Abnormal Inverse Current during Anion Deintercalation from Graphite Electrode

Abstract

It was taken for granted that the charge and discharge processes correspond with distinctly opposite directions of ionic flow when the energy storage mechanism of dual-ion battery was concerned. This common sense is challenged as we find a remarkable countercurrent in the cyclic voltammetric curve during the deintercalation of tetrafluoroborate anions from graphite electrode using ethylene carbonate solution. By electrochemical analysis, there is believed to be backflow of anions during the deintercalation process. The cause of this abnormal ionic flow relates to both the desolvation and resolvation of the intercalated anions inside the graphite electrode. Supportive evidence is provided.

Cooperation of Dimethyl and Diethyl Carbonates in Hexafluorophosphate Anion Intercalation into Graphite Electrode

“…Where the HT-MCMB (superficial layer broken) electrode is concerned, the difference between the two groups of curves is enlarged again. As is proven that the superficial layer of MCMB, which can be broken by a heat treatment, has the ability of partly desolvating during the intercalation of solvated ions, 22,23 the above CV results demonstrate that it is the difference between the solvation states of PF 6 − in OM and in EMC that causes a rate performance gap.…”

PF6– Intercalation into Graphite Electrode from Propylene Carbonate

“…In addition, the voltage increments in in situ XRD measurements were 0.02 V in the charge process and 0.05 V in the discharge process. The EQCM measurement was carried out by an RQCM Research Quartz Crystal Microbalance Monitor (MAXTEK, INFICON), which was introduced in our previous studies. , Infrared absorption spectra were measured by a VERTEX 70 in the wavenumber range of 450–4000 cm –1 . The nuclear magnetic resonance (NMR) measurements of 1 H, 7 Li, and 19 F in PC solutions were carried out on a BRUKER Avance III HD 500, where Si­(CH 3 ) 4 , 4 mol mL –1 LiClO 4 ethanol solution, and C 6 F 6 acted as the chemical shift references, respectively.…”

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

“…A graphite electrode was fabricated by homogeneously mixing 10 mg of natural graphite flakes (purified by Kansai Coke and Chemicals Co., Ltd.) and 5 mg of a conductive binder (teflonized acetylene black from Denka Co., Ltd.) and then pressing the mixture on a piece of aluminum mesh. The physical properties of natural graphite flakes have been given in the previous study. ,− The counter electrode in a cell was a lithium metal chip (purity ≥99.9%). The electrolyte solutions were LiPF 6 dissolved in the mixtures of PC and GBL (Shanghai Aladdin Biochemical Technology Co., Ltd.).…”