Positive electrode sodium supplementing additive, preparation method and application

Abstract

The invention discloses a positive electrode sodium supplement additive, a preparation method and application, the positive electrode sodium supplement additive comprises sodium carbonate and a composite conductive agent, and the mass ratio of the sodium carbonate to the composite conductive agent is (9-7): (1-3). The composite conductive agent comprises Super-P and NMF (Na (Ni1 / 3Fe1 / 3Mn1 / 3) O2); the mass ratio of Super-P to NMF is (1-2): (1-2), the composite conductive agent provided by the invention has lower decomposition voltage and higher capacity, and when the composite conductive agent is applied to a sodium ion battery positive electrode, the decomposition voltage is 3.89 V, and the capacity can reach 305 mAh / g. The defects of high Na2CO3 decomposition voltage and low capacity utilization are overcome. After being compounded with NMF, the composite conductive agent provided by the invention is applied to a sodium ion battery positive electrode, and shows higher first-circle charge capacity (197mAh / g) and more excellent cycle stability.

Description

Technical Field

[0001] The present invention relates to the field of sodium ion batteries, and more particularly to a positive electrode sodium supplement additive, a preparation method and an application thereof. Background Art

[0002] In recent years, sodium-ion batteries (SIBs) have attracted widespread attention due to their abundant, widespread, and low-cost sodium resources. Compared to lithium-ion batteries (LIBs), SIBs offer significant cost advantages for large-scale energy storage applications. During the initial charging process, limited sodium ions migrate from the cathode (e.g., layered oxides, polyanionic compounds, organic compounds, etc.) to the anode (e.g., hard carbon, soft carbon, etc.). These limited sodium ions are inevitably and irreversibly consumed due to side reactions and the formation of a solid electrolyte interface (SEI) film. This leads to a significant decrease in reversible capacity and energy density, posing a challenge to the development and rapid scale-up of SIBs. To address this issue, various strategies have been proposed, including interface regulation, electrolyte design, and sodium compensation. The former two are strategies for reducing sodium losses, while the latter is a loss compensation measure that has received considerable attention in recent years. Sodium compensation strategies can be categorized into physical, electrochemical, chemical, and cathode additive approaches. Physical approaches require the direct use of metallic sodium, but are difficult to commercialize on a large scale due to their high water and oxygen requirements and the uncontrollable degree of sodium compensation. Electrochemical methods face the problem of battery disassembly and reassembly, which is complex and costly and is only suitable for laboratory research. Chemical methods use sodium-containing aromatic solutions to soak electrodes or materials, involving organic solvents, and therefore have good application prospects under the premise of ensuring safety and recycling. The positive electrode additive method has received increasing attention in recent years due to its high safety, good process compatibility, controllable cost and wide application potential. Generally, an ideal additive should have the characteristics of high weight / volume capacity, high capacity utilization, moderate decomposition voltage, non-toxicity, good thermal / chemical stability, easy operation and low cost. Among them, sodium carbonate is abundant in resources, low in price, safe and easy to handle, and has a high theoretical decomposition capacity (506mAh / g). However, due to the poor electronic conductivity and ionic conductivity of sodium carbonate, its decomposition voltage is high and its actual capacity is low, which seriously hinders its development prospects as a positive electrode sodium supplement additive. Summary of the Invention

[0003] To address the shortcomings of the prior art, the present invention provides a method for preparing a composite conductive agent-modified sodium carbonate cathode sodium supplement and its application. By adding a composite conductive agent to sodium carbonate, this composite cathode sodium supplement exhibits low decomposition capacity and high actual capacity. When this composite conductive agent-modified sodium supplement is added to NMF, the battery also exhibits high capacity and excellent cycling performance.

[0004] To achieve the above purpose, the specific technical solutions of the present invention are as follows:

[0005] In a first aspect, the present invention provides a positive electrode sodium supplement additive, comprising sodium carbonate and a composite conductive agent, wherein the mass ratio of the sodium carbonate to the composite conductive agent is (9-7): (1-3).

[0006] The composite conductive agent (SP / NMF) includes Super-P (conductive carbon black, referred to as SP) and NMF (Na (Ni 1 / 3 Fe 1 / 3Mn 1 / 3 )O2); the mass ratio of Super-P and NMF is (1~2): (1~2).

[0007] In a second aspect, the present invention provides a method for preparing a positive electrode sodium supplement additive, comprising the following steps:

[0008] SP and NMF were mixed and ball-milled to obtain composite conductive agent SP / NMF;

[0009] Sodium carbonate and a composite conductive agent are mixed and ball-milled into a mixed powder to obtain a positive electrode sodium supplement additive SP / NMF-Na2CO3.

[0010] Further preferably, the preparation method of the composite conductive agent comprises the following steps: mixing Super-P and NMF, and ball-milling the mixture into a mixed powder to obtain a composite conductive agent, which is denoted as SP / NMF.

[0011] Further preferably, the specific operation of the ball milling is: using zirconium dioxide ball milling beads, the diameters of the zirconium dioxide ball milling beads are 4 / 10 / 15 mm respectively, the mass ratio of ball milling beads to material is 30:1, the ball milling speed is 700 rpm, the time is 5-10 hours, each rotation is 30 minutes, and the stop time is 10 minutes.

[0012] More preferably, the ball milling time is 5 to 10 hours.

[0013] More preferably, the ball milling time is 30 to 50 hours.

[0014] In a third aspect, the present invention provides a use of the SP / NMF-Na2CO3 sodium-supplementing additive or the SP / NMF-Na2CO3 sodium-supplementing additive prepared by the method in a positive electrode of a sodium ion battery.

[0015] In a fourth aspect, the present invention provides a sodium ion battery positive electrode active material, the raw materials of which include the SP / NMF-Na2CO3 sodium supplement additive and a sodium ion battery positive electrode material.

[0016] Further preferably, the ratio of the SP / NMF-Na2CO3 sodium-supplementing additive to the sodium-ion positive electrode material in the sodium-ion battery positive electrode active material is (10-30):(90-70).

[0017] Preferably, the raw materials of the sodium ion positive electrode material further include a conductive agent and a binder.

[0018] Compared with the prior art, the present invention is beneficial in that:

[0019] The composite conductive agent-improved sodium carbonate positive electrode sodium supplement additive provided by the present invention has a low decomposition voltage and a high capacity. When applied to the positive electrode of a sodium ion battery, the decomposition voltage is 3.89V and the capacity can reach 305mAh / g. This overcomes the shortcomings of Na2CO3, which has a high decomposition voltage and low capacity utilization. After the composite conductive agent-improved sodium carbonate positive electrode sodium supplement additive is compounded with NMF and applied to the positive electrode of a sodium ion battery, it exhibits a higher first-cycle charge capacity (197mAh / g) and better cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Charge and discharge curves of sodium supplement 3(2SP / NMF)-7Na2CO3.

[0021] Figure 2 Charge and discharge curves of the positive electrode active material 3[3(2SP / NMF)-7Na2CO3]-7NMF. Specific implementation methods

[0022] The technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0023] The invention provides a composite conductive agent for improving sodium carbonate positive electrode sodium supplementation, comprising Na2CO3, NMF and SP. The NMF and SP form a composite conductor and jointly promote the performance of Na2CO3 as a positive electrode sodium supplementation agent.

[0024] The preparation method of the composite conductive agent to improve the sodium carbonate positive electrode sodium supplement additive comprises the following steps:

[0025] S1. SP and NMF are mixed and ball-milled to obtain a composite conductive agent SP / NMF.

[0026] S2. The composite conductive agent SP / NMF and Na2CO3 are mixed and ball-milled to obtain a composite conductive agent improved sodium carbonate positive electrode sodium supplement additive (SP / NMF-Na2CO3).

[0027] Example 1

[0028] A composite conductive agent to improve sodium carbonate positive electrode sodium supplement additive, the preparation method is as follows:

[0029] (1) SP and NMF were mixed in a mass ratio of 2:1 and mechanically ball milled at 700 rpm for 10 h to obtain a composite conductive agent 2SP / NMF.

[0030] (2) The above-mentioned composite conductive agent 2SP / NMF and Na2CO3 in a mass ratio of 3:7 were mixed and mechanically ball-milled at 800 rpm for 40 h to obtain the composite conductive agent improved sodium carbonate positive electrode sodium supplement additive 3(2SP / NMF)-7Na2CO3.

[0031] Example 2

[0032] A composite conductive agent to improve sodium carbonate positive electrode sodium supplement additive, the preparation method is as follows:

[0033] (1) SP and NMF were mixed in a mass ratio of 2:1 and mechanically ball milled at 700 rpm for 10 h to obtain a composite conductive agent 2SP / NMF.

[0034] (2) The composite conductive agent 2SP / NMF and Na2CO3 with a mass ratio of 2:8 were mixed and mechanically ball-milled at 800 rpm for 40 h to obtain a composite conductive agent to improve the sodium carbonate positive electrode sodium supplement additive 2

[0035] (2SP / NMF)-8Na2CO3.

[0036] Example 3

[0037] A composite conductive agent to improve sodium carbonate positive electrode sodium supplement additive, the preparation method is as follows:

[0038] (1) SP and NMF were mixed in a mass ratio of 2:1 and mechanically ball milled at 700 rpm for 10 h to obtain a composite conductive agent 2SP / NMF.

[0039] (2) The above-mentioned composite conductive agent 2SP / NMF and Na2CO3 in a mass ratio of 1:9 were mixed and mechanically ball-milled at 800 rpm for 40 h to obtain the composite conductive agent improved sodium carbonate positive electrode sodium supplement additive 1(2SP / NMF)-9Na2CO3.

[0040] Comparative Example 1

[0041] A composite conductive agent to improve sodium carbonate positive electrode sodium supplement additive, the preparation method is as follows:

[0042] (1) SP and NMF were mixed in a mass ratio of 1:1 and mechanically ball milled at 700 rpm for 10 h to obtain a composite conductive agent SP / NMF.

[0043] (2) The composite conductive agent SP / NMF and Na2CO3 were mixed in a mass ratio of 3:7 and mechanically ball-milled at 800 rpm for 40 h to obtain the composite conductive agent improved sodium carbonate positive electrode sodium supplement additive 3(SP / NMF)-7Na2CO3.

[0044] Comparative Example 2

[0045] A composite conductive agent to improve sodium carbonate positive electrode sodium supplement additive, the preparation method is as follows:

[0046] (1) SP and NMF were mixed in a mass ratio of 1:1 and mechanically ball milled at 700 rpm for 10 h to obtain a composite conductive agent SP / NMF.

[0047] (2) The above composite conductive agent SP / NMF and Na2CO3 in a mass ratio of 2:8 were mixed and mechanically ball-milled at 800 rpm for 40 h to obtain the composite conductive agent improved sodium carbonate positive electrode sodium supplement additive 2(SP / NMF)-8Na2CO3.

[0048] Comparative Example 3

[0049] A composite conductive agent to improve sodium carbonate positive electrode sodium supplement additive, the preparation method is as follows:

[0050] (1) SP and NMF were mixed in a mass ratio of 1:1 and mechanically ball milled at 700 rpm for 10 h to obtain a composite conductive agent SP / NMF.

[0051] (2) The above composite conductive agent SP / NMF and Na2CO3 in a mass ratio of 1:9 were mixed and mechanically ball-milled at 800 rpm for 40 h to obtain the composite conductive agent improved sodium carbonate positive electrode sodium supplement additive 1(SP / NMF)-9Na2CO3.

[0052] Comparative Example 4

[0053] A composite conductive agent to improve sodium carbonate positive electrode sodium supplement additive, the preparation method is as follows:

[0054] (1) SP and NMF were mixed in a mass ratio of 1:2 and mechanically ball milled at 700 rpm for 10 h to obtain a composite conductive agent SP / 2NMF.

[0055] (2) The above composite conductive agent SP / 2NMF and Na2CO3 in a mass ratio of 3:7 were mixed and mechanically ball-milled at 800 rpm for 40 h to obtain the composite conductive agent improved sodium carbonate positive electrode sodium supplement additive 3(SP / 2NMF)-7Na2CO3.

[0056] Comparative Example 5

[0057] A composite conductive agent to improve sodium carbonate positive electrode sodium supplement additive, the preparation method is as follows:

[0058] (1) SP and NMF were mixed in a mass ratio of 1:2 and mechanically ball milled at 700 rpm for 10 h to obtain a composite conductive agent SP / 2NMF.

[0059] (2) The above composite conductive agent SP / 2NMF and Na2CO3 in a mass ratio of 2:8 were mixed and mechanically ball-milled at 800 rpm for 40 h to obtain the composite conductive agent improved sodium carbonate positive electrode sodium supplement additive 2(SP / 2NMF)-8Na2CO3.

[0060] Comparative Example 6

[0061] A composite conductive agent to improve sodium carbonate positive electrode sodium supplement additive, the preparation method is as follows:

[0062] (1) SP and NMF were mixed in a mass ratio of 1:2 and mechanically ball milled at 700 rpm for 10 h to obtain a composite conductive agent SP / 2NMF.

[0063] (2) The above-mentioned composite conductive agent SP / 2NMF and Na2CO3 in a mass ratio of 1:9 were mixed and mechanically ball-milled at 800 rpm for 40 h to obtain the composite conductive agent improved sodium carbonate positive electrode sodium supplement additive 1(SP / 2NMF)-9Na2CO3.

[0064] Comparative Example 7

[0065] A composite sodium carbonate positive electrode sodium supplement additive, the preparation method is as follows:

[0066] (1) SP and Na2CO3 with a mass ratio of 3:7 were mixed and mechanically ball-milled at 800 rpm for 50 h to obtain the composite sodium carbonate positive electrode sodium supplement additive 3SP-7Na2CO3.

[0067] Comparative Example 8

[0068] A composite sodium carbonate positive electrode sodium supplement additive, the preparation method is as follows:

[0069] (1) NMF and Na2CO3 were mixed in a mass ratio of 3:7 and mechanically ball-milled at 800 rpm for 50 h to obtain a composite sodium carbonate positive electrode sodium supplement additive 3NMF-7Na2CO3.

[0070] Comparative Example 9

[0071] A positive electrode sodium supplement additive, the preparation method is as follows:

[0072] (1) Na2CO3 was mechanically ball-milled at 800 rpm for 50 h to obtain the positive electrode sodium supplement Na2CO3.

[0073] Application Example 1

[0074] The sodium supplement additive obtained in Example 1 was added to NMF to obtain a positive electrode active material 1[3(2SP / NMF)-7Na2CO3]-9NMF, in which the sodium supplement additive accounted for 10% of the positive electrode active material.

[0075] Application Example 2

[0076] The sodium supplement additive obtained in Example 1 was added to NMF to obtain the positive electrode active material 2[3

[0077] (2SP / NMF)-7Na2CO3]-8NMF, the sodium supplement additive accounts for 20% of the positive electrode active material.

[0078] Application Example 3

[0079] The sodium supplement additive obtained in Example 1 was added to NMF to obtain the positive electrode active material 3[3

[0080] (2SP / NMF)-7Na2CO3]-7NMF, the sodium supplement additive accounts for 30% of the positive electrode active material.

[0081] Application Example 4

[0082] NMF is named as a positive electrode active material, and there is no sodium supplement additive in the positive electrode active material.

[0083] Test Case

[0084] The positive electrode sodium supplements prepared in Examples 1 to 3 and Comparative Examples 1 to 9 were respectively applied to the positive electrode of button-type sodium ion batteries. The button half-cells obtained by using Examples 1 to 3 and Comparative Examples 1 to 9 were A1 (3 (2SP / NMF) -7Na2CO3), A2 (2 (2SP / NMF) -8Na2CO3), A3 (1 (2SP / NMF) -9Na2CO3), B1 (3 (SP / NMF) -7Na2CO3), B2 (2 (SP / NMF) -8Na2CO3), B3 (1 (SP / NMF) -9Na2CO3), B4 (3 (SP / 2NMF) -7Na2CO3), B5 (2 (SP / 2NMF) -8Na2CO3), B6 ​​(1 (SP / 2NMF) -9Na2CO3), B7 (3SP-7Na2CO3), B8 (3NMF-7Na2CO3), and B9 (Na2CO3). The battery was tested as follows: a sodium supplement, a conductive agent, and a binder were weighed in a ratio of 70:20:10, stirred to prepare a slurry, coated on aluminum foil, dried, and pressed to form the battery's positive electrode. The conductive agent was SP, and the binder was PVDF. The electrolyte consisted of NaClO₄ / DMC:EC:EMC (volume ratio 1:1:1, concentration 1 mol / L). Metallic sodium served as the counter electrode, and the separator was a glass fiber membrane. The button-type sodium-ion battery was assembled in an argon-filled glove box. Electrochemical performance was measured on a Wuhan Blue Electric CT2001A battery tester over a voltage range of 2.5-4.3 V and a charge / discharge rate of 20 mA / g. The test results are shown in Table 1. As shown in Table 1, A1 exhibited a high charge capacity (303 mAh / g) and a low decomposition voltage (3.89 V). For B7 and B8, when SP and NMF act alone on Na2CO3, the actual capacity is very low and the decomposition voltage is very high. This shows that the mixed conductor composed of SP and NMF can jointly promote the capacity of Na2CO3 and reduce the decomposition voltage. Figure 1 shown.

[0085] The positive electrode active materials described in Examples 1-3 were applied to the positive electrodes of button-type sodium-ion batteries. The button-type half-cells assembled using these examples are C1, C2, and C3, respectively. The battery tests were conducted as follows: a sodium supplement, a conductive agent, and a binder were weighed in a ratio of 94:4:2, stirred to prepare a slurry, coated onto aluminum foil, dried, and pressed to produce the battery positive electrode. The conductive agent was SP, and the binder was PVDF. The electrolyte consisted of NaClO₄ / DMC:EC:EMC (volume ratio 1:1:1, concentration 1 mol / L). Metallic sodium served as the counter electrode, and a glass fiber membrane was used as the separator. The button-type sodium-ion batteries were assembled in an argon-filled glove box. Electrochemical performance was measured on a Wuhan Landian CT2001A battery tester over a voltage range of 2.0-4.3 V, at an initial charge / discharge rate of 20 mA / g, and at a cycling performance rate of 50 mA / g. The test results are shown in Table 2. As can be seen from Table 2, when the addition amount of sodium supplement additive in the positive electrode active material is 30%, the first cycle charging capacity is the highest (197 mAh / g). Figure 2 The cycling performance is also improved, with a capacity retention of 95% after 200 cycles.

[0086] Table 1: Electrochemical performance of Examples 1-3 and Comparative Examples 1-9.

[0087]

[0088]

[0089] Table 2: Electrochemical performance of application examples 1-3

[0090] Project Name First cycle charging capacity (mAh / g) Capacity retention rate (200 cycles) B1 150 80％ B2 152 85％ B3 197 95％ B4 166 89％

[0091] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A positive electrode sodium supplement additive, characterized in that The invention comprises sodium carbonate and a composite conductive agent, wherein the mass ratio of the sodium carbonate to the composite conductive agent is (9-7): (1-3).

2. A positive electrode sodium supplement additive according to claim 1, characterized in that The composite conductive agent includes Super-P and NMF; the mass ratio of the Super-P to the NMF is (1-2): (1-2).

3. A method for preparing a positive electrode sodium supplement additive, characterized in that: The following steps are involved: Super-P and NMF were mixed and ball-milled to obtain composite conductive agent SP / NMF; Sodium carbonate and a composite conductive agent are mixed and ball-milled into a mixed powder to obtain a positive electrode sodium supplement additive SP / NMF-Na2CO3.

4. The method for preparing the positive electrode sodium supplement additive according to claim 3, characterized in that: The preparation method of the composite conductive agent comprises the following steps: mixing Super-P and NMF, and ball-milling the mixture into a mixed powder to obtain a composite conductive agent, which is recorded as SP / NMF.

5. The method for preparing the positive electrode sodium supplement additive according to claim 3, characterized in that: The specific operation of the ball milling is: using zirconium dioxide ball milling beads, the diameters of the zirconium dioxide ball milling beads are 4 / 10 / 15 mm respectively, the mass ratio of ball milling beads to material is 30:1, the ball milling speed is 700 rpm, the time is 5-10 hours, each rotation is 30 minutes, and the rest time is 10 minutes.

6. The method for preparing the positive electrode sodium supplement additive according to claim 3, characterized in that: The ball milling time is 5 to 10 hours.

7. The method for preparing the positive electrode sodium supplement additive according to claim 3, characterized in that: The ball milling time is 30 to 50 hours.

8. The positive electrode sodium supplement additive according to any one of claims 1 to 7 is compounded with a sodium ion positive electrode material to obtain a sodium ion positive electrode active material, and used in a sodium ion battery positive electrode.

9. The sodium ion positive electrode active material according to claim 8, wherein The mass ratio of the sodium ion positive electrode material to the positive electrode sodium supplement additive is (90-70):(10:30).

10. A positive electrode material for a sodium ion battery, characterized in that: The raw materials include any one of the positive electrode sodium supplement additives according to claims 1-2, or include the positive electrode sodium supplement additive prepared by the method according to any one of claims 3-7, as well as a conductive agent and a binder.

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