Waste photovoltaic graphite-based recycled graphite anode active materials, their preparation and application

Abstract

This invention belongs to the field of waste photovoltaic graphite material recycling, specifically relating to a method for preparing a recycled graphite anode active material based on waste photovoltaic graphite. The method involves crushing and sieving graphite blocks from waste photovoltaic materials to obtain graphite powder. The graphite powder is then subjected to a two-stage gradient gasification process to obtain pretreated graphite. The pretreated graphite is dispersed in water and slurried, followed by the addition of a modifier with an A-structure and ultrasonic-assisted modification. Solid-liquid separation and drying are then performed to obtain modified graphite. The modified graphite, boron-containing modifier, and carbon source are dispersed in a solvent and then spray-granulated to obtain particles. These spray-granules are then carbonized and carbon-coated to obtain the aforementioned recycled graphite anode active material based on waste photovoltaic graphite. This invention also includes the active material obtained by the method and its applications. This invention is the first to achieve the regeneration of high-electrochemical-performance active materials from waste photovoltaic graphite.

Description

Technical Field

[0001] This invention relates to the field of waste photovoltaic material recycling, specifically to the field of recycled graphite anode active materials from waste photovoltaic graphite materials. Background Technology

[0002] With the rise of the photovoltaic industry, the volume of photovoltaic waste is increasing. Photovoltaic waste mainly includes silicon materials, silicon carbide materials, and graphite. However, current technologies primarily focus on the recycling of silicon-based materials.

[0003] For example, Chinese patent document CN117263189A discloses a method for preparing silicon-carbon composite material using photovoltaic diced wet silicon powder. The steps are as follows: purifying photovoltaic diced wet silicon powder by sulfation roasting to obtain purified silicon powder; purifying waste power battery graphite anode by sulfuric acid and hydrogen peroxide to obtain purified graphite; and ball milling the purified silicon powder and purified graphite powder at high energy to obtain silicon-carbon composite material.

[0004] For example, Chinese patent document CN104112850A discloses a method for preparing lithium-ion battery anode materials based on high-purity silicon waste from the photovoltaic industry. Specifically, it involves a series of treatments, such as purifying, etching, and surface modifying the high-purity silicon waste generated during the silicon wafer cutting process in the photovoltaic industry, and mixing the treated silicon with graphite anode materials in a certain proportion, to obtain micron or submicron silicon or silicon-graphite hybrid materials with controllable structure and composition.

[0005] For example, Chinese patent document CN117096329A discloses a method for preparing low-cost silicon-graphite anode active material and its application. First, photovoltaic silicon waste is used as raw material, copper alloy additives are added, and alloying treatment is carried out to prepare porous silicon material. Then, asphalt is added and dry ball milling is performed for modification. Next, high-temperature carbonization is carried out to form amorphous carbon-coated modified porous silicon material. Then, it is dispersed and composited with nano-graphite to obtain modified silicon-graphite anode active material in which modified porous silicon is uniformly doped on sheet graphite.

[0006] In summary, the recycling of photovoltaic waste mainly focuses on the recycling and regeneration of silicon-based materials. There are few methods for recycling graphite waste, which is widely present in the photovoltaic industry. In particular, the recycling of graphite anode active materials from waste photovoltaic graphite is still a blank in the industry. Summary of the Invention

[0007] To fill the industry gap in recycled graphite anode active materials from waste photovoltaic graphite materials, the primary objective of this invention is to provide a method for preparing recycled graphite anode active materials based on waste photovoltaic graphite, aiming to obtain graphite anode active materials with high electrochemical performance based on the recycling of waste photovoltaic graphite materials.

[0008] The second objective of this invention is to provide a recycled graphite anode active material based on waste photovoltaic graphite prepared by the aforementioned method and its application in batteries.

[0009] A third objective of this invention is to provide a battery, its negative electrode, and a negative electrode material.

[0010] Waste photovoltaic graphite is primarily isostatically pressed graphite waste, unlike other waste graphite such as waste battery graphite. It exhibits significantly higher tap density, exceptionally tight interlayer bonding, and greater difficulty in impurity removal. Furthermore, its intrinsic physicochemical structure is difficult to adapt to battery application requirements, and its structure may be further damaged under harsh impurity removal conditions. This makes it difficult to regenerate into graphite anode active materials, particularly to obtain graphite active materials that maintain excellent fast-charging performance under high areal loads. Due to these technical challenges, there is currently no solution in the industry for regenerating graphite anode materials from waste photovoltaic graphite. To address this problem, this invention, after in-depth research, provides the following improvement:

[0011] A method for preparing a recycled graphite anode active material based on waste photovoltaic graphite, comprising the following steps:

[0012] Step (1):

[0013] The graphite bulk material from waste photovoltaic materials is crushed and screened to obtain graphite powder. The graphite powder is then subjected to a two-stage gradient gasification treatment to obtain pretreated graphite.

[0014] The two-stage gradient gas conversion process includes a first-stage heat preservation process at atmosphere A and temperature T1, and a second-stage heat preservation process at temperature T2 after gas conversion to atmosphere B; atmosphere A is an oxidizing atmosphere, and temperature T1 is 200-350℃; atmosphere B is an atmosphere containing at least one of F source component and Cl source component, wherein T2 is 350-650℃, and T2 is greater than T1;

[0015] Step (2):

[0016] Pretreated graphite was dispersed in water and slurried, then a modifier of structure A was added, and the modification was carried out under ultrasonic assistance. After solid-liquid separation and drying, modified graphite was obtained.

[0017]

[0018] In Formula A, X is C and Y is S; or X is S and Y is O; R is a halogen, a C1-C6 alkyl group, a substituted alkyl group, or an alkylamino group.

[0019] Step (3):

[0020] Modified graphite, boron-containing modifier, and carbon source are dispersed in a solvent and then spray-granulated to obtain particles.

[0021] Step (4):

[0022] The particles from step (3) are carbonized and then coated with carbon to obtain the waste photovoltaic graphite-based recycled graphite anode active material.

[0023] To address the challenge of regenerating photovoltaic waste graphite into graphite anode materials due to its inherent structural characteristics, this invention innovatively pre-treats photovoltaic waste graphite under the aforementioned gas gradient conditions. This is combined with modification using Formula A, spray treatment assisted by a boron-containing modifier, and subsequent carbonization and carbon coating processes. This synergistic approach unexpectedly overcomes the limitations of the physicochemical characteristics of photovoltaic waste graphite, selectively removing harmful electrochemical impurities. Furthermore, it optimizes and repairs its physicochemical structure, making it suitable for battery applications, particularly under high surface load conditions. This improves the liquid absorption and electrochemical performance of the recycled graphite, especially its electrochemical performance under high surface load conditions, particularly its fast-charging performance.

[0024] In this invention, the graphite bulk material derived from waste photovoltaic materials originates from isostatically pressed graphite waste from the photovoltaic industry. Optionally, the fixed carbon content of the isostatically pressed graphite waste is above 90 wt%, for example, 92–98 wt%. The degree of graphitization can be 85–95%.

[0025] In this invention, the D50 of the crushed and sieved graphite powder is 3-20 μm, and can be further 5-15 μm.

[0026] In this invention, the two-stage gasification treatment and the combined control of atmosphere and temperature during the process help to overcome the physicochemical characteristics of waste photovoltaic materials, facilitate combination with other processes to selectively remove harmful electrochemical impurities, and also help to adjust their physicochemical structure to adapt them to battery applications, especially high surface load applications.

[0027] In this invention, the atmosphere A is a gas containing at least one gas a selected from air, oxygen, and ozone.

[0028] Preferably, the atmosphere A also contains a dilution gas; the dilution gas includes at least one of nitrogen and an inert gas.

[0029] Preferably, in the atmosphere A, the content of gas a is 0.5v% or more. For example, when gas a is air, the volume content of gas a in atmosphere A can be 50% to 100%. When gas a is oxygen, the volume content of gas a in atmosphere A can be 10% to 50%. When gas a is ozone, the volume content of gas a in atmosphere A can be 0.5% to 10%.

[0030] In this invention, the temperature of the first insulation stage can be 230-320°C, and more specifically 250-300°C.

[0031] Preferably, the first stage of heat preservation treatment lasts for 1 to 6 hours, and more preferably for 2 to 4 hours.

[0032] In this invention, after the first stage of heat preservation treatment, the temperature of the system is raised to temperature T2, and then the atmosphere is changed to atmosphere B for the second stage of heat preservation treatment.

[0033] In this invention, in atmosphere B, the F-containing source component and the Cl-containing source component are gaseous components containing their respective elements.

[0034] In this invention, the atmosphere B is preferably an atmosphere containing F source components. Research in this invention shows that using this preferred atmosphere allows for further synergistic integration with other processes, helping to better meet the requirements of recycled graphite active materials from photovoltaic waste graphite, and facilitating the acquisition of graphite active materials with superior performance.

[0035] Preferably, the F-containing source component includes at least one of fluorine gas, carbon tetrafluoride, nitrogen trifluoride, and sulfur hexafluoride.

[0036] In this invention, atmosphere B may also contain a dilution gas, which may include, for example, at least one of nitrogen or an inert gas.

[0037] In this invention, the atmosphere B contains 0.01–0.5 vol% of the F source component, which can be further 0.1–0.3 vol%.

[0038] In this invention, the temperature of the second insulation stage can be 380-580℃, and more specifically 400-550℃.

[0039] Preferably, the second insulation time is 1 to 10 hours, and more preferably 3 to 6 hours.

[0040] In this invention, in step (2), the liquid-solid ratio of pretreated graphite and water is 1 to 10 ml / g, and can be further 3 to 6 ml / g.

[0041] Preferably, the modifier of formula A includes formula A-1 and formula A-2;

[0042]

[0043] In formula A-1, R is Cl, trifluoromethyl, dialkylamino, or tert-butyl.

[0044] In formula A-2, R is a dialkylamino group.

[0045] In this invention, the modified agent A, which combines the formulas A-1 and A-2, can further achieve synergy. It can further adapt to the characteristics of photovoltaic waste graphite and endow the negative electrode material of the photovoltaic waste graphite with battery-compatible physicochemical characteristics, thereby further enhancing the electrochemical performance of the recycled graphite active material.

[0046] In this invention, the weight ratio of Formula A-1 to Formula A-2 in the modifier of Formula A is 1:0.1 to 10, and can be further 1:0.5 to 2.

[0047] Preferably, the weight ratio of graphite powder to modifier of formula A is 100:0.2 to 4, and more preferably it is 100:1 to 2.

[0048] Preferably, the ultrasonic power is above 100W, and more preferably 100-600W.

[0049] Preferably, the modification treatment time is 10 to 30 minutes.

[0050] In this invention, the boron-containing modifier includes one or more of boron oxide, boric acid, phenylboronic acid, potassium trifluoroborate, methylboronic acid, butylboronic acid, lithium metaborate, 2,4-dichlorophenylboronic acid, sodium tetraphenylborate, lithium tetraborate, triethyl borate, and potassium tetrafluoroborate.

[0051] Preferably, the mass ratio of modified graphite to boron-containing modifier is 100:0.5-5; more preferably, it is 100:1-2.

[0052] Preferably, the carbon source includes one or more of citric acid, sucrose, glucose, polyethylene glycol, etc.

[0053] Preferably, the mass ratio of modified graphite to carbon source is 100:5 to 18, and more preferably 100:10 to 15.

[0054] Preferably, the solvent is one or more of water, ethanol, tetrahydrofuran, toluene, and acetone.

[0055] There are no special requirements for the particle size after spraying, as long as it meets the requirements of battery application, for example, it can be 5 to 18 μm.

[0056] In this invention, modified graphite, carbon source, and boron-containing modifier are combined and further spray-treated to solve the problems of large polarization of regenerated active materials caused by large particle sharpness and unsatisfactory performance caused by high pressure compaction of electrode sheets in the stage of photovoltaic waste graphite regeneration.

[0057] In this invention, the sprayed material is subjected to conventional carbonization and carbon coating treatment to obtain recycled graphite active material.

[0058] As an example of an implementation scheme, in step (4), the carbonization process includes low-temperature carbonization and high-temperature carbonization, wherein the temperature of low-temperature carbonization is 350-500℃; the holding time at the low-temperature carbonization temperature is 4-8h; the temperature of the high-temperature carbonization process is 900-1500℃; and the high-temperature carbonization time is 4-8h.

[0059] In this invention, the carbon coating process can be achieved using conventional solid-phase, liquid-phase, and gas-phase carbon coating methods. Specifically, the carbon coating method used in this invention is gas-phase carbon deposition.

[0060] The aforementioned vapor-phase carbon deposition method is, for example, to introduce a carbon source containing atomization or vaporization into a temperature system that maintains high-temperature carbonization, and perform heat-insulating carbon coating treatment.

[0061] A preferred step (4) of the present invention is as follows: the particles from step (3) are pre-carbonized at low temperature in a protective atmosphere, followed by high temperature carbonization, and then the atmosphere is switched to a carbon source atmosphere under the high temperature carbonization conditions to perform gas phase carbon deposition treatment, thereby obtaining the desired product.

[0062] The carbon source atmosphere can be an atmosphere containing at least one carbon source gas selected from alkanes, alkenes, alkynes, and aromatics, and can further be one or more of methane, ethane, acetylene, benzene, etc.

[0063] In this invention, the carbon source atmosphere may also contain at least one of hydrogen and dilution gas.

[0064] Furthermore, the carbon source atmosphere is a mixture of carbon source gas and hydrogen in a volume ratio of 1:1 to 5.

[0065] In this invention, the carbon coating (carbon deposition) time can be 1 to 3 hours, and more specifically 1.5 to 2 hours.

[0066] In this invention, the protective atmosphere includes at least one of nitrogen and an inert gas.

[0067] The present invention also provides a recycled graphite anode active material based on waste photovoltaic graphite prepared by the preparation method described above.

[0068] The preparation method described in this invention can endow the prepared recycled material with special physicochemical characteristics, and the recycled material with these characteristics can unexpectedly exhibit excellent electrochemical performance, especially significantly improve its electrochemical performance under high surface loading.

[0069] The present invention also provides an application of the aforementioned waste photovoltaic graphite-based recycled graphite anode active material, which is used as an anode active material to prepare alkali metal ion batteries.

[0070] In this invention, the alkali metal ion battery includes a lithium-ion battery or a sodium-ion battery.

[0071] In this invention, the alkali metal ion battery, apart from the negative electrode active material described in this invention, can have other conventional components and parts.

[0072] The present invention also provides a negative electrode for an alkali metal ion battery, comprising a current collector and a negative electrode material composited thereon, wherein the negative electrode material comprises a negative electrode active material, a binder and a conductive agent, and the negative electrode active material comprises a waste photovoltaic graphite-based recycled graphite negative electrode active material prepared by the preparation method described in the present invention.

[0073] In this invention, the negative electrode, apart from containing the waste photovoltaic graphite-based recycled graphite negative electrode active material described in this invention, can have other conventional components and parts.

[0074] For example, in the negative electrode active material of the present invention, the content of the waste photovoltaic graphite-based recycled graphite negative electrode active material is above 80 wt.%; further, it can be a waste photovoltaic graphite-based recycled graphite negative electrode active material.

[0075] In this invention, the binder and conductive agent in the negative electrode material are both conventional in the field of ion batteries. Furthermore, the content of the negative electrode active material in the negative electrode material can be 80–95 wt%.

[0076] In this invention, the electrode sheet compaction density of the recycled graphite anode active material based on waste photovoltaic graphite is 1.8–2 g / cm³. 3 Furthermore, it can be 1.82–1.89 g / cm³. 3 The negative electrode described in this invention, thanks to the use of the recycled graphite negative electrode active material based on waste photovoltaic graphite, can still exhibit excellent fast-charging performance under high areal load.

[0077] The present invention also provides an alkali metal ion battery comprising the negative electrode described herein.

[0078] The battery described in this invention, apart from containing the waste photovoltaic graphite-based recycled graphite anode active material described in this invention, may use conventional components and parts.

[0079] Beneficial effects

[0080] This invention innovatively pre-treats photovoltaic waste graphite under the aforementioned gas gradient conditions, then combines it with modification using Formula A, spray treatment assisted by a boron-containing modifier, and subsequent carbonization and carbon coating processes. This combination unexpectedly achieves synergy, overcoming the physicochemical characteristics of photovoltaic waste graphite, selectively removing electrochemically harmful impurities. Furthermore, it optimizes and repairs its physicochemical structure, making it suitable for battery applications, especially for applications under high surface load conditions, thereby improving the performance of recycled graphite, particularly its electrochemical performance under high surface load conditions. Attached Figure Description

[0081] Figure 1 This is a SEM image of the regenerated graphite active material from Example 1. Detailed Implementation

[0082] The following examples illustrate the specific steps of the present invention. It should be understood that these examples are merely illustrative and not intended to limit the scope of the invention in any way. Various processes and methods not described in detail in this invention are conventional methods known in the art.

[0083] The aforementioned blocky graphite refers to isostatically pressed graphite waste from the photovoltaic industry. The raw material has a fixed carbon content of 94.2% and a graphitization degree of 90.4%.

[0084] Example 1

[0085] Step 1: Crush the photovoltaic waste block graphite and sieve it into graphite powder (D50 is 5.4±0.1μm);

[0086] Step 2: Place the powder from Step 1 in an atmosphere furnace. First, perform the first stage of heat preservation treatment at atmosphere A (air) and temperature T1 (250℃) (heat preservation time t1 is 3h). Then, heat the powder to temperature T2 (400℃) at a heating rate of 10℃ / min. After that, switch the atmosphere to atmosphere B (0.1v% F2-Ar mixture) and perform the second stage of heat preservation (heat preservation time t2 is 4h). Then, perform air jet milling and sieving to obtain pretreated graphite.

[0087] Step 3: The obtained pretreated graphite powder is slurried with water (liquid-solid ratio of 5ml / g), then formula A (in this case formula a, which is a compound of formula A-1 with R being trifluoromethyl, and formula A is the pretreated graphite powder weight ratio of 1:100) is added, followed by ultrasonic treatment (100W) for 15min, then solid-liquid separation, water washing, drying, and dispersion to obtain modified graphite;

[0088] Step 4: Mix the boron compound (boron oxide), carbon source (sucrose), and the modified graphite above in a weight ratio of 1:10:100, disperse them in water (liquid-solid ratio of 5 ml / g), and perform spray granulation to obtain graphite spray particles (particle size of 7±1 μm).

[0089] Step 5:

[0090] Graphite spray particles were placed in an atmosphere furnace and pre-carbonized at a low temperature of 400±20℃ (marked as T3) for 6 hours in an Ar atmosphere. Then, they were carbonized at a high temperature of 1000±20℃ (marked as T4) for 6 hours. The atmosphere was then switched to a mixed atmosphere of methane and hydrogen (volume ratio 1:4), and the deposition was carried out at this temperature for 2 hours. The furnace was then cooled to obtain the recycled graphite material.

[0091] Example 2

[0092] Compared with Example 1, the only difference is that the conditions in step 1 are changed, that is, the fixed carbon content of the waste photovoltaic graphite is 93.8% and the degree of graphitization is 89.2%. After crushing, it is sieved into graphite powder (D50 is 12.5±0.1μm). Other operations and parameters are the same as in Example 1.

[0093] Example 3

[0094] Compared to Example 1, the only difference is that the conditions in step 2 are changed, and the experimental groups are as follows:

[0095] Group A: Atmosphere A is a 30v% oxygen-argon mixture, temperature T1 is 300℃, and t1 is 2h; Atmosphere B is a 0.3v% F2-Ar atmosphere, temperature T2 is 550℃, and time t2 is 3h.

[0096] Group B: Replace F2 in atmosphere B with an equal volume of Cl2;

[0097] All other operations and parameters are the same as in Example 1.

[0098] Example 4

[0099] Compared to Example 1, the only difference is that the conditions in step 3 were changed, and the experimental groups were as follows:

[0100] Group A: Formula A is a compound of formula b, which is a compound of formula A-2 where R is dimethylamino;

[0101] Group B: Formula A is a complex of formulas a and b in a weight ratio of 1:1;

[0102] Group C: The obtained pretreated graphite powder was slurried with water (liquid-solid ratio of 6ml / g), then Formula A (formula a in this case, formula A is the weight ratio of pretreated graphite powder of 2:100) was added, followed by ultrasonic treatment (200W) for 10min, then solid-liquid separation, water washing, drying and dispersing to obtain modified graphite.

[0103] All other operations and parameters are the same as in Example 1.

[0104] Example 5

[0105] Compared with Example 1, the only difference is that the operation of step 4 is changed. Specifically, the boron compound (boric acid), carbon source (glucose), and the modified graphite are mixed evenly in a weight ratio of 1.5:15:100, dispersed in water (liquid-solid ratio of 8 ml / g), and sprayed to obtain graphite spray particles. All other operations and parameters are the same as in Example 1.

[0106] Example 6

[0107] Compared with Example 1, the only difference is that the conditions in step 5 are changed. Specifically, the low-temperature carbonization temperature is 450±20℃ and the carbonization time is 5h, the high-temperature carbonization temperature is 1100±20℃ and the high-temperature carbonization time is 5h; the mixed atmosphere in the deposition stage is acetylene-hydrogen (volume ratio of 1:1) and the deposition time is 1.5h. All other operations and parameters are the same as in Example 1.

[0108] Comparative Example 1

[0109] Compared with Example 1, the only difference is that atmosphere A is replaced with Ar, and all other operations and parameters are the same as in Example 1.

[0110] Comparative Example 2

[0111] Compared with Example 1, the only difference is that atmosphere B is replaced with Ar, while the operation and parameters are the same as in Example 1.

[0112] Comparative Example 3

[0113] Compared with Example 1, the only difference is that in step 2, the order of the first heat preservation and the second heat preservation is changed. That is, the powder in step 1 is heat-preserved in atmosphere B and temperature T2 for t2, then cooled to temperature T1, and then the atmosphere is switched to atmosphere A for heat preservation t1. The other operations and parameters are the same as in Example 1.

[0114] Comparative Example 4

[0115] Compared with Example 1, the only difference is that in step 3, ultrasound assistance is not performed; all other operations and parameters are the same as in Example 1.

[0116] Comparative Example 5

[0117] Compared with Example 1, the only difference is that in step 3, formula A is not added, while other operations and parameters are the same as in Example 1.

[0118] Comparative Example 6

[0119] Compared with Example 1, the only difference is that in step 4, no boride is added; all other operations and parameters are the same as in Example 1.

[0120] Comparative Example 7

[0121] Compared with Example 1, the only difference is that in step 4, the pulp is directly vacuum dried after slurrying without spraying. Other operations and parameters are the same as in Example 1.

[0122] III. Test:

[0123] 1. Electrochemical performance testing

[0124] The recycled graphite anode active material, binder (LA-133, CMC), and super carbon black from each case were uniformly mixed in a mass ratio of 92:3:3:2. Water was then added and stirred to form a uniform slurry. This slurry was coated onto copper foil and vacuum dried at 120℃ for 12 hours, yielding a graphite compaction density of 1.86±0.05 g / cm³. 3 The electrode sheet (graphite negative electrode sheet).

[0125] Using a CR2032 coin cell casing, with the obtained graphite negative electrode as the working electrode and a lithium metal sheet as the counter electrode, a Celgard 2400 separator, nickel foam as the current collector on the counter electrode side, and a solution of ethylene carbonate + dimethyl carbonate + diethyl carbonate (EC + DMC + DEC, 1:1:1) containing 1M LiPF6 as the electrolyte, the cells were assembled in a glove box under an argon atmosphere and then sealed using a sealing machine to obtain a coin cell lithium battery.

[0126] The battery cycle performance was tested at room temperature, with a test voltage range of 0.01V to 1.5V, and test rates of 0.1C and 6C. The results are shown in Table 1.

[0127] Table 1

[0128]

[0129] 2. Liquid absorption performance test

[0130] For each case, drop 50 μL of electrolyte (a solution of ethylene carbonate + dimethyl carbonate + diethyl carbonate (EC + DMC + DEC, 1:1:1) containing 1 M LiPF6) onto the graphite electrode and record the time it takes for the electrolyte to be completely absorbed by the electrode. The shorter the time, the better the electrolyte absorption performance of the electrode.

[0131] sample Aspiration time (min) Example 1 1.14 Example 2 1.09 Example 3A 1.11 Example 3B 1.24 Example 4A 1.09 Example 4B 1.00 Example 4C 1.10 Example 5 1.14 Example 6 1.07 Comparative Example 1 2.62 Comparative Example 2 2.24 Comparative Example 3 2.77 Comparative Example 4 2.66 Comparative Example 5 3.02 Comparative Example 6 2.75 Comparative Example 7 2.97

[0132] As shown in the table above, even under high compaction conditions, the electrode sheet prepared by the material obtained in the examples still has good liquid absorption performance, which can improve the overvoltage problem caused by high compaction density of traditional graphite anodes and meet the requirements of high-energy-density lithium-ion batteries for high-performance graphite anodes.

Claims

1. A method for preparing a recycled graphite anode active material based on waste photovoltaic graphite, characterized in that the steps include... include: Step (1): The graphite bulk material from waste photovoltaic materials is crushed and screened to obtain graphite powder. The graphite powder is then subjected to a two-stage gradient gasification treatment to obtain pretreated graphite. The two-stage gradient gas conversion process includes a first stage of heat preservation at a temperature of T1 under atmosphere A, and a second stage of heat preservation at a temperature of T2 after the gas is converted to atmosphere B. Atmosphere A is an oxidizing atmosphere with a temperature T1 of 200-350°C; Atmosphere B is an atmosphere containing at least one of an F source component and a Cl source component, wherein T2 is 350-650°C and T2 is greater than T1. Step (2): Pretreated graphite was dispersed in water and slurried, then a modifier of structure A was added, and the modification was carried out under ultrasonic assistance. After solid-liquid separation and drying, modified graphite was obtained. Formula A In Formula A, X is C and Y is S; or X is S and Y is O; R is a halogen, a C1-C6 alkyl group, a substituted alkyl group, or an alkylamino group. Step (3): Modified graphite, boron-containing modifier, and carbon source are dispersed in a solvent and then spray-granulated to obtain particles. Step (4): The particles from step (3) are carbonized and then coated with carbon to obtain the waste photovoltaic graphite-based recycled graphite anode active material.

2. The preparation method according to claim 1, characterized in that, The graphite block material derived from waste photovoltaic materials comes from isostatically pressed graphite waste from the photovoltaic industry.

3. The preparation method according to claim 2, characterized in that, The fixed carbon content of the isostatically pressed graphite waste is above 90 wt%; the degree of graphitization is 85-95%.

4. The preparation method according to claim 1, characterized in that, The D50 of the crushed and sieved graphite powder is 3–20 μm.

5. The preparation method according to claim 1, characterized in that, The atmosphere A is a gas containing at least one gas a selected from air, oxygen, and ozone.

6. The preparation method according to claim 5, characterized in that, The atmosphere A also contains a dilution gas; the dilution gas is an inert gas.

7. The preparation method according to claim 5, characterized in that, In the atmosphere A, the content of gas a is above 0.5v%.

8. The preparation method according to claim 1, characterized in that, The first stage of heat preservation treatment takes 1 to 6 hours.

9. The preparation method according to claim 1, characterized in that, Atmosphere B is an atmosphere containing F source components.

10. The preparation method according to claim 9, characterized in that, The F-containing source components include at least one of fluorine, carbon tetrafluoride, nitrogen trifluoride, and sulfur hexafluoride.

11. The preparation method according to claim 9, characterized in that, In the atmosphere B, the content of the F source component is 0.01 to 0.5 vol.

12. The preparation method according to claim 1, characterized in that, The second insulation period is 1 to 10 hours.

13. The preparation method according to claim 1, characterized in that, In step (2), the liquid-solid ratio of pretreated graphite and water is 1~10 ml / g.

14. The preparation method according to claim 1, characterized in that, The modified agent of formula A includes formula A-1 and formula A-2; Formula A-1 Formula A-2 In formula A-1, R is Cl, trifluoromethyl, dialkylamino, or tert-butyl. In formula A-2, R is a dialkylamino group.

15. The preparation method according to claim 14, characterized in that, In the modifier of formula A, the weight ratio of formula A-1 to formula A-2 is 1:0.1~10.

16. The preparation method according to claim 1, characterized in that, The weight ratio of graphite powder to modifier A is 100:0.2~4.

17. The preparation method according to claim 1, characterized in that, The power of ultrasound is above 100W.

18. The preparation method according to claim 17, characterized in that, The power of ultrasound is 100~600W.

19. The preparation method according to claim 1, characterized in that, The modification treatment time is 10 to 30 minutes.

20. The preparation method according to claim 1, characterized in that, The boron-containing modifier includes at least one of boron oxide, boric acid, phenylboronic acid, potassium trifluoroborate, methylboronic acid, butylboronic acid, lithium metaborate, 2,4-dichlorophenylboronic acid, sodium tetraphenylborate, dilithium tetraborate, triethyl borate, and potassium tetrafluoroborate.

21. The preparation method according to claim 1, characterized in that, The mass ratio of modified graphite to boron-containing modifier is 100:0.5~5.

22. The preparation method according to claim 1, characterized in that, The carbon source includes at least one of citric acid, sucrose, glucose, and polyethylene glycol.

23. The preparation method according to claim 1, characterized in that, The mass ratio of modified graphite to carbon source is 100:5~18.

24. The preparation method according to claim 1, characterized in that, The solvent is at least one of water, ethanol, tetrahydrofuran, toluene, and acetone.

25. The preparation method according to claim 1, characterized in that, The particle size after spraying is 5~18μm.

26. The preparation method according to claim 1, characterized in that, In step (4), the carbonization process includes low-temperature carbonization and high-temperature carbonization. The temperature of low-temperature carbonization is 350~500℃; the holding time at the low-temperature carbonization temperature is 4~8h; the temperature of high-temperature carbonization is 900~1500℃; and the time of high-temperature carbonization is 4~8h.

27. The preparation method according to claim 1, characterized in that, The carbon coating method is a vapor-phase carbon deposition method.

28. A recycled graphite anode active material based on waste photovoltaic graphite, prepared by the method according to any one of claims 1 to 27.

29. The application of a recycled graphite anode active material based on waste photovoltaic graphite prepared by the preparation method according to any one of claims 1 to 27, characterized in that, It is used as a negative electrode active material in the preparation of alkali metal ion batteries.

30. The application as described in claim 29, characterized in that, The alkali metal ion battery mentioned includes a lithium-ion battery or a sodium-ion battery.

31. A negative electrode for an alkali metal ion battery, comprising a current collector and a negative electrode material composited thereon, said negative electrode material comprising a negative electrode active material, a binder, and a conductive agent, characterized in that, The negative electrode active material comprises the waste photovoltaic graphite-based recycled graphite negative electrode active material prepared by the preparation method according to any one of claims 1 to 27.

32. The negative electrode of the alkali metal ion battery as described in claim 31, characterized in that, In the aforementioned negative electrode active material, the content of the waste photovoltaic graphite-based recycled graphite negative electrode active material is above 80 wt.%.

33. The negative electrode of the alkali metal ion battery as described in claim 31 or 32, characterized in that, In the aforementioned negative electrode, the compaction density of the electrode sheet of the recycled graphite negative electrode active material based on waste photovoltaic graphite is 1.8~2 g / cm³. 3 .

34. The negative electrode of the alkali metal ion battery as described in claim 33, characterized in that, The electrode compaction density of the waste photovoltaic graphite-based recycled graphite anode active material is 1.82~1.89 g / cm³. 3 .

35. An alkali metal ion battery, characterized in that, It includes the negative electrode as described in any one of claims 31 to 34.

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