Title of Invention

AN IMPROVED SUPER CAPACITOR

Abstract

An improved super capacitor characterized by two nickel electrodes and aqueous alkaline carbonate soaked in a glass mat separator capable of conducting ions only to get more than one layer of oxide in alkaline media, the said oxide layer/layers capable of intercalate-deintercalte with K+ ions in three dimensional way, the said electrodes and separators are encapsulated in a suitable protective container

Full Text

The present invention relates to "An improved super capacitor" Hitherto it has been proposed to use high area carbon, ruthenium oxide, iridium oxide and/or the mixtures of these oxides as electrodes, tetra alkyl ammonium salts, perchlorates of Li, Mg, Na and carbonates of K. Na etc, as electrolytes in non aqueous medium and/or aqueous medium in electrical double layer capacitors and/or supercapacitors Further Ni has not been used so far as the electrode for capacitor/super capacitor in any form. This is open to the objection that (i) Non aqueous media used in electrical double layer capacitors should be perfectly free from moisture, (ii) Solution of non aqueous media containing electrolytes should be handled only in a glove box or in special moisture proof equipment, (iii) Non aqueous media such as ethylene carbonate, propylene carbonate, y-butyro lactone and electrolytes mentioned above are somewhat costly items Further electrodes made using oxides like ruthenium oxide, iridium oxide are costly and are difficult and tedious to prepare, (iv) Electrodes in such capacitors were made up of carbon of different forms including fibres and carbon cloths. They should possess electrochemical, chemical and mechanical properties suitable for high area electrodes. Activation of such carbon materials is a tedious process, (v) Ni in any form has not been used so far as the electrode for capacitors The main object of the present invention is to provide "An improved super capacitor" which obviates the drawbacks as detailed above Accordingly the present invention provides an improved super capacitor which . c4^f^^t$&**s-eJ~ vy comprises two nickel electrodes and aqueous alkaline carbonate soaked in a glass mat separator capable of conducting ions only to get more than one layer of oxide in alkaline media, the said oxide layer/layers capable of intercalate-deintercalate with K+ ions in three dimensional way, the said electrodes and separators are encapsulated in a suitable protective container. In an embodiment of the present invention is the use of an aqueous alkali carbonate solution as the capacitor electrolyte in water and the use of NiO bearing Ni electrodes as electrodes. In another embodiment of the present invention is the use of polystyrene, glass or other micro porous fibre based materials as the ion conducting separators in this capacitor. In yet another embodiment of the present invention is the use of stainless steel or Ni based alloy or brass as current collectors for the electrodes to effectively distribute the current over the entire area of the electrodes of this capacitor, with the use of ordinary water based electrolytes without the decomposition of water from the electrolysis during the use of these capacitors obtaining very high cycle life, the cell voltage remaining as high as 2.5 to 2.7 V in the case of a fully charged capacitors which is highly cost effective and completely novel in nature The voltage of the capacitor is higher than the thermoneutral voltage because of intercalation of K* into NiO/Ni system and deintercalation of K from NiO/Ni system Intercalation-deintercalation has been mentioned in literature as one of the reasons for higher voltage and capacitance (pseudo-capacitance) of cells The above capacitor when charged by 2 mA/cm2 to 100 mA/cm2 DC current attains an OCV of 2.16 V within 2 to 3 minutes and the same can be discharged up to 90% of its capacity within a short period This charging and discharging can be made quickly even within a few seconds This is an indication that this capacitor possesses very fast response. When large number of such capacitors are connected both in series and/or parallel mode, the resulting capacitor will have very high voltage (OCV) and window (working limits of voltage), high energy and power densities. Since such capacitor banks are fast responding devices they may find application in electric vehicles, power backup for computers, mobile welding units and other military equipment. The following examples are given by way of illustration of the present invention and should not be construed to limit the scope of the present invention. The following typical examples are given to illustrate the invention EXAMPLE-1 Average characteristics of a single capacitor based on experimental results [Ni/K2CO3 (l.OM solution) / Ni system] EXAMPLE-3 Characteristics of Nickel Capacitors (Table Removed) Based on the above examples 1-3 the following observations can be made to highlight the novel type of the present invention 1. The novelty of the above capacitor is that the single capacitor of Ni/NiO/aq.K2CO3/Ni/NiO gives 2.5 to 2.7 V in the presence of aqueous electrolyte thereby proving that the non-aqueous solvents are not necessary This extraordinary behaviour has been achieved for the first time in the capacitor field as a whole. 2. All the ingredients are available in India, for example NiO bearing Ni electrodes are available with Ni-Cd or Ni-Fe manufacturers in India. Other ingredients are available in the battery industry (in the case of separators) and chemical industry (alkali carbonate). Hence the capacitor as a whole will be highly cost effective coupled with good performance characteristics 3. Capacitor banks made use of above system can give 104 J/kg which can be improved to 106 J/kg for use in hyper velocity guns and in electric vehicles 4. Using these capacitors low current, medium current and large current capacitor banks can be fabricated which may find use in circuits requiring high power pulses and current pulses and in computer memories The main advantages of the present invention are: 1 . Electrodes of these capacitor are namely Ni oxide bearing Ni are fabricated as per this investigations are based on Ni sponge, Ni mesh, Ni powder and/or sintered Ni and even Ni plated steel mesh can be used 2. The electrolyte of this capacitor is based on aqueous medium containing either 3. All the components of this capacitor are available in Indian market 4. In this capacitor the use of electrolytes such as tetra alkyl salts, C1O4 and other costly electrolytes has been totally avoided. 5. The use of non aqueous solvents has been avoided in this capacitor Electrolytes of this type of capacitor are based on water as solvent 6. Based on the above advantages from 1 to 6, this capacitor can be said to be economically highly competitive. 7. The noteworthy feature of this invention consists in the use of NiO bearing Ni electrode in combination with aqueous alkali carbonate solution to get high voltage window, capacity and power 8. To get high power density, high capacity and large voltage window, large number of single units of capacitors should be connected either in series or in parallel or in both the modes as the case may be 9. The mechanism by which charging and discharging processes are occurring in this type of capacitor is based on K ion intercalation and deintercalation This is a novelty which has not been so far attempted by anybody in the field of super capacitor. WE CLAIM: An improved super capacitor two nickel electrodes and aqueous alkaline carbonate soaked in a glass mat separator capable of conducting ions of&f to get more than one layer of oxide in alkaline media, the said oxide layer/layers ' £ajHjWet>f intercalate-deintercalate with K* ions in three dimensional way, the said electrodes and separators are encapsulated in a suitable protective container An improved super capacitor as claimed in claim 1 wherein the separator is pfefeatWy made of polystyrene, glass or other micro porous fibre based material An improved super capacitor substantially as herein described with reference to the examples.

Documents:

1403-del-1999-abstract.pdf

1403-del-1999-claims.pdf

1403-del-1999-correspondence-others.pdf

1403-del-1999-correspondence-po.pdf

1403-del-1999-description (complete).pdf

1403-del-1999-form-1.pdf

1403-del-1999-form-19.pdf

1403-del-1999-form-2.pdf