Enhancement of Lithium Anode Cyclability in Propylene Carbonate Electrolyte by  CO 2 Addition and Its Protective Effect Against  H 2 O  Impurity

Abstract

The charge‐discharge behavior of a lithium metal anode in propylene carbonate (PC) electrolyte containing added CO2 was investigated using in situ ac impedance measurements during galvanostatic cycling. In PC electrolyte with CO2 , the anode's cycle life was twice as long and its charge transfer resistance was smaller than in the same electrolyte without CO2 . These enhancements are observed only when lithium is electrodeposited in the presence of CO2 on nickel substrate; the enhancement does not occur when lithium is deposited without CO2 and is cycled with CO2 . Even large amounts of H2O in the electrolyte during cycling do not adversely affect the cycle life enhancement by CO2 . The CO2 enhancement seems to be due to products formed by reaction of lithium with CO2 on the electrodeposited lithium surface.

Liquefied gas electrolytes for electrochemical energy storage devices

“…In the fluoromethane system, the solvent itself forms a LiF layer when reduced, which removes the need for LiAsF 6 salt. In addition, the reduction of carbon dioxide to form Li carbonate has been shown to improve the impedance and cyclability of the Li metal anode (37), which is used to stabilize the electrode in the present study. More recently, other electrolyte systems have been shown to have high Li plating and stripping efficiencies without the use of LiAsF 6 , but none have demonstrated suitable oxidation stability for use with conventional 4 V cathode systems owing to the poor stability at increased potentials of these ether-based electrolytes (38).…”

A Review of Solid Electrolyte Interphases on Lithium Metal Anode

“…This issue is a great problem for practical Li–air cells and these compounds even corrode the Li metal during long cycling tests . However, Osaka and co‐workers reported that the long‐cycle‐life of Li anode was twice as long and its charge transfer resistance in propylene carbonate electrolyte with saturated CO 2 was smaller than that in the same electrolyte without CO 2 . Even with 3000 ppm H 2 O concentration in propylene carbonate electrolyte, cycle life was enhanced by CO 2 .…”

Dendrite‐Suppressed Lithium Plating from a Liquid Electrolyte via Wetting of Li3N

“…A second problem is that the Fermi level of lithium is about 1.2 eV above the lowest unoccupied molecular orbital of the liquid electrolyte, which means that a solid electrolyte interphase (SEI) must form on the surface of a lithium anode to passivate the reduction of the electrolyte by the anode; the SEI must be a Li + conductor and retain its interface with the solid anode over many charge/discharge cycles. Traditionally, it has been assumed that an artificial, uniform, mechanically robust, and thin solid SEI could block or prevent dendrite nucleation and growth during electrodeposition, and electrolyte additives such as H 2 O, CO 2 , and halogenated salts have been added to the electrolyte for the formation of a uniform and dense LiF or Li 2 CO 3 SEI that lowers the resistance to Li + transfer across the lithium/electrolyte interfaces and increases the cycling efficiency, but they do not completely suppress or block dendrite formation and growth . Artificial SEI coatings on a lithium anode have also been explored; thin‐film Al 2 O 3 and Li 3 N coatings have been reported to increase cycling stability of a lithium anode .…”