22nd International Symposium on Plasma Chemistry
July 5-10, 2015; Antwerp, Belgium
Synthesis of beta alumina electrolyte films using atmospheric plasma coating
technology
B.J. Bladergroen and V. Linkov
South African Institute for Advanced Materials Chemistry, University of the Western Cape, Bellville, South Africa
Abstract: Atmospheric plasma coating technology can be used to synthesize thin,
impervious films of Beta Alumina onto porous metallic substrate. Such films have the
potential to reduce the production cost of utility scale energy storage devices to the price
point of the power generation industry.
Keywords: beta alumina coating, Na-conductive film, Na-based batteries
+
e-
e-
Fe  Fe2+ + 2e-
β-alumina
e-
2Na+ + 2e-  2Na
e-
Na+
Na+
Wick
Liquid Na
NaCl + Fe
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liquid Sodium (Na). As for any battery technology, the
anode and cathode are separated by an electrolyte that
does conduct ions but does not conduct electrons. The
principle of a battery that can potentially meet the cost
targets for utility scale energy storage devices is provided
in Figure 1.
Liquid NaAlCl4
1. Introduction on Energy Storage
Utility scale electrical energy storage (EES) is
becoming increasingly important for utilities around the
world. The increase in peak demand, increasing
congestion in transmission and distribution systems, the
need to provide grid ancillary services critical to the
efficient and reliable operation of the grid, and the
increase in the need for high quality, reliable power are all
primary drivers in this market [1].
The rise of global energy consumption and the high cost
(both financially and environmentally) of fossil fuels have
recently forced the diversification of energy sources to
include renewable energy and energy storage.
Considering the intermittency of renewable energy, the
cost of renewable generation and the construction of new
transmission facilities, energy storage proves to be a
promising alternative measure to combat these challenges.
Storage technologies such as pumped hydro storage
(PHS) and compressed air energy storage (CAES) are
commercially developed technologies performing at a
feasible price point and capacity, however, are severely
restricted in terms of the physical site requirements for
construction. Battery technologies don’t have these
limitations and can become an alternative for large scale
energy storage.
Independent studies on the market prospects for the
various battery technologies show that the international
market for advanced batteries for utility energy storage
will grow into a multi-billion dollar industry within the
next few years [2]. Navigant research expects Li-ion
batteries to be a market leader at least until 2020,
however, it is expected that market position of batteries
designed for the utility market in particular is strongly
linked to the cost of their raw materials meaning that
batteries made from inherently cheap raw materials are
expected to become most competitive.
The Sodium Iron Chloride battery (Na-FeCl 2 ) has the
potential to meet the required cost targets, as is consists of
cost effective and abundant materials that provide the
electrochemical storage capacity. The cathode of this
battery consists of a mixture of Sodium Chloride (NaCl)
and Iron Chloride (FeCl 2 ), the anode is composed of
Fig. 1. Schematic overview of a Na-FeCl 2 battery cell
Zhaoyin Wen et al. has given a comprehensive
overview of achievements with regard to Na-based
battery research and development [3].
2. Market for low cost Na-conductive electrolyte
The electrolyte of choice for various Na-based batteries
is beta alumina, and preferably β''-Alumina (beta primeprime alumina) which is an isomorphic form of
aluminium oxide (Al 2 O 3 ).
To minimize the internal battery resistance, the
electrolyte layer needs to be as thin as possible. Despite
this desired requirement, commercially available Nabased batteries use self-supported Beta Alumina
electrolyte that are typically 1000 – 1500 micron thick.
Thinner layer simply do not provide the required
mechanical stability. The use of porous substrates
supporting thinner layers of beta alumina has been
considered, but adds to production process complexity.
The very high processing temperatures (1600 oC) required
to obtain dense and ion conductive beta alumina
separators are a serious drawback when the aim is to
produce low cost energy storage devices.
1
3. Atmospheric plasma coating technology
Research is currently being conducted to synthesize
Beta Alumina onto porous substrates that are far easier to
seal than self-supported ceramic components. The
synthesis process is orders of magnitude fasted and does
not require complicated and long thermal treatments. Less
material is required and lower internal battery resistance
is expected.
The use of atmospheric plasma coating for the synthesis
of beta alumina electrolyte films offers an opportunity for
drastic cost reduction of the thermal battery electrolyte
component.
More details about the equipment and how it is used to
synthesis beta alumina electrolyte films will be provided
during the conference. Figure 2 shows a photographic
image of the atmospheric plasma spray process.
Fig. 2. Atmospheric Plasma coating of Beta alumina onto
porous SS
4. Acknowledgement
The authors would like to acknowledge the Department of
Science and Technology for their financial contribution
through the High-end Infrastructure Development
programme.
5. References
[1] Rastler, D. Electric Power Research Institute, 2010.
[2] S. Jaffe and K.-A. Adamson, Navigant Research 2014.
[3] Zhaoyin Wen, Yingying Hu, Xiangwei Wu, Jinduo
Han and Zhonghua Gu. Adv Funct Mater. 23 (2013)
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