Easily dispersible alumina for lithium battery electrodes and method of making and use thereof

Abstract

The application belongs to the technical field of lithium ion battery materials and nano-powder processing, and particularly relates to easily dispersible aluminum oxide for lithium battery electrodes and a preparation method and application thereof. The easily dispersible aluminum oxide provided by the application has a core-shell structure with nano-aluminum oxide as a core and a cross-linked polymer layer as a shell, and is connected with the cross-linked polymer layer by a chemical bond. The nano-aluminum oxide and the cross-linked polymer layer are connected by a chemical bond between the nano-aluminum oxide and an activator, which enhances the binding force between the cross-linked polymer and the aluminum oxide, significantly improves the dispersibility of the nano-aluminum oxide by using the cross-linked polymer layer, effectively avoids agglomeration, and enables the aluminum oxide particles to be uniformly distributed on the positive electrode material due to the cross-linked layer during subsequent modification of the positive electrode material, thereby effectively improving the battery performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium ion battery materials and nano-powder processing, and particularly relates to easily dispersible aluminum oxide for lithium battery electrodes and a preparation method and application thereof. BACKGROUND

[0002] Lithium ion batteries are widely used in electric vehicles, medical devices, aerospace, portable electronic devices, energy storage and other fields. To further expand its use scenarios, it is crucial to improve the service life, electrical conductivity, high and low temperature performance and specific capacity of the positive electrode material of lithium ion batteries.

[0003] A lithium ion battery mainly consists of a positive electrode, a negative electrode, an electrolyte and a battery separator. During long-term cycling and use, the positive electrode material will produce high charge transfer impedance, leading to an increase in impedance in the battery and a loss of capacity at high discharge rates. In addition, the gradual decomposition of the electrolyte solution also occurs at the positive electrode, and its rate is related to the limits of battery temperature and working voltage.

[0004] Blending nano-inorganic additives in the positive electrode material or adding inorganic coatings on its surface, such as nano-Al2O3, AlPO4 or TiO2, is an effective method to inhibit the above phenomena.

[0005] However, the blending materials currently used in lithium ion batteries have the phenomenon of easy agglomeration, making it difficult to uniformly disperse on the surface of the positive electrode material, so the improvement of the performance of lithium batteries is still not ideal.

[0006] With the continuous maturity and development of lithium battery technology, it is particularly urgent to develop nano-inorganic additives with easy dispersibility. SUMMARY

[0007] To solve the above technical problems, the application provides easily dispersible aluminum oxide for lithium battery electrodes and a preparation method and application thereof. The easily dispersible aluminum oxide provided by the application has excellent and stable dispersibility and can be used to modify the positive electrode material of lithium ion electrodes to improve the performance of the battery.

[0008] To achieve the above application purposes, the embodiments of the application adopt the following technical solutions:

[0009] The first aspect of the application provides easily dispersible aluminum oxide for lithium battery electrodes, which has a core-shell structure with nano-aluminum oxide as the core and a cross-linked polymer layer as the shell, and the nano-aluminum oxide and the cross-linked polymer layer are connected by a chemical bond.

[0010] The cross-linked polymer layer is connected with the nano-alumina by chemical bonds, can form a firm and uniform coating on the surface of the nano-alumina, on the one hand, the cross-linked polymer layer can improve the dispersibility of the nano-alumina, overcome the defect that the nano-alumina is easy to agglomerate in the prior art, on the other hand, the chemical bond has strong binding force, so that the obtained easily dispersible alumina still maintains the core-shell structure in the subsequent preparation process of the positive electrode material, so that the dispersibility remains excellent and stable.

[0011] In combination with the first aspect, the mass of the nano-alumina is 70% to 99% of the easily dispersible alumina.

[0012] In combination with the first aspect, the nano-alumina is irregular cubic, flaky or spherical.

[0013] In combination with the first aspect, the particle size of the nano-alumina is: D10≥30nm, 100nm≤D50≤300nm, D90≤900nm.

[0014] In combination with the first aspect, the phase structure of the nano-alumina is α-alumina or γ-alumina, or a mixed phase of the two.

[0015] In combination with the first aspect, the thickness of the cross-linked polymer layer is 10-30nm.

[0016] The second aspect of the present application provides a preparation method of the above-mentioned easily dispersible alumina for lithium battery electrode, which specifically comprises the following steps:

[0017] S1, nano-alumina is prepared into alumina slurry;

[0018] S2, an activating agent is added to the alumina slurry, and after sufficient mixing, it is dried;

[0019] S3, a modifying agent is added to the product obtained in S2, mixed thoroughly, and dried to obtain the easily dispersible alumina powder.

[0020] The preparation method of the present application firstly mixes the alumina slurry with the activating agent, so that the nano-alumina and the activating agent are connected through chemical bonds, and a layer of activating agent is wrapped on the surface of the nano-alumina; then the modifying agent is added, the modifying agent reacts with the activating agent to form a covalent bond, and then a layer of cross-linked polymer is formed on the surface of the nano-alumina, the cross-linked polymer layer is connected with the nano-alumina through the chemical bond between the nano-alumina and the activating agent, and the nano-alumina particles are wrapped in the form of cross-linked network, rather than physical blending and adhesion, thereby significantly improving the firmness and uniformity of the cross-linked polymer coating on the surface of the nano-alumina, and finally forming the alumina particles with core-shell structure, i.e. the easily dispersible alumina for lithium battery electrode of the present application. The chemical bond between the nano-alumina and the cross-linked polymer layer enhances the bonding force between the cross-linked polymer and the nano-alumina, not only significantly improves the dispersibility of the nano-alumina by using the cross-linked polymer, but also makes the dispersibility remain excellent and stable in the subsequent modification process of the lithium ion battery positive electrode material.

[0021] In addition, the use of the activating agent makes the selection of the modifying agent diverse, the process operation is more flexible, and it is more conducive to actual production.

[0022] In combination with the second aspect, the method for preparing the alumina slurry from the nano-alumina can adopt the method of mixing the alumina with a dispersant and then grinding the alumina to a particle size of D10≥30nm, 100nm≤D50≤300nm, and D90≤900nm, and then obtaining the alumina slurry.

[0023] In combination with the second aspect, the activating agent is selected from at least one of polyethyleneimine, polyvinyl alcohol, p-phenylenediamine, m-phenylenediamine, and piperazine. The p-phenylenediamine, m-phenylenediamine, and piperazine all contain two amino groups, one of which can produce a hydrogen bond with the hydroxyl group on the surface of the nano-alumina to enhance the bonding force of the activating agent on the surface of the nano-alumina, and the other amino group provides an active site for reaction with the modifying agent. The polyethyleneimine contains multiple amino groups, part of which are combined with the hydroxyl group on the surface of the nano-alumina through hydrogen bonds, and the other part of which reacts with the modifying agent. The hydroxyl group of the polyvinyl alcohol can also be combined with the hydroxyl group on the surface of the nano-alumina through hydrogen bonds, and the uncombined hydroxyl group reacts with the modifying agent. The hydrogen bond force is stable, so that the activating agent can form an activating agent layer that can stably cover the surface of the nano-alumina by first combining with the nano-alumina in a solution state and then drying, laying a foundation for subsequent reaction with the modifying agent and forming a cross-linked polymer layer.

[0024] In combination with the second aspect, the drying method can be vacuum drying, air blowing drying, freeze drying, spray drying, etc.

[0025] In combination with the second aspect, the modifier comprises one or more compounds with the structural formula of "X-R-Y", wherein R is selected from substituted or unsubstituted C1-15 alkyl or alkoxy, substituted or unsubstituted benzene ring, or substituted or unsubstituted C2-15 alkenyloxy; X and Y are respectively a functional group capable of reacting with the activator. The modifier is capable of reacting with the activator and cross-linking with each other, thereby forming a cross-linked polymer layer wrapping the nano-alumina.

[0026] Optionally, part of the hydrogen atoms on R are substituted by halogen, such as chlorine, bromine, etc.

[0027] Optionally, X and Y are respectively and independently selected from amino, carboxylic acid, epoxy, acyl chloride or silanol.

[0028] Optionally, when the modifier is solid, the modifier further comprises water, alkane, benzene or alcohol.

[0029] Optionally, the activator is m-phenylenediamine, p-phenylenediamine or polyethyleneimine, and the modifier is alkane solution of fumaric dichloride, terephthalic dichloride or trimesic dichloride; or the activator is polyvinyl alcohol, and the modifier is propylene glycol epoxide or solution thereof or aqueous solution of polyacrylic acid; or the activator is polyethyleneimine, and the modifier is aqueous solution of polyacrylic acid.

[0030] Preferably, the activator is polyethyleneimine, and the modifier is aqueous solution of polyacrylic acid. In this condition, the battery prepared by using the obtained easily dispersible alumina modified lithium ion battery cathode material has higher specific capacity and life and cycle stability.

[0031] In combination with the second aspect, the time for sufficient mixing in S2 is 30-60 min.

[0032] In combination with the second aspect, the time for sufficient mixing in S3 is 30-60 min.

[0033] The third aspect of the present application provides application of the above-mentioned easily dispersible alumina for lithium battery electrode in coating modification of lithium ion battery cathode material. The lithium battery cathode is coated and modified by using the easily dispersible alumina provided by the present application, which can effectively improve the performance of lithium ion battery, such as service life and cycle number, etc. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 It is a structural schematic diagram of the easily dispersible alumina for lithium battery electrode of the present application;

[0035] Figure 2 It is an SEM photo of the alumina obtained in Example 1 of the present application;

[0036] Figure 3 It is an SEM photo of the alumina obtained in Comparative Example 2 of the present application. DETAILED DESCRIPTION

[0037] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with specific examples. It should be understood that the specific examples described herein are only used to explain the present application and not to limit the present application.

[0038] The positive electrode material of the lithium ion battery will generate high charge transfer impedance during long-term cycling and use, resulting in impedance growth in the battery and loss of capacity at high discharge rates; the positive electrode of the lithium ion battery will also be affected by the limits of battery temperature and working voltage to cause gradual decomposition of the electrolyte solution. Blending nano inorganic additives in the positive electrode material or adding inorganic coating on the surface thereof can inhibit the above phenomena, but the nano inorganic additives are prone to agglomeration and difficult to be uniformly dispersed on the surface of the positive electrode material, so the improvement of the performance of the lithium battery is still not ideal.

[0039] In order to solve this problem, the present application improves the nano alumina and provides an easily dispersible alumina for lithium battery electrode, which has a core-shell structure with nano alumina as the core and polymer as the shell, and the nano alumina and the polymer are connected by chemical bonds. The structural schematic diagram is shown as Figure 1 (A is the nano alumina core, C is the polymer grid-shaped shell, and B is the site connecting A and C),

[0040] As a specific example of the present application, the mass of the nano alumina is 70% to 99% of the easily dispersible alumina.

[0041] As a specific example of the present application, the nano alumina is irregular cubic, flaky or spherical.

[0042] As a specific example of the present application, the particle size of the nano alumina is: D10≥30nm, 100nm≤D50≤300nm, D90≤900nm.

[0043] As a specific example of the present application, the phase structure of the nano alumina is alpha-alumina or gamma-alumina, or a mixed phase of the two.

[0044] As a specific example of the present application, the thickness of the crosslinked polymer layer is 10 to 30nm.

[0045] In order to obtain the easily dispersible alumina with the above structure, the present application further provides a preparation method thereof, which specifically comprises the following steps:

[0046] S1, preparing nano alumina into alumina slurry;

[0047] S2, adding an activator to the alumina slurry, and drying after sufficient mixing;

[0048] S3, adding a modifier to the product obtained in S2, mixing thoroughly, drying, to obtain the easily dispersible alumina powder.

[0049] To ensure the formation of chemical bonds between the activator and the nano-alumina, as a specific embodiment of the present application, the activator can be selected from at least one of polyethyleneimine, polyvinyl alcohol, p-phenylenediamine, m-phenylenediamine and piperazine.

[0050] As a specific embodiment of the present application, the method for preparing the alumina slurry from the nano-alumina can adopt the following steps: mixing the alumina with a dispersant, and then grinding to obtain the alumina with a particle size of D10≥30nm, 100nm≤D50≤300nm, and D90≤900nm, thereby obtaining the alumina slurry.

[0051] As a further specific embodiment of the present application, the modifier comprises one or more compounds with a structural formula of "X-R-Y", wherein R is selected from substituted or unsubstituted C1-15 alkyl or alkoxy, substituted or unsubstituted benzene ring, or substituted or unsubstituted C2-15 alkenyloxy; X and Y are respectively functional groups capable of reacting with the activator, to ensure that the modifier can not only react with the activator, but also cross-link with each other, so as to form a cross-linked polymer layer wrapping the nano-alumina.

[0052] Exemplarily, part of the hydrogen atoms on R are substituted by halogen, such as chlorine, bromine, etc.

[0053] Exemplarily, X and Y are respectively and independently selected from amino, carboxylic acid, epoxy, acyl chloride or siloxy.

[0054] As a further specific embodiment of the present application, the modifier further comprises water, alkane, benzene or alcohol substances, to provide a reaction medium, so that the modifier can be in sufficient contact and reaction with the product obtained in S2, and form the cross-linked polymer layer.

[0055] To ensure the sufficient contact and reaction between the activator and the nano-alumina, and the sufficient contact and reaction between the modifier and the product obtained in S2, in the embodiments of the present application, the mixing time in S2 and S3 is 30-60min.

[0056] The embodiments of the present application are further described in the following examples.

[0057] Example 1

[0058] The present embodiment provides an easily dispersible alumina for lithium battery electrode, and a preparation method thereof.

[0059] (1) Grinding: 300kg of raw material spherical α-alumina is added into 1000kg of water, and ground in a ball mill, so that the particle size of the raw material is D10 of 84nm, D50 of 160nm, and D90 of 200nm.

[0060] (2) Activation: 3 kg of m-phenylenediamine was added to the material obtained in the previous step, and mixed for 45 min, and then spray dried at 60°C to obtain activated alumina powder;

[0061] (3) 300 kg of the activated alumina powder dried in step (2) was mixed with 300 kg of n-hexane solution containing 0.2%wt fumaric chloride for 45 min to achieve the modification process, and then spray dried at 60°C to obtain the easily dispersible alumina powder of the present embodiment.

[0062] Example 2

[0063] The present embodiment provides an easily dispersible alumina for lithium battery electrodes, and the preparation method thereof is as follows:

[0064] (1) Grinding: 300 kg of raw material flaky a-alumina was added to 1000 kg of water, and ground in a ball mill to make the particle size of the raw material D10 80 nm, D50 210 nm, and D90 420 nm;

[0065] (2) Activation: 3 kg of polyethyleneimine was added to the material obtained in the previous step, and mixed for 45 min, and then spray dried at 60°C to obtain activated alumina powder;

[0066] (3) 300 kg of the activated alumina powder dried in step (2) was mixed with 200 kg of n-hexane solution containing 0.1%wt terephthaloyl chloride for 45 min to achieve the modification process, and then spray dried at 60°C to obtain the easily dispersible alumina powder of the present embodiment, and the SEM photograph thereof is shown in Figure 2 .

[0067] Example 3

[0068] The present embodiment provides an easily dispersible alumina for lithium battery electrodes, and the preparation method thereof is as follows:

[0069] (1) Grinding: 500 kg of raw material spherical a-alumina was added to 1000 kg of water, and ground in a ball mill to make the particle size of the raw material D10 46 nm, D50 160 nm, and D90 200 nm;

[0070] (2) Activation: 2 kg of polyvinyl alcohol was added to the material obtained in the previous step, and mixed for 30 min, and then spray dried at 60°C to obtain activated alumina powder;

[0071] (3) Take 500 kg of the activated alumina powder dried in step (2) and mix it thoroughly with 300 kg of a 0.3% wt fumaric chloride solution in n-hexane for 30 min to achieve the modification process. Finally, dry the material in a freeze-drying oven to obtain the easily dispersible alumina powder of this example.

[0072] Example 4

[0073] This example provides an easily dispersible alumina for lithium battery electrodes, and the preparation method thereof is as follows:

[0074] (1) Grinding: Add 600 kg of raw material spherical a-alumina to 1000 kg of water and grind in a ball mill to make the raw material particle size D10 30 nm; D50 107 nm; D90 202 nm;

[0075] (2) Activation: Add 2 kg of polyethyleneimine to the material obtained in the previous step, mix for 30 min, and then spray dry at 60°C to obtain activated alumina powder;

[0076] (3) Take 500 kg of the activated alumina powder dried in step (2) and mix it thoroughly with 300 kg of a 0.3% wt fumaric chloride solution in n-hexane for 30 min to achieve the modification process. Finally, dry the material in a freeze-drying oven to obtain the easily dispersible alumina powder of this example.

[0077] Example 5

[0078] This example provides an easily dispersible alumina for lithium battery electrodes, and the preparation method thereof is as follows:

[0079] (1) Grinding: Add 400 kg of raw material irregular cubic γ-alumina to 1000 kg of water and grind in a ball mill to make the raw material particle size D10 66 nm; D50 122 nm; D90 365 nm;

[0080] (2) Activation: Add 2 kg of p-phenylenediamine to the material obtained in the previous step, mix for 30 min, and then freeze-dry to obtain activated alumina powder;

[0081] (3) Take 400 kg of the activated alumina powder dried in step (2) and mix it thoroughly with 300 kg of a 0.3% wt fumaric chloride solution in n-hexane for 30 min to achieve the modification process. Finally, dry the material in a freeze-drying oven to obtain the easily dispersible alumina powder of this example.

[0082] Example 6

[0083] This example provides an easily dispersible alumina for lithium battery electrodes, and the preparation method thereof is as follows:

[0084] (1) Grinding: 500 kg of raw irregular cubic γ-alumina was added into 1000 kg of water and ground in a ball mill to make the particle size of the raw material D10 83 nm; D50 151 nm; D90 478 nm;

[0085] (2) Activation: 1 kg of p-phenylenediamine and 1 kg of polyethyleneimine were added into the material obtained in the previous step, mixed for 45 min, and then freeze-dried to obtain activated alumina powder;

[0086] (3) 500 kg of the activated alumina powder dried in step (2) was mixed with 100 kg of n-hexane solution containing 0.2%wt fumaric chloride and 100 kg of n-hexane solution containing 0.1%wt trimesoyl chloride for 45 min to realize the modification process. Finally, the material was dried in a 80°C air oven to obtain the easily dispersible alumina powder of the example.

[0087] Example 7

[0088] The example provides an easily dispersible alumina for lithium battery electrode, and the preparation method thereof is:

[0089] (1) Grinding: 300 kg of raw spherical α-alumina and 300 kg of raw γ-alumina were added into 1000 kg of water and ground in a ball mill to make the particle size of the raw material D10 95 nm; D50 218 nm; D90 563 nm;

[0090] (2) Activation: 1.5 kg of piperazine was added into the material obtained in the previous step, mixed for 60 min, and then dried at 80°C by air blowing to obtain activated alumina powder;

[0091] (3) 300 kg of the activated alumina powder dried in step (2) was mixed with 80 kg of isomeric alkane solution containing 0.2%wt trimesoyl chloride for 60 min to realize the modification process. Finally, the material was dried in a 80°C air oven to obtain the easily dispersible alumina powder of the example.

[0092] Example 8

[0093] The example provides an easily dispersible alumina for lithium battery electrode, and the preparation method thereof is:

[0094] (1) Grinding: 600 kg of raw spherical γ-alumina was added into 1000 kg of water and ground in a ball mill to make the particle size of the raw material D10 60 nm; D50 158 nm; D90 477 nm;

[0095] (2) Activation: 1 kg of polyethyleneimine and 0.5 kg of piperazine were added to the material obtained in the previous step, and mixed for 40 min, and then dried by blowing at 80°C to obtain the activated alumina powder;

[0096] (3) 600 kg of the activated alumina powder dried in step (2) was mixed with 80 kg of isoparaffin solution containing 0.2% wt. isophthaloyl chloride and 30 kg of isoparaffin solution containing 0.3% terephthaloyl chloride for 40 min to achieve the modification process, and then dried in a 80°C blowing oven to obtain the easily dispersible alumina powder of the present example.

[0097] Example 9

[0098] The present example provides an easily dispersible alumina for lithium battery electrodes, and the preparation method thereof is as follows:

[0099] (1) Grinding: 400 kg of raw material spherical γ-alumina was added to 1000 kg of water, and ground in a ball mill to obtain a raw material with a particle size D10 of 50 nm, D50 of 232 nm, and D90 of 555 nm;

[0100] (2) Activation: 2 kg of polyvinyl alcohol was added to the material obtained in the previous step, and mixed for 40 min, and then dried by vacuum drying at 40°C to obtain the activated alumina powder;

[0101] (3) 400 kg of the activated alumina powder dried in step (2) was mixed with 100 kg of dioxane solution containing 10% wt. glycidol for 40 min to achieve the modification process, and then dried in a 40°C vacuum drying oven to obtain the easily dispersible alumina powder of the present example.

[0102] Example 10

[0103] The present example provides an easily dispersible alumina for lithium battery electrodes, and the preparation method thereof is as follows:

[0104] (1) Grinding: 600 kg of raw material flaky γ-alumina was added to 1000 kg of water, and ground in a ball mill to obtain a raw material with a particle size D10 of 122 nm, D50 of 239 nm, and D90 of 652 nm;

[0105] (2) Activation: 3 kg of polyethyleneimine was added to the material obtained in the previous step, and mixed for 50 min, and then dried by vacuum drying at 40°C to obtain the activated alumina powder;

[0106] (3) Take 600 kg of the activated alumina powder after drying in step (2) and mix with 200 kg of a mixed alkane (Isopar G) solution containing 0.1% wt terephthaloyl chloride for 50 min to achieve the modification process, and finally place the material in a vacuum drying oven at 40°C to dry, thereby obtaining the easily dispersible alumina powder of the present example.

[0107] Example 11

[0108] The present example provides an application of the easily dispersible alumina for lithium battery electrodes in coating modification of lithium ion battery cathode materials.

[0109] The easily dispersible alumina prepared in Example 1 is used to coat and modify lithium ion battery cathode material NCM811, and the test steps are as follows:

[0110] (1) Take lithium ion battery cathode material NCM811 and 1% of the easily dispersible alumina powder prepared in Example 1 by mass ratio, and mix uniformly in a high-speed mixer;

[0111] (2) Place the above mixed material in a high-temperature reaction furnace for calcination, with a calcination temperature of 400°C and a sintering time of 12 hours.

[0112] Example 12

[0113] The present example provides an application of the easily dispersible alumina for lithium battery electrodes in coating modification of lithium ion battery cathode materials.

[0114] The easily dispersible alumina prepared in Example 2 is used to coat and modify lithium ion battery cathode material NCM811, and the test steps are as follows:

[0115] (1) Take lithium ion battery cathode material NCM811 and 0.5% of the easily dispersible alumina powder prepared in Example 2 by mass ratio, and mix uniformly in a high-speed mixer;

[0116] (2) Place the above mixed material in a high-temperature reaction furnace for calcination, with a calcination temperature of 400°C and a sintering time of 12 hours.

[0117] Example 13

[0118] The present example provides an application of the easily dispersible alumina for lithium battery electrodes in coating modification of lithium ion battery cathode materials.

[0119] The easily dispersible alumina prepared in Example 3 is used to coat and modify lithium ion battery cathode material NCM811, and the test steps are as follows:

[0120] (1) Take the lithium ion battery cathode material NCM811 and the easy-to-disperse alumina powder prepared in Example 3 with a mass ratio of 0.5%, and mix them uniformly in a high-speed mixer;

[0121] (2) Place the mixed material in a high-temperature reaction furnace for calcination, with a calcination temperature of 400°C and a sintering time of 12 hours.

[0122] Example 14

[0123] This example provides an application of easy-to-disperse alumina for lithium battery electrodes in coating modification of lithium ion battery cathode materials.

[0124] The easy-to-disperse alumina prepared in Example 4 is used to coat and modify the lithium ion battery cathode material NCM811, and the test steps are as follows:

[0125] (1) Take the lithium ion battery cathode material NCM811 and the easy-to-disperse alumina powder prepared in Example 4 with a mass ratio of 0.8%, and mix them uniformly in a high-speed mixer;

[0126] (2) Place the mixed material in a high-temperature reaction furnace for calcination, with a calcination temperature of 400°C and a sintering time of 12 hours.

[0127] Comparative Example 1

[0128] This comparative example provides an alumina for lithium battery electrodes and its application in the preparation of lithium ion batteries. The preparation method of the alumina is basically the same as that of Example 1, except that it is activated and then ground again. The specific operation is as follows:

[0129] (1) Grinding: In 1000 kg of water, add 300 kg of raw material α-alumina, and grind in a ball mill to make the particle size D10 of the raw material 80 nm; D60 is 371 nm; D90 is 510 nm;

[0130] (2) Activation: Add 3 kg of m-phenylenediamine to the material obtained in the previous step, mix for 45 min, and then spray dry at 60°C. Grind again to make the particle size D10 of the raw material 34 nm; D50 is 101 nm; D90 is 208 nm; obtain activated alumina powder;

[0131] (3) Take 300 kg of the activated alumina powder dried in step (2) and mix it with 300 kg of n-hexane solution containing 0.2% fumaric chloride for 45 min to achieve the modification process. Finally, spray dry the material at 60°C to obtain the alumina powder of this comparative example.

[0132] The alumina powder prepared by the above method is used to coat and modify the lithium ion battery cathode material NCM811, and the test steps are as follows:

[0133] (1) Take the lithium ion battery cathode material NCM811 and the above-mentioned easily dispersible alumina powder with a mass ratio of 0.8%, and mix them uniformly in a high-speed mixer;

[0134] (2) Place the mixed material in a high-temperature reaction furnace for calcination, with a calcination temperature of 400°C and a sintering time of 12 hours.

[0135] Comparative Example 2

[0136] This comparative example provides an alumina for lithium battery electrodes and its application in the preparation of lithium ion batteries. The preparation method of the alumina is as follows:

[0137] (1) Grinding: In 1000 kg of water, add 500 kg of raw material α-alumina. Grind the raw material in a ball mill to a particle size D10 of 38 nm; D50 of 103 nm; D90 of 207 nm;

[0138] (2) Drying: Spray dry the material to obtain alumina powder, and the SEM photo is as shown in Figure 3 .

[0139] The alumina powder prepared by the above method is used for coating modification of lithium ion battery cathode material NCM811, and the test steps are as follows:

[0140] (1) Take the lithium ion battery cathode material NCM811 and the above-mentioned easily dispersible alumina powder with a mass ratio of 0.8%, and mix them uniformly in a high-speed mixer;

[0141] (2) Place the mixed material in a high-temperature reaction furnace for calcination, with a calcination temperature of 400°C and a sintering time of 12 hours.

[0142] Experimental Example

[0143] The coated and modified lithium ion battery cathode material NCM811 prepared in Examples 11-14 and Comparative Examples 1 and 2 is respectively made into button cells and compared, and the reversible specific capacity and capacity retention rate of the two at the 50th week are shown in Table 1 (test conditions are LR 2032, 45°C, 1C 3.0-4.25V, vs. Li+ / Li, and the charge and discharge equipment used is a Lan electric charge and discharge instrument):

[0144] Table 1 Comparison of cycle performance

[0145]

[0146] From the above data, it can be seen that the capacity retention rate of the battery obtained after the positive electrode is modified by the easily dispersible alumina electrode of the present application is generally better than that of the battery obtained after the positive electrode is modified by the unmodified alumina electrode. This is mainly because, after being treated by the present application, the dispersibility of the nano-alumina powder is obviously improved, which makes the nano-alumina powder more easily and uniformly dispersed on the surface of the electrode material, avoiding the agglomeration of the nano-alumina powder on the surface of the electrode material. The easily dispersible alumina powder of the present application is uniformly distributed on the surface of the electrode material, which can on the one hand enhance the stability of the electrode during use, and on the other hand, reduce the phenomenon of increased internal resistance and easy peeling of the battery caused by the agglomeration of alumina.

[0147] The preferred embodiments of the present application are described above, but the present application is not limited to the above, and any modification, equivalent replacement or improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An easily dispersible alumina for lithium battery electrodes, characterized by comprising, The structure is a core-shell structure with nano-alumina as the core and a cross-linked polymer layer as the shell, the nano-alumina and the cross-linked polymer layer are connected by hydrogen bonds, and the cross-linked polymer layer is composed of an activator and a modifier connected by chemical bonds; wherein the activator is selected from at least one of p-phenylenediamine, m-phenylenediamine and piperazine, and the modifier is an alkane solution of fumaric dichloride, terephthaloyl chloride or trimesoyl chloride; The preparation method of the easily dispersible alumina for lithium battery electrodes comprises the following steps: S1, nano-alumina is made into alumina slurry, specifically: alumina is mixed with a dispersant and ground to a particle size of D10 ≥ 30 nm, 100 nm ≤ D50 ≤ 300 nm, and D90 ≤ 900 nm, to obtain alumina slurry; S2, adding an activator to the alumina slurry, mixing thoroughly and drying; S3, adding a modifier to the product obtained in S2, mixing thoroughly, drying, to obtain the easily dispersible alumina powder.

2. The easily dispersible alumina for lithium battery electrodes according to claim 1, characterized by, The mass of the nano-alumina is 70% to 99% of the easily dispersible alumina; and / or The nano-alumina is irregular cubic, flaky or spherical; and / or The particle size of the nano-alumina is D10 ≥ 30 nm, 100 nm ≤ D50 ≤ 300 nm, and D90 ≤ 900 nm; and / or The phase structure of the nano-alumina is α-alumina or γ-alumina, or a mixture of the two; and / or The thickness of the cross-linked polymer layer is 10-30 nm.

3. The easily dispersible alumina for lithium battery electrodes according to any one of claims 1 to 2, characterized by, The mixing time in S2 is 30-60 min; and / or The mixing time in S3 is 30-60 min.

4. The use of the easily dispersible alumina for lithium battery electrodes according to any one of claims 1-3 in coating modification of lithium ion battery positive electrode materials.

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