CN115725841A - A method for removing lithium without hydrogen generation - Google Patents

Abstract

The invention discloses a method for removing lithium without generating hydrogen, which comprises: placing metal lithium-containing waste in a reaction furnace; A non-aqueous reactant; the reaction furnace is heated to make the metal lithium-containing waste and the anhydrous reactant react. The lithium removal method of the present invention is safe, non-combustible and non-explosive, and the processed lithium metal and other by-products can be further recycled.

Description

A method for removing lithium without hydrogen generation

technical field

The invention relates to the technical field of lithium battery waste treatment and resource recovery, in particular, the invention relates to a lithium removal method without hydrogen generation.

Background technique

Lithium-ion batteries have been widely used as energy storage devices in information technology, electric vehicles, aerospace and other fields because of their advantages such as high energy density, high voltage, good cycle performance, and small self-discharge. With the popularization and application of lithium-ion batteries, the disposal of lithium battery waste has also attracted increasing attention.

But generally speaking, the current methods of metal lithium waste disposal generally have relatively large safety risks.

Contents of the invention

In order to solve all or part of the above problems, the present invention provides a method for removing lithium without generating hydrogen, which can effectively solve the safety problems existing in the process of processing waste containing metal lithium.

Specifically, the present invention is achieved through the following technical solutions:

A method for removing lithium without hydrogen generation, comprising:

Place lithium metal waste in the reaction furnace;

Adding an anhydrous reactant selected from compound solid-phase reactant, gas-phase reactant and metal-phase reactant in the reaction furnace;

The reaction furnace is heated to react the lithium metal waste and the anhydrous reactant.

Optionally, during the process of heating the reaction furnace, the heating temperature is 80° C. to 1000° C., and the heating time is 1 minute to 3 hours.

Optionally, the anhydrous reactant is a compound solid phase reactant; preferably, the compound solid phase reactant is polysulfide Li ₂ S _x ; more preferably, x is 2, 4 or 6.

Optionally, the compound solid-phase reactant is added to the reaction furnace according to the molar ratio of the compound solid-phase reactant to the lithium in the metal lithium-containing waste being 1: (2-10).

Optionally, during the process of heating the reaction furnace, the heating temperature is 80°C-100°C, and the heating time is 30 minutes to 3 hours, preferably 2-3 hours.

Optionally, the anhydrous reactant is a gas phase reactant; preferably, the gas phase reactant is any one of nitrogen, sulfur dioxide and chlorine.

Optionally, according to the speed of 2L/min～10L/min and preferably 5L/min～10L/min, the gas phase reactant is passed into the reaction furnace; in the process of heating the reaction furnace, the heating temperature is 80°C～100°C , the heating time is 1 minute to 1 hour and preferably 0.5 to 1 hour.

Optionally, the safe lithium removal method without hydrogen generation also includes: electrolyzing the reactants obtained from the reaction of metal-containing lithium wastes and anhydrous reactants; returning the gas obtained from electrolysis to the reaction furnace, and/or recycling the electrolyzed Lithium metal obtained.

Alternatively, the anhydrous reactant is a metal phase reactant; preferably, the metal phase reactant is any metal except iron.

Optionally, during the process of heating the reaction furnace, the heating temperature is 100°C-1000°C, preferably 600°C-1000°C, and the heating time is 2-3 hours.

Compared with the prior art, the method for removing lithium produced without hydrogen of the present invention has at least the following beneficial effects:

The reactant used in the hydrogen-free lithium removal method of the present invention is an anhydrous reactant, thereby avoiding safety problems such as inflammability and explosion caused by violent reaction between metal lithium and water and generation of hydrogen.

By adopting the hydrogen-free lithium removal method of the present invention, the processed metal lithium and other by-products can also be recycled, which not only reduces the harm to the environment, but also effectively recovers resources.

Description of drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiment. The drawings are only for the purpose of illustrating a preferred embodiment and are not to be considered as limiting the invention. In the attached picture:

Fig. 1 shows the flow chart of the lithium removal method without hydrogen generation of the present invention.

Fig. 2 shows a flow chart of a lithium removal method using lithium polysulfide in a preferred embodiment of the present invention.

Fig. 3 shows a flow chart of a lithium removal method using a gas phase reactant in another preferred embodiment of the present invention.

Figure 4 shows a flow chart of a lithium removal process using metals other than iron in another preferred embodiment of the present invention.

Detailed ways

In order to fully understand the purpose, features and effects of the present invention, the present invention will be described in detail through the following specific embodiments, but the present invention is not limited thereto.

The inventors found that among the existing metal lithium recovery technologies for lithium batteries, common technologies include, for example, the Chinese invention patent application with application number 201711130452.1, which discloses a lithium recovery and reuse process. The method is to remove lithium by chemical precipitation, lower the temperature by liquid nitrogen, reduce the reactivity of lithium, react the cooled components with water, and precipitate lithium compounds; dissolve lithium salts in low-concentration In sulfuric acid, so that further purification can be carried out, while the LiOH produced in the reaction can finally be converted into LiCO ₃ by precipitation. However, during the synthesis of lithium compounds, lithium reacts violently with water and produces hydrogen, which poses a safety problem of flammability and explosion.

Another example is the Chinese invention patent application with application number 201510144800.5 which discloses a sodium potassium lithium and lithium slag waste treatment device. The treatment device is to slowly press the lithium slag into the hydrolysis pump through the lithium slag metering pump, and undergo a hydrolysis reaction with a large amount of water in the hydrolysis pump; High temperature, overpressure phenomenon, the hydrolysis temperature will not fluctuate greatly. However, lithium metal is very active, and in the presence of a large amount of water, a hydrolysis reaction will rapidly occur to generate a large amount of hydrogen; even if the reaction temperature is controlled by controlling the reaction amount and reaction speed of lithium slag, the risk of explosion that may be caused by hydrogen accumulation cannot be solved.

In view of the safety problems existing in the current lithium-containing waste treatment process, the present invention provides a method for removing lithium without hydrogen generation, as shown in Figure 1, the method includes the following steps:

Step S1: placing lithium metal waste in a reaction furnace.

The lithium removal method of the present invention has universal applicability and can be applied to any type of metal lithium waste. Specifically, the lithium removal method of the present invention is suitable for pure metal lithium waste, such as lithium scraps, lithium strip scraps, etc.; in addition, the lithium removal method of the present invention is also suitable for lithium-containing pole piece waste, for example, carbon system containing Lithium anode sheet waste, silicon system lithium-containing anode sheet waste, etc.

The lithium removal method of the present invention has no special requirements on the reaction furnace, and those skilled in the art can choose any conventional reaction furnace to implement the lithium removal method of the present invention according to actual needs.

Step S2: Adding an anhydrous reactant selected from compound solid-phase reactant, gas-phase reactant and metal-phase reactant into the reaction furnace.

Preferably, the compound solid phase reactant is polysulfide Li ₂ S _x ; more preferably, x is 2, 4 or 6. The inventors have found through research that using polysulfides to remove lithium from metal lithium waste has a mild reaction throughout the process, does not generate flammable gases such as hydrogen, and eventually forms lithium sulfate, which can be recycled.

Preferably, the gas phase reactant is any one of nitrogen, sulfur dioxide and chlorine. The inventor found through research that using nitrogen, sulfur dioxide or chlorine to remove lithium from metal lithium waste has a fast reaction speed and does not produce flammable gases such as hydrogen, and the corresponding lithium compounds produced can be re-transformed into metal lithium and lithium by electrolysis. Corresponding to the gas, and then realize the recovery.

Preferably, the metal phase reactant is any metal except iron. The inventors have found through research that metal lithium wastes are delithiated by fusion of metals other than iron with lithium metal wastes. This type of reaction is an in-situ reaction and does not produce flammable gases such as hydrogen. In addition, this treatment method is simple to operate, has a large production capacity, can directly form alloys, and has high economic benefits.

Step S3: heating the reaction furnace to make the waste containing lithium metal and the anhydrous reactant react. The heating temperature is selected from any temperature within the range of 80° C. to 1000° C. or a temperature in any range, and the heating time is from 1 minute to 3 hours.

The present invention will be further described in detail below in conjunction with the accompanying drawings for the three situations of compound solid-phase reactant, gas-phase reactant and metal-phase reactant.

Fig. 2 shows a flow chart of a lithium removal method using lithium polysulfide provided by a preferred embodiment of the present invention. In this embodiment, the graphite system pole piece waste (that is, the graphite system waste pole piece) is taken as an example for illustration. Those skilled in the art can understand that this is only exemplary, and the lithium removal method in this embodiment It is also applicable to pure metal lithium waste such as lithium shavings and lithium belt scraps, or other pole piece waste such as silicon system lithium-containing anode piece waste. As shown in Figure 2, the method for removing lithium comprises the following steps:

Step S101: placing the spent graphite system electrode sheet in the reaction furnace.

In order to ensure the full reaction of metallic lithium, the graphite-based waste pole piece is cut in advance, and the specific cutting size can be reasonably selected by those skilled in the art according to actual needs. After the cutting process, it can ensure that all positions of the spent pole pieces are in contact with the reactant, thereby ensuring the full reaction of metal lithium.

Step S102: adding lithium polysulfide into the reaction furnace.

The lithium polysulfide used in the present invention can be Li ₂ S ₂ , Li ₂ S ₄ or Li ₂ S ₆ . The molar ratio of the added lithium polysulfide to the metal lithium in the graphite system pole piece waste is 1: (2-10). For example, when lithium polysulfide can be Li ₂ S ₂ , the molar ratio of Li ₂ S ₂ to the metal lithium in graphite system pole piece waste can be 1:2; when lithium polysulfide can be Li ₂ S ₄ , The molar ratio of Li ₂ S ₂ to metal lithium in graphite system pole piece waste can be 1: (2~4); when lithium polysulfide can be Li ₂ S ₆ , Li ₂ S ₂ and graphite system pole piece waste The molar ratio of metal lithium in the compound can be 1:(2～10).

Step S103: heating the reaction furnace to make the graphite system pole piece waste react with lithium polysulfide.

The temperature adopted for heating the reaction furnace is 80° C. to 100° C., and the time for heating the reaction furnace is 30 minutes to 3 hours, and preferably 2 to 3 hours.

The chemical properties of lithium polysulfide are relatively active. Under heating conditions, lithium polysulfide will react with metallic lithium in graphite system pole piece waste to form lithium sulfide. Because the chemical properties of lithium polysulfide are relatively active, it only needs to be heated to 80 ° C to 100 ° C to cause the reaction to occur, and the reaction conditions are mild. Further, lithium sulfide is heated continuously in oxygen to form lithium sulfate, and the reaction in the whole process is mild, and flammable gases such as hydrogen will not be produced.

This step mainly involves the following chemical reactions:

Li ₂ S _x +(2x-2)Li→x Li ₂ S (x=2, 4 or 6)

Li ₂ S+2O ₂ →Li ₂ SO ₄

Step S104: recover lithium sulfate.

The specific recovery method can be any conventional method, and those skilled in the art can make a reasonable choice according to the needs, and details will not be repeated here.

Fig. 3 shows a flow chart of a lithium removal method using a gas phase reactant provided by a preferred embodiment of the present invention. In this embodiment, the graphite system pole piece waste is used as an example for illustration. Those skilled in the art can understand that this is only exemplary, and the lithium removal method in this embodiment is also applicable to lithium scraps, lithium belt scraps Other pure metal lithium waste or silicon system lithium-containing anode waste and other pole piece waste. As shown in Figure 3, the method for removing lithium comprises the following steps:

Step S201: placing the spent graphite system electrode sheet in the reaction furnace.

In order to ensure the full reaction of metallic lithium, the graphite-based waste pole piece is cut in advance, and the specific cutting size can be reasonably selected by those skilled in the art according to actual needs. After the cutting process, it can ensure that all positions of the spent pole pieces are in contact with the reactant, thereby ensuring the full reaction of metal lithium.

Step S202: feeding gas phase reactants into the reaction furnace.

The gas phase reactant used in the present invention is any one of nitrogen, sulfur dioxide and chlorine. The rate at which the gas phase reactants are fed into the reaction furnace is 2L/min˜10L/min, and preferably 5L/min˜10L/min.

Step S203: heating the reaction furnace to make the graphite system pole piece waste react with the gas phase reactant.

The temperature adopted for heating the reaction furnace is 80° C. to 100° C., and the time for heating the reaction furnace is 1 minute to 1 hour, and preferably 0.5 to 1 hour.

When nitrogen, sulfur dioxide or chlorine gas is used to remove lithium from graphite system pole piece waste, the reaction speed is fast, and it only needs to be heated to 80°C to 100°C to make nitrogen, sulfur dioxide or chlorine gas react with metal lithium quickly, and the production corresponds to Lithium compounds, the whole process conditions are mild, and flammable gases such as hydrogen will not be produced.

This step mainly involves the following chemical reactions:

N ₂ +2Li→2LiN

SO ₂ +2Li→Li ₂ S+O ₂

Cl ₂ +2Li→2LiCl

Step S204: Perform electrolysis on the reaction product, and transport the obtained gas back to the reaction furnace.

In the process of electrolyzing the reaction product, the electrolysis temperature used is 30°C-70°C, preferably 60°C-70°C, and the current density used is 1-3KA/m ³ , preferably 2-3KA/m ³ .

The electrolytic treatment in this step mainly involves the following chemical reactions:

2LiN→N ₂ +2Li

Li ₂ S+O ₂ →SO ₂ +2Li

2LiCl→Cl ₂ +2Li

The gas obtained by electrolysis is transported back to the reaction furnace, and is reused to react with the graphite system pole piece waste.

Step S205: recovering the metal lithium obtained by electrolysis.

The specific recovery method can be carried out by conventional methods, which will not be repeated here.

The above step S204 and step S205 are optional steps in the embodiment of the present invention, and there is no strict sequence between them. After electrolytic treatment, gas and lithium metal can be recovered simultaneously, or sequentially.

Fig. 4 shows a flow chart of a lithium removal method using metals other than iron provided by a preferred embodiment of the present invention. In this embodiment, the graphite system pole piece waste is used as an example for illustration. Those skilled in the art can understand that this is only exemplary, and the lithium removal method in this embodiment is also applicable to lithium scraps, lithium belt scraps Other pure metal lithium waste or silicon system lithium-containing anode waste and other pole piece waste. As shown in Figure 4, the method for removing lithium comprises the following steps:

Step S301: placing the spent graphite system electrode sheet in the reaction furnace.

In order to ensure the full reaction of metallic lithium, the graphite-based waste pole piece is cut in advance, and the specific cutting size can be reasonably selected by those skilled in the art according to actual needs. After the cutting process, it can ensure that all positions of the spent pole pieces are in contact with the reactant, thereby ensuring the full reaction of metal lithium.

Step S302: adding metals other than iron into the reaction furnace.

The inventor found through research that metal iron is difficult to fuse with metal lithium, so the present invention does not use iron. Other metals can be used in the present invention, for example, aluminum, magnesium, zinc, copper, and the like.

There is no special requirement for the amount of metal used in the present invention, as long as it can be fused with the waste pole piece. Those skilled in the art can make a reasonable choice according to the actual situation.

Step S303: heating the reaction furnace to make the waste electrode sheet of the graphite system react with the metal.

The temperature adopted for heating the reaction furnace is 100°C to 1000°C, preferably 600°C to 1000°C, and the time for heating the reaction furnace is 2 to 3 hours.

The reaction between the metal and graphite system waste pole pieces under high temperature conditions is an in-situ reaction, and flammable gases such as hydrogen will not be produced during the reaction. In addition, this treatment method is simple to operate, has a large production capacity, can directly form alloys, and has high economic benefits.

Step S304: purifying lithium metal.

The material obtained by the heating reaction is an alloy of carbon, pole piece (copper foil), metal, and lithium. For example, when aluminum and graphite system waste pole pieces are used for heating and reacting, a carbon-copper-aluminum-lithium alloy is obtained.

The alloy can be further used to purify lithium, and the specific purification method can be carried out by conventional methods, which will not be repeated here.

Example

The present invention is further illustrated below by means of examples, but the present invention is not limited to the scope of the examples. For the experimental methods not indicating specific conditions in the following examples, select according to conventional methods and conditions.

Embodiment 1～5 and comparative example 1～5

100 grams of spent graphite pole pieces with lithium films are processed. See Table 1 for specific parameters.

Effect detection:

(1) The amount of hydrogen generated during the reaction: Use a hydrogen concentration detector to detect the real-time hydrogen concentration generated during the reaction.

(2) Lithium sulfate recovery rate: 1-2g of the final product sample is digested in a mixed acid (hydrochloric acid + nitric acid) solution, and after being diluted 50-150 times, the absorbance is measured at 670.78nm in the atomic spectrum, and the lithium ion Compared with the standard absorbance curve of the standard, the concentration of lithium ions can be found out, and the recovery rate of lithium sulfate salt can be calculated.

(3) Recovery rate of copper pole piece: Calculate the recovery rate of copper foil by using the weight of copper foil containing theoretically treated pole piece ÷ the actual recovered copper foil weight × 100%.

Table 1

As can be seen from the data in Table 1, according to the method of the present invention, when polysulfides are used to remove lithium from the waste pole piece with lithium film, there is no hydrogen generation in the whole process, and the by-product sulfuric acid produced in the reaction process The recovery rate of lithium can reach more than 83%, and the recovery rate of copper pole piece can reach more than 80%. But, if do not adopt the substance ratio of the present invention (comparative example 1), do not adopt the reaction time of the present invention (comparative example 2), do not adopt the heating temperature condition of the present invention (comparative example 3 and comparative example 4), or do not adopt Lithium removal (comparative example 5) is performed on the polysulfide of the present invention, but the by-product recovery rate of the present invention cannot be realized or no hydrogen gas is produced in the whole process.

Embodiment 6～10 and comparative example 6～10

100 grams of spent graphite pole pieces with lithium films are processed. See Table 2 for specific parameters.

Effect detection:

(1) The amount of hydrogen generated during the reaction: Use a hydrogen concentration detector to detect the real-time hydrogen concentration generated during the reaction.

(2) Lithium metal treatment rate: put the treated pole piece into water, use the drainage method to collect the gas generated by the residual lithium on the pole piece and water, and calculate the amount of residual metal lithium through the gas volume, so as to calculate the treatment rate of metal lithium Rate.

(3) Recovery rate of copper pole piece: Calculate the recovery rate of copper foil by using the weight of copper foil containing theoretically treated pole piece ÷ the actual recovered copper foil weight × 100%.

Table 2

As can be seen from the data in Table 2, according to the method of the present invention, when nitrogen, sulfur dioxide or chlorine are used to remove lithium from the waste pole piece with lithium film, the treatment rate of lithium metal can reach more than 90%. No hydrogen is generated, and the recovery rate of copper pole pieces can reach more than 80%. However, although the gas (nitrogen) used in the present invention was adopted, the gas flow rate of the present invention (Comparative Example 6), the treatment time of the present invention (Comparative Example 7), and the heating temperature of the present invention (Comparative Example 7) were not adopted. 8 and Comparative Example 9), neither the lithium removal rate or the copper pole piece recovery rate of the present invention can be realized, or, although the process condition parameters of the present invention are adopted, the gas of the present invention (Comparative Example 10) is not used, nor can it be Realize the effect that no hydrogen is produced in the whole process.

Embodiment 11～13 and comparative example 11

100 grams of spent graphite pole pieces with lithium films are processed. See Table 3 for specific parameters.

Effect detection:

(1) The amount of hydrogen generated during the reaction: Use a hydrogen concentration detector to detect the real-time hydrogen concentration generated during the reaction.

(2) Alloy yield: use atomic absorption spectrometry to test the lithium content in the product alloy ÷ the metal lithium content of the actually processed pole piece × 100%.

table 3

It can be seen from the data in Table 3 that when metals other than iron are used to remove lithium from the waste pole piece with lithium film, while ensuring that no hydrogen is generated in the whole process, 100% lithium alloy can also be achieved. Yield.

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other substitutions, modifications, combinations, changes, Simplification, etc., should be equivalent replacement methods, and all are included in the protection scope of the present invention.

Claims (10)

1. A method for removing lithium without hydrogen generation, characterized in that, comprising: Put lithium metal waste in the reaction furnace; Adding an anhydrous reactant selected from compound solid-phase reactant, gas-phase reactant and metal-phase reactant in the reaction furnace; The reaction furnace is heated to make the lithium metal-containing waste and the anhydrous reactant react. 2. The method for removing lithium without hydrogen generation according to claim 1, characterized in that, in the process of heating the reaction furnace, the heating temperature is 80° C. to 1000° C., and the heating time is 1 minute to 3 hours. 3. The method for removing lithium produced without hydrogen according to claim 1 or 2, wherein the anhydrous reactant is a compound solid-phase reactant; preferably, the compound solid-phase reactant is a polysulfide Li ₂ S _x ; more preferably, x is 2, 4 or 6. 4. The method for removing lithium produced without hydrogen according to claim 3, characterized in that, according to the molar ratio of the compound solid-phase reactant to lithium in the metal-containing lithium waste is 1: (2～10) Add the compound solid phase reactant into the reaction furnace. 5. The lithium removal method without hydrogen generation according to any one of claims 1-4, characterized in that, in the process of heating the reaction furnace, the heating temperature is 80°C to 100°C, and the heating time is 30 minutes to 3 hours and preferably 2 to 3 hours. 6. The method for removing lithium produced without hydrogen according to any one of claims 1-5, wherein the anhydrous reactant is a gas phase reactant; preferably, the gas phase reactant is nitrogen, sulfur dioxide and Any of the chlorine gas. 7. The method for removing lithium without hydrogen generation according to any one of claims 1-6, characterized in that, according to the speed of 2L/min～10L/min and preferably 5L/min～10L/min, pass through the reaction furnace Into the gas phase reactant; in the process of heating the reaction furnace, the heating temperature is 80° C. to 100° C., and the heating time is 1 minute to 1 hour and preferably 0.5 to 1 hour. 8. The method for removing lithium produced without hydrogen according to any one of claims 1-7, wherein the method for removing lithium produced without hydrogen further comprises: electrolyzing the reactant obtained by reacting the metal-containing lithium waste and the anhydrous reactant; The gas obtained by electrolysis is returned to the reaction furnace, and/or the metal lithium obtained by electrolysis is recovered. 9. The method for removing lithium produced without hydrogen according to any one of claims 1-8, wherein the anhydrous reactant is a metal phase reactant; preferably, the metal phase reactant is iron removal Any other metal. 10. The lithium removal method without hydrogen generation according to any one of claims 1-9, characterized in that, in the process of heating the reaction furnace, the heating temperature is 100°C to 1000°C and preferably 600°C ~1000°C, the heating time is 2-3 hours.

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