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D

uring the last decade the rapid and growing demand for

wearable electronic devices such as biomedical

implants, smart cards or wireless sensors has triggered

a great revolution in the field of energy storage devices.Within this

context, the research and development of ultra-high performance

micro-batteries and micro-supercapacitors results in great interest

for integration into such systems. Thereby, micro-power sources for

energy harvesting, for example micro-supercapacitors, have

awakened an enormous interest in our society. In recent years,

several strategies have been devoted to increasing the energy and

power densities of these devices by designing advanced electrode

architectures, investigating innovative nanostructured materials

and electrolytes, or understanding the energy storage

mechanisms at the electrode-electrolyte interface. In spite of the

tremendous efforts carried out in this direction, the advent of

common-use miniaturised energy storage units remains a big

challenge for our society.

Research activities

Over the past years, CEA/INAC launched an important research

activity in the field of electrochemical energy storage, building on

its wide competences in the domain of silicon-based

nanostructured materials and on its state-of-the-art facilities for

the electrochemical characterisation of prototypes, as well as the

elaboration of electrodes. From the material perspective, INAC has

elaborated the bottom-up growth of highly doped silicon

nanowires (SiNW) by means of chemical vapour deposition (CVD)

using gold as catalyst. This strategy was designed regarding the

compatibility of this material with the microelectronics industry for

the building and miniaturisation of ‘on-chip’ micro-electronic

devices. In addition, SiNWs exhibit unique properties in terms of a

long cycling life, fast charging-discharging rate, wide operating

temperature range, and high power density, making them potential

candidates to be employed as energy storage electrodes. As a

result, INAC has consolidated its leadership in this area through

the co-ordination of several international and national projects.

Presently, NEST (Nanowires for Energy STorage) is a representative

collaborative research project – co-ordinated by Dr Gérard Bidan

(INAC) and funded under the Seventh Framework Programme –

encompassing four academic partners and two companies. This

project aims at developing ultra-high performance micro-

supercapacitors based on SiNWs by combining different

approaches based on four important pillars:

a) Electrode: INAC develops highly active surface electrodes

through the concept based on SiNWs’ hyper-nanostructure (Si

nanotrees, SiNTr), which allows the enhancement of specific

capacitance related to the energy storage capacity. In

collaboration with the Fraunhofer Institute for Applied Solid

State Physics, the Si nanostructures are coated with doped

nano-diamond films in order to enhance conductivity;

b) Electrolyte: In collaboration with the German company Iolitec

we design advanced electrolytes based on ionic liquid

structures in order to obtain a wide operating temperature

range (e.g. -70°C up to 90°C) and large electrochemical

windows (up to 4V);

c) Functionalisation: Deposition of pseudo-capacitive materials

on SiNTrs, for example conducting polymers or transition metal

oxides, represents a promising strategy to enhance the

electrochemical properties in terms of energy and power

densities. In this task, important collaborations between INAC

and CSIC (Barcelona) have been carried out; and

d) Device: Elaboration and testing of prototypes inspired by

commercial technologies based on pouch and coin cells in

tight collaboration with industrial and academic partners

The Institute of Nanoscience and Cryogenics (INAC) at CEA Grenoble, France,

develops novel concepts based on silicon nanostructures for efficient

electrochemical energy storage

Energy storage

50

I S S U E S E V E N

H O R I Z O N 2 0 2 0 P R O J E C T S : P O R TA L

www.horizon2020projects.com

P R O F I L E

S P E C I A L F E AT U R E : M AT E R I A L S

Fig. 1 a) Ragone plot of the energy storage domains for various energy

conversion systems; b) Branched silicon nanowires; c) SiNTrs coated

with an electroactive conducting polymer; and d) SiNWs produced at

large scale