Performance improvements for the all-copper redox flow battery: Membranes, electrodes, and electrolytes

Control-Oriented Electrochemical Model and Parameter Estimation for an All-Copper Redox Flow Battery

“…Only a single charge-discharge cycle was used to fit the single-cell parameters due to the clear presence of non-standard behaviour in the first two cycles seen in Figure 3. We presume the first cycle behaviour is due to limited chloride availability as reported in [13], while the drastic capacity loss from cycles 2 to 3 may be due to copper delamination. We fit the parameters in Table 1 using the genetic algorithm described in Section 4.…”

“…In the case of the diffusion cell, 20 mA was applied and 0.5 A for the single-cell flow battery, resulting in a current density of 20 mA/cm 2 for both test cases. The equipment, experimental procedure, and electrolyte preparation methods were performed as previously reported [13], and the FAP-330 anion exchange membrane obtained from FUMATECH BWT GmbH was used. In addition to this, extra experiments were performed on the FAP-330 sample originally used in 2021 and published in 2022 [13], during which it was operated for 1200 h (300 cycles) and then left in a solution of 1 M CuCl and 6 M HCl for over one and a half years before being retested in this paper.…”

“…Two sets of model parameters were identified using the respective data originally reported in [13] and the data obtained from the same membrane aged for 18 months in the CuRFB electrolyte. The data were downsampled to a sampling rate of 2 min to accommodate the much longer cycling time of the diffusion cell.…”

“…In a recent study, the performance of the CuRFB system has been improved through optimisation of the separator choice, electrode modifications, and operation optimisations [13]. The largest improvement originates from the reduction in the self-discharge rate of the system, extending the operational time without maintenance from the previous 9 h to over 210 h [13,14].…”

“…In a recent study, the performance of the CuRFB system has been improved through optimisation of the separator choice, electrode modifications, and operation optimisations [13]. The largest improvement originates from the reduction in the self-discharge rate of the system, extending the operational time without maintenance from the previous 9 h to over 210 h [13,14]. This is achieved by slowing the transport of Cu(II) (Equation ( 1)), formed during the charging process in the anolyte to the catholyte where metallic copper is deposited (Equation ( 2)).…”