Search

Li-air batteries are considered strong candidates for the next-generation energy storage systems designed for electrical transportation. However, low cyclability and current rates are two major drawbacks that hinder them from further realization. These issues necessitate the discovery of novel materials to significantly enhance the redox process of discharge products. In this study, a novel catalytic system comprised of tin sulfide (SnS) nanoflakes as a solid catalyst and tin iodide (SnI2) as a dual-functional electrolyte additive is discovered. This system enables operating the battery at high current rates up to 10 000 mA g−1 (corresponding to 1 mA cm−2). The SnS catalyst shows outstanding catalytic activity for both oxygen reduction and evolution reactions compared to carbon, noble metals, and other transition metal dichalcogenides. It also exhibits good structural integrity at high rates. The computations indicate numerous possible oxygen reduction sites without oxygen dissociations on the SnS surface through solution mechanism that is likely responsible for the formation of Li2O2. The calculations also indicate that the role of the SnI2 is not only reacting with the lithium anode to provide protection but reducing the charge potential by promoting catalytic decomposition of the Li2O2. This work provides new novel additives for designing high-rate Li-air batteries.

Stable operation of rechargeable lithium-based batteries at low temperatures is important for cold-climate applications, but is plagued by dendritic Li plating and unstable solid–electrolyte interphase (SEI). Here, we report on high-performance Li metal batteries under low-temperature and high-rate-charging conditions. The high performance is achieved by using a self-assembled monolayer of electrochemically active molecules on current collectors that regulates the nanostructure and composition of the SEI and deposition morphology of Li metal anodes. A multilayer SEI that contains a lithium fluoride-rich inner phase and amorphous outer layer effectively seals the Li surface, in contrast to the conventional SEI, which is non-passive at low temperatures. Consequently, galvanic Li corrosion and self-discharge are suppressed, stable Li deposition is achieved from −60 °C to 45 °C, and a Li | LiCoO2 cell with a capacity of 2.0 mAh cm−2 displays a 200-cycle life at −15 °C with a recharge time of 45 min. In addition to high energy, batteries need to possess high power and to be able to operate in all climates. Here, the authors present an electrochemically active monolayer-coated current collector that is used to produce high-performance Li metal batteries under low-temperature and high-rate-charging conditions.

From dictating the redox potential of electrolyte solvents to shaping the stability of solid-electrolyte interfaces, solvation plays a critical role in the electrochemistry of electrolytes. To efficiently design functional electrolytes for lithium batteries, it is particularly important to understand the relative solvating ability of each individual organic solvent, because most of the electrolyte systems are comprised of two or more electrolyte solvents. Using a newly developed internally referenced diffusion-ordered spectroscopy technique and diffusion coefficient–coordination ratio (D–α) analysis, we successfully constructed a solvating power series for common electrolyte solvents. We demonstrated the usefulness of this solvating power series in designing more reliable electrolyte system by selecting an appropriate fluorinated electrolyte solvent for a high-voltage lithium metal battery (LMB) as an example. For a methyl(2,2,2-trifluoroethyl)carbonate-based electrolyte, we identified fluoroethylene carbonate as a more desirable cyclic carbonate co-solvent than difluoroethylene carbonate for LMB due to its significantly higher ability to solvate lithium ions.

Understanding the decaying mechanism in lithium-ion batteries (LIBs) is critical to establishing a stable electrolyte system. Despite the advent of various novel electrolyte solvents designated for high-voltage LIBs, their working principles are not fully understood. Currently, oxidative decomposition of electrolytes is believed to be the major cause of capacity fade, and tremendous effort has been devoted to discovering a new electrolyte with enhanced anodic stability. However, the oxidative decomposition process cannot solely explain the rapid decay of some electrolyte systems with intrinsic high anodic stability when used with a high-nickel layered oxide cathode such as LiNi0.6Mn0.2Co0.2O2 (NMC622). In this report, a study of the quantitative structure-activity relationship was conducted to deepen the mechanistic understanding of the decay in high-voltage LIBs. The results obtained from the newly introduced molecular pair analysis and linear free-energy relationship (LFER) studies were highly consistent with the solvation-involved decaying mechanism in a high-nickel layered oxide cathode cycling at high voltage (> 4.5 V vs. Li/Li+). There was no evidence correlating the solvation ability of electrolyte solvents with the decay of a high-nickel layered oxide cathode cycling at a relatively low voltage (

Various organic compounds were investigated as co-solvents in an ionic liquid (IL), N,N-butylmethyl pyrrolidinium bis(trifluoromethylsulfonyl)imide (Pyr14TFSI), based electrolyte for Li-S batteries. For the Pyr14TFSI/Co-solvent binary system, only 1,3-dioxolane (DOL) afforded stable cycling performance with reasonable Coulombic efficiency (CE). Further increase in DOL concentration leads to a higher initial capacity but deteriorated CE. In an attempt to balance CE and capacity, 2.0 M LiTFSI Pyr14TFSI/DOL (2:1) exhibited optimal performance in terms of initial discharge capacity of 896 mAhg−1 and CE of 98.1% for over 200 cycle. The role of DOL and salt concentration interplay in the binary electrolyte was simulated by ab-initio molecular dynamics (AIMD). The solvation energy with varying co-solvent and LiTFSI salt concentration provides useful information when looking toward implementing other IL-based electrolyte systems for Li-S chemistry.

Seven partially fluorinated ethers (PFE) were studied as co-solvents for lithium-sulfur battery with the goal to understand the interplay between the molecular structure and the electrochemical properties, including capacity, Coulombic efficiency and SEI formation on the Li anode. Electrochemical cycling indicates a loose correlation between the Coulombic efficiency observed over 200 cycles and the fluorination degree of the PFE, which correlates with the computed pKa of the C–H bond of the ethers. PFE with lower pKa (