Redox shuttles are electrolyte additives capable of reversible oxidative-reductive reactions at a certain potential, thus providing overcharge protection and safe operation of lithium-ion batteries. Overcharge of lithium cells can give rise to undesirable chemical and electrochemical reactions between battery components and lead to thermal runaway, cell malfunction or possibly explosions.
Redox shuttles have defined redox potential, at which they can be oxidized on the positive electrode and form a radical cation. This then travels to the negative electrode through the electrolyte, where it is reduced and diffused back to the positive electrode for the next redox cycle. Shuttle molecules stay inactive until the redox potential of the redox shuttle is reached. Only when the cell is overcharged is the redox cycle of the redox shuttle molecules activated.
The redox potential of redox shuttles must be 0.3-0.4 V higher than the normal maximum operating potential of the cathode otherwise, shuttle molecules begin to operate before the cell is fully charged. However, the potential should not exceed the electrochemical stability window for conventional electrolytes, i.e., 4.5 V vs. Li/Li+. Recent progress in high-voltage cathode materials and electrolytes demands redox shuttles with even higher potentials (4.4 V to 4.9 V vs. Li/Li+).
Strem Chemicals, in collaboration with Argonne National Laboratory, offers redox shuttles with tunable redox potentials for standard cathode materials and electrolytes, as well as applications in high-voltage battery technologies.
ANL-RS2 (08-0215) and 08-0220 (ANL-RS21) exhibit redox potentials of 3.9 V and 4.05 V vs. Li/Li+ respectively.[3-4] Redox shuttles ANL-RS5 (15-1365), ANL-RS51 (15-1372), ANL-RS6 (15-1375) have a higher redox potential of about 4.5 V, 4.6 V and 4.8 V vs. Li/Li+ respectively.[5-7]
ANL redox shuttles are very soluble in standard aprotic non-aqueous carbonate-based electrolytes and the dissolved molecules are highly mobile throughout the cell.
Products mentioned in this blog and related links:
08-0215: Oxygen › 1,4-Di-t-butyl-2,5-bis(2-methoxyethoxy)benzene, 99+% Redox shuttle ANL-RS2, [1350770-63-6]
08-0220: Oxygen › 6,7-Dimethoxy-1,1,4,4-tetramethyl-1,2,3,4-tetrahydronaphthalene, 99+% Redox shuttle ANL-RS21, [22825-00-9]
15-1365: Phosphorus › (2,5-Dimethoxy-1,4-phenylene)bis(di-i-propylphosphine oxide), 99+% Redox shuttle ANL-RS5, [1426397-81-0]
15-1372: Phosphorus › (2,5-Dimethoxy-1,4-phenylene)bis(diethylphosphine oxide), 99+% Redox shuttle ANL-RS51, [1802015-49-1]
15-1375: Phosphorus › 2,5-Di-t-butyl-1,4-phenylene tetraethyl bis(phosphonate), 99+% Redox shuttle ANL-RS6, [1350767-15-5]
14-1925: Silicon › 2,2-Dimethyl-3,6,9-trioxa-2-siladecane, 99+% Electrolyte solvent ANL-1NM2, [62199-57-9]
14-1930: Silicon › 2,2-Dimethyl-3,6,9,12-tetroxa-2-silatridecane, 99+% Electrolyte Solvent ANL-1NM3, [864079-62-9]
14-1943: Silicon › 2,2,4,4-Tetramethyl-3,8,11,14,17-pentaoxa-2,4-disilaoctadecane, 99+% Electrolyte solvent ANL-2SM3, [855996-83-7]
14-1946: Silicon › 2,2-Dimethyl-4,7,10,13-tetraoxa-2-silatetradecane, 99+% Electrolyte solvent ANL-1S1M3, [864079-63-0]