Facilitating Tetrafluoroborate Intercalation into Graphite Electrodes from Ethylmethyl Carbonate‐Based Solutions

Abstract

Kinetically facile intercalation of anions into graphite electrodes is essential for the good performance of dual-ion batteries. The intercalation of BF 4 À anions into graphite electrodes is found to be strongly impeded in the electrolyte of 1.25 m LiBF 4 À ethylmethyl carbonate. For this, both the strong attraction between Li + and BF 4 À clusters and the special solvation state of the anion are to blame. Two strategies are employed to tailor the solvation states of ions in the solutions, which prove easy and effective in facilitating anion intercalation into graphite electrodes.

Abnormal Inverse Current during Anion Deintercalation from Graphite Electrode

“…This is caused by the strong ion-pair interaction between Li + and BF 4 – that severely prevents the anion intercalation. In the solutions dissolving both LiBF 4 and SBPBF 4 (say, 1/1 by molar ratio), the upper cutoff potential that the inverse current could be detected was lowered to 5.2 V. This is in accordance to the result of our previous findings …”

“…In the solutions dissolving both LiBF 4 and SBPBF 4 (say, 1/1 by molar ratio), the upper cutoff potential that the inverse current could be detected was lowered to 5.2 V. This is in accordance to the result of our previous findings. 41 Though supported by the above proof, there is still no visible method with which we can observe this abnormal process directly. On this occasion, finding out a counterexample will be a good way to step forward.…”

Metal‐Ion Capacitors with Anion Intercalation Process

“…In AC/AC configuration, any one of the AC electrodes is well enough for the strong adsorption ability. In contrast, the counter electrode does not need to provide such benefits, created an idea to substitute one of the AC by specific graphite electrode (especially KS‐series) as a cathode to boost the energy density of the EDLC in the term of “Megalo‐capacitance capacitor.” Yoshio and co‐workers [ 4,37–46 ] introduced a megalo‐capacitance capacitor by using graphitic carbon as the cathode in place of AC. The capacitor could store more energy (20 Wh kg −1 ) than the conventional EDLC capacitor, and the cost of the device could be reduced remarkably by eliminating expensive AC from the cathode.…”

Hexafluorophosphate Anion Intercalation into Graphite Electrodes from Propylene Carbonate/Gamma-Butyrolactone Solutions

“…The anions in use generally include PF 6 – , BF 4 – , , FSI – (bisfluorosulfonyl)­imide, and TFSI – (bistrifluoromethanesulfonyl)­imide. The solvents in DIBs may select propylene carbonate (PC), − ethylmethyl carbonate (EMC), − methyl acetate (MA), , gamma-butyrolactone (GBL), − and sulfolane (SL). , Sometimes ionic liquids have been applied in DIBs as well. − Right now, the close correlation between the storage behavior of anions in a graphite electrode and the solvation state of anions has been confirmed. ,, Therefore, it is an effective way to improve the performance of AGICs in DIBs by tailoring the solvation structures of anions.…”