阅读说明：本技术 一种锂电池正极材料用高纯硼酸的制备方法 (Preparation method of high-purity boric acid for lithium battery cathode material ) 是由 张志峰 周海东 余瑶辰 于 2021-01-25 设计创作，主要内容包括：本发明公开了一种锂电池正极材料用高纯硼酸的制备方法,包括以下步骤：S1：将八乙烯基笼型倍半硅氧烷和烯烃基氨基甲酸酯溶解于溶剂中,再加入引发剂,反应分离后,得到中间产物；S2：将其溶于过量的无水乙二胺中,进行酰胺重复单元的扩链反应,反应分离后,得到树状聚合中间体；S3：将其与烯烃基氨基甲酸酯进行接枝反应,再进行皂化反应和pH值调节,沉淀析出树状聚合物；S4：采用工业硼酸配制成硼酸饱和溶液,将树状聚合物加入其中,反应结束后结晶过滤,析出硼酸晶体,得到高纯硼酸晶体。本发明的硼酸制备方法,所制备得到的树状聚合物耐酸性好,硼酸中所含金属离子脱除率高,易于分离过滤,得到高纯硼酸,满足锂电池正极材料使用。(The invention discloses a preparation method of high-purity boric acid for a lithium battery anode material, which comprises the following steps: s1: dissolving octavinyl cage type silsesquioxane and alkenyl carbamate in a solvent, adding an initiator, and reacting and separating to obtain an intermediate product; s2: dissolving the obtained product in excessive anhydrous ethylenediamine, performing chain extension reaction of amide repeating units, and performing reaction separation to obtain a dendrimer; s3: grafting the dendrimer with alkylene carbamate, then performing saponification and pH value adjustment, and precipitating to separate out the dendrimer; s4: preparing boric acid saturated solution by using industrial boric acid, adding the dendrimer into the boric acid saturated solution, crystallizing and filtering after the reaction is finished, and precipitating boric acid crystals to obtain high-purity boric acid crystals. According to the preparation method of the boric acid, the prepared dendrimer has good acid resistance, the removal rate of metal ions contained in the boric acid is high, the separation and filtration are easy, and the high-purity boric acid is obtained and meets the use requirement of a lithium battery anode material.)

1. A preparation method of high-purity boric acid for a lithium battery positive electrode material is characterized by comprising the following steps:

s1: mixing a mixture of 1: dissolving 8-12 of octavinyl cage type silsesquioxane and alkenyl carbamate in a solvent, adding an initiator with the molar concentration of 0.01-0.05 mol/L, heating, condensing, refluxing, filtering under reduced pressure, washing the solid with distilled water for 2-3 times, filtering, and drying to obtain an intermediate product;

s2: dissolving the intermediate product obtained in the step S1 in excessive anhydrous ethylenediamine, heating to 50-55 ℃ to perform chain extension reaction of an amide repeating unit, reacting for 8-12 h, and performing reduced pressure distillation to obtain a dendrimer polymerization intermediate with a polyhedral oligomeric silsesquioxane center;

s3: dissolving the dendriform polymerization intermediate obtained in the step S2 in methanol, dropwise adding alkylene carbamate while stirring to perform a grafting reaction of the tail end of a branched chain, adding a lithium hydroxide solution after the reaction is completed to perform a saponification reaction, adjusting the pH value to 4.8-6.2 by using boric acid, and precipitating and separating out a plurality of highly branched dendriform polymers taking an amide repeating unit as a branched chain and taking a cage-type silsesquioxane center;

s4: adding industrial boric acid into deionized water, heating, stirring and dissolving to prepare a boric acid saturated solution, after the boric acid is completely dissolved, obtaining the calcium chelating capacity of the dendrimer according to the step S3, weighing a certain amount of the dendrimer as an adsorbent, adding the dendrimer into the boric acid saturated solution, immediately performing vacuum filtration while hot after the reaction is finished, filtering impurities, putting the filtrate into a refrigerator for refrigeration, precipitating boric acid crystals, performing suction filtration again, and drying to obtain high-purity boric acid crystals.

2. The method according to claim 1, wherein the alkylene carbamate is at least one selected from the group consisting of ethyl 5-hexen-1-yl carbamate, ethyl (2-methyl-4-penten-1-yl) carbamate, methyl (2, 2-dimethyl-4-penten-1-yl) carbamate, and methyl (3-hydroxy-3-methyl-4-penten-1-yl) carbamate.

3. The method for preparing high-purity boric acid for the positive electrode material of the lithium battery as claimed in claim 1, wherein the reaction temperature of the reflux reaction is 60-90 ℃ and the reaction time is 6-7 h.

4. The method of claim 1, wherein the initiator is at least one of t-butyl peroxybenzoate, dicumyl peroxide, diisopropyl peroxydicarbonate, benzoyl peroxide, ammonium persulfate, sodium persulfate, and potassium persulfate.

5. The method for preparing high-purity boric acid for the positive electrode material of a lithium battery as claimed in claim 1, wherein the addition amount of the initiator is 0.15-0.36% of the total mass of the reaction raw materials of the octavinyl cage-type silsesquioxane and the alkylene carbamate.

6. The method for preparing high-purity boric acid for a positive electrode material of a lithium battery as claimed in claim 1, wherein in step S2, the molar ratio of ethylenediamine to the intermediate product is 50 to 200: 1.

7. the method for preparing high-purity boric acid for a positive electrode material of a lithium battery as claimed in claim 1, wherein in step S3, the molar ratio of the alkenyl carbamate to the dendrimer intermediate is 8 to 8.8: 1.

8. the method of preparing high purity boric acid for a positive electrode material of a lithium battery as claimed in claim 1, wherein the temperature of the saturated solution of boric acid is 25 to 30 ℃ and the refrigerating temperature of the refrigerator is-5 to-10 ℃ in step S4.

Technical Field

The invention relates to the technical field of a preparation method of boric acid, in particular to a preparation method of high-purity boric acid for a lithium battery anode material.

Background

A "lithium battery" is a type of battery using a nonaqueous electrolyte solution with lithium metal or a lithium alloy as a positive/negative electrode material. The conventional lithium battery anode material mainly comprises lithium iron phosphate, nickel-cobalt-manganese ternary material and the like, the theoretical specific capacity of the lithium iron phosphate is about 170mAh/g, and researches show that the theoretical specific capacity of the lithium iron borate is about 220mAh/g and is larger than that of the lithium iron phosphate, and the material can be used as a substitute material of the lithium iron phosphate, has higher specific capacity, better conductivity and extremely small volume change rate. Lithium iron borate is gaining more and more attention as a novel lithium ion nanometer anode material.

In the preparation process of the lithium iron borate anode material, different boron sources, lithium sources and iron sources are required to be prepared, wherein the boron sources comprise boric acid, diboron trioxide and the like, the purity of domestic industrial boric acid is low and is generally between 99% and 99.5%, and the purity control of the lithium iron borate anode material is seriously influenced by the addition of the industrial boric acid, so that the electrochemical performance of a lithium battery is influenced.

Accordingly, a method for preparing high-purity boric acid for a lithium battery cathode material is needed.

Disclosure of Invention

In view of the defects of the prior art, the invention aims to provide a preparation method of high-purity boric acid for a lithium battery cathode material, so as to solve the problem that the use effect and the service life of a battery are influenced because industrial boric acid containing metal impurities cannot meet the use requirement of the lithium battery cathode material.

In order to achieve the above purposes, the technical scheme adopted by the invention is as follows:

a preparation method of high-purity boric acid for a lithium battery cathode material comprises the following steps:

s1: mixing a mixture of 1: dissolving 8-12 of octavinyl cage type silsesquioxane and alkenyl carbamate in a solvent, adding an initiator with the molar concentration of 0.01-0.05 mol/L, heating, condensing, refluxing, filtering under reduced pressure, washing the solid with distilled water for 2-3 times, filtering, and drying to obtain an intermediate product;

s2: dissolving the intermediate product obtained in the step S1 in excessive anhydrous ethylenediamine, heating to 50-55 ℃ to perform chain extension reaction of an amide repeating unit, reacting for 8-12 h, and performing reduced pressure distillation to obtain a dendrimer polymerization intermediate with a polyhedral oligomeric silsesquioxane center;

s3: dissolving the dendriform polymerization intermediate obtained in the step S2 in methanol, dropwise adding alkylene carbamate while stirring to perform a grafting reaction of the tail end of a branched chain, adding a lithium hydroxide solution after the reaction is completed to perform a saponification reaction, adjusting the pH value to 4.8-6.2 by using boric acid, and precipitating and separating out a plurality of highly branched dendriform polymers taking an amide repeating unit as a branched chain and taking a cage-type silsesquioxane center;

s4: adding industrial boric acid into deionized water, heating, stirring and dissolving to prepare a boric acid saturated solution, after the boric acid is completely dissolved, obtaining the calcium chelating capacity of the dendrimer according to the step S3, weighing a certain amount of the dendrimer as an adsorbent, adding the dendrimer into the boric acid saturated solution, immediately performing vacuum filtration while hot after the reaction is finished, filtering impurities, putting the filtrate into a refrigerator for refrigeration, precipitating boric acid crystals, performing suction filtration again, and drying to obtain high-purity boric acid crystals.

Preferably, the alkylene carbamate is at least one of ethyl 5-hexen-1-ylcarbamate, ethyl (2-methyl-4-penten-1-yl) carbamate, methyl (2, 2-dimethyl-4-penten-1-yl) carbamate, and methyl (3-hydroxy-3-methyl-4-penten-1-yl) carbamate.

Preferably, the reaction temperature of the reflux reaction is 60-90 ℃, and the reaction time is 6-7 h.

Preferably, the initiator is at least one of tert-butyl peroxybenzoate, dicumyl peroxide, diisopropyl peroxydicarbonate, benzoyl peroxide, ammonium persulfate, sodium persulfate and potassium persulfate.

Preferably, the addition amount of the initiator accounts for 0.15-0.36% of the total mass of the reaction raw materials of the octavinyl cage-type silsesquioxane and the alkenyl carbamate.

Preferably, in step S2, the molar ratio of ethylenediamine to intermediate product is 50 to 200: 1.

preferably, in step S3, the molar ratio of the alkenyl carbamate to the dendrimer intermediate is 8 to 8.8: 1.

preferably, in step S4, the temperature of the saturated boric acid solution is 25 to 30 ℃, and the refrigerating temperature of the refrigerator is-5 to-10 ℃.

The invention has the beneficial effects that:

the invention takes cage type silsesquioxane as a center, a polymer branch chain with a plurality of amide repeating units is grafted on the vertex angle of the cage type silsesquioxane, and a carboxylic acid group is grafted on the tail end of the highly branched branch chain. The carboxylic acid groups grafted at the tail ends reduce intermolecular force by utilizing a plurality of highly branched molecular chain structures taking cage-type silsesquioxane as the center, so that the carboxylic acid groups have higher coordination, and the carboxylic acid groups grafted at the tail ends combine with specific functional groups by utilizing the spatial distribution of branched chains to play a synergistic effect and combine with metal ions in a boric acid solution to form a three-dimensional highly crosslinked heavy metal organic matter, so that the migration of the metal ions is avoided, and the dendrimer has excellent acid resistance. The organic-inorganic hybrid structure cage-type silsesquioxane has extremely high stability and can resist the molecular tension between the branched chains, so that the stability of the dendrimer serving as an adsorbent is improved.

The carboxylic acid group is grafted to the amide group of the dendritic polymer branched chain taking the cage-type silsesquioxane as the center, and the electronegativity of the nitrogen atom on the amide group is large, so that the polarity of the oxygen atom in the carboxylic acid group is favorably increased, and the trapping capacity of metal ions is improved; the polyamide dendrimer taking the cage-type silsesquioxane as the center contains a large number of polyamide branched chains, so that the polyamide dendrimer has a higher bridging effect, can accelerate precipitation of metal organics after heavy metal capture, and is easy to separate and purify boric acid.

Detailed Description

The following description is presented to disclose the invention so as to enable any person skilled in the art to practice the invention. The preferred embodiments in the following description are given by way of example only, and other obvious variations will occur to those skilled in the art.

Example 1

The preparation method of the high-purity boric acid for the lithium battery cathode material comprises the following steps:

s1: mixing a mixture of 1: dissolving the octavinyl cage-type silsesquioxane and ethyl 5-hexene-1-yl carbamate of 8 in toluene, adding an initiator tert-butyl peroxybenzoate with the molar concentration of 0.01mol/L, wherein the addition amount of the initiator accounts for 0.15 percent of the total mass of reaction raw materials of the octavinyl cage-type silsesquioxane and the ethyl 5-hexene-1-yl carbamate, heating, condensing, refluxing and reacting at the reaction temperature of 60 ℃ for 7 hours, filtering under reduced pressure, washing the solid with distilled water for 3 times, filtering and drying to obtain an intermediate product;

s2: dissolving the intermediate product obtained in the step S1 in an excess of anhydrous ethylenediamine, wherein the molar ratio of the ethylenediamine to the intermediate product is 50: 1, heating to 50 ℃ to carry out chain extension reaction of an amide repeating unit, reacting for 8 hours, and carrying out reduced pressure distillation to obtain a dendrimer intermediate with a polyhedral oligomeric silsesquioxane center;

s3: dissolving the dendrimer obtained in the step S2 in methanol, and dropwise adding alkylene carbamate while stirring to perform a grafting reaction of the branch end, wherein the molar ratio of the alkylene carbamate to the dendrimer is 8.1: 1, adding a lithium hydroxide solution to carry out saponification reaction after the reaction is finished, then regulating the pH value to 5.1 by using boric acid, and precipitating and separating out a dendrimer which takes a cage-type silsesquioxane center and a plurality of highly branched amide repeating units as branched chains;

s4: adding industrial boric acid into deionized water, heating, stirring and dissolving to prepare a boric acid saturated solution, wherein the temperature of the boric acid saturated solution is 25 ℃, after the boric acid is completely dissolved, obtaining the calcium chelating capacity of the dendrimer according to the step S3, weighing a certain amount of dendrimer as an adsorbent, adding the dendrimer into the boric acid saturated solution, immediately performing vacuum filtration after the reaction is finished, filtering impurities, putting the filtrate into a refrigerator for refrigeration, wherein the refrigeration temperature of the refrigerator is-5 ℃, precipitating boric acid crystals, performing suction filtration again, and drying to obtain high-purity boric acid crystals.

The detection result shows that the dendrimer prepared in the embodiment has the capacity of adsorbing and chelating calcium ions of 214.3mg/g, and the purity of boric acid is 99.92%.

Example 2

The preparation method of the high-purity boric acid for the lithium battery cathode material comprises the following steps:

s1: mixing a mixture of 1: dissolving the octavinyl cage-type silsesquioxane and ethyl (2-methyl-4-penten-1-yl) carbamate in toluene, adding an initiator diisopropyl peroxydicarbonate with the molar concentration of 0.03mol/L, wherein the addition amount of the initiator accounts for 0.26 percent of the total mass of the reaction raw materials of the octavinyl cage-type silsesquioxane and the ethyl (2-methyl-4-penten-1-yl) carbamate, heating, condensing, refluxing, reacting at the reaction temperature of 90 ℃ for 6 hours, filtering under reduced pressure, washing the solid with distilled water for 3 times, filtering and drying to obtain an intermediate product;

s2: dissolving the intermediate product obtained in the step S1 in excess anhydrous ethylenediamine, wherein the molar ratio of the ethylenediamine to the intermediate product is 100: 1, heating to 55 ℃ to carry out chain extension reaction of an amide repeating unit, reacting for 10 hours, and then carrying out reduced pressure distillation to obtain a dendrimer intermediate with a polyhedral oligomeric silsesquioxane center;

s3: dissolving the dendrimer obtained in the step S2 in methanol, and dropwise adding alkylene carbamate while stirring to perform a grafting reaction of the branch end, wherein the molar ratio of the alkylene carbamate to the dendrimer is 8.3: 1, adding a lithium hydroxide solution to carry out saponification reaction after the reaction is finished, then regulating the pH value to 5.8 by using boric acid, and precipitating and separating out a dendrimer which takes a cage-type silsesquioxane center and a plurality of highly branched amide repeating units as branched chains;

s4: adding industrial boric acid into deionized water, heating, stirring and dissolving to prepare a boric acid saturated solution, wherein the temperature of the boric acid saturated solution is 30 ℃, after the boric acid is completely dissolved, obtaining the calcium chelating capacity of the dendrimer according to the step S3, weighing a certain amount of dendrimer as an adsorbent, adding the dendrimer into the boric acid saturated solution, immediately performing vacuum filtration after the reaction is finished, filtering impurities, putting the filtrate into a refrigerator for refrigeration, wherein the refrigeration temperature of the refrigerator is-10 ℃, precipitating boric acid crystals, performing suction filtration again, and drying to obtain high-purity boric acid crystals.

The detection result shows that the dendrimer prepared in the embodiment has the calcium ion adsorption and chelating capacity of 221.3mg/g, and the boric acid purity is 99.94%.

Example 3

The preparation method of the high-purity boric acid for the lithium battery cathode material comprises the following steps:

s1: mixing a mixture of 1: dissolving 8-12 of octavinyl cage-type silsesquioxane and methyl (2, 2-dimethyl-4-pentenyl-1-yl) carbamate in toluene, adding an initiator ammonium persulfate with the molar concentration of 0.05mol/L, wherein the addition amount of the initiator accounts for 0.36% of the total mass of reaction raw materials of the octavinyl cage-type silsesquioxane and the methyl (2, 2-dimethyl-4-pentenyl-1-yl) carbamate, heating, condensing, refluxing, reacting at the reaction temperature of 90 ℃ for 7 hours, filtering under reduced pressure, washing the solid with distilled water for 3 times, filtering and drying to obtain an intermediate product;

s2: dissolving the intermediate product obtained in the step S1 in excess anhydrous ethylenediamine, wherein the molar ratio of the ethylenediamine to the intermediate product is 200: 1, heating to 55 ℃ to carry out chain extension reaction of an amide repeating unit, reacting for 12 hours, and carrying out reduced pressure distillation to obtain a dendrimer intermediate with a polyhedral oligomeric silsesquioxane center;

s3: dissolving the dendrimer obtained in the step S2 in methanol, and dropwise adding alkylene carbamate while stirring to perform a grafting reaction of the branch end, wherein the molar ratio of the alkylene carbamate to the dendrimer is 8.8: 1, adding a lithium hydroxide solution to carry out saponification reaction after the reaction is finished, then regulating the pH value to be 6.2 by using boric acid, and precipitating and separating out a dendrimer which takes a cage-type silsesquioxane center and a plurality of highly branched amide repeating units as branched chains;

s4: adding industrial boric acid into deionized water, heating, stirring and dissolving to prepare a boric acid saturated solution, wherein the temperature of the boric acid saturated solution is 30 ℃, after the boric acid is completely dissolved, obtaining the calcium chelating capacity of the dendrimer according to the step S3, weighing a certain amount of dendrimer as an adsorbent, adding the dendrimer into the boric acid saturated solution, immediately performing vacuum filtration after the reaction is finished, filtering impurities, putting the filtrate into a refrigerator for refrigeration, wherein the refrigeration temperature of the refrigerator is-10 ℃, precipitating boric acid crystals, performing suction filtration again, and drying to obtain high-purity boric acid crystals.

The detection result shows that the dendrimer prepared in the embodiment has the capacity of adsorbing and chelating calcium ions of 235.1mg/g, and the purity of the boric acid is 99.93%.

The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are merely illustrative of the principles of the invention, but that various changes and modifications may be made without departing from the spirit and scope of the invention, which fall within the scope of the invention as claimed.