High Active Material Loading in Organic Electrodes Enabled by a Multifunctional Binder.

Organic electrodes are promising candidates for next-generation lithium-ion batteries due to their low cost and sustainable nature; however, they often suffer from very low conductivity and active material loadings. The conventional binder used in organic-based Li-ion batteries is poly(vinylidene fluoride) (PVDF), yet it is electrochemically inactive and thus occupies volume and mass without storing energy. Here, we report an organic mixed ionic-electronic conducting polymer, poly[norbornene-1,2-bis(C(O)OPEDOT)]--[norbornene-1,2-bis-(C(O)PEG)] denoted PEDOT--PEG for simplicity, as a cathode binder to address the aforementioned issues. The polymer contains a poly(3,4-ethylenedioxythiophene) (PEDOT) functionality to provide electronic conductivity, as well as poly(ethylene glycol) (PEG) chains to impart ionic conductivity to the cathode composite. We compare electrodes containing a perylene diimide (PDI) active material, conductive carbon, and a polymeric binder (either PVDF or PEDOT--PEG) with different weight ratios to study the impact of active material loading and type of binder on the performance of the cell. The lithium-ion cells prepared with the PEDOT--PEG polymer binder result in higher capacities and decreased impedance at all active material loadings compared to cathodes prepared with the PVDF-containing electrodes, demonstrating potential as a new binder to achieve higher active material loadings in organic electrodes. The strategy of preparing these polymers should be broadly applicable to other classes of mixed polymer conductors.