Properties enhancement of carboxymethyl cellulose with thermo-responsive polymer as solid polymer electrolyte for zinc ion battery

Abstract

A novel polymer host from carboxymethyl cellulose (CMC)/poly(N-isopropylacrylamide) (PNiPAM) was developed for a high safety solid polymer electrolyte (SPE) in a zinc ion battery. Effects of the PNiPAM loading level in the range of 0-40% by weight ( wt%) on the chemical, mechanical, thermal, and morphological properties of the CMC/PNiPAMx films (where x is the wt% of PNiPAM) were symmetrically investigated. The obtained CMC/PNiPAMx films showed a high compatibility between the polymers. The CMC/PNiPAM20 blend showed the greatest tensile strength and modulus at 37.9 MPa and 2.1 GPa, respectively. Moreover, the thermal degradation of CMC was retarded by the addition of PNiPAM. Scanning electron microscopy images of CMC/PNiPAM20 revealed a porous structure that likely supported Zn²⁺ movement in the SPEs containing zinc triflate, resulting in the high Zn²⁺ ion transference number (0.56) and ionic conductivity (1.68 × 10^-4 S cm^-1). Interestingly, the presence of PNiPAM in the CMC/PNiPAMx blends showed a greater stability during charge-discharge cyclic tests, indicating the ability of PNiPAM to suppress dendrite formation from causing a short circuit. The developed CMC/PNiPAM20 based SPE is a promising material for high ionic conductivity and stability in a Zn ion battery.

Figure 1

Representative FT-IR spectra of CMC/PNiPAMx polymers with PNiPAM contents of (a) 0 wt% (pure CMC), (b) 10 wt%, (c) 30 wt%, (d) 50 wt% and (e) 100 wt% (pure PNiPAM).

Figure 2

Tensile strength (filled circle) and tensile modulus (filled square) of CMC with different PNiPAM contents. Data are shown as the mean ± 1SD, derived from 5 independent repeats. The curves are drawn as guides to the eyes.

Figure 3

Representative DSC thermograms of CMC with PNiPAM contents of (a) 0 wt% (pure CMC), (b) 10 wt%, (c) 20 wt%, (d) 30 wt%, (e) 40 wt%, (f), 50 wt%, and (g) 100 wt% (pure PNiPAM).

Figure 4

Representative TGA thermograms showing the thermal degradation behavior of CMC with PNiPAM contents of (a) 0 wt% (pure CMC), (b) 10 wt%, (c) 20 wt%, (d) 30 wt%, (e) 40 wt%, and (e) 100 wt% (pure PNiPAM).

Figure 5

Representative SEM micrographs (× 1,000 magnification) of CMC with PNiPAM contents of (a) 0 wt% (pure CMC), (b) 100 wt% (pure PNiPAM), (c) 10 wt%, (d) 20 wt%, (e) 40 wt% and (f) 40 wt%.

Figure 6

Representative chronoamperometry profiles at room temperature in block cells using Zn metal as both electrodes with a step potential of 10 mV for the prepared CMC/PNiPAMx SPE films. Inset: The ${\text{t}}_{{\text{Zn}}^{2+}},$ of SPEs with different PNiPAM contents.

Figure 7

Representative Nyquist plots of the symmetrical cell for the CMC/PNiPAMx SPE systems with PNiPAM contents of (filled circle) 0 wt% (pure CMC), (filled square) 10 wt%, (filled diamond) 20 wt%, (filled triangle) 30 wt%, and (filled inverted triangle) 40 wt%.

Figure 8

Half Zn battery cell testing for charge/discharge scycle of (a) CMC, (b) CMC/PNiPAM20, and (c) 15 wt% Zn(Tf)₂ containing CMC/PNiPAM20.