CN115241555A - A kind of recycling and regeneration method of waste battery anode graphite - Google Patents

Abstract

The invention discloses a method for recycling waste battery negative electrode graphite, and relates to the field of lithium ion battery material recycling. According to the invention, the lithium carbonate fine powder and graphite are uniformly mixed to obtain the preliminary pre-lithiated graphite, and then the lithium atoms in the waste graphite are activated through calcination to realize double pre-lithiation. Lithium oxide generated in the process of high-temperature calcination of lithium carbonate becomes a fluxing agent, and the small-particle-size graphite is gathered together by utilizing the surface tension generated when the lithium oxide is cooled and shrunk in the slow cooling process, so that necessary conditions are provided for increasing the graphite particle size and reducing the specific surface area. And finally, coating the surface of the graphite by adopting a carbon source for heat treatment, thereby realizing high-value utilization of the cathode material of the retired lithium ion battery. According to the method, double pre-lithium, high-temperature calcination and carbon coating processes are organically integrated, the internal structure and the surface coating layer of the damaged graphite cathode material are simultaneously repaired, the first charge-discharge efficiency of the obtained regenerated graphite material is obviously improved, and large-scale preparation and production are facilitated.

Description

A kind of recycling method of waste battery anode graphite

technical field

The invention relates to the field of lithium ion battery material recovery, in particular to a method for recycling and regenerating negative electrode graphite of waste batteries.

Background technique

In recent years, energy and environmental problems have become increasingly prominent, and the development of new energy has become the general trend of energy strategy. Among them, electrochemical energy storage has been widely used all over the world due to the advantages of high energy storage efficiency, less dependence on the external environment, relatively mature technology, and wide application range. Thanks to the strong support of the state, new energy vehicles have achieved rapid development in China. However, as the "heart" of new energy vehicles, the life of the power battery is only 4-6 years. At present, the power batteries on the first batch of new energy vehicles in my country have fully ushered in the "retirement period". It is expected that by 2025, the cumulative amount of domestic power lithium batteries will be retired. Power lithium batteries contain many metal elements and organic substances. If they are not effectively treated after decommissioning, they will cause serious waste of resources and environmental pollution. Based on this, the state has issued a series of policies and regulations to guide the healthy development of the lithium battery recycling industry, and relevant research and industrialization have been highly valued.

At present, the material recovery of lithium batteries mainly focuses on positive active materials such as lithium, cobalt, nickel, manganese, etc., as well as valuable metals such as metal current collectors such as aluminum and copper. Due to the wide range of anode graphite sources and the low added value of recycling, the recycling technology and industrial development for anodes are still in their infancy. As an important strategic resource of the country, graphite reserves are limited and have very important economic value. As the number of retired power batteries increases year by year, it is imminent to recycle and reuse retired graphite.

At present, some recycling manufacturers can recycle waste graphite to obtain graphite materials as anode materials for lithium ion batteries. However, the first coulombic efficiency of the recovered graphite anode materials in practical applications is lower than that of fresh graphite anode materials. The reason is mainly because the decommissioned graphite has different degrees of structural damage in its bulk and surface after a long-term cycle, so it needs to be repaired by means of structural regeneration. Chinese patent CN 109524736 A discloses a method for recovering graphite in waste batteries and its application: using graphite slag recovered from waste batteries as recovery raw materials, pickling to obtain preliminary purified graphite, and then placing the preliminary purified graphite in a reactor The secondary purified graphite is obtained by oxidation, and finally the secondary purified graphite is coated and carbonized with pitch to obtain a regenerated graphite material. The use of carbon source to coat the graphite surface can improve and reconstruct its surface electron/ion transport channels to a certain extent, and reduce the generation of SEI. However, only the surface coating cannot effectively repair the crystal structure defects inside the decommissioned graphite, and the degree of graphitization inside the graphite has not been effectively improved. At the same time, pickling removes lithium in the activated anode powder to a certain extent, ignoring the positive role of lithium in the repair process of decommissioned graphite. Chinese patent CN 111924836 A discloses a method for recycling and regenerating negative electrode graphite of decommissioned lithium-ion batteries: decommissioned graphite is calcined to convert organic components into amorphous carbon, and the migration characteristics of lithium atoms at different temperatures are used to realize the pre-lithiation of decommissioned graphite change. However, on the one hand, only relying on a small amount of lithium remaining in retired graphite for pre-lithiation cannot meet the requirements for subsequent use. On the other hand, due to the damage of the crystal structure caused by the co-intercalation of solvated lithium ions into the graphite layer during the early battery cycle, and the damage of the anode particles during the separation of the current collector and the active material in the later stage, the obtained retired graphite has a smaller particle size. This leads to an increase in the contact area between the regenerated graphite and the electrolyte, an increase in side reactions, and finally a decrease in the first charge-discharge efficiency.

SUMMARY OF THE INVENTION

In view of the deficiencies of the prior art, the present invention proposes a method for recycling and reusing the negative electrode graphite of waste batteries. In the present invention, the lithium carbonate fine powder and the graphite are uniformly mixed for pre-lithiation, and then the lithium in the SEI of the original waste graphite is activated at high temperature and re-applied to the graphite to realize double pre-lithiation. In addition, lithium carbonate generates a small amount of lithium oxide as a flux at high temperature, and the surface tension generated by lithium oxide during the slow cooling process can aggregate the broken and small-sized graphite together, thus creating the necessary for increasing the graphite particle size and reducing the specific surface area. condition. Finally, the carbon source is used to coat the graphite surface and heat treatment, and finally realize the high-value utilization of the anode material of the retired lithium-ion battery. The method organically integrates double pre-lithium, high-temperature calcination and carbon coating processes, and repairs the damaged graphite anode material internal structure and surface structure at the same time.

In order to solve the above-mentioned technical problems, the present invention adopts the following technical solutions:

(1) Using the graphite mixture obtained from the dismantling of decommissioned batteries from different sources as the raw material, the decommissioned graphite powder and the copper foil are separated by the current collector stripping pretreatment;

(2) The decommissioned graphite powder obtained in step (1) is screened and classified by an electric vibrating screen machine, and the intermediate particle size sample obtained by the classification is recovered to obtain a crude graphite product;

(3) after uniformly mixing the obtained crude graphite product with the fine lithium carbonate powder, pre-lithiated graphite is obtained;

(4) calcining in an inert atmosphere, and cooling to room temperature after calcination to obtain double prelithiated graphite;

(5) The carbon source material is mixed with the double pre-lithiated graphite obtained in step (4), followed by carbon coating, and then carbonization of the coating layer is performed in a rotary furnace to obtain a regenerated graphite negative electrode material.

Preferably, the current collector stripping pretreatment in step (1) adopts one or more of pulverization-gas sorting, calcination, and solvent leaching.

Preferably, the screen mesh of the electric vibrating screen machine in step (2) is 300-2500 mesh.

Preferably, the particle size of the crude graphite product in step (2) is 5-50 microns.

Preferably, the inert atmosphere described in step (4) and step (5) is one or more of nitrogen gas, argon gas, and the like.

Preferably, in step (3), the particle size of the lithium carbonate fine powder is 100 nm-1000 nm, and the addition amount is 0.5%-10% of the mass of the crude graphite product.

Preferably, in the calcination process described in step (4), the temperature is first heated to 900-1200°C at a heating rate of 0.5-10°C/min, the calcination temperature is maintained for 1h-12h, and then slowly lowered to room temperature at a rate of 0.5-10°C/min .

Preferably, the carbon source in step (5) is one of coal pitch, petroleum pitch, emulsified pitch, citric acid, phenolic resin, chitosan, sucrose, polyvinyl alcohol, polyacryl alcohol or polyaniline or A variety of carbon sources are added in an amount of 0.1%-5% of the quality of the secondary treated graphite.

Preferably, the rotational speed of the rotary kiln described in step (5) is 25-150 r/min, and the calcination process in this rotary kiln is completed in two stages: the temperature of the first stage calcination process is 300-600°C, and the holding time is 300-600°C. The calcination temperature of the second stage is 900-1300°C, and the calcination time is 0.5h-12h; the heating rate in the calcination process is 1-10°C/min.

Preferably, the material mixing methods in step (3) and step (5) are one or more of mechanical mixing, pneumatic mixing, and impulse mixing.

Compared with the prior art, the beneficial effects of the present invention are:

(1) In the present invention, on the one hand, lithium carbonate fine powder and graphite are used to uniformly disperse in the mixture for pre-lithiation; , to achieve double pre-lithium;

(2) Part of the lithium oxide produced during the calcination of lithium carbonate in this method becomes a flux, and the surface tension generated by the shrinkage of lithium oxide during the slow cooling process will aggregate the broken and small-sized graphite together, thereby increasing the graphite particle size and particle size. Reducing the specific surface area provides the necessary conditions;

(3) In this method, the internal defects of graphite can be effectively repaired during the two high-temperature heat treatments, and the degree of graphitization can also be effectively improved;

(4) This method uses carbon source to coat the graphite surface, which can effectively improve and reconstruct its surface electron/ion transport channels, reduce the generation of SEI, and finally realize the high-value utilization of anode materials for retired lithium-ion batteries;

(5) The preparation process of the present invention is simple and easy to implement, and it is easy to realize large-scale production. The whole double pre-lithiation process is very simple, and the prepared regenerated negative electrode material has good consistency, which can effectively improve the first charge-discharge efficiency of regenerated graphite, and is worthy of market promotion.

Description of drawings

Fig. 1 is the process flow diagram of the recycling method of waste battery anode graphite according to the present invention.

Detailed ways

In order to facilitate understanding of the present invention, the present invention will be clearly and completely described below with reference to the specification and preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

Example 1

The recovery and regeneration method of the negative electrode graphite of the waste battery of the present embodiment, the steps are as follows:

(1) The negative pole pieces obtained from the dismantling of waste lithium-ion batteries of Company A are used as raw materials, and are processed by hammer crusher and universal crusher respectively. The processing time is 10min and 15min respectively, and the obtained fragments are screened. , so that the retired graphite and copper foil are separated to obtain crude graphite products.

(2) The nanoscale lithium carbonate powder (200nm) and the crude graphite product are fully ball-milled and dispersed in a planetary ball mill at a mass ratio of 1:50 to obtain a pre-lithiated graphite material with good dispersibility.

(3) The pre-lithiated graphite was calcined, firstly rising to 500°C at a heating rate of 5°C/min, then slowly rising to 1100°C at a heating rate of 1°C/min, holding time for 5h, and then heating at 1°C/min. min slowly cooled to 50 °C to obtain double pre-lithiated graphite.

(4) Mix the coal pitch and double prelithiated graphite uniformly by ball milling at a mass ratio of 1:100. In a rotary furnace of 100 r/min, with a heating rate of 1 °C/min, first keep it at 500 °C for 2 h, and then Incubate at 1200 °C for 1 h to obtain a regenerated graphite anode material.

Example 2

The recovery and regeneration method of the negative electrode graphite of the waste battery of the present embodiment, the steps are as follows:

(1) Using the negative electrode pieces obtained from the dismantling of the waste lithium-ion batteries of Company A as raw materials, weigh 1 part of the recovered negative electrode pieces and add 9 parts of pure water to it, and mechanically stir at 300 r/min at 60°C for 3 hours. After leaching, the leaching mixture is dried and then added to an automatic vibrating screen machine for classification to obtain a crude graphite product.

(2) The nanoscale lithium carbonate powder (200nm) and the crude graphite product are fully stirred and dispersed in a mixer according to a mass ratio of 1:30 to obtain a pre-lithiated graphite material with good dispersibility.

(3) The pre-lithiated graphite was calcined, firstly rising to 500°C at a heating rate of 5°C/min, then slowly rising to 950°C at a heating rate of 1°C/min, holding time for 12h, and then heating at 2°C/min. min slowly cooled to 50 °C to obtain double pre-lithiated graphite.

(4) Mix the phenolic resin and double pre-lithiated graphite uniformly according to the mass ratio of 3:97. In a rotary furnace of 120 r/min, at a heating rate of 2 °C/min, first keep it at 600 °C for 2 h, and then heat it at 600 °C for 2 hours. Heat preservation at 1000 °C for 1 h to obtain a regenerated graphite negative electrode material.

Example 3

The recovery and regeneration method of the negative electrode graphite of the waste battery of the present embodiment, the steps are as follows:

(1) The negative pole pieces obtained from the dismantling of waste lithium-ion batteries of Company A are used as raw materials, and are processed by hammer crusher and universal crusher respectively. The processing time is 15min and 20min respectively, and the obtained scraps are screened , so that the retired graphite and copper foil are separated to obtain crude graphite products.

(2) The nanoscale lithium carbonate powder (200nm) and the crude graphite product are fully stirred and dispersed in a ball mill according to a mass ratio of 1:50 to obtain a prelithiated graphite material with good dispersibility.

(3) The pre-lithiated graphite was calcined, firstly rising to 600°C at a heating rate of 5°C/min, then slowly rising to 1050°C at a heating rate of 1°C/min, holding time for 9h, and then heating at 1°C/min. Min slowly cooled to 50 °C to obtain double prelithiated graphite.

(4) Mix petroleum pitch and double pre-lithiated graphite uniformly in a mixer according to a mass ratio of 1:50. In a rotary furnace of 150r/min, at a heating rate of 1°C/min, first keep the temperature at 300°C 2h, and then kept at 1100°C for 2h to obtain a regenerated graphite anode material.

Example 4

The recovery and regeneration method of the negative electrode graphite of the waste battery of the present embodiment, the steps are as follows:

(1) Using the negative electrode piece obtained from the dismantling of the waste lithium ion battery of Company A as the raw material, weigh 1 part of the recovered negative electrode piece and add 8 parts of pure water to it, and mechanically stir it at 300r/min at 70°C for 1.5h The leaching is carried out, and the leaching mixture is dried and then added to an automatic vibrating screen machine for classification to obtain a crude graphite product.

(2) The nanoscale lithium carbonate powder (200nm) and the crude graphite product are fully stirred and dispersed in a mixer according to a mass ratio of 1:40 to obtain a pre-lithiated graphite material with good dispersibility.

(3) The pre-lithiated graphite was calcined, firstly rising to 600°C at a heating rate of 5°C/min, then slowly rising to 1100°C at a heating rate of 1°C/min, holding time for 12h, and then heating at 2°C/min. min slowly cooled to 50 °C to obtain double pre-lithiated graphite.

(4) Mix citric acid and double pre-lithiated graphite uniformly according to the mass ratio of 3:97. In a rotary furnace of 100 r/min, at a heating rate of 5 °C/min, first keep at 450 °C for 1 h, and then in a rotary furnace of 100 r/min. Heat preservation at 1100°C for 1 h to obtain a regenerated graphite anode material.

Example 5

The recovery and regeneration method of the negative electrode graphite of the waste battery of the present embodiment, the steps are as follows:

(1) The negative pole pieces obtained from the dismantling of waste lithium-ion batteries of Company A are used as raw materials, and are processed by hammer crusher and universal crusher respectively. The processing time is 8min and 15min respectively, and the obtained scraps are screened , so that the retired graphite and copper foil are separated to obtain crude graphite products.

(2) The nanoscale lithium carbonate powder (200nm) and the crude graphite product are fully stirred and dispersed in a ball mill according to a mass ratio of 1:35 to obtain a prelithiated graphite material with good dispersibility.

(3) The pre-lithiated graphite was calcined, firstly rising to 500°C at a heating rate of 5°C/min, then rising to 1200°C at a heating rate of 1°C/min, holding time for 5h, and then heating at 1°C/min The temperature was lowered to 50°C to obtain double prelithiated graphite.

(4) Mix sucrose and double pre-lithiated graphite in a mixer according to a mass ratio of 1:50, and in a rotary furnace of 120 r/min, at a heating rate of 10 °C/min, first keep the temperature at 400 °C 1h, and then kept at 1100°C for 3h to obtain the regenerated graphite anode material.

Comparative Example 1

Comparative Example The negative pole pieces obtained from the dismantling of waste lithium-ion batteries of Company A were used as raw materials, and were treated with a hammer crusher and a universal pulverizer respectively. The treatment time was 10min and 15min respectively. The decommissioned graphite is separated from the copper foil to obtain a crude graphite product.

The crude graphite is calcined, firstly rising to 500°C at a heating rate of 5°C/min to convert the organic components in the retired graphite into amorphous carbon, and then rising to 1100°C at a heating rate of 1°C/min, holding time for 5 h, and then cooled to 50 °C at 1 °C/min to obtain pre-lithiated graphite.

Then, the coal pitch and prelithiated graphite were uniformly ball-milled at a mass ratio of 1:100. In a rotary furnace of 100 r/min, at a heating rate of 1 °C/min, the temperature was first kept at 500 °C for 2 h, and then at 1200 °C. After holding for 1 h, a regenerated single-shot pre-lithiated graphite negative electrode material was obtained.

Comparative example 2~5

The only difference from Examples 2 to 5 is that the pre-lithiation in which the fine lithium carbonate powder and the crude graphite product are uniformly dispersed is not performed (the steps are the same as those in Comparative Example 1).

The following table is the particle size test result and electrochemical performance table of the double pre-lithiated regenerated graphite prepared in the above-mentioned Examples 1-5 and the single-pre-lithiated graphite negative material prepared in the Comparative Examples 1-5.

As can be seen from the above table, the particle size of the double prelithiated regenerated graphite prepared in the embodiment of the present invention is larger than that of the graphite material prepared in the comparative example, and the corresponding first discharge specific capacity and first charge and discharge efficiency are also significantly higher. The single-shot prelithiated graphite anode material prepared in the comparative example.

The foregoing has shown and described the basic principles and main features of the present invention, as well as the advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above-mentioned embodiments, and the descriptions in the above-mentioned embodiments and the description are only to illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have Various changes and modifications fall within the scope of the claimed invention. The claimed scope of the present invention is defined by the appended claims and their equivalents.

Claims (9)

1. a recovery and regeneration method of waste battery anode graphite, is characterized in that comprising the following steps: (1) Using the negative electrode sheet obtained from the dismantling of the decommissioned battery as the raw material, the decommissioned graphite powder and the copper foil are separated by the current collector stripping pretreatment; (2) The decommissioned graphite powder obtained in step (1) is screened and classified by an electric vibrating screen machine, and the intermediate particle size sample obtained by the classification is recovered to obtain a crude graphite product; (3) after uniformly mixing the obtained crude graphite product with the fine lithium carbonate powder, pre-lithiated graphite is obtained; (4) calcining the pre-lithiated graphite in an inert atmosphere, and cooling to room temperature after calcination to obtain double pre-lithiated graphite; (5) The carbon source material is mixed with the double pre-lithiated graphite obtained in step (4), and then carbon coating is performed, and then the coating layer is carbonized in an inert atmosphere of a rotary furnace to obtain a regenerated graphite negative electrode material. 2 . The method for recycling and regenerating negative electrode graphite of waste batteries according to claim 1 , wherein the current collector stripping pretreatment in step (1) adopts one of pulverization-gas sorting, calcination, and solvent leaching. 3 . or more. 3. The method for recycling and regenerating the negative electrode graphite of waste batteries according to claim 1, characterized in that: in step (2), the screen mesh of the electric vibrating screen machine is 300-2500 mesh; the particle size of the coarse graphite product is 5-50 microns. 4. The method for recycling and regenerating negative electrode graphite of waste batteries according to claim 1, characterized in that: the granularity of the lithium carbonate fine powder described in the step (3) is 100-1000 nm, and the addition amount is the mass of the crude graphite product of 0.5%-10%. 5 . The method for recycling and regenerating negative electrode graphite of waste batteries according to claim 1 , wherein the calcination process described in step (4) is first heated to 900-1200° C. at a heating rate of 0.5-10° C./min, 6 . The calcination temperature was maintained for 1h-12h, and then lowered to room temperature at 0.5-10°C/min. 6 . The method for recycling and regenerating negative electrode graphite of waste batteries according to claim 1 , wherein the inert atmosphere in step (4) and step (5) is one or more of nitrogen and argon. 7 . 7 . The method for recycling and regenerating negative electrode graphite of waste batteries according to claim 1 , wherein the carbon source material described in step (5) is coal pitch, petroleum pitch, emulsified pitch, citric acid, phenolic resin, shell One or more of polysaccharide, sucrose, polyvinyl alcohol, polyvinyl alcohol or polyaniline, and the added amount of carbon source material is 0.1%-5% of the mass of the double prelithiated graphite. 8 . The method for recycling and regenerating the negative electrode graphite of waste batteries according to claim 1 , wherein the rotating speed of the rotary kiln described in step (5) is 25-150 r/min, and the calcination process in the rotary kiln is divided into: 9 . Two stages are completed: the calcination temperature of the first stage is 300-600°C, and the holding time is 0.5-2.5h; the calcination temperature of the second stage is 900-1300°C, and the calcination time is 0.5h-12h; the heating rate in the calcination process is 1 -10°C/min. 9 . The method for recycling and regenerating negative electrode graphite of waste batteries according to claim 1 , wherein the material mixing method in step (3) and step (5) is one of mechanical mixing, pneumatic mixing, and impulse mixing. 10 . one or more.

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