Positive electrode lithium supplementing agent and preparation method therefor, positive electrode sheet, separator, battery and electrical device

Abstract

Provided in the present application are a positive electrode lithium supplementing agent and a preparation method therefor, a positive electrode sheet, a separator, a battery, and an electrical device. The positive electrode lithium supplementing agent of the present application comprises LiaMb(O1-xAx)c, wherein 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, 1<a≤8, 0<b≤1, 0<c<7 and 0<x<0.5. In the present application, oxygen atoms in the positive electrode lithium supplementing agent are doped with selected anions having electronegativity closer to that of metal cations, such that the intrinsic conductivity of the positive electrode lithium supplementing agent is significantly improved, thereby significantly improving the lithium supplementing performance.

Description

Positive electrode lithium supplementing agent, preparation method thereof, positive electrode sheet, separator, battery and electric device

[0001] The present application claims priority to the Chinese patent application No. 202411376538.2, filed on September 29, 2024, and entitled "Positive electrode lithium supplementing agent, preparation method thereof, positive electrode sheet, separator, battery and electric device", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application belongs to the technical field of batteries, and relates to a positive electrode lithium supplementing agent, a preparation method thereof, a positive electrode sheet, a separator, a battery and an electric device. BACKGROUND

[0003] With the rapid development of the new energy field and the increasing improvement of people's living standards, the requirements for the endurance time and service life of digital devices and electric vehicles are becoming higher and higher, so how to improve the energy density and cycle life of lithium ion batteries is a research hotspot in the battery field. The consumption of lithium ions is an important reason for the capacity attenuation of the battery, especially in the process of the first charge and discharge of the battery, the formation of the SEI film on the negative electrode surface will consume a large amount of active lithium, resulting in irreversible capacity loss of the battery.

[0004] Supplementing lithium is an important means to supplement additional active lithium for lithium ion batteries to offset the energy density attenuation caused by the consumption of active lithium. The conventional supplementing lithium methods include negative electrode supplementing lithium and positive electrode supplementing lithium, wherein the negative electrode supplementing lithium needs to use n-butyl lithium or lithium metal, etc., and the supplementing lithium is difficult and dangerous, which is difficult to be applied in industrialization. The positive electrode supplementing lithium is to add a compound that is easy to be delithiated at high pressure in the positive electrode, which is relatively safe to use and is convenient for industrialization application.

[0005] The commonly used positive electrode supplementing lithium agents at present include Li5FeO4, Li2NiO2, Li6CoO4, Li2O2, etc., which generally have the problem of poor conductivity. Taking Li5FeO4 as an example, its electrical conductivity is very low, only 10 -9 S / cm order of magnitude, which is almost an insulating compound. In the prior art, the conductivity of the material is usually improved by metal doping, but the above-mentioned means has limited improvement on the intrinsic conductivity of the material, and it is still difficult to make the material fully play its supplementing lithium characteristics. SUMMARY

[0006] The present application provides a positive electrode lithium supplementing agent, a preparation method thereof, a positive electrode sheet, a separator, a battery and an electric device. The present application selects an anion with a more similar electronegativity to the metal cation to dope the oxygen atom in the positive electrode lithium supplementing agent, so that the intrinsic conductivity of the positive electrode lithium supplementing agent is significantly improved, and the supplementing lithium performance is significantly improved.

[0007] The first aspect of the present application provides a positive electrode lithium supplement agent, wherein the positive electrode lithium supplement agent comprises Li a M b (O 1-x A x ) c , wherein M comprises one or more of Fe, Ni, Mn, Cu, Zn, Co, Cr, Zr, Sb, Ti, V, Mo, Sn, A comprises one or more of S, Se, Te, 1

[0008] The positive electrode lithium supplement agent as described above, wherein 0

[0009] The positive electrode lithium supplement agent as described above, wherein the D50 particle size of the positive electrode lithium supplement agent is 10-30 μm.

[0010] The positive electrode lithium supplement agent as described above, wherein the surface of the positive electrode lithium supplement agent is further coated with a conductive carbon layer.

[0011] The positive electrode lithium supplement agent as described above, wherein the thickness of the conductive carbon layer is 100-200 nm.

[0012] The positive electrode lithium supplement agent as described above, wherein the conductive carbon layer accounts for 1%-8% of the mass content of the positive electrode lithium supplement agent.

[0013] The second aspect of the present application provides a preparation method of the positive electrode lithium supplement agent as described above, comprising the following steps:

[0014] Mixing the lithium source, the M source and the A source uniformly according to the stoichiometric ratio and then performing sintering treatment to obtain the positive electrode lithium supplement agent.

[0015] The preparation method as described above, wherein the lithium source comprises one or more of LiOH, Li2O, Li2O2 and Li2CO3;

[0016] And / or, the M source comprises one or more of the oxides, hydroxides, carbonates and nitrates of the element M;

[0017] And / or, the A source comprises one or more of the lithium compounds, iron compounds, organic compounds containing the element A and binary inorganic compounds containing the elements A and M of the element A.

[0018] The preparation method as described above, wherein the sintering treatment is performed at a temperature of 500-1200 ℃ for 6-100 hours.

[0019] The preparation method as described above, wherein after the sintering treatment, the material after the sintering treatment is mixed with a carbon source uniformly, and then the mixed material is subjected to heat treatment to obtain the positive electrode lithium supplement agent with a conductive carbon layer coated on the surface.

[0020] The preparation method as described above, wherein the carbon source comprises one or more of carbon black, graphene, carbon nanotube, fullerene, sucrose, glucose, pitch, polydopamine, resorcinol, formaldehyde, starch, sucrose, sodium carboxymethyl cellulose, polyvinylidene fluoride, polyvinylpyrrolidone, tannic acid, polyvinyl alcohol, polypyrrole, vitamin C, polyethylene glycol, anthracene or aniline.

[0021] The preparation method as described above, wherein a mass ratio of the material after the sintering treatment and the carbon source is (1-y):y, wherein 0≤y≤0.1.

[0022] The preparation method as described above, wherein the heat treatment is performed at a temperature of 80-1000℃ for 3-15 hours.

[0023] The third aspect of the present application provides a positive electrode tab, comprising a positive electrode current collector and a positive electrode active material layer arranged on at least one side surface of the positive electrode current collector, wherein the positive electrode active material layer comprises the positive electrode lithium supplementing agent provided in the first aspect of the present application.

[0024] The fourth aspect of the present application provides a separator, comprising a separator substrate and a lithium supplementing layer arranged on one side surface of the separator substrate, wherein the lithium supplementing layer comprises the positive electrode lithium supplementing agent provided in the first aspect of the present application.

[0025] The fifth aspect of the present application provides a battery, comprising the positive electrode tab provided in the third aspect of the present application and / or the separator provided in the fourth aspect of the present application.

[0026] The sixth aspect of the present application provides an electric device, comprising the battery provided in the fifth aspect of the present application.

[0027] The implementation of the present application has at least the following beneficial effects:

[0028] 1) The positive electrode lithium supplementing agent of the present application comprises 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, Sn, A includes one or more of S, Se, Te, 1 < a < 8, 0 < b < 1, 0 < c < 7, 0 < x < 0.5. The application replaces and dopes the O element in the positive electrode lithium supplementing agent with the A element with a closer electronegativity to the metal, such as S, Se, Te, compared with the bonding effect of the metal and O, the degree of overlap of the electron cloud of the metal and the A element is increased when the metal and the A element are bonded, the covalent bond component is stronger, the number of delocalized electrons that can move freely is increased, the band gap of the material is reduced, and the intrinsic conductivity of the material is significantly improved, thereby having a better lithium supplementing effect.

[0029] 2) The positive electrode tab, the separator and the battery provided by the application can supplement the active lithium loss of the battery in the first charge and discharge process and the cycle process, so that the battery has higher first cycle coulombic efficiency and cycle performance. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is a bonding diagram of Fe 3+ , respectively, with O 2- , S 2- , Se 2- element. DETAILED DESCRIPTION

[0031] To make the purpose, technical scheme and advantages of the application clearer, the technical scheme in the embodiments of the application will be described clearly and completely below in conjunction with the embodiments of the application. Obviously, the described embodiments are some embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the application.

[0032] The conventional positive electrode lithium supplementing agent, such as Li5FeO4, Li2NiO2, Li6CoO4, Li2O2, etc., has a large difference in electronegativity between the metal element and the anion O, a low degree of overlap of the electron cloud, and fewer delocalized electrons that can move freely, resulting in poor conductivity and thus poor lithium supplementing effect.

[0033] Based on this, the first aspect of the application provides a positive electrode lithium supplementing agent, 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, Sn, A includes one or more of S, Se, Te, 1 < a < 8, 0 < b < 1, 0 < c < 7, 0 < x < 0.5.

[0034] The present application uses A elements such as sulfur (S), selenium (Se), tellurium (Te) and the like to replace and dope anion of oxygen (O) element in the traditional positive electrode lithium supplement material. 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 changed to be strong, the number of delocalized electrons that can move freely is increased, the band gap of the material is reduced, the intrinsic conductivity of the material is significantly improved, and thus the lithium supplement effect is better.

[0035] Taking the M element in the lithium supplement matrix as an example, taking the iron (Fe) element as an example, for the convenience of objective comparison, the atomic radius, ionic radius and electronegativity of iron (Fe), oxygen (O), sulfur (S) and selenium (Se) are listed in Table 1.

[0036] Table 1

[0037] As shown in Table 1, compared with the O element, the atomic radius and ionic radius of S and Se are larger, and the electronegativity is closer to the iron Fe element. The specific comparison can be made by using the graphical method, and Fig. 1 is a bonding diagram of Fe 3+ respectively with O 2- , S 2- , Se 2- element, as shown in Fig. 1, the ionic radius of O 2- , S 2- , Se 2- increases gradually, and the degree of electron cloud overlap between them and Fe 3+ also gradually increases, the covalent bond component is enhanced, the intrinsic conductivity of the material is obviously improved, and thus the lithium supplement performance is improved.

[0038] The inventors have studied the doping amount of the A element, and found that when 0 < x ≤ 0.3, the lithium supplement effect of the positive electrode lithium supplement agent is more excellent. In a preferred embodiment, the D50 particle size of the positive electrode lithium supplement agent is 10-30 μm. When the D50 particle size of the positive electrode lithium supplement agent is less than 10 μm, the particles are easy to agglomerate and the contact area between the particles and the electrolyte is too large, which is easy to cause decomposition and gas production; when the D50 particle size of the positive electrode lithium supplement agent is greater than 30 μm, the specific surface area of the material is too small, which is not conducive to the development of the lithium supplement capacity. Exemplarily, the D50 particle size of the positive electrode lithium supplement agent 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 formed by any two of the above numbers.

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

[0040] Further, the thickness of the conductive carbon layer is 100-200 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 effectively protect the lithium supplementing active material, resulting in poor environmental tolerance. Controlling the thickness of the conductive carbon layer within the above range can effectively protect the lithium supplementing active material while reducing the adverse effects on the battery energy density. For example, the thickness of the conductive carbon layer is 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, 200 nm, or a range formed by any two of the above values.

[0041] In a specific embodiment, the conductive carbon layer accounts for 1-8% of the mass content of the positive electrode lithium supplementing agent. 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 supplementing agent, and it can also avoid excessive use of the conductive carbon layer which has a negative impact on the lithium supplementing capacity of the positive electrode lithium supplementing agent. For example, the conductive carbon layer accounts for 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8% of the mass content of the positive electrode lithium supplementing agent, or a range formed by any two of the above values.

[0042] The second aspect of the present application provides a preparation method of a positive electrode lithium supplementing agent, which comprises the following steps:

[0043] The lithium source, the M source, and the A source are mixed uniformly according to the stoichiometric ratio and then subjected to sintering treatment to obtain the positive electrode lithium supplementing agent.

[0044] The above method obtains the positive electrode lithium supplementing agent by solid-phase mixing and sintering. The method does not need to add a solvent, but only needs to mix and sinter the lithium source, the M source, and the A source under solid-phase conditions. Compared with the coprecipitation method and the molten salt method, the high-temperature solid-phase mixing and sintering method is more efficient and convenient, and is more suitable for industrial production.

[0045] The application does not make specific limitations on the types of lithium source, M source and A source. 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 A element, iron compounds of A element, organic compounds containing A element and binary inorganic compounds containing A element and M element.

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

[0047] To avoid the interference of impurities and moisture in the air, the sintering treatment is performed in 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 temperature of the sintering treatment is 500-1200°C, preferably 700-1000°C; and the time is 6-100 hours, preferably 12-30 hours. The sintering within the above temperature and time range is not only conducive to the formation of the material structure and the doping of the A element, but also can sufficiently remove the moisture on the surface and inside of the material, avoiding the side reactions caused by the moisture.

[0049] It is worth mentioning that the heating and cooling rates are also important factors affecting the performance of the material. If the heating and cooling rates are too high, the material is prone to deformation, affecting the product quality. If the heating and cooling rates are too slow, the production time will be too long. To balance the product quality and efficiency, the heating rate is controlled to be 3-10°C / min, preferably 4-7°C / min. The cooling mode is selected to be natural cooling in the furnace.

[0050] In a specific embodiment, after the sintering treatment, the material after the sintering treatment is mixed with a carbon source uniformly, and then the mixed material is subjected to heat treatment to obtain the positive electrode lithium supplementing agent coated with a conductive carbon layer on the surface.

[0051] The above process is a process of coating a conductive carbon layer on the surface of the lithium supplementing active material. The application does not make specific limitations on the types of carbon source, which can be selected from carbon sources commonly used in the art for forming a conductive carbon layer, including but not limited to one or more of carbon black, graphene, carbon nanotube, fullerene, sucrose, glucose, pitch, polydopamine, resorcinol, formaldehyde, starch, sucrose, sodium carboxymethyl cellulose, polyvinylidene fluoride, polyvinylpyrrolidone, tannic acid, polyvinyl alcohol, polypyrrole, vitamin C, polyethylene glycol, anthracene or aniline.

[0052] Further, the mass ratio of the sintered material and the carbon source is (1-y):y, wherein 0

[0053] The mixture of the sintered material and the carbon source is subjected to heat treatment, which is more conducive to the coating process. Specifically, the heat treatment is performed at a temperature of 80-1000°C for 3-15 hours, preferably 6-12 hours. When the carbon source is selected from inorganic materials such as carbon black, graphene, carbon nanotubes, and fullerenes, the heat treatment can be performed at a lower temperature, for example, 80-300°C. When the carbon source is selected from organic materials such as sucrose, glucose, pitch, polydopamine, resorcinol, formaldehyde, starch, sucrose, sodium carboxymethyl cellulose, polyvinylidene fluoride, polyvinylpyrrolidone, tannic acid, polyvinyl alcohol, polypyrrole, vitamin C, polyethylene glycol, anthracene, or aniline, the heat treatment needs to be performed at a higher temperature to ensure carbonization of the organic material, for example, 500-1000°C.

[0054] The third aspect of the present application provides a positive electrode tab, comprising a positive electrode current collector and a positive electrode active material layer arranged on at least one side surface of the positive electrode current collector, wherein the positive electrode active material layer comprises the positive electrode lithium supplementing agent provided in the first aspect of the present application.

[0055] The positive electrode tab of the present application can exhibit excellent lithium supplementing effect when applied in a battery due to the inclusion of the above-mentioned positive electrode lithium supplementing agent.

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

[0057] The positive electrode active material layer of the present application comprises, in addition to the positive electrode lithium supplementing agent, positive electrode active material, conductive agent, and binder, etc.

[0058] The positive electrode active material includes, but is not limited to, one or more of lithium cobaltate, lithium nickelate, lithium manganate, lithium manganate, nickel-cobalt-manganese ternary material, nickel-cobalt-aluminum ternary material, lithium iron phosphate, lithium nickel manganate, and lithium-rich manganese-based material.

[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), polyvinylpyrrolidone, polytetrafluoroethylene, and styrene butadiene rubber (SBR).

[0061] The more the positive electrode lithium supplement agent in the positive electrode active material layer, the more excellent the lithium supplement effect can be played, but too much positive electrode lithium supplement agent will inevitably lead to a decrease in the content of the positive electrode active material, which is not conducive to the improvement of the capacity and energy density of the positive electrode sheet. Based on the above consideration, the mass content of the positive electrode active material in the positive electrode active material layer is not less than 90%, and the mass content of the positive electrode lithium supplement agent is not higher than 10%.

[0062] In a specific embodiment, the positive electrode sheet can be prepared by dispersing the positive electrode active material, the positive electrode lithium supplement agent, the conductive agent and the binder in the solvent in a proportion to obtain a slurry, and then coating the slurry on at least one surface of the positive electrode current collector, drying, slitting and rolling to obtain the positive electrode sheet.

[0063] The fourth aspect of the present application provides a separator, comprising a separator substrate and a lithium supplement layer arranged on one side surface of the separator substrate, wherein the lithium supplement layer comprises the positive electrode lithium supplement agent provided in the first aspect.

[0064] The function of the separator is to separate the positive electrode sheet and the negative electrode sheet to prevent short circuiting and to allow the free passage of lithium ions. It should be noted that in the application process of the separator of the present application, the side surface provided with the lithium supplement layer is arranged opposite to the separator, so as to make the lithium supplement layer play the effect of supplementing lithium to the positive electrode.

[0065] The type of the separator substrate is not specifically limited in the present application, and it can be selected from the porous separators commonly used in the art, which have 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 an embodiment, the separator of the present application can form a lithium supplement layer by coating or depositing the positive electrode lithium supplement agent on the surface of the separator substrate, thereby obtaining a separator with a lithium supplement 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] Considering the difference in the bonding force of the positive electrode lithium supplement agent to different types of separator substrates, a binder can be added to the lithium supplement layer to enhance the adhesion strength of the lithium supplement layer to the separator substrate, thereby enhancing its performance.

[0068] The fifth aspect of the present application provides a battery comprising the positive electrode sheet provided in the third aspect and / or the separator provided in the fourth aspect. Since the battery comprises the positive electrode sheet and / or the separator provided with the positive electrode lithium supplement agent, the battery has higher first cycle coulombic efficiency and more excellent cycle performance in use.

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

[0070] The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. The negative electrode current collector can be selected from the negative electrode current collectors commonly used in the art, such as a 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 comprises a negative electrode active material, a conductive agent and a binder. The negative electrode active material can be selected from the negative electrode active materials commonly 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 the conductive agent and the binder in the positive electrode sheet, which will not be described herein.

[0071] The electrolyte is a medium present between the positive electrode sheet and the negative electrode sheet for conducting lithium ions. It can be a gel-state, solid-state or liquid-state electrolyte, and the type of the electrolyte is not particularly limited in the present application, which can be selected from the gel-state, solid-state or liquid-state electrolytes commonly used in the art.

[0072] In a specific embodiment, the battery of the present application can be prepared by sequentially stacking the positive electrode sheet, the separator and the negative electrode sheet, obtaining the battery cell through a stacking or winding process, and then performing processes such as baking, liquid injection, formation and packaging.

[0073] The sixth aspect of the present application provides a power consuming device comprising the battery as described above. The type of the power consuming device is not particularly limited in the present application, which can be any power consuming device comprising the battery, including but not limited to a mobile phone, a portable device, a notebook computer, an electric bicycle, an electric vehicle, an electric toy, an energy storage device and the like.

[0074] The positive electrode lithium supplementing agent, the preparation method and the application thereof provided by the present application will be specifically introduced below 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, which can be obtained by commercial purchase, and 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 test method is as follows: the CP-SEM test method is used, the sample is first treated by CP sectioning, and then the microstructure is observed in the SEM to determine the thickness of the conductive carbon layer.

[0077] D50 particle size test method: a Malvern laser particle size analyzer is used to detect the particle size distribution of the particles, and the particle size value corresponding to the cumulative distribution percentage of 50% is taken.

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

[0079] Example 1

[0080] The embodiment provides a positive electrode lithium supplement agent, which comprises a lithium supplement substrate and a conductive carbon layer coated on the surface of the lithium supplement substrate, the lithium supplement substrate is composed of Li5Fe(O 0.975 S 0.025 )4, the thickness of the conductive carbon layer is 100 nm, and the D50 particle size of the positive electrode lithium supplement agent is 20 mu m, and the preparation method comprises the following steps:

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

[0082] 2) the Li5FeO 3.9 S 0.1 powder and carbon black are uniformly mixed according to a mass ratio of 98:2 to obtain a second mixture; the second mixture is heated to 120 DEG C at a heating rate of 5 DEG C / min, and naturally cooled to room temperature after heat preservation for 5 hours, to obtain the positive electrode lithium supplement agent.

[0083] Example 2

[0084] The embodiment provides a positive electrode lithium supplement agent, which comprises a lithium supplement substrate and a conductive carbon layer coated on the surface of the lithium supplement substrate, the lithium supplement substrate is composed of Li5Fe(O 0.925 S 0.075 )4, the thickness of the conductive carbon layer is 100 nm, and the D50 particle size of the positive electrode lithium supplement agent is 20 mu m, and the preparation method comprises the following steps:

[0085] Example 3

[0086] The embodiment provides a positive electrode lithium supplement agent, which comprises a lithium supplement substrate and a conductive carbon layer coated on the surface of the lithium supplement substrate, the lithium supplement substrate is composed of Li5Fe(O 0.875 S 0.125 )4, the thickness of the conductive carbon layer is 100 nm, and the D50 particle size of the positive electrode lithium supplement agent is 20 mu m, and the preparation method comprises the following steps:

[0087] Example 4

[0088] The embodiment provides a positive electrode lithium supplementing agent, which comprises a lithium supplementing matrix and a conductive carbon layer coated on the surface of the lithium supplementing matrix, the lithium supplementing matrix is composed of Li5Fe(O 0.975 Se 0.025 )4, the thickness of the conductive carbon layer is 100 nm, and the D50 particle size of the positive electrode lithium supplementing agent is 20 mu m.

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

[0090] 2) the Li5FeO 3.9 Se 0.1 powder and carbon black are uniformly mixed according to a mass ratio of 98:2 to obtain a second mixture; the second mixture is heated to 120 DEG C at a heating rate of 5 DEG C / min, and naturally cooled to room temperature after being kept at 120 DEG C for 5 h to obtain the positive electrode lithium supplementing agent.

[0091] Embodiment 5

[0092] The embodiment provides a positive electrode lithium supplementing agent, which comprises a lithium supplementing matrix and a conductive carbon layer coated on the surface of the lithium supplementing matrix, the lithium supplementing matrix is composed of Li5Fe(O 0.925 Se 0.075 )4, the thickness of the conductive carbon layer is 100 nm, and the D50 particle size of the positive electrode lithium supplementing agent is 20 mu m.

[0093] Embodiment 6

[0094] The embodiment provides a positive electrode lithium supplementing agent, which comprises a lithium supplementing matrix and a conductive carbon layer coated on the surface of the lithium supplementing matrix, the lithium supplementing matrix is composed of Li5Fe(O 0.875 Se 0.125 )4, the thickness of the conductive carbon layer is 100 nm, and the D50 particle size of the positive electrode lithium supplementing agent is 20 mu m.

[0095] Embodiment 7

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

[0097] 1) A first mixture is obtained by mixing and grinding lithium hydroxide, iron oxide and lithium sulfide according to a molar ratio of 4.6:0.5:0.2; the first mixture is placed in a muffle furnace, heated to 800 DEG C at a heating rate of 6 DEG C / min under a nitrogen atmosphere, and cooled to room temperature after heat preservation for 24 h, to obtain Li5Fe (OH) 4 powder. 0.95 S 0.05 )4 powder.

[0098] 2) The Li5Fe (OH) 4 powder and carbon black are uniformly mixed according to a mass ratio of 98:2 to obtain a second mixture; the second mixture is heated to 120 DEG C at a heating rate of 5 DEG C / min, and naturally cooled to room temperature after heat preservation for 5 h, to obtain the positive electrode lithium supplementing agent. 0.95 S 0.05 )4, the thickness of the conductive carbon layer is 100 nm, the D50 particle size of the positive electrode lithium supplementing agent is 20 pm, and the preparation method comprises the following steps:

[0099] Example 8

[0100] The positive electrode lithium supplementing agent provided in the embodiment comprises a lithium supplementing matrix and a conductive carbon layer coated on the surface of the lithium supplementing matrix, the lithium supplementing matrix is composed of Li5Fe (OH) 4, the thickness of the conductive carbon layer is 100 nm, and the D50 particle size of the positive electrode lithium supplementing agent is 20 pm. 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 supplementing agent is 20 pm, and the preparation method comprises the following steps:

[0101] Example 9

[0102] The positive electrode lithium supplementing agent provided in the embodiment comprises a lithium supplementing matrix and a conductive carbon layer coated on the surface of the lithium supplementing matrix, the lithium supplementing matrix is composed of Li5Fe (OH) 4, the thickness of the conductive carbon layer is 100 nm, and the D50 particle size of the positive electrode lithium supplementing agent is 20 pm. 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 supplementing agent is 20 pm, and the preparation method comprises the following steps:

[0103] Example 10

[0104] The positive electrode lithium supplementing agent provided in the embodiment comprises a lithium supplementing matrix and a conductive carbon layer coated on the surface of the lithium supplementing matrix, the lithium supplementing matrix is composed of Li5Fe (OH) 4, the thickness of the conductive carbon layer is 100 nm, and the D50 particle size of the positive electrode lithium supplementing agent is 20 pm. 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 supplementing agent is 20 μm, and the 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 by 3.4:0.5:0.8.

[0105] Example 11

[0106] The example provides a positive electrode lithium supplementing agent, which comprises a lithium supplementing matrix and a conductive carbon layer coated on the surface of the lithium supplementing matrix, and the composition of the lithium supplementing 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 supplementing agent is 20 μm, and the 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 by 2.6:0.5:1.2.

[0107] Example 12

[0108] The example provides a positive electrode lithium supplementing agent, which comprises a lithium supplementing matrix and a conductive carbon layer coated on the surface of the lithium supplementing matrix, and the composition of the lithium supplementing 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 supplementing agent is 20 μm, and the 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] The example provides a positive electrode lithium supplementing agent, which comprises a lithium supplementing matrix and a conductive carbon layer coated on the surface of the lithium supplementing matrix, and the composition of the lithium supplementing 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 supplementing agent is 20 μm, and the 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] The example provides a positive electrode lithium supplementing agent, which comprises a lithium supplementing matrix and a conductive carbon layer coated on the surface of the lithium supplementing matrix, and the composition of the lithium supplementing matrix is Li5Fe(O 0.9 S 0.1)4, the thickness of the conductive carbon layer is 150 nm, the D50 particle size of the positive electrode lithium supplementing agent is 20 pm, and the preparation method is basically the same as that of Example 7, except that in step 2), the mass ratio of Li5Fe (OH) 16 and carbon black is replaced by 96:4. 0.9 S 0.1 )4, the thickness of the conductive carbon layer is 150 nm, the D50 particle size of the positive electrode lithium supplementing agent is 20 pm, and the preparation method is basically the same as that of Example 7, except that in step 2), the mass ratio of Li5Fe (OH) 16 and carbon black is replaced by 96:4.

[0113] Example 15

[0114] The example provides a positive electrode lithium supplementing agent, which comprises a lithium supplementing matrix and a conductive carbon layer coated on the surface of the lithium supplementing matrix, the lithium supplementing matrix is composed of Li5Fe (OH) 16, the thickness of the conductive carbon layer is 180 nm, and the D50 particle size of the positive electrode lithium supplementing agent is 20 pm. 0.9 S 0.1 )4, the thickness of the conductive carbon layer is 150 nm, the D50 particle size of the positive electrode lithium supplementing agent is 20 pm, and the preparation method is basically the same as that of Example 7, except that in step 2), the mass ratio of Li5Fe (OH) 16 and carbon black is replaced by 96:4. 0.9 S 0.1 )4, the thickness of the conductive carbon layer is 150 nm, the D50 particle size of the positive electrode lithium supplementing agent is 20 pm, and the preparation method is basically the same as that of Example 7, except that in step 2), the mass ratio of Li5Fe (OH) 16 and carbon black is replaced by 96:4.

[0115] Example 16

[0116] The example provides a positive electrode lithium supplementing agent, which comprises a lithium supplementing matrix and a conductive carbon layer coated on the surface of the lithium supplementing matrix, the lithium supplementing matrix is composed of Li5Fe (OH) 16, the thickness of the conductive carbon layer is 180 nm, and the D50 particle size of the positive electrode lithium supplementing agent is 20 pm. 0.9 S 0.1 )4, the thickness of the conductive carbon layer is 150 nm, the D50 particle size of the positive electrode lithium supplementing agent is 20 pm, and the preparation method is basically the same as that of Example 7, except that in step 2), the mass ratio of Li5Fe (OH) 16 and carbon black is replaced by 96:4.

[0117] Example 17

[0118] The example provides a positive electrode lithium supplementing agent, which comprises a lithium supplementing matrix and a conductive carbon layer coated on the surface of the lithium supplementing matrix, the lithium supplementing matrix is composed of Li5Fe (OH) 16, the thickness of the conductive carbon layer is 180 nm, and the D50 particle size of the positive electrode lithium supplementing agent is 20 pm. 0.9 S 0.1 )4, the thickness of the conductive carbon layer is 150 nm, the D50 particle size of the positive electrode lithium supplementing agent is 20 pm, and the preparation method is basically the same as that of Example 7, except that in step 2), the mass ratio of Li5Fe (OH) 16 and carbon black is replaced by 96:4.

[0119] Example 18

[0120] The example provides a positive electrode lithium supplementing agent, which comprises a lithium supplementing matrix and a conductive carbon layer coated on the surface of the lithium supplementing matrix, the lithium supplementing matrix is composed of Li5Fe (OH) 16, the thickness of the conductive carbon layer is 180 nm, and the D50 particle size of the positive electrode lithium supplementing agent is 20 pm. 0.9 S 0.1 )4, the thickness of the conductive carbon layer is 150 nm, the D50 particle size of the positive electrode lithium supplementing agent is 20 pm, and the preparation method is basically the same as that of Example 7, except that in step 2), the mass ratio of Li5Fe (OH) 16 and carbon black is replaced by 96:4.

[0121] Example 19

[0122] The embodiment provides a positive electrode lithium supplement agent, which comprises a lithium supplement substrate and a conductive carbon layer coated on the surface of the lithium supplement substrate, the lithium supplement substrate is composed of Li5Fe(O 0.9 S 0.1 The thickness of the conductive carbon layer is 100 nm, and the D50 particle size of the positive electrode lithium supplement agent is 20 mu m. The preparation method is basically the same as that in Embodiment 7, except that in step 2), the carbon source material is replaced by polyethylene glycol, and the holding temperature is replaced by 950 DEG C.

[0123] Embodiment 20

[0124] The embodiment provides a positive electrode lithium supplement agent, which comprises a lithium supplement substrate and a conductive carbon layer coated on the surface of the lithium supplement substrate, the lithium supplement substrate is composed of Li5Fe(O 0.8 S 0.2 The thickness of the conductive carbon layer is 100 nm, and the D50 particle size of the positive electrode lithium supplement agent is 20 mu m. The preparation method is basically the same as that in Embodiment 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] The comparative example provides a positive electrode lithium supplement agent, which comprises a lithium supplement substrate and a conductive carbon layer coated on the surface of the lithium supplement substrate, the lithium supplement substrate is composed of Li5FeO4, the thickness of the conductive carbon layer is 100 nm, and the D50 particle size of the positive electrode lithium supplement agent is 20 mu m. The preparation method is basically the same as that in Embodiment 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] The comparative example provides a positive electrode lithium supplement agent, which comprises a lithium supplement substrate and a conductive carbon layer coated on the surface of the lithium supplement substrate, the lithium supplement substrate is composed of Li5Fe 0.8 Co 0.2 O4, the thickness of the conductive carbon layer is 100 nm, and the D50 particle size of the positive electrode lithium supplement agent is 20 mu m. The preparation method is basically the same as that in Embodiment 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] The comparative example provides a positive electrode lithium supplement agent, which comprises a lithium supplement substrate and a conductive carbon layer coated on the surface of the lithium supplement substrate. The lithium supplement substrate is composed of Li2NiO2, the thickness of the conductive carbon layer is 100 nm, and the D50 particle size of the positive electrode lithium supplement agent is 20 μm. 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 at a molar ratio of 2:1.

[0131] Test example

[0132] I. The positive electrode lithium supplement agents in the above examples and comparative examples are tested for the following performances:

[0133] 1. Resistivity

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

[0135] 2. Moisture absorption rate

[0136] Test method: The moisture absorption rate of the positive electrode lithium supplement agent is tested in a constant temperature and humidity chamber at 25°C and 40% humidity, with a test interval of 20 min. The moisture absorption rate of the material is obtained according to the formula v = (m1-m2) / t, where m1 and m2 are the masses of the material before and after testing, and t is the test interval time, which is 20 min in this case. The test results are shown in Table 2.

[0137] 3. Residual alkali content

[0138] Test method: The residual alkali on the surface of the positive electrode lithium supplement agent is dissolved out using methanol as the solvent to obtain a test solution. The test solution is tested by potentiometric titration, and a 0.01M HCl standard solution is used for titration to obtain a titration curve. The contents of LiOH and Li2CO3 in the positive electrode lithium supplement agent are tested respectively. The test results are shown in Table 2.

[0139] II. The positive electrode lithium supplement agents in the above examples and comparative examples are respectively prepared into positive electrode sheets, and then assembled into CR2025 button cells with metal lithium negative electrodes, electrolyte and separators according to the following method:

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

[0141] The positive electrode sheet, lithium battery commercial diaphragm and metal lithium sheet were stacked in sequence, and electrolyte (the electrolyte was composed of a mixed solution of ethylene carbonate (EC), diethyl carbonate (DEC) and methyl ethyl carbonate (EMC) in a volume ratio of 1:1:1, and the solute was 1.0 mol / L of LiPF6) was dripped, and a button cell was assembled.

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

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

[0144] Test method: at 25°C, using the button cell test channel of Xinwei, the button cell was charged and discharged at a charge-discharge rate of 0.05C in the range of 2.5-4.3V, the charge specific capacity and discharge specific capacity of the battery were recorded respectively, and the irreversible capacity of the battery was calculated according to the charge specific capacity minus the discharge specific capacity. The test results are shown in Table 2.

[0145] Table 2

[0146] From Table 2, the following conclusions can be drawn:

[0147] 1) By comparing Examples 1-13 with Comparative Examples 1-2, Example 20 and Comparative Example 3, it can be seen that replacing and doping O with anions such as S, Se and Te can significantly improve the resistivity and irreversible lithium supplement capacity of the positive electrode lithium supplement agent, and bring better coating effect, significantly reduce the moisture absorption rate and residual alkali, and effectively improve the environmental stability. Although the metal Co is used to replace and dope iron in Comparative Example 2, the resistivity, lithium supplement capacity and coating effect are also improved, but the improvement degree is obviously lower than that of the above anion doping replacement scheme.

[0148] 2) By comparing Examples 1-3, 7-11 and 14-15, it can be seen that as the S doping amount and carbon coating amount increase, the resistivity of the positive electrode lithium supplement agent gradually decreases, the irreversible lithium supplement capacity increases accordingly, and the moisture absorption rate and residual alkali decrease accordingly.

[0149] 3) By comparing Examples 8, 16 and 17, it can be seen that as the D50 particle size of the positive electrode lithium supplement agent increases, the resistivity, moisture absorption rate and residual alkali content of the positive electrode lithium supplement agent gradually decrease, and the irreversible capacity has little difference.

[0150] 4) By comparing with Examples 8, 18-19, it can be seen that sucrose and polyethylene glycol as carbon sources have lower resistivity than carbon black, but the positive electrode lithium supplement obtained by sucrose and polyethylene glycol as carbon sources has lower irreversible capacity, and the moisture absorption rate and residual alkali content are also relatively high. The reason is that sucrose and polyethylene glycol as organic carbon sources, after carbonization treatment, have higher graphitization degree and better conductivity, but after carbonization, the residual carbon content will also decrease compared with the input amount, resulting in that the coating effect is not as good as that of the same amount of carbon black, so the moisture absorption and residual alkali content are relatively high.

[0151] The above examples are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can still be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A positive electrode lithium replenishing agent, characterized in that, The positive electrode lithium supplementing agent comprises Li a M b (O 1-x A x ) c , wherein M comprises one or more of Fe, Ni, Mn, Cu, Zn, Co, Cr, Zr, Sb, Ti, V, Mo, Sn, A comprises one or more of S, Se, Te, 1 2. The positive-electrode lithium supplementing agent according to claim 1, characterized by 0＜x≤0.3。 3. The positive-electrode lithium supplementing agent according to claim 1 or 2, characterized by, The D50 particle size of the positive electrode lithium supplement agent is 10-30 μm.

4. The positive-electrode lithium supplementing agent according to any one of claims 1 to 3, characterized by, The surface of the positive electrode lithium supplement agent is further coated with a conductive carbon layer.

5. The positive-electrode lithium supplementing agent according to claim 4, characterized by The thickness of the conductive carbon layer is 100-200 nm.

6. The positive-electrode lithium supplementing agent according to claim 4 or 5, characterized by, The conductive carbon layer accounts for 1%-8% of the mass content of the positive electrode lithium supplement agent.

7. A method for producing the positive-electrode lithium supplementing agent according to any one of claims 1 to 6, characterized by, The method comprises the following steps: The lithium source, M source and A source are mixed according to stoichiometric ratios and then subjected to sintering treatment to obtain the positive electrode lithium supplement agent.

8. The method for preparing the positive electrode lithium replenishing agent according to claim 7, characterized in that, The lithium source comprises one or more of LiOH, Li2O, Li2O2 and Li2CO3. The M source comprises one or more of oxides, hydroxides, carbonates and nitrates of element M. The A source comprises one or more of lithium compounds, iron compounds, organic compounds containing element A and binary inorganic compounds containing elements A and M.

9. The method of producing a positive-electrode lithium supplementing agent according to claim 7 or 8, characterized by, The sintering treatment is performed at a temperature of 500-1200 ℃ for 6-100 hours.

10. The method for preparing a positive-electrode lithium supplementing agent according to any one of claims 7 to 9, characterized by, After the sintering treatment, the material after the sintering treatment is mixed with a carbon source to obtain the positive electrode lithium supplement agent coated with a conductive carbon layer.

11. The method for preparing the positive electrode lithium replenishing agent according to claim 10, characterized in that, The carbon source comprises one or more of carbon black, graphene, carbon nanotubes, fullerenes, sucrose, glucose, pitch, polydopamine, resorcinol, formaldehyde, starch, sucrose, sodium carboxymethyl cellulose, polyvinylidene fluoride, polyvinylpyrrolidone, tannic acid, polyvinyl alcohol, polypyrrole, vitamin C, polyethylene glycol, anthracene or aniline.

12. The method of producing a positive-electrode lithium supplementing agent according to claim 10 or 11, characterized by, The mass ratio of the material after the sintering treatment to the carbon source is (1-y):y, wherein 0 13. The method of producing a positive-electrode lithium supplementing agent according to any one of claims 10 to 12, characterized in that, The heat treatment is performed at a temperature of 80-1000 ℃ for 3-15 hours.

14. A positive electrode sheet characterized by comprising: The positive electrode active material layer comprises the positive electrode lithium supplement agent according to any one of claims 1-6.

15. A diaphragm characterized by, The lithium supplement layer comprises the positive electrode lithium supplement agent according to any one of claims 1-6.

16. A battery, characterized by The battery comprises the positive electrode sheet according to claim 14 and / or the separator according to claim 15.

17. An electrical device, characterized by The battery comprises the battery according to claim 16.

Images