CN100593515C - Method of preparing waterless lithium terafluoroborate - Google Patents

Abstract

The invention relates to a method for preparing an anhydrous lithium tetrafluoroborate which comprises the following steps: a lithium source including lithium hydroxide, lithium carbonate, and the like, reacts with fluorine hydride and boric acid to obtain lithium tetrafluoroborate solution, then the lithium tetrafluoroborate solution is condensed, crystallized and recrystallized, ground, and vacuum dried to obtain the anhydrous lithium tetrafluoroborate. The method of the invention adopts a staged temperature rise control, the process of the preparation is simple, raw materials are cheap andthe preparation cost is low, no organic solvent is used during the synthetic process, no poison is produced, therefore, the method accords with the concept of green environmental protection, the anhydrous lithium tetrafluoroborate prepared by the method is determined by a X-ray diffraction map, the diffraction peak is clear and sharp and completely matches the standard card, which shows that the product prepared by the method of the invention is anhydrous LiBF4 with complete crystal form, the quality of the product is equal to the quality of the anhydrous lithium tetrafluoroborate prepared bythe reaction of lithium fluoride and boron trifluoride.

Description

A kind of preparation method of waterless lithium terafluoroborate

Technical field

The invention belongs to chemical field, relate to a kind of preparation of lithium salts, relate in particular to a kind of preparation method of lithium ion battery electrolyte waterless lithium terafluoroborate.

Background technology

Electrolyte solution is the important component part of lithium ion battery, plays a part between positive and negative electrode, to carry the ionic conduction electric current, and be to finish the indispensable part of electrochemical reaction.Selecting suitable electrolyte also is the key of the good lithium ion battery of acquisition high-energy-density and power density, long circulation life and safety performance, and the quality of its performance directly influences the optimization in Properties and the raising of lithium ion battery.The used lithium salts of lithium ion battery is generally LiPF ₆, LiBF ₄, LiClO ₄, LiAsF ₆, LiCF ₃SO ₃, LiN (CF ₃SO ₂) ₂Or LiC (CF ₃SO ₂) ₃Deng material.When above-mentioned lithium salts was dissolved in the non-aqueous solvent, that specific conductivity is the highest was LiAsF ₆And LiPF ₆, be LiClO secondly ₄, be LiBF secondly again ₄, that minimum is LiCF ₃SO ₃Though LiAsF ₆Can not decompose when easy purifying and disposal, but have toxicity, contaminate environment, its application is restricted; LiClO ₄Then, therefore mainly be limited to experimental study because of its strong oxidizing property can cause safety problem.LiN (CF ₃SO ₂) ₂Though have high electroconductibility and excellent thermostability, it just begins aluminium foil is produced very strong corrosive nature about 4V, thereby can't use.And LiAsF ₆LiCF ₃SO ₃, LiN (CF ₃SO ₂) ₂Or LiC (CF ₃SO ₂) ₃Preparation cost is higher relatively and be difficult for purifying.Lithium ion battery is to use LiPF basically at present ₆Be electrolytic salt, LiPF ₆/ EC+DMC (methylcarbonate) is the best electrolytic solution of generally acknowledging at present, but because preparation is quite complicated, costs an arm and a leg, and poor heat stability, and is very responsive to water.Therefore seek the ionogen that is suitable for cheaply and remain a crucial problem.Have a large amount of research to be devoted to the synthetic of new salt at present, these salt great majority are some lithium-borate complexes and Trilithium phosphate title complex.In numerous electrolyte lithium salts, the LiBF4 base electrolyte has better heat stability, and is not too responsive to ambient moisture, can effectively prevent the advantages such as corrosion of Al collector electrode, and become one of most possible lithium salts that substitutes existing lithium ion battery electrolyte.

At present, the preparation method about LiBF4 mainly contains: three kinds of aqua-solution method, solid phase-vapor phase process and non-aqueous solution methods.Solid phase-vapor phase process adopts Quilonum Retard or lithium fluoride and boron trifluoride reaction, and conversion unit requires high, and process control is strict, reacts inhomogeneous, and reaction efficiency is low, and the ingredient requirement height, costs an arm and a leg, and these factors have all limited this method and moved towards scale production; The non-aqueous solution method mainly is to make lithium fluoride be suspended in some can form title complex with boron trifluoride, in the LiBF4 organic solvent that solubleness is big therein, obtains waterless lithium terafluoroborate with boron trifluoride reaction; This method reaction efficiency height, the product purity height can directly obtain high-pure anhydrous LiBF4, but owing to adopt ether organic solvent usually, so the use of this method is restricted.Aqua-solution method adopts boric acid to react with aqueous hydrogen fluoride solution and obtains Tetrafluoroboric acid, obtains LiBF4 solution with Quilonum Retard generation neutralization reaction again, and crystallization gets the hydration LiBF4, through dewater waterless lithium terafluoroborate.This method does not adopt boron trifluoride, and the hydrogen fluoride amount of using is few, and enter into product substantially, so this method raw material is easy to get, can utilize salt lake primary lithium product salt, cost is low, and low, the environmental friendliness of production process energy consumption, but cause solid fusion, parcel in the exsiccant process easily, influence the effect of dehydration, reduced the purity of synthetic LiBF4, and owing to adopted a large amount of ethanol as extraction agent, environment is had certain pollution, and improved production cost, so this method never is used for actual production.

Summary of the invention

The objective of the invention is to prepare the defective that LiBF4 exists, put forward low, the eco-friendly method for preparing the lithium ion battery electrolyte waterless lithium terafluoroborate of a kind of cost at the prior art aqua-solution method.

The present invention prepares the method for waterless lithium terafluoroborate, comprises following processing step:

(1) under-15～5 ℃ low temperature, boric acid is slowly joined in the aqueous hydrogen fluoride solution, under agitation reacted 10～30 minutes, obtain Tetrafluoroboric acid solution; Compound with lithium slowly joins in the above-mentioned Tetrafluoroboric acid solution again, obtains the aqueous solution of LiBF4, and the concentration that then aqueous solution of LiBF4 is concentrated into LiBF4 is 60%～75%; Described boric acid and hydrofluoric mol ratio 1: 0.95～1: 1.02; The mol ratio of lithium and boric acid is 1: 0.98～1: 1.00 in the lithium compound;

(2) with concentrated solution 5～50 ℃ of following crystallizations 2～72 hours, filter, filtrate is returned mother liquor, and crystal is dissolved in distilled water, the distilled water of adding just makes crystal dissolve fully, in 5～40 ℃ of following recrystallizations 2～72 hours, filter then, crystal;

(3) with the above-mentioned crystal that obtains at 35 ℃～50 ℃, vacuum tightness is the vacuum drying oven inner drying 2～8 hours of 550～600mmHg, be warming up to 65 ℃～80 ℃ again, continued dry 2～8 hours, continue to be warming up to 90 ℃～160 ℃ then, dry 6～24 hours, obtain the waterless lithium terafluoroborate of white powder.

Lithium compound of the present invention is lithium hydroxide or Quilonum Retard or Lithium Oxide 98min.

The waterless lithium terafluoroborate of the inventive method preparation is measured through X ray diffracting spectrum, and its diffraction peak is clear and sharp-pointed, and is corresponding fully with standard card, illustrates that the product of the present invention's preparation is anhydrous LiBF ₄, and complete in crystal formation; Measure wherein lithium content through the ICP-OES method, the tetraphenylarsonium chloride arsenic precipitator method are measured wherein boron, fluorine content, determine that its chemical formula is LiBF ₄

The LiBF4 of the present invention's preparation is suitable by the quality product that lithium fluoride and boron trifluoride reaction prepare waterless lithium terafluoroborate with employing at present.

The present invention has the following advantages compared to existing technology:

1, the present invention adopts the method for crystallization, recrystallization, effectively removes the LiF in the solution, has improved the purity of LiBF4 product; Adopt the solvent environmentally safe of water simultaneously as recrystallization;

2, the present invention adopts staged intensification drying process, the anhydrous LiBF of product ₄Quality better, complete in crystal formation;

3, preparation process of the present invention is simple, and raw material cheaply is easy to get, and preparation cost is low;

4, building-up process of the present invention does not adopt organic solvent, and the toxicological harmless deposits yields meets the environmental protection notion.

Description of drawings

Fig. 1 prepares the improved aqua-solution method schema of waterless lithium terafluoroborate for the present invention

Fig. 2 is the X ray diffracting spectrum of the material of embodiment of the invention preparation

Fig. 3 is the FT-IR collection of illustrative plates of the material of embodiment of the invention preparation

Embodiment

Embodiment one

Taking by weighing massfraction is about 40% (the analytically pure hydrofluoric acid that the method demarcation of employing GB GB620-93 is bought, its massfraction is about 40.87%, when using hydrofluoric acid in the foreign literature generally all is to say that massfraction is about 48%, aqueous hydrogen fluoride solution 209g down together), put into ice bath, and use magnetic stirrer, after 10 minutes, add 66.1g boric acid slowly, about 50 minutes, add.Add the back and continue to stir 30 minutes, then the 40.6g Quilonum Retard is slowly joined in the above-mentioned mixing solutions, add about 30 minutes, filter, filtrate is placed under the infrared lamp and concentrates, and makes the content of LiBF4 be about 70%.Concentrated solution is put into water bath with thermostatic control about 40 ℃, 12 hours after-filtration, filtrate is returned mother liquor.Solid phase makes crystallization dissolving fully just with an amount of dissolved in distilled water, and solution is placed water bath with thermostatic control about 40 ℃ once more.72 hours after-filtration, filtrate is returned mother liquor, and solid phase is put into vacuum drying oven.About 50 ℃, 560mmHg dry 5 hours down, be warming up to then about 80 ℃, continued dry 5 hours, solid is taken out from vacuum drying oven, grind, and then put into vacuum drying oven, drying is 24 hours about 100 ℃, under the 560mmHg, obtains the waterless lithium terafluoroborate product of white powder.

Embodiment two

Take by weighing massfraction and be about 40% aqueous hydrogen fluoride solution 104.4g, put into ice bath, and use magnetic stirrer, after 10 minutes, add 33g boric acid slowly, about 50 minutes, add.Add the back and continue to stir 30 minutes, then the 20.3g Quilonum Retard is slowly joined in the above-mentioned mixing solutions, add about 30 minutes, filter, filtrate is placed under the infrared lamp and concentrates, and makes the content of LiBF4 be about 70%.Concentrated solution is put into water bath with thermostatic control about 5 ℃, 2 hours after-filtration, filtrate is returned mother liquor.Solid phase is put into vacuum drying oven.About 50 ℃, 560mmHg dry 5 hours down, be warming up to then about 80 ℃, continued dry 5 hours, solid is taken out from vacuum drying oven, grind, and then put into vacuum drying oven, drying is 10 hours about 140 ℃, under the 560mmHg, obtains the waterless lithium terafluoroborate product of white powder.

Embodiment three

Take by weighing massfraction and be about 40% aqueous hydrogen fluoride solution 105g, put into ice bath, and use magnetic stirrer, after 10 minutes, add 33g boric acid slowly, about 50 minutes, add.Add the back and continue to stir 30 minutes, then with 20.9gLiOHH ₂O slowly joins in the above-mentioned mixing solutions, adds about 30 minutes, filters, and filtrate is placed under the infrared lamp and concentrates, and makes the content of LiBF4 be about 70%.Concentrated solution is put into water bath with thermostatic control about 40 ℃, 12 hours after-filtration, filtrate is returned mother liquor.Solid phase makes crystallization dissolving fully just with an amount of dissolved in distilled water, and solution is placed water bath with thermostatic control about 30 ℃ once more.72 hours after-filtration, filtrate is returned mother liquor, and solid phase is put into vacuum drying oven.About 50 ℃, 560mmHg dry 5 hours down, be warming up to then about 80 ℃, continued dry 5 hours, solid is taken out from vacuum drying oven, grind, and then put into vacuum drying oven, drying is 12 hours about 120 ℃, under the 560mmHg, obtains the waterless lithium terafluoroborate product of white powder.

Claims (2)

1, a kind of preparation method of waterless lithium terafluoroborate comprises following processing step:

(1) under-15 ℃～5 ℃ low temperature, boric acid is slowly joined in the aqueous hydrogen fluoride solution, under agitation reacted 10～30 minutes, obtain Tetrafluoroboric acid solution; The compound of lithium is slowly joined in the above-mentioned Tetrafluoroboric acid solution, obtain the aqueous solution of LiBF4, the concentration that is concentrated into LiBF4 is 60%～75%; Described boric acid and hydrofluoric mol ratio are 1: 0.95～1: 1.02; The add-on of the compound of lithium and the mol ratio of boric acid are 1: 0.98～1: 1.00;

(2) with concentrated solution 5 ℃～50 ℃ following crystallizations 2 hours～72 hours, filter, and crystal be dissolved in distilled water, in 5～40 ℃ of following recrystallizations 2～72 hours, filter then, grind, crystal;

(3) with the above-mentioned crystal that obtains at 35 ℃～50 ℃, vacuum tightness is the vacuum drying oven inner drying 2～8 hours of 550～600mmHg, be warming up to 65 ℃～80 ℃ again, continued dry 2～8 hours, continue to be warming up to 90 ℃～160 ℃ then, dry 6～24 hours, obtain the waterless lithium terafluoroborate of white powder.

2, the preparation method of waterless lithium terafluoroborate according to claim 1, it is characterized in that: the compound of described lithium is lithium hydroxide or Quilonum Retard or Lithium Oxide 98min.

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