Ultralow-concentration electrolyte for lithium-ion batteries
Lithium salts make batteries powerful but expensive. An ultralow-concentration electrolyte based on the lithium
salt LiDFOB may be a more economical and more sustainable alternative.
Cells using these electrolytes and conventional electrodes have been
demonstrated to have high performance, as reported by a research team to
the journal Angewandte Chemie. In addition, the electrolyte could
facilitate both production and recycling of the batteries.
© Wiley-VCH, re-use with credit to 'Angewandte Chemie' and a link to the original article.
Lithium-ion batteries (LIBs) provide power to smartphones
and tablets, drive electric vehicles, and store electricity at power
plants. The main components of most LIBs are lithium cobalt oxide (LCO)
cathodes, graphite anodes, and liquid electrolytes that deliver mobile
ions for the decoupled cathode and anode reactions. These electrolytes
determine the properties of the interphase layer that forms on the
electrodes and thus affect features such as battery cycling performance.
However, commercial electrolytes are still mostly based on a system
formulated over 30 years ago: 1.0 to 1.2 mol/L lithium
hexafluorophosphate (LiPF6) in carboxylic acid esters
(“carbonate solvent”). Over the last ten years, high-concentration
electrolytes (> 3 mol/L) have been developed, increasing battery
performance by favoring the formation of robust inorganic-dominated
interphase layers. However, these electrolytes have high viscosity, poor
wetting ability, and inferior conductivity. The large amounts of lithium
salts required also make them very expensive, often a critical parameter
for feasibility. To reduce costs, research has also begun into
ultralow-concentration electrolytes (< 0.3 mol/L). The drawback for
these has been that the battery cell decomposes more solvent than the
few salt anions, which leads to an organic-dominated and less stable
interphase layer.
A team led by Jinliang Yuan, Lan Xia, and Xianyong Wu at
Ningbo University (China) and the University of Puerto Rico-Rio Piedras
Campus (USA) has now developed an ultralow-concentration electrolyte
that may be suitable for practical application in lithium-ion batteries:
LiDFOB/EC-DMC. LiDFOB (lithium difluoro(oxalato)borate) is a common
additive and significantly cheaper than LiPF6. EC-DMC (ethyl
carbonate/dimethyl carbonate) is a commercial carbonate solvent. The
electrolyte has a potentially record-breaking low salt content of 2
weight percent (0.16 mol/L) but a sufficiently high ionic conductivity
(4.6 mS/cm) to operate a battery. In addition, the properties of the DFOB–
anions allow for the formation of an inorganic-dominated, robust
interphase layer on LCO and graphite electrodes, resulting in
outstanding cycling stability in half and full cells.
While the LiPF6 in current use decomposes in the
presence of moisture, releasing highly toxic and corrosive hydrogen
fluoride gas (HF), LiDFOB is water- and air-stable. Instead of strict
dry room conditions, LIBs with LiDFOB can be made under ambient
conditions—an additional cost-saving feature. Recycling would also be
significantly less problematic and lead to more sustainability.
(3174 characters)
About the Author
Dr Lan Xia is an Associate Professor at Ningbo University
and has been working in the rechargeable batteries area for over 15
years. Her research focuses on the smart thermal-responsive strategies
for lithium-ion batteries as well as design, synthesis and
characterization of potential electrolyte solvents and electrolyte
additives for batteries.
Copy free of charge—we would appreciate a transcript/link of your
article. The original articles that our press releases are based on can
be found in our online pressroom.