# Enhancing electrochemical intermediate solvation through electrolyte anion selection to increase nonaqueous Li-O$_2$ battery capacity

**Authors:** Colin M. Burke, Vikram Pande, Abhishek Khetan, Venkatasubramanian Viswanathan, Bryan D. McCloskey  
**arXiv:** [1503.07925](https://arxiv.org/abs/1503.07925)  
**Date:** 2015-03-26  
**Summary page:** https://www.summarizepaper.com/en/paper/1503.07925v1/

## Key points

- Nonaqueous Li-O$_2$ batteries are promising due to high theoretical specific energy
- Challenge: lithium peroxide passivates battery cathode, reducing cell capacities
- Study by Colin M. Burke et al.: Selecting appropriate salt anion in electrolyte solution can enhance Li-O$_2$ cell capacity four-fold
- Enhancement attributed to increased stability of Li$^+$ ions in solution, promoting solubility of intermediates and formation of Li$_2$O$_2$
- Breakthrough strategy mitigates need for electrolyte solvent with conflicting properties, paving way for high-capacity and rechargeable batteries
- Implications extend beyond Li-O$_2$ batteries to enhancing Coulombic efficiency in various electrochemical systems, such as Li-S batteries

## Summary

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In the realm of 'beyond Li-ion' battery technologies, nonaqueous Li-O$_2$ batteries have emerged as a promising candidate due to their exceptionally high theoretical specific energy. However, one major hurdle in their development lies in the electronically insulating nature of the primary discharge product, lithium peroxide. This compound tends to passivate the battery cathode upon formation, leading to diminished overall cell capacities. Recent efforts have focused on enhancing solubility to address this challenge, but existing strategies often compromise the electrochemical stability of the system, thereby impacting battery rechargeability. In a groundbreaking study by Colin M. Burke and colleagues, it was demonstrated that selecting the appropriate salt anion in the electrolyte solution can lead to a remarkable improvement in Li-O$_2$ cell capacity – exceeding four-fold enhancement. Through a combination of $^7$Li nuclear magnetic resonance and modeling techniques, the researchers confirmed that this enhancement is attributed to increased stability of Li$^+$ ions in solution. This enhanced stability subsequently promotes solubility of intermediates, facilitating the formation of Li$_2$O$_2$. By leveraging this novel strategy, researchers can mitigate the arduous task of identifying an electrolyte solvent with conflicting properties – high intermediate solubility and solvent stability. This breakthrough paves the way for developing an electrolyte that not only offers high capacity but also ensures rechargeability. The implications of this research extend beyond nonaqueous Li-O$_2$ batteries; it presents a generalizable model and strategy that could enhance Coulombic efficiency in various electrochemical systems. For instance, applications in Li-S batteries where improving intermediate stability in solution could trigger desired mechanisms of product formation are foreseeable. The findings from this study published in Proc. Natl. Acad. Sci. U S A hold significant promise for advancing next-generation energy storage technologies towards higher performance and sustainability goals.