High-performance sodium–organic battery by realizing four-sodium storage in disodium rhodizonate. Issue 11 (November 2017)

• Record Type: Journal Article
• Authors: Lee, Minah; Hong, Jihyun; Lopez, Jeffrey; Sun, Yongming; Feng, Dawei; Lim, Kipil; Chueh, William; Toney, Michael; Cui, Yi; Bao, Zhenan
• Is Part Of: Nature energy. Volume 2: Issue 11(2017)
• Page Start: 861
• Page End: 868
• Publication Date: 2017-11
• Subjects: Power resources -- Periodicals; Energy development -- Periodicals; Renewable energy sources -- Periodicals; Energy policy -- Periodicals; Electric power systems -- Periodicals; 333.7905
• DOI: 10.1038/s41560-017-0014-y
• Languages: English
• ISSNs: 2058-7546

Abstract

Abstract Sodium-ion batteries (SIBs) for grid-scale applications need active materials that combine a high energy density with sustainability. Given the high theoretical specific capacity 501 mAh g−1, and Earth abundance of disodium rhodizonate (Na2 C6 O6 ), it is one of the most promising cathodes for SIBs. However, substantially lower reversible capacities have been obtained compared with the theoretical value and the understanding of this discrepancy has been limited. Here, we reveal that irreversible phase transformation of Na2 C6 O6 during cycling is the origin of the deteriorating redox activity of Na2 C6 O6 . The active-particle size and electrolyte conditions were identified as key factors to decrease the activation barrier of the phase transformation during desodiation. On the basis of this understanding, we achieved four-sodium storage in a Na2 C6 O6 electrode with a reversible capacity of 484 mAh g−1, an energy density of 726 Wh kg−1 cathode, an energy efficiency above 87% and a good cycle retention. Sodium-ion batteries are a cost-effective alternative to lithium-ion for large-scale energy storage. Here Bao et al. develop a cathode based on biomass-derived ionic crystals that enables a four-sodium ion storage mechanism leading to exceptionally high specific capacity and energy density.