Quantitative Analysis of Origin of Lithium Inventory Loss and Interface Evolution over Extended Fast Charge Aging in Li Ion Batteries.

During the extreme fast charging (XFC) of lithium-ion batteries, lithium inventory loss (LLI) and reaction mechanisms at the anode/electrolyte interface are crucial factors in performance and safety. Determining the causes of LLI and quantifying them remain an essential challenge. We present mechanistic research on the evolution and interactions of aging mechanisms at the anode/electrolyte interface. We used NMC532/graphite pouch cells charged at rates of 1, 6, and 9 C up to 1000 cycles for our investigation. The cell components were characterized after cycling using electrochemical measurements, inductively coupled plasma optical emission spectroscopy, 7Li solid-state nuclear magnetic resonance spectroscopy, and high-performance liquid chromatography/mass spectrometry. The results indicate that cells charged at 1 C exhibit no Li plating, and the increase of SEI thickness is the dominant source of the Li loss. In contrast, Li loss in cells charged at 9 C is related to the formation of the metallic plating layers (42%) the SEI layer (38.1%) and irreversible intercalation into the bulk graphite (19%). XPS analysis suggests that the charging rate has little influence on the evolution of SEI composition. The interactions between competing aging mechanisms were evaluated by a correlation analysis. The quantitative method established in this work provides a comprehensive analytical framework for understanding the synergistic coupling of anodic degradation mechanisms, forecasting SEI failure scenarios, and assessing the XFC lithium-ion battery capacity fade.

Exploring the Promise of Multifunctional "Zintl-Phase-Forming" Electrolytes for Si-Based Full Cells.

Li-M-Si ternary Zintl phases have gained attention recently due to their high structural stability, which can improve the cycling stability compared to a bulk Si electrode. Adding multivalent cation salts (such as Mg2+ and Ca2+) in the electrolyte was proven to be a simple way to form Li-M-Si ternary phases in situ in Si-based Li-ion cells. To explore the promise of Zintl-phase-forming electrolytes, we systematically investigated their application in pouch cells via electrochemical and multiscale postmortem analysis. The introduction of multivalent cations, such as Mg2+, during charging can form LixMySi ternary phases. They can stabilize Si anions and reduce side reactions with electrolyte, improving the bulk stability. More importantly, Mg2+ and Ca2+ incorporate into interfacial side reactions and generate inorganic-rich solid-electrolyte interphase, thus enhancing the interfacial stability. Therefore, the full cells with Zintl-phase-forming electrolytes achieve higher capacity retentions at the C/3 rate after 100 cycles, compared to a baseline electrolyte. Additionally, strategies for mitigating the electrode-level fractures of Si were evaluated to make the best use of Zintl-phase-forming electrolytes. This work highlights the significance of synergistic impact of multifunctional additives to stabilize both bulk and interface chemistry in high-energy Si anode materials for Li-ion batteries.

Toward practical issues: Identification and mitigation of the impurity effect in glyme solvents on the reversibility of Mg plating/stripping in Mg batteries.

Reversible electrochemical magnesium plating/stripping processes are important for the development of high-energy-density Mg batteries based on Mg anodes. Ether glyme solutions such as monoglyme (G1), diglyme (G2), and triglyme (G3) with the MgTFSI2 salt are one of the conventional and commonly used electrolytes that can obtain the reversible behavior of Mg electrodes. However, the electrolyte cathodic efficiency is argued to be limited due to the enormous parasitic reductive decomposition and passivation, which is governed by impurities. In this work, a systematic identification of the impurities in these systems and their effect on the Mg deposition-dissolution processes is reported. The mitigation methods generally used for eliminating impurities are evaluated, and their beneficial effects on the improved reactivity are also discussed. By comparing the performances, we proposed a necessary conditioning protocol that can be easy to handle and much safer toward the practical application of MgTFSI2/glyme electrolytes containing impurities.

Understanding the Effect of Cathode Composition on the Interface and Crosstalk in NMC/Si Full Cells.

Crosstalk between the cathode and the anode in lithium-ion batteries has a great impact on performance, safety, and cycle lifetime. However, no report exists for a systematic investigation on crosstalk behavior in silicon (Si)-based cells as a function of transition metal composition in cathodes. We studied the effect of crosstalk on degradation of Si-rich anodes in full cells with different cathodes having the same crystal structure but different transition metal compositions, such as LiNi1/3Mn1/3Co1/3O2 (NM111), LiNi0.5Mn0.3Co0.2O2 (NMC532), and LiNi0.8Mn0.1Co0.1O2 (NMC811). We found that the transition metal composition in cathodes, especially Mn ion concentration, significantly affects electrolyte decomposition reactions, even from very early cycles. This change causes differences in the solid electrolyte interphase (SEI) chemistry of each aged Si sample. As a result, each of the aged Si samples has a different electrochemistry, in terms of initial Coulombic efficiency and the mechanism of capacity fade.

Enabling High-Temperature and High-Voltage Lithium-Ion Battery Performance through a Novel Cathode Surface-Targeted Additive.

Lithium-ion batteries (LIBs) are being used in locations and applications never imagined when they were first conceived. To enable this broad range of applications, it has become necessary for LIBs to be stable to an ever broader range of conditions, including temperature and energy. Unfortunately, while negative electrodes have received a great deal of focus in electrolyte development, stabilization of positive electrodes remains an elusive target. Here, we report a novel additive that shows the ability to protect positive electrodes against elevated temperatures and voltages. This additive can be used in small quantities, and its targeted behavior allows it to remain functional in complex electrolyte packages. This can prove an effective approach to targeting specific aspects of cell performance.

Chemical Interplay of Silicon and Graphite in a Composite Electrode in SEI Formation.

We investigated the effect of the Si/graphite weight ratio in half-cells on the solid electrolyte interphase (SEI) layer's chemistry. The nominal concentrations of active materials were (wt % Si/wt % Gr) 15/73, 30/58, 60/28, and 80/0. The electrolyte in the cells consisted of either 1.2 M LiPF6 in ethylene carbonate/ethyl methyl carbonate (3:7 by wt) or 1.2 M LiPF6 in ethylene carbonate:ethyl methyl carbonate (3:7 by wt) + 10 wt % fluoroethylene carbonate. These coin cells were cycled five times at the C/10 rate. As expected, the addition of silicon to the electrode significantly increased the measured capacity. Examination of the aged composite material showed that the electrolyte influenced the concentration of chemical environments on the surface. Depth profiling revealed that these concentrations of surface environments changed with sputtering time. A statistics-of-mixtures model was used to deconvolute how silicon and graphite interacted during the formation of these species and how the interaction changed with depth.

In Situ Localized Polysulfide Injector for the Activation of Bulk Lithium Sulfide.

The activation of commercial Li2S remains to be one of the key challenges against its commercialization as a starting cathode material for a sulfur-based Li-ion battery system. In this work we take advantage of the lower oxidation potential of commercial Na2S (1-3 wt%) to serve as an in situ and local polysulfide injector for the activation of commercial Li2S (70 wt%). In contrast to applying pre-solvated redox mediators, this technique allows for the activation of commercial Li2S at lower voltages with an electrolyte content as low as 3 µL mg-1Li2S at 3 mgmgLi2S cm-2 and 4 µL mg-1Li2S at 6.5 mgLi2S cm-2 without any other material modification.

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.

New insights into the electrode mechanism of lithium sulfur batteries via air-free post-test analysis.

Effects of the volume expansion and shrinkage of Li2S cathodes on electrochemical cycle life are investigated via post-test analysis without exposure to air. The engineered electrodes that confine volume changes within micro-reactors have significantly longer life than the electrodes without the micro-reactor structure, providing the first unambiguous evidence of the importance of confining volume changes for improved battery performance.

What every dentist should know about coffee.

Coffee is one of the most widely consumed beverages throughout the world. Its stimulating nature is responsible for much of its popularity, which paradoxically has resulted in its reputation for negative effects on consumer health. This review will address recent research on the systemic and dental health effects of coffee. Many of its supposed harmful effects have been disproved, while many protective and beneficial roles for coffee are emerging.

Double-masked, randomized, placebo-controlled study to evaluate the efficacy and tolerability of intranasal K305 (3% tetracaine plus 0.05% oxymetazoline) in anesthetizing maxillary teeth.

BACKGROUND: The authors compared the local anesthetic efficacy and safety of an intranasally administered formulation of tetracaine and oxymetazoline (K305) with placebo in adult participants undergoing single dental restorative procedures in teeth nos. 4 through 13. METHODS: The authors screened and allocated 150 participants in a double-masked, randomized fashion to either K305 or placebo nasal spray. The authors delivered the study drug as two 0.2-milliliter sprays separated by 4 minutes inside the nostril on the side ipsilateral to the tooth being treated. The authors administered a third 0.2-mL spray, if necessary, and administered 4% articaine with 1:200,000 epinephrine by means of injection if anesthesia was inadequate. Safety evaluations included participant reports of adverse events, vital signs, and alcohol sniff tests during the 2-hour study period and at a 1-day follow-up visit. The primary efficacy end point was anesthetic success defined as the completion of the dental procedure without the need for rescue injectable local anesthetic. The authors evaluated differences in success rates observed between K305 and placebo by using a 1-sided Fisher exact test. RESULTS: The overall success rates were 88.0% (95% confidence interval, 80.0-93.6) and 28% (95% confidence interval, 16.2-42.5) for K305 and placebo, respectively (P < .0001). The most frequent adverse effects in the K305 group were rhinorrhea (57.0%) and nasal congestion (26.0%). No serious adverse events occurred during this study. CONCLUSIONS: K305 was effective and well tolerated during restorative procedures in adult participants. PRACTICAL IMPLICATIONS: K305 provides a needleless alternative for obtaining maxillary pulpal anesthesia on premolars, canines, and incisors.

Understanding the effect of a fluorinated ether on the performance of lithium-sulfur batteries.

A high performance Li-S battery with novel fluoroether-based electrolyte was reported. The fluorinated electrolyte prevents the polysulfide shuttling effect and improves the Coulombic efficiency and capacity retention of the Li-S battery. Reversible redox reaction of the sulfur electrode in the presence of fluoroether TTE was systematically investigated. Electrochemical tests and post-test analysis using HPLC, XPS, and SEM/EDS were performed to examine the electrode and the electrolyte after cycling. The results demonstrate that TTE as a cosolvent mitigates polysulfide dissolution and promotes conversion kinetics from polysulfides to Li2S/Li2S2. Furthermore, TTE participates in a redox reaction on both electrodes, forming a solid electrolyte interphase (SEI) which further prevents parasitic reactions and thus improves the utilization of the active material.

Probing thermally induced decomposition of delithiated Li(1.2-x)Ni(0.15)Mn(0.55)Co(0.1)O2 by in situ high-energy X-ray diffraction.

Safety of lithium-ion batteries has been a major barrier to large-scale applications. For better understanding the failure mechanism of battery materials under thermal abuse, the decomposition of a delithiated high energy cathode material, Li1.2-xNi0.15Mn0.55Co0.1O2, in the stainless-steel high pressure capsules was investigated by in situ high energy X-ray diffraction. The data revealed that the thermally induced decomposition of the delithiated transition metal (TM) oxide was strongly influenced by the presence of electrolyte components. When there was no electrolyte, the layered structure for the delithiated TM oxide was changed to a disordered Li1-xM2O4-type spinel, which started at ca. 266 °C. The disordered Li1-xM2O4-type spinel was decomposed to a disordered M3O4-type spinel phase, which started at ca. 327 °C. In the presence of organic solvent, the layered structure was decomposed to a disordered M3O4-type spinel phase, and the onset temperature of the decomposition was ca. 216 °C. When the LiPF6 salt was also present, the onset temperature of the decomposition was changed to ca. 249 °C with the formation of MnF2 phase. The results suggest that a proper optimization of the electrolyte component, that is, the organic solvent and the lithium salt, can alter the decomposition pathway of delithiated cathodes, leading to improved safety of lithium-ion batteries.

A XANES study of LiVPO4F: a factor analysis approach.

Evolving factor analysis (EFA) of X-ray absorption near-edge spectroscopy (XANES) data is shown to be a useful tool to understand the phase relationships and compositional ranges of stability in the LiVPO4F-VPO4F system. EFA was used to calculate the concentration of phases versus state-of-charge in a lithium-ion battery and true XANES spectra. The results of EFA showed that, indeed, three phases were present during cycling of a LiVPO4F∥Li cell: LiVPO4F, LixVPO4F, and VPO4F. In contrast to what was reported by others, the second phase was not a fixed composition with x = 0.67, but, instead, existed over a range of lithium stoichiometry, x = 0.25 to 0.80. EFA results also showed that the reactions leading to these phases are reversible.