Lithium supplement agent and preparation method thereof, lithium ion battery, battery pack and electric equipment

Abstract

The invention provides a lithium supplement agent and a preparation method thereof, a lithium ion battery, a battery pack and electric equipment. The lithium supplement agent comprises lithium supplement particles and a coating layer coating the surfaces of the lithium supplement particles, the coating layer comprises a temperature-sensitive material, and the solubility of the temperature-sensitive material in the electrolyte is in positive correlation with the temperature. Therefore, the lithium supplementing agent disclosed by the invention can adjust the speed of releasing active lithium according to the ambient temperature, so that the function of adaptively adjusting the lithium supplementing speed in different temperature regions of a battery cell is realized, the lithium supplementing speed and the lithium supplementing amount in a high-temperature region are improved, and the lithium supplementing speed in a low-temperature region is delayed; therefore, the consistency of the service life of the battery cell in different temperature areas is improved, excessive lithium supplement in local areas is prevented, and the service life of the battery cell is greatly prolonged.

Description

Technical Field

[0001] The present invention relates to the field of material technology, and in particular to a lithium supplement and a preparation method thereof, a lithium ion battery, a battery pack and electrical equipment. Background Art

[0002] Due to the large aspect ratio of the blade cell, the large impedance of the foil, and the uneven current distribution at different positions, there is a large temperature difference in different areas during the charging process, and the degree of capacity attenuation is inconsistent.

[0003] At a certain moment in the charging process, the temperature of different parts of the battery cell is different. For example, there is a certain temperature difference between the middle and the edge of the battery cell. The temperature difference in some areas can even exceed 15°C or higher. For the parts with higher battery cell temperatures, the negative electrode SEI film (solid electrolyte interface film) grows faster, more active lithium is consumed, and the capacity decays rapidly. More active lithium needs to be replenished to slow down the capacity decay rate. For the parts with lower battery cell temperatures, the negative electrode SEI film grows slower, less active lithium is consumed, and the capacity decays slowly. Too much active lithium does not need to be replenished. Too much active lithium replenishment will lead to lithium precipitation in this area, which is likely to cause safety problems. Summary of the Invention

[0004] The present invention aims to at least partially address one of the technical problems in the related art. To this end, one object of the present invention is to provide a lithium replenisher that can adjust the rate of active lithium release based on changes in battery cell temperature, thereby enabling adaptive regulation of the lithium replenishment rate in different battery cell temperature zones.

[0005] In one aspect of the present invention, the present invention provides a lithium supplement agent. According to an embodiment of the present invention, the lithium supplement agent includes lithium supplement particles and a coating layer coated on the surface of the lithium supplement particles, wherein the coating layer includes a temperature-sensitive material, and the solubility of the temperature-sensitive material in the electrolyte is positively correlated with the temperature. Thus, after the temperature-sensitive material in the coating layer is dissolved by the electrolyte, the lithium supplement agent can break through the coating layer and be released into the electrolyte or directly embedded in the positive and negative active materials of the battery to achieve the effect of lithium supplementation, and the dissolution of the temperature-sensitive material in the electrolyte is related to the temperature of the electrolyte. As the temperature increases, the greater the solubility of the temperature-sensitive material in the electrolyte, the faster the release of the lithium supplement agent in the electrolyte. Therefore, the lithium supplement agent of the present invention can adjust the speed of releasing active lithium according to the ambient temperature, realize the function of adaptively adjusting the lithium supplement speed in different temperature zones of the battery cell, improve the lithium supplement speed and lithium supplement amount in the high temperature zone, delay the lithium supplement speed in the low temperature zone, thereby improving the consistency of the life of the battery cell in different temperature zones, and preventing excessive lithium supplementation in local areas, thereby greatly improving the life of the battery cell.

[0006] According to an embodiment of the present invention, the thermosensitive material includes an organic thermosensitive material and / or an inorganic thermosensitive material, the organic thermosensitive material includes at least one of alkanes, alkenes, alkynes, aromatic hydrocarbons, halogenated hydrocarbons, alcohols, phenols, ethers, aldehydes, ketones, carboxylic acids, lipids, amines, amides or amino acids, and the inorganic sensitive material includes at least one of oxides, salt inorganic substances and alkaline inorganic substances.

[0007] According to an embodiment of the present invention, the organic temperature-sensitive material includes at least one of ethylene carbonate, propylene sulfate, modified propylene sulfate, 4-methylethylene sulfite, hydroxypropyl methylcellulose, and modified hydroxypropyl methylcellulose, and the inorganic sensitive material includes at least one of lithium nitrate, magnesium nitrate, and potassium nitrate.

[0008] According to an embodiment of the present invention, the coating layer further comprises a porous material. Optionally, the porous material comprises at least one of ceramics, aluminum oxide, aluminum alloy, magnesium oxide, titanium oxide, titanium alloy, and carbon material.

[0009] According to an embodiment of the present invention, the porosity of the porous material is 50% to 90%.

[0010] According to an embodiment of the present invention, based on the total mass of the coating layer, the mass percentage of the porous material is less than or equal to 50%.

[0011] According to an embodiment of the present invention, the particle size of the lithium supplement particles is 50% to 99% of the particle size of the lithium supplement agent.

[0012] In another aspect, the present invention provides a method for preparing the aforementioned lithium supplement. According to an embodiment of the present invention, the method for preparing the lithium supplement includes: providing lithium supplement particles; and forming a coating layer on the surface of the lithium supplement particles. Thus, in the lithium supplement prepared by the above method, only after the temperature-sensitive material in the coating layer is dissolved by the electrolyte can the lithium supplement break through the coating layer and be released into the electrolyte or directly embedded in the positive and negative active materials of the battery, thereby achieving the lithium supplement effect. The dissolution of the temperature-sensitive material in the electrolyte is related to the temperature of the electrolyte. As the temperature increases, the solubility of the temperature-sensitive material in the electrolyte increases, resulting in faster release of the lithium supplement in the electrolyte. Therefore, the lithium supplement of the present invention can adjust the rate of release of active lithium according to the ambient temperature, realizing the function of adaptively adjusting the lithium supplement rate in different temperature zones of the battery cell, increasing the lithium supplement rate and amount in the high temperature zone, and slowing the lithium supplement rate in the low temperature zone, thereby improving the consistency of the battery cell life in different temperature zones and preventing excessive lithium supplementation in local areas, thereby greatly improving the battery cell life.

[0013] According to an embodiment of the present invention, a method of forming the coating layer includes mechanical mixing, chemical vapor deposition, physical vapor deposition or atomic layer deposition.

[0014] In another aspect of the present invention, a lithium-ion battery is provided. According to an embodiment of the present invention, the lithium-ion battery comprises: a positive electrode plate, a separator, and a negative electrode plate arranged in an overlapping manner, the positive electrode plate comprising a first current collector and a positive electrode film layer located on the surface of the first current collector, the negative electrode plate comprising a second current collector and a negative electrode film layer located on the surface of the second current collector; an electrolyte; and the aforementioned lithium replenisher, the lithium replenisher being located in at least one of the positive electrode film layer, the negative electrode film layer, or the separator. Thus, the lithium replenisher in the lithium-ion battery can adjust the rate at which it releases active lithium according to the ambient temperature, thereby realizing the function of adaptively adjusting the lithium replenishment rate in different temperature zones of the battery cell, thereby improving the consistency of the battery cell's life in different temperature zones and preventing excessive lithium replenishment in local areas, thereby greatly improving the battery life.

[0015] According to an embodiment of the present invention, the lithium supplement agent is located in the positive electrode film layer, and based on the total mass of the positive electrode film layer, the mass percentage of the lithium supplement agent is 0.1% to 5%; and / or, the lithium supplement agent is located in the negative electrode film layer, and based on the total mass of the negative electrode film layer, the mass percentage of the lithium supplement agent is 0.1% to 5%; and / or, the lithium supplement agent is located in the diaphragm, and based on the total mass of the diaphragm, the mass percentage of the lithium supplement agent is 0.1% to 5%.

[0016] According to an embodiment of the present invention, the electrolyte includes a solubilizer.

[0017] According to an embodiment of the present invention, based on the total molar amount of the electrolyte, the molar amount of the solubilizer accounts for less than or equal to 10% in terms of molar percentage.

[0018] In another aspect, the present invention provides a battery pack. According to an embodiment of the present invention, the battery pack includes the lithium-ion batteries described above. As a result, the lithium-ion batteries in the battery pack have a better lithium replenishment effect, helping to extend the battery's service life. Those skilled in the art will appreciate that the battery pack possesses all the features and advantages of the lithium replenisher described above, and further details will not be provided here.

[0019] In another aspect, the present invention provides an electrical device. According to an embodiment of the present invention, the electrical device includes the aforementioned battery pack. As a result, the battery of the electrical device has better battery performance.

[0020] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0022] Figure 1 Schematic diagram of the structure of a lithium supplement in one embodiment of the present invention.

[0023] Figure 2 It is a test curve diagram of the active lithium release amount in different embodiments.

[0024] Figure 3 1 is a graph showing the temperature and active lithium release rate at different regions of the battery cell in Example 1;

[0025] Figure 4 is a scanning electron microscope image of the lithium element in Example 7;

[0026] Figure 5 This is a scanning electron microscope image of the lithium supplement in Example 7.

[0027] Reference numerals: 100 lithium supplement agent; 20 coating layer; 10 lithium supplement particle. DETAILED DESCRIPTION

[0028] Below, the scheme of the present invention will be explained in conjunction with embodiment.It will be understood by those skilled in the art that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention.In the embodiment, if specific technology or conditions are not indicated, the technology or conditions described in the literature in this area or the product instructions are used.The reagents or instruments used are not indicated by the manufacturer, and are all conventional products that can be obtained by commercial purchase.

[0029] The present invention is described below with reference to specific examples. It should be noted that these examples are merely illustrative and do not limit the present invention in any way.

[0030] The solubility of a material in a solution satisfies: Where S1 and S2 are the solubilities at temperatures T1 and T2, respectively; ΔH is the dissolution enthalpy, and R is the molar gas constant, representing the solubility of different substances at different temperatures. Based on this principle, the inventors applied it to lithium supplements. By coating the surface of lithium supplement particles with a temperature-sensitive material that has varying solubility at different temperatures, the release rate of the lithium supplement particles can be rationally designed.

[0031] Based on this, in one aspect of the present invention, the present invention provides a lithium supplement. According to an embodiment of the present invention, referring to Figure 1The lithium supplement agent 100 includes lithium supplement particles 10 and a coating layer 20 coated on the surface of the lithium supplement particles 10. The coating layer 20 includes a temperature-sensitive material whose solubility in the electrolyte is positively correlated with temperature. Therefore, the lithium supplement agent is a composite material with a core-shell structure. Only after the temperature-sensitive material in the coating layer is dissolved by the electrolyte and the coating layer is destroyed, can the lithium supplement particles come into contact with the electrolyte. That is, the lithium supplement agent can break through the coating layer and be released into the electrolyte or directly embedded in the positive and negative active materials of the battery, achieving the lithium supplement effect. The dissolution of the temperature-sensitive material in the electrolyte is related to the temperature of the electrolyte. As the temperature increases, the solubility of the temperature-sensitive material in the electrolyte increases, resulting in faster release of the lithium supplement agent in the electrolyte. Therefore, the lithium supplement agent of the present invention can adjust the rate of active lithium release according to the ambient temperature. This lithium replenisher is applied to the battery cells to realize the function of adaptively adjusting the lithium replenishment speed in different temperature zones of the battery cells, increasing the lithium replenishment speed and amount in high temperature zones, and slowing down the lithium replenishment speed in low temperature zones, thereby improving the consistency of the battery cell life in different temperature zones and preventing excessive lithium replenishment in local areas, thereby greatly improving the battery cell life.

[0032] According to some embodiments of the present invention, the specific material of the lithium supplement may be at least one of metallic lithium, lithium salts, inorganic lithium compounds, and organic lithium compounds.

[0033] According to some embodiments of the present invention, the temperature-sensitive material includes an organic temperature-sensitive material and / or an inorganic temperature-sensitive material.

[0034] In some embodiments, the organic temperature-sensitive material includes at least one of alkanes, alkenes, alkynes, aromatic hydrocarbons, halogenated hydrocarbons, alcohols, phenols, ethers, aldehydes, ketones, carboxylic acids, lipids, amines, amides, or amino acids. In some specific embodiments, the organic temperature-sensitive material includes at least one of ethylene carbonate, propylene sulfate, modified propylene sulfate, 4-methylethylene sulfite, hydroxypropyl methylcellulose, and modified hydroxypropyl methylcellulose. Within the typical temperature range of a battery, the solubility of the organic temperature-sensitive material in the electrolyte changes significantly with temperature. That is, the temperature-sensitive material exhibits a relatively sensitive solubility change with changes in electrolyte temperature, thereby enabling the lithium replenisher to have a relatively sensitive and adaptive adjustment function for the lithium replenishment rate.

[0035] Wherein, in some embodiments, above-mentioned modified propylene sulfate can be the copolymerization of propylene sulfate and other monomers (such as styrene, acrylamide), the copolymer formed, so that the hydrophobicity of propylene sulfate can be regulated, and its heat resistance is improved.In certain embodiments, modified hydroxypropyl methylcellulose can be hydroxypropyl methylcellulose and cross-linking agent (such as glutaraldehyde, epichlorohydrin etc. cross-linking agent) are cross-linked, the network structure formed, improves its temperature responsiveness.Further, above-mentioned modified propylene sulfate and modified hydroxypropyl methylcellulose can be purchased and obtained.

[0036] In some embodiments, the inorganic sensitive material includes at least one of an oxide, an inorganic salt, and an inorganic alkali. In some specific embodiments, the inorganic sensitive material includes at least one of lithium nitrate, magnesium nitrate, and potassium nitrate. Within the typical temperature range of a battery, the solubility of the organic temperature-sensitive material in the electrolyte changes significantly with temperature. In other words, the temperature-sensitive material exhibits a relatively sensitive solubility change with changes in electrolyte temperature, thereby enabling the lithium replenisher to have a relatively sensitive and adaptive function for adjusting the rate of lithium replenishment.

[0037] According to some embodiments of the present invention, the dissolution rate (or solubility) of the aforementioned temperature-sensitive materials in the electrolyte is positively correlated with temperature, i.e., the higher the temperature, the greater the dissolution rate (or solubility). In some embodiments, the solubility of the temperature-sensitive material in the electrolyte is very low at low temperatures (less than 0°C), and some temperature-sensitive materials even have a solubility limit close to 0. Furthermore, the aforementioned temperature-sensitive materials, after dissolving in the electrolyte, do not adversely affect the electrolyte.

[0038] According to some embodiments of the present invention, the coating layer further comprises a porous material. The porous material has pores, and the electrolyte enters the coating layer through the pores. Therefore, in addition to gradually dissolving the temperature-sensitive material outside the coating layer, the electrolyte can also dissolve the temperature-sensitive material in the pores (or in the coating layer), thereby further increasing the dissolution rate of the temperature-sensitive material.

[0039] According to some embodiments of the present invention, the porous material includes at least one of ceramic, aluminum oxide, aluminum alloy, magnesium oxide, titanium oxide, titanium alloy, and carbon material. The porous material has a relatively good porosity and is stable, and even if dissolved by the electrolyte, it will not adversely affect the electrolyte.

[0040] According to some embodiments of the present invention, the addition of a porous material and the amount of porous material can be selected based on the solubility of the specific thermosensitive material. In some embodiments, a porous material can be mixed into a relatively low-solubility thermosensitive material to form a coating layer, thereby increasing the dissolution rate of the thermosensitive material and accelerating lithium replenishment. In other embodiments, for thermosensitive materials with higher solubility, no porous material or a small amount of porous material can be added to the coating layer to avoid excessive lithium replenishment. According to some embodiments of the present invention, based on the total mass of the coating layer, the mass percentage of the porous material is less than or equal to 50%, for example, the mass percentage of the porous material is 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, 10%, 5%, 1%, 0, etc. This can effectively accelerate the dissolution of the thermosensitive material while avoiding excessive porous material or insufficient temperature-sensitive material, which is detrimental to the release of lithium-replenishing particles.

[0041] According to some embodiments of the present invention, the porosity of the porous material is 50% to 90%, such as 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, etc. Therefore, the porous material with a higher porosity can significantly accelerate the dissolution of the temperature-sensitive material in the coating layer, thereby accelerating the release rate of the lithium-supplementing particles.

[0042] According to some embodiments of the present invention, the particle size (or diameter) of the lithium supplementing particles is 50% to 99% of the particle size (or diameter) of the lithium supplementing agent, such as 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99%, etc., and the thickness of the coating layer is 0.5% to 25% of the particle size of the lithium supplementing agent. Therefore, lithium supplementing particles and the coating layer of the aforementioned sizes can achieve an optimal coating effect, preventing the lithium supplementing particles from being directly exposed. During the dissolution process, the coating layer does not take a long time to dissolve, thus preventing slow lithium supplementation and affecting the lithium supplementation effect.

[0043] In another aspect of the present invention, the present invention provides a method for preparing the aforementioned lithium supplement. According to an embodiment of the present invention, the method for preparing the lithium supplement comprises:

[0044] S100: Provide lithium supplement particles.

[0045] S200: forming a coating layer on the surface of the lithium supplement particles.

[0046] According to some embodiments of the present invention, the coating layer may be formed by mechanical mixing, i.e., the coating layer is coated on the surface of the lithium-supplementing particles by high-speed mechanical mixing. This method is simple and easy to implement, has a mature process, and is low in cost.

[0047] In some specific embodiments, the coating layer is applied to the surface of the lithium-supplementing particles through high-speed mechanical mixing. Specifically, the steps may include: uniformly mixing the lithium-supplementing particles with a temperature-sensitive material in a high-speed mixer to produce a lithium-supplementing agent. In some embodiments, the temperature-sensitive material comprises 1% to 10% by weight of the total weight of the mixture of the lithium-supplementing particles and the temperature-sensitive material, i.e., 90% to 99% by weight of the lithium-supplementing particles. In some embodiments, the high-speed mixer is first rotated at a speed of 1800 to 2300 rpm for 10 to 20 minutes, and then at a speed of 800 to 1300 rpm for 1 to 5 minutes.

[0048] According to some embodiments of the present invention, the coating layer may be formed by chemical vapor deposition, physical vapor deposition, or atomic layer deposition, which can form a relatively dense coating layer on the surface of the lithium-supplementing particles.

[0049] According to an embodiment of the present invention, the lithium replenisher prepared by the above method can only break through the coating layer and be released into the electrolyte or directly embedded in the positive and negative active materials of the battery after the temperature-sensitive material in the coating layer is dissolved by the electrolyte, thereby achieving the function of lithium replenishment. The dissolution of the temperature-sensitive material in the electrolyte is related to the temperature of the electrolyte. As the temperature increases, the solubility of the temperature-sensitive material in the electrolyte increases, and the release of the lithium replenisher in the electrolyte becomes faster. Therefore, the lithium replenisher of the present invention can adjust the rate of releasing active lithium according to the ambient temperature, thereby realizing the function of adaptively adjusting the lithium replenishment rate in different temperature zones of the battery cell, increasing the lithium replenishment rate and lithium replenishment amount in the high temperature zone, and delaying the lithium replenishment rate in the low temperature zone, thereby improving the consistency of the life of the battery cell in different temperature zones, and preventing excessive lithium replenishment in local areas, thereby greatly improving the life of the battery cell.

[0050] In another aspect of the present invention, a lithium-ion battery is provided. According to an embodiment of the present invention, the lithium-ion battery comprises: a positive electrode plate, a separator, and a negative electrode plate arranged in an overlapping manner, the positive electrode plate comprising a first current collector and a positive electrode film layer located on the surface of the first current collector, and the negative electrode plate comprising a second current collector and a negative electrode film layer located on the surface of the second current collector; an electrolyte; and the aforementioned lithium replenisher, wherein the lithium replenisher is located in at least one of the positive electrode film layer, the negative electrode film layer, or the separator. Thus, the lithium replenisher in the lithium-ion battery can adjust the rate at which it releases active lithium according to the ambient temperature, thereby realizing the function of adaptively adjusting the lithium replenishment rate in different temperature zones of the battery cell, thereby improving the consistency of the battery cell's life in different temperature zones and preventing excessive lithium replenishment in local areas, thereby greatly improving the battery life.

[0051] According to some embodiments of the present invention, the lithium replenisher is located in the positive electrode film layer. Based on the total mass of the positive electrode film layer, the mass percentage of the lithium replenisher is 0.1% to 5%, such as 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc. The lithium replenisher in the above proportion can effectively achieve a good lithium replenishment effect on the battery.

[0052] According to some embodiments of the present invention, the lithium replenisher is located in the negative electrode film layer. Based on the total mass of the negative electrode film layer, the mass percentage of the lithium replenisher is 0.1% to 5%, such as 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc. The lithium replenisher in the above proportion can effectively achieve a good lithium replenishment effect on the battery.

[0053] According to some embodiments of the present invention, the lithium replenisher is located in the separator. Based on the total mass of the separator, the mass percentage of the lithium replenisher is 0.1% to 5%, such as 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc. The lithium replenisher in the above proportion can effectively achieve a good lithium replenishment effect on the battery.

[0054] According to some embodiments of the present invention, the lithium supplement may be located only in the positive electrode film layer, the negative electrode film layer or the separator, or may be located in multiple locations in the positive electrode film layer, the negative electrode film layer or the separator, for example, in the positive electrode film layer and the negative electrode film layer, or in the positive electrode film layer and the separator, or in the negative electrode film layer and the separator, or in the positive electrode film layer, the negative electrode film layer and the separator, or in the positive electrode film layer, the negative electrode film layer and the separator at the same time.

[0055] According to some embodiments of the present invention, the electrolyte includes a solubilizer. Thus, the presence of the solubilizer in the electrolyte can accelerate the dissolution of the temperature-sensitive material, thereby achieving a faster dissolution rate and a faster dissolution amount.

[0056] According to some embodiments of the present invention, based on the total molar amount of the electrolyte, the molar amount of the solubilizer is less than or equal to 10%, such as 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0, etc., calculated as a percentage by mole.

[0057] According to some embodiments of the present invention, the solubilizer may be a carbonate. In some specific embodiments, the solubilizer may be at least one of ethylene carbonate and propylene carbonate.

[0058] In another aspect, the present invention provides a battery pack. According to an embodiment of the present invention, the battery pack includes the lithium-ion batteries described above. As a result, the lithium-ion batteries in the battery pack have a better lithium replenishment effect, helping to extend the battery's service life. Those skilled in the art will appreciate that the battery pack possesses all the features and advantages of the lithium replenisher described above, and further details will not be provided here.

[0059] In another aspect, the present invention provides an electrical device. According to an embodiment of the present invention, the electrical device includes the aforementioned battery pack. As a result, the battery of the electrical device has better battery performance.

[0060] In some embodiments of the present invention, specific types of electrical equipment may include but are not limited to 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 and other equipment.

[0061] Example

[0062] Example 1

[0063] Coatings made of ethylene carbonate, modified propylene sulfate, modified hydroxypropyl methylcellulose, lithium nitrate, and magnesium nitrate were selected as temperature-sensitive materials, and then the coating to be tested was thoroughly ground, sieved through a 400-mesh sieve, and 1g was placed in 1L of electrolyte. After sealing, it was placed at a certain temperature and allowed to stand for 24 hours. The electrolyte was filtered, dried, and weighed to obtain the mass of the remaining solid, thereby determining the content of the solid coating dissolved in the electrolyte, that is, the solubility of the solid at a certain temperature. The test results are shown in Table 1. Among them, the components and proportions of the electrolyte include: LiPF6, LiFSI (lithium bis(trifluoromethanesulfonyl imide), EC (ethylene carbonate), EMC (ethyl methyl carbonate), and DMC (dimethyl carbonate), with their mass percentages being 10%, 2%, 29%, 33%, and 26%, respectively.

[0064] Table 1

[0065]

[0066] It can be seen that the solubility of the above-mentioned temperature-sensitive material in the electrolyte is different at different temperatures, which shows that applying it to the coating layer can enable the lithium replenisher of the present invention to have the function of adaptively adjusting the lithium replenishment speed.

[0067] Example 2

[0068] Lithium element is used as lithium supplement particles, and lithium element and ethylene carbonate (5% by mass of ethylene carbonate and 95% by mass of lithium element) are mixed and placed in a high-speed mixer. The high-speed mixer is first rotated at a speed of 2000 rpm for 15 minutes, and then rotated at a speed of 1000 rpm for 3 minutes to obtain a lithium supplement agent with a coating layer coated on the surface of the lithium element.

[0069] Example 3

[0070] The only difference from Example 2 is that the temperature-sensitive material is modified propylene sulfate.

[0071] Example 4

[0072] The only difference from Example 2 is that the temperature-sensitive material is modified hydroxypropyl methylcellulose.

[0073] Example 5

[0074] The only difference from Example 2 is that the temperature-sensitive material is lithium nitrate.

[0075] Example 6

[0076] The only difference from Example 2 is that the lithium-supplementing particles are lithium carbonate and the temperature-sensitive material is magnesium nitrate.

[0077] Example 7

[0078] Using lithium as a lithium supplement particle, lithium, aluminum oxide (porous material) and magnesium nitrate (mass fractions of 95%, 2.5%, and 2.5%, respectively) were mixed and placed in a high-speed mixer. The high-speed mixer was first rotated at a speed of 2000 rpm for 15 minutes, and then rotated at a speed of 1000 rpm for 3 minutes to obtain a lithium supplement agent with a coating layer on the surface of the lithium. The electron microscope images of the lithium and the lithium supplement agent can be referred to respectively. Figure 4 and Figure 5 , by comparison, Figure 5 After the surface of the lithium element is coated with a coating layer, the surface has a relatively large porous structure.

[0079] Comparative Example 1

[0080] The lithium supplement is simply lithium and does not have a coating layer.

[0081] Prepare the test button cell:

[0082] Positive electrode: 1. According to the mass ratio, active material: conductive carbon black: PVDF = 90:5:5 are weighed (the active material includes lithium iron phosphate positive electrode material and lithium supplement agent, and the lithium supplement agent is the lithium supplement agent in the above-mentioned Examples 2 to 7 and Comparative Example 1, and the mass ratio of lithium iron phosphate positive electrode material and lithium supplement agent is 88:2). Dissolve PVDF in NMP (volume ratio PVDF:NMP = 1:9) and stir until completely dissolved. Add conductive agent and active material, ball mill and mix for 4-6 hours (speed 300rpm) to obtain a uniform slurry; 2. Evenly coat the slurry on aluminum foil (thickness 15μm) with a coating thickness of 130μm (wet film). Dry in a vacuum oven at 120℃ for 12 hours to remove the solvent; 3. Use a roller press to compact to an electrode density of 3g / cm 3 (pressure 15MPa) to obtain a positive electrode film layer. The dried electrode sheet is cut into the required size (such as a 14mm diameter disc for button batteries) to obtain a positive electrode sheet. Based on the total mass of the positive electrode film layer, the mass percentage of the lithium supplement is 0.1% to 5%.

[0083] Negative electrode: 1. Dissolve CMC in water (volume ratio CMC:water = 1.5:50) and stir until dissolved. Add graphite and conductive agent and ball mill for 4 hours (speed 300rpm). Finally, add SBR latex and stir for 1 hour. 2. Coat the slurry on copper foil (thickness 10μm) to a coating thickness of about 100μm (wet film). Dry in a vacuum oven at 80℃ for 12 hours. 3. Roll to an electrode density of 1.6g / cm 3 (pressure 8MPa) to obtain the negative electrode film layer. Cut it into a size that matches the positive electrode (slightly larger than the positive electrode) to obtain the negative electrode sheet.

[0084] Battery Assembly:

[0085] Diaphragm: Celgard 2400 (PP / PE / PP three-layer composite film, thickness 25 μm).

[0086] Housing: Stainless steel CR2032 housing.

[0087] Steps: Lamination: Place in the following order: positive electrode shell → positive electrode sheet → diaphragm → negative electrode sheet → gasket → spring sheet → negative electrode shell. Liquid Injection: Add 80μL of electrolyte to the diaphragm and allow to soak for 30 minutes. Sealing: Press tightly with a sealing machine (pressure 1.5 tons).

[0088] Comparative Example 2

[0089] The steps for preparing the test battery are basically the same as those described above, except that no lithium supplement is added.

[0090] The active lithium release and cycle performance of the test cells were tested, and the test results are shown in Table 2 below. The cell cycle life test method is as follows: the cell is placed at the corresponding temperature (25°C, 45°C) for 8 hours, charged to 3.8V at 1C, then placed for 30 minutes, and discharged to 2V at 1C, then placed for 30 minutes. This charge and discharge process is repeated 200 times. The percentage of the 200th discharge capacity to the first discharge capacity is the 200-cycle capacity retention rate.

[0091] Table 2

[0092]

[0093]

[0094] The release rate curves of active lithium in Examples 2 to 6 and Comparative Example 1 can be found in Figure 2 , it can be seen that, depending on the different coated thermosensitive materials, the release rate of the active lithium (i.e., lithium-replenishing particles) dissolved in the electrolyte varies at different temperatures, thereby achieving the effect of adaptively adjusting the lithium-replenishing rate in different temperature regions. Among them, according to the data in Table 2, in Examples 6 and 7, the thermosensitive material is magnesium nitrate. After the porous material is added to Example 7, the amount of active lithium released during the heating process is increased compared to Example 6, indicating that the addition of the porous material can increase the dissolution rate of the thermosensitive material and accelerate the release rate of the active lithium.

[0095] The test battery prepared in Example 3 was selected to test the temperature of different areas of the battery cell and the release rate of active lithium. The test results can be found in Figure 3 As shown. Figure 3 It can be seen that after adding the temperature-sensitive lithium replenisher into the battery cell, the temperature changes in different areas during the charging process of the battery cell are quite different, and the release rate of active lithium is also proportional to the temperature. The active lithium release rate is fast in the high temperature area, and the active lithium release rate is slow in the low temperature area, thereby achieving the effect of adaptively adjusting the lithium replenishment rate in different temperature areas, greatly improving the battery cell life and the consistency of life in different areas, and preventing the risk of lithium plating.

[0096] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features. Throughout the description of this application, "plurality" means two or more, unless otherwise specifically defined.

[0097] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0098] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A lithium supplement, characterized in that: The invention comprises lithium-supplementing particles and a coating layer coated on the surface of the lithium-supplementing particles, wherein the coating layer comprises a temperature-sensitive material, and the solubility of the temperature-sensitive material in the electrolyte is positively correlated with the temperature.

2. The lithium supplement according to claim 1, characterized in that The thermosensitive material includes an organic thermosensitive material and / or an inorganic thermosensitive material, the organic thermosensitive material includes at least one of alkanes, alkenes, alkynes, aromatic hydrocarbons, halogenated hydrocarbons, alcohols, phenols, ethers, aldehydes, ketones, carboxylic acids, lipids, amines, amides or amino acids, and the inorganic sensitive material includes at least one of oxides, salt inorganic substances and alkaline inorganic substances.

3. The lithium supplement according to claim 2, characterized in that The organic temperature-sensitive material includes at least one of ethylene carbonate, propylene sulfate, modified propylene sulfate, 4-methylethylene sulfite, hydroxypropyl methylcellulose, and modified hydroxypropyl methylcellulose; the inorganic sensitive material includes at least one of lithium nitrate, magnesium nitrate, and potassium nitrate.

4. The lithium supplement according to any one of claims 1 to 3, characterized in that The coating layer also includes a porous material, Optionally, the porous material includes at least one of ceramics, aluminum oxide, aluminum alloy, magnesium oxide, titanium oxide, titanium alloy, and carbon material.

5. The lithium supplement according to claim 4, characterized in that The porosity of the porous material is 50% to 90%.

6. The lithium supplement according to claim 4 or 5, characterized in that Based on the total mass of the coating layer, the mass percentage of the porous material is less than or equal to 50%.

7. The lithium supplement according to any one of claims 1 to 6, characterized in that The particle size of the lithium supplement particles is 50% to 99% of the particle size of the lithium supplement agent.

8. A method for preparing the lithium supplement according to any one of claims 1 to 7, characterized in that: include: Provide lithium supplement particles; A coating layer is formed on the surface of the lithium supplement particles.

9. The method according to claim 8, characterized in that Methods for forming the coating layer include mechanical mixing, chemical vapor deposition, physical vapor deposition, or atomic layer deposition.

10. A lithium ion battery, characterized in that: include: A positive electrode sheet, a separator, and a negative electrode sheet are sequentially overlapped, wherein the positive electrode sheet includes a first current collector and a positive electrode film layer located on a surface of the first current collector, and the negative electrode sheet includes a second current collector and a negative electrode film layer located on a surface of the second current collector; electrolyte; The lithium supplement according to any one of claims 1 to 7, wherein the lithium supplement is located in at least one of the positive electrode film layer, the negative electrode film layer, or the separator.

11. The lithium-ion battery according to claim 10, wherein: The lithium supplement agent is located in the positive electrode film layer, and based on the total mass of the positive electrode film layer, the mass percentage of the lithium supplement agent is 0.1% to 5%; And / or, the lithium supplement agent is located in the negative electrode film layer, and based on the total mass of the negative electrode film layer, the mass percentage of the lithium supplement agent is 0.1% to 5%; And / or, the lithium supplement agent is located in the separator, and based on the total mass of the separator, the mass percentage of the lithium supplement agent is 0.1% to 5%.

12. The lithium-ion battery according to claim 10 or 11, characterized in that The electrolyte includes a solubilizing agent.

13. The lithium-ion battery according to claim 12, wherein: Based on the total molar amount of the electrolyte, the molar amount of the solubilizer accounts for less than or equal to 10% in terms of molar percentage.

14. A battery pack, characterized in that: A lithium ion battery comprising the lithium ion battery according to any one of claims 10 to 13.

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

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