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Issue 23, 2020
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Approaching the voltage and energy density limits of potassium–selenium battery chemistry in a concentrated ether-based electrolyte

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Abstract

Potassium–selenium (K–Se) batteries offer fairly high theoretical voltage (∼1.88 V) and energy density (∼1275 W h kgSe−1). However, in practice, their operation voltage is so far limited to ∼1.4 V, resulting in insufficient energy utilization and mechanistic understanding. Here, it is demonstrated for the first time that K–Se batteries operating in concentrated ether-based electrolytes follow distinctive reaction pathways involving reversible stepwise conversion reactions from Se to K2Sex (x = 5, 3, 2, 1). The presence of redox intermediates K2Se5 at ∼2.3 V and K2Se3 at ∼2.1 V, in contrast with previous reports, enables record-high average discharge plateau voltage (1.85 V) and energy density (998 W h kgSe−1 or 502 W h kgK2Se−1), both approaching the theoretical limits and surpassing those of previously reported Na/K/Al–Se batteries. Moreover, experimental analysis and first-principles calculations reveal that the effective suppression of detrimental polyselenide dissolution/shuttling in concentrated electrolytes, together with high electron conductibility of Se/K2Sex, enables fast reaction kinetics, efficient utilization of Se, and long-term cyclability of up to 350 cycles, which are impracticable in either K–S counterparts or K–Se batteries with low/moderate-concentration electrolytes. This work may pave the way for mechanistic understanding and full energy utilization of K–Se battery chemistry.

Graphical abstract: Approaching the voltage and energy density limits of potassium–selenium battery chemistry in a concentrated ether-based electrolyte

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Supplementary files

Article information


Submitted
11 Mar 2020
Accepted
23 May 2020
First published
25 May 2020

This article is Open Access
All publication charges for this article have been paid for by the Royal Society of Chemistry

Chem. Sci., 2020,11, 6045-6052
Article type
Edge Article

Approaching the voltage and energy density limits of potassium–selenium battery chemistry in a concentrated ether-based electrolyte

Q. Liu, W. Deng, Y. Pan and C. Sun, Chem. Sci., 2020, 11, 6045
DOI: 10.1039/D0SC01474E

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