Lithium supplement agent and preparation method thereof, positive plate, battery, battery pack and electric equipment

Abstract

The invention provides a lithium supplement agent and a preparation method thereof, a positive plate, a battery, a battery pack and electric equipment, the lithium supplement agent comprises a lithium supplement material and a coating layer existing on the surface of the lithium supplement material, and the coating layer comprises lithium-containing fluoride. The lithium supplement agent provided by the invention has relatively high stability and excellent dynamic performance, the lithium supplement effect of the lithium supplement agent can be improved, and the cycle performance of the battery is improved.

Description

Technical Field

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

[0002] Lithium-ion batteries are widely used in portable electronic devices, electric vehicles, and energy storage systems due to their high energy density and long cycle life. However, irreversible capacity loss often occurs during the first charge and discharge cycles of a battery, primarily due to structural changes in the electrode materials and interfacial side reactions caused by electrolyte decomposition. The introduction of lithium supplements can compensate for this irreversible capacity loss and improve the battery's initial Coulombic efficiency.

[0003] However, existing lithium supplements suffer from inadequate stability and kinetic performance, which hinders their charge capacity, limiting their lithium replenishment effectiveness and the cycling performance of lithium-supplemented batteries. Therefore, developing lithium supplements with high stability and excellent kinetic performance has become a pressing technical challenge. Summary of the Invention

[0004] The main purpose of the present invention is to provide a lithium supplement agent with high stability and excellent kinetic performance, which is conducive to the performance of the charge capacity of the lithium supplement agent, improves the lithium supplement effect of the lithium supplement agent, and improves the cycle performance of the battery.

[0005] The present invention also provides a method for preparing a lithium supplement agent, which can prepare the lithium supplement agent and has simple process and low cost.

[0006] The present invention also provides a positive electrode sheet, comprising the above-mentioned lithium supplement agent or the lithium supplement agent prepared by the above-mentioned lithium supplement agent preparation method. Therefore, the positive electrode sheet is applied to a battery to improve the cycle performance of the battery.

[0007] The present invention also provides a battery comprising the lithium supplement agent, or the lithium supplement agent prepared according to the preparation method of the lithium supplement agent, or the positive electrode sheet. Therefore, the battery has excellent cycle performance.

[0008] The present invention also provides a battery pack comprising the lithium supplement, or the lithium supplement prepared according to the method for preparing the lithium supplement, or the positive electrode sheet, or the battery. Therefore, the battery pack has excellent cycle performance.

[0009] The present invention also provides an electrical device comprising the lithium supplement, or the lithium supplement prepared according to the method for preparing the lithium supplement, or the positive electrode sheet, or the battery, or the battery pack. Therefore, the battery performance of the electrical device is relatively excellent.

[0010] In a first aspect, the present invention provides a lithium supplement agent, comprising a lithium supplement material and a coating layer present on the surface of the lithium supplement material, wherein the coating layer comprises lithium fluoride.

[0011] The lithium supplement agent mentioned above, the chemical formula of the lithium fluoride is Li x M y F z , wherein 0<x≤3, 0<y≤1, 0<z≤6, and M is selected from at least one of Al, Zr, Ti, Si, Sb, Bi, In, and Ga.

[0012] As described above, the lithium supplement agent, the lithium fluoride includes at least one of LiAlF4, Li3AlF6, Li2ZrF6, Li2TiF6, Li2SiF6, LiSbF6, LiBiF4, LiInF4 and LiGaF4, preferably LiAlF4 and / or Li3AlF6.

[0013] The lithium supplement agent as described above, wherein the mass percentage of the lithium fluoride-containing lithium supplement agent is 0.1%-10%, preferably 0.5%-2%;

[0014] And / or, the coating layer has a thickness of 1 nm to 500 nm.

[0015] The lithium supplement agent as described above, wherein the lithium supplement material includes at least one of Li2NiO2, Li6CoO4, and Li5FeO4;

[0016] And / or, the particle size Dn50 of the lithium supplementing material is 500 nm-15 μm.

[0017] As described above, the lithium supplement material includes a core and a transition layer, the transition layer exists between the core and the coating layer, the core includes at least one of Li2NiO2, Li6CoO4, and Li5FeO4, and the transition layer includes at least one of Li2NiO2, Li6CoO4, and Li5FeO4.

[0018] The lithium supplement as described above, wherein the transition layer comprises at least one of a rock salt phase, a rock salt-like phase, a spinel-like structure, and a layered structure;

[0019] And / or, the thickness of the transition layer is 2nm-200nm;

[0020] And / or, the transition layer contains element X, the element X is selected from at least one of Al, Zr, Ti, Si, Sb, Bi, In, and Ga, and the mass percentage of the element X in the transition layer is 0.1%-20%;

[0021] And / or, the transition layer contains F element, and the mass percentage of the F element in the transition layer is 0.1%-70%.

[0022] In a second aspect, the present invention provides a method for preparing the lithium supplement as described above, comprising the following steps:

[0023] The lithium supplement material and the coating agent are mixed and then sintered to obtain the lithium supplement agent; wherein the coating agent includes lithium fluoride.

[0024] In the above-mentioned method for preparing the lithium supplement, the sintering treatment is performed at a temperature of 300° C. to 600° C. and for a time of 0.5 h to 6 h.

[0025] In a third aspect, the present invention provides a positive electrode sheet, comprising the lithium supplement agent as described above or the lithium supplement agent prepared according to the preparation method of the lithium supplement agent as described above.

[0026] In a fourth aspect, the present invention provides a battery comprising the lithium supplement agent as described above, or a lithium supplement agent prepared according to the method for preparing the lithium supplement agent as described above, or the positive electrode sheet as described above.

[0027] In a fifth aspect, the present invention provides a battery pack, comprising the lithium supplement as described above, or a lithium supplement prepared according to the method for preparing the lithium supplement as described above, or the positive electrode sheet as described above, or the battery as described above.

[0028] In a sixth aspect, the present invention provides an electrical device comprising the lithium supplement as described above, or a lithium supplement prepared according to the method for preparing the lithium supplement as described above, or a positive electrode sheet as described above, or a battery as described above, or a battery pack as described above.

[0029] The lithium supplement agent provided by the present invention has a coating layer comprising a lithium fluoride. The lithium fluoride has excellent chemical stability and good lithium ion conductivity, can effectively prevent the lithium supplement material from reacting adversely with the electrolyte or other active substances, inhibit the formation of residual alkali, and can promote the rapid migration of lithium ions, thereby improving the stability and kinetic performance of the lithium supplement agent, facilitating the utilization of the charge capacity of the lithium supplement agent, improving the lithium supplement effect of the lithium supplement agent, and enhancing the cycle performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] To more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the following briefly introduces the drawings required for use in the embodiments of the present invention or related technologies. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0031] Figure 1 A schematic structural diagram of a lithium supplement provided by the present invention;

[0032] Figure 2 This is a schematic structural diagram of another lithium supplement provided by the present invention.

[0033] Description of reference numerals:

[0034] 1-lithium replenishing material; 2-coating layer; 11-core; 12-transition layer. DETAILED DESCRIPTION

[0035] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0036] The performance of lithium-ion batteries depends largely on the chemical stability and electrochemical activity of their electrode materials. With the increasing demand for high-energy-density and long-life batteries, the introduction of lithium supplements has become an effective strategy to address irreversible capacity loss during the first cycle. Lithium supplements, such as Li₂NiO₂, have attracted considerable attention due to their high theoretical specific capacity and their ability to improve initial coulombic efficiency. However, these materials react readily with water and carbon dioxide in the presence of air, resulting in decreased electrochemical activity and increased safety risks.

[0037] To address these challenges, existing technologies generally adopt surface coating methods, such as carbon coating, to prevent direct contact with the environment by forming a protective layer on the surface of the lithium supplement.

[0038] However, the inventors of this application have discovered that conventional coating materials often exhibit deficiencies in stability and kinetic performance in practical applications. This deficiency not only limits the effectiveness of lithium supplements but also can affect their charge capacity, resulting in poor lithium replenishment and reduced battery cycling performance. Using lithium-containing fluorides as coating agents, however, can significantly improve the stability and kinetic performance of lithium supplements, facilitating their charge capacity utilization, enhancing their lithium replenishment effectiveness, and improving battery cycling performance.

[0039] Based on this, in a first aspect, the present invention provides a lithium supplement agent, comprising a lithium supplement material 1 and a coating layer 2 present on the surface of the lithium supplement material 1, wherein the coating layer 2 comprises lithium fluoride.

[0040] The lithium supplement agent provided by the present invention has a coating layer 2 on the surface of the lithium supplement material 1. The coating layer 2 includes a lithium fluoride, which can improve the stability and kinetic performance of the lithium supplement agent, facilitate the utilization of the charge capacity of the lithium supplement agent, improve the lithium supplement effect of the lithium supplement agent, and be applied to a battery to improve the cycle performance of the battery.

[0041] The reason for this is that lithium fluoride has excellent chemical stability. As a coating layer 2, it can effectively prevent the lithium supplement material 1 from reacting adversely with the electrolyte or other active substances, inhibit the formation of residual alkali, help extend the service life of the lithium supplement, and reduce the occurrence of side reactions; on the other hand, it can form a stable interface between the lithium supplement material 1 and the electrolyte, reduce interfacial impedance, facilitate the smooth transmission of lithium ions, and improve the charge and discharge efficiency of the battery. In addition, lithium fluoride has good lithium ion conductivity, which can promote the rapid migration of lithium ions, thereby improving the kinetic performance of the lithium supplement, which is particularly important for the rapid charge and discharge process. At the same time, the coating layer 2 can also provide a certain degree of mechanical protection, preventing the lithium supplement material 1 from pulverizing or breaking due to volume changes or other mechanical stresses during the cycle, thereby maintaining the structural integrity of the material, improving the stability and kinetic performance of the material, and facilitating the utilization of the charge capacity of the lithium supplement material, improving its lithium supplement effect, and thus improving the cycle performance of the battery.

[0042] Therefore, the lithium supplement agent provided by the present invention has a coating layer 2 including a lithium fluoride. The lithium fluoride has excellent chemical stability and good lithium ion conductivity, can effectively prevent the lithium supplement material 1 from reacting adversely with the electrolyte or other active substances, inhibit the formation of residual alkali, and can promote the rapid migration of lithium ions, thereby improving the stability and kinetic performance of the lithium supplement agent, which is beneficial to the performance of the charge capacity of the lithium supplement agent, improving the lithium supplement effect of the lithium supplement agent, and improving the cycle performance of the battery.

[0043] In some embodiments of the present invention, the chemical formula of the lithium fluoride is Li x M y F z , wherein 0<x≤3, 0<y≤1, 0<z≤6, and M is selected from at least one of Al, Zr, Ti, Si, Sb, Bi, In, and Ga.

[0044] Illustratively, x can be 0.01, 0.5, 1, 1.5, 2, 3, or a range consisting of any two thereof; y can be 0.01, 0.3, 0.5, 0.7, 0.9, 1, or a range consisting of any two thereof; and z can be 0.01, 1, 2, 3, 4, 5, 6, or a range consisting of any two thereof.

[0045] The lithium-containing fluoride of the present invention can further improve the stability of the lithium supplement agent, thereby improving the lithium supplement effect of the lithium supplement agent and improving the cycle performance of the battery.

[0046] In some embodiments of the present invention, the lithium fluoride includes at least one of LiAlF4, Li3AlF6, Li2ZrF6, Li2TiF6, Li2SiF6, LiSbF6, LiBiF4, LiInF4 and LiGaF4, preferably LiAlF4 and / or Li3AlF6.

[0047] It should be noted that when the lithium fluoride includes LiAlF4 and / or Li3AlF6, the Al element and the F element can obtain a deeper doping depth, which can further improve the structural stability of the lithium replenisher, thereby improving the lithium replenishment effect of the lithium replenisher and improving the cycle performance of the battery.

[0048] In some embodiments of the present invention, the mass percentage of lithium fluoride in the lithium supplement agent is 0.1%-10%, for example, it can be 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10% or any two thereof, preferably 0.5%-2%.

[0049] The lithium fluoride content of the lithium supplement in the present invention is within the above-mentioned range. This effectively forms a stable coating layer 2, reduces side reactions between the electrolyte and the electrode material, and improves the overall electrochemical stability of the battery. Furthermore, the lithium fluoride exhibits excellent lithium ion conductivity, promoting rapid lithium ion transport. An appropriate amount of lithium fluoride can improve the battery's charge and discharge efficiency without significantly increasing interfacial impedance.

[0050] When the mass percentage of lithium fluoride in the lithium supplement agent is 0.5%-2%, the overall electrochemical stability of the battery can be further improved, and the charge and discharge efficiency of the battery can be increased.

[0051] In some embodiments of the present invention, the thickness of the coating layer 2 is 1 nm-500 nm, for example, it can be 1 nm, 10 nm, 20 nm, 50 nm, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm or a range consisting of any two thereof.

[0052] The thickness of the coating layer 2 in the present invention is within the above range, which can form a stable interface between the lithium supplement material 1 and the electrolyte, reduce the interfacial impedance, and help improve the lithium ion transmission efficiency and the overall electrochemical performance of the battery. It can also effectively isolate the direct contact between the lithium supplement material 1 and the electrolyte, preventing adverse chemical reactions from occurring, thereby improving the chemical stability of the lithium supplement agent, and then improving the lithium supplement effect of the lithium supplement agent, and increasing the cycle life of the battery. In addition, the thickness of the coating layer 2 is sufficient to provide mechanical protection, preventing the lithium supplement material 1 from pulverizing or breaking due to volume changes or other mechanical stresses during the charge and discharge process, which is beneficial to maintaining the structural integrity of the material. At the same time, the thickness of the coating layer 2 will not significantly increase the diffusion path of lithium ions, thereby maintaining or even enhancing the kinetic properties of the lithium supplement agent and supporting rapid charge and discharge.

[0053] The thickness of the coating layer 2 of the present invention can be determined by cutting the lithium supplement agent, measuring the thickness of the coating layer 2 in the cross section using a transmission electron microscope (TEM), and taking the average thickness of 20 particles to obtain the thickness of the coating layer 2 .

[0054] In some embodiments of the present invention, the lithium supplement material 1 includes at least one of Li2NiO2, Li6CoO4, and Li5FeO4.

[0055] In the present invention, the lithium-supplementing material 1, comprising the aforementioned materials, can provide a large amount of lithium ions for the battery's charge and discharge processes, thereby facilitating the full utilization of the lithium-supplementing material's charge capacity. Furthermore, the lithium-supplementing material 1 exhibits excellent cycle stability during the charge and discharge processes, effectively reducing capacity decay and extending the battery's service life.

[0056] The lithium supplement material 1 of the present invention can be purchased from commercial sources or prepared by conventional methods in the art.

[0057] In some embodiments of the present invention, the particle size Dn50 of the lithium supplementing material 1 is 500 nm-15 μm, for example, 500 nm, 1 μm, 2 μm, 5 μm, 10 μm, 15 μm or any two thereof.

[0058] In the present invention, the particle size Dn50 of the lithium supplement material 1 is within the above range, which is conducive to the coating of the lithium supplement material 1 by the coating layer 2, so that the lithium supplement agent formed after coating has better stability and dynamic performance, thereby improving the lithium supplement effect of the lithium supplement agent and improving the cycle performance of the battery.

[0059] The particle size Dn50 of the lithium supplement material 1 of the present invention refers to the particle size corresponding to when the cumulative distribution percentage reaches 50%.

[0060] The particle size Dn50 of the lithium supplement material 1 of the present invention can be measured by a laser particle size analyzer.

[0061] In some embodiments of the present invention, the lithium supplement material includes a core 11 and a transition layer 12, the transition layer 12 exists between the core 11 and the coating layer 2, the core 11 includes at least one of Li2NiO2, Li6CoO4, and Li5FeO4, and the transition layer 12 includes at least one of Li2NiO2, Li6CoO4, and Li5FeO4.

[0062] The presence of transition layer 12 effectively buffers the interfacial stress between core 11 and coating 2, reducing interfacial reactions and impedance, and improving overall interfacial stability. Furthermore, transition layer 12 prevents direct contact between the electrolyte and core 11, reducing the occurrence of side reactions and helping to maintain the integrity of the electrode material and the amount of active lithium, thereby increasing the battery's energy density. Furthermore, transition layer 12 acts as a buffer layer, absorbing and dissipating mechanical stress caused by volume changes, reducing material pulverization and structural damage, and thus improving the battery's cycle life.

[0063] The materials in the core 11 and the transition layer 12 have high chemical stability and structural stability, which can improve the structural integrity of the lithium supplement during the charge and discharge process and reduce the expansion and contraction of the material.

[0064] In some embodiments of the present invention, the transition layer 12 includes at least one of a rock salt phase, a rock salt-like phase, a spinel-like structure, and a layered structure.

[0065] It should be noted that when the lithium-supplementing material 1 is Li₂NiO₂, the transition layer 12 is a rock salt phase. When the lithium-supplementing material 1 is Li₅FeO₄, the transition layer 12 is a rock salt-like phase. When the lithium-supplementing material 1 is Li₆CoO₄, the transition layer 12 is a mixed disordered phase, including layered, rock salt-like, and spinel-like phases. The stability of these transition layers 12 is superior to that of the uncoated lithium-supplementing material 1, and they can serve as passivation layers.

[0066] The rock salt phase and rock salt-like phase in the transition layer 12 of the present invention have excellent ionic conductivity and chemical stability, promoting lithium ion transport and improving the battery's cycling performance. The spinel-like structure has three-dimensional lithium ion channels, which help increase the migration rate of lithium ions. The layered structure provides rapid lithium ion insertion and extraction pathways, enhancing kinetic performance.

[0067] In some embodiments, the thickness of the transition layer 12 is 2 nm-200 nm, for example, 2 nm, 10 nm, 50 nm, 100 nm, 200 nm, or a range consisting of any two thereof.

[0068] The thickness of the transition layer 12 of the present invention is within the above range, which can further improve the structural stability of the lithium supplement agent, facilitate the utilization of the charge capacity of the lithium supplement agent, improve the lithium supplement effect of the lithium supplement agent, and enhance the cycle performance of the battery.

[0069] In the lithium-containing fluoride of the present invention, the M and F elements are easily doped into the bulk phase of the lithium-supplementing material 1 due to their suitable ionic radius and low valence, obtaining a certain doping depth, and then forming a transition layer 12 including the X and F elements on the surface of the coated particles.

[0070] In some embodiments, the transition layer 12 contains element X, and element X is selected from at least one of Al, Zr, Ti, Si, Sb, Bi, In, and Ga. In the transition layer 12, the mass percentage of element X is 0.1%-20%, for example, 0.1%, 0.5%, 1%, 5%, 10%, 15%, 20%, or a range consisting of any two thereof.

[0071] In some embodiments, the transition layer 12 contains F element, and the mass percentage of F element in the transition layer 12 is 0.1%-70%, for example, it can be 0.1%, 0.5%, 1%, 5%, 10%, 20%, 30%, 40%, 50%, 60%, 65%, 70% or a range consisting of any two of them.

[0072] In the present invention, the mass percentages of the X element and the F element are within the above ranges, which can further improve the mechanical properties and chemical stability of the transition layer 12, prevent adverse reactions from occurring, and improve the chemical stability of the lithium supplement.

[0073] In the present invention, the thickness of the transition layer 12 can be determined by cutting the lithium supplement agent, measuring the thickness of the transition layer 12 in the cross section using a transmission electron microscope (TEM), and taking the average thickness of 20 particles to obtain the thickness of the transition layer 12 .

[0074] The mass percentages of the X element and the F element in the transition layer 12 of the present invention can be measured by spherical aberration transmission electron microscopy and electron energy loss spectroscopy (EELS).

[0075] In a second aspect, the present invention provides a method for preparing the lithium supplement agent as described above, comprising the following steps: mixing a lithium supplement material and a coating agent, and then sintering the mixture to obtain the lithium supplement agent; wherein the coating agent comprises a lithium fluoride.

[0076] In the present invention, the mixture formed by mixing the lithium supplement material and the coating agent is sintered, so that the structure of the formed coating layer can be relatively stable and a transition layer can be formed at the same time.

[0077] Specifically, the mixture of the lithium-supplementing material and the coating agent can be spray-dried under an inert atmosphere to uniformly disperse the mixture of the lithium-supplementing material 1 and the coating agent into fine particles, thereby achieving pre-coating and facilitating the formation of a uniform coating layer 2. The spray-drying pressure can be 0.2 MPa-1 MPa, the inlet temperature can be 100°C-300°C, the outlet temperature can be 80°C-100°C, and the feed rate can be 0.5 L / h-2 L / h.

[0078] Sintering is performed in an oxygen atmosphere. This oxygen atmosphere helps repair oxygen defects in the lithium supplement, preventing the formation of oxygen vacancies and improving the electrochemical performance and cycle stability of the lithium supplement. Furthermore, sintering promotes the doping of M and F elements into the bulk of the lithium supplement material 1, forming a transition layer 12.

[0079] The preparation method of the lithium supplement provided by the present invention can prepare the lithium supplement provided by the first aspect of the present invention, and the lithium supplement has excellent structural stability and dynamic performance, which is conducive to the performance of the charge capacity of the lithium supplement, improves the lithium supplement effect of the lithium supplement, and improves the cycle performance of the battery.

[0080] In some embodiments of the present invention, the sintering temperature is 300° C. to 600° C., for example, 300° C., 350° C., 400° C., 450° C., 500° C., 550° C., 600° C., or any two thereof. The sintering time is 0.5 h to 6 h, for example, 0.5 h, 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, or any two thereof.

[0081] The sintering temperature in the present invention is within the above range, which enables the lithium supplement agent to achieve good crystallization, helps form a stable phase structure, and improves the electrochemical performance of the lithium supplement agent. It also prevents the lithium supplement agent from over-sintering or phase transformation at excessively high temperatures, thereby maintaining the structural integrity of the lithium supplement agent.

[0082] The sintering time in the present invention, within the aforementioned range, allows for sufficient reaction within the lithium supplement, improving the mechanical and chemical stability of the supplement. Furthermore, proper time control prevents excessive particle growth, maintains particle size, and thus optimizes specific surface area and kinetic performance.

[0083] In addition, the temperature and time of the sintering treatment in the present invention will also affect the thickness of the transition layer 12 and the content of the X element and the F element in the transition layer 12.

[0084] In some embodiments, the mass ratio of the lithium supplement material 1 to the coating agent is 1:(0.001-0.05), for example, it can be 1:0.001, 1:0.005, 1:0.01, 1:0.02, 1:0.03, 1:0.04, 1:0.05 or a range consisting of any two thereof.

[0085] In the present invention, the mass ratio of the lithium-supplementing material 1 to the coating agent is within the above range, and a coating layer 2 of suitable thickness can be formed, which can effectively isolate the direct contact between the lithium-supplementing material 1 and the electrolyte, prevent adverse chemical reactions from occurring, thereby improving the chemical stability of the lithium-supplementing agent, and further improving the lithium-supplementing effect of the lithium-supplementing agent and improving the cycle performance of the battery.

[0086] In a third aspect, the present invention provides a positive electrode sheet comprising the lithium supplement agent as described above or the lithium supplement agent prepared according to the preparation method as described above.

[0087] The positive electrode sheet of the present invention can be prepared by conventional technical means in the field. Specifically, the above-mentioned lithium supplement agent, positive electrode active material, conductive agent, and binder can be uniformly dispersed in a solvent to obtain a positive electrode active layer slurry, and then the positive electrode active layer slurry is coated on at least one functional surface of the positive electrode current collector. After drying, the positive electrode sheet of the present invention can be obtained.

[0088] The present invention does not particularly limit the specific types of conductive agents and adhesives. The conductive agent, adhesive and other components can be selected from conventional substances in the field. For example, the conductive agent can be selected from one or more of conductive carbon black, carbon nanotubes, conductive graphite, and graphene, and the adhesive can be selected from one or more of polyvinylidene fluoride (PVDF), acrylic acid-modified PVDF, polyacrylate polymers, polyimide, styrene-butadiene rubber, and styrene-propylene rubber.

[0089] The present invention does not specifically limit the coating method, and any coating method such as gravure coating, extrusion coating, spray coating, screen printing, etc. can be used to coat the positive electrode active layer slurry.

[0090] The positive electrode sheet provided by the present invention includes the above-mentioned lithium supplement agent. Therefore, the positive electrode sheet is applied to a battery to improve the cycle performance of the battery.

[0091] In a fourth aspect, the present invention provides a battery comprising the lithium supplement as described above, or the lithium supplement prepared according to the preparation method as described above, or the positive electrode sheet as described above. The battery has the advantages corresponding to the above positive electrode sheet, which will not be described in detail.

[0092] The battery of the present invention includes, in addition to the positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte. The composition of the negative electrode sheet can refer to conventional negative electrode sheets in the art, and the separator can also be a separator commonly used in the art, such as PP film, PE film, etc.

[0093] The battery of the present invention can be prepared by conventional methods in the field. Specifically, the positive electrode sheet, the separator and the negative electrode sheet can be stacked in sequence, and then the battery core can be obtained through a lamination or winding process, and then through baking, liquid injection, formation, packaging and other processes to obtain the above-mentioned battery.

[0094] In a fifth aspect, the present invention provides a battery pack comprising the lithium supplement as described above, or the lithium supplement prepared according to the preparation method as described above, or the positive electrode sheet as described above, or the battery as described above. The battery pack has the advantages corresponding to the above-mentioned positive electrode sheet, which will not be repeated.

[0095] The battery pack of the present invention includes at least two batteries as described above, and these batteries can be electrically connected by conventional methods in the art, such as series connection, parallel connection, or a combination of these connection methods, without particular limitation.

[0096] In a sixth aspect, the present invention provides an electrical device comprising the lithium supplement as described above, or the lithium supplement prepared according to the preparation method as described above, or the positive electrode sheet as described above, or the battery as described above, or the battery pack as described above. The electrical device has the advantages corresponding to the above-mentioned positive electrode sheet, which will not be repeated here.

[0097] The electrical equipment of the present invention can be conventional electrical equipment in the field, such as power equipment (such as electric vehicles), electronic equipment (such as computers, mobile phones, digital cameras, printers, fax machines, etc.), wearable devices (such as watches, bracelets, VR glasses, etc.), household appliances (such as air conditioners, refrigerators, washing machines, microwave ovens, etc.), etc., without special restrictions.

[0098] The technical solution of the present invention is further described below with reference to specific embodiments.

[0099] Example 1

[0100] The preparation method of the lithium supplement agent of this embodiment comprises the following steps:

[0101] 1) An appropriate amount of lithium fluoride (LiAlF4) as a coating agent is added to N-methylpyrrolidone (NMP) under an argon atmosphere, and the lithium-supplementing material (Li2NiO2) is stirred and mixed to obtain a mixture. The mass ratio of the lithium-supplementing material to the coating agent is 1:0.001.

[0102] 2) Under an argon atmosphere, the mixture was fed into a spray dryer for spray drying to obtain a lithium supplement precursor; the pressure was controlled to be 0.5 MPa, the inlet temperature was 210° C., the outlet temperature was 95° C., and the feed rate was 0.8 L / h.

[0103] 3) The lithium supplement material precursor was placed in a sintering furnace and sintered in an oxygen atmosphere for 2 hours at a temperature of 600° C. After sintering, the precursor was sieved to obtain the lithium supplement material. The particle size Dn50 of the lithium supplement material was 10,000 nm.

[0104] The lithium supplement agent includes a lithium supplement material Li2NiO2 and a coating layer LiAlF4 on the surface of the lithium supplement material. The lithium supplement material also includes a transition layer, which is a rock salt phase.

[0105] Example 2

[0106] The preparation method of the lithium supplement agent of Example 2 is basically the same as that of Example 1, except that the mass ratio of the lithium supplement material and the coating agent is changed to 1:0.005, so that the mass percentage of the lithium fluoride-containing lithium supplement agent is 0.5%, the coating layer thickness is 10 nm, the content of the X element in the transition layer is 1.3%, the content of the F element in the transition layer is 2.8%, and the transition layer thickness is 10 nm.

[0107] Example 3

[0108] The preparation method of the lithium supplement agent of Example 3 is basically the same as that of Example 1, except that the mass ratio of the lithium supplement material and the coating agent is changed to 1:0.01, so that the mass percentage of the lithium fluoride-containing lithium supplement agent is 1%, the coating layer thickness is 45 nm, the content of the X element in the transition layer is 3.3%, the content of the F element in the transition layer is 6.9%, and the thickness of the transition layer is 25 nm.

[0109] Example 4

[0110] The preparation method of the lithium supplement agent of Example 4 is basically the same as that of Example 1, except that the mass ratio of the lithium supplement material and the coating agent is changed to 1:0.02, so that the mass percentage of the lithium fluoride-containing lithium supplement agent is 2%, the thickness of the coating layer is 88 nm, the content of the X element in the transition layer is 5.4%, the content of the F element in the transition layer is 11.7%, and the thickness of the transition layer is 44 nm.

[0111] Example 5

[0112] The preparation method of the lithium supplement agent of Example 5 is basically the same as that of Example 1, except that the mass ratio of the lithium supplement material and the coating agent is changed to 1:0.1, so that the mass percentage of the lithium fluoride-containing lithium supplement agent is 10%, the thickness of the coating layer is 497 nm, the content of the X element in the transition layer is 7.2%, the content of the F element in the transition layer is 15.7%, and the thickness of the transition layer is 197 nm.

[0113] Example 6

[0114] The preparation method of the lithium supplement agent of Example 6 is basically the same as that of Example 1, except that the mass ratio of the lithium supplement material and the coating agent is changed to 1:0.12, so that the mass percentage of the lithium fluoride-containing lithium supplement agent is 12%, the coating layer thickness is 545 nm, the content of the X element in the transition layer is 8.1%, the content of the F element in the transition layer is 17.3%, and the thickness of the transition layer is 214 nm.

[0115] Example 7

[0116] The preparation method of the lithium supplement agent of Example 7 is basically the same as that of Example 3, except that the particle size Dn50 of the lithium supplement material Li2NiO2 is changed to 500nm, so that the coating layer thickness is 65nm, the content of the X element in the transition layer is 4.2%, the content of the F element in the transition layer is 7.4%, and the transition layer thickness is 32nm.

[0117] Example 8

[0118] The preparation method of the lithium supplement agent of Example 8 is basically the same as that of Example 3, except that the particle size Dn50 of the lithium supplement material Li2NiO2 is changed to 15000nm, so that the coating layer thickness is 37nm, the content of the X element in the transition layer is 2.9%, the content of the F element in the transition layer is 6.1%, and the transition layer thickness is 22nm.

[0119] Example 9

[0120] The preparation method of the lithium supplement agent in Example 9 is basically the same as that in Example 3, except that the sintering temperature is changed to 300°C and the sintering time is changed to 0.5h, so that the coating layer thickness is 47nm, the content of the X element in the transition layer is 0.1%, the content of the F element in the transition layer is 0.2%, and the transition layer thickness is 2nm.

[0121] Example 10

[0122] The preparation method of the lithium supplement agent in Example 10 is basically the same as that in Example 3, except that the sintering temperature is changed to 600°C and the sintering time is changed to 6 hours, so that the coating layer thickness is 24 nm, the content of the X element in the transition layer is 20%, the content of the F element in the transition layer is 68%, and the transition layer thickness is 56 nm.

[0123] Example 11

[0124] The preparation method of the lithium supplement agent in Example 11 is basically the same as that in Example 3, except that the coating agent is changed to Li3AlF6, so that the coating layer thickness is 47nm, the content of the X element in the transition layer is 3.5%, the content of the F element in the transition layer is 7.4%, and the transition layer thickness is 27nm.

[0125] Example 12

[0126] The preparation method of the lithium supplement agent of Example 12 is basically the same as that of Example 3, except that the coating agent is changed to Li3AlF6 and the lithium supplement material is Li6CoO4, so that the coating layer thickness is 55nm, the F element content in the transition layer is 6.7%, and the transition layer thickness is 20nm.

[0127] Example 13

[0128] The preparation method of the lithium supplement agent of Example 13 is basically the same as that of Example 3, except that the coating agent is changed to Li3AlF6 and the lithium supplement material is Li5FeO4, so that the coating layer thickness is 40nm, the content of the X element in the transition layer is 4.1%, the content of the F element in the transition layer is 11.3%, and the transition layer thickness is 82nm.

[0129] Example 14

[0130] The preparation method of the lithium supplement agent in Example 14 is basically the same as that in Example 3, except that the coating agent is changed to Li2ZrF6, so that the coating layer thickness is 42nm, the content of the X element in the transition layer is 3.2%, the content of the F element in the transition layer is 6.8%, and the transition layer thickness is 31nm.

[0131] Example 15

[0132] The preparation method of the lithium supplement agent in Example 15 is basically the same as that in Example 3, except that the coating agent is changed to Li2TiF6, so that the coating layer thickness is 52nm, the content of the X element in the transition layer is 2.9%, the content of the F element in the transition layer is 6.4%, and the transition layer thickness is 20nm.

[0133] Example 16

[0134] The preparation method of the lithium supplement agent in Example 16 is basically the same as that in Example 3, except that the coating agent is changed to Li2SiF6, so that the coating layer thickness is 46nm, the content of the X element in the transition layer is 2.8%, the content of the F element in the transition layer is 5.9%, and the transition layer thickness is 23nm.

[0135] Example 17

[0136] The preparation method of the lithium supplement agent in Example 17 is basically the same as that in Example 3, except that the coating agent is changed to LiSbF6, so that the content of X element in the transition layer is 3.4%, the content of F element in the transition layer is 7.1%, and the thickness of the transition layer is 21nm.

[0137] Example 18

[0138] The preparation method of the lithium supplement agent in Example 18 is basically the same as that in Example 3, except that the coating agent is changed to LiBiF4, so that the coating layer thickness is 41nm, the content of the X element in the transition layer is 3.3%, the content of the F element in the transition layer is 6.9%, and the transition layer thickness is 32nm.

[0139] Example 19

[0140] The preparation method of the lithium supplement agent in Example 19 is basically the same as that in Example 3, except that the coating agent is changed to LiInF4, so that the content of X element in the transition layer is 3.2%, the content of F element in the transition layer is 6.9%, and the thickness of the transition layer is 23nm.

[0141] Example 20

[0142] The preparation method of the lithium supplement agent in Example 20 is basically the same as that in Example 3, except that the coating agent is changed to LiGaF4, so that the coating layer thickness is 44nm, the content of the X element in the transition layer is 3.5%, the content of the F element in the transition layer is 7.6%, and the transition layer thickness is 26nm.

[0143] Comparative Example 1

[0144] The lithium supplement in Comparative Example 1 is Li2NiO2, and no surface coating is performed.

[0145] Comparative Example 2

[0146] The preparation methods of the lithium supplement agent of Comparative Example 2 and Example 1 are basically the same, except that Al2O3 is used as the coating agent.

[0147] Comparative Example 3

[0148] The preparation methods of the lithium supplement agent of Comparative Example 3 and Example 1 are basically the same, except that TiO2 is used as the coating agent.

[0149] Comparative Example 4

[0150] The preparation method of the lithium supplement agent of Comparative Example 4 is basically the same as that of Example 1, except that LiNi 0.33 Co 0.33 Mn 0.33 O2 is used as a coating agent.

[0151] Comparative Example 5

[0152] The lithium supplement in Comparative Example 5 is Li5FeO4, and no surface coating is performed.

[0153] Comparative Example 6

[0154] The lithium supplement in Comparative Example 6 is Li6CoO4, which is not surface coated.

[0155] Test example:

[0156] The lithium supplements from the examples and comparative examples, along with conductive carbon black and PVDF, were dispersed in NMP at a mass ratio of 8:1:1. The cathode sheets were prepared through slurry preparation, coating, drying, and roller pressing. A battery was assembled in an argon-filled glove box using a lithium metal sheet as the anode, a Celgard 2400 polypropylene membrane as the separator, and a mixed solution of EC and DMC (1:1 by volume) containing 1 mol / L lithium hexafluorophosphate as the electrolyte.

[0157] 1. Dn50: Use laser particle size analyzer to test the particle size Dn50 of lithium supplement material.

[0158] 2. Coating layer thickness, transition layer thickness: The coating layer or transition layer thickness of the present invention can be obtained by cutting the lithium supplement agent, measuring the thickness of the coating layer or transition layer of the cross section using a transmission electron microscope (TEM), and taking the average thickness of 20 particles to obtain the coating layer or transition layer thickness.

[0159] 3. X and F content in the transition layer: Testing was performed using spherical aberration transmission electron microscopy and electron energy loss spectroscopy (EELS). Specifically, the particle locations to be observed were calibrated using spherical aberration transmission electron microscopy, and then EELS was used to scan and analyze the particles to obtain the elemental distribution map and specific content.

[0160] 4. Charge gram capacity test: Using the LAND battery test system, charge the battery to 4.2V at a constant current of 1C, then charge it at a constant voltage of 4.2V until the current is equal to 0.03C. The charge capacity at this time is recorded as the 1C charge gram capacity.

[0161] 5. After the lithium supplement powder was allowed to stand at a temperature of 25°C and an ambient humidity of 40% for 24 hours, a battery was made according to the above steps and charged at a constant current rate of 1C to 4.2V. Then, the battery was charged at a constant voltage at 4.2V to a current equal to 0.03C. The charging capacity at this time was recorded as the 1C charging capacity in grams after the powder was allowed to stand for 24 hours.

[0162] 6. Cycling Performance: The positive electrode active material NCM333, lithium supplement, conductive carbon black, and PVDF from the examples and comparative examples were dispersed in NMP at a mass ratio of 7.8:0.2:1:1. The positive electrode sheets were prepared by slurry preparation, coating, drying, and roller pressing. A battery was assembled in an argon-filled glove box using a lithium metal sheet as the negative electrode, a Celgard 2400 polypropylene film as the separator, and a mixed solution of EC and DMC (1:1 by volume) containing 1 mol / L lithium hexafluorophosphate as the electrolyte.

[0163] At 25°C, charge the battery to 4.2V at a constant current rate of 1C, charge it to a current rate of 0.5C at 4.2V, and then discharge it to 2.5V at a discharge rate of 1C. Repeat this charge and discharge cycle 300 times and measure the discharge capacity Q1 at the first cycle and the discharge capacity Q at the 300th cycle. 300 The capacity retention rate after 300 cycles is Q = Q 300 / Q1*100%.

[0164] Table 1

[0165]

[0166]

[0167] As can be seen from Table 1, compared with Comparative Examples 1-6, the lithium supplement provided by the present invention has a coating layer comprising a lithium fluoride. The lithium fluoride has excellent chemical stability and good lithium ion conductivity, can effectively prevent the lithium supplement material from reacting adversely with the electrolyte or other active substances, inhibit the formation of residual alkali, and can promote the rapid migration of lithium ions, thereby improving the stability and kinetic performance of the lithium supplement, which is beneficial to the performance of the charge capacity of the lithium supplement, improving the lithium supplement effect of the lithium supplement, and improving the cycle performance of the battery.

[0168] Comparisons with Examples 1-6 show that when the mass percentage of the lithium-containing fluoride in the lithium-supplementing agent is 0.1%-10%, the coating layer thickness is 1nm-500nm, and the transition layer thickness is 2nm-200nm, the lithium-supplementing agent's lithium-supplementing effect can be further improved, thereby enhancing the battery's cycling performance. In particular, when the mass percentage of the lithium-containing fluoride in the lithium-supplementing agent is 0.5%-2%, the lithium-supplementing effect of the lithium-supplementing agent can be further improved, thereby enhancing the battery's cycling performance.

[0169] By comparing Example 3, Example 11 and Examples 14-20, it can be seen that when the lithium fluoride containing lithium is LiAlF4 and / or Li3AlF6, the lithium replenishing effect of the lithium replenishing agent can be further improved, thereby improving the cycle performance of the battery.

[0170] 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 lithium supplement, characterized in that: The invention comprises a lithium-supplementing material and a coating layer on the surface of the lithium-supplementing material, wherein the coating layer comprises lithium-containing fluoride.

2. The lithium supplement according to claim 1, characterized in that The chemical formula of the lithium fluoride is Li x M y F z , wherein 0<x≤3, 0<y≤1, 0<z≤6, and M is selected from at least one of Al, Zr, Ti, Si, Sb, Bi, In, and Ga.

3. The lithium supplement according to claim 1 or 2, characterized in that The lithium fluoride includes at least one of LiAlF4, Li3AlF6, Li2ZrF6, Li2TiF6, Li2SiF6, LiSbF6, LiBiF4, LiInF4 and LiGaF4, preferably LiAlF4 and / or Li3AlF6.

4. The lithium supplement according to any one of claims 1 to 3, characterized in that The mass percentage of the lithium-containing fluoride in the lithium supplement agent is 0.1%-10%, preferably 0.5%-2%; And / or, the coating layer has a thickness of 1 nm to 500 nm.

5. The lithium supplement according to any one of claims 1 to 4, characterized in that The lithium supplement material includes at least one of Li2NiO2, Li6CoO4, and Li5FeO4; And / or, the particle size Dn50 of the lithium supplementing material is 500 nm-15 μm.

6. The lithium supplement according to any one of claims 1 to 5, characterized in that: The lithium supplement material includes a core and a transition layer, wherein the transition layer exists between the core and the coating layer, the core includes at least one of Li2NiO2, Li6CoO4, and Li5FeO4, and the transition layer includes at least one of Li2NiO2, Li6CoO4, and Li5FeO4.

7. The lithium supplement according to claim 6, characterized in that The transition layer comprises at least one of a rock salt phase, a rock salt-like phase, a spinel-like structure, and a layered structure; And / or, the thickness of the transition layer is 2nm-200nm; And / or, the transition layer contains element X, the element X is selected from at least one of Al, Zr, Ti, Si, Sb, Bi, In, and Ga, and the mass percentage of the element X in the transition layer is 0.1%-20%; And / or, the transition layer contains F element, and the mass percentage of the F element in the transition layer is 0.1%-70%.

8. A method for preparing the lithium supplement according to any one of claims 1 to 7, characterized in that: The following steps are involved: The lithium supplement material and the coating agent are mixed and then sintered to obtain the lithium supplement agent; wherein the coating agent includes lithium fluoride.

9. The method for preparing a lithium supplement according to claim 8, wherein: The sintering treatment is performed at a temperature of 300° C. to 600° C. and for a time of 0.5 h to 6 h.

10. A positive electrode sheet, characterized in that: The lithium supplement comprises the lithium supplement according to any one of claims 1 to 7 or the lithium supplement prepared according to the preparation method of the lithium supplement according to claim 8 or 9.

11. A battery, characterized in that: The invention comprises the lithium supplement agent according to any one of claims 1 to 7, or the lithium supplement agent prepared according to the preparation method of the lithium supplement agent according to claim 8 or 9, or the positive electrode sheet according to claim 10.

12. A battery pack, characterized in that: The invention comprises the lithium supplement agent according to any one of claims 1 to 7, or the lithium supplement agent prepared according to the preparation method of the lithium supplement agent according to claim 8 or 9, or the positive electrode sheet according to claim 10, or the battery according to claim 11.

13. An electrical device, characterized in that: The invention comprises the lithium supplement agent according to any one of claims 1 to 7, or the lithium supplement agent prepared according to the preparation method of the lithium supplement agent according to claim 8 or 9, or the positive electrode sheet according to claim 10, or the battery according to claim 11, or the battery pack according to claim 12.

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