A heat treatment method of a sodium-ion battery metal oxide positive electrode material, a sodium-ion secondary battery and a preparation method

Abstract

The application discloses a heat treatment method of a sodium ion battery metal oxide positive electrode material, a sodium ion secondary battery and a preparation method. x The molecular formula of the sodium ion battery metal oxide positive electrode material is Na MO2, 0.6<=x<=1, and M is a metal element, including Fe, Mn and Ni. 3+ In the application, appropriate oxygen vacancies are generated on the surface of the positive electrode material, the generation of the oxygen vacancies can reduce the average valence of the transition metal and strengthen the pseudo-capacitance behavior of the positive electrode, thereby improving the battery capacity; for the manganese-based oxide positive electrode material, the oxygen vacancies near Mn can relieve Jahn-Teller distortion, thereby improving the cycle performance. The whole process is simple in operation, strong in controllability, good in repeatability and suitable for large-scale production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery manufacturing, and particularly relates to a heat treatment method of a sodium-ion battery metal oxide positive electrode material and a sodium-ion secondary battery and a preparation method. BACKGROUND

[0002] As a representative of high-performance secondary batteries, lithium-ion batteries have rapidly gained market recognition since commercialization. However, due to the scarcity and uneven distribution of lithium resources, lithium-ion batteries gradually cannot meet the growing demand of mobile terminals, electric vehicles and energy storage industries. Sodium-ion batteries, which have similar working principles to lithium-ion batteries, have the advantages of abundant raw materials, low cost, environmental friendliness, no self-discharge, good safety, etc., and thus become an important supplement to lithium batteries.

[0003] The positive electrode material is an important component of the battery, which affects the working voltage and specific capacity of the battery. The positive electrode material of the sodium-ion battery mainly includes metal oxides, polyanion compounds, prussian blue analogues, etc. Among them, metal oxides have the advantages of suitable working potential, simple synthesis, etc., and are considered as promising positive electrode materials. In particular, Fe-Mn-Ni ternary layered positive electrodes have the advantages of high theoretical capacity, good cycle stability, wide raw material sources, no pollution, etc., and are most suitable for commercial large-scale application (ACS Appl. Mater. Interfaces 2020, 12, 51397-51408).

[0004] The current metal oxide positive electrode material is generally prepared by high-temperature solid-phase method. The addition of a quenching step after high-temperature sintering has the effects of reducing sodium loss, generating oxygen vacancies on the surface of the positive electrode material, and thus improving the capacity, cycle stability and rate performance (Adv. Funct. Mater. 2021, 31, 2101475). For this process, the cooling rate of quenching can be further adjusted to achieve optimal battery performance. However, there are also problems in the preparation of oxide positive electrodes. After sintering, the oxide often has a lot of residual alkali. The use of traditional wet process in the slurry preparation stage of the battery preparation process will cause problems such as many slurry particles, slurry water absorption forming jelly-like gel, etc., which will further make coating difficult, the surface density of the electrode uneven, and the battery consistency poor (CN 117096257 A). Therefore, a more efficient and suitable slurry preparation process needs to be developed. SUMMARY

[0005] In order to further improve the battery performance and overcome the problem of many slurry particles in the coating process of the positive electrode material in the prior art, and the formation of jelly-like gel after water absorption, the application provides a heat treatment method of a sodium ion battery metal oxide positive electrode material, a sodium ion secondary battery and a preparation method.

[0006] In order to achieve the above purpose, the application adopts the following technical solutions:

[0007] A heat treatment method of a sodium ion battery metal oxide positive electrode material, comprising the following steps:

[0008] Preparation of a precursor: uniformly mixing anhydrous sodium carbonate, a metal oxide and a dispersing agent, drying to obtain a positive electrode material precursor;

[0009] Heat treatment: calcining the positive electrode material precursor, quenching, the average quenching rate being 55-70 DEG C / min, to obtain a sodium ion battery metal oxide positive electrode material;

[0010] The molecular formula of the sodium ion battery metal oxide positive electrode material is Na x MO2, wherein 0.6 < x < 1, M is a metal element, including Fe, Mn and Ni.

[0011] Further, the calcination temperature is 850-950 DEG C, the time is 10-15 h, and the average quenching rate is 55-70 DEG C / min.

[0012] Further, the temperature is raised to 850-950 DEG C at a temperature raising rate of 3-5 DEG C / min.

[0013] Further, the anhydrous sodium carbonate, the metal oxide and the dispersing agent are uniformly mixed, specifically: the anhydrous sodium carbonate, the metal oxide, the dispersing agent and the ball milling beads are ball milled and uniformly mixed.

[0014] The mass ratio of the mixture of the anhydrous sodium carbonate and the metal oxide to the dispersing agent is 1:0.9-1.

[0015] Further, the mass ratio of the mixture of the anhydrous sodium carbonate and the metal oxide to the ball milling beads is 1:0.5-1, the rotation speed of the ball milling is 500-700 r / min, and the time is 5-7 h.

[0016] Further, the dispersing agent is isopropyl alcohol, anhydrous ethanol or acetone.

[0017] Further, the metal oxide is a mixture of one or both of MnO2 and Mn2O3 and Fe2O3 and NiO.

[0018] Further, the metal oxide includes one or more of MgO, ZnO, Al2O3, TiO2, CuO and CoO.

[0019] A sodium-ion secondary battery of a sodium-ion battery metal oxide positive electrode material.

[0020] A preparation method of a sodium-ion secondary battery, comprising the following steps:

[0021] Mixing the binder and the solvent to prepare a colloidal solvent, then adding the positive electrode material and the conductive agent dry mixing product into the colloidal solvent, and ball milling to prepare a slurry; wherein the rotation speed of the ball milling is 800-1000 r / min, and the time is 5-10 min.

[0022] Uniformly coating the slurry on a current collector, drying and cutting to obtain an electrode sheet, assembling to obtain the sodium-ion secondary battery.

[0023] Compared with the prior art, the present application has the following beneficial effects:

[0024] The metal oxide material heat treatment method provided by the present application creatively controls the cooling speed of the quenching process on the basis of the traditional solid-phase reaction, and the appropriate cooling speed can reduce the sodium loss caused by slow cooling and thus improve the initial coulomb efficiency of the full battery, so that the average cooling speed of the quenching in the present application is 55-70 ℃ / min, and at the same time, appropriate oxygen vacancies are generated on the surface of the positive electrode material, the generation of the oxygen vacancies can reduce the average valence of the transition metal and strengthen the pseudo-capacitance behavior of the positive electrode and thus improve the battery capacity, in addition, for the manganese-based oxide positive electrode material, the oxygen vacancies near Mn 3+ The whole preparation process of the present application is simple in operation, strong in controllability, good in repeatability and suitable for large-scale production.

[0025] In the preparation method of the sodium-ion secondary battery provided by the present application, the binder and the solvent are first mixed to prepare a colloidal solvent, then the positive electrode material and the conductive agent dry mixing product are added into the colloidal solvent to prepare a slurry, and finally the slurry particle size is reduced by ball milling. The slurry preparation time is short, which can avoid the slurry deterioration caused by long-time mixing; the short-time ball milling at the end of the slurry preparation process can reduce the slurry particles, improve the slurry fineness, and at the same time, avoid the influence of the mechanical effect and thermal effect of long-time ball milling on the slurry and the positive electrode material. The slurry prepared in the present application has few particles, high fineness and appropriate fluidity, the electrode sheet has no point or linear defects, the whole process is simple in operation, good in controllability, rapid in operation, and suitable for use in large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 NaNi 0.33 Fe0.33 Mn 0.33 Third cycle charge-discharge curves of O2;

[0027] Figure 2 NaNi 0.33 Fe 0.33 Mn 0.33 Cycle performance of O2;

[0028] Figure 3 NaNi 0.33 Fe 0.33 Mn 0.33 Rate performance of O2;

[0029] Figure 4 NaNi 0.25 Fe 0.5 Mn 0.25 Third cycle charge-discharge curves of O2;

[0030] Figure 5 NaMg 0.1 Ni 0.23 Fe 0.33 Mn 0.33 Third cycle charge-discharge curves of O2;

[0031] Figure 6 NaMg 0.05 Ni 0.28 Fe 0.33 Mn 0.33 Third cycle charge-discharge curves of O2;

[0032] Figure 7 NaZn 0.05 Ni 0.33 Fe 0.26 Mn 0.36 Third cycle charge-discharge curves of O2;

[0033] Figure 8 NaMg 0.2 Ni 0.13 Fe 0.33 Mn 0.33 Third cycle charge-discharge curves of O2. DETAILED DESCRIPTION

[0034] For the purpose of facilitating the understanding of the present application, a more complete description of the present application will be given below with reference to the relevant drawings. The preferred embodiments of the present application are shown in the drawings. However, the present application can be realized in various different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0035] In a first aspect, a heat treatment method of a sodium-ion battery metal oxide cathode material is provided, the cathode material has a molecular formula of Na x MO2, wherein 0.6 < x ≤ 1, M is a metal element, and contains a combination of one or more of Fe, Mn, and Ni, and can contain a combination of one or more of Mg, Zn, Al, Ti, Cu, and Co, and the preparation method comprises the following steps:

[0036] Preparation of the precursor: mix anhydrous sodium carbonate, metal oxide, and dispersant, ball mill, dry, and obtain the cathode material precursor; heat treatment: calcine the cathode material precursor in air, quench, control the quenching speed, and obtain the sodium-ion battery metal oxide cathode material.

[0037] Anhydrous sodium carbonate and metal oxide are mixed in a stoichiometric ratio, and there is no excess anhydrous sodium carbonate (generally, a slight excess of sodium carbonate is added in a conventional solid-phase reaction to compensate for sodium loss).

[0038] The specific process of ball milling after mixing anhydrous sodium carbonate, metal oxide, and dispersant is as follows: anhydrous sodium carbonate, metal oxide, dispersant, and ball milling beads are sequentially added to a mixing tank, the mass ratio of solid (a mixture of anhydrous sodium carbonate and metal oxide) to liquid (dispersant) is 1:0.9-1, the mass ratio of solid to ball milling beads is 1:0.5-1, the dispersant is isopropanol, anhydrous ethanol, or acetone, the ball milling beads and the mixing tank are made of polytetrafluoroethylene, the mixing tank is placed in a planetary centrifugal mixer, the rotation speed is set to 500-700 r / min, and the time is 5-7 h. The metal oxide is a mixture of one or both of MnO2 and Mn2O3 and Fe2O3 and NiO, and preferably, the metal oxide further contains a combination of one or more of MgO, ZnO, Al2O3, TiO2, CuO, and CoO.

[0039] The process of calcining the cathode material precursor in air, quenching, and controlling the quenching speed to obtain the sodium-ion battery metal oxide cathode material comprises the following steps: the cathode material is added to an alumina crucible, placed in a muffle furnace, the calcination temperature is set to 850-950℃, the heating rate is 3-5℃ / min, the time is 10-15 h, after the calcination is completed, the cathode material is quenched to 100℃ on a metal plate, the cooling rate of the quenching process is controlled, and after the quenching is completed, the material is quickly moved into an argon-filled glove box for storage.

[0040] The metal plate is made of red copper or 304 stainless steel.

[0041] The average cooling rate of the quenching process is 55-70℃ / min. The material cooling rate is related to the surface area of the metal plate. For a fixed mass of positive electrode material, a metal plate with a corresponding surface area is selected for quenching, so that the average cooling rate is within the range of 55-70℃ / min.

[0042] In a second aspect, a method for preparing a secondary battery containing the above-mentioned sodium-ion battery metal oxide positive electrode material, comprising the following steps:

[0043] S1. Add the binder PVDF and the solvent NMP to the mixing tank in a mass ratio of 1:35-45, and place it in a planetary centrifugal mixer, set the rotation speed to 800-1200r / min, and the time to 30min, to obtain a gluey solvent;

[0044] S2. Add the positive electrode material and the conductive agent Super P to the mixing tank, and place it in a planetary centrifugal mixer, set the rotation speed to 800-1200r / min, and dry mix for 30-90s, to obtain a mixture; wherein the mass ratio of the positive electrode material, Super P and PVDF in step S1 is 7:2:1;

[0045] S3. Add the dry mixed mixture obtained in S2 to the gluey solvent obtained in step S1, and place it in a planetary centrifugal mixer, set the rotation speed to 800-1200r / min, and mix for 10-15min, to obtain a slurry;

[0046] S4. Add ball milling beads to the slurry obtained in S3, and place it in a planetary centrifugal mixer, set the rotation speed to 800-1000r / min, and mix for another 5-10min to improve the fineness;

[0047] S5. Uniformly coat the slurry obtained in S4 on the current collector, dry and cut to obtain an electrode sheet, and assemble the battery.

[0048] Example 1

[0049] (1) Weigh 3.34g Na2CO3, 1.58g NiO, 1.68g Fe2O3 and 1.83g MnO2, and add them to 7g isopropyl alcohol, then add 3.5g ball milling beads, and place them in a planetary mixer, set the rotation speed to 600r / min, and the time to 6h, so that the solids are fully mixed and uniform, then vacuum dry the obtained product at 60℃ for 8h to obtain a positive electrode material precursor;

[0050] (2) Place the precursor obtained in step (1) in a muffle furnace, set the temperature to 850℃, and heat for 12h, with a heating rate of 5℃ / min;

[0051] (3) After heating, the product in step (2) is immediately placed on a 20 cm * 20 cm * 0.6 cm copper metal plate, and the temperature is reduced to 102℃ after 12 min, to obtain the positive material NaNi 0.33 Fe 0.33 Mn 0.33 O2, which is immediately transferred to an argon-filled glove box for storage;

[0052] (4) 0.1 g of PVDF is weighed into 4 g of NMP and placed in a planetary mixer for mixing, with a rotation speed of 1200 r / min and a time of 30 min to obtain a colloidal solvent; 0.7 g of the positive material obtained in step (3) and 0.2 g of Super P are dry-mixed, with a mixing rotation speed of 1200 r / min and a time of 90 s; the dry-mixed positive material and Super P are added to the colloidal solvent, with a mixing rotation speed of 1200 r / min and a time of 10 min; 0.5 g of ball milling beads is added to the slurry, with a mixing rotation speed of 800 r / min and a time of 5 min, to obtain a positive material slurry;

[0053] (5) The slurry obtained in step (4) is uniformly coated on an aluminum foil, which is vacuum dried at 60℃ for 6 h and then cut into a circular electrode with a diameter of 12 mm;

[0054] (6) The electrode obtained in step (5) is assembled into a battery in an argon atmosphere glove box, with metallic sodium as the counter electrode, glass fiber as the separator, and 1 mol / L NaClO4 in propylene carbonate (PC) / ethyl methyl carbonate (EMC) (volume ratio 1:1) as the electrolyte, with 2% mass fraction of fluoroethylene carbonate (FEC) as the electrolyte additive, to form a CR2032 button cell; a constant current charge and discharge mode is used for charge and discharge test at a current density of 0.1C; the test conditions are a discharge cutoff voltage of 2V and a charge cutoff voltage of 4.3V.

[0055] Figure 1 The positive material NaNi 0.33 Fe 0.33 Mn 0.33 O2 half-cell, and the third cycle charge and discharge curve shows that the reversible capacity is 140 mAh / g.

[0056] Figure 2 The positive material NaNi 0.33 Fe 0.33 Mn 0.33 O2 half-cell, and the third cycle charge and discharge curve shows that the reversible capacity is 140 mAh / g.

[0057] Figure 3The positive electrode material NaNi 0.33 Fe 0.33 Mn 0.33 The rate performance curve of the O2 half-cell can be seen that the capacity retention rate is high at 2C and the rate performance is good.

[0058] Example 2

[0059] (1) 2.38 g of Na2CO3, 0.84 g of NiO, 1.79 g of Fe2O3 and 0.98 g of MnO2 were weighed and added to 5 g of isopropyl alcohol, 2.5 g of ball milling beads were added, and the mixture was placed in a planetary mixer, set at a speed of 500 r / min for 6 h, so that the solids were fully and uniformly mixed. The obtained product was vacuum dried at 60℃ for 8 h to obtain a positive electrode material precursor;

[0060] (2) The precursor obtained in step (1) was calcined in a muffle furnace, the temperature was set to 850℃, the heating time was 12 h, and the temperature rising speed was 5℃ / min;

[0061] (3) After heating, the product in step (2) was immediately placed on a purple copper metal plate with a size of 20 cm*10 cm*0.6 cm, and the temperature dropped to 106℃ after 13 min, obtaining a positive electrode material NaNi 0.25 Fe 0.5 Mn 0.25 O2, which was immediately transferred to an argon-filled glove box for storage;

[0062] (4) 0.1 g of PVDF was weighed and added to 4 g of NMP, and the mixture was placed in a planetary mixer for mixing, set at a speed of 1200 r / min for 30 min to obtain a gel-like solvent; 0.7 g of the positive electrode material obtained in step (3) and 0.2 g of SuperP were dry-mixed, set at a mixing speed of 1200 r / min for 90 s; the dry-mixed positive electrode material and Super P were added to the gel-like solvent, set at a mixing speed of 1200 r / min for 10 min; 0.5 g of ball milling beads was added to the slurry, set at a mixing speed of 800 r / min for 5 min to obtain a positive electrode material slurry;

[0063] (5) The slurry obtained in step (4) was uniformly coated on an aluminum foil, which was vacuum dried at 60℃ for 6 h and then cut into a circular electrode with a diameter of 12 mm;

[0064] (6) The pole piece obtained in step (5) is assembled into a battery in an argon atmosphere glove box, with metal sodium as a counter electrode, glass fiber as a diaphragm, 1 mol / L NaClO4 propylene carbonate (PC) / ethyl methyl carbonate (EMC) (volume ratio 1:1) solution as an electrolyte, 2% mass fraction of fluoroethylene carbonate (FEC) as an electrolyte additive, to assemble a CR2032 button cell; a constant current charge and discharge mode is used, and charge and discharge test is carried out at a current density of 0.1C; the test conditions are that the discharge cutoff voltage is 2V, and the charge cutoff voltage is 4.3V.

[0065] Figure 4 The positive electrode material NaNi 0.25 Fe 0.5 Mn 0.25 The third cycle charge and discharge curve of O2 shows that the reversible capacity is 126mAh / g.

[0066] Example 3

[0067] (1) 3.45g of Na2CO3, 1.12g of NiO, 1.73g of Fe2O3, 1.89g of MnO2 and 0.26g of MgO are weighed and added to 7g of isopropanol, 3.5g of ball milling beads are further added, and the mixture is placed in a planetary mixer, the rotation speed is set to 600r / min, and the time is 6h, so that the solids are fully and uniformly mixed, then the obtained product is vacuum dried at 60℃ for 8h to obtain a positive electrode material precursor;

[0068] (2) The precursor obtained in step (1) is calcined in a muffle furnace, the temperature is set to 900℃, the heating time is 15h, and the temperature rising speed is 5℃ / min;

[0069] (3) After heating, the product in step (2) is immediately placed on a 20cm*20cm*0.6cm copper metal plate, and the temperature is reduced to 100℃ after 13min, to obtain a positive electrode material NaMg 0.1 Ni 0.23 Fe 0.33 Mn 0.33 O2, which is immediately transferred to an argon-filled glove box for storage;

[0070] (4) take 0.1 g PVDF into 4.5 g NMP, put into a planetary mixer, set the rotation speed to 1200 r / min, time 30 min, to obtain a gluey solvent; take 0.7 g of the positive material obtained in step (3) and 0.2 g Super P for dry mixing, set the mixing rotation speed to 1200 r / min, time 90 s; add the dry mixed positive material and Super P into the gluey solvent, set the mixing rotation speed to 1200 r / min, time 15 min; add 0.5 g of ball milling beads into the slurry, set the mixing rotation speed to 800 r / min, time 10 min, to obtain a positive material slurry;

[0071] (5) evenly coat the slurry obtained in step (4) on an aluminum foil, vacuum dry at 60℃ for 6 h, and cut into a circular electrode with a diameter of 12 mm;

[0072] (6) assemble the electrode obtained in step (5) into a battery in an argon atmosphere glove box, use metal sodium as a counter electrode, use glass fiber as a separator, use 1 mol / L NaClO4 propylene carbonate (PC) / ethyl methyl carbonate (EMC) (volume ratio 1:1) solution as an electrolyte, 2% mass fraction of fluoroethylene carbonate (FEC) as an electrolyte additive, to assemble a CR2032 button cell; use a constant current charge and discharge mode, perform charge and discharge test at a current density of 0.1C; the test conditions are discharge cut-off voltage of 1.5 V and charge cut-off voltage of 4.3 V.

[0073] Figure 5 The positive material NaMg 0.1 Ni 0.23 Fe 0.33 Mn 0.33 O2 prepared for Example 3, and the third cycle charge and discharge curve thereof shows that the reversible capacity is 152 mAh / g.

[0074] Example 4

[0075] (1) take 0.97 g Na2CO3, 0.38 g NiO, 0.49 g Fe2O3, 0.53 g MnO2 and 0.04 g MgO into 2 g of isopropyl alcohol, add 1 g of ball milling beads, put into a planetary mixer, set the rotation speed to 500 r / min, time 5 h, to fully mix and uniformly mix the solids, then vacuum dry the obtained product at 60℃ for 8 h to obtain a positive material precursor;

[0076] (2) put the precursor obtained in step (1) into a muffle furnace, set the temperature to 900℃, heating time 15 h, and the heating rate to 5℃ / min;

[0077] (3) After heating is completed, the product in step (2) is immediately placed on a 20 cm*20 cm*0.4 cm 304 stainless steel metal plate, and the temperature is reduced to 102°C after 14 min to obtain a positive electrode material NaMg 0.05 Ni 0.28 Fe 0.33 Mn 0.33 O2, which is immediately transferred to an argon-filled glove box for storage;

[0078] (4) 0.1 g of PVDF is weighed into 4.5 g of NMP, and placed in a planetary mixer for mixing, with a rotation speed of 1200 r / min and a time of 30 min to obtain a gluey solvent; 0.7 g of the positive electrode material obtained in step (3) and 0.2 g of Super P are dry-mixed, with a mixing rotation speed of 1200 r / min and a time of 90 s; the dry-mixed positive electrode material and Super P are added to the gluey solvent, with a mixing rotation speed of 1200 r / min and a time of 15 min; 0.5 g of ball milling beads is added to the slurry, with a mixing rotation speed of 800 r / min and a time of 10 min to obtain a positive electrode material slurry;

[0079] (5) The slurry obtained in step (4) is uniformly coated on an aluminum foil, and after vacuum drying at 60°C for 6 h, it is cut into a circular electrode with a diameter of 12 mm;

[0080] (6) The electrode obtained in step (5) is assembled into a battery in an argon atmosphere glove box, with metallic sodium as the counter electrode, glass fiber as the separator, and a 1 mol / L NaClO4 solution of propylene carbonate (PC) / ethyl methyl carbonate (EMC) (volume ratio 1:1) as the electrolyte, 2% mass fraction of fluoroethylene carbonate (FEC) as an electrolyte additive, to assemble a CR2032 button cell; a constant current charge and discharge mode is used, and the charge and discharge test is carried out at a current density of 0.1C; the test conditions are a discharge cut-off voltage of 1.5V and a charge cut-off voltage of 4.3V.

[0081] Figure 6 The third cycle charge and discharge curve of the positive electrode material NaMg 0.05 Ni 0.28 Fe 0.33 Mn 0.33 O2 prepared in Example 4, and it can be known that the reversible capacity is 160 mAh / g.

[0082] Example 5

[0083] (1) Take 2.36 g of Na2CO3, 1.10 g of NiO, 0.93 g of Fe2O3, 1.40 g of MnO2 and 0.18 g of ZnO and add them to 7 g of isopropyl alcohol, then add 3.5 g of ball milling beads, place them in a planetary mixer, set the rotation speed to 600 r / min, and mix for 7 h to make the solids fully and uniformly mixed, then vacuum dry the obtained product at 60°C for 8 h to obtain a positive electrode material precursor;

[0084] (2) Place the precursor obtained in step (1) in a muffle furnace and calcine it at a temperature of 900°C for 15 h, with a heating rate of 5°C / min;

[0085] (3) Immediately after heating, place the product in step (2) on a 20 cm*20 cm*0.6 cm copper metal plate, and after 12 min, the temperature drops to 100°C, to obtain a positive electrode material NaZn 0.05 Ni 0.33 Fe 0.26 Mn 0.36 O2, immediately transfer it to an argon-filled glove box for storage;

[0086] (4) Take 0.1 g of PVDF and add it to 4.5 g of NMP, place them in a planetary mixer and mix them, set the rotation speed to 1200 r / min, and mix for 30 min to obtain a gel-like solvent; take 0.7 g of the positive electrode material obtained in step (3) and 0.2 g of Super P and dry mix them, set the mixing rotation speed to 1200 r / min, and mix for 90 s; add the dry-mixed positive electrode material and Super P to the gel-like solvent, set the mixing rotation speed to 1200 r / min, and mix for 15 min; add 0.5 g of ball milling beads to the slurry, set the mixing rotation speed to 800 r / min, and mix for 10 min to obtain a positive electrode material slurry;

[0087] (5) Uniformly coat the slurry obtained in step (4) on an aluminum foil, vacuum dry it at 60°C for 6 h, and then cut it into a circular electrode with a diameter of 12 mm;

[0088] (6) Assemble the electrode obtained in step (5) into a battery in an argon atmosphere glove box, use metallic sodium as the counter electrode, use glass fiber as the separator, use 1 mol / L NaClO4 propylene carbonate (PC) / ethyl methyl carbonate (EMC) (volume ratio 1:1) solution as the electrolyte, and 2% mass fraction of fluoroethylene carbonate (FEC) as the electrolyte additive, to assemble a CR2032 button cell; use a constant current charge and discharge mode, and perform charge and discharge tests at a current density of 0.1C; the test conditions are a discharge cutoff voltage of 1.5 V and a charge cutoff voltage of 4.3 V.

[0089] Figure 7The positive electrode material NaZn prepared in Example 5 0.05 Ni 0.33 Fe 0.26 Mn 0.36 The third cycle charge-discharge curve of O2 shows that the reversible capacity is 144 mAh / g.

[0090] Example 6

[0091] (1) 2.55 g of Na2CO3, 0.49 g of NiO, 1.28 g of Fe2O3, 1.39 g of MnO2 and 0.38 g of MgO were weighed and added to 5 g of isopropyl alcohol, 2.5 g of ball milling beads were added, and the mixture was placed in a planetary mixer, set at a speed of 600 r / min for 6 h, so that the solids were fully and uniformly mixed. The obtained product was vacuum dried at 60°C for 8 h to obtain a positive electrode material precursor;

[0092] (2) The precursor obtained in step (1) was calcined in a muffle furnace, with a temperature setting of 900°C and a heating time of 15 h, and a temperature rising speed of 5°C / min;

[0093] (3) After heating, the product in step (2) was immediately placed on a purple copper metal plate with a size of 20 cm*10 cm*0.6 cm, and the temperature dropped to 104°C after 12 min, to obtain a positive electrode material NaMg 0.2 Ni 0.13 Fe 0.33 Mn 0.33 O2, which was immediately transferred to an argon-filled glove box for storage;

[0094] (4) 0.1 g of PVDF was weighed and added to 4 g of NMP, and the mixture was placed in a planetary mixer for mixing, set at a speed of 1200 r / min for 30 min, to obtain a gel-like solvent; 0.7 g of the positive electrode material obtained in step (3) and 0.2 g of SuperP were dry-mixed, set at a mixing speed of 1200 r / min for 90 s; the dry-mixed positive electrode material and SuperP were added to the gel-like solvent, set at a mixing speed of 1200 r / min for 15 min; 0.5 g of ball milling beads was added to the slurry, set at a mixing speed of 800 r / min for 10 min, to obtain a positive electrode material slurry;

[0095] (5) The slurry obtained in step (4) was uniformly coated on an aluminum foil, which was vacuum dried at 60°C for 6 h and then cut into a circular electrode with a diameter of 12 mm;

[0096] (6) The pole piece obtained in step (5) is assembled into a battery in an argon atmosphere glove box, with metal sodium as a counter electrode, glass fiber as a diaphragm, 1 mol / L NaClO4 propylene carbonate (PC) / ethyl methyl carbonate (EMC) (volume ratio 1:1) solution as an electrolyte, 2% mass fraction of fluoroethylene carbonate (FEC) as an electrolyte additive, and assembled into a CR2032 button cell; a constant current charge and discharge mode is used, and charge and discharge test is carried out at a current density of 0.1C; the test conditions are that the discharge cutoff voltage is 1.5V, and the charging cutoff voltage is 4.3V.

[0097] Figure 8 The positive electrode material NaMg 0.2 Ni 0.13 Fe 0.33 Mn 0.33 The third cycle charge-discharge curve of O2 shows that the reversible capacity is 139mAh / g

[0098] Example 7

[0099] A heat treatment method of a sodium ion battery metal oxide positive electrode material, the positive electrode material has a molecular formula of Na 0.67 Ni 0.33 Fe 0.33 Mn 0.33 O2, comprising the following steps:

[0100] According to the stoichiometric ratio, anhydrous sodium carbonate, a metal oxide, a dispersing agent and ball milling beads are sequentially added into a mixing tank, the mass ratio of the solid (a mixture of anhydrous sodium carbonate and the metal oxide) to the liquid (the dispersing agent) is 1:0.9, the mass ratio of the solid to the ball milling beads is 1:0.5, the ball milling beads and the mixing tank are made of polytetrafluoroethylene, the mixing tank is placed in a planetary centrifugal mixer, and the rotation speed is set to 500r / min and the time is set to 7h. The metal oxide is a mixture of Mn2O3, Fe2O3 and NiO.

[0101] The positive electrode material is added into an alumina crucible, placed in a muffle furnace, the calcination temperature is set to 950℃, the heating rate is set to 3℃ / min, and the time is set to 15h, after the calcination is completed, the positive electrode material is quenched to 100℃ on a metal plate, the cooling rate of the quenching process is controlled, and after the quenching is completed, the material is quickly moved into an argon-filled glove box for storage.

[0102] The metal plate is red copper.

[0103] The average cooling rate of the quenching process is 65℃ / min.

[0104] Example 8

[0105] A heat treatment method of a sodium-ion battery metal oxide positive electrode material, the positive electrode material has a molecular formula of Na 0.8 Ni 0.23 Fe 0.2 Mn 0.51 Al 0.05 O2, comprising the following steps:

[0106] According to the stoichiometric ratio, anhydrous sodium carbonate, a metal oxide, a dispersant and ball milling beads are sequentially added into a mixing tank, the mass ratio of the solid (a mixture of anhydrous sodium carbonate and the metal oxide) to the liquid (the dispersant) is 1:1, the mass ratio of the solid to the ball milling beads is 1:0.6, the ball milling beads and the mixing tank are made of polytetrafluoroethylene, the mixing tank is placed in a planetary centrifugal mixer, the rotation speed is set to 700 r / min, and the time is 5 h. The metal oxide is a mixture of MnO2, Mn2O3, Fe2O3, NiO and Al2O3.

[0107] The positive electrode material is added into an alumina crucible, which is placed in a muffle furnace, the calcination temperature is set to 950 DEG C, the heating rate is 4 DEG C / min, and the time is 10 h. After the calcination is completed, the positive electrode material is placed on a metal plate and quenched to 100 DEG C, the cooling rate of the quenching process is controlled, and after the quenching is completed, the material is quickly moved into an argon-filled glove box for storage.

[0108] The metal plate is made of 304 stainless steel.

[0109] The average cooling rate of the quenching process is 60 DEG C / min.

[0110] Example 9

[0111] A heat treatment method of a sodium-ion battery metal oxide positive electrode material, the positive electrode material has a molecular formula of Na 0.9 Ni 0.28 Fe 0.25 Mn 0.41 Ti 0.05 O2, comprising the following steps:

[0112] According to the stoichiometric ratio, anhydrous sodium carbonate, a metal oxide, a dispersant and ball milling beads are sequentially added into a mixing tank, the mass ratio of the solid (a mixture of anhydrous sodium carbonate and the metal oxide) to the liquid (the dispersant) is 1:0.9, the mass ratio of the solid to the ball milling beads is 1:0.8, the ball milling beads and the mixing tank are made of polytetrafluoroethylene, the mixing tank is placed in a planetary centrifugal mixer, the rotation speed is set to 600 r / min, and the time is 6 h. The metal oxide is a mixture of MnO2, Mn2O3, Fe2O3, NiO and TiO2.

[0113] The positive electrode material is added into an alumina crucible, which is placed in a muffle furnace, the calcination temperature is set to 900 DEG C, the heating rate is 5 DEG C / min, and the time is 12h, after the calcination is completed, the positive electrode material is placed on a metal plate and quenched to 100 DEG C, the cooling rate of the quenching process is controlled, and after the quenching is completed, the material is quickly moved into an argon-filled glove box for storage.

[0114] The metal plate is made of 304 stainless steel.

[0115] The average cooling rate of the quenching process is 70 DEG C / min.

[0116] Example 10

[0117] A heat treatment method of a sodium ion battery metal oxide positive electrode material, the positive electrode material has a molecular formula of NaNi 0.23 Fe 0.33 Mn 0.33 Cu 0.05 Co 0.05 O2, comprising the following steps:

[0118] According to the stoichiometric ratio, anhydrous sodium carbonate, a metal oxide, a dispersing agent and ball milling beads are sequentially added into a mixing tank, the mass ratio of the solid (a mixture of anhydrous sodium carbonate and the metal oxide) to the liquid (the dispersing agent) is 1:0.95, the mass ratio of the solid to the ball milling beads is 1:1, the ball milling beads and the mixing tank are made of polytetrafluoroethylene, the mixing tank is placed in a planetary centrifugal mixer, and the rotation speed is set to 550 r / min for 6h. The metal oxide is a mixture of MnO2, Fe2O3, NiO, CuO and CoO.

[0119] The positive electrode material is added into an alumina crucible, which is placed in a muffle furnace, the calcination temperature is set to 920 DEG C, the heating rate is 3 DEG C / min, and the time is 13h, after the calcination is completed, the positive electrode material is placed on a metal plate and quenched to 100 DEG C, the cooling rate of the quenching process is controlled, and after the quenching is completed, the material is quickly moved into an argon-filled glove box for storage.

[0120] The metal plate is made of red copper.

[0121] The average cooling rate of the quenching process is 55 DEG C / min.

[0122] The above only describes the best embodiments of the present application, but cannot be understood as a limitation on the claims. The present application is not limited to the above embodiments, and the specific structure allows changes. Any changes made within the protection scope of the independent claims of the present application are within the protection scope of the present application.

[0123] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

Claims

1. A method of heat treatment of a sodium-ion battery metal oxide cathode material, characterized in that, Includes the following steps: Anhydrous sodium carbonate, metal oxide and dispersant are mixed evenly and dried to obtain the cathode material precursor. The cathode material precursor is calcined and quenched to obtain sodium-ion battery metal oxide cathode material. The molecular formula of the sodium-ion battery metal oxide positive electrode material is Na x MO2, wherein 0.6 < x < 1, M is a metal element, including Fe, Mn, and Ni; The mass ratio of the mixture of anhydrous sodium carbonate and metal oxide to the dispersant is 1:0.9~1; The dispersant used isopropanol, anhydrous ethanol, or acetone; The metal oxide is one or two of MnO2 and Mn2O3, mixed with Fe2O3 and NiO; The average cooling rate of quenching is 55~70℃ / min; The calcination temperature is 850~950℃, and the time is 10~15h; The mass ratio of the mixture of anhydrous sodium carbonate and metal oxide to the milling beads is 1:0.5~1, the milling speed is 500~700 r / min, and the time is 5~7 h.

2. The heat treatment method of sodium-ion battery metal oxide cathode materials according to claim 1, characterized in that, Heating to 850-950℃ at a heating rate of 3-5℃ / min.

3. The heat treatment method for the sodium-ion battery metal oxide cathode material according to claim 1, characterized in that, Anhydrous sodium carbonate, metal oxide, and dispersant are mixed evenly. Specifically, anhydrous sodium carbonate, metal oxide, dispersant, and milling beads are ball-milled and mixed evenly.

4. The heat treatment method for the sodium-ion battery metal oxide cathode material according to claim 1, characterized in that, Metal oxidation also includes one or more of MgO, ZnO, Al2O3, CuO, and CoO.

5. A sodium-ion secondary battery comprising a sodium-ion battery metal oxide cathode material prepared by the heat treatment method according to any one of claims 1-4.

6. A method for preparing a sodium-ion secondary battery as described in claim 5, characterized in that, Includes the following steps: A gel-like solvent is prepared by mixing a binder and a solvent. Then, a dry-mixed product of a positive electrode material and a conductive agent is added to the gel-like solvent and ball-milled to obtain a slurry. The ball milling speed is 800~1000 r / min and the time is 5~10 min. The slurry is evenly coated onto the current collector, dried, and cut to obtain the electrode sheet, which is then assembled to obtain a sodium-ion secondary battery.

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