NEST Nanowires for Energy Storage Grant Agreement number 309143

Project public website address httpwwwproject-nesteunest

Publishable summary (midterm results) 1 - Summary description of project context and objectives The NEST project aims to demonstrate and develop a new kind of low volume (can reach the millimeter

size) supercapacitors devices able to drastically enhance the energy storage capacity while at the same

time ensuring that the constituting components and their assembly are compatible with low cost

process more specifically with embedded sensor technologies One of the primary targets of the project

is therefore to validate the integrated electrode and electrolyte designs to produce a micro-

supercapacitor via a process compatible with microelectronics processes that can withstand solder

reflow (280degC for few seconds) for the bonding on different sheet electrodes This has not been

achieved yet and constitutes one major issue when one wants to get small volume and high capacity

This demand has been intensified by the recent rise in interest in lead-free solders due to environmental

concerns so there has been an increase in the amount of electronic equipment that uses high melting

point solders Under these circumstances there is a real need for developing thermally stable energy

storage devices The NEST project proposes to take advantage of the very large surface area (80 to 750

cm2 of Si surface cm

2 of substrate) offered by silicon nanowires (SiNWs) and silicon nanotrees (SiNTs)

to drastically enhance the performance of on-chip supercapacitors The specific energy (frac12 CU2) will be

further increased by specific coating of these Si-nanostructures either with diamond to enlarge the

electro-chemical window (ieU) or with ECPs or metallic oxides (MnO2) for enhancing the

pseudocapacitance behaviour A simple calculation using 90 microFcm

2 as starting value leads to specific capacitance ranging from

7 mFcm2 for SiNWs up to 68 mFcm

2 for SiNTs

2 - Description of work performed and main results 21 - Technical specifications

The technological constraints of the different materials (nanowires coating and electrolytes

temperature range and resistance to reflow) and the feasible supercapacitor performance specifications

(capacitance equivalent series resistance energy and power densities cycle life and temperature

operating window) were detailed at the very beginning of the NEST project Optimal performances

aimed for were achieved and even exceeded but never reached all together On the light of these first

results (which could be improved) the technical specifications were revisited A more specific application

of micro-supercapacitors in wireless autonomous sensors for aeronautics was selected A new set of

requirements involving new parameters namely a wide operating temperature range and a low self-

discharge current were determined

22 - New electrode structures

SiNWs and SiNTs samples were realized by Vapor Liquid Solid mechanism (VLS) in Chemical Vapor

Deposition (CVD) reactor (figure 1) by CEA and distributed to other partners Gold is used as catalyst in

different forms i) Colloids to obtain homogenous diameter from 20 nm to 200 nm ii) Dewetted gold

thin film to obtain higher density of NWs but with inhomogeneous diameter The length of the

nanostructures is managed by the time of the growth from 5 microm to 50 microm (or more if needed) We have

shown that the best performance of the supercapacitors is obtained with highly doped nanostructures

Highly boron-doped nanocrystalline diamond (BBD) films were produced on a 3-inch Si substrate Pure

diamond nanowires (DNWs) samples were successfully realized by ICP etching of pure diamond

substrates by FHG and delivered to partners Seeding of SiNWs by nano-diamonds particles using

colloidal diamond suspension in water with typical particle size of 5 nm was achieved while keeping the

integrity of the SiNWs (attachment to the substrate) Then the overgrowth with BDD with complete

coverage of SiNWs was successfully achieved by FHG and samples delivered to partners

Figure 1 (Left image) SEM image of SiNWs (Right image) SEM image of SiNTrs

23 - Electrolyte amp pseudocapacitance

SiNWs and diamond-coated Si nanowires (D-SiNWs) were successfully functionalized with

electroconducting polymers ECPs (polypyrrole PEDOT amp PAni) by CEA Electrodeposition of ECP films

on SiNWs was achieved with complete coverage Key factors such as polymerization charge and

deposition time allowed to control the thickness of the organic coating obtaining sub-micrometric

thickness However electropolymerisations of pyrrole and EDOT on pure diamond nanowires are limited

to the top of the surface Alternative electrochemical technique will be developed

1 aprotic IL and 8 protic ILs were tailor-made by IOLITEC Based on ESW thermal treatment and

electropolymerisation criteria aprotic and protic ILs were selected

Figure 2 (Left image) SEM image of conducting polymer (PEDOT)-coated silicon nanowires

(Right image) SEM image of PPy-coated diamondsilicon nanowires Inset cross sectional view of PPy on diamond coated SiNWs recorded at 45deg tilted angle

24 - Electrochemical characterization in a 3-electrode cell of materials (electrodes and electrolyte)

A starting set of 15 preselected aprotic ionic liquids (ILs) provided by IOLITEC was successively

restricted to 7 then 4 ILs taking into account a set of criteria (low viscosity high conductivity and high

electrochemical window and reflow treatment) compatible with the prepared electrodes (see above)

Electrochemical stability windows of ILs were not modified in the presence of silicon or diamond

nanostructures (ESW = 5-6 V) SiNWs exhibit almost perfect capacitance behavior reaching good values

(200-300microFcm2) The morphology of the SiNWs SiNTrs and D-SiNWs remained unchanged even after

millions of successive charge-discharge cycles

Figure 3 Structure of the electrochemical cell in a 3-electrode configuration

Symmetric micro-supercapacitors (2 electrodes in a face-to-face configuration) based on SiNWs and

SiNTs provide an excellent stability after 8106 galvanostatic charge-discharge curves with a loss of

capacitance of 25 in presence of PMPyrr BTA using a wide voltage of 4 V valid for applications

Pure diamond nanowires electrodes appear very promising in term of specific capacitance energy

density power (40 mWcm2) while keeping an outstanding electrochemical stability after millions of

galvanostatic cycles in presence of ion-conducting protic HN222BTA using a wide voltage of 4V Reflow

results (thermal treatment during 40s at 280degC) are very positive and ILs exhibit even better ESW after

reflow probably because of water trace elimination This opens a route to improve PEDOT coating

stability under cycling

25 - Assembling Setup amp prototype

Supercapacitor elementary cell (SPEC) using a sandwich type configuration (eg 2-stacked

electrodes) was designed to study the best combinations electrodeelectrolyte selected from the 3-

electrode cell set-up studies

The assembly in symmetrical set-ups decreases the capacitance strongly from 300-200 microFcm2 to 23

- 9 microFcm2 while the cell voltage remains good (4 V) These results reflect that optimization in the design

of the prototype is required Functionalized SiNWs (eg ECPs-coated SiNWs) showed similar tendencies

in both configurations

The capacitive properties of hybrid pseudo-capacitors (eg conducting polymer coated SiNWs) in a

2-electrode configuration in terms of specific capacitance (C = 11 mFcm2) power (P = 22 mJcm2) and

energy densities (E = 029 mWcm2) were found to present amazing results compared with SiNWs based

EDLCs C = 11 mFcm2 P = 22 mJcm

2 and E = 029 mWcm

2 respectively However cyclability and

operating voltage fall to 3500 cycles and 15 V respectively

Figure 4 Digital camera images showing the parts of the micro-supercapacitor prototype a) Structure of the cell b) Top and down view of the device and c) PEDOT coated-SiNWs electrodes for the

micro-supercapacitor device Scale bar 1 cm

Counter electrode Platinum

Working electrode SiNWsSiNTrsDiNWs

Reference electrode Ag Ag+

3 ndash Conclusions expected final results and potential impacts

Combinations of nano- Si and diamond-based electrodes with ILs and redox coatings have been

successfully obtained and demonstrate the expected synergetic effects to reach good supercapacitor

performances However in order to gather the remarkable cyclability (gt million cycles) of pure SiNWs D-

SiNWs or pure D-NWs electrodes with the amazing high capacitance of ECPs coatings further studies are

needed

Electrochemical experiments will be carried out in pre-thermally treated ILs Elimination of traces

of water and other volatile impurities may open the route to improve PEDOT and PPy stability under

cycling Development of further protic and aprotic ILs with selectively chosen chemical structures and

properties)

Alternative electrochemical techniques based on pulse polymerization are in progress in order to

get uniform organic coating on diamond nanowires in order to facilitate the diffusion of the species and

improve the nucleation sites

Reflow treatments carried out on pure Si electrodes demonstrate a remarkable stability of the

combinations of Si or diamond-based electrodes with ILs However some points must be deepened

The protic DEMA OTf optimal for PAni electrodeposition undergoes a color change during reflow

treatment Does this correspond to a change in the electrochemical properties for electrodepo-sition and

cycling Other new protic ILs recently synthesized by IOLITEC will be tested to challenge DEMA OTf

Reflow treatment in the presence of ECPs should be carried out

Diamond coated SiNWs (D-SINWs) electrodes present comparable cyclability to pure SiNWs-based

supercapacitors with the advantage to be used in more conductive protic ILs resulting in higher specific

capacitance and energy density

First experiments regarding mixtures of different ILs respective of ILs and organic solvents are

ongoing

Aqueous electrolytes (primary reason for involving diamond electrodes due to its high

overpotential towards water) should be tested with diamond-based substrates (D-SiNWs and pure

DNWs) to increase the power of the supercaps However in this case reflow treatment could not be

implemented

In the second part of the NEST project the two WPs dedicated to prototypes assembling and

performance characterizations will take off

Of course a feed-back will allow for continuing to select the best combination in order to comply

with the requirements specified in revised technical specifications

Packaging of SiNWs and sealing developments appear crucial with respect to ILs and SiNWs

integrity For the assembly of the prototype special attention should be given to avoid crushing of

SiNWs The design of the elementary cell will be examined either in a face-to-face or in an interdigitated

configuration (with may prevent SiNWs crushing)

References (selected) 1) D Aradilla G Bidan P Gentile P Weathers F Thissandier V Ruiz P Gomez-Romero T J Schubert

H Sahin and S Sadki Novel hybrid micro-ultracapacitor based on conducting polymer coated silicon nanowires for electrochemical energy storage RSC Adv 2014 4 26462

2) D Aradilla P Gentile G Bidan V Ruiz P Gomez-Romero T J Schubert H Sahin E Frackowiak and S Sadki High performance of symmetric micro-supercapacitors based on silicon nanowires using N-methyl-N-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide as electrolyte NanoEnergy 2014 httpdxdoiorg101016jnanoen201407001

colloidal diamond suspension in water with typical particle size of 5 nm was achieved while keeping the

integrity of the SiNWs (attachment to the substrate) Then the overgrowth with BDD with complete

coverage of SiNWs was successfully achieved by FHG and samples delivered to partners

Figure 1 (Left image) SEM image of SiNWs (Right image) SEM image of SiNTrs

23 - Electrolyte amp pseudocapacitance

SiNWs and diamond-coated Si nanowires (D-SiNWs) were successfully functionalized with

electroconducting polymers ECPs (polypyrrole PEDOT amp PAni) by CEA Electrodeposition of ECP films

on SiNWs was achieved with complete coverage Key factors such as polymerization charge and

deposition time allowed to control the thickness of the organic coating obtaining sub-micrometric

thickness However electropolymerisations of pyrrole and EDOT on pure diamond nanowires are limited

to the top of the surface Alternative electrochemical technique will be developed

1 aprotic IL and 8 protic ILs were tailor-made by IOLITEC Based on ESW thermal treatment and

electropolymerisation criteria aprotic and protic ILs were selected

Figure 2 (Left image) SEM image of conducting polymer (PEDOT)-coated silicon nanowires

(Right image) SEM image of PPy-coated diamondsilicon nanowires Inset cross sectional view of PPy on diamond coated SiNWs recorded at 45deg tilted angle

24 - Electrochemical characterization in a 3-electrode cell of materials (electrodes and electrolyte)

A starting set of 15 preselected aprotic ionic liquids (ILs) provided by IOLITEC was successively

restricted to 7 then 4 ILs taking into account a set of criteria (low viscosity high conductivity and high

electrochemical window and reflow treatment) compatible with the prepared electrodes (see above)

Electrochemical stability windows of ILs were not modified in the presence of silicon or diamond

nanostructures (ESW = 5-6 V) SiNWs exhibit almost perfect capacitance behavior reaching good values

(200-300microFcm2) The morphology of the SiNWs SiNTrs and D-SiNWs remained unchanged even after

millions of successive charge-discharge cycles

Figure 3 Structure of the electrochemical cell in a 3-electrode configuration

Symmetric micro-supercapacitors (2 electrodes in a face-to-face configuration) based on SiNWs and

SiNTs provide an excellent stability after 8106 galvanostatic charge-discharge curves with a loss of

capacitance of 25 in presence of PMPyrr BTA using a wide voltage of 4 V valid for applications

Pure diamond nanowires electrodes appear very promising in term of specific capacitance energy

density power (40 mWcm2) while keeping an outstanding electrochemical stability after millions of

galvanostatic cycles in presence of ion-conducting protic HN222BTA using a wide voltage of 4V Reflow

results (thermal treatment during 40s at 280degC) are very positive and ILs exhibit even better ESW after

reflow probably because of water trace elimination This opens a route to improve PEDOT coating

stability under cycling

25 - Assembling Setup amp prototype

Supercapacitor elementary cell (SPEC) using a sandwich type configuration (eg 2-stacked

electrodes) was designed to study the best combinations electrodeelectrolyte selected from the 3-

electrode cell set-up studies

The assembly in symmetrical set-ups decreases the capacitance strongly from 300-200 microFcm2 to 23

- 9 microFcm2 while the cell voltage remains good (4 V) These results reflect that optimization in the design

of the prototype is required Functionalized SiNWs (eg ECPs-coated SiNWs) showed similar tendencies

in both configurations

The capacitive properties of hybrid pseudo-capacitors (eg conducting polymer coated SiNWs) in a

2-electrode configuration in terms of specific capacitance (C = 11 mFcm2) power (P = 22 mJcm2) and

energy densities (E = 029 mWcm2) were found to present amazing results compared with SiNWs based

EDLCs C = 11 mFcm2 P = 22 mJcm

2 and E = 029 mWcm

2 respectively However cyclability and

operating voltage fall to 3500 cycles and 15 V respectively

Figure 4 Digital camera images showing the parts of the micro-supercapacitor prototype a) Structure of the cell b) Top and down view of the device and c) PEDOT coated-SiNWs electrodes for the

micro-supercapacitor device Scale bar 1 cm

Counter electrode Platinum

Working electrode SiNWsSiNTrsDiNWs

Reference electrode Ag Ag+

3 ndash Conclusions expected final results and potential impacts

Combinations of nano- Si and diamond-based electrodes with ILs and redox coatings have been

successfully obtained and demonstrate the expected synergetic effects to reach good supercapacitor

performances However in order to gather the remarkable cyclability (gt million cycles) of pure SiNWs D-

SiNWs or pure D-NWs electrodes with the amazing high capacitance of ECPs coatings further studies are

needed

Electrochemical experiments will be carried out in pre-thermally treated ILs Elimination of traces

of water and other volatile impurities may open the route to improve PEDOT and PPy stability under

cycling Development of further protic and aprotic ILs with selectively chosen chemical structures and

properties)

Alternative electrochemical techniques based on pulse polymerization are in progress in order to

get uniform organic coating on diamond nanowires in order to facilitate the diffusion of the species and

improve the nucleation sites

Reflow treatments carried out on pure Si electrodes demonstrate a remarkable stability of the

combinations of Si or diamond-based electrodes with ILs However some points must be deepened

The protic DEMA OTf optimal for PAni electrodeposition undergoes a color change during reflow

treatment Does this correspond to a change in the electrochemical properties for electrodepo-sition and

cycling Other new protic ILs recently synthesized by IOLITEC will be tested to challenge DEMA OTf

Reflow treatment in the presence of ECPs should be carried out

Diamond coated SiNWs (D-SINWs) electrodes present comparable cyclability to pure SiNWs-based

supercapacitors with the advantage to be used in more conductive protic ILs resulting in higher specific

capacitance and energy density

First experiments regarding mixtures of different ILs respective of ILs and organic solvents are

ongoing

Aqueous electrolytes (primary reason for involving diamond electrodes due to its high

overpotential towards water) should be tested with diamond-based substrates (D-SiNWs and pure

DNWs) to increase the power of the supercaps However in this case reflow treatment could not be

implemented

In the second part of the NEST project the two WPs dedicated to prototypes assembling and

performance characterizations will take off

Of course a feed-back will allow for continuing to select the best combination in order to comply

with the requirements specified in revised technical specifications

Packaging of SiNWs and sealing developments appear crucial with respect to ILs and SiNWs

integrity For the assembly of the prototype special attention should be given to avoid crushing of

SiNWs The design of the elementary cell will be examined either in a face-to-face or in an interdigitated

configuration (with may prevent SiNWs crushing)

References (selected) 1) D Aradilla G Bidan P Gentile P Weathers F Thissandier V Ruiz P Gomez-Romero T J Schubert

H Sahin and S Sadki Novel hybrid micro-ultracapacitor based on conducting polymer coated silicon nanowires for electrochemical energy storage RSC Adv 2014 4 26462

2) D Aradilla P Gentile G Bidan V Ruiz P Gomez-Romero T J Schubert H Sahin E Frackowiak and S Sadki High performance of symmetric micro-supercapacitors based on silicon nanowires using N-methyl-N-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide as electrolyte NanoEnergy 2014 httpdxdoiorg101016jnanoen201407001

Figure 3 Structure of the electrochemical cell in a 3-electrode configuration

Symmetric micro-supercapacitors (2 electrodes in a face-to-face configuration) based on SiNWs and

SiNTs provide an excellent stability after 8106 galvanostatic charge-discharge curves with a loss of

capacitance of 25 in presence of PMPyrr BTA using a wide voltage of 4 V valid for applications

Pure diamond nanowires electrodes appear very promising in term of specific capacitance energy

density power (40 mWcm2) while keeping an outstanding electrochemical stability after millions of

galvanostatic cycles in presence of ion-conducting protic HN222BTA using a wide voltage of 4V Reflow

results (thermal treatment during 40s at 280degC) are very positive and ILs exhibit even better ESW after

reflow probably because of water trace elimination This opens a route to improve PEDOT coating

stability under cycling

25 - Assembling Setup amp prototype

Supercapacitor elementary cell (SPEC) using a sandwich type configuration (eg 2-stacked

electrodes) was designed to study the best combinations electrodeelectrolyte selected from the 3-

electrode cell set-up studies

The assembly in symmetrical set-ups decreases the capacitance strongly from 300-200 microFcm2 to 23

- 9 microFcm2 while the cell voltage remains good (4 V) These results reflect that optimization in the design

of the prototype is required Functionalized SiNWs (eg ECPs-coated SiNWs) showed similar tendencies

in both configurations

The capacitive properties of hybrid pseudo-capacitors (eg conducting polymer coated SiNWs) in a

2-electrode configuration in terms of specific capacitance (C = 11 mFcm2) power (P = 22 mJcm2) and

energy densities (E = 029 mWcm2) were found to present amazing results compared with SiNWs based

EDLCs C = 11 mFcm2 P = 22 mJcm

2 and E = 029 mWcm

2 respectively However cyclability and

operating voltage fall to 3500 cycles and 15 V respectively

Figure 4 Digital camera images showing the parts of the micro-supercapacitor prototype a) Structure of the cell b) Top and down view of the device and c) PEDOT coated-SiNWs electrodes for the

micro-supercapacitor device Scale bar 1 cm

Counter electrode Platinum

Working electrode SiNWsSiNTrsDiNWs

Reference electrode Ag Ag+

3 ndash Conclusions expected final results and potential impacts

Combinations of nano- Si and diamond-based electrodes with ILs and redox coatings have been

successfully obtained and demonstrate the expected synergetic effects to reach good supercapacitor

performances However in order to gather the remarkable cyclability (gt million cycles) of pure SiNWs D-

SiNWs or pure D-NWs electrodes with the amazing high capacitance of ECPs coatings further studies are

needed

Electrochemical experiments will be carried out in pre-thermally treated ILs Elimination of traces

of water and other volatile impurities may open the route to improve PEDOT and PPy stability under

cycling Development of further protic and aprotic ILs with selectively chosen chemical structures and

properties)

Alternative electrochemical techniques based on pulse polymerization are in progress in order to

get uniform organic coating on diamond nanowires in order to facilitate the diffusion of the species and

improve the nucleation sites

Reflow treatments carried out on pure Si electrodes demonstrate a remarkable stability of the

combinations of Si or diamond-based electrodes with ILs However some points must be deepened

The protic DEMA OTf optimal for PAni electrodeposition undergoes a color change during reflow

treatment Does this correspond to a change in the electrochemical properties for electrodepo-sition and

cycling Other new protic ILs recently synthesized by IOLITEC will be tested to challenge DEMA OTf

Reflow treatment in the presence of ECPs should be carried out

Diamond coated SiNWs (D-SINWs) electrodes present comparable cyclability to pure SiNWs-based

supercapacitors with the advantage to be used in more conductive protic ILs resulting in higher specific

capacitance and energy density

First experiments regarding mixtures of different ILs respective of ILs and organic solvents are

ongoing

Aqueous electrolytes (primary reason for involving diamond electrodes due to its high

overpotential towards water) should be tested with diamond-based substrates (D-SiNWs and pure

DNWs) to increase the power of the supercaps However in this case reflow treatment could not be

implemented

In the second part of the NEST project the two WPs dedicated to prototypes assembling and

performance characterizations will take off

Of course a feed-back will allow for continuing to select the best combination in order to comply

with the requirements specified in revised technical specifications

Packaging of SiNWs and sealing developments appear crucial with respect to ILs and SiNWs

integrity For the assembly of the prototype special attention should be given to avoid crushing of

SiNWs The design of the elementary cell will be examined either in a face-to-face or in an interdigitated

configuration (with may prevent SiNWs crushing)

References (selected) 1) D Aradilla G Bidan P Gentile P Weathers F Thissandier V Ruiz P Gomez-Romero T J Schubert

H Sahin and S Sadki Novel hybrid micro-ultracapacitor based on conducting polymer coated silicon nanowires for electrochemical energy storage RSC Adv 2014 4 26462

2) D Aradilla P Gentile G Bidan V Ruiz P Gomez-Romero T J Schubert H Sahin E Frackowiak and S Sadki High performance of symmetric micro-supercapacitors based on silicon nanowires using N-methyl-N-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide as electrolyte NanoEnergy 2014 httpdxdoiorg101016jnanoen201407001

3 ndash Conclusions expected final results and potential impacts

Combinations of nano- Si and diamond-based electrodes with ILs and redox coatings have been

successfully obtained and demonstrate the expected synergetic effects to reach good supercapacitor

performances However in order to gather the remarkable cyclability (gt million cycles) of pure SiNWs D-

SiNWs or pure D-NWs electrodes with the amazing high capacitance of ECPs coatings further studies are

needed

Electrochemical experiments will be carried out in pre-thermally treated ILs Elimination of traces

of water and other volatile impurities may open the route to improve PEDOT and PPy stability under

cycling Development of further protic and aprotic ILs with selectively chosen chemical structures and

properties)

Alternative electrochemical techniques based on pulse polymerization are in progress in order to

get uniform organic coating on diamond nanowires in order to facilitate the diffusion of the species and

improve the nucleation sites

Reflow treatments carried out on pure Si electrodes demonstrate a remarkable stability of the

combinations of Si or diamond-based electrodes with ILs However some points must be deepened

The protic DEMA OTf optimal for PAni electrodeposition undergoes a color change during reflow

treatment Does this correspond to a change in the electrochemical properties for electrodepo-sition and

cycling Other new protic ILs recently synthesized by IOLITEC will be tested to challenge DEMA OTf

Reflow treatment in the presence of ECPs should be carried out

Diamond coated SiNWs (D-SINWs) electrodes present comparable cyclability to pure SiNWs-based

supercapacitors with the advantage to be used in more conductive protic ILs resulting in higher specific

capacitance and energy density

First experiments regarding mixtures of different ILs respective of ILs and organic solvents are

ongoing

Aqueous electrolytes (primary reason for involving diamond electrodes due to its high

overpotential towards water) should be tested with diamond-based substrates (D-SiNWs and pure

DNWs) to increase the power of the supercaps However in this case reflow treatment could not be

implemented

In the second part of the NEST project the two WPs dedicated to prototypes assembling and

performance characterizations will take off

Of course a feed-back will allow for continuing to select the best combination in order to comply

with the requirements specified in revised technical specifications

Packaging of SiNWs and sealing developments appear crucial with respect to ILs and SiNWs

integrity For the assembly of the prototype special attention should be given to avoid crushing of

SiNWs The design of the elementary cell will be examined either in a face-to-face or in an interdigitated

configuration (with may prevent SiNWs crushing)

References (selected) 1) D Aradilla G Bidan P Gentile P Weathers F Thissandier V Ruiz P Gomez-Romero T J Schubert

H Sahin and S Sadki Novel hybrid micro-ultracapacitor based on conducting polymer coated silicon nanowires for electrochemical energy storage RSC Adv 2014 4 26462

2) D Aradilla P Gentile G Bidan V Ruiz P Gomez-Romero T J Schubert H Sahin E Frackowiak and S Sadki High performance of symmetric micro-supercapacitors based on silicon nanowires using N-methyl-N-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide as electrolyte NanoEnergy 2014 httpdxdoiorg101016jnanoen201407001