Sodium-ion battery positive electrode material as well as preparation method and application thereof

Abstract

The invention discloses a sodium ion battery positive electrode material and a preparation method and application thereof.The preparation method includes the steps that a polyarylimide / graphene hybrid is prepared through polymerization of tris (4-aminophenyl) amine, 1, 4, 5, 8-naphthalene tetracarboxylic anhydride and graphene, a short sodium ion diffusion channel is provided based on a pi-pi conjugated structure and a unique porous structure of the hybrid, and therefore the sodium ion battery positive electrode material can be used for preparing the sodium ion battery positive electrode material. Carriers are transferred to PAI, electrons and sodium ions can completely enter rich redox active carbonyl, the chemical stability and the thermal stability of the COF in the redox process are guaranteed, strong pi-pi interaction exists between COF and graphene by adding graphene, imine bonds can be effectively protected against dissociation under the electrochemical condition, and the performance of the COF is improved. The structure not only enhances the utilization rate of an active material, but also promotes the release of stress / strain, prevents the frame from being crushed, and under the driving of pi-pi stacking interaction, the crystal PAI can be easily integrated with the graphene (PAI (at) GO), thereby improving the conductivity of ions.

Description

Technical Field

[0001] The present invention belongs to the technical field of sodium ion battery positive electrode materials, and in particular relates to a sodium ion battery positive electrode material and a preparation method and application thereof. Background Art

[0002] Sodium-ion batteries have a similar working principle to lithium-ion batteries, and sodium resources are abundant and evenly distributed around the world. They also have certain advantages in specific aspects such as safety, fast charging capabilities, and low-temperature performance, and have attracted much attention. Therefore, sodium-ion batteries are expected to be used in large-scale energy storage, electric vehicles, low-temperature characteristic batteries, etc.

[0003] Sodium ion batteries are composed of positive electrode materials, negative electrode materials, conductive agents, binders, electrolytes, and separators. The electrode active materials are the core of the battery. The electrode active materials can be divided into organic electrode materials and inorganic electrode materials. The lattice oxygen redox reaction of inorganic materials may lead to the release of oxygen at high working voltages, which will cause structural damage and catalytic decomposition of the electrolyte. Organic electrode materials are mainly composed of abundant elements such as C, H, O, and N. The raw materials are widely available and low in cost. The molecules are highly designable. By introducing functional groups to design the molecular structure in a targeted manner, their electrochemical properties can be regulated. Compared with inorganic materials, organic materials are environmentally friendly and flexible in structure. They are less affected by the radius of embedded metal ions, effectively avoiding volume expansion during discharge, and have good chemical / electrochemical compatibility with most traditional / new electrolytes, making them more promising for application.

[0004] Despite the above advantages of organic compound cathode materials, they still face serious dissolution problems and low conductivity in the liquid electrolyte of rechargeable metal ion batteries. In order to solve the above problems, researchers have carried out many studies. The study found that the crystalline polyaromatic imide (PAI) synthesized by the polycondensation reaction between tri(4-aminophenyl)amine (TAPA) and 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA) has the customizability of customizable redox building units and ordered skeletons and nanopores. However, since PAI itself is an insulating polymer, directly using it as an electrode active material will significantly increase the internal resistance of the electrode, limit the efficiency of electron transfer, and slow its diffusion kinetics, resulting in poor battery rate performance and poor conductivity. At the same time, PAI has low toughness (elongation at break is usually <10%), and it is easy to produce microcracks due to repeated stress, resulting in collapse of the electrode structure and decreased cycle life. In addition, the strong polarity and high crystallinity of PAI may lead to poor wettability with certain organic electrolytes (such as ester solvents), increasing the interface resistance.

[0005] Therefore, how to use crystalline polyarylimide (PAI) as an electrode active material and solve its defects such as poor conductivity and sensitive volume expansion in batteries is a technical problem that needs to be solved urgently. Summary of the invention

[0006] The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

[0007] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0008] Therefore, the purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for preparing a positive electrode material for a sodium ion battery.

[0009] In order to solve the above technical problems, the present invention provides the following technical solutions: comprising:

[0010] Tris(4-aminophenyl)amine and 1,4,5,8-naphthalenetetracarboxylic anhydride are added to the graphene solution and subjected to ultrasonic treatment to obtain a mixed solution I, wherein the molar ratio of tris(4-aminophenyl)amine, 1,4,5,8-naphthalenetetracarboxylic anhydride to graphene in the mixed solution I is 1:1.5:17.3-97.7;

[0011] The mixed solution I is subjected to a freeze-pump-thaw cycle, and then passed through a flame-sealed reaction container and placed in an oven for thermal polymerization treatment to obtain a sodium ion battery positive electrode material.

[0012] As a preferred embodiment of the method for preparing the positive electrode material of the sodium ion battery of the present invention, the organic solvent is composed of mesitylene, dimethyl-2-imidazolidinone and isoquinoline in a volume ratio of 1:1-3:0.2-0.4.

[0013] As a preferred solution of the method for preparing the positive electrode material of the sodium ion battery of the present invention, the graphene solution is obtained by dissolving graphene in an organic solvent, wherein the mass concentration of the graphene is 20% to 70%.

[0014] As a preferred embodiment of the method for preparing the positive electrode material for a sodium ion battery of the present invention, the ultrasonic power of the ultrasonic treatment is 180 to 2200 W, and the ultrasonic time is 20 to 30 min.

[0015] As a preferred embodiment of the method for preparing the positive electrode material for a sodium ion battery of the present invention, the number of cycles of the freeze-pump-thaw cycle is 4 to 5 times.

[0016] As a preferred embodiment of the method for preparing the positive electrode material for sodium ion batteries of the present invention, the treatment temperature of the thermal polymerization treatment is 180-200° C. and the treatment time is 3-5 days.

[0017] Another object of the present invention is to provide a positive electrode material for a sodium ion battery.

[0018] Another object of the present invention is to provide a sodium ion battery positive electrode material for use in preparing a sodium ion battery positive electrode.

[0019] To solve the above technical problems, the present invention provides the following technical solution: comprising: mixing the sodium ion battery positive electrode material with carbon black and polyvinylidene fluoride in a mass ratio of 7:2:1 and then uniformly coating the mixture on pure aluminum foil by a coating method to obtain a sodium ion battery positive electrode.

[0020] Another object of the present invention is to provide a sodium ion battery positive electrode, using the sodium ion battery positive electrode as the positive electrode and a pure sodium sheet as the counter electrode to assemble into a sodium ion button half-cell, and perform electrochemical testing, wherein the charge and discharge voltage range of the test is 1.5 to 3.5 V;

[0021] The positive electrode is at a current density of 0.1A g -1 The capacity after 70 cycles is 30.2~53.2mAh g -1 , rate capacity is 2.9~25.5mAh g -1 .

[0022] Beneficial effects of the present invention:

[0023] (1) The present invention prepares a polyaromatic imide hybrid organic cathode material with a large system by a solvothermal method. During the solvothermal process, the composite of tri(4-aminophenyl)amine, 1,4,5,8-naphthalenetetracarboxylic anhydride and graphene is completed in one step, which can fully utilize the active sites.

[0024] (2) The present invention uses tri(4-aminophenyl)amine and 1,4,5,8-naphthalenetetracarboxylic anhydride as organic monomers and graphene to prepare polymer materials. The present invention can use rich π conjugated redox active units, through the action of van der Waals force and electrostatics, so that the aromatic ring in the polyarylimide molecule and the π electron cloud of graphene are tightly combined through π-π stacking to form a composite material (PAI@GO), which effectively utilizes redox active sites, has designable raw materials, simple structure and low cost.

[0025] (3) The present invention effectively overcomes the problems of poor conductivity and volume expansion sensitivity of PAI in sodium ion batteries by introducing the conductive network and nano-enhancement effect of GO, while giving it multifunctional characteristics, providing new ideas for the design of high-safety and long-life sodium batteries.

[0026] (4) In the present invention, graphene, with its high conductivity and excellent mechanical strength, combined with the chemical stability and heat resistance of polyarylimide, exerts a synergistic effect in this composite structure. The interaction between high molecular weight polyimide and graphene not only reduces the solubility of the material, but also significantly improves the conductivity, thereby greatly improving the material's cycle performance and chemical stability.

[0027] (5) The polyaromatic imide and graphene hybrid organic positive electrode material prepared by the method of the present invention has high reversible capacity, very good cycle stability and rate performance, and has broad application prospects in the field of sodium ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

[0029] Figure 1 This is a morphology picture of the polyaromatic imide and graphene hybrid material prepared in Example 1.

[0030] Figure 2 This is the Fourier transform infrared spectrum of the positive electrode material prepared in Example 1.

[0031] Figure 3 The graphs show the cycle performance and rate performance of sodium ion button-type half-cells assembled from the positive electrode materials of Example 1 and Comparative Example 1.

[0032] Figure 4 The graphs show the cycle performance and rate performance of sodium ion button-type half-cells assembled from the positive electrode materials of Examples 1 to 4.

[0033] Figure 5 The figure is a comparison chart of the cycle performance and rate performance of sodium ion button half-cells assembled with the electrode material prepared in Example 5 and the electrode material prepared in Example 1. DETAILED DESCRIPTION

[0034] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0035] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0036] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0037] Unless otherwise specified, the raw materials used in the present invention are all commercially available in the art.

[0038] The application test method in the present invention refers to:

[0039] The positive electrode material prepared in the embodiment or comparative example was used as the positive electrode, and the pure sodium sheet was used as the counter electrode to assemble a sodium ion button half-cell for electrochemical testing. The charge and discharge voltage range of the test was 1.5 to 3.5 V, and the tests were all carried out at room temperature.

[0040] Example 1

[0041] This embodiment provides a method for preparing a positive electrode for a sodium ion battery, specifically:

[0042] 1) Graphene was placed in a dry glass tube and added into a solvent mixed with dimethyl-2-imidazolidinone / mesitylene / isoquinoline in a volume ratio of 3:1:0.4 and stirred for 1 hour to obtain a graphene solution with a mass concentration of 58%;

[0043] Tris(4-aminophenyl)amine and 1,4,5,8-naphthalenetetracarboxylic anhydride were added to the graphene solution at a molar ratio of 1:1.5, and ultrasonic treatment was performed at a power of 200 W for 20 min to obtain a mixed solution I (wherein the molar ratio of graphene, tris(4-aminophenyl)amine and 1,4,5,8-naphthalenetetracarboxylic anhydride was 81:1:1.5);

[0044] The mixed solution I was subjected to four freeze-pump-thaw cycles, and the glass tube was sealed by flame, placed in an oven, and treated at 200° C. for 5 days to obtain the positive electrode material polyaromatic imide hybrid of this embodiment, denoted as PAI@GO. Figure 1 This is the morphology of the material.

[0045] 2) PAI@GO was mixed with carbon black and polyvinyl difluoride in a mass ratio of 7:2:1 and then uniformly coated on pure aluminum foil (99.6%) by a coating method to prepare the positive electrode material of this embodiment. Figure 2 The Fourier transform infrared spectrum (FTIR) of the cathode material shows that the 1650, 1780 and 1723 cm -1 Three characteristic peaks are shown at the top, the first peak originates from the stretching vibration of the formed CNC part, and the second two peaks come from the asymmetric / symmetric vibration of the C=O group of the six-membered imide ring, proving that the material was successfully synthesized.

[0046] Comparative Example 1

[0047] The difference between this comparative example and Example 1 is that the graphene in step 1) of Example 1 is omitted, and the direct condensation reaction of tri(4-aminophenyl)amine and 1,4,5,8-naphthalenetetracarboxylic anhydride is omitted, and the remaining steps and processes are referred to Example 1 to obtain the positive electrode material of this comparative example, which is recorded as PAI.

[0048] Figure 3 The positive electrode material of Example 1 and the positive electrode material of Comparative Example 1 are the cycle performance diagram and rate performance diagram as positive electrode materials for sodium ion batteries, Figure 3 (a) It can be seen that PAI@GO exhibits a satisfactory discharge capacity of 53.2 mAh g in the initial cycle. -1 , with a Coulombic efficiency of 91.12% (CE%). From the second cycle onwards, it showed significant capacity retention after long-term cycling. After 70 cycles, the capacity was still 51.9 mAh g -1 The specific capacity of PAI is relatively low in the initial discharge, and the capacity remains low but relatively stable in subsequent cycles. Figure 3 It can be seen from (b) that the rate performance of Comparative Example 1 is also much lower than that of Example 1.

[0049] Example 2

[0050] The difference between this embodiment and embodiment 1 is that the mass percentage of graphene in the mixed solution I in step 1) of embodiment 1 is adjusted to 23%, so that the molar ratio of graphene, tris(4-aminophenyl)amine and 1,4,5,8-naphthalenetetracarboxylic anhydride in the mixed solution I is 17.8:1:1.5, and the remaining steps and processes are all referred to embodiment 1 to obtain the positive electrode material of this embodiment, which is recorded as PAI@23%GO.

[0051] Example 3

[0052] The difference between this embodiment and embodiment 1 is that the mass percentage of graphene in the mixed solution I in step 1) of embodiment 1 is adjusted to 41%, so that the molar ratio of graphene, tris(4-aminophenyl)amine and 1,4,5,8-naphthalenetetracarboxylic anhydride in the mixed solution I is 40.6:1:1.5, and the remaining steps and processes are all referred to embodiment 1 to obtain the positive electrode material of this embodiment, which is recorded as PAI@41%GO.

[0053] Example 4

[0054] The difference between this embodiment and embodiment 1 is that the mass percentage of graphene in the mixed solution I in step 1) of embodiment 1 is adjusted to 50%, so that the molar ratio of graphene, tris(4-aminophenyl)amine and 1,4,5,8-naphthalenetetracarboxylic anhydride in the mixed solution I is 57.6:1:1.5, and the remaining steps and processes are all referred to embodiment 1 to obtain the positive electrode material of this embodiment, which is recorded as PAI@50%GO.

[0055] Example 5

[0056] The difference between this embodiment and embodiment 1 is that the mass percentage of graphene in the mixed solution I in step 1) of embodiment 1 is adjusted to 70%, so that the molar ratio of graphene, tris(4-aminophenyl)amine and 1,4,5,8-naphthalenetetracarboxylic anhydride in the mixed solution I is 97.7:1:1.5, and the remaining steps and processes are all referred to embodiment 1 to obtain the positive electrode material of this embodiment, which is recorded as PAI@70%GO.

[0057] The related properties of the positive electrode materials prepared in Examples 1 to 5 and Comparative Example 1 as positive electrodes of lithium ion batteries were measured. The results are shown in Table 1 and Figure 4 , Figure 5 shown.

[0058] Table 1

[0059] Capacity / cycle number / current density Rate capacity / current density Example 1 <![CDATA[53.2mAhg -1 / 70 / 0.1Ag -1 ]]> <![CDATA[25.5mAhg -1 / 1Ag -1 ]]> Comparative Example 1 <![CDATA[32.1mAhg -1 / 70 / 0.1Ag -1 ]]> <![CDATA[4.2mAhg -1 / 1Ag -1 ]]> Example 2 <![CDATA[30.2mAhg -1 / 70 / 0.1Ag -1 ]]> <![CDATA[12.8mAhg -1 / 1Ag -1 ]]> Example 3 <![CDATA[51.4mAhg -1 / 70 / 0.1Ag -1 ]]> <![CDATA[18.9mAhg -1 / 1Ag -1 ]]> Example 4 <![CDATA[39.7mAhg -1 / 70 / 0.1Ag -1 ]]> <![CDATA[2.9mAhg -1 / 1Ag -1 ]]> Example 5 <![CDATA[34.5mAhg -1 / 70 / 0.1Ag -1 ]]> <![CDATA[22mAhg -1 / 1Ag -1 ]]>

[0060] Figure 4 (a) and (b) are comparisons of the cycle performance and rate performance of sodium ion button-type half-cells assembled from the electrode materials prepared in Examples 2 to 4 and the electrode materials prepared in Example 1, respectively. Figure 5 (a) and (b) are comparisons of the cycle performance and rate performance of sodium ion button-type half-cells assembled from the electrode materials prepared in Example 5 and the electrode materials prepared in Example 1. Figure 4 As can be seen from Figure (5), the amount of graphene added has a certain influence on the capacity and stability of the electrode material. The initial capacity and stability of Example 2 are lower than those of Example 1. The capacity of Example 3 is worse than that of Example 2. The capacity of Comparative Example 1 after the cycle is much lower than that of Example 1 from the initial capacity, and the rate performance is also far inferior to that of Example 1. Although the proportion of graphene in Example 5 is relatively high, Figure 5 It can be seen that its cycle and rate performance are far inferior to those of Example 1.

[0061] It can be seen that the application of PAI and graphene composite for sodium ion batteries shows excellent results, which is due to the unique two-dimensional sheet structure and interface characteristics of graphene (GO): its continuous two-dimensional network provides an efficient channel for sodium ion transmission, and inhibits the volume expansion of electrode materials through mechanical interlocking between sheets; at the same time, the rich oxygen-containing groups on the surface of GO form strong chemical bonds with polyarylimide (PAI), significantly improving the interface stability. And experiments have found that the composite of carbon nanotubes (CNT) and PAI has the defect of easily causing stress concentration. Therefore, the GO-based composite material of this application is more competitive in high-rate charge and discharge and long cycle life, providing a new strategy for the design of positive electrode materials for sodium ion batteries.

[0062] In summary, the present invention prepares a polyaromatic imide / graphene hybrid by polymerizing tri(4-aminophenyl)amine, 1,4,5,8-naphthalenetetracarboxylic anhydride and graphene. Based on the π-π conjugated structure of the hybrid and its unique porous structure, a short sodium ion diffusion channel is provided. The carrier transfer to PAI is conducive to the complete entry of electrons and sodium ions into the abundant redox active carbonyl groups, thereby ensuring its chemical stability and thermal stability during the redox process.

[0063] The carbonyl (C=O)-containing imide compound between tri(4-aminophenyl)amine and 1,4,5,8-naphthalenetetracarboxylic anhydride provides high capacity for sodium-ion batteries. The high molecular weight polyimide formed can largely suppress the solubility problem and improve the cycle performance. By adding graphene, a strong π-π interaction exists between COF and graphene, which can effectively protect the imide bond from dissociation under electrochemical conditions. Its structure not only enhances the utilization of active materials, but also promotes the release of stress / strain and prevents framework crushing. Driven by the π-π stacking interaction, crystalline PAI can be easily integrated with graphene (PAI@GO) to improve the conductivity of ions.

[0064] At the same time, the high molecular weight of polyimide further reduces the dissolution of the material in the electrolyte, making the material more stable. Electrochemical experimental data show that the electrode material has good conductivity and is a positive electrode material for sodium ion batteries with a stable cycle life.

[0065] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for preparing a positive electrode material for a sodium ion battery, characterized in that: include, Tris(4-aminophenyl)amine and 1,4,5,8-naphthalenetetracarboxylic anhydride are added to the graphene solution and subjected to ultrasonic treatment to obtain a mixed solution I, wherein the molar ratio of tris(4-aminophenyl)amine, 1,4,5,8-naphthalenetetracarboxylic anhydride to graphene in the mixed solution I is 1:1.5:17.3-97.7; The mixed solution I is subjected to a freeze-pump-thaw cycle, and then passed through a flame-sealed reaction container and placed in an oven for thermal polymerization treatment to obtain a sodium ion battery positive electrode material.

2. The method for preparing a positive electrode material for a sodium ion battery according to claim 1, wherein: The organic solvent is composed of mesitylene, dimethyl-2-imidazolidinone and isoquinoline, and the volume ratio is 1:1-3:0.2-0.

4.

3. The method for preparing a positive electrode material for a sodium ion battery according to claim 2, characterized in that: The graphene solution is obtained by dissolving graphene in an organic solvent, wherein the mass concentration of the graphene is 20% to 70%.

4. The method for preparing a positive electrode material for a sodium ion battery according to claim 3, characterized in that: The ultrasonic power of the ultrasonic treatment is 180-2200W, and the ultrasonic time is 20-30min.

5. The method for preparing the positive electrode material for a sodium ion battery according to claim 3, characterized in that: The number of cycles of the freeze-pump-thaw cycle is 4 to 5 times.

6. The method for preparing a positive electrode material for a sodium ion battery according to claim 3, characterized in that: The treatment temperature of the thermal polymerization treatment is 180-200° C., and the treatment time is 3-5 days.

7. A sodium ion battery positive electrode material prepared by the preparation method according to any one of claims 1 to 6.

8. The use of the sodium ion battery positive electrode material according to claim 7 in preparing a sodium ion battery positive electrode, characterized in that: The sodium ion battery positive electrode material is mixed with carbon black and polyvinylidene fluoride in a mass ratio of 7:2:1 and then evenly coated on a pure aluminum foil by a coating method to obtain a sodium ion battery positive electrode.

9. The sodium ion battery positive electrode according to claim 8, characterized in that: The sodium ion battery positive electrode was used as the positive electrode and the pure sodium sheet was used as the counter electrode to assemble a sodium ion button half-cell for electrochemical testing. The charge and discharge voltage range of the test was 1.5 to 3.5 V. The positive electrode was at a current density of 0.1 Ag. -1 The capacity after 70 cycles is 30.2~53.2mAhg -1 .

10. The sodium ion battery positive electrode according to claim 9, characterized in that: The positive electrode is at a current density of 0.1Ag -1 The rate capacity is 2.9~25.5mAh g -1 .

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