WO2018139979A1 - Performance enhancement material for accumulators - Google Patents

Performance enhancement material for accumulators Download PDF

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Publication number
WO2018139979A1
WO2018139979A1 PCT/TR2017/050044 TR2017050044W WO2018139979A1 WO 2018139979 A1 WO2018139979 A1 WO 2018139979A1 TR 2017050044 W TR2017050044 W TR 2017050044W WO 2018139979 A1 WO2018139979 A1 WO 2018139979A1
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Prior art keywords
lead
mixture
graphene
concentration
formulation
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PCT/TR2017/050044
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French (fr)
Inventor
Murat ÖZBEK
Original Assignee
Oezbek Murat
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Priority to PCT/TR2017/050044 priority Critical patent/WO2018139979A1/en
Publication of WO2018139979A1 publication Critical patent/WO2018139979A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/14—Electrodes for lead-acid accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/14—Electrodes for lead-acid accumulators
    • H01M4/16—Processes of manufacture
    • H01M4/20—Processes of manufacture of pasted electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/56—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of lead
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/14—Electrodes for lead-acid accumulators
    • H01M4/16—Processes of manufacture
    • H01M4/20—Processes of manufacture of pasted electrodes
    • H01M4/21—Drying of pasted electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present invention relates to a performance enhancement material for accumulators. More particularly, the present invention relates to a paste for performance enhancement in lead-acid type rechargeable batteries.
  • Lead-acid type rechargeable batteries generally have multiple plates comprising lead, positioned distant from each other such that neighboring plates do not contact each other. For prefention of direct contact, neighboring plates are further separated from each other using membranes. Remaining volumes between neighbouring plates are at least partly filled with an aqueous acidic solution generally comprising sulfuric acid with a specific gravity of 1.20 to 1.25.
  • Such batteries generally comprise lead oxide and red lead mixed with an aqueous solution of sulfuric acid. Lead oxide reacts with the sulfuric acid and thus gets reversibly converted to lead sulfate at charging of the battery. At discharge, the lead sulfate is converted back to lead oxide.
  • the present lead-acid type rechargeable batteries have an energy capacity generally lower than various other battery systems.
  • Anode plates of the present lead-acid type rechargeable batteries are generally prone to get damaged/disintegrated as a result of corrosion, and fragments or particles detached from those plates cause short circuits in the batteries.
  • Primary object of the present invention is to eliminate the above-mentioned shortcomings in the prior art.
  • Another object of the present invention is to provide a low-cost mixture for use as performance enhancing coating material on composite anode plates.
  • a further object of the present invention is to provide a low-cost performance enhancing composite anode plate to be used in rechargeable accumulators for enhancing their capacity, stability and economic life.
  • the present invention proposes a mixture for coating onto lead-based plates of lead- acid type rechargeable batteries, wherein the mixture comprises graphene obtained from dry ice.
  • the concentration of graphene can be within the range between 0.05 wt. % to 1 wt.% with respect to the total weight of the mixture.
  • the mixture can also comprise inorganic fibres, lead monoxide and red lead along with the graphene.
  • the mixture can have the below formulation where the concentration values are given in weight percentages with respect to the total weight of the formulation:
  • inorganic fibres 0.04 wt. % to 0.07 wt. %
  • the sulfuric acid concentration can be within the range between 3.85 wt. % and 5.55 wt. % with respect to the total weight of the formulation.
  • the graphene concentration can be within the range between 0.1 wt. % and 0.3 wt. % with respect to the total weight of the formulation.
  • the present invention further proposes a lead-based plate for being used as battery plate in lead-acid type rechargeable batteries, at least partly coated with a coating layer comprising graphene obtained from dry ice.
  • the coating layer can further comprise one or more lead oxide, one or more lead sulfate and inorganic fibres.
  • the graphene concentration here can be within the range between 0.06 wt.% and 1.22 wt.% with respect to the total weight of the layer, which can be considered as corresponding to removal of water content in a mixture used as starting material in obtention of the layer.
  • the range can more preferably be between 0.12 wt.% and 0.33 wt.%.
  • the concentration of inorganic fibres can be within the range between 0.045 wt.% and 0.1 wt.% with respect to the total weight of the layer.
  • the present invention further proposes a lead-acid type rechargeable battery comprising one or more of such plate(s).
  • the present invention further proposes respective methods.
  • One of the methods is related to preparation of a mixture for coating onto lead- based plates of lead-acid type rechargeable batteries, comprising the steps of:
  • the addition of graphene can be performed later than the addition of sulfuric acid onto the paste.
  • the mixture used in said method can have the below final formulation:
  • inorganic fibres 0.04 wt. % to 0.07 wt. %
  • the present invention also relates to a method for obtaining a lead-based plate for being used as battery plate in lead-acid type rechargeable batteries, comprising the steps of: a. at least partly coating of a lead-based subject with an aqueous mixture comprising graphene obtained from dry ice; thus obtaining a composite intermediate product with a wet coating layer,
  • the mixture can further comprise inorganic fibres, lead monoxide and red lead.
  • Said method can further comprise pressing of the wet coating layer so as to remove any entrapped air therein, between the steps (a) and (b).
  • the lead-based subject can be in form of a grid and the mixture can have the below formulation where the concentration values are given in weight percentages with respect to the total weight of the formulation:
  • inorganic fibres 0.04 wt. % to 0.07 wt. %
  • Graphene recently finds a wide use in various fields of technology. It has a large specific surface area (1500 m 2 /g), high mechanical stability (160 GPa), high thermal conductivity (5000 W/mK), and a high electrical conductivity (2000 S/cm). There are various graphene production methods and each method results in product properties/structures different than those available with the other methods.
  • Graphene obtained from dry ice can be described as having mainly a cubic morphology comprising superimposed layers (generally 2 to 10 layers) having a length or width (e.g. diagonal or side-length) within a range between 50 nm and 200 nm.
  • an aspect of the present invention relates to a mixture for use in accumulators or lead-acid type rechargeable batteries.
  • the mixture comprises graphene obtained from dry ice.
  • the concentration of graphene can be within the range between 0.05 wt. % to 1 wt.% with respect to the total weight of the mixture.
  • the mixture can further comprise inorganic fibres, lead monoxide, red lead (i.e. Lead (II, IV) oxide), sulfuric acid and water.
  • the inorganic fibres can be glass fibres as being inert against acidic character of the mixture.
  • a preferred formulation for the mixture can be given as follows, where the concentration values are given in weight percentages with respect to the total weight of the formulation:
  • the present invention proposes a method for preparing the mixture.
  • the mixture can be availed by performing at lea: ;t the following sequential method steps: i. obtention of a blend comprising lead monoxide, red lead and inorganic fibres, ii. obtention of a paste by mixing the blend with water,
  • the addition of graphene is performed later than the addition of sulfuric acid onto the paste.
  • the sulfuric acid added onto the paste is preferably in form of an aqueous solution thereof.
  • a final sulfuric acid concentration of 10 wt. % in 100 grams of the final mixture can be achieved by introduction of 10 grams of 40 B° aqueous H 2 S0 4 solution (40 degrees Baume corresponding to an H 2 S0 4 concentration 48.10%(w/w), and specific gravity of 1.3810), with the rest of the ingredients in their respective and complementary amounts.
  • the calculation can be easily adapted for various initial and final concentrations of sulfuric acid. Presence of sulfuric acid enables partly conversion of lead monoxide to lead sulfate, and thus provides an electrochemical charge to the mixture to some extent, beforehand any use of the mixture.
  • the mixture can be applied onto surfaces of plates in preparation of accumulators, particularly on lead-based plates of lead-acid type rechargeable batteries.
  • the present invention further proposes a plate for lead-acid type rechargeable batteries, the plate being at least partly coated with a layer of coating comprising graphene.
  • the concentration of graphene can be within the range between 0.05 wt. % to 1 wt.% with respect to the total weight of the mixture before applying onto the plate as layer material.
  • the coating corresponds to an at least partly dried form of any of the mixture formulations as described above.
  • any remaining amounts of water and sulfuric acid can be omitted in the formulation of the layer, which corresponds to the dried form of the mixture.
  • any non-evaporated sulfuric acid can be considered to have reacted with several lead oxides in the mixture to end up as lead sulfates.
  • the graphene concentration in the layer is preferably arranged such that it remains within the range between 0.06 wt.% and 1.22 wt.%, more preferably within the range between 0.12 wt.% and 0.33 wt.% wherein the concentration is given in weight percentage with respect to the total weight of the mixture prior to being applied onto the plate, or before curing.
  • Highly positive effects of graphene is available even with such low concentrations of graphene (e.g. up to 0.33 wt.%) thanks to being obtained according to 'dry ice' method (i.e. obtained from dry ice); and this corresponds to a further improvement in terms of costs.
  • the layer can thus comprise a mixture of lead oxide(s), lead sulfate(s), inorganic fibre(s) and graphene.
  • the concentration of inorganic fibres is within the range between 0.045 wt.% and 0.1 wt.%; wherein the concentrations are given in weight percentages with respect to the total weight of the layer.
  • the plate according to the present invention can be prepared by performing a method comprising the following steps: a. at least partly coating of a lead-based subject with an aqueous mixture comprising graphene obtained from dry ice, thus obtaining a composite intermediate product with a wet coating layer,
  • drying of the wet coating layer on the composite intermediate product provided that the temperature at the coating layer is maintained at or below 60°C throughout the drying step. Preventing the coating layer temperature from exceeding 60°C can be ensured e.g. by subjecting the coating layer to a gaseous medium (e.g. air) kept at a temperature at or below 60°C, or any of various possible ways.
  • a gaseous medium e.g. air
  • the coating layer temperature at step (b) being maintained not higher than 60°C prevents over-conversion of lead oxides to lead sulfates, and this ensures an enhanced adhesion and integrality of the layer obtained upon drying of the wet coating layer corresponding to the above mentioned 'layer'.
  • the method comprises pressing the wet coating layer for enhancing the density by removing any entrapped air, between the steps (a) and (b).
  • the lead-based subject is in form of a grid, for an even more enhanced adhesion and mechanical stability of the layer.
  • the preferred mixture formulation given above is observed to provide a more favorable adhesion and mechanical stability when it is coated onto at least a part of a lead-based subject in form of a grid.
  • the plate according to the present invention provides an enhanced economic life to an accumulator (or lead-acid type battery) without significant decrease in performance.
  • the performance can be evaluated in terms of number of discharging /re-charging cycles in which the capacity of the accumulator remains 29% or higher than its original maximum capacity value.
  • An economic life expectancy of above 400, and even above 600 cycles is expectable from an accumulator equipped with the plate(s) according to the present invention.
  • the present invention further proposes an accumulator, or a lead-acid type battery, comprising one or more plates as described above.
  • capacity is considered as a quantity corresponding to the amount of energy (in Ah, or 'Ampers x hours') harvestable from a battery calculable by multiplying the current intensity obtained, with respective discharge duration, preferably at a potential difference of maximum 12 V DC (V: Volts, DC: direct current).
  • V Volts, DC: direct current
  • the original maximum capacity value is the amount of energy available from a new and fully charged accumulator (in e.g. Ah).
  • the mixture was coated onto lead-based grid plates (plate in form of a grid) on both sides of plates; and each coated plate was then pressed between two opposing surfaces, so as to remove any gap inside the mixture by forcing any air bubble out of the coating mixture.
  • lead-based grid plates plate in form of a grid
  • the composite plates were dried under a temperature below 60°C to avoid the above-mentioned conversion of lead oxides.
  • a temperature within the range between 40°C and 50°C is preferred to maintain a safety margin below 60°C.
  • the drying was performed for 24 hours, but this value may vary in accordance with drying parameters e.g. selection of natural or forced convection, or humidity level of air used in drying.
  • a planar plate could be used instead of the plate in form of a grid; and the coating step would result in a composite battery plate having a layer of the coating mixture on each coated side of the plate.
  • coating the plate being in form of a grid results in a layer with even more enhanced contact surface area between the lead- based plate material and the coating layer.
  • both sides of the lead- based plate material in form of a grid being coated and then pressed, results in that the coating mixture coated on both sides reach to each other and provide a thicker layer with the lead-based grid embedded thereinto; and a composite battery plate with enhanced chemical contact surface area is obtained.
  • the (composite-) plates were put into contact with an acid (here, sulfuric acid) solution so as to obtain the lead-acid type rechargeable battery according to the present invention.
  • an acid here, sulfuric acid
  • five of the plates as prepared in accordance with the method described above, as anodes, were put into cooperation with same number of cathode plates to form a battery.
  • the battery was charged for 10 hours using a current of 10 Amperes, and thus a theoretical energy storage value of 100 Ah was obtained.
  • New Battery Reference Battery Charge 10 A, 10 h (100 Ah) 10 A, 10 h (100 Ah)
  • Discharge capacity of the exemplary new battery is observed to be higher (40,59 Ah) than that of the reference battery (32,43 Ah). This corresponds to an increase of almost 25.29% in the discharge capacity, thanks to the coating formulation applied onto the plates according to the present invention.
  • This enhancement in the battery is achievable even without necessitating coating of any part of the other than one or more of its anodes battery (e.g. cathodes).
  • the properties of anode(s) are enhanced to such extent where the electrical conductivity of lead (as cathode material in lead-acid type rechargeable batteries) suffices the cathodes to perform properly without necessitating to be coated with the mixture.
  • the new battery has provided a higher efficiency when compared to the reference battery, where the only difference between the new and reference batteries was the presence of graphene in the mixture used in coating of plates of the new battery. Furthermore, rapid drop in current values being started later (3.42 h) than that observed with the reference battery (2.83 h) corresponds to a longer cycle life made available with the battery according to the present invention, thanks to the presence of graphene in the mixture used in coating of the plates according to the present invention.
  • the present invention provides prolonged cycle duration with more stabile current values per unit weight of rechargeable lead-acid type rechargeable batteries.
  • the conversion of lead oxides into lead sulfates can be achieved with an enhanced yield.
  • the discharge capacity of the batteries are also improved with the presence of graphene.
  • the high mechanical resistance and thermal conductivity availed thanks to the presence of graphene in the mixture provides prolonged economic life to the battery plates and thus to the battery, by preventing short circuits due to disintegration damages on the plates.
  • Graphene obtained from dry ice has enhanced the conversion of lead oxide in the coating layer on the composite plates according to the present invention, into lead sulfates, in terms of both yield (relatable to battery capacity) and reaction rate (relatable to stable current values at discharge) when compared to the reference battery.
  • Such graphene improves the contact between the coating layer and the lead-based plate (which mainly has a surface comprising lead oxide), thus minimizing the internal resistance inside the composite plate and thus inside the resulting battery as a whole.
  • the mixture comprising graphene obtained from dry ice provides the enhanced properties to the battery by coating the anode(s) even without necessitating coating the cathodes. This further minimizes the cost of battery, since coating only the anodes is sufficient to obtain the battery with superior properties according to the present invention.

Abstract

The present invention proposes a mixture for coating onto lead-based plates of lead- acid type rechargeable batteries, wherein the mixture comprises graphene obtained from dry ice; and a relevant preparation method for the mixture. The present invention further proposes an anode plate for use in batteries, batteries with such plate(s), and the preparation method thereof.

Description

PERFORMANCE ENHANCEMENT MATERIAL FOR ACCUMULATORS
The present invention relates to a performance enhancement material for accumulators. More particularly, the present invention relates to a paste for performance enhancement in lead-acid type rechargeable batteries.
Lead-acid type rechargeable batteries generally have multiple plates comprising lead, positioned distant from each other such that neighboring plates do not contact each other. For prefention of direct contact, neighboring plates are further separated from each other using membranes. Remaining volumes between neighbouring plates are at least partly filled with an aqueous acidic solution generally comprising sulfuric acid with a specific gravity of 1.20 to 1.25. Such batteries generally comprise lead oxide and red lead mixed with an aqueous solution of sulfuric acid. Lead oxide reacts with the sulfuric acid and thus gets reversibly converted to lead sulfate at charging of the battery. At discharge, the lead sulfate is converted back to lead oxide. The present lead-acid type rechargeable batteries have an energy capacity generally lower than various other battery systems.
Durations at effective discharging (with rather stable current values) available with the present lead-acid type rechargeable batteries are generally short and needs to be improved.
Anode plates of the present lead-acid type rechargeable batteries are generally prone to get damaged/disintegrated as a result of corrosion, and fragments or particles detached from those plates cause short circuits in the batteries. Primary object of the present invention is to eliminate the above-mentioned shortcomings in the prior art.
Another object of the present invention is to provide a low-cost mixture for use as performance enhancing coating material on composite anode plates. A further object of the present invention is to provide a low-cost performance enhancing composite anode plate to be used in rechargeable accumulators for enhancing their capacity, stability and economic life. The present invention proposes a mixture for coating onto lead-based plates of lead- acid type rechargeable batteries, wherein the mixture comprises graphene obtained from dry ice. The concentration of graphene can be within the range between 0.05 wt. % to 1 wt.% with respect to the total weight of the mixture. The mixture can also comprise inorganic fibres, lead monoxide and red lead along with the graphene.
The mixture can have the below formulation where the concentration values are given in weight percentages with respect to the total weight of the formulation:
Component: Concentration:
lead monoxide 75 wt. % to 82 wt. %
inorganic fibres 0.04 wt. % to 0.07 wt. %
red lead 1 wt. % to 7 wt. %
sulfuric acid 3.5 wt. % to 6 wt. %
graphene obtained from dry ice 0.05 wt. % to 1
water complementary amount.
The sulfuric acid concentration can be within the range between 3.85 wt. % and 5.55 wt. % with respect to the total weight of the formulation.
The graphene concentration can be within the range between 0.1 wt. % and 0.3 wt. % with respect to the total weight of the formulation.
The present invention further proposes a lead-based plate for being used as battery plate in lead-acid type rechargeable batteries, at least partly coated with a coating layer comprising graphene obtained from dry ice. The coating layer can further comprise one or more lead oxide, one or more lead sulfate and inorganic fibres.
The graphene concentration here can be within the range between 0.06 wt.% and 1.22 wt.% with respect to the total weight of the layer, which can be considered as corresponding to removal of water content in a mixture used as starting material in obtention of the layer. The range can more preferably be between 0.12 wt.% and 0.33 wt.%. The concentration of inorganic fibres can be within the range between 0.045 wt.% and 0.1 wt.% with respect to the total weight of the layer.
The present invention further proposes a lead-acid type rechargeable battery comprising one or more of such plate(s).
In accordance with the above disclosed entities, the present invention further proposes respective methods.
One of the methods is related to preparation of a mixture for coating onto lead- based plates of lead-acid type rechargeable batteries, comprising the steps of:
i. obtention of a blend comprising lead monoxide, red lead and
inorganic fibres,
ii. obtention of a paste by mixing the blend with water,
iii. addition of sulfuric acid and graphene onto the paste.
Here, the addition of graphene can be performed later than the addition of sulfuric acid onto the paste.
The mixture used in said method can have the below final formulation:
Component: Concentration:
lead monoxide 75 wt. % to 82 wt. %
inorganic fibres 0.04 wt. % to 0.07 wt. %
red lead 1 wt. % to 7 wt. %
sulfuric acid 3.5 wt. % to 6 wt. %
graphene obtained from dry ice 0.05 wt. % to 1
water complementary amount. where the concentration values are given in weight percentages with respect to the total weight of the formulation.
The present invention also relates to a method for obtaining a lead-based plate for being used as battery plate in lead-acid type rechargeable batteries, comprising the steps of: a. at least partly coating of a lead-based subject with an aqueous mixture comprising graphene obtained from dry ice; thus obtaining a composite intermediate product with a wet coating layer,
b. drying of the wet coating layer on the composite intermediate product, provided that the temperature at the coating layer is maintained at or below 60°C throughout the drying step. The mixture can further comprise inorganic fibres, lead monoxide and red lead.
Said method can further comprise pressing of the wet coating layer so as to remove any entrapped air therein, between the steps (a) and (b).
Here, the lead-based subject can be in form of a grid and the mixture can have the below formulation where the concentration values are given in weight percentages with respect to the total weight of the formulation:
Component: Concentration:
lead monoxide 75 wt. % to 82 wt. %
inorganic fibres 0.04 wt. % to 0.07 wt. %
red lead 1 wt. % to 7 wt. %
sulfuric acid 3.5 wt. % to 6 wt. %
graphene obtained from dry ice 0.05 wt. % to 1
water complementary amount.
Graphene recently finds a wide use in various fields of technology. It has a large specific surface area (1500 m2/g), high mechanical stability (160 GPa), high thermal conductivity (5000 W/mK), and a high electrical conductivity (2000 S/cm). There are various graphene production methods and each method results in product properties/structures different than those available with the other methods. Graphene obtained from dry ice can be described as having mainly a cubic morphology comprising superimposed layers (generally 2 to 10 layers) having a length or width (e.g. diagonal or side-length) within a range between 50 nm and 200 nm. These properties are considered by the inventor to have a potential of being very useful to be utilized in a mixture to be coated onto plates to be employed in batteries; more particularly onto anode plates for lead-acid type rechargeable batteries. Examples to dry ice method are available in US 9 340 430 B2 or in Zhang et.al., doi: 10.1016/j.cplett.2013.11.014.
Accordingly, an aspect of the present invention relates to a mixture for use in accumulators or lead-acid type rechargeable batteries. The mixture comprises graphene obtained from dry ice. The concentration of graphene can be within the range between 0.05 wt. % to 1 wt.% with respect to the total weight of the mixture. The mixture can further comprise inorganic fibres, lead monoxide, red lead (i.e. Lead (II, IV) oxide), sulfuric acid and water. The inorganic fibres can be glass fibres as being inert against acidic character of the mixture.
A preferred formulation for the mixture can be given as follows, where the concentration values are given in weight percentages with respect to the total weight of the formulation:
Component Concentration (wt. %)
lead monoxide 75 to 82
inorganic fibres 0.04 to 0.07
red lead 1 to 7
sulfuric acid 3.5 to 6, preferably 3.85 to 5.55 graphene obtained from dry ice 0.05 to 1, preferably 0.1 to 0.3 water complementary amount
Accordingly, the present invention proposes a method for preparing the mixture. The mixture can be availed by performing at lea: ;t the following sequential method steps: i. obtention of a blend comprising lead monoxide, red lead and inorganic fibres, ii. obtention of a paste by mixing the blend with water,
iii. addition of sulfuric acid and graphene onto the paste.
In a preferred mode of the method, the addition of graphene is performed later than the addition of sulfuric acid onto the paste.
The sulfuric acid added onto the paste is preferably in form of an aqueous solution thereof. As an example helpful for calculation, a final sulfuric acid concentration of 10 wt. % in 100 grams of the final mixture can be achieved by introduction of 10 grams of 40 B° aqueous H2S04 solution (40 degrees Baume corresponding to an H2S04 concentration 48.10%(w/w), and specific gravity of 1.3810), with the rest of the ingredients in their respective and complementary amounts. The calculation can be easily adapted for various initial and final concentrations of sulfuric acid. Presence of sulfuric acid enables partly conversion of lead monoxide to lead sulfate, and thus provides an electrochemical charge to the mixture to some extent, beforehand any use of the mixture.
The mixture can be applied onto surfaces of plates in preparation of accumulators, particularly on lead-based plates of lead-acid type rechargeable batteries. Thus, the present invention further proposes a plate for lead-acid type rechargeable batteries, the plate being at least partly coated with a layer of coating comprising graphene. The concentration of graphene can be within the range between 0.05 wt. % to 1 wt.% with respect to the total weight of the mixture before applying onto the plate as layer material.
The coating (or layer) corresponds to an at least partly dried form of any of the mixture formulations as described above. Upon evaporation, any remaining amounts of water and sulfuric acid can be omitted in the formulation of the layer, which corresponds to the dried form of the mixture. Furthermore, any non-evaporated sulfuric acid can be considered to have reacted with several lead oxides in the mixture to end up as lead sulfates. The graphene concentration in the layer is preferably arranged such that it remains within the range between 0.06 wt.% and 1.22 wt.%, more preferably within the range between 0.12 wt.% and 0.33 wt.% wherein the concentration is given in weight percentage with respect to the total weight of the mixture prior to being applied onto the plate, or before curing. Highly positive effects of graphene is available even with such low concentrations of graphene (e.g. up to 0.33 wt.%) thanks to being obtained according to 'dry ice' method (i.e. obtained from dry ice); and this corresponds to a further improvement in terms of costs. The layer can thus comprise a mixture of lead oxide(s), lead sulfate(s), inorganic fibre(s) and graphene. Preferably, the concentration of inorganic fibres is within the range between 0.045 wt.% and 0.1 wt.%; wherein the concentrations are given in weight percentages with respect to the total weight of the layer. The plate according to the present invention can be prepared by performing a method comprising the following steps: a. at least partly coating of a lead-based subject with an aqueous mixture comprising graphene obtained from dry ice, thus obtaining a composite intermediate product with a wet coating layer,
b. drying of the wet coating layer on the composite intermediate product, provided that the temperature at the coating layer is maintained at or below 60°C throughout the drying step. Preventing the coating layer temperature from exceeding 60°C can be ensured e.g. by subjecting the coating layer to a gaseous medium (e.g. air) kept at a temperature at or below 60°C, or any of various possible ways.
The coating layer temperature at step (b) being maintained not higher than 60°C prevents over-conversion of lead oxides to lead sulfates, and this ensures an enhanced adhesion and integrality of the layer obtained upon drying of the wet coating layer corresponding to the above mentioned 'layer'.
Preferably, the method comprises pressing the wet coating layer for enhancing the density by removing any entrapped air, between the steps (a) and (b). Preferably, the lead-based subject is in form of a grid, for an even more enhanced adhesion and mechanical stability of the layer. Especially the preferred mixture formulation given above is observed to provide a more favorable adhesion and mechanical stability when it is coated onto at least a part of a lead-based subject in form of a grid.
The plate according to the present invention provides an enhanced economic life to an accumulator (or lead-acid type battery) without significant decrease in performance. The performance can be evaluated in terms of number of discharging /re-charging cycles in which the capacity of the accumulator remains 29% or higher than its original maximum capacity value. An economic life expectancy of above 400, and even above 600 cycles is expectable from an accumulator equipped with the plate(s) according to the present invention. Accordingly, the present invention further proposes an accumulator, or a lead-acid type battery, comprising one or more plates as described above.
Here, capacity is considered as a quantity corresponding to the amount of energy (in Ah, or 'Ampers x hours') harvestable from a battery calculable by multiplying the current intensity obtained, with respective discharge duration, preferably at a potential difference of maximum 12 V DC (V: Volts, DC: direct current). The original maximum capacity value is the amount of energy available from a new and fully charged accumulator (in e.g. Ah). EXAMPLE:
For an exemplary experiment, a mixture (10000 grams) according to the present invention was prepared by performing the following steps:
- blending 7916 grams of lead monoxide with 198 grams of red lead and 6 grams of glass fibres,
- adding 908 grams of water (i.e. at complementary amount) to the blend, and mixing until obtaining a paste; and
- further mixing he paste upon addition of 952 grams of aqueous sulfuric acid (40 degrees Baume) and 20 grams of graphene. Clearly, the graphene concentration here corresponds to only 0.2 wt.% with regard to the total weight of the mixture. The addition of sulfuric acid was performed slowly under constant mixing, in order to maintain the temperature of the mixture below 60°C to avoid conversion of lead oxides to lead sulfates to an unfavorable extent.
The mixture was coated onto lead-based grid plates (plate in form of a grid) on both sides of plates; and each coated plate was then pressed between two opposing surfaces, so as to remove any gap inside the mixture by forcing any air bubble out of the coating mixture. Thus a plurality of composite plates was obtained.
The composite plates were dried under a temperature below 60°C to avoid the above-mentioned conversion of lead oxides. A temperature within the range between 40°C and 50°C is preferred to maintain a safety margin below 60°C. The drying was performed for 24 hours, but this value may vary in accordance with drying parameters e.g. selection of natural or forced convection, or humidity level of air used in drying.
Coating only one side would also give comparable results, yet coating both sides is preferred.
A planar plate could be used instead of the plate in form of a grid; and the coating step would result in a composite battery plate having a layer of the coating mixture on each coated side of the plate. Yet, coating the plate being in form of a grid results in a layer with even more enhanced contact surface area between the lead- based plate material and the coating layer. Furthermore, both sides of the lead- based plate material in form of a grid being coated and then pressed, results in that the coating mixture coated on both sides reach to each other and provide a thicker layer with the lead-based grid embedded thereinto; and a composite battery plate with enhanced chemical contact surface area is obtained. The (composite-) plates were put into contact with an acid (here, sulfuric acid) solution so as to obtain the lead-acid type rechargeable battery according to the present invention. In the performance tests, five of the plates as prepared in accordance with the method described above, as anodes, were put into cooperation with same number of cathode plates to form a battery. The battery was charged for 10 hours using a current of 10 Amperes, and thus a theoretical energy storage value of 100 Ah was obtained.
For comparison, five further composite plates with graphene-less coatings (with formulation similar to the above described mixture, with the only difference that this one is prepared without addition of graphene), as anodes, were also put into cooperation with same number of cathode plates to form a reference battery. The reference battery was also charged for 10 hours using a current of 10 Amperes, and thus a theoretical energy storage value of 100 Ah was obtained.
Identical discharging apparatuses were set for both of said batteries, and potential difference (Voltage) and current (Amperage) values versus discharge time were recorded.
In a single discharge, mean current values obtained from the battery with the plates according to the present invention (new battery) and the reference battery was calculated as 11.88 A and 11.46 A, for 3.42 hours and 2.83 hours; where rapid drops in momentary current values were observed from around 205th minute (new battery) and 170th minute (reference), respectively. This information is summarized in the below table:
Table. Comparative performance test results for the new and reference batteries
New Battery Reference Battery Charge: 10 A, 10 h (100 Ah) 10 A, 10 h (100 Ah)
Discharge: 11.88 A, 3.42 h (40.63 Ah) 11.46 A, 2.83 h (32.43 Ah)
Rapid drop at: 3.42 h 2.83 h Discharge capacity of the exemplary new battery is observed to be higher (40,59 Ah) than that of the reference battery (32,43 Ah). This corresponds to an increase of almost 25.29% in the discharge capacity, thanks to the coating formulation applied onto the plates according to the present invention.This enhancement in the battery is achievable even without necessitating coating of any part of the other than one or more of its anodes battery (e.g. cathodes). With the mixture according to the present invention, the properties of anode(s) are enhanced to such extent where the electrical conductivity of lead (as cathode material in lead-acid type rechargeable batteries) suffices the cathodes to perform properly without necessitating to be coated with the mixture.
Thus, the new battery has provided a higher efficiency when compared to the reference battery, where the only difference between the new and reference batteries was the presence of graphene in the mixture used in coating of plates of the new battery. Furthermore, rapid drop in current values being started later (3.42 h) than that observed with the reference battery (2.83 h) corresponds to a longer cycle life made available with the battery according to the present invention, thanks to the presence of graphene in the mixture used in coating of the plates according to the present invention. From another aspect, recoverable energy density values at discharge of the new and reference batteries were calculated as 61.59 Wh/kg (total energy recovered at discharge in 'Watts x hours' per unit weight of the battery, in 'kilograms') and 48.77 Wh/kg, respectively; which correspond to an increment of [(61.59/48.77) - 1=] 26.28% in recoverable energy density of batteries made with the technology according to the present invention. Thus the present invention provides prolonged cycle duration with more stabile current values per unit weight of rechargeable lead-acid type rechargeable batteries.
Surprisingly, it is observed that at the first four cycles of charging/discharging, the total energy dischargeable from the battery according to the present invention is observed to slightly increase at about 5 percent. This means, a total discharged energy of 38.6 Ah recorded at the first discharge, was observed to increase at each subsequent cycle until the fourth, and reached up to 40.63 Ah at the discharge in the fourth cycle. Then, the total discharged energy value started to slightly drop in further subsequent cycles. This effect can potentially be attributed to the presence of graphene along with red lead and the lead monoxide in the mixture, which have a weight ratio with respect to each other (lead monoxide : red lead) preferably within the range between 1070 and 2050. Thanks to the high electrical conductivity and large surface area of graphene at its unit mass, the conversion of lead oxides into lead sulfates can be achieved with an enhanced yield. The discharge capacity of the batteries are also improved with the presence of graphene. Also the high mechanical resistance and thermal conductivity availed thanks to the presence of graphene in the mixture provides prolonged economic life to the battery plates and thus to the battery, by preventing short circuits due to disintegration damages on the plates.
Graphene used in the experiments was obtained from dry ice with the method summarized below:
Metallic magnesium and/or calcium particles are put into dry ice. Upon provision of activation energy, metallic content reacts with carbon dioxide, resulting in production of graphene with oxides of said metal(s), in accordance with the below reactions (I.I, I. II). Hydrochloric acid was added onto the reaction products until reaching to neutral pH in accordance with the below reactions (II. I, II. II). Then purified graphene is obtained upon removal of salts by rinsing the product with water; then the graphene is dried. This is a rapid and facile method for production of graphene nano powders; thus minimizes the process and product-related costs related to the present invention. 2 Mg + C02 → 2 MgO + C (graphene flakes) (I.I)
2 Ca + C02 → 2 CaO + C (graphene flakes) (I. II)
MgO + HCI → MgCI2 + H20 (neutralization) (II. I)
CaO + HCI → CaCI2 + H20 (neutralization) (II. II)
Graphene obtained from dry ice has enhanced the conversion of lead oxide in the coating layer on the composite plates according to the present invention, into lead sulfates, in terms of both yield (relatable to battery capacity) and reaction rate (relatable to stable current values at discharge) when compared to the reference battery. Such graphene improves the contact between the coating layer and the lead-based plate (which mainly has a surface comprising lead oxide), thus minimizing the internal resistance inside the composite plate and thus inside the resulting battery as a whole. As a result, the mixture comprising graphene obtained from dry ice provides the enhanced properties to the battery by coating the anode(s) even without necessitating coating the cathodes. This further minimizes the cost of battery, since coating only the anodes is sufficient to obtain the battery with superior properties according to the present invention. Thus, the below objects are achieved with the improvements according to the the present invention:
elimination of the above-mentioned shortcomings in the prior art,
provision of a low-cost mixture for use as performance enhancing coating material on composite anode plates,
- provision of a low-cost performance enhancing composite anode plate to be used in rechargeable accumulators for enhancing their capacity, stability and economic life.

Claims

Claims
A mixture for coating onto lead-based plates of lead-acid type rechargeable batteries, the mixture comprising inorganic fibres, lead monoxide, red lead and graphene obtained from dry ice.
The mixture according to the claim 1, with the below formulation where the concentration values are given in weight percentages with respect to the total weight of the formulation:
Component: Concentration:
lead monoxide 75 wt. % to 82 wt. %
inorganic fibres 0.04 wt. % to 0.07 wt. %
red lead 1 wt. % to 7 wt. %
sulfuric acid 3.5 wt. % to 6 wt. %
graphene obtained from dry ice 0.05 wt. % to 1
water complementary amount.
The mixture according to the claim 2, wherein the sulfuric acid concentration is within the range between 3.85 wt. % and 5.55 wt. % with respect to the total weight of the formulation.
The mixture according to the claim 2, wherein the graphene concentration is within the range between 0.1 wt. % and 0.3 wt. % with respect to the total weight of the formulation.
A lead-based plate for being used as battery plate in lead-acid type rechargeable batteries, at least partly coated with a coating layer comprising graphene obtained from dry ice.
6. The plate according to the claim 5, wherein graphene concentration is within the range between 0.06 wt.% and 1.22 wt.% with respect to the total weight of the layer. The plate according to the claim 6, said range being between 0.12 wt.% and 0.33 wt.%.
The plate according to any of the claims 5 or 6, wherein the coating layer further comprises inorganic fibres at a concentration within the range between 0.045 wt.% and 0.1 wt.% with respect to the total weight of the layer.
9. A lead-acid type rechargeable battery comprising one or more plate according to any of the claims 5 to 8.
10. Method for preparation of a mixture for coating onto lead-based plates of lead- acid type rechargeable batteries, comprising the steps of:
iv. obtention of a blend comprising lead monoxide, red lead and
inorganic fibres,
v. obtention of a paste by mixing the blend with water,
vi. addition of sulfuric acid and graphene obtained from dry ice,
onto the paste.
11. Method according to the claim 10, wherein the addition of graphene performed later than the addition of sulfuric acid onto the paste.
12. Method according to any of the claims 10 or 11, wherein the mixture has the below final formulation:
Component: Concentration:
lead monoxide 75 wt. % to 82 wt. %
inorganic fibres 0.04 wt. % to 0.07 wt. %
red lead 1 wt. % to 7 wt. %
sulfuric acid 3.5 wt. % to 6 wt. %
graphene obtained from dry ice 0.05 wt. % to 1
water complementary amount. where the concentration values are given in weight percentages with respect to the total weight of the formulation.
13. A method for obtaining a lead-based plate for being used as battery plate in lead-acid type rechargeable batteries, comprising the steps of: a. at least partly coating of a lead-based subject with an aqueous mixture comprising graphene obtained from dry ice; thus obtaining a composite intermediate product with a wet coating layer,
b. drying of the wet coating layer on the composite intermediate product, provided that the temperature at the coating layer is maintained at or below 60°C throughout the drying step.
14. The method according to the claim 13, further comprising pressing of the wet coating layer so as to remove any entrapped air therein, between the steps (a) and (b).
15. The method according to any of the claims 13 or 14, wherein the lead-based subject is in form of a grid and the mixture has the below formulation where the concentration values are given in weight percentages with respect to the total weight of the formulation:
Component: Concentration:
lead monoxide 75 wt. % to 82 wt. %
inorganic fibres 0.04 wt. % to 0.07 wt. %
red lead 1 wt. % to 7 wt. %
sulfuric acid 3.5 wt. % to 6 wt. %
graphene obtained from dry ice 0.05 wt. % to 1
water complementary amount.
PCT/TR2017/050044 2017-01-27 2017-01-27 Performance enhancement material for accumulators WO2018139979A1 (en)

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