 μm; after rolling, the thickness was 18 μm. The mass ratio of the lithium-supplementing agent residue to the positive electrode active material after delithiation was 15:100. The room-temperature resistivity of the lithium-supplementing assembly after delithiation was 500 Ω·cm.

[0070] Example 10

[0071] The differences from Example 1 are as follows: before rolling, the thickness of the lithium-supplementing layer was 3 μm; after rolling, the thickness was 1 μm. The mass ratio of lithium-supplementing agent to positive electrode active material was 0.8:100. After delithiation, the room-temperature resistivity of the lithium-supplementing assembly was 200 Ω·cm.

[0072] Example 11

[0073] The differences from Example 1 are as follows: the lithium-replenishing layer comprises 50 wt.% of a lithium-replenishing agent (specifically Li₂NiO₂), 40 wt.% of a conductive agent (specifically Super P), and 10 wt.% of a binder. The mass ratio of the residual lithium-replenishing agent to the positive electrode active material after delithiation is 2:100. The room-temperature resistivity of the lithium-replenishing assembly after delithiation is 4 Ω·cm.

[0074] Example 12

[0075] The only difference from Example 1 is that the lithium supplement agent is replaced with Li2O2. The room temperature resistivity of the lithium supplement component after delithiation is 300Ω·cm.

[0076] In order to highlight the beneficial effects of the embodiments of the present application, the following comparative examples are provided.

[0077] Comparative Example 1

[0078] The only difference from Example 1 is that the lithium replenishing layer is replaced by a conductive layer, the conductive layer includes 80 wt.% of a conductive agent and 20% of a binder, and the thickness of the conductive layer is 2 μm.

[0079] Comparative Example 2

[0080] The only difference from Example 1 is that the lithium replenishment layer comprises 74.5 wt.% of a lithium replenisher (specifically Li₂NiO₂), 0.5 wt.% of a conductive agent (specifically Super P), and 25 wt.% of a binder (specifically polyvinylidene fluoride). The specific surface area of ​​the conductive agent is equal to the specific surface area of ​​the lithium replenisher (0.3). After delithiation, the room temperature resistivity of the lithium replenishment component is 2200 Ω·cm.

[0081] Performance Testing

[0082] (1) Preparation of test cells: The positive electrodes of the above-mentioned embodiments and comparative examples were respectively assembled with negative electrode sheets to form test cells, wherein the negative electrode sheets comprised a current collector (specifically copper foil) and a negative electrode material layer disposed on the surface of the current collector, wherein the negative electrode material layer consisted of graphite, a conductive agent, and a binder in a mass ratio of 95:3:2, and the electrolyte was an organic solution of lithium hexafluorophosphate with a concentration of 1.2 mol / L, wherein the solvent was an EC:DMC:EMC in a mass ratio of 1:1:1:. After formation, the test cells of the embodiments and comparative examples were obtained. The formation process was as follows: charging at 0.05C for 3 h, standing for 10 min, and then charging at 0.2C to 3.8 V.

[0083] (2) Rate performance test: The discharge capacity of each battery at different rates such as 0.5C, 1C, 2C, and 3C is tested at 25°C to determine how it changes with the number of cycles. The voltage range is 2.5V-3.8V. When calculating the capacity, the mass ratio of the discharge capacity at a certain current density to the positive electrode active material is used as the discharge capacity at that current density. Table 1 summarizes the ratio of the first-cycle discharge capacity of each battery at a rate of 3C to the first-cycle discharge capacity at 0.5C (3C / 0.5C). The test results of each battery are summarized in Table 1.

[0084] (3) Cycle life: The battery was tested for charge and discharge cycles at 0.33C and 0.5C at 25±1°C. The steps were as follows: 10 min of idling time, 0.5C constant current charging to 3.8V, constant voltage charging to 0.05C cutoff, 10 min of idling time, and 0.5C constant power discharging to 2.5V. This cycle was considered one cycle. This step was repeated until the battery's capacity retention reached 80%, which was the number of cycles required. This was the battery's cycle life.

[0085] (4) Energy density: In addition, the discharge curve of each battery obtained by charging and discharging at the above 0.1C constant current is integrated and divided by the first cycle discharge capacity to obtain the average voltage of each battery, that is, the charge and discharge voltage platform. The weight energy density of each battery is then calculated according to the following formula:

[0086] Gravimetric energy density = fractional capacity × average voltage platform / battery weight, where fractional capacity refers to the capacity at the aforementioned 0.1C discharge. The results are summarized in Table 1.

[0087] (5) Battery DC internal resistance: At 50% SOC, 2C discharge for 30s, the ratio of the voltage difference before and after discharge to the current is the DC internal resistance (DCIR).

[0088] (6) 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 peel strength test was performed at a peeling angle of 180°.

[0089] Table 1

[0090] It can be seen from the data in Table 1 that the lithium supplement component provided in the embodiments of the present application can be used to provide a battery with high energy density, cycle performance and rate performance.

[0091] 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. A lithium supplement component, characterized in that, It includes a current collector and a lithium supplement layer provided on at least one surface of the current collector; after the lithium supplement layer de-lithifies, the room-temperature resistivity of the lithium supplement component is 2 Ω·m - 2000 Ω·m.

2. The lithium supplement component according to claim 1, characterized in that, The room-temperature resistivity of the lithium supplement component after de-lithification is 2 Ω·m - 1000 Ω·m.

3. The lithium supplement component according to claim 1, wherein The thickness of the current collector is 7 μm - 20 μm; the thickness of the lithium supplement layer is 3 μm - 20 μm.

4. The lithium supplement component according to claim 1, wherein The lithium supplement layer includes a lithium supplement agent, a conductive agent, and a binder. Based on the total mass of the lithium supplement layer, the mass content of the lithium supplement agent is 50% - 90%, the mass content of the conductive agent is 1% - 40%; the mass content of the binder is 1% - 20%.

5. The lithium supplement component according to claim 1, characterized in that, The lithium supplement layer includes a lithium supplement agent, and the particle size D50 of the lithium supplement agent is in the range of 0.5 μm - 20 μm.

6. The lithium supplement component according to any one of claims 1-5, characterized in that, The lithium supplement layer includes a lithium supplement agent, and the lithium supplement agent includes at least one Li x A y and / or a metal oxide of lithium; wherein, x > 0, 0 < y ≤ 3, and the 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; 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.

7. The lithium supplement component according to any one of claims 1-6, characterized in that, The lithium supplement layer includes a conductive agent, and the size of at least one dimension of the conductive agent is less than or equal to 200 nm.

8. The lithium supplement component according to any one of claims 1-7, characterized in that, The lithium supplement layer includes a conductive agent, and the conductive agent includes at least one of porous carbon, acetylene black, carbon nanotubes, carbon black, Ketjen black, graphene, Mxenes.

9. The lithium supplement component according to any one of claims 1-8, characterized in that The lithium supplement layer includes a binder, and the binder includes at least one of polyvinylidene fluoride, polyvinyl alcohol, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylonitrile, polyacrylic acid, sodium alginate, and styrene-butadiene rubber.

10. The lithium supplement component according to any one of claims 1-9, characterized in that, The particle size D50 of the residue of the lithium supplement agent after de-lithification is in the range of 0.4 μm - 18 μm.

11. The lithium supplement component according to any one of claims 1-10, characterized in that, 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 (0.1 - 10):1; optionally, 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 (0.5 - 5):1; optionally, 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.

12. A positive electrode, characterized in that, The positive electrode includes the lithium supplement component as described in any one of claims 1 - 11 and a positive electrode material layer, and the positive electrode material layer is provided on the surface of the lithium supplement layer facing away from the current collector.

13. The positive electrode according to claim 12, characterized in that, After the lithium supplement layer de-lithifies, the thickness of the lithium supplement layer is in the range of 1 μm - 15 μm.

14. The positive electrode according to claim 12 or 13, characterized in that, The positive electrode material layer includes a positive electrode active material, the lithium supplement layer includes a lithium supplement agent, and the mass ratio of the lithium supplement agent to the positive electrode active material is in the range of (0.2 - 10):

100.

15. A secondary battery, characterized in that, The secondary battery includes the positive electrode as described in any one of claims 12 - 14.

16. The secondary battery according to claim 15, wherein The room-temperature resistivity of the positive electrode is 1 Ω·m - 100 Ω·m.

17. An electrical device, characterized in that, The electrical device includes the secondary battery as described in claim 15 or 16.

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