Stackable bipolar pouch cells with corrosion-resistant current collectors enable high-power aqueous electrochemical energy storage

• Published in: Energy & environmental science 2018-10, Vol.11 (10), p.2865-2875
• Main Authors: Evanko, Brian, Yoo, Seung Joon, Lipton, Jason, Chun, Sang-Eun, Moskovits, Martin, Ji, Xiulei, Boettcher, Shannon W., Stucky, Galen D.
• Format: Article
• Language: English
• Subjects: Accumulators; Aqueous electrolytes; Architecture; Batteries; Bipolar cells; Black carbon; Carbon black; Cations; Collectors; Corrosion; Corrosion cell; Corrosion resistance; Cost analysis; Design; Electrical conductivity; Electrical resistivity; Electrochemistry; Electrolytic cells; Energy storage; Flux density; Foils; Metals; Organic chemistry; Packaging; Polyethylene; Polyethylenes; Storage systems; Test procedures; Weight reduction
• ISSN: 1754-5692; 1754-5706
• DOI: 10.1039/C8EE00546J

A critical bottleneck in the development of aqueous electrochemical energy storage systems is the lack of viable complete cell designs. We report a metal-free, bipolar pouch cell designed with carbon black/polyethylene composite film (CBPE) current collectors as a practical cell architecture. The light-weight, corrosion-resistant CBPE provides stable operation in a variety of aqueous electrolytes over a ∼2.5 V potential range. Because CBPE is heat-sealable, it serves simultaneously as both the pouch cell packaging and seal in addition to its use as a current collector. Although this non-metallic composite has a low electrical conductivity relative to metal foils, current travels only a short distance in the through-plane direction of the current collector in the bipolar cell configuration. This shorter path length lowers the effective electrical resistance, making the design suitable for high-power applications. We test the cell architecture using an aqueous ZnBr 2 battery chemistry and incorporate tetrabutylammonium cations to improve the intrinsic low Coulombic efficiency and fast self-discharge of non-flow ZnBr 2 cells. These devices demonstrate a cell-level energy density of 50 W h L −1 at a 10C rate (0.5 kW L −1 ), with less than 1% capacity loss over 500 cycles. A large-area (>6 cm 2 ) 4-cell stack is built to illustrate that the pouch cells are scalable to practical dimensions and stackable without sacrificing performance. The device operates in the range of 6–7 V and has an internal self-balancing mechanism that prevents any individual cell in the stack from overcharging. The results thus demonstrate both a conceptually new cell architecture that is broadly applicable to many aqueous electrolyte chemistries and a specific high-performance example thereof.