Composite positive electrode and battery using the composite electrode

Abstract

The application provides a composite positive electrode, which comprises 40-95 parts by mass of carbon powder, 1-58 parts by mass of sulfur powder, 0.5-5 parts by mass of an additive A, 0.5-13 parts by mass of an additive B, 8-18 parts by mass of a binder and a substrate. After the prepared positive electrode material is added with the additive A and the additive B, the components enhance the uniformity of the slurry, reduce the overall internal resistance of the battery, improve the current density of the battery, and thus meet the design requirements of high voltage and large current. After the slurry is coated on a metal sheet to form the positive electrode, the sulfur element is effectively fixed, the shuttle effect of the sulfur element is reduced, and the cycle efficiency and the energy density of the aluminum-sulfur battery are greatly improved.

Description

Technical Field

[0001] This invention relates to the field of chemical electrode material manufacturing processes, and more specifically, to a composite positive electrode and a battery using the composite electrode. Background Technology

[0002] For the past 30 years, lithium-ion batteries have been a crucial component of the electric vehicle and grid-scale energy storage markets. However, batteries composed of liquid electrolytes often contain flammable and combustible components, posing safety risks. Furthermore, their energy density is gradually approaching its theoretical limit. In this context, replacing flammable liquid electrolytes with solid-state electrolytes to manufacture all-solid-state batteries has been seen as a strategic choice to improve both energy density and safety.

[0003] Lithium-ion batteries are currently the best performing electrochemical energy storage devices overall, but their theoretical specific capacity limits their specific energy. Sulfur and aluminum, as electrode materials, have advantages such as high theoretical specific capacity, abundant reserves, low price, and environmental friendliness. They have significant advantages, especially in energy density and cost. Therefore, aluminum-sulfur batteries are a promising secondary battery system.

[0004] However, the industrial application of aluminum-sulfur batteries faces difficulties mainly due to the following problems with the sulfur cathode: (1) Elemental sulfur has poor electronic and ionic conductivity, which is detrimental to the electrochemical performance of the battery.

[0005] (2) The intermediate discharge products of aluminum-sulfur batteries will dissolve into the organic electrolyte, increasing the viscosity of the electrolyte and reducing ionic conductivity. Polysulfide ions can migrate between the positive and negative electrodes, resulting in loss of active materials and waste of electrical energy (shuttle effect).

[0006] Therefore, solving the problem of sulfur cathode materials ultimately boils down to solving the conductivity problem of active sulfur in the cathode material and the problem of inhibiting sulfur dissolution. Summary of the Invention

[0007] To address the problems in the prior art, the present invention provides a composite positive electrode, the components of which include 40-95 parts by weight of carbon powder, 1-58 parts by weight of sulfur powder, 0.5-5 parts by weight of additive A, 0.5-13 parts by weight of additive B, and 8-18 parts by weight of binder and substrate.

[0008] Furthermore, the carbon powder can be various carbon materials such as spherical graphite, carbon nanoparticles, carbon nanotubes, carbon nanofibers, activated carbon, and graphene.

[0009] Furthermore, additive A is one of polyurethane, modified acrylate, polyetheramine, polystyrene maleic anhydride, polyvinylpyrrolidone, polyacrylamide, polyvinyl alcohol, carboxylic acid silicone, and polyether.

[0010] Furthermore, additive B is one of acetylene black, polythiophene, super carbon black, Ketjen black, and polyaniline.

[0011] Furthermore, the substrate is one of aluminum foil, copper foil, nickel foil, aluminum foam, copper foam, and nickel foam.

[0012] Furthermore, the method for preparing the composite cathode provided by the present invention includes the following steps: Step 1: Mix the carbon powder and sulfur powder evenly, add the ketone solvent in a vacuum and stir to disperse evenly; Step 2: Add component A and component B to the solvent in step 1 to obtain a carbon dispersion and stir for 24 hours.

[0013] Step 3: Dissolve PVC in a ketone solvent at an appropriate temperature to obtain PVC adhesive solution; Step 4: Add the PVC adhesive from Step 3 to the carbon slurry from Step 2 and stir for 3-24 hours to obtain the positive electrode slurry; Step 5: Coat the positive electrode slurry from Step 4 onto the metal substrate and dry it in an oven until the solvent is completely evaporated and a solid film is formed to obtain the positive electrode material.

[0014] Furthermore, the ketone solvent mentioned in steps 1 and 3 includes one or more of acetone, acetone, and pyrrolidone.

[0015] Furthermore, the dissolution temperature in step 4 is 40~130°C.

[0016] Furthermore, the drying temperature in step 5 is 60~200°C.

[0017] Furthermore, the present invention also provides a battery using the composite positive electrode provided by the present invention, comprising a composite positive electrode, a negative electrode, and an electrolyte. Furthermore, the negative electrode material can be either aluminum foil or graphite.

[0018] Furthermore, the electrolyte comprises anhydrous aluminum chloride, an organic ammonium halide, and an inorganic salt additive. The organic ammonium halide is one of a tetrasubstituted alkane halide, a trisubstituted alkane halide, or a disubstituted alkane halide. The inorganic salt additive is one or more of sodium chloride, potassium chloride, and lithium chloride.

[0019] The beneficial effects of this invention are: The cathode material prepared by this invention can reduce the overall internal resistance of the battery and increase the current density of the battery, thereby achieving the design requirements of high voltage and high current. Compared with the traditional low voltage and low current battery design, it can achieve higher energy density. The cathode material prepared by this invention can effectively fix sulfur elements on the cathode sheet, reduce sulfur dissolution during charging and discharging, reduce shuttle effect, and improve the cycle efficiency of secondary batteries, which has important industrial value.

[0020] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Attached Figure Description

[0021] Figure 1 The viscosity and conductivity of the positive electrode slurry prepared in Examples 1-8 of this invention. Detailed Implementation

[0022] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0023] ① Preparation of the positive electrode: Step 1: Mix 72g of carbon powder and 15g of sulfur powder evenly, then add 90g of acetone solvent and disperse evenly for 24 hours to obtain carbon dispersion; Step 2: Add 2g of component A (polyurethane) and 1g of component B (acetylene black) to the carbon dispersion from Step 1, and stir under vacuum for 24 hours to obtain a carbon slurry. Step 3: Dissolve 10g of PVC in 58g of acetone solvent at a suitable temperature of 75°C to obtain PVC adhesive solution; Step 4: Add the PVC adhesive from Step 3 to the carbon slurry from Step 2 and stir for 24 hours to obtain the positive electrode slurry; Step 5: Coat the positive electrode slurry from Step 4 onto a 0.08 mm aluminum foil and dry it in a 110°C oven until the solvent is completely evaporated and a solid film is formed, thus obtaining the positive electrode material.

[0024] ②Preparation of the negative electrode: The negative electrode is metallic aluminum, which is prepared into aluminum foil electrodes through rolling, cutting, and cleaning. ③Preparation of electrolytes: Step 1: Weigh 275.36g of triethylamine hydrochloride, 5.9g of NaCl, 5.9g of KCl, and 29.6g of LiCl, mix them, seal them, and dry them in an oven at 105℃ for 12 hours to completely remove the moisture from the sample. Step 2: Weigh 400g of reagent-pure anhydrous aluminum chloride in a glove box, mix it with the mixture in Step 1 to form an ionic liquid, and stir it thoroughly for 8 hours to obtain a liquid molten salt electrolyte.

[0025] ④ Battery manufacturing: The separator is made of glass filter paper (6-ply 1 / 2-inch, Whatman 934-AH). The positive electrode, separator, and negative electrode are sequentially placed in the outer packaging, and molten salt electrolyte is injected between the positive and negative electrodes. Then, encapsulation, settling, formation, shaping, and capacity testing are performed to fabricate an aluminum-sulfur battery with dimensions of 40×100×100mm. 3 .

[0026] The battery provided by this invention achieves the charging and discharging of an aluminum-sulfur secondary battery through the movement of aluminum heptachloride anions or aluminum tetrachloride anions between the positive and negative electrodes. During charging, elemental sulfur at the positive electrode loses electrons and becomes sulfur (S). + Subsequently, it reacts with free aluminum heptachloride anions or aluminum tetrachloride anions in the liquid low-temperature molten salt electrolyte to form the compound disulfide dichloride. The negative electrode can be regarded as Al 3+ Electron-gaining reduction yields elemental aluminum. The reaction equation is: Anode reaction: 6S + 6AlCl4 - / 6Al2Cl6 - -6e = 3S₂Cl₂ + 6AlCl₃ Cathode reaction: 2Al 3+ +6e=2Al; During discharge, the elemental aluminum at the negative electrode oxidizes and loses charge to become Al. 3 +, at the positive electrode, disulfur dichloride gains electrons and is reduced to elemental sulfur. The reaction equation is: Negative electrode reaction: 2Al – 6e = 2Al 3 + Positive electrode reaction: 3S₂Cl₂ + 6e⁻ + 6AlCl₃ = 6S + 6AlCl₄ - / 6Al2Cl6 - . Example 2

[0027] ① Preparation of the positive electrode: Step 1: Mix 72g of carbon powder and 15g of sulfur powder evenly, then add 90g of acetone solvent and disperse evenly for 24 hours to obtain carbon dispersion; Step 2: Add 2g of component A (polyurethane) and 1g of component B (polythiophene) to the carbon dispersion from Step 1, and stir under vacuum for 24 hours to obtain a carbon slurry. Step 3: Dissolve 10g of PVC in 58g of acetone solvent at a suitable temperature of 75°C to obtain PVC adhesive solution; Step 4: Add the PVC adhesive from Step 3 to the carbon slurry from Step 2 and stir for 24 hours to obtain the positive electrode slurry; Step 5: Coat the positive electrode slurry from Step 4 onto a 0.08 mm aluminum foil and dry it in a 110°C oven until the solvent is completely evaporated and a solid film is formed, thus obtaining the positive electrode material.

[0028] The other steps in this embodiment are the same as in Embodiment 1. Example 3

[0029] ① Preparation of the positive electrode: Step 1: Mix 72g of carbon powder and 15g of sulfur powder evenly, then add 90g of acetone solvent and disperse evenly for 24 hours to obtain carbon dispersion; Step 2: Add 2g of component A (polyetheramine) and 1g of component B (acetylene black) to the carbon dispersion from Step 1, and stir under vacuum for 24 hours to obtain a carbon slurry. Step 3: Dissolve 10g of PVC in 58g of acetone solvent at a suitable temperature of 75°C to obtain PVC adhesive solution; Step 4: Add the PVC adhesive from Step 3 to the carbon slurry from Step 2 and stir for 24 hours to obtain the positive electrode slurry; Step 5: Coat the positive electrode slurry from Step 4 onto a 0.08 mm aluminum foil and dry it in a 110°C oven until the solvent is completely evaporated and a solid film is formed, thus obtaining the positive electrode material.

[0030] The other steps in this embodiment are the same as in Embodiment 1. Example 4

[0031] ① Preparation of the positive electrode: Step 1: Mix 72g of carbon powder and 15g of sulfur powder evenly, then add 90g of butanone solvent and disperse evenly for 24 hours to obtain carbon dispersion; Step 2: Add 2g of component A (polyurethane) and 1g of component B (acetylene black) to the carbon dispersion from Step 1, and stir under vacuum for 24 hours to obtain a carbon slurry. Step 3: Dissolve 10g of PVC in 58g of butanone solvent at a suitable temperature of 75°C to obtain PVC adhesive solution; Step 4: Add the PVC adhesive from Step 3 to the carbon slurry from Step 2 and stir for 24 hours to obtain the positive electrode slurry; Step 5: Coat the positive electrode slurry from Step 4 onto a 0.08 mm aluminum foil and dry it in a 110°C oven until the solvent is completely evaporated and a solid film is formed, thus obtaining the positive electrode material.

[0032] The other steps in this embodiment are the same as in Embodiment 1. Example 5

[0033] ① Preparation of the positive electrode: Step 1: Mix 72g of carbon powder and 15g of sulfur powder evenly, then add 90g of acetone solvent and disperse evenly for 24 hours to obtain carbon dispersion; Step 2: Add 1g of component B acetylene black to the carbon dispersion from step 1, and stir under vacuum for 24 hours to obtain carbon slurry; Step 3: Dissolve 10g of PVC in 58g of acetone solvent at a suitable temperature of 75°C to obtain PVC adhesive solution; Step 4: Add the PVC adhesive from Step 3 to the carbon slurry from Step 2 and stir for 24 hours to obtain the positive electrode slurry; Step 5: Coat the positive electrode slurry from Step 4 onto a 0.08 mm aluminum foil and dry it in a 110°C oven until the solvent is completely evaporated and a solid film is formed, thus obtaining the positive electrode material.

[0034] The other steps in this embodiment are the same as in Embodiment 1. Example 6

[0035] ① Preparation of the positive electrode: Step 1: Mix 72g of carbon powder and 15g of sulfur powder evenly, then add 90g of acetone solvent and disperse evenly for 24 hours to obtain carbon dispersion; Step 2: Add 2g of component A polyurethane to the carbon dispersion from step 1, and stir under vacuum for 24 hours to obtain carbon slurry; Step 3: Dissolve 10g of PVC in 58g of acetone solvent at a suitable temperature of 75°C to obtain PVC adhesive solution; Step 4: Add the PVC adhesive from Step 3 to the carbon slurry from Step 2 and stir for 24 hours to obtain the positive electrode slurry; Step 5: Coat the positive electrode slurry from Step 4 onto a 0.08 mm aluminum foil and dry it in a 110°C oven until the solvent is completely evaporated and a solid film is formed, thus obtaining the positive electrode material.

[0036] The other steps in this embodiment are the same as in Embodiment 1. Example 7

[0037] ① Preparation of the positive electrode: Step 1: Mix 63g of carbon powder and 24g of sulfur powder evenly, then add 90g of acetone solvent and disperse evenly for 24h to obtain carbon dispersion; Step 2: Add 2g of component A (polyurethane) and 1g of component B (acetylene black) to the carbon dispersion from Step 1, and stir under vacuum for 24 hours to obtain a carbon slurry. Step 3: Dissolve 10g of PVC in 58g of acetone solvent at a suitable temperature of 75°C to obtain PVC adhesive solution; Step 4: Add the PVC adhesive from Step 3 to the carbon slurry from Step 2 and stir for 24 hours to obtain the positive electrode slurry; Step 5: Coat the positive electrode slurry from Step 4 onto a 0.08 mm aluminum foil and dry it in a 110°C oven until the solvent is completely evaporated and a solid film is formed, thus obtaining the positive electrode material.

[0038] The other steps in this embodiment are the same as in Embodiment 1. Example 8

[0039] ① Preparation of the positive electrode: Step 1: Mix 72g of carbon powder and 15g of sulfur powder evenly, then add 90g of acetone solvent and disperse evenly for 24 hours to obtain carbon dispersion; Step 2: Add 2g of component A (polyurethane) and 1g of component B (acetylene black) to the carbon dispersion from Step 1, and stir under vacuum for 24 hours to obtain a carbon slurry. Step 3: Dissolve 10g of PVC in 58g of acetone solvent at a suitable temperature of 75°C to obtain PVC adhesive solution; Step 4: Add the PVC adhesive from Step 3 to the carbon slurry from Step 2 and stir for 24 hours to obtain the positive electrode slurry; Step 5: Coat the positive electrode slurry from Step 4 onto 0.8mm nickel foam and dry it in an oven at 110°C until the solvent is completely evaporated and a solid film is formed, thus obtaining the positive electrode material.

[0040] The other steps in this embodiment are the same as in Embodiment 1.

[0041] Comparative Example 1 ① Preparation of the positive electrode: Step 1: Mix 72g of carbon powder and 15g of sulfur powder evenly, then add 90g of acetone solvent and disperse evenly for 24h to obtain carbon dispersion. Stir under vacuum for 24h. Step 2: Dissolve 10g of PVC in 58g of acetone solvent at a suitable temperature of 75°C to obtain PVC adhesive solution; Step 3: Add the PVC adhesive from Step 2 to the carbon-sulfur mixture from Step 1 and stir for 24 hours to obtain the positive electrode slurry; Step 4: Coat the positive electrode slurry from Step 3 onto a 0.08 mm thick aluminum foil and dry it in a 110°C oven until the solvent is completely evaporated and a solid film is formed, thus obtaining the positive electrode material.

[0042] The other steps in this embodiment are the same as in Embodiment 1.

[0043] The positive electrode slurry prepared in the embodiment of the present invention was tested for viscosity and conductivity at 20°C using a viscometer and a conductivity meter, respectively. The resistance of the electrode prepared in the embodiment was tested using an electrode resistance meter BER2500 at a flat pressure of 5 MPa. The results are shown in Table 1.

[0044] Table 1

[0045] As can be seen from the data of Examples 1 to 8 and Comparative Example 1 in Table 1, after adding additive A in the embodiments of the present invention, the viscosity of the slurry decreased significantly, to 1 / 3 to 2 / 3 of that without additive A. This proves that additive A provided by the present invention has a good effect on the dispersion of solids in the mixture system, which is beneficial to improving the coating efficiency of the slurry and solving the problem that high solid content of the slurry will reduce viscosity.

[0046] A comparison of Examples 1 and 3 shows that different additives A affect the slurry viscosity in the examples, thus affecting the electrochemical performance of the positive electrode. The polyurethane additive A used in Example 1 exhibits better dispersibility and a relatively lower slurry viscosity, which helps to ensure more uniform slurry coating, resulting in better film-forming properties, mechanical properties, and relatively higher conductivity of the positive electrode.

[0047] When the electrode was used in the performance test of the button cell, the results showed that the energy density of the cell could reach more than 350Wh / kg.

[0048] After activating the battery prepared in the embodiment of the present invention with a current of 80 mA / g, the battery was subjected to charge-discharge cycle test with a current of 500 mA / g (charged to 4.2V), and the energy density and cycle life of the battery (energy density of discharge on the 20th cycle / maximum energy density * 100%) were measured. The results are shown in Table 2.

[0049] Table 2

[0050] As can be seen from the data of the examples and comparative examples in Table 2, after adding components A and B, component A enhances the uniformity of the slurry, and component B enhances the conductivity of the slurry. After being coated on the metal sheet to form the positive electrode, it effectively fixes the sulfur element to a certain extent, reduces the shuttle effect of the sulfur element, and significantly improves the cycle efficiency and energy density of the aluminum-sulfur battery.

[0051] The cathode material prepared by this invention can reduce the overall internal resistance of the battery and increase the current density of the battery, thereby achieving the design requirements of high voltage and high current. Compared with the traditional low voltage and low current battery design, it can achieve higher energy density and has important industrial value.

[0052] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions conceived without inventive effort should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A composite positive electrode, characterized in that, Its components include 40-95 parts by weight of carbon powder, 1-58 parts by weight of sulfur powder, 0.5-5 parts by weight of additive A, 0.5-13 parts by weight of additive B, and 8-18 parts by weight of binder and substrate.

2. The composite positive electrode according to claim 1, characterized in that, The carbon powder is one or more of spherical graphite, carbon nanoparticles, carbon nanotubes, carbon nanofibers, activated carbon, and graphene.

3. The composite positive electrode according to claim 1, characterized in that, The additive A is one of polyurethane, modified acrylate, polyetheramine, polystyrene maleic anhydride, polyvinylpyrrolidone, polyacrylamide, polyvinyl alcohol, carboxylic acid silicone, and polyether.

4. The composite positive electrode according to claim 1, characterized in that, The auxiliary agent B is one of acetylene black, polythiophene, super carbon black, Ketjen black, and polyaniline.

5. The composite positive electrode according to claim 1, characterized in that, The substrate is one of aluminum foil, copper foil, nickel foil, aluminum foam, copper foam, and nickel foam.

6. The composite positive electrode according to claim 1, characterized in that, Its preparation method includes the following steps: Step 1: Mix the carbon powder and sulfur powder evenly, add the ketone solvent in a vacuum and stir to disperse evenly; Step 2: Add component A and component B to the solvent in Step 1 to obtain a carbon dispersion and stir for 24 hours; Step 3: Dissolve PVC in a ketone solvent at an appropriate temperature to obtain PVC adhesive solution; Step 4: Add the PVC adhesive from Step 3 to the carbon slurry from Step 2 and stir for 3-24 hours to obtain the positive electrode slurry; Step 5: Coat the positive electrode slurry from Step 4 onto the metal substrate and dry it in an oven until the solvent is completely evaporated and a solid film is formed to obtain the positive electrode material.

7. The composite positive electrode according to claim 6, characterized in that, The ketone solvent mentioned in steps 1 and 3 of the preparation method includes one or more of acetone, acetone, and pyrrolidone.

8. The composite positive electrode according to claim 6, characterized in that, The dissolution temperature in step 4 is 40~130°C.

9. The composite positive electrode according to claim 6, characterized in that, The drying temperature in step 5 is 60~200°C.

10. A battery using a composite positive electrode, characterized in that, It includes a composite positive electrode, a negative electrode, and an electrolyte, wherein the negative electrode material is selected from aluminum foil or graphite.

Images