Mass and Charge Transfer in a Polymeric NiSalen Complex at Subzero Temperatures

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Science

Background:

• Electrochemical energy storage systems face performance degradation at low temperatures.
• Reduced capacity and power at subzero temperatures are linked to counterion injection difficulties.
• Salen-type polymers show promise for developing low-temperature energy storage materials.

Purpose of the Study:

• To investigate the electrochemical performance of poly[Ni(CH3Salen)] electrode materials at subzero temperatures.
• To identify the limiting factors for electrochemical performance in these materials at low temperatures.
• To explore methods for enhancing the charge transfer and overall performance of these materials in cold environments.

Main Methods:

• Synthesis of poly[Ni(CH3Salen)]-based electrode materials from various electrolytes.
• Electrochemical characterization using cyclic voltammetry, electrochemical impedance spectroscopy, and quartz crystal microgravimetry.
• Testing conducted across a temperature range of -40 °C to 20 °C.

Main Results:

• At subzero temperatures, electrochemical performance is primarily limited by ion injection into the polymer film and slow diffusion within the film.
• Electrode materials based on poly[Ni(CH3Salen)] exhibit reduced performance at temperatures below 0 °C.
• Deposition of the polymer from solutions containing larger cations leads to the formation of porous structures.

Conclusions:

• The formation of porous structures, facilitated by larger cations during polymer deposition, enhances counterion diffusion.
• Improved counterion diffusion leads to enhanced charge transfer, significantly boosting electrochemical performance at low temperatures.
• This approach offers a viable strategy for developing robust electrochemical energy storage for cold environments.