Poly(vinylphenoxazine) as Fast-Charging Cathode Material for Organic Batteries

Abstract

Organic cathode materials are attractive for a new generation of more sustainable batteries due to their comparably low environmental footprint and toxicity. There is a continued quest for new compounds that meet the requirements of a competitive potential and a good cycling performance. We herein present phenoxazine-based polymers as cathode materials with good cycling stability, excellent rate performance, and a high discharge potential of 3.52 V vs Li|Li+ in composite electrodes. At the ultra-fast rate of 100C, a cross-linked phenoxazine poly­(vinylene) showed only slow capacity decay over 10 000 cycles with a capacity retention of 74% in cycle 10 000. Mechanistic investigations using UV/vis/near-infrared (NIR) spectroscopy and density functional theory (DFT) calculations unveiled that unlike in the homologous phenothiazine polymers, π-interactions played a minor role in phenoxazine-based polymers. Our study is the first to present phenoxazine as a redox-active unit for cathode materials and shows that an elemental change of one atom (S vs O compared to known phenothiazine-based polymers) can have a profound effect on electrochemical performance.

Utilizing Latent Multi‐Redox Activity of p‐Type Organic Cathode Materials toward High Energy Density Lithium‐Organic Batteries

“…It is highlighted that it is the first report that shows that PXZ and PTZ-based electrodes can exhibit reversible two single-electron redox reactions, while only a single-electron redox reaction could be previously achievable for similar organic electrode materials. [31][32][33][34][35] Figure 4e depicts the quantitative voltage upshift from DMPZ to PXZ and PTZ derivatives for the first and second reduction potentials, which indicates approximately 0.50 V increase, consistent with the DFT predictions. Moreover, even after charge/ discharge cycle up to 4.5 V, there was no significant change in ex situ Fourier-transform infrared spectroscopy spectra of the PXZ and PTZ derivatives, which indicates the chemical reversibility ( Figure S7, Supporting Information).…”

A low-cost and Li-rich organic coating on a Li4Ti5O12anode material enabling Li-ion battery cycling at subzero temperatures

“…Organic molecules demonstrated faster lithium ion transfer, as observed in organic electrodes. [30][31][32] Therefore, the incorporation of electrochemically active organic molecules at the surface of LTO should be an interesting trend of research. Based on these observations, the use of single and active organic molecules, which can be well dispersed on active electrode particles by physical absorption (effective covering of the surface) must be suitable for achieving high-performance anode materials at high C-rates and low temperatures.…”

Polymer‐Based Batteries—Flexible and Thin Energy Storage Systems

“…Additionally, a thianthrene‐containing polymer was utilized for an all‐organic battery with poly(extended‐tetrathiafulvalene (poly(exTTF)). [ 64 ] Recently, also phenothiazine polymers [ 65,66 ] (Figure 3) and a polymer of the related phenoxazine [ 67 ] were applied as cathode materials and due to strong ππ‐interactions between the phenothiazine groups in the poly(vinylphenothiazine) PVMPT in their oxidized states, a high cycling stability, and rate capability was obtained. [ 68,69 ] Batteries based on these materials feature a self‐discharge of ≈10% within 3 days, which is comparable to other systems.…”