LiNO3is a widely used salt‐additive that markedly improves the stability of ether‐based electrolytes at a Li metal anode but is generally regarded as incompatible with alkyl carbonates. Here we find that contrary to common wisdom, cyclic carbonate solvents such as ethylene carbonate can dissolve up to 0.7 M LiNO3without any additives, largely improving the anode reversibility. We demonstrate the significance of our findings by upgrading various state‐of‐the‐art carbonate electrolytes with LiNO3, which provides large improvements in batteries composed of thin lithium (50 μm) anode and high voltage cathodes. Capacity retentions of 90.5 % after 600 cycles and 92.5 % after 200 cycles are reported for LiNi0.6Mn0.2Co0.2O2(2 mAh cm−2, 0.5 C) and LiNi0.8Mn0.1Co0.1O2cathode (4 mAh cm−2, 0.2 C), respectively. 1 Ah pouch cells (≈300 Wh kg−1) retain more than 87.9 % after 100 cycles at 0.5 C. This work illustrates that reforming traditional carbonate electrolytes provides a scalable, cost‐effective approach towards practical LMBs.
In the presence of Lewis acid salts, the cyclic ether, dioxolane (DOL), is known to undergo ring-opening polymerization inside electrochemical cells to form solid-state polymer batteries with good interfacial charge-transport properties. Here we report that LiNO3, which is unable to ring-open DOL, possesses a previously unknown ability to coordinate with and strain DOL molecules in bulk liquids, completely arresting their crystallization. The strained DOL electrolytes exhibit physical properties analogous to amorphous polymers, including a prominent glass transition, elevated moduli, and low activation entropy for ion transport, but manifest unusually high, liquidlike ionic conductivities (e.g., 1 mS/cm) at temperatures as low as −50 °C. Systematic electrochemical studies reveal that the electrolytes also promote reversible cycling of Li metal anodes with high Coulombic efficiency (CE) on both conventional planar substrates (1 mAh/cm2over 1,000 cycles with 99.1% CE; 3 mAh/cm2over 300 cycles with 99.2% CE) and unconventional, nonplanar/three-dimensional (3D) substrates (10 mAh/cm2over 100 cycles with 99.3% CE). Our finding that LiNO3promotes reversibility of Li metal electrodes in liquid DOL electrolytes by a physical mechanism provides a possible solution to a long-standing puzzle in the field about the versatility of LiNO3salt additives for enhancing reversibility of Li metal electrodes in essentially any aprotic liquid electrolyte solvent. As a first step toward understanding practical benefits of these findings, we create functional Li||lithium iron phosphate (LFP) batteries in which LFP cathodes with high capacity (5 to 10 mAh/cm2) are paired with thin (50 μm) lithium metal anodes, and investigate their galvanostatic electrochemical cycling behaviors.
more » « less- NSF-PAR ID:
- 10196763
- Publisher / Repository:
- Proceedings of the National Academy of Sciences
- Date Published:
- Journal Name:
- Proceedings of the National Academy of Sciences
- Volume:
- 117
- Issue:
- 42
- ISSN:
- 0027-8424
- Page Range / eLocation ID:
- p. 26053-26060
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract LiNO3is a widely used salt‐additive that markedly improves the stability of ether‐based electrolytes at a Li metal anode but is generally regarded as incompatible with alkyl carbonates. Here we find that contrary to common wisdom, cyclic carbonate solvents such as ethylene carbonate can dissolve up to 0.7 M LiNO3without any additives, largely improving the anode reversibility. We demonstrate the significance of our findings by upgrading various state‐of‐the‐art carbonate electrolytes with LiNO3, which provides large improvements in batteries composed of thin lithium (50 μm) anode and high voltage cathodes. Capacity retentions of 90.5 % after 600 cycles and 92.5 % after 200 cycles are reported for LiNi0.6Mn0.2Co0.2O2(2 mAh cm−2, 0.5 C) and LiNi0.8Mn0.1Co0.1O2cathode (4 mAh cm−2, 0.2 C), respectively. 1 Ah pouch cells (≈300 Wh kg−1) retain more than 87.9 % after 100 cycles at 0.5 C. This work illustrates that reforming traditional carbonate electrolytes provides a scalable, cost‐effective approach towards practical LMBs.
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