Patent Application
20130196212
1. Technical Field
The invention generally relates to batteries, particularly to a kind of battery with voltage of 1.5V and being exchangeable with traditional carbon-zinc battery, alkaline battery, Ni—MH battery, Ni—Cd battery, Ni—Zn battery and Zn-air battery.
2. Related Art
The reason why Zn—Mn batteries have always occupied a certain market share for over 100 years is their cheap and abundant production materials. Performance of Zn—Mn batteries, however, is difficult to be improved. Also, there is no room for cost down. And because of razor-thin profits, weaker and weaker the market competitiveness of Zn—Mn batteries is. Contrarily, alkaline batteries have been developing in aspects of performance and cost reduction since they appeared in the market. Thus the future of alkaline batteries is still worthy of being expected. But price competition of alkaline batteries will be fierce because the current technology of alkaline batteries tends to be mature. On the other hand, lithium primary batteries will expand their applications in the field of heavy load.
Batteries must constantly improve to have higher capacity, higher energy density, longer durability, longer shelf-life and cheaper price to satisfy the requirements of modern electronic apparatuses. Currently, the primary market share is occupied by low-end batteries which can not satisfy the requirement of heavy load. Although alkaline Zn—Mn batteries have been increased their ability of heavy load, they still can not satisfy market requirements. For example, a typical digital camera using an alkaline Zn—Mn battery can continuously take only about 70 shots, but it can continuously take 788 shots when using a lithium battery. Lithium battery is 11 times over alkaline Zn—Mn battery in durability, and the number of times will be much more if discontinuously taking shots. Further, a lithium battery is a half of an alkaline Zn—Mn battery in weight. A Zn−Ni may support about 500 shots, but its shelf-life is too short and it's too heavy in weight. Lithium batteries have the best performance in all aspects.
Secondary batteries have become popular due to recyclability, but they still can not replace primary batteries because of long charging time, short shelf-life, low capacity and insufficient safety. Therefore, primary batteries still occupy an important market share, especially the 1.5 volt batteries.
An object of the invention is to provide a high energy battery and the manufacture thereof which can improve large current discharge ability, environment friendliness and safety. By the improvement of battery composition and manufacturing method, the energy density of battery of the invention is at least two times over ordinary alkaline battery under a certain condition of discharge.
To accomplish the above object, the battery of the invention includes:
a positive electrode comprising 80%-90% of pyrite, up to 3.5% of conductive carbon black, 3%-5% of graphite, 2%-4% of oxide or lithium oxide and 1%-4% of water-soluble adhesive, wherein the percentage is by weight, purity and a particle size of the pyrite are above 90% and smaller than 44 μm, respectively; an average particle size, a BET specific surface area and an ash content of the graphite are 5-18 μm, 11-14 m2/g and lower than 0.1%, respectively; the oxide is selected from MnO2, TiO2, LiCoO2′, LiMnO2′, LiNiO2′, Li2TiO3′, and Li4Ti5O12,
a negative electrode comprising lithium metal or a lithium-aluminum alloy, wherein an aluminum content of the lithium-aluminum alloy are 0.05%-0.1%, and a thickness is 0.1-0.2 mm;
an electrolyte comprising:
a separator made of polyethylene resins.
In the battery of the invention, the adhesive is selected one or two of polyvinyl alcohol (PVA), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), carboxymethylcellulose (CMC) and Styrene-Butadiene-Rubber (SBR), the CMC and the SBR or the PVDF and NMP is 1%-4% of the pyrite in weight.
In the battery of the invention, a proportion of contents of the organic solvent is 0-10% of the PC, 15%-30% of the DME, 15%-80% of the DOL, 0-30% of the NMP or the SFL and 0-5% of the DMI.
In the battery of the invention, the inorganic salt solute is selected from LiClO4 and LiI, whose molar concentration is 0.8-1.2 mol/L.
In the battery of the invention, a maximum effective aperture of the separator is 0.08-0.12 μm, porosity is 40%-50% and impedance is 30-50 m 0/mm2.
The battery of the invention further comprises a current collector made of aluminum foil whose thickness is 16-25 μm and tabs made of stainless steel belt, nickel plated steel belt or nickel belt, whose thickness is 0.05-0.1 mm.
The battery of the invention further comprises an endcap with explosion-proof and overcurrent-proof function, wherein the endcap comprises a 4-layered composite membrane composed of polyethylene (PE), aluminum, polyethylene (PE) and silicone and a 3-layered thermistor composed of copper foil, conductive carbon black and copper foil; a total thickness of the composite membrane is 0.14-0.22 mm; respective thickness of the 4 layers is 0.03-0.05 mm, 0.03-0.05 mm, 0.03-0.05 mm and 0.05-0.07 mm; an impedance of each layer of the thermistor is lower than 32 mO.
The method for manufacturing the above battery includes the steps of:
a) mixing pyrite, graphite, acetylene black, and lithium oxide into a mixture;
b) mixing the mixture with water and adhesive into a pulp;
c) coating the pulp on a positive current collector; and
d) heating, rolling, slitting and shaping the positive current collector with the pulp;
wherein the water is 50%-150% of the pyrite in weight.
In the battery of the invention, a heating temperature in step d) is 50-130° C., a thickness is 0.10-0.25 mm and a porosity is 30-45%.
In the battery of the invention, the pyrite is processed by:
a) spreading the pyrite on a stainless steel tray;
b) putting the pyrite on the tray in an oven to be heated in a temperature range of 100-700° C. and within a period of 1-24 hours; and
c) sealing up the heated pyrite with a bag and storing up in a shady and arid place.
In the battery of the invention, the pyrite is processed with acid, alkali and deionized water, wherein the acid is selected from sulfuric acid, hydrochloric acid, phosphoric acid and acetic acid, and the alkali is selected from sodium hydroxide, potassium hydroxide and ammonia water.
The method of the invention further comprises the steps of:
e) drying the positive electrode plate;
f) winding the negative electrode and separator under a relative humidity lower than 1%; and
g) loading materials into a casing and sealing up the casing.
in which, reference number 1 is a pulp, 2 is aluminum foil, 3 is a scraper, 4 is a roller, 5 is a thermistor, 6 is a stainless steel sheet, 7 is an explosion-proof membrane, 8 is an upper pad, 9 is lower cover, 10 is a sealing ring, 11 is a steel casing, 12 is a upper cover, 13 is a positive tab, 14 is a positive electrode, 15 is a separator, 16 is a negative electrode, 17 is a negative tab, “a” is an alkaline battery, “b” is a Zn—Ni battery, “c” is a Ni—MH battery and “d” is the high energy battery of the invention.
The battery of the invention is composed of a positive electrode, a negative electrode and electrolyte, wherein a pyrite serves as the positive active material, a lithium-aluminum alloy serves as the negative material and a mixture of an organic solvent and an inorganic salt solute serves as the electrolyte.
As abovementioned, the positive active material of the invention is a pyrite (formula: FeS2). The pyrite must be processed in advance. The process of pyrite is shattering and screening with particle size not larger than 0.044 mm. Further, the pyrite must be processed by at least one of the following two methods. The one is heat treatment: a) spreading the pyrite on a stainless steel tray; b) putting the pyrite on the tray in an oven to be heated in a temperature range of 100-700□ and within a period of 1-24 hours; and c) sealing up the heated pyrite with a bag and storing up in a shady and arid place. The other one is chemical treatment, which is processing the pyrite with acid, alkali and deionized water, wherein the acid may be sulfuric acid, hydrochloric acid, phosphoric acid or acetic acid, and the alkali may be sodium hydroxide, potassium hydroxide or ammonia water.
The positive conducting additives of the battery may be two or more of graphite, acetylene black, metallic powder, oxide and lithium oxide.
The positive adhesive of the battery may be one or two of polyvinyl alcohol (PVA), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), carboxymethylcellulose (CMC) and Styrene-Butadiene-Rubber (SBR).
The positive current collector of the battery is aluminum foil whose thickness is 16-25 μm. The tabs are made of stainless steel belt, nickel plated steel belt or nickel belt, whose thickness is 0.05-0.1 mm.
The positive electrode of the battery is made by: a) mixing the positive active material and the positive conducting additives into a pulp; b) coating the pulp on the positive current collector; and c) rolling, slitting and shaping the positive current collector with the pulp, as shown in
The negative active material of the battery is foil of lithium-aluminum alloy, wherein the aluminum content is 0.05%-0.1%.
The battery of the invention uses a mixture of an organic solvent and an inorganic salt solute to serve as the electrolyte. The inorganic salt may be one or more of lithium perchlorate (LiClO4), lithium trifluoromethanesulphonate (LiCF3SO3), lithium iodide (LiI), lithium hexafluoroarsenate (LiAsF6) and lithium tetrafluoroborate (LiBF4). The organic solvent may be a mixture of three or more of n-methyl pyrrolidone (NMP), 1,2-propylene carbonate (PC), ethylene glycol dimethyl ether (DME), 1,3-dioxolane (DOL), isoxazoles, tetrahydrofuran (THF) and dimethyl sulfoxide (DMSO).
The endcap of the battery is provided with an explosion-proof and overcurrent-proof device as shown in
The assembling process of the battery is: a) drying the positive electrode plate; b) winding the negative electrode and separator under a relative humidity lower than 1%; and c) loading the abovementioned materials into a casing and sealing up the casing.
The chemical equation of discharge reaction of the battery is:
FeS2+4Li→Fe+2Li2S
And the chemical mechanism of discharge reaction of the battery is:
FeS2+4Li→2Li+Li2FeS2→Fe+2Li2S
The structure of the battery is shown in
The open-circuit voltage will be higher than 2V if iron disulfide material contains impurities. But purifying iron disulfide material will cost a lot. The method of the invention adopts a unique technique to overcome the problem of overhigh open-circuit voltage. And the performance of discharge is improved, especially in high drain uses. Detailed comparative data is shown in Table 1.
2. Unique electrolyte:
LiClO4 is a common electrolyte in lithium primary batteries, but iron disulfide may be oxidized by it to generate harmful gas in batteries. This will raise a problem of gas distension. The improved electrolyte and additives overcome this problem.
3. Great safety:
Safety is an important issue of lithium batteries, especially for cylindrical Li—FeS2 batteries. An explosion-proof membrane and the PTC are employed to guarantee safety of batteries. A detailed test data is shown in Table 2.
The pyrite must be shattered and screened with 75% passing through sieve with 200 meshes (particle size not larger than 0.076 mm) and 25% passing through sieve with 325 meshes (particle size not larger than 0.044 mm). Purity is 99.44%. The sulphur content and iron content are 53.15% and 46.5%, respectively. The impurities are SiO2 with content less than 0.1%, MgO with content not larger than 0.1%, Al2O3 with content less than 0.15%, CaO with content not larger than 0.1% and acid-soluble iron with content less than 0.38%.
The processing method is described as the following:
1) Pyrite is loaded in a plastic pail and is mixed with diluted hydrochloric acid at 1%-2% HCl. Then the pyrite is stirred for 30 minutes.
2) Wait for precipitation. Then add water to stir and filter repeatedly until the filtered water is about pH7.
3) Drench the pyrite with NaOH solution at 10% for 12-15 hours.
4) Load the pyrite with NaOH solution in an iron pail and heat up the iron pail with stirring for 1 hour.
5) Wait for precipitation. Then add water to stir and filter repeatedly until the filtered water is about pH7. Wash the pyrite with deionized water twice.
The method for manufacturing positive electrode includes the steps of:
a) Mixing the pyrite from the abovementioned method, graphite, acetylene black and zinc powder in a proportion of 90%, 4%, 4% and 2% into a mixture;
b) Grinding the mixture for 2 hours;
c) Mashing the mixture with polyvinylidene fluoride (PVDF) as adhesive and n-methyl pyrrolidone (NMP) as solvent into a jelly;
d) Coating the jelly on an aluminum foil;
e) Heating the aluminum foil with the jelly at 100□; and
f) Rolling the heated aluminum foil with the jelly to a thickness of 0.18 mm.
The negative active material of the battery is a sheet of lithium-aluminum alloy whose aluminum content is 0.3%.
The electrolyte of the battery is lithium iodide whose molar concentration is 1.0 mol/L
The organic solvent is propylene carbonate (PC), ethylene glycol dimethyl ether (DME), 1,3-dioxolane (DOL), n-methyl pyrrolidone (NMP) and isoxazole (DMI), whose proportion is 5:20:70:3:2.
Experimentally, the battery of the invention with AA size may have a capacity of 2900 mAh or above. (discharge manner: 1000 mA constant current discharge, cut-off voltage: 0.8V)
A comparison between the battery and other 1.5V batteries is shown in
It will be appreciated by persons skilled in the art that the above embodiment has been described by way of example only and not in any limitative sense, and that various alterations and modifications are possible without departure from the scope of the invention as defined by the appended claims.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/CN08/00030 | 1/3/2008 | WO | 00 | 11/21/2011 |
