Ramcharan Entity1 moves closer to commercialisation of a low-cost supercapacitor

Ramcharan Company (P) Limited – Entity1 has developed and patented an asymmetric supercapacitor with native and Mg-enriched phyllosilicates as cathode and graphite or carbon black as anode. The fabricated supercapacitor cell exhibited a specific capacity of 440.998 F/g @ 10mA/cm2 for graphite anode and 560 F/g for carbon black anode. This capacity observed is three and two times higher than the market available supercapacitors (~ 230 F/g).

“Supercapacitors are the next-generation energy storage devices. The main aim of RCPL-Entity1 is to reconcile the seemingly incompatible conventional capacitor, which has high power density, and rechargeable batteries, which have a high energy density, thus bridging the gap”, said Kaushik Palicha from Entity 1.

Supercapacitors can play a significant role in energy storage devices as they can store a large amount of charges between two electrode plates with minimum distance, thus paving a path to miniature and portable energy storage devices. Based on the storage principle, there are two main types: electric double-layer capacitors (EDLC) and pseudo-capacitors.

– In EDLC, charges are stored due to the electrostatic forces (physical forces) observed between the electrodes and the electrolyte due to the generation of a Helmholtz electrical double layer. Here, no new chemical bonds are formed. These supercapacitors usually incorporate carbon-based electrode materials as the active electrode material.

– In pseudo capacitors, the charges are stored as a result of the actual transfer of electrons or charges between the electrode and electrolyte (redox reactions). They are usually made from transition metallic oxides or conducting polymers.

Thus, the combination of EDLC and pseudo capacitor forms a hybrid capacitor, which can be of three different types:

(1) Composites, where electrodes have carbon derivatives along with conducting polymer or metal oxides;

(2) Asymmetric, where one electrode is an EDLC electrode, and the other electrode is a faradic electrode;

(3) Battery-like, where a supercapacitor electrode is coupled with a battery-type electrode.

Metal oxides, along with other inorganic compounds, can exhibit pseudo-capacitance along with electrically operated hydrogen production. Carbon-based symmetric micro-supercapacitors have been reported to have greater specific capacitance, cyclic stability, and specific energy using conventional organic binders and separators. Highly efficient self-healing poly electrodes with high flexibility, mechanical endurance and electrochemical character using SWCNTs (Single Walled Carbon NanoTubes) are also available. Some studies employing the biological chitosan and CNT nanocomposite as electrode material were also investigated, which led to the enhancement of supercapacitors.

In the present invention, naturally available phyllosilicates rich in iron and Mg-enriched were used as cathode for supercapacitor applications. The anode material employed is graphite and/or carbon black.

The cycle stability is approximately 2500, and the capacity retention is 32% & 4% in phyllosilicates/graphite & phyllosilicates/Carbon black supercapacitors, respectively, after 2392 cycles. The Mg-enriched phyllosilicate possesses the chemical composition of ((Ca)x-y(Al,Mg)2-x+y Fez-y(Si4O10)(OH)z·nH2O); where the increment in Mg2+ stoichiometry is balanced by a decrement in Ca2+, Al3+, Fe2+ stoichiometry of the native phyllosilicate. The redox potential of the phyllosilicates is at 2.38V in the cathodic and anodic scan with respect to Ag/AgCl. This indicates the perfect Mg2+ deposition and stripping characteristics of the phyllosilicates (both native and Mg-enriched).

This demonstrates the utility of the phyllosilicates as electrodes for energy storage devices such as supercapacitors. Thus, phyllosilicates explicitly support the nature of Mg2+ intercalation in their lattice both in octahedral and tetrahedral sites, as shown below:

The specific parameters of the present invention of utilizing environmentally benign phyllosilicates as supercapacitor electrode material are represented in the table below:

The major advantages of the invention are:

1. Naturally abundant and cost-effective phyllosilicates as cathode.

2. The common-ion rich phyllosilicates (e.g. Na-rich for Na₂SO₄, Ca-rich for CaSO₄ and Mg-rich for MgSO₄) facilitates faster ion transport.

3. Very low IR drop ~ 60-80 mΩ

4. Non-carbon or very minimal carbon-based device.

5. Completely recyclable.

6. Specific capacitance as high as ~ 500 F/g @ 10 mA/cm².

7. Long life (longevity); Limited or no self-discharge.

8. Specific energy as high as 30 Wh/kg and Specific power as high as 500 W/kg.

What is the relevance of this patent/technology? 

Presently, energy security in the international arena, transportation including air, rail and road, telecommunications and carbon footprints make the miniaturization of clean green energy storage devices inevitable. Supercapacitors have a significant role as they can store a large amount of charge between two electrode plates with minimum distance, thus paving a path to miniature and portable energy storage devices.

What are the potential areas of application?

The developed devices have industrial applicability in Stationary Energy Storage, automobiles, air transportation, Railways, buses, trucks, e-scooters, e-cycles and e-rickshaws, mobiles, laptops, tablets, walkie-talkies, drones, bio-medical devices.

What is the path to market launch/commercialisation, and how will this technology be deployed on target applications?

Currently, we are working with E-trucks for mobility and railroad applications. Based on feedback from these applications, we will look at growing markets. Our advantage is that these are made from locally made material, giving it a significant supply chain, costing & ease of use advantage.

TRL of this technology

We are at TRL 7 in some applications & 8 in one application.

Authored by:

Ramcharan Company (P) Limited – Entity1, Chennai

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