Metal ion battery having ionomer membrane separator and free-standing electrode

1. An energy storage device comprising Zn as an anode, electrodeposited V 2 O 5 on functionalized carbon as a cathode, sulfonated tetrafluoroethylene copolymer (STC) as a cation selective ionomer membrane separator and ZnSO 4 as an electrolyte.

2. The energy storage device as claimed in claim 1 , wherein the device further comprises of a free-standing electrode.

3. The energy storage device as claimed in claim 1 , wherein the device is a battery.

4. The energy storage device as claimed in claim 3 , wherein said battery exhibits outstanding cycling stability with a retention of 85% after 1300 cycles at 5 A g −1 current density and with a retention of 88% after 1800 cycles at 10 A g −1 current density.

5. The energy storage device as claimed in claim 3 , wherein said battery provides an energy density of 250-400 W h kg −1.

6. A process for fabrication of the energy storage device as claimed in claim 1 , wherein said process comprises:

a. subjecting a piece of a pristine carbon paper (pCP) to anodization or electrochemical functionalization by applying a bias potential of 10 V to 20 V for 5 to 10 mins in a two-electrode cell assembly in an electrolyte solution to obtain a functionalized carbon paper;

b. carrying electrochemical deposition on the functionalized carbon paper with a cathode active material to obtain a cathode active material deposited carbon paper; and

c. assembling the device, a piece of metal foil as an anode and an electrolyte impregnated ionomer membrane as a separator cum electrolyte.

7. The process as claimed in claim 6 , wherein the active material is V 2 O 5 , the metal is Zn and the ionomer membrane is STC.

8. The process as claimed in claim 6 , wherein in step (a) the electrolyte is Na 2 SO 4 and in step (c) the electrolyte is ZnSO 4 .