Engineering Papers⌕ Search

Engineering topics

Wainright, Jesse

Publications and source records attributed to Wainright, Jesse.

5 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

An All-Soluble Fe/Mn-Based Alkaline Redox Flow Battery System

Redox flow batteries (RFBs) are membrane-separated rechargeable flow cells with redox electrolytes, offering the potential for large-scale energy storage and supporting renewable energy grids. Yet, creating a cost-effective, high-performance RFB system is challenging. In this work, we investigate an Fe/Mn RFB alkaline system based on the [(TEA)Fe–O–Fe(TEA)] 3– / 4– and MnO 4 – / 2– redox couples with a theoretical cell voltage of ~1.43 V. This combination has not been systematically studied previously, but it can lead to a very low-cost and sustainable materials for high energy storage. Constant current cycling tests were performed at ±41 mA cm –2 between 20% and 80% SOC over 800 h (400 cycles) with an apparent Coulombic efficiency (CE) approaching 100%, while the voltage efficiency (VE) gradually decreased from ~75.3% to ~61.4% due to increasing internal resistances. Finally, the voltage efficiency loss can be mitigated through a periodic acid treatment to remove MnO 2 deposits from the separator.

25 ENERGY STORAGE↗
DOE OSTI2024

Ionic Diffusion in Slurry Electrolytes for Redox Flow Batteries

Slurry electrodes have been proposed as a method to decouple the storage and power capacities of hybrid redox flow batteries by allowing the reduced metal to adhere to a flowing dispersion of electrically conductive particles rather than accumulate in the flow cell. In this work, the ionic mass transport through these slurry electrolytes is investigated via voltammetry at a rotating disc electrode and in a parallel channel flow cell. A modified Levich equation, i l = 0.6 2 nFC ω 1 / 2 ν − 1 / 6 ( D + r 2 Φ ω m ) 2 / 3 , is developed to describe limiting currents to a rotating disc electrode when using a particle filled electrolyte. Mass transfer is demonstrated to be enhanced by greater particle loading so long as there are sufficient particles such that their respective flow velocity boundary layers interact. In the flow cell, faradaic current in a carbon black slurry electrolyte was observed to decrease over time. This suggests that the carbon particles adhere and accumulate on the stationary electrode, impeding mass transport by imposing diffusion path tortuosity. This accumulation is undesirable in hybrid redox flow batteries as it encourages metal deposition in the cell, limiting the scalability of the technology.

Electrochemistry↗
NASA NTRS1993

The electrolyte challenge for a direct methanol-air polymer electrolyte fuel cell operating at temperatures up to 200 C

Novel polymer electrolytes are being evaluated for use in a direct methanol-air fuel cell operating at temperatures in excess of 100 C. The evaluation includes tests of thermal stability, ionic conductivity, and vapor transport characteristics. The preliminary results obtained to date indicate that a high temperature polymer electrolyte fuel cell is feasible. For example, Nafion 117 when equilibrated with phosphoric acid has a conductivity of at least 0.4 Omega(exp -1)cm(exp -1) at temperatures up to 200 C in the presence of 400 torr of water vapor and methanol vapor cross over equivalent to 1 mA/cm(exp 2) under a one atmosphere methanol pressure differential at 135 C. Novel polymers are also showing similar encouraging results. The flexibility to modify and optimize the properties by custom synthesis of these novel polymers presents an exciting opportunity to develop an efficient and compact methanol fuel cell.

Savinell, Robert↗