Lithium-ion battery components, cathode materials, secondary batteries, and electrical equipment.

Abstract

This application provides a lithium replenishment component, a positive electrode, a secondary battery, and an electrical device. The lithium replenishment component includes 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. It not only provides lithium replenishment but also maintains a low resistivity after the lithium replenishment layer is delithiated, thereby improving the battery's energy density while maintaining its rate performance.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to lithium replenishment components, positive electrodes, secondary batteries, and electrical equipment. Background Technology

[0002] Lithium replenishment technology is an effective means to improve battery energy density while simultaneously enhancing cycle life and storage performance. Positive electrode lithium replenishment is favored due to its stability, low cost, and ease of synthesis. However, if the positive electrode lithium replenisher is directly mixed into the positive electrode material layer, residues may remain after releasing active lithium ions, affecting ion transport. Alternatively, the lithium replenisher may generate gas during decomposition, impacting the structural stability of the active material layer and hindering subsequent battery performance. If a separate lithium replenishment layer is placed in the positive electrode, the resistivity of the lithium replenisher remains high after delithiation, affecting the electron transport rate in the battery's current path and thus negatively impacting rate performance. Furthermore, the high resistivity of the lithium replenishment layer after delithiation necessitates coating the current collector surface with a conductive carbon layer to improve electrode conductivity, increasing costs and also affecting battery energy density. Summary of the Invention

[0003] In view of this, embodiments of this application provide a lithium replenishment component, a positive electrode, a secondary battery, and an electrical device, which not only have a lithium replenishment effect, but also maintain a low resistivity after the lithium replenishment layer is delithiated, thereby improving the battery energy density while taking into account the battery's rate performance.

[0004] The first aspect of this application provides a lithium replenishment component, including a current collector and a lithium replenishment layer disposed on at least one side 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.

[0005] This lithium replenishment component retains good electronic conductivity after delithiation and also facilitates ion transport, thus enabling the electrodes to fully perform during battery charge-discharge cycles, especially in terms of rate performance. Furthermore, the lithium replenishment layer in this component provides lithium replenishment, improving the battery's energy density and cycle life.

[0006] Optionally, the room temperature resistivity of the lithium replenishment component after delithiation is 2Ω·m-1000Ω·m.

[0007] Optionally, the thickness of the current collector is 7μm-20μm; the thickness of the lithium replenishment layer is 3μm-20μm.

[0008] Optionally, 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%.

[0009] Optionally, 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 to 20 μm.

[0010] Optionally, the lithium supplement layer includes a lithium supplement agent, and the lithium supplement agent includes at least one Li x A y and / or lithium oxide; wherein, x > 0, 0 < y ≤ 3, and element A includes at least one of C, N, O, P, and S;

[0011] The metal oxide of lithium includes LiM 1 O2, LiM 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.

[0012] Optionally, 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.

[0013] Optionally, 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, and Mxenes.

[0014] Optionally, 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.

[0015] Optionally, the particle size D50 of the residue after delithiation of the lithium supplement agent is in the range of 0.4 μm to 18 μm.

[0016] Optionally, the ratio of the sum of the surface areas of the conductive agents to the sum of the surface areas of the lithium replenishing agents is (0.1-10):1; alternatively, the ratio of the sum of the surface areas of the conductive agents to the sum of the surface areas of the lithium replenishing agents is (0.5-5):1; alternatively, the ratio of the sum of the surface areas of the conductive agents to the sum of the surface areas of the lithium replenishing agents is (0.8-3):1.

[0017] A second aspect of this application also provides a positive electrode, including the lithium replenishment component and a positive electrode material layer provided in the first aspect of this application. The positive electrode material layer is disposed on the surface of the lithium replenishment layer facing away from the current collector. Due to the use of the positive electrode of this application embodiment, the secondary battery can simultaneously possess high energy density, long cycle life, low internal resistance, and good rate performance.

[0018] Optionally, the thickness of the lithium replenishment layer is in the range of 3μm-20μm; the thickness of the current collector is in the range of 7μm-20μm.

[0019] Optionally, the positive electrode material layer includes a positive electrode active material, and the mass ratio of the lithium supplement to the positive electrode active material is in the range of (0.2-10):100.

[0020] A third aspect of this application provides a secondary battery, including the positive electrode provided in the second aspect of this application.

[0021] Optionally, the secondary battery includes a positive electrode, a negative electrode, and an electrolyte and a separator located between the positive and negative electrode.

[0022] Optionally, the room temperature resistivity of the positive electrode is 1 Ω·m to 100 Ω·m.

[0023] The fourth aspect of this application provides an electrical device, including the secondary battery provided in the third aspect of this application. Because the electrical device is powered by the secondary battery provided in the embodiments of this application, it has a strong battery life and can also have a certain degree of fast charging performance, making it highly competitive in the market.

[0024] Optionally, the aforementioned electrical equipment includes, but is not limited to, 3C electronic devices, powered vehicles, and energy storage systems. Powered vehicles include, but are not limited to, new energy vehicles and electric bicycles. Detailed Implementation

[0025] This application provides a lithium replenishment component, including a current collector and a lithium replenishment layer disposed on at least one side 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.

[0026] The lithium replenishment component provided in this application embodiment retains a resistivity of 2Ω·m-2000Ω·m after lithium removal from the lithium replenishment layer, exhibiting good electronic conductivity. This allows the electrode to fully utilize its performance during battery charge-discharge cycles. The lithium replenishment layer in this component provides lithium replenishment, improving the battery's energy density and cycle performance. After lithium removal, it also functions as a conductive layer. Compared to existing batteries using electrodes with lithium replenishment layers, this not only improves rate performance but also eliminates the need for an additional conductive layer on the current collector surface (e.g., replacing carbon foil), further enhancing battery energy density. It also ensures a sufficiently low resistivity for the final electrode, reducing internal resistance and facilitating optimal battery performance.

[0027] In this embodiment, the lithium replenishment layer can be disposed on one side of the current collector or on opposite sides of the current collector. In this embodiment, the lithium replenishment component can be used as a positive electrode. In this embodiment, the current collector in the lithium replenishment component can be any lithium-ion battery current collector known in the art. When applied to the positive electrode, a current collector suitable for the positive electrode of a lithium secondary battery is selected, such as aluminum foil.

[0028] In this embodiment, room temperature refers to the ambient temperature when testing resistivity. In most cases, room temperature in this embodiment refers to 25±2℃.

[0029] In this embodiment, the room temperature resistivity of the lithium replenishment component after delithiation is measured using a two-electrode method. Specifically, a battery is assembled from the positive and negative electrodes, including the lithium replenishment component. The negative electrode includes 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 is composed of graphite, a conductive agent, and a binder in a mass ratio of 95:3:2. The electrolyte is a 1.2 mol / L lithium hexafluorophosphate organic solution, wherein the solvent is EC:DMC:EMC in a mass ratio of 1:1:1:. The battery is formed, and the formation process includes: charging at 0.05C for 3 hours, standing for 10 minutes, and then charging at 0.2C to 3.8V. After formation, the battery is discharged to a SOC of 0, the positive electrode is disassembled, and the positive electrode is immersed in the solvent dimethyl carbonate (DMC) for 10-20 minutes to remove the positive electrode material (e.g., when the positive electrode includes both the lithium replenishment component and the positive electrode material layer, the positive electrode material layer is removed), thus obtaining the lithium replenishment component after delithiation. The resistivity of the lithium replenishment component after delithiation was tested: The lithium replenishment component was placed between two electrodes (with the two surfaces of the lithium replenishment component in the thickness direction facing the electrodes). A pressure of 25 MPa was applied to the electrodes, and a certain current was applied. The voltage across the electrodes was measured, and the resistance of the sample was calculated. The lithium content of the lithium replenishing agent in the lithium replenishment layer was 10-25% of the original lithium replenishing agent. The room temperature resistivity of the lithium replenishment component after delithiation was obtained. In this application, the specific method for delithiating the lithium replenishment layer can also refer to the steps described above for obtaining the lithium replenishment component after delithiation.

[0030] In this embodiment, after the lithium replenishment layer is delithiated, the room temperature resistivity of the lithium replenishment component (i.e., the lithium replenishment component after delithiation) can be 2 Ω·m, 5 Ω·m, 10 Ω·m, 15 Ω·m, 20 Ω·m, 25 Ω·m, 30 Ω·m, 50 Ω·m, 100 Ω·m, 200 Ω·m, 300 Ω·m, 500 Ω·m, 1000 Ω·m, 1100 Ω·m, 1200 Ω·m, 1300 Ω·m, 1400 Ω·m, 1500 Ω·m, 1800 Ω·m, 2000 Ω·m, etc. It is understandable that if the above resistivity is too high, it will affect the battery performance. In this case, the corresponding room temperature resistivity of the lithium replenishment component (i.e., the lithium replenishment component before delithiation) is 1 Ω·cm-500 Ω·cm.

[0031] In some embodiments of this application, after delithiation of the lithium replenishment layer, the room temperature resistivity of the lithium replenishment component (i.e., the lithium replenishment component after delithiation) is 2 Ω·m-1000 Ω·m. Exemplarily, the room temperature resistivity of the lithium replenishment component after delithiation can be 2 Ω·m, 10 Ω·m, 100 Ω·m, 200 Ω·m, 300 Ω·m, 400 Ω·m, 500 Ω·m, 600 Ω·m, 700 Ω·m, 800 Ω·m, 900 Ω·m, etc. This is more beneficial to the rate performance of the battery. Correspondingly, the room temperature resistivity of the lithium replenishment component at this time (i.e., the lithium replenishment component before delithiation) is 1 Ω·cm-300 Ω·cm. For example, the room temperature resistivity of the lithium replenishment component before delithiation can be 5 Ω·cm, 10 Ω·cm, 20 Ω·cm, 50 Ω·cm, 100 Ω·cm, 150 Ω·cm, 200 Ω·cm, 220 Ω·cm, 250 Ω·cm, 260 Ω·cm, 280 Ω·cm, 300 Ω·cm, etc.

[0032] In some specific embodiments of this 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 5 Ω·m-800 Ω·m. Exemplarily, the room temperature resistivity of the lithium replenishment component after delithiation can be 5 Ω·cm, 10 Ω·cm, 20 Ω·cm, 50 Ω·cm, 100 Ω·cm, 150 Ω·cm, 250 Ω·cm, 350 Ω·cm, 450 Ω·cm, 550 Ω·cm, 650 Ω·cm, 750 Ω·cm, etc. Correspondingly, the room temperature resistivity of the lithium replenishment component at this time (i.e., the lithium replenishment component before delithiation) is 2 Ω·cm-200 Ω·cm. For example, the room temperature resistivity of the lithium replenishment component before lithium removal can be 2 Ω·cm, 5 Ω·cm, 10 Ω·cm, 15 Ω·cm, 25 Ω·cm, 35 Ω·cm, 55 Ω·cm, 75 Ω·cm, 95 Ω·cm, 105 Ω·cm, 115 Ω·cm, 125 Ω·cm, 135 Ω·cm, 145 Ω·cm, 155 Ω·cm, 165 Ω·cm, 175 Ω·cm, 185 Ω·cm, 195 Ω·cm, etc.

[0033] In some embodiments of this application, the thickness of the lithium replenishment layer is 3μm-20μm. Exemplarily, the thickness of the lithium replenishment layer can be 3μm, 4μm, 5μm, 8μm, 10μm, 12μm, 15μm, 18μm, 20μm, etc. Controlling the thickness of the lithium replenishment layer within the above range helps to ensure a high energy density of the battery, and allows for better control of the electron path in the current collector and cathode material layers, improving the electron transport efficiency of the internal current path of the battery. Furthermore, it also results in higher mechanical strength of the lithium replenishment component. Here, the thickness of the lithium replenishment layer refers to the state before lithium removal.

[0034] 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.

[0035] 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 conducive 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.

[0036] 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 conducive to the extraction of lithium ions, can ensure good mechanical strength of the lithium supplement layer, is also conducive to 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 conductivity of the lithium supplement layer after delithiation, which is conducive 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%.

[0037] 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 Includes at least one of Al, Nb, Co, Mn, Ni, Mo, Ru, and Cr, where 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. Among them, Li... x A y Lithium supplements may include, but are not limited to, Li3N, Li2C2, Li2S, Li2O, Li2CO3, Li2C2O4, Li3P, etc., and mixtures of the above substances are not limited to.

[0038] In some specific embodiments, 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. The above-mentioned lithium replenishing agent does not generate additional gas during the delithiation process (battery formation process), thus maintaining the original structure of the lithium replenishing layer (without creating vacancies), further reducing the resistivity of the lithium replenishing component after delithiation, and also helping to maintain the structural stability of the electrode. Furthermore, its residue after delithiation still has a certain degree of activity, which is beneficial to the transport of active ions (lithium ions) in the battery.

[0039] In some embodiments of this application, the conductive agent has a dimension of at least one dimension that is less than or equal to 200 nm. Exemplarily, the dimension 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. This facilitates the coating of the conductive agent on the surface of the lithium replenishment particles, thereby further reducing the resistivity of the lithium replenishment component before and after lithium removal.

[0040] In some embodiments of this 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, 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, Super P, acetylene black, carbon nanotubes, carbon black, Ketjen black, graphene, and Mxenes, with at least one dimension having a size less than or equal to 200 nm.

[0041] In some embodiments of this application, the lithium replenishment layer further includes a binder; the binder comprises 1%-20% by mass in the lithium replenishment layer. Exemplarily, 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 when the lithium replenishment component is applied to the electrode, an appropriate amount of binder in the lithium replenishment layer can also improve the bonding strength between the active material layer (e.g., the positive electrode material layer) and the current collector, further ensuring improved battery rate performance and cycle life.

[0042] In some embodiments of this 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. The above-mentioned binders have good adhesion, which not only enhances the structural stability of the lithium replenishment layer itself but also improves the structural stability of the final electrode.

[0043] In some embodiments of this 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%.

[0044] In some embodiments of this application, the lithium replenishment material layer also includes a dispersant. An appropriate amount of dispersant helps disperse the conductive agent, which is more conducive to reducing the conductivity of the lithium replenishment component before and after delithiation. 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 conductive agent.

[0045] In some embodiments of this application, the dispersant includes, but is not limited to, at least one of polyvinylpyrrolidone (PVP), sodium dodecyl sulfate (SDS), perfluoroalkyl ether alcoholamine salt, perfluoroalkyl ether quaternary ammonium salt, hexadecyltrimethylammonium bromide (CTAB), dodecyltrimethylammonium bromide, and dodecylpyridine bromide.

[0046] In some embodiments of this application, the ratio of the sum of the surface areas of the conductive agents to the sum of the surface areas of the lithium replenishing 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 replenishing agents is (0.5-5):1. Further, 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 replenishing agents is (0.8-3):1. For example, the ratio of the sum of the surface areas of the conductive agents to the sum of the surface areas of the lithium replenishing agents 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, etc. Controlling the surface area ratio of the two within the above range is beneficial to improving the dispersion and adsorption of the conductive agent on the surface of the lithium replenishing agent, further promoting the coating of the lithium replenishing agent particles by the conductive agent, thereby further reducing the resistivity of the lithium replenishing layer before and after delithiation; at the same time, further improving the dispersion characteristics of the conductive agent and the lithium replenishing agent is also beneficial to further improving the mechanical strength of the lithium replenishing layer before and after delithiation, which is beneficial to the cycle stability of the battery.

[0047] In this embodiment of the application, a combination of scanning laser particle size analyzer and specific surface area analyzer can be used to test the sum of the surface areas of the conductive agent and the sum of the surface areas of the lithium replenishing agent, and further measure the ratio of the sum of their surface areas. Specifically, this includes: taking a unit mass (mg) of the lithium replenishing layer material and placing it in a solvent to remove any binders that may be present in the lithium replenishing layer; washing and drying the obtained solid and weighing the mass (m1) of the solid; measuring the gas adsorption curve of the solid using a gas adsorption-desorption analyzer and calculating the specific surface area (Am) of a unit mass of the lithium replenishing layer material using a BET model.2 / g, then the total surface area of ​​this lithium-replenishing layer material is S=m1*A, in m 2 The solid was subjected to a laser particle size analyzer to obtain the particle size distribution curve of the lithium supplement. The curve was then integrated to obtain the sum of the surface areas S1 m of the lithium supplement. 2 Therefore, 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.

[0048] It should also be noted that the above 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, which can be selected by those skilled in the art according to the actual situation. The test conditions of the above gas adsorption-desorption instrument are: maintaining a degassing time ≥30 min and a degassing temperature ≥100℃ during the test to obtain the gas adsorption-desorption curve of the above solid, and further obtaining A. 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.

[0049] This application also provides a positive electrode, including a positive electrode material layer and a lithium replenishment component provided in this application embodiment; the positive electrode material layer is disposed on the surface of the lithium replenishment layer facing away from the current collector. The inert layer formed after lithium removal from the lithium replenishment layer does not hinder the transfer of lithium ions in the positive electrode during charging and discharging. Due to the presence of the lithium replenishment component provided in this application embodiment, the positive electrode has both a lithium replenishment layer, which can improve the energy density of the battery, and maintain a low resistivity, which is beneficial for reducing the internal resistance of the battery and improving battery performance. Furthermore, the aforementioned lithium replenishment component can also improve the peel strength of the positive electrode, which is beneficial for the structural stability of the positive electrode.

[0050] In this embodiment, a lithium replenishment layer may be provided on one side surface of the current collector. In this case, a positive electrode material layer may be provided on the side surface of the lithium replenishment layer facing away from the current collector, and a positive electrode material layer may also be provided on the opposite side surface of the current collector. Alternatively, lithium replenishment layers may be provided on both opposite sides of the current collector, and a positive electrode material layer may be provided on both sides of the lithium replenishment layer surface.

[0051] In some embodiments of this application, in the lithium replenishment component of the positive electrode, the thickness of the current collector is 7μm-20μm; and the thickness of the lithium replenishment layer is 1μm-15μm. In other embodiments, after the positive electrode is rolled, the thickness of the current collector is 7μm-20μm; and the thickness of the lithium replenishment layer is 1μm-11μm. Exemplarily, after rolling, the thickness of the lithium replenishment layer can be 1μm, 2μm, 5μm, 8μm, 10μm, etc. Here, the thickness of the lithium replenishment layer refers to the state after lithium removal. It should also be noted that in the embodiments of this application, in the positive electrode after rolling, the thickness of the lithium replenishment layer is not significantly different before and after lithium removal.

[0052] In some embodiments of this application, the room temperature resistivity of the positive electrode is 1 Ω·m to 100 Ω·m. Exemplarily, the room temperature resistivity of the positive electrode can be 1 Ω·m, 5 Ω·m, 10 Ω·m, 15 Ω·m, 20 Ω·m, 25 Ω·m, 30 Ω·m, 50 Ω·m, 60 Ω·m, 70 Ω·m, 80 Ω·m, 90 Ω·m, 100 Ω·m, etc. In the embodiments of this application, the room temperature resistivity of the positive electrode refers to the overall resistivity of the positive electrode after lithium removal from the lithium replenishment layer, including the resistivity of the current collector, the lithium replenishment layer after lithium removal, and the positive electrode material layer. The specific testing method is similar to the room temperature resistivity testing method for the lithium replenishment component after lithium removal, the only difference being that the positive electrode material layer does not need to be removed. In the embodiments of this application, the room temperature resistivity of the positive electrode is measured using a two-electrode method.

[0053] In some embodiments of this application, the mass ratio of lithium replenishing agent to positive electrode active material in the positive electrode is (0.2-10):100. Exemplarily, the mass ratio of lithium replenishing agent to 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 within the above range is beneficial to the final battery performance, and those skilled in the art can choose according to actual needs.

[0054] This application also provides a secondary battery, including the positive electrode provided in this application embodiment. The secondary battery can be a liquid battery with an electrolyte or a solid-state battery. Due to the use of the positive electrode from this application embodiment, the secondary battery can possess both high energy density, long cycle life, and good rate performance.

[0055] In some embodiments of this application, the secondary battery includes a positive electrode, a negative electrode, a separator, and an electrolyte disposed between the positive and negative electrode. In the embodiments of this application, the negative electrode can be any negative electrode known in the art, and this application does not impose any limitation on it.

[0056] Understandably, the lithium replenishing agent undergoes complete or partial delithiation during battery formation. During subsequent charge-discharge cycles, the original lithium replenishing agent transforms into a residue, and the lithium replenishing layer correspondingly transforms into a material layer comprising the residue and a conductive agent. In some embodiments, the lithium layer also transforms into a material layer comprising the residue, a conductive agent, and a binder.

[0057] Understandably, the particle size of the lithium replenishing agent will change after delithiation. Accordingly, in some embodiments, the particle size of the residue of the lithium replenishing agent after delithiation is in the range of 0.4 μm-18 μm. Exemplarily, the particle size of the residue of the lithium replenishing agent after delithiation can be 0.4 μm, 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, etc.

[0058] This application also provides an electrical device, including the secondary battery provided in this application embodiment. Because the electrical device is powered by the secondary battery provided in this application embodiment, it has a strong battery life and can also have a certain degree of fast charging performance, making it highly competitive in the market.

[0059] In some embodiments of this application, the aforementioned electrical equipment includes, but is not limited to, 3C electronic devices, powered vehicles, and energy storage systems. Powered vehicles include, but are not limited to, new energy vehicles and electric bicycles.

[0060] The technical solution of this application is further described below with reference to several embodiments.

[0061] Example 1

[0062] A lithium replenishment component includes a current collector and a lithium replenishment layer disposed on the surface of the current collector. The current collector is an aluminum foil with a thickness of 15 μm, and the lithium replenishment layer has a thickness of 10 μm. The lithium replenishment layer comprises 75 wt.% lithium replenishing agent (specifically Li₂NiO₂), 20 wt.% conductive agent (specifically Super P), and 5 wt.% binder (specifically polyvinylidene fluoride). The surface area of ​​the conductive agent is equal to the surface area of ​​the lithium replenishment agent (3), the D50 particle size of the lithium replenishment agent is 3.0 μm, and the particle size of the conductive agent is 30–120 nm.

[0063] A positive electrode slurry is coated on the surface of the lithium replenishment component (i.e., the surface of the lithium replenishment layer facing away from the current collector) to obtain a positive electrode material layer. This 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 replenishment component with the positive electrode material layer is then rolled, resulting in a lithium replenishment layer thickness of 5 μm.

[0064] After delithiation, the room temperature resistivity of the above-mentioned lithium replenishment component is 10 Ω·cm, and the mass ratio of the lithium replenishment residue to the positive electrode active material is 1:20. The particle size D50 of the lithium replenishment residue after delithiation is 2.5 μm.

[0065] Example 2

[0066] The difference from Example 1 is that the lithium replenishment layer comprises 90 wt.% lithium replenishing agent (specifically Li2NiO2), 1 wt.% conductive agent (specifically Super P), and 9 wt.% binder, and 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 30–120 nm.

[0067] The surface area of ​​the conductive agent is equal to the surface area of ​​the lithium replenishing agent (1). The room temperature resistivity of the lithium replenishing component after delithiation is 100 Ω·cm. The mass ratio of the lithium replenishing agent residue to the positive electrode active material after delithiation is 1:16.7. The particle size D50 of the lithium replenishing agent residue after delithiation is 2.5 μm.

[0068] Example 3

[0069] The difference from Example 1 is that the lithium replenishment layer includes 79 wt.% lithium replenishing agent (specifically Li2NiO2), 1 wt.% conductive agent (specifically Super P) and 20 wt.% binder. The D50 particle size of the lithium replenishing agent is 8 μm and the particle size of the conductive agent is 30-120 nm.

[0070] Surface area of ​​conductive agent: Surface area of ​​lithium replenishing agent = 0.8; room temperature resistivity of lithium replenishing component after delithiation: 500 Ω·cm; mass ratio of lithium replenishing agent residue to positive electrode active material after delithiation: 1:19; particle size D50 of lithium replenishing agent residue after delithiation: 7.2 μm.

[0071] Example 4

[0072] The difference from Example 1 is that the lithium replenishing layer comprises 90 wt.% lithium replenishing agent (specifically Li2NiO2), 1 wt.% conductive agent (specifically Super P), and 9 wt.% binder. The D50 particle size of the lithium replenishing agent is 0.5 μm, and the particle size of the conductive agent is 30–120 nm.

[0073] The surface area of ​​the conductive agent is 1.5 times that of the lithium replenishing agent. The room temperature resistivity of the lithium replenishing component after delithiation is 200 Ω·cm, and the mass ratio of the lithium replenishing agent residue to the positive electrode active material after delithiation is 1:16.7. The particle size of the lithium replenishing agent residue after delithiation is 0.45 μm.

[0074] Example 5

[0075] The difference from Example 1 is that the conductive agent is replaced with graphite with a particle size of 220nm-300nm. The room temperature resistivity of the lithium replenishment component after delithiation is 150Ω·cm.

[0076] Example 6

[0077] The differences from Example 1 are as follows: the particle size of the conductive agent is 30–120 nm, the D50 of the lithium replenishing agent is 20 μm, the surface area ratio of the conductive agent to the lithium replenishing agent is 8:1, and the room temperature resistivity of the lithium replenishing component after delithiation is 4 Ω·cm. The particle size of the lithium replenishing agent residue after delithiation is 18 μm.

[0078] Example 7

[0079] The difference from Example 1 is that the D50 particle size of the lithium replenishing agent 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 replenishing agent is 10:1; the room temperature resistivity of the lithium replenishing component after delithiation is 3 Ω·cm. The particle size of the lithium replenishing agent residue after delithiation is 0.9 μm.

[0080] Example 8

[0081] The difference from Example 1 is that the D50 particle size of the lithium replenishing agent is 3 μm, the particle size of the conductive agent is 20-100 nm, the surface area ratio of the conductive agent to the surface area of ​​the lithium replenishing agent is 2:1, and the room temperature resistivity of the lithium replenishing component after delithiation is 5 Ω·cm.

[0082] Example 9

[0083] The difference from Example 1 is that the thickness of the lithium replenishment layer was 30 μm before rolling and 18 μm after rolling. The mass ratio of the lithium replenishment agent residue to the positive electrode active material after delithiation was 15:100. The room temperature resistivity of the lithium replenishment component after delithiation was 500 Ω·cm.

[0084] Example 10

[0085] The difference from Example 1 is that the thickness of the lithium replenishment layer was 3 μm before rolling and 1 μm after rolling. The mass ratio of lithium replenishment agent to positive electrode active material was 0.8:100. The room temperature resistivity of the lithium replenishment component after delithiation was 200 Ω·cm.

[0086] Example 11

[0087] The difference from Example 1 is that the lithium replenishment layer includes 50 wt.% lithium replenishing agent (specifically Li2NiO2), 40 wt.% conductive agent (specifically Super P), and 10 wt.% binder. The mass ratio of the lithium replenishing agent residue after delithiation to the positive electrode active material is 2:100. The room temperature resistivity of the lithium replenishment component after delithiation is 4 Ω·cm.

[0088] Example 12

[0089] The only difference from Example 1 is that the lithium replenishing agent is replaced with Li2O2. The room temperature resistivity of the lithium replenishing component after delithiation is 300 Ω·cm.

[0090] To highlight the beneficial effects of the embodiments of this application, the following comparative examples are provided.

[0091] Comparative Example 1

[0092] The only difference from Example 1 is that the lithium replenishment layer is replaced with a conductive layer, which comprises 80 wt.% conductive agent and 20% binder, wherein the thickness of the conductive layer is 2 μm.

[0093] Comparative Example 2

[0094] The only difference from Example 1 is that the lithium replenishment layer comprises 74.5 wt.% lithium replenishing agent (specifically Li2NiO2), 0.5 wt.% conductive agent (specifically Super P), and 25 wt.% binder (specifically polyvinylidene fluoride). The specific surface area of ​​the conductive agent is 0.3, and after delithiation, the room temperature resistivity of the lithium replenishment component is 2200 Ω·cm.

[0095] Performance testing

[0096] (1) Preparation of test batteries: The positive electrodes of the above embodiments and comparative examples were assembled with negative electrode sheets to form test batteries. The negative electrode sheet includes 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 is composed of graphite, conductive agent, and binder in a mass ratio of 95:3:2. The electrolyte is a lithium hexafluorophosphate organic solution with a concentration of 1.2 mol / L, wherein the solvent is EC:DMC:EMC in a mass ratio of 1:1:1:. After formation, the test batteries of the embodiments and comparative examples are obtained. The formation process is as follows: charging at 0.05C for 3 hours, standing for 10 minutes, and then charging at 0.2C to 3.8V.

[0097] (2) Rate Performance Test: The discharge capacity of each battery was tested at 25℃ at different rates (0.5C, 1C, 2C, and 3C) as a function of the number of cycles, with a voltage range of 2.5V-3.8V. When calculating the capacity, the discharge capacity at a certain current density was used as the mass ratio of the positive electrode active material to 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. The test results for each battery are summarized in Table 1.

[0098] (3) Cycle life: Under the condition of 25±1℃, the battery is charged and discharged at 0.33C and discharged at 0.5CP for charge-discharge cycle test. The steps are as follows: rest for 10min; charge at 0.5C constant current to 3.8V, charge at constant voltage to 0.05C cutoff; rest for 10min; discharge at 0.5CP constant power to 2.5V, which is 1 cycle. Repeat this step and test the number of cycles when the battery capacity retention rate is 80%, which is the cycle life of the battery.

[0099] (4) Energy Density: Furthermore, the discharge curves obtained from the above-mentioned 0.1C constant current charge-discharge curves of each battery are integrated and divided by the first discharge capacity to obtain the average voltage of each battery, i.e., the charge-discharge voltage plateau. The gravimetric energy density of each battery is then calculated using the following formula:

[0100] Weight energy density = capacity per unit capacity × average voltage plateau / battery weight, where capacity per unit capacity refers to the capacity of the aforementioned 0.1C discharge. The results are summarized in Table 1.

[0101] (5) Battery DC internal resistance: When the battery is at 50% SOC and discharged at 2C for 30s, the ratio of the voltage difference before and after discharge to the current is the DC internal resistance (DCIR).

[0102] (6) Peel strength test of positive electrode: Using a universal tensile testing machine, each positive electrode is cut into strips with a width of 40mm and a length of 150-200mm, and the peel angle is 180° to perform the peel strength test.

[0103] Table 1

[0104]

[0105]

[0106] As can be seen from the data in Table 1, the lithium replenishment component provided in this application embodiment can be used to provide a battery with high energy density, cycle performance and rate performance.

[0107] The above description is an exemplary embodiment of this application. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principles of this application, and these improvements and modifications are also considered to be within the scope of protection of this application.

Claims

1. A lithium replenishment component, characterized in that, It includes a current collector and a lithium replenishment layer disposed on at least one side surface of the current collector; after the lithium replenishment layer is delithiated, the room temperature resistivity of the lithium replenishment component is 2 Ω·m-2000 Ω·m; The lithium replenishment layer includes a lithium replenishing agent, and the particle size D50 of the lithium replenishing agent residue after delithiation is in the range of 0.4μm-18μm; The lithium replenishment layer includes a conductive agent, wherein the conductive agent has at least one dimension with a size less than or equal to 200 nm.

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

3. The lithium replenishment component according to claim 1, characterized in that, The thickness of the current collector is 7μm-20μm; the thickness of the lithium replenishment layer is 3μm-20μm.

4. The lithium replenishment component according to claim 1, characterized in that, The lithium replenishing layer also includes 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%.

5. The lithium replenishment component according to claim 1, characterized in that, The particle size D50 of the lithium supplement is in the range of 0.5 μm to 20 μm.

6. The lithium replenishment 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 A element includes at least one of C, N, O, P, and S; The lithium metal oxide includes Li2M. 1 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 Includes at least one of Ni, Mn, Cu, Fe, Cr, and Mo; M 2 Including 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, where 0 ≤ a ≤ 1; M 4 Includes at least one of Ni, Fe, Cu, and Ru, 0 ≤ b ≤ 1; M 5 It contains at least one of Ni, Mn, Fe, Mo, Zr, Si, Cu, and Cr.

7. The lithium replenishment component according to any one of claims 1-6, characterized in that, The conductive agent includes at least one of porous carbon, acetylene black, carbon nanotubes, carbon black, Ketjen black, graphene, and Mxenes.

8. The lithium replenishment component according to any one of claims 1-7, characterized in that, The lithium replenishment layer includes an adhesive, which includes at least one of polyvinylidene fluoride, polyvinyl alcohol, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylonitrile, polyacrylic acid, sodium alginate, and styrene-butadiene rubber.

9. The lithium replenishment component according to any one of claims 1-8, characterized in that, The ratio of the sum of the surface areas of the conductive agents to the sum of the surface areas of the lithium replenishing agents is (0.1-10):

1.

10. The lithium replenishment component according to claim 9, characterized in that, The ratio of the sum of the surface areas of the conductive agents to the sum of the surface areas of the lithium replenishing agents is (0.5-5):

1.

11. The lithium replenishment component according to claim 10, characterized in that, The ratio of the sum of the surface areas of the conductive agents to the sum of the surface areas of the lithium replenishing agents is (0.8-3):

1.

12. A positive electrode, characterized in that, The positive electrode includes a lithium replenishment component and a positive electrode material layer as described in any one of claims 1-11, wherein the positive electrode material layer is disposed on the surface of the lithium replenishment layer opposite to the current collector.

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

14. The positive electrode according to claim 12, characterized in that, The positive electrode material layer includes a positive electrode active material, and the mass ratio of the lithium supplement 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 a positive electrode as described in any one of claims 12-14.

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

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

Images