Sodium ion battery and preparation method thereof

Abstract

The invention provides a sodium ion battery and a preparation method thereof, and relates to the technical field of sodium ion batteries. The sodium ion battery comprises a positive electrode, a negative electrode, electrolyte and a diaphragm, the electrolyte comprises a first additive and a second additive; the negative electrode comprises a negative electrode active material; the mass percentage content of the first additive in the electrolyte is A%; the mass percentage content of the second additive in the electrolyte is B%; the specific surface area of the negative active material is C, and the unit is m < 2 > / g; the sodium ion battery satisfies the following relational expressions: 0.01 < = A < = 5, 0.01 < = B < = 5, 0.02 < = A / B < = 4, and 0.01 < = (A + B) / C < = 3. According to the sodium ion battery provided by the invention, a stable CEI film is formed on the surface of the positive electrode, and a stable SEI film is formed on the surface of the negative electrode, so that side reaction of the battery is inhibited, circulating gas production is reduced, and the circulating performance is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and in particular to a sodium ion battery and a preparation method thereof. Background Art

[0002] Lithium-ion batteries are widely used in consumer electronics, electric vehicles, energy storage and other fields due to their high energy density and cycle performance. However, the shortage of lithium resources has led to an increase in the price of lithium salts, which has restricted the development of lithium-ion batteries. Sodium-ion batteries have a tendency to gradually replace lithium batteries in the fields of energy storage and small power due to their low cost, good low-temperature performance and long service life.

[0003] However, there are still some problems and challenges in the practical application of sodium-ion batteries, such as low cycle life, poor high-temperature performance, etc. Therefore, it is particularly important to improve the performance of sodium-ion batteries. Summary of the invention

[0004] Based on the technical problems existing in the background technology, the present invention proposes a sodium ion battery and a preparation method thereof.

[0005] A sodium ion battery proposed by the present invention comprises a positive electrode, a negative electrode, an electrolyte and a separator; the electrolyte comprises a first additive and a second additive; the negative electrode comprises a negative electrode active material; the mass percentage content of the first additive in the electrolyte is A%; the mass percentage content of the second additive in the electrolyte is B%; the specific surface area of ​​the negative electrode active material is C, in units of m 2 / g; the sodium ion battery satisfies the following relationship: 0.01≤A≤5, 0.01≤B≤5, 0.02≤A / B≤4, 0.01≤(A+B) / C≤3.

[0006] The first additive and the second additive in the sodium ion battery of the present invention form a stable interface film on the surface of the positive and negative electrodes through a synergistic effect, and at the same time, the negative electrode ratio table C and the first additive and the second additive are controlled to satisfy the relationship of 0.01≤(A+B) / C≤3, which can make the interface film denser and more uniform, reduce the interface side reaction and the generation of gas in the cycle, thereby improving the cycle performance.

[0007] Preferably, the first additive has a structural formula shown in formula (I):

[0008]

[0009] R1 is selected from any one of a C1-C6 straight chain or branched saturated or unsaturated alkyl group, a C1-C6 straight chain or branched alkyl group completely or partially substituted by F, and a C1-C6 straight chain or branched ether group; R2 is selected from any one of a C1-C6 saturated or unsaturated straight chain or branched alkyl group, a C1-C6 straight chain or branched alkyl group completely or partially substituted by F, a C1-C6 straight chain or branched silane group, and a cyano group; R3 is selected from F, C1-C 20 Straight or branched alkyl, C1~C 20 Alkyl substituted amine, substituted or unsubstituted C6~C 20 Aryl, cyano, F-substituted C1~C 20 Any one of a straight chain or branched alkane, a C1 to C6 straight chain or branched silane group.

[0010] The first additive contains a sulfacyl group, which can form a S-containing interface film on the surface of the positive and negative electrodes, which helps to reduce interface side reactions.

[0011] More preferably, the first additive is selected from one or more of compounds 1 to 5:

[0012]

[0013] Among them, the CAS number of compound 1 is 88986-32-7, the CAS number of compound 2 is 138797-14-5, the CAS number of compound 3 is 291306-38-2, the CAS number of compound 4 is 865706-01-0, and the CAS number of compound 5 is 1032763-23-7.

[0014] Preferably, the second additive is phenylmaleic anhydride.

[0015] On the one hand, phenylmaleic anhydride can remove water and acid, and on the other hand, it can cooperate with compound 1 to form an organic-inorganic combined interface film to reduce the gas generated by side reactions, thereby improving the cycle performance.

[0016] Preferably, the negative electrode active material includes one or more of soft carbon, hard carbon, carbon nanotubes, expanded graphite, and graphene; and the specific surface area C of the negative electrode active material is in the range of 1≤C≤5.

[0017] The specific surface area of ​​the negative electrode active material within a certain range helps to make the interface film more dense and uniform, reduce interface side reactions and gas generation during the cycle, and thus improve the cycle performance.

[0018] Preferably, the electrolyte also includes sodium hexafluorophosphate or sodium bis(fluorosulfonyl)imide.

[0019] Preferably, the electrolyte further includes a non-aqueous organic solvent, which is selected from one or more of carbonates, carboxylates, and ethers.

[0020] Preferably, the positive electrode includes a positive electrode active material, which is selected from one or more of layered transition metal oxides, Prussian compounds, phosphate compounds, and sulfate compounds.

[0021] More preferably, the chemical formula of the layered transition metal oxide is Na a M b O c , where 0 < a ≤ 1, 0 < b ≤ 1, 1 < c ≤ 2, and M is selected from one or more of Cr, Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb, and V; the chemical formula of the Prussian compound is Na d M[M′(CN)6] e ·fH2O, M and M′ are transition metals, and 0 < d ≤ 2, 0 < e ≤ 1, 0 < f ≤ 20; the chemical formula of the phosphate compound is Na2MPO4F, and M is selected from one or two of Fe and Mn; the chemical formula of the sulfate compound is Na2M(SO4)2·2H2O, and M is selected from one or more of Cr, Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb, and V.

[0022] The present invention also provides a method for preparing a sodium-ion battery, which includes the following steps: making a battery cell by laminating a positive electrode sheet, a separator, and a negative electrode sheet, and then making a sodium-ion battery through processes such as packaging, adding electrolyte, forming, and grading.

[0023] The method for preparing the sodium-ion battery of the present invention is simple, and the prepared sodium-ion battery solves the problem of gas generation during cycling and resulting in cycling degradation in the prior art.

[0024] The beneficial effects of the present invention are as follows:

[0025] In the sodium-ion battery of the present invention, the first additive and the second additive form a stable interfacial film on the surfaces of the positive and negative electrodes through synergistic effects. At the same time, by controlling the specific surface area C of the negative electrode and the first additive and the second additive to satisfy the relationship of 0.01 ≤ (A + B) / C ≤ 3, the interfacial film can be made more dense and uniform, reducing interfacial side reactions and gas generation during cycling, thereby improving the cycling performance. Specific Embodiments

[0026] The technical solutions of the present invention are described in detail through specific examples.

[0027] The materials, reagents, etc. used in the following examples and comparative examples can be obtained from commercial sources without special instructions.

[0028] Example 1

[0029] A method for preparing a sodium ion battery comprises the following steps:

[0030] (1) Preparation of electrolyte: The electrolyte was prepared in a glove box with an argon atmosphere and a water / oxygen content of less than 1 ppm. Propylene carbonate (PC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a weight ratio of PC:EMC:DEC=3:5:2. Then, additives were added, dissolved, and stirred thoroughly. Then, sodium hexafluorophosphate was added and mixed evenly to obtain an electrolyte.

[0031] (2) Preparation of positive electrode: The nickel iron sodium manganese oxide ternary material NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2, binder PVDF and conductive agent Super P are evenly mixed in a mass ratio of 97:1.5:1.5 to form a sodium ion battery positive electrode slurry with a certain viscosity. The mixed slurry is coated on both sides of an aluminum foil, dried and rolled to obtain a positive electrode sheet.

[0032] (3) Preparation of negative electrode: hard carbon and conductive agent SuperP, thickener CMC, and binder SBR (styrene-butadiene rubber latex) were mixed in a mass ratio of 96:1:1:2 to make a slurry, mixed evenly, and coated on both sides of the copper foil with the mixed slurry, and then dried and rolled to obtain a negative electrode sheet.

[0033] (4) Preparation of sodium ion batteries: The positive electrode sheets, separators and negative electrode sheets are stacked to form a square battery cell, which is packaged with aluminum-plastic film and filled with the sodium ion battery electrolyte prepared above. After the steps of formation and capacity separation, a soft-pack sodium ion battery with a capacity of 1.8 Ah is produced.

[0034] Embodiments 2 to 10

[0035] The only difference from Example 1 is that the specific surface area of ​​the additive and the negative electrode is different, see Table 1 for details.

[0036] Comparative Examples 1 to 5

[0037] The only difference from Example 1 is that the specific surface area of ​​the additive and the negative electrode is different, see Table 1 for details.

[0038] Table 1

[0039]

[0040]

[0041] The 1.8A sodium ion batteries assembled in the above-mentioned Examples 1 to 10 and Comparative Examples 1 to 5 were respectively subjected to high voltage and high temperature performance tests, and the specific test methods are as follows:

[0042] Gas production test of sodium ion battery during 45℃ cycling:

[0043] At room temperature (25°C), the initial volume V3 of the battery was measured by the water discharge method. Then, the battery was charged to 4.0V at a constant current of 0.9A, and then charged to a current of <0.18A at a constant voltage of 4.0V. Then, the battery was discharged to 1.5V at a constant current of 0.9A. The above charge and discharge cycle was repeated 6 times to set the battery to constant capacity (the constant capacity was recorded as C0), and the battery was allowed to stand for 30 minutes between each charge and discharge.

[0044] Place the sodium ion battery in a 45°C constant temperature box and let it stand for 6 hours to allow the sodium ion battery to reach a constant temperature. Charge to 4.0V with a constant current of 1C0, then charge to a current of <0.1C0 with a constant voltage of 4.0V, and discharge to 1.5V with a constant current of 1C0. Repeat the above cycle, and let the battery stand for 30 minutes between each charge and discharge. Measure the initial volume V0, measure the battery volume every 100 weeks, and calculate the battery gas production. Taking the battery volume V4 of the 400th week as an example, the battery gas production of the 100th week = (V4-V3) / C0. At the same time, calculate the capacity retention rate = the discharge capacity C8 / C0*100% of the 800th week, where C8 is the capacity after 800 cycles. The test results are shown in Table 2.

[0045] Table 2

[0046]

[0047]

[0048] It can be seen from Tables of Examples 1-10 and Comparative Examples 1-5 that the first additive and the second additive form a stable interface film on the surface of the positive and negative electrodes through synergistic action. At the same time, the negative electrode ratio Table C and the first type of additive and the second type of additive are controlled to satisfy the relationship of 0.01≤(A+B) / C≤3, which can make the interface film denser and more uniform, reduce interface side reactions and gas generation during circulation, and thus improve cycle performance.

[0049] In summary, the sodium ion battery provided by the present invention has a low gas production under high temperature conditions and has good cycle performance. The sodium ion battery provided by the present invention forms a stable CEI film on the positive electrode surface and a stable SEI film on the negative electrode surface, inhibits the occurrence of battery side reactions, reduces gas production during the cycle, and improves cycle performance.

[0050] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A sodium ion battery, characterized in that: The invention comprises a positive electrode, a negative electrode, an electrolyte and a separator; the electrolyte comprises a first additive and a second additive; the negative electrode comprises a negative electrode active material; the mass percentage of the first additive in the electrolyte is A%; the mass percentage of the second additive in the electrolyte is B%; the specific surface area of ​​the negative electrode active material is C, in m 2 / g; the sodium ion battery satisfies the following relationship: 0.01≤A≤5, 0.02≤A / B≤4, 0.01≤(A+B) / C≤3.

2. The sodium ion battery according to claim 1, characterized in that The first additive has a structural formula shown in formula (I): R1 is selected from any one of a C1-C6 straight chain or branched saturated or unsaturated alkyl group, a C1-C6 straight chain or branched alkyl group completely or partially substituted by F, and a C1-C6 straight chain or branched ether group; R2 is selected from any one of a C1-C6 saturated or unsaturated straight chain or branched alkyl group, a C1-C6 straight chain or branched alkyl group completely or partially substituted by F, a C1-C6 straight chain or branched silane group, and a cyano group; R3 is selected from F, C1-C 20 Straight or branched alkyl, C1~C 20 Alkyl substituted amine, substituted or unsubstituted C6~C 20 Aryl, cyano, F-substituted C1~C 20 Any one of a straight chain or branched alkane, a C1 to C6 straight chain or branched silane group.

3. The sodium ion battery according to claim 1, characterized in that: The first additive is selected from one or more of compounds 1 to 5:

4. The sodium ion battery according to claim 1, characterized in that The second additive is phenylmaleic anhydride, and the mass percentage of the second additive in the electrolyte is B%, 0.01≤B≤5.

5. The sodium ion battery according to claim 1, characterized in that: The negative electrode active material includes one or more of soft carbon, hard carbon, carbon nanotubes, expanded graphite, and graphene; the specific surface area C of the negative electrode active material is in the range of 1≤C≤5.

6. The sodium ion battery according to claim 1, characterized in that: The electrolyte also includes a non-aqueous organic solvent, which is selected from one or more of carbonates, carboxylates, and ethers.

7. The sodium ion battery according to claim 1, characterized in that: The positive electrode comprises a positive electrode active material, and the positive electrode active material is selected from one or more of layered transition metal oxides, Prussian compounds, phosphate compounds, and sulfate compounds.

8. The sodium ion battery according to claim 7, characterized in that: The chemical formula of the layered transition metal oxide is Na a M b O c , where 0 < a ≤ 1, 0 < b ≤ 1, 1 < c ≤ 2, and M is selected from one or more of Cr, Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb, V; the chemical formula of the Prussian compound is Na d M[M′(CN)6] e ·fH2O, M and M′ are transition metals, and 0 < d ≤ 2, 0 < e ≤ 1, 0 < f ≤ 20; the chemical formula of the phosphate compound is Na2MPO4F, and M is selected from one or two of Fe and Mn; the chemical formula of the sulfate compound is Na2M(SO4)2·2H2O, and M is selected from one or more of Cr, Fe, Co, Ni, Cu, Mn, Sn, Mo, Sb, V.

9. A method for preparing a sodium ion battery according to any one of claims 1 to 8, characterized in that: The following steps are involved: The positive electrode sheets, separators and negative electrode sheets are stacked to form a battery cell, which is then packaged, filled with electrolyte, formed and divided into capacities to form a sodium ion battery.

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