The development of sodium-ion batteries (SIBs) is hindered by the low working voltage, and poor rate and cycling performance. Although great efforts have been made, the application of SIBs is still a challenge.
Our group has developed a multi-ion strategy for sodium-ion full batteries. In this design, expanded graphite and Sn foil were used as the cathode and anode, respectively. A hybrid electrolyte containing Na+, Li+, and PF6- ions were designed. The optimized full batteries delivered a high working voltage of about 4.0 V, which is one of the best results of reported sodium-ion full batteries due to the high intercalation potential of PF6- anions. Moreover, good rate performance up to 30 C and high cycling stability over 500 cycles at 5 C (capacity retention of 95%) were also achieved, which was attributed to the reduced charge transfer resistance and the volume expansion by hybridizing lithium ions with small ionic radius. This work provided a novel strategy to enhance the electrochemical performance of SIBs. This study, entitled "A Multi-Ion Strategy towards Rechargeable Sodium-Ion Full Batteries with High Working Voltage and Rate Capability," was published online in Angewandte Chemie International Edition as cover paper.
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