Low-temperature supercapacitor and preparation method thereof

Abstract

The invention discloses a low-temperature supercapacitor and a preparation method thereof, and belongs to the field of capacitors. The low-temperature supercapacitor comprises a positive electrode plate, a negative electrode plate, a diaphragm between the positive electrode plate and the negative electrode plate, and an electrolyte, the negative electrode plate comprises a current collector and an electrode coating layer; the active material of the electrode coating layer is active carbon; the active carbon in the negative electrode plate has a double-peak pore structure; the bimodal pore structure comprises micropores and mesopores; the electrolyte comprises an organic solvent and electrolyte salt; the electrolyte salt is spiro quaternary ammonium salt. The lowest use temperature of the super capacitor can reach-100 DEG C, the working voltage window of the capacitor is gradually increased along with the reduction of the use temperature, energy and power density higher than room temperature can be realized at a low temperature, and the capacity is not obviously reduced when the super capacitor works in an extremely low temperature environment of-70 DEG C; and the material has the properties of high charging and discharging speed, high power density, small internal resistance and long cycle life.

Description

Technical Field

[0001] The present application relates to a low-temperature supercapacitor and a preparation method thereof, and belongs to the field of capacitors. Background Art

[0002] As a new type of energy storage device, supercapacitors have a series of advantages. Such as fast charging and discharging capabilities, long cycle life, wide operating temperature range, safety, pollution-free and other characteristics. They are widely used in consumer electronics, rail transportation, power facilities, military defense and other fields, and have become a hot topic of concern in academia and industry. However, the performance of supercapacitors is affected by ambient temperature. When the temperature is below -40°C, the performance of the capacitor will decay rapidly due to the influence of the electrode material structure and the properties of the electrolyte, which seriously limits the application of capacitors in extremely low temperature areas, such as high altitude areas, polar regions, space exploration, etc. Therefore, it is very necessary to develop capacitors that can withstand extreme low temperature environments.

[0003] Most of the electrode materials of low-temperature capacitors reported in the literature are porous carbon materials prepared in small batches in the laboratory. This method is difficult to scale up and has high production costs, which is not conducive to the demand for materials in the large-scale preparation of low-temperature capacitors. Therefore, directly using the currently large-scale and low-cost commercial activated carbon as the electrode material to build a low-temperature capacitor based on commercial activated carbon is expected to solve the above bottleneck problem. Summary of the invention

[0004] According to one aspect of the present application, a low-temperature supercapacitor is provided, and the minimum operating temperature of the supercapacitor can reach -100°C. In addition, as the operating temperature decreases, the operating voltage window of the capacitor gradually increases, and higher energy and power density can be achieved at low temperatures than at room temperature. When working in an extreme low temperature environment of -70°C, the capacity does not decrease significantly, and the supercapacitor has the performance of fast charging and discharging speed, high power density, low internal resistance, and long cycle life.

[0005] The low-temperature supercapacitor comprises: positive and negative electrode sheets, a diaphragm between the positive and negative electrode sheets, and an electrolyte;

[0006] The positive and negative electrode sheets include current collectors and electrode coating layers;

[0007] The active material of the electrode coating layer is activated carbon;

[0008] The activated carbon has a bimodal pore structure;

[0009] The bimodal pore structure includes micropores and mesopores;

[0010] The electrolyte comprises an organic solvent and an electrolyte salt;

[0011] The electrolyte salt is a spirocyclic quaternary ammonium salt.

[0012] Optionally, the organic solvent includes organic solvent A and / or organic solvent B;

[0013] Optionally, the pore size of the mesopore is 2 to 10 nm; preferably, the pore size of the mesopore is 2 to 4 nm.

[0014] Optionally, the pore size of the mesopores is independently selected from any value of 2.5 nm, 3 nm, 4 nm, 6 nm, 8 nm, 10 nm, and a range of the above two values.

[0015] The pore size of the mesopores described in this application does not include 2 nm.

[0016] Optionally, the pore size of the micropores is 0.5-2 nm; preferably, the pore size of the micropores is 1-2 nm.

[0017] Optionally, the pore size of the micropores is independently selected from any value of 0.5 nm, 0.8 nm, 1 nm, 1.5 nm, 1.8 nm, 2 nm, and a range of the above two values.

[0018] Optionally, the activated carbon is selected from any one or more of YP80F, YP50F, and BC10.

[0019] Optionally, in the activated carbon, the volume of mesopores accounts for 50% to 90%.

[0020] Optionally, in the activated carbon, the proportion of the mesopore volume is independently selected from any value of 50%, 60%, 70%, 80%, 85%, 90% or a range of any two of the above.

[0021] Optionally, the organic solvent A is methyl formate.

[0022] Optionally, the organic solvent B is propylene carbonate and / or acetonitrile.

[0023] Optionally, the spirocyclic quaternary ammonium salt is tetrafluoroborate spirocyclic quaternary ammonium salt.

[0024] Optionally, the concentration of the electrolyte salt in the electrolyte is 0.1-2M; further preferably, the concentration of the electrolyte salt in the electrolyte is 0.3-1.5M; further preferably, the concentration of the electrolyte salt in the electrolyte is 0.35-0.6M.

[0025] M in this application refers to mol / L.

[0026] Optionally, the concentration of the electrolyte salt in the electrolyte is independently selected from any value of 0.1M, 0.3M, 0.5M, 0.8M, 1M, 1.5M, 2M and a range of the above two values.

[0027] Optionally, the volume ratio of the organic solvent A to the organic solvent B is (1:9):(9:1); preferably, the volume ratio of the organic solvent A to the organic solvent B is (5-9):(2-4).

[0028] Optionally, the volume ratio of the organic solvent A to the organic solvent B is independently selected from any value of 1:9, 5:2, 5:3, 5:4, 7:3, 8:3, 9:3, 9:1 and a range of the above two values.

[0029] Optionally, the current collector is selected from any one of metal aluminum foil, nickel foam, and stainless steel mesh.

[0030] Optionally, the electrode coating layer further includes a conductive agent and / or a binder.

[0031] Optionally, the conductive agent is Ketjen black and / or acetylene black.

[0032] Optionally, the binder is any one or more of sodium carboxymethyl cellulose, polytetrafluoroethylene, and styrene-butadiene rubber.

[0033] Optionally, the separator is selected from any one of polypropylene, porous fiber, and polyolefin resin.

[0034] Optionally, the low-temperature supercapacitor further includes a casing.

[0035] Optionally, the shell is an aluminum-plastic film soft package or a steel shell or an aluminum shell.

[0036] Optionally, the low-temperature supercapacitor is a double-layer capacitor, and the lowest operating temperature can reach -100°C.

[0037] Optionally, the operating temperature of the double-layer capacitor is independently selected from any value of -70°C, -80°C, -90°C, -100°C, -50°C, -20°C, 0°C, 10°C, 25°C, or a range of any two of the above.

[0038] On the other hand, the present application provides a method for preparing the low-temperature supercapacitor, comprising: stacking a positive electrode sheet, a separator, and a negative electrode sheet in sequence to form a compact structure, and adding an electrolyte to obtain a supercapacitor.

[0039] Optionally, the electrolyte is added and then sealed with a shell.

[0040] Optionally, the preparation method of the positive electrode sheet and the negative electrode sheet independently comprises: coating a mixture including active materials, conductive agents and binders on a current collector, and drying to obtain the positive electrode sheet or the negative electrode sheet.

[0041] Optionally, the weight ratio of the active material, the conductive agent and the binder is (70-100):(1-15):(1-20); preferably, the weight ratio of the active material, the conductive agent and the binder is (80-95):(2-10):(4-14).

[0042] Optionally, during the preparation process of the electrode sheet and the negative electrode sheet, after drying, they are cut into circles or rectangles.

[0043] Optionally, the preparation method of the electrolyte includes: dissolving an electrolyte salt in an organic solvent to obtain.

[0044] The beneficial effects of this application include:

[0045] (1) The present application directly uses commercial activated carbon as the electrode material to prepare low-temperature resistant capacitors. Compared with the electrode materials reported in the literature, this application has the advantages of scalable production and low cost, and it is easy to realize the mass production of low-temperature resistant capacitors in the later stage.

[0046] (2) The electrolyte used in the present application uses low melting point, low viscosity methyl formate and high dielectric constant propylene carbonate or acetonitrile as solvents, which reduces or avoids the use of toxic solvent acetonitrile to a certain extent. The electrolyte components in the present application are cheap and easy to obtain, the assembly process is simple, and it is easy to apply industrially.

[0047] (3) The minimum operating temperature of the capacitor prepared in this application is -100°C. As the operating temperature decreases, the operating voltage window of the capacitor gradually increases. At low temperatures, higher energy and power density can be achieved than at room temperature. Moreover, when working in an extreme low temperature environment of -70°C, the capacity does not decrease significantly.

[0048] (4) The capacitor has the advantages of fast charging and discharging speed, high power density, low internal resistance, and long cycle life, and is expected to meet the technical requirements of high-performance capacitors in the civil or military fields in extremely low temperature areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 Scanning electron microscope images of three commercial activated carbons.

[0050] Figure 2 XRD and Raman curves of three commercial activated carbons.

[0051] Figure 3 Pore ​​size distribution curves of three commercial activated carbons.

[0052] Figure 4 Cyclic voltammetry curves at different temperatures for capacitors assembled based on three commercial activated carbons, with the electrolyte solvent being mixed solvent 1.

[0053] Figure 5This is a low-temperature capacitor assembled based on commercial activated carbon (YP80F), with a comparison of the working voltage at room temperature and low temperature, as well as a comparison of the energy density and power density. The electrolyte solvent is mixed solvent 1.

[0054] Figure 6 The cyclic voltammetry curves at different temperatures for a low-temperature capacitor assembled based on commercial activated carbon (YP80F). The electrolyte solvent is mixed solvent 2. DETAILED DESCRIPTION

[0055] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0056] Unless otherwise specified, the raw materials in the examples of this application were purchased from commercial sources.

[0057] Example 1

[0058] A low-temperature supercapacitor consists of a shell, positive and negative electrode sheets, a diaphragm and an electrolyte placed in the shell.

[0059] The active material on the positive and negative electrode sheets is a commercial activated carbon.

[0060] The electrolyte consists of tetrafluoroborate spirocyclic quaternary ammonium salt and an organic solvent, and the organic solvent is methyl formate and acetonitrile; or methyl formate and propylene carbonate.

[0061] The preparation method of the positive and negative electrode sheets is as follows:

[0062] 300 mg of commercial activated carbon (BC10, YP50F and YP80F) were weighed respectively, placed in a small beaker, transferred to a vacuum oven, and vacuum dried at 100°C for 8 h to remove trace water adsorbed in the activated carbon.

[0063] Weigh 88 mg of three kinds of activated carbon respectively, mix them evenly with 4 mg of conductive agent (Ketjen black) and 4 mg of binder (sodium carboxymethyl cellulose) during grinding, add 4 mg of styrene-butadiene rubber emulsion (brand name SBR-307, purchased from Kelude), add 1 mL of water, grind to a slurry of a certain viscosity, apply it on the carbon-coated aluminum foil, transfer to an oven and dry overnight. Cut into discs of the same diameter with a slicer to obtain three kinds of pole pieces respectively.

[0064] Figure 1 These are scanning electron microscope images of the three activated carbons in Example 1, where a is the scanning electron microscope image of BC10, b is the scanning electron microscope image of YP50F, and c is the scanning electron microscope image of YP80F. Figure 1 It shows that the three carbon materials have irregular sizes and no uniform morphology.

[0065] Figure 2These are the XRD and Raman curves of the three activated carbons in Example 1, where a is the XRD curve of the three activated carbons, and b is the Raman curve of the three activated carbons. Figure 2 It shows that the three carbon materials all have the typical peak structure of carbon materials.

[0066] Figure 3 The pore size distribution curves of the three activated carbons in Example 1 show that the activated carbon (YP80F) has abundant micropores and mesopores. Meanwhile, the mesopore size of YP80F is mainly distributed in the range of 2-4 nm, and the mesopore volume accounts for about 70%. The other two activated carbons are mainly micropores with less mesopore content.

[0067] Example 2

[0068] Methyl formate, propylene carbonate and acetonitrile are subjected to dehydration treatment to obtain an organic solvent after dehydration. The specific operation is as follows:

[0069] Take 200 ml of methyl formate, propylene carbonate and acetonitrile respectively, add 40 g of molecular sieve (the molecular sieve is pre-dried at 400° C. for 4 h) to remove trace amounts of water in the solvent.

[0070] The preparation method of the electrolyte is as follows:

[0071] In a glove box, 30 ml of propylene carbonate and 70 ml of methyl formate were measured and placed in a conical flask. The mixture was stirred at room temperature for 6 h with a magnetic stirrer at a stirring speed of 400 rpm until uniformly mixed. The mixture was used as mixed solvent 1.

[0072] 30 ml of acetonitrile and 70 ml of methyl formate were measured and placed in a conical flask. The mixture was stirred at room temperature for 6 h with a magnetic stirrer at a stirring speed of 400 rpm until uniformly mixed. The mixture was used as mixed solvent 2.

[0073] Preparation of low-temperature electrolyte: Dissolve 7.46g, 11.73g, 18.12g, and 21.32g of tetrafluoroborate spirocyclic quaternary ammonium salt (SBP-BF4) in a mixed solvent 1 of 70ml methyl formate and 30ml propylene carbonate, stir with a magnetic stirrer at room temperature for 10h at a stirring speed of 400rpm, and mix well to obtain a series of low-temperature electrolytes of different concentrations. The concentrations of the electrolyte are 0.35M, 0.55M, 0.85M, and 1M.

[0074] 7.46g, 11.73g, 18.12g, 21.32g of tetrafluoroborate spirocyclic quaternary ammonium salt (SBP-BF4) were dissolved in 70ml of methyl formate and 30ml of acetonitrile mixed solvent 2, stirred at room temperature for 10h with a magnetic stirrer at a stirring speed of 400rpm, and mixed evenly to obtain a series of low-temperature electrolytes with different concentrations. The concentrations of the electrolytes are 0.35M, 0.55M, 0.85M, and 1M.

[0075] Example 3

[0076] The three pole pieces prepared in Example 1 were respectively used to assemble into symmetrical capacitors in a glove box, wherein the electrolyte used was the electrolyte prepared in Example 2 (with a concentration of 0.55 M), and the diaphragm was a polypropylene diaphragm of model 3501.

[0077] Test Example 1

[0078] The electrochemical performance of the assembled capacitor was tested at room temperature and low temperature using an electrochemical workstation CHI 760E, and the size of the curve integral area was compared.

[0079] Figure 4 The room temperature and low temperature electrochemical performance of the capacitors prepared based on three commercial activated carbons in Example 3, and the electrolyte solvent is mixed solvent 1. Among them, the scan rate is 100mV / s; a is the room temperature and low temperature electrochemical performance of the capacitor prepared by BC10, b is the room temperature and low temperature electrochemical performance of the capacitor prepared by YP50F, and c is the room temperature and low temperature electrochemical performance of the capacitor prepared by YP80F. The test results show that: in an extreme low temperature environment of -70°C, the cyclic voltammetry curve of the capacitor assembled based on YP80F as the electrode material is almost the same as the curve of the room temperature test, indicating that the electrochemical performance at low temperature has almost no decrease, proving that the capacitor assembled based on commercial activated carbon (YP80F) has excellent low temperature electrochemical performance. In contrast, the performance of the capacitor assembled based on commercial activated carbon (BC10, YP50F) decreases significantly as the temperature decreases.

[0080] Figure 5 For low-temperature capacitors assembled based on commercial activated carbon (YP80F), the working voltage at room temperature and low temperature, as well as the energy density and power density are compared. The electrolyte solvent is mixed solvent 1. It is proved that the capacitors assembled based on commercial activated carbon (YP80F) can achieve a wider working voltage at low temperature, and thus can achieve higher energy and power density at low temperature than at room temperature.

[0081] Figure 6The room temperature and low temperature electrochemical performance of the capacitor prepared based on commercial activated carbon YP80F in Example 3, the electrolyte solvent is mixed solvent 2. Among them, the sweep rate is 100mV / s. The test results show that: in an extreme low temperature environment of -70°C, the cyclic voltammetry curve of the capacitor assembled based on YP80F as the electrode material is almost the same as the curve of the room temperature test, indicating that the electrochemical performance at low temperature has almost no decrease, proving that the capacitor assembled based on commercial activated carbon (YP80F) has excellent low temperature electrochemical performance.

[0082] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A low-temperature supercapacitor, characterized in that: include: Positive and negative electrode sheets, a separator between the positive and negative electrode sheets, and an electrolyte; The positive and negative electrode sheets include current collectors and electrode coating layers; The active material of the electrode coating layer is activated carbon; The activated carbon has a bimodal pore structure; The bimodal pore structure includes micropores and mesopores; The electrolyte solution includes an organic solvent and an electrolyte salt.

2. The low-temperature supercapacitor according to claim 1, characterized in that: The electrolyte salt is a spirocyclic quaternary ammonium salt; Preferably, the spirocyclic quaternary ammonium salt comprises tetrafluoroborate spirocyclic quaternary ammonium salt.

3. The low-temperature supercapacitor according to claim 1, characterized in that: The organic solvent includes organic solvent A and / or organic solvent B; The organic solvent A is methyl formate; The organic solvent B is propylene carbonate and / or acetonitrile.

4. A low-temperature supercapacitor according to claim 1, characterized in that: The pore size of the mesopores is 2 to 10 nm; Preferably, the pore size of the mesopores is 2 to 4 nm.

5. A low-temperature supercapacitor according to claim 1, characterized in that: The pore size of the micropores is 0.5 to 2 nm; Preferably, the pore size of the micropores is 1 to 2 nm; Preferably, in the activated carbon, the volume of mesopores accounts for 50% to 90%.

6. The low-temperature supercapacitor according to claim 1, characterized in that: The concentration of the electrolyte salt in the electrolyte is 0.1-2M; Preferably, the concentration of the electrolyte salt in the electrolyte is 0.3-1.5M.

7. The low-temperature supercapacitor according to claim 1, characterized in that: The volume ratio of the organic solvent A to the organic solvent B is (1:9):(9:1).

8. The low-temperature supercapacitor according to claim 1, characterized in that: The low-temperature supercapacitor is a double-layer capacitor with a minimum operating temperature of -100°C.

9. A method for preparing a low-temperature supercapacitor according to any one of claims 1 to 8, characterized in that: include: The positive electrode sheet, the separator, and the negative electrode sheet are stacked in sequence to form a compact structure, and an electrolyte is added to obtain a supercapacitor.

10. The method for preparing a low-temperature supercapacitor according to claim 9, characterized in that: The preparation methods of the positive electrode sheet and the negative electrode sheet independently include: coating a mixture including active materials, conductive agents and binders on a current collector, and drying to obtain a positive electrode sheet or a negative electrode sheet; The weight ratio of the active material, the conductive agent and the binder is (70-100): (1-15): (1-20).

Images