Budou nové Pb Aku

[Jaroslav Lukeš]

Aqueous batteries, such as the lead–acid and vanadium-redox-flow
types, display restricted volumetric energy densities (less than 100
watt-hours per litre)1,2, lagging far behind non-aqueous lithium-ion
batteries (300–400 watt-hours per litre)3,4. The primary reason for
this inferiority is the narrow electrochemical stability window of water,
which limits the operational voltage of aqueous batteries. In attempts
to overcome this limitation, research has focused on important param-
eters such as the charge-storing site and the number of electrons trans-
ferred per redox-active material unit, for example. However, these
attempts have frequently encountered problems related to sluggish
electrochemical and chemical reactions, leading to recharge failures.
Now, writing in Nature Energy, Xianfeng Li and colleagues5 at the
Dalian Institute of Chemical Physics and the University of Chinese
Academy of Sciences address this kinetics challenge by demonstrating
a fast iodide/iodate (I−/IO3−) redox process at the positive electrode
(catholyte) of an aqueous flow battery. The key aspect of their work
is the utilization of a hetero-halogen electrolyte containing I− and Br−,
facilitating multiple electron transfers as I− converts to I5+ (representing
the formal charge of IO3−). This battery also benefits from a high concen-
tration of redox species (6 molar I−), resulting in high energy density.

These hetero-halogen systems showcase very high capacity. Cou-
pling a 6 molar I− plus 1 molar Br − electrolyte with a Cd/Cd2+ anolyte,
Li and colleagues showed that their cell delivers a specific capacity
of around 850 ampere-hour per litre. They estimate an energy den-
sity of approximately 1,200 watt-hours per litre for a half-cell with
hetero-halogen species. To avoid Cd plating on the negative electrode,
the team also tested silicotungstic acid or vanadium ions in the anolyte
and demonstrated their potential use in aqueous batteries.

 From a techno-economic perspective, Li and colleagues estimate
their I−/IO3− systems to be approximately four times less expensive than
LiFePO4 in lithium-ion batteries. However, there could be a scarcity of
suitable counterpart electrolytes at the negative electrode. For exam-
ple, silicotungstic acid or vanadium ions have lower solubility and lower
numbers of electron transfer than I−/IO3−, necessitating high volumes
of anolyte to operate the full cell. Consequently, this requirement leads
to increased overall costs.

https://doi.org/10.1038/s41560-024-01514-w
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