Composite sodium supplementing agent, electrode plate, sodium ion battery and preparation method of composite sodium supplementing agent
By preparing a composite sodium replenishing agent, which combines sodium-containing compounds and metal materials, the problem of irreversible loss during the first charge of sodium-ion batteries was solved, thereby improving the energy density and safety of sodium-ion batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-31
- Publication Date
- 2026-03-20
AI Technical Summary
Existing sodium-ion batteries suffer irreversible sodium ion loss during the first charge, which limits the improvement of energy density. Furthermore, existing sodium replenishment agents pose safety risks or have incomplete decomposition issues.
A composite sodium supplement agent, consisting of a mixture of sodium-containing compounds and metallic materials, is prepared by methods such as mechanical ball milling, spray drying, freeze drying, or heat treatment. Combined with conductive additives, it forms a tightly bonded composite sodium supplement agent for use in the electrode sheets of sodium-ion batteries.
It effectively compensates for the irreversible losses of sodium-ion batteries during the first charge, improves the first coulombic efficiency, increases the energy density of sodium-ion batteries, and does not produce gas after decomposition, thus exhibiting structural stability.
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Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of battery functional material preparation, and particularly relates to a composite sodium supplementing agent, an electrode sheet, a sodium ion battery and a preparation method of the composite sodium supplementing agent. BACKGROUND
[0002] In related technologies, the commonly used graphite negative electrode of a lithium ion battery has a large volume expansion rate when applied in a sodium battery system, and a hard carbon negative electrode used for replacement will consume a large amount of sodium ions to form a solid electrolyte interface film (SEI) in the first charging process, causing irreversible loss of the battery capacity, which seriously restricts the improvement of the energy density of the sodium ion battery. In order to compensate for the sodium loss caused by the formation of the SEI film, many self-sacrificial sodium supplementing agents on the positive electrode side have been explored in the industry, and NaN3, Na3P and Na2S have safety risks in the use process; Na2O2, Na2O and Na2CO3 will produce oxygen after decomposition, which will have unpredictable effects in the battery; and an organic sodium supplementing agent such as Na2C2O4 cannot be completely decomposed in the electrochemical window of the electrolyte without any treatment because of its high decomposition voltage; therefore, developing an efficient and safe sodium supplementing technology is crucial for promoting the commercialization process of the sodium ion battery. SUMMARY
[0003] The application aims to provide a composite sodium supplementing agent, an electrode sheet, a sodium ion battery and a preparation method of the composite sodium supplementing agent, which can effectively compensate for the irreversible sodium ion loss of the sodium ion battery in the first charging process, improve the first coulomb efficiency, and further improve the energy density of the sodium ion battery when the composite sodium supplementing agent prepared by the method is used in combination with a positive electrode active material.
[0004] To achieve the above-mentioned purpose, the application provides a composite sodium supplementing agent, which comprises a sodium-containing compound and a metal material, the sodium-containing compound and the metal material are mixed in a predetermined molar ratio, and the molar ratio of the sodium-containing compound to the metal material is 1:10-100:1; wherein the sodium-containing compound is at least one of sodium sulfate, sodium oxalate and sodium formate, the metal material is at least one of a metal element and a metal oxide, the metal element is at least one of Cu, Fe, Ni, Mn, Co, Zn and Sn, and the metal oxide is at least one of Cu2O, FeO, NiO, MnO, CoO, ZnO and SnO.
[0005] As a further scheme of the application, the composite sodium supplementing agent further comprises a conductive additive, the conductive additive is at least one of graphene, carbon black, acetylene black and conductive carbon black, and the addition amount of the conductive additive is 1%-80% of the total mass of the composite sodium supplementing agent.
[0006] The application further provides a preparation method of the composite sodium supplement agent, comprising the following steps: S1, mixing the sodium-containing compound and the metal material according to a predetermined molar ratio, performing mechanical ball milling in a planetary ball mill under a protective atmosphere, introducing a solvent, controlling the ball-to-material ratio to be (1-20):1, the rotating speed to be 300-2000 r / min, and the ball milling time to be 0.1-12 h, and obtaining a composite precursor powder; and S2, treating the composite precursor powder by a mechanical method to obtain the composite sodium supplement agent powder; wherein the mechanical method comprises a spray drying method, a freeze drying method, a heat treatment method or a sintering method.
[0007] As a further scheme of the application, in S1, an electrically conductive additive is added to the sodium-containing compound and the metal material, and the addition amount of the electrically conductive additive is 0.1%-80% of the total mass of the composite sodium supplement agent.
[0008] As a further scheme of the application, the spray drying method is that: the composite precursor powder obtained in S1 is subjected to spray drying, the inlet temperature is controlled to be 100-300 DEG C, the outlet temperature is controlled to be 100-200 DEG C, the feeding speed is 100-300 mL / h, and after being taken out, the composite precursor powder is ground and dried at 100-150 DEG C for 10-12 h to obtain the composite sodium supplement agent powder; the freeze drying method is that: the composite precursor powder obtained in S1 is rapidly frozen at-200 DEG C to-50 DEG C, and dried under vacuum for 8-15 h, and after being taken out, the composite precursor powder is ground and dried at 100-150 DEG C for 0.1-48 h to obtain the composite sodium supplement agent powder; the heat treatment method is that: the composite precursor powder obtained in S1 is placed in a reaction kettle, the temperature is 60-300 DEG C, the heat preservation time is 0.1-48 h, and after being taken out, the composite precursor powder is ground and dried at 100-300 DEG C for 0.1-48 h to obtain the composite sodium supplement agent powder; and the sintering method is that: the composite powder precursor obtained in S1 is placed in a tube furnace for sintering, the temperature range is 200-800 DEG C under a protective atmosphere, the heat preservation time is 0.1-12 h, and after being taken out, the composite powder precursor is ground and dried at 100-150 DEG C for 0.1-48 h to obtain the composite sodium supplement agent powder.
[0009] As a further scheme of the application, the protective atmosphere is nitrogen or argon, and the solvent is ethanol or deionized water.
[0010] The application further provides an electrode sheet, comprising the composite sodium supplement agent.
[0011] The application further provides a sodium ion battery, comprising the electrode sheet.
[0012] Compared with the prior art, the application has the following beneficial effects: The sodium source of the composite sodium supplement agent is at least one of sodium sulfate, sodium oxalate and sodium formate, has high air stability, is environment-friendly, has a wide source and low price, and is suitable for large-scale production and application.
[0013] The sodium sulfate is combined with metal materials through a series of methods such as crushing and heat treatment, the decomposition voltage of single sodium salt is reduced, the prepared composite sodium sulfate / metal composite sodium supplement agent has good air stability, has low decomposition voltage, high utilization rate, is suitable for various electrode materials and electrolytes, and has a wide application scene; no gas is generated after decomposition to destroy the electrode structure; and the metal materials can improve the conductivity of the electrode to a certain extent.
[0014] The composite sodium supplement agent is combined with the positive active material, can effectively compensate for the irreversible loss of sodium ions in the first charging of the sodium ion battery, improve the first coulomb efficiency, and further improve the energy density of the sodium ion battery. DETAILED DESCRIPTION
[0015] I. Preparation method of the composite sodium supplement agent, assembly into a button cell and charging and discharging test.
[0016] Example 1
[0017] S1, Na2SO4 and Cu were ball milled by a planetary ball mill at a molar ratio of 1:1, the solvent was ethanol, protective gas N2 was introduced before ball milling, the ball-to-material ratio was 10:1, the rotation speed was adjusted to 600 r / min, the ball milling time was 6 h, and Na2SO4 / Cu composite sodium supplement agent powder was obtained after drying.
[0018] S2, the Na2SO4 / Cu composite sodium supplement agent powder obtained in S2, Super P and PVDF were uniformly mixed at a mass ratio of 8:1:1, then coated on an aluminum foil, dried, rolled, punched to obtain an electrode sheet.
[0019] S3, the electrode sheet obtained in S2 was assembled into a button cell with a sodium sheet, and charging and discharging were performed in a voltage range of 2-4.4 V at a rate of 0.1 C, the first charge specific capacity was 247.2 mAh / g, the discharge specific capacity was 4.5 mAh / g, the first coulomb efficiency was 1.8%, and the decomposition voltage was 3.3 V.
[0020] Example 2
[0021] S1, Na2SO4 and Cu2O were ball milled by a planetary ball mill at a molar ratio of 1:1, the solvent was ethanol, protective gas N2 was introduced before ball milling, the ball-to-material ratio was 10:1, the rotation speed was adjusted to 600 r / min, the ball milling time was 6 h, and Na2SO4 / Cu2O composite sodium supplement agent powder was obtained after drying.
[0022] S2, the Na2SO4 / Cu2O composite sodium supplement powder obtained in S2, Super P and PVDF were uniformly mixed in a mass ratio of 8:1:1, coated on an aluminum foil, dried, rolled, and punched to obtain an electrode sheet.
[0023] S3, the electrode sheet obtained in S2 was assembled with a sodium sheet into a button cell, and charge-discharge was performed in a voltage range of 2-4.4 V at a rate of 0.1 C, the initial charge specific capacity was 217.3 mAh / g, the discharge specific capacity was 5.1 mAh / g, the initial coulombic efficiency was 2.3%, and the decomposition voltage was 3.4 V.
[0024] Example 3
[0025] S1, Na2SO4 and FeO were ball milled in a planetary ball mill in a molar ratio of 1:1, with ethanol as the solvent, N2 was introduced before ball milling, the ball-to-material ratio was 10:1, the rotation speed was adjusted to 600 r / min, and the ball milling time was 6 h, and Na2SO4 / FeO composite sodium supplement powder was obtained after drying.
[0026] S2, the Na2SO4 / FeO composite sodium supplement powder obtained in S2, Super P and PVDF were uniformly mixed in a mass ratio of 8:1:1, coated on an aluminum foil, dried, rolled, and punched to obtain an electrode sheet.
[0027] S3, the electrode sheet obtained in S2 was assembled with a sodium sheet into a button cell, and charge-discharge was performed in a voltage range of 2-4.4 V at a rate of 0.1 C, the initial charge specific capacity was 202.3 mAh / g, the discharge specific capacity was 4.1 mAh / g, the initial coulombic efficiency was 2.02%, and the decomposition voltage was 3.55 V.
[0028] Example 4
[0029] S1, Na2SO4 and MnO were ball milled in a planetary ball mill in a molar ratio of 1:1, with ethanol as the solvent, N2 was introduced before ball milling, the ball-to-material ratio was 10:1, the rotation speed was adjusted to 600 r / min, and the ball milling time was 6 h, and Na2SO4 / MnO composite sodium supplement powder was obtained after drying.
[0030] S2, the Na2SO4 / MnO composite sodium supplement powder obtained in S2, Super P and PVDF were uniformly mixed in a mass ratio of 8:1:1, coated on an aluminum foil, dried, rolled, and punched to obtain an electrode sheet.
[0031] S3, the electrode sheet obtained in S2 was assembled with a sodium sheet into a button cell, and charge-discharge was performed in a voltage range of 2-4.4 V at a rate of 0.1 C, the initial charge specific capacity was 225.3 mAh / g, the discharge specific capacity was 7.5 mAh / g, the initial coulombic efficiency was 3.3%, and the decomposition voltage was 3.49 V.
[0032] Example 5
[0033] The difference from Example 1 is that the preparation method is a spray drying method, and the specific preparation method is as follows: S1, Na2SO4 and Cu were ball milled by a planetary ball mill with a molar ratio of 1:1, the solvent was deionized water, N2 was introduced before ball milling, the ball-to-material ratio was 10:1, the rotation speed was adjusted to 600 r / min, and the ball milling time was 6 h to obtain Na2SO4 / Cu composite precursor powder.
[0034] S2, the Na2SO4 / Cu composite precursor powder obtained in S1 was subjected to spray drying, the inlet temperature was 150°C, the outlet temperature was 120°C, the feeding speed was 200 mL / h, and after taking the material, it was dried at 100°C for 12 h to obtain Na2SO4 / Cu composite sodium supplement powder.
[0035] S3, the Na2SO4 / Cu composite sodium supplement powder obtained in S2, Super P and PVDF were uniformly mixed in a mass ratio of 8:1:1, then coated on aluminum foil, dried, rolled, and punched to obtain an electrode sheet.
[0036] S4, the electrode sheet obtained in S3 and a sodium sheet were assembled into a button cell, and the button cell was subjected to charge and discharge in a voltage range of 2-4.4 V at a rate of 0.1C, the initial charge specific capacity was 237.3 mAh / g, the discharge specific capacity was 4.8 mAh / g, the initial coulombic efficiency was 2.0%, and the decomposition voltage was 3.4 V.
[0037] Example 6
[0038] The difference from Example 1 is that the preparation method is a freeze-drying method, and the specific preparation method is as follows: S1, Na2SO4 and Cu were ball milled by a planetary ball mill with a molar ratio of 1:1, the solvent was deionized water, N2 was introduced before ball milling, the ball-to-material ratio was 10:1, the rotation speed was adjusted to 600 r / min, and the ball milling time was 6 h to obtain Na2SO4 / Cu composite precursor powder.
[0039] S2, the composite precursor powder obtained in S1 was subjected to freeze-drying, frozen at -80°C for 2 h, vacuumized for 10 h, ground after taking out, and dried at 120°C for 12 h to obtain Na2SO4 / Cu composite sodium supplement powder.
[0040] S3, the Na2SO4 / Cu composite sodium supplement powder obtained in S2, Super P and PVDF were uniformly mixed in a mass ratio of 8:1:1, then coated on aluminum foil, dried, rolled, and punched to obtain an electrode sheet.
[0041] S4, the pole piece obtained in S3 is assembled with sodium sheet to form a button cell, and charging and discharging are performed in the voltage range of 2-4.4 V, the rate is 0.1 C, the initial charge specific capacity is 234.2 mAh / g, the discharge specific capacity is 5.2 mAh / g, the initial coulombic efficiency is 2.2%, and the decomposition voltage is 3.35 V.
[0042] Example 7
[0043] The difference from Example 1 is that heat treatment is placed in a reaction kettle, and the specific manufacturing method is as follows: S1, Na2SO4 and Cu are ball milled by a planetary ball mill at a molar ratio of 1:1, the solvent is ethanol, protective gas N2 is introduced before ball milling, the ball-to-material ratio is 10:1, the rotation speed is adjusted to 600 r / min, and the ball milling time is 6 h, to obtain Na2SO4 / Cu composite precursor powder.
[0044] S2, the Na2SO4 / Cu composite precursor powder obtained in S1 is placed in a reaction kettle, heat treated at 200°C for 6 h, taken out after cooling, ground, and dried at 120°C for 12 h to obtain Na2SO4 / Cu composite sodium supplement powder.
[0045] S3, the Na2SO4 / Cu composite sodium supplement powder obtained in S2, Super P and PVDF are uniformly mixed at a mass ratio of 8:1:1, coated on an aluminum foil, dried, rolled, and punched to obtain a pole piece.
[0046] S4, the pole piece obtained in S3 is assembled with sodium sheet to form a button cell, and charging and discharging are performed in the voltage range of 2-4.4 V, the rate is 0.1 C, the initial charge specific capacity is 234.2 mAh / g, the discharge specific capacity is 5.2 mAh / g, the initial coulombic efficiency is 2.2%, and the decomposition voltage is 3.35 V.
[0047] Example 8
[0048] The difference from Example 1 is that heat treatment is placed in a reaction kettle, and the specific manufacturing method is as follows: S1, Na2SO4 and Cu are ball milled by a planetary ball mill at a molar ratio of 1:1, the solvent is ethanol, protective gas N2 is introduced before ball milling, the ball-to-material ratio is 10:1, the rotation speed is adjusted to 600 r / min, and the ball milling time is 6 h, to obtain Na2SO4 / Cu composite precursor powder.
[0049] S2, the Na2SO4 / Cu composite precursor powder obtained in S1 is placed in a reaction kettle, heat treated at 200°C for 6 h, taken out after cooling, ground, and dried at 120°C for 12 h to obtain Na2SO4 / Cu composite sodium supplement powder.
[0050] S3, the Na2SO4 / Cu composite sodium supplement powder obtained in S2, Super P and PVDF were uniformly mixed in a mass ratio of 8:1:1, coated on an aluminum foil, dried, rolled, and punched to obtain an electrode sheet.
[0051] S4, the electrode sheet obtained in S3 was assembled with a sodium sheet into a button cell, and charge-discharge was performed in a voltage range of 2-4.4 V at a rate of 0.1 C, the initial charge specific capacity was 250.3 mAh / g, the discharge specific capacity was 7.8 mAh / g, the initial coulombic efficiency was 3.1%, and the decomposition voltage was 3.31 V. The performance of the composite sodium supplement after heat treatment hardly changed.
[0052] Example 9
[0053] S1, sodium oxalate (Na2C2O4) and Cu were ball milled in a planetary ball mill in a molar ratio of 1:1, the solvent was ethanol, N2 was introduced before ball milling, the ball-to-material ratio was 10:1, the rotation speed was adjusted to 600 r / min, the ball milling time was 6 h, and the Na2C2O4 / Cu composite sodium supplement powder was obtained after drying.
[0054] S2, the Na2C2O4 / Cu composite sodium supplement powder obtained in S2, Super P and PVDF were uniformly mixed in a mass ratio of 8:1:1, coated on an aluminum foil, dried, rolled, and punched to obtain an electrode sheet.
[0055] S3, the electrode sheet obtained in S2 was assembled with a sodium sheet into a button cell, and charge-discharge was performed in a voltage range of 2-4.4 V at a rate of 0.1 C, the initial charge specific capacity was 270.2 mAh / g, the discharge specific capacity was 6.5 mAh / g, the initial coulombic efficiency was 2.4%, and the decomposition voltage was 3.9 V.
[0056] Example 10
[0057] The difference from Example 1 was that 10% of the total mass of the composite sodium supplement was added with graphene, and other parameters were unchanged, and the test results were that the initial charge specific capacity was 249.6 mAh / g, the discharge specific capacity was 8.5 mAh / g, the initial coulombic efficiency was 2.6%, and the decomposition voltage was 3.28 V. Although the addition of the conductive agent improved the charge specific capacity, the improvement was limited.
[0058] Examples 11-12 Compared with Example 1, the ball milling time was adjusted, the ratio of Na2SO4 and Cu was unchanged, and other parameters were unchanged, as follows: Example 11 differed from Example 1 in that the ball milling time in step S1 was adjusted to 3 h.
[0059] Example 12 differed from Example 1 in that the ball milling time in step S1 was adjusted to 12 h.
[0060] The test results are as follows:
[0061] Compared with Example 1, the ball milling time of Example 11 is reduced to 3 h, and the first cycle specific capacity of the obtained composite sodium supplement agent is reduced from 247.2 mAh / g to 208.2 mAh / g, and the decomposition voltage is increased from 3.3 V to 3.7 V, indicating that the shorter ball milling time leads to insufficient mechanical fusion of Na2SO4 and Cu, and the interface bonding force between the two is weak, which increases the electrochemical reaction impedance and reduces the active material utilization rate; the ball milling time of Example 12 is extended to 12 h, and the first cycle specific capacity of the obtained composite sodium supplement agent is increased from 247.2 mAh / g to 249.8 mAh / g, although there is an improvement, but the improvement is limited, indicating that the excessive extension of the ball milling time is not significant for the performance improvement.
[0062] Examples 13-18 Compared with Example 1, the metal element is adjusted to Fe, Ni, Mn, Co, Zn, and Sn, respectively, as follows: Example 13 differs from Example 1 in that the metal element is adjusted to Fe, and the molar ratio of Na2SO4 to Fe is 3:2.
[0063] Example 14 differs from Example 1 in that the metal element is adjusted to Ni, and the molar ratio of Na2SO4 to Ni is 1:2.
[0064] Example 15 differs from Example 1 in that the metal element is adjusted to Mn, and the molar ratio of Na2SO4 to Mn is 1:1.
[0065] Example 16 differs from Example 1 in that the metal element is adjusted to Co, and the molar ratio of Na2SO4 to Co is 1:1.
[0066] Example 17 differs from Example 1 in that the metal element is adjusted to Zn, and the molar ratio of Na2SO4 to Zn is 1:1.
[0067] Example 18 differs from Example 1 in that the metal element is adjusted to Sn, and the molar ratio of Na2SO4 to Sn is 1:1.
[0068] The test results are as follows:
[0069] Comparative Example 1 The difference between Example 1 and Comparative Example 1 is that only a single Na2SO4 is used as a sodium supplement agent, and the rest of the process and parameters remain unchanged, and the specific operation steps are as follows: S1, Na2SO4 was ball milled by a planetary ball mill, the solvent was ethanol, N2 was introduced before ball milling, the ball-to-material ratio was 10:1, the rotation speed was adjusted to 600 r / min, the ball milling time was 6 h, and Na2SO4 powder was obtained after drying.
[0070] S2, the Na2SO4 powder obtained in S2, Super P and PVDF were uniformly mixed according to a mass ratio of 8:1:1, and then coated on an aluminum foil, dried, rolled, and punched to obtain an electrode sheet.
[0071] S3, the electrode sheet obtained in S2 and a sodium sheet were assembled into a button cell, and the button cell was subjected to charge and discharge in a voltage range of 2-4.4 V at a rate of 0.1 C, the initial charge specific capacity was 13 mAh / g, the discharge specific capacity was 1.8 mAh / g, the initial coulombic efficiency was 13.8%, and the decomposition voltage was 4.35 V. Due to the extremely low intrinsic electronic conductivity of Na2SO4, it is difficult to form an effective electron transport channel during charge and discharge, which leads to the fact that Na2SO4 cannot effectively decompose in the electrochemical window of the conventional electrolyte, and thus cannot provide effective sodium supplement capacity.
[0072] II. The composite sodium supplement agent powder was incorporated into the positive electrode active material to prepare a positive electrode sheet, and the positive electrode sheet was subjected to charge and discharge test.
[0073] The composite sodium supplement agent powder can be directly incorporated into the positive electrode active material to prepare a positive electrode sheet, and the addition amount of the composite sodium supplement agent is 1%-50% of the positive electrode active material; or the composite sodium supplement agent can be mixed with conductive carbon black, polyvinylidene fluoride and N-methyl pyrrolidone to prepare a slurry with a solid content of 1%-30%, and the slurry is sprayed onto the surface of the positive electrode sheet or the surface of the separator.
[0074] Example 19
[0075] S1, the composite sodium supplement agent obtained in Example 1 was incorporated into Na 2.4 Fe 1.8 (SO4)3 positive electrode active material, and the mass ratio of the positive electrode active material, the composite sodium supplement agent, Super P and PVDF was 72:8:10:10, the mixture was coated on an aluminum foil, dried, rolled, and punched to obtain a positive electrode sheet.
[0076] S2, hard carbon, Super P, CMC and SBR were uniformly mixed according to a mass ratio of 92:4:2:2, and then coated on an aluminum foil, dried, rolled, and punched to obtain a negative electrode sheet.
[0077] S3, the positive and negative electrode sheets obtained in S1 and S2 were assembled into a full cell, and the NP ratio was 1.05, and the full cell was subjected to charge and discharge test in a voltage range of 2-4.4 V at a rate of 0.1 C.
[0078] Example 20
[0079] S1: Compound sodium supplement agent, Super P, PVDF, NMP were mixed to form a slurry with solid content of 5%.
[0080] S2: Na 2.4 Fe 1.8 After uniform mixing of Na (SO4)3, Super P, and PVDF, the mixture was coated on an aluminum foil, dried, and rolled to obtain a positive electrode sheet.
[0081] S3: Hard carbon, Super P, CMC, and SBR were uniformly mixed in a mass ratio of 92:4:2:2, coated on an aluminum foil, dried, rolled, and punched to obtain a negative electrode sheet.
[0082] S4: The positive and negative electrode sheets obtained in S2 and S3 were assembled into a full battery with an NP ratio of 1.05, and charge-discharge tests were conducted at 0.1C within a voltage range of 2-4.4V.
[0083] Example 21
[0084] S1: Compound sodium supplement agent, Super P, PVDF, NMP were mixed to form a slurry with solid content of 5%.
[0085] S2: Na 2.4 Fe 1.8 After uniform mixing of Na (SO4)3, Super P, and PVDF, the mixture was coated on an aluminum foil, dried, and rolled to obtain a positive electrode sheet.
[0086] S3: The slurry obtained in S1 was sprayed onto the surface of a separator using an atomizer, and the mass of the compound sodium supplement agent was controlled to be 10% of the mass of the positive electrode active material.
[0087] S4: Hard carbon, Super P, CMC, and SBR were uniformly mixed in a mass ratio of 92:4:2:2, coated on an aluminum foil, dried, rolled, and punched to obtain a negative electrode sheet.
[0088] S5: The positive electrode sheet, separator, and negative electrode sheet obtained in S2, S3, and S4 were assembled into a full battery with an NP ratio of 1.05, and charge-discharge tests were conducted at 0.1C within a voltage range of 2-4.4V.
[0089] Comparative Example 2 S1: Na 2.4 Fe 1.8 After uniform mixing of Na (SO4)3, Super P, and PVDF in a ratio of 80:10:10 with NMP, the mixture was coated on an aluminum foil, dried, rolled, and punched to obtain a positive electrode sheet.
[0090] S2, hard carbon, Super P, CMC, SBR are uniformly mixed according to the mass ratio of 92:4:2:2, coated on aluminum foil, dried, rolled, and punched to obtain a negative electrode sheet.
[0091] S3, the positive electrode sheet, the separator and the negative electrode sheet obtained in S1 and S2 are assembled into a full battery, the NP ratio is 1.05, and the charge-discharge test is carried out at 0.1C in the voltage range of 2-4.4V.
[0092] The results are as follows:
[0093] Examples 22-26, compared with Example 19, the difference lies in adjusting the positive active material, and the rest of the process and parameters remain unchanged, and the results are as follows:
[0094] Examples 22-26, the composite sodium supplement is added to the positive active material, or sprayed on the surface of the positive electrode sheet or the separator, and the first coulomb efficiency is more than 90%, which is much higher than the first coulomb efficiency of the full battery without adding the composite sodium supplement to the positive active material in Comparative Example 2.
[0095] During ball milling and / or sintering, the metal material forms a close micro-composite interface with Na2SO4, which not only provides a continuous electron conduction network, greatly improving the conductivity of Na2SO4, but also may catalyze the decomposition reaction of Na2SO4, reduce its actual decomposition overpotential, and make it decompose and release sodium ions at a more suitable voltage.
[0096] Spray drying and freeze drying as an alternative, the key point is to prepare a porous, loose microstructure, which increases the contact area of electrolyte and material and accelerates the ion transmission rate.
[0097] The above is only the preferred embodiment of the present application, and does not limit the present application in any way. Any person skilled in the art, without departing from the scope of the technical solutions of the present application, makes any form of equivalent replacement or modification of the technical solutions and technical contents disclosed by the present application, and still belongs to the protection scope of the present application.
Claims
1. A compound sodium supplement, characterized in that, include: A sodium-containing compound and a metallic material, wherein the sodium-containing compound and the metallic material are mixed at a predetermined molar ratio of 1:10 to 100:1; Wherein, the sodium-containing compound is at least one of sodium sulfate, sodium oxalate, and sodium formate; the metallic material is at least one of elemental metal and metal oxide; the elemental metal is at least one of Cu, Fe, Ni, Mn, Co, Zn, and Sn; and the metal oxide is at least one of Cu2O, FeO, NiO, MnO, CoO, ZnO, and SnO.
2. The compound sodium supplement according to claim 1, characterized in that, Also includes: The conductive additive is at least one of graphene, carbon black, acetylene black, and conductive carbon black, and the amount of the conductive additive added is 1% to 80% of the total mass of the composite sodium supplement.
3. A method for preparing the compound sodium supplement as described in claim 1 or 2, characterized in that, Includes the following steps: S1. The sodium-containing compound and the metal material are mixed at a predetermined molar ratio, and mechanically ball-milled in a planetary ball mill under a protective atmosphere. A solvent is introduced, and the ball-to-material ratio is controlled at (1~20):
1. The rotation speed is 300~2000 r / min, and the ball-milling time is 0.1~12 h to obtain composite precursor powder. S2. The composite precursor powder is processed by mechanical methods to obtain composite sodium supplement powder; wherein the mechanical methods include drying, spray drying, freeze drying, heat treatment or sintering.
4. The preparation method of the compound sodium supplement according to claim 3, characterized in that, In S1, a conductive additive is added to the sodium-containing compound and the metal material, wherein the amount of the conductive additive added is 0.1% to 80% of the total mass of the composite sodium supplement.
5. The method for preparing the compound sodium supplement according to claim 3, characterized in that, The spray drying method is as follows: the composite precursor powder obtained in S1 is spray dried, the inlet temperature is controlled at 100~300℃, the outlet temperature is controlled at 100~200℃, the feed rate is 100~300mL / h, after being taken out, it is ground and dried at 100~150℃ for 10~12h to obtain the composite sodium supplement powder. The freeze-drying method is as follows: the composite precursor powder obtained in S1 is rapidly frozen at -200℃ to -50℃ and dried under vacuum for 8 to 15 hours. After being taken out, it is ground and dried at 100 to 150℃ for 0.1 to 48 hours to obtain the composite sodium supplement powder. The heat treatment method is as follows: the composite precursor powder obtained in S1 is placed in a reaction vessel at a temperature of 60~300℃ for 0.1~24h, then removed, ground, and dried at 100~300℃ for 0.1~48h to obtain the composite sodium supplement powder. The sintering method is as follows: the composite powder precursor obtained in S1 is placed in a tube furnace for sintering under a protective atmosphere at a temperature range of 200~800℃ for a holding time of 0.1~12h. After removal, it is ground and dried at 100~150℃ for 0.1~48h to obtain the composite sodium supplement powder.
6. The method for preparing the compound sodium supplement according to claim 5, characterized in that, The protective atmosphere is nitrogen or argon; the solvent is ethanol or deionized water.
7. An electrode sheet, characterized in that, include: The compound sodium supplement according to claim 1 or 2.
8. A sodium-ion battery, characterized in that, include: The electrode sheet according to claim 7.