WO2024040906A1 - 一种回收锂离子电池电解液的方法 - Google Patents

一种回收锂离子电池电解液的方法 Download PDF

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Publication number
WO2024040906A1
WO2024040906A1 PCT/CN2023/079084 CN2023079084W WO2024040906A1 WO 2024040906 A1 WO2024040906 A1 WO 2024040906A1 CN 2023079084 W CN2023079084 W CN 2023079084W WO 2024040906 A1 WO2024040906 A1 WO 2024040906A1
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Prior art keywords
liquid
electrolyte
carbon tetrachloride
lithium
solid
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English (en)
French (fr)
Inventor
余海军
谢英豪
李爱霞
张学梅
李长东
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Hunan Brunp Recycling Technology Co Ltd
Guangdong Brunp Recycling Technology Co Ltd
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Hunan Brunp Recycling Technology Co Ltd
Guangdong Brunp Recycling Technology Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
    • C01D15/00—Lithium compounds
    • C01D15/005—Lithium hexafluorophosphate
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C17/00—Preparation of halogenated hydrocarbons
    • C07C17/38—Separation; Purification; Stabilisation; Use of additives
    • C07C17/395—Separation; Purification; Stabilisation; Use of additives by treatment giving rise to a chemical modification of at least one compound
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D317/00—Heterocyclic compounds containing five-membered rings having two oxygen atoms as the only ring hetero atoms
    • C07D317/08—Heterocyclic compounds containing five-membered rings having two oxygen atoms as the only ring hetero atoms having the hetero atoms in positions 1 and 3
    • C07D317/10—Heterocyclic compounds containing five-membered rings having two oxygen atoms as the only ring hetero atoms having the hetero atoms in positions 1 and 3 not condensed with other rings
    • C07D317/32—Heterocyclic compounds containing five-membered rings having two oxygen atoms as the only ring hetero atoms having the hetero atoms in positions 1 and 3 not condensed with other rings with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
    • C07D317/34—Oxygen atoms
    • C07D317/36—Alkylene carbonates; Substituted alkylene carbonates
    • C07D317/38—Ethylene carbonate
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/54—Reclaiming serviceable parts of waste accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/84—Recycling of batteries or fuel cells

Definitions

  • the invention belongs to the technical field of battery recycling, and specifically relates to a method for recycling lithium-ion battery electrolyte.
  • Organic liquid electrolyte generally consists of three parts: electrolyte lithium salt, organic solvent and additives.
  • the electrolyte salts in currently commercially available electrolyte solutions are generally lithium salts such as LiPF 6 , LiCF 3 SO 3 and LiBF 4.
  • Commonly used solvents include ethylene carbonate (EC), propylene carbonate (PC), and dimethyl carbonate (DMC). , methyl ethyl carbonate (EMC), etc.
  • Additives are non-essential components in the electrolyte and are added in small amounts.
  • the composition of the electrolyte is complex, especially the presence of LiPF 6 , which makes the electrolyte prone to decomposition when exposed to the external environment, producing toxic and harmful substances.
  • the electrolyte Since the electrolyte is volatile and difficult to recycle, there is little research and treatment specifically focused on electrolyte recycling. The volatilization of the electrolyte will produce an unpleasant pungent odor. The lithium salt in the electrolyte will hydrolyze to produce toxic arsenide, phosphide and fluoride, which is very harmful to the human body and the environment and has become an unavoidable problem.
  • Patent application CN108666644A discloses a method for recovering fluorine and lithium from lithium battery waste electrolyte.
  • CaO or Ca(OH) 2 is used to react with lithium battery waste electrolyte.
  • Ca 2+ reacts with fluorine ions in the electrolyte to generate CaF. 2.
  • a multi-stage manganese fiber adsorption column and a titanium fiber adsorption column are used to physically adsorb lithium ions to recover fluorine and lithium in the electrolyte.
  • Patent application CN108155434A discloses a method for recovering lithium from waste electrolyte of lithium ion batteries.
  • the waste electrolyte is mixed with a halide solution containing a large cation radius, and PF 6 -1 in the electrolyte is separated as a whole. , and the lithium-containing solution obtained after separation is subjected to deep purification and lithium precipitation treatment to obtain lithium carbonate. Neither of the above two methods can completely recover the expensive lithium hexafluorophosphate electrolyte salt.
  • Patent application CN110203949A discloses a method of recycling the electrolyte by using a vacuum distillation method to distill the waste electrolyte under reduced pressure and separate each component one by one.
  • the distillation process is complex and the composition of the electrolyte is complex. After long-term circulation, the electrolyte decomposes into small molecular substances, which is difficult to recycle.
  • the present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention proposes a method for recovering lithium-ion battery electrolyte, which can completely recover high-purity lithium hexafluorophosphate, and the recovered organic solvent has low impurities.
  • a method for recycling lithium-ion battery electrolyte including the following steps:
  • step S1 the freezing temperature is -60°C or lower.
  • step S2 the solid-liquid ratio of the battery core and carbon tetrachloride is 100-200g/L.
  • step S2 the soaking time is 10-30 minutes.
  • step S2 after the soaking is completed, a washing process is also included: taking out the soaked battery core to obtain a post-soaking liquid, rinse the battery core with carbon tetrachloride, and the resulting rinsed liquid is mixed with After soaking, the liquids are mixed and filtered to obtain the first liquid phase.
  • step S3 the volume ratio of acetonitrile and the first liquid phase is 20-60 mL/L.
  • step S3 the pressure of the evaporation and concentration is -0.1 to -0.08MPa, the temperature is 65-70°C, and the evaporation and concentration is until the volume of the first liquid phase is reduced to 1/4 of the original volume. -1/5.
  • step S4 the cooling crystallization temperature is -15 to -10°C.
  • step S4 the temperature of the anhydrous hydrogen fluoride washing is 0-5°C. Since subsequent drying is performed at low temperatures, residues on the solid surface (such as high-boiling organic matter) are difficult to remove, affecting the purity. Surface impurities need to be removed through washing. Anhydrous hydrogen fluoride as a detergent has a good washing effect.
  • step S4 the drying is performed under negative pressure, the pressure is -0.1 to -0.08MPa, the drying temperature is 0-5°C, and the time is 12-24h.
  • step S4 the rectification is atmospheric distillation, and the temperature is 120-140°C. This distillation temperature can ensure that almost all small molecule impurities are evaporated.
  • step S4 when the low-boiling substance contains a low-boiling organic solvent that needs to be recovered, the low-boiling substance can be selectively condensed and separated during the distillation process to recover the required organic solvent. Solvent.
  • step S5 the volume ratio of the low boiling matter to the aqueous potassium permanganate solution is 1: (0.5-2.0), and the concentration of the aqueous potassium permanganate solution is 1-2 mol/ L.
  • step S5 after removing the water phase, crude carbon tetrachloride is obtained, and the solid-liquid ratio of quicklime and crude carbon tetrachloride is 20-50g/L.
  • This invention first freezes the waste lithium-ion batteries and then disassembles them to avoid the volatilization and decomposition of the electrolyte from polluting the environment.
  • the disassembled battery core is placed in carbon tetrachloride to dissolve all the electrolyte in carbon tetrachloride, and acetonitrile is further added to complex the electrolyte solute lithium hexafluorophosphate with acetonitrile to form stable Li(CH 3 CN) 4 PF 6 , to protect lithium hexafluorophosphate from decomposition during subsequent negative pressure evaporation and concentration.
  • Li(CH 3 CN) 4 PF 6 in carbon tetrachloride is then used to cool and crystallize. After further drying treatment, Li(CH 3 CN) 4 PF 6 is decomplexed to obtain high purity. Lithium hexafluorophosphate.
  • the present invention utilizes the low boiling point and high stability characteristics of carbon tetrachloride to retain it during subsequent atmospheric distillation. High boiling point substances such as ethylene carbonate are removed. High boiling substances can be directly used as solvents for electrolytes. After collecting small molecular substances with low boiling points and carbon tetrachloride, the small molecular substances are removed by potassium permanganate and dehydrated by quicklime. , to obtain anhydrous carbon tetrachloride so that it can be reused.
  • Figure 1 is a process flow diagram of Embodiment 1 of the present invention.
  • a method of recycling lithium-ion battery electrolyte refers to Figure 1, the specific process is:
  • Step 1 After discharging the used lithium-ion batteries, use liquid nitrogen to freeze them to below -60°C;
  • Step 2 Disassemble the frozen used lithium-ion battery and take out the battery core containing the electrolyte
  • Step 3 Soak the battery core in anhydrous carbon tetrachloride for 10 minutes according to the solid-liquid ratio of 100g/L;
  • Step 4 Take out the battery core and rinse it with anhydrous carbon tetrachloride. Mix the washing liquid with the carbon tetrachloride in step 3 to obtain a mixed solution;
  • Step 5 Filter the mixture, remove the filter residue, and obtain the filtrate
  • the main component of the evaporated liquid is carbon tetrachloride, which can be recycled;
  • Step 7 Cool the concentrated solution to -15°C and filter with suction to obtain solid and filtrate;
  • Step 8 Wash the solid with anhydrous hydrogen fluoride at 0°C, and then dry it in a nitrogen atmosphere. Control the pressure at -0.1 to -0.08MPa and the temperature at 0°C for 24 hours to obtain the lithium hexafluorophosphate product;
  • Step 9 Perform normal pressure distillation of the filtrate obtained in Step 8 at a distillation temperature of 120°C to obtain low boiling matter and high boiling matter.
  • the high boiling matter can be directly used as a solvent for the electrolyte;
  • Step 10 After collecting the low boiling matter, add 1 mol/L potassium permanganate aqueous solution according to the volume ratio of 1:1, mix and let it stand. After removing the water phase, add quicklime according to the solid-liquid ratio of 20g/L, and solidify. The liquid is separated to obtain anhydrous carbon tetrachloride, which is mixed with the evaporated liquid obtained in step 6 and reused for soaking and rinsing the battery core.
  • a method for recycling lithium-ion battery electrolyte is:
  • Step 1 After discharging the used lithium-ion batteries, use liquid nitrogen to freeze them to below -60°C;
  • Step 2 Disassemble the frozen used lithium-ion battery and take out the battery core containing the electrolyte
  • Step 3 Soak the battery core in anhydrous carbon tetrachloride for 20 minutes according to the solid-liquid ratio of 150g/L;
  • Step 4 Take out the battery core and rinse it with anhydrous carbon tetrachloride. Mix the washing liquid with the carbon tetrachloride in step 3 to obtain a mixed solution;
  • Step 5 Filter the mixture, remove the filter residue, and obtain the filtrate
  • the main component of the evaporated liquid is carbon tetrachloride, which can be recycled;
  • Step 7 Cool the concentrated solution to -12°C and filter with suction to obtain solid and filtrate;
  • Step 8 Wash the solid with anhydrous hydrogen fluoride at 3°C and dry it in a nitrogen atmosphere. Control the pressure at -0.1 to -0.08MPa and the temperature at 3°C for 18 hours to obtain the lithium hexafluorophosphate product;
  • Step 9 Perform atmospheric distillation of the filtrate obtained in Step 8 at a distillation temperature of 130°C to obtain low boiling matter and high boiling matter.
  • the high boiling matter can be directly used as a solvent for the electrolyte;
  • Step 10 After collecting the low boiling matter, add 1.5 mol/L potassium permanganate aqueous solution according to the volume ratio of 1:1, mix and let it stand. After removing the water phase, add quicklime according to the solid-liquid ratio of 30g/L. Solid-liquid separation to obtain anhydrous tetrachloride Carbon, mix it with the evaporated liquid obtained in step 6 and reuse it for soaking and rinsing the battery cells.
  • a method for recycling lithium-ion battery electrolyte is:
  • Step 1 After discharging the used lithium-ion batteries, use liquid nitrogen to freeze them to below -60°C;
  • Step 2 Disassemble the frozen used lithium-ion battery and take out the battery core containing the electrolyte
  • Step 3 Soak the battery core in anhydrous carbon tetrachloride for 30 minutes according to the solid-liquid ratio of 200g/L;
  • Step 4 Take out the battery core and rinse it with anhydrous carbon tetrachloride. Mix the washing liquid with the carbon tetrachloride in step 3 to obtain a mixed solution;
  • Step 5 Filter the mixture, remove the filter residue, and obtain the filtrate
  • the main component of the evaporated liquid is carbon tetrachloride, which can be recycled;
  • Step 7 Cool the concentrated solution to -10°C and filter with suction to obtain solid and filtrate;
  • Step 8 Wash the solid with anhydrous hydrogen fluoride at 5°C and dry it in a nitrogen atmosphere. Control the pressure at -0.1 to -0.08MPa and the temperature at 5°C for 12 hours to obtain the lithium hexafluorophosphate product;
  • Step 9 Perform atmospheric distillation of the filtrate obtained in Step 8 at a distillation temperature of 140°C to obtain low boiling matter and high boiling matter.
  • the high boiling matter can be directly used as a solvent for the electrolyte;
  • Step 10 After collecting the low boiling matter, add 2mol/L potassium permanganate aqueous solution according to the volume ratio of 1:1, mix and let it stand. After removing the water phase, add quicklime according to the solid-liquid ratio of 50g/L, and solidify. The liquid is separated to obtain anhydrous carbon tetrachloride, which is mixed with the evaporated liquid obtained in step 6 and reused for soaking and rinsing the battery core.
  • step 3 is soaked with acetonitrile.
  • the specific process is:
  • Step 1 After discharging the used lithium-ion batteries, use liquid nitrogen to freeze them to below -60°C;
  • Step 2 Disassemble the frozen used lithium-ion battery and take out the battery core containing the electrolyte
  • Step 3 Soak the battery core in anhydrous acetonitrile for 30 minutes according to the solid-liquid ratio of 200g/L;
  • Step 4 Take out the battery core and rinse it with anhydrous acetonitrile. Mix the washing solution with the acetonitrile solution in step 3 to obtain a mixed solution;
  • Step 5 Filter the mixture, remove the filter residue, and obtain the filtrate
  • Step 6 Evaporate and concentrate the filtrate at a pressure of -0.1MPa and a temperature of 70°C until the volume of the filtrate is reduced to 1/5 of the original volume to obtain an evaporated liquid and a concentrated liquid.
  • the main component of the evaporated liquid is acetonitrile, which can be recycled;
  • Step 7 Cool the concentrated solution to -10°C and filter with suction to obtain solid and filtrate;
  • Step 8 Wash the solid with anhydrous hydrogen fluoride at 5°C and dry it in a nitrogen atmosphere. Control the pressure at -0.1 to -0.08MPa and the temperature at 5°C for 12 hours to obtain the lithium hexafluorophosphate product;
  • Step 9 Perform atmospheric distillation of the filtrate obtained in Step 8 at a distillation temperature of 140°C to obtain low boiling matter and high boiling matter.
  • the high boiling matter can be directly used as a solvent for the electrolyte;
  • Step 10 After collecting the low boiling matter, add 2 mol/L potassium permanganate aqueous solution according to the volume ratio of 1:1, mix and let stand without layering.
  • the yield of lithium hexafluorophosphate obtained in the comparative example and the organic solvent used is significantly lower than that of the example. This is due to the use of acetonitrile soaking in step 3 of the comparative example. Acetonitrile and lithium hexafluorophosphate may directly crystallize, and subsequent solid-liquid separation may occur. The crystals remain in the solid phase and cannot be recovered, resulting in the loss of lithium hexafluorophosphate and acetonitrile.

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Abstract

本发明公开了一种回收锂离子电池电解液的方法，通过冷冻废旧锂离子电池，再进行拆解，避免电解液的挥发和分解污染环境，拆解后的电芯置于四氯化碳中，使电解液全部溶于四氯化碳，并加入乙腈，使电解液溶质六氟磷酸锂与乙腈发生络合，形成稳定的Li(CH3CN)4PF6，在负压蒸发浓缩时保护六氟磷酸锂，避免其分解，浓缩液经冷却结晶，析出的固体通过干燥处理解络合，得到六氟磷酸锂。

Description

一种回收锂离子电池电解液的方法 技术领域
本发明属于电池回收技术领域，具体涉及一种回收锂离子电池电解液的方法。
背景技术
目前废旧锂离子电池的回收研究主要集中在正负极材料和集流体的回收上，而对于电解液回收的关注较少。目前在各种商用锂离子电池系统中，有机液体电解液仍为市场主要的电解液材料。有机液体电解液一般由三部分组成：电解质锂盐、有机溶剂和添加剂。目前商用的电解质溶液中的电解质盐一般为LiPF6、LiCF3SO3和LiBF4等锂盐，常用的溶剂有碳酸乙烯酯(EC)、碳酸丙烯酯(PC)、碳酸二甲酯(DMC)、甲基乙基碳酸酯(EMC)等。添加剂作为电解液中非必要成分，添加量少。电解液成分复杂，尤其是LiPF6的存在使电解液接触外界环境就易发生分解，产生有毒有害物质。
由于电解液易挥发，回收难度较大，很少专门针对电解液回收进行研究和处理。电解液的挥发会产生难闻的刺激性气味，电解液中的锂盐水解产生有毒的砷化物、磷化物及氟化物，对人体及环境危害很大，成为一个难以回避的问题。
专利申请CN108666644A公开了一种从锂电池废电解液中回收氟和锂的方法，采用CaO或Ca(OH)2与锂电池废电解液反应，Ca2+与电解液中的氟离子反应生成CaF2，之后采用多级锰纤维吸附柱和钛纤维吸附柱进行物理定向吸附锂离子，从而回收电解液中的氟和锂。专利申请CN108155434A公开了一种从锂离子电池废电解液中回收锂的方法，是将废电解液与一种含大阳离子半径的卤化物溶液混合反应，将电解液中的PF6 -1整体分离，并将分离后所得含锂溶液进行深度净化和沉锂处理后得到碳酸锂。以上两种方法，均无法完整回收价值昂贵的六氟磷酸锂电解质盐。
专利申请CN110203949A公开了采用减压蒸馏的方法，将废旧电解液进行减压蒸馏，逐一分离各个组分，从而达到回收电解液的方法。然而，蒸馏工艺复杂，电解液成分复杂，且经过长期的循环，电解液分解为小分子物质，很难再循环使用。
电解液处置不当会带来严重的安全和环境问题。同时，电解液本身附加值高，尤其是六氟磷酸锂是电解液成本最重要的组成部分，约占到电解液总成本的43％。因此，如何合理回收电解液中的电解质盐以及溶剂是值得深入研究的问题。
发明内容
本发明旨在至少解决上述现有技术中存在的技术问题之一。为此，本发明提出一种一种回收锂离子电池电解液的方法，能够完整回收高纯度的六氟磷酸锂，而且回收的有机溶剂杂质较低。
根据本发明的一个方面，提出了一种回收锂离子电池电解液的方法，包括以下步骤：
S1：废旧锂离子电池经放电后，采用液氮冷冻，将冷冻后的废旧锂离子电池拆解，得到含有电解液的电芯；
S2：将所述电芯置于四氯化碳中浸泡，固液分离，得到第一液相；
S3：将所述第一液相和乙腈混合，在负压下进行蒸发浓缩，得到蒸发液和浓缩液，所述蒸发液的主要成分为四氯化碳；
S4：将所述浓缩液进行冷却析晶，固液分离，得到第二液相和固体；所述固体经无水氟化氢洗涤后，在惰性气氛下干燥，得到六氟磷酸锂；所述第二液相进行精馏得到低沸物和高沸物；
S5：所述低沸物与高锰酸钾水溶液混合后静置，去除水相后，加入生石灰，固液分离得到无水四氯化碳。
在本发明的一些实施方式中，步骤S1中，所述冷冻的温度为-60℃以下。
在本发明的一些实施方式中，步骤S2中，所述电芯和四氯化碳的固液比为100-200g/L。
在本发明的一些实施方式中，步骤S2中，所述浸泡的时间为10-30min。
在本发明的一些实施方式中，步骤S2中，所述浸泡结束后，还包括洗涤工序：取出浸泡后的电芯，得到浸泡后液，用四氯化碳冲洗电芯，所得冲洗后液与浸泡后液混合，过滤后即得所述第一液相。
在本发明的一些实施方式中，步骤S3中，所述乙腈和第一液相的体积比为20-60mL/L。
在本发明的一些实施方式中，步骤S3中，所述蒸发浓缩的压强为-0.1至-0.08MPa，温度为65-70℃，蒸发浓缩至第一液相体积缩小至原体积的1/4-1/5。
在本发明的一些实施方式中，步骤S4中，所述冷却析晶的温度为-15至-10℃。
在本发明的一些实施方式中，步骤S4中，所述无水氟化氢洗涤的温度为0-5℃。由于后续干燥在低温下进行，使得固体表面的残留物(如高沸点的有机物)不易除去，影响纯度，需经过洗涤除去表面杂质，无水氟化氢作洗涤剂具有很好的洗涤效果。
在本发明的一些实施方式中，步骤S4中，所述干燥在负压下进行，压力为-0.1至-0.08MPa，干燥的温度为0-5℃，时间为12-24h。
在本发明的一些实施方式中，步骤S4中，所述精馏为常压精馏，温度为120-140℃。该精馏温度能保证小分子杂质几乎全部蒸出。
在本发明的一些实施方式中，步骤S4中，当所述低沸物中含有需要回收的低沸点有机溶剂时，所述低沸物在精馏过程可进行选择性冷凝分离，回收所需有机溶剂。
在本发明的一些实施方式中，步骤S5中，所述低沸物与高锰酸钾水溶液的体积比为1：(0.5-2.0)，所述高锰酸钾水溶液的浓度为1-2mol/L。
在本发明的一些实施方式中，步骤S5中，所述去除水相后，得到四氯化碳粗品，生石灰与四氯化碳粗品的固液比为20-50g/L。
根据本发明的一种优选的实施方式，至少具有以下有益效果：
1、本发明首先通过冷冻废旧锂离子电池，再进行拆解，避免电解液的挥发和分解污染环境。拆解后的电芯置于四氯化碳中，使电解液全部溶于四氯化碳，并进一步加入乙腈，使电解液溶质六氟磷酸锂与乙腈发生络合，形成稳定的Li(CH3CN)4PF6，在后续进行负压蒸发浓缩时，保护六氟磷酸锂，避免其产生分解。再利用Li(CH3CN)4PF6在四氯化碳中溶解度较低的现象，冷却结晶析出，通过进一步的干燥处理使Li(CH3CN)4PF6解络合，得到高纯度的六氟磷酸锂。
2、由于电解液经过长期的循环使用，产生了很多小分子物质，很难再循环使用，本发明利用四氯化碳低沸点、高稳定性的特征，在后续进行常压精馏时，保留了碳酸乙烯酯等高沸点物质，高沸物可直接作为电解液的溶剂，低沸点的小分子物质及四氯化碳经收集后，通过高锰酸钾去除小分子物质，并由生石灰脱水处理，得到无水四氯化碳，使其能够重新利用。
附图说明
下面结合附图和实施例对本发明做进一步的说明，其中：
图1为本发明实施例1的工艺流程图。
具体实施方式
以下将结合实施例对本发明的构思及产生的技术效果进行清楚、完整地描述，以充分地理解本发明的目的、特征和效果。显然，所描述的实施例只是本发明的一部分实施例，而不是全部实施例，基于本发明的实施例，本领域的技术人员在不付出创造性劳动的前提下所获得的其他实施例，均属于本发明保护的范围。
实施例1
一种回收锂离子电池电解液的方法，参照图1，具体过程为：
步骤1，废旧锂离子电池经放电后，采用液氮冷冻至-60℃以下；
步骤2，将冷冻后的废旧锂离子电池拆解，取出含有电解液的电芯；
步骤3，按照固液比100g/L将电芯置于无水四氯化碳中浸泡10min；
步骤4，取出电芯，并用无水四氯化碳冲洗，洗涤液与步骤3的四氯化碳混合，得到混合液；
步骤5，将混合液过滤，去除滤渣，得到滤液；
步骤6，按照体积比乙腈/滤液＝20mL/L，向滤液中加入无水乙腈，均匀混合后在压强为-0.08MPa、温度为70℃，蒸发浓缩至滤液体积缩小至原体积的1/5，得到蒸发液与浓缩液，蒸发液主要成分即为四氯化碳，可循环使用；
步骤7，将浓缩液冷却至-15℃，抽滤，得到固体和滤液；
步骤8，用无水氟化氢将固体在0℃下洗涤后，在氮气氛围下干燥，控制压力在-0.1至-0.08MPa，温度为0℃，持续24h，得到六氟磷酸锂产品；
步骤9，将步骤8所得滤液进行常压精馏，精馏温度为120℃，得到低沸物和高沸物，高沸物可直接作为电解液的溶剂；
步骤10，将低沸物收集后，按照体积比1:1，加入1mol/L的高锰酸钾水溶液，混合后静置，去除水相后，按照固液比20g/L，加入生石灰，固液分离，得到无水四氯化碳，与步骤6所得蒸发液混合后重新用于电芯的浸泡和冲洗。
实施例2
一种回收锂离子电池电解液的方法，具体过程为：
步骤1，废旧锂离子电池经放电后，采用液氮冷冻至-60℃以下；
步骤2，将冷冻后的废旧锂离子电池拆解，取出含有电解液的电芯；
步骤3，按照固液比150g/L将电芯置于无水四氯化碳中浸泡20min；
步骤4，取出电芯，并用无水四氯化碳冲洗，洗涤液与步骤3的四氯化碳混合，得到混合液；
步骤5，将混合液过滤，去除滤渣，得到滤液；
步骤6，按照体积比乙腈/滤液＝30mL/L，向滤液中加入无水乙腈，均匀混合后在压强为-0.09MPa、温度为68℃，蒸发浓缩至滤液体积缩小至原体积的1/4，得到蒸发液与浓缩液，蒸发液主要成分即为四氯化碳，可循环使用；
步骤7，将浓缩液冷却至-12℃，抽滤，得到固体和滤液；
步骤8，用无水氟化氢将固体在3℃下洗涤后，在氮气氛围下干燥，控制压力在-0.1至-0.08MPa，温度为3℃，持续18h，得到六氟磷酸锂产品；
步骤9，将步骤8所得滤液进行常压精馏，精馏温度为130℃，得到低沸物和高沸物，高沸物可直接作为电解液的溶剂；
步骤10，将低沸物收集后，按照体积比1:1，加入1.5mol/L的高锰酸钾水溶液，混合后静置，去除水相后，按照固液比30g/L，加入生石灰，固液分离，得到无水四氯化 碳，与步骤6所得蒸发液混合后重新用于电芯的浸泡和冲洗。
实施例3
一种回收锂离子电池电解液的方法，具体过程为：
步骤1，废旧锂离子电池经放电后，采用液氮冷冻至-60℃以下；
步骤2，将冷冻后的废旧锂离子电池拆解，取出含有电解液的电芯；
步骤3，按照固液比200g/L将电芯置于无水四氯化碳中浸泡30min；
步骤4，取出电芯，并用无水四氯化碳冲洗，洗涤液与步骤3的四氯化碳混合，得到混合液；
步骤5，将混合液过滤，去除滤渣，得到滤液；
步骤6，按照体积比乙腈/滤液＝60mL/L，向滤液中加入无水乙腈，均匀混合后在压强为-0.1MPa、温度为65℃，蒸发浓缩至滤液体积缩小至原体积的1/5，得到蒸发液与浓缩液，蒸发液主要成分即为四氯化碳，可循环使用；
步骤7，将浓缩液冷却至-10℃，抽滤，得到固体和滤液；
步骤8，用无水氟化氢将固体在5℃下洗涤后，在氮气氛围下干燥，控制压力在-0.1至-0.08MPa，温度为5℃，持续12h，得到六氟磷酸锂产品；
步骤9，将步骤8所得滤液进行常压精馏，精馏温度为140℃，得到低沸物和高沸物，高沸物可直接作为电解液的溶剂；
步骤10，将低沸物收集后，按照体积比1:1，加入2mol/L的高锰酸钾水溶液，混合后静置，去除水相后，按照固液比50g/L，加入生石灰，固液分离，得到无水四氯化碳，与步骤6所得蒸发液混合后重新用于电芯的浸泡和冲洗。
对比例
一种回收锂离子电池电解液的方法，与实施例3的主要区别在于，步骤3用乙腈浸泡，具体过程为：
步骤1，废旧锂离子电池经放电后，采用液氮冷冻至-60℃以下；
步骤2，将冷冻后的废旧锂离子电池拆解，取出含有电解液的电芯；
步骤3，按照固液比200g/L将电芯置于无水乙腈中浸泡30min；
步骤4，取出电芯，并用无水乙腈冲洗，洗涤液与步骤3的乙腈溶液混合，得到混合液；
步骤5，将混合液过滤，去除滤渣，得到滤液；
步骤6，将滤液在压强为-0.1MPa、温度为70℃，蒸发浓缩至滤液体积缩小至原体积的1/5，得到蒸发液与浓缩液，蒸发液主要成分即为乙腈，可循环使用；
步骤7，将浓缩液冷却至-10℃，抽滤，得到固体和滤液；
步骤8，用无水氟化氢将固体在5℃下洗涤后，在氮气氛围下干燥，控制压力在-0.1至-0.08MPa，温度为5℃，持续12h，得到六氟磷酸锂产品；
步骤9，将步骤8所得滤液进行常压精馏，精馏温度为140℃，得到低沸物和高沸物，高沸物可直接作为电解液的溶剂；
步骤10，将低沸物收集后，按照体积比1:1，加入2mol/L的高锰酸钾水溶液，混合后静置，溶液不分层。
检测实施例1-3和对比例所得六氟磷酸锂产品纯度及有机溶剂的收率，结果如表1所示。
表1
由表1可见，对比例所得六氟磷酸锂和使用的有机溶剂的收率明显比实施例低得多，这是由于对比例步骤3使用了乙腈浸泡，乙腈与六氟磷酸锂可能会直接结晶，后续固液分离，结晶物留在固相中，无法回收，导致六氟磷酸锂和乙腈损失。
上面结合附图对本发明实施例作了详细说明，但是本发明不限于上述实施例，在所 属技术领域普通技术人员所具备的知识范围内，还可以在不脱离本发明宗旨的前提下作出各种变化。此外，在不冲突的情况下，本发明的实施例及实施例中的特征可以相互组合。

Claims (10)

  1. 一种回收锂离子电池电解液的方法，其特征在于，包括以下步骤：
    S1：废旧锂离子电池经放电后，采用液氮冷冻，将冷冻后的废旧锂离子电池拆解，得到含有电解液的电芯；
    S2：将所述电芯置于四氯化碳中浸泡，固液分离，得到第一液相；
    S3：将所述第一液相和乙腈混合，在负压下进行蒸发浓缩，得到蒸发液和浓缩液，所述蒸发液的主要成分为四氯化碳；
    S4：将所述浓缩液进行冷却析晶，固液分离，得到第二液相和固体；所述固体经无水氟化氢洗涤后，在惰性气氛下干燥，得到六氟磷酸锂；所述第二液相进行精馏得到低沸物和高沸物；
    S5：所述低沸物与高锰酸钾水溶液混合后静置，去除水相后，加入生石灰，固液分离得到无水四氯化碳。
  2. 根据权利要求1所述的方法，其特征在于，步骤S2中，所述电芯和四氯化碳的固液比为100-200g/L。
  3. 根据权利要求1所述的方法，其特征在于，步骤S2中，所述浸泡结束后，还包括洗涤工序：取出浸泡后的电芯，得到浸泡后液，用四氯化碳冲洗电芯，所得冲洗后液与浸泡后液混合，过滤后即得所述第一液相。
  4. 根据权利要求1所述的方法，其特征在于，步骤S3中，所述乙腈和第一液相的体积比为20-60mL/L。
  5. 根据权利要求1所述的方法，其特征在于，步骤S3中，所述蒸发浓缩的压强为-0.1至-0.08MPa，温度为65-70℃，蒸发浓缩至第一液相体积缩小至原体积的1/4-1/5。
  6. 根据权利要求1所述的方法，其特征在于，步骤S4中，所述冷却析晶的温度为-15～-10℃。
  7. 根据权利要求1所述的方法，其特征在于，步骤S4中，所述干燥在负压下进行，压力为-0.1至-0.08MPa，干燥的温度为0-5℃，时间为12-24h。
  8. 根据权利要求1所述的方法，其特征在于，步骤S4中，所述精馏为常压精馏，温度为120-140℃。
  9. 根据权利要求1所述的方法，其特征在于，步骤S5中，所述低沸物与高锰酸钾水溶液的体积比为1：(0.5-2.0)，所述高锰酸钾水溶液的浓度为1-2mol/L。
  10. 根据权利要求1所述的方法，其特征在于，步骤S5中，所述去除水相后，得到四氯化碳粗品，生石灰与四氯化碳粗品的固液比为20-50g/L。
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