Positive lithium supplement agent and preparation method thereof, positive pole piece, diaphragm, battery and electric equipment

Abstract

The invention provides a positive lithium supplement agent and a preparation method thereof, a positive pole piece, a diaphragm, a battery and electric equipment. The positive electrode lithium supplementing agent comprises LiaMb (O1-xAx) c, M comprises one or more of Fe, Ni, Mn, Cu, Zn, Co, Cr, Zr, Sb, Ti, V, Mo and Sn, A comprises one or more of S, Se and Te, a is larger than 1 and smaller than or equal to 8, b is larger than 0 and smaller than or equal to 1, c is larger than 0 and smaller than 7, and x is larger than 0 and smaller than 0.5. The oxygen atoms in the positive electrode lithium supplement agent are doped by selecting anions with electronegativity closer to that of metal cations, so that the intrinsic conductivity of the positive electrode lithium supplement agent is remarkably improved, and the lithium supplement performance is remarkably improved.

Description

Technical Field

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

[0002] With the rapid development of new energy and the increasing standard of living, demands for the battery life and service life of digital devices and electric vehicles are becoming increasingly stringent. Therefore, improving the energy density and cycle life of lithium-ion batteries has become a research hotspot in the battery field. Lithium ion consumption is a major cause of battery capacity degradation, especially during the initial charge and discharge process. The formation of a SEI film on the negative electrode surface by the electrolyte consumes a large amount of active lithium, leading to irreversible capacity loss.

[0003] Lithium replenishment is an important method for adding additional active lithium to lithium-ion batteries to offset the energy density loss caused by active lithium depletion. Conventional lithium replenishment methods include negative electrode replenishment and positive electrode replenishment. Negative electrode replenishment requires the use of n-butyl lithium or lithium metal, which is difficult and dangerous, making it difficult to commercialize. Positive electrode replenishment involves adding compounds that are easily delithiated under high voltage to the positive electrode. This method is relatively safe and suitable for industrial applications.

[0004] Currently, the commonly used positive electrode lithium supplements include Li5FeO4, Li2NiO2, Li6CoO4, Li2O2, etc., which generally have the problem of poor conductivity. Taking Li5FeO4 as an example, its conductivity is very low, only 10 -9 S / cm level, which is almost an insulating compound. In the existing technology, the conductivity of the material is usually improved by metal doping. However, the above method has limited effect on the improvement of the intrinsic conductivity of the material, and it is still difficult for the material to fully exert its lithium replenishment properties. Summary of the Invention

[0005] The present invention provides a positive electrode lithium replenisher and a preparation method thereof, a positive electrode plate, a separator, a battery and an electrical device. The present invention dopes the oxygen atoms in the positive electrode lithium replenisher with anions having an electronegativity closer to that of metal cations, thereby significantly improving the intrinsic conductivity of the positive electrode lithium replenisher and thus significantly improving the lithium replenishment performance.

[0006] The first aspect of the present invention provides a positive electrode lithium supplement, the positive electrode lithium supplement comprises Li a M b (O 1-x A x ) c, wherein M includes one or more of Fe, Ni, Mn, Cu, Zn, Co, Cr, Zr, Sb, Ti, V, Mo, and Sn, A includes one or more of S, Se, and Te, 1<a≤8, 0<b≤1, 0<c<7, and 0<x<1.

[0007] The positive electrode lithium supplement as described above, wherein 0<x≤0.3.

[0008] The positive electrode lithium replenisher as described above, wherein the D50 particle size of the positive electrode lithium replenisher is 10 to 30 μm.

[0009] The positive electrode lithium replenisher as described above, wherein the surface of the positive electrode lithium replenisher is further coated with a conductive carbon layer.

[0010] In the positive electrode lithium supplement as described above, the thickness of the conductive carbon layer is 100 to 200 nm.

[0011] In the positive electrode lithium replenisher as described above, the conductive carbon layer accounts for 1% to 8% of the mass content of the positive electrode lithium replenisher.

[0012] A second aspect of the present invention provides a method for preparing the positive electrode lithium supplement as described above, comprising the following steps:

[0013] The lithium source, M source and A source are mixed uniformly according to a stoichiometric ratio and then sintered to obtain the positive electrode lithium supplement agent.

[0014] The preparation method as described above, wherein the lithium source comprises one or more of LiOH, Li2O, Li2O2, and Li2CO3;

[0015] and / or, the M source includes one or more of the oxide, hydroxide, carbonate, and nitrate of element M;

[0016] And / or, the source A includes one or more of a lithium compound of element A, an iron compound, an organic compound containing element A, and a binary inorganic compound containing element A and element M.

[0017] In the preparation method as described above, the sintering treatment is performed at a temperature of 500 to 1200° C. and for a time of 6 to 100 hours.

[0018] The preparation method as described above, wherein, after the sintering treatment, further comprises: mixing the sintered material with a carbon source evenly, and then heat-treating the mixed material to obtain the positive electrode lithium supplement.

[0019] The preparation method as described above, wherein the carbon source includes one or more of carbon black, graphene, carbon nanotubes, fullerenes, sucrose, glucose, asphalt, polydopamine, resorcinol, formaldehyde, starch, sucrose, sodium carboxymethyl cellulose, polyvinylidene fluoride, polyvinyl pyrrolidone, tannic acid, polyvinyl alcohol, polypyrrole, vitamin C, polyethylene glycol, anthracene or aniline.

[0020] In the preparation method as described above, the mass ratio of the sintered material to the carbon source is (1-y):y, wherein 0≤y≤0.1.

[0021] In the preparation method as described above, the heat treatment temperature is 80-1000° C. and the time is 3-15 hours.

[0022] The third aspect of the present invention provides a positive electrode plate, comprising a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector, wherein the positive electrode active material layer comprises the positive electrode lithium supplement provided by the first aspect of the present invention.

[0023] A fourth aspect of the present invention provides a diaphragm, comprising a diaphragm substrate and a lithium replenishing layer disposed on one surface of the diaphragm substrate, wherein the lithium replenishing layer comprises the positive electrode lithium replenishing agent provided by the first aspect of the present invention.

[0024] A fifth aspect of the present invention provides a battery, comprising the positive electrode sheet provided by the third aspect of the present invention and / or the separator provided by the fourth aspect of the present invention.

[0025] A sixth aspect of the present invention provides an electrical device comprising the battery provided by the fifth aspect of the present invention.

[0026] The implementation of the present invention has at least the following beneficial effects:

[0027] 1) The positive lithium supplement of the present invention includes Li a M b (O 1-x A x ) c , M includes one or more of Fe, Ni, Mn, Cu, Zn, Co, Cr, Zr, Sb, Ti, V, Mo, and Sn, A includes one or more of S, Se, and Te, 1<a≤8, 0<b≤1, 0<c<7, and 0<x<0.5. The present invention uses A elements such as S, Se, and Te, whose electronegativity is closer to that of metals, to perform anion substitution doping on the O element in the positive electrode lithium replenisher. Compared with the bonding effect between metals and O, when the metal and A elements form a bond, the overlap of the electron clouds of the two increases, the covalent bond component becomes stronger, the number of freely movable delocalized electrons increases, the band gap of the material is reduced, and the intrinsic conductivity of the material is significantly improved, thereby having a better lithium replenishment effect.

[0028] 2) The positive electrode plate, separator and battery provided by the present invention include the above-mentioned positive electrode lithium replenisher, so they can replenish the active lithium loss of the battery during the initial charge and discharge process and the cycle process, so that the battery has higher first-cycle coulombic efficiency and cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Fe 3+ Respectively with O 2- 、S 2- 、Se 2- Schematic diagram of the bonding of elements. DETAILED DESCRIPTION

[0030] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0031] Traditional positive electrode lithium replenishers, such as Li5FeO4, Li2NiO2, Li6CoO4, Li2O2, etc., have a large difference in electronegativity between the metal element and the anion O, a low degree of electron cloud overlap, and fewer freely moving delocalized electrons, resulting in poor conductivity and thus poor lithium replenishment effect.

[0032] Based on this, the first aspect of the present invention provides a positive electrode lithium supplement, including Li a M b (O 1-x A x ) c , wherein M includes one or more of Fe, Ni, Mn, Cu, Zn, Co, Cr, Zr, Sb, Ti, V, Mo, and Sn, A includes one or more of S, Se, and Te, 1<a≤8, 0<b≤1, 0<c<7, and 0<x<0.5.

[0033] The present invention uses A elements such as S, Se, and Te to replace the O element in the traditional positive electrode lithium supplement material with anion doping. The electronegativity of the A element is closer to the electronegativity between the M metal and the Li metal, the degree of electron cloud overlap between the metal and the A element is increased, the covalent bond component is strengthened, the number of freely movable delocalized electrons is increased, the material band gap is reduced, and the intrinsic conductivity of the material is significantly improved, thereby having a better lithium supplement effect.

[0034] Taking Fe as an example, the atomic radius, ionic radius and electronegativity of Fe, O, S and Se are listed in Table 1 for objective comparison.

[0035] Table 1

[0036]

[0037] As shown in Table 1, compared to O, S and Se have larger atomic radius and ionic radius, and their electronegativity is closer to that of Fe. A graphic comparison can be used to show the specific comparison. Figure 1 Fe 3+ Respectively with O 2- 、S 2- 、Se 2- Schematic diagram of the bonding of elements, such as Figure 1 As shown, O 2- 、S 2- 、Se 2- The ionic radius of Fe 3+ The degree of electron cloud overlap between them also gradually increases, the covalent bond component is enhanced, and the intrinsic conductivity of the material is significantly improved, thereby improving the lithium replenishment performance.

[0038] The inventors studied the doping amount of element A and found that when 0<x≤0.3, the lithium replenishing effect of the positive electrode lithium replenisher is better. In a preferred embodiment, the D50 particle size of the positive electrode lithium replenisher is 10 to 30 μm. When the D50 particle size of the positive electrode lithium replenisher is less than 10 μm, the particles are easy to agglomerate and the contact area with the electrolyte is too large, which easily leads to decomposition and gas production; when the D50 particle size of the positive electrode lithium replenisher is greater than 30 μm, the specific surface area of ​​the material is too small, which is not conducive to the lithium replenishment capacity. Exemplarily, the D50 particle size of the positive electrode lithium replenisher can be 10 μm, 13 μm, 15 μm, 17 μm, 19 μm, 20 μm, 23 μm, 25 μm, 27 μm, 29 μm, 30 μm or a range consisting of any two of the above values.

[0039] In a preferred embodiment, the surface of the positive electrode lithium replenisher is further coated with a conductive carbon layer. The conductive carbon layer can further enhance the conductivity of the positive electrode lithium replenisher and improve its lithium replenishment performance. In addition, A elements such as S, Se, and Te have a better affinity for the carbon element in the conductive carbon layer, which facilitates the conductive carbon layer to be tightly coated on the surface of the positive electrode lithium replenisher, forming a more complete and dense conductive carbon layer, thereby effectively improving the environmental tolerance of the positive electrode lithium replenisher, avoiding side reactions between the lithium replenisher active material and moisture and carbon dioxide in the air, reducing the amount of residual alkali on the surface, improving the dispersibility of the slurry, and reducing its coating difficulty.

[0040] Furthermore, the thickness of the conductive carbon layer is 100 to 200 nm. If the thickness of the conductive carbon layer is too large, it will be detrimental to the improvement of the battery energy density; if the thickness of the conductive carbon layer is too small, it will be difficult to fully and effectively protect the lithium-replenishing active material, resulting in poor environmental tolerance. The thickness of the conductive carbon layer is controlled within the above range, while achieving effective protection of the lithium-replenishing active material and reducing the adverse effects on the battery energy density. Exemplarily, the thickness of the conductive carbon layer is 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, 200 nm or a range consisting of any two of the above values.

[0041] In a specific embodiment, the conductive carbon layer accounts for 1% to 8% of the mass content of the positive electrode lithium replenisher. Within the above mass content range, it is beneficial to achieve uniform coating of the conductive carbon layer on the surface of the positive electrode lithium replenisher, and it can also avoid excessive use of the conductive carbon layer and the negative impact on the lithium replenishment capacity of the positive electrode lithium replenisher. Exemplarily, the conductive carbon layer accounts for 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8% of the mass content of the positive electrode lithium replenisher, or a range consisting of any two of the above values.

[0042] A second aspect of the present invention provides a method for preparing a positive electrode lithium supplement, the method comprising the following steps:

[0043] The lithium source, M source and A source are mixed uniformly according to a stoichiometric ratio and then sintered to obtain the positive electrode lithium supplement agent.

[0044] The above method obtains the positive electrode lithium supplement agent through solid-phase mixed sintering. It does not require the addition of solvents. It only requires the lithium source, M source, and A source to be mixed and sintered under solid-phase conditions. Compared with the co-precipitation method and the molten salt method, the high-temperature solid-phase mixed sintering method is more efficient and convenient, and more suitable for industrial production.

[0045] The present invention does not specifically limit the types of lithium source, M source, and A source, wherein the lithium source includes but is not limited to one or more of LiOH, Li2O, Li2O2, and Li2CO3; the M source includes but is not limited to one or more of oxides, hydroxides, carbonates, and nitrates of element M; and the A source includes one or more of lithium compounds of element A, iron compounds, organic substances containing element A, and binary inorganic compounds containing element A and element M.

[0046] Specifically, the source A can be selected from one or more of Li2S, Li2S2, Fe2S3, Li2Se, Li2Se2, Fe2Se3, Li2Te, Li2Te2, Fe2Te3, and thiourea.

[0047] In order to avoid interference from impurities and moisture in the air, the sintering process is carried out under an inert atmosphere, wherein the inert gas can be selected from one or more of argon, nitrogen, helium, and neon.

[0048] In a specific embodiment, the sintering temperature is 500-1200°C, preferably 700-1000°C, and the sintering time is 6-100 hours, preferably 12-30 hours. Sintering within this temperature and time range not only facilitates the formation of the material structure and the doping of the A element, but also fully removes moisture from the surface and interior of the material, avoiding side reactions caused by moisture.

[0049] It's worth noting that heating and cooling rates are also crucial factors influencing material performance. Excessively high heating and cooling rates can easily cause material deformation, impacting product quality, while too slow heating and cooling rates can lead to excessively long production times. To balance high product quality and efficiency, the heating rate is controlled within a range of 3-10°C / min, preferably 4-7°C / min. Natural cooling with the furnace is the preferred cooling method.

[0050] In a specific embodiment, after the sintering treatment, the method further includes: uniformly mixing the sintered material with a carbon source, and heat-treating the mixed material to obtain the positive electrode lithium supplement.

[0051] The above process is the process of coating the surface of the lithium-supplementing active material with a conductive carbon layer. The present invention does not specifically limit the type of carbon source; it can be selected from carbon sources commonly used in the art for forming conductive carbon layers, including but not limited to one or more of carbon black, graphene, carbon nanotubes, fullerenes, sucrose, glucose, asphalt, polydopamine, resorcinol, formaldehyde, starch, sucrose, sodium carboxymethyl cellulose, polyvinylidene fluoride, polyvinyl pyrrolidone, tannic acid, polyvinyl alcohol, polypyrrole, vitamin C, polyethylene glycol, anthracene, or aniline.

[0052] Furthermore, the mass ratio of the sintered material to the carbon source is (1-y):y, where 0 < y ≤ 0.08. Controlling the mass ratio of the sintered material to the carbon source within this range not only facilitates the formation of a dense and complete coating layer on the surface of the lithium-supplemented substrate, but also prevents the adverse effects of excessive carbon source addition on battery energy density.

[0053] By heat-treating the mixture of the sintered material and the carbon source, it is more conducive to the coating process. Specifically, the temperature of the heat treatment is 80 to 1000 ° C, and the time is 3 to 15 hours, preferably 6 to 12 hours. When the carbon source is selected from inorganic materials such as carbon black, graphene, carbon nanotubes, fullerenes, etc., the heat treatment can be carried out at a lower temperature, such as 80 to 300 ° C; when the carbon source is selected from organic materials such as sucrose, glucose, asphalt, polydopamine, resorcinol, formaldehyde, starch, sucrose, sodium carboxymethyl cellulose, polyvinylidene fluoride, polyvinyl pyrrolidone, tannic acid, polyvinyl alcohol, polypyrrole, vitamin C, polyethylene glycol, anthracene or aniline, the heat treatment needs to be carried out at a higher temperature to ensure the carbonization of the organic matter, such as 500 to 1000 ° C.

[0054] A third aspect of the present invention provides a positive electrode plate, comprising a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector, wherein the positive electrode active material layer comprises the positive electrode lithium supplement provided by the first aspect of the present invention.

[0055] Since the positive electrode plate of the present invention includes the positive electrode lithium replenishing agent, it can exert an excellent lithium replenishing effect when used in a battery.

[0056] The positive electrode current collector of the present invention can be selected from positive electrode current collectors commonly used in the art, such as aluminum foil.

[0057] The positive electrode active material layer of the present invention includes components such as a positive electrode active substance, a conductive agent and a binder in addition to the positive electrode lithium supplement.

[0058] Among them, the positive electrode active material includes but is not limited to one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium manganese oxide, nickel cobalt manganese ternary material, nickel cobalt aluminum ternary material, lithium iron phosphate, lithium nickel manganese oxide, lithium-rich manganese-based materials, etc.

[0059] The conductive agent includes, but is not limited to, one or more of conductive carbon black, Super-C, acetylene black, Ketjen black, and carbon nanofiber.

[0060] The binder includes, but is not limited to, one or more of polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC-Na), polyvinyl pyrrolidone, polytetrafluoroethylene, and styrene-butadiene rubber (SBR).

[0061] The more positive electrode lithium replenisher in the positive electrode active material layer, the better the lithium replenishment effect. However, too much positive electrode lithium replenisher will inevitably reduce the content of the positive electrode active material, which is not conducive to improving the positive electrode sheet capacity and battery energy density. Based on the above considerations, the mass content of the positive electrode active material in the positive electrode active material layer is controlled to be no less than 90%, and the mass content of the positive electrode lithium replenisher is controlled to be no more than 10%.

[0062] In a specific embodiment, the positive electrode sheet can be prepared by the following method: the positive electrode active material, the positive electrode lithium supplement, the conductive agent and the binder are dispersed in a solvent in proportion to obtain a slurry, and the slurry is then coated on at least one surface of the positive electrode collector. The positive electrode sheet can be obtained after drying, slitting and rolling.

[0063] A fourth aspect of the present invention provides a diaphragm, comprising a diaphragm substrate and a lithium replenishing layer disposed on one surface of the diaphragm substrate, wherein the lithium replenishing layer comprises the positive electrode lithium replenishing agent provided in the first aspect.

[0064] The function of the separator is to separate the positive and negative electrodes, preventing contact and short circuiting between them while allowing lithium ions to pass freely. It should be noted that during use of the separator of the present invention, the surface on which the lithium replenishment layer is provided faces the separator, allowing the lithium replenishment layer to fully replenish the positive electrode.

[0065] The present invention does not specifically limit the type of the membrane substrate, and it can be selected from porous membranes conventionally used in the art with good chemical stability and mechanical stability, including but not limited to one or more of polypropylene, polyethylene, glass fiber, and non-woven fabric.

[0066] In one embodiment, the separator of the present invention can be formed by coating or depositing a positive electrode lithium replenishing agent on the surface of the separator substrate to form a lithium replenishing layer, thereby obtaining a separator having a composite lithium replenishing layer. The coating can be performed by spraying, spin coating, slurry coating, etc., and the deposition can be performed by physical deposition or chemical deposition.

[0067] Taking into account the difference in bonding strength between the positive electrode lithium replenisher and different types of diaphragm matrices, a binder can be added to the lithium replenishing layer to enhance the bonding strength between the lithium replenishing layer and the diaphragm matrix, thereby enhancing its performance.

[0068] A fifth aspect of the present invention provides a battery comprising the positive electrode sheet provided in the third aspect and / or the separator provided in the fourth aspect. Because the battery includes the positive electrode sheet and / or separator comprising the positive lithium replenisher, the battery exhibits a higher first-cycle coulombic efficiency and superior cycle performance during use.

[0069] The battery of the present invention includes, in addition to the above-mentioned positive electrode sheet and / or separator, a negative electrode sheet.

[0070] Among them, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector. Among them, the negative electrode current collector can be selected from the negative electrode current collectors conventionally used in the art, such as copper foil. The negative electrode active material layer can also refer to the conventional composition in the art, for example, the negative electrode active material layer includes a negative electrode active substance, a conductive agent and a binder. The negative electrode active substance can be selected from the negative electrode active substances conventionally used in the art, including but not limited to one or more of natural graphite, artificial graphite, silicon-carbon material, silicon-oxygen material, and hard carbon. The composition of the conductive agent and the binder can refer to the types of conductive agent and binder in the positive electrode sheet, which will not be repeated here.

[0071] The electrolyte is a medium between the positive and negative electrodes that conducts lithium ions. It can be a gel, solid, or liquid electrolyte. This application does not specifically limit the type of electrolyte; it can be selected from gel, solid, or liquid electrolytes commonly used in the art.

[0072] In a specific embodiment, the battery of the present invention can be prepared by the following method: the positive electrode sheet, the separator and the negative electrode sheet are stacked in sequence, and the battery core is obtained by a lamination or winding process, and then the battery of the present invention is obtained through baking, liquid injection, formation, packaging and other processes.

[0073] A sixth aspect of the present invention provides an electrical device comprising the battery described above. The present invention does not particularly limit the type of electrical device; the device may be any electrical device comprising the battery, including but not limited to mobile phones, portable devices, laptop computers, electric bicycles, electric vehicles, electric toys, and energy storage devices.

[0074] The following will introduce the positive electrode lithium supplement provided by the present invention and its preparation method and application in detail through specific examples.

[0075] Unless otherwise specified, the reagents, materials, and instruments used in the following examples are conventional reagents, conventional materials, and conventional instruments in the art and can be obtained commercially. The reagents involved can also be synthesized by conventional methods in the art.

[0076] In the following examples and comparative examples, the conductive carbon layer thickness is tested by using a CP-SEM test method, firstly cutting a cross section of the sample using CP, and then observing its microscopic morphology using SEM to determine the thickness of the conductive carbon layer.

[0077] D50 particle size test method: Use Malvern laser particle size analyzer to detect the particle size distribution of the particles, and take the particle size value corresponding to when the cumulative distribution percentage reaches 50%.

[0078] In the following examples, the particle size of the positive electrode lithium replenisher D50 is controlled by selecting lithium replenisher core materials with different particle sizes and controlling the thickness of the conductive carbon layer.

[0079] Example 1

[0080] This embodiment provides a positive electrode lithium supplement agent, including a lithium supplement matrix and a conductive carbon layer coated on the surface of the lithium supplement matrix. The composition of the lithium supplement matrix is ​​Li5Fe(O 0.975 S 0.025 ) 4, the thickness of the conductive carbon layer is 100nm, the D50 particle size of the positive electrode lithium supplement is 20μm, and the preparation method thereof comprises the following steps:

[0081] 1) lithium hydroxide, iron oxide and lithium sulfide were mixed and ground in a molar ratio of 4.8:0.5:0.1 to obtain a first mixture; the first mixture was placed in a muffle furnace, and heated to 800°C at a heating rate of 6°C / min under a nitrogen atmosphere, kept at this temperature for 24 hours, and then cooled to room temperature with the furnace to obtain Li5Fe(O 0.975 S 0.025 )4 powder.

[0082] 2) Li5FeO 3.9 S 0.1 The powder and carbon black were evenly mixed in a mass ratio of 98:2 to obtain a second mixture; the second mixture was heated to 120° C. at a heating rate of 5° C. / min, kept warm for 5 hours, and then naturally cooled to room temperature to obtain a positive electrode lithium supplement.

[0083] Example 2

[0084] This embodiment provides a positive electrode lithium supplement agent, including a lithium supplement matrix and a conductive carbon layer coated on the surface of the lithium supplement matrix. The composition of the lithium supplement matrix is ​​Li5Fe(O 0.925 S 0.075 )4, the thickness of the conductive carbon layer is 100 nm, the D50 particle size of the positive electrode lithium replenisher is 20 μm, and its preparation method is basically the same as that in Example 1, except that: in step 1), the molar ratio of lithium hydroxide, iron oxide and lithium sulfide is replaced with 4.4:0.5:0.3.

[0085] Example 3

[0086] This embodiment provides a positive electrode lithium supplement agent, including a lithium supplement matrix and a conductive carbon layer coated on the surface of the lithium supplement matrix. The composition of the lithium supplement matrix is ​​Li5Fe(O 0.875 S 0.125 )4, the thickness of the conductive carbon layer is 100 nm, the D50 particle size of the positive electrode lithium replenisher is 20 μm, and its preparation method is basically the same as that in Example 1, except that: in step 1), the molar ratio of lithium hydroxide, iron oxide and lithium sulfide is replaced with 4:0.5:0.5.

[0087] Example 4

[0088] This embodiment provides a positive electrode lithium supplement agent, including a lithium supplement matrix and a conductive carbon layer coated on the surface of the lithium supplement matrix. The composition of the lithium supplement matrix is ​​Li5Fe(O 0.975 Se 0.025 ) 4, the thickness of the conductive carbon layer is 100nm, the D50 particle size of the positive electrode lithium supplement is 20μm, and the preparation method thereof comprises the following steps:

[0089] 1) lithium hydroxide, iron oxide and iron selenide were mixed and ground in a molar ratio of 4.8:0.5:0.1 to obtain a first mixture; the first mixture was placed in a muffle furnace, and heated to 800°C at a heating rate of 6°C / min under a nitrogen atmosphere, kept at this temperature for 24 hours, and then cooled to room temperature with the furnace to obtain Li5Fe(O 0.975 Se 0.025 )4 powder.

[0090] 2) Li5FeO 3.9 Se 0.1 The powder and carbon black were evenly mixed in a mass ratio of 98:2 to obtain a second mixture; the second mixture was heated to 120° C. at a heating rate of 5° C. / min, kept warm for 5 hours, and then naturally cooled to room temperature to obtain a positive electrode lithium supplement.

[0091] Example 5

[0092] This embodiment provides a positive electrode lithium supplement agent, including a lithium supplement matrix and a conductive carbon layer coated on the surface of the lithium supplement matrix. The composition of the lithium supplement matrix is ​​Li5Fe(O 0.925 Se 0.075 )4, the thickness of the conductive carbon layer is 100 nm, the D50 particle size of the positive electrode lithium replenisher is 20 μm, and its preparation method is basically the same as that of Example 4, except that: in step 1), the molar ratio of lithium hydroxide, iron oxide and iron selenide is replaced with 4.4:0.5:0.3.

[0093] Example 6

[0094] This embodiment provides a positive electrode lithium supplement agent, including a lithium supplement matrix and a conductive carbon layer coated on the surface of the lithium supplement matrix. The composition of the lithium supplement matrix is ​​Li5Fe(O 0.875 Se 0.125 )4, the thickness of the conductive carbon layer is 100 nm, the D50 particle size of the positive electrode lithium replenisher is 20 μm, and its preparation method is basically the same as that of Example 4, except that: in step 1), the molar ratio of lithium hydroxide, iron oxide and iron selenide is replaced with 4:0.5:0.5.

[0095] Example 7

[0096] This embodiment provides a positive electrode lithium supplement agent, including a lithium supplement matrix and a conductive carbon layer coated on the surface of the lithium supplement matrix. The composition of the lithium supplement matrix is ​​Li5Fe(O0.95 S 0.05 ) 4, the thickness of the conductive carbon layer is 100nm, the D50 particle size of the positive electrode lithium supplement is 20μm, and the preparation method thereof comprises the following steps:

[0097] 1) lithium hydroxide, iron oxide and lithium sulfide were mixed and ground in a molar ratio of 4.6:0.5:0.2 to obtain a first mixture; the first mixture was placed in a muffle furnace, and heated to 800°C at a heating rate of 6°C / min under a nitrogen atmosphere, kept at this temperature for 24 hours, and then cooled to room temperature with the furnace to obtain Li5Fe(O 0.95 S 0.05 )4 powder.

[0098] 2) Li5Fe(O 0.95 S 0.05 )4 powder and carbon black are evenly mixed in a mass ratio of 98:2 to obtain a second mixture; the second mixture is heated to 120°C at a heating rate of 5°C / min, kept warm for 5 hours, and then naturally cooled to room temperature to obtain a positive electrode lithium replenisher.

[0099] Example 8

[0100] This embodiment provides a positive electrode lithium supplement agent, including a lithium supplement matrix and a conductive carbon layer coated on the surface of the lithium supplement matrix. The composition of the lithium supplement matrix is ​​Li5Fe(O 0.9 S 0.1 )4, the thickness of the conductive carbon layer is 100 nm, the D50 particle size of the positive electrode lithium replenisher is 20 μm, and its preparation method is basically the same as that of Example 7, except that: in step 1), the molar ratio of lithium hydroxide, iron oxide and lithium sulfide is replaced with 4.2:0.5:0.4.

[0101] Example 9

[0102] This embodiment provides a positive electrode lithium supplement agent, including a lithium supplement matrix and a conductive carbon layer coated on the surface of the lithium supplement matrix. The composition of the lithium supplement matrix is ​​Li5Fe(O 0.85 S 0.15 )4, the thickness of the conductive carbon layer is 100 nm, the D50 particle size of the positive electrode lithium replenisher is 20 μm, and its preparation method is basically the same as that of Example 7, except that: in step 1), the molar ratio of lithium hydroxide, iron oxide and lithium sulfide is replaced with 3.8:0.5:0.6.

[0103] Example 10

[0104] This embodiment provides a positive electrode lithium supplement agent, including a lithium supplement matrix and a conductive carbon layer coated on the surface of the lithium supplement matrix. The composition of the lithium supplement matrix is ​​Li5Fe(O 0.8 S 0.2)4, the thickness of the conductive carbon layer is 100 nm, the D50 particle size of the positive electrode lithium replenisher is 20 μm, and its preparation method is basically the same as that of Example 7, except that: in step 1), the molar ratio of lithium hydroxide, iron oxide and lithium sulfide is replaced with 3.4:0.5:0.8.

[0105] Example 11

[0106] This embodiment provides a positive electrode lithium supplement agent, including a lithium supplement matrix and a conductive carbon layer coated on the surface of the lithium supplement matrix. The composition of the lithium supplement matrix is ​​Li5Fe(O 0.7 S 0.3 )4, the thickness of the conductive carbon layer is 100 nm, the D50 particle size of the positive electrode lithium replenisher is 20 μm, and its preparation method is basically the same as that of Example 7, except that: in step 1), the molar ratio of lithium hydroxide, iron oxide and lithium sulfide is replaced with 2.6:0.5:1.2.

[0107] Example 12

[0108] This embodiment provides a positive electrode lithium supplement agent, including a lithium supplement matrix and a conductive carbon layer coated on the surface of the lithium supplement matrix. The composition of the lithium supplement matrix is ​​Li5Fe(O 0.9 Se 0.1 )4, the thickness of the conductive carbon layer is 100 nm, the D50 particle size of the positive electrode lithium replenisher is 20 μm, and its preparation method is basically the same as that of Example 7, except that: in step 1), lithium sulfide is replaced by lithium selenide, and the molar ratio of lithium hydroxide, iron oxide and lithium selenide is 4.2:0.5:0.4.

[0109] Example 13

[0110] This embodiment provides a positive electrode lithium supplement agent, including a lithium supplement matrix and a conductive carbon layer coated on the surface of the lithium supplement matrix. The composition of the lithium supplement matrix is ​​Li5Fe(O 0.9 Te 0.1 )4, the thickness of the conductive carbon layer is 100 nm, the D50 particle size of the positive electrode lithium replenisher is 20 μm, and its preparation method is basically the same as that of Example 7, except that: in step 1), lithium sulfide is replaced by lithium telluride, and the molar ratio of lithium hydroxide, iron oxide and lithium telluride is 4.2:0.5:0.4.

[0111] Example 14

[0112] This embodiment provides a positive electrode lithium supplement agent, including a lithium supplement matrix and a conductive carbon layer coated on the surface of the lithium supplement matrix. The composition of the lithium supplement matrix is ​​Li5Fe(O 0.9 S 0.1)4, the thickness of the conductive carbon layer is 150nm, the D50 particle size of the positive electrode lithium supplement is 20μm, and the preparation method is basically the same as that of Example 7, except that: in step 2), Li5Fe(O 0.9 S 0.1 )4 The mass ratio of powder and carbon black is replaced with 96:4.

[0113] Example 15

[0114] This embodiment provides a positive electrode lithium supplement agent, including a lithium supplement matrix and a conductive carbon layer coated on the surface of the lithium supplement matrix. The composition of the lithium supplement matrix is ​​Li5Fe(O 0.9 S 0.1 )4, the thickness of the conductive carbon layer is 180nm, the D50 particle size of the positive electrode lithium supplement is 20μm, and its preparation method is basically the same as that of Example 7, except that: in step 2), Li5Fe(O 0.9 S 0.1 )4 The mass ratio of powder and carbon black is changed to 94:6.

[0115] Example 16

[0116] This embodiment provides a positive electrode lithium supplement agent, including a lithium supplement matrix and a conductive carbon layer coated on the surface of the lithium supplement matrix. The composition of the lithium supplement matrix is ​​Li5Fe(O 0.9 S 0.1 )4, the thickness of the conductive carbon layer is 100nm, and its preparation method is basically the same as that of Example 7, except that: the D50 particle size of the positive electrode lithium supplement is 10μm.

[0117] Example 17

[0118] This embodiment provides a positive electrode lithium supplement agent, including a lithium supplement matrix and a conductive carbon layer coated on the surface of the lithium supplement matrix. The composition of the lithium supplement matrix is ​​Li5Fe(O 0.9 S 0.1 )4, the thickness of the conductive carbon layer is 100nm, and its preparation method is basically the same as that of Example 7, except that: the D50 particle size of the positive electrode lithium supplement is 30μm.

[0119] Example 18

[0120] This embodiment provides a positive electrode lithium supplement agent, including a lithium supplement matrix and a conductive carbon layer coated on the surface of the lithium supplement matrix. The composition of the lithium supplement matrix is ​​Li5Fe(O 0.9 S 0.1 )4, the thickness of the conductive carbon layer is 100 nm, the D50 particle size of the positive electrode lithium supplement is 20 μm, and its preparation method is basically the same as that of Example 7, except that: in step 2), the carbon source material is replaced by sucrose, and the insulation temperature is replaced by 950°C.

[0121] Example 19

[0122] This embodiment provides a positive electrode lithium supplement agent, including a lithium supplement matrix and a conductive carbon layer coated on the surface of the lithium supplement matrix. The composition of the lithium supplement matrix is ​​Li5Fe(O 0.9 S 0.1 )4, the thickness of the conductive carbon layer is 100 nm, the D50 particle size of the positive electrode lithium replenisher is 20 μm, and its preparation method is basically the same as that in Example 7, except that: in step 2), the carbon source material is replaced by polyethylene glycol, and the insulation temperature is replaced by 950°C.

[0123] Example 20

[0124] This embodiment provides a positive electrode lithium supplement agent, including a lithium supplement matrix and a conductive carbon layer coated on the surface of the lithium supplement matrix. The composition of the lithium supplement matrix is ​​Li2Ni(O 0.8 S 0.2 )2, the thickness of the conductive carbon layer is 100 nm, the D50 particle size of the positive electrode lithium replenisher is 20 μm, and its preparation method is basically the same as that in Example 7, except that: in step 1), the first mixture is replaced by a sample obtained by mixing and grinding lithium hydroxide, nickel oxide, and lithium sulfide in a molar ratio of 1.2:1:0.4.

[0125] Comparative Example 1

[0126] This comparative example provides a positive electrode lithium replenisher, including a lithium replenisher matrix and a conductive carbon layer coated on the surface of the lithium replenisher matrix. The composition of the lithium replenisher matrix is ​​Li5FeO4, the thickness of the conductive carbon layer is 100 nm, and the D50 particle size of the positive electrode lithium replenisher is 20 μm. The preparation method is basically the same as that in Example 1, except that: in step 1), the first mixture is replaced by a sample obtained by mixing and grinding lithium hydroxide and iron oxide in a molar ratio of 5:0.5.

[0127] Comparative Example 2

[0128] This comparative example provides a positive electrode lithium supplement agent, including a lithium supplement matrix and a conductive carbon layer coated on the surface of the lithium supplement matrix. The composition of the lithium supplement matrix is ​​Li5Fe 0.8 Co 0.2 O4, the thickness of the conductive carbon layer is 100 nm, the D50 particle size of the positive electrode lithium supplement is 20 μm, and the preparation method is basically the same as that in Example 1, except that: in step 1), the first mixture is replaced by a sample obtained by mixing and grinding lithium hydroxide, iron oxide, and cobalt oxide in a molar ratio of 5:0.8:0.2.

[0129] Comparative Example 3

[0130] This comparative example provides a positive electrode lithium replenisher, including a lithium replenisher matrix and a conductive carbon layer coated on the surface of the lithium replenisher matrix. The composition of the lithium replenisher matrix is ​​Li2NiO2, the thickness of the conductive carbon layer is 100nm, and the D50 particle size of the positive electrode lithium replenisher is 20μm. The preparation method is basically the same as that of Example 1, except that: in step 1), the first mixture is replaced by a sample obtained by mixing and grinding lithium hydroxide and nickel oxide in a molar ratio of 2:1.

[0131] Test Case

[0132] 1. The following performance tests were conducted on the positive electrode lithium supplement agents of the above examples and comparative examples:

[0133] 1. Resistivity

[0134] Test method: The resistivity of the positive electrode lithium supplement was tested using a powder resistivity meter at 25°C. The test results are shown in Table 2.

[0135] 2. Moisture absorption rate

[0136] Test Method: Moisture absorption rate of the positive electrode lithium supplement was tested in a constant temperature and humidity chamber at 25°C and 40% humidity, with a test interval of 20 minutes. The moisture absorption rate of the material was calculated using the formula v = (m1 - m2) / t, where m1 and m2 are the material masses before and after the test, respectively, and t is the test interval, which was 20 minutes in this case. The test results are shown in Table 2.

[0137] 3. Residual alkali content

[0138] Test method: Methanol was used as a solvent to dissolve the residual alkali on the surface of the positive electrode lithium replenisher to obtain a test solution. This solution was then subjected to potentiometric titration using a 0.01M HCl standard solution to generate a titration curve. The LiOH and Li2CO3 contents in the positive electrode lithium replenisher were measured, respectively. The test results are shown in Table 2.

[0139] 2. The positive electrode lithium supplement agents of the above examples and comparative examples were respectively made into positive electrode sheets, and then assembled with the metal lithium negative electrode, electrolyte and separator according to the following method to obtain CR2025 button batteries. The method is as follows:

[0140] The positive electrode lithium supplement agent, acetylene black, and PVDF were mixed in a mass ratio of 90:5:5, and dispersed in NMP solvent to obtain a positive electrode slurry. The positive electrode slurry was coated on the surface of aluminum foil, vacuum dried, cut, and pressed to obtain a positive electrode sheet.

[0141] After stacking the positive electrode sheet, lithium battery commercial separator, and metal lithium sheet in sequence, the electrolyte (the electrolyte composition is a solvent of a mixture of ethylene carbonate (EC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC) in a volume ratio of 1:1:1, and the solute is 1.0 mol / L LiPF6) is dripped into it to assemble a button battery.

[0142] The button cell assembled above was tested for the following properties:

[0143] 1. Charge specific capacity, discharge specific capacity, and irreversible capacity

[0144] Test method: At 25°C, using a Xinwei button cell test channel, the button cell was charged and discharged at a charge / discharge rate of 0.05C within a cutoff voltage range of 2.5 to 4.3V. The battery's charge and discharge specific capacities were recorded. The irreversible capacity of the battery was calculated by subtracting the discharge specific capacity from the charge specific capacity. The test results are shown in Table 2.

[0145] Table 2

[0146]

[0147]

[0148] The following conclusions can be drawn from Table 2:

[0149] 1) By comparing Examples 1 to 13 with Comparative Examples 1 to 2, Example 20, and Comparative Example 3, it can be seen that the use of anions such as S, Se, and Te to replace doping O has a significant improvement in the resistivity and irreversible lithium replenishment capacity of the positive electrode lithium replenisher, and brings a better coating effect, the moisture absorption rate and residual alkali are greatly reduced, and its environmental stability is effectively improved. In Comparative Example 2, metal Co is used to replace iron by doping. Although it can also improve the resistivity, lithium replenishment capacity, and coating effect, the degree of improvement is obviously worse than the above anion doping replacement scheme.

[0150] 2) By comparing Examples 1 to 3, 7 to 11, and 14 to 15, it can be seen that with the increase in the S doping amount and the carbon coating amount, the resistivity of the positive electrode lithium replenisher gradually decreases, the irreversible lithium replenishment capacity increases accordingly, and the moisture absorption rate and residual alkali decrease accordingly.

[0151] 3) By comparing Examples 8 and 16 to 17, it can be seen that as the particle size of the positive electrode lithium replenisher D50 increases, the resistivity, moisture absorption rate and residual alkali content of the positive electrode lithium replenisher gradually decrease, while the irreversible capacity does not differ much.

[0152] 4) Comparison of Examples 8 and 18-19 shows that sucrose and polyethylene glycol as carbon sources have lower resistivity than carbon black. However, the positive electrode lithium supplement obtained with sucrose and polyethylene glycol as carbon sources has a lower irreversible capacity, and the moisture absorption rate and residual alkali content are also relatively high. This is because sucrose and polyethylene glycol, as organic carbon sources, have a higher degree of graphitization and better conductivity after carbonization. However, after carbonization, the residual carbon content is also reduced compared to the input amount, resulting in a lower coating effect than the same amount of carbon black added. As a result, the moisture absorption and residual alkali content are relatively high.

[0153] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A positive electrode lithium supplement, characterized in that: The positive electrode lithium supplement includes Li a M b (O 1-x A x ) c , wherein M includes one or more of Fe, Ni, Mn, Cu, Zn, Co, Cr, Zr, Sb, Ti, V, Mo, and Sn, A includes one or more of S, Se, and Te, 1<a≤8, 0<b≤1, 0<c<7, and 0<x<0.

5.

2. The positive electrode lithium supplement according to claim 1, characterized in that 0＜x≤0.3。 3. The positive electrode lithium supplement according to claim 1 or 2, characterized in that The D50 particle size of the positive electrode lithium supplement is 10 to 30 μm.

4. The positive electrode lithium supplement according to any one of claims 1 to 3, characterized in that The surface of the positive electrode lithium supplement is also coated with a conductive carbon layer.

5. The positive electrode lithium supplement according to claim 4, characterized in that The thickness of the conductive carbon layer is 100-200 nm.

6. The positive electrode lithium supplement according to claim 4 or 5, characterized in that The conductive carbon layer accounts for 1% to 8% of the mass content of the positive electrode lithium replenisher.

7. A method for preparing the positive electrode lithium supplement according to any one of claims 1 to 6, characterized in that: The following steps are involved: The lithium source, M source and A source are mixed uniformly according to a stoichiometric ratio and then sintered to obtain the positive electrode lithium supplement agent.

8. The preparation method according to claim 7, characterized in that The lithium source includes one or more of LiOH, Li2O, Li2O2, and Li2CO3; and / or, the M source includes one or more of the oxide, hydroxide, carbonate, and nitrate of element M; And / or, the source A includes one or more of a lithium compound of element A, an iron compound, an organic compound containing element A, and a binary inorganic compound containing element A and element M.

9. The preparation method according to claim 7 or 8, characterized in that The sintering process is carried out at a temperature of 500 to 1200° C. and for a time of 6 to 100 hours.

10. The preparation method according to any one of claims 7 to 9, characterized in that: After the sintering treatment, the method further includes: uniformly mixing the sintered material with a carbon source, and heat-treating the mixed material to obtain the positive electrode lithium supplement.

11. The preparation method according to claim 10, characterized in that: The carbon source includes one or more of carbon black, graphene, carbon nanotubes, fullerene, sucrose, glucose, asphalt, polydopamine, resorcinol, formaldehyde, starch, sucrose, sodium carboxymethyl cellulose, polyvinylidene fluoride, polyvinyl pyrrolidone, tannic acid, polyvinyl alcohol, polypyrrole, vitamin C, polyethylene glycol, anthracene or aniline.

12. The preparation method according to claim 10 or 11, characterized in that: The mass ratio of the sintered material to the carbon source is (1-y):y, wherein 0<y≤0.

08.

13. The preparation method according to any one of claims 10 to 12, characterized in that: The heat treatment temperature is 80-1000° C. and the time is 3-15 hours.

14. A positive electrode plate, characterized in that: The invention comprises a positive electrode current collector and a positive electrode active material layer provided on at least one side surface of the positive electrode current collector, wherein the positive electrode active material layer comprises the positive electrode lithium supplement agent according to any one of claims 1 to 6.

15. A diaphragm, characterized in that: The invention comprises a diaphragm substrate and a lithium replenishing layer arranged on one side surface of the diaphragm substrate, wherein the lithium replenishing layer comprises the positive electrode lithium replenishing agent according to any one of claims 1 to 6.

16. A battery, characterized in that: It includes the positive electrode sheet according to claim 14 and / or the separator according to claim 15.

17. An electrical device, characterized in that: Including the battery according to claim 16.

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