Abstract
Reversibility of an electrode reaction is important for energy-efficient rechargeable batteries with a long battery life. Additional oxygen-redox reactions have become an intensive area of research to achieve a larger specific capacity of the positive electrode materials. However, most oxygen-redox electrodes exhibit a large voltage hysteresis >0.5 V upon charge/discharge, and hence possess unacceptably poor energy efficiency. The hysteresis is thought to originate from the formation of peroxide-like O22− dimers during the oxygen-redox reaction. Therefore, avoiding O-O dimer formation is an essential challenge to overcome. Here, we focus on Na2-xMn3O7, which we recently identified to exhibit a large reversible oxygen-redox capacity with an extremely small polarization of 0.04 V. Using spectroscopic and magnetic measurements, the existence of stable O−• was identified in Na2-xMn3O7. Computations reveal that O−• is thermodynamically favorable over the peroxide-like O22− dimer as a result of hole stabilization through a (σ + π) multiorbital Mn-O bond.
Highlights
Reversibility of an electrode reaction is important for energy-efficient rechargeable batteries with a long battery life
As energy efficiency is crucial for energy storage devices, the voltage hysteresis of oxygen-redox electrodes should be addressed for their practical application
The emergence of a new emission peak at 523 eV in the resonant inelastic Xray scattering (RIXS) spectrum for charged Na2-xMn3O7 is typical for charged oxygen-redox electrodes[5,24,28,39,40]
Summary
Reversibility of an electrode reaction is important for energy-efficient rechargeable batteries with a long battery life. Most oxygen-redox electrodes exhibit a large voltage hysteresis >0.5 V upon charge/discharge, and possess unacceptably poor energy efficiency. The hysteresis is thought to originate from the formation of peroxide-like O22− dimers during the oxygen-redox reaction. 1234567890():,; Lithium-ion batteries are presently the de facto standard power sources for portable electronic devices and electric vehicles due to their high energy density and efficiency relying on intercalation chemistry, whereby a host electrode material reversibly accommodates lithium ions without a large structural change[1,2,3]. Lithium-rich transition metal oxides (Li1+xM1-xO2, M = transition metal) are promising large-capacity positive electrode materials for lithium-ion batteries, as they exhibit accumulative redox reactions of M and O4–6. As energy efficiency is crucial for energy storage devices, the voltage hysteresis of oxygen-redox electrodes should be addressed for their practical application
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
