Lithium supplement material and preparation method thereof, positive pole piece, battery and electric device

Abstract

The invention discloses a lithium supplementing material and a preparation method thereof, a positive pole piece, a battery and a power utilization device, the lithium supplementing material comprises an inner core, a first coating layer and a second coating layer, the inner core comprises a first lithium-containing substance, and the lithium removal potential of the first lithium-containing substance is less than or equal to 4V; the first coating layer is formed on at least part of the surface of the inner core, the first coating layer comprises a second lithium-containing substance, and the lithium removal potential of the second lithium-containing substance is greater than 4V; the second coating layer is formed on at least part of the surface, far away from the inner core, of the first coating layer. When a battery is charged and discharged, the inner core firstly releases lithium ions, and the first coating layer only releases the lithium ions at a certain potential, so that the probability of overcharge of a battery cell can be reduced, the lithium ions are slowly released, the stability of the lithium supplementing material is improved, and the cycle performance of the battery containing the lithium supplementing material is improved.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, and specifically, to a lithium supplement material, a preparation method thereof, a positive electrode sheet, a battery, 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, long cycle life, good rate performance, etc. During the first charge and discharge process of the battery, the electrolyte will form a solid electrolyte interface film (SEI film) on the surface of the negative electrode. The formation of the SEI film will consume a large amount of active lithium ions, thereby resulting in a low Coulombic efficiency in the first cycle of the battery. During the charge and discharge cycle of the battery, the cracking and pulverization of the positive active material particles, the thickening and repair of the SEI film, etc. will all consume active lithium ions, thereby causing a significant decline in the cycle performance of the battery. By adding a lithium supplement material, the first cycle efficiency, energy density, and cycle life of the lithium battery can be improved.

[0003] However, the current lithium supplement materials have poor stability, resulting in poor cycle performance of the batteries containing them.

[0004] It should be noted that the above statements are only used to provide background technical information related to the present application, and do not necessarily constitute prior art. Summary of the Invention

[0005] In view of the technical problems existing in the background art, the present application provides a lithium supplement material, aiming to solve the problem of poor cycle performance of the batteries containing it.

[0006] To achieve the above object, a first aspect of the present application provides a lithium supplement material, comprising: a core, the core comprising a first lithium-containing substance, the de-lithiation potential of the first lithium-containing substance being less than or equal to 4V; a first coating layer, the first coating layer being formed on at least a part of the surface of the core, the first coating layer comprising a second lithium-containing substance, the de-lithiation potential of the second lithium-containing substance being greater than 4V; a second coating layer, the second coating layer being formed on at least a part of the surface of the first coating layer and / or the core.

[0007] Thus, when the lithium supplement material is charged and discharged in the battery, the core first releases lithium ions, and the first coating layer releases lithium ions at a certain potential, which can reduce the probability of overcharging of the battery cell and slowly release lithium ions, improve the stability of the lithium supplement material, and improve the cycle performance of the battery containing it.

[0008] In some embodiments, the mass ratio of the first lithium-containing substance to the second lithium-containing substance is (1 - 9):1, and can be optionally (1 - 2):1. Thus, the stability of the lithium supplement material can be improved, and the cycle performance of the battery containing it can be improved.

[0009] In some embodiments, the de-lithiation potential of the first lithium-containing material is 1.5V - 4V. Thereby, the stability of the lithium supplement material can be improved, and the cycle performance of the battery containing the same can be enhanced.

[0010] In some embodiments, the volume average particle size D v 50 of the first lithium-containing material is 0.1μm - 5μm, and can be optionally 2μm - 3μm. Thereby, the stability of the lithium supplement material can be improved, and the cycle performance of the battery containing the same can be enhanced.

[0011] In some embodiments, the first lithium-containing material includes Li 2 O, Li 2 O 2 、Li 3 N, Li 2 C 2 O 4 、Li 2 C 4 O 4 or at least one of lithium citrate. Thereby, the stability of the lithium supplement material can be improved, and the cycle performance of the battery containing the same can be enhanced.

[0012] In some embodiments, the core further includes a catalyst, and the catalyst includes Li x MO y 、magnesium diboride, titanium diboride, zirconium diboride, tungsten boride or lanthanum hexaboride, wherein M includes at least one of Ni, Co, Mn, Mo, Al, Fe, Ti, Cu, Mg or V, 1≤x≤6, 2≤y≤4. Thereby, the stability of the lithium supplement material can be improved, and the cycle performance of the battery containing the same can be enhanced.

[0013] In some embodiments, the mass ratio of the first lithium-containing material to the catalyst is 1:(0.01 - 0.1), and can be optionally 1:(0.05 - 0.1). Thereby, the stability of the lithium supplement material can be improved, and the cycle performance of the battery containing the same can be enhanced.

[0014] In some embodiments, based on the total mass of the core, the mass proportion of the catalyst is 1% - 9%, and can be optionally 5% - 9%. Thereby, the stability of the lithium supplement material can be improved, and the cycle performance of the battery containing the same can be enhanced.

[0015] In some embodiments, the thickness of the first coating layer ≤5μm, and can be optionally 0.5μm - 5μm, and further optionally 2μm - 3μm. Thereby, the stability of the lithium supplement material can be improved, and the cycle performance of the battery containing the same can be enhanced.

[0016] In some embodiments, the de-lithiation potential of the second lithium-containing substance is 4.5V - 6V. Thereby, the stability of the lithium supplement material can be improved, and the cycling performance of the battery containing it can be enhanced.

[0017] In some embodiments, the volume-average particle size D v 50 of the second lithium-containing substance is 0.1 μm - 1 μm, and can be optionally 0.5 μm - 1 μm. Thereby, the stability of the lithium supplement material can be improved, and the cycling performance of the battery containing it can be enhanced.

[0018] In some embodiments, the second lithium-containing substance includes Li 2 CO 3 、Li 2 SO 4 、Li 3 BO 3 、Li 3 PO 4 、 lithium metasilicate or lithium orthosilicate or at least one of them. Thereby, the stability of the lithium supplement material can be improved, and the cycling performance of the battery containing it can be enhanced.

[0019] In some embodiments, the first coating layer further includes a reducing agent, and the reducing agent includes at least one of elemental sulfur, molybdenum sulfide, tungsten sulfide, titanium sulfide, lithium sulfide, magnesium sulfide, calcium sulfide, lanthanum sulfide, tantalum sulfide, iron sulfide, elemental phosphorus, iron phosphide, boron phosphide, nickel phosphide, lithium phosphide, zinc phosphide, elemental boron, cobalt boride, molybdenum boride, calcium boride or aluminum boride. Thereby, the stability of the lithium supplement material can be improved, and the cycling performance of the battery containing it can be enhanced.

[0020] In some embodiments, the volume-average particle size D v 50 of the reducing agent is 10 nm - 5 μm, and can be optionally 500 nm - 2 μm. Thereby, the stability of the lithium supplement material can be improved, and the cycling performance of the battery containing it can be enhanced.

[0021] In some embodiments, the mass ratio of the second lithium-containing substance to the reducing agent is (1.5 - 9):1, and can be optionally (3 - 6):1. Thereby, the stability of the lithium supplement material can be improved, and the cycling performance of the battery containing it can be enhanced.

[0022] In some embodiments, based on the total mass of the first coating layer, the mass proportion of the reducing agent is 10% - 40%, and can be optionally 15% - 25%. Thereby, the stability of the lithium supplement material can be improved, and the cycling performance of the battery containing it can be enhanced.

[0023] In some embodiments, the ionic conductivity of the second coating layer is 10 -7 S / cm - 10 -3 S / cm, and can be optionally 10-4 S / cm - 10 -3 S / cm. Thus, the stability of the lithium - supplementing material can be improved, and the cycle performance of the battery containing the same can be enhanced.

[0024] In some embodiments, the thickness of the second coating layer ≤ 100 nm, optionally 1 nm - 100 nm, and further optionally 2 nm - 15 nm. Thus, the stability of the lithium - supplementing material can be improved, and the cycle performance of the battery containing the same can be enhanced.

[0025] In some embodiments, the second coating layer includes at least one of graphite, graphene, carbon nanotubes, carbon fibers, acetylene black, soft carbon, hard carbon, or amorphous carbon. Thus, the stability of the lithium - supplementing material can be improved, and the cycle performance of the battery containing the same can be enhanced.

[0026] In some embodiments, the volume - average particle size D v 50 of the lithium - supplementing material is 0.1 μm - 5 μm, optionally 4 μm - 5 μm. Thus, the stability of the lithium - supplementing material can be improved, and the cycle performance of the battery containing the same can be enhanced.

[0027] In a second aspect of the present application, a method for preparing a lithium - supplementing material is provided, including: forming a first coating layer on at least a part of the surface of the core, the core includes a first lithium - containing substance, the de - lithiation potential of the first lithium - containing substance is less than or equal to 4V, the first coating layer includes a second lithium - containing substance, the de - lithiation potential of the second lithium - containing substance is greater than 4V; forming a second coating layer on at least a part of the surface of the first coating layer away from the core to obtain the lithium - supplementing material.

[0028] Thus, the lithium - supplementing material prepared by the above - mentioned method of the present application can improve the stability of the lithium - supplementing material and enhance the cycle performance of the battery containing the same.

[0029] In a third aspect of the present application, a positive electrode sheet is provided, including the lithium - supplementing material described in the first aspect of the present application, or the lithium - supplementing material prepared by the method described in the second aspect. Thus, the positive electrode sheet has all the features and advantages of the aforementioned lithium - supplementing material and the method for preparing the lithium - supplementing material, which will not be elaborated herein.

[0030] In some embodiments, the positive electrode sheet includes a positive electrode active material, the positive electrode active material includes at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, or lithium nickel cobalt aluminum oxide. Optionally, the positive electrode active material includes lithium nickel cobalt manganese oxide.

[0031] In the fourth aspect of the present application, a battery is proposed, which includes the positive electrode sheet described in the third aspect of the present application. Thus, the battery has excellent cycling performance.

[0032] In the fifth aspect of the present application, an electrical device is proposed, which includes the battery described in the fourth aspect. Thus, the electrical device includes all the features and advantages of the aforementioned battery, which will not be elaborated herein. Description of the Drawings

[0033] The above and / or additional aspects and advantages of the present application will become apparent and be easily understood from the description of the embodiments in conjunction with the following drawings, where:

[0034] Figure 1 is a schematic structural diagram of a lithium supplement material according to an embodiment of the present application;

[0035] Figure 2 is a schematic structural diagram of a lithium supplement material according to another embodiment of the present application;

[0036] Figure 3 is a schematic structural diagram of a lithium supplement material according to still another embodiment of the present application;

[0037] Figure 4 is a schematic diagram of a battery cell according to an embodiment of the present application;

[0038] Figure 5 is Figure 4 the exploded view of the battery cell shown in an embodiment of the present application;

[0039] Figure 6 is a schematic diagram of a battery module according to an embodiment of the present application;

[0040] Figure 7 is a schematic diagram of a battery pack according to an embodiment of the present application;

[0041] Figure 8 is Figure 7 the exploded view of the battery pack shown in an embodiment of the present application;

[0042] Figure 9 is a schematic diagram of an electrical device using the battery as a power source according to an embodiment of the present application;

[0043] Figure 10 are the voltage curves and temperature curves of the batteries of Example 1 and Comparative Example 5 of the present application;

[0044] Figure 11 are the pictures of the batteries of Example 1 and Comparative Example 5 of the present application after charging for 8000 s.

[0045] Description of the Reference Numerals:

[0046] 1 Battery pack; 2 Upper box body; 3 Lower box body; 4 Battery module; 5 Battery cell;

[0047] 51 Housing; 52 Electrode assembly; 53 Top cover assembly;

[0048] 100: Core; 101: First lithium-containing substance; 102: Catalyst; 200: First coating layer; 201: Second lithium-containing substance; 202: Reducing agent; 300: Second coating layer. Detailed implementation manners

[0049] Hereinafter, the implementation manners of the lithium supplementing material, its preparation method, the positive electrode sheet, the battery, and the electrical device of the present application specifically disclosed will be described in detail with appropriate reference to the drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to prevent the following descriptions from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter recited in the claims.

[0050] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a specific range. The ranges defined in this way can include the end values or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In the present application, unless otherwise stated, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" have been fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. In addition, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0051] If there is no special instruction, all implementation manners and optional implementation manners of the present application can be combined with each other to form a new technical solution.

[0052] If there is no special instruction, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0053] Unless otherwise specified, all steps of the present application can be carried out sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method can include steps (a) and (b) carried out sequentially, or steps (b) and (a) carried out sequentially. For example, if it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0054] In the description of the present application, "a plurality of" means two or more.

[0055] In the description of the present application, "A and / or B" can include the case of A alone, the case of B alone, and any one of the cases of A and B. Here, A and B are only for example, and they can be any technical features connected by "and / or" in the present application.

[0056] Secondary batteries are not only applied to energy storage power systems such as hydropower, thermal power, wind power and solar power stations, but also widely applied to electric vehicles such as electric bicycles, electric motorcycles and electric cars, as well as multiple fields such as military equipment and aerospace.

[0057] On the one hand, the lithium supplementing material can fill the loss of active lithium ions caused by the formation of SEI during the first charge and discharge process of the battery, so that the battery has enough reversible active lithium ions during subsequent cycle processes, improving the energy density of the battery; on the other hand, the lithium supplementing material can also be used to make up for the lithium consumption occurring during the cycle process, improving the cycle performance of the battery.

[0058] For the lithium supplementing material, on the one hand, most of the active lithium ions in the lithium supplementing material will be completely released during the first charge and discharge process of the battery, making the lithium supplementing material unable to continuously supplement active lithium ions in the later stage of the charge and discharge cycle, thus leading to a significant decline in the cycle performance in the later stage of battery use. In addition, when the battery continues to charge, the voltage continues to rise, the electrolyte decomposes and reacts with the positive and negative electrodes, generating heat and gas sharply, and the probability of the battery experiencing thermal runaway is high; on the other hand, the substance used as the lithium supplementing material is generally relatively active and easily reacts with moisture and oxygen in the air to deteriorate, resulting in a decline in the cycle performance of the battery.

[0059] In this application, the de-lithiation potential of the first lithium-containing material in the core is less than or equal to 4V. During the charge and discharge of the battery, it will preferentially release active lithium ions, playing a role in lithium supplementation. The de-lithiation potential of the second lithium-containing material in the first coating layer is greater than 4V, and it can de-lithiate at high potentials, enabling the active lithium ions in the lithium supplementation material to be slowly released, reducing the occurrence of the "overcharge" phenomenon, and further reducing the probability of battery thermal runaway. On the other hand, due to the low de-lithiation potential of the first lithium-containing material, it is relatively reactive. The first coating layer and the second coating layer outside the core form two layers of coating outside the core. Compared with the case of a single protective layer, the protection effect on the core is better, improving the stability of the lithium supplementation material. In summary, the lithium supplementation material proposed in this application has good lithium supplementation effect and good stability, improving the cycle performance of the battery containing it.

[0060] The lithium supplementation material disclosed in the embodiments of this application is applicable to secondary batteries, and the batteries disclosed in the embodiments of this application can be used in electrical equipment using the battery as a power source or various energy storage systems using the battery as an energy storage element. The electrical equipment may include, but is not limited to, mobile phones, tablets, laptop computers, electric toys, power tools, battery cars, electric vehicles, ships, spacecraft, and the like. Among them, the electric toys may include fixed or mobile electric toys, such as game consoles, electric vehicle toys, electric ship toys, and electric aircraft toys, etc. The spacecraft may include airplanes, rockets, space shuttles, and spaceships, etc.

[0061] In the first aspect of this application, this application proposes a lithium supplementation material. Referring to Figure 1 , the lithium supplementation material includes: a core 100, a first coating layer 200, and a second coating layer 300. Among them, the core 100 includes a first lithium-containing material 101, and the de-lithiation potential of the first lithium-containing material 101 is less than or equal to 4V; the first coating layer 200 is formed on at least part of the surface of the core 100, the first coating layer 200 includes a second lithium-containing material 201, and the de-lithiation potential of the second lithium-containing material 201 is greater than 4V; the second coating layer 300 is formed on at least part of the surface of the first coating layer 200 and / or the core 100.

[0062] The present application has at least the beneficial effects described as follows: The de-lithiation potential of the first lithium-containing substance 101 in the core 100 is less than or equal to 4V, and during the charge and discharge of the battery, it will preferentially release active lithium ions, playing a role in lithium supplementation. The de-lithiation potential of the second lithium-containing substance 201 in the first coating layer 200 is greater than 4V, and it can de-lithiate at a high potential, enabling the active lithium ions in the lithium supplementation material to be slowly released, reducing the occurrence of the "overcharge" phenomenon, and further reducing the probability of battery thermal runaway. On the other hand, due to the low de-lithiation potential of the first lithium-containing substance 101, which is relatively active, the first coating layer 200 and the second coating layer 300 outside the core 100 form two layers of coating outside the core 100. Compared with the case of a single protective layer, the protection effect on the core 100 is better, which can achieve physical isolation between the lithium supplementation material and air, reduce the air sensitivity of the lithium supplementation material, improve the interfacial stability of the lithium supplementation material, and improve the storage performance and processing performance. In summary, the lithium supplementation material proposed in the present application has good lithium supplementation effect and good stability, improving the cycle performance of the battery containing it.

[0063] It can be understood that the first lithium-containing substance refers to a class of substances containing lithium elements, and the second lithium-containing substance refers to another class of substances containing lithium elements. In addition, the present application includes this situation: the first coating layer is incompletely coated on the surface of the core, that is, a part of the core is in contact with the second coating layer.

[0064] It can be understood that the de-lithiation potential refers to the potential at which the lithium-containing substance starts to de-lithiate, which can be obtained through the galvanostatic charge-discharge capacity test. Specifically:

[0065] 1) Mix the lithium-containing substance, conductive carbon black SP, and polyvinylidene fluoride (PVDF) in a mass ratio of 90:5:5, use N-methylpyrrolidone (NMP) as a solvent to prepare a uniform and stable slurry, then coat the slurry on an aluminum foil, bake it at 80°C for 24h, and cold-press and punch to obtain a positive electrode of the content compound;

[0066] 2) Combine the positive electrode of the lithium-containing compound in step 1) with a negative electrode of a lithium metal sheet to assemble a coin cell;

[0067] 3) Perform a charge-discharge capacity test on the coin cell in step 2) through an electrochemical workstation to obtain the de-lithiation potential.

[0068] In some embodiments, the de-lithiation potential of the first lithium-containing material is less than or equal to 4V. For example, the de-lithiation potential of the first lithium-containing material can be 0.1V - 4V, 0.5V - 3.9V, 0.7V - 3.7V, 0.9V - 3.5V, 1V - 3V, 1.2V - 2.8V, 1.5V - 2.5V, 1.8V - 2.3V, 2V - 2.2V, etc. Specifically, the de-lithiation potential of the first lithium-containing material is limited within the above range. During the charge and discharge of the battery, the first lithium-containing material will preferentially release active lithium ions, playing a role in lithium supplementation. Moreover, the first lithium-containing material in the core, together with the first coating layer and the second coating layer, has a good lithium supplementation effect and good stability, improving the cycle performance of the battery containing it. In some other embodiments, the de-lithiation potential of the first lithium-containing material is 1.5V - 4V.

[0069] In some embodiments, the de-lithiation potential of the second lithium-containing material is greater than 4V. For example, the de-lithiation potential of the second lithium-containing material can be 4.1V - 20V, 4.5V - 19V, 5V - 18V, 6V - 17V, 7V - 16V, 8V - 15V, 9V - 14V, 11V - 13V, etc. Specifically, the de-lithiation potential of the second lithium-containing material is limited within the above range. It can de-lithiate at a high potential, enabling the active lithium ions in the lithium supplementation material to be slowly released, reducing the occurrence of the "overcharge" phenomenon, and further reducing the probability of battery thermal runaway. In addition, the first coating layer and the second coating layer outside the core form two layers of coating outside the core. Compared with the case of a single protective layer, the protection effect on the core is better, improving the stability of the lithium supplementation material and the cycle performance of the battery containing it. In some other embodiments, the de-lithiation potential of the second lithium-containing material is 4.5V - 6V.

[0070] In some embodiments, the mass ratio of the first lithium-containing substance to the second lithium-containing substance is (1-9):1. For example, the mass ratio of the first lithium-containing substance to the second lithium-containing substance can be (1-8.9):1, (1.5-8.5):1, (2-8):1, (2.5-7.5):1, (3-7):1, (3.5-6.5):1, (4-6):1, (4.5-5.5):1, (5-5.5):1, etc. Specifically, when the mass ratio of the first lithium-containing substance to the second lithium-containing substance is controlled within the above range, the first lithium-containing substance will preferentially release active lithium ions during battery charge and discharge, playing a role in lithium supplementation. The second lithium-containing substance can de-lithiate at high potentials. The first lithium-containing substance and the second lithium-containing substance cooperate to enable the slow release of active lithium ions in the lithium supplementation material, reducing the occurrence of the "overcharge" phenomenon, and thus reducing the probability of battery thermal runaway. Moreover, within the above mass ratio range of the first lithium-containing substance and the second lithium-containing substance, the lithium supplementation material has good stability and can improve the cycle performance of the battery containing it. In some other embodiments, the mass ratio of the first lithium-containing substance to the second lithium-containing substance is (1-2):1.

[0071] In some embodiments, the volume average particle size D v 50 of the first lithium-containing substance is 0.1 μm - 5 μm. For example, the volume average particle size D v 50 of the first lithium-containing substance can be 0.1 μm - 4.9 μm, 0.3 μm - 4.7 μm, 0.5 μm - 4.5 μm, 1 μm - 4 μm, 1.5 μm - 3.5 μm, 2 μm - 3 μm, 2.5 μm - 3 μm, etc. Specifically, when the volume average particle size D v 50 of the first lithium-containing substance is limited within the above range, when the de-lithiation potential of the first lithium-containing substance is reached, the first lithium-containing substance can easily release active lithium ions. And within the above particle size range, the migration paths of electrons and ions are shortened, which can promote the release of a large amount of active lithium ions, providing a high lithium supplementation capacity and improving the cycle performance of the battery. In some other embodiments, the volume average particle size D v 50 of the first lithium-containing substance is 2 μm - 3 μm.

[0072] The aforementioned volume average particle size D v 50 refers to the particle size corresponding to when the cumulative volume distribution percentage of the particles reaches 50%.

[0073] The "volume average particle size D v 50" of the present application has the well-known meaning in the art and can be measured by the well-known instruments and methods in the art. As an example, the particle size of the first lithium-containing substance can be measured by laser diffraction particle size analysis method. Specifically, the volume average particle size D v50 can be measured by using a laser particle size analyzer (such as Malvern Master Size 3000) with reference to GB / T 19077-2016.

[0074] In some embodiments, the first lithium-containing substance includes Li 2 O, Li 2 O 2 、Li 3 N、Li 2 C 2 O 4 、Li 2 C 4 O 4 or at least one of lithium citrate. After the above compounds preferentially release lithium ions, gases are generated and discharged outside the battery, and the above substances are completely consumed without mass residue, resulting in a large number of voids in the core, shortening the diffusion path of lithium ions, having a high lithium ion transmission efficiency, and at the same time having more electrochemically reactive sites that can participate in the reaction, and the lithium-depleted products will not react with the electrolyte side reaction, improving the cycle performance of the battery containing it.

[0075] In some embodiments, please refer to Figure 2 , the core 100 further includes a catalyst 102, and the catalyst 102 includes Li x MO y 、at least one of magnesium diboride, titanium diboride, zirconium diboride, tungsten boride or lanthanum hexaboride, M includes at least one of Ni, Co, Mn, Mo, Al, Fe, Ti, Cu, Mg or V, 2≤x≤6, 2≤y≤4. For example, 2≤x≤6, 3≤x≤6, 3≤x≤5, 4≤x≤5; 2≤y≤3, 3≤y≤4, etc. Specifically, the above catalyst 102 can undergo an in-situ reaction with the first lithium-containing substance 101 during charge and discharge, and can catalyze it to release more active lithium ions at a lower potential, improving the cycle performance of the battery containing it.

[0076] In some embodiments, the mass ratio of the first lithium-containing substance to the catalyst is 1:(0.01 - 0.1). For example, the mass ratio of the first lithium-containing substance to the catalyst can be 1:(0.01 - 0.09), 1:(0.02 - 0.08), 1:(0.03 - 0.07), 1:(0.04 - 0.06), etc. Controlling the mass ratio of the first lithium-containing substance to the catalyst within the above range can promote the in-situ reaction of the catalyst with the first lithium-containing substance during charge and discharge, and can catalyze it to release more active lithium ions at a lower potential, improving the cycle performance of the battery containing it. In some other embodiments, the mass ratio of the first lithium-containing substance to the catalyst is 1:(0.05 - 0.1).

[0077] In some embodiments, based on the total mass of the core, the mass ratio of the catalyst is 1%-9%. For example, based on the total mass of the core, the mass ratio of the catalyst can be 1%-9%, 1%-8.9%, 1.5%-8.5%, 2%-8%, 2.5%-7.5%, 3%-7%, 3.5%-6.5%, 4%-6%, 4.5%-5.5%, etc. Controlling the mass ratio of the catalyst within the above range can promote the in-situ reaction of the catalyst with the first lithium-containing substance during charge and discharge, can catalyze it to release more active lithium ions at a lower potential, and improve the cycle performance of the battery containing it. In other embodiments, based on the total mass of the core, the mass ratio of the catalyst is 5%-9%.

[0078] In some embodiments, the thickness of the first coating layer ≤ 5 μm. For example, the thickness of the first coating layer can be 0.5 nm - 4.9 μm, 1 nm - 4.5 μm, 10 nm - 4 μm, 100 nm - 3.5 μm, 500 nm - 3 μm, 1 μm - 2.5 μm, 1.5 μm - 2 μm, etc. Controlling the thickness of the first coating layer within the above range can de-lithiate at a high potential, enabling the active lithium ions in the lithium supplement material to be slowly released, reducing the occurrence of the "overcharge" phenomenon, and further reducing the probability of battery thermal runaway. Moreover, the above thickness is appropriate, which is conducive to the transmission of lithium ions; in addition, the first coating layer and the second coating layer with the above thickness outside the core form two layers of coating outside the core. Compared with the case of a single protective layer, the protection effect on the core is good, improving the stability of the lithium supplement material and the cycle performance of the battery containing it. In other embodiments, the thickness of the first coating layer is 0.5 μm - 5 μm, such as 2 μm - 3 μm.

[0079] The "thickness" in this application has the meaning well-known in the art and can be measured by instruments and methods well-known in the art. As an example, the thickness of the first coating layer can be tested and obtained by the following method:

[0080] It is obtained by cross-sectional profile analysis by ion polishing (CP).

[0081] In some embodiments, the volume average particle size D v 50 of the second lithium-containing substance is 0.1 μm - 1 μm. For example, the volume average particle size D v 50 of the second lithium-containing substance can be 0.1 μm - 0.9 μm, 0.2 μm - 0.8 μm, 0.3 μm - 0.7 μm, 0.4 μm - 0.6 μm, 0.5 μm - 0.6 μm, 0.4 μm - 0.5 μm, etc. Specifically, the volume average particle size D vWhen limited within the above range, when the de-lithiation potential of the second lithium-containing material is reached, the second lithium-containing material can easily release active lithium ions. Moreover, within the above particle size range, the migration paths of electrons and ions are shortened, which can promote the release of a large amount of active lithium ions, provide a high lithium compensation capacity, and improve the cycle performance of the battery. In addition, the second lithium-containing material with the above particle size forms a first coating layer, which has a good protective effect on the core, improves the stability of the lithium compensation material, and improves the cycle performance of the battery containing it. In some other embodiments, the volume average particle size D v 50 of the second lithium-containing material is 0.5 μm - 1 μm.

[0082] In some embodiments, the second lithium-containing material includes Li 2 CO 3 、Li 2 SO 4 、Li 3 BO 3 、Li 3 PO 4 、lithium metasilicate or lithium orthosilicate, or at least one of them. Specifically, when using the above second lithium-containing material, when their de-lithiation potential is reached, active lithium ions can be easily released, a large amount of active lithium ions can be released, a high lithium compensation capacity can be provided, and the cycle performance of the battery can be improved. The second lithium-containing material and the first lithium-containing material act together, so that the active lithium ions in the lithium compensation material can be slowly released, reducing the occurrence of the "overcharge" phenomenon, and thus the probability of battery thermal runaway can be reduced. In addition, the first coating layer formed by the second lithium-containing material with the above particle size has a good protective effect on the core, improves the stability of the lithium compensation material, and improves the cycle performance of the battery containing it.

[0083] In some embodiments, referring to Figure 3 , the first coating layer 200 further includes a reducing agent 202, and the reducing agent 202 includes at least one of elemental sulfur, molybdenum sulfide, tungsten sulfide, titanium sulfide, lithium sulfide, magnesium sulfide, calcium sulfide, lanthanum sulfide, tantalum sulfide, iron sulfide, elemental phosphorus, iron phosphide, boron phosphide, nickel phosphide, lithium phosphide, zinc phosphide, elemental boron, cobalt boride, molybdenum boride, calcium boride or aluminum boride. Specifically, at a relatively high voltage, the above reducing agent 202 can undergo an oxidation-reduction reaction with the second lithium-containing material 201, prompting the second lithium-containing material 201 to release a large amount of active lithium ions, providing a high lithium compensation capacity, and improving the cycle performance of the battery. The second lithium-containing material 201 and the first lithium-containing material 101 act together, so that the active lithium ions in the lithium compensation material can be slowly released, reducing the occurrence of the "overcharge" phenomenon, and thus the probability of battery thermal runaway can be reduced. In addition, the first coating layer 200 has a good protective effect on the core 100, improves the stability of the lithium compensation material, and improves the cycle performance of the battery containing it.

[0084] It is understandable that in the embodiments of the present application Figures 1-3 the first lithium-containing substance 101, the catalyst 102, the second lithium-containing substance 201 and the reducing agent 202 in only serve as examples that the above substances are included in the core 100 or the first coating layer 200, and do not represent the content or particle size of the above substances.

[0085] In some embodiments, the volume average particle size D v 50 of the reducing agent is 10 nm - 5 μm. For example, the volume average particle size D v 50 of the reducing agent can be 10 nm - 4.9 μm, 50 nm - 4.5 μm, 100 nm - 4 μm, 500 nm - 3.5 μm, 1 μm - 3 μm. Specifically, when the volume average particle size D v 50 of the reducing agent is limited within the above range, at a relatively high voltage, the reducing agent can easily react with the second lithium-containing substance, prompting the second lithium-containing substance to release a large amount of active lithium ions, reducing the occurrence of the "overcharge" phenomenon, and further reducing the probability of battery thermal runaway. In addition, the first coating layer formed by the reducing agent with the above particle size has a good protective effect on the core, improves the stability of the lithium supplement material, and improves the cycle performance of the battery containing it. In some other embodiments, the volume average particle size D v 50 of the reducing agent is 500 nm - 2 μm.

[0086] In some embodiments, the mass ratio of the second lithium-containing substance to the reducing agent is (1.5 - 9):1. For example, the mass ratio of the second lithium-containing substance to the reducing agent can be (1.5 - 8.9):1, (2 - 8.5):1, (2.5 - 8):1, (3 - 7.5):1, (3.5 - 7):1, (4 - 6.5):1, (4.5 - 6):1, (5 - 5.5):1, etc. Specifically, when the mass ratio of the second lithium-containing substance to the reducing agent is limited within the above range, at a relatively high voltage, the reducing agent can easily react with the second lithium-containing substance, prompting the second lithium-containing substance to release a large amount of active lithium ions, reducing the occurrence of the "overcharge" phenomenon, and further reducing the probability of battery thermal runaway. In addition, the first coating layer formed by the reducing agent with the above particle size has a good protective effect on the core, improves the stability of the lithium supplement material, and improves the cycle performance of the battery containing it. In some other embodiments, the mass ratio of the second lithium-containing substance to the reducing agent is (3 - 6):1.

[0087] In some embodiments, based on the total mass of the first coating layer, the mass proportion of the reducing agent is 10%-40%. For example, based on the total mass of the first coating layer, the mass proportion of the reducing agent can be 10%-39%, 15%-35%, 20%-30%, 22%-25%, etc. Specifically, by controlling the mass proportion of the reducing agent within the above range, at a relatively high voltage, the reducing agent can easily react with the second lithium-containing substance, prompting the second lithium-containing substance to release a large amount of active lithium ions, reducing the occurrence of the "overcharging" phenomenon, and further reducing the probability of battery thermal runaway. In addition, the first coating layer formed by the reducing agent with the above particle size has a good protective effect on the core, improving the stability of the lithium supplement material and the cycle performance of the battery containing it. In some other embodiments, based on the total mass of the first coating layer, the mass proportion of the reducing agent is 15%-25%.

[0088] In some embodiments, the ionic conductivity of the second coating layer is 10 -7 S / cm - 10 -3 S / cm. For example, the ionic conductivity of the second coating layer can be 10 -7 S / cm - 9.9×10 -4 S / cm, 10 -6 S / cm - 10 -4 S / cm, 10 -6 S / cm - 10 - 5 S / cm, 10 -5 S / cm - 10 -4 S / cm, etc. Specifically, by limiting the ionic conductivity of the second coating layer within the above range, the electrical conductivity of the lithium supplement material can be improved, effectively inhibiting the erosion of the lithium supplement material by the electrolyte. At the same time, it can allow active lithium ions to freely intercalate and deintercalate, and the second coating layer can act together with the first coating layer to effectively block the contact reaction between moisture and carbon dioxide in the air and the core lithium supplement material, improving the chemical stability of the lithium supplement material in the air and enhancing the cycle performance of the battery containing it. In some other embodiments, the ionic conductivity of the second coating layer is 10 -4 S / cm - 10 - 3 S / cm.

[0089] In some embodiments, the thickness of the second coating layer ≤ 100 nm. For example, the thickness of the second coating layer can be 1 nm - 99 nm, 5 nm - 95 nm, 10 nm - 90 nm, 20 nm - 80 nm, 30 nm - 70 nm, 40 nm - 60 nm, etc. Specifically, when the thickness of the second coating layer is controlled within the above range, on the one hand, the thickness of the second coating layer is moderate, which is conducive to the transmission of lithium ions. On the other hand, the second coating layer and the first coating layer act together to form a two-layer coating. Compared with the case of a single protective layer, the protection effect on the core is better, which can achieve physical isolation from air, reduce air sensitivity, improve the interfacial stability of the lithium supplement material, improve the storage performance and processing performance, and improve the cycle performance of the battery containing it. In some other embodiments, the thickness of the second coating layer is 1 nm - 100 nm, such as 2 nm - 15 nm.

[0090] In some embodiments, the second coating layer includes at least one of graphite, graphene, carbon nanotubes, carbon fibers, acetylene black, soft carbon, hard carbon, or amorphous carbon. Specifically, when the material of the second coating layer is at least one of the above substances, it can improve the electrical conductivity of the lithium supplement material, effectively inhibit the erosion of the electrolyte on the lithium supplement material, and at the same time allow lithium ions to freely intercalate and deintercalate. The second coating layer composed of the above substances can act together with the first coating layer to effectively block the contact reaction between moisture and carbon dioxide in the air and the core lithium supplement material, improve the chemical stability of the lithium supplement material in the air, and enhance the cycle performance of the battery containing it.

[0091] In some embodiments, the volume average particle size D v 50 of the lithium supplement material is 0.1 μm - 5 μm. For example, the volume average particle size D v 50 of the lithium supplement material can be 0.1 μm - 4.9 μm, 0.5 μm - 4.5 μm, 1 μm - 4 μm, 1.5 μm - 3.5 μm, 2 μm - 3 μm, 2.5 μm - 3 μm, etc. Specifically, when the volume average particle size D v 50 of the lithium supplement material in the embodiments of the present application is controlled within the above range, it can promote the slow release of active lithium ions in the lithium supplement material, reduce the occurrence of the "overcharge" phenomenon, and further reduce the probability of battery thermal runaway; and the first coating layer and the second coating layer outside the core form a two-layer coating outside the core. Compared with the case of a single protective layer, the protection effect on the core is better, and the stability of the lithium supplement material is improved. In some other embodiments, the volume average particle size D v 50 of the lithium supplement material is 4 μm - 5 μm.

[0092] In a second aspect of the present application, a method for preparing the aforementioned lithium supplement material is proposed. Thus, the aforementioned lithium supplement material can be prepared by a relatively simple method. Specifically, the method for preparing the lithium supplement material includes:

[0093] S100: forming a first coating layer on at least a part of the surface of the inner core, the inner core includes a first lithium-containing substance, the de-lithiation potential of the first lithium-containing substance is less than or equal to 4V, the first coating layer includes a second lithium-containing substance, and the de-lithiation potential of the second lithium-containing substance is greater than 4V

[0094] S200: forming a second coating layer on at least a part of the surface of the first coating layer away from the inner core to obtain the lithium supplement material.

[0095] Specifically, for the lithium supplement material prepared by the method proposed in the embodiments of the present application, the de-lithiation potential of the first lithium-containing substance in the inner core is less than or equal to 4V, and active lithium ions will be preferentially released during the charge and discharge of the battery, playing a role in supplementing lithium. The de-lithiation potential of the second lithium-containing substance in the first coating layer is greater than 4V, and it can de-lithiate at a high potential, so that the active lithium ions in the lithium supplement material can be slowly released, reducing the occurrence of the "overcharge" phenomenon, and further reducing the probability of battery thermal runaway; on the other hand, due to the low de-lithiation potential of the first lithium-containing substance and relatively high activity, the first coating layer and the second coating layer outside the inner core form two layers of coating outside the inner core. Compared with the case of a single protective layer, the protection effect on the inner core is better, which can achieve physical isolation from the air, reduce air sensitivity, improve the interface stability of the lithium supplement material, and improve the storage performance and processing performance. In summary, the lithium supplement material prepared in the present application has a good lithium supplement effect and good stability, improving the cycle performance of the battery containing it.

[0096] In a third aspect of the present application, the present application proposes a positive electrode plate, including the lithium supplement material described in the first aspect of the present application, or the lithium supplement material prepared by the method described in the second aspect.

[0097] In some embodiments, the positive electrode plate includes a positive current collector and a positive active material layer located on at least one surface of the positive current collector. The positive active material layer includes a positive active material and a lithium supplement material, and the lithium supplement material includes the lithium supplement material described in the first aspect of the present application, or the lithium supplement material prepared by the method described in the second aspect. Thus, the positive electrode plate has all the characteristics and advantages of the aforementioned lithium supplement material and the method for preparing the lithium supplement material, which will not be elaborated here.

[0098] As an example, the positive current collector has two surfaces opposite to each other in its own thickness direction, and the positive active material layer is disposed on any one or both of the two opposite surfaces of the positive current collector.

[0099] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0100] In some embodiments, when the battery is a lithium-ion battery, the positive electrode active material may be a positive electrode active material known in the art for lithium-ion batteries.

[0101] As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO 2 ), lithium nickel oxide (such as LiNiO 2 ), lithium manganese oxide (such as LiMnO 2 , LiMn 2 O 4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (which may also be abbreviated as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (which may also be abbreviated as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (which may also be abbreviated as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (which may also be abbreviated as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O 2(which can also be abbreviated as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.8 Co 0.15 Al 0.05 O 2 ), and at least one of its modified compounds. Examples of olivine-structured lithium-containing phosphates can include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (which can also be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and at least one of a composite material of lithium manganese iron phosphate and carbon. The modified compounds of the above materials can be doping modification and / or surface coating modification of the materials.

[0102] In some other embodiments, the positive electrode active material includes lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (which can also be abbreviated as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (which can also be abbreviated as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (which can also be abbreviated as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (which can also be abbreviated as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (which can also be abbreviated as NCM 811 )) and at least one of its modified compounds, etc. Thus, the lithium supplement material of the present application can supplement lithium ions for the above ternary materials in a targeted manner, improving the cycle performance of the battery containing it.

[0103] During the charge and discharge process of the battery, the deintercalation and consumption of Li will occur, and the molar content of Li is different when the battery is discharged to different states. In the list of positive electrode active materials in the present application, the molar content of Li is the initial state of the material, that is, the state before feeding. When the positive electrode active material is applied to the battery system, the molar content of Li will change after charge and discharge cycles.

[0104] In the enumeration of the positive electrode active material in this application, the molar content of O is only the theoretical value. The release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

[0105] In some embodiments, the positive electrode active material layer may further optionally include a binder.

[0106] As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0107] In some embodiments, the positive electrode active material layer may further optionally include a conductive agent.

[0108] As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0109] In some embodiments, the positive electrode plate can be prepared by the following method: dispersing the components for preparing the positive electrode plate, such as the positive electrode active material, lithium supplement material, conductive agent, binder, and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector, and after processes such as drying and cold pressing, the positive electrode plate can be obtained.

[0110] In some embodiments, the positive electrode plate can be prepared by the following method: dispersing the positive electrode active material, conductive agent, binder, and any other components in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector, and after processes such as drying and cold pressing, to form a positive electrode active material layer, and then using spraying, secondary coating, etc. on the positive electrode active material layer to composite the lithium supplement material with the positive electrode active material layer.

[0111] In the fourth aspect of this application, this application provides a battery, including the positive electrode plate described in the third aspect. Thus, this battery includes all the features and advantages of the aforementioned positive electrode plate, which will not be elaborated here.

[0112] Generally, a battery includes a positive electrode plate, a negative electrode plate, an electrolyte, and a separator. During the charge and discharge process of the battery, active ions intercalate and deintercalate back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate. The separator is disposed between the positive electrode plate and the negative electrode plate, mainly serving to prevent short circuit between the positive electrode and the negative electrode, and at the same time allowing active metal ions to pass through.

[0113] [Negative electrode plate]

[0114] The negative electrode plate 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, and the negative electrode active material layer includes a negative electrode active material.

[0115] As an example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode active material layer is provided on any one or both of the two opposite surfaces of the negative electrode current collector.

[0116] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, copper foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0117] In some embodiments, the negative electrode active material can be a negative electrode active material known in the art for batteries. As an example, the negative electrode active material can include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based materials include at least one of elemental silicon, silicon oxide compounds, silicon nitride composites, and silicon alloys. The tin-based materials include at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as battery negative electrode active materials can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0118] In some embodiments, the negative electrode active material layer may optionally further include a binder. The binder includes at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0119] In some embodiments, the negative electrode active material layer may optionally further include a conductive agent. The conductive agent includes at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0120] In some embodiments, the negative electrode active material layer may optionally further include other additives, such as thickeners (such as sodium carboxymethyl cellulose (CMC-Na)), etc.

[0121] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder, and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after processes such as drying and cold pressing, the negative electrode sheet can be obtained.

[0122] [Electrolyte]

[0123] The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. There is no specific limitation on the type of the electrolyte in this application, and it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or all-solid-state.

[0124] In some embodiments, the electrolyte uses an electrolytic solution. The electrolytic solution includes an electrolyte salt and a solvent.

[0125] In some embodiments, the electrolyte salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium difluoro(bis(oxalato))phosphate, and lithium tetrafluoro(oxalato)phosphate.

[0126] In some embodiments, the solvent includes at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0127] In some embodiments, the electrolytic solution may optionally include additives. For example, the additives can include negative electrode film-forming additives, positive electrode film-forming additives, and can also include additives that can improve certain performance of the battery, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature or low-temperature performance of the battery, etc.

[0128] [Separator]

[0129] In some embodiments, the battery further includes a separator. There is no particular limitation on the type of the separator in this application, and any porous structure separator with good chemical stability and mechanical stability can be selected.

[0130] In some embodiments, the material of the separator membrane includes at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0131] The battery of the present application includes a battery cell form, a battery module form, and a battery pack form. The battery, battery module, and battery pack of the present application will be described below with reference to the accompanying drawings as appropriate.

[0132] In some embodiments, the positive electrode plate, negative electrode plate, and separator membrane can be made into an electrode assembly by a winding process or a stacking process.

[0133] In some embodiments, the battery may include an outer package. The outer package can be used to encapsulate the above electrode assembly and electrolyte.

[0134] In some embodiments, the outer package of the battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the battery can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic. As plastics, polypropylene, polybutylene terephthalate, and polybutylene succinate can be listed, etc.

[0135] The present application has no particular limitation on the shape of the battery, and it can be cylindrical, square, or any other arbitrary shape. For example, Figure 4 is a battery cell of a square structure as an example.

[0136] In some embodiments, referring to Figure 5 , the outer package may include a housing 51 and a top cover assembly 53. Among them, the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the top cover assembly 53 can be covered on the opening to close the receiving cavity. The positive electrode plate, negative electrode plate, and separator membrane can form an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. The number of electrode assemblies 52 contained in the battery cell can be one or more, and those skilled in the art can select according to specific actual needs.

[0137] In some embodiments, the battery can be assembled into a battery module. The number of batteries contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0138] Figure 6 is a battery module 4 as an example. Referring to Figure 6, in the battery module 4, a plurality of battery cells may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other arbitrary manner. Further, the plurality of battery cells may be fixed by fasteners.

[0139] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells are accommodated in the accommodation space.

[0140] In some embodiments, the above battery module may also be assembled into a battery pack. The number of battery modules included in the battery pack may be one or more, and those skilled in the art may select the specific number according to the application and capacity of the battery pack.

[0141] Figure 7 and Figure 8 is a battery pack 1 as an example. Refer to Figure 7 and Figure 8 , in the battery pack 1, a battery box and a plurality of battery modules 4 disposed in the battery box may be included. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery module 4. The plurality of battery modules 4 may be arranged in the battery box in any manner.

[0142] In the fifth aspect of the present application, the present application provides an electrical device including the battery described in the fourth aspect of the present application. Thus, the electrical device includes all the features and advantages of the foregoing battery, which will not be elaborated herein.

[0143] The battery, battery module, and battery pack can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc., but not limited thereto.

[0144] As the electrical device, the battery, battery module, or battery pack can be selected according to its usage requirements.

[0145] Figure 9 is an electrical device as an example. The electrical device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the high power and high energy density requirements of the electrical device for the battery, a battery pack or a battery module can be adopted.

[0146] As another example of the device, it can be a mobile phone, a tablet computer, a laptop computer, etc. This device usually requires thinness and lightness, and a battery can be used as the power source.

[0147] The solution of the present application will be described below through specific embodiments. It should be noted that the following embodiments are only used to illustrate the present application and should not be regarded as limiting the scope of the present application. For those without specific technologies or conditions indicated in the embodiments, the technologies or conditions described in the literature in this field or according to the product specifications are followed. For the reagents or instruments without the manufacturer indicated, they are all conventional products that can be obtained through commercial purchase.

[0148] Example 1

[0149] Preparation of lithium supplement material:

[0150] 1) Transfer 10 g of lithium citrate and 0.5 g of zirconium diboride catalyst to a ball mill jar, grind at a speed of 600 r / min for 2 hours, and then transfer the mixed material to a tube furnace and sinter at 700 °C for 10 hours in an inert atmosphere to obtain a lithium supplement core;

[0151] 2) Mix 1 g of lithium orthosilicate (Li 4 SiO 4 ) and 0.2 g of MoS 2 reductant evenly, place them in a ball mill jar, grind at a speed of 600 r / min for 2 hours, and then put the mixed material into a sealed container and heat it at 120 °C for 4 h in a vacuum oven to obtain the first lithium supplement coating layer;

[0152] 3) Uniformly mix 10 g of the lithium supplement core material in step 1), 5 g of the first lithium supplement coating layer material in step 2), and 1 g of sucrose. Put the obtained mixture into a tube furnace and heat-treat it at 650 °C for 10 h under the protection of argon to obtain a double-layer coated lithium supplement material.

[0153] Preparation of the positive electrode plate:

[0154] Mix the positive electrode active material LiFePO 4 , the aforementioned lithium supplement material, the conductive agent acetylene black, and the binder according to a weight ratio of 95:2:1:2. Stir well in an N-methylpyrrolidone solvent (NMP) system until evenly mixed to obtain a positive electrode slurry. Coat the positive electrode slurry on the positive electrode current collector aluminum foil, dry it, and cold-press it to obtain a positive electrode plate.

[0155] Preparation of the negative electrode plate:

[0156] Mix the negative electrode active material artificial graphite, the conductive agent acetylene black, the binder styrene-butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) according to a weight ratio of 96.5:0.7:1.8:1. Stir well in a deionized water solvent system until evenly mixed to obtain a negative electrode slurry. Coat the negative electrode slurry on the negative electrode current collector copper foil, dry it, and cold-press it to obtain a negative electrode plate.

[0157] Preparation of the electrolyte:

[0158] At 25 °C, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain a mixed solvent. Then, LiPF 6 was dissolved in the above-mentioned mixed solvent to obtain an electrolyte solution, where the concentration of LiPF 6 was 1 mol / L.

[0159] Preparation of the battery:

[0160] A polypropylene film was used as the separator. The positive electrode plate, the separator, and the negative electrode plate were stacked in sequence, with the separator placed between the positive electrode plate and the negative electrode plate to play a separating role, and then wound to obtain a bare battery cell. The bare battery cell was placed in an outer package, the electrolyte solution was injected and sealed to obtain the battery.

[0161] The differences between Examples 2 - 57 and Comparative Examples 1 - 5 and Example 1 are shown in Table 1.

[0162] Comparative Example 1 has no second coating layer, Comparative Example 2 has no core, Comparative Example 3 has no first coating layer, Comparative Example 4 uses Li 2 O 2 as the lithium supplement material, and no lithium supplement material is added to the positive electrode plate of Comparative Example 5, and the rest is the same as Example 1.

[0163] Table 1

[0164]

[0165]

[0166]

[0167] The batteries in Examples 1 - 57 and Comparative Examples 1 - 5 were tested as follows: The test results are shown in Table 2.

[0168] 1. First-cycle efficiency test: At 25 °C, the battery was charged at a constant current of 0.33C to the charging cut-off voltage, and then charged at a constant voltage to 0.05C. The charging capacity E c0 was measured. Dividing E c0 by the mass of the positive electrode active material in the battery, the charging specific capacity can be obtained. That is: Charging specific capacity (mAh / g) = First-cycle charging capacity / Mass of the positive electrode active material.

[0169] Take the above-mentioned charged battery and discharge it at a constant current of 0.33C to the discharge cut-off voltage. The discharge capacity was measured as E d0 . Dividing E d0 by the mass of the positive electrode active material in the battery, the discharge specific capacity can be obtained. That is: Discharge specific capacity (mAh / g) = First-cycle discharge capacity / Mass of the positive electrode active material.

[0170] Initial cycle efficiency = specific discharge capacity in the first cycle / specific charge capacity in the first cycle.

[0171] 2. Cycling performance test:

[0172] Charge the battery at a rate of 0.5C to a voltage of 3.65V at room temperature (25°C), and then discharge it at a rate of 0.5C to a voltage of 2.5V. The reversible capacity measured is E. 0 . Cycle 500 times according to the above charge-discharge process, and obtain the reversible capacity and denote it as E. n , where n = 500. The capacity retention rate ε of the battery after 500 cycles at 25°C is ε = (E n - E 0 ) / E 0 ×100%.

[0173] 3. Determination of overcharge prevention effect:

[0174] Preparation of soft-pack battery:

[0175] Preparation of positive electrode sheet:

[0176] Add the positive active material (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 ), composite lithium supplement material, binder polyvinylidene fluoride (PVDF), conductive agent Super-P, and conductive agent CNT into N-methylpyrrolidone (NMP) according to the required weight ratio of 89.3:1:2.2:7:0.5, and stir to make a homogeneous positive electrode slurry; coat the positive electrode slurry on both sides of the positive electrode current collector, and obtain the positive electrode sheet after drying, cold pressing, and slitting;

[0177] Preparation of negative electrode sheet:

[0178] Add the negative active material artificial graphite, sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), conductive agent Super-P, and conductive agent CNT into deionized water according to the required weight ratio of 95.2:1.2:2.1:1.45:0.05, and stir to make a homogeneous negative electrode slurry; coat the negative electrode slurry on both sides of the negative electrode current collector, and obtain the negative electrode sheet after drying, cold pressing, and slitting;

[0179] Preparation of lithium-ion battery:

[0180] Wind and assemble the prepared negative electrode sheet and positive electrode sheet with the separator to make a soft-pack battery cell core. Put the battery cell core into the outer package, inject electrolyte into it, seal it, and perform formation to obtain a lithium-ion secondary battery;

[0181] The electrolyte is 1mol / L LiPF6 +EC+EMC, the separator is a polyethylene microporous membrane.

[0182] At a voltage of 10 V and a current of 5 A, the batteries of Example 1 and Comparative Example 5 were charged, and the curves of battery temperature and voltage changing with time, namely the temperature curve and the voltage curve, were obtained Figure 10 . Figure 11 It is a picture of the batteries of Comparative Example 5 and Example 1 after being charged at a voltage of 10 V and a current of 5 A for 8000 s.

[0183] Refer to Figure 10 , it can be seen from the temperature curves of Example 1 and Comparative Example 5 that under a continuous voltage of 10 V and a current of 5 A, the temperature change of the battery in Example 1 is not significant and remains at a relatively low temperature (below 100 °C), while the temperature of the battery in Comparative Example 5 suddenly rises above 150 °C at 6000 s - 7000 s and then fails; it can be seen from the voltage curves of Example 1 and Comparative Example 5 that under a continuous voltage of 10 V and a current of 5 A, after the voltage of the battery in Example 1 reaches 10 V (at 6000 s - 7000 s), the voltage drops to about 4 V, while the voltage of the battery in Comparative Example 5 reaches 10 V at 6000 s - 7000 s and then suddenly drops to 0 V, indicating that the battery fails. It can be seen that the lithium supplement material of the embodiment of the present application can reduce the occurrence of the "overcharge" phenomenon, and thus can reduce the probability of battery thermal runaway.

[0184] Refer to Figure 11 , it can be seen that the battery of Comparative Example 5 catches fire after being charged at a voltage of 10 V and a current of 5 A for 8000 s, and the battery of Example 1 is still normal after being charged at a voltage of 10 V and a current of 5 A for 8000 s. It can be seen that the lithium supplement material of the embodiment of the present application can reduce the occurrence of the "overcharge" phenomenon, and thus can reduce the probability of battery thermal runaway.

[0185] Table 2

[0186]

[0187]

[0188] Conclusion: It can be seen from Table 2 that in Examples 1 - 57 of the present application, with a core and two coating layers, when the battery is charged and discharged, the core first releases lithium ions, and the first coating layer releases lithium ions only at a certain potential, which can reduce the probability of overcharging of the battery cell, slowly release lithium ions, improve the stability of the lithium supplement material, and improve the cycle performance of the battery containing it. The lithium supplement agents used in Comparative Examples 1 - 5 are not within the scope of the lithium supplement agent of the present application, or no lithium supplement agent is used, and the initial efficiency and cycle performance of the battery are significantly reduced. It can be seen that the lithium supplement agent proposed in the present application can significantly improve the cycle performance of the battery containing it.

[0189] It should be noted that this application is not limited to the above embodiments. The above embodiments are only examples, and embodiments having the same constitution and achieving the same effects as the technical idea within the scope of the technical solution of this application are all included in the technical scope of this application. In addition, within the scope of not departing from the gist of this application, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways constructed by combining some constituent elements in the embodiments are also included in the scope of this application.

Claims

1. A lithium supplement material, characterized in that, it comprises: a core, the core comprising a first lithium-containing substance, and the de-lithiation potential of the first lithium-containing substance being less than or equal to 4V; a first coating layer, the first coating layer being formed on at least part of the surface of the core, the first coating layer comprising a second lithium-containing substance, and the de-lithiation potential of the second lithium-containing substance being greater than 4V; a second coating layer, the second coating layer being formed on at least part of the surface of the first coating layer and / or the core.

2. The lithium supplement material according to claim 1, characterized in that, the mass ratio of the first lithium-containing substance to the second lithium-containing substance is (1 - 9):1, and may be optionally (1 - 2):

1.

3. The lithium supplement material according to claim 1 or 2, characterized in that, the de-lithiation potential of the first lithium-containing substance is 1.5V - 4V.

4. The lithium supplement material according to any one of claims 1 - 3, characterized in that, The volume average particle size D of the first lithium-containing material v 50 is 0.1 μm - 5 μm, and may be optionally 2 μm - 3 μm.

5. The lithium supplement material according to any one of claims 1 - 4, characterized in that, The first lithium-containing substance includes Li 2 O, Li 2 O 2 , Li 3 N, Li 2 C 2 O 4 , Li 2 C 4 O 4 or at least one of lithium citrate.

6. The lithium supplement material according to any one of claims 1 - 5, characterized in that, The core further includes a catalyst, and the catalyst includes Li x MO y , at least one of magnesium diboride, titanium diboride, zirconium diboride, tungsten boride or lanthanum hexaboride, M includes at least one of Ni, Co, Mn, Mo, Al, Fe, Ti, Cu, Mg or V, 1≤x≤6, 2≤y≤4.

7. The lithium supplement material according to claim 6, characterized in that, the mass ratio of the first lithium-containing substance to the catalyst is 1:(0.01 - 0.1), and may be optionally 1:(0.05 - 0.1).

8. The lithium supplement material according to claim 6 or 7, characterized in that, based on the total mass of the core, the mass proportion of the catalyst is 1% - 9%, and may be optionally 5% - 9%.

9. The lithium supplement material according to any one of claims 1 - 8, characterized in that, the thickness of the first coating layer ≤ 5μm, may be optionally 0.5μm - 5μm, and further may be optionally 2μm - 3μm.

10. The lithium supplement material according to any one of claims 1 - 9, characterized in that, the de-lithiation potential of the second lithium-containing substance is 4.5V - 6V.

11. The lithium supplement material according to any one of claims 1 - 10, characterized in that, The volume average particle diameter D of the second lithium-containing substance v 50 is 0.1 μm - 1 μm, and may be optionally 0.5 μm - 1 μm.

12. The lithium supplement material according to any one of claims 1 - 11, characterized in that, The second lithium-containing substance includes Li 2 CO 3 、Li 2 SO 4 、Li 3 BO 3 、Li 3 PO 4 、 or at least one of lithium metasilicate or lithium orthosilicate.

13. The lithium supplement material according to any one of claims 1 - 12, characterized in that, the first coating layer further comprises a reducing agent, and the reducing agent comprises at least one of elemental sulfur, molybdenum sulfide, tungsten sulfide, titanium sulfide, lithium sulfide, magnesium sulfide, calcium sulfide, lanthanum sulfide, tantalum sulfide, iron sulfide, elemental phosphorus, iron phosphide, boron phosphide, nickel phosphide, lithium phosphide, zinc phosphide, elemental boron, cobalt boride, molybdenum boride, calcium boride or aluminum boride.

14. The lithium supplement material according to claim 13, characterized in that, The volume average particle size D of the reducing agent v 50 is 10 nm - 5 μm, and may be optionally 500 nm - 2 μm.

15. The lithium supplement material according to claim 13 or 14, characterized in that, the mass ratio of the second lithium-containing substance to the reducing agent is (1.5 - 9):1, and may be optionally (3 - 6):

1.

16. The lithium supplement material according to any one of claims 13 - 15, characterized in that, based on the total mass of the first coating layer, the mass proportion of the reducing agent is 10% - 40%, and may be optionally 15% - 25%.

17. The lithium supplement material according to any one of claims 1-16, characterized in that, The ionic conductivity of the second coating layer is 10 -7 S / cm - 10 -3 S / cm, and it can be optionally 10 -4 S / cm - 10 -3 S / cm.

18. The lithium supplement material according to any one of claims 1-17, characterized in that, the thickness of the second coating layer ≤ 100 nm, optionally 1 nm - 100 nm, and further optionally 2 nm - 15 nm.

19. The lithium supplement material according to any one of claims 1-18, characterized in that, the second coating layer comprises at least one of graphite, graphene, carbon nanotubes, carbon fibers, acetylene black, soft carbon, hard carbon or amorphous carbon.

20. The lithium supplement material according to any one of claims 1-19, characterized in that, The volume average particle size D of the lithium supplement material v 50 is 0.1 μm - 5 μm, and can be optionally 4 μm - 5 μm.

21. A method for preparing a lithium supplement material, characterized in that, comprising: forming a first coating layer on at least a part of the surface of the inner core, the inner core comprises a first lithium-containing substance, the de-lithiation potential of the first lithium-containing substance is less than or equal to 4 V, the first coating layer comprises a second lithium-containing substance, the de-lithiation potential of the second lithium-containing substance is greater than 4 V; forming a second coating layer on at least a part of the surface of the first coating layer away from the inner core to obtain a lithium supplement material.

22. A positive electrode sheet, characterized in that, comprises the lithium supplement material according to any one of claims 1-20, or the lithium supplement material prepared by the method described in claim 21.

23. The positive electrode sheet according to claim 22, characterized in that, the positive electrode sheet comprises a positive electrode active material, the positive electrode active material comprises at least one of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide, optionally, the positive electrode active material comprises lithium nickel cobalt manganese oxide.

24. A battery, characterized in that, comprises the positive electrode sheet according to claim 22 or 23.

25. An electrical device, characterized in that, comprises the battery according to claim 24.

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