A method for improving the physical properties of PVDF-based secondary battery slurry by adding calcium salts

Abstract

This invention discloses a method for improving the physical properties of PVDF-based secondary battery slurry by adding calcium salts, relating to the field of battery slurry improvement technology. The method includes the following steps: Step 1: Weighing calcium salt and dissolving it in water to obtain a calcium salt solution, which is then mixed with an organic solvent; Step 2: Weighing PVDF and adding it to the solution while stirring to dissolve the binder in the organic solvent, resulting in a viscous liquid; Step 3: Weighing a conductive agent and adding it to the viscous liquid while stirring to mix the conductive agent and binder, resulting in a dispersion system; Step 4: Weighing an active material and adding it to the dispersion system while stirring to mix the active material with the conductive agent and binder, resulting in a battery slurry; Step 5: Coating the battery slurry onto a current collector, and then drying the coated electrode. By adding trace amounts of calcium salts to the slurry, the PVDF binder is rapidly dispersed in the organic solvent, effectively improving the adhesion between the battery slurry and the aluminum foil current collector.

Description

Technical Field

[0001] This invention relates to the field of battery slurry improvement technology, specifically a method for improving the physical properties of PVDF-based secondary battery slurry by adding calcium salts. Background Technology

[0002] The mixing and dispersion process of the battery electrode slurry has a greater than 30% impact on product quality in the entire production process of ion batteries, making it the most important step in the entire production process. In the manufacturing of ion battery electrodes, the positive electrode slurry is composed of binders, conductive agents, and positive electrode materials, while the negative electrode slurry is composed of binders and graphite carbon powder. The preparation of both positive and negative electrode slurries involves a series of processes such as mixing, dissolving, and dispersing liquids with liquids and liquids with solids, and these processes are accompanied by changes in temperature, viscosity, and environment. In the positive and negative electrode slurries, the dispersion and uniformity of particulate active materials directly affect the movement of ions between the two electrodes of the battery. Therefore, the mixing and dispersion of the slurry materials of each electrode is crucial in the production of ion batteries. The quality of slurry dispersion directly affects the quality of subsequent ion battery electrode production and the performance of the product.

[0003] With the rapid development of secondary batteries, the preparation of electrode materials for secondary batteries has received widespread attention. It is well known that electrode preparation is a crucial factor affecting battery performance. Battery electrodes are obtained by uniformly dispersing active materials, binders, and conductive agents in an organic solvent, coating them onto a current collector, and then drying and cutting them into sheets. High-performance electrode sheets are related not only to the performance of the active materials but also to the dispersion effect of the binder and conductive agent in the solvent, and the adhesion of the battery slurry to the current collector; however, existing battery electrodes have some shortcomings, such as:

[0004] In the manufacturing process of most existing battery electrodes, the binder and conductive agent are directly dispersed in the solvent, which often leads to problems such as reduced dispersion of the binder and conductive agent in the solvent and reduced adhesion of the battery slurry to the current collector.

[0005] Therefore, we propose a method for adding calcium salts to improve the physical properties of PVDF-based secondary battery slurry in order to solve the problems mentioned above. Summary of the Invention

[0006] The purpose of this invention is to provide a method for improving the physical properties of PVDF-based secondary battery slurry by adding calcium salts, in order to solve the problems mentioned in the background art. In the manufacturing process of most existing battery electrodes, since the binder and conductive agent are directly dispersed in the solvent, the dispersion effect of the binder and conductive agent in the solvent and the adhesion of the battery slurry to the current collector are often reduced.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a method for improving the physical properties of PVDF-based secondary battery slurry by adding calcium salts, comprising the following steps:

[0008] Step 1:

[0009] Weigh 0.1-5% by weight of calcium salt, which is the total weight of the battery active materials, and dissolve it in water at a mass-to-volume ratio of 1:1-1:3 to obtain a calcium salt solution; add organic solvent dropwise to the calcium salt solution and mix; Step 2:

[0010] Weigh out PVDF and add it to the solution obtained in step one. Stir magnetically at a stirring speed of 100-400 rpm for 1-2 hours to completely dissolve the binder in the organic solvent, thereby obtaining a viscous liquid.

[0011] Step 3:

[0012] Weigh the conductive agent into the viscous liquid obtained in step two, and stir magnetically at a stirring speed of 100-400 rpm for 1-2 hours to ensure that the conductive agent and the binder are fully and evenly mixed to obtain a dispersion system; wherein the conductive carbon black is a carbon black with low or high resistance properties; it can impart conductive or antistatic properties to the product.

[0013] Step Four:

[0014] Weigh out the active material and add it to the dispersion system obtained in step three. Stir magnetically at a stirring speed of 100-400 rpm for 8-10 hours to ensure that the active material is fully mixed with the conductive agent and binder to obtain the battery slurry.

[0015] Step 5:

[0016] The battery slurry obtained in step four is uniformly coated on the current collector with a thickness of 100-300 micrometers. The coated electrode is dried in a forced-air drying oven at 80-110℃ for 1-4 hours, and then dried in a vacuum drying oven at 90-120℃ for 6-9 hours.

[0017] Step Six:

[0018] Cut the electrode sheet obtained in step five into pieces to obtain the electrode sheet for the secondary battery.

[0019] By adding trace amounts of calcium salt to the slurry, the PVDF binder is rapidly dispersed in the organic solvent, effectively improving the adhesion between the battery slurry and the aluminum foil current collector, and also increasing the roughness of the electrode material. The electrode material prepared by this invention has a higher specific surface area, and the adhesion of the slurry to the aluminum foil is significantly enhanced, thereby improving the physical properties of the electrode sheet and resulting in a secondary battery with better electrochemical performance.

[0020] As a preferred technical solution of the present invention, the calcium salt is at least one of calcium nitrite, calcium chloride, calcium nitrate, calcium carbonate, calcium bicarbonate, calcium bromide and calcium iodide, and the calcium content of each of the seven calcium salt materials is not less than 0.1%.

[0021] The melting point of calcium nitrite is 390℃, the flash point is 110℃, and the density is 2.23; the melting point of calcium chloride is 772℃, the flash point is 1650℃, and the density is 1.09; the melting point of calcium nitrate is 591℃, the boiling point is 130-140℃, and the density is 2.36; the melting point of calcium carbonate is 825℃, the boiling point is 800℃, and the density is 2.93; the melting point of calcium bromide is 730℃, the boiling point is 806-812℃, and the density is 3.35; and the melting point of calcium iodide is 779℃, the boiling point is 1100℃, and the density is 3.96.

[0022] The above technical solution enables the battery electrode to be made of different materials in different environments during the manufacturing process, thereby increasing the equipment's material selectivity.

[0023] As a preferred embodiment of the present invention, the organic solvent is at least one of N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide.

[0024] The above technical solution enables the battery electrode to be manufactured using different materials depending on the environment, thereby increasing the equipment's material selectivity and allowing the battery electrode to be manufactured using materials selected according to different environments.

[0025] As a preferred technical solution of the present invention, the conductive agent is at least one of conductive carbon black, carbon nanotubes, graphene, and conductive graphite. The conductive carbon black has a small particle size, a particularly large specific surface area, and good conductivity, and can play a role in absorbing and retaining liquid in the battery.

[0026] The above technical solution enables conductive carbon black particles to better conduct electricity during use, thereby increasing the conductivity of battery electrodes.

[0027] As a preferred embodiment of the present invention, the active material includes all organic electrode materials and inorganic electrode materials, wherein the organic electrode materials include P-type organic battery materials, such as carbonyl organic battery materials; and the inorganic electrode materials include lithium titanate, carbon-based anode materials, etc.

[0028] The above technical solution allows for the control of the amount of organic and inorganic electrode materials used depending on the application environment, increasing the selectivity of the battery electrode during manufacturing.

[0029] As a preferred embodiment of the present invention, the current collector includes at least one of copper foil current collector or aluminum foil current collector.

[0030] The above technical solution enables the battery electrode to be made of different materials in different environments during the manufacturing process, thereby increasing the equipment's material selectivity.

[0031] As a preferred technical solution of the present invention, the blower drying oven and the vacuum drying oven need to be isolated from the plasma during use to prevent excessive impurities from appearing in the plasma during drying.

[0032] The above technical solution can prevent excessive impurities from entering the plasma during the manufacturing process of the battery electrode, thereby affecting the quality of the battery electrode.

[0033] As a preferred technical solution of the present invention, adding a trace amount of inorganic calcium salt during the electrode material homogenization process can improve the wetting performance of the active material and achieve the effect of improving the dispersibility of the binder PVDF and the active material.

[0034] The above technical solution can improve the affinity between the binder and the organic solvent by adding calcium salt, allowing the binder to dissolve better in the organic solvent and improving the adhesion of the slurry to the current collector.

[0035] As a preferred technical solution of the present invention, the prepared lithium iron phosphate electrode material can be well attached to the aluminum foil and exhibits a rough electrode surface with a larger specific surface area. Using lithium sheet as counter electrode, LiPF6 electrolyte, and glass fiber as separator to assemble button battery, the resulting battery has better cycle performance than the battery constructed by directly homogenizing electrode sheet without adding calcium chloride.

[0036] The above technical solution enables the battery to have better cycle performance by constructing a full cell compared to the battery constructed by directly homogenizing electrode sheets without adding calcium salts.

[0037] Compared with the prior art, the beneficial effects of the present invention are: by adding a trace amount of calcium salt to the slurry, the PVDF binder is rapidly dispersed in the organic solvent, which effectively improves the adhesion between the battery slurry and the aluminum foil current collector, and also improves the roughness of the electrode material; the electrode material prepared by the present invention has a higher specific surface area, and the adhesion of the slurry to the aluminum foil is significantly enhanced, thereby improving the physical properties of the electrode sheet, and the prepared secondary battery has better electrochemical performance.

[0038] Furthermore, when constructing a full cell using electrodes prepared with this technology, the resulting cell exhibits better cycle performance compared to cells constructed using electrodes prepared directly by homogenization without the addition of calcium salts.

[0039] Furthermore, the addition of calcium salts improves the affinity between the binder and organic solvents, allowing the binder to dissolve more readily in the organic solvents. This enhances the adhesion of the slurry to the current collector and increases the viscosity of the battery plasma during manufacturing. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the battery slurry manufacturing process of the present invention;

[0041] Figure 2 This is a schematic diagram showing the adhesion of the electrode after the addition of calcium salts.

[0042] Figure 3 A schematic diagram illustrating the adhesion of the pre-electrode sheet before adding calcium salts;

[0043] Figure 4 Battery charge-discharge diagrams were constructed for P-type organic material electrodes after the addition of calcium salts;

[0044] Figure 5 Battery charge-discharge diagrams were constructed for P-type organic material electrodes before the addition of calcium salts. Detailed Implementation

[0045] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0046] Example 1:

[0047] Please see Figure 1-5 This invention provides a technical solution: a method for improving the physical properties of PVDF-based secondary battery slurry by adding calcium salts, comprising the following steps:

[0048] Step 1:

[0049] Weigh out 5% of the total mass of the battery materials in calcium chloride, add water at a mass-to-volume ratio of 1:3 to dissolve it, and obtain a calcium chloride solution; add MNMP dropwise to the calcium salt solution and mix.

[0050] Step Two:

[0051] Weigh 1g of PVDF and add it to the solution obtained in step one. Add NMP again to cover the adhesive. Stir magnetically at a stirring speed of 100-400rpm for 2 hours to completely dissolve PVDF in the organic solvent.

[0052] PVDF is a fusible fluorocarbon resin for coatings, homopolymerized from vinylidene fluoride (VDF) with a purity of ≥99%. It has an oxygen index of 46%, is non-flammable, has a crystallinity of 65%–78%, and a density of 1.77–1.80. It features the strongest toughness, low coefficient of friction, strong corrosion resistance, aging resistance, weather resistance, and good radiation resistance.

[0053] Step 3:

[0054] Weigh 2g of conductive carbon black and add it to the viscous liquid obtained in step two. Stir magnetically at a stirring speed of 100-400rpm for 2 hours to ensure that the conductive carbon black and PVDF are fully and evenly mixed.

[0055] Conductive carbon black is a type of carbon black with low or high resistance properties; it can impart conductivity or antistatic properties to products; and it has small particle size, large and rough specific surface area, high structure, and clean surface; the particle size of conductive carbon black is 30-45nm, the specific surface area is 120-130m2 / g, and the compaction density is 280-300g / L.

[0056] Step Four:

[0057] Weigh 6.5g of lithium iron phosphate battery material and add it to the dispersion system obtained in step three. Stir magnetically at a stirring speed of 100-400rpm for 8 hours to ensure that lithium iron phosphate is fully mixed with conductive carbon black and PVDF, and obtain a battery slurry with appropriate viscosity.

[0058] Step 5:

[0059] The battery slurry obtained in step four is uniformly coated on the aluminum foil current collector with a thickness of 100 micrometers. The coated electrode is dried at 80°C for 1 hour in a forced-air drying oven and then dried at 120°C for 9 hours in a vacuum drying oven.

[0060] Step Six:

[0061] Cut the electrode sheet obtained in step five into pieces to obtain the electrode sheet for the secondary battery; the adhesion force of the electrode sheet is measured to be 1.2N according to the method shown in the patent "A testing tool for the adhesion force of water-soluble electrode sheet of lithium-ion battery" (CN201464346U).

[0062] The calcium salt is at least one of calcium nitrite, calcium chloride, calcium nitrate, calcium carbonate, calcium bicarbonate, calcium bromide, and calcium iodide, and the calcium content of each of the seven calcium salt materials is not less than 0.1%.

[0063] Calcium nitrite has a melting point of 390℃, a flash point of 110℃, and a density of 2.23; calcium chloride has a melting point of 772℃, a flash point of 1650℃, and a density of 1.09; calcium nitrate has a melting point of 591℃, a boiling point of 130-140℃, and a density of 2.36; calcium carbonate has a melting point of 825℃, a boiling point of 800℃, and a density of 2.93; calcium bromide has a melting point of 730℃, a boiling point of 806-812℃, and a density of 3.35; and calcium iodide has a melting point of 779℃, a boiling point of 1100℃, and a density of 3.96.

[0064] The organic solvent is at least one of N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide; wherein N,N-dimethylformamide has a melting point of -61℃, a boiling point of 153℃, and a density of 1.03, is a colorless and transparent liquid, is a polar inert solvent, and is classified as a toxic substance; N,N-dimethylacetamide has a melting point of -20℃, a boiling point of 164℃-166℃, and a density of 0.94, is a colorless and transparent liquid, and is classified as a toxic substance;

[0065] The conductive agent is at least one of conductive carbon black, carbon nanotubes, graphene, and conductive graphite. The conductive carbon black has a small particle size, a particularly large specific surface area, and good conductivity. In the battery, it can play the role of absorbing and retaining liquid.

[0066] The active material includes all organic and inorganic electrode materials, with organic electrode materials containing abundant carbon, hydrogen, and oxygen; while inorganic electrode materials contain materials such as platinum and graphite; the current collector includes at least one of copper foil current collector or aluminum foil current collector;

[0067] When using forced-air drying ovens and vacuum drying ovens, they must be isolated from the plasma to prevent excessive impurities from appearing in the plasma during drying. Adding trace amounts of inorganic calcium salts during the electrode material homogenization process can improve the wetting performance of the active material and enhance the dispersibility between the binder PVDF and the active material.

[0068] The prepared lithium iron phosphate electrode material can adhere well to aluminum foil and exhibits a rough electrode surface with a larger specific surface area. Using lithium sheet as counter electrode, LiPF6 electrolyte, and glass fiber as separator to assemble button cell batteries, the resulting batteries have better cycle performance compared to batteries constructed by directly homogenizing electrode sheets without adding calcium chloride.

[0069] Example 2:

[0070] The difference between this embodiment and Embodiment 1 is that: a method for improving the physical properties of PVDF-based secondary battery slurry by adding calcium salts includes the following steps:

[0071] Step 1:

[0072] Weigh out 5% of the total mass of the battery materials in calcium nitrate, add water at a mass-to-volume ratio of 1:3 to dissolve it, and obtain a calcium nitrate solution; add MNMP dropwise to the calcium salt solution and mix.

[0073] Step Two:

[0074] Weigh 1g of PVDF and add it to the solution obtained in step one. Add NMP again to cover the adhesive. Stir magnetically at a stirring speed of 100-400rpm for 2 hours to completely dissolve PVDF in the organic solvent.

[0075] PVDF is a fusible fluorocarbon resin for coatings, homopolymerized from vinylidene fluoride (VDF) with a purity of ≥99%. It has an oxygen index of 46%, is non-flammable, has a crystallinity of 65%–78%, and a density of 1.77–1.80. It features the strongest toughness, low coefficient of friction, strong corrosion resistance, aging resistance, weather resistance, and good radiation resistance.

[0076] Step 3:

[0077] Weigh 2g of conductive carbon black and add it to the viscous liquid obtained in step two. Stir magnetically at a stirring speed of 100-400rpm for 2 hours to ensure that the conductive carbon black and PVDF are fully and evenly mixed.

[0078] Conductive carbon black is a type of carbon black with low or high resistance properties; it can impart conductivity or antistatic properties to products; and it has small particle size, large and rough specific surface area, high structure, and clean surface; the particle size of conductive carbon black is 30-45nm, the specific surface area is 120-130m2 / g, and the compaction density is 280-300g / L.

[0079] Step Four:

[0080] Weigh 5g of organic polyimide organic battery material and add it to the dispersion system obtained in step three. Stir magnetically at a stirring speed of 100-400rpm for 8 hours to ensure that the polyimide is fully mixed with conductive carbon black and PVDF, and obtain a battery slurry with appropriate viscosity.

[0081] Step 5:

[0082] The battery slurry obtained in step four is uniformly coated on the aluminum foil current collector with a thickness of 100 micrometers. The coated electrode is dried at 80°C for 1 hour in a forced-air drying oven and then dried at 120°C for 9 hours in a vacuum drying oven.

[0083] Step Six:

[0084] Cut the electrode sheet obtained in step five into pieces to obtain the electrode sheet for the secondary battery; the adhesion force of the electrode sheet is measured to be 1.1N according to the method shown in the patent "A testing tool for the adhesion force of water-soluble electrode sheet of lithium-ion battery" (CN201464346U).

[0085] The calcium salt is at least one of calcium nitrite, calcium chloride, calcium nitrate, calcium carbonate, calcium bicarbonate, calcium bromide, and calcium iodide, and the calcium content of each of the seven calcium salt materials is not less than 0.1%.

[0086] Calcium nitrite has a melting point of 390℃, a flash point of 110℃, and a density of 2.23; calcium chloride has a melting point of 772℃, a flash point of 1650℃, and a density of 1.09; calcium nitrate has a melting point of 591℃, a boiling point of 130-140℃, and a density of 2.36; calcium carbonate has a melting point of 825℃, a boiling point of 800℃, and a density of 2.93; calcium bromide has a melting point of 730℃, a boiling point of 806-812℃, and a density of 3.35; and calcium iodide has a melting point of 779℃, a boiling point of 1100℃, and a density of 3.96.

[0087] The organic solvent is at least one of N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide; wherein N,N-dimethylformamide has a melting point of -61℃, a boiling point of 153℃, and a density of 1.03, is a colorless and transparent liquid, is a polar inert solvent, and is classified as a toxic substance; N,N-dimethylacetamide has a melting point of -20℃, a boiling point of 164℃-166℃, and a density of 0.94, is a colorless and transparent liquid, and is classified as a toxic substance;

[0088] The conductive agent is at least one of conductive carbon black, carbon nanotubes, graphene, and conductive graphite. The conductive carbon black has a small particle size, a particularly large specific surface area, and good conductivity. In the battery, it can play the role of absorbing and retaining liquid.

[0089] The active material includes all organic and inorganic electrode materials, with organic electrode materials containing abundant carbon, hydrogen, and oxygen; while inorganic electrode materials contain materials such as platinum and graphite; the current collector includes at least one of copper foil current collector or aluminum foil current collector;

[0090] When using forced-air drying ovens and vacuum drying ovens, they must be isolated from the plasma to prevent excessive impurities from appearing in the plasma during drying. Adding trace amounts of inorganic calcium salts during the electrode material homogenization process can improve the wetting performance of the active material and enhance the dispersibility between the binder PVDF and the active material.

[0091] The prepared lithium iron phosphate electrode material can adhere well to aluminum foil and exhibits a rough electrode surface with a larger specific surface area. Using lithium sheet as counter electrode, LiPF6 electrolyte, and glass fiber as separator to assemble button cell batteries, the resulting batteries have better cycle performance compared to batteries constructed by directly homogenizing electrode sheets without adding calcium chloride.

[0092] This completes a series of tasks. The contents not described in detail in this specification are existing technologies known to those skilled in the art.

[0093] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method of improving the physical properties of a PVDF-based secondary battery slurry by adding a calcium salt, characterized by, The method comprises the following steps: Step one: Take 0.1-5% of the total weight of the battery active material as the weight of calcium salt, add water in a mass-volume ratio of 1:1-1:3 to dissolve, and obtain a calcium salt solution; add an organic solvent dropwise to the calcium salt solution and mix; Step two: Take PVDF and add it to the solution obtained in step one, and magnetically stir at a stirring speed of 100-400 rpm for 1-2 h to completely dissolve the binder in the organic solvent, thereby obtaining a viscous liquid; Step three: Take the conductive agent and add it to the viscous liquid obtained in step two, and magnetically stir at a stirring speed of 100-400 rpm for 1-2 h to fully mix the conductive agent and the binder, thereby obtaining a dispersion system; Step four: Take the active material and add it to the dispersion system obtained in step three, and magnetically stir at a stirring speed of 100-400 rpm for 8-10 h to fully mix the active material, the conductive agent, and the binder, thereby obtaining a battery slurry; Step five: Coat the battery slurry obtained in step four on the current collector at a thickness of 100-300 microns, and bake the coated electrode sheet in a blast drying oven at 80-110℃ for 1-4 h, and then bake it in a vacuum drying oven at 90-120℃ for 6-9 h; Step six: Cut the electrode sheet obtained in step five to obtain the electrode sheet of the secondary battery.

2. The method of improving the physical properties of PVDF based secondary battery slurry by adding calcium salt according to claim 1, characterized in that, The calcium salt is at least one of calcium nitrite, calcium chloride, calcium nitrate, calcium carbonate, calcium bicarbonate, calcium bromide, and calcium iodide, and the calcium content of the seven calcium salt materials is not less than 0.1%; The melting point of calcium nitrite is 390℃, the flash point is 110℃, and the density is 2.23; the melting point of calcium chloride is 772℃, the flash point is 1650℃, and the density is 1.09; the melting point of calcium nitrate is 591℃, the boiling point is 130-140℃, and the density is 2.36; the melting point of calcium carbonate is 825℃, the boiling point is 800℃, and the density is 2.93; the melting point of calcium bromide is 730℃, the boiling point is 806-812℃, and the density is 3.35; the melting point of calcium iodide is 779℃, the boiling point is 1100℃, and the density is 3.

96.

3. The method of improving the physical properties of PVDF based secondary battery slurry by adding calcium salt as claimed in claim 1, wherein, The organic solvent in step two is at least one of N-methyl pyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide.

4. The method of improving the physical properties of PVDF based secondary battery slurry by adding calcium salt as claimed in claim 1, wherein, The conductive agent is at least one of conductive carbon black, carbon nanotubes, graphene, and conductive graphite, and the conductive carbon black has a small particle size, a particularly large specific surface area, and good conductivity, and can absorb and preserve liquid in the battery.

5. The method of improving the physical properties of PVDF based secondary battery slurry by adding calcium salt as claimed in claim 1, wherein, The active material includes all organic electrode materials and inorganic electrode materials, wherein the organic electrode material includes P-type organic battery material such as carbonyl-based organic battery material, and the inorganic electrode material includes lithium titanate and carbon-based negative electrode material.

6. The method of improving the physical properties of PVDF based secondary battery slurry by adding calcium salt as claimed in claim 1, wherein, The current collector includes at least one of copper foil current collector and aluminum foil current collector.

7. The method of improving the physical properties of PVDF based secondary battery slurry by adding calcium salt as claimed in claim 1, wherein, When the blast drying oven and the vacuum drying oven are used, they need to be isolated from the plasma to prevent excessive impurities from appearing when the plasma is dried.

8. The method of improving the physical properties of PVDF based secondary battery slurry by adding calcium salt as claimed in claim 1, wherein, Adding a small amount of inorganic calcium salt during the electrode material homogenization process can improve the wetting performance of the active material and improve the dispersibility of the binder PVDF and the active material.

9. The method of improving the physical properties of PVDF based secondary battery slurry by adding calcium salt as claimed in claim 1, wherein, The prepared lithium iron phosphate pole piece electrode material and P-type organic electrode material can be well attached to the aluminum foil, and the obtained battery has better cycle performance compared with the battery constructed by the electrode piece prepared by directly homogenizing without adding calcium salt.

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