阅读说明：本技术 废旧锂离子电池电解液中六氟磷酸锂无害化利用方法 (Harmless utilization method of lithium hexafluorophosphate in waste lithium ion battery electrolyte ) 是由 刘艳侠 张鹏飞 张海涛 李晶晶 马立彬 张锁江 于 2020-06-29 设计创作，主要内容包括：本发明提供一种废旧锂离子电池电解液中六氟磷酸锂无害化利用方法,将废旧电解液中六氟磷酸锂的氟、磷有效分离,锂、氟以氟化锂形式高值化回收利用,磷无害化处理,从而实现六氟磷酸锂无害化的同时进行高值化利用。本发明可以有效提高废旧锂离子电池电解液回收的经济价值,避免有害物质产生,减少环境污染,对电池材料回收前处理及整个电池回收产业有重要意义。(The invention provides a harmless utilization method of lithium hexafluorophosphate in waste lithium ion battery electrolyte, which effectively separates fluorine and phosphorus of lithium hexafluorophosphate in the waste electrolyte, recycles lithium and fluorine in a lithium fluoride form in a high-valued manner, and carries out harmless treatment on phosphorus, thereby realizing the harmless utilization of lithium hexafluorophosphate and simultaneously carrying out high-valued utilization. The method can effectively improve the economic value of the recovery of the electrolyte of the waste lithium ion battery, avoid the generation of harmful substances, reduce the environmental pollution and have important significance on the pretreatment of the recovery of battery materials and the whole battery recovery industry.)

1. A harmless utilization method of lithium hexafluorophosphate in waste lithium ion battery electrolyte is characterized by comprising the following steps:

(1) adding water into the waste electrolyte, fully reacting under the heating condition, filtering, washing and separating out lithium fluoride precipitate, collecting gas generated by the reaction, absorbing the gas by using a lithium salt solution, filtering and washing to obtain lithium fluoride precipitate;

(2) and (3) adding a phosphorus removing agent into the fully reacted solution in the step (1) to enable the content of phosphorus in the solvent to be less than 1.0 mg/L.

2. The harmless utilization method of lithium hexafluorophosphate in the electrolyte of the waste lithium ion battery according to claim 1, is characterized in that: the mass of the water added in the step (1) is 0.1-15% of the mass of the waste electrolyte.

3. The harmless utilization method of lithium hexafluorophosphate in the electrolyte of the waste lithium ion battery according to claim 1, is characterized in that: the reaction temperature in the step (1) is 30-150 ℃, and the reaction time is 0.5-48 h.

4. The harmless utilization method of lithium hexafluorophosphate in the electrolyte of the waste lithium ion battery according to claim 1, is characterized in that: and (2) introducing inert gas or decompressing to accelerate the escape of gas generated by the reaction in the step (1).

5. The harmless utilization method of lithium hexafluorophosphate in the electrolyte of the waste lithium ion battery according to claim 1, is characterized in that: the lithium salt in the step (1) is one or more of lithium hydroxide, lithium carbonate, lithium nitrate and lithium acetate.

6. The harmless utilization method of lithium hexafluorophosphate in the electrolyte of the waste lithium ion battery according to claim 1, is characterized in that: and (3) the phosphorus removing agent in the step (2) is one or more of metal salt, alkali liquor or aluminum-magnesium-based composite salt.

Technical Field

The invention relates to the field of lithium ion batteries, in particular to a harmless utilization method of lithium hexafluorophosphate in a waste lithium ion battery electrolyte.

Background

The lithium ion power battery is used as a key component of a new energy automobile, and benefits from rapid development of the new energy automobile, and the loading capacity is increased dramatically year by year. The service life of the new energy automobile power battery is generally 5-8 years, the new energy automobile power battery in China will meet the retirement tide, and according to prediction, the scrappage of the power lithium battery in 2020 is 32.2GWh, the scrappage in 2023 is 101GWh, and the market scale of the new energy automobile power battery can reach 300 million yuan. The problem that the power battery of the electric automobile is not properly disposed after retirement can cause a plurality of problems, and on one hand, environmental influence and potential safety hazard can be brought to the society; on the other hand, valuable resources are wasted, which goes against the basic principle of national sustainable development and is not beneficial to the sustainable and healthy development of new energy industry. At present, the recovery of the waste lithium ion battery is mainly focused on the anode material, and the research on the recovery of the electrolyte is few. The lithium battery electrolyte generally comprises lithium salt, an organic solvent and an additive, wherein the common lithium salt is mainly lithium hexafluorophosphate, the organic solvent is mainly a carbonate solvent, and the additive content is low. Fluorine in the lithium salt of the electrolyte belongs to national non-renewable resource strategic resources, and if the lithium salt is not efficiently cleaned and recycled after the battery core is retired, huge environmental pollution and serious resource waste are caused. The fluorine-containing lithium salt (lithium hexafluorophosphate) in the electrolyte has poor stability and is easy to thermally decompose and hydrolyze to produce a product PF₅、HF、POF₃And the like, which can cause serious harm to human bodies, atmosphere, water and soil. Lithium hexafluorophosphate in the electrolyte has higher added value, and how to recover the lithium hexafluorophosphate and realize high-value utilization is a problem worthy of deep research.

At present, lithium hexafluorophosphate in the electrolyte is mainly treated by recovering lithium element, and the lithium hexafluorophosphate is mainly subjected to harmless treatment on fluorine element. The patent CN108808156A is to send the recovered waste electrolyte into a solvent separation device, add water, and when the solution is layered, the upper layer liquid is the organic solvent; the lower layer liquid is sent to a precipitation process for precipitation to respectively obtain a lithium-containing solution and calcium fluoride, although the method can reduce the pollution of fluorine to the environment and recover lithium resources, the calcium fluoride is low in price and affects the value of fluorine element. Patent CN104105803A discloses adding an alkali solution to a lithium-containing solution to adjust the pH to 9 or more to form a precipitate of a phosphate and a fluoride salt, separating and removing the formed precipitate, and then adding carbon dioxide or a water-soluble carbonate to the lithium-containing filtrate to precipitate lithium carbonate. The lithium in the process is recovered in the form of lithium carbonate, the fluorine and the phosphorus are recovered in the form of the precipitation of phosphate and fluoride salt, the difference of the optimal precipitation pH values of the two substances is not large, the operation flexibility is reduced, the process control is difficult, the separation is not easy, and the lithium carbonate is relatively low in price, so that the values of the lithium and the fluorine are influenced.

At present, lithium element in lithium hexafluorophosphate is mainly industrially recycled, lithium is mainly recycled in a lithium carbonate form, fluorine element is mainly subjected to harmless treatment, the mass fraction of lithium in lithium hexafluorophosphate is only 4.57%, and the mass fraction of fluorine is as high as 75.04%, if the recycling of lithium element is only considered, the resource is greatly wasted, the price of lithium carbonate is 7 ten thousand per ton, the value of lithium fluoride is as high as 14 ten thousand per ton, if lithium and fluorine in lithium hexafluorophosphate can be converted into lithium fluoride for high-value utilization, and fluorine and phosphorus can be effectively separated, the economic value of battery recycling can be greatly improved.

Disclosure of Invention

The invention provides a method for harmless and high-value utilization of lithium hexafluorophosphate in waste lithium ion battery electrolyte, aiming at effectively separating fluorine and phosphorus in lithium hexafluorophosphate, recovering lithium and fluorine in a high-value manner by using lithium fluoride, and performing harmless treatment on phosphorus, so that the waste electrolyte is subjected to harmless and high-value utilization. The method can improve the economic value of recycling the electrolyte of the waste lithium ion battery, and has important significance for the pretreatment of battery material recycling and the whole battery recycling industry.

The technical scheme for realizing the invention is as follows:

a harmless utilization method of lithium hexafluorophosphate in waste lithium ion battery electrolyte comprises the following steps:

(1) adding water into the waste electrolyte, fully reacting under the heating condition, filtering, washing and separating out lithium fluoride precipitate, collecting gas generated by the reaction, absorbing the gas by using a lithium salt solution, filtering and washing to obtain lithium fluoride precipitate;

(2) and (2) adding a phosphorus removal agent into the fully reacted solution in the step (1) to enable the phosphorus content in the solvent to be less than 1.0 mg/L (the detection method is determined according to GB11893-89, and the total phosphorus content is determined according to GB 8978-1996).

The mass of the water added in the step (1) is 0.1-15% of the mass of the waste electrolyte.

The reaction temperature in the step (1) is 30-150 ℃, and the reaction time is 0.5-48 h.

And (2) introducing inert gas or decompressing to accelerate the escape of gas generated by the reaction in the step (1).

The lithium salt in the step (1) is one or more of lithium hydroxide, lithium carbonate, lithium nitrate and lithium acetate.

And (3) the phosphorus removing agent in the step (2) is one or more of metal salt, alkali liquor or aluminum-magnesium-based composite salt.

The invention has the beneficial effects that: the method carries out harmless treatment on the lithium hexafluorophosphate in the waste electrolyte and simultaneously realizes high-value utilization. The invention improves the economic value of battery recovery, avoids the pollution of lithium hexafluorophosphate to the environment and has important significance for the whole battery recovery process.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a process flow chart of a harmless and high-value utilization method of lithium hexafluorophosphate in a waste lithium ion battery electrolyte.

Detailed Description

The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without inventive effort based on the embodiments of the present invention, are within the scope of the present invention.