Selection of Redox Mediators for Reactivating Dead Li in Lithium Metal Batteries

Abstract

Li metal batteries have suffered from dendrite growth and its derived dead Li formation for a long time. A new lithium restoration method through the shuttling of redox mediators has been proposed recently. However, the side reaction of severe self‐discharge often occurs when some redox mediators are used. Here, a selection principle of redox mediators for reactivating dead Li in lithium metal batteries is put forward, which is able to reactivate the dead Li effectively and reduce the self‐discharge at the same time. Three redox mediators of ferrocene (Fc), 10‐methylphenothiazine (MPT), and thianthrene (Th) with different redox potentials are tested in LiFePO4|Cu anode‐free Li metal batteries to clarify the selection principle. Furthermore, 2,2,6,6‐tetramethylpiperidinooxy (TEMPO), which is speculated to be a suitable one for reactivating dead Li in lithium metal batteries, is verified. This work provides a universal selection principle of redox mediators and may boost its practical application in Li metal batteries.

Clay‐Originated Two‐Dimensional Holey Silica Separator for Dendrite‐Free Lithium Metal Anode

“…The peak at 3.3 V corresponds to the reduction of Fe 3+ to Fe 2+ accompanied by the intercalation of Li ions, while the peak at 3.5 V is ascribed to the oxidation of Fe 2+ to Fe 3+ associated with the extraction of Li + . [57,58] At the same scan rate of 0.5 mV s −1 (Figure 4g), the peak current of the ASN-Sep-based battery is almost 1.5 times higher than that of the PP-Sep-based battery, indicating significantly enhanced reaction kinetics. The peak current (I p ) shows a linear relationship as a function of the square root of scan rate (v 0.5 ) (Figure S26c, Supporting Information).…”

Solutions to the Challenges of Lithium–Sulfur Batteries by Carbon Nanotubes

“…[37] The detached large lithium debris (referred to as the "dead lithium") from the conductive current collector is no longer electrochemically active and does not contribute to the energy capacity. [38] Adding to the problem, the volume expansion, associated with the repetitive fracture and growth of the solid electrolyte interface (SEI) by the unstable lithium metal reacting with materials in the electrolyte (such as the soluble polysulfides from the cathode), aggravates the anode corrosion and the subsequent uncontrolled dendrite growth. [39] Eventually, the incessant volume expansion and the corresponding structural collapse of the anode accompanied by the irreversible loss of lithium metal result in poor cycling stability and short circuits for LSBs due to the dendrites piercing through the separator, as shown in Figure 3c.…”

Recycling inactive lithium in lithium–sulfur batteries using organic polysulfide redox

“…Recycling inactive Li using redox, such as the redox of iodine redox (I 3 − /I − ), 10-methylphenothiazine, and 2,2,6,6-tetramethylpiperidinooxy, has been employed to reclaim inactive Li in Li metal batteries. [48][49][50][51] However, highly reactive soluble LiPSs in working Li-S batteries severely challenge the recycling of inactive Li. The reaction between soluble LiPSs and redox agents will deactivate the redox agents, while the sulfur redox reactions in Li-S batteries will also be affected in turn.…”