Spontaneous aggregation of lithium ion coordination polymers in fluorinated electrolytes for high-voltage batteries.

Fluorinated carbonates are pursued as liquid electrolyte solvents for high-voltage Li-ion batteries. Here we report aggregation of [Li(+)(FEC)3]n polymer species in fluoroethylene carbonate containing electrolytes and scrutinize the causes for this behavior.

In situ Synchrotron X-ray Metrology Boosted by Automated Data Analysis for Real-time Monitoring of Cathode Calcination.

Synchrotron X-ray-based in situ metrology is advantageous for monitoring the synthesis of battery materials, offering high throughput, high spatial and temporal resolution, and chemical sensitivity. However, the rapid generation of massive data poses a challenge to on-site, on-the-fly analysis needed for real-time process monitoring. Here, a weighted lagged cross-correlation (WLCC) similarity approach is presented for automated data analysis, which merges with in situ synchrotron X-ray diffraction metrology to monitor the calcination process of the archetypal nickel-based cathode, LiNiO2. The WLCC approach, incorporating variables that account for peak shifts and width changes associated with structural transformations, enables rapid extraction of phase progression within 10 seconds from tens of diffraction patterns. Details are captured, from initial precursors to intermediates and the final layered LiNiO2, providing information for agile on-site adjustments during experiments and complementing post hoc diffraction analysis by offering insights into early-stage phase nucleation and growth. Expanding this data-powered platform paves the way for real time calcination process monitoring and control, which is pivotal to quality control in battery cathode manufacturing.

In Situ Insights into Cathode Calcination for Predictive Synthesis: Kinetic Crystallization of LiNiO2 from Hydroxides.

Calcination is a solid-state synthesis process widely deployed in battery cathode manufacturing. However, its inherent complexity associated with elusive intermediates hinders the predictive synthesis of high-performance cathode materials. Here, correlative in situ X-ray absorption/scattering spectroscopy is used to investigate the calcination of nickel-based cathodes, focusing specifically on the archetypal LiNiO2 from Ni(OH)2. Combining in situ observation with data-driven analysis reveals concurrent lithiation and dehydration of Ni(OH)2 and consequently, the low-temperature crystallization of layered LiNiO2 alongside lithiated rocksalts. Following early nucleation, LiNiO2 undergoes sluggish crystallization and structural ordering while depleting rocksalts; ultimately, it turns into a structurally-ordered layered phase upon full lithiation but remains small in size. Subsequent high-temperature sintering induces rapid crystal growth, accompanied by undesired delithiation and structural degradation. These observations are further corroborated by mesoscale modeling, emphasizing that, even though calcination is thermally driven and favors transformation towards thermodynamically equilibrium phases, the actual phase propagation and crystallization can be kinetically tuned via lithiation, providing freedom for structural and morphological control during cathode calcination.

Cobalt-free composite-structured cathodes with lithium-stoichiometry control for sustainable lithium-ion batteries.

Lithium-ion batteries play a crucial role in decarbonizing transportation and power grids, but their reliance on high-cost, earth-scarce cobalt in the commonly employed high-energy layered Li(NiMnCo)O2 cathodes raises supply-chain and sustainability concerns. Despite numerous attempts to address this challenge, eliminating Co from Li(NiMnCo)O2 remains elusive, as doing so detrimentally affects its layering and cycling stability. Here, we report on the rational stoichiometry control in synthesizing Li-deficient composite-structured LiNi0.95Mn0.05O2, comprising intergrown layered and rocksalt phases, which outperforms traditional layered counterparts. Through multiscale-correlated experimental characterization and computational modeling on the calcination process, we unveil the role of Li-deficiency in suppressing the rocksalt-to-layered phase transformation and crystal growth, leading to small-sized composites with the desired low anisotropic lattice expansion/contraction during charging and discharging. As a consequence, Li-deficient LiNi0.95Mn0.05O2 delivers 90% first-cycle Coulombic efficiency, 90% capacity retention, and close-to-zero voltage fade for 100 deep cycles, showing its potential as a Co-free cathode for sustainable Li-ion batteries.

A fluorinated cation introduces new interphasial chemistries to enable high-voltage lithium metal batteries.

Fluorides have been identified as a key ingredient in interphases supporting aggressive battery chemistries. While the precursor for these fluorides must be pre-stored in electrolyte components and only delivered at extreme potentials, the chemical source of fluorine so far has been confined to either negatively-charge anions or fluorinated molecules, whose presence in the inner-Helmholtz layer of electrodes, and consequently their contribution to the interphasial chemistry, is restricted. To pre-store fluorine source on positive-charged species, here we show a cation that carries fluorine in its structure is synthesized and its contribution to interphasial chemistry is explored for the very first time. An electrolyte carrying fluorine in both cation and anion brings unprecedented interphasial chemistries that translate into superior battery performance of a lithium-metal battery, including high Coulombic efficiency of up to 99.98%, and Li0-dendrite prevention for 900 hours. The significance of this fluorinated cation undoubtedly extends to other advanced battery systems beyond lithium, all of which universally require kinetic protection of highly fluorinated interphases.

Fluorinated High-Voltage Electrolytes To Stabilize Nickel-Rich Lithium Batteries.

As state-of-the-art (SOA) lithium-ion (Li-ion) batteries approach their specific energy limit (∼250 Wh kg-1), layer-structured, nickel-rich (Ni-rich) lithium transition metal oxide-based cathode materials, e.g., LiNi0.8Mn0.1Co0.1O2 (NMC811), have attracted great interest owing to their practical high specific capacities (>200 mAhg-1). Coupled with their high average discharge voltages (∼4 V vs Li/Li+), Ni-rich cathode-based lithium batteries possess a great potential to achieve much higher specific energies (>350 Wh kg-1 at the cell level) than the SOA Li-ion counterparts. In addition, Ni-rich oxides are low-cost battery cathode materials due to their low cobalt contents. However, Ni-rich cathode-based lithium batteries suffer quick capacity degradations upon cycling, particularly at high upper cutoff voltages (e.g., ≥4.5 V vs Li/Li+), due to crystal structure changes of the active cathode materials and parasitic side reactions at the electrolyte/electrode interfaces. In this study, a fluorinated-solvent-based, high-voltage stable electrolyte (HVE), i.e., 1 M Li bis(trifluoromethanesulfonyl)imide (LiTFSI) in fluoroethylene carbonate (FEC), bis(2,2,2-trifluoroethyl) carbonate (FDEC), and methyl (2,2,2-trifluoroethyl) carbonate (FEMC) with Li difluoro(oxalate)borate (LiDFOB) additive, was formulated and evaluated in Li/NMC811 battery cells. To the best of our knowledge, this class of electrolyte has not been investigated for Ni-rich cathode-based lithium batteries. Li/NMC811 cells with HVE exhibited a superior long-term cycle performance stability, maintaining ∼80% capacity after ∼500 cycles at a high cutoff voltage of 4.5 V (vs Li/Li+) than a baseline carbonate-solvent-based electrolyte (BE). The superior cycle stability of the Li/NMC811 cells is attributed to the inherently high-voltage stability of HVE, supported by the physical and electrochemical analyses. This conclusion is supported by our density functional theory (DFT) modeling where HVE shows a less tendency of deprotonation/oxidation than BE, leading to the observed cycle stability. The findings in this study are important to help tackle the technical challenges facing Ni-rich cathode-based lithium batteries to realize their high energy density potentials with a long cycle life.

A fluorine-substituted pyrrolidinium-based ionic liquid for high-voltage Li-ion batteries.

A fluorine-substituted ionic liquid based on a pyrrolidinium cation and a bis(fluorosulfonyl)imide anion was synthesized using a facile one-step reaction. The resulting ionic liquid is highly pure and when dissolved with LiFSI, the IL-based electrolyte showed good compatibility both in Li and graphite anodes, and superior voltage stability is demonstrated in a LiNi0.5Mn0.3Co0.2O2 cell.

Stabilized Electrode/Electrolyte Interphase by a Saturated Ionic Liquid Electrolyte for High-Voltage NMC532/Si-Graphite Cells.

Nonaqueous electrolyte has become one of the technical barriers in enabling Li-ion battery comprising of a high voltage cathode and high capacity anode. In this work, we demonstrate a saturated piperidinum bis(fluorosulfonyl)imide ionic liquid (IL) with a LiFSI salt not only supports the redox reaction on the cathode at high voltages, but also shows exceptional kinetic stability on the lithiated anode as evidenced by its improved cycling performance in a NMC532/Si-graphite full cells cycled between 4.6 and 3.0 V. On the basis of the spectroscopic/microscopic analysis and molecular dynamics (MD) simulations, the superior performance of the cells is attributed to the formation of solid-electrolyte-interphase on both electrode as well as unique solvation structure where a deadlocked coordination network is established at the saturated state, which prevents transition metal dissolution into the electrolyte via a solvation process.

Selective killing of nonreplicating mycobacteria.

Antibiotics are typically more effective against replicating rather than nonreplicating bacteria. However, a major need in global health is to eradicate persistent or nonreplicating subpopulations of bacteria such as Mycobacterium tuberculosis (Mtb). Hence, identifying chemical inhibitors that selectively kill bacteria that are not replicating is of practical importance. To address this, we screened for inhibitors of dihydrolipoamide acyltransferase (DlaT), an enzyme required by Mtb to cause tuberculosis in guinea pigs and used by the bacterium to resist nitric oxide-derived reactive nitrogen intermediates, a stress encountered in the host. Chemical screening for inhibitors of Mtb DlaT identified select rhodanines as compounds that almost exclusively kill nonreplicating mycobacteria in synergy with products of host immunity, such as nitric oxide and hypoxia, and are effective on bacteria within macrophages, a cellular reservoir for latent Mtb. Compounds that kill nonreplicating pathogens in cooperation with host immunity could complement the conventional chemotherapy of infectious disease.

Pyranocoumarin, a novel anti-TB pharmacophore: synthesis and biological evaluation against Mycobacterium tuberculosis.

Pyranocoumarin compounds were identified to embody a novel and unique pharmacophore for anti-TB activity. A systematic approach was taken to investigate the structural characteristics. Focused libraries of compounds were synthesized and evaluated for their anti-TB activity in primary screening assays. Compounds shown to be active were further determined for MIC and MBC values. Three of the four bactericidal compounds (16, 17c, and 18f) were amino derivatives, with MIC values of 16 microg/mL and respective MBC values of 32, 32, and 64 microg/mL.