In only a few decades, lithium-ion batteries have revolutionized technologies, enabling the proliferation of portable devices and electric vehicles1, with substantial benefits for society. However, the rapid growth in technology has highlighted the ethical and environmental challenges of mining lithium, cobalt and other mineral ore resources, and the issues associated with the safe usage and non-hazardous disposal of batteries2. Only a small fraction of lithium-ion batteries are recycled, further exacerbating global material supply of strategic elements3,4,5. A potential alternative is to use organic-based redox-active materials6,7,8 to develop rechargeable batteries that originate from ethically sourced, sustainable materials and enable on-demand deconstruction and reconstruction. Making such batteries is challenging because the active materials must be stable during operation but degradable at end of life. Further, the degradation products should be either environmentally benign or recyclable for reconstruction into a new battery. Here we demonstrate a metal-free, polypeptide-based battery, in which viologens and nitroxide radicals are incorporated as redox-active groups along polypeptide backbones to function as anode and cathode materials, respectively. These redox-active polypeptides perform as active materials that are stable during battery operation and subsequently degrade on demand in acidic conditions to generate amino acids, other building blocks and degradation products. Such a polypeptide-based battery is a first step to addressing the need for alternative chemistries for green and sustainable batteries in a future circular economy.
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This work was financially supported by the National Science Foundation (DMR-1507429, DMR-1905818, CHE-2003771 and DMREF-1629094; K.L.W. and T.P.N.; synthesis and structural characterization), the Welch Foundation (A-0001, K.L.W.; A-1717, C.-H.Y.) and the US Department of Energy Office of Science (DE-SC0014006; J.L.L. and A.D.E.; electrochemical measurements). A.D.E. acknowledges support by a National Science Foundation Graduate Research Fellowship.
The authors declare no competing interests.
Peer review information Nature thanks Jung Ho Kim, David Mercerreyes and Ulrich Schubert for their contribution to the peer review of this work.
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Extended data figures and tables
a, The half sandwich cell: viol-Cl or biTEMPO polypeptide composite working electrode and lithium metal reference electrode, with a filter-paper separator. b, The full sandwich cell: viol-Cl polypeptide composite working electrode and biTEMPO polypeptide composite reference electrode, with a filter-paper separator.
Extended Data Fig. 3 Electrochemical performance of full cell without polypeptide active material as a control.
Electrochemical characterization of a PVDF + CB symmetric full cell is shown, including cyclic voltammograms (i), charge–discharge curves (ii) and cycling response at 1C (iii) (PVDF + CB composite electrode, 0.5 M TBACF3SO3 in PC and filter paper, PVDF + CB composite electrode). The composite electrodes were cast in an identical manner to the polypeptide composite electrodes, with a composition of 86 wt% CB and 14 wt% PVDF on ITO-coated glass substrates. After 250 cycles, the capacity was 1.7 mA h g−1, whereas the capacity of the polypeptide-based full cell was 7.5 mA h g−1 (Fig. 4g–i).
a, b, Scanning electron micrographs of the viol-Cl polypeptide composite electrode (a) and the biTEMPO polypeptide composite electrode (b), before (i) and after (ii) 50 charge–discharge cycles in the full sandwich cell configuration (viol-Cl polypeptide composite electrode, 0.5 M TBACF3SO3 in PC and filter paper, biTEMPO polypeptide composite electrode).
Dose–response curves for redox-active polypeptides. Data are expressed as mean ± s.d. of three determinations. The statistical analysis was performed using GraphPad Prism, with the black lines representing four-parameter fits.
Dose–response curves for redox-active polypeptides after acid degradation. Data are expressed as mean ± s.d. of three determinations. The statistical analysis was performed using GraphPad Prism, with the black lines representing four-parameter fits.
Comparison of IC50 values of viologen polypeptide, biTEMPO polypeptide, viologen analogue, biTEMPO analogue and their degraded products.
This file contains supplementary experimental procedures for additional electrochemistry characterizations and the synthetic details for the viologen and BiTEMPO polypeptides and their analogs. Spectral data (NMR and FTIR) is provided for all the synthesized species. Supplementary Figures are provided for electrochemical, degradation, and cell viability studies.
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Nguyen, T.P., Easley, A.D., Kang, N. et al. Polypeptide organic radical batteries. Nature 593, 61–66 (2021). https://doi.org/10.1038/s41586-021-03399-1
Nature Reviews Materials (2021)