The preparation method of LiODFB electrolytic salt
The application divides an application, the application number of original bill: 2011101689535, and invention and created name: a kind of preparation method of difluorine oxalic acid boracic acid lithium electrolytic salt, the applying date:
2011-6-22.
Technical field
The present invention relates to the manufacturing technology field of lithium ion battery electrolyte salt, specifically is the preparation method of a kind of difluorine oxalic acid boracic acid lithium (LiODFB) electrolytic salt.
Background technology
At present, commercial lithium salts commonly used is lithium hexafluoro phosphate (LiPF
6), LiPF
6Facile hydrolysis, poor heat stability can form HF when residual water contacts in airborne moisture or the solvent immediately, and the performance of battery is had a negative impact.Common LiPF
6Share with NSC 11801 (EC) and to be made into electrolytic solution and could to form effective solid electrolyte phase interface (SEI) film at negative pole, but the fusing point of EC higher (37 ℃), limited the low temperature use properties of battery.
Now, a large amount of research begins to be devoted to the synthetic of novel lithium salts and to use, and hope can be found and can replace existing lithium salts, the novel substance that performance is more excellent.LiBF4 (LiBF
4) with respect to LiPF
6Insensitive to ambient moisture, charge migration resistance is little at low temperatures, thereby low-temperature performance is better than LiPF
6, but use can cause the capacity of lithium ion battery and coulombic efficiency to descend separately; Biethyl diacid lithium borate (LiBOB) Heat stability is good, has good electrochemical stability, can form stable and fine and close SEI film at graphite, improved the cycle performance of battery, but dissolving hardly in the solvent (particularly linear carbonates class) of part low-k, and the SEI membrane resistance that forms is very big, and low-temperature performance is relatively poor, and application is restricted.
What industry attracted most attention at present is to comprise half LiBOB and half LiBF in the molecular structure
4Novel lithium salts---the LiODFB of molecule.Because LiODFB has LiBF
4Part-structure, so low-temperature performance increases, have simultaneously the part-structure of LiBOB again, also have excellent high, and so responsive unlike the impurity of LiBOB and moisture.The solubleness of LiODFB in the linear carbonate solvent is bigger, therefore has higher specific conductivity, and can make low solvent PC(-49 ℃ of fusing point) form stable SEI film on the graphite cathode surface, provide favourable prerequisite for solving battery low temperature use problem.The positive electrode material of the manganese base of LiODFB and iron-based has good thermostability, and LiODFB can also improve the anti-abuse of lithium ion battery.Because it combines LiBOB and LiBF LiODFB
4The advantage of two kinds of lithium salts, its over-all properties are better than present any lithium salts, are expected to become the novel lithium salts that substitutes existing electrolyte lithium salt.
The preparation of LiODFB compounds is at first with LiBF
4, CH (CF
3)
2OLi and H
2C
2O
4Being raw material, is reaction medium (EP:1195834A2) with carbonic ether or the non-proton solution of acetonitrile (AN) isopolarity, and the purity of products therefrom is lower.
11The B nucleus magnetic resonance shows, unreacted LiBF
4Content up to more than 15%, and LiBF
4Close with the solubleness of LiODFB in common organic solvent, separate comparatively difficulty.Improved method is (EP:1308449A2): be solvent with carbonic ether or AN at low temperatures, at reaction promoter AlCl
3Or SiCl
4Effect under, make H
2C
2O
4With LiBF
4Direct reaction generates LiODFB.The purity of improving the back products therefrom has significantly raising, unreacted LiBF
4Content be down to about 0.5%.But should reaction generate corrosive HF, and temperature low excessively (50 ℃), raw material is LiBF simultaneously
4, cause preparation cost higher.
For overcoming these shortcomings, S.S.Zhang is with BF
3O (CH
2CH
3)
2With Li
2C
2O
4In DMC, react, prepared the higher LiODFB of purity.The thick product of gained LiODFB carries out recrystallization with DMC or other aprotic solvent, reached the service requirements of lithium ion battery electrolyte lithium salts behind recrystallization, this method shows great superiority in material choice and preparation condition, has become the general method for making of LiODFB.But the used boron trifluoride ether solution of raw material has strong impulse and strong corrosion, meets the naked light burning, and pyrolytic decomposition produces poisonous gas, meets moisture hydrolysis immediately aloft, generates the hydrogen fluoride smog of severe toxicity during decomposition.So this method weak point has: (1) brings harm to staff's health and environment, and (2) have higher requirement to the corrosion resistance nature of equipment, and (3) cost of investment is big.
Summary of the invention
The technical problem to be solved in the present invention is: a kind of safety and environmental protection is provided and the corrosion resistance nature of equipment is required the preparation synthesis technique of lower difluorine oxalic acid boracic acid lithium salt.
For solving the problems of the technologies described above, the technical solution used in the present invention is: adopting the lower fluorine-containing salt compounds of toxicity is raw material, carry out the high temperature solid-state pre-treatment after mixing with boron-containing compound, lithium-containing compound, then react the generation white product with the oxalate compound in solvent again, this white product obtains difluorine oxalic acid boracic acid lithium after purifying.Concrete processing step is as follows:
1, raw materials pretreatment
In grinding in ball grinder, then that ball milling is good raw material places retort furnace with fluorine-containing salt compounds, lithium-containing compound, boron-containing compound, and the heating that heats up makes it to react.
The mol ratio of above-mentioned fluorine element, elemental lithium, boron is 2~6:2~6:1~3, the ball milling time is 0.5 hour~20 hours, the ball milling temperature is 5 ℃~80 ℃, heat treatment environment is air, nitrogen, argon gas or vacuum environment, treatment temp is 80 ℃~850 ℃, and the reaction times is 2 hours~24 hours.
Above-mentioned fluorine-containing salt compounds comprises: one or more in lithium fluoride, Neutral ammonium fluoride, ammonium bifluoride, ammonium borofluoride, the magnesium fluoride; Described lithium compound comprises: one or more in lithium hydroxide, Quilonum Retard, lithium bicarbonate, Lithium Oxide 98min, lithium fluoride, the oxalic acid hydrogen lithium; Described boron compound comprises: one or more in boric acid, borax, boron trioxide, the metaboric acid.
2, product preparation
The raw material that above-mentioned pyroprocessing is crossed moves in the solvent, to be mixedly adds a certain amount of oxalate compound to this solvent again after evenly, with removal of solvents, obtains white product after reacting completely.
Above-mentioned oxalate is 1~5:1~3 with the ratio of boron, and the reaction times is 1 hour~12 hours, and temperature of reaction is 0 ℃~160 ℃.
Above-mentioned oxalate compound comprises: one or more in lithium oxalate, the oxalic acid.Above-mentioned solvent comprises: one or more in water, ether, glycol dimethyl ether, methylcarbonate, acetonitrile, ethyl acetate, acetone, dioxolane, Methyl ethyl carbonate, the diethyl carbonate.
3, product is purified
The white product that step 2 is obtained is put into container after grinding, and adds purification solvent post-heating, cooling back filtering insolubles, and evaporative crystallization obtains desired difluorine oxalic acid boracic acid lithium, can repeatedly purify as required.
The used solvent of above-mentioned purification comprises: one or more in methylcarbonate, ethanol, acetonitrile, acetone, Methyl ethyl carbonate, diethyl carbonate, dioxolane, the ethyl acetate.
The invention has the beneficial effects as follows: material toxicity is little, and corrodibility is low, and environmental friendliness does not have harsh requirements such as anticorrosive, high pressure resistant to equipment, and preparation technology is simple, and less investment is fit to industrial mass production.
Description of drawings
The X-ray diffractogram of the difluorine oxalic acid boracic acid lithium that Fig. 1 obtains for synthesis technique of the present invention.
Embodiment
The invention will be further described below by specific examples, but the present invention should not only limit to these embodiment.
Embodiment one
Adopting lithium fluoride, boric acid and oxalic acid is the feedstock production difluorine oxalic acid boracic acid lithium.
Step 1, get boric acid 30.9g, lithium fluoride 26g puts into ball grinder, 5 ℃ of following mixing and ball milling 12 hours, the planetary ball mill rotating speed is 380 rev/mins.
Step 2, the raw material that above-mentioned ball milling is good place retort furnace, are warming up to 350 ℃ under nitrogen protection, and constant temperature 20 hours makes it to carry out complete reaction.
Step 3, the raw material after the above-mentioned processing is transferred in the suitable quantity of water, heats while stirring, treat to add 94.8g oxalic acid again after it mixes, after reacting completely solution is put into air dry oven and remove moisture, obtain white product.
Step 4, with the white product porphyrize, then put into container, add the 1500g methylcarbonate, the encloses container post-heating also stirs, and little boiling namely stops heating, cooling back filtering insolubles, evaporated filtrate stops heating when muddy to appearance, cooling back adds a small amount of isopropyl ether, treats that crystal separates out after-filtration fully and obtain the 67g difluorine oxalic acid boracic acid lithium, and its purity is 99.56% after testing.
Embodiment two
Adopting lithium fluoride, boron trioxide and oxalic acid is the feedstock production difluorine oxalic acid boracic acid lithium.
Step 1, get boron trioxide 17.5g, lithium fluoride 26g puts into ball grinder, 5 ℃ of following mixing and ball milling 12 hours, the planetary ball mill rotating speed is 380 rev/mins.
Step 2, the raw material that above-mentioned ball milling is good place retort furnace, are warming up to 400 ℃ under nitrogen protection, and constant temperature 20 hours makes it to carry out complete reaction.
Step 3, the raw material after the above-mentioned processing is transferred to suitable quantity of water, heats while stirring, treat to add 94.8g oxalic acid again after it mixes, after reacting completely solution is put into air dry oven and remove moisture, obtain white product.
Step 4, with the white product porphyrize, then put into the opening reactor, add the 1500g methylcarbonate, the encloses container post-heating also stirs, little boiling namely stops heating.Cooling back filtering insolubles, evaporated filtrate is to occurring stopping heating when muddy, the cooling back adds a small amount of isopropyl ether, treat crystal separate out fully after the filtering solvent namely obtain the 64g difluorine oxalic acid boracic acid lithium, its purity is 99.62% after testing.