(47c) Negative Electrolyte Additive and Heteroatom Co-Doping of Positive Electrode for Improving Electrical Performance of Vanadium Redox Flow Battery

Negative
Electrolyte Additive and Heteroatom Co-Doping of Positive Electrode for
Improving Electrical Performance of Vanadium Redox Flow Battery

Abstract

Photovoltaics, wind and nuclear power are the sources
for satisfying the energy need of the growing economy.  The renewable energy technologies feeds
significant electricity to the grid intermittently and hence effective energy
storage technologies are required for load shifting.  Redox flow batteries (RFBs) is an energy
storage technology revisited for the above said purpose.  Among RFBs, vanadium redox flow battery
(VRFB) is the most matured in terms of development and deployment.

However, it is suffering with issues like low capacity
retention ADDIN EN.CITE  ADDIN EN.CITE.DATA 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¹ 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3C2F75726C733E3C656C656374726F6E69632D7265736F757263652D6E756D3E31302E313032312F616D353034363432323C2F656C656374726F6E69632D7265736F757263652D6E756D3E3C2F7265636F72643E3C2F436974653E3C2F456E644E6F74653E00
and poor round-trip energy efficiency (EE). EE is a
product of coulombic and voltage efficiency (VE). To address these issues,
researchers have tried various additives to the positive electrolyte ADDIN EN.CITE
<EndNote><Cite><Author>Corcuera</Author><Year>2012</Year><RecNum>4</RecNum><DisplayText><style and electrolyte rebalancing methods for the vanadium redox flow
battery</title><secondary-title>European Chemical
Bulletin</secondary-title></titles><periodical><full-title>European
Chemical
Bulletin</full-title></periodical><pages>511-519</pages><volume>1</volume><number>12</number><dates><year>2012</year></dates><urls></urls></record></Cite></EndNote>² and electrode activation strategies ADDIN EN.CITE
<EndNote><Cite><Author>Wu</Author><Year>2016</Year><RecNum>5</RecNum><DisplayText><style db-id="t55rvpwf85zw9weptavpaxzsradpxfv0vsew">5</key></foreign-keys><ref-type
name="Journal
Article">17</ref-type><contributors><authors><author>Wu,
Lantao</author><author>Shen, Yi</author><author>Yu,
Lihong</author><author>Xi, Jingyu</author><author>Qiu,
Xinping</author></authors></contributors><titles><title>Boosting
vanadium flow battery performance by nitrogen-doped carbon nanospheres
electrocatalyst</title><secondary-title>Nano
Energy</secondary-title></titles><periodical><full-title>Nano
Energy</full-title></periodical><pages>19-28</pages><volume>28</volume><dates><year>2016</year></dates><isbn>2211-2855</isbn><urls></urls></record></Cite><Cite><Author>Kabtamu</Author><Year>2016</Year><RecNum>3</RecNum><record><rec-number>3</rec-number><foreign-keys><key
app="EN"
db-id="t55rvpwf85zw9weptavpaxzsradpxfv0vsew">3</key></foreign-keys><ref-type
name="Journal
Article">17</ref-type><contributors><authors><author>Kabtamu,
Daniel Manaye</author><author>Chen,
Jian-Yu</author><author>Chang,
Yu-Chung</author><author>Wang,
Chen-Hao</author></authors></contributors><titles><title>Electrocatalytic
activity of Nb-doped hexagonal WO3 nanowire-modified graphite felt as a
positive electrode for vanadium redox flow batteries</title><secondary-title>Journal
of Materials Chemistry
A</secondary-title></titles><periodical><full-title>Journal
of Materials Chemistry
A</full-title></periodical><pages>11472-11480</pages><volume>4</volume><number>29</number><dates><year>2016</year></dates><publisher>The
Royal Society of Chemistry</publisher><isbn>2050-7488</isbn><work-type>10.1039/C6TA03936G</work-type><urls><related-urls><url>http://dx.doi.org/10.1039/C6TA03936G</url></related-urls></urls><electronic-resource-num>10.1039/C6TA03936G</electronic-resource-num></record></Cite></EndNote>³.
Sources of capacity fade is multitude, namely (i) H₂ evolution at
negative electrode, (ii) V₂O₅ precipitation due to
thermal instability of positive electrolyte, (iii) and the self-discharge due
to the reaction between positive and negative electrolyte via membrane
crossover. But, most of the organic additives are for the positive electrolyte and
they are not stable in highly oxidising condition of VO₂⁺.
 For the first time, we have explored
an organic additive, D-fructose, to the negative electrolyte and arrested the
capacity fade significantly ADDIN EN.CITE
<EndNote><Cite><Author>Pasala</Author><Year>2017</Year><RecNum>2</RecNum><DisplayText><style Redox Balancing of Vanadium Redox Flow Battery Using D-Fructose
as Negative Electrolyte
Additive</title><secondary-title>ChemistrySelect</secondary-title></titles><periodical><full-title>ChemistrySelect</full-title></periodical><pages>720-727</pages><volume>2</volume><number>2</number><keywords><keyword>D-fructose</keyword><keyword>fructose
crossover</keyword><keyword>hydrogen evolution</keyword><keyword>negative
electrolyte</keyword><keyword>vanadium redox flow
battery.</keyword></keywords><dates><year>2017</year></dates><isbn>2365-6549</isbn><urls><related-urls><url>http://dx.doi.org/10.1002/slct.201601417</url></related-urls></urls><electronic-resource-num>10.1002/slct.201601417</electronic-resource-num></record></Cite></EndNote>⁴ mainly targeting H₂ evolution and
self-discharge.

Recently we are studying N and P co-doped carbon derived
from microcrystalline cellulose as a catalyst for the positive electrode and
enhanced the EE and VE by 7.7 and 6.8 %, respectively.  We have demonstrated 50 continuous cycles
with minimal (< 5 %) capacity fade. In this presentation, optimization of N
and P co-doping, effect of D-fructose in negative electrode kinetics and
capacity retention, and flow battery performance optimization would be
discussed in detail.  1.5 M VO²⁺
in 2.5 M H₂SO₄ and 1.5 M V³⁺ in 2.5 M H₂SO₄
are used as catholyte and anolyte respectively during charging in a 50 cm²
VRFB cell.  The average
state-of-charge (SOC) of the VRFB was around 70 % with a cut-off voltages of
1.6 V and 0.8 V during charging and discharging, respectively.   Fig. 1 compares the capacity
retention for the VRFB constructed using carbon felt positive electrode, and N
and P co-doped carbon based positive electrode (with and without Fructose
additive used in the negative electrolyte).  As can be seen, there is a tremendous
improvement in the capacity retention.

Capacity retention plot of VRFB constructed using
positive electrode made of (a) carbon felt, (b) N and P co-doped carbon felt,
(c) N and P co-doped carbon felt with D-fructose in the negative electrolyte.

References

 ADDIN EN.REFLIST 1.              Jia,
C.; Liu, Q.; Sun, C.-J.; Yang, F.; Ren, Y.; Heald, S. M.; Liu, Y.; Li, Z.-F.;
Lu, W.; Xie, J., In Situ X-ray Near-Edge Absorption Spectroscopy Investigation
of the State of Charge of All-Vanadium Redox Flow Batteries. ACS Applied Materials & Interfaces 2014, 6 (20), 17920-17925.

2.              Corcuera,
S.; Skyllas-Kazacos, M., State-of-charge monitoring and electrolyte rebalancing
methods for the vanadium redox flow battery. European Chemical Bulletin 2012,
1 (12), 511-519.

3.              (a)
Wu, L.; Shen, Y.; Yu, L.; Xi, J.; Qiu, X., Boosting vanadium flow battery
performance by nitrogen-doped carbon nanospheres electrocatalyst. Nano Energy 2016, 28, 19-28; (b) Kabtamu, D. M.; Chen, J.-Y.; Chang,
Y.-C.; Wang, C.-H., Electrocatalytic activity of Nb-doped hexagonal WO3
nanowire-modified graphite felt as a positive electrode for vanadium redox flow
batteries. Journal of Materials Chemistry
A 2016, 4 (29), 11472-11480.

4.              Pasala,
V.; Ramanujam, K., On In–situ Redox Balancing of Vanadium Redox Flow Battery
Using D-Fructose as Negative Electrolyte Additive. ChemistrySelect 2017, 2 (2), 720-727.