Positive electrode lithium supplement and preparation method thereof, positive electrode sheet, battery and electrical equipment

Abstract

The present application provides a positive electrode lithium supplement and a preparation method thereof, a positive electrode sheet, a battery, and an electrical device. The lithium content of a first lithium supplement is higher than that of a second lithium supplement, and the delithiation voltage corresponding to the first lithium supplement is higher than the delithiation voltage corresponding to the second lithium supplement. This allows the current to be preferentially distributed to the second lithium supplement, which has a lower delithiation voltage, during the delithiation process. This allows the electrochemical reaction rate of the first lithium supplement to be controlled, suppressing the generation of oxygen free radicals during the delithiation process of the first lithium supplement, and reducing the gas production of the first lithium supplement. Furthermore, one of the first lithium supplement and the second lithium supplement is coated on at least a portion of the surface of the other, shortening the distance between the particles of the first lithium supplement and the second lithium supplement, allowing the second lithium supplement to effectively compensate for the charge of the first lithium supplement. This allows the increase in metal valence during the delithiation process of the first lithium supplement to be suppressed, reducing the occurrence of side reactions, and effectively improving the capacity retention rate of the battery.

Description

Technical Field

[0001] The present application relates to the field of batteries, and in particular to a positive electrode lithium supplement and a preparation method thereof, a positive electrode sheet, a battery and an electrical device. Background Art

[0002] In lithium-ion batteries, lithium loss is an important factor affecting battery capacity.

[0003] At present, lithium replenishment technology is mainly used to add additional lithium sources in the battery manufacturing process to compensate for the irreversible lithium loss in the first charge and discharge cycle, which helps to increase the initial capacity of the battery.

[0004] However, the additional lithium source may produce large amounts of gas and cause many side reactions during the delithiation process, which may affect the battery's capacity retention rate. Summary of the Invention

[0005] The embodiments of the present application provide a positive electrode lithium supplement and a preparation method thereof, a positive electrode sheet, a battery, and an electrical device to reduce gas production and improve battery performance.

[0006] In a first aspect, an embodiment of the present application provides a positive electrode lithium supplement, comprising:

[0007] a first lithium supplement and a second lithium supplement, wherein one of the first lithium supplement and the second lithium supplement is coated on at least a portion of the surface of the other;

[0008] The lithium content of the first lithium supplement is higher than the lithium content of the second lithium supplement;

[0009] The chemical formula of the first lithium supplement includes Li a M b O c , M is at least one of Ni, Cr, Co, Mn, Fe, Al, Cu, V, Ti, and Re;

[0010] 0<a≤6, 0<b≤3, 0<c≤6;

[0011] And / or, the chemical formula of the second lithium supplement includes Li x N y O z , N is at least one of Ni, Cr, Co, Mn, Fe, Al, Cu, V, Ti, Ru, and Mo;

[0012] 0<x≤3, 0<y≤3, 0<z≤4.

[0013] In a possible embodiment, the first lithium supplement includes at least one of Li5FeO4, Li6CoO4, Li4CoO4, and Li5ReO6;

[0014] And / or, the second lithium supplement includes Li2NiO2, Li2RuO3, Li2MnO3, Li2MoO3, Li 0.65 Ni 1.35 At least one of O2.

[0015] In a possible embodiment, at least a portion of the surface of the positive electrode lithium supplement agent is coated with a carbon coating layer.

[0016] In a possible implementation, the mass ratio of the carbon coating layer to the positive electrode lithium replenisher is 0.1%-5%.

[0017] In one possible implementation,

[0018] Before the first lithium supplement agent is delithiated, the valence state of M is at least one of +2, +3, +4 and +7;

[0019] And / or, after the first lithium supplement agent is delithiated, the valence state of M is at least one of +3 and +4.

[0020] In one possible embodiment, the volume of the first lithium supplement agent after delithiation is 40%-80% of the volume of the first lithium supplement agent before delithiation;

[0021] And / or, the volume of the second lithium supplement agent after delithiation is 70%-90% of the volume of the second lithium supplement agent before delithiation.

[0022] In one possible embodiment, the delithiation voltage of the first lithium supplement agent is 3.4V-4.4V;

[0023] And / or, the delithiation voltage of the second lithium supplement is 3.4V-4.5V.

[0024] In a possible implementation, the mass ratio of the second lithium supplement agent to the first lithium supplement agent is 10:100-70:100.

[0025] In one possible embodiment, the Dv50 of the first lithium supplement is 1 μm to 15 μm;

[0026] And / or, the Dv50 of the second lithium supplement is 0.2 μm to 12 μm.

[0027] In one possible embodiment, the first lithium supplement has a specific charge capacity of 400 mAh / g to 1200 mAh / g;

[0028] And / or, the second lithium supplement has a specific charge capacity of 240 mAh / g to 550 mAh / g.

[0029] In one possible embodiment, the specific surface area of ​​the positive electrode lithium supplement is 1m2 / g-20m 2 / g.

[0030] In a second aspect, an embodiment of the present application provides a method for preparing the positive electrode lithium supplement agent according to the first aspect, the method comprising:

[0031] The first lithium replenishing agent and the second lithium replenishing agent are mixed and then sintered to obtain the positive electrode lithium replenishing agent.

[0032] In a possible embodiment, the first lithium supplement agent and the second lithium supplement agent are mixed and then sintered, comprising:

[0033] performing a first sintering process on a first lithium supplement agent precursor to obtain a first lithium supplement agent;

[0034] performing a second sintering process on the second lithium supplement agent precursor to obtain the second lithium supplement agent;

[0035] The first lithium supplement agent, the second lithium supplement agent and a carbon source are mixed and subjected to a third sintering treatment.

[0036] In a possible embodiment, the temperature of the first sintering process is lower than the temperature of the third sintering process;

[0037] And / or, the temperature of the second sintering process is lower than the temperature of the third sintering process.

[0038] In one possible embodiment, the temperature of the first sintering treatment is 350° C.-650° C.;

[0039] And / or, the temperature of the second sintering treatment is 350°C-650°C;

[0040] And / or, the temperature of the third sintering treatment is 650° C.-900° C.;

[0041] And / or, the first sintering treatment time is 2h-24h;

[0042] And / or, the second sintering treatment time is 2h-24h;

[0043] And / or, the third sintering treatment takes 2 hours to 24 hours.

[0044] In a third aspect, an embodiment of the present application provides a positive electrode sheet, which includes the positive electrode lithium replenisher described in the first aspect or the positive electrode lithium replenisher prepared by the preparation method of the positive electrode lithium replenisher described in the second aspect.

[0045] In a fourth aspect, an embodiment of the present application provides a battery comprising the positive electrode sheet described in the third aspect.

[0046] In a fifth aspect, an embodiment of the present application provides an electrical device comprising the battery described in the fourth aspect.

[0047] The positive electrode lithium supplement agent and its preparation method, positive electrode sheet, battery and electrical equipment provided in the embodiment of the present application include a first lithium supplement agent and a second lithium supplement agent. The lithium content of the first lithium supplement agent is higher than the lithium content of the second lithium supplement agent. Then, the delithiation voltage corresponding to the first lithium supplement agent is higher than the delithiation voltage corresponding to the second lithium supplement agent, so that the current is preferentially allocated to the second lithium supplement agent with a lower delithiation voltage during the delithiation process, thereby controlling the electrochemical reaction rate of the first lithium supplement agent, suppressing the generation of oxygen free radicals during the delithiation process of the first delithiation agent, and reducing the gas production of the first lithium supplement agent. Moreover, one of the first lithium supplement agent and the second lithium supplement agent is coated on at least part of the surface of the other, which can shorten the distance between the particles of the first lithium supplement agent and the second lithium supplement agent, so that the second lithium supplement agent can effectively compensate for the charge of the first lithium supplement agent, thereby suppressing the increase of the metal valence state during the delithiation process of the first lithium supplement agent and reducing the occurrence of side reactions. By reducing the gas production of the first lithium supplement agent and the occurrence of side reactions, the capacity retention rate of the battery can be effectively improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0049] Figure 1 A schematic structural diagram of a positive electrode lithium supplement provided in this application;

[0050] Figure 2 This is a schematic structural diagram of another positive electrode lithium supplement provided in this application.

[0051] The above drawings illustrate specific embodiments of the present application, which will be described in more detail below. These drawings and the textual description are not intended to limit the scope of the present application in any way, but rather to illustrate the concepts of the present application to those skilled in the art by reference to specific embodiments. DETAILED DESCRIPTION

[0052] Exemplary embodiments will be described in detail herein, with examples illustrated in the accompanying drawings. In the following description, when referring to the drawings, identical numerals in different figures represent identical or similar elements, unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all embodiments consistent with the present application. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present application, as detailed in the appended claims.

[0053] With technological advancements and growing market demand, higher requirements are being placed on power and energy storage batteries, particularly in terms of energy density, cycle life, and calendar life. In lithium-ion batteries, lithium loss is a significant factor affecting battery capacity. Lithium replenishment technology, by adding an additional lithium source during the battery manufacturing process, compensates for the irreversible lithium loss during the initial charge and discharge cycle, helping to increase the battery's initial capacity, thereby boosting energy density, cycle life, and calendar life.

[0054] For example, the material system of ternary lithium batteries is developing towards a high-nickel positive electrode and a silicon-based negative electrode. The silicon-based negative electrode can include silicon oxide and graphite. During the first charge of a lithium-ion battery, lithium ions are extracted from the positive electrode material and embedded in the silicon oxide negative electrode material, thereby consuming some lithium. This process can also be called the first lithium insertion of silicon oxide and the consumption of effective lithium. Lithium replenishment technology can replenish the effective lithium consumed by the first lithium insertion of silicon oxide in ternary lithium batteries, thereby increasing the battery's energy density and improving the battery's cycle life and calendar life.

[0055] For another example, while lithium iron phosphate batteries are optimizing their material systems to improve battery energy density, they are also continuously developing in the direction of improving battery cycle life and storage performance. For example, when the material system is a lithium iron phosphate positive electrode and a graphite negative electrode, lithium replenishment technology can improve battery energy density to a certain extent. At the same time, pre-stored lithium can be introduced into the battery system. The pre-stored lithium continuously replenishes the active lithium consumed by the cycle during the battery cycle, thereby significantly improving the battery cycle life and storage performance. In addition, in order to further improve the battery energy density, a negative electrode with a high specific capacity can be selected, such as a silicon-based and graphite composite negative electrode. The optional material system is a lithium iron phosphate positive electrode and a silicon oxide plus graphite negative electrode. However, due to the low initial coulombic efficiency of the negative electrode, the lithium in the positive electrode material is irreversibly consumed, thereby limiting the improvement of the battery energy density. The lithium replenishment technology can introduce exogenous lithium to make up for the irreversible consumption of effective lithium. In addition, the applicant took into consideration that although the capacity of lithium iron phosphate manganese phosphate is not much different from that of lithium iron phosphate, it has a higher operating voltage. It is possible to consider combining the lithium iron phosphate manganese positive electrode with a silicon-based plus graphite negative electrode, combined with lithium replenishment technology, to further improve the battery energy density, cycle life and calendar life.

[0056] Currently, available lithium replenishment technologies include: negative electrode replenishment, positive electrode replenishment, electrolyte replenishment, separator replenishment, current collector replenishment, and electrochemical replenishment. Positive electrode replenishment involves directly adding a positive electrode replenisher to the positive electrode slurry during the homogenization process. This requires less process improvement and eliminates the need for modifications to the production environment and equipment, making it more suitable for existing lithium-ion battery manufacturing processes.

[0057] Existing positive electrode lithium supplements can be divided into three categories: the first category is binary lithium-containing compounds, such as Li2O, Li2O2, LiF, Li2S, Li3N, etc.; the second category is ternary lithium-containing compounds, such as Li5FeO4, Li6CoO4, Li4CoO4, Li2NiO2, Li5ReO6, Li2RuO3, Li2MnO3, Li2MoO3, Li 0.65 Ni 1.35 O2, etc.; the third category is organic lithium salts, such as Li2DHBN (3,4-dihydroxybenzonitrile lithium salt), Li2C2O4, Li2C4O4, Li2C3O5, Li2C4O6, etc.

[0058] However, the first and third types of cathode lithium supplements have high decomposition voltages and produce significant gassing, limiting their effectiveness in practical applications. Among the second type of cathode lithium supplements, Li5FeO4 and Li2NiO2 use low-cost metals and have lower decomposition voltages, leading to their increasing use in practical applications.

[0059] However, Li2NiO2 has a low discharge capacity and a high reversible capacity, resulting in a low effective lithium source for Li2NiO2. For example, with a theoretical discharge capacity of 340 mAh / g and an actual reversible capacity of 83 mAh / g, the effective lithium available for Li2NiO2 as a lithium replenishment source is 76%. Li5FeO4, on the other hand, has a higher theoretical specific capacity (e.g., 867 mAh / g), and in actual applications, the first delithiation releases approximately four Li+ atoms, resulting in an irreversible lithium source of 693 mAh / g. Therefore, from the perspective of lithium replenishment, Li5FeO4 is more suitable as a positive electrode lithium replenisher.

[0060] The applicant discovered that Li5FeO4, as a positive electrode lithium supplement, can be applied primarily by directly adding it to the positive electrode slurry. A positive electrode sheet is obtained through a coating-baking process, with Li5FeO4 particles uniformly distributed within the active film layer. The Li5FeO4 particles currently added are relatively large (Dv50 of 7μm to 9μm), an order of magnitude larger than those in lithium iron phosphate positive electrode active materials. This allows Li5FeO4 to fully release four available Li+ atoms at a higher decomposition voltage (e.g., 4.3V). During this process, as Li5FeO4 delithiates, Fe undergoes oxidation, increasing its valence from +3 to +4, producing residual Fe oxides. These residues can slowly release oxygen or oxygen free radicals during charge and discharge. Furthermore, the delithiation process also releases significant amounts of oxygen, leading to severe gassing during battery cycling or storage. Furthermore, metal (Ni and Fe) dissolution can increase safety risks.

[0061] At present, research on positive electrode lithium supplements mainly focuses on the selection of the lithium supplement itself, as well as the synthesis, material composition and structure optimization of the positive electrode lithium supplement. For example, the performance of the lithium supplement is improved by coating, doping or in situ growth.

[0062] However, the lack of optimization for battery gassing and thermal safety after lithium depletion by the lithium supplement has led to negative effects such as gassing and reduced thermal safety during the use of the lithium supplement. Furthermore, during the lithium depletion process, the metal in the lithium supplement may undergo phase changes and increase in metal valence, leading to an increase in side reactions in the battery system. Side reactions include, for example, metal redox reactions and catalytic electrolyte decomposition reactions. These issues, such as gassing, reduced thermal safety, and increased side reactions during the use of the lithium supplement, can affect the battery's capacity retention.

[0063] In view of this, an embodiment of the present application proposes a positive electrode lithium supplement, which comprises secondary particles composed of two different lithium supplements, a first lithium supplement and a second lithium supplement, wherein one of the first lithium supplement and the second lithium supplement is coated on at least a portion of the surface of the other.

[0064] Materials with high lithium content have a higher delithiation voltage because lithium ions occupy more lattice sites and need to overcome a stronger Li-O bond energy to release lithium ions. Therefore, when the lithium content of the first lithium replenisher is higher than that of the second lithium replenisher, the delithiation voltage corresponding to the first lithium replenisher is higher than that of the second lithium replenisher. This allows the current to be preferentially distributed to the second lithium replenisher (with a lower delithiation voltage) during the delithiation process. This can control the electrochemical reaction rate of the first lithium replenisher, inhibit the generation of oxygen free radicals during the delithiation process, and reduce the gas production of the first lithium replenisher.

[0065] Moreover, one of the first lithium supplement agent and the second lithium supplement agent is coated on at least a portion of the surface of the other, which can shorten the distance between the particles of the first lithium supplement agent and the second lithium supplement agent, so that the second lithium supplement agent can effectively compensate the charge of the first lithium supplement agent, thereby suppressing the increase of the metal valence during the delithiation process of the first lithium supplement agent and reducing the reaction of side reactions.

[0066] By reducing the gas production of the first lithium supplement and the occurrence of side reactions, the capacity retention rate of the battery can be effectively improved.

[0067] For example, the residue after delithiation of the second lithium supplement agent can be a stable oxide, which further reduces the gas production of the positive electrode lithium supplement agent, and at the same time helps to stabilize the electrochemical environment around the first lithium supplement agent and the second lithium supplement agent, which is beneficial to control the dissolution of metals in the first lithium supplement agent and the second lithium supplement agent, and further reduces the occurrence of side reactions.

[0068] It should be noted that since the lithium content of the first lithium supplement is higher than that of the second lithium supplement, the first lithium supplement can provide more lithium, and the volume ratio of the first lithium supplement after delithiation to that before delithiation is less than the volume ratio of the second lithium supplement after delithiation to that before delithiation. The positive electrode lithium supplement proposed in the embodiment of the present application is a secondary particle composed of the first lithium supplement and the second lithium supplement, that is, the first lithium supplement, the second lithium supplement, and the positive electrode lithium supplement can exist in the form of particles.

[0069] For example, lithium deintercalation can cause cracks, pores or lattice distortion in the material. High-resolution cross-sectional imaging using FIB-SEM (focused ion beam-scanning electron microscopy) can be used to compare the degree of morphological damage in different areas. Areas with more severe damage usually correspond to higher lithium extraction amounts (lithium content). EDS (energy dispersive X-ray spectroscopy) spectrum analysis is used to analyze the atomic ratio changes of transition metals (such as Fe, Ni, Co, and Mn) and oxygen elements: the valence state of transition metals increases (such as → ) is usually accompanied by the release of lithium ions, and its uneven distribution can indirectly reflect the difference in lithium content.

[0070] In some embodiments, the chemical formula of the first lithium supplement comprises Li a M b O c , M is at least one of Ni, Cr, Co, Mn, Fe, Al, Cu, V, Ti, and Re; 0<a≤6, 0<b≤3, 0<c≤6.

[0071] Wherein, a represents the number of lithium atoms, which can affect the amount of lithium ions released by the first lithium supplement agent; b represents the number of metal M, which can affect the electrochemical properties and stability of the first lithium supplement agent; c represents the number of oxygen atoms, which can affect the crystal structure of the first lithium supplement agent; 0<a≤6, 0<b≤3, 0<c≤6, thereby meeting the lithium supplement demand.

[0072] For example, a can be 0.1, 0.4, 0.7, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, or a range consisting of any two thereof.

[0073] b can be 0.1, 0.3, 0.6, 1, 1.4, 1.7, 2, 2.3, 2.6, 2.8, 3 or a range consisting of any two thereof.

[0074] c can be 0.1, 0.4, 0.7, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6 or a range consisting of any two thereof.

[0075] In some embodiments, the chemical formula of the second lithium supplement includes Li x N yO z , N is at least one of Ni, Cr, Co, Mn, Fe, Al, Cu, V, Ti, Ru, and Mo; 0<x≤3, 0<y≤3, 0<z≤4.

[0076] Among them, x represents the number of lithium atoms, which can affect the amount of lithium ions released by the second lithium supplement agent; y represents the number of metal N, which can affect the electrochemical properties and stability of the second lithium supplement agent; z represents the number of oxygen atoms, which can affect the crystal structure of the second lithium supplement agent, 0<x≤3, 0<y≤3, 0<z≤4, thereby assisting the first lithium supplement agent in solving the above-mentioned problems such as gas production, phase change, and side reactions.

[0077] For example, x can be 0.1, 0.3, 0.8, 1.1, 1.2, 1.4, 1.5, 1, 7, 1.8, 2, 2.2, 2.4, 2.5, 2.7, 2.9, 3, or a range consisting of any two thereof.

[0078] y may be 0.1, 0.3, 0.6, 1, 1.4, 1.7, 2, 2.3, 2.6, 2.8, 3, or a range consisting of any two thereof.

[0079] z can be 0.1, 0.3, 0.6, 1, 1.4, 1.7, 2, 2.3, 2.6, 2.8, 3, 3.2, 3.4, 3.6, 3.8, 4 or a range consisting of any two thereof.

[0080] For example, the first lithium supplement can be lithium-rich lithium ferrite, and the second lithium supplement can be lithium-rich lithium nickelate. Since Fe oxidation occurs during the delithiation process of lithium-rich lithium ferrite, the valence state increases and becomes an unstable oxidation state, which may lead to an increase in side reactions. During the delithiation process of lithium-rich lithium nickelate, the valence state of Ni changes from +2 to +4. The second lithium supplement can act as an electron donor to provide charge compensation for the first lithium supplement during the delithiation process, so that the increase in the metal valence state in the first lithium supplement is effectively suppressed, reducing the occurrence of side reactions. Moreover, one of lithium-rich nickelate and lithium-rich lithium ferrite is coated on at least part of the surface of the other, which can shorten the distance between the lithium supplement particles, so that lithium-rich lithium nickelate can more effectively compensate for the charge of lithium-rich lithium ferrite, further reducing the occurrence of side reactions.

[0081] For example, the lithium-rich lithium nickelate may be coated on at least a portion of the surface of the lithium-rich lithium ferrite, or the lithium-rich lithium ferrite may be coated on at least a portion of the surface of the lithium-rich lithium nickelate. For example, when the particle size of the lithium-rich lithium nickelate is smaller than the particle size of the lithium-rich lithium ferrite, the lithium-rich lithium nickelate is coated on the surface of the lithium-rich lithium ferrite; when the particle size of the lithium-rich lithium ferrite is smaller than the particle size of the lithium-rich lithium nickelate, the lithium-rich lithium ferrite is coated on the surface of the lithium-rich lithium nickelate.

[0082] In some optional embodiments, at least a portion of the surface of the positive electrode lithium supplement is coated with a carbon coating layer, which can form a barrier to prevent external moisture from invading the first lithium supplement and the second lithium supplement, slowing down the water absorption failure rate of the first lithium supplement and the second lithium supplement. At the same time, the physical barrier formed by the carbon coating layer also effectively reduces the risk of metal dissolution in the residues after delithiation of the first lithium supplement and the second lithium supplement.

[0083] In some embodiments, the second lithium supplement agent and the carbon coating layer form a composite coating layer for the first lithium supplement agent, and the composite coating layer improves the water absorption failure resistance of the first lithium supplement agent. The carbon coating layer and the second lithium supplement agent form a double coating relative to the first lithium supplement agent, more effectively preventing external moisture from invading the first lithium supplement agent. Furthermore, the second lithium supplement agent, bound by the carbon coating layer, is closely connected to the first lithium supplement agent and has abundant electron pathways. This allows current to be preferentially distributed to the second lithium supplement agent during the delithiation process, reducing the decomposition polarization of the first lithium supplement agent. Furthermore, the physical proximity of the second lithium supplement agent allows the second lithium supplement agent to more effectively provide charge compensation for the first lithium supplement agent.

[0084] For example, the second lithium supplement agent can cover a portion of the surface of the first lithium supplement agent, and the carbon coating layer covers a portion of the surface of the first lithium supplement agent and a portion of the surface of the second lithium supplement agent, such as Figure 1 The second lithium supplement agent may also cover the entire surface of the first lithium supplement agent, and the carbon coating layer covers the entire surface of the second lithium supplement agent.

[0085] In some embodiments, a carbon coating layer is coated on the outer surfaces of the first and second lithium supplement agents, forming a binding effect on the first and second lithium supplement agents, ensuring an electron pathway for the first and second lithium supplement agents, improving the lithium ion insertion and extraction pathways in the two lithium supplement agents, and improving the electrochemical performance of the battery. Furthermore, the carbon coating layer can form a barrier to prevent external moisture from invading the first and second lithium supplement agents, slowing the rate of water absorption failure of the first and second lithium supplement agents. Furthermore, the physical barrier formed by the carbon coating layer effectively reduces the risk of metal dissolution in the residues left after delithiation of the first and second lithium supplement agents.

[0086] For example, the second lithium supplement agent can cover part of the surface of the first lithium supplement agent, and the carbon coating layer can cover the surfaces of the first lithium supplement agent and the second lithium supplement agent, such as Figure 2 As shown, the carbon coating layer slows down the water absorption failure rate of the first lithium supplement agent and the second lithium supplement agent, and reduces the risk of metal dissolution in the residues after delithiation of the first lithium supplement agent and the second lithium supplement agent.

[0087] In some examples, the mass of the carbon coating layer accounts for 0.1%-5% of the mass of the positive electrode lithium supplement. The mass ratio of the carbon coating layer affects the thickness of the carbon coating layer and also affects the coating integrity of the carbon coating layer, which in turn affects the power performance, cycle performance, and storage performance of the battery product. By adjusting the mass ratio, the carbon coating layer can have a more appropriate thickness and coating integrity, thereby improving the power performance, cycle performance, and storage performance of the battery product.

[0088] For example, the mass proportion of the carbon coating layer in the positive electrode lithium supplement can be 0.1%, 0.5%, 0.8%, 1%, 1.3%, 1.8%, 2%, 2.4%, 2.7%, 3%, 3.5%, 4%, 4.5%, 5% or a range consisting of any two thereof.

[0089] As an implementation method, the first lithium supplement includes at least one of Li5FeO4, Li6CoO4, Li4CoO4, and Li5ReO6. The lithium content of the first lithium supplement is relatively high, thereby improving the battery energy density and extending the battery cycle life.

[0090] As an implementation method, the second lithium supplement includes Li2NiO2, Li2RuO3, Li2MnO3, Li2MoO3, Li 0.65 Ni 1.35 O2, the product after the second lithium supplement agent is delithiated is a stable oxide with a lower gas production.

[0091] In some examples, during the first delithiation process of the second lithium supplement agent, as Li+ is removed, the valence of the metal N in the second lithium supplement agent increases, and the valence of the metal N can be at least one of +2, +3 and +4, so that the residue after the second lithium supplement agent is delithiation is a stable oxide. For example, the second lithium supplement agent is Li2NiO2, and the residue after the second lithium supplement agent is delithiation is Li2NiO2, Li 1.5 NiO2, LiNiO2, Li 0.5 At least one of NiO2 and NiO2.

[0092] During the first lithium supplementation process, as Li+ is released, the valence of the metal M in the first lithium supplementation agent increases. The increase in the valence of the metal M is accompanied by the precipitation of oxygen, and there is O 2- , O - Correspondingly, the valence state of M is at least one of +2, +3, +4 and +7. In this case, M is prone to undergo redox reactions, resulting in an increase in side reactions.

[0093] Since the delithiation of the second lithium supplement can also compensate for the charge of the first lithium supplement, the increase in the metal valence in the first lithium supplement is reduced, so that the increase in the metal valence in the first lithium supplement is effectively suppressed, thereby reducing the occurrence of side reactions. Accordingly, after the first lithium supplement is delithiated, the valence state of M exists in at least one of +3 and +4. For example, the first lithium supplement is Li5FeO4, and the product after the first lithium supplement is delithiated is Li3FeO 3.5 , LiFeO2.

[0094] As an implementation method, XRD (X-ray Diffractometer), XPS (X-ray photoelectron spectroscopy), and synchrotron radiation small-angle X-ray can be used to detect the valence state of the metal M in the first lithium supplement, the residue after delithiation from the first lithium supplement, the valence state of the metal N in the second lithium supplement, and the residue after delithiation from the second lithium supplement. Furthermore, these detection methods can detect that virtually no oxygen or oxygen free radicals are released during delithiation from the second lithium supplement.

[0095] In some embodiments, the first lithium supplement agent is in the form of particles. After delithiation, the particles collapse, and the volume of the first lithium supplement agent after delithiation is 40%-80% of the volume of the first lithium supplement agent before delithiation. Because the second lithium supplement agent coats at least a portion of the surface of the first lithium supplement agent, particle shrinkage and collapse are reduced, thereby reducing the volume change of the first lithium supplement agent before and after delithiation, and improving electrical contact between the positive electrode active materials.

[0096] In some embodiments, the second lithium replenisher has low gas production, and the product after delithiation is a stable oxide. Therefore, the volume change of the second lithium replenisher after delithiation is small. The volume of the second lithium replenisher after delithiation is 70%-90% of the volume of the second lithium replenisher before delithiation.

[0097] As an implementation method, SEM-FIB modeling can be used for quantification. The volume of the void structure where the lithium supplement particles are located after delithiation can be quantified, and the volume of the particles themselves after delithiation can also be quantified.

[0098] It should be noted that the relative positions of the first lithium supplement agent after delithiation and the second lithium supplement agent after delithiation do not change. For example, the second lithium supplement agent after delithiation can be distributed on part or all of the surface of the first lithium supplement agent after delithiation.

[0099] In some embodiments, the delithiation voltage range of the first lithium supplement can be 3.4V-4.4V. Lowering the upper limit of the delithiation voltage can effectively mitigate side reactions within the battery and reduce the risk of metal dissolution in the residue after the decomposition of the lithium supplement. However, if the upper limit of the delithiation voltage is too low, it will affect the delithiation depth of the lithium supplement and affect the lithium replenishment effect of the lithium supplement. Within this voltage range, the decomposition polarization of the first lithium supplement is relatively small, resulting in a more gradual phase transition during the delithiation process. This gentle phase transition can reduce cracks in the first lithium supplement after delithiation and prevent drastic volume changes, helping to provide a stable lithium source, while also improving the thermal stability of the battery and enhancing battery safety.

[0100] The delithiation voltage range of the second lithium replenisher can be 3.4V-4.5V. Within this voltage range, there is no obvious phase change phenomenon during the delithiation process of the second lithium replenisher, thereby improving the thermal stability of the battery.

[0101] It should be noted that during the decomposition process of lithium removal, when the decomposition voltage is higher than 3.65V, the second lithium supplement can obtain the decomposition current before the first lithium supplement, so that the decomposition polarization of the first lithium supplement becomes smaller, thereby causing a more moderate phase change during the decomposition process of lithium removal.

[0102] For example, the delithiation voltage of the first lithium supplement may be 3.4-4.3 V, further 3.4-4.1 V, and further 3.4-4.0 V, so as to reduce the decomposition polarization of the first lithium supplement.

[0103] The delithiation voltage of the second lithium supplement may be 3.4-4.3V, further 3.4-4.1V, and further 3.4-4.0V.

[0104] It should be noted that the delithiation voltage of the lithium supplement is related to the material of the lithium supplement itself.

[0105] As a specific implementation method, the pore distribution of the lithium supplement agent particles can be quantified by SEM-FIB to observe the cracks of the lithium supplement agent after delithiation, thereby evaluating the rationality of the delithiation voltage.

[0106] In some embodiments, the mass ratio of the second lithium supplement to the first lithium supplement can be 10:100-70:100. The mass ratio of the second lithium supplement to the first lithium supplement is related to the specific capacity of the positive electrode lithium supplement. The higher the proportion of the second lithium supplement, the lower the delithiation specific capacity of the positive electrode lithium supplement, but it can better suppress the delithiation phase transition of the first lithium supplement and the increase in the metal valence state in the first lithium supplement. The lower the proportion of the second lithium supplement, the higher the delithiation specific capacity of the positive electrode lithium supplement. By using the mass ratio within the above range, lithium secondary batteries using the above positive electrode lithium supplement can meet different application scenarios.

[0107] For example, the mass ratio of the second lithium supplement agent to the first lithium supplement agent can be 10:100, 15:100, 20:100, 25:100, 30:100, 35:100, 40:100, 45:100, 50:100, 55:100, 60:100, 70:100 or a range consisting of any two thereof.

[0108] In some embodiments, the particle sizes of the first and second lithium supplements range from submicron to micron. The average particle size of the first lithium supplement may be larger than the average particle size of the second lithium supplement, and the particle size of the first lithium supplement may be of the same order of magnitude as the particle size of the second lithium supplement. When the particle sizes of the first and second lithium supplements are both micron-sized, the two materials form secondary particles with a twin structure. When the particle size of the first lithium supplement is larger than that of the second lithium supplement, the second lithium supplement is coated on the surface of the first lithium supplement and encapsulated by a carbon coating. In both cases, the secondary particles are composed of the first and second lithium supplements, and the second lithium supplement can function as both a lithium supplement and a stabilizer.

[0109] The reduction in the particle size of the second lithium replenisher shortens the path for lithium ion escape and increases the interfacial area of ​​the second lithium replenisher for lithium decomposition, thereby obtaining more decomposition current during the decomposition and delithiation process, thereby reducing the polarization of the first lithium replenisher during the first charging and decomposition process, and inhibiting the phase change and metal valence increase of the first material.

[0110] In some examples, the Dv50 of the first lithium supplement can be 1 μm to 15 μm, meaning that the particle size corresponding to 50% of the cumulative volume of the first lithium supplement is 1 μm to 15 μm. This particle size range facilitates the processing of the material particles and the processing stability of the slurry during slurrying.

[0111] For example, the Dv50 of the first lithium supplement may be 1 μm, 2 μm, 4 μm, 5 μm, 7 μm, 8 μm, 10 μm, 11 μm, 12 μm, 14 μm, 15 μm, or a range consisting of any two thereof.

[0112] For example, the Dv50 of the first lithium supplement may be 1 μm to 12 μm, or further may be 2 μm to 10 μm.

[0113] In some examples, the Dv50 of the second lithium supplement can be 0.2 μm to 12 μm, meaning that when the cumulative volume percentage of the second lithium supplement reaches 50%, the corresponding particle size is 0.2 μm to 12 μm. This particle size range facilitates the processing of material particles and the processing stability of the slurry during slurrying.

[0114] For example, the Dv50 of the second lithium supplement may also be 0.2 μm, 0.4 μm, 0.8 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, or a range consisting of any two thereof.

[0115] For example, the Dv50 of the second lithium supplement may be 0.2 μm to 10 μm, and further may be 0.4 μm to 8 μm.

[0116] In some embodiments, the first lithium supplement may have a specific charge capacity of 400 mAh / g to 1200 mAh / g. The first lithium supplement is a primary lithium supplement and has a larger specific charge capacity, thereby being able to provide more lithium ions and improve the capacity and performance of the battery.

[0117] For example, the charge capacity of the first lithium supplement may be 400 mAh / g, 500 mAh / g, 600 mAh / g, 700 mAh / g, 800 mAh / g, 900 mAh / g, 1000 mAh / g, 1100 mAh / g, 1200 mAh / g, or a range consisting of any two thereof.

[0118] The second lithium supplement agent may have a specific charge capacity of 240 mAh / g to 550 mAh / g. The second lithium supplement agent is an auxiliary lithium supplement agent with a smaller specific charge capacity, thereby assisting the first lithium supplement agent in providing lithium ions.

[0119] For example, the charge capacity of the second lithium supplement may be 240 mAh / g, 300 mAh / g, 350 mAh / g, 400 mAh / g, 450 mAh / g, 500 mAh / g, 550 mAh / g, or a range consisting of any two thereof.

[0120] In some embodiments, the specific surface area of ​​the positive electrode lithium supplement can be 1m 2 / g-20m 2 / g, which makes the positive electrode lithium supplement have higher reactivity or adsorption capacity.

[0121] For example, the specific surface area of ​​the positive electrode lithium supplement can be 1m 2 / g, 2m 2 / g、5m 2 / g、8m 2 / g, 10 m 2 / g, 12 m 2 / g, 15 m 2 / g, 18 m 2 / g, 20 m 2 / g or a range consisting of any two thereof.

[0122] For example, the specific surface area of ​​the positive electrode lithium supplement can be 2m 2 / g-18m 2 / g, further, it can be 6 m 2 / g-15m 2 / g.

[0123] The present invention also provides a method for preparing the positive electrode lithium supplement, comprising the following steps:

[0124] The first lithium replenishing agent and the second lithium replenishing agent are mixed and then sintered to obtain a positive electrode lithium replenishing agent.

[0125] The above method obtains the positive electrode lithium replenisher through solid-phase mixed sintering. It does not require the addition of solvent. It only requires the first lithium replenisher and the second lithium replenisher to be mixed and sintered under solid-phase conditions. The high-temperature solid-phase mixed sintering method is more efficient and convenient and more suitable for industrial production.

[0126] For example, the first lithium replenisher is lithium-rich lithium ferrite, and the second lithium replenisher is lithium-rich lithium nickelate. In the process of sintering the lithium-rich lithium ferrite and lithium-rich lithium nickelate into secondary particles, the nickel element in the lithium-rich nickelate is doped into the lithium-rich lithium nickelate, so that the structural stability of the lithium-rich lithium ferrite is improved, the conductivity is improved, and the polarization effect of the decomposition process is reduced. In addition, it not only reduces the risk of iron dissolution in the residue after decomposition, but also improves the water absorption failure of the lithium-rich lithium ferrite particles.

[0127] In some embodiments, a first lithium supplement agent precursor is subjected to a first sintering process to obtain a first lithium supplement agent, and a second lithium supplement agent precursor is subjected to a second sintering process to obtain a second lithium supplement agent. After obtaining the first lithium supplement agent and the second lithium supplement agent, the first lithium supplement agent and the second lithium supplement agent can be mixed and then ball milled so that the second lithium supplement agent can be coated on at least a portion of the surface of the first lithium supplement agent, or the first lithium supplement agent can be coated on at least a portion of the surface of the second lithium supplement agent.

[0128] In some embodiments, after the first and second lithium supplement agents are mixed and ball-milled, they may be subjected to a third sintering process with a carbon source to coat the surfaces of the first and second lithium supplement agents with carbon.

[0129] As a specific implementation method, the first lithium supplement agent and the second lithium supplement agent can be crushed to corresponding particle sizes, for example, the particle size of the first lithium supplement agent is larger than the particle size of the second lithium supplement agent. Then, the first lithium supplement agent and the second lithium supplement agent are sintered.

[0130] In some embodiments, the temperature of the first sintering process may be 350° C.-650° C. Setting this temperature range helps to obtain a stable lithium supplement.

[0131] For example, the temperature of the first sintering process may be 350° C., 400° C., 450° C., 500° C., 550° C., 600° C., 650° C., or a range consisting of any two thereof.

[0132] In some embodiments, the temperature of the second sintering process may be 350° C.-650° C. Setting this temperature range helps to obtain a stable lithium supplement.

[0133] For example, the temperature of the second sintering process may be 350° C., 400° C., 450° C., 500° C., 550° C., 600° C., 650° C., or a range consisting of any two thereof.

[0134] In some embodiments, the temperature of the third sintering process may be 650° C.-900° C. By setting this temperature range, a carbon coating layer may be coated on the surfaces of the first lithium supplement agent and the second lithium supplement agent.

[0135] For example, the temperature of the third sintering process may be 650° C., 700° C., 750° C., 800° C., 850° C., 900° C., or a range consisting of any two thereof.

[0136] As a specific implementation manner, the first sintering process and the second sintering process are both performed under a protective atmosphere, and the protective atmosphere includes a nitrogen atmosphere or an argon atmosphere.

[0137] In some embodiments, the first sintering treatment may last for 2 hours to 24 hours, which helps the second lithium supplement agent to coat the surface of the first lithium supplement agent.

[0138] For example, the time of the first sintering treatment can be 2 h, 3 h, 5 h, 8 h, 10 h, 12 h, 15 h, 18 h, 20 h, 22 h, 24 h, or a range consisting of any two thereof.

[0139] In some examples, the second sintering treatment may last for 2 hours to 24 hours, which helps the carbon coating layer to coat the surfaces of the first lithium supplement agent and the second lithium supplement agent.

[0140] For example, the time of the second sintering treatment can be 2 h, 3 h, 5 h, 8 h, 10 h, 12 h, 15 h, 18 h, 20 h, 22 h, 24 h, or a range consisting of any two thereof.

[0141] In some examples, the third sintering treatment may last for 2 hours to 24 hours, which helps the carbon coating layer to coat the surfaces of the first lithium supplement agent and the second lithium supplement agent.

[0142] For example, the time of the third sintering treatment can be 2 h, 3 h, 5 h, 8 h, 10 h, 12 h, 15 h, 18 h, 20 h, 22 h, 24 h, or a range consisting of any two thereof.

[0143] The embodiment of the present application further provides a positive electrode sheet, which includes the above-mentioned positive electrode lithium replenisher or the positive electrode lithium replenisher prepared by the above-mentioned preparation method.

[0144] Since the positive electrode sheet of the present application includes the above-mentioned positive electrode lithium replenishing agent, it can exert an excellent lithium replenishing effect when used in a battery.

[0145] In a specific embodiment of the present application, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer arranged on at least one side of the positive electrode current collector, and the positive electrode active material layer includes the above-mentioned positive electrode lithium replenisher or the positive electrode lithium replenisher prepared by the above-mentioned preparation method.

[0146] The positive electrode current collector of the present application can be selected from positive electrode current collectors commonly used in the art, such as aluminum foil.

[0147] The positive electrode active material layer of the present application includes components such as a positive electrode active material, a conductive agent and a binder in addition to the positive electrode lithium supplement.

[0148] Among them, the positive electrode active material includes but is not limited to one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium manganese oxide, nickel cobalt manganese ternary material, nickel cobalt aluminum ternary material, lithium iron phosphate, lithium nickel manganese oxide, lithium-rich manganese-based materials, etc.

[0149] The conductive agent includes, but is not limited to, one or more of conductive carbon black, Super-C, acetylene black, Ketjen black, and carbon nanofiber.

[0150] The binder includes, but is not limited to, one or more of polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC-Na), polyvinyl pyrrolidone, polytetrafluoroethylene, and styrene-butadiene rubber (SBR).

[0151] In a specific implementation, the positive electrode sheet can be prepared by the following method: the positive electrode active material, the positive electrode lithium supplement, the conductive agent and the binder are dispersed in a solvent in proportion to obtain a slurry, and the slurry is then coated on at least one surface of the positive electrode current collector. The positive electrode sheet can be obtained after drying, slitting and rolling.

[0152] The present application also provides a battery comprising the aforementioned positive electrode sheet. Since the battery comprises the aforementioned positive electrode sheet with the positive electrode lithium replenisher, the battery has a higher first-cycle coulombic efficiency and more excellent cycle performance during use.

[0153] The battery of the present invention includes, in addition to the above-mentioned positive electrode sheet, a separator and a negative electrode sheet.

[0154] The function of the separator is to separate the positive and negative electrodes, preventing contact and short circuits between them while allowing lithium ions to pass freely. It should be noted that during use, the surface of the separator with the lithium replenishment layer is positioned opposite the separator, allowing the lithium replenishment layer to fully replenish the positive electrode.

[0155] The separator can be a porous separator conventionally used in the art with good chemical stability and mechanical stability, including but not limited to one or more of polypropylene, polyethylene, glass fiber, and non-woven fabric.

[0156] In one possible embodiment, the separator of the present invention can be formed by coating or depositing a positive electrode lithium replenishing agent on the surface of the separator substrate to form a lithium replenishing layer, thereby obtaining a separator having a composite lithium replenishing layer. The coating can be performed by spraying, spin coating, slurry coating, etc., and the deposition can be performed by physical deposition or chemical deposition.

[0157] Taking into account the difference in bonding strength between the positive electrode lithium replenisher and different types of diaphragm matrices, a binder can be added to the lithium replenishing layer to enhance the bonding strength between the lithium replenishing layer and the diaphragm matrix, thereby enhancing its performance.

[0158] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector. The negative electrode current collector can be selected from the negative electrode current collectors conventionally used in the art, such as copper foil. The negative electrode active material layer can also refer to the conventional composition in the art. For example, the negative electrode active material layer includes a negative electrode active substance, a conductive agent and a binder. The negative electrode active substance can be selected from the negative electrode active substances conventionally used in the art, including but not limited to one or more of natural graphite, artificial graphite, silicon-carbon material, silicon-oxygen material, and hard carbon. The composition of the conductive agent and the binder can refer to the types of conductive agent and binder in the positive electrode sheet, which will not be repeated here.

[0159] The electrolyte is a medium between the positive and negative electrodes that conducts lithium ions. It can be a gel, solid, or liquid electrolyte. This application does not specifically limit the type of electrolyte; it can be selected from gel, solid, or liquid electrolytes commonly used in the art.

[0160] In a specific embodiment, the battery of the present application can be prepared by the following method:

[0161] The positive electrode active material, positive electrode lithium supplement, conductive agent and binder are dispersed in a solvent in proportion to obtain a slurry, and the slurry is then coated on at least one side of the positive electrode current collector, and the positive electrode sheet is obtained after drying, slitting and rolling.

[0162] Coating or depositing a positive electrode lithium replenishing agent on the surface of a diaphragm substrate to obtain a diaphragm composited with a lithium replenishing layer;

[0163] The negative electrode active material, conductive agent and binder are dispersed in a solvent in proportion to obtain a slurry, and the slurry is then coated on at least one side of the negative electrode current collector, and the negative electrode sheet is obtained after drying, slitting and rolling.

[0164] After the positive electrode sheet, separator and negative electrode sheet are stacked in sequence, a battery cell is obtained through a lamination or winding process, and then the battery of the present application can be obtained through baking, liquid injection, formation, packaging and other processes.

[0165] The batteries of the present application may include battery cells, battery modules, and battery packs. In some embodiments, battery cells may be assembled into a battery module, which may contain one or more battery cells, with the specific number selected by those skilled in the art based on the application and capacity of the battery module. In some embodiments, battery modules may also be assembled into a battery pack, which may contain one or more battery modules, with the specific number selected by those skilled in the art based on the application and capacity of the battery pack.

[0166] There is no particular restriction on the specific type of battery in this application. For example, from the perspective of shape, the battery includes but is not limited to square shell batteries, soft pack batteries and cylindrical batteries, etc., and this application does not impose any particular restrictions. From the perspective of the core structure, the core of the battery can be a wound core (i.e., the positive electrode sheet, the negative electrode sheet and the separator are stacked and then wound to form the core), or it can be a laminated core (i.e., multiple positive electrode sheets, negative electrode sheets and separators are stacked to form the core). The outer shell can be a hard shell (such as a steel shell, a hard plastic shell, etc.), or a soft shell (such as an aluminum plastic film, a bag-type soft shell, etc.). This application does not impose any particular restrictions.

[0167] An embodiment of the present application further provides an electrical device including the above-mentioned battery. The electrical device has advantages corresponding to the above-mentioned positive electrode sheet, which will not be described in detail.

[0168] The electrical equipment in the embodiments of the present application can be conventional electrical equipment in the field, such as power equipment (such as electric vehicles, electric cars), electronic equipment (such as mobile phones, tablets, laptops, digital cameras, etc.), wearable devices (such as watches, bracelets, VR glasses, etc.), energy storage power stations, etc., without special restrictions.

[0169] The battery provided by the present invention, its preparation method and application will be specifically introduced below through specific embodiments.

[0170] Unless otherwise specified, the reagents, materials, and instruments used in the following examples are conventional reagents, conventional materials, and conventional instruments in the art and can be obtained commercially. The reagents involved can also be synthesized by conventional methods in the art.

[0171] Example 1

[0172] (1) lithium oxide (Li2O) and iron oxide (Fe2O3) were weighed at a molar ratio of 5.5:1 and mixed to obtain a first lithium supplement precursor;

[0173] (2) lithium oxide (Li2O) and nickel oxide (NiO) were weighed at a molar ratio of 1.1:1 and mixed to obtain a second lithium supplement precursor;

[0174] (3) subjecting the first lithium supplement precursor obtained in step (1) to a first sintering treatment at 650° C. for 12 h to obtain the first lithium supplement Li5FeO4;

[0175] (4) subjecting the second lithium replenisher precursor obtained in step (2) to a first sintering treatment at 650° C. for 12 h to obtain the second lithium replenisher Li2NiO2;

[0176] (5) Li5FeO4 and Li2NiO2 obtained from the first sintering treatment were weighed, mixed in a 1:1 molar ratio, and ball milled for 2 h;

[0177] (6) The Li5FeO4 and Li2NiO2 mixture obtained by ball milling was weighed and mixed with glucose in a ratio of 100:5.

[0178] (7) The mixture of step (6) is subjected to a second sintering treatment at 850° C. for 8 h to obtain a positive electrode lithium supplement having a carbon-coated surface;

[0179] (8) The positive electrode lithium supplement obtained in step (7) uses a specific surface area of ​​3m 2 / g, the Dv50 of the first lithium replenisher is 7μm, the Dv50 of the second lithium replenisher is 5μm, the mass percentage of the second lithium replenisher to the first lithium replenisher is 50%, and the mass percentage of carbon is 2%. The positive electrode replenisher is mixed with lithium iron phosphate, SP, PVDF, and NMP in a mass ratio of 2:100:2:2.5:60 to prepare a positive electrode slurry. The obtained positive electrode slurry is evenly coated on aluminum foil and vacuum dried to obtain a positive electrode sheet.

[0180] (9) Hard carbon, SP, CMC, SBR and deionized water were mixed evenly in a mass ratio of 90:4:3:3:50, and then coated on an aluminum foil current collector. After drying, the negative electrode sheet was obtained by roller pressing.

[0181] (10) The positive electrode lithium supplement agent is evenly coated on a 14 μm polypropylene (PP) separator and vacuum dried to obtain a separator.

[0182] (10) Stacking the positive electrode sheet, negative electrode sheet, and separator in order to obtain a core;

[0183] (11) After the core is encased, 1 mol / l LiPF6 (lithium hexafluorophosphate) electrolyte is injected, and the battery is obtained after formation and capacity separation.

[0184] Example 2

[0185] The difference from Example 1 is that in step (8), a specific surface area of ​​1m 2 / g, the Dv50 of the first lithium replenisher is 7μm, the Dv50 of the second lithium replenisher is 5μm, the mass percentage of the second lithium replenisher and the first lithium replenisher is 50%, and the mass percentage of carbon is 2%.

[0186] Example 3

[0187] The difference from Example 1 is that in step (8), a specific surface area of ​​10m 2 / g, the Dv50 of the first lithium replenisher is 7μm, the Dv50 of the second lithium replenisher is 5μm, the mass percentage of the second lithium replenisher and the first lithium replenisher is 50%, and the mass percentage of carbon is 2%.

[0188] Example 4

[0189] The difference from Example 1 is that in step (8), a specific surface area of ​​20 m 2 / g, the Dv50 of the first lithium replenisher is 7μm, the Dv50 of the second lithium replenisher is 5μm, the mass percentage of the second lithium replenisher and the first lithium replenisher is 50%, and the mass percentage of carbon is 2%.

[0190] Example 5

[0191] The difference from Example 1 is that in step (8), a specific surface area of ​​0.2 m 2 / g, the Dv50 of the first lithium replenisher is 7μm, the Dv50 of the second lithium replenisher is 5μm, the mass percentage of the second lithium replenisher and the first lithium replenisher is 50%, and the mass percentage of carbon is 2%.

[0192] Example 6

[0193] The difference from Example 1 is that in step (8), a specific surface area of ​​21m 2 / g, the Dv50 of the first lithium replenisher is 7μm, the Dv50 of the second lithium replenisher is 5μm, the mass percentage of the second lithium replenisher and the first lithium replenisher is 50%, and the mass percentage of carbon is 2%.

[0194] Example 7

[0195] The difference from Example 1 is that in step (8), a specific surface area of ​​3m 2 / g, the Dv50 of the first lithium replenisher is 1 μm, the Dv50 of the second lithium replenisher is 5 μm, the mass percentage of the second lithium replenisher to the first lithium replenisher is 50%, and the mass percentage of carbon is 2%.

[0196] Example 8

[0197] The difference from Example 1 is that in step (8), a specific surface area of ​​3m 2 / g, the Dv50 of the first lithium replenisher is 8μm, the Dv50 of the second lithium replenisher is 5μm, the mass percentage of the second lithium replenisher to the first lithium replenisher is 50%, and the mass percentage of carbon is 2%.

[0198] Example 9

[0199] The difference from Example 1 is that in step (8), a specific surface area of ​​3m 2 / g, the Dv50 of the first lithium replenisher is 15μm, the Dv50 of the second lithium replenisher is 5μm, the mass percentage of the second lithium replenisher to the first lithium replenisher is 50%, and the mass percentage of carbon is 2%.

[0200] Example 10

[0201] The difference from Example 1 is that in step (8), a specific surface area of ​​3m 2 / g, the Dv50 of the first lithium replenisher is 0.2μm, the Dv50 of the second lithium replenisher is 5μm, the mass percentage of the second lithium replenisher and the first lithium replenisher is 50%, and the mass percentage of carbon is 2%.

[0202] Example 11

[0203] The difference from Example 1 is that in step (8), a specific surface area of ​​3m 2 / g, the Dv50 of the first lithium replenisher is 16μm, the Dv50 of the second lithium replenisher is 5μm, the mass percentage of the second lithium replenisher to the first lithium replenisher is 50%, and the mass percentage of carbon is 2%.

[0204] Example 12

[0205] The difference from Example 1 is that in step (8), a specific surface area of ​​3m 2 / g, the Dv50 of the first lithium replenisher is 7μm, the Dv50 of the second lithium replenisher is 0.2μm, the mass percentage of the second lithium replenisher to the first lithium replenisher is 50%, and the mass percentage of carbon is 2%.

[0206] Example 13

[0207] The difference from Example 1 is that in step (8), a specific surface area of ​​3m2 / g, the Dv50 of the first lithium replenisher is 7μm, the Dv50 of the second lithium replenisher is 6μm, the mass percentage of the second lithium replenisher and the first lithium replenisher is 50%, and the mass percentage of carbon is 2%.

[0208] Example 14

[0209] The difference from Example 1 is that in step (8), a specific surface area of ​​3m 2 / g, the Dv50 of the first lithium replenisher is 7μm, the Dv50 of the second lithium replenisher is 12μm, the mass percentage of the second lithium replenisher to the first lithium replenisher is 50%, and the mass percentage of carbon is 2%.

[0210] Example 15

[0211] The difference from Example 1 is that in step (8), a specific surface area of ​​3m 2 / g, the Dv50 of the first lithium replenisher is 7μm, the Dv50 of the second lithium replenisher is 0.1μm, the mass percentage of the second lithium replenisher to the first lithium replenisher is 50%, and the mass percentage of carbon is 2%.

[0212] Example 16

[0213] The difference from Example 1 is that in step (8), a specific surface area of ​​3m 2 / g, the Dv50 of the first lithium replenisher is 7μm, the Dv50 of the second lithium replenisher is 13μm, the mass percentage of the second lithium replenisher and the first lithium replenisher is 50%, and the mass percentage of carbon is 2%.

[0214] Example 17

[0215] The difference from Example 1 is that in step (8), a specific surface area of ​​3m 2 / g, the Dv50 of the first lithium replenisher is 7μm, the Dv50 of the second lithium replenisher is 5μm, the mass percentage of the second lithium replenisher and the first lithium replenisher is 10%, and the mass percentage of carbon is 2%.

[0216] Example 18

[0217] The difference from Example 1 is that in step (8), a specific surface area of ​​3m 2 / g, the Dv50 of the first lithium replenisher is 7μm, the Dv50 of the second lithium replenisher is 5μm, the mass percentage of the second lithium replenisher and the first lithium replenisher is 40%, and the mass percentage of carbon is 2%.

[0218] Example 19

[0219] The difference from Example 1 is that in step (8), a specific surface area of ​​3m 2 / g, the Dv50 of the first lithium replenisher is 7μm, the Dv50 of the second lithium replenisher is 5μm, the mass percentage of the second lithium replenisher and the first lithium replenisher is 70%, and the mass percentage of carbon is 2%.

[0220] Example 20

[0221] The difference from Example 1 is that in step (8), a specific surface area of ​​3m 2 / g, the Dv50 of the first lithium replenisher is 7μm, the Dv50 of the second lithium replenisher is 5μm, the mass percentage of the second lithium replenisher and the first lithium replenisher is 8%, and the mass percentage of carbon is 2%.

[0222] Example 21

[0223] The difference from Example 1 is that in step (8), a specific surface area of ​​3m 2 / g, the Dv50 of the first lithium replenisher is 7μm, the Dv50 of the second lithium replenisher is 5μm, the mass percentage of the second lithium replenisher to the first lithium replenisher is 72%, and the mass percentage of carbon is 2%.

[0224] Example 22

[0225] The difference from Example 1 is that in step (8), a specific surface area of ​​3m 2 / g, the Dv50 of the first lithium replenisher is 7μm, the Dv50 of the second lithium replenisher is 5μm, the mass percentage of the second lithium replenisher to the first lithium replenisher is 50%, and the mass percentage of carbon is 0.1%.

[0226] Example 23

[0227] The difference from Example 1 is that in step (8), a specific surface area of ​​3m 2 / g, the Dv50 of the first lithium replenisher is 7μm, the Dv50 of the second lithium replenisher is 5μm, the mass percentage of the second lithium replenisher to the first lithium replenisher is 50%, and the mass percentage of carbon is 3%.

[0228] Example 24

[0229] The difference from Example 1 is that in step (8), a specific surface area of ​​3m 2 / g, the Dv50 of the first lithium replenisher is 7μm, the Dv50 of the second lithium replenisher is 5μm, the mass percentage of the second lithium replenisher to the first lithium replenisher is 50%, and the mass percentage of carbon is 3%.

[0230] Example 25

[0231] The difference from Example 1 is that in step (8), a specific surface area of ​​3m 2 / g, the Dv50 of the first lithium replenisher is 7μm, the Dv50 of the second lithium replenisher is 5μm, the mass percentage of the second lithium replenisher to the first lithium replenisher is 50%, and the mass percentage of carbon is 0.

[0232] Example 26

[0233] The difference from Example 1 is that in step (8), a specific surface area of ​​3m 2 / g, the Dv50 of the first lithium replenisher is 7μm, the Dv50 of the second lithium replenisher is 5μm, the mass percentage of the second lithium replenisher and the first lithium replenisher is 50%, and the mass percentage of carbon is 6%.

[0234] Example 27

[0235] The difference from Example 1 is that in step (1), lithium oxide (Li2O) and cobalt oxide (Co3O4) are weighed at a molar ratio of 5.5:1 and mixed to obtain the first lithium supplement agent precursor.

[0236] Example 28

[0237] The difference from Example 1 is that in step (2), lithium oxide (Li2O) and copper oxide (CuO) are weighed at a molar ratio of 1.1:1 and mixed to obtain a second lithium supplement agent precursor.

[0238] Comparative Example 1

[0239] The difference from Example 1 is that steps (2), (4) and (5) are removed, and in step (6), the Li5FeO4 obtained in step (1) and glucose are weighed and mixed in a ratio of 100:5.

[0240] Comparative Example 2

[0241] The difference from Example 1 is that steps (1), (3) and (5) are removed, and in step (6), the Li2NiO2 obtained in step (2) and glucose are weighed and mixed in a ratio of 100:5.

[0242] The following performance tests were performed on the positive electrode lithium supplement, positive electrode sheet, and battery of each embodiment and comparative example. The performance test results are shown in Table 1.

[0243] 1. Specific surface area

[0244] The positive electrode lithium supplement agent was tested according to the "Determination of the specific surface area of ​​solid substances by gas adsorption BET method" (GB / T 19587-2017) to measure its specific surface area.

[0245] 2. Particle size Dv50

[0246] The volume particle size distribution of the positive electrode lithium supplement is tested using a Malvern 3000 laser particle size analyzer. For example, reference can be made to GB / T 19077.1.

[0247] 3. Carbon mass ratio

[0248] The mass ratio of the carbon coating layer to the positive electrode lithium supplement agent was obtained by thermogravimetric analysis (TGA) test.

[0249] Principle: Under program-controlled temperature, the mass of a substance is measured as it changes with temperature or time. The carbon coating will burn and decompose at a certain temperature. The thermogravimetric analyzer records the mass change of the sample during heating and calculates the mass percentage of the carbon coating.

[0250] Procedure: Place an appropriate amount of lithium supplement material sample into the crucible of a thermogravimetric analyzer and heat to a high temperature at a specific heating rate to completely burn the carbon. Calculate the carbon content based on the difference in mass before and after combustion.

[0251] 4. Volume ratio after delithiation to before delithiation

[0252] The volume of the lithium supplement before and after delithiation is measured using FIB-SEM. Appropriate sizes (e.g., 200μm*200μm) are selected from different areas of the electrode after formation. These areas are sliced ​​and scanned layer by layer to form a multi-layer two-dimensional image. The multi-layer two-dimensional imaging data is then reconstructed into three dimensions. The volume of the lithium supplement particles in the electrode does not collapse due to delithiation. The reconstructed and summed volume of all the lithium supplement particles in the selected area is the volume of that area before the lithium supplement is removed. The volume of the lithium supplement particles after delithiation is also calculated using the above method: the volume ratio before delithiation to that after delithiation = volume after delithiation / volume before delithiation * 100%.

[0253] 5. Gas production performance

[0254] Adjust the battery SOC to 100%, 90%, 80%, 70%, 60%, 50%, 40%, 30%, 20%, 10%, and 0% in sequence. After storing at 60°C for 28 days, test the battery weight using the drainage method, and calculate and count the battery gas production based on the weight difference.

[0255] 6. Cycling Performance: Charge the battery at 45°C under constant current (CC) charging at 0.5C until the voltage reaches 3.7V. Then switch to constant voltage (CV) charging until the current drops to 0.05C. The battery is then discharged at 0.5C until the voltage drops to 2.3V. The battery capacity at this point is recorded as C1. After 1000 cycles of this cycle, the battery capacity is recorded as C1000. Check the battery capacity retention relative to the pre-cycle capacity: Battery Capacity Retention = C1000 / C1*100%.

[0256] 7. Rate Performance: The battery is charged at 25°C under constant current (CC) charging at a current of 0.5C until the voltage reaches 3.7V. The battery is then switched to constant voltage (CV) charging until the current drops to 0.05C. The battery is discharged at a current of 0.1C to a voltage of 2.3V. The battery capacity at this point is recorded as C1. The battery capacity is discharged at a current of 2C to a voltage of 2.3V. The battery capacity at this point is recorded as C2. The 2C / 0.1C capacity retention rate is calculated as: C2 / C1*100%.

[0257] Table 1

[0258] Table 2

[0259]

[0260] The following conclusions can be drawn from Tables 1 and 2:

[0261] 1) It can be seen from Examples 1 to 28 and Comparative Examples 1 and 2 that when the specific surface area of ​​the positive electrode lithium replenisher, the Dv50 of the first lithium replenisher, the Dv50 of the second lithium replenisher, the mass percentage of the second lithium replenisher to the first lithium replenisher, and the mass percentage of carbon are within the ranges of the embodiments of the present invention, it is helpful to reduce the gas production of the first lithium replenisher after delithiation and improve the capacity retention rate of the battery.

[0262] 2) It can be seen from Examples 1 to 6 that the specific surface area of ​​the positive electrode lithium supplement is 1m 2 / g-20m 2 / g range, the gas production of the first lithium supplement after delithiation will be reduced, and the capacity retention rate of the battery will be improved.

[0263] 3) According to Examples 1 and 7 to 11, it can be seen that the Dv50 of the first lithium supplement is in the range of 1 μm-15 μm, which will reduce the gas production of the first lithium supplement after delithiation and improve the capacity retention rate of the battery.

[0264] 4) According to Examples 1 and 12 to 16, it can be seen that the Dv50 of the second lithium supplement is in the range of 0.2 μm-12 μm, which will reduce the gas production of the first lithium supplement after delithiation and improve the capacity retention rate of the battery.

[0265] 5) According to Examples 1 and 17 to 21, a mass ratio of the second lithium replenisher to the first lithium replenisher of 10:100 to 70:100 can reduce the gas production of the first lithium replenisher after delithiation and improve the battery capacity retention rate.

[0266] 6) According to Examples 1 and 22 to 26, it can be seen that by coating the surface of the positive electrode lithium replenisher with a carbon coating layer, and the mass percentage of carbon to the positive electrode lithium replenisher being in the range of 0.1% to 5%, the gas production of the first lithium replenisher after delithiation can be reduced, thereby improving the capacity retention rate of the battery.

[0267] 7) According to Examples 27 and 28 and Comparative Examples 1 and 2, it can be seen that when the specific surface area of ​​the positive electrode lithium replenisher, the Dv50 of the first lithium replenisher, the Dv50 of the second lithium replenisher, the mass percentage of the second lithium replenisher to the first lithium replenisher, and the mass percentage of carbon are within the ranges of the embodiments of the present invention, the first lithium replenisher is Li6CoO4 or the second lithium replenisher is Li2CuO2, which can also reduce the gas production of the first lithium replenisher after delithiation and improve the capacity retention rate of the battery.

[0268] Finally, it should be noted that those skilled in the art will readily identify other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. The present invention is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art not disclosed herein. The present invention is not limited to the precise structure described above and illustrated in the accompanying drawings, and various modifications and variations may be made without departing from the scope thereof. The scope of the present invention is limited solely by the appended claims.

Claims

1. A positive electrode lithium supplement, characterized in that: include: a first lithium supplement and a second lithium supplement, wherein one of the first lithium supplement and the second lithium supplement is coated on at least a portion of the surface of the other; The lithium content of the first lithium supplement is higher than the lithium content of the second lithium supplement; The chemical formula of the first lithium supplement includes Li a M b O c , M is at least one of Ni, Cr, Co, Mn, Fe, Al, Cu, V, Ti, and Re; 0<a≤6, 0<b≤3, 0<c≤6; And / or, the chemical formula of the second lithium supplement includes Li x N y O z , N is at least one of Ni, Cr, Co, Mn, Fe, Al, Cu, V, Ti, Ru, and Mo; 0<x≤3, 0<y≤3, 0<z≤4; The mass ratio of the second lithium supplement agent to the first lithium supplement agent is 40:100-70:100, the Dv50 of the first lithium supplement agent is 1 μm-15 μm, and the Dv50 of the second lithium supplement agent is 0.2 μm-12 μm; The volume of the first lithium supplement after delithiation is 40%-80% of the volume of the first lithium supplement before delithiation, and the volume of the second lithium supplement after delithiation is 70%-90% of the volume of the second lithium supplement before delithiation.

2. The positive electrode lithium supplement according to claim 1, characterized in that The first lithium supplement comprises at least one of Li5FeO4, Li6CoO4, Li4CoO4, and Li5ReO6; And / or, the second lithium supplement includes Li2NiO2, Li2RuO3, Li2MnO3, Li2MoO3, Li 0.65 Ni 1.35 At least one of O2.

3. The positive electrode lithium supplement according to claim 1, characterized in that At least a portion of the surface of the positive electrode lithium supplement agent is coated with a carbon coating layer.

4. The positive electrode lithium supplement according to claim 3, characterized in that The mass ratio of the carbon coating layer to the positive electrode lithium replenisher is 0.1%-5%.

5. The positive electrode lithium supplement according to claim 1, characterized in that Before the first lithium supplement agent is delithiated, the valence state of M is at least one of +2, +3, +4 and +7; And / or, after the first lithium supplement agent is delithiated, the valence state of M is at least one of +3 and +4.

6. The positive electrode lithium supplement according to any one of claims 1 to 5, characterized in that: The delithiation voltage of the first lithium supplement is 3.4V-4.4V; And / or, the delithiation voltage of the second lithium supplement is 3.4V-4.5V.

7. The positive electrode lithium supplement according to any one of claims 1 to 5, characterized in that: The first lithium supplement has a specific charge capacity of 400 mAh / g to 1200 mAh / g; And / or, the second lithium supplement has a specific charge capacity of 240 mAh / g to 550 mAh / g.

8. The positive electrode lithium supplement according to any one of claims 1 to 5, characterized in that: The specific surface area of ​​the positive electrode lithium supplement is 1m 2 / g-20m 2 / g.

9. A method for preparing a positive electrode lithium supplement according to any one of claims 1 to 8, characterized in that: The method comprises: The first lithium replenishing agent and the second lithium replenishing agent are mixed and then sintered to obtain the positive electrode lithium replenishing agent.

10. The preparation method according to claim 9, characterized in that The first lithium supplement agent and the second lithium supplement agent are mixed and then sintered, comprising: performing a first sintering treatment on a first lithium supplement agent precursor to obtain a first lithium supplement agent; performing a second sintering process on the second lithium supplement agent precursor to obtain the second lithium supplement agent; The first lithium supplement agent, the second lithium supplement agent and a carbon source are mixed and subjected to a third sintering process.

11. The preparation method according to claim 10, characterized in that: The temperature of the first sintering process is lower than the temperature of the third sintering process; And / or, the temperature of the second sintering process is lower than the temperature of the third sintering process.

12. The preparation method according to claim 10 or 11, characterized in that: The temperature of the first sintering treatment is 350°C-650°C; And / or, the temperature of the second sintering treatment is 350°C-650°C; And / or, the temperature of the third sintering treatment is 650° C.-900° C.; And / or, the first sintering treatment time is 2h-24h; And / or, the second sintering treatment time is 2h-24h; And / or, the third sintering treatment takes 2 hours to 24 hours.

13. A positive electrode sheet, characterized in that: The positive electrode sheet includes the positive electrode lithium replenisher according to any one of claims 1 to 8 or the positive electrode lithium replenisher prepared by the preparation method of the positive electrode lithium replenisher according to any one of claims 9 to 12.

14. A battery, characterized in that: Including the positive electrode sheet according to claim 13.

15. An electrical device, characterized in that: Including the battery according to claim 14.

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