Lithium supplement material and preparation method thereof, positive pole piece, secondary battery and electronic equipment

Abstract

The invention relates to the technical field of batteries, in particular to a lithium supplementing material and a preparation method thereof, a positive pole piece and a secondary battery. The lithium supplementing material provided by the invention comprises a lithium-rich material and a carbon material doped in the lithium-rich material, the mass ratio of the element C in the lithium supplementing material is 0.3-37.5%. The lithium supplementing material is rich in C content, and the rich C content forms a rapid and low-resistance electron conduction channel in the lithium-rich material, so that the conductivity and the lithium supplementing efficiency are remarkably improved.

Description

Technical Field

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

[0002] During the initial charge and discharge cycle of a battery, such as a lithium-ion secondary battery, the negative electrode surface undergoes a critical change: the formation of a solid electrolyte interface (SEI) film. While this chemical process is crucial for the proper functioning of the battery, it also inevitably consumes the battery's limited active lithium and electrolyte resources, leading to a shortened cycle life and reduced energy density, impacting the battery's overall performance.

[0003] To compensate for the irreversible capacity loss caused by SEI formation and further improve the battery's energy density and other electrical properties, scientists have proposed a method for lithium replenishment at the positive electrode. However, despite the potential of this approach, current lithium replenishment materials face a significant challenge: poor electrical conductivity. This issue not only affects the efficiency of lithium replenishment but also limits the industrial production of lithium replenishment materials and their widespread application in practical applications. Therefore, the development of lithium replenishment materials with high conductivity is of great significance. Summary of the Invention

[0004] The present invention provides a lithium-supplementing material, wherein the lithium-supplementing material is rich in carbon content. The rich carbon content forms a fast and low-resistance electron conduction channel inside the lithium-rich material, thereby significantly improving the electrical conductivity and lithium-supplementing efficiency.

[0005] The present invention provides a lithium-supplementing material, comprising: a lithium-rich material and a carbon material doped in the lithium-rich material; the mass proportion of the C element in the lithium-supplementing material is 0.3-37.5%.

[0006] According to the lithium supplement material described above, the mass proportion of the C element in the lithium supplement material is 0.75-16%.

[0007] According to the lithium supplement material described above, the molar ratio of C and O elements in the lithium supplement material is 0.75-8%.

[0008] According to the lithium-supplementing material described above, the carbon material is a one-dimensional carbon material, and at least one one-dimensional carbon material runs through a single particle of the lithium-rich material.

[0009] According to the lithium-supplementing material described above, a single particle of the lithium-rich material is penetrated by multiple one-dimensional carbon materials, and the multiple one-dimensional carbon materials are staggered and stacked at least inside the lithium-rich particle.

[0010] According to the lithium supplement material described above, the diameter of the one-dimensional carbon material is 1-50 nm.

[0011] According to the lithium-supplementing material described above, the maximum length of a single particle of the lithium-rich material is 0.1-100 μm.

[0012] In the lithium supplement material described above, the carbon material is carbon nanotubes or carbon nanofibers.

[0013] According to the lithium-supplementing material described above, the structural formula of the lithium-rich material is Li 1+x A y O z , wherein 0<x<10, 0<y<6, 0<z<13, and A is one or more of Ni, Co, Fe, Cu, Mg, Mn, Cr, Zn, Ti, Zr, Nb, and Mo.

[0014] According to the lithium supplement material described above, the carbon material is a needle-shaped carbon nanomaterial.

[0015] The lithium supplement material described above, wherein the needle-shaped carbon nanomaterial is formed by processing at least one of carbon nanotubes, carbon nanofibers, carbon nanospheres and graphene.

[0016] The present invention also provides a method for preparing a lithium-supplementing material, comprising a process of dry-mixing a mixture comprising a lithium-rich material and a carbon material and then calcining the mixture to obtain the lithium-supplementing material.

[0017] The present invention provides a method for preparing a lithium-supplementing material. By adopting a dry mixing method to mix carbon material into the interior of lithium-rich particles and then calcining them, the doping effect is better. The method is green and pollution-free, no post-processing is required after preparation, the cost is low, and it is suitable for industrialization.

[0018] The carbon material described in the preparation method above is a one-dimensional carbon material, and the length of the one-dimensional carbon material is greater than the maximum length of a single particle of the lithium-rich material.

[0019] According to the preparation method described above, the dry mixing method is ball milling, the ball milling speed is 200-400 rpm, the ball milling time is 2-5 hours, and the mass ratio of grinding balls to the mixture is (0.5-1):100.

[0020] According to the above preparation method, the calcination temperature is 450-950°C and the calcination time is 8-100h.

[0021] According to the above preparation method, the calcination temperature is 700-800°C and the calcination time is 10-30h.

[0022] The present invention also provides a positive electrode material, comprising an active material and a lithium-supplementing material, wherein the lithium-supplementing material is the above-mentioned lithium-supplementing material or the lithium-supplementing material prepared by the above-mentioned preparation method.

[0023] The present invention also provides a positive electrode sheet comprising the positive electrode material.

[0024] The present invention also provides a secondary battery comprising the above-mentioned positive electrode sheet.

[0025] The present invention also provides an electronic device comprising the secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a planar schematic diagram of the lithium supplement material provided by the present invention;

[0027] Figure 2 This is a 3D schematic diagram of the lithium supplement material provided by the present invention;

[0028] Figure 3 The EDS test results and C and O elemental analysis results of the lithium-supplementing materials prepared in Example 5 and Example 8, wherein A and B are the EDS graphs of the lithium-supplementing materials C and O in Example 8, and C and D are the EDS graphs of the lithium-supplementing materials C and O in Example 5;

[0029] Figure 4 These are the test results of the charge capacity of lithium-ion batteries prepared using the lithium-supplementing materials in Examples 4 and 8. 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] The present invention provides a lithium-supplementing material, comprising a lithium-rich material and a carbon material doped in the lithium-rich material, wherein the mass proportion of the C element in the lithium-supplementing material is 0.3-37.5%.

[0032] The lithium-replenishing material is rich in C content, which forms a fast and low-resistance electron conduction channel inside the lithium-rich material particles, thereby significantly improving the electrical conductivity and lithium-replenishing efficiency.

[0033] In the present invention, the mass proportion of the C element is 0.3-37.5%, for example, it can be 0.3%, 0.6%, 0.75%, 0.9%, 1.2%, 1.5%, 2%, 2.5%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 30%, 35%, 37.5% and the range between any two of the above values.

[0034] In practical applications, for lithium-supplementing materials of the same mass, when the carbon material content is too much, the content of the active material lithium-rich material will inevitably decrease. When the carbon material is too much and reaches above the threshold, it will cause redundancy in improving conductivity. Therefore, the mass proportion of the C element is 0.75-16%, for example, it can be 0.75%, 0.9%, 1.2%, 1.5%, 2%, 2.5%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 16% and the range between any two of the above values. More preferably, the mass proportion of the C element is 0.75-8%, at which time the material has better lithium-supplementing performance and conductivity.

[0035] In some embodiments of the present invention, Figure 1 As shown, the lithium-supplementing material includes a lithium-rich material 2 and a one-dimensional carbon material 1, and at least one one-dimensional carbon material runs through a single particle of the lithium-rich material.

[0036] By adopting a one-dimensional carbon material and introducing it into the interior of lithium-rich particles, while ensuring that the one-dimensional carbon material penetrates the lithium-rich particles, a fast and low-resistance electron conduction channel is formed at least within the interior of the lithium-rich particles through the penetrating one-dimensional carbon material, thereby further improving the conductivity and lithium replenishment efficiency. In addition, due to the improved electron conduction path, the decomposition efficiency of the lithium-rich material is higher, further improving the actual discharge capacity. In addition, the elasticity and toughness of the one-dimensional carbon material can provide mechanical support for the electrode material, effectively mitigating the side reactions between the lithium-rich material and the electrolyte caused by particle breakage during the decomposition process.

[0037] It should be noted that the morphology of the lithium-rich material particles is not particularly limited, and can be regular spherical particles, irregular polygonal particles, or rod-shaped particles. The form in which the one-dimensional carbon material penetrates the lithium-rich material particles is also not particularly limited. For example, when a single particle of the lithium-rich material is rod-shaped, the one-dimensional carbon material can penetrate the particle in the direction of maximum length or at the position of minimum diameter.

[0038] Penetration, as used herein, refers to the one-dimensional carbon material penetrating two opposing surfaces of a particle. The one-dimensional carbon material may extend beyond the particle surface at least on one end, or may be flush with the particle surface. When the one-dimensional carbon material extends beyond the particle surface, it can also form a fast, low-resistance conductive pathway between the particles. When the one-dimensional carbon material is flush with the particle surface, it forms a fast, low-resistance conductive pathway only within the particle.

[0039] It is not difficult to understand that the more one-dimensional carbon materials penetrate a single particle, the better the conductivity. In some embodiments of the present invention, a single particle of lithium-rich material penetrates multiple one-dimensional carbon materials, and the multiple one-dimensional carbon materials are staggered and stacked at least inside the lithium-rich particle. This staggered stacking can form an efficient electron transport network (i.e., a three-dimensional nano-network skeleton, see Figure 2 ), further improving the conductivity of lithium-rich materials. During the decomposition process of lithium-supplementing materials, it can significantly improve the electron mobility and the uniformity of electrochemical reactions, so that lithium-rich materials with different particle sizes can be fully decomposed, thereby avoiding the situation where lithium-supplementing materials cannot be fully decomposed due to large particles and small particles are excessively decomposed.

[0040] The essence of the one-dimensional carbon material is a carbon material with excellent electrical conductivity, which improves the electrical conductivity of the lithium-rich material by penetrating the lithium-rich material. There is no special restriction on the selection of the one-dimensional carbon material, as long as it has the ability to penetrate the particles. Exemplarily, the one-dimensional carbon material is a carbon nanotube or a carbon nanofiber. In other specific embodiments of the present invention, the one-dimensional carbon material is a needle-shaped carbon nanomaterial, which can be processed by at least one of carbon nanotubes, carbon nanofibers, carbon nanospheres and graphene.

[0041] In some specific embodiments of the present invention, the diameter of the one-dimensional carbon material is 1-50 nm, such as 1 nm, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm or a range consisting of any two of the above values.

[0042] The lithium-rich material is the main body for replenishing lithium. During the first charging process, the lithium ions in the lithium-rich material can be released and migrate to the negative electrode of the battery to offset the irreversible lithium loss caused by the formation of the SEI film, thereby increasing the total capacity and energy density of the battery. The lithium-rich material used in the present invention is not particularly limited and can be a structure of Li 1+x A y O z Represented by, wherein 0<x<10, 0<y<6, 0<z<13, A is one or more of Ni, Co, Fe, Cu, Mg, Mn, Cr, Zn, Ti, Zr, Nb, and Mo.

[0043] In some embodiments of the present invention, the lithium-rich material is lithium ferrite particles (LiFeO4). The preparation method for the lithium-rich lithium ferrite particles is not particularly limited and can be prepared using conventional methods in the art. In some embodiments of the present invention, the lithium ferrite particles are prepared by mixing an iron source, a lithium source, a carbon source, and a solvent (such as water), spray-drying the mixture to obtain a precursor, sintering the precursor, and then crushing it to obtain the lithium-rich lithium ferrite particles. In the above method, the iron source, lithium source, and carbon source are not specifically limited. Exemplarily, the iron source is one or more of nano-iron oxide, Fe2O3, Fe3O4 and FeO, wherein nano-iron oxide is preferred, especially nano-iron oxide spherical particles, the particle size may be 10-500nm, such as 10nm, 20nm, 50nm, 80nm, 100nm, 200nm, 300nm, 400nm, 500nm or a range consisting of any two of the above values, preferably 50-200nm, the particle size of the nano-iron oxide particles within the above range can form an effective particle size combination with the positive electrode active material.

[0044] In some specific embodiments of the present invention, during the preparation of lithium ferrite particles, a dispersant, such as octyl polyoxyethylene ether, polyethylene glycol octylphenyl ether, or polyvinyl pyrrolidone, may be added to the mixture of the iron source, lithium source, carbon source, and solvent. The mass ratio of the dispersant to the carbon source is 0 to 1:1, preferably 0.01 to 0.1:1. The addition of the dispersant can assist in the adequate dispersion and mixing of the iron source, lithium source, and carbon source, thereby preventing sedimentation during the spray drying process.

[0045] In other embodiments of the present invention, the mixture is continuously stirred, preferably mechanically, before spray drying to prevent sedimentation and uneven material. The inlet air temperature for spray drying is 120-00°C, preferably 120-260°C, and more preferably 140-180°C. Controlling the inlet air temperature for spray drying within the above range can ensure sufficient reaction of the reactants while preventing overreaction from affecting product properties. Exemplarily, the inlet air temperature for spray drying is 120°C, 130°C, 140°C, 150°C, 160°C, 190°C, 200°C, 220°C, 240°C, 250°C, 300°C, or a range consisting of any two of the above values. The outlet air temperature is 60-150°C, preferably 70-90°C. Exemplarily, the outlet air temperature for spray drying is 60°C, 70°C, 80°C, 90°C, 100°C, 120°C, 150°C, or a range consisting of any two of the above values.

[0046] In some embodiments of the present invention, the maximum length of a single particle of the lithium-rich material is 0.1-100 μm, such as 0.1 μm, 1 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, or a range consisting of any two of the above values. The maximum length mentioned above refers to the maximum dimension of a single particle in a particular direction. For example, when the particle is a rod-shaped particle, the maximum length is the length of the rod-shaped particle, and when the particle is a spherical particle, the maximum length is the diameter of the particle.

[0047] The present invention also provides a method for preparing the above-mentioned lithium-supplementing material, comprising dry-mixing a mixture comprising a lithium-rich material and a carbon material and then calcining the mixture to obtain the lithium-supplementing material. The proportion of the carbon material in the mixture can be adjusted according to the mass proportion of the C element in the target product, such as 0.3%, 0.6%, 0.75%, 0.9%, 1.2%, 1.5%, 2%, 2.5%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 30%, 35%, 37.5%, or a range consisting of any two of the above values, preferably 0.75-16%, and more preferably 0.75-8%.

[0048] The dry mixing method and the specific carbon dosage are used to ensure that the carbon material can be better doped in the lithium-rich material, thereby ensuring better conductivity and lithium replenishment effect.

[0049] In some embodiments of the present invention, a one-dimensional material is used as a raw material, and the length of the one-dimensional carbon material in the mixture is ensured to be greater than the maximum length of a single particle of the lithium-rich material. The understanding of the maximum length here can refer to the above description and will not be repeated here. The lithium-supplementing material prepared by the above method has better conductivity. The reason for analysis is: the number of one-dimensional carbon materials is much higher than the number of lithium-rich material particles. A single lithium-rich material particle can be distributed with dozens or even hundreds of thousands of one-dimensional carbon materials. The two are mixed by dry method. The one-dimensional carbon material can be inserted into the interior of the particle. Because the length of the one-dimensional carbon material is greater than the maximum length of a single particle of the lithium-rich material, the one-dimensional carbon material can penetrate a single particle of the lithium-rich material. Multiple penetrated one-dimensional carbon materials are staggered and stacked inside the lithium-rich material particles to form a three-dimensional carbon material skeleton. The lithium-rich material particles have more carbon active sites. Therefore, the final lithium-supplementing material has better conductivity.

[0050] In some specific embodiments of the present invention, the length of the one-dimensional carbon material is 1-100 μm, such as 1 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm or a range consisting of any two of the above values, preferably 2-20 μm.

[0051] In the present invention, by controlling the one-dimensional carbon material to account for 0.1-40% of the total mass of the mixed material, such as 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 7.5%, 10%, 15%, 20%, 25%, 30%, 35%, 37.5%, 40% and ranges between any two of the above values, preferably 0.1-7.5%, it is ensured that dozens or even hundreds or thousands of one-dimensional carbon materials can be distributed in a single lithium-rich particle during dry mixing, thereby ensuring that at least one one-dimensional carbon material can penetrate a single particle, and preventing excessive carbon material from affecting its lithium replenishment effect.

[0052] Furthermore, during dry mixing, the distribution of the one-dimensional carbon material is random, resulting in the resulting bulk lithium-replenishing material being supported by a one-dimensional carbon material with no fixed orientation. This randomly (disordered) distribution of the one-dimensional carbon material provides more carbon active sites, improving the conductivity of the lithium-rich material and increasing the decomposition rate of the lithium-replenishing material in the finished battery. The carbon active sites can be detected using EDS, where the detection area is the surface of the lithium-rich material. EDS analysis reveals that the carbon active sites are distributed in a point-like pattern (rather than in other forms such as long strips) on the surface of the lithium-rich material particles, indicating that the one-dimensional carbon material is embedded within the lithium-rich material particles.

[0053] Dry mixing involves directly mixing the carbon material and lithium-rich particles without adding a solvent. This ensures that the carbon material is incorporated into the lithium-rich particles and that the one-dimensional carbon material penetrates the lithium-rich particles. The dry mixing method is not particularly limited and can be mechanically mixed, or it can be ground or ball-milled. Grounding or ball-milling is preferred, as it can ensure better penetration.

[0054] Exemplarily, the one-dimensional carbon material and the lithium-rich particles are mixed by ball milling, and the ball milling speed is 200-400 rpm, such as 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, and a range between any two of the above values. The ball milling time is 2-5 hours, such as 2 hours, 3 hours, 4 hours, 5 hours, and a range between any two of the above values. The mass ratio of the grinding balls to the total material is (0.5-1):100, such as 0.5:100, 0.6:100, 0.7:100, 0.8:100, 0.9:100, 1:100, and a range between any two of the above ratios.

[0055] It should be explained that when mechanical mixing is used, the part of the one-dimensional carbon material protruding from the lithium-rich particles will usually be broken by collision, so the particle size and shape of the lithium-supplementing material finally obtained depend on the particle size and shape of the lithium-rich material.

[0056] It is understood that to avoid interference from impurities and moisture in the air, the calcination process is performed under an inert atmosphere, wherein the inert gas can be selected from one or more of argon, nitrogen, helium, and neon. Under the protection of the inert gas, side reactions are avoided, and the product has high purity, good air stability, and uniform particle size distribution.

[0057] In a specific embodiment, the calcination temperature is 450-950°C, such as 450°C, 550°C, 650°C, 700°C, 750°C, 850°C, 900°C, 950°C and the range between any two of the above values. The time is 8-100 hours, such as 8h, 10h, 20h, 30h, 40h, 50h, 60h, 70h, 80h, 90h, 100h and the range between any two of the above values. Calcination within the above temperature and time range can not only ensure that the calcination is sufficient to obtain a target product with high purity, but also will not destroy the bulk structure of the target product. Exemplarily, in some specific embodiments of the present invention, the calcination temperature is 700-800°C and the calcination time is 10-30 hours. The performance of the material prepared under these conditions can be further improved.

[0058] The present invention also provides a positive electrode material, comprising an active material and a lithium-supplementing material, wherein the lithium-supplementing material is the lithium-supplementing material described above or prepared by the method described above.

[0059] The active material is not particularly limited. Exemplarily, the active material is one or more of lithium cobalt oxide, lithium nickel oxide, 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 materials.

[0060] It is understood that the positive electrode material generally also includes a conductive agent and a binder. There is no particular limitation on the selection of the conductive agent and the binder. Exemplarily, the conductive agent is one or more of conductive carbon black, graphene, acetylene black, Ketjen black, and carbon nanofibers, and the binder is one or more of polyvinylidene fluoride, sodium carboxymethyl cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, and styrene-butadiene rubber.

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

[0062] The present invention also provides a positive electrode sheet, which includes the positive electrode material mentioned above.

[0063] The present invention also provides a secondary battery, which includes the above-mentioned positive electrode sheet.

[0064] The present invention also provides an electronic device comprising the aforementioned secondary battery. Exemplarily, the electronic device is a mobile device such as a smartphone, tablet computer, or laptop computer; an electronic transportation device such as an electric car, electric bicycle, electric scooter, or electric balancing scooter; a portable electronic device such as a digital camera, portable speaker, Bluetooth headset / headphone box; and a smart home device such as a smart door lock, smart camera, electronic cigarette, flashlight, headlamp, or power tool.

[0065] The present invention is described in detail below with reference to specific embodiments.

[0066] Example 1

[0067] A lithium-supplementing material A1 includes a lithium-rich material Li5FeO4 and carbon nanotubes. The lithium-supplementing material is prepared by the following method:

[0068] (1) Lithium hydroxide and nano-iron oxide were mixed in a molar ratio of 5.18:1, and an appropriate amount of water was added. The precursor obtained by spray drying was placed in a high-speed mixer for mixing (speed 950 rpm, time 12 min). After mixing, the mixture was placed in an inert gas Ar atmosphere for sintering. After heating to 450 ° C at a rate of 5 ° C / min, the mixture was heated at 10 m 3 The sintering was completed at an Ar flow rate of 1 / h for 5 hours to obtain large solid particles of lithium-rich lithium ferrite. The obtained solid was roughly crushed and further crushed using an air flow method to obtain the target lithium-rich lithium ferrite powder.

[0069] (2) Carbon nanotubes (20 μm in length and 5 nm in diameter) and lithium-rich lithium ferrite powder were ball milled in a jar at a mass ratio of 0.75:99.25 for 3 h at a speed of 300 rpm. The mass ratio of grinding balls to materials (carbon nanotubes and lithium ferrite powder) was 0.75:99.25. The ground material was sieved through a 500-mesh sieve, and the material below the sieve was used as the target material.

[0070] (3) Take the target material and place it in an inert gas Ar protection for calcination. After heating to 450℃ at a heating rate of 5℃ / min, 3 The calcination was completed and then cooled to obtain the positive electrode lithium supplement material A1.

[0071] EDS analysis shows that carbon active sites are distributed in a dotted pattern on the surface of the particles. The particle diameter D50 of lithium-replenishing material A1 is 9 μm. The mass proportion of carbon is 0.75%.

[0072] Example 2

[0073] A lithium supplement material A2 is prepared in the same manner as in Example 1, except that the mass ratio of carbon nanotubes to lithium ferrite powder is 1.5:98.5.

[0074] EDS analysis shows that carbon active sites are distributed in a dotted pattern on the surface of the particles, with the mass fraction of carbon being 1.5%.

[0075] Example 3

[0076] A lithium supplement material A3 is prepared in the same manner as in Example 1, except that the mass ratio of carbon nanotubes to lithium ferrite powder is 2.25:97.75.

[0077] EDS analysis shows that carbon active sites are distributed in a dot-like pattern on the surface of the particles, with the mass fraction of carbon being 2.25%.

[0078] Example 4

[0079] A lithium supplement material A4 is prepared in the same manner as in Example 1, except that the mass ratio of carbon nanotubes to lithium ferrite powder is 3.75:96.25.

[0080] EDS analysis shows that carbon active sites are distributed in a dot-like pattern on the surface of the particles, with the mass fraction of carbon being 3.75%.

[0081] Example 5

[0082] A lithium supplement material A5 is prepared in the same manner as in Example 1, except that the mass ratio of carbon nanotubes to lithium ferrite powder is 7.5:92.5.

[0083] EDS analysis shows that carbon active sites are distributed in a dotted pattern on the particle surface, with the mass fraction of carbon being 7.5%.

[0084] Example 6

[0085] A lithium supplement material A6 was prepared in the same manner as in Example 1, except that the mass ratio of carbon nanotubes to lithium ferrite powder was 15.01:84.99.

[0086] EDS analysis shows that carbon active sites are distributed in a dot-like pattern on the surface of the particles, with the mass proportion of carbon being 15.01%.

[0087] Example 7

[0088] A lithium supplement material A7 is prepared in the same manner as in Example 1, except that the mass ratio of carbon nanotubes to lithium ferrite powder is 37.5:62.5.

[0089] EDS analysis shows that carbon active sites are distributed in a dotted pattern on the surface of the particles, with the mass proportion of carbon being 37.5%.

[0090] Example 8

[0091] A lithium supplement material A8, which differs from Example 5 in that it is prepared by the following method:

[0092] (1) Lithium hydroxide and nano-iron oxide were mixed in a molar ratio of 5.18:1, and an appropriate amount of water was added. The precursor obtained by spray drying was placed in a high-speed mixer for mixing (speed 950 rpm, time 12 min). After mixing, the mixture was placed in an inert gas Ar atmosphere for sintering. After heating to 450 ° C at a rate of 5 ° C / min, the mixture was heated at 10 m 3 The sintering process is then continued for 5 hours at a ventilation rate of 1 / h to obtain large solid particles of lithium-rich lithium ferrite. The obtained solid is roughly crushed and further crushed using an airflow method to obtain the target lithium-rich lithium ferrite powder.

[0093] (2) dispersing carbon nanotubes in ethyl acetate to prepare a suspension;

[0094] (3) After the carbon nanotube suspension and the lithium-rich lithium ferrite powder are mixed, solid-liquid separation is performed to form a target material. The ratio of the carbon nanotubes to the lithium-rich lithium ferrite powder in the suspension is the same as the ratio of the carbon nanotubes to the lithium-rich lithium ferrite powder during dry mixing in Example 5, and the mass fraction of the carbon nanotubes in the solution is 4.5%;

[0095] (4) Take the target material and place it in an inert gas Ar protection for calcination. After heating to 450℃ at a heating rate of 5℃ / min, 3 / h ventilation rate for 10 hours, and after calcination, cooling to obtain positive electrode lithium supplement A8;

[0096] EDS analysis shows that the carbon active sites are distributed in a planar pattern, and the particle diameter of the lithium-replenishing material A8 is 9 μm. The mass proportion of the carbon element is 7.5%.

[0097] Example 9

[0098] A lithium-supplementing material A9, comprising a lithium-rich material Li2NiO2 and carbon nanofibers, is prepared by the following method:

[0099] (1) Lithium hydroxide and nickel nitrate were mixed in a molar ratio of 1:1, and an appropriate amount of water was added. The precursor obtained by spray drying was placed in a high-speed mixer for mixing (speed 950 rpm, time 12 min). After mixing, the mixture was placed in an inert gas Ar atmosphere for sintering. After heating to 650 ° C at a heating rate of 5 ° C / min, the mixture was heated at 10 m 3 The sintering was completed at an Ar flow rate of 1 / h for 8 hours to obtain large solid particles of lithium-rich lithium nickelate. The obtained solid was roughly crushed and further crushed using an air flow method to obtain the target lithium-rich lithium nickelate powder.

[0100] (2) Carbon nanofibers (20 μm in length and 5 nm in diameter) and lithium nickelate-rich powder were ball milled in a jar at a mass ratio of 5.7:94.3 for 3 h at a speed of 300 rpm and a ball-to-material ratio of 4:1. The ground material was sieved through a 500-mesh sieve, and the material below the sieve was used as the target material.

[0101] (3) Take the target material and place it in an inert gas Ar protection for calcination. After heating to 850℃ at a heating rate of 5℃ / min, 3 The calcination was completed and then cooled to obtain the positive electrode lithium supplement material A9.

[0102] EDS detection shows that the C active sites are distributed in a point-like manner on the surface of the particles, and the particle diameter D50 of the lithium-replenishing material A9 is 9 μm.

[0103] Comparative Example 1

[0104] A lithium supplement material D1 is Li5FeO4 without carbon nanotubes. The only difference between this material and Example 2 is that no carbon nanotubes are added during sintering.

[0105] Test analysis:

[0106] (1) The lithium-supplementing materials in the above-mentioned embodiments and comparative examples are made into positive electrode sheets, which are then assembled with negative electrode sheets, electrolytes, and separators in the following manner to obtain lithium-ion batteries:

[0107] The positive electrode lithium supplement material was mixed with conductive carbon black and PVDF in a weight ratio of 96%:2%:2% respectively, and the positive electrode slurry was obtained by dispersion. The slurry was coated on the aluminum foil current collector, and the positive electrode surface density was 4.12g / cm 3 Roll pressing is performed to prepare a positive electrode sheet.

[0108] Artificial graphite, styrene diene rubber, sodium carboxymethyl cellulose, and conductive carbon black were mixed in a weight ratio of 94%:3%:2%:1%, dispersed in water, and mixed using a double planetary mixer to create a negative electrode slurry. This slurry was then coated onto a copper current collector, followed by roll pressing and drying to produce a negative electrode sheet.

[0109] The positive electrode sheet, negative electrode sheet and separator are assembled into a lithium-ion battery and injected with a non-aqueous electrolyte. The electrolyte is 1 mol LiPF6 dissolved in a solvent of DMC / EMC / DEC (mass ratio 1:1:1). The positive electrode sheet size is 53mm*43mm, and the battery cell adopts a combination of 3 negative electrodes and 2 positive electrodes.

[0110] The assembled lithium-ion battery was subjected to a charge capacity test. After standing for 4 hours at 25°C, the battery was initially charged to 4.55V at 0.1C and then charged to 0.025C at a constant voltage. The battery's charge capacity was recorded. The gram capacity of the lithium supplement was calculated as: charge capacity / (areal density * positive electrode sheet size / active material ratio). The decomposition time refers to the time it takes to charge to 4.55V. The test results are shown in Table 1.

[0111] Table 1

[0112]

[0113] As can be seen from Examples 1-7 above, when the mass percentage of the C element in the lithium-supplementing material is within the range of 0.3-37.5%, the gram capacity and decomposition time of the lithium-supplementing material can be maintained within an optimal range, both meeting application requirements. When the mass percentage of the C element in the lithium-supplementing material is 0.75-16%, it can better balance the gram capacity and decomposition time. In particular, when the mass percentage of the C element in the lithium-supplementing material is within the range of 0.75-8%, the gram capacity and decomposition time of the material do not change much.

[0114] It can be seen from Examples 1-4 and Example 8 that although the C doping amount is less than that of Example 8, the decomposition time is much shorter than that of the material prepared by wet mixing in Example 8.

[0115] (2) The lithium-rich lithium ferrite powders obtained in Example 5 and Example 8 were subjected to EDS testing. The test area was the particle surface. The test results are as follows: Figure 3 shown.

[0116] Depend on Figure 3It can be seen that Example 8, due to its wet process, was distributed in agglomerates during the dispersion process and had a granular morphology after calcination. The lithium-rich ferrite powder prepared by the dry process in Example 5 was an irregular cube after mechanical crushing. EDS shows that the C active sites in the lithium-rich ferrite powder prepared by the dry process are distributed in a point-like manner (rather than in other forms such as long strips) on the surface of the lithium-rich material particles, indicating that the one-dimensional carbon material is inserted into the lithium-rich material particles. In addition, the lithium-rich ferrite powder prepared by the dry process has more C elements distributed on the surface, indicating that it has more active sites.

[0117] In order to further quantify that Example 5 can provide more active sites than Example 8, the particle surface was tested using O as the calibration element in the EDS test. The higher the ratio of C to O elements, the more C active sites there are. Figure 3 As shown in Table 2 below:

[0118] Table 2

[0119]

[0120] Depend on Figure 4 As can be seen from Table 2, compared with Example 8, the number of C active sites on the surface of the material particles prepared in Example 5 is 2.8 times that in Example 8.

[0121] (2) The lithium-supplementing materials obtained in Example 5 and Example 8 are made into positive electrodes, and then assembled with negative electrodes, electrolytes, and separators according to the following method to obtain lithium-ion batteries:

[0122] Lithium iron phosphate, the positive electrode lithium supplement material in Example 5 or Example 8, conductive carbon black, and PVDF were mixed in a weight ratio of 100:90:3.5:2.5, and a positive electrode slurry was obtained by dispersion. The slurry was coated on an aluminum foil current collector, and the positive electrode surface density was 4g / cm 3 Roll pressing is performed to prepare a positive electrode sheet;

[0123] Artificial graphite, styrene diene rubber, sodium carboxymethyl cellulose, and conductive carbon black were mixed in a weight ratio of 94%:3%:2%:1%, and the mixture was dispersed in water and mixed using a double planetary mixer to produce a negative electrode slurry. This slurry was then coated onto a copper current collector, followed by roll pressing and drying to produce a negative electrode sheet.

[0124] The positive electrode sheet, negative electrode sheet, and separator were assembled into a lithium-ion battery and then injected with a non-aqueous electrolyte consisting of 1 mol LiPF6 dissolved in a solvent with a DMC / EMC / DEC mass ratio of 1:1:1. The positive electrode sheet was 53mm*43mm in size, and the battery cell used a combination of three negative electrodes and two positive electrodes. The charge capacity of the assembled lithium-ion battery was tested:

[0125] Test method: After standing at 25℃ for 4 hours, conduct the first charge capacity test. The test conditions are: 0.2C charging to 3.8V, constant voltage charging to 0.01C, 0.2C charging to 3.95V, constant voltage charging to 0.01C and 0.2C charging to 4.3V. Record the battery charging time. The test results are as follows: Figure 3 shown.

[0126] Depend on Figure 4 It can be seen that the lithium-supplementing material prepared in Example 5 is mixed into the LFP battery, which can save about 60 minutes of decomposition time compared with the lithium-supplementing material prepared in Example 8, thereby improving production efficiency.

[0127] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. 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 lithium supplement material, characterized in that: include: Lithium-rich materials and carbon materials doped in lithium-rich materials; The mass proportion of the C element in the lithium supplement material is 0.3-37.5%.

2. The lithium supplement material according to claim 1, characterized in that The mass proportion of the C element in the lithium supplement material is 0.75-16%; and / or The mass proportion of the C element in the lithium supplement material is 0.75-8%.

3. The lithium supplement material according to claim 1 or 2, characterized in that The carbon material is a one-dimensional carbon material, and at least one one-dimensional carbon material runs through a single particle of the lithium-rich material.

4. The lithium supplement material according to claim 3, characterized in that A single particle of the lithium-rich material has multiple one-dimensional carbon materials running through it, and the multiple one-dimensional carbon materials are staggered and stacked at least inside the lithium-rich material particle.

5. The lithium supplement material according to claim 3 or 4, characterized in that The diameter of the one-dimensional carbon material is 1-50 nm; and / or The maximum length of a single particle of the lithium-rich material is 0.1-100 μm.

6. The lithium supplement material according to any one of claims 1 to 5, characterized in that: The carbon material is carbon nanotubes or carbon nanofibers; and / or The structural formula of the lithium-rich material is Li 1+x A y O z , wherein 0<x<10, 0<y<6, 0<z<13, and A is one or more of Ni, Co, Fe, Cu, Mg, Mn, Cr, Zn, Ti, Zr, Nb, and Mo.

7. The lithium supplement material according to any one of claims 1 to 6, characterized in that: The carbon material is a needle-shaped carbon nanomaterial.

8. The lithium supplement material according to claim 7, characterized in that The needle-shaped carbon nanomaterial is formed by processing at least one of carbon nanotubes, carbon nanofibers, carbon nanospheres and graphene.

9. A method for preparing the lithium supplement material according to any one of claims 1 to 8, characterized in that: The invention comprises a process of dry-mixing a mixture of lithium-rich material and carbon material and then calcining the mixture to obtain a lithium-supplementing material.

10. The method for preparing the lithium supplement material according to claim 9, characterized in that: The carbon material is a one-dimensional carbon material, and the length of the one-dimensional carbon material is greater than the maximum length of a single particle of the lithium-rich material.

11. The method for preparing the lithium supplement material according to claim 9 or 10, characterized in that: The dry mixing method is ball milling, the ball milling speed is 200-400 rpm, the ball milling time is 2-5 hours, and the mass ratio of grinding balls to the mixture is (0.5-1):

100.

12. The preparation method according to any one of claims 9 to 11, characterized in that: The calcination temperature is 450-950°C, and the calcination time is 8-100h.

13. The preparation method according to claim 12, characterized in that The calcination temperature is 700-800°C, and the calcination time is 10-30h.

14. A positive electrode material, characterized in that The invention comprises an active material and a lithium-supplementing material, wherein the lithium-supplementing material is the lithium-supplementing material according to any one of claims 1 to 8 or the lithium-supplementing material prepared by the preparation method according to any one of claims 9 to 13.

15. A positive electrode sheet, characterized in that: Comprising the positive electrode material according to claim 14.

16. A secondary battery, characterized in that: Including the positive electrode sheet according to claim 15.

17. An electronic device, characterized in that: The secondary battery according to claim 16 is included.

Images