Understanding the Critical Role of the Ag Nanophase in Boosting the Initial Reversibility of Transition Metal Oxide Anodes for Lithium-Ion Batteries

Abstract

The initial reversible capacity, a critical impediment in transition metal oxide-based anodes, is augmented in conversion-reaction-involved CoO anodes for lithium-ion batteries, by incorporating a chemically synthesized Ag nanophase. With an increase in the added amount of Ag nanophase from 5 to 15 wt %, the initial capacity loss decreases linearly up to 31.7%. The Ag nanophase maintains its pristine metallic nature without undergoing phase transformations, even during repeated vigorous electrochemical reactions of the active CoO phase. Complementary ex situ chemical/physical analyses suggest that the Ag nanophase promotes the catalytic generation of reversible gel-like/polymeric films wherein lithium ions are stored capacitively in the low-voltage region below 0.7 V during discharging. These scientific findings would provide a heretofore unrecognized pathway to resolving a major issue associated with the critical irreversibility in conversion-type transition metal oxide anodes.

Preparation of ZnFe2O4/α-Fe2O3 Nanocomposites From Sulfuric Acid Leaching Liquor of Jarosite Residue and Their Application in Lithium-Ion Batteries

“…Each plot consists of one depressed semicircle or two semicircles in the high to moderate frequency region and an inclined line in the low frequency region. The depressed semicircles can be assigned to the resistance of Li + migrating through the SEI film and the charge-transfer resistance at electrode/electrolyte interface (denoted as R sf+ct ), and the inclined line represents the Warburg impedance related to Li + diffusion process into the bulk of the electrode (Wang et al, 2015 ; Li et al, 2016 ; Kong et al, 2017 ; Lee et al, 2017 ). Before cycling, the Warburg straight line is almost vertical to the real-axis (capacitive behavior), suggesting that there is almost no detectable Li + intercalation in the electrode for fresh cell.…”

Using nanoconfinement to inhibit the degradation pathways of conversion-metal oxide anodes for highly stable fast-charging Li-ion batteries

“…[30][31][32] Second, there is an entropic penalty associated with the repetitive restructuring and collapse of the parent host (MO / M + Li 2 O), [32][33][34] which can lead to the growth of larger particles and phase segregation to minimize surface free energy. Third, there can be continued growth of the solid electrolyte interphase (SEI) due to physical changes in the electrode during charge/discharge, [35][36][37][38][39] which can reduce the electrode capacity during cycling through both increased irreversible capacity loss as well as particle detachment and metal trapping within the SEI. [40][41][42][43] Finally, through reaction either with excess electrolyte or the SEI, MOs undergo a side reaction that forces them to higher oxidation states during their lifetimea reaction that lowers their achievable coulombic efficiency (but not their achievable capacity since the reaction does not consume Li) 9 .…”

Electrostatically Assembled Silicon–Carbon Composites Employing Amine-Functionalized Carbon Intra-interconnections for Lithium-Ion Battery Anodes

“…Transition metal oxide- and Si-based anodes have been regarded as promising alternatives. Metal oxide-based anodes, governed by a conversion reaction, have theoretical capacities superior to those of graphite depending on their compositions, − and silicon has a high theoretical capacity of ∼4200 mAh/g. − However, both anodic materials have significant drawbacks that should be resolved for practical applications. Si-based anodes suffer from a low electrical conductivity and a high volumetric expansion during lithiation reaction.…”