Adjusting the state of pitch anode for effective oxidation with suppressed graphitization and enhanced Na storage performances

作者：Li, Fangyu; Tao, Huachao; Yang, Xuelin^*

来源：IONICS, 2022, 28(11): 5141-5151.

DOI：10.1007/s11581-022-04734-w

• Incompletely carbonized pitch
• Sodium-ion battery
• Oxidation
• Suppressed graphitization
• Enhanced electrochemical performances

Pitch has captured extensive interest as an anode material for sodium-ion batteries due to the abundant resources, low cost, and improvable reversible capacity through oxidation; however, not all the oxidations are effective. Here, a precise low-temperature pyrolysis strategy is successfully adopted to affirm the effective oxidation precursor. The results indicate that adjusting the state of pitch before oxidation can realize different structural conversions and Na storage performances during high-temperature carbonization. Carbonized pristine pitch (P-1400) and carbonized oxidized pitch, whose precursor is pyrolyzed at 600 degrees C (P600-N+S-1400), both show graphite-like microcrystallite structures and deliver reversible capacities 92.4 and 93.1 mAh g(-1 )(at 20 mA g(-1)) with 48.8 and 47.6% initial coulombic efficiencies, respectively. In comparison, carbonized oxidized pitch, whose precursor is pyrolyzed at 400 degrees C (P400-N+S-1400), displays a typical amorphous structure and increases the reversible capacity to 315.1 mAh g(-1) (at 20 mA g(-1)) with 61.4% initial coulombic efficiency. Only incompletely carbonized pitch can have effective oxidation with suppressed graphitization and enhanced electrochemical performances.