Dispersing agent as well as preparation method and application thereof

Abstract

The invention provides a dispersing agent as well as a preparation method and application thereof. The dispersing agent is prepared from the following raw materials: a component A, a component B and a sulfonation reagent, the component A is prepared from polyhydric alcohols with the carbon number of C8-C20; and the component B comprises an acid compound and / or an anhydride compound. The dispersing agent provided by the invention is added in the preparation process of the lithium manganese iron phosphate, so that the problem of overhigh viscosity of slurry caused by small particle size formed by grinding in the grinding process can be solved, the agglomeration is reduced, and meanwhile, the dispersing agent basically exists in a carbon residue manner after being sintered, and basically has no influence on the performance of the lithium manganese iron phosphate.

Description

Technical Field

[0001] The invention belongs to the technical field of dispersants, and specifically relates to a dispersant and a preparation method and application thereof. Background Art

[0002] Lithium manganese iron phosphate has a similar structure to lithium iron phosphate and has better safety. At the same time, it has a dual voltage platform of 4.1V and 3.4V and has a higher energy density. However, its disadvantages are also very obvious, such as low lithium ion diffusion rate and poor electronic conductivity, which in turn affects its electrical performance.

[0003] CN114649517A discloses a method for preparing a nano-scale carbon composite lithium iron manganese phosphate positive electrode material for a lithium ion battery, the preparation method comprising the following steps: (1) preparing a nano-scale manganese oxalate precursor; (2) preparing a nano-scale ferrous oxalate precursor; (3) mixing and grinding the nano-scale manganese oxalate precursor, the nano-scale ferrous oxalate precursor, a lithium source, a carbon source and a phosphorus source to obtain a slurry; (4) spray-drying and granulating the slurry to obtain a semi-finished product powder; (5) sintering the semi-finished product powder in a protective gas atmosphere; (6) crushing the sintered powder to obtain a nano-scale lithium iron manganese phosphate positive electrode material.

[0004] CN117996049A discloses a carbon-coated lithium manganese iron phosphate material and a preparation method and application thereof. The preparation method comprises: mixing a lithium source, a manganese source, an iron source, a phosphorus source and a carbon source in a solvent, and subjecting the mixture to centrifugal drying, heat treatment and calcination to obtain the carbon-coated lithium manganese iron phosphate material.

[0005] The existing process mainly improves the electrical properties of lithium manganese iron phosphate by grinding nano-crystallization and carbon coating, and achieves certain results. However, there are problems such as excessive slurry viscosity, easy agglomeration, and uneven carbon coating due to the pursuit of small particle size during the grinding process.

[0006] Therefore, it is necessary to develop a dispersant that can solve the problem of excessive slurry viscosity caused by too small abrasive particles. Summary of the invention

[0007] In view of the shortcomings of the prior art, the present invention aims to provide a dispersant and a preparation method and application thereof. Adding the dispersant in the preparation process of lithium manganese iron phosphate can solve the problem of excessive viscosity of the slurry caused by the small particle size formed during grinding, reduce agglomeration, and at the same time, the dispersant basically exists in the form of residual carbon after the sintering process, and has basically no effect on the performance of lithium manganese iron phosphate.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a dispersant, wherein the raw materials for preparing the dispersant include component A, component B and a sulfonated reagent;

[0010] The A component includes a polyol of C8 to C20 (e.g., C10, C12, C14, C16 or C18, etc.);

[0011] The B component includes an acid compound and / or an acid anhydride compound.

[0012] In the present invention, the dispersant prepared by using C8-C20 polyols, acid compounds and / or anhydride compounds and sulfonated reagents as raw materials has the characteristic of good dispersing effect. Adding the dispersant in the preparation process of lithium manganese iron phosphate can solve the problem of excessive viscosity of the slurry caused by small particle size formed during grinding, and reduce agglomeration. At the same time, the dispersant basically exists in the form of residual carbon after the sintering process, and has basically no effect on the performance of lithium manganese iron phosphate.

[0013] Preferably, the C8-C20 polyol includes a C8-C20 straight-chain polyol and / or a C8-C20 branched-chain polyol.

[0014] Preferably, the C8-C20 linear polyol includes any one of n-octanol, n-decanol, lauryl alcohol, n-tetradecanol, n-hexadecanol, n-octadecyl alcohol or n-eicosanol, or a combination of at least two thereof.

[0015] Preferably, the acid compound includes any one of acetic acid, acrylic acid or succinic acid, or a combination of at least two of them.

[0016] Preferably, the acid anhydride compound comprises maleic anhydride.

[0017] Preferably, the sulfonating agent comprises any one of sulfuric acid, propane sultone, aminosulfonic acid or chlorosulfonic acid, or a combination of at least two thereof.

[0018] In a second aspect, the present invention provides a method for preparing the dispersant according to the first aspect, the preparation method comprising the following steps:

[0019] (1) mixing component A and component B, reacting to obtain a polyester compound;

[0020] (2) The polyester compound obtained in step (1) and a sulfonating agent are mixed and reacted to obtain the dispersant.

[0021] Preferably, the molar ratio of component A to component B is 1:(1.05-1.4), for example, 1:1, 1:1.15, 1:1.2, 1:1.25, 1:1.3 or 1:1.35, etc.

[0022] Preferably, the molar ratio of the polyester compound to the sulfonated reagent is 1:(1.1-2.5), for example, 1:1.3, 1:1.5, 1:1.7, 1:1.9, 1:2.1 or 1:2.3, etc.

[0023] Preferably, the mixing in step (1) further comprises mixing with an inhibitor, a solvent and a catalyst.

[0024] Preferably, the polymerization inhibitor includes any one of hydroquinone, p-hydroxyanisole, diethylhydroxylamine or 1,1-diphenyl-2-trinitrophenylhydrazine (DPPH) or a combination of at least two thereof.

[0025] Preferably, the solvent comprises anhydrous toluene.

[0026] Preferably, the catalyst comprises any one of p-toluenesulfonic acid, a cation exchange resin or zirconium oxide, or a combination of at least two thereof.

[0027] Preferably, based on the total mass of component A, component B, solvent, inhibitor and catalyst as 100%, the total mass of the inhibitor and catalyst is 0.1% to 1%, for example, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8% or 0.9%, etc.

[0028] Preferably, the mass ratio of the polymerization inhibitor to the catalyst is (0.8-1):1, for example, 0.82:1, 0.84:1, 0.86:1, 0.88:1, 0.9:1, 0.92:1, 0.94:1, 0.96:1 or 0.98:1, etc.

[0029] Preferably, the reaction in step (1) is carried out under an inert gas atmosphere.

[0030] Preferably, the reaction temperature in step (1) is 110-150°C (e.g., 115°C, 120°C, 125°C, 130°C, 135°C, 140°C or 145°C, etc.), and the reaction time is 2-6h (e.g., 2.5h, 3h, 3.5h, 4h, 4.5h, 5h or 5.5h, etc.).

[0031] Preferably, after the reaction in step (1), the reaction further comprises the steps of rotary evaporation, water washing and filtering.

[0032] Preferably, the mixing in step (2) further comprises mixing with isopropanol.

[0033] Preferably, the mass ratio of the polyester compound to isopropyl alcohol is 1:(5-10), for example, 1:5.5, 1:6, 1:6.5, 1:7, 1:7.5, 1:8, 1:8.5, 1:9 or 1:9.5, etc.

[0034] Preferably, the reaction temperature in step (2) is -20 to 95°C (e.g., -10°C, 0°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C or 90°C, etc.), and the reaction time is 2 to 10 h, e.g., 3 h, 4 h, 5 h, 6 h, 7 h, 8 h or 9 h, etc.

[0035] Preferably, the reaction in step (2) further includes a drying step.

[0036] Preferably, the preparation method specifically comprises the following steps:

[0037] (1) Component A and component B are mixed, the molar ratio of component A to component B is 1:(1.05-1.4), a mixed solution of an inhibitor and a solvent and a catalyst are added, the total mass of the inhibitor and the catalyst is 0.1%-1%, and the mass ratio of the inhibitor and the catalyst is (0.8-1):1, based on the total mass of component A, component B, solvent, inhibitor and catalyst as 100%, the reaction is carried out under an inert gas atmosphere at a reaction temperature of 110-150° C. and a reaction time of 2-6 hours, rotary evaporation, water washing and filtering to obtain a polyester compound.

[0038] (2) The polyester compound obtained in step (1) and isopropanol are mixed in a mass ratio of 1:(5-10), and then mixed with a sulfonating agent, wherein the molar ratio of the polyester compound to the sulfonating agent is 1:(1.1-2.5), reacted at -20-95°C for 2-10 hours, and dried to obtain the dispersant.

[0039] In a third aspect, the present invention provides a method for preparing lithium manganese iron phosphate, the preparation method comprising the following steps: grinding and mixing the dispersant, small molecule alcohol, water, phosphorus source, manganese source, lithium source, iron source and carbon source as described in the first aspect, spray drying, and sintering to obtain the lithium manganese iron phosphate.

[0040] Preferably, the preparation method specifically comprises the following steps:

[0041] (a) Mixing the dispersant described in the first aspect, a small molecule alcohol and a portion of water to obtain a dispersant aqueous solution.

[0042] (b) grinding and mixing the phosphorus source, manganese source, lithium source, iron source, carbon source, remaining water and the dispersant aqueous solution obtained in step (a) to obtain a slurry.

[0043] (c) spray drying and sintering the slurry obtained in (b) to obtain the lithium manganese iron phosphate.

[0044] In the present invention, by preparing the dispersant as described in the first aspect into a dispersant aqueous solution and then mixing it with other components in step (a), the time-consuming problem caused by directly mixing the dispersant with other components to form a slurry can be avoided, thereby reducing the time consumption. Adding a small molecule alcohol during the preparation of the dispersant aqueous solution in step (a) can prevent severe foaming during stirring, which may cause equipment failure.

[0045] Preferably, the small molecule alcohol includes C2-C6 (eg, C3, C4 or C5, etc.) alcohol.

[0046] Preferably, the mass concentration of the dispersant in the dispersant aqueous solution is 1wt% to 3wt%, for example, 1.2wt%, 1.4wt%, 1.6wt%, 1.8wt%, 2wt%, 2.2wt%, 2.4wt%, 2.6wt% or 2.8wt%, etc.

[0047] Preferably, the mass concentration of the small molecule alcohol in the dispersant aqueous solution is 0.05wt% to 0.2wt%, for example, 0.06wt%, 0.08wt%, 0.10wt%, 0.12wt%, 0.14wt%, 0.16wt% or 0.18wt%.

[0048] Preferably, the phosphorus source includes any one of phosphoric acid, lithium dihydrogen phosphate, lithium phosphate or iron phosphate, or a combination of at least two thereof.

[0049] Preferably, the manganese source includes any one of trimanganese tetraoxide, manganese carbonate or manganese dioxide, or a combination of at least two of them.

[0050] Preferably, the lithium source includes any one of lithium carbonate, lithium phosphate or lithium dihydrogen phosphate, or a combination of at least two of them.

[0051] Preferably, the iron source includes any one of ferrous sulfate, ferrous oxalate, ferric oxide or ferrosoferric oxide, or a combination of at least two of the above.

[0052] Preferably, the carbon source includes any one of glucose, sucrose or polyethylene glycol, or a combination of at least two of them.

[0053] Preferably, the grinding speed in step (b) is 1300-1700 rpm (for example, 1350 rpm, 1400 rpm, 1450 rpm, 1500 rpm, 1550 rpm, 1600 rpm or 1650 rpm, etc.), and the grinding time is 30-120 min (for example, 40 min, 50 min, 60 min, 70 min, 80 min, 90 min, 100 min or 110 min, etc.).

[0054] Preferably, the grinding and mixing in step (b) further comprises grinding and mixing with additives.

[0055] Preferably, based on the total molar amount of the phosphorus source, manganese source, lithium source and iron source as 100%, the molar amount of the phosphorus source is 30% to 40% (for example, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38% or 39%, etc.), the molar amount of the manganese source is 10% to 20% (for example, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18% or 19%, etc.), the molar amount of the lithium source is 30% to 42% (30%, 32%, 34%, 36%, 38% or 40%, etc.), and the molar amount of the iron source is 10% to 20% (for example, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18% or 19%, etc.).

[0056] Preferably, based on the total mass of the slurry as 100%, the total mass of the phosphorus source, manganese source, lithium source and iron source is 25% to 45% (for example, 27%, 29%, 31%, 33%, 35%, 37%, 39%, 41% or 43%, etc.), the mass of the carbon source is 1% to 4% (for example, 1.5%, 2%, 2.5%, 3% or 3.5%, etc.), the mass of the dispersant aqueous solution is 1.2% to 3% (for example, 1.4%, 1.6%, 1.8%, 2.0%, 2.2%, 2.4%, 2.6% or 2.8%, etc.), and the mass of the remaining water is 48% to 72.8% (for example, 50%, 55%, 60%, 65% or 70%, etc.).

[0057] Preferably, the grinding and mixing in step (b) further comprises grinding and mixing with additives.

[0058] Preferably, based on the total mass of the slurry as 100%, the mass of the additive is 0.1% to 1% (0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8% or 0.9%, etc.).

[0059] Preferably, the sintering temperature in step (c) is 700-785°C (for example, 710°C, 720°C, 730°C, 740°C, 750°C, 760°C, 770°C or 780°C, etc.), and the sintering time is 5-12h (for example, 6h, 7h, 8h, 9h, 10h or 11h, etc.).

[0060] In a fourth aspect, the present invention provides a lithium manganese iron phosphate, which is prepared by the preparation method described in the third aspect.

[0061] Preferably, the particle size of the lithium manganese iron phosphate is 0.5-1.3 μm, for example, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm or 1.2 μm.

[0062] In a fifth aspect, the present invention provides a positive electrode sheet, wherein the positive electrode sheet comprises the lithium manganese iron phosphate as described in the fourth aspect.

[0063] In a sixth aspect, the present invention provides a lithium-ion battery, wherein the lithium-ion battery comprises the lithium iron manganese phosphate as described in the fourth aspect or the positive electrode sheet as described in the fifth aspect.

[0064] Compared with the prior art, the present invention has the following beneficial effects:

[0065] In the present invention, the dispersant prepared by using C8-C20 polyols, acid compounds and / or anhydride compounds and sulfonated reagents as raw materials has the characteristic of good dispersing effect. Adding the dispersant in the preparation process of lithium manganese iron phosphate can solve the problem of excessive viscosity of the slurry caused by small particle size formed during grinding and reduce agglomeration. In addition, the dispersant basically exists in the form of residual carbon after the sintering process, and has basically no effect on the performance of lithium manganese iron phosphate. DETAILED DESCRIPTION

[0066] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0067] Example 1

[0068] This embodiment provides a dispersant and a preparation method thereof and a preparation method of lithium manganese iron phosphate. The preparation method of the dispersant is as follows:

[0069] (1) adding component A to a three-necked flask, and then adding component B, a mixed solution of an inhibitor and a solvent, and a catalyst, wherein the molar ratio of component A to component B is 1:1.2, and based on the total mass of component A, component B, solvent, inhibitor and catalyst as 100%, the total mass of the inhibitor and catalyst is 0.5%, and the mass ratio of the inhibitor and catalyst is 0.9:1, reacting under an inert gas atmosphere at a reaction temperature of 130° C. for a reaction time of 4 h, removing the solvent by rotary evaporation, washing with water at 55° C., filtering, and drying to obtain a polyester compound;

[0070] The component A is lauryl alcohol, the component B is maleic anhydride, the inhibitor is hydroquinone, the solvent is anhydrous toluene, and the catalyst is p-toluenesulfonic acid.

[0071] (2) mixing the polyester compound obtained in step (1) and isopropanol in a mass ratio of 1:7 and adding them into a three-necked flask, then adding a sulfonating agent and mixing, wherein the molar ratio of the polyester compound to the sulfonating agent is 1:1.3, reacting at 65° C. for 3 h, and drying to obtain the dispersant;

[0072] The above sulfonating agent is propane sultone.

[0073] The preparation method of the lithium manganese iron phosphate is as follows:

[0074] (a) mixing the above dispersant, a small molecule alcohol and a portion of water to obtain a dispersant aqueous solution, wherein the mass concentration of the dispersant in the dispersant aqueous solution is 2 wt %, and the mass concentration of the small molecule alcohol is 0.1 wt %;

[0075] The above-mentioned small molecule alcohol is ethanol.

[0076] (b) mixing 0.3 mol of a phosphorus source, 0.20 mol of a manganese source, 0.32 mol of a lithium source, 0.18 mol of an iron source, a carbon source, the remaining water, and the dispersant aqueous solution obtained in step (a), and grinding at 1500 rpm for 60 min to obtain a slurry, wherein the total mass of the phosphorus source, manganese source, lithium source and iron source is 30%, the mass of the carbon source is 4%, the mass of the dispersant aqueous solution is 2%, and the mass of the remaining water is 64% based on the total mass of the slurry as 100%;

[0077] The phosphorus source is phosphoric acid, the manganese source is manganese carbonate, the lithium source is lithium carbonate, the iron source is iron oxide, and the carbon source is glucose.

[0078] (c) spray drying the slurry obtained in (b), and sintering at 750° C. for 10 h to obtain the lithium manganese iron phosphate.

[0079] Example 2

[0080] This embodiment provides a dispersant and a preparation method thereof and a preparation method of lithium manganese iron phosphate. The preparation method of the dispersant is as follows:

[0081] (1) adding component A to a three-necked flask, and then adding component B, a mixed solution of an inhibitor and a solvent, and a catalyst, wherein the molar ratio of component A to component B is 1:1.2, and based on the total mass of component A, component B, solvent, inhibitor and catalyst as 100%, the total mass of the inhibitor and catalyst is 0.5%, and the mass ratio of the inhibitor and catalyst is 0.9:1, reacting under an inert gas atmosphere at a reaction temperature of 110° C. for a reaction time of 2 h, removing the solvent by rotary evaporation, washing with water at 40° C., filtering, and drying to obtain a polyester compound;

[0082] The component A is lauryl alcohol, the component B is maleic anhydride, the inhibitor is hydroquinone, the solvent is anhydrous toluene, and the catalyst is p-toluenesulfonic acid.

[0083] (2) mixing the polyester compound obtained in step (1) and isopropanol in a mass ratio of 1:7 and adding them into a three-necked flask, then adding a sulfonating agent and mixing, wherein the molar ratio of the polyester compound to the sulfonating agent is 1:1.3, reacting at 50° C. for 4 hours, and drying to obtain the dispersant;

[0084] The above sulfonating agent is propane sultone.

[0085] The preparation method of the lithium manganese iron phosphate is as follows:

[0086] (a) mixing the above dispersant, a small molecule alcohol and water to obtain a dispersant aqueous solution, wherein the mass concentration of the dispersant in the dispersant aqueous solution is 2 wt %, and the mass concentration of the small molecule alcohol is 0.1 wt %;

[0087] The above-mentioned small molecule alcohol is isopropanol.

[0088] (b) mixing 0.3 mol of a phosphorus source, 0.20 mol of a manganese source, 0.32 mol of a lithium source, 0.18 mol of an iron source, a carbon source, the remaining water, and the dispersant aqueous solution obtained in step (a), and grinding at 1500 rpm for 60 min to obtain a slurry, wherein the total mass of the phosphorus source, manganese source, lithium source and iron source is 30%, the mass of the carbon source is 4%, the mass of the dispersant aqueous solution is 2%, and the mass of the remaining water is 64% based on the total mass of the slurry as 100%;

[0089] The phosphorus source is phosphoric acid, the manganese source is manganese carbonate, the lithium source is lithium carbonate, the iron source is iron oxide, and the carbon source is glucose.

[0090] (c) spray drying the slurry obtained in (b), and sintering at 750° C. for 10 h to obtain the lithium manganese iron phosphate.

[0091] Example 3

[0092] This embodiment provides a dispersant and a preparation method thereof and a preparation method of lithium manganese iron phosphate. The preparation method of the dispersant is as follows:

[0093] (1) adding component A to a three-necked flask, and then adding component B, a mixed solution of an inhibitor and a solvent, and a catalyst, wherein the molar ratio of component A to component B is 1:1.2, and based on the total mass of component A, component B, solvent, inhibitor and catalyst as 100%, the total mass of the inhibitor and catalyst is 0.5%, and the mass ratio of the inhibitor and catalyst is 0.9:1, reacting under an inert gas atmosphere at a reaction temperature of 150° C. for a reaction time of 6 h, removing the solvent by rotary evaporation, washing with water at 40° C., filtering, and drying to obtain a polyester compound;

[0094] The component A is lauryl alcohol, the component B is maleic anhydride, the inhibitor is hydroquinone, the solvent is anhydrous toluene, and the catalyst is p-toluenesulfonic acid.

[0095] (2) mixing the polyester compound obtained in step (1) and isopropanol in a mass ratio of 1:7 and adding them into a three-necked flask, then adding a sulfonating agent and mixing, wherein the molar ratio of the polyester compound to the sulfonating agent is 1:1.3, reacting at 90° C. for 8 h, and drying to obtain the dispersant;

[0096] The above sulfonating agent is propane sultone.

[0097] The preparation method of the lithium manganese iron phosphate is as follows:

[0098] (a) mixing the above dispersant, a small molecule alcohol and water to obtain a dispersant aqueous solution, wherein the mass concentration of the dispersant in the dispersant aqueous solution is 2 wt %, and the mass concentration of the small molecule alcohol is 0.1 wt %;

[0099] The above-mentioned small molecule alcohol is isopropanol.

[0100] (b) mixing 0.3 mol of a phosphorus source, 0.20 mol of a manganese source, 0.32 mol of a lithium source, 0.18 mol of an iron source, a carbon source, the remaining water, and the dispersant aqueous solution obtained in step (a), and grinding at 1500 rpm for 60 min to obtain a slurry, wherein the total mass of the phosphorus source, manganese source, lithium source and iron source is 30%, the mass of the carbon source is 4%, the mass of the dispersant aqueous solution is 2%, and the mass of the remaining water is 64% based on the total mass of the slurry as 100%;

[0101] The phosphorus source is phosphoric acid, the manganese source is manganese carbonate, the lithium source is lithium carbonate, the iron source is iron oxide, and the carbon source is glucose.

[0102] (c) spray drying the slurry obtained in (b), and sintering at 750° C. for 10 h to obtain the lithium manganese iron phosphate.

[0103] Example 4

[0104] This embodiment provides a dispersant and a preparation method thereof and a preparation method of lithium manganese iron phosphate. The only difference between this embodiment and embodiment 1 is that component A is 2-butyloctanol, and other conditions are the same as those in embodiment 1.

[0105] Example 5

[0106] This embodiment provides a dispersant and a preparation method thereof and a preparation method of lithium manganese iron phosphate. The only difference between this embodiment and embodiment 1 is that component B is acetic acid, and other conditions are the same as those in embodiment 1.

[0107] Example 6

[0108] This embodiment provides a dispersant and a preparation method thereof and a preparation method of lithium manganese iron phosphate. The only difference between this embodiment and embodiment 1 is that component B is acrylic acid, and other conditions are the same as those in embodiment 1.

[0109] Example 7

[0110] This embodiment provides a dispersant and a preparation method thereof and a preparation method of lithium manganese iron phosphate. The only difference between the present embodiment and embodiment 1 is that the sulfonating agent is chlorosulfonic acid, the reaction temperature in step (2) is adjusted to -20°C, and the other conditions are the same as those in embodiment 1.

[0111] Example 8

[0112] This embodiment provides a dispersant and a preparation method thereof and a preparation method of lithium manganese iron phosphate. The difference between the present embodiment and the preparation method of lithium manganese iron phosphate is that the mass concentration of the dispersant in the dispersant aqueous solution in step (a) of the preparation method of lithium manganese iron phosphate is adjusted to 1.2%, and the mass of the remaining water is adjusted to 64.8%. Other conditions are the same as those in Example 1.

[0113] Example 9

[0114] This embodiment provides a dispersant and a preparation method thereof and a preparation method of lithium manganese iron phosphate. The difference between the present embodiment and the preparation method of lithium manganese iron phosphate is that the mass concentration of the dispersant in the dispersant aqueous solution in step (a) of the preparation method of lithium manganese iron phosphate is adjusted to 3wt%, and the mass of the remaining water is adjusted to 63%. Other conditions are the same as those in Example 1.

[0115] Example 10

[0116] This embodiment provides a dispersant and a preparation method thereof and a preparation method of lithium manganese iron phosphate. The only difference between the present embodiment and the embodiment 1 is that the molar ratio of component A to component B is adjusted to 1:1.45, and other conditions are the same as those in the embodiment 1.

[0117] Embodiment 11

[0118] This embodiment provides a dispersant and a preparation method thereof and a preparation method of lithium manganese iron phosphate. The only difference between the present embodiment and the embodiment 1 is that the molar ratio of component A to component B is adjusted to 1:1, and other conditions are the same as those in the embodiment 1.

[0119] Example 12

[0120] This embodiment provides a dispersant and a preparation method thereof and a preparation method of lithium manganese iron phosphate. The only difference between the dispersant and the embodiment 1 is that the molar ratio of the polyester compound and the sulfonated reagent is adjusted to 1:1, and other conditions are the same as those in the embodiment 1.

[0121] Embodiment 13

[0122] This embodiment provides a dispersant and a preparation method thereof and a preparation method of lithium manganese iron phosphate. The only difference between the dispersant and the embodiment 1 is that the molar ratio of the polyester compound and the sulfonated reagent is adjusted to 1:2.6, and the other conditions are the same as those in the embodiment 1.

[0123] Comparative Example 1

[0124] This comparative example provides a method for preparing lithium manganese iron phosphate, which is different from Example 1 only in that no dispersant is added in the method for preparing lithium manganese iron phosphate, and other conditions are the same as those in Example 1.

[0125] Comparative Example 2

[0126] This comparative example provides a method for preparing lithium manganese iron phosphate, which differs from Example 1 only in that the dispersant in the method for preparing lithium manganese iron phosphate is replaced with sodium dodecyl sulfate (SDS) of the same mass, and other conditions are the same as those in Example 1.

[0127] Performance Testing

[0128] (1) Viscosity of slurry: The viscosity of the slurry prepared in step (b) of the preparation method of lithium manganese iron phosphate provided in the test examples and comparative examples was measured by using an NDJ viscometer. An appropriate amount of slurry with a qualified sand-grinded particle size was placed in a measuring sleeve. A No. 2 rotor was used at room temperature to measure the viscosity at 12 r / min.

[0129] (2) Particle size: The particle size of the lithium manganese iron phosphate dispersed in the slurry prepared in step (b) of the preparation method of lithium manganese iron phosphate provided in the test examples and comparative examples was measured using a Malvern laser particle size analyzer.

[0130] The test results are shown in Table 1 below:

[0131] Table 1

[0132]

[0133]

[0134] It can be seen from the content of Table 1 that the viscosity of the slurry obtained in step (b) of the preparation method of lithium manganese iron phosphate provided in Example 1-13 is 891mPa·s~1389mPa·s, and the particle size of lithium manganese iron phosphate dispersed in the slurry is 0.253μm~0.275μm.

[0135] By comparing Examples 1, 5, and 6, it can be seen that the B component is selected from acetic acid (Example 5), and the dispersant obtained with a relatively small molecular weight has a slightly poor viscosity reduction effect; the B component is preferably maleic anhydride (Example 1) The dispersant obtained has a better viscosity reduction effect.

[0136] Compared with Example 1, if the mass concentration of the dispersant in the dispersant aqueous solution is too small (Example 8), the dispersion and viscosity reduction effect is slightly poor; if the mass concentration of the dispersant in the dispersant aqueous solution is too large (Example 9), the dispersion effect is also poor. Too high a concentration causes the critical micelle concentration of the solution to be exceeded, resulting in a decrease in the interfacial activity.

[0137] Compared with Example 1, if the molar amount of component B is too high (Example 10), the residual component B in the reaction system is too high, resulting in poor dispersing effect of the prepared dispersant; if the molar amount of component B is too low (Example 11), the reaction is incomplete and the dispersing effect of the prepared dispersant is also slightly poor. It can be seen that the performance of the dispersant prepared by controlling the molar ratio of component A and component B within a specific range is better.

[0138] Compared with Example 1, if the molar ratio of the polyester compound and the sulfonated reagent is too large (Example 12), the sulfonation reaction is incomplete and the dispersing effect of the obtained dispersant is poor; if the molar ratio of the polyester compound and the sulfonated reagent is too small (Example 13), the effect on the dispersion performance is small.

[0139] Compared with Example 1, if no dispersant is added (Comparative Example 1), the viscosity of the slurry prepared in step (b) of the preparation method of lithium manganese iron phosphate is greatly increased, and the particle size of the dispersed lithium manganese iron phosphate is enlarged.

[0140] Compared with Example 1, if the dispersant provided in Example 1 is replaced with sodium dodecyl sulfate of the same mass (Comparative Example 1), the viscosity of the slurry prepared in step (b) of the preparation method of lithium manganese iron phosphate increases.

[0141] The applicant declares that the present invention illustrates a dispersant and its preparation method and application through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned embodiments, that is, it does not mean that the present invention must rely on the above-mentioned embodiments to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of various raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A dispersant, characterized in that: The raw materials for preparing the dispersant include component A, component B and a sulfonated reagent; The A component includes a C8-C20 polyol; The B component includes an acid compound and / or an acid anhydride compound.

2. The dispersant according to claim 1, characterized in that The C8-C20 polyols include C8-C20 straight-chain polyols and / or C8-C20 branched-chain polyols; Preferably, the acid compound includes any one of acetic acid, acrylic acid or succinic acid, or a combination of at least two thereof; Preferably, the acid anhydride compound comprises maleic anhydride; Preferably, the sulfonating agent comprises any one of sulfuric acid, propane sultone, aminosulfonic acid or chlorosulfonic acid, or a combination of at least two thereof.

3. A method for preparing a dispersant as claimed in claim 1 or 2, characterized in that: The preparation method comprises the following steps: (1) mixing component A and component B, reacting to obtain a polyester compound; (2) The polyester compound obtained in step (1) and a sulfonating agent are mixed and reacted to obtain the dispersant.

4. The preparation method according to claim 3, characterized in that: The molar ratio of component A to component B is 1:(1.05-1.4); Preferably, the molar ratio of the polyester compound to the sulfonated reagent is 1:(1.1-2.5); Preferably, the mixing in step (1) further comprises mixing with an inhibitor, a solvent and a catalyst; Preferably, the polymerization inhibitor comprises any one or a combination of at least two of hydroquinone, p-hydroxyanisole, diethylhydroxylamine or 1,1-diphenyl-2-trinitrophenylhydrazine; Preferably, the solvent comprises anhydrous toluene; Preferably, the catalyst comprises any one or a combination of at least two of p-toluenesulfonic acid, a cation exchange resin or zirconium oxide; Preferably, based on the total mass of component A, component B, solvent, inhibitor and catalyst as 100%, the total mass of the inhibitor and catalyst is 0.1% to 1%; Preferably, the mass ratio of the inhibitor to the catalyst is (0.8-1):1; Preferably, the reaction in step (1) is carried out under an inert gas atmosphere; Preferably, the reaction temperature in step (1) is 110-150° C., and the reaction time is 2-6 hours; Preferably, after the reaction in step (1), the steps of rotary evaporation, washing and filtering are also included; Preferably, the mixing in step (2) further comprises mixing with isopropanol; Preferably, the mass ratio of the polyester compound to isopropanol is 1:(5-10); Preferably, the reaction temperature in step (2) is -20 to 95°C, and the reaction time is 2 to 10 hours; Preferably, the reaction in step (2) further includes a drying step.

5. The preparation method according to claim 3 or 4, characterized in that: The preparation method specifically comprises the following steps: (1) mixing component A and component B, wherein the molar ratio of component A to component B is 1:(1.05-1.4), adding a mixed solution of an inhibitor and a solvent and a catalyst, wherein the total mass of the inhibitor and the catalyst is 0.1%-1%, based on the total mass of component A, component B, the solvent, the inhibitor and the catalyst being 100%, the total mass of the inhibitor and the catalyst is 0.1%-1%, and the mass ratio of the inhibitor and the catalyst is (0.8-1):1, reacting under an inert gas atmosphere at a reaction temperature of 110-150° C. for a reaction time of 2-6 hours, rotary evaporating, washing with water and filtering to obtain a polyester compound; (2) The polyester compound obtained in step (1) and isopropanol are mixed in a mass ratio of 1:(5-10), and then mixed with a sulfonating agent, wherein the molar ratio of the polyester compound to the sulfonating agent is 1:(1.1-2.5), reacted at -20-95°C for 2-10 hours, and dried to obtain the dispersant.

6. A method for preparing lithium manganese iron phosphate, characterized in that: The preparation method comprises the following steps: grinding and mixing the dispersant as claimed in claim 1 or 2, a small molecule alcohol, water, a phosphorus source, a manganese source, a lithium source, an iron source and a carbon source, spray drying, and sintering to obtain the lithium manganese iron phosphate.

7. The preparation method according to claim 6, characterized in that: The preparation method specifically comprises the following steps: (a) mixing the dispersant as claimed in claim 1 or 2, a small molecule alcohol and a portion of water to obtain a dispersant aqueous solution; (b) grinding and mixing the phosphorus source, manganese source, lithium source, iron source, carbon source, remaining water and the dispersant aqueous solution obtained in step (a) to obtain a slurry; (c) spray drying and sintering the slurry obtained in (b) to obtain the lithium manganese iron phosphate; Preferably, the mass concentration of the dispersant in the dispersant aqueous solution is 1wt% to 3wt%; Preferably, the mass concentration of the small molecule alcohol in the dispersant aqueous solution is 0.05wt% to 0.2wt%; Preferably, the phosphorus source includes any one of phosphoric acid, lithium dihydrogen phosphate, lithium phosphate or iron phosphate, or a combination of at least two thereof; Preferably, the manganese source includes any one or a combination of at least two of manganese tetraoxide, manganese carbonate or manganese dioxide; Preferably, the lithium source includes any one of lithium carbonate, lithium phosphate or lithium dihydrogen phosphate, or a combination of at least two of them; Preferably, the iron source includes any one of ferrous sulfate, ferrous oxalate, ferric oxide or ferrosoferric oxide, or a combination of at least two of the above; Preferably, the carbon source comprises any one of glucose, sucrose or polyethylene glycol or a combination of at least two of them; Preferably, the grinding speed in step (b) is 1300-1700 rpm, and the grinding time is 30-120 min; Preferably, based on the total molar amount of the phosphorus source, manganese source, lithium source and iron source as 100%, the molar amount of the phosphorus source is 30% to 40%, the molar amount of the manganese source is 10% to 20%, the molar amount of the lithium source is 30% to 42%, and the molar amount of the iron source is 10% to 20%; Preferably, based on the total mass of the slurry being 100%, the total mass of the phosphorus source, manganese source, lithium source and iron source is 25% to 45%, the mass of the carbon source is 1% to 4%, the mass of the dispersant aqueous solution is 1.2% to 3%, and the mass of the remaining water is 48% to 72.8%; Preferably, the sintering temperature in step (c) is 700-785° C., and the sintering time is 5-12 hours.

8. A lithium manganese iron phosphate, characterized in that: The lithium manganese iron phosphate is prepared by the preparation method described in claim 6 or 7.

9. A positive electrode sheet, characterized in that: The positive electrode sheet includes the lithium manganese iron phosphate as described in claim 8.

10. A lithium ion battery, characterized in that: The lithium-ion battery comprises the lithium iron manganese phosphate as claimed in claim 8 or the positive electrode sheet as claimed in claim 9.

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