Organoboron-thiophene-based polymer electrodes for high-performance lithium-ion batteries

Abstract

Polymer electrodes are drawing widespread attention to the future generation of lithium-ion battery materials. However, weak electrochemical performance of organic anode materials still exists, such as low capacity, low rate performance, and low cyclability. Herein, we successfully constructed a donor-acceptor thiophene-based polymer (PBT-1) by introducing an organoboron unit. The charge delocalization and lower LUMO energy level due to the unique structure enabled good performance in electrochemical tests with a reversible capacity of 405 mA h g^-1 at 0.5 A g^-1 and over 10 000 cycles at 1 A g^-1. Moreover, electron paramagnetic resonance (EPR) spectra revealed that the unique stable spin system in the PBT-1 backbone during cycling provides a fundamental explanation for the highly stable electrochemical performance. This work offers a reliable reference for the design of organic anode materials and expands the potential application directions of organoboron chemistry.

Scheme 1. Synthetic route of the conjugated polymer PBT-1.

Fig. 1. (a) Calculated HOMO and LUMO energy levels and (b) MESP map of the polymer fragments.

Fig. 2. (a) CV curves of the PBT-1 electrode measured at a scan rate of 0.2 mV s⁻¹. (b and c) Charge and discharge curves at 45 mA g⁻¹. (d) Rate capability of PBT-1 at different current densities.

Fig. 3. Cycling stability of PBT-1 at (a) 45, (b) 500, and (c) 1000 mA g⁻¹.

Fig. 4. (a) Charge/discharge profile of the PBT-1 anode at the second cycle at 0.2 A g⁻¹, and the select points were denoted in the curve. Normalized (b) and original (c) first-derivative EPR spectra at the selected points indicated in (a). (d) Absorption EPR spectra at the three selected potentials.