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Sodium Borates: Expanding the Electrolyte Selection for Sodium-Ion Batteries.

Published version
Peer-reviewed

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Authors

Ould, Darren MC 
Riesgo-Gonzalez, Victor  ORCID logo  https://orcid.org/0000-0002-2433-8562

Abstract

Sodium-ion batteries (SIBs) are a promising grid-level storage technology due to the abundance and low cost of sodium. The development of new electrolytes for SIBs is imperative since it impacts battery life and capacity. Currently, sodium hexafluorophosphate (NaPF6 ) is used as the benchmark salt, but is highly hygroscopic and generates toxic HF. This work describes the synthesis of a series of sodium borate salts, with electrochemical studies revealing that Na[B(hfip)4 ]⋅DME (hfip=hexafluoroisopropyloxy, Oi PrF ) and Na[B(pp)2 ] (pp=perfluorinated pinacolato, O2 C2 (CF3 )4 ) have excellent electrochemical performance. The [B(pp)2 ]- anion also exhibits a high tolerance to air and water. Both electrolytes give more stable electrode-electrolyte interfaces than conventionally used NaPF6 , as demonstrated by impedance spectroscopy and cyclic voltammetry. Furthermore, they give greater cycling stability and comparable capacity to NaPF6 for SIBs, as shown in commercial pouch cells.

Description

Keywords

Batteries, Electrolytes, Main Group Synthesis, SEI, Sodium-Ion Batteries

Journal Title

Angew Chem Int Ed Engl

Conference Name

Journal ISSN

1433-7851
1521-3773

Volume Title

Publisher

Wiley
Sponsorship
European Commission Horizon 2020 (H2020) ERC (835073)