Sodium ion battery, negative electrode sheet, negative electrode sheet material and preparation method thereof

Abstract

The present invention discloses a novel in-situ dual-alloy-doped carbon anode material for sodium-ion batteries. Using inexpensive cassava starch as the carbon material, this sodium-ion battery exhibits improved cycle capacity and lifespan. The addition of cobalt ferrite significantly increases the specific capacity. Using cassava starch as the substrate effectively alleviates the dendrite and volume expansion issues that occur during charge and discharge in sodium-ion batteries. The addition of cobalt ferrite (CoFe2O4) significantly increases the battery's charge and discharge capacity. Furthermore, due to the high degree of disorder and numerous active sites in the prepared carbon material, cycle performance is improved and capacity decay is reduced during charge and discharge. More importantly, the Co3Fe7 dual alloy is generated in situ during pyrolysis. This simple preparation method allows for large-scale production, enabling large-scale commercialization.

Description

Technical Field

[0001] The present invention belongs to the field of new energy materials and energy storage technology, and in particular designs a novel in-situ sodium ion battery, a negative electrode plate, a negative electrode plate material and a preparation method thereof. Background Art

[0002] With the development of the economy and science and technology, humanity's energy structure is continuously shifting towards clean and sustainable energy. Currently, lithium-ion batteries, with their high energy density and long cycle life, have become the primary power source for consumer electronics and play a vital role. However, with the development of high-energy mobile devices, the uneven global distribution of lithium metal has led to rising prices, making it difficult for lithium-ion batteries to meet current market demand.

[0003] Sodium (Na) and lithium (Li) are elements in the same main group, sharing similar chemical properties. Furthermore, Na is abundant and widely distributed in the Earth's crust. Its low charge-to-mass ratio, high stability, low solvation effect, and wide redox electrochemical window facilitate the construction of stable battery systems. Consequently, sodium-ion batteries have become a research hotspot in electrochemical energy storage technology in recent years and are expected to be a key option for future grid energy storage.

[0004] Currently, sodium-ion battery anode materials are primarily classified into three categories based on their sodium ion storage mechanisms: carbon materials; transition metal oxides, sulfides, and phosphides; and alloy materials (such as Bi, P, and Sb). Of these three categories, materials based on conversion reactions have higher theoretical capacities and lower operating potentials and are considered the most promising anode materials.

[0005] While hard carbon is simple to manufacture and inexpensive, its capacity struggles to meet market demand. Transition metal phosphides suffer from low electrical conductivity and irreversible volume expansion during long cycles, leading to battery electrode rupture. This significantly reduces the cycling and rate capabilities of the electrode material, significantly limiting its application. Summary of the Invention

[0006] After research, the inventors found that: because the alloy material has a high theoretical capacity, although the large volume expansion during the charge and discharge cycle causes the anode electrode to disintegrate and the capacity to drop rapidly, and the cycle stability is relatively poor, but after research, it was found that the dual alloy can effectively prevent particle aggregation and electrochemical sintering, thereby improving the excellent cycle stability of the battery.

[0007] Based on the above research findings, one purpose of the present invention is to address the problems of low capacity of hard carbon materials and poor long-cycle performance caused by volume expansion during the cycle of single alloys and metal oxides, and to provide a new in-situ dual-alloy sodium ion battery negative electrode material, and significantly improve its charge and discharge capacity and cycle performance.

[0008] The present invention adopts the following technical solutions:

[0009] A method for preparing a negative electrode material for a sodium ion battery comprises the following steps:

[0010] The carbon-based material was obtained by pyrolyzing cassava starch at 1100°C at a heating rate of 5°C / min.

[0011] The obtained carbon-based material and cobalt ferrite are uniformly mixed in a mass ratio of 3:1;

[0012] The mixed material is pyrolyzed at a heating rate of 5°C / min to 1100°C under inert gas and kept warm for 2 to 3 hours to finally obtain a sodium ion battery negative electrode material.

[0013] Preferably, the uniform mixing method includes: grinding the obtained carbon-based material and cobalt ferrite at a mass ratio of 3:1 for 6 to 8 hours, and uniformly mixing the cobalt ferrite and the carbon-based material.

[0014] Preferably, the obtained carbon-based material and cobalt ferrite are ball-milled in a ball mill for 8 hours.

[0015] Preferably, the mixed material is pyrolyzed at 1100° C. for 2 hours.

[0016] A sodium ion battery negative electrode material, characterized in that it is prepared using the preparation method described above.

[0017] A method for preparing a sodium ion battery negative electrode plate comprises: preparing a slurry by mixing the sodium ion battery negative electrode material, a conductive agent, and an adhesive in a predetermined mass ratio, uniformly coating the prepared slurry on a copper foil, and drying the slurry for a predetermined time to obtain the sodium ion battery negative electrode plate.

[0018] Preferably, the predetermined mass ratio is 8:1:1.

[0019] A sodium ion battery comprising:

[0020] A counter electrode, comprising a negative electrode sheet of a sodium ion battery and a sodium sheet prepared by the above preparation method;

[0021] diaphragm;

[0022] electrolyte.

[0023] Preferably, the diaphragm is a glass fiber diaphragm.

[0024] Beneficial effects

[0025] First, this invention utilizes a novel in-situ dual-alloy sodium-ion battery anode material, which modifies the battery electrode process dynamics. This optimized battery reaction electrodynamics increases the reaction rate and reduces the resistance between the electrode and the electrolyte. This increases the battery capacity and, more importantly, the battery cycle life.

[0026] 2. The test results of the assembled half-battery show that the battery has good stability, low resistance during charging and discharging, and can significantly increase the capacity.

[0027] Third, the raw materials selected for this synthesis scheme are inexpensive, and the formula is simple and easy to prepare during the preparation process, which is conducive to mass production.

[0028] With reference to the following description and accompanying drawings, specific embodiments of the present invention are disclosed in detail, indicating the manner in which the principles of the present invention can be employed. It should be understood that the embodiments of the present invention are not limited in scope thereby. The embodiments of the present invention encompass numerous variations, modifications, and equivalents within the spirit and scope of the appended claims.

[0029] Features described and / or illustrated with respect to one embodiment may be used in the same or similar manner in one or more other embodiments, combined with features in other embodiments, or substituted for features in other embodiments.

[0030] It should be emphasized that the term "include / comprising" when used herein refers to the presence of features, integers, steps or components, but does not exclude the presence or addition of one or more other features, integers, steps or components. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without paying any creative labor.

[0032] Figure 1 These are SEM images of TS@2:1, TS@3:1, and TS@4:1 prepared in Example 1;

[0033] Figure 2 is the EDS image of TS@3:1 prepared in Example 1;

[0034] Figure 3 The current density in Example 3 is 50 mA g -1 Sodium ion half-cell charge and discharge curves;

[0035] Figure 4 The current density of Example 4 is 20 mA g -1 -10A g -1 Sodium ion half-cell rate performance;

[0036] Figure 5 The current density of Example 5 is 1A g -1 Long cycle curve of sodium ion half-cell;

[0037] Figure 6 The current density of Example 6 is 1A g -1 Long cycle curve of sodium ion half-cell;

[0038] Figure 7 The current density of Example 7 is 1A g -1 Long cycle curve of sodium ion half-cell;

[0039] Figure 8 This is the sodium ion half-cell impedance test of Example 8 before cycling. DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0042] Example 1:

[0043] First, cassava starch was pyrolyzed at 1100°C at a rate of 5°C / min to obtain a carbon-based material. The obtained carbon-based material and cobalt ferrite were then ball-milled in a ball mill at different mass ratios of 2:1, 3:1, and 4:1 for 8 hours to uniformly disperse the cobalt ferrite on the carbon-based material. Finally, the material was pyrolyzed at 1100°C at a heating rate of 5°C / min under inert gas for 3 hours to obtain the obtained material.

[0044] like Figure 1As shown in the figure, the alloy distribution after TS@2:1 synthesis is uneven, resulting in poor cycling stability. TS@4:1 forms a relatively small amount of alloy during pyrolysis, failing to meet market demand for increased capacity. However, the morphological characteristics of TS@3:1, where the Co3Fe7 synthesized in one step is evenly dispersed on the carbon layer, not only improve its capacity but also enhance its cycling stability.

[0045] The effects need to be described in detail with reference to the accompanying drawings.

[0046] Example 2:

[0047] First, cassava starch was pyrolyzed at 1100°C at a rate of 5°C / min to obtain a carbon-based material. The obtained carbon-based material and cobalt ferrite were then ball-milled in a ball mill at different mass ratios of 2:1, 3:1, and 4:1 for 8 hours to uniformly disperse the cobalt ferrite on the carbon-based material. Finally, the material was pyrolyzed at 1100°C at a heating rate of 5°C / min under inert gas for 3 hours to obtain the obtained material.

[0048] in, Figure 1 It shows the morphological characteristics of the material, but does not show the uniform distribution of its elements. Figure 2 The results of the distribution of each atom of TS@3:1 are shown. Figure 2 As shown, the material is mainly composed of four elements: C, O, Fe, and Co, and the Co3Fe7 alloy formed after in-situ synthesis is evenly distributed on the disordered carbon layer.

[0049] Example 3:

[0050] The material prepared in this example and the conductive agent adhesive were mixed in a mass ratio of 8:1:1 to prepare a slurry, which was evenly coated on a copper foil and dried overnight in a vacuum drying oven. The resulting electrode was used as the working electrode and the sodium sheet was used as the counter electrode. The diaphragm was a glass fiber diaphragm, and the electrolyte was 1M NaPF6indiglyme. Finally, a 2016 button-type sodium ion half-cell was assembled and charge and discharge tests were performed. The test voltage window was 0.013 V and the test current was 50 mAg-1.

[0051] according to Figure 3 It can be seen that although CoFe2O4 has a high first-cycle capacity, its initial coulombic efficiency is the lowest and its capacity loss is high. Although TS has a high initial coulombic efficiency, its capacity does not meet market demand. Among the in-situ synthesized TS@2:1, TS@3:1, and TS@4:1, TS@3:1 has the highest initial coulombic efficiency and the best capacity retention, demonstrating excellent cycling stability in later long cycles.

[0052] Example 4:

[0053] The material prepared in this embodiment and the conductive agent adhesive were prepared into a slurry in a mass ratio of 8:1:1, evenly coated on a copper foil, and dried in a vacuum drying oven overnight. The electrode sheet finally obtained was used as the working electrode and the sodium sheet as the counter electrode; the diaphragm was a glass fiber diaphragm, and the electrolyte was 1MNaPF6indiglyme; finally, a 2016 button-type sodium ion half-cell was assembled and charge and discharge tests were performed. The test voltage window was 0.013V, and the test current was 20mAg-1, 50mAg-1, 100mAg-1, 500mAg-1, 1Ag-1, 2Ag-1, 5Ag-1, and 10Ag-1. Finally, the current recovery rate performance was tested at 20mAg-1.

[0054] Example 5:

[0055] The material prepared in this example and the conductive agent adhesive were mixed in a mass ratio of 8:1:1 to prepare a slurry, which was evenly coated on a copper foil and dried overnight in a vacuum drying oven. The resulting electrode was used as the working electrode and the sodium sheet was used as the counter electrode. The diaphragm was a glass fiber diaphragm, and the electrolyte was 1M NaPF6indiglyme. Finally, a 2016 button-type sodium ion half-cell was assembled and charge and discharge tests were performed. The test voltage window was 0.013 V, the test current was 1 Ag-1, and the test cycle was 200 charge and discharge cycles.

[0056] Example 6

[0057] A slurry was prepared with CoFe2O4 and a conductive agent adhesive in a mass ratio of 8:1:1 in this embodiment, evenly coated on a copper foil, and dried overnight in a vacuum drying oven. The resulting electrode was used as a working electrode and the sodium sheet was used as a counter electrode. The diaphragm was a glass fiber diaphragm, and the electrolyte was 1MNaPF6indiglyme. Finally, a 2016 button-type sodium ion half-cell was assembled and electrochemical testing was performed. The test voltage window was 0.013 V, the test current was 1 Ag-1, and the test cycle was 200 charge and discharge cycles.

[0058] Example 7:

[0059] A slurry was prepared with the TS of this embodiment and the conductive agent adhesive in a mass ratio of 8:1:1, evenly coated on a copper foil, and dried overnight in a vacuum drying oven. The resulting electrode was used as the working electrode and the sodium sheet was used as the counter electrode; the diaphragm was a glass fiber diaphragm, and the electrolyte was 1M NaPF6indiglyme; finally, a 2016 button-type sodium ion half-cell was assembled and electrochemical testing was performed. The test voltage window was 0.013 V, the test current was 1 Ag-1, and the test cycle was 200 charge and discharge cycles.

[0060] Example 8:

[0061] The materials TS and TS@3:1 prepared in this example were respectively mixed with a conductive agent and adhesive in a mass ratio of 8:1:1 to prepare a slurry, which was evenly coated on a copper foil and dried overnight in a vacuum drying oven. The resulting electrode was used as the working electrode and the sodium sheet as the counter electrode. The separator was a glass fiber separator, and the electrolyte was 1M NaPF6indiglyme. Finally, a 2016 button-type sodium ion half-cell was assembled, and an electrochemical impedance spectroscopy test was performed before charging and discharging.

[0062] Impedance testing and fitting show that the impedance of TS@3:1 is significantly lower than that of TS, with the difference in impedance between the two being nearly 2 times. This also demonstrates that the in-situ synthesis of Co3Fe7 during the pyrolysis process can significantly reduce the material's impedance and significantly improve its conductivity. This reduces the barrier to Na+ shuttling during charge and discharge, allowing for the transport of large amounts of Na+ for insertion and deinsertion in a short period of time, thereby improving the battery's rate performance and capacity.

[0063] In summary, the embodiments of the present invention provide a novel in-situ dual-alloy doped carbon sodium ion battery negative electrode material, which can use cheap cassava starch as the carbon material to enable the sodium ion battery to have better cycle capacity and life. The addition of cobalt ferrite can significantly improve the specific capacity.

[0064] Furthermore, the embodiment of the present invention uses cassava starch as a base material to effectively alleviate the problems of dendrites and volume expansion generated during the charge and discharge of sodium ion batteries. The addition of cobalt ferrite (CoFe2O4) can significantly increase the charge and discharge capacity of the battery.

[0065] Furthermore, the carbon material prepared in this invention exhibits a high degree of disorder and numerous active sites, which improves cycling performance and reduces capacity decay during charge and discharge. More importantly, the in-situ generation of a Co3Fe7 dual alloy during pyrolysis makes this method simple and amenable to large-scale production, enabling large-scale commercialization.

[0066] Any numerical value cited herein includes all values ​​of the lower and upper values ​​in increments of one unit from the lower value to the upper value, provided that there is at least a two-unit interval between any lower value and any higher value. For example, if the value of a component quantity or process variable (e.g., temperature, pressure, time, etc.) is stated to be from 1 to 90, preferably from 20 to 80, and more preferably from 30 to 70, it is intended to illustrate that values ​​such as 15 to 85, 22 to 68, 43 to 51, 30 to 32, etc. are also explicitly listed in this specification. For values ​​less than 1, one unit is appropriately considered to be 0.0001, 0.001, 0.01, 0.1. These are merely examples intended to be clear, and it is to be understood that all possible combinations of numerical values ​​listed between the lowest and highest values ​​are expressly set forth in this specification in a similar manner.

[0067] Unless otherwise indicated, all ranges include the endpoints and all numbers between the endpoints. When used with a range, "about" or "approximately" applies to both endpoints of the range. Thus, "about 20 to 30" is intended to cover "about 20 to about 30," including at least the specified endpoints.

[0068] It should be understood that the above description is for illustration and not for limitation. Many embodiments and many applications beyond the examples provided will be apparent to those skilled in the art upon reading the above description. Therefore, the scope of the present teachings should not be determined with reference to the above description, but rather with reference to the appended claims and the full scope of equivalents to which such claims are entitled. For the purpose of comprehensiveness, all articles and references, including disclosures of patent applications and publications, are incorporated herein by reference. The omission of any aspect of the subject matter disclosed herein from the foregoing claims is not intended to be a disclaimer of such subject matter, nor should it be assumed that the inventors did not consider such subject matter to be part of the disclosed inventive subject matter.

Claims

1. A method for preparing a negative electrode material for a sodium ion battery, characterized in that: The following steps are involved: The carbon-based material was obtained by pyrolyzing cassava starch at 1100°C at a heating rate of 5°C / min. The obtained carbon-based material and cobalt ferrite are uniformly mixed in a mass ratio of 3:1; The mixed material is pyrolyzed at a heating rate of 5°C / min to 1100°C under inert gas and kept warm for 2 to 3 hours to finally obtain a sodium ion battery negative electrode material.

2. The preparation method according to claim 1, wherein The uniform mixing method includes: grinding the obtained carbon-based material and cobalt ferrite at a mass ratio of 3:1 for 6 to 8 hours, and uniformly mixing the cobalt ferrite and the carbon-based material.

3. The preparation method according to claim 2, wherein The obtained carbon-based material and cobalt ferrite were ball-milled in a ball mill for 8 hours.

4. The preparation method according to claim 1, wherein The mixed material was pyrolyzed at 1100°C for 2 hours.

5. A sodium ion battery negative electrode material, characterized in that It is prepared by the preparation method according to any one of claims 1 to 4.

6. A method for preparing a negative electrode sheet for a sodium ion battery, characterized in that: include: The sodium ion battery negative electrode material according to claim 5 and a conductive agent and a binder are prepared into a slurry in a predetermined mass ratio, the prepared slurry is evenly coated on a copper foil, and then dried for a predetermined time to obtain a sodium ion battery negative electrode sheet.

7. The preparation method according to claim 6, wherein The predetermined mass ratio is 8:1:

1.

8. A sodium ion battery, characterized in that: include: A counter electrode comprising a negative electrode sheet for a sodium ion battery and a sodium sheet obtained by the preparation method according to claim 6; diaphragm; electrolyte.

9. The sodium ion battery according to claim 8, wherein The diaphragm is a glass fiber diaphragm.

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