A lithium supplement and its preparation method and application

Abstract

The present invention provides a lithium supplement agent and a preparation method and application thereof, wherein the lithium supplement agent includes lithium oxalate, a carbon material, a catalyst and a modifier, wherein the modifier includes at least one of a fast ion conductor and / or a lithium affinity agent; wherein the mass ratio of lithium oxalate, the carbon material, the catalyst and the modifier is (70-95): (2.5-14): (2.5-14): (0.1-1). Through the synergistic effect of lithium oxalate, the carbon material, the catalyst and the modifier, the initial decomposition voltage and the average decomposition voltage of lithium oxalate are significantly reduced, and the lithium supplement effect of lithium oxalate is improved. wherein, the addition of a fast ion conductor and / or a lithium affinity agent can assist in reducing the initial decomposition voltage of lithium oxalate, so that lithium ions can be released from lithium oxalate faster, accelerate the migration of lithium ions on the surface of the electrode material, and reduce the internal resistance. The lithium supplement agent provided by the present invention has high electrochemical activity, a decomposition voltage as low as 4.14V, and a large specific surface area, and can be in good contact with the electrode material and the electrolyte.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a lithium supplement agent and a preparation method and application thereof. Background Art

[0002] Pre-lithiation technology plays an important role in the development of lithium-ion batteries with high energy density and long cycle life. At present, pre-physical and chemical technologies are mainly divided into positive electrode and negative electrode pre-lithiation. Compared with positive electrode pre-lithiation, negative electrode pre-lithiation faces the problems of high reaction activity and poor stability of active lithium sources. However, the lithium sources of positive electrode lithium replenishment reagents such as Li3P, Li2S and Li5FeO4 also have reaction residues and poor stability in humid air, which seriously limits their application scenarios and scale. Therefore, the development direction of positive electrode lithium replenishers is low reaction residue, high lithium replenishment capacity and high air stability.

[0003] After lithium oxalate (Li2C2O4) is completely decomposed in the battery, the product is carbon dioxide (CO2). During the battery formation process, CO2 can be completely discharged from the battery system to achieve no residue. In addition, lithium oxalate has high air stability and safety. Therefore, the characteristics of no residue, high capacity and high air stability make lithium oxalate an ideal lithium supplement.

[0004] However, the actual decomposition potential of unmodified lithium oxalate is as high as 4.7 V, which severely limits its application as a positive electrode lithium supplement additive. Therefore, it is urgent to provide a modified lithium oxalate lithium supplement agent to solve the problems of high decomposition voltage, low decomposition efficiency and small application range of lithium oxalate in the prior art. Summary of the invention

[0005] The technical problems to be solved by the present invention are that lithium oxalate has high decomposition voltage, low decomposition efficiency, and small application range.

[0006] In order to solve the above problems, the present invention provides a lithium supplement agent, which includes lithium oxalate, a carbon material, a catalyst and a modifier, and the modifier includes at least one of a fast ion conductor and / or a lithium-philic agent; wherein the mass ratio of lithium oxalate, carbon material, catalyst and modifier is (70-95): (2.5-14): (2.5-14): (0.1-1).

[0007] The lithium supplement provided by the present invention comprises lithium oxalate, a carbon material, a catalyst and a modifier, wherein lithium oxalate is used as a core component of the lithium supplement and is used in a battery to supplement active lithium ions consumed when forming an SEI film, thereby improving the cycle performance and energy density of the battery; the carbon material is used to improve the conductivity and structural stability of the electrode, which helps the battery maintain performance during the charge and discharge process; the catalyst can reduce the reaction activation energy, thereby reducing the initial decomposition voltage of lithium oxalate and accelerating the decomposition reaction of lithium oxalate; the modifier comprises a fast ion conductor and / or a lithium affinity agent, and the modifier can significantly increase the migration rate of lithium ions on the surface of the lithium supplement and accelerate the release of lithium ions, thereby optimizing the transmission efficiency of lithium ions.

[0008] Through the synergistic effect of lithium oxalate, carbon material, catalyst and modifier, the present invention can be applied to batteries to significantly improve the energy density and cycle life of the battery. The addition of fast ion conductors and / or lithium affinity agents allows lithium ions to escape from the surface of lithium oxalate materials more quickly, thereby increasing the migration rate of lithium ions, thereby reducing the decomposition voltage of lithium oxalate and making the decomposition faster.

[0009] In any of the above technical solutions, the lithium supplement agent is a hollow spherical particle, and some of the particles have a hollow rupture structure.

[0010] Hollow spherical particles refer to the hollow spherical structure formed during the preparation of the lithium supplement. This structure makes the particles physically have a lower density and a larger specific surface area, allowing them to better contact with the electrode material. The rupture or collapse of the hollow spherical particles increases the contact area with the electrode material and the wettability of the electrolyte, which can provide a better lithium supplement effect.

[0011] In any of the above technical solutions, the proportion of particles with hollow fracture structures to the total number of particles is 10%-99%.

[0012] Particles with hollow fracture structures have a higher proportion, which can increase the surface area and porosity of the material, thereby increasing the contact area with the electrode material and the wettability of the electrolyte, thereby improving the lithium replenishment effect of the lithium replenisher.

[0013] In any of the above technical solutions, the specific surface area of ​​the lithium supplement is 60m 2 / g-170m 2 / g.

[0014] The lithium supplement agent provided by the present invention has a hollow rupture structure, which enables the lithium supplement agent to have a higher specific surface area, which not only increases the contact area with the electrode material, but also improves the wettability with the electrolyte, thereby ensuring a better lithium supplement effect.

[0015] In any of the above technical solutions, the fast ion conductor includes Li4Ti5O 12, Li3PO4, Li2Zr2(PO4)3, LiPO2F2, LiF, LiNO3, LiAlO2; and / or the lithium-philic agent includes at least one of Si, S, P; and / or the catalyst includes at least one of a transition metal element and a transition metal compound; and / or the carbon material includes at least one of Ketjen black, Super-P conductive carbon black, CNTs, redox graphene, polyvinyl pyrrolidone, and tannic acid.

[0016] Fast ion conductors have excellent ion transport capabilities and structural stability. When added in appropriate amounts, they can improve the surface conductivity of the material and accelerate the release of lithium ions without reducing the performance of the material itself. LiPO2F2 has a three-dimensional structure in the crystal structure. Free lithium ions can diffuse freely in multiple directions in three-dimensional space, further enriching the diffusion path of lithium ions and reducing impedance, thereby achieving the purpose of reducing the decomposition voltage of lithium oxalate and promoting the decomposition of lithium oxalate; Li4Ti5O 12 As a fast ion conductor, it can not only improve the conductivity, but also has the characteristic of "zero strain". + When the lattice constant and volume change of the crystal are very small, it can stably promote the decomposition reaction of lithium oxalate, and its chemical properties are stable and it does not react with the electrolyte.

[0017] Transition metals, such as iron, cobalt, and nickel, can effectively catalyze a variety of chemical reactions due to their unique electronic structure and variable oxidation state. The use of transition metal catalysts can significantly increase the rate of chemical reactions, allowing reactions to be completed quickly under milder conditions, thereby saving energy and time. Transition metal compounds show high efficiency and specific activity in catalyzing specific types of reactions, such as molybdenum trioxide and cobalt oxide, which have high chemical reactivity and selectivity.

[0018] Ketjen black (KB) is a highly structured conductive carbon black with high specific surface area and conductivity. Super-P conductive carbon black is an ultrafine carbon black with excellent conductivity and stability. Carbon nanotubes (CNTs) have ultra-high strength and conductivity and are used to strengthen conductive channels in composite materials and electronic devices. Redox graphene has a unique two-dimensional structure and excellent electronic conductivity. Polyvinyl pyrrolidone (PVP) is added as a stabilizer and dispersant together with other carbon sources to improve the processability and compatibility of the material and reduce agglomeration. Tannic acid has an excellent coating effect. Under neutral conditions, it can be immediately coated on the surface of the material, and can achieve controllable and uniform coating of the material. The above carbon materials can provide excellent conductivity and thermal stability, and improve the overall performance of the final product.

[0019] The present invention also provides a method for preparing a lithium supplement, which is used to prepare the lithium supplement as described above, and the preparation method comprises the following steps: S100: dissolving lithium oxalate, and then adding a carbon material, a catalyst and a modifier to obtain a mixed solution; S200: sequentially performing ultrasonic dispersion, spray drying and crushing on the mixed solution to obtain a lithium supplement; wherein the mass fraction of lithium oxalate in the mixed solution is 1%-5.5%.

[0020] The present invention provides a preparation method for preparing a lithium supplement agent, firstly dissolving lithium oxalate in a suitable solvent, then adding a carbon material, a catalyst and a modifier, this step is intended to reduce the initial decomposition voltage and the average decomposition voltage of lithium oxalate by adding the modifier, and at the same time improve the lithium supplement effect of lithium oxalate. Then, the obtained mixed solution is ultrasonically dispersed to ensure that the components in the mixture are evenly distributed. After that, the solution is converted into a powder by spray drying technology, and finally crushed to obtain a fine-grained lithium supplement agent.

[0021] In the preparation method, the content of lithium oxalate is controlled at a mass fraction of 1%-5.5%. By reducing the concentration of lithium oxalate in the slurry, the lithium supplement particles after spray drying have an irregular spherical shape and form a hollow structure. The hollow structure increases the specific surface area of ​​the material, allowing the material to better contact with the electrode material.

[0022] In any of the above technical solutions, the treatment time of ultrasonic dispersion is 1.5h-2.5h; and / or the inlet air temperature of spray drying is 200℃-260℃; and / or the feed rate of spray drying is 35r / min-45r / min.

[0023] In this embodiment, the processing time of ultrasonic dispersion is set between 1.5h-2.5h to achieve the optimal dispersion effect of each component in the solution and avoid the degradation of material performance that may be caused by excessive processing. The inlet air temperature of the spray drying is set between 200℃-260℃. This temperature range is determined based on the comprehensive consideration of the thermal stability of the chemical substances involved and the spray drying efficiency to ensure that the material maintains chemical and structural integrity during the conversion into dry powder. The feed rate of spray drying is set to 35r / min-45r / min, which helps to ensure uniform drying of the material and avoid agglomeration while maintaining high efficiency. The special preparation technology spray drying process is used so that the generated lithium supplement particles have a hollow structure, which not only increases the contact area with the electrode material, but also improves the wettability with the electrolyte.

[0024] The present invention also provides a positive electrode material, which includes the lithium supplement agent as described above.

[0025] The present invention also provides a lithium ion battery, which comprises a positive electrode sheet, a separator and a negative electrode sheet, wherein the positive electrode sheet comprises the positive electrode material as described above.

[0026] After adopting the technical solution of the present invention, the following technical effects can be achieved:

[0027] The lithium supplement provided by the present invention comprises lithium oxalate, a carbon material, a catalyst and a modifier. Through the synergistic effect of lithium oxalate, the carbon material, the catalyst and the modifier, the initial decomposition voltage and the average decomposition voltage of lithium oxalate are significantly reduced, and the lithium supplement effect of lithium oxalate is improved. Among them, the addition of a fast ion conductor and / or a lithium affinity agent can help reduce the initial decomposition voltage of lithium oxalate, so that lithium ions can be released from lithium oxalate faster, accelerate the migration of lithium ions on the surface of the electrode material, and reduce the internal resistance. The lithium supplement provided by the present invention has high electrochemical activity, a decomposition voltage as low as 4.14V, and a large specific surface area, and can be in good contact with the electrode material and the electrolyte. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0029] Figure 1 This is an electron microscope image of the lithium supplement provided in Example 1 of the present invention;

[0030] Figure 2 This is an electron microscope image of the lithium supplement provided in Example 3 of the present invention;

[0031] Figure 3 This is an electron microscope image of the lithium supplement provided in Example 4 of the present invention. DETAILED DESCRIPTION

[0032] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only 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 creative work are within the scope of protection of the present invention.

[0033] An embodiment of the present invention provides a lithium supplement, which includes lithium oxalate, a carbon material, a catalyst and a modifier, wherein the modifier includes at least one of a fast ion conductor and / or a lithium-philic agent; wherein the mass ratio of lithium oxalate, the carbon material, the catalyst and the modifier is (70-95): (2.5-14): (2.5-14): (0.1-1).

[0034] The lithium supplement provided by the present invention comprises lithium oxalate, a carbon material, a catalyst and a modifier, wherein lithium oxalate is used as a core component of the lithium supplement and is used in a battery to supplement active lithium ions consumed when forming an SEI film, thereby improving the cycle performance and energy density of the battery; the carbon material is used to improve the conductivity and structural stability of the electrode, which helps the battery maintain performance during the charge and discharge process; the catalyst can reduce the reaction activation energy, thereby reducing the initial decomposition voltage of lithium oxalate and accelerating the decomposition reaction of lithium oxalate; the modifier comprises a fast ion conductor and / or a lithium affinity agent, and the modifier can significantly increase the migration rate of lithium ions on the surface of the lithium supplement and accelerate the release of lithium ions, thereby optimizing the transmission efficiency of lithium ions.

[0035] Through the synergistic effect of lithium oxalate, carbon material, catalyst and modifier, the present invention can be applied to batteries to significantly improve the energy density and cycle life of the battery. The addition of fast ion conductors and / or lithium affinity agents allows lithium ions to escape from the surface of lithium oxalate materials more quickly, thereby increasing the migration rate of lithium ions, thereby reducing the decomposition voltage of lithium oxalate and making the decomposition faster.

[0036] In some embodiments of the present application, the lithium supplement is a hollow spherical particle, and some of the particles have a hollow fracture structure.

[0037] Hollow spherical particles refer to the hollow spherical structure formed by the lithium supplement during the preparation process. This structure makes the particles physically have a lower density and a larger specific surface area, so that they can better contact with the electrode material. The rupture or collapse of the hollow spherical particles increases the contact area with the electrode material and the wettability of the electrolyte, which can better provide the lithium supplement effect. It should be noted that the spherical structure of the particles is irregular in shape.

[0038] In some embodiments of the present application, the number of particles having a hollow fracture structure accounts for 10%-99% of the total number of particles.

[0039] Particles with hollow fracture structures have a higher proportion, which can increase the surface area and porosity of the material, thereby increasing the contact area with the electrode material and the wettability of the electrolyte, thereby improving the lithium replenishment effect of the lithium replenisher.

[0040] It should be noted that the statistical method for the crushing ratio of lithium supplement particles is to compare them with uncrushed materials, count the number of crushed materials and the number of uncrushed materials, and the ratio of the number of crushed materials to the sum of the number of crushed materials and the number of uncrushed materials is the crushing ratio; among them, the number of crushed materials is the number of crushed materials observed from the electron microscope image, and the number of uncrushed materials is the number of uncrushed materials observed from the electron microscope image. Each group is counted three times and the average value is taken.

[0041] In some embodiments of the present application, the specific surface area of ​​the lithium supplement is 60 m 2 / g-170m 2 / g.

[0042] The lithium supplement agent provided by the present invention has a hollow rupture structure, which enables the lithium supplement agent to have a higher specific surface area, which not only increases the contact area with the electrode material, but also improves the wettability with the electrolyte, thereby ensuring a better lithium supplement effect.

[0043] In some embodiments of the present application, the fast ion conductor includes Li4Ti5O 12 , Li3PO4, Li2Zr2(PO4)3, LiPO2F2, LiF, LiNO3, LiAlO2; and / or the lithium-philic agent includes at least one of Si, S, P; and / or the catalyst includes at least one of a transition metal element and a transition metal compound; and / or the carbon material includes at least one of Ketjen black, Super-P conductive carbon black, CNTs, redox graphene, polyvinyl pyrrolidone, and tannic acid.

[0044] Fast ion conductors have excellent ion transport capabilities and structural stability. When added in appropriate amounts, they can improve the surface conductivity of the material and accelerate the release of lithium ions without reducing the performance of the material itself. LiPO2F2 has a three-dimensional structure in the crystal structure. Free lithium ions can diffuse freely in multiple directions in three-dimensional space, further enriching the diffusion path of lithium ions and reducing impedance, thereby achieving the purpose of reducing the decomposition voltage of lithium oxalate and promoting the decomposition of lithium oxalate; Li4Ti5O 12 As a fast ion conductor, it can not only improve the conductivity, but also has the characteristic of "zero strain". + When the lattice constant and volume change of the crystal are very small, it can stably promote the decomposition reaction of lithium oxalate, and its chemical properties are stable and it does not react with the electrolyte.

[0045] Transition metals, such as iron, cobalt, and nickel, can effectively catalyze a variety of chemical reactions due to their unique electronic structure and variable oxidation state. The use of transition metal catalysts can significantly increase the rate of chemical reactions, allowing reactions to be completed quickly under milder conditions, thereby saving energy and time. Transition metal compounds show high efficiency and specific activity in catalyzing specific types of reactions, such as molybdenum trioxide, cobalt oxide, etc. Molybdenum trioxide is preferred because of its high chemical reactivity and selectivity.

[0046] Ketjen black (KB) is a highly structured conductive carbon black with high specific surface area and conductivity. Super-P conductive carbon black is an ultrafine carbon black with excellent conductivity and stability. Carbon nanotubes (CNTs) have ultra-high strength and conductivity and are used to strengthen conductive channels in composite materials and electronic devices. Redox graphene has a unique two-dimensional structure and excellent electronic conductivity. Polyvinyl pyrrolidone (PVP) is added as a stabilizer and dispersant together with other carbon sources to improve the processability and compatibility of the material and reduce agglomeration. Tannic acid has an excellent coating effect. Under neutral conditions, it can be immediately coated on the surface of the material, and can achieve controllable and uniform coating of the material. The above carbon materials can provide excellent conductivity and thermal stability, and improve the overall performance of the final product.

[0047] An embodiment of the present invention further provides a method for preparing a lithium supplement, which is used to prepare the lithium supplement as described above, and the preparation method comprises the following steps: S100: dissolving lithium oxalate, and then adding a carbon material, a catalyst and a modifier to obtain a mixed solution; S200: sequentially performing ultrasonic dispersion, spray drying and crushing on the mixed solution to obtain a lithium supplement; wherein the mass fraction of lithium oxalate in the mixed solution is 1%-5.5%.

[0048] The present invention provides a preparation method for preparing a lithium supplement agent, firstly dissolving lithium oxalate in a suitable solvent, then adding a carbon material, a catalyst and a modifier, this step is intended to reduce the initial decomposition voltage and the average decomposition voltage of lithium oxalate by adding the modifier, and at the same time improve the lithium supplement effect of lithium oxalate. Then, the obtained mixed solution is ultrasonically dispersed to ensure that the components in the mixture are evenly distributed. After that, the solution is converted into a powder by spray drying technology, and finally crushed to obtain a fine-grained lithium supplement agent.

[0049] The atomizer used in the spray drying process is a centrifugal or two-fluid atomizer, and the preferred atomizer is a two-fluid atomizer. The droplets are transported to the atomizer cavity by high-pressure airflow, and the droplets evaporate instantly under high temperature conditions to obtain dry solid particles. The lithium supplement particles obtained under the airflow have a hollow rupture or collapsed structure. Crushing treatment includes but is not limited to steel mills, juicers, rollers, etc.

[0050] In the preparation method, the content of lithium oxalate is controlled at a mass fraction of 1%-5.5%. By reducing the concentration of lithium oxalate in the slurry, the lithium supplement particles after spray drying have an irregular spherical shape and form a hollow structure. The hollow structure increases the specific surface area of ​​the material, allowing the material to better contact with the electrode material.

[0051] In some embodiments of the present application, the treatment time of ultrasonic dispersion is 1.5h-2.5h; and / or the inlet air temperature of spray drying is 200℃-260℃; and / or the feed rate of spray drying is 35r / min-45r / min.

[0052] In this embodiment, the processing time of ultrasonic dispersion is set between 1.5h-2.5h to achieve the optimal dispersion effect of each component in the solution and avoid the degradation of material performance that may be caused by excessive processing. The inlet air temperature of the spray drying is set between 200℃-260℃. This temperature range is determined based on the comprehensive consideration of the thermal stability of the chemical substances involved and the spray drying efficiency to ensure that the material maintains chemical and structural integrity during the conversion into dry powder. The feed rate of spray drying is set to 35r / min-45r / min, which helps to ensure uniform drying of the material and avoid agglomeration while maintaining high efficiency. The special preparation technology spray drying process is used so that the generated lithium supplement particles have a hollow structure, which not only increases the contact area with the electrode material, but also improves the wettability with the electrolyte.

[0053] By precisely controlling the time of ultrasonic dispersion and the temperature and speed of spray drying, the uniformity and performance stability of the final lithium supplement can be maximized. By controlling the parameters of these key process steps, the optimal performance of the lithium supplement in the battery can be ensured, thereby improving the energy density and cycle life of the battery.

[0054] An embodiment of the present invention further provides a positive electrode material, which includes the lithium supplement agent as described above.

[0055] An embodiment of the present invention further provides a lithium-ion battery, which includes a positive electrode sheet, a separator and a negative electrode sheet, wherein the positive electrode sheet includes the positive electrode material as described above.

[0056] The positive electrode sheet can be prepared by conventional technical means in the art. Specifically, the above-mentioned lithium oxalate lithium supplement, positive electrode active material, conductive agent, and binder can be uniformly dispersed in a solvent to obtain a positive electrode active layer slurry, and then the positive electrode active layer slurry is coated on at least one functional surface of the positive electrode collector. After drying, the positive electrode sheet of the present invention can be obtained. In addition to the positive electrode sheet, the lithium ion battery of the present invention also includes a diaphragm, a negative electrode sheet, and an electrolyte. Among them, the composition of the negative electrode sheet can refer to the conventional negative electrode sheet in the art, and the diaphragm can also use the diaphragm conventionally used in the art, such as PP film, PE film, etc.

[0057] An embodiment of the present invention further provides a method for preparing a lithium-ion battery, which is used to prepare the lithium-ion battery as described above, and comprises the following steps: stacking a positive electrode sheet, a separator, and a negative electrode sheet in sequence, and packaging them to obtain a lithium-ion battery.

[0058] The lithium-ion battery of the present invention can be prepared by conventional methods in the art. Specifically, the positive electrode sheet, the separator and the negative electrode sheet can be stacked in sequence, and then a battery cell can be obtained through a stacking or winding process, and then the above-mentioned lithium-ion battery can be obtained through baking, liquid injection, formation, packaging and other processes.

[0059] Example 1

[0060] S1, 80g lithium oxalate, 9.5g molybdenum trioxide, 0.5g LiPO2F2, 10g Ketjen black were added to water, wherein the mass fraction of lithium oxalate in the above mixed solution was 1wt%, and ultrasonic equipment was turned on for ultrasonic dispersion for 1 h to form a uniformly mixed suspension;

[0061] S2. Drying is performed using a spray drying device, which is a two-fluid atomizer. The inlet air temperature of the spray drying is 240°C and the feed speed is 40r / min.

[0062] S3. After spraying, the mixture is crushed and then vacuum dried at 200° C. to obtain a modified lithium oxalate lithium supplement.

[0063] Examples 2-28 and Comparative Examples 1-5 adopted the same preparation method as Example 1, and the differences are shown in Table 1.

[0064] Test conditions: The prepared lithium oxalate lithium supplement was subjected to constant current and constant voltage charging test of button half-cell, with a test current of 0.1C (nominal capacity 525mAh / g), a cut-off voltage of 4.35V, and a constant voltage cut-off current of 0.05C. The obtained charge specific capacity is the decomposition capacity of lithium oxalate, and the starting decomposition voltage is read from the charging curve. The obtained average charging voltage is the average decomposition voltage of lithium oxalate. See Table 1 for specific test results.

[0065] Table 1 Preparation parameters and test results of Examples 1-28 and Comparative Examples 1-5

[0066]

[0067]

[0068]

[0069] Table 2 Crushing ratio and specific surface area test results of Examples 1-28 and Comparative Examples 1-5

[0070]

[0071] Figure 1 This is an electron microscope image of the lithium supplement provided in Example 1; Figure 2 This is an electron microscope image of the lithium supplement provided in Example 3; Figure 3This is an electron microscope image of the lithium supplement provided in Example 4.

[0072] According to the comparison of Examples 1-4, during the preparation process, by reducing the concentration of lithium oxalate in the feed solution, the particles of the lithium supplement agent have irregular spherical shapes, and after crushing, a hollow fracture structure is formed. As the concentration decreases from 5.5% to 1%, the concentration of the lithium oxalate solution decreases, and the degree of crushing gradually increases. After crushing, the specific surface area of ​​the material is increased, so that the material can better contact with the electrode material. Figure 1-3 As shown, the lithium supplements of Examples 1, 3, and 4 all have a hollow rupture structure, but the lithium supplement in Example 1 has a higher degree of fragmentation and a higher decomposition capacity.

[0073] According to the comparison between Examples 1, 27 and Comparative Example 1, it can be seen that as the proportion of lithium oxalate changes, the material decomposition capacity is proportional to the proportion of lithium oxalate, but the lower carbon content and catalyst will make the decomposition voltage of the material higher, which is not suitable for mainstream battery systems.

[0074] According to the comparison between Examples 1 and 4, the maximum solubility of lithium oxalate is 5.5% in the solution. If excessive addition is made, lithium oxalate will not dissolve, resulting in uneven spraying and affecting the subsequent crushing effect.

[0075] According to the comparison of Examples 1-4, the concentration of lithium oxalate in the slurry is different, and the morphology after crushing is different. The degree of crushing is higher at low concentrations, which greatly increases the contact area with the electrode material and the wettability of the electrolyte. It decomposes more completely during the formation and can provide a better lithium supplement effect.

[0076] According to the comparison between Example 1 and Comparative Example 2, a fast ion conductor and / or a lithium-philic agent is added during the preparation process. The modifier has a higher ionic conductivity, can improve the lithium ion release performance, and reduce the initial decomposition voltage of lithium oxalate delithiation.

[0077] According to the comparison between Example 1 and Example 28, in the spray drying process, the atomizer used is preferably a two-fluid atomizer, and the droplets are transported to the sprayer cavity by a high-pressure airflow. The droplets evaporate instantly under high temperature conditions to obtain dry solid particles. The lithium supplement particles obtained under the airflow have a hollow rupture structure.

[0078] 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 aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A lithium supplement, characterized in that: The lithium supplement agent comprises lithium oxalate, a carbon material, a catalyst and a modifier, wherein the modifier comprises at least one of a fast ion conductor and / or a lithium affinity agent; Wherein, the mass ratio of the lithium oxalate, the carbon material, the catalyst and the modifier is (70-95): (2.5-14): (2.5-14): (0.1-1); The fast ion conductor includes Li4Ti5O 12 , at least one of Li3PO4, Li2Zr2(PO4)3, LiPO2F2, LiF, LiNO3, and LiAlO2; The lithium-philic agent includes at least one of Si, S, and P; The lithium supplement agent is a hollow spherical particle, and some of the particles have a hollow rupture structure; The proportion of the number of particles with hollow fracture structures to the total number of particles is 58.8%-99%.

2. The lithium supplement according to claim 1, characterized in that: The specific surface area of ​​the lithium supplement is 60m 2 / g-170m 2 / g.

3. The lithium supplement according to claim 1, characterized in that: The catalyst comprises at least one of a transition metal element and a transition metal compound; and / or The carbon material includes at least one of Ketjen black, Super-P conductive carbon black, CNTs, and redox graphene.

4. A method for preparing a lithium supplement, characterized in that: The preparation method is used to prepare the lithium supplement according to any one of claims 1 to 3, and the preparation method comprises the following steps: S100: dissolving the lithium oxalate, and then adding the carbon material, the catalyst and the modifier to obtain a mixed solution; S200: subjecting the mixed solution to ultrasonic dispersion, spray drying, and crushing treatments in sequence to obtain the lithium supplement; Wherein, the mass fraction of the lithium oxalate in the mixed solution is 1%-5.5%.

5. The preparation method according to claim 4, characterized in that: The ultrasonic dispersion treatment time is 1.5h-2.5h; and / or The inlet air temperature of the spray drying is 200°C-260°C; and / or The feed rate of the spray drying is 35r / min-45r / min.

6. A positive electrode material, characterized in that: The positive electrode material includes the lithium supplement agent according to any one of claims 1 to 3.

7. A lithium ion battery, characterized in that: The lithium-ion battery comprises a positive electrode sheet, a separator and a negative electrode sheet, and the positive electrode sheet comprises the positive electrode material as claimed in claim 6.

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