Low-temperature aqueous selenium-based cascade battery and preparation method thereof

Abstract

The invention provides a low-temperature aqueous selenium-based cascade battery and a preparation method thereof, and relates to the technical field of aqueous batteries. The low-temperature aqueous selenium-based cascade battery comprises a low-temperature-resistant electrolyte, a Se-coated CNT positive electrode and a negative electrode, wherein the low-temperature-resistant electrolyte comprises a Cu (ClO4) 2 solution; and assembling the Se-coated CNT positive electrode, the glass fiber diaphragm and the negative electrode into a battery in sequence, and then injecting electrolyte to obtain the low-temperature water-based selenium-based cascade battery. The copper ions in the electrolyte and the Se-coated CNT positive electrode are subjected to a four-electron transfer reaction at first, and after Se of the positive electrode is completely converted into Cu2Se, the copper ions in the electrolyte on one side of the positive electrode can be reduced to generate Cu, so that the battery can be continuously discharged. And the electrolyte still can be kept in a liquid state at the temperature of-70 DEG C, so that the low-temperature aqueous selenium-based battery not only naturally couples two electrochemical reactions in the same reaction cavity to obtain a cascade battery, but also has relatively excellent low-temperature performance.

Description

Technical Field

[0001] The present invention relates to the technical field of aqueous batteries, and in particular to a low-temperature aqueous selenium-based cascade battery and a preparation method thereof. Background Art

[0002] Aqueous batteries are known for their low cost, safety, reliability and environmental protection, and show great potential in large-scale energy storage. However, they encounter great challenges when operating in low-temperature environments. Due to the high freezing point of water, aqueous electrolytes are prone to freezing. At present, there are two main strategies to achieve antifreeze function in aqueous electrolytes: the use of organic additives and high-concentration salts. When organic additives are used, the unique advantages of aqueous electrolytes, such as environmental friendliness and safety, will be affected to a certain extent due to the introduction of these additives. The high-concentration salt strategy has problems such as low ionic conductivity, high cost and low energy density. It is very necessary but also extremely challenging to improve the low-temperature electrochemical performance of aqueous batteries while maintaining the inherent safety, reaction kinetics and battery energy density of aqueous batteries.

[0003] In addition, current electrochemical cells are usually based on a redox reaction, and it is impossible to couple two different electrochemical reactions in the same reaction chamber. Therefore, a cascade battery refers to an electrochemical cell that can couple two electrochemical reactions in the same reaction chamber (Adv. Mater. 2021, 2105480), which is a new type of energy storage system. Cascade batteries have many advantages. First, multiple battery reactions are directly integrated inside the battery, avoiding the use of inactive connecting materials required for external integration of multiple batteries, saving corresponding costs, and improving the intrinsic safety of the battery; secondly, compared with traditional batteries, the inactive reaction chamber of the battery is more fully utilized. The reaction chamber of the battery refers to a reaction chamber mainly composed of an inactive current collector, a diaphragm and an external package to accommodate the redox reaction of the battery. In theory, the capacity and energy density of the battery at the device level (i.e. considering the mass or volume of the entire battery device) are directly affected by the mass of the inactive reaction chamber used; third, it is expected to obtain high area specific capacity and energy density. In practical applications, the energy density and area specific capacity of the battery are very critical. For traditional batteries, increasing the area load of active materials is the most direct and effective way to obtain high area performance. However, for traditional batteries based on solid active materials, too high an active material load means thick electrodes, which will bring about problems such as long ion transmission distance, slow mass transfer, and high internal resistance. Therefore, too high an area load will damage the electrochemical performance of the battery.

[0004] Current low-temperature aqueous batteries are relatively limited in low-temperature operating temperature, specific capacity and energy density. Most of them are within the range of 0 to -40°C, below 300mAh / g, and below 300Wh / kg, which makes it difficult to meet the needs of more practical applications. Therefore, how to disclose a high-performance, low-temperature resistant aqueous cascade battery is an urgent problem to be solved by those skilled in the art. Summary of the invention

[0005] The purpose of the present invention is to provide a low-temperature aqueous selenium-based cascade battery and a preparation method thereof, so as to solve the problem that the electrochemical properties of existing aqueous batteries, such as specific capacity and energy density, are limited in a low-temperature environment.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a low-temperature aqueous selenium-based cascade battery, the battery comprising a low-temperature resistant electrolyte, a Se@CNT positive electrode, and a negative electrode;

[0008] The low temperature resistant electrolyte includes Cu(ClO4)2 solution;

[0009] The preparation method of the Se@CNT positive electrode is to mix and grind a selenium-carbon composite material, a conductive agent, a binder and a solvent to obtain an intermediate slurry, and apply the intermediate slurry on the surface of a current collector to obtain a Se@CNT positive electrode material;

[0010] The negative electrode is copper or zinc.

[0011] Preferably, the concentration of the Cu(ClO4)2 solution is 1 to 5 mol / kg.

[0012] Preferably, the mass ratio of the selenium-carbon composite material, the conductive agent, the binder and the solvent is 5-10:0.1-2:0.1-2:100-120.

[0013] Preferably, the preparation method of the selenium-carbon composite material is to mix selenium powder and carbon nanotube material, grind and calcine to obtain the selenium-carbon composite material;

[0014] The mass ratio of the selenium powder to the carbon nanotube material is 60-80:20-40;

[0015] The calcination temperature is 240-280°C and the calcination time is 10-15h;

[0016] The heating rate of the calcination is 3-8°C / min.

[0017] Preferably, the conductive agent includes one or more of carbon black, acetylene black and graphene;

[0018] The binder is polyvinylidene fluoride and / or polytetrafluoroethylene;

[0019] The solvent is N-methylpyrrolidone and / or alcohol.

[0020] Preferably, the coating amount of the intermediate slurry on the surface of the current collector is 1-2 mg / cm 2 .

[0021] Preferably, the current collector is a 400-mesh stainless steel mesh or carbon cloth.

[0022] The present invention also provides a method for preparing a low-temperature aqueous selenium-based cascade battery, comprising the following steps:

[0023] The battery is assembled in the order of Se@CNT positive electrode, glass fiber separator, and negative electrode, and then the electrolyte is injected to obtain a low-temperature aqueous selenium-based cascade battery.

[0024] The present invention has at least the following beneficial effects:

[0025] This application uses Cu(ClO4)2 solution as the electrolyte. The chalotropic anion ClO in the electrolyte 4- , which can destroy the hydrogen bond network structure in the original aqueous solution, thereby obtaining a low freezing point and ensuring that the aqueous battery can be used normally under low temperature conditions. 2+ The four-electron transfer reaction is first realized with the Se@CNT positive electrode. When the Se in the positive electrode is completely converted into Cu2Se, the Cu in the electrolyte on the positive electrode side 2+ It can also be reduced to generate Cu, so that the battery can continue to discharge. Therefore, without changing the structure of the battery or replacing the electrolyte or electrode, the low-temperature aqueous selenium-based battery naturally couples the two electrochemical reactions in the same reaction chamber to obtain a cascade battery, thereby improving the battery's discharge capacity and energy density. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is an optical photograph of 3.5 mol / kg Cu(ClO4)2 electrolyte stored at -70℃ for 60 min;

[0027] Figure 2 This is the differential scanning calorimetry test curve of 3.5 mol / kg Cu(ClO4)2 electrolyte;

[0028] Figure 3 The charge and discharge curve of the low-temperature aqueous Cu-Se cascade battery prepared in Example 1 at 0 to -50°C;

[0029] Figure 4 This is a schematic diagram of the physical assembly structure of the low-temperature aqueous Zn-Se cascade battery prepared in Example 2;

[0030] Figure 5 The charge and discharge curve of the warm water Zn-Se cascade battery prepared in Example 2 at -50°C;

[0031] Figure 6 The data is a comparison of the low-temperature electrochemical performance of the low-temperature aqueous Zn-Se cascade battery prepared in Example 2 and previously reported low-temperature aqueous batteries. DETAILED DESCRIPTION

[0032] The present invention provides a low-temperature aqueous selenium-based cascade battery, the battery comprising a low-temperature resistant electrolyte, a Se@CNT positive electrode, and a negative electrode;

[0033] The low temperature resistant electrolyte includes Cu(ClO4)2 solution;

[0034] The preparation method of the Se@CNT positive electrode is to mix and grind a selenium-carbon composite material, a conductive agent, a binder and a solvent to obtain an intermediate slurry, and apply the intermediate slurry on the surface of a current collector to obtain a Se@CNT positive electrode material;

[0035] The negative electrode is copper or zinc.

[0036] In the present invention, the concentration of the Cu(ClO4)2 solution is 1 to 5 mol / kg, preferably 2 to 4 mol / kg, more preferably 2.5 to 3.5 mol / kg, and more preferably 3 to 3.2 mol / kg.

[0037] In the present invention, the mass ratio of the selenium-carbon composite material, the conductive agent, the binder and the solvent is 5-10: 0.1-2: 0.1-2: 100-120, preferably 6-9: 0.5-1.5: 0.5-1.5: 105-115, further preferably 7-8: 0.8-1.2: 0.8-1.2: 108-112, and more preferably 7-8: 1: 1: 110.

[0038] In the present invention, the preparation method of the selenium-carbon composite material is to mix selenium powder and carbon nanotube material, grind and calcine to obtain the selenium-carbon composite material.

[0039] In the present invention, the calcination atmosphere is an inert gas atmosphere, which may be an argon atmosphere and / or a nitrogen atmosphere, and is preferably an argon atmosphere due to its lower cost.

[0040] In the present invention, the mass ratio of the selenium powder to the carbon nanotube material is 60-80:20-40, preferably 65-75:25-35, and more preferably 68-73:28-33.

[0041] In the present invention, the grinding is dry grinding and wet grinding performed sequentially.

[0042] In the present invention, the dry grinding time is 30 to 90 seconds, preferably 50 to 70 seconds, and more preferably 55 to 65 seconds.

[0043] In the present invention, the wet grinding time is 10 to 30 minutes, preferably 15 to 25 minutes, and more preferably 18 to 22 minutes.

[0044] In the present invention, the solvent for wet grinding is ethanol, and the mass ratio of ethanol to grinding material is 5-10:0.5-1.5, preferably 6-9:0.7-1.2, and more preferably 7-8:0.9-1.0.

[0045] In the present invention, the calcination temperature is 240-280° C., preferably 250-270° C., and more preferably 255-265° C.; the calcination time is 10-15 h, preferably 11-14 h, and more preferably 12-13 h.

[0046] In the present invention, the heating rate of the calcination is 3 to 8°C / min, preferably 4 to 7°C / min, and more preferably 5 to 6°C / min.

[0047] In the present invention, the conductive agent includes one or more of carbon black, acetylene black and graphene.

[0048] In the present invention, the binder is polyvinylidene fluoride and / or polytetrafluoroethylene.

[0049] In the present invention, the solvent is N-methylpyrrolidone and / or alcohol.

[0050] In the present invention, the coating amount of the intermediate slurry on the surface of the current collector is 1-2 mg / cm 2 , preferably 1.2 to 1.8 mg / cm 2 , more preferably 1.4 to 1.6 mg / cm 2 .

[0051] In the present invention, the current collector is a 400-mesh stainless steel mesh or a carbon cloth.

[0052] In the present invention, after the intermediate slurry is coated on the surface of the current collector, a drying step is also included. The drying temperature is 50 to 70°C, preferably 55 to 65°C, and more preferably 58 to 62°C. The drying time is 10 to 14 hours, preferably 11 to 13 hours, and more preferably 11.5 to 12.5 hours.

[0053] The present invention also provides a method for preparing a low-temperature aqueous selenium-based cascade battery, comprising the following steps:

[0054] The battery is assembled in the order of Se@CNT positive electrode, glass fiber separator, and negative electrode, and then the electrolyte is injected to obtain a low-temperature aqueous selenium-based cascade battery.

[0055] The cascade reaction mechanism of the positive electrode of the present invention is that selenium first reacts with Cu in the low-temperature resistant aqueous electrolyte. 2+ The reaction occurs with four electron transfer, and the reaction equation is When Se is completely converted into Cu2Se, the copper ions in the electrolyte will continue to react further to generate copper on the Cu2Se positive electrode. The reaction equation is:

[0056] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0057] Example 1

[0058] Preparation of selenium-carbon composite materials:

[0059] Under argon protective atmosphere, selenium powder and carbon nanotubes (outer diameter of 30-50nm, length <10μm) were mixed in a mass ratio of 70:30 and dry-ground for 60s. After adding ethanol, the mixture was wet-ground for 20min (the ratio of the added amount of ethanol to the total mass of selenium powder and carbon nanotubes was 5:1). The mixture was placed in a tubular furnace and heated to 260°C at a rate of 5°C / min. The mixture was kept at this temperature for 12h to obtain a selenium-carbon composite material.

[0060] Preparation of positive electrode:

[0061] The selenium-carbon composite material, carbon black, polyvinylidene fluoride and N-methylpyrrolidone were mixed in a mass ratio of 8:1:1:100 and ground for 20 minutes to obtain an intermediate slurry; the intermediate slurry was coated on a 400-mesh stainless steel mesh current collector with a coating amount of 2 mg / cm 2 , and the Se@CNT cathode was obtained after drying in a vacuum oven at 60 °C for 12 h.

[0062] Preparation of low-temperature aqueous Cu-Se cascade battery:

[0063] The positive electrode material prepared in the above manner and the copper negative electrode and 3.5 mol / kg Cu(ClO4)2 solution were assembled in a CR2032 button cell. Specifically, the positive electrode shell, Se@CNT positive electrode, glass fiber separator, Cu negative electrode, gasket, spring sheet, and negative electrode shell were assembled in this order. The glass fiber separator was Whatman GF / D model, and the amount of electrolyte added was 200 μL.

[0064] The electrolyte of this embodiment (3.5 mol / kg Cu(ClO4)2 solution) was subjected to a low temperature freezing test. The results are as follows: Figure 1As shown, from Figure 1 It can be seen that the Cu(ClO4)2 electrolyte remains liquid after being stored at -70°C for 60 min, proving that it has excellent antifreeze properties.

[0065] The electrolyte of this embodiment was subjected to differential scanning calorimetry test, and the results are as follows Figure 2 As shown, its freezing point can reach -96°C. It is its ultra-low freezing point that ensures its antifreeze performance and also provides a guarantee for the performance of low-temperature aqueous cascade batteries.

[0066] The aqueous Cu-Se cascade battery assembled in this example was charged and discharged at 0 to -50°C with a current density of 0.2 A / g. The results are as follows: Figure 3 As shown, from Figure 3 It can be seen that within the temperature range of 0 to -50°C, the battery can work normally and undergo cascade reactions, the discharge capacity can reach 2000mAh / g, and it has a small polarization voltage.

[0067] The reaction mechanism of the low-temperature aqueous Cu-Se cascade battery of this embodiment is: the positive electrode couples two electrochemical reactions, the first step is: The second step is: The negative electrode reaction is: It is precisely by leveraging the unique advantages of the cascade reaction and the excellent low-temperature performance of the electrolyte that the low-temperature aqueous Cu-Se cascade battery achieves ultra-high low-temperature electrochemical performance.

[0068] Example 2

[0069] The preparation process of the selenium-carbon composite material and the positive electrode is the same as that in Example 1.

[0070] Preparation of low-temperature aqueous Zn-Se cascade battery:

[0071] The aqueous Zn-Se cascade battery was assembled in a homemade battery mold in the order of Se@CNT positive electrode, low-temperature electrolyte Cu(ClO4)2 (concentration of 3.5 mol / kg), anion exchange membrane, low-temperature electrolyte Zn(ClO4)2 (concentration of 3.5 mol / kg), and Zn foil. The amount of low-temperature electrolyte added was 1 mL. The battery structure is as follows: Figure 4 As shown, the positive electrode is a Se@CNT positive electrode, the negative electrode is a Zn metal foil, the electrolyte in the positive electrode reaction zone is a Cu(ClO4)2 solution, and the electrolyte in the negative electrode reaction zone is a Zn(ClO4)2 solution.

[0072] The aqueous Zn-Se cascade battery assembled in this example was subjected to charge and discharge tests at -50°C. Figure 5 As shown, from Figure 5It can be seen that due to the lower redox potential of the zinc negative electrode (-0.76V vs. SHE), the excellent low-temperature performance of the electrolyte and the unique advantages of the cascade reaction, the low-temperature aqueous Zn-Se cascade battery first has an output voltage of ~1.1V at -50°C. After Se is converted to Cu2Se, it can continue to discharge at ~0.95V, achieving an ultra-high specific capacity of 2000mAh / g. After calculation, the energy density has also reached an unprecedented 2090Wh / kg.

[0073] The reaction mechanism of the low-temperature aqueous Zn-Se cascade battery of this embodiment is: the positive electrode couples two electrochemical reactions, the first step is: The second step is: The negative electrode reaction is:

[0074] The performance of the low-temperature aqueous Zn-Se cascade battery prepared above is compared with the low-temperature aqueous batteries reported in recent years. Figure 6 As shown, from Figure 6 It can be seen that the low-temperature aqueous Zn-Se cascade battery has achieved significant improvements in low-temperature temperature, specific capacity, and energy density, far exceeding the electrochemical performance of previously reported low-temperature aqueous batteries. Figure 6 The low temperature batteries and their references are:

[0075] ALO / CF, 2m HF4+2m Mn(BF4)2, Adv.Funct.Mater.2021,31,2010127;

[0076] Zn / MnO2, 3M Zn(ClO4)2, Adv.Mater.2022,34,2201510;

[0077] NTP / AC, 2M NaClO4+0.3DMSO, Angew.Chem.Int.Ed.2019, 58, 16994–16999;

[0078] Zn / MnO2, AF, Energy Environ. Sci., 2019, 12, 706-715;

[0079] Zn / LiFePO4, ZL-PAAM, Adv.Funct.Mater.2020,30,1907218;

[0080] Zn / PANI, 7.5m ZnCl2, Nat.Commun.2020,11,4463;

[0081] Zn / MnO2, 3M Zn(ClO4)2+0.1M MnSO4, EcoMat.2022;4:e12165;

[0082] Zn / Ni, 1M KOH+0.3DMSO, Angew.Chem.Int.Ed.2022, 61, e202212767;

[0083] Zn / h-VOW, PAM, Mater. Today Energy 2019, 14, 100361.

[0084] In the present invention, the cascade battery has many advantages. First, two batteries are integrated internally, eliminating the use of inactive connecting materials required for external integration; second, compared with traditional batteries, the inactive reaction chamber of the battery is more fully utilized; third, high area capacity and energy density can be obtained.

[0085] In the present invention, by introducing a cascade reaction into a low-temperature aqueous battery, an ultra-high discharge specific capacity of 2000mAh / g and an ultra-high energy density of 2090Wh / kg are obtained at an ultra-low temperature of -50°C. This not only significantly broadens the scope of use of aqueous batteries and allows them to work normally at an ultra-low temperature of -50°C, but also greatly improves the low-temperature electrochemical performance of aqueous batteries, which has important research significance for the development of high-performance low-temperature aqueous batteries.

[0086] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A low-temperature aqueous selenium-based cascade battery, characterized in that: The battery comprises a low temperature resistant electrolyte, a Se@CNT positive electrode and a negative electrode; The low temperature resistant electrolyte includes Cu(ClO4)2 solution; The preparation method of the Se@CNT positive electrode is to mix and grind a selenium-carbon composite material, a conductive agent, a binder and a solvent to obtain an intermediate slurry, and apply the intermediate slurry on the surface of a current collector to obtain a Se@CNT positive electrode material; The negative electrode is copper or zinc.

2. A low-temperature aqueous selenium-based cascade battery according to claim 1, characterized in that: The concentration of the Cu(ClO4)2 solution is 1-5 mol / kg.

3. A low-temperature aqueous selenium-based cascade battery according to claim 2, characterized in that: The mass ratio of the selenium-carbon composite material, the conductive agent, the binder and the solvent is 5-10:0.1-2:0.1-2:100-120.

4. A low-temperature aqueous selenium-based cascade battery according to claim 3, characterized in that: The preparation method of the selenium-carbon composite material is to mix selenium powder and carbon nanotube material, grind and calcine to obtain the selenium-carbon composite material; The mass ratio of the selenium powder to the carbon nanotube material is 60-80:20-40; The calcination temperature is 240-280°C and the calcination time is 10-15h; The heating rate of the calcination is 3-8°C / min.

5. A low-temperature aqueous selenium-based cascade battery according to any one of claims 1 to 4, characterized in that: The conductive agent includes one or more of carbon black, acetylene black and graphene; The binder is polyvinylidene fluoride and / or polytetrafluoroethylene; The solvent is N-methylpyrrolidone and / or alcohol.

6. A low-temperature aqueous selenium-based cascade battery according to claim 5, characterized in that: The coating amount of the intermediate slurry on the surface of the current collector is 1-2 mg / cm 2 .

7. A low-temperature aqueous selenium-based cascade battery according to claim 6, characterized in that: The current collector is a 400-mesh stainless steel mesh or a carbon cloth.

8. A method for preparing a low-temperature aqueous selenium-based cascade battery according to any one of claims 1 to 7, characterized in that: The following steps are involved: The battery is assembled in the order of Se@CNT positive electrode, glass fiber separator, and negative electrode, and then the electrolyte is injected to obtain a low-temperature aqueous selenium-based cascade battery.

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