Fluorination modified battery positive electrode material and preparation method thereof

Abstract

The invention belongs to the technical field of materials, and provides a fluorinated modified battery positive electrode material and a preparation method thereof. The method comprises the following steps: putting a positive plate into a NaOH solution to dissolve aluminum foil, and filtering and drying to obtain waste positive electrode powder; placing the waste positive electrode powder and polytetrafluoroethylene powder in a ball milling tank for ball milling to obtain mixed powder; calcining the mixed powder in a tubular furnace in an argon atmosphere to obtain calcined mixed powder; and adding a lithium source into the calcined mixed powder, and annealing in a muffle furnace in an air atmosphere to obtain the fluorinated modified battery positive electrode material. According to the method, fluorine doping is adopted to improve the lithium ion transmission capacity of the phase change layer, the structural characteristics of the waste lithium ion battery are reserved, and the residual capacity and metal elements of the positive electrode material of the waste lithium ion battery are utilized to the maximum extent. According to the obtained regenerated positive electrode material, the migration-in and migration-out capability of lithium ions is enhanced, the improvement of the battery capacity is facilitated, and the precipitation of lattice oxygen in the charging and discharging process is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of materials, and particularly relates to a fluorinated modified cathode material for batteries and a preparation method thereof. Background Art

[0002] Lithium-ion batteries are widely used in industries such as new energy vehicles, digital electronics, large-scale energy storage, and special devices. The comprehensive utilization of failed lithium-ion batteries includes two ways: cascade utilization and direct recycling. The methods of direct recycling include pyrometallurgy, hydrometallurgy, and direct regeneration. The pyrometallurgical process is simple, but it has high energy consumption, serious pollution, and low recovery rate. The recovered Ni-Co alloy needs to be further separated, and a large amount of lithium is lost in the smelting slag. Hydrometallurgy includes two steps. One step is the leaching of the cathode material of waste lithium-ion batteries, and the other step is the separation of metal elements in the leaching solution. However, lithium loss will occur while extracting and recovering transition metal elements, and the use of a large amount of chemical reagents in the recovery process will pose a serious environmental threat. The waste battery still retains about 80% of its original capacity, and any process that destroys its internal energy or economic value will be inefficient. Therefore, direct regeneration is the most economical and effective recovery method.

[0003] Lithium cobaltate and ternary lithium-ion batteries will suffer from serious lithium loss, phase change, cation mixing, and transition metal dissolution during long-term electrochemical cycling, which will damage their crystal structures and reduce their electrochemical performance. Currently, the existing regeneration methods include solid-state regeneration, electrochemical regeneration, and eutectic molten salt regeneration. The common feature of these methods is to restore their electrochemical performance by repairing the layered structure of the cathode material.

[0004] The information disclosed in this background art section is only intended to enhance the overall understanding of the present invention and should not be regarded as an admission or any form of implication that this information constitutes prior art already known to those of ordinary skill in the art. Summary of the Invention

[0005] The object of the present invention is to propose a fluorinated modified cathode material for batteries and a preparation method thereof to solve the problems of low capacity utilization rate and low metal recovery rate during the recycling process of waste lithium-ion batteries. The feature of this method is to base on the phase change characteristics of the waste cathode material itself, dope and modify it, improve the adverse effect of the phase change layer on the lithium ion transmission performance, and finally regenerate a cathode material with higher lithium ion migration efficiency through lithium supplementation.

[0006] The present invention provides a preparation method of a fluorinated modified cathode material for batteries, which has the following characteristics and includes the following steps:

[0007] Step S1, placing the cathode sheet in a NaOH solution to dissolve the aluminum foil, and obtaining waste cathode powder after filtration and drying;

[0008] Step S2: Place the waste cathode powder and polytetrafluoroethylene powder in a ball milling jar at a mass ratio of 1:0.1 - 1:0.4 and ball mill for a predetermined time to obtain a mixed powder;

[0009] Step S3: Calcinate the mixed powder in a tubular furnace at 600°C - 700°C for a predetermined time under an argon atmosphere to obtain the calcined mixed powder;

[0010] Step S4: Add a lithium source to the calcined mixed powder at a mass ratio of the calcined mixed powder to lithium hydroxide in the lithium source of 1:1.05, and anneal at 800°C for a predetermined time in a muffle furnace under an air atmosphere to obtain the regenerated cathode material, i.e., the fluorinated modified battery cathode material.

[0011] In the preparation method of the fluorinated modified battery cathode material provided by the present invention, it may further have the following characteristics: Among them, in step S2, place the waste cathode powder and polytetrafluoroethylene powder in an agate ball milling jar at a mass ratio of 100:1, ball mill at a speed of 600 r / min for 30 min, rinse the powder in the agate ball milling jar with deionized water after ball milling, and then dry in an oven at 60°C for 12 h to obtain the mixed powder; In step S3, put the mixed powder into a porcelain boat, and calcinate at 700°C for 2 h in a tubular furnace under an argon atmosphere at a heating rate of 5°C / min.

[0012] In the preparation method of the fluorinated modified battery cathode material provided by the present invention, it may further have the following characteristics: Among them, in step S2, the particle size of the polytetrafluoroethylene powder is 8 μm - 12 μm, the ball milling beads are 10 1-mm and 5 5-mm agate ball milling beads, and the ball mill is a planetary ball mill.

[0013] In the preparation method of the fluorinated modified battery cathode material provided by the present invention, it may further have the following characteristics: Among them, in step S4, add a lithium source to the calcined mixed powder at a mass ratio of the calcined mixed powder to lithium hydroxide in the lithium source of 1:1.05, and anneal at 800°C for 10 h in a muffle furnace under an air atmosphere to obtain the regenerated cathode material, i.e., the fluorinated modified battery cathode material.

[0014] In the preparation method of the fluorinated modified battery cathode material provided by the present invention, it may further have the following characteristics: Among them, in step S4, the lithium source is LiOH-KOH, where the molar ratio of LiOH to KOH is 7:3, and the mass ratio of the calcined mixed powder to LiOH-KOH is 1:2.

[0015] In the preparation method of the fluorinated modified battery cathode material provided by the present invention, it may further have the following characteristics: Among them, the lithium source is LiOH, and the mass ratio of the calcined mixed powder to LiOH is 1:1.05.

[0016] In the preparation method of the fluorinated modified battery cathode material provided by the present invention, it may further have the following characteristics: wherein, in step S4, the lithium source is Li 2 CO 3 , and the mass ratio of the mixed powder after calcination to Li 2 CO 3 is 1:1.5.

[0017] In the preparation method of the fluorinated modified battery cathode material provided by the present invention, it may further have the following characteristics: wherein, in step S1, the positive electrode sheet is placed in a NaOH solution with a mass concentration of 5% to dissolve the aluminum foil.

[0018] In the preparation method of the fluorinated modified battery cathode material provided by the present invention, it may further have the following characteristics: wherein, in step S1, the positive electrode sheet comes from a waste battery, the battery is a lithium cobalt oxide battery or a ternary battery, and the detailed steps of the disassembly method of the positive electrode sheet are as follows:

[0019] Place the waste battery in a 7%wt NaCl solution and discharge it until no bubbles emerge. Then, place the discharged waste battery in a glove box filled with argon, disassemble the battery case with scissors, soak the peeled positive electrode sheet in an ethanol solution, and after 30 minutes, rinse the soaked positive electrode sheet under a running tap to wash away the ethanol and electrolyte on the surface. Then, lay the positive electrode sheet flat in a fume hood to dry, and obtain the disassembled positive electrode sheet, that is, the positive electrode sheet.

[0020] The present invention also provides a fluorinated modified battery cathode material, which is characterized in that it is prepared by the preparation method of the fluorinated modified battery cathode material.

[0021] Functions and effects of the invention

[0022] A fluorinated modified battery cathode material and its preparation method provided by the present invention. Since this method uses fluorine doping to improve the lithium ion transport ability of the phase change layer, retains the structural characteristics of the waste lithium ion battery, and maximally utilizes the remaining capacity and metal elements of the waste lithium ion battery cathode material.

[0023] Furthermore, since the present invention adopts a direct regeneration method, compared with the traditional method, it reduces the loss of metal elements and chemical reagents.

[0024] Furthermore, the regenerated cathode material obtained by the present invention, due to the effective lithium ion penetration network on the surface, strengthens the ability of lithium ions to migrate in and out, which is beneficial to the improvement of the battery capacity. Since fluorine doping occupies the oxygen sites, it reduces the precipitation of lattice oxygen during charge and discharge, stabilizes the structure of the cathode material, and is beneficial to the enhancement of the battery cycle performance.

[0025] Therefore, the regeneration method of the present invention can efficiently utilize the characteristics of waste lithium-ion batteries to regenerate a cathode material with better capacity and cycling performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is the X-ray diffraction pattern of the regenerated LCO cathode material in Example 1 of the present invention;

[0027] Figure 2 is the X-ray photoelectron spectroscopy pattern of the regenerated LCO cathode material in Example 1 of the present invention;

[0028] Figure 3 is the scanning electron microscopy image of the regenerated LCO cathode material in Example 1 of the present invention;

[0029] Figure 4 is the transmission electron microscopy image of the regenerated LCO cathode material in Example 1 of the present invention;

[0030] Figure 5 is the X-ray diffraction pattern of the regenerated NCM cathode material in Example 2 of the present invention;

[0031] Figure 6 is the X-ray photoelectron spectroscopy pattern of the regenerated NCM cathode material in Example 2 of the present invention;

[0032] Figure 7 is the scanning electron microscopy image of the regenerated NCM cathode material in Example 2 of the present invention;

[0033] Figure 8 is the transmission electron microscopy image of the regenerated NCM cathode material in Example 2 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] In order to make the technical means, creative features, achieved purposes and effects of the present invention easy to understand, the following specifically describes a fluorinated modified battery cathode material and its preparation method according to the present invention in combination with embodiments and drawings.

[0035] Unless otherwise specified, the raw materials used in the present invention are all purchased through general commercial channels. All test standards not mentioned are national standards.

[0036] The source information of some materials and instruments involved in the embodiments is as follows:

[0037] Polytetrafluoroethylene powder, purchased from the official website of the exploration platform, CAS: 9002-84-0, purity 99.9%, particle size 4-8μm;

[0038] LiOH, Li 2 CO 3Purchased from the official website of the exploration platform, CAS 1310-65-2 and 554-13-2, purity 99%+;

[0039] KOH was purchased from the official website of Aladdin Reagent, CAS: 1310-58-3, purity ≥ 85.0%.

[0040] The waste lithium cobalt oxide batteries come from the waste batteries of Apple mobile phones, and the waste ternary batteries come from CATL. The disassembly methods of the two positive electrodes are the same, and the detailed steps are as follows: the waste batteries are discharged in a 7%wt NaCl solution until no bubbles emerge, and then the discharged waste batteries are placed in a glove box filled with argon gas, and the battery shell is disassembled with scissors, and the peeled positive electrode sheets are soaked in an ethanol solution. After 30 minutes, the soaked positive electrode sheets are rinsed under a running tap, and after rinsing the ethanol and electrolyte on the surface, the positive electrode sheets are laid flat in a fume hood to dry, and the disassembled positive electrode sheets are obtained, which are the positive electrode sheets required in the following embodiments.

[0041] <Example 1>

[0042] This embodiment provides a method for preparing a fluorinated battery positive electrode material, which specifically includes the following steps:

[0043] Step S1, soaking the disassembled LCO positive electrode sheet in an ethanol solution for 30 minutes to remove the electrolyte, then rinsing the positive electrode sheet and drying it naturally, placing the dried positive electrode sheet in a 5%wtNaOH solution to dissolve the aluminum foil, filtering and drying to obtain waste positive electrode powder. The waste positive electrode powder is the waste LCO material.

[0044] Step S2, placing the waste positive electrode powder and polytetrafluoroethylene powder in an agate ball mill, ball milling at 600 r / min for 30 minutes, rinsing and collecting the mixed powder with deionized water after ball milling, and drying in an oven at 60° C. for 12 hours.

[0045] The mass ratio of positive electrode powder to polytetrafluoroethylene is 100:1. Here, 0.5 g of positive electrode powder and 0.01 g of polytetrafluoroethylene powder are weighed. The particle size of polytetrafluoroethylene powder is 8-12 μm. The ball milling beads are 10 1 mm and 5 5 mm agate ball milling beads. The ball mill is a planetary ball mill.

[0046] Step S3, putting the ground mixed powder into a porcelain boat, and calcining it in a tube furnace at a heating rate of 5°C / min to 700°C for 2h under an argon atmosphere.

[0047] Step S4, weighing the mass of the calcined mixed powder, adding LiOH-KOH as a lithium source, and annealing at 800° C. in a muffle furnace under air atmosphere for 10 h to obtain a regenerated LCO positive electrode material.

[0048] The mass ratio of the calcined mixed powder to LiOH-KOH is 1:2, and 5% excess lithium source is used to compensate for lithium loss at high temperatures.

[0049] The obtained regenerated cathode material of lithium cobalt oxide battery was measured by an X-ray diffractometer (model D / Max-2550PC produced by Rigaku, Japan). The X-ray diffraction patterns of the obtained regenerated cathode material of lithium cobalt oxide battery and the waste lithium cobalt oxide cathode material are as Figure 1 shown.

[0050] From Figure 1 it can be seen that the main peaks (003), (104), and (101) of the regenerated LCO correspond to the standard card of lithium cobalt oxide one by one (the standard card comes from the jade database), and the peaks of (006) and (012) have good splitting, indicating that the regenerated cathode material has good crystal structure and crystallinity.

[0051] The surface layer of the obtained regenerated lithium cobalt oxide material was measured by an X-ray photoelectron spectroscopy (Thermo Fisher Scientific, USA, model Escalab 250xi). The energy spectrum of the obtained regenerated material is as Figure 2 shown. From Figure 2 it can be seen that a peak appears at 685 eV in the F1s spectrum. After verification, the peak at this binding energy represents F - ions. Therefore, fluorine exists in the surface phase transition layer in ionic valence state, indicating the effectiveness of fluorine doping.

[0052] The obtained nano-regenerated LCO cathode material and the waste LCO material were scanned by a scanning electron microscope (model JSM-7800F produced by Nippon Corporation). The scanning electron microscope image of the obtained regenerated cathode material of lithium cobalt oxide battery is as Figure 3 (b) shown, and the scanning electron microscope image of the waste LCO material is as Figure 3 (a) shown. From Figure 3 (b) it can be seen that the surface of the regenerated cathode material of lithium cobalt oxide is relatively smooth, while Figure 3 (a) is the waste LCO material, whose surface is rough and has large cracks. The comparison between the two reflects that the crystallinity and layered structure of the regenerated LCO have been restored, indicating the successful regeneration of the waste lithium cobalt oxide cathode material.

[0053] The obtained nano-regenerated cathode material of lithium cobalt oxide battery and the waste LCO material were scanned by a field emission transmission electron microscope (model JEM-2100F produced by Nippon Corporation). The transmission electron microscope images of the obtained regenerated cathode material of lithium cobalt oxide battery are as Figure 4 (c), 4(d) shown, and the transmission electron microscope images of the waste LCO material are as Figure 4 (a), 4(b) shown.

[0054] From Figure 4 It can be seen from (c) that the regenerated lithium cobalt oxide cathode material has an ordered and clear lattice structure, while Figure 4 (a) shows that the surface of the waste lithium cobalt oxide material has a disordered and chaotic structure. According to Figure 4 (b), the lattice points of the waste material show a circular ring and irregular lattice arrangement, indicating that it has a polycrystalline structure and there is a disordered phase transition layer on its surface. While Figure 4 (d) shows that the lattice points of the regenerated material show a regular arrangement, which is a single crystal lattice of a typical hexagonal crystal system, indicating successful regeneration and the disappearance of the phase transition layer after lithium compensation and repair. This shows the successful regeneration of the waste lithium cobalt oxide cathode material.

[0055] <Example 2>

[0056] A fluorinated modified battery cathode material and its preparation method specifically include the following steps:

[0057] Step S1: Immerse the disassembled NCM cathode sheet in an ethanol solution for 30 min to remove the electrolyte, then rinse the cathode sheet and let it dry naturally. Place the dried cathode sheet in a 5%wt NaOH solution to dissolve the aluminum foil, and filter and dry to obtain waste cathode powder. This waste cathode powder is waste ternary cathode material.

[0058] Step S2: Place the waste cathode powder and polytetrafluoroethylene powder in an agate ball milling jar, ball mill at 600 r / min for 30 min. After ball milling, rinse with deionized water and collect the mixed powder, and dry it in an oven at 60 °C for 12 h.

[0059] The mass ratio of the cathode powder to polytetrafluoroethylene is 100:1. Here, 0.5 g of cathode powder and 0.01 g of polytetrafluoroethylene powder are weighed. The particle size of the polytetrafluoroethylene powder is 8 - 12 μm, the ball milling beads are 10 pieces of 1 mm and 5 pieces of 5 mm agate ball milling beads, and the ball mill is a planetary ball mill.

[0060] Step S3: Put the milled mixed powder into a porcelain boat, and under an argon atmosphere, calcine it in a tubular furnace at a heating rate of 5 °C / min to 700 °C for 2 h.

[0061] Step S4: Weigh the mass of the calcined mixed powder, add LiOH - KOH as the lithium source, and anneal it in a muffle furnace at 800 °C for 10 h in an air atmosphere to obtain the regenerated NCM cathode material.

[0062] The mass ratio of the calcined mixed powder to LiOH - KOH is 1:2, and 5% of the excess lithium source is used to compensate for lithium loss at high temperatures.

[0063] The regenerated ternary cathode material obtained above was measured using an X-ray diffractometer (model D / Max-2550PC produced by Rigaku, Japan). The X-ray diffraction patterns of the obtained regenerated ternary cathode material (regenerated NCM) and the waste ternary cathode material (waste NCM) are as follows Figure 5 shown. From Figure 5 it can be seen that compared with the ternary standard card (the standard card is from the jade database), the peak pattern of the regenerated ternary cathode material is complete and clear, and the main peaks (003), (104), and (101) coincide with the standard card. However, the waste NCM cathode shows split peaks, such as on the (101) and (104) peaks, indicating the presence of impurity phases in the waste NCM.

[0064] The surface layer of the regenerated ternary material obtained above was measured using an X-ray photoelectron spectroscope (model Escalab 250xi produced by Thermo Fisher Scientific, USA). The energy spectrum of the obtained regenerated material is as follows Figure 6 shown. From Figure 6 it can be seen that a peak of 685.5 eV appears in the F1s spectrum, which is the characteristic peak of F - , indicating that fluorine exists in the surface phase transition layer in an ionic valence state, which demonstrates the effectiveness of fluorine doping.

[0065] The above-obtained nano-regenerated ternary cathode material and the waste ternary cathode material were scanned using a scanning electron microscope (model JSM-7800F produced by JEOL Ltd., Japan). The scanning electron microscope images of the obtained regenerated ternary cathode material are as follows Figure 7 (b), and the scanning electron microscope image of the waste ternary cathode material is as follows Figure 7 (a). From Figure 7 (a) it can be seen that the particles of the waste NCM show obvious cracks and irregular particles appear around them, indicating that there are more impurities, while the surface of the regenerated ternary cathode material is relatively flat and smooth ( Figure 7 (b)).

[0066] The above-obtained nano-regenerated ternary cathode material and the waste ternary cathode material were scanned using a field emission transmission electron microscope (model JEM-2100F produced by JEOL Ltd., Japan). The transmission electron microscope images of the obtained regenerated ternary cathode material are as follows Figure 8 (c), 8(d), and the transmission electron microscope images of the waste ternary cathode material are as follows Figure 8 (a), 8(b).

[0067] From Figure 8 (c) it can be seen that the regenerated ternary cathode material has an ordered and clear layered lattice structure, and Figure 8 the dot pattern in (d) shows a regular dot pattern of a single-layered structure, indicating successful regeneration, while the lattice fringes of the waste ternary material are chaotic ( Figure 8(a)), and Figure 8 (b)'s dot matrix diagram presents a blurred aperture, which is more in line with polycrystalline materials, indicating the presence of a phase change layer on its surface. This indicates the successful regeneration of the waste ternary cathode material.

[0068] <Example 3>

[0069] A fluorinated modified battery cathode material and its preparation method specifically include the following steps:

[0070] Step S1, Immerse the disassembled NCM cathode sheet in an ethanol solution for 30 min to remove the electrolyte, then rinse the cathode sheet and let it dry naturally. Place the dried cathode sheet in a 5% wt NaOH solution to dissolve the aluminum foil, and obtain the waste cathode powder after filtration and drying;

[0071] Step S2, Place the waste cathode powder and polytetrafluoroethylene powder in an agate ball milling jar, ball mill at 600 r / min for 30 min. After ball milling, rinse with deionized water and collect the mixed powder, and dry it in an oven at 60 °C for 12 h;

[0072] The mass ratio of the cathode powder to polytetrafluoroethylene is 100:4. Here, 0.5 g of the cathode powder and 0.01 g of the polytetrafluoroethylene powder are weighed. The particle size of the polytetrafluoroethylene powder is 8 - 12 μm, the ball milling beads are 10 pieces of 1 mm and 5 pieces of 5 mm agate material ball milling beads, and the ball mill is a planetary ball mill;

[0073] Step S3, Put the milled mixed powder into a porcelain boat, and under the protection of an argon atmosphere, calcine it in a tubular furnace at a heating rate of 5 °C / min to 700 °C for 2 h;

[0074] Step S4, Weigh the mass of the calcined mixed powder, add Li 2 CO 3 As the lithium source, anneal it in a muffle furnace at 800 °C for 10 h in an air atmosphere to obtain the regenerated NCM cathode material.

[0075] The mass ratio of the calcined mixed powder to Li 2 CO 3 is 1:1.5, and 5% of the excess lithium source is used to compensate for lithium loss at high temperatures.

[0076] <Example 4>

[0077] A fluorinated modified battery cathode material and its preparation method specifically include the following steps:

[0078] Step S1, Immerse the disassembled LCO cathode sheet in an ethanol solution for 30 min to remove the electrolyte, then rinse the cathode sheet and let it dry naturally. Place the dried cathode sheet in a 5% wt NaOH solution to dissolve the aluminum foil, and obtain the waste cathode powder after filtration and drying;

[0079] Step S2: Place the waste cathode powder and polytetrafluoroethylene powder in an agate ball milling jar, ball mill at 600 r / min for 30 min. After ball milling, rinse with deionized water and collect the mixed powder, then dry it in an oven at 60 °C for 12 h;

[0080] The mass ratio of the cathode powder to polytetrafluoroethylene is 100:2. Here, 0.5 g of cathode powder and 0.01 g of polytetrafluoroethylene powder are weighed. The particle size of the polytetrafluoroethylene powder is 8 - 12 μm, and the ball milling beads are 10 agate beads of 1 mm and 5 agate beads of 5 mm. The ball mill is a planetary ball mill;

[0081] Step S3: Put the milled mixed powder into a porcelain boat, and calcine it in a tube furnace at a heating rate of 5 °C / min to 700 °C for 2 h under the protection of an argon atmosphere;

[0082] Step S4: Weigh the mass of the calcined mixed powder, add Li 2 CO 3 as the lithium source, and anneal it in a muffle furnace at 800 °C for 10 h in an air atmosphere to obtain the regenerated LCO cathode material.

[0083] The mass ratio of the calcined mixed powder to Li 2 CO 3 is 1:1.5, and 5% excess lithium source is used to compensate for lithium loss at high temperature.

[0084] <Example 5>

[0085] A fluorinated modified battery cathode material and its preparation method specifically include the following steps:

[0086] Step S1: Immerse the disassembled LCO cathode sheet in an ethanol solution for 30 min to remove the electrolyte, then rinse the cathode sheet and let it dry naturally. Cut the dried cathode sheet into blocks of 1 cm × 2 cm, put them into a porcelain boat, and heat it in a tube furnace in an air atmosphere at a rate of 5 °C / min to 550 °C, and calcine for 3 h. Separate the calcined cathode material from the aluminum foil;

[0087] Step S2: Place the waste cathode powder and polytetrafluoroethylene powder in an agate ball milling jar, ball mill at 600 r / min for 30 min. After ball milling, rinse with deionized water and collect the mixed powder, then dry it in an oven at 60 °C for 12 h;

[0088] The mass ratio of the cathode powder to polytetrafluoroethylene is 100:1. Here, 0.5 g of cathode powder and 0.01 g of polytetrafluoroethylene powder are weighed. The particle size of the polytetrafluoroethylene powder is 8 - 12 μm, and the ball milling beads are 10 agate beads of 1 mm and 5 agate beads of 5 mm. The ball mill is a planetary ball mill;

[0089] Step S3: Put the ground mixed powder into a porcelain boat. Under the protection of an argon atmosphere, in a tube furnace, heat it at a heating rate of 5 °C / min to 600 °C and calcine for 2 h.

[0090] Step S4: Weigh the mass of the calcined mixed powder, add LiOH as the lithium source, and anneal it at 800 °C for 10 h in a muffle furnace under an air atmosphere to obtain the regenerated LCO cathode material.

[0091] The mass ratio of the calcined mixed powder to LiOH is 1:1.05, and 5% excess lithium source is used to compensate for lithium loss at high temperatures.

[0092] <Example 6>

[0093] A fluorinated modified battery cathode material and its preparation method specifically include the following steps:

[0094] Step S1: Immerse the disassembled NCM cathode sheet in an ethanol solution for 30 min to remove the electrolyte, then rinse the cathode sheet and let it dry naturally. Cut the dried cathode sheet into blocks of 1 cm × 2 cm, put them into a porcelain boat, and in a tube furnace under an air atmosphere, heat it at a rate of 5 °C / min to 550 °C and calcine for 3 h. Separate the calcined cathode material from the aluminum foil.

[0095] Step S2: Put the waste cathode powder and polytetrafluoroethylene powder into an agate ball milling jar, ball mill at 600 r / min for 2 h. After ball milling, rinse with deionized water and collect the mixed powder, and dry it in an oven at 60 °C for 12 h.

[0096] The mass ratio of the cathode powder to polytetrafluoroethylene is 100:1. Here, 0.5 g of cathode powder and 0.01 g of polytetrafluoroethylene powder are weighed. The particle size of the polytetrafluoroethylene powder is 8 - 12 μm, the ball milling beads are 10 pieces of 1 mm and 5 pieces of 5 mm agate ball milling beads, and the ball mill is a planetary ball mill.

[0097] Step S3: Put the ground mixed powder into a porcelain boat. Under the protection of an argon atmosphere, in a tube furnace, heat it at a heating rate of 5 °C / min to 700 °C and calcine for 2 h.

[0098] Step S4: Weigh the mass of the calcined mixed powder, add LiOH as the lithium source, and anneal it at 800 °C for 10 h in a muffle furnace under an air atmosphere to obtain the regenerated NCM cathode material.

[0099] The mass ratio of the calcined mixed powder to LiOH is 1:1.05, and 5% excess lithium source is used to compensate for lithium loss at high temperatures.

[0100] Functions and effects of the examples

[0101] Embodiments of the present invention are based on the characteristics of waste lithium-ion batteries for modification and regeneration. Although the structure of lithium cobalt oxide batteries collapses during charge and discharge due to lithium loss and changes in the valence state of transition metals, and the generated spinel phase or rock salt phase hinders the migration of lithium ions during subsequent lithium supplementation, to improve the lithium ion supplementation efficiency, fluorine elements are incorporated into the waste cathode material for modification. The presence of fluoride ions tends to maximize the lithium content around them. The doping of a large number of fluoride ions can effectively change the lithium ion penetration network of the spinel phase and the rock salt phase, and a cathode material with good performance can be obtained through subsequent lithium supplementation. The regenerated cathode material obtained by this preparation method has a better lithium ion penetration network and a more stable structure.

[0102] This method uses fluorine doping to improve the lithium ion transport ability of the phase change layer, and regenerates a new cathode material through one-step doping and one-step annealing without destroying the structure of the waste material, making the most of the remaining capacity and metal elements of the waste lithium-ion battery cathode material. The doped fluoride ions occupy the oxygen sites and stabilize the lattice structure, improving the lithium supplementation efficiency and the structural stability at the same time.

[0103] Furthermore, since this method adopts a direct regeneration method, compared with traditional methods, it reduces the loss of metal elements and chemical reagents.

[0104] Furthermore, the regenerated cathode material obtained by this method, due to the effective lithium ion penetration network on the surface, strengthens the ability of lithium ions to migrate in and out, which is beneficial to the improvement of battery capacity. Since fluorine doping occupies the oxygen sites, the precipitation of lattice oxygen during charge and discharge is reduced, and the structure of the cathode material is stabilized, which is beneficial to the enhancement of battery cycle performance.

[0105] In summary, an embodiment of the present invention provides a fluorinated modified battery cathode material and its preparation method. Since it retains the characteristics of the waste cathode material and makes the most of its crystal structure, it directly regenerates a biphasic cathode material with a better lithium ion penetration network, and can efficiently utilize the characteristics of waste lithium-ion batteries to regenerate a cathode material with better capacity and cycle performance.

[0106] The above embodiments are preferred cases of the present invention and are not used to limit the protection scope of the present invention.

Claims

1. A method for preparing a fluorinated battery positive electrode material, characterized in that: The following steps are involved: Step S1, placing the positive electrode sheet in a NaOH solution to dissolve the aluminum foil, and obtaining waste positive electrode powder after filtering and drying; Step S2, placing the waste positive electrode powder and polytetrafluoroethylene powder in a ball mill according to a mass ratio of 1:0.1 to 1:0.4 and ball milling for a predetermined time to obtain a mixed powder; Step S3, calcining the mixed powder in a tube furnace at 600° C. to 700° C. for a predetermined time under an argon atmosphere to obtain a calcined mixed powder; Step S4, according to the mass ratio of the calcined mixed powder to the lithium hydroxide in the lithium source being 1:1.05, the lithium source is added to the calcined mixed powder, and annealed at 800° C. in a muffle furnace under an air atmosphere for a predetermined time to obtain a regenerated positive electrode material, i.e., a fluorinated modified battery positive electrode material.

2. The method for preparing the fluorinated battery positive electrode material according to claim 1, characterized in that: in, In step S2, the waste positive electrode powder and polytetrafluoroethylene powder are placed in an agate ball mill at a mass ratio of 100:1, and ball milled at a speed of 600 r / min for 30 minutes. After ball milling, the powder in the agate ball mill is washed and collected with deionized water, and then dried in an oven at 60° C. for 12 hours to obtain a mixed powder; In step S3, the mixed powder is placed in a porcelain boat and calcined in a tube furnace at a heating rate of 5°C / min to 700°C for 2h under an argon atmosphere.

3. The method for preparing the fluorinated battery positive electrode material according to claim 2, characterized in that: in, In step S2, the particle size of the polytetrafluoroethylene powder is 8 μm to 12 μm, the ball milling beads are 10 1 mm and 5 5 mm agate ball milling beads, and the ball mill is a planetary ball mill.

4. The method for preparing the fluorinated battery positive electrode material according to claim 1, characterized in that: in, In step S4, according to the mass ratio of the calcined mixed powder to the lithium hydroxide in the lithium source being 1:1.05, the lithium source is added to the calcined mixed powder, and annealed at 800° C. for 10 hours in a muffle furnace under an air atmosphere to obtain a regenerated positive electrode material, i.e., a fluorinated modified battery positive electrode material.

5. The method for preparing the fluorinated battery positive electrode material according to claim 4, characterized in that: in, In step S4, the lithium source is LiOH-KOH, wherein the molar ratio of LiOH to KOH is 7:3, and the mass ratio of the calcined mixed powder to the LiOH-KOH is 1:

2.

6. The method for preparing the fluorinated battery positive electrode material according to claim 4, characterized in that: in, The lithium source is LiOH, and the mass ratio of the calcined mixed powder to the LiOH is 1:1.

05.

7. The method for preparing the fluorinated battery positive electrode material according to claim 4, characterized in that: in, In step S4, the lithium source is Li2CO3, and the mass ratio of the calcined mixed powder to the Li2CO3 is 1:1.

5.

8. The method for preparing the fluorinated battery positive electrode material according to claim 1, characterized in that: in, In step S1, the positive electrode sheet is placed in a NaOH solution with a mass concentration of 2% to dissolve the aluminum foil.

9. The method for preparing the fluorinated battery positive electrode material according to claim 1, characterized in that: in, In step S1, the positive electrode sheet comes from a waste battery, and the battery is a lithium cobalt oxide battery or a ternary battery. The detailed steps of the method for disassembling the positive electrode sheet are as follows: The waste battery is discharged in a 7%wt NaCl solution until no bubbles emerge, and then the discharged waste battery is placed in a glove box filled with argon gas, the battery shell is disassembled with scissors, and the peeled positive electrode sheet is soaked in an ethanol solution. After 30 minutes, the soaked positive electrode sheet is rinsed under a running tap to rinse off the ethanol and electrolyte on the surface, and then the positive electrode sheet is spread flat in a fume hood to dry, thereby obtaining a disassembled positive electrode sheet, namely the positive electrode sheet.

10. A fluorinated battery positive electrode material, characterized in that: The material is prepared by the method for preparing a fluorinated battery positive electrode material according to any one of claims 1 to 9.

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