Abstract
Sodium-ion batteries cannot employ graphite which is a typical negative electrode material for lithium-ion batteries. This is principally because sodium-ion cannot intercalate deeply into graphite, which has been a mystery for many years. Here, the mechanism of electrochemical sodium-ion intercalation into graphitic materials was investigated by using Raman spectroscopy and X-ray diffraction measurement to solve the question. Low stage sodium graphite intercalation compound (Na-GIC) was formed electrochemically only near the surface of graphite by potential holding above the sodium metal deposition potential. On the other hand, the high stage Na-GIC was formed electrochemically in the bulk at the sodium metal deposition potential. In addition, the apparent diffusion distance and the apparent diffusion coefficient of sodium-ion inside graphite were calculated using chronopotentiograms and potentiostatic intermittent titration technique. As a result, the sodium-ion diffusion inside spherical graphite was not slow enough to explain the limited reactivity. Hence, the limitation of sodium-ion intercalation into graphite might be originated from not the kinetic limitation inside graphite but the thermodynamic limitation.
Highlights
Sodium-ion batteries cannot employ graphite which is a typical negative electrode material for lithium-ion batteries
Reaction of intercalated species and graphite leads to graphite intercalation compounds (GICs), and the GICs can be prepared by various methods such as vapor method, chemical solution method, etc.[5]
To the best of our knowledge, this result is the first finding of the electrochemical formation of low stage Na-GICs even only near the surface of graphite above the sodium metal deposition potential
Summary
Sodium-ion batteries cannot employ graphite which is a typical negative electrode material for lithium-ion batteries This is principally because sodium-ion cannot intercalate deeply into graphite, which has been a mystery for many years. Large-scale applications of LIBs such as plug-in hybrid electric vehicles (HEV), electric vehicles (EV) and stationary power storages have attracted much attention principally due to the reduction of carbon dioxide For these applications, vast lithium must be consumed, resulting in the future shortage of lithium sources.[1]. Hard carbons are mainly used in SIBs and the reversible capacity was reported to be about 200 mA h g−1 .1,3,4 This is because the sodium-ion intercalation/deintercalation capacity of graphite was negligibly small.[2] If sodium-ion can be sufficiently intercalated into graphite, low cost and high volumetric energy density of SIBs can be fabricated.
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.
