Do these 3 things before closing this tab:
1Repair Windows errors before they cause bigger problems2Scan for outdated or missing drivers - takes under a minute3Clear out junk files and repair common Windows errorsiTechGuides is reader-supported. When you buy through links on our site, we may earn an affiliate commission. As an Amazon Associate I earn from qualifying purchases. Learn more
A 2022 laboratory study tested a metal-free redox flow battery built with redox-active polypeptides. The cell produced a measurable voltage and high coulombic efficiency, but retained 60% of its starting capacity after 500 charge–discharge cycles. It is an early materials result, not a commercial or grid-scale battery.
How peptide-based redox flow batteries work
A redox flow battery stores energy in liquid electrolytes held in separate reservoirs and circulated through an electrochemical cell. In the system studied by Liang and colleagues, the active materials were polypeptide scaffolds carrying redox-active groups: a TEMPO-based polypeptide in the catholyte and a viologen-based polypeptide in the anolyte. These are synthesized research materials, not consumer peptide products.
During charging and discharging, the redox-active groups take up or release electrons. The liquid electrolytes flow through the cell, where an ion-exchange membrane separates the two sides while allowing ions to move and maintain charge balance. The researchers investigated whether the larger polypeptide-bound redox materials could cross the separator less readily than comparable small molecules.
Quick wins for a faster PC:
Scan for outdated or missing drivers - takes under a minuteDriver Scan →Clear out junk files and repair common Windows errorsFree Scan →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →What the 2022 experiment tested
The team reported a non-aqueous laboratory cell using acetonitrile and 0.5 M tetraethylammonium bis(trifluoromethanesulfonyl)imide as supporting electrolyte. Each reservoir contained 7.5 mL. The anolyte concentration was 50 mM and the catholyte concentration was 25 mM, both expressed by repeat unit. The cell used an anion-exchange membrane.
#1 Best Overall
In separator comparisons with Daramic 175 and FAPQ 375 PP, the authors reported less crossover for the polypeptides than for small-molecule analogues. FAPQ 375 PP was the most effective separator in those tests. These findings describe the particular comparative experiments, not a validated separator for a finished or full-scale battery.
Performance and capacity after cycling
| Measure | Result reported by the study | Condition or qualification |
|---|---|---|
| Output voltage | 1.1 V | Laboratory cell |
| Maximum capacity | 0.53 A h L−1, or 39% of theoretical capacity | At 10 mA cm−2 |
| Capacity utilization | 59% of theoretical capacity | At a lower discharge current of 5 mA cm−2 |
| Coulombic efficiency | More than 99.5% | Reported for the tested cell |
| Capacity retained | 60% of initial capacity | After 500 charge–discharge cycles |
| Capacity fade | About 0.1% per cycle | Over the 500-cycle test |
The headline answer to “how much capacity remained?” is 60% after 500 cycles. That result is distinct from coulombic efficiency: high coulombic efficiency indicates that charge returned during a cycle was close to charge put in, but it does not mean the cell preserved all of its usable capacity over repeated cycling.
Why current density matters
Capacity utilization depended on how quickly the cell was asked to deliver current. The study reported 39% of theoretical capacity at 10 mA cm−2 and 59% at 5 mA cm−2. In a variable-rate experiment, accessible capacity fell as current density rose, with complete capacity loss at 20 mA cm−2 in that test. Those measurements apply to this cell and test protocol; they should not be generalized to other flow-battery chemistries.
Recommended Free Tools
What the cycling result says about durability
Post-cycling analyses indicated that the polypeptide backbone and ester linkages remained stable. The authors attributed the noticeable capacity fade as likely resulting from degradation of the redox-active groups. The results therefore point to a material-design challenge: preserving the active redox chemistry over repeated use, even when parts of the molecular scaffold appear stable.
What this result does—and does not—establish
The experiment demonstrates that a non-aqueous flow cell using metal-free polypeptide redox materials can cycle and deliver measurable electrochemical performance. It also reports a crossover advantage for those materials in the paper’s separator comparisons.
It does not demonstrate a packaged battery, grid deployment, commercial recyclability, or cost competitiveness. The authors frame degradability on demand and more sustainable large-scale storage as future potential. The study is an early step toward those goals, not proof that end-of-life recovery or commercial operation has been achieved.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Study details
The results come from Liang, Nguyen, Attanayake, Easley, Lutkenhaus, Wooley, and Odom, “Metal-free polypeptide redox flow batteries,” published in Materials Advances in 2022 and first published on 12 July 2022. Read the paper via its DOI.
The Tool Desk
Outbyte PC Repair FREERepair Windows errors before they cause bigger problemsFix Now →Outbyte Driver Updater FREEFix the driver behind crashes, sound loss and screen glitchesFind Drivers →Quick Recap
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
