Lithium supplementing material, preparation method thereof, positive electrode sheet and secondary battery

Abstract

A lithium replenishment material and its preparation method, a positive electrode sheet, and a secondary battery are disclosed. The lithium replenishment material includes a core and a deposition layer. The core comprises a lithium-rich compound. The deposition layer coats the outer layer of the core and is a film layer of nanometer size or smaller. The lithium replenishment material provided by this application has high water absorption resistance and strong stability.

Description

Technical Field

[0001] This application relates to the field of secondary battery technology, specifically to a lithium replenishment material and its preparation method, a positive electrode sheet, and a secondary battery. Background Technology

[0002] During the first charge of a lithium-ion battery, a large amount of solid electrolyte interface film forms on the surface of the negative electrode, consuming the limited lithium ions and electrolyte in the battery, causing irreversible capacity loss, reducing the energy density of the lithium-ion rechargeable battery, and limiting the application of lithium-ion batteries. In existing technologies, adding lithium-replenishing materials to the positive electrode material can effectively compensate for the initial irreversible capacity loss of lithium batteries.

[0003] However, existing lithium replenishment materials have poor water absorption resistance and structural stability, making them highly susceptible to moisture absorption and deterioration in humid environments. This ultimately weakens the structural strength and degrades the electrochemical performance of the materials, making them unsuitable for long-term storage or long-distance transportation. Therefore, improving the water absorption resistance and stability of lithium replenishment materials has become a crucial issue. Summary of the Invention

[0004] The purpose of this application is to provide a lithium supplement material and its preparation method, a positive electrode sheet, and a secondary battery.

[0005] This application provides the following technical solution:

[0006] In a first aspect, this application provides a lithium replenishment material, comprising a core and a deposition layer, wherein the core comprises a lithium-rich compound; the deposition layer covers the outer layer of the core, and the deposition layer is a film layer of nanometer scale or below.

[0007] The lithium replenishment material provided in this application has a deposition layer on the outer layer of the core, which isolates the lithium-rich compounds in the core from the external environment, thereby preventing moisture from the external environment from penetrating into the core. This gives the lithium replenishment material better water resistance and stability. At the same time, the deposition layer provided in this application is a film layer of nanometer scale or below, which has a higher density than existing coating layers. Therefore, the deposition layer further controls the absorption of water from the outside by the core of the lithium replenishment material, thereby extending the storage time of the lithium replenishment material.

[0008] In one embodiment, the deposited layer comprises a single-atom deposited layer and / or an oxide nanofilm layer obtained by atomic layer deposition technology.

[0009] In one embodiment, the density ρ1 of the deposited layer satisfies the relationship: 2 g / cm³ 3 ≤ρ1≤4.2g / cm 3By controlling the density of the deposited layer within the aforementioned range, a high density can be achieved, thereby further controlling the absorption of water from the core and enabling the lithium replenishment material to have a longer storage time.

[0010] In one embodiment, the lithium replenishment material further includes a pre-coating layer, which coats the outer surface of the core, and the deposition layer coats the outer surfaces of both the core and the pre-coating layer. By pre-coating the outer surface of the lithium-rich compound core with nanoscale oxide particles, the specific surface area of ​​the lithium replenishment material is increased, providing an excellent environment for the subsequent deposition layer. Compared to the outer surface of the core, the pre-coating layer formed by the oxide particles has higher roughness and specific surface area, avoiding the uneven coating phenomenon that occurs when the deposition layer is directly placed on the outer surface of the core. The pre-coating layer between the deposition layer and the core makes the coating of the deposition layer more uniform, ensuring the integrity and sealing of the outer surface, thereby enabling the lithium replenishment material provided in this application to have better water absorption resistance and stability.

[0011] In one embodiment, the lithium replenishment material further includes a carbon layer, which coats the outer layer of the deposited layer.

[0012] In one embodiment, the core is a secondary particle, which includes a plurality of primary particles, and there are deposits between the primary particles in the secondary particles, the deposits including deposited particles at the nanometer scale or below.

[0013] In one embodiment, the density ρ2 of the pre-coating layer satisfies the following relationship: 1.5 g / cm³ 3 ≤ρ2≤3g / cm 3 .

[0014] In one embodiment, the density of the deposited layer is greater than the density of the pre-coated layer.

[0015] In one embodiment, the particle size D10 of the core satisfies the relationship: D10 ≥ 2 μm. When the particle size D10 of the core meets the above range, the core can have a larger size than the oxide particles, and the area of ​​the outer surface of the core is also larger, making it easier for nanoscale oxide particles to adhere or for atoms to be deposited, further reducing the difficulty of the preparation process. Furthermore, when the core meets the above range, the oxide particles can also be selected with a wider range of particle sizes (the upper limit of the oxide particle size is larger), which is beneficial for the selection of oxide particles and reduces the cost of the preparation process. When the particle size of the core is smaller than the above range, the particle size of the core is too small, which will make it difficult for nanoscale oxides to adhere, resulting in uneven coating.

[0016] In one embodiment, the specific surface area S1 of the kernel satisfies the relationship: S1≤3m 2 / g. Controlling the specific surface area of ​​the core within a suitable range is to provide a more suitable adhesion environment for the oxide particles. Understandably, the larger the specific surface area of ​​the core, the greater the roughness of its outer surface, which is more conducive to the adhesion of oxide particles compared to a smooth surface, thereby further reducing the difficulty of the preparation process.

[0017] In one embodiment, the material of the deposited layer is one or more of alumina, silicon dioxide, and titanium dioxide.

[0018] In one embodiment, the pre-coating layer has gaps, and at least a portion of the deposited layer fills these gaps. Specifically, the pre-coating layer can be formed by a plurality of oxide particles interconnecting on the outer surface of the core, thus the pre-coating layer may have partial gaps, which may be formed due to insufficient interconnection of the oxide particles. The fact that at least a portion of the deposited layer fills these gaps in the pre-coating layer reduces the size of the gaps, preventing moisture from the external environment from penetrating into the core through these gaps.

[0019] In one embodiment, at least a portion of the deposited layer directly covers the outer surface of the core. Due to the presence of gaps in the pre-coating layer, at least a portion of the atomic deposition agent can pass through the gaps and deposit on the outer surface of the core. The advantage of directly covering the outer surface of the core with at least a portion of the deposited layer is that it fills the formed gaps while simultaneously coating the core, improving the water resistance of the lithium-supplementing material; furthermore, when using the same mass of atomic deposition agent, the outermost deposited layer can be thinned.

[0020] In one embodiment, the pre-coating layer comprises oxide particles and a lubricant mixed together.

[0021] In one embodiment, the oxide particles include one or more of aluminum oxide, silicon dioxide, and titanium dioxide.

[0022] In one embodiment, the oxide particles have a particle size of 1 nm to 100 nm. The particle size of the oxide particles, as determined by the pores, facilitates control over the thickness of the formed pre-coating layer and the lithium replenishment effect of the lithium replenishment material. It is understood that the pre-coating layer is formed by interconnected oxide particles; therefore, compared to an equal number of oxide particles, smaller oxide particles result in a thinner pre-coating layer. Furthermore, controlling the oxide particles within the aforementioned range also allows for control over the proportion of gaps formed in the pre-coating layer.

[0023] In one embodiment, the specific surface area S2 of the oxide particles satisfies the following relationship: S2 ≥ 50 m² 2 / g. Controlling the specific surface area of ​​oxide particles within the above-mentioned range serves two purposes: firstly, it enhances their adhesion to the core; secondly, it provides a favorable environment for the deposition layer. Understandably, a larger specific surface area of ​​oxide particles allows for greater surface roughness, which, compared to a smooth surface, is more conducive to bonding with the core, thereby improving the structural stability of the pre-coated layer. Similarly, a rough outer surface reduces the difficulty of deposition layer formation, providing an excellent environment for the atomic deposition agent and facilitating deposition.

[0024] In one embodiment, the lubricant includes at least one of graphite and boron nitride.

[0025] In one embodiment, the mass ratio of the oxide particles to the lubricant is 1:(0.1 to 0.8). By controlling the ratio of oxide particles to lubricant, the uniformity of the oxide particles coating the outer surface of the core can be controlled. It is understood that if the proportion of lubricant is lower than the above ratio, insufficient lubrication will result in the oxide particles easily accumulating, thus failing to form a relatively uniform pre-coating layer; if the proportion of lubricant is higher than the above ratio, lubricant accumulation will occur, meaning that some oxide particles will not be able to form a continuous deposition and cooperate with the deposition layer.

[0026] In one embodiment, the mass ratio of the core, the pre-coating layer, and the deposited layer is 100:(0.01-10):(0.01-5). By controlling the mass ratio of the core, the pre-coating layer, and the deposited layer within a suitable range, not only can the thickness of the pre-coating layer and the deposited layer be adjusted to provide a good sealing environment, but the lithium-supplementing material can also maintain good electrochemical performance.

[0027] In one embodiment, the thickness A1 of the pre-coating layer is 1 nm to 200 nm. The pre-coating layer is used to create an environment for the deposition layer without affecting the efficiency of lithium ion extraction from the core. Therefore, after ensuring that the pre-coating layer has a certain thickness for deposition, the pre-coating layer should not be too thick. The thickness of the pre-coating layer within the above range can meet the deposition requirements without affecting the lithium ion extraction efficiency.

[0028] In one embodiment, the thickness A2 of the deposited layer is 1 nm to 200 nm. The deposited layer is used to achieve a dense encapsulation, thereby protecting the core. A thickness within this range allows the lithium-ion extraction efficiency to be maintained while still protecting the core.

[0029] In one embodiment, the thicknesses of the pre-coating layer and the deposition layer satisfy the relationship: 1 ≤ A1 / A2 ≤ 40. By controlling the thickness ratio of the pre-coating layer and the deposition layer within the above range, it is beneficial to control the thickness of the pre-coating layer or the deposition layer, thereby avoiding the phenomenon of an excessively thick deposition layer while ensuring that the pre-coating layer achieves complete coverage.

[0030] In one embodiment, the lithium-rich compound has the chemical formula including Li x M y O z and Li w At least one of A; wherein 0 < x ≤ 6, 0 < y ≤ 3, 0 < z ≤ 4, 0 < w ≤ 5; M is at least one element selected from Fe, Co, Ni, Mn, V, Cu, Mo, Al, Ti, and Mg, and A is at least one element selected from C, N, O, P, S, F, B, and Se.

[0031] Secondly, this application provides a method for preparing a lithium-rich material, comprising: uniformly mixing a lithium source and a first metal source and then sintering them together to obtain a lithium-rich compound; depositing a deposit on the outer layer of the lithium-rich compound to obtain a lithium-rich material; the lithium-rich material comprising a core and a deposit layer, the core comprising the lithium-rich compound, and the deposit forming the deposit layer.

[0032] Thirdly, this application also provides a positive electrode sheet, the positive electrode sheet comprising a current collector and an active material layer disposed on the current collector, the active material layer comprising a positive electrode material and a lithium supplement material as described in any one of the embodiments of the first aspect, or the active material layer comprising a lithium supplement material obtained by a method for preparing a positive electrode material and a lithium supplement material as described in any one of the embodiments of the second aspect.

[0033] Fourthly, this application also provides a secondary battery, the secondary battery comprising a negative electrode, a separator, and the positive electrode described in the third aspect. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0035] Figure 1 This is a schematic cross-sectional view of the lithium replenishment material in one embodiment;

[0036] Figure 2 This is a partial cross-sectional schematic diagram of the lithium replenishment material in one embodiment;

[0037] Figure 3 This is a partial cross-sectional schematic diagram of a lithium replenishment material including a lubricant in one embodiment;

[0038] Figure 4 This is a schematic diagram of the cross-sectional structure of a lithium-supplementing material that is a secondary particle in one embodiment.

[0039] Figure 5 This is a flowchart of a method for preparing a lithium-supplementing material in one embodiment;

[0040] Figure 6 for Figure 5 The detailed flowchart of step S20;

[0041] Figure 7 This is a SEM image of the pre-coating layer of the lithium replenishment material in one embodiment;

[0042] Figure 8 This is a TEM image of the lithium replenishment material from another perspective. Detailed Implementation

[0043] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0044] It should be noted that when a component is said to be "fixed" to another component, it can be directly on the other component or it can be in a middle component. When a component is said to be "connected" to another component, it can be directly connected to the other component or it may be in a middle component.

[0045] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in this application's specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used in this application includes any and all combinations of one or more of the associated listed items.

[0046] The following detailed description of some embodiments of this application is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0047] Firstly, this application provides a lithium replenishment material, comprising a core and a deposition layer, wherein the core comprises a lithium-rich compound; the deposition layer coats the outer layer of the core, and the deposition layer is a film layer of nanometer size or smaller. It should be noted that the deposition layer can be directly coated on the outer surface of the lithium replenishment material; alternatively, other layers can be provided between the core and the deposition layer. Specifically, the outer surface of the core is coated with other coating layers, and the deposition layer then coats the outer surface of the core and the outer surface of these coating layers.

[0048] Specifically, the core of the lithium replenishment material can mainly consist of lithium-rich compounds. These compounds are the core that provides lithium ions, and their chemical formulas are not specifically limited. Optionally, the core shape can be spherical, near-spherical, or other irregular shapes. By adding lithium-rich compound-based core materials to the electrode, the lithium replenishment material acts as a "sacrificial agent" during the first charging cycle, releasing as many lithium ions as possible at once to replenish the irreversible lithium ions consumed in the formation of the SEI film at the negative electrode. This maintains an ample supply of lithium ions within the battery system, improving the battery's initial efficiency and overall electrochemical performance.

[0049] In one embodiment, the lithium-rich compound has the chemical formula including Li x M y O z and Li w At least one of A; wherein 0 < x ≤ 6, 0 < y ≤ 3, 0 < z ≤ 4, 0 < w ≤ 5; M is at least one element selected from Fe, Co, Ni, Mn, V, Cu, Mo, Al, Ti, and Mg, and A is at least one element selected from C, N, O, P, S, F, B, and Se. In specific embodiments, the lithium-rich compound may be Li5FeO4, Li6MnO4, Li6CoO4, Li6ZnO4, Li2NiO2, Li2CuO2, Li2CoO2, Li2MnO2, or Li2Ni 0.5 Mn 1.5 At least one of O4, etc. It should be noted that some of the above-mentioned lithium-rich compounds can be directly used as lithium-rich cathode materials, such as Li2NiO2, Li2CuO2, Li2CoO2, Li2MnO2, and Li2Ni. 0.5 Mn 1.5 O4.

[0050] The deposition layer is a film composed of nanoscale and smaller deposits. Specifically, nanoscale deposits include nanoparticles, and smaller deposits include atomic or molecular-level particles.

[0051] In one embodiment, the deposited layer includes a single-atom deposited layer and / or an oxide nanofilm layer obtained by atomic layer deposition (ALD). Specifically, the deposited layer can be a single-atom deposited layer obtained by ALD, and this layer can be a single-atom layer or a nanolayer composed of atoms or molecules. Optionally, when the deposited layer is a single-atom deposited layer, different atomic deposition agents can be selected according to the different materials, including but not limited to one or more of trimethylaluminum, triethylaluminum, triisobutylaluminum, tetra(diethylamino)titanium, triethylsilane, tetraethylsilane, and tetra(ethylmethylamino)zirconium.

[0052] Optionally, the deposited layer can also be an oxide nanofilm. For example, the oxide nanofilm can be a layer obtained by reacting the single-atom deposited layer described above with oxygen, specifically made of materials such as alumina, titanium dioxide, silicon dioxide, or zirconium dioxide. Alternatively, nanoscale oxide layers can be directly formed on the outer layer of the core using vapor deposition technology. Of course, oxide nanofilms can also be obtained using other techniques.

[0053] Optionally, the deposited layer can be multi-layered; for example, it may include both a single-atom deposited layer and an oxide nanofilm layer; or it may include at least one single-atom deposited layer or an oxide nanofilm layer.

[0054] Understandably, the sedimentary layer should be composed of atomic, molecular, or nanoscale particles. Furthermore, the specific formation method of the sedimentary layer is not limited. Controlling the composition of the sedimentary layer within these size ranges makes it easier to obtain denser layers, thereby achieving a dense coating of the core and further reducing the ingress of external water into the core.

[0055] The lithium replenishment material provided in this application has a deposition layer on the outer layer of the core, which isolates the lithium-rich compounds in the core from the external environment, thereby preventing moisture from the external environment from penetrating into the core. This gives the lithium replenishment material better water resistance and stability. The deposition layer provided in this application has a higher density than existing coating layers, which allows the lithium replenishment material to further control the absorption of water from the outside by the core through the deposition layer as an outer coating layer. Therefore, the lithium replenishment material can have a longer storage time.

[0056] In one embodiment, the density ρ1 of the deposited layer satisfies the relationship: 2 g / cm³ 3 ≤ρ1≤4.2g / cm 3 By controlling the density of the deposited layer within the aforementioned range, a high degree of compactness is achieved, which further controls the absorption of water from the core, resulting in a longer storage time for the lithium-supplementing material. It can be understood that the higher the density of the deposited layer, the higher its compactness and the better the film tightness.

[0057] In one implementation method, please refer to Figure 1 The lithium replenishment material also includes a pre-coating layer 20, which covers the outer surface of the core 10, and a deposition layer 30 covers the outer surfaces of the core 10 and the pre-coating layer 20.

[0058] Specifically, the pre-coating layer 20 can be a continuous layer formed by the interconnection of oxide particles 21. Optionally, the oxide particles 21 can be nanoparticles with nanoscale dimensions prepared by vapor deposition. The oxide particles 21 include, but are not limited to, one or more of fumed alumina, fumed silica, and fumed titanium dioxide. It is understood that the pre-coating layer 20 can be formed by the interconnection of a large number of oxide particles 21 on the outer surface of the core 10, so the pre-coating layer 20 can have some gaps, which may be formed due to insufficient interconnection of the oxide particles 21.

[0059] Optionally, the particle size of oxide particles 21 should be smaller than that of the core 10, and the oxide particles 21 can have a large particle size distribution range. This allows the oxide particles 21 to form a relatively dense pre-coating layer 20, while also ensuring that the proportion of gaps in the pre-coating layer 20 is small, thereby preventing moisture from the external environment from penetrating into the core 10 through the gaps in the pre-coating layer 20.

[0060] Optionally, the material of the deposited layer 30 can be the same as or different from the material of the pre-coating layer 20. For example, the pre-coating layer 20 can be composed of vapor-phase nano-alumina particles, while the deposited layer 30 can be composed of molecular-level alumina; the deposited layer 30 can also be composed of molecular-level silicon dioxide.

[0061] Optionally, some sediments can also penetrate the gaps in the pre-coating layer 20 and directly coat the outer surface of the core 10. Understandably, since the sediments are smaller than the oxide particles 21 and may even be smaller than the width of the gaps in the pre-coating layer 20, they can directly connect to the core 10 through the gaps during deposition. The advantage is that the sediments can fill the gaps in the pre-coating layer 20, thereby reducing the size of the gaps and preventing moisture from the external environment from penetrating into the core 10 through the gaps in the pre-coating layer 20.

[0062] This application increases the specific surface area of ​​the lithium replenishment material by pre-coating the outer surface of a lithium-rich compound core with nanoscale oxide particles, providing an excellent environment for subsequent deposition. The pre-coating layer formed by the oxide particles has higher roughness and specific surface area compared to the outer surface of the core, avoiding the uneven coating that occurs when the deposition layer is directly placed on the outer surface of the core. The pre-coating layer between the deposition layer and the core ensures more uniform coating of the deposition layer, guaranteeing the integrity and sealing of the outer surface. This results in the lithium replenishment material provided by this application exhibiting superior water resistance and stability.

[0063] In one embodiment, the lithium replenishment material further includes a carbon layer (not shown in the figure), which coats the outer layer of the deposited layer. Specifically, the carbon layer is composed of carbon materials, including one or more of graphite, carbon black, hard carbon, soft carbon, and amorphous carbon.

[0064] In one embodiment, the core 10 is a secondary particle, which includes multiple primary particles, with deposits between the primary particles. Specifically, the core 10 can be a secondary particle composed of multiple primary particles, thus the core 10 may have gaps formed by the connection of multiple primary particles. The deposits can be the main material constituting the deposition layer 30, and the deposits can be deposited into the gaps between the multiple primary particles; the deposits can even coat the primary particles, such as... Figure 4 As shown. Preferably, in the above-mentioned structure where the core 10 is a secondary particle, metal elements can be doped into the core or the interface layer using atomic layer deposition technology, thereby improving the conductivity inside the core.

[0065] In one embodiment, the density ρ2 of the pre-coating layer satisfies the relationship: 1.5 g / cm³ 3 ≤ρ2≤3g / cm 3 .

[0066] In one embodiment, the density of the sedimentary layer is greater than the density of the pre-coating layer. Specifically, setting the density of the sedimentary layer to be greater than the density of the pre-coating layer is to ensure that the sedimentary layer has a high density, thereby protecting the core from external moisture erosion.

[0067] In one embodiment, the core particle size D10 satisfies the relationship: D10 ≥ 2 μm. Here, D10 refers to the particle size on the particle size distribution curve corresponding to a volume smaller than 10% of the total volume. Preferably, the specific range of the core particle size D10 can be 2 μm to 8 μm. Controlling the core particle size is to provide a more suitable adhesion environment for nanoscale and smaller particles, and also to facilitate atomic deposition. It is understood that when the core particle size D10 meets the above range, the core can have a larger size than the oxide particles, and the outer surface area of ​​the core is also larger, making it easier for nanoscale oxide particles to adhere, further reducing the difficulty of the fabrication process; furthermore, when the core meets the above range, a wider range of oxide particle sizes can be selected (the upper limit of the oxide particle size is larger), which is beneficial for the selection of oxide particles and reduces the cost of the fabrication process.

[0068] When the core particle size D10 is smaller than the above range, the small core size makes it more difficult for oxide particles to adhere, and narrows the range of available oxide particles. Simultaneously, the small core size also increases the difficulty of core fabrication, making it difficult to control the cost of lithium supplementation materials. When the core particle size D10 is larger than the above range, it results in lower compaction density when using lithium supplementation materials to fabricate positive electrode sheets, which is detrimental to improving the capacity of lithium batteries.

[0069] In one implementation, the specific surface area S1 of the kernel satisfies the following relationship: S1≤3m 2 / g. Preferably, the specific surface area of ​​the kernel can be in the range of 0m². 2 / g~1m 2 / g. Specifically, the specific surface area S1 of the kernel can be, but is not limited to, 0.1m². 2 / g, 0.2m 2 / g, 0.5m 2 / g, 0.8m 2 / g, 1m 2 / g、2m 2 / g、3m 2 / g. Controlling the specific surface area of ​​the core within a suitable range is to provide a more suitable adhesion environment for the oxide particles. Understandably, the larger the specific surface area of ​​the core, the greater the roughness of its outer surface, which is more conducive to the adhesion of oxide particles compared to a smooth surface, thereby further reducing the difficulty of the preparation process.

[0070] In one embodiment, the material of the deposited layer is one or more combinations of alumina, silicon dioxide, and titanium dioxide. Specifically, based on the above embodiments, the deposited layer can be formed by the reaction of the atomic deposition agent mentioned above with oxygen. Therefore, the material of the deposited layer depends on the atomic deposition agent selected. It can be understood that the deposited layer can be formed by placing the atomic deposition agent on a pre-coating layer, and then allowing the atomic deposition agent to completely react with oxygen to form the final deposited layer. Of course, to accelerate the reaction, a high-temperature reaction can also be used.

[0071] In one implementation method, please refer to Figure 2 The pre-coating layer 20 has gaps, and at least a portion of the deposited layer 30 fills these gaps. Specifically, the pre-coating layer 20 can be formed by a plurality of oxide particles 21 interconnecting on the outer surface of the core 10, so the pre-coating layer 20 can have partial gaps, which may be formed due to insufficient interconnection of the oxide particles 21. The fact that at least a portion of the deposited layer 30 fills these gaps in the pre-coating layer 20 reduces the size of the gaps and prevents moisture from the external environment from penetrating into the core 10 through these gaps.

[0072] In one implementation method, please refer to Figure 2 At least a portion of the deposition layer 30 directly coats the outer surface of the core 10. Understandably, due to the presence of gaps in the pre-coating layer 20, at least a portion of the atomic deposition agent can pass through these gaps and deposit on the outer surface of the core 10. The advantage of having at least a portion of the deposition layer 30 directly coat the outer surface of the core 10 is that it fills the formed gaps while simultaneously coating the core 10, improving the water resistance of the lithium replenishment material; furthermore, when using the same mass of atomic deposition agent, the outermost deposition layer 30 can be thinned.

[0073] In one implementation method, please refer to Figure 3 The pre-coating layer 20 comprises mixed oxide particles 21 and a lubricant 22, wherein the lubricant 22 comprises at least one of graphite and boron nitride. Specifically, the lubricant 22 may be added together with the oxide particles 21 during the fabrication of the pre-coating layer 20, so that residual lubricant 22 may be present in the formed pre-coating layer 20. The purpose of adding the lubricant 22 is to enhance mixing, since the fabrication method of the pre-coating layer 20 can use solid-phase mixing, that is, directly mixing the core 10 and the oxide particles 21. Therefore, in order to reduce static electricity between solid particles and to make the mixing more thorough, the lubricant 22 (such as graphite or boron nitride) can be used. In this way, the gas-phase nanoscale oxide particles 21 can be more uniformly distributed on the surface of the lithium replenishing particles. Of course, in other embodiments, the lubricant 22 may also be paraffin or other volatile substances, so no lubricant 22 may remain in the final lithium replenishing material.

[0074] In one embodiment, the oxide particles have a particle size of 1 nm to 100 nm. Specifically, the particle size of the oxide particles can be, but is not limited to, 8 nm, 10 nm, 12 nm, 14 nm, 16 nm, 18 nm, 20 nm, 30 nm, 50 nm, 80 nm, and 100 nm. Controlling the particle size of the oxide particles through the pores helps control the thickness of the formed pre-coating layer and the lithium replenishment effect of the lithium replenishment material. It is understood that the pre-coating layer is formed by interconnecting oxide particles, so compared to the same number of oxide particles, the smaller the particle size, the thinner the pre-coating layer. Furthermore, controlling the oxide particles within the above-mentioned range also allows control over the proportion of gaps formed in the pre-coating layer. When the particle size of oxide particles is smaller than the above range, the difficulty of obtaining oxide particles increases, and oxide particles are more likely to form local accumulation, which will lead to uneven thickness of the pre-coating layer and is not conducive to the formation of the pre-coating layer. When the particle size of oxide particles is larger than the above range, the overall thickness of the pre-coating layer will be thicker, and the weight ratio of the pre-coating layer will increase. However, since oxide particles do not contribute lithium ions, the overall specific capacity of the lithium replenishment material will be reduced, resulting in a deviation in the lithium replenishment effect of the lithium replenishment material.

[0075] In one embodiment, the specific surface area S2 of the oxide particles satisfies the following relationship: S2 ≥ 50 m² 2 / g. Preferably, the specific surface area S2 of the oxide particles can be in the range of 50m². 2 / g~200m 2 / g. Specifically, the specific surface area S2 of the oxide particles can be, but is not limited to, 50m². 2 / g、80m 2 / g, 100m 2 / g, 150m 2 / g、200m 2 / g. Controlling the specific surface area of ​​oxide particles within the above-mentioned range serves two purposes: firstly, it enhances their adhesion to the core; secondly, it provides a favorable environment for the deposition layer. Understandably, a larger specific surface area of ​​oxide particles allows for greater surface roughness, which, compared to a smooth surface, is more conducive to bonding with the core, thereby improving the structural stability of the pre-coated layer. Similarly, a rough outer surface reduces the difficulty of deposition layer formation, providing an excellent environment for the atomic deposition agent and facilitating deposition.

[0076] In one embodiment, the mass ratio of oxide particles to lubricant in the pre-coating layer of the lithium-supplementing material is 1:(0.1-0.8). Specifically, the mass ratio of oxide particles to lubricant can be, but is not limited to, 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, or 1:0.8. It should be noted that a higher amount of lubricant needs to be added during the preparation of the pre-coating layer of the lithium-supplementing material. This is because some lubricants, such as paraffin wax, will volatilize at high temperatures, while other lubricants, such as graphite, may be partially consumed during the preparation process. Preferably, the mass ratio of oxide particles to lubricant added during the preparation process is 1:(0.1-5). By controlling the ratio of oxide particles to lubricant, the uniformity of oxide particle coating on the outer surface of the core can be controlled. Understandably, when the lubricant ratio is lower than the above-mentioned ratio, insufficient lubrication will result in the easy accumulation of oxide particles, thus failing to form a relatively uniform pre-coating layer. When the lubricant ratio is higher than the above-mentioned ratio, lubricant accumulation will occur, meaning that some oxide particles will not be able to form a continuous deposition and cooperate with the deposition layer. At the same time, if a non-conductive lubricant (such as boron nitride) is used, when the lubricant ratio is high, the overall conductivity of the lithium supplementation material will be poor due to the lack of conductivity of the lubricant, making it difficult for lithium ions to be inserted or removed.

[0077] In one embodiment, the pre-coating layer includes a sub-coating layer (not shown in the figure), which can be formed from the lubricant described in the above embodiments, coating a portion of the outer surface of the core or the outer surface of the oxide particles. It is understood that when the proportion of lubricant approaches the upper limit in the above embodiments, some lubricant can interconnect to form the sub-coating layer. The advantage of this structure is that it not only further protects the core from external moisture erosion but also provides a conductive environment (such as graphite), increasing the lithium-ion insertion / extraction efficiency of the lithium-filling material.

[0078] In one embodiment, the mass ratio of the core, pre-coating layer, and deposited layer is 100:(0.01–10):(0.01–5). Specifically, the mass ratio of the core, pre-coating layer, and deposited layer can be, but is not limited to, 100:0.01:0.01, 100:0.01:5, 100:10:0.01, 100:5:3, 100:5:5, or 100:10:3. By controlling the mass ratio of the core, pre-coating layer, and deposited layer within a suitable range, not only can the thickness of the pre-coating layer and the deposited layer be adjusted to provide a good sealing environment, but the lithium-supplementing material can also maintain good electrochemical performance. When the proportion of the core is less than the above range, the pre-coating layer or the deposition layer has too high a weight. Since the pre-coating layer or the deposition layer does not contribute lithium ions, it will reduce the overall specific capacity of the lithium replenishment material. When the proportion of the core is greater than the above range, the pre-coating layer or the deposition layer has too low a weight. This may result in the pre-coating layer or the deposition layer being too thin or not fully coated, which is not conducive to creating a good sealing environment.

[0079] Preferably, the mass ratio of the core, pre-coating layer, and deposition layer is 100:(0.01-5):(0.01-3). More preferably, it is 100:(0.01-3):(0.01-1).

[0080] In one embodiment, the thickness A1 of the pre-coating layer is 1 nm to 200 nm. Specifically, the thickness A1 of the pre-coating layer can be, but is not limited to, 1 nm, 2 nm, 3 nm, 5 nm, 8 nm, 10 nm, 15 nm, 30 nm, 50 nm, 80 nm, 120 nm, 150 nm, and 200 nm. Understandably, the pre-coating layer is designed to create an environment for the deposition layer without affecting the efficiency of lithium-ion extraction from the core. Therefore, after ensuring that the pre-coating layer has a certain thickness suitable for deposition, excessive thickness should be avoided. A pre-coating layer thickness within the aforementioned range can satisfy deposition requirements without affecting lithium-ion extraction efficiency. When the thickness of the pre-coating layer is less than the aforementioned range, the particle size requirement for oxide particles is higher (requiring smaller particle size), increasing the difficulty of obtaining oxide particles and correspondingly increasing the difficulty of fabricating the pre-coating layer (increasing the small particle packing ratio). When the thickness of the pre-coating layer is greater than the aforementioned range, since the pre-coating layer does not contribute lithium ions, it will reduce the overall specific capacity of the lithium replenishment material.

[0081] In one embodiment, the thickness A2 of the deposited layer is 1 nm to 200 nm. Specifically, the thickness A2 of the deposited layer can be, but is not limited to, 1 nm, 2 nm, 3 nm, 5 nm, 8 nm, 10 nm, 15 nm, 30 nm, 50 nm, 80 nm, 120 nm, 150 nm, and 200 nm. The deposited layer is used to achieve a dense encapsulation, thereby protecting the core. A thickness of the deposited layer within the above range can ensure core protection without affecting lithium-ion extraction efficiency. When the thickness of the deposited layer is less than the above range, the requirements for atomic deposition are higher (higher precision), which is not conducive to improving the yield of the lithium replenishment material; when the thickness of the deposited layer is greater than the above range, since the deposited layer does not contribute lithium ions, it will reduce the overall specific capacity of the lithium replenishment material.

[0082] In one embodiment, the thicknesses of the pre-coating layer and the deposition layer satisfy the relationship: 1 ≤ A1 / A2 ≤ 40. Specifically, A1 / A2 can be, but is not limited to, 1, 2, 5, 8, 12, 20, 30, or 40. By controlling the thickness ratio of the pre-coating layer to the deposition layer within the above range, it is beneficial to control the thickness of the pre-coating layer or the deposition layer, thereby ensuring complete coverage of the pre-coating layer while avoiding an excessively thick deposition layer. When the ratio is less than the above range, it indicates that the pre-coating layer is too thin, increasing the difficulty of its fabrication; when the ratio is greater than the above range, it indicates that the deposition layer is too thin, which can easily lead to incomplete or weak coverage.

[0083] Secondly, this application also provides a method for preparing a lithium-supplementing material, please refer to... Figure 5 Specifically, it is used in the preparation of the lithium supplementation material in the first aspect. Its preparation method includes the following steps:

[0084] Step S10: The lithium source and the first metal source are uniformly mixed and then sintered together to obtain a lithium-rich compound.

[0085] Step S20: Deposit is placed on the outer layer of the lithium-rich compound to obtain a lithium-replenishing material.

[0086] The lithium replenishment material consists of a core and a deposition layer. The core contains lithium-rich compounds, and the deposits form the deposition layer. The density ρ1 of the deposition layer satisfies the relationship: 2 g / cm³. 3 ≤ρ1≤4.2g / cm 3 .

[0087] For details, please refer to Figure 6 Step S20 includes:

[0088] Step S21: After solid-phase mixing of lithium-rich compound and oxide particles, the mixture is treated at high temperature to obtain a first lithium replenishing material. The first lithium replenishing material includes a core containing lithium-rich compound and a pre-coating layer containing oxide particles, with the pre-coating layer covering the outer surface of the core.

[0089] Step S22: Deposits are placed on the outer surface of the first lithium replenishing material, and the deposits form a deposition layer to obtain the second lithium replenishing material.

[0090] Optionally, in step S10, the lithium-rich compound can be formed by co-sintering a lithium source and a first metal source, and the specific chemical formula can be as provided in the first aspect. The lithium source can be one or more of lithium oxide, lithium hydroxide, lithium acetate, lithium carbonate, lithium fluoride, and lithium chloride. Preferably, the first metal source can be an iron source, a manganese source, and a nickel source; the iron source can be one or more of ferric acetate, ferric nitrate, ferric sulfate, ferric hydroxide, ferric chloride, and ferric oxide. The manganese source can be one or more of manganese acetate, manganese nitrate, manganese monoxide, manganese sulfate, manganese hydroxide, and manganese dichloride. The nickel source can be one or more of nickel acetate, nickel nitrate, nickel oxide, nickel sulfate, nickel hydroxide, and nickel chloride. Preferably, the lithium source and the first metal source can be mixed in a liquid phase, and the solvent used can be one or more of methanol, glycerol, ethanol, and water.

[0091] Optionally, the oxygen content in the lithium-rich compound sintering environment needs to be controlled below 50 ppm to prevent Mn from entering the sintering environment. 2+ and Ni 2+ Oxidation. Therefore, it should be carried out under a protective atmosphere, specifically one or more of nitrogen, helium, argon, and neon.

[0092] Optionally, the oxide particles in step S21 may be those provided in the first aspect, which will not be elaborated here.

[0093] Optionally, a lubricant may also be added in step S21. The lubricant includes one or more of paraffin wax, graphite, boron nitride, silicone oil, glycerin, tetrabutyl titanate, propylene glycol, and molybdenum disulfide. It is understood that volatile lubricants such as paraffin wax will evaporate after high-temperature sintering and therefore will not remain in the lithium replenishment material, while non-volatile lubricants such as graphite and boron nitride will remain in the lithium replenishment material.

[0094] Optionally, the oxide particles and lubricant can be added in stages. For example, after mixing, the oxide particles and lubricant can be divided into three batches: batch one, batch two, and batch three, and these three batches are added to the lithium-rich compound sequentially. The first batch contains the largest amount of oxide particles and lubricant, with the amounts decreasing progressively towards the third batch. The advantage of this method is that it allows for a more uniform coating of the core by the oxide particles, avoiding particle accumulation that can occur with a single addition.

[0095] Optionally, in step S21, the temperature of the high-temperature treatment can be 400℃ to 700℃, and the time of the high-temperature treatment can be 1h to 6h.

[0096] Optionally, in step S22, the first lithium replenishment material can be placed in the reaction chamber of the atomic deposition equipment beforehand. The atomic deposition agent is first heated and vaporized to obtain a gaseous atomic deposition agent. Then, the gaseous atomic deposition agent is introduced in a pulsed manner to deposit the first lithium replenishment material, thereby obtaining the second lithium replenishment material. The second lithium replenishment material includes a core, a pre-coating layer, and a deposition layer. The specific structure of the lithium replenishment material in the first aspect can be referred to, and will not be elaborated here.

[0097] Optionally, in step S22, the atomic deposition agent includes one or more of trimethylaluminum, triethylaluminum, triisobutylaluminum, tetra(diethylamino)titanium, triethylsilane, tetraethylsilane, and tetra(ethylmethylamino)zirconium.

[0098] Optionally, in step S22, the temperature of the deposition environment is -10℃ to 200℃. Preferably, the temperature of the deposition environment is 50℃ to 150℃. Controlling the deposition environment within this temperature range results in a better coating effect after deposition. When the temperature is below the above range, the coating effect is poor; when the temperature is above the above range, the atomic deposition agent reacts too quickly, the deposition rate is difficult to control, and there is a certain degree of danger.

[0099] Thirdly, this application also provides a positive electrode sheet, which includes a current collector and an active material layer disposed on the current collector. The active material layer includes a positive electrode material and a lithium replenishment material as described in the first aspect, or the active material layer includes a lithium replenishment material obtained by a method for preparing a positive electrode material and a lithium replenishment material as described in the second aspect. The positive electrode sheet provided by this application, because it contains the aforementioned lithium replenishment material, and this lithium replenishment material can provide compensation for the active lithium ions consumed during the first charge of the battery due to the formation of the SEI film, effectively maintains the specific capacity of the positive electrode sheet and improves the capacity retention rate of the positive electrode sheet. Simultaneously, the lithium replenishment material can release lithium polysulfides to eliminate lithium plating, which not only maintains the performance of the positive electrode sheet but also improves its service life.

[0100] In one embodiment, the positive electrode sheet includes a positive current collector, and a positive active layer is formed on the positive current collector. The positive active layer includes components such as a positive electrode material, a conductive agent, and a binder. This application does not specifically limit these materials, and appropriate materials can be selected according to actual application requirements. The positive current collector includes, but is not limited to, any one of copper foil and aluminum foil. The positive active material can be a phosphate positive active material or a ternary positive active material. In specific embodiments, it includes one or more of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxide phosphate, lithium fluorinated vanadium phosphate, lithium titanate, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide. The conductive agent includes one or more of graphite, carbon black, acetylene black, graphene, carbon fiber, C60, and carbon nanotubes, and the content of the conductive agent in the positive active layer is 3wt%-5wt%. The types of binders include one or more of polyvinylidene chloride, soluble polytetrafluoroethylene, styrene-butadiene rubber, hydroxypropyl methylcellulose, methylcellulose, carboxymethylcellulose, polyvinyl alcohol, acrylonitrile copolymer, sodium alginate, chitosan and chitosan derivatives, and the content of the binder in the positive electrode active layer is 2wt%-4wt%.

[0101] In one embodiment, the content of the lithium replenishing material in the positive electrode material can be controlled at 1%-6% of the mass of the positive electrode active material. This ratio can precisely compensate for the loss of active lithium during the first charge of the battery. If the amount of lithium replenishing material added to the positive electrode is too low, the lost active lithium in the positive electrode material cannot be fully replenished, which is not conducive to improving the energy density and capacity retention of the battery. If the amount of lithium replenishing material added to the positive electrode material is too high, it may cause severe lithium plating on the negative electrode and increase costs. In some specific embodiments, the mass percentage of the lithium replenishing material in the positive electrode material can be 1%, 2%, 4%, 6%, etc.

[0102] Fourthly, this application also provides a secondary battery, which includes a negative electrode, a separator, and the aforementioned positive electrode.

[0103] In one embodiment, the secondary battery is a lithium-ion secondary battery.

[0104] This application embodiment involves a surface treatment process for the lithium replenishment material. Specifically, the surface of the lithium replenishment material is first pre-coated, followed by atomic layer deposition. This ensures the integrity and sealing of the encapsulation on the surface of the lithium replenishment material and effectively improves the density of the coating layer. The lithium replenishment material treated in this way exhibits a water absorption rate of less than 50 ppm / s, more preferably less than 10 ppm / s, in air at 25°C and 30-35% relative humidity; and a water absorption rate of less than 20 ppm / s, more preferably less than 5 ppm / s, in air at 25°C and 20-25% relative humidity. The lithium-ion battery assembled using this lithium replenishment material has an initial charge capacity greater than 500 mAh / g, more preferably greater than 600 mAh / g, and can even reach over 750 mAh / g.

[0105] The technical solution of the present invention will be described in detail below through specific embodiments.

[0106] Example 1

[0107] This embodiment provides a lithium replenishment material and its preparation method. The lithium replenishment material includes a core, a pre-coating layer, and a deposition layer. Please refer to... Figure 7 and Figure 8 The chemical formula of the lithium-rich compound is Li. 3.5 Fe 0.5 Ni 0.4 Mn 0.1 O3, the pre-coating layer is made of titanium dioxide, and the deposited layer is an alumina nanofilm.

[0108] The preparation method of this lithium supplement material includes the following steps:

[0109] (1) Weigh a certain amount of lithium hydroxide, iron acetate, nickel acetate and manganese acetate in a molar ratio of 3.5:0.5:0.4:0.1, add an appropriate amount of methanol solvent, mix in the liquid phase, and use sol-gel or co-precipitation method to prepare a precursor with a nanoscale porous structure.

[0110] (2) The precursor prepared in (1) was sintered in a nitrogen atmosphere for 7 h at a sintering temperature of 800 °C, with the oxygen content controlled below 50 ppm, to prepare Li. 3.5 Fe 0.5 Ni 0.4 Mn 0.1 O3 lithium-rich compounds.

[0111] (3) The lithium-rich compound prepared in (2) was sieved and classified, and lithium-rich compounds with a particle size D10 ≥ 2 μm were selected. The lithium-rich compound, fumed nano-sized titanium dioxide, and graphite were mixed in a solid phase at a mass ratio of 100:9:1. The mixture was then subjected to high-temperature treatment under a nitrogen atmosphere at 600℃ for 3 hours. This yielded the first lithium-replenishing material with a pre-coated core.

[0112] (3) The first lithium replenishing material prepared in (3) is placed in the reaction chamber of an atomic deposition apparatus. Trimethylaluminum is first heated and vaporized to obtain gaseous trimethylaluminum. Then, gaseous trimethylaluminum is introduced in a pulsed manner to deposit the first lithium replenishing material, thereby obtaining the second lithium replenishing material. The deposition temperature is 100℃.

[0113] In the second lithium replenishment material, the mass ratio of the core, the pre-coating layer and the deposition layer is 100:10:1, the thickness of the pre-coating layer is 200 nm, the particle size of titanium dioxide is 80 nm, and the thickness of the deposition layer is 40 nm.

[0114] Example 2

[0115] The lithium replenishment material provided in this embodiment differs from the lithium replenishment material in Example 1 only in that the mass ratio of the core, pre-coating layer, and deposition layer in the lithium replenishment material provided in this embodiment is 100:10:5, the thickness of the pre-coating layer is 200nm, the particle size of titanium dioxide is 80nm, and the thickness of the deposition layer is 200nm.

[0116] Example 3

[0117] The lithium replenishment material provided in this embodiment differs from the lithium replenishment material in Example 1 only in that the mass ratio of the core, pre-coating layer, and deposition layer in the lithium replenishment material provided in this embodiment is 100:10:3, the thickness of the pre-coating layer is 200nm, the particle size of titanium dioxide is 80nm, and the thickness of the deposition layer is 120nm.

[0118] Example 4

[0119] The lithium replenishment material provided in this embodiment differs from the lithium replenishment material in Example 1 only in that the titanium dioxide particle size in the pre-coating layer in this embodiment is 40 nm.

[0120] Example 5

[0121] The lithium replenishment material provided in this embodiment differs from the lithium replenishment material in Example 1 only in that the titanium dioxide particle size in the pre-coating layer in this embodiment is 60 nm.

[0122] Example 6

[0123] The lithium replenishment material provided in this embodiment differs from the lithium replenishment material in Example 1 only in that the deposition layer in this embodiment is an alumina nanofilm layer.

[0124] Example 7

[0125] The lithium replenishment material provided in this embodiment differs from the lithium replenishment material in Embodiment 1 only in that the lithium replenishment material in this embodiment includes a core and a deposition layer, but does not contain a pre-coating layer.

[0126] Comparative Example 1

[0127] The lithium replenishment material provided in this comparative example differs from the lithium replenishment material in Example 1 only in that the lithium replenishment material in this comparative example does not contain a pre-coating layer or a deposition layer.

[0128] Comparative Example 2

[0129] The lithium replenishment material provided in this comparative example differs from the lithium replenishment material in Example 1 only in that the lithium replenishment material in this example includes a core and a coating layer, but does not contain a deposition layer, and the coating layer is a carbon layer.

[0130] Test 1:

[0131] The lithium replenishing materials provided in Examples 1 to 7 and the lithium replenishing materials provided in Comparative Examples 1 to 2 were subjected to water absorption tests according to the following methods:

[0132] (1) Control the ambient temperature of the experimental chamber at 25℃ and the relative humidity at 20%-25% or 30%-35%.

[0133] (2) Weigh the same mass of the sample to be tested into a container and spread the sample to increase the contact area. Place the container together with the sample on the analytical balance. After the reading stabilizes, turn on the timer and record the mass of the analytical balance as the value of 0 min.

[0134] (3) Then, record the values ​​displayed by the analytical balance at 5 min, 10 min, 15 min and 20 min respectively, and calculate the average absorption data from 10 min to 20 min.

[0135] The formula for calculating the water absorption rate of lithium supplementation materials is as follows:

[0136] V = (W t2 -W t1 ) / (W0·(T2-T1)); Unit: ppm / s

[0137] Where W0 is the initial weight of the sample to be tested, W t1 W is the weight at T1 (10 min). t2 The weight is T2 (20 min).

[0138] Test 2:

[0139] The lithium replenishment materials provided in Examples 1 to 7 and the lithium replenishment materials provided in Comparative Examples 1 and 2 were assembled into positive electrodes and lithium-ion batteries respectively according to the following methods:

[0140] Positive electrode: The lithium supplement material, SP and PVDF are mixed in a mass ratio of 90:4:6 to form a positive electrode slurry. The positive electrode slurry is coated on the surface of aluminum foil, vacuum dried at 110°C overnight, and rolled to obtain a positive electrode sheet.

[0141] Negative electrode: Lithium foil;

[0142] Electrolyte: Ethyl carbonate and ethyl methyl carbonate are mixed in a volume ratio of 3:7, and LiPF6 is added to form an electrolyte with a concentration of 1 mol / L.

[0143] Diaphragm: Polypropylene microporous diaphragm;

[0144] Lithium-ion battery assembly: Assemble button-type lithium-ion full cells in an inert atmosphere glove box according to the assembly sequence of graphite negative electrode sheet - separator - electrolyte - positive electrode sheet.

[0145] The electrochemical performance of each lithium-ion battery assembled in the above lithium-ion battery examples was tested under the following conditions:

[0146] Constant current and constant voltage charging, first charge / discharge voltage 2.5-4.3V, current 0.1C, cut-off current 0.01C.

[0147] The test results of the above-mentioned lithium replenishment materials and lithium-ion batteries are shown in Table 1 below:

[0148] Table 1

[0149]

[0150]

[0151] From the SEM and TEM images of Example 1 ( Figure 7 and Figure 8 As can be seen, the method provided in this application can achieve good coating of lithium-rich compounds. Among them, Figure 7 The SEM image shows the lithium replenishment material with only a pre-coating layer. Its outer surface is relatively rough, which provides a good environment for the subsequent coating and deposition layer. Moreover, since the pre-coating layer provides more attachment sites for the deposition layer, a more uniform coating effect can be achieved. Figure 8 The TEM image shows the state of the lithium-supplementing material coated with the deposited layer, where A is the core, B is the pre-coating layer, and C is the deposited layer. The image shows that the pre-coating layer and the deposited layer achieve uniform and complete coating of the core, thus concluding that pre-setting a pre-coating layer is beneficial for improving the uniformity of the deposited layer.

[0152] As can be seen from the test results of Examples 1 and 7 and Comparative Example 1 in Table 1, the water absorption rate of the lithium replenishment material coated with the deposition layer is significantly reduced, while maintaining high electrochemical performance. Furthermore, the use of a pre-coating layer further enhances the water absorption resistance of the lithium replenishment material, demonstrating that the pre-coating layer improves the coating effect of the deposition layer. Therefore, the lithium replenishment material provided in this application has a longer shelf life and exhibits superior product performance after storage.

[0153] As can be seen from the test results of Example 1 and Comparative Example 2 in Table 1, the lithium replenishment material with only a pre-coating layer cannot achieve high water absorption resistance, that is, the pre-coating layer cannot provide dense protection for the core. Therefore, it is necessary to combine the pre-coating layer with the deposition layer to obtain a lithium replenishment material with high water absorption resistance.

[0154] As can be seen from the test results of Examples 1-3 in Table 1, the thickness of the deposited layer is directly related to the water absorption resistance of the lithium replenishment material. The greater the thickness of the deposited layer (or the larger the mass percentage of the deposited layer), the lower the water absorption rate (and the stronger the water absorption resistance). However, the thickness of the deposited layer is inversely proportional to the capacity of the secondary battery; this is because a thicker deposited layer creates a stronger barrier to lithium-ion release, leading to a decrease in the electrical performance of the secondary battery. Therefore, in industrial production, the thickness of the deposited layer can be appropriately adjusted according to the required storage time of the lithium replenishment material or the required electrochemical performance of the lithium replenishment material.

[0155] As can be seen from the test results of Examples 1 and 4-5 in Table 1, the size of the nano-oxide particles used in the pre-coating layer is also related to the water absorption resistance of the lithium replenishment material. Specifically, the smaller the particle size of the nano-oxide particles, the better the water absorption resistance of the lithium replenishment material.

[0156] As can be seen from the test results of Examples 1 and 6 in Table 1, the solution provided in this application can be applied to deposition layers composed of different materials.

[0157] In the description of the embodiments of this application, it should be noted that the orientation or positional relationship of the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and other indicators are based on the orientation or positional relationship of the drawings, and are only for the convenience of describing this application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0158] The above-disclosed embodiments are merely preferred embodiments of this application and should not be construed as limiting the scope of this application. Those skilled in the art will understand that all or part of the processes for implementing the above embodiments and equivalent variations made in accordance with the claims of this application are still within the scope of this application.

Claims

1. A lithium supplementing material, characterized by, include: The core, including lithium-rich compounds; A deposition layer, covering the outer layer of the core, wherein the deposition layer is a film layer of nanometer scale or below, and the material of the deposition layer is one or more of alumina, silicon dioxide, titanium dioxide, and zirconium dioxide; The lithium replenishment material further includes a pre-coating layer, which coats the outer surface of the core, and the deposition layer coats the outer surfaces of the core and the pre-coating layer; the pre-coating layer includes mixed oxide particles and a lubricant, and the lubricant includes one or more of paraffin wax, graphite, boron nitride, silicone oil, glycerin, tetrabutyl titanate, propylene glycol, and molybdenum disulfide.

2. The lithium replenishment material according to claim 1, characterized in that, The deposition layer comprises a monatomic deposition layer and / or an oxide nanofilm layer obtained by atomic layer deposition technology; and / or, the density p1 of the deposition layer satisfies the relationship: 2 g / cm 3 ≤ p1 ≤ 4.2 g / cm 3 . 3.The lithium supplementing material of claim 1, wherein, The lithium replenishment material also includes a carbon layer, which coats the outer layer of the deposited layer; And / or, the core is a secondary particle, the secondary particle comprising a plurality of primary particles, with deposits between the primary particles in the secondary particle.

4. The lithium replenishment material according to claim 1, characterized in that, The density ρ2 of the pre-coated layer satisfies the following relationship: 1.5 g / cm³ 3 ≤ρ2≤3g / cm 3 ; And / or, the density of the deposited layer is greater than the density of the pre-coating layer; And / or, the particle size D10 of the kernel satisfies the relationship: D10≥2μm; and / or the specific surface area S1 of the core satisfies the relationship: S1 < 3m 2 / g.

5. The lithium replenishment material according to claim 1, characterized in that, The pre-coating layer has gaps, and at least part of the deposited layer fills the gaps; And / or, at least part of the deposited layer directly covers the outer surface of the core.

6. The lithium replenishment material according to claim 1, characterized in that, The mass ratio of the oxide particles to the lubricant is 1:(0.1~0.8). And / or, the particle size d of the oxide particles is 1 nm to 100 nm; and / or the specific surface area S2 of the oxide particles satisfies the relationship: S2≥ 50 m2 / g. 2 / g.

7. The lithium replenishment material according to claim 1, characterized in that, The mass ratio of the core, the pre-coating layer, and the deposition layer is 100:(0.01~10):(0.01~5). And / or, the thickness A1 of the pre-coating layer is 1 nm to 200 nm; And / or, the thickness A2 of the deposited layer is 1 nm to 200 nm; And / or, the thicknesses of the pre-coating layer and the deposited layer satisfy the relationship: 1≤A1 / A2≤40.

8. A method for preparing a lithium supplement material, characterized in that, The preparation method is used to prepare the lithium supplementation material as described in any one of claims 1-7, comprising: The lithium source and the first metal source are uniformly mixed and then sintered together to obtain a lithium-rich compound. A deposit is disposed on the outer layer of the lithium-rich compound to obtain a lithium-replenishing material; the lithium-replenishing material includes a core and a deposition layer, the core including the lithium-rich compound, and the deposit forming the deposition layer.

9. A positive electrode sheet characterized by comprising: The positive electrode includes a current collector and an active material layer disposed on the current collector, the active material layer including a positive electrode material and a lithium supplement material as described in any one of claims 1-7; or, the active material layer includes a positive electrode material and a lithium supplement material obtained by the preparation method of the lithium supplement material as described in claim 8.

10. A secondary battery characterized by comprising: The secondary battery includes a negative electrode, a separator, and a positive electrode as described in claim 9.

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