Granulation additive and manufacturing method of high-reliability lithium ion battery using granulation additive

Abstract

The invention belongs to the technical field of battery materials, and provides a granulation additive and a manufacturing method of a high-reliability lithium ion battery using the granulation additive. The granulation additive is polyether water-soluble resin obtained by carrying out ring-opening polymerization reaction on an organic compound A under the action of an organic weak base compound B serving as an initiator and a solvent C, the granulation additive has high cohesiveness and good conductivity, and can be used as a flexible binder to be matched with a conventional binder for use. The granulation additive has bonding and granulation effects in a positive electrode granulation process, has the functions of smoothing positive electrode powder particles and improving the uniformity of the positive electrode powder, and can solve the problems of poor bonding force, stability reduction and internal resistance increase under a high-temperature use working condition when only a conventional binder is used by using the granulation additive. And the stability and reliability of the positive electrode and the battery cell are effectively improved.

Description

Technical Field

[0001] The present invention belongs to the field of battery materials, and relates to a granulation additive and a method for manufacturing a highly reliable lithium-ion battery using the same. Background Art

[0002] Lithium manganese button batteries, which have advantages such as high energy density, long life, and stable output voltage, are widely used in small electronic devices. In the prior art, a granulation process is usually adopted to mix active substances, conductive agents, binders, etc., and form particles with a certain size and shape through granulation, so as to improve the fluidity of the positive electrode powder, increase the compaction density, conductivity, optimize the wettability and processing performance, and reduce dust pollution.

[0003] In this granulation process, the binder plays a key role and affects various aspects such as the granulation process and the performance of the granulation product. Traditional positive electrode granulation processes for lithium batteries commonly use PTFE emulsions and polyacrylic acid binders. The positive electrode powder obtained by granulation with these binders often has problems such as uneven particle size, poor fluidity, and insufficient bonding strength, resulting in limited battery performance.

[0004] Therefore, it is necessary to develop a new positive electrode granulation scheme that can effectively improve the granulation uniformity through a simple and feasible process, thereby enhancing the performance of the granulated positive electrode material, positive electrode, and battery, and ensuring the high reliability of the battery core. Summary of the Invention

[0005] In view of the problems existing in the prior art, the purpose of the present invention is to provide a granulation additive and a method for manufacturing a highly reliable lithium-ion battery using the same. In the method, a granulation additive is added to the positive electrode material of the battery. The granulation additive is a polyether-based water-soluble resin obtained by ring-opening polymerization of organic compound A under the action of organic weak base compound B as an initiator and solvent. This granulation additive has high adhesiveness and good electrical conductivity, and can be used as a flexible binder in combination with conventional binders. This granulation additive plays a role in bonding and granulation in the granulation process, and has the function of making the positive electrode powder particles smooth and improving the uniformity of the positive electrode powder. By using this granulation additive, the problems of poor bonding force, decreased stability, and increased internal resistance under high-temperature operating conditions when only using conventional binders can be solved, thereby effectively enhancing the stability and reliability of the positive electrode and the battery core.

[0006] To achieve this purpose, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a granulation additive for a cathode material, the granulation additive comprising a polyether-based water-soluble resin; the polyether-based water-soluble resin is prepared by subjecting an organic compound A to a ring-opening polymerization reaction under the action of an organic weak base compound B as an initiator and a solvent C; the organic compound A comprises at least one of an ether compound containing an ether functional group (R-O-R′) and / or an epoxy compound containing an epoxy group (-C 2 H 4 O).

[0008] The granulation additive of the present invention can produce excellent effects in at least the following four aspects:

[0009] 1) Effectively improve the uniformity of the cathode granulation powder: During the granulation process of the cathode material, the growth process of the particles mainly includes the following four stages: ① wetting and nucleation; ② growth; ③ coalescence; ④ fragmentation. The granulation additive has a relatively large particle size and can serve as a nucleation point after wetting. Particles with a smaller particle size will adhere to the surface of larger-sized particles. The wet particles grow into large particles under the action of external mechanical force and capillary force. The granulation additive has a unique C-O-C main chain skeleton structure, and the ether oxygen atoms in its polymer chain contain shared electron pairs and have a strong tendency to form hydrogen bonds, which enables the polyether-based water-soluble resin particles to adsorb on the surface of solid particles, forming a bilayer structure. This bilayer structure can increase the degree of wetting of solid particles by water, keep the solid particles away from each other due to electrostatic repulsion, achieve a good dispersion effect, and make the cathode active material, conductive agent, and binder disperse evenly.

[0010] 2) Effectively improve the adhesion between various materials: First, the granulation additive of the present invention has excellent water solubility and thickening properties. The granulation additive is a completely water-soluble polymer, and this characteristic enables it to be easily mixed with water to form a uniform solution for granulation. At the same time, it also has high thickening properties and can exhibit a high viscosity even at a very low concentration. This thickening effect mainly comes from the network structure formed by its molecular chains in the aqueous solution, and this network structure can increase the viscosity and consistency of the solution, thereby making it have better adhesive properties. Second, as described above, the granulation additive also has excellent adsorption properties. When the granulation additive comes into contact with the surface of the particles to be bonded, a part of its molecular chains will interact with the molecules on the particle surface, forming an adsorption phenomenon. This adsorption increases the contact area between the binder and the particle surface, thereby improving the adhesion and sticking force. This adsorption enables the granulation additive to effectively bind to the particle surfaces of various materials and form a firm bond.

[0011] 3) Effectively promote ion conduction: There are oxygen atoms in the polymer chain segments of the granulation additive. Due to the electronegativity of oxygen atoms, lithium ions are adsorbed near the oxygen atoms and continuously undergo the coordination and dissociation processes. The oxygen atoms and lithium ions in its chain segments can continuously carry out the coordination and dissociation processes to achieve the migration of lithium ions. Under the action of an electric field, its chain segments start to move, breaking the balance of the gravitational force around lithium ions, enabling lithium ions to jump from one oxygen atom to another, thus achieving ion conduction.

[0012] 4) Effectively improve the electrical conductivity of the positive electrode, reduce the internal resistance, and enhance the stability and reliability: As described above, the granulation additive makes the active material and the conductive agent bond more fully, more evenly, and with better adhesion. Under high-temperature operating conditions, it can also maintain the stability of the positive electrode and enhance the reliability of the battery cell.

[0013] The following are the preferred technical solutions of the present invention, but not the limitations of the technical solutions provided by the present invention. Through the following technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved.

[0014] As a preferred technical solution of the present invention, the ether compound includes at least one of vinyl methyl ether, polyether copolymer of propylene oxide and ethylene oxide, or polyether polyol.

[0015] Preferably, the polyether polyol includes at least one of polypropylene glycol, polypropylene triol, or polytetrahydrofuran glycol.

[0016] Preferably, the epoxy compound includes epoxyalkane, and the epoxyalkane includes at least one of epichlorohydrin, styrene oxide, ethylene oxide, cyclohexene oxide, or 1,2-epoxybutane.

[0017] As a preferred technical solution of the present invention, the organic weak base compound B includes at least one of potassium diisopropylamide, sodium dihexylamide, or potassium dibenzyl.

[0018] Preferably, the solvent C includes diglycol and / or tetrahydrofuran.

[0019] Preferably, the weight-average molecular weight of the polyether water-soluble resin is 500,000 to 8,000,000, such as 1,000,000, 2,000,000, 3,000,000, and 4,000,000, etc., and more preferably 1,000,000 to 4,000,000.

[0020] Preferably, the polyether water-soluble resin is granular, and the average particle size is 100 to 500 μm, such as 100 μm, 150 μm, 200 μm, 300 μm, or 500 μm, etc.

[0021] In the present invention, the polyether-based water-soluble resin has a relatively small particle size, which can have better solubility and dispersibility, but can be reasonably adjusted within a preferred range according to actual conditions.

[0022] In a second aspect, the present invention provides a granulation method for a positive electrode material, and the granulation method includes:

[0023] First, mix the positive electrode active material and the conductive agent to obtain a mixture, and then mix the mixture, the binder

[0024] and the granulation additive described in the first aspect for a second time, and then perform granulation and baking in sequence to obtain the positive electrode granulated powder.

[0025] In the granulation method of the present invention, the binder combined with the granulation additive can further improve the stability and safety of the battery, but compared with the prior art without using the granulation additive, the dosage of the binder in the present invention is less.

[0026] As a preferred technical solution of the present invention, the positive electrode active material includes a positive electrode active material; the positive electrode active material includes a manganese-containing oxide; the manganese-containing oxide includes manganese dioxide; the specific surface area of the positive electrode active material is 10-30 m 2 / g, such as 10 m 2 / g, 17 m 2 / g, 20 m 2 / g, 25 m 2 / g or 30 m 2 / g, etc.

[0027] In a lithium manganese dioxide battery, if the specific surface area of the positive electrode active material is too low, there will tend to be phenomena such as low open-circuit voltage and low load voltage, and the pulse performance will decline; while if the specific surface area is too high, the active sites of the active material will increase, and side reactions with the electrolyte are likely to occur under high-temperature storage conditions, resulting in adverse phenomena such as gas generation.

[0028] Preferably, the conductive agent includes a first conductive agent and a second conductive agent; the first conductive agent includes graphite; the second conductive agent includes at least one of acetylene black, conductive carbon black, carbon nanotubes, Ketjen black or graphene.

[0029] Preferably, the particle size D 50 of the first conductive agent is 10-80 μm, such as 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm or 80 μm, etc., and preferably 20-50 μm.

[0030] Preferably, the specific surface area of the first conductive agent is 10-40 m2 / g, such as 10 m 2 / g, 15 m 2 / g, 20 m 2 / g, 25 m 2 / g, 30 m 2 / g, 35 m 2 / g or 40 m 2 / g, etc., preferably 20 - 40 m 2 / g.

[0031] Preferably, the specific surface area of the second conductive agent is 50 - 800 m 2 / g, such as 500 m 2 / g, 600 m 2 / g, 700 m 2 / g or 800 m 2 / g, etc., more preferably 500 - 800 m 2 / g.

[0032] In the present invention, the specific surface area of the first conductive agent, graphite, is relatively large, providing more channels for lithium ion migration, which can improve the theoretical capacity; the specific surface area of the second conductive agent has a positive correlation with its oil absorption value. The larger the specific surface area, the higher the oil absorption value, which is more beneficial to the wetting and liquid absorption performance of the positive electrode.

[0033] Preferably, the mass ratio of the first conductive agent to the second conductive agent is 1:(0.1 - 1.5), such as 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1.0, 1:1.1, 1:1.2, 1:1.3, 1:1.4 or 1:1.5, etc., preferably 1:(0.2 - 1).

[0034] Preferably, the binder includes polytetrafluoroethylene (PTFE).

[0035] Preferably, based on the mass of the positive electrode granulated powder being 100%, the positive electrode active material accounts for 85% - 95%, the conductive agent accounts for 4% - 10%, the binder accounts for 0.8% - 3.5%, preferably 2.5% - 3.5%; the granulation additive accounts for 0.2% - 1.5%, preferably 0.5% - 1.5%.

[0036] As a preferred technical solution of the present invention, the method of the first mixing includes ball milling, and the time of the ball milling is 2 - 4 h, such as 2 h, 2.5 h, 3 h or 4 h, etc., but is not limited to the listed values, and other unlisted values within the above numerical range are equally applicable.

[0037] Preferably, the binder is pre-diluted into a binder solution, and the second mixing is carried out using the binder solution. The mass multiple of dilution is 6 to 10 times, preferably 8 times.

[0038] Preferably, the binder solution is a polytetrafluoroethylene emulsion.

[0039] Preferably, the baking temperature is 170 to 190 °C, such as 170 °C, 173 °C, 175 °C, 178 °C, 180 °C, 185 °C, 188 °C or 190 °C, etc., and preferably 180 °C.

[0040] Preferably, the baking is carried out until the water content is between 0.5 wt% and 1.5 wt%, such as 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, 1 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt% or 1.5 wt%, etc. At this time, the powder has good fluidity, which is beneficial to the subsequent tablet pressing (stamping forming) process.

[0041] Preferably, the granulation method of the positive electrode material further includes sieving after the baking to obtain positive electrode granulated powder with a mesh size of 20 to 100.

[0042] In a third aspect, the present invention provides a positive electrode granulated powder, which is obtained according to the granulation method described in the second aspect.

[0043] In a fourth aspect, the present invention provides a method for manufacturing a positive electrode sheet, which includes pressing the positive electrode granulated powder described in the third aspect to obtain a positive electrode sheet.

[0044] Preferably, the pressing method includes stamping forming. The pressure of the stamping forming is 8 to 10 tons, such as 8 tons, 8.3 tons, 8.5 tons, 8.8 tons, 9 tons, 9.3 tons, 9.5 tons, 9.8 tons or 10 tons, etc., and preferably 9 tons. The pressure holding time is 0.01 to 0.3 s, such as 0.01 s, 0.05 s, 0.08 s, 0.1 s, 0.13 s, 0.15 s, 0.18 s, 0.2 s, 0.23 s, 0.25 s, 0.28 s or 0.3 s, etc., and preferably 0.1 s.

[0045] In a fifth aspect, the present invention provides a positive electrode sheet, which is obtained according to the manufacturing method described in the fourth aspect.

[0046] In a sixth aspect, the present invention provides a battery, which contains the positive electrode sheet described in the fifth aspect.

[0047] In the present invention, after stamping, the obtained positive electrode sheet is vacuum baked at 190 - 210 °C, such as 190 °C, 195 °C, 200 °C, 205 °C or 210 °C, etc., for 10 - 16 h, such as 10 h, 11 h, 12 h, 13 h, 14 h, 15 h or 16 h, etc., and then it can be used for cell assembly.

[0048] It should be noted that due to space limitations and to avoid redundancy, the present invention does not exhaustively list all suitable values, nor is it limited only to the listed values. Other unlisted values within the above value range are equally applicable.

[0049] Compared with the prior art solutions, the present invention has at least the following beneficial effects:

[0050] The granulation additive is a polyether - type water - soluble resin obtained by the polymerization reaction of a specific organic compound A and an organic weak base compound B; this granulation additive has high adhesiveness and good electrical conductivity, and can be used as a flexible binder in combination with conventional binders. This granulation additive plays a role in bonding and granulation in the granulation process, has the function of making the positive electrode powder particles smooth and improving the uniformity of the positive electrode powder. By using this granulation additive, the problems of poor adhesion, decreased stability and increased internal resistance under high - temperature operating conditions when only using conventional binders can be solved, thereby effectively improving the stability and reliability of the positive electrode and the cell. Detailed Embodiments

[0051] The technical solutions of the present invention will be further described below through specific embodiments.

[0052] Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0053] Example 1

[0054] This example provides a granulation additive for a positive electrode material. The granulation additive is composed of a polyether - type water - soluble resin; the polyether - type water - soluble resin is obtained by ring - opening polymerization of organic compound A in organic weak base compound B as the initiator and solvent C; the organic compound A is ethylene oxide, the organic weak base compound B is potassium diisopropylamide, and the solvent C is tetrahydrofuran.

[0055] The synthesis method of the polyether - type water - soluble resin includes:

[0056] S1: Add potassium diisopropylamide and tetrahydrofuran into a high-pressure reactor, stir until in a homogeneous dispersion state, then purge with nitrogen to remove oxygen, and add ethylene oxide. Among them, calculated based on the total mass being 100%, ethylene oxide, potassium diisopropylamide and tetrahydrofuran account for 10% - 45%, 0.0002% - 0.005% and 20% - 90% respectively.

[0057] S2: Supplement nitrogen to a pressure of 0.2 MPa - 1.5 MPa, set the temperature to 40°C - 60°C, carry out the reaction under these conditions until the system pressure no longer drops.

[0058] S3: Discharge nitrogen, and obtain the polyether water-soluble resin after vacuum distillation.

[0059] The molecular weight of the above polyether water-soluble resin is 2.6 million, and the average particle size of the particles is 300 μm.

[0060] Example 2

[0061] This example provides a granulation additive for a cathode material, and the granulation additive is composed of a polyether water-soluble resin; the polyether water-soluble resin is obtained by ring-opening polymerization of organic compound A in organic weak base compound B as an initiator and solvent C; the organic compound A is epichlorohydrin, the organic weak base compound B is diphenylmethyl potassium, and the solvent C is tetrahydrofuran, where,

[0062] The polyether water-soluble resin is synthesized according to the same step sequence and numerical conditions as in Example 1, with a molecular weight of 1 million and an average particle size of 200 μm for the particles.

[0063] Example 3

[0064] This example provides a granulation additive for a cathode material, and the granulation additive is composed of a polyether water-soluble resin; the polyether water-soluble resin is obtained by ring-opening polymerization of organic compound A in organic weak base compound B as an initiator and solvent C; the organic compound A is 1,2-epoxybutane, the organic weak base compound B is sodium dihexylamide, and the solvent C is tetrahydrofuran,

[0065] The polyether water-soluble resin is synthesized according to the same step sequence and numerical conditions as in Example 1, with a molecular weight of 4 million and an average particle size of 400 μm for the particles.

[0066] Application Example 1

[0067] This application example provides a granulation method for a cathode material, and the granulation method includes:

[0068] The positive electrode active material and the conductive agent are subjected to a first mixing to obtain a mixed material. The positive electrode active material is manganese dioxide as the positive electrode active material, and the specific surface area is 20 m 2 / g; the conductive agent includes a first conductive agent and a second conductive agent; the first conductive agent is graphite, and the second conductive agent is acetylene black. The particle size D 50 of the first conductive agent is 35 μm, and the specific surface area is 20 m 2 / g; the specific surface area of the second conductive agent is 65 m 2 / g; the mass ratio of the first conductive agent to the second conductive agent is 1:1; the method of the first mixing is ball milling for 4 h; then, the granulation additives provided in Examples 1 to 3 are respectively subjected to a second mixing with the mixed material and the binder. The second mixing includes first mixing the mixed material with the granulation additive, and then adding the binder for mixing; the binder is polytetrafluoroethylene, specifically, a polytetrafluoroethylene emulsion obtained by diluting polytetrafluoroethylene by 8 times the mass is used, and then granulation is carried out in sequence, and then baking is carried out at 180 °C until the water content is 0.8 wt%, and then screening with 20 - 100 meshes is carried out, and the material on the 100 - mesh sieve is the positive electrode granulated powder. Based on the mass of the positive electrode granulated powder being 100%, the positive electrode active material accounts for 90%, the conductive agent accounts for 6%, the binder accounts for 3.5%, and the granulation additive accounts for 0.5%.

[0069] Application Example 2

[0070] This application example provides a granulation method for a positive electrode material. The granulation method uses the granulation additive provided in Example 1, but the granulation method adjusts the proportion of the binder from 3.5% to 3%, and at the same time adjusts the proportion of the granulation additive from 0.5% to 1%. Except for the above, other conditions are exactly the same as those in Application Example 1.

[0071] Application Example 3

[0072] This application example provides a granulation method for a positive electrode material. The granulation method uses the granulation additive provided in Example 1, but the granulation method adjusts the proportion of the binder from 3.5% to 2.5%, and at the same time adjusts the proportion of the granulation additive from 0.5% to 1.5%. Except for the above, other conditions are exactly the same as those in Application Example 1.

[0073] Application Example 4

[0074] This application example provides a granulation method for a positive electrode material. The granulation method uses the granulation additive provided in Example 1, but the granulation method adjusts the ratio of the first conductive agent to the second conductive agent from 1:1 to 1:0.2. Except for the above, other conditions are exactly the same as those in Application Example 1.

[0075] Application Example 5

[0076] This application example provides a granulation method for a cathode material. The granulation method uses the granulation additive provided in Example 1, but in the granulation method, the ratio of the first conductive agent to the second conductive agent is adjusted from 1:1 to 1:1.5. Except for the above, other conditions are exactly the same as those in Application Example 1.

[0077] Application Example 6

[0078] This application example provides a granulation method for a cathode material. The granulation method uses the granulation additive provided in Example 1, but in the granulation method, the second conductive agent is replaced by Ketjenblack, and the specific surface area of Ketjenblack is 500 m 2 / g. Except for the above, other conditions are exactly the same as those in Application Example 1.

[0079] Application Example 7

[0080] This application example provides a granulation method for a cathode material. The granulation method uses the granulation additive provided in Example 1, but in the granulation method, the second conductive agent is replaced by carbon nanotubes, and the specific surface area of the carbon nanotubes is 800 m 2 / g. Except for the above, other conditions are exactly the same as those in Application Example 1.

[0081] Application Example 8

[0082] This application example provides a granulation method for a cathode material. The granulation method uses the granulation additive provided in Example 1, but in the granulation method, the process of the second mixing is adjusted, that is, the second mixing includes first mixing the mixture with the binder, and then adding the granulation additive for mixing. Except for the above, other conditions are exactly the same as those in Application Example 1.

[0083] Application Example 9

[0084] This application example provides a granulation method for a cathode material. The granulation method uses the granulation additive provided in Example 1, but in the granulation method, the time of the first mixing is adjusted from 4 h to 6 h, and at the same time, the process of the second mixing is adjusted, that is, the second mixing includes first mixing the mixture with the binder, and then adding the granulation additive for mixing. Except for the above, other conditions are exactly the same as those in Application Example 1.

[0085] Application Comparative Example 1

[0086] This application comparative example provides a granulation method for a cathode material. The granulation method does not use the granulation additive, but uses an equal amount of binder for substitution. Except for the above, other conditions are exactly the same as those in Application Example 1.

[0087] Application Comparative Example 2

[0088] The comparative example of this application provides a granulation method for a cathode material. In this granulation method, polyacrylonitrile is used to replace the granulation additive. Except for the above, other conditions are exactly the same as those in Application Example 1.

[0089] Comparative Application Example 3

[0090] The comparative example of this application provides a granulation method for a cathode material. In this granulation method, sodium polyacrylate is used to replace the granulation additive. Except for the above, other conditions are exactly the same as those in Application Example 1.

[0091] Characterization and Testing

[0092] Ⅰ. Powder utilization rate: Test the weight ratio of particles with a size of 20 - 100 mesh in all the granulated cathode powder.

[0093] Ⅱ. Flow rate range: It is represented by the time required for 50 g of granulated cathode powder to flow through a standard funnel with a specified pore size. Taking the range of the flow rates measured 10 times as the evaluation criterion, the smaller the range, the more uniform the particles.

[0094] Ⅲ. Conductivity range: The test equipment is a four-probe powder resistivity & compaction density meter from Yuaneng Technology Co., Ltd. Test the compaction-conductivity of the granulated cathode powder 10 times, and read the conductivity value when the compaction is 2.9 g / cm 3 as the test value. Taking the range of the 10 tests as the evaluation criterion, the more uniform the distribution of the active material and the conductive agent in the cathode material, the smaller the range.

[0095] Ⅳ. Electrochemical performance: Press the granulated cathode powder into tablets. The pressing is carried out by stamping, with a pressure of 9 tons and a holding time of 0.1 s to obtain cathode sheets; the obtained cathode sheets are vacuum baked (dried) at 200 °C for 13 h, and then assembled into CR2032 batteries in a dry environment with a dew point lower than -45 °C. Among them, metallic lithium is used as the negative electrode sheet, polypropylene is used as the separator, and the electrolyte includes 1 mol / L lithium perchlorate and a volume ratio of 1:1 of propylene carbonate and ethylene glycol dimethyl ether. After the obtained battery cells are cleaned, pre-discharged, and aged, test the internal resistance of the battery cells, and then test the internal resistance of the battery cells after storing at 125 °C in a high-temperature environment for 300 h to show the stability.

[0096] The above results are recorded in Table 1.

[0097] Table 1

[0098]

[0099] Analysis of the data in Table 1 shows that:

[0100] It can be seen from the comparison between Application Example 1 and Comparative Application Examples 1-3 that the utilization rate of the positive electrode granulated powder obtained by adopting the technical solution of adding granulation additives of the present invention is higher, and the differences in flow rate and conductivity are smaller, indicating that the positive electrode particles and the positive electrode components are more uniform, which is beneficial to improving the stability of the positive electrode. After the battery cell is stored at high temperature, the increase in the internal resistance of the battery cell can be slowed down.

[0101] It can be seen from the comparison between Application Example 2 and Application Example 3 that when the content of the granulation additive > 1%, the utilization rate of the powder will decrease slightly, and the differences in flow rate and conductivity will increase, affecting the uniformity of the positive electrode powder. The positive electrode obtained by adopting the technical solution of adding granulation additives of the present invention can improve the bonding effect between manganese dioxide, the conductive agent and the binder, and improve the stability of the positive electrode. After the battery cell is stored at high temperature, the increase in the internal resistance of the battery cell can be slowed down.

[0102] By comparing the data of Application Example 1, Application Example 4 and Application Example 5, it is found that when acetylene black is used as the second conductive agent, the ratio of the first conductive agent to the second conductive agent has little influence on the powder uniformity. When the ratio of graphite to acetylene black is 1:1.5, the conductivity of the positive electrode can be improved and the internal resistance can be reduced.

[0103] By comparing the data of Application Example 1, Application Example 6 and Application Example 7, it can be found that the selection of the conductive agent and its proportion in the positive electrode raw materials have little influence on the powder uniformity. However, when carbon nanotubes are used as the second conductive agent, due to the high specific surface area and high reactivity of carbon nanotubes, a continuous conductive network is formed in the positive electrode powder, which can further improve the overall conductivity of the positive electrode, reduce the internal resistance, and improve the performance of the battery cell.

[0104] By comparing Application Example 1, Application Example 8 and Application Example 9, it can be found that the addition sequence of the granulation additive and the PTFE emulsion has little influence on the positive electrode powder. The pretreatment time of the raw materials, that is, the ball milling time of the positive electrode active material and the conductive agent, will affect the uniformity of the positive electrode powder. The ball milling time is not less than 4 h. Considering the production efficiency, the ball milling time is preferably 4 h.

[0105] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0106] In addition, it should be noted that, in the above specific embodiments, the various specific technical features described can be combined in any appropriate manner without conflict. In order to avoid unnecessary repetition, the present invention will not separately describe various possible combination methods.

[0107] In addition, any combination can be made among various different embodiments of the present invention, as long as it does not violate the idea of the present invention, and it should also be regarded as the content disclosed by the present invention.

Claims

1. A granulation additive for positive electrode material, characterized in that: The granulation additive comprises a polyether water-soluble resin; the polyether water-soluble resin is prepared by subjecting an organic compound A to a ring-opening polymerization reaction under the action of an organic weak base compound B as an initiator and a solvent C; the organic compound A comprises at least one of an ether compound containing an ether functional group and / or an epoxy compound containing an epoxy group.

2. The granulation additive for positive electrode material according to claim 1, characterized in that The ether compound includes at least one of vinyl methyl ether, propylene oxide-ethylene oxide mixed polyether or polyether polyol; Preferably, the polyether polyol comprises at least one of polyoxypropylene diol, polyoxypropylene triol or polytetramethylene glycol; Preferably, the epoxy compound includes an alkylene oxide, and the alkylene oxide includes at least one of epichlorohydrin, styrene oxide, ethylene oxide, cyclohexene oxide or 1,2-butylene oxide.

3. The granulation additive for positive electrode material according to claim 1, characterized in that: The organic weak base compound B includes at least one of potassium diisopropylamide, sodium dihexylamide or diphenylmethyl potassium; Preferably, the solvent C comprises triethylene glycol and / or tetrahydrofuran; Preferably, the weight average molecular weight of the polyether water-soluble resin is 500,000 to 8,000,000, preferably 1,000,000 to 4,000,000; Preferably, the polyether water-soluble resin is in granular form with an average particle size of 100 to 500 μm.

4. A method for granulating a positive electrode material, characterized in that: The granulation method comprises: The positive electrode active material and the conductive agent are first mixed to obtain a mixture, and the mixture, the binder and the granulation additive according to claim 1 or 2 are second mixed, and then granulated and baked in sequence to obtain positive electrode granulated powder.

5. The method for granulating a positive electrode material according to claim 4, characterized in that: The positive electrode active material includes a positive electrode active material; the positive electrode active material includes a manganese-containing oxide; the manganese-containing oxide includes manganese dioxide; the specific surface area of ​​the positive electrode active material is 10 to 30 m 2 / g; Preferably, the conductive agent includes a first conductive agent and a second conductive agent; the first conductive agent includes graphite; the second conductive agent includes at least one of acetylene black, conductive carbon black, carbon nanotubes, Ketjen black or graphene; Preferably, the particle size D of the first conductive agent is 50 10 to 80 μm, preferably 20 to 50 μm; Preferably, the specific surface area of ​​the first conductive agent is 10 to 40 m 2 / g, preferably 20 to 40 m 2 / g; Preferably, the specific surface area of ​​the second conductive agent is 50 to 800 m 2 / g, preferably 500 to 800 m 2 / g; Preferably, the mass ratio of the first conductive agent to the second conductive agent is 1:(0.1-1.5); Preferably, the binder comprises polytetrafluoroethylene; Preferably, based on 100% of the mass of the positive electrode granulated powder, the positive electrode active material accounts for 85% to 95%, the conductive agent accounts for 4% to 10%, the binder accounts for 0.8% to 3.5%, and the granulation additive accounts for 0.2% to 1.5%.

6. The method for granulating a positive electrode material according to claim 4 or 5, characterized in that: The first mixing method includes ball milling, and the ball milling time is 2 to 4 hours; Preferably, the baking temperature is 170-190°C; Preferably, the baking is performed until the moisture content is between 0.5wt% and 1.5wt%; Preferably, the positive electrode material granulation method further comprises screening after the baking to obtain a positive electrode granulated powder with a mesh size of 20 to 100.

7. A positive electrode granulated powder, characterized in that: Obtained according to the granulation method according to any one of claims 4 to 6.

8. A method for manufacturing a positive electrode sheet, characterized in that: The manufacturing method comprises: pressing the positive electrode granulated powder according to claim 7 into sheets to obtain positive electrode sheets; Preferably, the tabletting method includes stamping, the stamping pressure is 8 to 10 tons, and the holding time is 0.01 to 0.3 seconds; Preferably, after the stamping, the obtained positive electrode sheet is vacuum baked at 190-210° C. for 10-16 hours before being used for battery cell assembly.

9. A positive electrode sheet, characterized in that: Obtained according to the manufacturing method according to claim 8.

10. A battery, characterized in that: A positive electrode sheet comprising the positive electrode sheet according to claim 9.

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