CN115414908B

CN115414908B - Lithium ion battery electrolyte solvent water removing agent and preparation method and application thereof

Info

Publication number: CN115414908B
Application number: CN202210910834.0A
Authority: CN
Inventors: 杨建建; 陈世安; 谭礼林; 梁智敏; 莫世广; 刘志锐; 丁湘浓; 于争飞; 王熙
Original assignee: Guangdong Laboratory Of Chemistry And Fine Chemicals
Current assignee: Guangdong Laboratory Of Chemistry And Fine Chemicals
Priority date: 2022-07-29
Filing date: 2022-07-29
Publication date: 2024-03-15
Anticipated expiration: 2042-07-29
Also published as: CN115414908A

Abstract

The invention discloses a water scavenger for lithium ion battery electrolyte and a preparation method and application thereof, belonging to the technical field of lithium ion battery electrolyte.

Description

Lithium ion battery electrolyte solvent water removing agent and preparation method and application thereof

Technical Field

The invention belongs to the technical field of lithium ion battery electrolyte production, and particularly relates to a preparation method of a lithium ion battery electrolyte solvent water scavenger, and also relates to the lithium ion battery electrolyte solvent water scavenger prepared by the method and also relates to application of the water scavenger.

Background

The lithium ion battery is a secondary battery which is formed by respectively using two compounds capable of reversibly intercalating and deintercalating lithium ions as positive and negative electrodes, wherein during charging, lithium ions are deintercalated from a positive electrode, are intercalated into a negative electrode through an electrolyte, and the negative electrode is in a lithium-rich state, and during discharging, the negative electrode is opposite, so that people can visually refer to the lithium ion battery as a rocking chair type battery by a unique mechanism that the charge and discharge of the battery are completed by transferring lithium ions between the positive electrode and the negative electrode. Since the development of lithium ion batteries in the 70 th century, as the population increases and the global resources are limited, research and development of lithium ion batteries having the advantages of light weight, large capacity, no memory effect, no toxic substances and the like are being carried out, the development of lithium ion batteries is today, the application fields of lithium ion batteries are developed from the original mobile phones and notebooks to Bluetooth headsets, digital products, electric tools, electric bicycles, electric automobiles, aviation tools, solar energy, military industry fields and the like, and the application range of lithium ion batteries is further expanded and spread to various fields in life as research is continued.

As an important component of lithium ion batteries, the electrolyte is called the "blood" of the battery, which serves as an ion conductor for conduction between the positive and negative electrodes of the battery, and the performance of the battery is directly affected by the performance of the battery. The lithium ion battery electrolyte mainly comprises lithium salt, an organic solvent and various functional additives, and has important influence on various performances of the lithium ion battery, such as capacity, internal resistance, circulation, multiplying power, safety and the like. The electrolyte is generally formed by a cyclic carbonate solvent such as Ethylene Carbonate (EC), propylene Carbonate (PC) and a chain carbonate solvent such as dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC) and the like, and has the characteristics of good electrochemical stability, high dielectric constant, low melting point, high flash point, safety, no toxicity and the like.

Currently, electrolyte solute lithium salt LiPF ₆ Because of high solubility in carbonate solvents, higher conductivity and better stability to graphite negative electrodes, the lithium ion battery is the main lithium salt type of commercial electrolyte at present, however LiPF ₆ The thermal stability is poor and the battery is sensitive to moisture, and the battery can be decomposed to generate free acid when meeting trace water, so that the battery performance can be obviously deteriorated. The most common solution is to remove water by passing the carbonate-based organic solvent constituting one of the electrolytes through a 4A or 5A molecular sieve before producing the electrolyte. However, although the molecular sieves can remove moisture in the solvent or other impurities affecting the electrochemical performance of the electrolyte, as the molecular sieves are aluminosilicate and have acid in the structure, the carbonate solvent is decomposed, the impurity content in the electrolyte solvent is increased, the purity of the produced electrolyte is reduced, the impurity adsorption content of the molecular sieves is correspondingly increased along with the prolonged service time, the dewatering efficiency of the molecular sieves is reduced, and the replacement service cycle of the molecular sieves is shortened. In addition, along with the improvement of specific energy density of the lithium ion battery, the ternary positive electrode material with low cost, high voltage and high gram capacity, such as nickel cobalt lithium manganate, nickel cobalt lithium aluminate and the like, is widely applied to the lithium ion battery, especially the power lithium ion battery, and is considered as the main current positive electrode material of the next generation lithium ion battery, but the ternary positive electrode material has strong water absorption, especially under high voltage and higher nickel content, the conventional electrolyte decomposition process is greatly accelerated, so that the gas expansion is serious, and the cycle performance is poor. Therefore, the moisture content of the electrolyte must be strictly controlled during the production and use processes, so that the purity of the product can be ensured.

Therefore, the water scavenger which has high water adsorption capacity and does not cause solvolysis of the electrolyte of the lithium ion battery is obtained, and has important practical significance.

Disclosure of Invention

In order to solve the problems that the existing lithium ion battery electrolyte solvent water remover is easy to cause decomposition of carbonate solvents, and further influences the purity of the electrolyte, the water removing effect of a molecular sieve and the service period to be shortened, the invention provides the lithium ion battery electrolyte solvent water remover after a great deal of researches are carried out on the existing lithium ion battery electrolyte.

In a first aspect of the invention, the invention provides a method for preparing a solvent water scavenger for lithium ion battery electrolyte, which comprises the following steps in sequence:

(S1) mixing a silicon source, a structure directing agent, strong alkali and water, stirring for 3-10h, crystallizing at 60-170 ℃ for 2-30h, and then cooling, washing, drying and roasting to obtain a molecular sieve modifier;

(S2) uniformly mixing the molecular sieve modifier, the molecular sieve powder, the lubricant and the water obtained in the step (S1) to obtain a mixture;

And (S3) carrying out molding treatment and roasting on the mixture obtained in the step (S2) to obtain the lithium ion battery electrolyte solvent water scavenger.

The existing molecular sieve is easy to cause decomposition of carbonate solvent due to acidity, so that the content of impurities in the electrolyte is increased, the purity of the electrolyte is reduced, and meanwhile, the molecular sieve adsorbs more and more impurities, so that the water removal effect of the molecular sieve is reduced, and the service life is shortened. The molecular sieve modifier is subjected to hydrothermal liquid phase crystallization and high-temperature roasting, and then is mixed with molecular sieve powder, and is molded and roasted to obtain the water scavenger. Obviously, the molecular sieve modifier is physically mixed with the molecular sieve, and then is molded, dried and roasted, and the acid property of the molecular sieve is modulated in the process, so that the water scavenger can greatly reduce the problem of carbonate solvolysis caused by the existing molecular sieve water scavenger, and has higher water removal efficiency. It should be noted that the mode of mixing the molecular sieve modifier with the molecular sieve powder for modification is very convenient, and is favorable for realizing industrialization, particularly, the final roasting process ensures that the water scavenger obtains a certain mechanical strength, and simultaneously, solid exchange reaction occurs at high temperature, and silicon-containing oxide migrates into the surface of the molecular sieve and the position of an orifice to form a new Al-O-Si bond, thereby realizing the purposes of modifying the 4A molecular sieve and modulating the acidity. In addition, as the service time is prolonged, compared with an unmodified molecular sieve, impurities introduced and adsorbed by the water scavenger due to decomposition of the carbonate solvent are correspondingly reduced, and the time for the problem of reduced water removal efficiency caused by adsorption of the impurities by the molecular sieve is correspondingly prolonged, so that the replacement and use frequency of the molecular sieve is reduced, and the use and maintenance cost of the molecular sieve is saved.

Preferably, in the above method, the silicon source in the step (S1) is at least one of methyl orthosilicate, tetraethyl orthosilicate, propyl orthosilicate, butyl orthosilicate, polyphenylmethylsiloxane, and hexamethyl silyl ether.

More preferably, in the above method, the silicon source in the step (S1) is tetraethyl orthosilicate.

The carbonate solvent for the lithium ion battery can be decomposed by two modes of acid catalysis and base catalysis, so that the decomposition of the carbonate under the acid catalysis condition can be inhibited by reducing the acid amount of the outer surface of the molecular sieve. In other words, on the premise of small influence on the specific surface area and pore volume of the molecular sieve, the decomposition of the carbonic ester solvent can be inhibited by adjusting the acid amount of the molecular sieve, and the molecular sieve modifier and the molecular sieve powder are mixed, molded and dried, and finally the roasting process is carried out, so that the water scavenger obtains certain mechanical strength, simultaneously, solid exchange reaction occurs at high temperature, and silicon-containing oxide migrates to the surface of the molecular sieve and the position of an orifice to form a new Al-O-Si bond, thereby realizing the purpose of modifying and adjusting the acidity of the 4A molecular sieve and further inhibiting the decomposition of the carbonic ester solvent.

Preferably, in the above method, the structure directing agent in the step (S1) is an organic structure directing agent, such as tetrapropylammonium bromide, tetramethylammonium hydroxide, tetrapropylammonium hydroxide, ethylenediamine, tetraethylammonium, methyltriethylammonium, propyltriethylammonium, diethyldipropylammonium, diethyldimethylammonium, choline, N-trimethyl-1-adamantylammonium hydroxide, butylamine, and the like.

More preferably, in the above method, the structure directing agent in the step (S1) is one or more of tetrapropylammonium bromide, tetramethylammonium hydroxide, tetrapropylammonium hydroxide, ethylenediamine, tetraethylammonium, methyltriethylammonium, propyltriethylammonium, diethyldipropylammonium, and particularly preferably tetrapropylammonium hydroxide and/or tetrapropylammonium bromide. The structure directing agent is a necessary template for synthesizing the molecular sieve modifier in the present invention and is critical for forming the molecular sieve modifier of a specific structure.

Preferably, in the above method, the strong base in the step (S1) is sodium hydroxide and/or potassium hydroxide, and these strong bases can promote the hydrolysis and polymerization of the silicon source tetraethyl orthosilicate, and can adjust the pH of the reaction system between 10 and 13, which is beneficial to the synthesis of the molecular sieve modifier.

Preferably, in the above method, the water in the step (S1) is deionized water or other water having a resistivity of more than 0.5 mega ohm-cm to ensure that no other impurities are introduced.

Preferably, in the above method, the molar ratio of silica, structure directing agent, strong base to water in the silicon source in the step (S1) is 1: (0.01-1.0): (0.001-0.1): (10-300).

Preferably, in the above method, the crystallization condition in the step (S1) is: the temperature is 80-150deg.C, the time is 6-24h, more preferably 110-130deg.C, and the time is 8-18h.

In the above method, the washing step in the step (S1) may be performed by first separating solid from liquid water in the cooled reaction system and then washing with water for at least 2 times to remove unreacted substances.

Further preferably, the solid-liquid separation may be performed by filtering, centrifuging, or standing for more than 1 hour to remove supernatant, or other liquid removal methods, and the present invention is not limited thereto.

Preferably, in the above method, the washing in the step (S1) is performed with water, and the water is deionized water or other water with resistivity greater than 0.5 megohm-cm, so as to ensure that no other impurities are introduced, thereby affecting the subsequent water removal performance.

Preferably, in the above method, the drying condition in the step (S1) is: the temperature is 100-110 ℃ and the time is 10-18h.

Preferably, in the above method, the conditions for performing the calcination in the step (S1) are: under the air atmosphere or the oxygen atmosphere, the temperature is 550-650 ℃ and the time is 5-7h. The roasting process is to remove the structure guiding agent in the system, the structure guiding agent is adopted for forming a specific pore structure when synthesizing the molecular sieve modifier, and mainly plays a role of a template for forming the specific pore structure, and after synthesis, the specific pore structure can be formed only by roasting. Therefore, the structure guiding agent used in the preparation process of the molecular sieve modifier is removed by the roasting, and the combination of the molecular sieve modifier and the molecular sieve to be modified can be more sufficient after the structure guiding agent is removed by the roasting, so that the molecular sieve modifier is favorable for being migrated to the surface and the orifice position of the molecular sieve to form a new Al-O-Si bond, and the adjustment of the acidity of the molecular sieve to be modified is realized.

Preferably, in the above method, the molecular sieve powder in the step (S2) is at least one of 4A molecular sieve powder, 3A molecular sieve powder, 5A molecular sieve powder.

Preferably, in the above method, in the step (S2), the parts by weight of the molecular sieve powder, the molecular sieve modifier, the lubricant and the water are respectively:

further preferably, in the above method, the parts by weight of the molecular sieve powder, the molecular sieve modifier, the lubricant and the water in the step (S2) are respectively:

the water scavenger of the invention needs to be added with a certain amount of water in the molding treatment process, and the water content of 3-5 parts is most suitable, otherwise, if no water is added, the obtained water scavenger is easy to collapse and has insufficient mechanical strength. In addition, the addition amount of the molecular sieve modifier needs to be strictly controlled, so that the aim of modulating the acidity can be fulfilled, and the original pore structure of the molecular sieve is not blocked.

Preferably, in the above method, in the step (S2), the molecular sieve powder is mixed with the molecular sieve modifier, the lubricant and the water, and the molecular sieve, the lubricant and the water are uniformly mixed to obtain a material, and then the molecular sieve modifier is added and uniformly mixed to obtain the mixture.

Preferably, in the above method, the mass ratio of the molecular sieve modifier to the molecular sieve powder in the step (S2) is 1 (16-25).

Preferably, in the above method, the lubricant in the step (S2) is sesbania powder and/or graphite, more preferably sesbania powder.

In the invention, the sesbania powder is mainly used as a lubricant, is beneficial to molding, and graphite can be used as the lubricant, but compared with the sesbania powder, the sesbania powder is more environment-friendly, because the sesbania powder is prepared by crushing and sieving endosperm of sesbania seeds of leguminous plants, and the sesbania powder has the characteristics of better water solubility, high viscosity, colloid binding property, flocculation, salt resistance and the like, and the main components are galactose and mannose.

Preferably, in the above method, the mass ratio of the molecular sieve powder to the lubricant in the step (S2) is (16-25): 1. If the lubricant is insufficient, the lubrication effect is insufficient, and the demolding effect is affected, so that the water remover is easy to collapse after molding; and if the lubricant amount is too much, the demolding is too fast due to too high lubrication degree, so that the mechanical strength of the water removing agent is insufficient, in addition, the proportion of the lubricant is too high, the proportion of the molecular sieve in the water removing agent can be reduced, the water absorption rate of the formed water removing agent is influenced, the use amount of the water removing agent can be increased, and the water removing cost is further improved.

Preferably, in the above method, the water in the step (S2) is deionized water or other water having a resistivity of more than 0.5 mega ohm-cm, to avoid introducing unnecessary impurities into the molecular sieve.

Preferably, in the above method, the forming treatment in the step (S3) includes extrusion molding, tabletting molding, ball molding or spray granulation molding. The water scavenger can be filled into an adsorption tower or an adsorption column only after molding, so that electrolyte solvent can flow through gaps among particles, if the water scavenger is in a powder form, the electrolyte cannot pass through and can cause blockage, and in addition, the powdery water scavenger can also remain in the electrolyte solvent to pollute the electrolyte solvent, so that molding treatment is needed to ensure that the form of the final water scavenger is non-powdery.

Further preferably, in the above method, the molding treatment in the step (S3) is tablet molding, specifically, the mixture obtained in the step (S2) is first granulated in a granulator, and then the granulator product is placed in a tablet press for tablet molding. Through the mode of granulating before tabletting, the binding agent and the cross-linking agent are not needed, so that the molecular sieve modifier is tightly contacted with the molecular sieve, and the molding method is simple, low in cost and beneficial to popularization and use.

Most preferably, in the above method, the granulating pressure in the granulator during the tabletting and molding is 0.5-1 Mpa, the feeding and filling amount of the tablet press is 2mL, and the pressure is 4-6 Mpa

Preferably, in the above method, the conditions for performing the calcination in the step (S3) are: under the air atmosphere or the oxygen atmosphere, the temperature is 550-650 ℃ and the time is 4-10 hours, so that the lubricant is removed to avoid influencing the diffusion performance of the molecular sieve. In addition, the lubricant can be removed by roasting to play a role in pore-forming, a certain amount of pore channels can be formed in the formed adsorbent after the lubricant is removed by roasting, and the diffusion of electrolyte solvent in water removal is facilitated.

The molecular sieve modifier is obtained by pre-crystallizing and roasting a silicon source, and then the molecular sieve modifier is molded and roasted with molecular sieve powder, so that the adjustment of the acidity of the molecular sieve is realized, the obtained water scavenger has higher water removal efficiency, the problem of decomposition of carbonate solvents caused by the molecular sieve water scavenger can be greatly reduced, the purity of the electrolyte solvent can be improved while water is adsorbed, and the market competitiveness of the electrolyte product can be greatly improved.

According to a second aspect of the present invention, there is also provided a water scavenger prepared by the above method.

According to a third aspect of the present invention there is also provided the use of a water scavenger prepared by the above method wherein the use is for solvent removal of lithium ion battery electrolyte.

The water scavenger disclosed by the invention has higher water removal efficiency, can greatly reduce the problem of decomposition of carbonate solvents caused by the existing water scavenger, can adsorb water and improve the purity of electrolyte solvents, and further can greatly improve the product competitiveness of the electrolyte. Along with the extension of the service time, compared with an unmodified molecular sieve, the impurity content of the water scavenger introduced and adsorbed by the carbonate solvent is correspondingly reduced, so that the time for the problem of reduced water removal efficiency caused by impurity adsorption of the molecular sieve water scavenger is correspondingly prolonged, the replacement and use frequency of the molecular sieve water scavenger is reduced, and the use and maintenance cost of the molecular sieve water scavenger is saved.

Compared with the prior art, the modified molecular sieve is used as a core component of the water scavenger, the molecular sieve and the self-made molecular sieve modifier are molded and roasted to realize the modification of the molecular sieve, the preparation process is simple, the cost is low, the obtained water scavenger has higher structural strength, the loss of the water scavenger caused by structural damage in the water scavenging process of the electrolyte can be prevented, and meanwhile, the problem of introducing solid impurities into the electrolyte is avoided.

Drawings

FIG. 1 is a diagram showing N of a water scavenger prepared in example 1 of the present invention ₂ Adsorption isotherm plot;

FIG. 2 is a NH value of a water scavenger prepared in example 1 of the present invention ₃ -a TPD map;

FIG. 3 is a graph showing pore size distribution of the water scavenger prepared in example 1 of the present invention;

FIG. 4 is an XRD pattern of the water scavenger prepared in example 1 of the present invention and an unmodified 4A molecular sieve.

Detailed Description

In order to more clearly describe the embodiments of the present invention or technical solutions in the prior art, the technical solutions of the present invention will be described in detail with specific embodiments.

In the following examples, the water used was deionized water to avoid introducing unwanted impurities, the molecular sieve powder was 4A molecular sieve powder having a particle size of 4 μm; the particle size of the graphite powder is 50 meshes; tetraethyl orthosilicate was purchased from national pharmaceutical chemicals limited, analytically pure, oxide content 28.6 wt%; tetrapropylammonium hydroxide (TPAOH) was an aqueous tetrapropylammonium hydroxide solution available from the scientific company of enokii, beijing, wherein the mass fraction of tetrapropylammonium hydroxide was 25%; sodium hydroxide was purchased from beijing chemical reagent company, analytically pure. The calcination referred to in the examples below was carried out under an air atmosphere unless otherwise specified.

Inventive examples

Inventive example 1

(S1) mixing and stirring 100.00g of tetraethyl orthosilicate, 193.60g of tetrapropylammonium hydroxide aqueous solution, 0.228g of sodium hydroxide and 643.93g of water for 5 hours, then loading into a reaction kettle and crystallizing at 120 ℃ for 14 hours, then cooling to room temperature, and centrifugally collecting solid matters, then washing 2 times, drying at 105 ℃ for 10 hours, and finally roasting at 600 ℃ for 5 hours to obtain a molecular sieve modifier, wherein the mole ratio of silicon dioxide, a structure directing agent, strong alkali and water in the tetraethyl orthosilicate is 1:0.5:0.012:90.

(S2) weighing 50g of 4A molecular sieve powder, 2g of sesbania powder and 3g of water, uniformly mixing, and then adding 3g of molecular sieve modifier and uniformly mixing to obtain a mixture.

And (S3) granulating the mixture in a granulator, then placing the granulator product into a tablet press for compression molding to obtain tablets, wherein the granulating pressure in the granulator is 0.8Mpa, the feeding and filling amount of the tablet press is 2mL, the pressure is 5Mpa, finally placing the tablets into a tube furnace and roasting for 6 hours at 600 ℃, and cooling to obtain the dehydrator for the lithium ion battery electrolyte, which is denoted as A1.

Inventive example 2

(S1) mixing and stirring 100.00g of tetraethyl orthosilicate, 193.60g of tetrapropylammonium hydroxide aqueous solution, 0.228g of sodium hydroxide and 643.93g of water for 5 hours, then loading into a reaction kettle and crystallizing at 130 ℃ for 10 hours, then cooling to room temperature, and centrifugally collecting solids, then washing 2 times, drying at 105 ℃ for 10 hours, and finally roasting at 550 ℃ for 5 hours to obtain a molecular sieve modifier, wherein the mole ratio of silicon dioxide, a structure directing agent, strong alkali and water in the tetraethyl orthosilicate is 1:0.5:0.012:90.

(S2) weighing 50g of 4A molecular sieve powder, 2g of sesbania powder and 4g of water, uniformly mixing, and then adding 3g of molecular sieve modifier and uniformly mixing to obtain a mixture.

And (S3) granulating the mixture in a granulator, then placing the granulator product into a tablet press for compression molding to obtain tablets, wherein the granulating pressure in the granulator is 0.8Mpa, the feeding and filling amount of the tablet press is 2mL, the pressure is 5Mpa, finally placing the tablets into a tube furnace and roasting for 6 hours at the temperature of 650 ℃, and cooling to obtain the dehydrator for the lithium ion battery electrolyte, which is marked as A2.

Inventive example 3

(S1) mixing and stirring 100.00g of tetraethyl orthosilicate, 193.60g of tetrapropylammonium hydroxide aqueous solution, 0.228g of sodium hydroxide and 643.93 of water for 5 hours, then loading into a reaction kettle and crystallizing at 130 ℃ for 8 hours, then cooling to room temperature, and centrifugally collecting solid, then washing 2 times, drying at 105 ℃ for 10 hours, and finally roasting at 550 ℃ for 5 hours to obtain a molecular sieve modifier, wherein the mole ratio of silicon dioxide, a structure directing agent, strong alkali and water in the tetraethyl orthosilicate is 1:0.5:0.012:90.

(S2) weighing 50g of 4A molecular sieve powder, 3g of sesbania powder and 3g of water, uniformly mixing, and then adding 3g of molecular sieve modifier and uniformly mixing to obtain a mixture.

And (S3) granulating the mixture in a granulator, then placing the granulator product into a tablet press for compression molding to obtain tablets, wherein the granulating pressure in the granulator is 0.8Mpa, the feeding and filling amount of the tablet press is 2mL, the pressure is 5Mpa, finally placing the tablets into a tube furnace and roasting for 6h at 600 ℃, and cooling to obtain the dehydrator for the lithium ion battery electrolyte, which is denoted as A3.

Inventive example 4

(S1) mixing and stirring 100.00g of tetraethyl orthosilicate, 193.60g of tetrapropylammonium hydroxide aqueous solution, 0.228g of sodium hydroxide and 643.93g of water for 5 hours, then loading into a reaction kettle and crystallizing at 120 ℃ for 14 hours, then cooling to room temperature, and centrifugally collecting solid matters, then washing 2 times, drying at 105 ℃ for 10 hours, and finally roasting at 550 ℃ for 5 hours to obtain a molecular sieve modifier, wherein the mole ratio of silicon dioxide, a structure directing agent, strong alkali and water in the tetraethyl orthosilicate is 1:0.5:0.012:90.

(S2) weighing 50g of 4A molecular sieve powder, 2g of sesbania powder and 3g of water, uniformly mixing, and then adding 2.5g of molecular sieve modifier and uniformly mixing to obtain a mixture.

And (S3) granulating the mixture in a granulator, then placing the granulator product into a tablet press for compression molding to obtain tablets, wherein the granulating pressure in the granulator is 0.8Mpa, the feeding and filling amount of the tablet press is 2mL, the pressure is 5Mpa, finally placing the tablets into a tube furnace and roasting for 6 hours at 600 ℃, and cooling to obtain the dehydrator for the lithium ion battery electrolyte, which is marked as A4.

Inventive example 5

(S1) mixing and stirring 100.00g of tetraethyl orthosilicate, 193.60g of tetrapropylammonium hydroxide aqueous solution, 0.381g of sodium hydroxide and 729.70g of water for 5 hours, then loading into a reaction kettle and crystallizing at 120 ℃ for 14 hours, then cooling to room temperature, and centrifugally collecting solid, then washing 2 times, drying at 105 ℃ for 10 hours, and finally roasting at 600 ℃ for 6 hours to obtain a molecular sieve modifier, wherein the mole ratio of silicon dioxide, a structure directing agent, strong alkali and water in the tetraethyl orthosilicate is 1:0.5:0.020:100.

And (S3) granulating the mixture in a granulator, then placing the granulator product into a tablet press for compression molding to obtain tablets, wherein the granulating pressure in the granulator is 0.8Mpa, the feeding and filling amount of the tablet press is 2mL, the pressure is 5Mpa, finally placing the tablets into a tube furnace and roasting for 6 hours at the temperature of 650 ℃, and cooling to obtain the dehydrator for the lithium ion battery electrolyte, which is marked as A5.

Inventive example 6

(S1) mixing and stirring 100.00g of tetraethyl orthosilicate, 309.77g of tetrapropylammonium hydroxide aqueous solution, 0.571g of sodium hydroxide and 1071.46g of water for 5 hours, then loading into a reaction kettle and crystallizing at 120 ℃ for 4 hours, then cooling to room temperature, and centrifugally collecting solids, then washing 2 times, drying at 105 ℃ for 10 hours, and finally roasting at 630 ℃ for 5 hours to obtain a molecular sieve modifier, wherein the mole ratio of silicon dioxide, a structure directing agent, strong alkali and water in the tetraethyl orthosilicate is 1:0.8:0.03:150.

(S2) weighing 50g of 4A molecular sieve powder, 3g of sesbania powder and 5g of water, uniformly mixing, and then adding 2g of molecular sieve modifier and uniformly mixing to obtain a mixture.

And (S3) granulating the mixture in a granulator, then placing the granulator product into a tablet press for compression molding to obtain tablets, wherein the granulating pressure in the granulator is 0.8Mpa, the feeding and filling amount of the tablet press is 2mL, the pressure is 5Mpa, finally placing the tablets into a tube furnace and roasting for 6 hours at the temperature of 650 ℃, and cooling to obtain the dehydrator for the lithium ion battery electrolyte, which is marked as A6.

Inventive example 7

(S1) mixing and stirring 100.00g of tetraethyl orthosilicate, 232.32g of tetrapropylammonium hydroxide aqueous solution, 0.952g of sodium hydroxide and 1558.42g of water for 5 hours, then loading into a reaction kettle and crystallizing at 110 ℃ for 16 hours, then cooling to room temperature, and centrifugally collecting solid matters, then washing 2 times, drying at 105 ℃ for 10 hours, and finally roasting at 600 ℃ for 5 hours to obtain the molecular sieve modifier, wherein the mole ratio of silicon dioxide, the structure directing agent, strong alkali and water in the tetraethyl orthosilicate is 1:0.6:0.05:200.

(S2) weighing 50g of 4A molecular sieve powder, 2g of sesbania powder and 6g of water, uniformly mixing, and then adding 4g of molecular sieve modifier and uniformly mixing to obtain a mixture.

And (S3) granulating the mixture in a granulator, then placing the granulator product into a tablet press for compression molding to obtain tablets, wherein the granulating pressure in the granulator is 0.8Mpa, the feeding and filling amount of the tablet press is 2mL, the pressure is 5Mpa, finally placing the tablets into a tube furnace and roasting for 6 hours at 600 ℃, and cooling to obtain the dehydrator for the lithium ion battery electrolyte, which is marked as A7.

Comparative examples

Comparative example 1

(S1) weighing 50g of 4A molecular sieve powder, 2g of sesbania powder and 3g of water, uniformly mixing, and then adding 3g of quartz sand (with the particle size of 100 meshes) and uniformly mixing to obtain a mixture.

(S2) granulating the mixture in a granulator, then placing the granulator product into a tablet press for tabletting and forming to obtain tablets, wherein the granulating pressure in the granulator is 0.8Mpa, the feeding and filling amount of the tablet press is 2mL, the pressure is 5Mpa, and finally placing the tablets into a tube furnace and roasting for 6h at 600 ℃, and cooling to obtain a water removing agent which is marked as B1.

Comparative example 2

(S1) mixing and stirring 100.00g of tetraethyl orthosilicate, 193.60g of tetrapropylammonium hydroxide aqueous solution, 0.228g of sodium hydroxide and 643.93g of water for 5 hours, then loading into a reaction kettle and crystallizing at 90 ℃ for 14 hours, then cooling to room temperature, and centrifugally collecting solids, then washing with water for 2 times, then drying at 105 ℃ for 10 hours, and finally roasting at 600 ℃ for 5 hours to obtain a molecular sieve modifier, wherein the molar ratio of silicon dioxide, a structure directing agent, strong alkali and water in the tetraethyl orthosilicate is 1:0.5:0.012:90.

(S2) weighing 50g of 4A molecular sieve powder, 2g of white dextrin and 3g of water, uniformly mixing, and then adding 3g of molecular sieve modifier and uniformly mixing to obtain a mixture.

And (S3) granulating the mixture in a granulator, then placing the granulator product into a tablet press for tabletting and forming to obtain tablets, wherein the granulating pressure in the granulator is 0.8Mpa, the feeding and filling amount of the tablet press is 2mL, the pressure is 5Mpa, and finally placing the tablets into a tube furnace and roasting for 6h at 600 ℃, and cooling to obtain the water scavenger, which is denoted as B2.

Comparative example 3

(S1) mixing and stirring 100.00g of tetraethyl orthosilicate, 193.60g of tetrapropylammonium hydroxide aqueous solution, 0.228g of sodium hydroxide and 643.93g of water for 5 hours, then loading into a reaction kettle and crystallizing at 100 ℃ for 14 hours, then cooling to room temperature, and centrifugally collecting solids, then washing with water for 2 times, then drying at 105 ℃ for 10 hours, and finally roasting at 600 ℃ for 5 hours to obtain a molecular sieve modifier, wherein the molar ratio of silicon dioxide, a structure directing agent, strong alkali and water in the tetraethyl orthosilicate is 1:0.5:0.012:90.

(S2) weighing 50g of 4A molecular sieve powder and 2g of sesbania powder, uniformly mixing, and then adding 3g of molecular sieve modifier and uniformly mixing to obtain a mixture.

(S3) granulating the mixture in a granulator, then placing the granulator product into a tablet press for tabletting and forming to obtain tablets, wherein the granulating pressure in the granulator is 0.8Mpa, the feeding and filling amount of the tablet press is 2mL, the pressure is 5Mpa, and finally placing the tablets into a tube furnace and roasting for 6h at 600 ℃, and cooling to obtain the water scavenger, which is denoted as B3.

Comparative example 4

(S1) 100.00g of tetraethyl orthosilicate, 193.60g of tetrapropylammonium hydroxide aqueous solution, 0.228g of sodium hydroxide and 643.93g of water are mixed and stirred for 5 hours, then the mixture is filled into a reaction kettle and crystallized at 120 ℃ for 14 hours, then cooled to room temperature, and the solid is centrifugally collected, then washed with water for 2 times, and then dried at 105 ℃ for 10 hours, so as to obtain a molecular sieve modifier, wherein the mole ratio of silicon dioxide, a structure directing agent, strong base and water in the tetraethyl orthosilicate is 1:0.5:0.012:90.

And (S3) placing the mixture into a tablet press for tablet compression molding to obtain tablets, wherein the feeding filling amount of the tablet press is 2mL, the pressure is 5Mpa, finally placing the tablets into a tube furnace and roasting for 6 hours at 600 ℃, and cooling to obtain a water removing agent, which is marked as B4.

Comparative example 5

And (S3) granulating the mixture in a granulator, then placing the granulator product into a tablet press for tabletting and forming to obtain tablets, wherein the granulating pressure in the granulator is 0.8Mpa, the feeding and filling amount of the tablet press is 2mL, the pressure is 5Mpa, and finally placing the tablets into a tube furnace and roasting for 6 hours under nitrogen atmosphere and at 600 ℃, and cooling to obtain the water scavenger, which is denoted as B5.

Comparative example 6

And (S3) granulating the mixture in a granulator, then placing the granulator product into a tablet press for tabletting and forming to obtain tablets, wherein the granulating pressure in the granulator is 0.8Mpa, the feeding and filling amount of the tablet press is 2mL, the pressure is 5Mpa, and finally placing the tablets into a tube furnace and roasting for 6h at 400 ℃, and cooling to obtain the water scavenger, which is denoted as B6.

Comparative example 7

And (S3) granulating the mixture in a granulator, then placing the granulator product into a tablet press for tabletting and forming to obtain tablets, wherein the granulating pressure in the granulator is 0.8Mpa, the feeding and filling amount of the tablet press is 2mL, the pressure is 5Mpa, and finally placing the tablets into a tube furnace and roasting for 6h at 700 ℃, and cooling to obtain the water scavenger, which is denoted as B7.

Comparative example 8

(S1) 17.26g of tetraethyl orthosilicate, 33.41g of tetrapropylammonium hydroxide aqueous solution, 0.0394g of sodium hydroxide and 643.93g of water are mixed and stirred for 5 hours, then charged into a reaction kettle and crystallized at 120 ℃ for 14 hours, then cooled to room temperature, and centrifuged to collect solids, then washed with water for 2 times, then dried at 105 ℃ for 10 hours, and finally calcined at 600 ℃ for 5 hours to obtain a molecular sieve modifier, wherein the mole ratio of silica, structure directing agent, strong base to water in the tetraethyl orthosilicate is 0.2:0.5:0.012:90.

And (S3) granulating the mixture in a granulator, then placing the granulator product into a tablet press for tabletting and forming to obtain tablets, wherein the granulating pressure in the granulator is 0.8Mpa, the feeding and filling amount of the tablet press is 2mL, the pressure is 5Mpa, and finally placing the tablets into a tube furnace and roasting for 6h at 600 ℃, and cooling to obtain the water scavenger, which is denoted as B8.

Comparative example 9

(S1) mixing 332.59g tetraethyl orthosilicate, 643.91g tetrapropylammonium hydroxide aqueous solution, 0.7596g sodium hydroxide and 643.93g water and stirring for 5 hours, then charging into a reaction kettle and crystallizing at 120 ℃ for 14 hours, then cooling to room temperature, and centrifuging to collect solid, then washing with water for 2 times, then drying at 105 ℃ for 10 hours, and finally roasting at 600 ℃ for 5 hours to obtain a molecular sieve modifier, wherein the mole ratio of silicon dioxide, structure directing agent, strong base and water in the tetraethyl orthosilicate is 2.4:0.5:0.012:90.

(S3) granulating the mixture in a granulator, then placing the granulator product into a tablet press for tabletting and forming to obtain tablets, wherein the granulating pressure in the granulator is 0.8Mpa, the feeding and filling amount of the tablet press is 2mL, the pressure is 5Mpa, and finally placing the tablets into a tube furnace and roasting for 6h at 600 ℃, and cooling to obtain the water scavenger, which is denoted as B9.

Comparative example 10

(S2) weighing 50g of 4A molecular sieve powder, 2g of sesbania powder and 3g of water, uniformly mixing, and then adding 0.5g of molecular sieve modifier and uniformly mixing to obtain a mixture.

(S3) granulating the mixture in a granulator, then placing the granulator product into a tablet press for tabletting and forming to obtain tablets, wherein the granulating pressure in the granulator is 0.8Mpa, the feeding and filling amount of the tablet press is 2mL, the pressure is 5Mpa, and finally placing the tablets into a tube furnace and roasting for 6h at 600 ℃, and cooling to obtain the water scavenger, which is denoted as B10.

Comparative example 11

(S2) weighing 50g of 4A molecular sieve powder, 2g of sesbania powder and 5g of water, uniformly mixing, and then adding 10g of molecular sieve modifier and uniformly mixing to obtain a mixture.

(S3) granulating the mixture in a granulator, then placing the granulator product into a tablet press for tabletting and forming to obtain tablets, wherein the granulating pressure in the granulator is 0.8Mpa, the feeding and filling amount of the tablet press is 2mL, the pressure is 5Mpa, and finally placing the tablets into a tube furnace and roasting for 6h at 600 ℃, and cooling to obtain the water scavenger, which is denoted as B11.

Test examples

Test example 1 pore size test

The water scavenger A1 and unmodified 4A molecular sieve powder prepared in inventive example 1 were subjected to the following test procedures, the test results of which are shown in Table 1 below and in FIGS. 1 to 4.

N ₂ Adsorption isothermal adsorption curve determination: n was measured using a QUADRASORBSI adsorber from Quantachrome, inc. of America Kang Da ₂ Adsorption-desorption isotherms, wherein the micropore volume(V _mic ) Total specific surface area (S) _Bet ) Obtained by a t-plot method, and the selection point range is p/p ₀ =0.2 to 0.4, mesoporous volume (V _meso ) From the total pore volume (V _tot ) Minus the micropore volume (V) _mi ) Calculated to obtain V _meso ＝V _tot -V _mic The aperture distribution adopts BJH or DFT adsorption branch model.

NH ₃ Temperature programmed desorption (NH) ₃ -TPD) determination: NH was measured using an Autochem pi 2920 full-automatic temperature-programmed chemisorber from Micromeritics, inc. of America ₃ During measurement, firstly tabletting and granulating the sample to 20-40 meshes, then fixing 0.1g of sample particles in the middle of a quartz tube, and activating the sample for 1h by heating up to 550 ℃ at a heating rate of 10 ℃/min under the inert gas atmosphere of carrier gas (He) with the inert gas atmosphere of 30 ml/min; then the temperature was reduced to 120℃at a rate of 10℃per minute, followed by the use of a mixed gas of ammonia and helium (volume ratio V (NH) ₃ ): v (He) =15: 85 30ml/min, then switching to helium He purge for 30-40 min until baseline is stable, and raising the temperature to 700 ℃ at 10 ℃/min for NH ₃ And (3) temperature programming desorption, wherein a Thermal Conductivity Detector (TCD) is used for collecting the generated signals in the desorption process.

Table 1N ₂ Pore structure parameter table obtained by adsorption and desorption data

Sample of	Specific surface area (m) ² /g)	Micropore volume (cm) ³ /g)	Mesoporous pore volume (cm) ³ /g)
				Unmodified 4A molecular sieves	412	0.153	0.041
A1	386	0.143	0.031

N of FIG. 1 ₂ Adsorption-desorption isotherm plot is the direct data obtained by the adsorption apparatus, according to N ₂ The data of adsorption-desorption isotherms are used for obtaining pore structure parameters and pore size distribution diagrams of the water scavenger by applying a numerical model, namely table 1 and fig. 3. Specifically, as shown in table 1, the total specific surface area and pore volume of the water scavenger prepared in example 1 of the present invention were reduced compared to the unmodified 4A molecular sieve, and the analysis may be due to the coating of the molecular sieve modifier on the external surface of the molecular sieve. As can be seen from FIG. 3, compared with the unmodified 4A molecular sieve, the most probable pore diameter of the water scavenger prepared in example 1 of the present invention is shifted left, but the shifting range is small, which indicates that the blocking degree of the pore canal caused by modifying the outer surface of the molecular sieve by the coating of the molecular sieve modifier is small.

In addition, from the NH of FIG. 2 ₃ Temperature programmed desorption (NH) ₃ TPD) graph shows that two desorption peaks appear in two samples, the desorption peak at low temperature is the desorption of ammonia gas on weak acid position, the desorption peak at high temperature is the desorption of ammonia gas on strong acid position, and the peak heights of the strong acid peak and the weak acid peak of the modified molecular sieve are reduced, namely NH ₃ A decrease in the TPD peak area, i.e. a decrease in the acid amount; meanwhile, the desorption peak of the modified molecular sieve on the weak acid position shifts to low temperature, namely the weak acid strength is reduced, which indicates that the external surface of the modified molecular sieve is not introduced with acid, so that the acid strength and the acid quantity are reduced, and the decomposition caused by catalysis of acid sites on the surface of the molecular sieve when the carbonate solvent for the lithium ion battery is dehydrated through the molecular sieve can be reduced to a certain extentProblems.

As can be seen from fig. 4, the water scavenger prepared in inventive example 1 showed characteristic diffraction peaks of MFI-type zeolite molecular sieve at 7.9 ° and 8.8 ° compared with the unmodified 4A molecular sieve, indicating that the present invention realizes modification of 4A molecular sieve.

Test example 2 Water removal test

The water scavengers A1 to A7 prepared in invention examples 1 to 7 and the water scavengers B1 to B11 prepared in comparative examples 1 to 11 were subjected to a single water removal experiment and a plurality of water removal experiments for recycling the solvent of the lithium ion battery electrolyte, and the test results are shown in table 2 below. The solvent of the lithium ion battery electrolyte is a commercial carbonate mixed solvent, and consists of dimethyl carbonate and diethyl carbonate in a volume ratio of 1:1, wherein the water content is 10ppm and the purity is 99.9951 percent measured before a water removal experiment.

The single water removal experiment comprises the following specific steps: in a glove box, taking 20mL of a carbonate mixed solvent for lithium ion battery electrolyte, putting 5g of a water removing agent into a sample bottle, covering a sample bottle cover, standing for 30min, taking supernatant, and measuring the water content and purity of the carbonate mixed solvent in the sample bottle.

The specific steps of the water removal experiment for recycling for multiple times are as follows: and in a glove box, pouring out the residual supernatant in the single water removal experiment sample bottle, re-adding 20mL of unused commercial carbonate mixed solvent into the sample bottle, standing for 30min, taking the supernatant, measuring the water content and purity of the carbonate mixed solvent in the sample bottle, repeating the operation for 20 times, and testing and recycling for 20 times, wherein the water content and purity of the carbonate mixed solvent are treated by the water remover.

TABLE 2 Performance test results

As can be seen from Table 1, the water scavenger of examples 1-7 of the present invention not only has higher water removal efficiency, but also can effectively inhibit solvolysis of the electrolyte while adsorbing water as compared with the unmodified molecular sieve. Compared with the comparative examples, the water scavenger obtained by modifying the molecular sieve according to the examples of the present invention has a remarkable improvement in both the water scavenging effect and the inhibition of solvolysis of the electrolyte, particularly a particularly excellent water scavenging effect, compared with the unmodified molecular sieve. The preparation method of the invention has influence on the performance of the water remover no matter the amount of each raw material such as lubricant, the type of the lubricant and the setting of each parameter in the preparation process, and is concretely as follows.

Compared with comparative examples 2-4 and 9-11, the molecular sieve powder is replaced by ZSM molecular sieve, the vacuum pumping is not performed, the shaking is not performed after the vacuum pumping, the lubricant is too much or too little, the amount of tetraethyl orthosilicate is too little, the performance of the obtained water scavenger is obviously reduced, the water scavenger is not only represented by single water removal but also represented by multiple water removal, the water scavenger obtained can not achieve the standard water removal effect in the water removal process of the lithium ion battery electrolyte solvent, and the purity of the carbonate solvent is also obviously reduced.

Compared with the water scavengers B2 and B3 prepared in comparative examples 2 and 3, in which the comparative example 2 replaces the lubricant with white dextrin, there may be insufficient lubrication effect, which affects the release effect, and the comparative example 3 does not add water in step (S2), which easily causes easy collapse of the molecular sieve after molding, and thus the water removal performance of the obtained water scavenger is significantly reduced.

Compared with comparative example 4, the molecular sieve modifier was not calcined alone, so unreacted silicon source and tetrapropylammonium hydroxide were not removed in advance, a certain amount of pores, which are favorable for diffusion of electrolyte solvent during water removal, were not formed in the molecular sieve modifier, and thus the performance of the prepared water scavenger was significantly degraded.

Compared with comparative example 5, when roasting is finally performed, under the nitrogen atmosphere, the sesbania powder cannot be completely burnt, rich pore structures cannot be formed in the water scavenger, diffusion of electrolyte solvents is not facilitated, and the performance of the prepared water scavenger is remarkably reduced.

It should be noted that when the final calcination is performed, the performance of the water scavenger is affected by too high or too low calcination temperature, because if the calcination temperature is too low, the combination of the molecular sieve modifier and the molecular sieve to be modified may be insufficient, the condition of solid exchange reaction may not be reached, new Al-O-Si bonds may not be formed on the surface and the orifice of the molecular sieve, and the modification of the acidity of the molecular sieve to be modified may not be realized. And if the roasting temperature is too high, the molecular sieve modifier is easy to agglomerate on the surface of the molecular sieve to be modified, so that local pore channels are blocked, the modification is uneven, the modification effect is affected, and finally the performance of the water removing agent is affected.

Tetraethyl orthosilicate cannot be completely decomposed and converted into silicon oxide, and the molecular sieve is insufficiently modified; when the roasting temperature is too high, tetraethyl orthosilicate is easy to agglomerate when being decomposed into silicon oxide species, and further the silicon oxide species are unevenly distributed on the surface of the molecular sieve, so that the modification effect is affected, and finally the performance of the water removing agent is affected.

Compared with the water scavenger B8-B11 prepared in comparative examples 8-11, the modification of the water scavenger does not achieve a better effect due to too much or too little molecular sieve modifier or too much or too little silicon source.

In addition, the water removing agent can delay the time of the problem of reduced water removing efficiency caused by the adsorption of impurities by the molecular sieve, so that the replacement and use frequency of the water removing agent can be obviously reduced, the use and maintenance cost of the water removing agent can be saved, and the water removing agent has excellent application prospect.

Variations and modifications to the above would be obvious to persons skilled in the art to which the invention pertains from the foregoing description and teachings. Therefore, the invention is not limited to the specific embodiments disclosed and described above, but some modifications and changes of the invention should be also included in the scope of the claims of the invention. In addition, although specific terms are used in the present specification, these terms are for convenience of description only and do not limit the present invention in any way.

Claims

1. The application of the water scavenger is characterized in that the water scavenger is used for removing water from carbonate solvents of electrolyte of lithium ion batteries, and the preparation method of the water scavenger sequentially comprises the following steps:

the silicon source is tetraethyl orthosilicate;

the structure directing agent is tetrapropylammonium hydroxide;

the molar ratio of silicon dioxide, structure directing agent, strong alkali and water in the silicon source is 1: (0.01-1.0): (0.001-0.1): (10-300);

the conditions for roasting the stirred system in the step (S1) are as follows: the temperature is 550-650 ℃ and the time is 5-7h;

in the step (S2), the weight parts of the molecular sieve powder, the molecular sieve modifier, the lubricant and the water are respectively as follows:

45-60 parts of molecular sieve powder

1-5 parts of molecular sieve modifier

Lubricant 2-4 parts

1-10 parts of water;

the molecular sieve powder is 4A molecular sieve powder;

the lubricant is sesbania powder;

(S3) carrying out molding treatment and roasting on the mixture obtained in the step (S2) to obtain the water remover;

The conditions for firing in step (S3) are: under the air atmosphere or the oxygen atmosphere, the temperature is 550-650 ℃ and the time is 4-10h.

2. Use of a water scavenger according to claim 1, wherein the strong base in step (S1) is sodium hydroxide and/or potassium hydroxide.

3. The use of a water scavenger according to claim 1, wherein the water in step (S1) is deionized water.