Method for synthesizing positive electrode lithium supplement agent through ultrafast high-temperature heating and application of positive electrode lithium supplement agent

Abstract

The invention discloses a method for synthesizing a positive electrode lithium supplement agent through ultrafast high-temperature heating and application of the positive electrode lithium supplement agent. The method comprises the following steps: S1, preparing positive electrode lithium supplement agent precursor powder; and S2, spreading the positive electrode lithium supplement agent precursor powder on a heating substrate, connecting two ends of the heating substrate to a constant current power supply, and carrying out ultrafast high-temperature heating and cooling in a specific gas atmosphere to obtain the positive electrode lithium supplement agent. The method for synthesizing the positive electrode lithium supplement agent through ultrafast high-temperature heating has the characteristics of high temperature rising and lowering speed (10-105 DEG C / s) and short heat treatment time (millisecond-second), and is low in energy and gas consumption, economical and efficient.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery material manufacturing and application, and specifically relates to a method for synthesizing a positive electrode lithium replenisher by ultrafast high-temperature heating and the application of the positive electrode lithium replenisher. Background Art

[0002] Lithium-ion batteries (LIBs) are widely used in portable electronic devices, new energy vehicles, and renewable energy systems due to their high energy density, no memory effect, and environmental friendliness. Some promising cathode materials [such as LiCoO2, LiMn2O4, LiNi x Mn y Co z O2 and LiFePO4 (LFP)] have been widely used in commercial lithium-ion batteries. However, during the first charge process, the formation of the SEI film on the negative electrode side consumes the active lithium in the positive electrode, resulting in a decrease in battery capacity and a reduction in the initial coulombic efficiency (ICE), which seriously limits the further development of lithium-ion batteries. Generally, the formation of the SEI film is inevitable for lithium-ion batteries because the organic electrolyte is reduced / decomposed on the surface of the negative electrode during the first charge of the lithium-ion battery, thereby forming a solid electrolyte interface (SEI) film. Therefore, solving the problem of lithium loss in the positive electrode material caused by the SEI film is of great significance for the development of high-performance lithium-ion batteries.

[0003] In addition, the main reason for the failure of the positive electrode in retired batteries is lithium loss, and compensating for lithium loss is also crucial for repairing and regenerating waste positive electrode materials. Adding additional lithium sources to the battery is an effective solution to compensate for the loss of lithium in the first cycle. Therefore, this solution is called pre-lithiation. The pre-lithiation agent provides excess lithium during the first cycle to compensate for the lithium consumed in the formation of the SEI film and inactivated in subsequent cycles. The additional lithium source is beneficial to maintain a higher reversible capacity of the battery, prevent deep cycling of the anode and stabilize the anode. Generally, according to the location where the pre-lithiation agent is added in the battery, it can be divided into anode pre-lithiation agents and cathode pre-lithiation agents. Negative electrode pre-lithiation agents mainly include lithium foil, lithium powder and lithium silicide, but due to the low potential, high chemical reactivity and high cost of these agents, they are incompatible with existing battery manufacturing technology, which further limits the practical application of this type of pre-lithiation agent. Positive electrode pre-lithiation agents include sacrificial lithium compounds, conversion nanocomposites and lithium-rich transition metal oxides. Sacrificial lithium compounds (such as Li2O and Li2O2, etc.) will produce gas to crack the electrode after lithium supplementation, resulting in a decrease in reversible capacity. Conversion nanocomposites (such as M / Li2O and M / LiF, M=Co, Ni, Fe, etc.) require molten lithium during the synthesis process, and the residual substances after lithium supplementation will reduce the energy density of the battery. Lithium-rich transition metal oxides (such as Li5FeO4, Li5AlO4, Li6CoO4, Li2CuO2 and Li2NiO2, etc.) are relatively safe. By mixing an appropriate amount of lithium-rich transition metal oxides with traditional positive electrode materials, the initial charging capacity of the relevant positive electrode materials can be increased, thereby achieving the effect of lithium supplementation. Therefore, they have good application prospects as positive electrode pre-lithiation agents.

[0004] However, the conventional preparation method of the pre-lithiation reagent is to obtain it by high-temperature sintering in a traditional tube furnace. Although the crystal quality and purity of the pre-lithiation reagent sintered after high-temperature sintering are good, the preparation process is long (14 to 72 hours), energy consumption is high, and the prepared particle size is large (tens of microns), which is not conducive to Li + transmission. Chinese patent application CN117813263A discloses a positive electrode lithium supplement agent and its precursor, preparation method and application. The positive electrode lithium supplement agent precursor includes a core material and a shell material coated on the surface of the core material; the shell material of the precursor is adsorbed on the core material, and can react with the lithium source at low temperature to generate a lithium-containing metal oxide wrapped on the surface of the core material, and promote the lithium source to react with Ni(OH)2 to form a good solid solution, thereby reducing the sintering temperature, which is conducive to obtaining a high-purity lithium supplement agent material. Although the preparation temperature of this method is low, the preparation time of this method is too long, the preparation process is complicated, the conditions are relatively harsh, and the particle size of the positive electrode lithium supplement agent obtained is relatively large (D 50 1μm-3μm), which needs further improvement. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for synthesizing a positive electrode lithium replenisher by ultrafast high-temperature heating and the application of the positive electrode lithium replenisher, aiming to provide a simple, efficient, low-energy consumption rapid preparation technology to achieve the rapid synthesis of high-purity, nano-scale positive electrode lithium replenishers.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A method for synthesizing a positive electrode lithium supplement by ultrafast high-temperature heating, comprising the following steps:

[0008] S1. preparing cathode lithium supplement agent precursor powder;

[0009] S2. Spread the cathode lithium supplement agent precursor powder on a heating substrate, connect both ends of the heating substrate to a constant current power supply, perform ultrafast high-temperature heating under a specific gas atmosphere, and cool to obtain the cathode lithium supplement agent.

[0010] Preferably, in step S1, the specific preparation process of the positive electrode lithium supplement agent precursor powder is as follows: lithium oxide and metal oxide are mixed and ball milled, and the positive electrode lithium supplement agent precursor powder is obtained after the ball milling is completed.

[0011] Preferably, the metal oxide is one or more of Al2O3, CoO, Fe2O3, Fe3O4, NiO, and CuO; the molar ratio of lithium oxide to metal oxide is 1-7:1, for example, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 4.5:1, 6:1, 6.5:1, 7:1 can be selected, including but not limited to the listed values, and other values ​​not listed within the numerical range are also applicable.

[0012] Preferably, the rotation speed of the ball mill is 300-600rpm, for example, 300rpm, 350rpm, 400rpm, 450rpm, 500rpm, 550rpm, and 600rpm can be selected; the time is 6-12h, for example, 6h, 7h, 8h, 9h, 10h, 11h, and 12h can be selected; including but not limited to the listed values, other values ​​not listed within the numerical range are also applicable.

[0013] Preferably, in step S2, the atmosphere of the ultrafast high temperature heating is a non-reducing inert atmosphere; the non-reducing inert atmosphere is nitrogen, helium or argon.

[0014] Preferably, the heating substrate in step S2 is any one of a carbon-based heating substrate or a non-carbon-based heating substrate; the carbon-based heating substrate is any one of carbon paper, carbon cloth, carbon felt, graphene film or graphite paper; the non-carbon-based heating substrate is any one of stainless steel foil, nickel foil, Al2O3 ceramic sheet, etc.

[0015] Preferably, the temperature of the ultrafast high temperature heating is 600-1200°C, for example, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, 1200°C, 1400°C, 1600°C, 1800°C; the time is 100ms-400s, for example, 100ms, 200 s, 30s, 40s, 500ms, 600ms, 700ms, 800ms, 900ms, 1s, 2s, 3s, 4s, 5s, 6s, 7s, 8s, 9s, 10s, 20s, 30s, 40s, 50s, 60s, 70s, 80s, 90s, 100s, 200s, 300s, 400s; including but not limited to the listed values, other values ​​not listed within the numerical range are equally applicable.

[0016] Preferably, the heating rate of the ultrafast high temperature heating in step S2 is 10-10 5 ℃ / s, for example, 10℃ / s, 20℃ / s, 30℃ / s, 40℃ / s, 50℃ / s, 60℃ / s, 70℃ / s, 80℃ / s, 90℃ / s, 100℃ / s, 200℃ / s, 300℃ / s, 400℃ / s, 500℃ / s, 1000℃ / s, 2000℃ / s, 3000℃ / s, 4000℃ / s, 5000℃ / s, 10000℃ / s, 20000℃ / s, 30000℃ / s, 40000℃ / s, 50000℃ / s, 10 5 ℃ / s; the cooling rate is 10-10 3 ℃ / s, for example, 10℃ / s, 20℃ / s, 30℃ / s, 40℃ / s, 50℃ / s, 60℃ / s, 70℃ / s, 80℃ / s, 90℃ / s, 100℃ / s, 200℃ / s, 300℃ / s, 400℃ / s, 500℃ / s, 1000℃ / s can be selected; including but not limited to the listed values, other values ​​not listed within the numerical range are also applicable.

[0017] The present invention also protects a positive electrode lithium supplement prepared by the method as described above.

[0018] The present invention also protects the use of the positive electrode lithium supplement agent as described above in the preparation of lithium ion batteries.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The method for synthesizing a positive electrode lithium supplement by ultrafast high-temperature heating provided by the present invention has a fast heating and cooling speed (10 to 10 5 ℃ / s), short heat treatment time (milliseconds to seconds), as well as the advantages of low energy consumption, low carbon dioxide emissions, and economical and high efficiency.

[0021] (2) The particle size of the positive electrode lithium supplement agent synthesized by ultrafast high-temperature heating in the present invention is nanometer-level, which can not only increase the specific surface area, but also promote the rapid lithium removal of the lithium supplement agent to meet the application requirements of rapid lithium supplementation; at the same time, it improves the conductivity of the lithium supplement agent and greatly shortens the Li + The transmission distance is beneficial to the full utilization of lithium ions in the lithium supplement, thereby reducing the amount of lithium supplement and the manufacturing cost of the battery; the positive electrode lithium supplement material has high purity and good stability, which is beneficial to the preparation of lithium-ion batteries with better charging capacity and charging first efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the temperature curve of synthesizing Li5FeO4 using the ultrafast high temperature heating method in Example 2 of the present invention;

[0023] Figure 2 The XRD pattern of Li5FeO4 synthesized in Implementation 1-3 of the present invention;

[0024] Figure 3 is the XRD pattern of Li5AlO4 synthesized in Example 4 of the present invention;

[0025] Figure 4 is the XRD pattern of Li6CoO4 synthesized in Example 6 of the present invention;

[0026] Figure 5 is a SEM image of Li5FeO4 synthesized in Example 2 of the present invention;

[0027] Figure 6 The first cycle charge and discharge curve of Li5FeO4 synthesized in Examples 1-3 of the present invention;

[0028] Figure 7 It is a comparison chart of different rate performances of Example 8 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Example 1

[0031] A method for synthesizing a positive electrode lithium supplement by ultrafast high-temperature heating, comprising the following steps:

[0032] S1. Lithium oxide and iron oxide (Fe2O3) were weighed at a molar ratio of 5.5:1, and then the mixture of the two substances was ball-milled at a speed of 400 rpm for 8 h using a planetary ball mill to obtain a Li5FeO4 precursor powder;

[0033] S2. In an argon-filled glove box (water and oxygen content less than 0.1 ppm), 50 mg of dried Li5FeO4 precursor powder was spread on a carbon paper of size 2×4 cm, and ultrafast high-temperature heating was performed at a heating rate of 200°C / s under an argon atmosphere. After heating to 800°C, the temperature was kept for 20s, and then cooled at a cooling rate of 80°C / s. After cooling, Li5FeO4 powder was obtained, which was the positive electrode lithium supplement, and it was stored in an argon-filled glove box.

[0034] Example 2

[0035] A method for synthesizing a positive electrode lithium supplement by ultrafast high-temperature heating, comprising the following steps:

[0036] S1. Lithium oxide and iron oxide (Fe2O3) were weighed at a molar ratio of 5.5:1, and then the mixture of the two substances was ball-milled at a speed of 400 rpm for 8 h using a planetary ball mill to obtain a Li5FeO4 precursor powder;

[0037] S2. In an argon-filled glove box (water and oxygen content is less than 0.1 ppm), 50 mg of dried Li5FeO4 precursor powder is spread on a carbon paper of size 2×4 cm, and ultrafast high temperature heating is performed at a heating rate of 300°C / s under an argon atmosphere. After heating to 900°C, the temperature is kept for 20s, and then cooled at a cooling rate of 150°C / s. After cooling, Li5FeO4 powder is obtained, which is the positive electrode lithium supplement, and it is stored in an argon-filled glove box;

[0038] Among them, the temperature curve of synthesizing Li5FeO4 using ultrafast high temperature heating method is as follows Figure 1 shown.

[0039] Example 3

[0040] A method for synthesizing a positive electrode lithium supplement by ultrafast high-temperature heating, comprising the following steps:

[0041] S1. Lithium oxide and iron oxide (Fe2O3) were weighed at a molar ratio of 5.5:1, and then the mixture of the two substances was ball-milled at a speed of 400 rpm for 8 h using a planetary ball mill to obtain a Li5FeO4 precursor powder;

[0042] S2. In an argon-filled glove box (water and oxygen content less than 0.1 ppm), 50 mg of dried Li5FeO4 precursor powder was spread on a carbon paper of size 2×4 cm, and ultrafast high-temperature heating was performed at a heating rate of 400°C / s under an argon atmosphere. After heating to 1000°C, the temperature was kept for 20s, and then cooled at a cooling rate of 300°C / s. After cooling, Li5FeO4 powder was obtained, which was the positive electrode lithium supplement, and it was stored in an argon-filled glove box.

[0043] Example 4

[0044] A method for synthesizing a positive electrode lithium supplement by ultrafast high-temperature heating, comprising the following steps:

[0045] S1, weighing lithium oxide and aluminum oxide (Al2O3) at a molar ratio of 5.5:1, and then using a planetary ball mill to mill the mixture of the two substances at a speed of 400 rpm for 8 hours to obtain Li5AlO4 precursor powder;

[0046] S2. In an argon-filled glove box (water and oxygen content less than 0.1 ppm), 50 mg of dried Li5AlO4 precursor powder was spread on a carbon paper of size 2×4 cm, and ultrafast high-temperature heating was performed at a heating rate of 300°C / s under an argon atmosphere. After heating to 900°C, the temperature was kept for 10s, and then cooled at a cooling rate of 150°C / s. After cooling, Li5AlO4 powder was obtained, which was the positive electrode lithium supplement, and it was stored in an argon-filled glove box.

[0047] Example 5

[0048] A method for synthesizing a positive electrode lithium supplement by ultrafast high-temperature heating, comprising the following steps:

[0049] S1, weighing lithium oxide and aluminum oxide (Al2O3) at a molar ratio of 5.5:1, and then using a planetary ball mill to mill the mixture of the two substances at a speed of 400 rpm for 8 hours to obtain Li5AlO4 precursor powder;

[0050] S2. In an argon-filled glove box (water and oxygen content less than 0.1 ppm), 50 mg of dried Li5AlO4 precursor powder was spread on a carbon paper of size 2×4 cm, and ultrafast high-temperature heating was performed at a heating rate of 200°C / s under an argon atmosphere. After heating to 900°C, the temperature was kept for 20s, and then cooled at a cooling rate of 80°C / s. After cooling, Li5AlO4 powder was obtained, which was the positive electrode lithium supplement, and it was stored in an argon-filled glove box.

[0051] Example 6

[0052] A method for synthesizing a positive electrode lithium supplement by ultrafast high-temperature heating, comprising the following steps:

[0053] S1. Lithium oxide and cobalt monoxide (CoO) were weighed in a molar ratio of 6.25:1, and then the mixture of the two substances was ball-milled at a speed of 400 rpm for 8 h using a planetary ball mill to obtain a Li6CoO4 precursor powder;

[0054] S2. In an argon-filled glove box (water and oxygen content less than 0.1 ppm), 50 mg of dried Li6CoO4 precursor powder was spread on a carbon paper of size 2×4 cm, and ultrafast high-temperature heating was performed at a heating rate of 200°C / s under an argon atmosphere. After heating to 900°C, the temperature was kept for 40s, and then cooled at a cooling rate of 80°C / s. After cooling, Li6CoO4 powder was obtained, which was the positive electrode lithium supplement, and it was stored in an argon-filled glove box.

[0055] Example 7

[0056] A method for synthesizing a positive electrode lithium supplement by ultrafast high-temperature heating, comprising the following steps:

[0057] S1. Lithium oxide and cobalt monoxide (CoO) were weighed in a molar ratio of 6.25:1, and then the mixture of the two substances was ball-milled at a speed of 400 rpm for 8 h using a planetary ball mill to obtain a Li6CoO4 precursor powder;

[0058] S2. In an argon-filled glove box (water and oxygen content less than 0.1 ppm), 50 mg of dried Li6CoO4 precursor powder was spread on a carbon paper of size 2×4 cm, and ultrafast high-temperature heating was performed at a heating rate of 200°C / s under an argon atmosphere. After heating to 900°C, the temperature was kept for 50s, and then cooled at a cooling rate of 80°C / s. After cooling, Li6CoO4 powder was obtained, which was the positive electrode lithium supplement, and it was stored in an argon-filled glove box.

[0059] Example 8

[0060] According to a certain mass ratio, 5 mg of Li5FeO4 obtained in Example 2, 75 mg of waste LFP, 10 mg of PVDF, and 10 mg of acetylene black were weighed and added to 5 Ml of N-methylpyrrolidone to prepare a positive electrode slurry, which was coated on an aluminum foil and then vacuum-baked to obtain an electrode sheet. The electrode sheet was assembled into a button cell and subjected to a constant current charge and discharge test.

[0061] Comparative Example 1

[0062] According to a certain mass ratio, 80 mg of waste LFP, 10 mg of PVDF, 10 mg of acetylene black, etc. were weighed and added to 5 mL of N-methylpyrrolidone solution to prepare the positive electrode slurry, which was coated on aluminum foil and then vacuum-baked to obtain the electrode sheet. The electrode sheet was assembled into a button cell and constant current charge and discharge test was carried out.

[0063] The temperature of ultrafast high temperature heating synthesis of Li5FeO4 in Example 2 was monitored to obtain Figure 1 ; XRD test was performed on the Li5FeO4 synthesized in Example 1-3 to obtain Figure 2 The XRD spectra of Li5AlO4 and Li6CoO4 synthesized in Examples 4 and 6 were tested by XRD, and the results were Figure 3 and Figure 4 The XRD spectrum shown in FIG. 1 is obtained by scanning electron microscopy to characterize the morphology of Li5FeO4 synthesized at ultrafast temperature in Example 2. Figure 5 The Li5FeO4 synthesized in Example 1-3 was prepared into a battery, and its capacity was tested at 0.1C, and the obtained Figure 6 Taking the synthesized Li5FeO4 as an example to demonstrate the application potential of the positive electrode lithium supplement in the regeneration and repair of failed positive electrodes, the button cells assembled in Comparative Example 1 and Example 8 were tested for their rate performance at 0.1C, 0.2C, 0.5C, 1C, 2C, 5C, and 10C. Figure 7 .

[0064] Depend on Figure 1 It can be seen that the temperature and time for synthesizing Li5FeO4 in Example 2 are 900°C and 20s respectively.

[0065] Depend on Figure 2 It can be seen that the main diffraction peaks of Li5FeO4 synthesized at 800, 900, and 1000℃ are similar, all corresponding to the PDF card of Li5FeO4 (PDF#24-0623), and no other obvious impurity peaks are observed, indicating that this method has produced high-purity Li5FeO4 materials. However, with the increase of temperature, the intensity of the diffraction peaks is also different. Among them, the diffraction peak of Li5FeO4 synthesized at 900℃ is the sharpest, the sample has the best crystallinity, and the crystal form is also the most complete.

[0066] Depend on Figure 3 , Figure 4 It can be seen that Li5AlO4 and Li6CoO4 can also be synthesized by ultrafast high-temperature synthesis method, and their main diffraction peaks correspond to PDF#70-0432 and PDF#38-1140 respectively, and there are no other obvious impurity peaks. This reflects the universal application of ultrafast high-temperature synthesis method for the rapid synthesis of positive electrode lithium supplements.

[0067] Depend on Figure 5 It can be seen that the particle size of Li5FeO4 synthesized at 900℃ is 50-200nm, and the particles are relatively small.

[0068] Depend on Figure 6 It can be seen that the charging capacity of Li5FeO4 positive electrode lithium supplement synthesized at different temperatures is in the order of 900℃>800℃>1000℃.

[0069] Depend on Figure 7 It can be seen that Li5FeO4 can replenish the lithium ions lost in the failed LFP, thereby restoring and improving the discharge capacity of the spent LFP.

[0070] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for synthesizing a positive electrode lithium supplement by ultrafast high temperature heating, characterized in that: The following steps are involved: S1. preparing cathode lithium supplementation agent precursor powder; S2. Spread the cathode lithium supplement agent precursor powder on a heating substrate, connect both ends of the heating substrate to a constant current power supply, perform ultrafast high-temperature heating under a specific gas atmosphere, and cool to obtain the cathode lithium supplement agent.

2. The method according to claim 1, characterized in that: In step S1, the specific preparation process of the positive electrode lithium supplement agent precursor powder is as follows: lithium oxide and metal oxide are mixed and ball milled, and the positive electrode lithium supplement agent precursor powder is obtained after the ball milling is completed.

3. The method according to claim 2, characterized in that The metal oxide is one or more of Al2O3, CoO, Fe2O3, Fe3O4, NiO, and CuO; and the molar ratio of the lithium oxide to the metal oxide is 1-7:

1.

4. The method according to claim 2, characterized in that: The ball milling speed is 300-600 rpm, and the time is 6-12 hours.

5. The method according to claim 1, characterized in that In step S2, the atmosphere of the ultrafast high temperature heating is a non-reducing inert atmosphere; the non-reducing inert atmosphere is nitrogen, helium or argon.

6. The method according to claim 1, characterized in that The heating substrate in step S2 is any one of a carbon-based heating substrate or a non-carbon-based heating substrate; the carbon-based heating substrate is any one of carbon paper, carbon cloth, carbon felt, graphene film or graphite paper; the non-carbon-based heating substrate is any one of stainless steel foil, nickel foil, Al2O3 ceramic sheet, etc.

7. The method according to claim 1, characterized in that The ultrafast high temperature heating in step S2 has a temperature of 500-1800° C. and a time of 100 ms-400 s.

8. The method according to claim 1, characterized in that The heating rate of the ultrafast high temperature heating in step S2 is 10-10 5 ℃ / s, the cooling rate is 10-10 3 ℃ / s.

9. A positive electrode lithium supplement prepared by the method according to any one of claims 1 to 8.

10. Use of the positive electrode lithium supplement agent according to claim 9 in the preparation of lithium ion batteries.

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