KR20220033231A - Preparing method for electrolyte salt - Google Patents

Abstract

The present invention relates to a method for manufacturing electrolytic salt. More specifically, a lithium compound and a boron compound are pulverized into particles having a size in a specific range, the pulverized product and an oxalic acid compound are dispersed in water, and reactants dispersed in water are reacted to form lithium-boron complex salt. According to the present invention, the electrolytic salt can be manufactured in a more improved yield, and when the electrolytic salt is added to an electrolyte of a battery, battery performance can be improved.

Description

Manufacturing method of electrolytic salt {PREPARING METHOD FOR ELECTROLYTE SALT}

The present invention relates to a method for preparing an electrolyte salt, and more particularly, to prepare an electrolyte salt added to an electrolyte solution in an improved yield to improve the efficiency and lifespan of the battery, and to improve battery performance when added to the electrolyte solution of the battery It relates to a method for preparing a lithium-boron complex salt, which can further improve the effect.

Lithium secondary batteries enable smooth movement of lithium ions by putting an electrolyte between the positive and negative electrodes, and the use of electrical energy by the method in which electricity is generated or consumed by redox reactions following insertion and desorption from the positive and negative electrodes. make it easy Lithium interest batteries have been actively used with the spread of small mobile devices, and in recent years, as their use has been gradually expanded to large devices such as electric vehicles, the output and capacity of the battery are improved, the output at high and low temperatures is improved, and the battery Various methods for improving battery performance, such as extending the lifespan, have been tried.

Lithium secondary batteries generally include LiPF ₆ having high conductivity and excellent electrochemical stability as a lithium salt. However, during storage or use of the battery, lithium salts in the electrolyte are decomposed to deteriorate the performance of the battery or generate corrosive by-products, thereby reducing the stability of the battery, and thus shortening the life of the battery. , an electrolyte additive that can prevent decomposition of the electrolyte is used as a method to solve this problem.

Lithium bisoxalatoborate (LiBOB), which is widely used as an electrolyte additive, has a manufacturing method introduced through Korean Patent Document 10-0716373. The above document discloses a method for preparing a lithium compound, oxalic acid, and boric acid by mixing and reacting in an aqueous solution state, wherein the concentration of the reaction mixture solution is about 2 to 3 wt %, and the concentration of the reaction tank is dilute, so the productivity is low, so it is not economical there is In addition, when an organic solvent that forms an azeotrope with water is used as the reaction solvent, there may be a problem in that the performance of the battery is deteriorated when added to the electrolyte due to the solvent remaining in the granules of the prepared LiBOB. Furthermore, in the case of the granules of LiBOB prepared through the above method, the solubility in the battery electrolyte is not sufficient, so it takes a long time to dissolve, and there is a problem in that insoluble crystals are precipitated.

On the other hand, in order to solve the above problem, a method of mixing and reacting reaction raw materials in a powder state without dissolving them has been attempted, but in this case, an acidic raw material such as oxalic acid and a basic raw material such as lithium hydroxide are mixed. As a result, the reaction raw material powder gradually gets wet as water is generated, and this causes the reaction raw material powder to become stiff, making it difficult to uniformly mix. Accordingly, there is a problem in that the purity of the reaction is low and the reaction yield is low, such as a decrease in reaction efficiency and generation of by-products because contact between the reaction raw materials is not made smoothly.

Korean Patent Registration 10-0716373 B1

In order to solve the problems of the prior art as described above, an object of the present invention is to provide a method for preparing an electrolyte salt having an improved yield.

Another object of the present invention is to provide a method for preparing an electrolyte salt that exhibits high purity and is excellent in improving battery performance when added to a battery electrolyte.

The above and other objects of the present invention can all be achieved by the present invention described below.

In order to achieve the above object, the present invention is a pulverized product by i) pulverizing a lithium compound and a boron compound into particles having a number average particle diameter (D _n50 ) of 0.5 to 100 μm and a maximum particle diameter (D _n99 ) of 250 to 500 μm forming a; ii) dispersing the pulverized product together with an oxalic acid compound in water to form a dispersion mixture; and iii) reacting the dispersion mixture to produce a lithium-boron complex salt.

The manufacturing method of the electrolyte salt according to the present invention is economically advantageous because the yield is improved, and the purity is improved, so that when it is added to the electrolyte of a lithium secondary battery, the battery performance improvement effect and the lifespan improvement effect are further improved.

1 shows the XRD crystal pattern measurement results of Example 1 (a) and Comparative Example 2 (b) of the present invention.

Hereinafter, the present invention will be described in detail.

The present inventors have been researching a method for improving the purity of an electrolyte salt added to the electrolyte of a lithium secondary battery in a more stable and high yield to improve battery performance, while researching a method for improving the purity of lithium source and lithium It was confirmed that all of the above objects could be achieved by pulverizing the materials reacting together in the form of particles of a certain size and reacting them in a dispersion medium, and based on this, the present invention was completed.

The method for producing an electrolytic salt according to embodiments of the present invention is i) pulverizing a lithium compound and a boron compound into particles having a number average particle diameter (D _n50 ) of 0.5 to 100 μm and a maximum particle diameter (D _n99 ) of 250 to 500 μm Forming a pulverized product, ii) dispersing the pulverized product together with an oxalic acid compound in water to form a dispersion mixture, and iii) reacting the dispersion mixture to form a lithium-boron complex salt do it with According to the present invention, a lithium compound and a boron compound, which are reaction raw materials, as described above, are first crushed into particles of a specific size, and then dispersed in water together with an oxalic acid compound and reacted, thereby stably producing a desired electrolyte salt with a better yield. , there is an excellent effect of obtaining a high-purity electrolytic salt.

In the present description, “dispersing the pulverized material together” means not only when the dispersed pulverized materials are simultaneously added to the dispersion medium, but also when the pulverized materials are added to the dispersion medium and then dispersed together in the dispersing medium includes

In the present description, the number average particle diameter (D _n50 ) means the particle diameter at the point of 50% of the cumulative distribution rate of the particle size measured using the Malvern Mastersizer 3000 (Malvern Instruments, Inc.), and the maximum particle diameter ( D _n99 ) means the particle size at the 99% cumulative distribution rate.

In step i), the lithium compound and the boron compound can be pulverized into particles having a number average particle diameter (D _n50 ) of 0.5 to 100 μm, preferably 1 to 50 μm, more preferably 10 to 30 μm. can In this case, the maximum particle diameter (D _n99 ) may be less than 500 μm, preferably less than 400 μm, more preferably less than 300 μm, or the maximum particle diameter (D _n99 ) of the pulverized particles is 250 to 500 μm, preferably 260 to 400 μm, more preferably 270 to 300 μm, and most preferably 270 to 290 μm. When dispersed in water within the above range, wetting is facilitated, and precipitation of reactants is prevented, thereby improving dispersibility and reactivity to water, and there is an effect that the electrolytic salt production efficiency is more excellent. In the present invention, the reaction participation rate of the reactants can be further increased, and the electrolytic salt production efficiency is further improved by pulverizing and using the solid reaction raw material to have a particle diameter in the limited range as described above, unlike the simple pulverization and dispersing in water and then reacting. can be

In step i), for example, when the lithium compound and the boron compound are pulverized, they may be individually pulverized using a separate pulverizer. When a basic lithium compound and an acidic boron compound are mixed and pulverized together, an acid-base reaction may occur, although it appears in a solid state. In this case, lithium salt and water are generated, making it difficult to mix the reactants smoothly. , the dispersibility in water may decrease and the reaction efficiency may decrease. Accordingly, the lithium compound and boron compound, which are solid reaction raw materials, are preferably individually pulverized using a separate pulverizer, and the pulverization may be preferably dry pulverization using a dry pulverizer. In this case, since the reactants in the powder state can be uniformly dispersed by preventing agglomeration of the reactants in the powder state by the water generated through the acid-base reaction between the reactants in the dry powder state, there is an effect of improving the reaction efficiency.

The pulverizer may be, for example, a mechanical pulverizing pulverizer, preferably a ball mill or an air jet mill, and more preferably a ball mill. When a ball bowling machine is used, for example, since the raw material is pulverized using a ceramic material such as zirconia beads, it has the advantage of being free from metallic contamination sources that may be introduced from metallic mechanical device members such as stainless steel or titanium. It has the effect of pulverizing raw materials with high purity. In the case of using an air jet mill, the particle size distribution is narrow and fine particles can be obtained, so that it is possible to obtain the effect of easy dispersion and increased reaction efficiency in the subsequent dispersion process and reaction.

In step ii), the pulverized product of the pulverized lithium compound and the boron compound is dispersed in water together with the oxalic acid compound so that the reactants are homogeneously mixed in a reaction medium. In a preferred example, step ii) comprises: ii-1) dispersing the pulverized product by dispersing it in water; and ii-2) dispersing an oxalic acid compound in the water in which the pulverized product is dispersed.

In this case, in step ii), the pulverized lithium compound, pulverized boron compound, and oxalic acid compound may be dispersed in water to a concentration of 40 to 95 wt % based on the total solid content in water, for example. The total reactant concentration added to the water may be preferably 50 to 90% by weight, more preferably 60 to 88% by weight, and most preferably 65 to 85% by weight, based on the solid content, within the above range. Since the concentration of the reactant is high, the productivity is improved, and the forward reaction of the electrolytic salt production reaction is dominant, so that the reaction efficiency is improved.

In the case of lithium hydroxide monohydrate as an example of the lithium compound, the theoretical solubility at 20 ° C. is about 22.3 wt %, and in the case of boric acid as an example of the boron compound, the theoretical solubility at 20 ° C is about 4.7 wt %, the present invention is as described above When the reactant is added to water, it is characterized in that the remaining undissolved reactant is evenly dispersed in water by adding an excess exceeding the saturation solubility.

In the prior art, when preparing an electrolyte salt, an electrolyte salt was prepared by simply dissolving reaction raw materials such as a lithium compound, a boron compound, and an oxalic acid compound in water. In this case, a lithium cation and an oxalate anion (C ₂ O ₄ ^2- ) reacts to generate a by-product called lithium oxalate (Li ₂ -C ₂ O ₄ ), and thus the purity of the electrolytic salt decreases.

In the present invention, unlike the prior art, the pulverized product of the lithium compound and the boron compound is simultaneously or sequentially added to water in an excess exceeding the saturated solubility as described above, dispersed in water while stirring at high speed, and then the oxalic acid compound is added It is characterized in that it reacts. The lithium compound and boron compound particles are partially dissolved in water while being added to the water, but the remaining particles that are not dissolved are evenly dispersed at a high speed to form a dispersed phase. Through this, the surface of the lithium compound particles dispersed in water is vitrified by the boron compound, that is, a kind of protective film is formed, thereby slowing the ionization rate of lithium. As the ionization rate of lithium is slowed, even when an oxalic acid compound is added, the above-described by-products can be prevented from being generated, and the forward reaction of the electrolytic salt production is dominant, thereby improving the purity of the electrolytic salt. The present invention can increase the reaction participation rate of the reactants by finely pulverizing the reactants as described above and evenly dispersing them in water. By controlling the reaction rate, it is possible to prevent the formation of by-products, and as a result, the reaction efficiency is improved, so that the electrolytic salt can be prepared with high purity and high yield.

The molar ratio of the lithium compound, boron compound, and oxalic acid compound introduced into the reaction system may be, for example, 1: 0.5 to 2: 1-3, preferably 1: 0.7 to 1.2: 1.5 to 2, more preferably 1: 0.8 to 1.1: It may be 1.5 to 2.5, and there is an economically more advantageous advantage by improving the yield of the desired electrolytic salt without reacting and wasted reaction raw materials within this range.

The lithium compound used in the preparation of the electrolytic salt may be, for example, lithium hydroxide, lithium hydroxide hydrate, lithium carbonate, or lithium oxide, preferably lithium hydroxide or lithium hydroxide hydrate. In this case, generation of by-products can be suppressed and the efficiency of generating a desired electrolytic salt can be further improved.

The boron compound used in the preparation of the electrolytic salt may be, for example, boric acid, boric acid ester or borate, preferably boric acid, in which case the generation of by-products is suppressed and the efficiency of generating the desired electrolytic salt can be further improved. .

The oxalic acid compound used in the preparation of the electrolytic salt may be, for example, oxalic acid, oxalic acid hydrate, or oxalate, and preferably may be oxalic acid or oxalic acid dihydrate, and in this case as well, it suppresses the production of by-products and produces a desired electrolytic salt. Efficiency can be further improved.

The lithium-boron complex salt, which is an electrolyte salt prepared through the above preparation method, may preferably be LiBC ₄ O ₈ . LiBC ₄ O ₈ is an electrolyte salt useful as an electrolyte additive because it has an excellent effect of improving ionization and electrolyte mobility while preventing the decomposition of lithium salts in the battery electrolyte, and in particular, greatly increasing the battery usage/storage temperature. ₄ O ₈ can be stably produced in high yield and has high purity, so that the effect of improving battery performance by adding LiBC ₄ O ₈ can be further improved.

The reaction of step iii) may be performed, for example, at a temperature of 30 to 240° C. for 5 to 20 hours. The reaction temperature may be preferably 40 to 120 °C, more preferably 50 to 100 °C, and the reaction time is preferably 7 to 15 hours, more preferably 10 to 13 hours. there is. In this case, the electrolytic salt can be easily prepared by carrying out the reaction at a relatively low temperature, and there is an effect that the reaction efficiency is more excellent. The reaction may preferably be carried out under a non-reactive atmosphere such as nitrogen.

In the method for preparing an electrolyte salt of the present invention, for example, the lithium-boron complex salt produced in step iii) is dried at a temperature of 80 to 320° C. and 0.1 to 1 atm (atm) for 5 to 24 hours to obtain a lithium-boron complex salt powder. It may further include the step of obtaining The drying temperature condition may be preferably 100 to 250 °C, more preferably 150 to 220 °C, and the pressure condition is preferably 0.5 to 0.7 atmosphere. In addition, drying may be performed for 5 to 20 hours, more preferably 8 to 13 hours under the above temperature and pressure conditions, and within this range, drying of the reaction product proceeds with high efficiency, thereby improving manufacturing efficiency. .

In the dried lithium-boron complex salt, that is, the electrolyte salt, for example, the amount of residual solvent in the dried powder state may be 10 ppm or less. Here, the solvent included in the residual solvent amount is excluding the carbonate-based solvent, and refers to water and a purification solvent, and the purification solvent may be, for example, acetonitrile. The amount of residual solvent may be preferably 5 ppm or less, more preferably 2 ppm or less, through which the battery performance is prevented from being deteriorated due to the residual of unnecessary reaction solvent except for the carbonate-based solvent, which is a component of the non-aqueous electrolyte. can

The present invention may further include the step of dissolving the obtained lithium-boron complex salt powder in a carbonate-based solvent and filtering it to obtain a lithium-boron complex salt solution having a concentration of 2 to 20% by weight, through which the final There is an advantage that can further improve the purity of the obtained electrolytic salt. The lithium-boron complex salt solution may be formed to have a concentration of preferably 3 to 15% by weight, more preferably 5 to 10% by weight, and in this case, solubility in the battery electrolyte is improved and dissolved quickly when added to the electrolyte and to prevent the formation of insoluble matter, and finally, the effect of improving the performance of the battery can be further improved.

The carbonate-based solvent used in the above step is, for example, ethylene carbonate (EC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate (PC), dipropyl carbonate (DPC) , butylene carbonate, may be at least one selected from the group consisting of methylpropyl carbonate and ethylpropyl carbonate, and preferably, it may be a mixed solvent of 2 to 3 types selected from the group consisting of EC, DEC, EMC and DMC. Preferably, for mixing EC and DEC, a mixed solvent containing DMC or DEC in a volume ratio of 1:1 to 7:2 to 4, more preferably EC and EMC in a volume ratio of 1:0.5 to 1.5 for mixing In this case, compatibility with the electrolyte may be further improved, thereby improving the efficiency of adding the electrolyte salt to the battery electrolyte.

In addition, the electrolyte salt prepared through the above preparation method is, for example, dissolved in the carbonate-based solvent, that is, the insoluble content of the lithium-boron complex salt solution is 0.5 wt% or less, preferably 0.1 wt% or less, more preferably It may be less than 0.05% by weight, and through this, there is an excellent effect that the battery performance improvement effect is further improved as a battery electrolyte additive.

The present invention provides an electrolyte solution for a battery comprising an electrolyte salt prepared by the method for preparing an electrolyte salt. The electrolyte is an electrolyte of a non-aqueous lithium secondary battery, and includes the electrolyte salt as an electrolyte additive, an organic solvent, and a lithium salt.

The organic solvent may be, for example, a carbonate-based organic solvent, specifically ethylene carbonate (EC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate (PC), di It may be an organic solvent containing at least one selected from the group consisting of propyl carbonate (DPC), butylene carbonate, methylpropyl carbonate, and ethylpropyl carbonate.

The organic solvent may be, for example, one type or a mixed solvent of two or more types, and preferably, an organic solvent having high ionic conductivity and a viscosity of the solvent having high ionic conductivity so as to increase the charge/discharge performance of the battery to be applied to the battery. A low-viscosity organic solvent that can be adjusted to have an appropriate viscosity may be mixed and used as a mixed solvent.

EC and PC may be used as an example of the organic solvent having a high dielectric constant, and EMC, DMC, and DEC may be used as the low viscosity organic solvent, and the high dielectric constant and low viscosity organic solvent is 2: It is preferable to use the mixture in a volume of 8 to 8:2. More specifically, it may be a ternary mixed solvent of EC or PC, EMC and DEC, and a ratio of EC or PC, EMC and DEC may be 3: 3 to 5: 2 to 4.

When the organic solvent contains water, lithium ions in the electrolyte may be hydrolyzed, so the water content in the organic solvent is preferably controlled to be 150 ppm or less, preferably 100 ppm or less.

The lithium salt may be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery, and specifically, LiPF ₆ , LiBF ₄ , LiCl, LiBr, LiI, LiClO ₄ , LiB ₁₀ Cl ₁₀ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiAlCl ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, and (CF ₃ SO ₂ ) ₂ NLi may include at least one selected from the group consisting of there is. Preferably, it may be LiPF ₆ .

When the lithium salt is dissolved in the electrolyte, the lithium salt functions as a source of lithium ions in the lithium secondary battery, and may promote movement of lithium ions between the positive electrode and the negative electrode. Accordingly, the lithium salt is preferably included in a concentration of about 0.6 mol% to 2 mol% of the electrolyte. If the concentration of the lithium salt is less than 0.6 mol%, the conductivity of the electrolyte may be lowered, and thus electrolyte performance may be deteriorated. Considering the conductivity of the electrolyte and the mobility of lithium ions, the lithium salt may be included in the electrolyte in an amount of preferably 0.7 mol% to 1.6 mol%, more preferably 0.8 mol% to 1.5 mol%.

The electrolyte solution for a battery of the present invention, for example, in addition to the electrolyte salt prepared by the method for preparing an electrolyte salt, an additive ( Hereinafter, referred to as other additives) may be further included.

The other additive component may include, for example, a metal phosphate-based compound.

The metal phosphate-based compound is selected from the group consisting of lithium difluoro (bisoxalato) phosphate (LiDFOP), lithium tetrafluoro oxalato phosphate (LiTFOP), lithium difluorophosphate and lithium trioxalato phosphate. more than one

The metal phosphate-based compound is a component added to improve the performance of a lithium secondary battery, a lithium ion capacitor, etc., and may be included in the electrolyte in an amount of 0.3 to 1.5 wt%, preferably 0.7 to 1.2 wt%. When the content of the metal phosphate-based compound satisfies the above range, it is preferable in terms of improving the low-temperature characteristics and cycle characteristics of the battery.

As another example, the present invention may provide a secondary battery including the electrolyte, wherein the secondary battery includes a negative electrode and a positive electrode. It is characterized in that it comprises a separation foil interposed between the negative electrode and the positive electrode, and the electrolyte solution for the battery.

The positive electrode may be prepared by, for example, mixing a positive electrode active material, a binder, and optionally a conductive agent to prepare a composition for forming a positive electrode active material layer, and then applying it to a positive electrode current collector such as aluminum foil.

The positive active material may be, for example, a typical NCM (lithium nickel manganese cobalt oxide, LiNiMnCoO ₂ ) positive electrode active material used in lithium secondary batteries, specifically, the formula Li[NixCo _1-xy Mn _y ]O ₂ (where 0 It may be a lithium composite metal oxide in the form of <x<0.5, 0<y<0.5), but is not limited thereto.

Variables x and y of the formula Li[NixCo _1-xy Mn _y ]O ₂ of the lithium composite metal oxide are, for example, 0.0001<x<0.5, 0.0001<y<0.5, or 0.001<x<0.3, 0.001<y<0.3 can be

As another example of the positive active material, a compound capable of reversible intercalation and de-intercalation of lithium (a lithiated intercalation compound) may be used.

Among the above compounds, LiCoO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiNi _x Mn _(1-x) O ₂ (provided that 0<x<1), and LiM1 _x M2 _y O ₂ (provided that 0≤x≤1, 0≤y≤1, 0≤x+y≤1, M1 and M2 are each independently any one selected from the group consisting of Al, Sr, Mg and La ), preferably at least one selected from the group consisting of.

The negative electrode may be prepared by, for example, mixing a negative electrode active material, a binder, and optionally a conductive agent to prepare a composition for forming the negative electrode active material layer, and then applying it to a negative electrode current collector such as copper foil.

As the anode active material, for example, a compound capable of reversible intercalation and deintercalation of lithium may be used.

Specific examples of the anode active material may be carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon. In addition to the carbonaceous material, a metal compound capable of alloying with lithium, or a composite including a metal compound and a carbonaceous material may be used as the negative electrode active material, and may be graphite, for example.

As the metal capable of alloying with lithium, for example, at least one of Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy may be used.

In addition, a metal lithium thin film may be used as the negative electrode active material. As the negative active material, in view of high stability, any one or more selected from the group consisting of crystalline carbon, amorphous carbon, carbon composite material, lithium metal, and an alloy containing lithium may be used.

The secondary battery of the present invention includes the electrolyte salt prepared by the method for preparing an electrolyte salt of the present invention as an electrolyte additive, thereby improving battery characteristics such as battery charge resistance, output characteristics, capacity recovery characteristics at low and high temperatures, and lifespan characteristics has a further improved effect.

Specifically, the secondary battery comprising the electrolyte salt of the present invention in the electrolyte has a lifespan efficiency of 85% or more, preferably 88% or more, more preferably 90 % or more, and in this case, the lifespan efficiency of the battery is excellent and the battery life is greatly improved. Accordingly, since the secondary battery including the electrolyte prepared by the method for preparing an electrolyte salt of the present invention in an electrolyte solution is suitable for long-term use in various environments, the usage and efficiency of the battery can be further expanded.

Hereinafter, preferred examples are presented to help the understanding of the present invention, but the following examples are merely illustrative of the present invention, and it will be apparent to those skilled in the art that various changes and modifications are possible within the scope and spirit of the present invention, It goes without saying that such variations and modifications fall within the scope of the appended claims.

Example 1

i) Pulverization of lithium compounds and boron compounds

LiOH·H ₂ O with a maximum particle diameter of D _n99 of 980 μm as a lithium compound, and H ₃ BO ₃ with a D _n99 of 1,140 μm as a boron compound were dry pulverized with an air jet mill, respectively, with a number average particle diameter of D _n50 of 15 μm and A pulverized product having a size of 13 μm was obtained.

ii) Dispersion of reactants

1L of distilled water was put into a 3-neck flask with a capacity of 5L, and 6.25 mol (387g) of H ₃ BO ₃ (D ₅₀ =13 μm) was added thereto, and then evenly dispersed using a high-speed stirrer. Using a heating mantle, the temperature inside the reactor was maintained at 40° C. (the first section temperature) and maintained for 1 hour. Here, 6.25 mol (264 g) of LiOH·H ₂ O (D ₅₀ =15 μm) was added and then evenly dispersed using high-speed stirring. Using a heating mantle, the temperature inside the reactor was set to 50° C. (the second section temperature) and maintained for 1 hour. When sufficiently dispersed to form a homogeneous mixture, 12.5 mol (1,580 g) of H ₂ C ₂ O ₄ ·2H ₂ O was added as an oxalic acid compound and then completely dissolved. The total solid content concentration in the reaction tank was set to 69% by weight.

iii) Reaction and production of lithium-boron complex salts

Using a heating mantle, the temperature inside the reactor was maintained at 80° C. (the third section temperature) and maintained for 6 hours. The obtained compound was transferred to a glass container with a lid, placed in a dryer preheated to 200° C., and dried under reduced pressure by lowering the internal pressure of the dryer by 30 mmHg per hour for 12 hours to obtain a dried lithium-boron complex salt.

iv) Filtration of the obtained lithium-boron complex salt

The obtained dry lithium-boron complex salt was dissolved in a carbonate-based solvent in which EC and EMC were mixed in a weight ratio of 1:1 to a concentration of 10% by weight, and insoluble matter was removed through membrane filtration.

ⅴ) Preparation of electrolyte

DMC, EMC, and EC were composed of a background solvent in a volume ratio of 1:1:1, and the filtered lithium-boron complex salt was added at a concentration of 1.25% by weight, and then 1.2M of LiPF ₆ and LiBF ₄ were added as electrolytes. It was added and sufficiently dissolved to prepare an electrolyte solution for a battery.

Example 2

In Example 1, it was carried out in the same manner as in Example 1, except that the reaction temperature of the third section was changed to 60 °C.

Example 3

In Example 1, it was carried out in the same manner as in Example 1, except that the solid content concentration inside the reaction tank was changed to 78 wt%, and the reaction temperature of the third section was changed to 60 °C.

Example 4

In Example 1, the boric acid compound was changed to H ₃ BO ₃ having a D _n50 of 44 μm, and the same as in Example 1 was performed except that the reaction temperature of the third section was changed to 60°C.

Comparative Example 1

In Example 1, LiOH·H ₂ O having a D _n99 of 980 μm and H ₃ BO ₃ having a D _n99 of 1,140 μm were introduced into the reactor without a grinding process, and the same procedure as in Example 1 was performed.

Comparative Example 2

In Example 1, LiOH·H ₂ O having a D _n99 of 980 μm and H ₃ BO ₃ having a D _n99 of 1,140 μm were introduced into the reactor without a grinding process, and the solids concentration of the reactor was 78% by weight, and the third Except for changing the reaction temperature of the section to 60 ℃ was carried out in the same manner as in Example 1.

Reference Example 1

In Example 1, the D _n50 of the pulverized LiOH·H ₂ O particles was 52 μm, the D _n50 of the pulverized H ₃ BO ₃ particles was changed to 44 μm, and the purification solvent used in the filtration step was acetonitrile. Except that, it was carried out in the same manner as in Example 1.

Reference Example 2

In Example 1, the solid content concentration of the reaction tank was 15 wt%, and the same procedure as in Example 1 was carried out except that the reaction temperature of the third section was changed to 60°C.

manufacture of batteries

Li (Ni _0.5 Co _0.2 Mn _0.3 )O ₂ 92 wt% as a positive active material, 4 wt% of carbon black as a conductive agent, and 4 wt% of polyvinylidene fluoride (PVdF) as a binder N-methyl- as a solvent It was added to 2-pyrrolidone (NMP) to prepare a positive electrode mixture slurry. The positive electrode mixture slurry was applied to an aluminum (Al) thin film as a positive electrode current collector having a thickness of about 20 μm, dried to prepare a positive electrode, and then a positive electrode was manufactured by performing a roll press.

Carbon powder as an anode active material, PVdF as a binder, and carbon black as a conductive agent in 96 wt%, 3 wt%, and 1 wt%, respectively, were added to NMP as a solvent to prepare an anode mixture slurry. The negative electrode mixture slurry was applied to a 10 μm-thick copper (Cu) thin film as a negative electrode current collector, dried to prepare a negative electrode, and then roll press was performed to prepare a negative electrode.

After preparing a pouch-type battery in a conventional manner with a separator consisting of three layers of polypropylene/polyethylene/polypropylene (PP/PE/PP) for the positive and negative electrodes prepared as described above, Examples 1 to 4, Comparative Examples The electrolyte solution prepared in 1 and 2 and Reference Examples 1 and 2 was injected to complete the manufacture of a lithium secondary battery.

test example

In order to evaluate the yield, water of crystallization, specific surface area, residual solvent, insoluble content, and the performance of the secondary battery containing the electrolyte salt prepared above, the performance was measured by the following method, and the results are shown in Table 1 and 1 is shown.

(a) Filtration yield: It is expressed as the ratio of the amount of electrolyte obtained actually obtained after filtration to the theoretical amount obtained. When the amount of insoluble matter filtered through the filter is large, the yield is reduced.

(b) Crystalline water: Crystalline water XRD when the obtained powder (LiBC ₄ O ₈ ) was measured by X-ray diffraction (XRD, X-ray diffraction) and the main XRD pattern (2 theta 19.4°) was normalized to 1. The signal sensitivity of the pattern (2theta 20.1°) was expressed as a magnitude (integer, no unit, closer to 0, the less determinable). The crystal water value was calculated using Equation 1 below, and the coefficient (10000) was determined in conjunction with the Karl Fischer moisture titration result.

[Equation 1]

Number of crystals (ppm) = {(Signal sensitivity of the main XRD pattern)/(Signal sensitivity of the number of crystals XRD pattern)}*(Coefficient 10000)

(c) Turbidity value: The prepared electrolyte solution was aged for 7 days at room temperature and then recorded through the NTU turbidity meter.

(d) Residual solvent: ACN applied as an organic solvent was quantified as a standard material using gas chromatography.

(e) Insoluble content: Ultrafine particulate insoluble content that has not been filtered after the filtration process in step iv). After removing the solvent from the filtered solution using a rotary evaporator to obtain a solid content, sample with 5% dilute hydrochloric acid After collecting the lithium, the concentration of lithium is quantified through ICP-OES measurement. Through this, the fraction of insoluble matter was calibrated.

(f) Battery life efficiency: The lithium secondary batteries prepared in Examples and Comparative Examples were left at room temperature overnight, and then charged and discharged using a secondary battery charge/discharge tester. First, it was charged at 4.2V (0.5C rate) under CC (Constant current)/CV (Constant voltage) conditions at 25° C., and after resting for 10 minutes, it was discharged to 2.7V under CC (0.5C rate) conditions. At this time, the standard capacity (Normal capacity) was 1000mAh. The charging and discharging were performed as 1 cycle, and after repeated 300 cycles, the capacity according to the charging and discharging was measured. The maintenance ratio of the discharge capacity after 300 cycles compared to the discharge capacity of 1 cycle was calculated.

(g) Measurement of average particle size: The sample powder was completely dispersed in an insoluble solvent at 0.5% using an ultrasonic disperser. The dispersion was injected into a particle size analyzer to measure the number average particle size of the particles dispersed in the dispersion.

division Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Reference Example 1 Reference Example 2 Filtration yield
(%) 99 97 95 92 68 54 89 unobtainable crystal water
(ppm) 43 35 52 91 1299 962 293 - Turbidity value 4.3 3.8 4.6 6.7 11.2 9.6 14.5 - residual solvent
(ppm) non-detection non-detection non-detection non-detection non-detection non-detection 78 - insoluble matter
(%) 0.01 0.02 0.01 0.03 0.01 0.02 0.16 - Capacity retention rate
(%) 96 92 94 89 78 74 6% -

As shown in Table 1, Examples 1 to 4 of the present invention had a high filtration yield of 92% or more, a low crystal water of 91 ppm or less, a turbidity value of 6.7 or less, and no residual solvent was detected. , it can be seen that the production yield and purity of the electrolytic salt are very high as the insoluble content is also low as 0.03%. In addition, it can be seen that the capacity retention rate of the battery prepared by putting it in the battery electrolyte is 89% or more, indicating that the battery life extension effect is excellent.

On the other hand, in the case of Comparative Examples 1 and 2, it can be seen that the filtration yield was decreased, the number of crystals was greatly increased, and the turbidity value was high. It was also found that the capacity retention rate of the batteries prepared by adding Comparative Examples 1 and 2 to the battery electrolyte was also lower than that of the Examples of the present invention.

1 shows the XRD crystal pattern measurement results of Example 1 (a) and Comparative Example 2 (b) of the present invention. In FIG. 1 , the XRD crystal pattern of LiBC ₄ O ₈ is observed at 19.4°, and the XRD crystal pattern of crystalline water (LiBC ₄ O ₈ ) (H ₂ O) is observed at 20.1°. Crystalline water is moisture that cannot be removed even by drying or vacuum drying, and refers to moisture mixed in the crystal structure when a composite crystal is formed.

Referring to FIG. 1 , it can be seen that the XRD crystal pattern of Example 1 has a low peak at 20.1° and thus almost no number of crystals. On the other hand, in the XRD crystal pattern of Comparative Example 2, a peak appeared at 20.1°, indicating that in Comparative Example 2, a large amount of crystal water was present in the crystals of the synthesized electrolyte salt.

Claims (14)

i) pulverizing the lithium compound and the boron compound into particles having a number average particle diameter (D _n50 ) of 0.5 to 100 μm and a maximum particle diameter (D _n99 ) of 250 to 500 μm to form a pulverized product;
ii) dispersing the pulverized product together with an oxalic acid compound in water to form a dispersion mixture; and
iii) reacting the dispersion mixture to produce a lithium-boron complex salt;
A method for producing an electrolytic salt.
According to claim 1,
In step i), the lithium compound and the boron compound are separately pulverized using a separate pulverizer.
A method for producing an electrolytic salt.
3. The method of claim 2,
The grinder is characterized in that it is selected from the group consisting of a ball mill and an air jet mill
A method for producing an electrolytic salt.
According to claim 1,
The step ii) includes: ii-1) dispersing the pulverized product by putting it in water; and ii-2) dispersing the oxalic acid compound in the water in which the pulverized product is dispersed.
A method for producing an electrolytic salt.
According to claim 1,
In step ii), the lithium compound, the boron compound and the oxalic acid compound are dispersed in water at a concentration of 40 to 95% by weight based on the total solid content.
A method for producing an electrolytic salt.
According to claim 1,
The molar ratio of the lithium compound, boron compound, and oxalic acid compound added to the reaction is 1: 0.5 to 2: 1-3, characterized in that
A method for producing an electrolytic salt.
According to claim 1,
The lithium compound is lithium hydroxide, lithium hydroxide hydrate, lithium carbonate, or lithium oxide, characterized in that
A method for producing an electrolytic salt.
According to claim 1,
The boron compound is characterized in that boric acid, boric acid ester or borate
A method for producing an electrolytic salt.
According to claim 1,
The oxalic acid compound is characterized in that oxalic acid, oxalic acid hydrate, or oxalate
A method for producing an electrolytic salt.
According to claim 1,
The lithium-boron complex salt is LiBC ₄ O ₈
A method for producing an electrolytic salt.
According to claim 1,
The reaction in step iii), characterized in that it is carried out at a temperature of 30 to 240 ℃ for 5 to 20 hours
A method for producing an electrolytic salt.
According to claim 1,
Drying the lithium-boron complex salt produced in step iii) at a temperature of 80 to 320° C. and 0.1 to 1 atm for 5 to 24 hours to obtain a lithium-boron complex salt powder; characterized by further comprising to do
A method for producing an electrolytic salt.
According to claim 1,
Dissolving the obtained lithium-boron complex salt powder in a carbonate-based solvent and filtering it to obtain a lithium-boron complex salt solution having a concentration of 2 to 20% by weight; characterized in that it further comprises
A method for producing an electrolytic salt.
14. The method of claim 13,
The carbonate-based solvent is ethylene carbonate (EC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate (PC), dipropyl carbonate (DPC), butylene carbonate, methylpropyl Characterized in that at least one selected from the group consisting of carbonate and ethylpropyl carbonate
A method for producing an electrolytic salt.

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