Potassium ion battery negative electrode iron thiophosphate nanosheet material and preparation method and application thereof

Abstract

The application belongs to a potassium ion battery negative electrode ferriphosphate nanosheet material and a preparation method and application thereof, and the nanosheet material preparation method comprises the following steps: placing lithium iron phosphate positive electrode powder obtained from a waste lithium iron phosphate battery in an acid solution and heating and stirring, dissolving the lithium iron phosphate in the positive electrode powder by an acid immersion method, and obtaining an acid immersion liquid containing iron, lithium and phosphate ions by centrifugation and filtration; stirring the acid immersion liquid containing iron, lithium and phosphate ions, and simultaneously adding an alkali solution to adjust the solution pH value to 4-6, so as to obtain a ferric hydroxide precipitate liquid, and performing centrifugation, washing and drying on the ferric hydroxide suspension to obtain pure ferric hydroxide powder; and through gas-solid two-phase reaction of the ferric hydroxide powder and phosphorus pentasulfide vapor, the above-mentioned powder and excess phosphorus pentasulfide are mixed to obtain a ferriphosphate nanosheet material mixed with phosphorus pentasulfide, so that the waste lithium iron phosphate battery positive electrode material can be recycled.

Description

TECHNICAL FIELD

[0001] The application relates to a utilization method of waste gas lithium iron phosphate battery positive electrode material, in particular to a method for preparing potassium ion battery negative electrode iron thiophosphate nanosheet material from waste gas lithium iron phosphate battery positive electrode material and application of the method. BACKGROUND

[0002] With the vigorous development of the new energy automobile market in recent years, the power battery market dominated by lithium ion batteries has experienced explosive growth. However, more and more retired waste lithium ion batteries need to be reasonably and efficiently treated, recycled and reused, so as to effectively reduce the waste of valuable metal resources, reduce production costs, and also prevent the waste power battery from causing irreversible harm to the environment.

[0003] Potassium and lithium have similar chemical properties, and are abundant in the earth's crust and low in price, so potassium ion batteries are considered to be energy storage devices that can replace lithium ion batteries for large-scale applications. However, since the potassium ion radius (1.33 Å) is much larger than the lithium ion radius (0.76 Å), the difficulty of deintercalation of potassium ions in the charging and discharging process is increased, so that the traditional graphite negative electrode of lithium ion batteries cannot be directly used in potassium ion batteries. Therefore, it is necessary to develop a high-specific-energy potassium ion battery negative electrode to improve its specific capacity and cycle life.

[0004] Transition metal thiophosphate (MPS3) is a typical low-cost two-dimensional layered material, in which the iron thiophosphate (iron thiophosphate) negative electrode material has a very high theoretical capacity (1318 mAh g -1 ) and a large interlayer spacing (6.4 Å), and shows high potential in potassium ion batteries. However, iron thiophosphate also has the common problems of conversion-type materials, such as poor conductivity and severe volume expansion during the reaction. SUMMARY

[0005] To solve the above technical problems, the application provides a potassium ion battery negative electrode iron thiophosphate nanosheet material and a preparation method and application thereof,

[0006] The preparation method of the potassium ion battery negative electrode iron thiophosphate nanosheet material comprises the following steps:

[0007] The lithium iron phosphate positive electrode powder obtained from the waste lithium iron phosphate battery is placed in an acidic solution and heated and stirred, the lithium iron phosphate in the positive electrode powder is dissolved by acid leaching, and an acid leaching solution containing iron, lithium and phosphate ions is obtained by centrifugation and filtration;

[0008] Stir the acid leaching solution containing iron, lithium, phosphate ions, and add alkali liquor at the same time to adjust the pH value of the solution to 4-6 to obtain a ferric hydroxide precipitate, and centrifuge, wash and dry the ferric hydroxide suspension to obtain pure ferric hydroxide powder;

[0009] The above-mentioned ferric hydroxide powder and excess phosphorus pentasulfide are respectively placed at the bottom of the outer tube and the inner tube of a single-pass quartz sleeve, the inner and outer tubes of the single-pass quartz tube are oppositely nested, and the whole is placed in a multi-temperature section tube furnace under an argon atmosphere, so that the gas-solid two-phase reaction of the ferric hydroxide powder and the phosphorus pentasulfide vapor is carried out to obtain an iron thiophosphate nanosheet material mixed with phosphorus pentasulfide.

[0010] The above-mentioned iron thiophosphate nanosheet material mixed with phosphorus pentasulfide is placed in an argon atmosphere, and the excess phosphorus pentasulfide is removed by calcination to obtain a pure iron thiophosphate nanosheet material.

[0011] According to an embodiment of the present application, the mass ratio of ferric hydroxide powder to phosphorus pentasulfide placed at the bottom of the outer tube and the inner tube of a single-pass quartz sleeve is 1: (2-3).

[0012] According to an embodiment of the present application, when the gas-solid two-phase reaction of the ferric hydroxide powder and the phosphorus pentasulfide vapor is carried out, the target holding temperature of the temperature zone where phosphorus pentasulfide and ferric hydroxide are located is respectively set to 250-300 DEG C and 450-500 DEG C.

[0013] According to an embodiment of the present application, before placing the positive electrode sheet of the discarded waste lithium iron phosphate battery in a muffle furnace for calcination, the method further comprises:

[0014] The discarded waste lithium iron phosphate battery is discharged in brine, that is, first remove the outer packaging of the single cell retired lithium iron phosphate battery, expose the aluminum shell, and place it in a 3-5 L sodium chloride solution with a concentration of 2 M for discharge.

[0015] According to an embodiment of the present application, before placing the positive electrode sheet of the discarded waste lithium iron phosphate battery in a muffle furnace for calcination, and after discharging in brine, the method further comprises:

[0016] The positive electrode sheet obtained after discharging in brine is calcined, such as being placed in a muffle furnace for calcination, to preliminarily remove the binder and the current collector aluminum foil, and obtain a lithium iron phosphate positive electrode powder.

[0017] According to an embodiment of the present application, the holding temperature during calcination is 400-600 DEG C, the holding time is 1-3 h, and the obtained positive electrode powder after separation is taken out.

[0018] According to one embodiment of the present application, while stirring the acid leaching solution containing iron, lithium and phosphate ions, an alkali solution is added to adjust the pH value of the solution to obtain a ferric hydroxide suspension, and before calcining the positive plate of the discarded lithium iron phosphate battery in a muffle furnace, the method further comprises:

[0019] The pH value of the supernatant after removing the ferric hydroxide precipitate is continuously adjusted to 11-13, and the lithium phosphate precipitate is obtained by concentration and crystallization to separate out lithium phosphate.

[0020] According to one embodiment of the present application, the iron thiophosphate nanosheet material mixed with phosphorus pentasulfide is placed in a tube furnace and heated to 200-300 DEG C for 30-60 min, and then kept for 1-3 h to remove excess phosphorus pentasulfide.

[0021] According to another aspect of the present application, the present application also provides a potassium ion battery negative electrode iron thiophosphate nanosheet material prepared by the method described above.

[0022] According to another aspect of the present application, the present application also provides the use of the potassium ion battery negative electrode iron thiophosphate nanosheet material prepared by the method described above in the anode material of a potassium ion battery.

[0023] Advantages

[0024] Compared with the prior art, the present application has the following advantages:

[0025] 1. The present application uses a traditional hydrothermal method, and the entire preparation process is simple, the conditions are moderate, safe, the raw materials are cheap and easy to obtain, the equipment requirements are low, and mass production is easy.

[0026] 2. The preparation method of the present application uses the positive electrode material of the retired waste lithium iron phosphate battery as the raw material, which has significant economic benefits. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The flow chart of the preparation method of the potassium ion battery negative electrode iron thiophosphate nanosheet material of one embodiment of the present application is shown.

[0028] Figure 2 is the X-ray diffraction pattern of the iron thiophosphate nanosheet material prepared in Example 5;

[0029] Figure 3 is the SEM image of the iron thiophosphate nanosheet material prepared in Example 5;

[0030] Figure 4 is the cyclic voltammogram of the iron thiophosphate nanosheet material prepared in Example 5;

[0031] Figure 5 is the specific capacity of the iron thiophosphate nanosheet material prepared in Example 5 at 2 A g-1 Cyclic voltammogram at current density. DETAILED DESCRIPTION

[0032] The following description is presented to enable any person skilled in the art to practice the present application as claimed. The preferred embodiments disclosed herein are only examples of the present application and alternative embodiments will be apparent to those skilled in the art upon reading the following description. The detailed description includes specific details for the purpose of providing a thorough understanding of the present application. However, it will be apparent to those skilled in the art that the present application can be practiced without these specific details. In some instances, well-known structures and functions have not been described in detail in order to avoid obscuring the concept of the present application.

[0033] Reference Figure 1 A method for preparing a potassium ion battery negative electrode iron thiophosphate nanosheet material according to a preferred embodiment of the present application will be described in detail below, wherein the method for preparing the potassium ion battery negative electrode iron thiophosphate nanosheet material is prepared by using waste lithium iron phosphate batteries as raw materials to make potassium ion battery negative electrode iron thiophosphate nanosheet material, so as to achieve the purpose of turning waste into treasure.

[0034] Specifically, the method for preparing the potassium ion battery negative electrode iron thiophosphate nanosheet material comprises:

[0035] The method for preparing the potassium ion battery negative electrode iron thiophosphate nanosheet material comprises:

[0036] S1001, the lithium iron phosphate positive electrode powder obtained from the waste lithium iron phosphate battery is placed in an acidic solution and heated and stirred, the lithium iron phosphate in the positive electrode powder is dissolved by acid leaching, and an acid leaching solution containing iron, lithium and phosphate ions is obtained by centrifugation and filtration.

[0037] In one embodiment, the single addition of lithium iron phosphate positive electrode powder is 1-3 g. The acidic solution is 15-45 mL of 1M sulfuric acid, hydrochloric acid or nitric acid solution, the heating temperature is 45-70 ℃, and the stirring speed is 200-600 r / min for 2-4 h.

[0038] S1002, stirring the acid leaching solution containing iron, lithium and phosphate ions, and simultaneously adding alkali to adjust the pH value of the solution to 4-6 to obtain a ferric hydroxide precipitate, and centrifuging, washing and drying the ferric hydroxide suspension to obtain pure ferric hydroxide powder;

[0039] Preferably, in the step S1002, the stirring speed is 300-500 r / min, and the stirring time is 2-4 h.

[0040] Preferably, the added alkali is any one or a combination of two or more selected from potassium hydroxide, sodium hydroxide or sodium carbonate.

[0041] The preparation method of the potassium ion battery negative electrode iron thiophosphate nanosheet material comprises the following steps:

[0042] S1003, the iron hydroxide powder and excess diphosphorus pentasulfide are respectively placed at the bottom of the outer tube and the inner tube of a single-pass quartz sleeve, the tube openings of the inner tube and the outer tube of the single-pass quartz sleeve are oppositely nested, and the whole is placed in a multi-temperature zone tube furnace under an argon atmosphere, so as to obtain the iron thiophosphate nanosheet material mixed with diphosphorus pentasulfide through the gas-solid two-phase reaction of the iron hydroxide powder and diphosphorus pentasulfide vapor;

[0043] Preferably, the target holding temperatures of the temperature zones where the diphosphorus pentasulfide and the iron hydroxide are located are respectively set to 250-300 DEG C and 450-500 DEG C, and the target temperature is simultaneously raised to the target temperature through 25-45 min and then held for 45-90 min, and after natural cooling, the iron thiophosphate nanosheet material mixed with diphosphorus pentasulfide can be obtained.

[0044] Preferably, the mass ratio of the iron hydroxide powder to the diphosphorus pentasulfide is 1: (2-3). It is worth mentioning that, in an ideal case, when the mass ratio of the two is 1:1, the iron thiophosphate can be generated. However, the melting point and the boiling point of the diphosphorus pentasulfide are relatively low, and the diphosphorus pentasulfide is easy to be lost in the heating process. In order to ensure that the iron hydroxide is completely converted into the iron thiophosphate, excess diphosphorus pentasulfide is added.

[0045] The preparation method of the potassium ion battery negative electrode iron thiophosphate nanosheet material further comprises the following steps:

[0046] S1004, the iron thiophosphate nanosheet material mixed with diphosphorus pentasulfide is placed in an argon atmosphere, and the excess diphosphorus pentasulfide is removed through calcination, so as to obtain a more pure iron thiophosphate nanosheet material.

[0047] It is worth mentioning that, in the step S1004, the iron thiophosphate nanosheet material mixed with diphosphorus pentasulfide is placed in a tube furnace and heated to 200-300 DEG C through 30-60 min and then held for 1-3 h, so as to remove the excess diphosphorus pentasulfide.

[0048] Preferably, before the positive electrode sheet of the discarded waste lithium iron phosphate battery is placed in a muffle furnace for calcination, the method further comprises the following steps:

[0049] S2001, the discarded waste lithium iron phosphate battery is discharged in salt water. Specifically, first, the outer packaging of the single cell retired lithium iron phosphate battery is removed, the aluminum shell is exposed, and the aluminum shell is placed in a 3-5 L sodium chloride solution with a concentration of 2 M for discharge.

[0050] Further preferably, before the positive electrode sheet of the discarded waste lithium iron phosphate battery is placed in a muffle furnace for calcination, and after the salt water discharge is performed, the method further comprises the following steps:

[0051] S3001, calcining the positive electrode sheet obtained after discharging the brine, such as placing it in a muffle furnace to remove the binder and the current collector aluminum foil, to obtain a lithium iron phosphate positive electrode powder.

[0052] Specifically, in the step S3001, the holding temperature during calcination is 400-600°C, and the holding time is 1-3h, and the positive electrode powder obtained after separation is removed.

[0053] Preferably, while stirring the acid leaching solution containing iron, lithium, and phosphate ions, an alkali solution is added to adjust the pH value of the solution to obtain a ferric hydroxide suspension;

[0054] S4001, continue to adjust the pH value of the supernatant after removing the ferric hydroxide precipitate to 11-13, and concentrate and crystallize to obtain a lithium phosphate precipitate to separate the lithium phosphate. That is, not only can the pure ferric thiophosphate nanosheet material be prepared by the method of the application, but also the lithium phosphate can be separated.

[0055] Example 1

[0056] The preparation method and application of the retired lithium iron phosphate battery positive electrode material for the preparation of the ferric thiophosphate negative electrode of the potassium ion battery provided by the embodiment are as follows:

[0057] Step one, discharging the retired lithium ion battery. Remove the outer packaging of the single retired lithium iron phosphate battery to expose the aluminum shell, and then place it in a 5 L sodium chloride solution with a concentration of 2 M for 1 day.

[0058] Step two, disassembling and sorting the discharged battery to obtain a positive electrode. The disassembled and crushed waste lithium iron phosphate electrode material is sorted into waste positive electrode material and waste negative electrode material according to their physical and chemical properties.

[0059] Step three, calcining the positive electrode in a muffle furnace to remove the binder and the current collector. 1 g of lithium iron phosphate positive electrode material is stirred in 15 mL of 1 M sulfuric acid solution at a stirring speed of 500 r / min for 4 h, and a lithium iron phosphate acid leaching solution is obtained after solid-liquid separation.

[0060] Step four, adjusting the pH value of the obtained acid leaching solution to 4 by adding sodium hydroxide solution dropwise, centrifuging, washing, and drying to obtain red-brown ferric hydroxide.

[0061] Step five, iron hydroxide and phosphorus pentasulfide with a mass ratio of 1:2 were respectively placed at the bottom of the outer tube and the inner tube of a single-pass quartz sleeve, the inner and outer tubes were nested at the orifice, and the whole was placed in a multi-temperature zone tube furnace under argon atmosphere, and the phosphorus pentasulfide was placed at the upstream position. The temperature zones where the phosphorus pentasulfide and the iron hydroxide were located were respectively heated to 250℃ and 450℃ at a heating rate of 5℃ / min. After 1h of heat preservation, the iron thiophosphate nanosheet material was obtained after natural cooling.

[0062] Step six, the iron thiophosphate nanosheet material was placed in a tube furnace under argon atmosphere, and heated to 200℃ at a heating rate of 10℃ / min, and then heat preserved for 1h. After natural cooling, the pure iron thiophosphate nanosheet material was obtained.

[0063] Example 2

[0064] The preparation method and application of the retired lithium iron phosphate battery positive material for recycling as the negative electrode of the potassium ion battery provided in this example are the same as those in Example 1, except that the pH value of the acid leaching solution is adjusted to 6 in step four.

[0065] Example 3

[0066] The preparation method and application of the retired lithium iron phosphate battery positive material for recycling as the negative electrode of the potassium ion battery provided in this example are the same as those in Example 2, except that the temperature zone where the phosphorus pentasulfide is located is heated to 290℃, the temperature zone where the iron hydroxide is located is heated to 480℃, and the heat preservation time is 90min in step five.

[0067] Example 4

[0068] The preparation method and application of the retired lithium iron phosphate battery positive material for recycling as the negative electrode of the potassium ion battery provided in this example are the same as those in Example 3, except that the heating rate is 5℃ / min in step six.

[0069] Example 5

[0070] The preparation method and application of the retired lithium iron phosphate battery positive material for recycling as the negative electrode of the potassium ion battery provided in this example are the same as those in Example 4, except that the heat preservation temperature is 300℃ and the heat preservation time is 2h in step six.

[0071] The XRD pattern of the iron thiophosphate nanosheet obtained in Example 5 is shown in Figure 2 The diffraction peaks of the iron thiophosphate nanosheet obtained in Example 5 correspond to the FePS3 crystal face (ICSD number: 633080) standard card respectively. The formation of the FePS3 structure is revealed. At the same time, there is no other impurity peak in the spectrum, which indicates that high-purity FePS3 is successfully prepared.

[0072] SEM images of iron thiophosphate nanosheets are shown below. Figure 3 As shown, the iron thiophosphate nanosheets obtained in Example 5 exhibit a two-dimensional sheet structure, thus possessing advantages such as high specific surface area and convenient ion transport channels.

[0073] The obtained iron thiophosphate nanosheets were mixed with conductive agent Super-P and binder (PVDF, polyvinylidene fluoride) at a mass ratio of 7:2:1. Then, an appropriate amount of NMP was added as a solvent, and the mixture was stirred thoroughly. The resulting slurry was coated onto carbon-coated aluminum foil and dried under vacuum at 90°C for 12 hours. 12mm diameter discs were then punched out using a die-cutting machine and compacted at 10 MPa to obtain the positive electrode of a coin cell. In an argon-filled glove box, using potassium foil as the negative electrode, 1 mol / L KFSI EC:DEC (potassium bis(fluorosulfonyl)imide dissolved in ethylene carbonate:diethyl carbonate) = 1:1 Vol% as the electrolyte, and a glass fiber separator (GF / D), coin cells were fabricated according to the coin cell assembly sequence. In this embodiment, a BTS testing system from Shenzhen Neware Co., Ltd. was used for constant current charge-discharge testing at room temperature from 0.01 to 3.0 V. The cyclic voltammetry is shown below. Figure 4 As shown, the scan rate was 0.2 mV s⁻¹, and the voltage range of the CV curve was 0.01–3.0 V. For the initial cathode scan of H-FePS3@C, the significant peak at 1.26 V is likely due to the initial formation of K₂ by the insertion of K₂. + The strong reduction peak at 0.50 V is attributed to the irreversible breaking of the PS bond, resulting in a potassium-based reaction that produces K3P, Fe, and K2S. During charging, the two oxidation peaks at 0.71 V and 1.53 V indicate multi-step potassium removal to form K. x FeS3 and P, especially FePS3, cannot renormalize after the irreversible breaking of the PS bond. In subsequent cycles, K... x FeS3 and P reversibility provides capacity.

[0074] like Figure 5 As shown, in 2A g -1 It still maintains 105 mAh g after 2000 cycles at current density. -1 The discharge specific capacity fully demonstrates that the iron thiophosphate nanosheets prepared in this invention have excellent cycle performance when applied to potassium-ion batteries, and are promising anode materials for potassium-ion batteries.

[0075] Those skilled in the art should understand that the embodiments of the present invention described above and shown in the accompanying drawings are merely examples and do not limit the invention. The advantages of the present invention have been fully and effectively realized. The functional and structural principles of the present invention have been demonstrated and explained in the embodiments; any variations or modifications can be made to the implementation of the present invention without departing from these principles.

Claims

1. A method for preparing iron thiophosphate nanosheets as the negative electrode material for potassium-ion batteries, characterized in that, The preparation method of the potassium-ion battery negative electrode iron thiophosphate nanosheet material includes the following steps: The lithium iron phosphate cathode powder obtained from the waste lithium iron phosphate battery is placed in an acidic solution and heated and stirred. The lithium iron phosphate in the cathode powder is dissolved by acid leaching. The acid leaching solution containing iron, lithium and phosphate ions is obtained by centrifugation and filtration. Stir the acid leaching solution containing iron, lithium and phosphate ions, and simultaneously add alkali solution to adjust the pH of the solution to 4-6 to obtain ferric hydroxide precipitate. Then, centrifuge, wash and dry the ferric hydroxide suspension to obtain pure ferric hydroxide powder. The above-mentioned iron hydroxide powder and excess phosphorus pentasulfide were placed at the bottom of the outer tube and inner tube of a single-channel quartz tube, respectively. The inner and outer tube openings of the single-channel quartz tube were nested relative to each other, and the whole was placed in a multi-temperature tube furnace under an argon atmosphere. The iron hydroxide powder and phosphorus pentasulfide vapor were reacted in a gas-solid two-phase reaction to obtain iron thiophosphate nanosheets mixed with phosphorus pentasulfide. The above-mentioned iron thiophosphate nanosheet material mixed with phosphorus pentasulfide was placed in an argon atmosphere and the excess phosphorus pentasulfide was removed by calcination to obtain pure iron thiophosphate nanosheet material.

2. The method for preparing the potassium-ion battery negative electrode iron thiophosphate nanosheet material according to claim 1, characterized in that, The mass ratio of iron hydroxide powder to phosphorus pentasulfide is 1:(2-3) placed at the bottom of the outer and inner tubes of the single-pass quartz sleeve.

3. The method for preparing the potassium-ion battery negative electrode iron thiophosphate nanosheet material according to claim 1, characterized in that, When ferric hydroxide powder reacts with phosphorus pentasulfide vapor in a gas-solid two-phase reaction, the target holding temperatures for the temperature zones containing phosphorus pentasulfide and ferric hydroxide are set at 250–300 °C and 450–500 °C, respectively.

4. The method for preparing the potassium-ion battery negative electrode iron thiophosphate nanosheet material according to any one of claims 1 to 3, characterized in that, Before placing the waste lithium iron phosphate battery positive electrode sheet in a muffle furnace for calcination, the method further includes: Discarded lithium iron phosphate batteries are discharged using salt water. This involves first removing the outer packaging of a single retired lithium iron phosphate battery to expose the aluminum casing, and then discharging it in 3–5 L of a 2 M sodium chloride solution.

5. The method for preparing the potassium-ion battery negative electrode iron thiophosphate nanosheet material according to claim 4, characterized in that, Before placing the positive electrode of the discarded lithium iron phosphate battery in a muffle furnace for calcination, and after performing brine discharge, the method further includes: The positive electrode sheet obtained after salt water discharge is calcined to initially remove the binder and current collector aluminum foil, thus obtaining lithium iron phosphate positive electrode powder.

6. The method for preparing the potassium-ion battery negative electrode iron thiophosphate nanosheet material according to claim 5, characterized in that, The calcination temperature is 400-600℃ and the holding time is 1-3h. The positive electrode powder obtained after separation is then removed.

7. The method for preparing the potassium-ion battery negative electrode iron thiophosphate nanosheet material according to claim 4, characterized in that, While stirring an acid leaching solution containing iron, lithium, and phosphate ions, an alkaline solution is added to adjust the pH value of the solution to obtain a ferric hydroxide suspension. The method further includes: The pH of the supernatant after removing the ferric hydroxide precipitate was adjusted to 11-13, and the solution was concentrated and crystallized to obtain lithium phosphate precipitate, so as to separate lithium phosphate.

8. The method for preparing potassium-ion battery negative electrode iron thiophosphate nanosheets according to claim 1, wherein the iron thiophosphate nanosheets mixed with phosphorus pentasulfide are placed in a tube furnace and heated to 200-300°C for 30-60 minutes, and held at that temperature for 1-3 hours to remove excess phosphorus pentasulfide.

9. A potassium-ion battery anode material of iron thiophosphate nanosheets, characterized in that, It is made by any of the methods described in claims 1 to 8.

10. The use of the potassium-ion battery negative electrode iron thiophosphate nanosheet material prepared by any one of claims 1 to 8, characterized in that, Used in potassium-ion battery anode materials.

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