Ionic conductivity enhancement in PEO:CuSCN solid polymer electrolyte by the incorporation of nickel-chloride

• Effect of NiCl2 on ionic conductivity enhancement in PEO9 CuSCN is reported.
• 10 wt% NiCl2 showed the highest conductivity of 1.8 × 10− 7 S cm− 1 at 30 °C.
• The Tg has reduced by about 30 °C due to the addition of 10 wt% NiCl2.
• Conductivity enhancement could be due to increased polymer segmental mobility.

Copper-ion based solid polymer electrolytes exhibit interesting electrochemical properties, environmental stability and lower fabrication cost compared to lithium ion based systems. Although, poly(ethylene oxide)(PEO)-based solid polymer electrolytes have been extensively studied, those incorporating copper salts have not been explored much. One major drawback in these electrolytes is the low ionic conductivity at room temperature. In this work, we attempted to enhance the ionic conductivity of PEO9CuSCN polymer electrolyte by the incorporation of NiCl2. Incorporation of 10 wt% NiCl2 showed the highest conductivity enhancement with almost two orders of magnitude increase. The ionic conductivity value at 30 °C increased from 3.1 × 10− 9 S cm− 1 for the NiCl2-free electrolyte to 1.8 × 10− 7 S cm− 1 for the 10 wt% NiCl2 incorporated electrolyte. This was associated with a significant reduction in Tg by about 30 °C from − 53 °C for PEO9 CuSCN to − 83 °C for PEO9 CuSCN + 10 wt% NiCl2, indicating an increased segmental flexibility of the polymer chains for NiCl2 added electrolyte.

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