阅读说明：本技术 一种海藻酸镁锂的制备方法及应用 (Preparation method and application of magnesium lithium alginate ) 是由 刘兴勇 徐涛 唐俊峰 刘双双 刘春苗 王清 孙暖暖 于 2020-12-21 设计创作，主要内容包括：本发明提出了一种海藻酸镁锂的制备方法及应用,包括以下步骤(1)褐藻碱消化制备海藻酸；(2)将海藻酸与一定比例的氢氧化锂、氢氧化镁同时发生液态中和反应,反应40-60min,调节溶液PH为5-6,离心、干燥、粉碎,制备的海藻酸镁锂,作为粘结剂和锂源,应用于锂离子电池正负极材料的制备,其中海藻酸镁锂用量为锂电池正负极材料重量的5％-20％。解决现有技术中海藻酸盐作为锂离子电池粘结剂存在的导电性不好、PH调节能力较差的技术问题。本发明制备工艺设计合理,制得的海藻酸镁锂能够提供锂源,导电性能显著提高,还可以调节正负极材料PH值。(The invention provides a preparation method and application of lithium magnesium alginate, which comprises the following steps of (1) preparing alginic acid by algin digestion; (2) alginic acid and lithium hydroxide and magnesium hydroxide in a certain proportion simultaneously undergo liquid neutralization reaction for 40-60min, the pH of the solution is adjusted to 5-6, and the solution is centrifuged, dried and crushed to prepare magnesium lithium alginate which is used as a binder and a lithium source and is applied to the preparation of positive and negative electrode materials of a lithium ion battery, wherein the dosage of the magnesium lithium alginate is 5-20% of the weight of the positive and negative electrode materials of the lithium ion battery. Solves the technical problems of poor conductivity and poor PH regulation capability of alginate used as a lithium ion battery binder in the prior art. The preparation process is reasonable in design, the prepared magnesium lithium alginate can provide a lithium source, the conductivity is remarkably improved, and the pH value of the anode material and the cathode material can be adjusted.)

1. The preparation method of the magnesium lithium alginate is characterized by comprising the following steps:

(1) preparing alginic acid by digesting the algin;

(2) and (2) simultaneously carrying out liquid neutralization reaction on alginic acid and lithium hydroxide and magnesium hydroxide in a certain proportion for 40-60min, adjusting the pH of the solution to 5-6, centrifuging, drying and crushing to obtain the lithium magnesium alginate, wherein the total weight of the lithium hydroxide and the magnesium hydroxide is 8-16% of the weight of the alginic acid.

2. The method for preparing the lithium magnesium alginate according to claim 1, wherein the mass percent of the alkali in the step (1) is 15-20%, and the digestion temperature is 60-65 ℃.

3. The preparation method of lithium magnesium alginate according to claim 1, wherein the weight parts of lithium hydroxide and magnesium hydroxide in the step (2) are 2:8-8: 2.

4. The method for preparing lithium magnesium alginate according to claim 3, wherein the weight portion of the lithium hydroxide and the magnesium hydroxide in the step (2) is 4: 6.

5. The method for preparing lithium magnesium alginate according to claim 1, wherein the solvent for the liquid neutralization reaction in the step (2) is an aqueous alcohol solution with a volume percentage concentration of 60-85%.

6. The application of the magnesium lithium alginate in the step (2) of claim 1 is characterized in that the magnesium lithium alginate is used as a binder and a lithium source and is applied to the preparation of the anode and cathode materials of the lithium ion battery, wherein the dosage of the magnesium lithium alginate is 5-20% of the weight of the anode and cathode materials of the lithium ion battery.

7. The use of the magnesium lithium alginate of claim 6, wherein the positive and negative electrode materials of the lithium battery comprise positive and negative electrode active materials, a conductive agent, a binder, deionized water and a current collector.

Technical Field

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a preparation method and application of alginate, in particular to a preparation method and application of magnesium lithium alginate.

Background

Lithium ion batteries are secondary reversible batteries. Because of the advantages of high specific capacity, long cycle life, small size, light weight, no memory effect and the like, the lithium ion battery is the battery system with the best comprehensive performance at present and is one of the most effective energy storage devices all the time. Currently, they have been widely used in various fields such as various portable devices, electric vehicles, military materials, and Energy Storage Systems (ESS).

Currently, research on batteries has focused mainly on the preparation of active materials for electrodes, and little attention has been paid to inactive ingredients of electrodes, such as binders. Many studies now indicate that many important characteristics of batteries include stability and irreversible capacity loss, which are associated to a large extent with binders. The main functions of the binder include ensuring the uniformity and safety of active substances during pulping, playing a role in binding active substance particles and binding the active substances on a current collector, thereby improving the cycle stability and rate capability of the lithium ion battery. The selection of the binder requires that the binder has thermal stability in the drying process, can be wetted by electrolyte, does not react and is not easy to burn, has higher ion and electron conductivity, low price and dosage and the like. The algin is a product with the largest output, the largest variety and the widest application in seaweed industry, and comprises alkali metal salts such as water-soluble sodium alginate, potassium alginate, lithium alginate, ammonium alginate and the like, water-insoluble alginic acid and alginic acid salts combined with metal ions with more than two valences.

The alginate is used as the lithium ion battery binder, and has the advantages of water solubility, no toxicity, difficult degradation and strong binding power. And the polarity is strong, which is beneficial to ensuring the action between the adhesive and the active substance particles and the strong adsorption with the copper foil substrate. The carboxyl of the alginate exists naturally, and is distributed in the molecule more uniformly, so that an SEI film is formed more favorably. However, water-soluble monovalent metal alginate salts (including sodium alginate, potassium alginate, and ammonium alginate) have poor conductivity and poor pH regulation due to their monomolecular chain structure, and thus cannot meet the desired requirements. Although the invention patent of "a high-energy lithium battery negative electrode slurry and a preparation method thereof" according to prior art application No. CN201810736285.3 discloses a technical scheme that "the binder is sodium alginate, the cross-linking agent is an aqueous solution containing divalent metal cations, and the buffer solution has a pH value of 2-5", wherein the cations are calcium ions and strontium ions. Although the method has a certain effect, the operation is complicated, the formed calcium alginate and strontium alginate have poor flexibility, a lithium source cannot be provided, the application range has certain limitation, and the calcium alginate and strontium alginate can only be used as a binder of a negative pole piece.

Disclosure of Invention

The invention provides a preparation method and application of magnesium lithium alginate, and solves the technical problems of poor conductivity and poor pH regulation capability of alginate serving as a lithium ion battery binder in the prior art.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of lithium magnesium alginate comprises the following steps:

(1) preparing alginic acid by digesting the algin;

(2) and (2) simultaneously carrying out liquid neutralization reaction on alginic acid and lithium hydroxide and magnesium hydroxide in a certain proportion for 40-60min, adjusting the pH of the solution to 5-6, centrifuging, drying and crushing to obtain the lithium magnesium alginate, wherein the total weight of the lithium hydroxide and the magnesium hydroxide is 8-16% of the weight of the alginic acid. The brown algae may be Laminaria japonica, Macrocystis, Fucus, etc.

Preferably, the mass percent of the alkali in the step (1) is 15-20%, and the digestion temperature is 60-65 ℃.

Preferably, the weight parts of the lithium hydroxide and the magnesium hydroxide in the step (2) are 2:8-8: 2.

Preferably, the weight part of the lithium hydroxide and the magnesium hydroxide in the step (2) is 4: 6.

Preferably, the solvent for the liquid neutralization reaction in the step (2) is an alcohol water solution, and the volume percentage concentration is 60-85%.

The preparation method of the magnesium lithium alginate comprises the step (2) of taking the magnesium lithium alginate as a binder and a lithium source and applying the magnesium lithium alginate to the preparation of the anode and cathode materials of the lithium ion battery, wherein the dosage of the magnesium lithium alginate is 5-20% of the weight of the anode and cathode materials of the lithium ion battery.

Preferably, the positive and negative electrode material of the lithium battery consists of positive and negative electrode active substances, a conductive agent, a binder, deionized water and a current collector.

The lithium ion battery comprises a battery shell, a positive pole piece, a negative pole piece, a diaphragm and electrolyte, wherein the positive pole piece, the negative pole piece, the diaphragm and the electrolyte are sealed in the shell.

The lithium battery cathode material is a carbon-based and silicon-based material, wherein the carbon-based material comprises artificial graphite, natural graphite, mesocarbon microbeads, carbon nanotubes, graphene, various hard carbon and soft carbon and the like; the silicon-based material mainly includes silicon-carbon composite and the like. The positive electrode material is lithium cobaltate, lithium manganate, lithium nickelate (LiNi0.5Mn)₄O₄₎Lithium nickel cobalt manganese (ternary) oxide, lithium iron phosphate, and the like.

Has the following beneficial effects:

the invention provides a preparation method and application of magnesium lithium alginate,

(1) the natural polymer lithium magnesium alginate binder prepared by the invention is a compound of monovalent lithium alginate and divalent magnesium alginate, has an amorphous structure, can provide mechanical strength, supplements a lithium source, has an obvious flame retardant effect, and passes Mg between molecules²⁺The connection, the molecular chain is smooth, which is beneficial to the electron transmission.

(2) The natural polymer magnesium lithium alginate binder prepared by the invention has the pH value of 5-6, is beneficial to adjusting the pH value of the anode material and the cathode material, and prevents the pH value from being too high due to a water-based solvent, thereby improving the whole electrochemical performance.

(3) The prepared magnesium lithium alginate can improve the action of a binding agent for synthesizing a membrane, has good dispersibility, is beneficial to ensuring the mutual binding action between the binding agent and active substance particles and strong adsorbability with a copper foil or aluminum foil substrate, can provide a lithium source, can also adjust the pH value of a positive electrode material and a negative electrode material, and avoids the problem of pH rise caused by using water as a solvent.

In conclusion, the preparation method and the application of the magnesium lithium alginate provided by the invention have the advantages that the preparation process is reasonable in design, the prepared magnesium lithium alginate can provide a lithium source, the conductivity is obviously improved, the pH value of a positive electrode material and a negative electrode material can be adjusted, and the technical problems of poor conductivity and poor pH adjusting capability of alginate as a lithium ion battery binder in the prior art are solved.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not to be construed as limiting the invention.

Example 1

Preparation of magnesium lithium alginate

Alginic acid is prepared by algin digestion, the mass percent of the alkalis is 15 percent, and the digestion temperature is 60 ℃; weighing 125g of alginic acid, 2g of lithium hydroxide and 8g of magnesium hydroxide, simultaneously carrying out liquid neutralization reaction, reacting for 40min by taking an alcohol aqueous solution as a solvent for the liquid neutralization reaction and regulating the pH of the solution to be 5-6, centrifuging, drying and crushing to obtain the magnesium lithium alginate.

Weighing 8gLiNi_0.5Mn₄O₄1g of conductive agent and 0.5g of magnesium lithium alginate, grinding uniformly, adding deionized water, mixing uniformly to obtain a positive electrode material, weighing 8g of silicon carbon material, 1g of conductive agent and 0.5g of magnesium lithium alginate, grinding uniformly, adding deionized water, mixing uniformly to obtain a negative electrode material, coating the negative electrode material on an aluminum foil and a copper foil respectively, drying in vacuum at 120 ℃ to obtain a pole piece with the diameter of 12mm, and transferring the pole piece into a glove box to assemble a button cell with the specification of 2032. And then testing the electrochemical performance of the battery by using an electrochemical workstation and a battery blue electricity system respectively.

Example 2

Alginic acid is prepared by digesting the algin, the mass percent of the alkalis is 20 percent, and the digestion temperature is 65 ℃; weighing 62.5g of alginic acid, 4g of lithium hydroxide and 6g of magnesium hydroxide, simultaneously carrying out liquid neutralization reaction, reacting for 60min by taking an alcohol aqueous solution as a solvent for the liquid neutralization reaction and adjusting the pH of the solution to be 5-6, centrifuging, drying and crushing to obtain the magnesium lithium alginate.

Weighing 8gLiNi_0.5Mn₄O₄1g of conductive agent and 2g of magnesium lithium alginate are uniformly ground, added with deionized water and uniformly mixed to serve as a positive electrode material, 8g of silicon carbon material, 1g of conductive agent and 2g of magnesium lithium alginate are weighed to be uniformly ground, added with deionized water and uniformly mixed to serve as a negative electrode material, the negative electrode material is respectively coated on an aluminum foil and a copper foil, a pole piece with the diameter of 12mm is prepared after vacuum drying at 120 ℃, and the pole piece is transferred into a glove box to be assembled into a button cell with the specification of 2032. And then testing the electrochemical performance of the battery by using an electrochemical workstation and a battery blue electricity system respectively.

Example 3

Alginic acid is prepared by digesting the algin, the mass percent of the alkalis is 20 percent, and the digestion temperature is 65 ℃; weighing 62.5g of alginic acid, 8g of lithium hydroxide and 2g of magnesium hydroxide, simultaneously carrying out liquid neutralization reaction, reacting for 60min by using an alcohol water solution as a solvent for the liquid neutralization reaction and adjusting the pH of the solution to be 5-6, centrifuging, drying and crushing to obtain the magnesium lithium alginate.

Weighing 8gLiNi_0.5Mn₄O₄1g of conductive agent and 1g of magnesium lithium alginate are uniformly ground, added with deionized water and uniformly mixed to serve as a positive electrode material, 8g of silicon carbon material, 1g of conductive agent and 1g of magnesium lithium alginate are weighed to be uniformly ground, added with deionized water and uniformly mixed to serve as a negative electrode material, the negative electrode material is respectively coated on an aluminum foil and a copper foil, a pole piece with the diameter of 12mm is prepared after vacuum drying at 120 ℃, and the pole piece is transferred into a glove box to be assembled into a button cell with the specification of 2032. And then testing the electrochemical performance of the battery by using an electrochemical workstation and a battery blue electricity system respectively.

Comparative example 1

Alginic acid is prepared by digesting the algin, the mass percent of the alkalis is 20 percent, and the digestion temperature is 65 ℃; weighing 62.5g of alginic acid and 10g of lithium hydroxide to perform liquid neutralization reaction, wherein the solvent of the liquid neutralization reaction is an alcohol water solution, the volume percentage concentration is 85%, reacting for 60min, adjusting the pH of the solution to be 5-6, centrifuging, drying and crushing to obtain the lithium alginate.

Weighing 8gLiNi_0.5Mn₄O₄The preparation method comprises the following steps of grinding 1g of conductive agent and 1g of lithium alginate uniformly, adding deionized water, mixing uniformly, taking the mixture as a positive electrode material, weighing 8g of silicon carbon material, 1g of conductive agent and 1g of lithium alginate, grinding uniformly, adding deionized water, mixing uniformly, taking the mixture as a negative electrode material, coating the negative electrode material on an aluminum foil and a copper foil respectively, drying in vacuum at 120 ℃ to prepare a pole piece with the diameter of 12mm, and transferring the pole piece into a glove box to assemble the button cell with the specification of 2032. And then testing the electrochemical performance of the battery by using an electrochemical workstation and a battery blue electricity system respectively.

Comparative example 2

Alginic acid is prepared by digesting the algin, the mass percent of the alkalis is 20 percent, and the digestion temperature is 65 ℃; weighing 62.5g of alginic acid and 10g of magnesium hydroxide to perform liquid neutralization reaction, wherein the solvent of the liquid neutralization reaction is an alcohol water solution, the volume percentage concentration is 85%, reacting for 60min, adjusting the pH of the solution to be 5-6, centrifuging, drying and crushing to obtain the magnesium alginate.

Weighing 8gLiNi_0.5Mn₄O₄1g of conductive agent and 1g of magnesium alginate are uniformly ground, and are uniformly mixed with deionized water to serve as an anode material, 8g of silicon carbon material, 1g of conductive agent and 1g of magnesium alginate are weighed, uniformly ground, added with deionized water to be uniformly mixed to serve as a cathode material, the cathode material is respectively coated on an aluminum foil and a copper foil, and is vacuum-dried at 120 ℃ to prepare a pole piece with the diameter of 12mm, and the pole piece is transferred into a glove box to be assembled into a button cell with the specification of 2032. And then testing the electrochemical performance of the battery by using an electrochemical workstation and a battery blue electricity system respectively.

The experimental results of the example 1, the example 2 and the example 3 are compared with the experimental results of the comparative example 1 and the comparative example 2, and the results mainly include the first discharge capacity, the first coulombic efficiency, the capacity retention rate after 500-cycle charge and discharge, and the electrochemical impedance index, and are shown in table 1.

TABLE 1 results of electrochemical Performance experiments

As can be seen from table 1, the electrochemical performance of the magnesium lithium alginate prepared by the technical scheme of the invention is obviously superior to that of comparative examples 1 and 2, wherein the electrochemical comprehensive quality of example 2 is the best, the conductivity is strong, the impedance is small, the service life is long, and it can be seen that the magnesium lithium alginate prepared by the invention can provide a lithium source when applied to the preparation of the positive electrode and the negative electrode of a lithium battery, thereby remarkably improving the conductivity of the lithium battery and prolonging the service life of the battery.

It is to be understood that the above description is not intended to limit the present invention, and the present invention is not limited to the above examples, and any changes, additions or substitutions, which are within the spirit of the present invention, by a person of ordinary skill in the art, should fall within the scope of the present invention.