| 초록 |
H2SO4-doped dense polybenzimidazole (PBI) membranes based on poly[2,2′-(2-benzimidazole-p-phenylene)-5,5′-bibenzimidazole] (BIpPBI) containing benzimidazole side groups were developed for use in vanadium redox flow batteries (VRFBs). Many basic properties of BIpPBI were characterized and compared with conventional mPBI. The BIpPBI membrane has an entirely amorphous structure because of the presence of additional benzimidazole side groups, and the absorption of both H2SO4 and water were significantly improved compared to those of the mPBI membrane. Finally, the VRFB assembled with BIpPBI had higher coulomb efficiencies (＞99%) and energy efficiencies (78–95%) than Nafion 115 under a wide range of current densities (20–100 mA cm-2). More importantly, the VRFB with BIpPBI exhibited a stable cycling performance, running for 200 charge-discharge cycles with 4.0% energy efficiency decay and 81.5% capacity retention. |
