POSITIVE PARTICLE ELECTRODE FOR A SECONDARY BATTERY AND METHOD FOR PRODUCING SAME FROM A NANOFIBRE MEMBRANE STRUCTURE

Abstract

A positive electrode of an active material of interconnected polycrystalline and porous particles for secondary battery has been developed to achieve greater diffusion, excellent specific capacity and life cycle. The active material of the positive electrode for secondary battery is obtained from a hot-pressing process to which the composite fiber membrane is subjected with the precursors of the active metals and the polymer, obtaining morphologies such as monocrystalline particles, two-dimensional plates, and bars.

Claims

1. A method for manufacturing an active material as a positive electrode for a secondary lithium-ion, sodium ion, or magnesium ion batteries, the method comprising the step of thermally and pressure-treating membrane of fibers initially composed of a mixture of precursor metals and polymers.

2. The method of claim 1, the metal precursor includes at least two metals are selected from the group consisting of alkaline such as lithium, sodium, potassium or rubidium; alkaline earth such as beryllium, magnesium, calcium or strontium; transition metals such as titanium, vanadium, chromium, manganese, iron, chromium, nickel, copper, zinc, palladium molybdenum and silver, and metals from group 13 and 14 such as aluminum, indium, titanium, tin, and germanium.

3. The method of claim 1, further including at least one non-metal elements such as phosphorus, carbon, fluoride, or sulfur.

4. The method of claim 1, the polymers is selected from the group consisting of: polyvinyl alcohol (PVA), polyvinyl acetate (PVAc), polyethylene oxide (PEO), polyurethane, urethane polyether, polyurethane copolymer, cellulose acetate, cellulose butyrate acetate, cellulose acetate propionate, bromomethacrylate acrylate (PMMA), polymethyl acrylate (PMA), polyacrylic copolymer, polyvinyl acetate bit copolymer, alcohol furil poly-flops (PPFA), polystyrene, polystyrenecopolymer, poly(polypropylene oxide) (PPO), polyethylene oxide copolymer, copolymer polylypropylene oxide, polycarbonate (PC), polyvinyl chloride (PVC), polycaprolactone, polyvinylpyrrolidone (PVP), pool polyvinyl fluoride, polydenpul fluoride copolymer vinlidene, polyamide, polyacrylonitrile (PAN), tar, an mixture thereof.

5. The method of claim 1, wherein the membranes of the fibers are produced from a method of fiber production such as electrospinning, forcespinning, forcelectrospinning, melt-blown, flash spinning, or electrostatic melt-blown.

6. The method of claim 1, in which the hot press process to obtain the individual or combined morphology of: crystals, poser fibers, channels, nano and micro plates, as well as porous 2D morphologies of a positive active material for rechargeable lithium battery, to which in the process of its manufacture is applied a continuous pressure between 1 to 10 bar and the temperature in the range 250 to 1000° C. to the fiber membrane of the precursor metals and the polymer in an air or oxidizing or inert atmosphere or combination.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIGS. 1a-1d show images of the electronic scanning microscope showing 3-D monocrystalline particles from different morphologies of LiMn.sub.2O.sub.4 obtained from fiber membranes with metals precursors (Li and Mn), and polymers (PEO, PVAc, PVA, PAN), and hot pressing at 700° C.;

[0024] FIGS. 1e-1f show images of the electronic scanning microscope showing 3-D blocks

[0025] FIGS. 1g-1w show images of the electronic scanning microscope showing a 2-D porous plates;

[0026] FIGS. 1x-1y show images of the electronic scanning microscope showing a 1-D bars

[0027] FIG. 2—Specific discharge capacity performed at room temperature of the compound LiMn.sub.2O.sub.4 obtained from hot pressing at 700° C. of the fiber membrane with lithium, manganese and PVA polymer precursor metals;

[0028] FIG. 3a shows the x-ray diffraction that shows that the material obtained is LiMn.sub.2O.sub.4 with the 227 spatial group corresponding to the spinel; and

[0029] FIG. 3b shows the x-ray diffraction showing that the material obtained is LiMn.sub.2OR.sub.4 and also co-exists Mn.sub.2Or.sub.3.

DETAILED DESCRIPTION OF THE INVENTION

[0030] The present invention aims to offer more effective solution alternatives proposing new morphologies in 1-D, 2-D and 3-D of active material for positive electrode of battery ensuring better electrochemical properties such as those materialized according to life cycle, ion diffusion and energy, compared to proposals solution for the same purpose of manufacturing positive electrode for rechargeable battery of: lithium, sodium or magnesium that do not yet fully meet the requirements of current demand of the market for these types of rechargeable batteries. Most of the above technical solutions are based on a method for the manufacture of polycrystallines, porous two-dimensional plates, open fiber channels and morphology type “brain surface” of active material to be used as a positive electrode in rechargeable lithium-ion, sodium ion or magnesium ion battery; obtained from using fiber membrane with precursor metals and polymers, which were then subjected to a hot-pressing process.

[0031] For the synthesis of the fibers that we propose in this invention can use the electrospinning method and its derivatives or any equivalent process that allow general a mat or membranes of fibers, in which the average diameter of the fibers can be 10 to 2000 nm, preferably with diameter from 50 to 1000 nm. Fibers can include two or more metals and one or more non-precursor metals:

[0032] 1. Alkaline metals (preferably, but not limited to: Li, Na, K, Rb)

[0033] 2. Alkaline earth metals (preferably, but not limited to: Be, Mg, Ca, Sr),

[0034] 3. Transition metals (preferably, but not limited to: Ti, V, Cr, Mn, Fe Co, Ni, Cu, Zn, Mo, Pd, Ag, Au)

[0035] 4. Block metals p (preferably, but not limited to: Al, In, TI, Sn, Ge).

[0036] 5. Non-metals (preferably, but not limited to: P, C, O, S)

[0037] In the process of the synthesis of these fibers, the precursor compounds without limitation, can be: acetates, carbonates, nitrates, metal oxides, hydroxides and liquid solutions; preferably proposed can be acetates, carbonates and nitrates. As for the polymer can be selected from a wide group of variants, such as polyvinyl alcohol (PVA), polyvinyl acetate (PVAc), Polyethylene oxide (PEO), polyurethane, urethane polyether, polyurethane copolymer, cellulose acetate, cellulose butyrate acetate, cellulose acetate propionate, bromomethacrylate acrylate (PMMA), acrylate polymethyl (PMA), polyacrylic copolymer, copolymerorpolyvinyl acetate bit, fury poly-flops alcohol (PPFA), polystyrene, polystyrenecopolymer, poly (polypropylene oxide) (PPO), polyethylene oxide copolymer, polypropylene oxide copolymer, polycarbonate (PC), polyvinyl chloride (PVC), polycaprolactone, polyvinylpyrrolidone (PVP), polyvinyl fluoride poly vinylidene fluoride copolymer, polyamide, polyacrylonitrile (PAN), tar, among other polymers. Preferably to use: PVA, PEO, PVAc, PMA and PAN. Water, dimethylformamide, acetone, methanol, ether or toluene can be used as a solvent.

[0038] The method to produce fibers and environmental conditions can vary from an electric field, centrifugal force, melting or blowing. To produce polycrystals, in the form of porous two-dimensional plates and other 2D and 3D morphologies, the fiber membrane is used, composed of the precursors of the activated material or for positive electrode of rechargeable bating and polymer or polymers, which undergoes a hot pressing process, where temperature conditions can go preferably between 250 and 1000° C., and at a pressure preferably between 1 and 10 bar, in an oxidizing or inert atmosphere or combination between them and in a time range of 0.5 to 75 h.

Example 1

[0039] The metal precursors used are lithium dihydrate acetate, manganese acetate (II) tetrahydrate, which were used to obtain LiMn.sub.2O.sub.4.

[0040] A solution was prepared by mixing in the range of 2 to 20% (% by weight) of PVA, 72 to 90% (% by weight) of distilled water, and 8% (% by weight) of the precursors Li, Mn in stochiometric proportion of Li:Mn of 1:2. The reagents were mixed from 3 to 4 hours at 80° C. until completely dissolved. The solution obtained was used to produce fibers by centrifuge extraction using electric field. The fibers obtained were calcined for 24 hours at a temperature between 450° C. and 800° C., in air, pressed between two plates of 4-inch diameter non-porous alumina and 250 g mass.

[0041] Electrochemical tests were performed in CR2032 coin-type battery, manufactured in a glove box in argon atmosphere. The cathode was formed from a mixture by weight of 80% LiMn.sub.2O.sub.4 material, 10% Super P carbon and 10% polyvinyl fluoride on a 16 mm diameter disc of aluminum foil. Celgard 2400 was used as separator, as electrolyte 1M LiPF.sub.6 in ethylene carbonate and ethyl methyl carbonate (50:50 vol %) and metallic lithium as a counting electrode.

[0042] FIGS. 1i, 1k, 1l, 1u, 1v, 1x, 1y show images taken with the electronic scanning microscope (SEM), it can be seen porous plaque morphology made up of 200 nm bonded grains. In FIG. 2 you can see the specific discharge capacity for the manufactured battery, it shows a high capacity of 130 mAh/g and a capacity retention of 96% after 150 cycles. FIG. 3(a) shows the x-ray diffraction that shows that the material obtained is LiMn.sub.2O.sub.4 with the 227 spatial group corresponding to the spinel.

Example 2

[0043] A solution similar to Example 1 is prepared, and fibers are produced in a similar way. The obtained fibers were subjected to calcination for 24 hours pressed between two porous alumina plates of 2 inches in diameter and mass 250 g, with pores of 4 m to 6 m.

[0044] Electrochemical tests were performed with the same procedure as in example 1.

[0045] FIGS. 1q, 1r, show photographs taken with the SEM, where it can be seen porous plate-type morphology formed by 1 μm grains attached.

Example 3

[0046] A solution similar to Example 1 is prepared. The fibers obtained were calcinated for 24 hours pressed between two porous alumina plates 2 inches in diameter and mass 250 g, with pores of 1 m to 3 m at atmospheric pressure in air.

[0047] Electrochemical tests are performed with the same procedure as in example 1.

[0048] FIGS. 1a, 1f, 1e, 1n, 1w show images taken with the SEM where both porous plate structures and 500 nm particles are verified.

Example 4

[0049] The metal precursors used are lithium dihydrate acetate, manganese acetate (II) tetrahydrate, which were used to obtain LiMn.sub.2O.sub.4.

[0050] A solution was prepared by mixing in the range of 2 to 20% (% by weight) of PEO, 72 to 90% (% by weight) of distilled water, and 8% (% by weight) of the precursors Li, Mn in stochiometric proportion of Li:Mn of 1:2. The reagents were mixed from 3 to 4 hours at 80° C. until completely dissolved. The solution obtained was used to produce fibers by centrifuge extraction using electric field. The fibers obtained were calcined for 24 hours at a temperature between 450° C. and 800° C., in pressed air between two plates of 4-inch diameter non-porous alumina and 250 g mass.

[0051] Electrochemical tests are performed with the same procedure as in example 1.

[0052] FIGS. 1b, 1g, 1h, 1j, 1o, 1s,1t show images taken with the SEM showing porousplate-type morphology as well as particles. FIG. 3(b) shows the x-ray diffraction showing that the material obtained is LiMn.sub.2OR.sub.4 and also co-exists Mn.sub.2Or.sub.3.

Example 5

[0053] The metal precursors are sodium acetate trihydrate, manganese acetate tetrahydrate to obtain NaMn.sub.2or.sub.4.

[0054] It is prepared a solution by mixing in the range of 2 to 20% (% by weight) of PVA, 72 to 90% (% by weight) of distilled water, and 8% (% by weight) of the precursors Na, Mn in stochiometric proportion of Na:Mn 1:2. The reagents were mixed from 3 to 4 hours at 80° C. until completely dissolved. The obtained solution is used to produce fibers by centrifuge extraction applying electric field. The fibers obtained are calcined for 24 hours pressed between two porous alumina plates 2 inches in diameter and mass 250 g, with pores from 1 mm to 3 m, at a temperature understood between 450° C. and 800° C., with pores from 1 mm to 3 m at atmospheric pressure in air.

[0055] Electrochemical tests are performed on CR2032 coin-type battery, manufactured in a glove box in argon atmosphere. The cathode is formed from a mixture by weight of 80% NaMn.sub.2Or.sub.4 material, 10% Super P carbon and 10% polyvinyl fluoride on a 16 mm diameter disc of paper Aluminum. Celgard 2400 is used as a separator, as electrolyte 1M NaPF.sub.6 in ethylene carbonate and ethyl methyl carbonate (50:50 vol %) and metallic sodium as a counting electrode.

Example 6

[0056] The metal precursors are magnesium acetate tetrahydrate, manganese acetate tetrahydrate to obtain MgMn.sub.2O.sub.4.

[0057] It is prepared a solution by mixing in the range of 2 to 20% (% by weight) of PVA, 72 to 90% (% by weight) of distilled water, and 8% (% by weight) of the precursors Na, Mn in stochiometric proportion of Mg:Mn 1:2. The reagents were mixed from 3 to 4 hours at 80° C. until completely dissolved. The obtained solution is used to produce fibers by centrifuge extraction applying electric field. The fibers obtained are calcined for 24 hours pressed between two porous alumina plates of 2 inches in diameter and mass 250 g, with pores of 1 m to 3 m, at a temperature between 450° C. and 800° C., with pores from 1 mm to 3 m at atmospheric pressure in the air.

[0058] Electrochemical tests are performed on CR2032 coin-type battery, manufactured in a glove box in argon atmosphere. The cathode is formed from a mixture by weight of 80% MgMn.sub.2Or.sub.4 material, 10% Super P carbon and 10% polyvinyl fluoride on a 16 mm diameter disc of paper Aluminum. Celgard 2400 is used as a separator, sand used propylene carbonate containing 0.2M magnesium acetate and 0.1M aluminum chloride as electrolyte, magnesium metal as a counting electrode.