Redox Flow

JCESR investigates the replacement of solid electrodes with energy-dense liquids that charge and discharge as they flow through the battery and undergo reduction and oxidation (“redox”) reactions. These redox flow batteries store large amounts of energy inexpensively and are well-suited to the grid.

JCESR introduced a new direction in flow battery research: using inexpensive and versatile organic molecules as the energy storing redox materials. Organic molecules are highly tunable, with a wealth of pendant molecules that significantly alter activity, solubility and stability when attached to the basic redox molecule. JCESR chooses not only the active molecule but also its configuration, attaching active molecules to polymer backbones to form redox-active polymers (RAPs) and cross-linking the polymers to form redox-active colloids (RACs).

The new macromolecular redox configurations open a wide new horizon of basic phenomena for controlling activity, solubility, and stability of battery materials. The challenge is to identify organic working ions and chemical reactions that exchange many electrons over a large operating voltage that are stable for many cycles between the charged and discharged states. A second challenge is finding electrolytes that effectively work with the organic working ion in all its intermediate charge states without harmful side reactions.

JCESR replaces the solid electrodes in conventional lithium-ion batteries with energy-dense organic liquids that charge and discharge as they flow through the battery. The organic molecules in these redox flow batteries are highly versatile and can be tailored to store large amounts of energy inexpensively, a key requirement for the grid.

A critical component in flow batteries is the separator, which physically and electronically separates the positive and negative electrodes while allowing free passage of the charged working ion between the electrodes. JCESR is pursuing two novel approaches:

  1. JCESR uses off-the-shelf Cellguard porous separators, which are highly effective with redox-active polymers and colloids because their larger size keeps them from flowing across the membrane.
  2. JCESR is pursuing a polymer membrane with adjustable nanoscale porosity able to be customized for smaller, single redox-active molecules.

Research Highlights

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