Novel Electrolyte Systems for Improving Energy Density and Power Density of Li-O₂ Batteries

Abstract

Capacities and power density of Li-O 2 batteries are closed contacted with physical properties of electrolyte. In this work, we research the electrochemical performance of the mixed electrolyte between dimethylsulfoxide (DMSO) and N, N-dimethylacetamide (DMA), firstly. The cell with 70% of DMA mixed electrolyte exhibited high discharge rate capability and low over-potential that the charge platform is below 3.6V at a current density of 0.2 mA cm -2 . The titration result showed that DMA is more stable than DMSO in Li-O 2 batteries. It is because that the stability of high donor number (DN) solvent is less than that of the low DN solvent in Li-O 2 batteries, even though high DN solvent has a high discharge capacities. 1, 2 Based on this, we proposed a new strategy; namely, by combining a relative stable solvent with low DN and a stable additive as the cell electrolyte, the relationship between high capacity and high stability could be balanced. A novel type electrolyte additive, octamethylcyclotetrasiloxane (OMTS), is applied to Li-O 2 batteries with TEGDME-based electrolyte with low DN. The electrochemical tests show that, With an optimal OMTS content (10% OMTS), the cell displayed a discharge capacity of 6778 mAh g -1 at 0.05 mA cm -2 , and its discharge capacity still has an acceptable capacity of 1823mAh g -1 at an ultra-high current density of 1 mA cm -2 . Specially, the capacity retention of the cell with optimal OMTS content is more than double that of the cell with no OMTS additive at large current density of 1 mA cm -2 . The further NMR and Li 2 O 2 yield measurements during discharge indicate that OMTS additive does not alter the discharge product and compromise the stability of electrolyte. Figure 1

Key findings

• ▸The cell with 70% of DMA mixed electrolyte exhibited high discharge rate capability and low over-potential that the charge platform is below 3.
• ▸2 mA cm⁻².
• ▸The titration result showed that DMA is more stable than DMSO in Li-O₂ batteries.
• ▸The electrochemical tests show that, With an optimal OMTS content (10% OMTS), the cell displayed a discharge capacity of 6778 mAh g⁻¹ at 0.
• ▸05 mA cm⁻², and its discharge capacity still has an acceptable capacity of 1823mAh g⁻¹ at an ultra-high current density of 1 mA cm⁻².

Keywords

Identifiers

DOI

10.1149/ma2019-04/6/348

Journal

ECS Meeting Abstracts

Year

2019