High Electrolyte Concentrations Research Articles

Relating Chemo-Mechanical Hysteresis and Formation Protocols for Anode-Free Lithium Metal Batteries

Cell formation is an energy and time-intensive empirically-guided process crucial to manufacturing secondary lithium-ion batteries. As the rechargeable battery industry moves towards manufacturing lithium metal batteries—where a metallic lithium negative electrode is used instead of a porous graphite composite—the cell formation process may need reconsidering. The effects of formation rate and cycling protocol on lithium metal battery performance are poorly understood. In this work, we used operando acoustic transmission to measure physical changes during the formation cycles and the effect of formation cycling protocols on the long-term cycling of anode-free lithium metal pouch cells—where all the lithium inventory comes from the positive electrode and is deposited as metallic lithium on copper foil during initial charge. We show that a faster C/3 formation protocol results in comparable cycling performance and cell stiffness change to a slower C/10 formation step. Variations in acoustic metrics across different electrolytes tested are attributed to differences in gas formation, cell swelling, and lithium deposition morphology. NMC811 cathodes paired with a high-concentration ether electrolyte are shown to be particularly prone to gas formation, which is mitigated by using a localized high-concentration ether electrolyte and single-crystal NMC532. The results highlight differences in formation behavior between anode-free lithium metal cells and lithium-ion cells. These are important to consider when bringing new manufacturing plants online for lithium metal batteries.

Water/DMSO-Based Hybrid Electrolyte and Urea Additive Engineering for Performance Regulation in Aqueous Sodium Batteries

Electrochemical energy storage devices are of interest, especially aqueous sodium ion batteries (ASIBs), due to their safety, low-cost, and environmental friendliness. However, ASIBs suffer from poor cyclic stability and a narrow electrochemical window, which hinders their large-scale application. Compared to the traditional dilute saline electrolytes, high concentration electrolytes show a wider potential window. In this study, we designed a novel NaClO4-H2O/DMSO-Urea hybrid electrolyte to suppress these problems, in which DMSO and Urea create a synergistic effect. The formation of hydrogen bonds between DMSO and H2O reduced water activity, thereby suppressing the hydrogen evolution reaction. The addition of DMSO resulted in the reduction from −1.2 to −1.6 V for the hydrogen evolution potential. Therefore, we were able to expand the electrochemical window on the basis of reducing the concentration of sodium salts. Moreover, the addition of Urea facilitated formation of a stable solid electrolyte interface on the electrode surface, which improved the cycling stability of NVP/C (Na3V2(PO3)4/C) symmetric cell which exhibited a specific capacity of 59.7 mAh g−1 with the retention capacity of 80.1% after 200 cycles at 1 C. This work points out a promising strategy for developing stable and wide voltage aqueous electrolyte.

Electron-repulsion effect of anti-solvent strategy for long-cycle nickel sulfide-containing potassium-ion batteries

Transition metal dichalcogenides experience severe structural degradation when used as anodes in potassium-ion batteries, resulting in undesirable electrochemical behaviors. To tackle this challenge, a novel approach involving "anti-solvent-enhanced local high-concentration electrolytes" was proposed to enhance the electrochemical stability of transition metal dichalcogenides for potassium-ion storage. This improvement is attributed to the facilitation of the aggregation of local solvation structures within the ether-based electrolyte. We demonstrate the effectiveness of this method by utilizing nickel sulfide composite materials. By diluting the ether-based high-concentration electrolyte with 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (HFE) anti-solvent, the nickel sulfide containing anode achieved an ultra-high specific capacity of 382 mAh g−1 after 1500 cycles at 1 A g−1. We found that the HFE anti-solvent, with its high concentration of negatively charged fluorine atoms, exerts a strong electron-repulsion effect on the bis(fluorosulfonyl)imide anions, promoting the aggregation of local solvation structures. It not only lowers the desolvation energy but also exhibits high stability during interactions with the interface, thereby improving and keeping the K-ion’s migration ability. This, in turn, improves the cycling stability of the electrode during the potassiation-depotassiation process. We believe that this new strategy of improving potassium-ion storage performance will drive advancements in related fields.

Compatibility and effect of capacity ratios between Na3V2(PO4)3 and hard carbon in highly concentrated sodium bis (fluorosulfonyl) imide electrolyte

From the standpoint of preserving the Earth's resources and ensuring the long-term viability of humanity, it is imperative to transition away from lithium-ion batteries. High-performance and safe sodium-ion batteries have recently emerged as promising advanced batteries for application in stationary energy storage, attributed to their low cost and abundance of sodium ion. We demonstrate the compatibility and effect of the negative-positive capacity ratio in full-cell Na3V2(PO4)3 and hard carbon in high-concentration electrolytes. Thanks to the excellent oxidation stability of the electrolyte, during 100 cycles, the full cell with a negative-positive capacity ratio of 1.1 demonstrated a consistent capacity of around 100 mAh g-1 with a capacity retention of 90.7%, whereas the full cell with a ratio of 1.0 showed a steady discharge capacity of roughly 90 mAh g-1 with a capacity retention of approaching 100% at a current density of C/5.

The Effect of Lysozyme on the Aggregation and Charging of Oxidized Carbon Nanohorn (CNHox) in Aqueous Solution

To clarify the effect of proteins on the charging and aggregation–dispersion characteristics of oxidized carbon nanohorn (CNHox), we measured the electrophoretic mobility and stability ratios as a function of concentrations of a model protein, lysozyme (LSZ), and KCl. The zeta potential from the electrophoretic mobility of CNHox was neutralized and reversed by the addition of oppositely charged LSZ. Electrical and hydrophobic interactions between CNHox and LSZ can be attributed to the adsorption and charge reversal of CNHox. The stability ratio of CNHox in the presence or absence of LSZ showed Derjaguin–Landau and Verwey–Overbeek (DLVO) theory-like behavior. That is, the slow aggregation regime, fast aggregation regime, and critical coagulation concentration (CCC) were identified. At the isoelectric point, only the fast aggregation regime was shown. The existence of patch-charge attraction due to the charge heterogeneity on the surface was inferred to have happened due to the enhanced aggregation of CNHox at high LSZ dosage and low electrolyte concentration. The relationship between critical coagulation ionic strength and surface charge density at low LSZ dosage showed that the aggregation of CNHox is in line with the DLVO theory. An obvious decrement in the Hamaker constant at high LSZ dosage can probably be found due to an increased interaction of LSZ-covered parts.

Covalently grafting multihydroxy hyperbranched polymer on the surface of Ti3C2Tx MXene with remarkably enhanced colloidal stability and functionality for photothermal therapy

While MXenes have garnered acknowledgment for their remarkable photothermal properties, their practical usage has been hindered by their limited stability in aqueous mediums and vulnerability to external environmental factors. To address this issue, herein, we propose a simple and feasible method to enhance Ti3C2Tx MXene by utilizing its Ti-OH groups to directly initiate the ring-opening polymerization of glycidol. This process leads to covalently grafting multihydroxy hyperbranched polyglycerol (HPG) on the surface of MXene. The resulting Ti3C2-HPG nanohybrid demonstrates excellent aqueous dispersibility, favorable colloidal stability, and a customizable surface, thanks to the introduction of HPG. Moreover, it can withstand challenging conditions, such as extreme pH levels, high concentrations of electrolyte and bovine serum protein, and long-time storage. The abundant hydroxyl groups allow for easy modification, as demonstrated by the conjugation of rhodamine B. Preliminary in vitro and in vivo studies have unveiled that Ti3C2-HPG exhibits low cytotoxicity and exceptional photothermal performance for effectively destroying cancer cells, thus establishing it as a highly promising photothermal agent for photothermal therapy. This study thus open a new avenue for improving the stability and surface functionality of MXenes, enabling them to meet the specific requirements of practical applications.

Communication—Anodization of Aluminum in Phosphoric Acid Containing Glycerol at 30 °C

Aluminum was anodized in a phosphoric acid solution containing glycerol. Anodization in high concentration and high temperature electrolytes typically faces challenges due to the chemical dissolution of the anodic film. However, we found that the maximum attainable film thickness could be doubled by incorporating glycerol into the electrolyte. This enhancement was more effective under conditions of high concentration and temperature than in environments with lower concentrations and temperatures.

The effect of NaOH concentration on ferrate electrosynthesis

AbstractThis study investigated the electrochemical characteristics of mild steel anode in NaOH solutions with concentrations ranging from 8 to 16 m to elucidate their impact on the electrochemical synthesis of ferrate and determine the optimal electrolyte concentration for this process. The electrochemical properties of anode material were determined using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and the Tafel polarization. The ferrate concentration was determined by UV–vis method and the conductivity of electrolytes was evaluated through EIS measurement in the high‐frequent range. The results showed that a passive layer easily formed on the anode surface in NaOH solution with a concentration range of 8–12 m, preventing the formation of ferrate. Conversely, at higher electrolyte concentrations (14 and 16 m NaOH), the dissolution capability of the passive layer was enhanced, resulting in a better ability to synthesize ferrate.

Revealing the key role of non-solvating diluents for fast-charging and low temperature Li-ion batteries

Fast-charging and low temperature operation are of vital importance for the further development of lithium-ion batteries (LIBs), which is hindered by the utilization of conventional carbonate-based electrolytes due to their slow kinetics, narrow operating temperature and voltage range. Herein, an acetonitrile (AN)-based localized high-concentration electrolyte (LHCE) is proposed to retain liquid state and high ionic conductivity at ultra-low temperatures while possessing high oxidation stability. We originally reveal the excellent thermal shielding effect of non-solvating diluent to prevent the aggregation of Li+ solvates as temperature drops, maintaining the merits of fast Li+ transport and facile desolvation as at room temperature, which bestows the graphite electrode with remarkable low temperature performance (264 mA h g−1 at −20 °C). Remarkably, an extremely high capacity retention of 97% is achieved for high-voltage high-energy graphite||NCM batteries after 250 cycles at −20 °C, and a high capacity of 110 mA h g−1 (71% of its room-temperature capacity) is retained at −30 °C. The study unveils the key role of the non-solvating diluents and provides instructive guidance in designing electrolytes towards fast-charging and low temperature LIBs.

Cycling performance of Li metal anode in localized high concentration electrolyte and dynamic mechanism analysis

In this work, we investigated the apparent cycling performance of lithium metal at different chemical compositions and series current densities; examined the microscopic morphology and thickness variation of the deposition layer on the surface of lithium metal anode and the concentration-depth distribution of trace elements in the solid electrolyte interphase (SEI) film; and characterized the kinetic behavior and features of the elementary steps (mass transfer, charge transfer, electro-crystallization) at Li-electrolyte interface using microelectrode technology and various electrochemical test methods. The results show that the lithium metal anode has better cycling performance in high concentration and localized high concentration electrolyte. At the same time, the experimental results confirm that the formation of spherical crystal nucleus is favored only under certain chemical conditions and certain reaction rate; under these conditions, the induction period and the self-smoothing process of critical crystal nucleus can be found. It suggests that there are determined causal among the apparent performance of lithium metal anode, the kinetic parameters of the interfacial charge transfer step and the electro-crystallization step, and these correlations can be used as a reference for screening and evaluating electrolyte systems and battery operating conditions, providing a reliable kinetic basis for future work.

Regulating Electrolyte Solvation Structures via Diluent-Solvent Interactions for Safe High-Voltage Lithium Metal Batteries.

Local high concentration electrolytes (LHCEs) have been proved to be one of the most promising systems to stabilize both high voltage cathodes and Li metal anode for next-generation batteries. However, the solvation structures and interactions among different species in LHCEs are still convoluted, which bottlenecks the further breakthrough on electrolyte development. Here, it is demonstrated that the hydrogen bonding interaction between diluent and solvent is crucial for the construction of LHCEs and corresponding interphase chemistries. The 2,2,2-trifluoroethyl trifluoromethane sulfonate (TFSF) is selected as diluent with the solvent dimethoxy-ethane (DME) to prepare a non-flammable LHCE for high voltage LMBs. This is first find that the hydrogen bonding interaction between TFSF and DME solvent tailors the electrolyte solvation structures by weakening the coordination of DME molecules to Li+ cations and allows more participation of anions in the first solvation shell, leading to the formation of aggregates (AGGs) clusters which are conducive to generating inorganic solid/cathodic electrolyte interphases (SEI/CEIs). The proposed TFSF based LHCE enables the Li||NCM811 (LiNi0.8Mn0.1O2) batteries to realize >80% capacity retention with a high average Coulombic efficiency of 99.8% for 230 cycles under aggressive conditions (NCM811 cathode: 3.4mAhcm-2, cut-off voltage: 4.4V, and 20µm Li foil).

Molecular anchoring of free solvents for high-voltage and high-safety lithium metal batteries

Constraining the electrochemical reactivity of free solvent molecules is pivotal for developing high-voltage lithium metal batteries, especially for ether solvents with high Li metal compatibility but low oxidation stability ( <4.0 V vs Li+/Li). The typical high concentration electrolyte approach relies on nearly saturated Li+ coordination to ether molecules, which is confronted with severe side reactions under high voltages ( >4.4 V) and extensive exothermic reactions between Li metal and reactive anions. Herein, we propose a molecular anchoring approach to restrict the interfacial reactivity of free ether solvents in diluted electrolytes. The hydrogen-bonding interactions from the anchoring solvent effectively suppress excessive ether side reactions and enhances the stability of nickel rich cathodes at 4.7 V, despite the extremely low Li+/ether molar ratio (1:9) and the absence of typical anion-derived interphase. Furthermore, the exothermic processes under thermal abuse conditions are mitigated due to the reduced reactivity of anions, which effectively postpones the battery thermal runaway.

Quantifying Protein Shape to Elucidate Its Influence on Solution Viscosity in High-Concentration Electrolyte Solutions.

Therapeutic proteins with a high concentration and low viscosity are highly desirable for subcutaneous and certain local injections. The shape of a protein is known to influence solution viscosity; however, the precise quantification of protein shape and its relative impact compared to other factors like charge-charge interactions remains unclear. In this study, we utilized seven model proteins of varying shapes and experimentally determined their shape factors (v) based on Einstein's viscosity theory, which correlate strongly with the ratios of the proteins' surface area to the 2/3 power of their respective volumes, based on protein crystal structures resolved experimentally or predicted by AlphaFold. This finding confirms the feasibility of computationally estimating protein shape factors from amino acid sequences alone. Furthermore, our results demonstrated that, in high-concentration electrolyte solutions, a more spherical protein shape increases the protein's critical concentration (C*), the transition concentration beyond which protein viscosity increases exponentially relative to concentration increases. In summary, our work elucidates protein shape as a key determinant of solution viscosity through quantitative analysis and comparison with other contributing factors. This provides insights into molecular engineering strategies to optimize the molecular design of therapeutic proteins, thus optimizing their viscosity.

Evaluation of the Stability of Newborn Hospital Parenteral Nutrition Solutions.

(1) Background: parenteral nutrition (PN) solutions are an extremely complex mixture. It is composed of a multitude of chemical elements that can give rise to a large number of interactions that condition its stability and safety. The aim of this study was to evaluate the stability of PN solutions for preterm infants. (2) Methods: eight samples were prepared according to the protocol for prescribing PN in preterm infants. Samples PN1-PN7 had the normal progression of macronutrients and standard amounts of micronutrients for a 1 kg preterm infant. The PN8 sample had a high concentration of electrolytes, with the idea of forcing stability limits. Samples were stored both at room temperature and under refrigeration. Measurements of globule size, pH, density, and viscosity were performed in both storage protocols on different days after processing. (3) Results: the changes in the composition of the samples did not affect the evolution of the stability at the different measurement times and temperatures. Viscosity was affected by the compositional changes made in the PN samples, but no alterations due to time or temperature were observed. Density and pH remained stable, without significant changes due to time, storage temperature, or different composition. (4) Conclusion: all samples remained stable during the study period and did not undergo significant alterations due to compositional changes or different experimental conditions.

Dual-salt strategy tuning the solvation structure to achieve high cycling stability for FeS2 cathodes

Pyrite FeS2, as a promising conversion-type cathode material, faces rapid capacity degradation due to challenges such as polysulfide shuttle and massive volume changes. Herein, a localized high-concentration electrolyte (LHCE) based on dual-salt lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulphonyl)imide (LiTFSI) is designed to address the challenges. By the dual-salt strategy, we tailor a more desirable solvation structure than that in the single-salt system. Specifically, the solvation structure involving FSI− and TFSI− enables milder electrolyte decomposition, which reduces initial capacity loss. Meanwhile, it facilitates the formation of a stable and flexible cathode/electrolyte interphase (CEI), effectively mitigating side effects and accommodating volume changes. Consequently, the micro-sized FeS2 realizes a capacity of 641 mAh g−1 after 600 cycles with a retention rate of 90%, significantly improving the cycling stability of the FeS2 cathode. This work underscores the pivotal role of solvation structure in modulating electrochemical performances and provides a simple and effective electrolyte design concept for conversion-type cathodes.

Stabilizing cathode-electrolyte interphase by localized high-concentration electrolytes for high-voltage sodium-ion batteries

Sodium-ion batteries (SIBs) operating under high-voltages suffer from unstable cathode-electrolyte interphase (CEI) formed on the cathode surface, resulting in continuous electrolyte decomposition, surface reconstruction, transition metal dissolution, and eventually capacity decay. Therefore, designing high-voltage electrolyte and constructing the robust CEI are critical for high-energy SIBs. Herein, a localized high-concentration electrolyte (LHCE) is fabricated by dissolving sodium hexafluorophosphate in methyl ethyl carbonate, fluorinated ethylene carbonate and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, which demonstrates oxidative stability exceeding 6 V relative to Na+/Na. The dense and homogeneous inorganics-rich CEIs are generated by the preferential decomposition of PF6− anions during the electrochemical charge to 4.4 V, which lower interface impedance, facilitate Na+ transportation and suppress subsequent side reactions. Consequently, the cell integrating high-voltage P2-Na0.7Li0.03Mg0.03Ni0.27Mn0.6Ti0.07O2 cathode and Na anode exhibits a capacity retention of 87.3% after 200 cycles and a high-rate discharge capacity of 84 mA h g−1 at 20 C under a high cut-off voltage of 4.4 V. This work offers a feasible pathway to tailor electrolyte chemistry and interphase properties for practical next generation high-voltage SIBs.

Metal‐free two‐dimensional phosphorene‐based electrocatalyst with covalent P–N heterointerfacial reconstruction for electrolyte‐lean lithium–sulfur batteries

AbstractThe use of lithium–sulfur batteries under high sulfur loading and low electrolyte concentrations is severely restricted by the detrimental shuttling behavior of polysulfides and the sluggish kinetics in redox processes. Two‐dimensional (2D) few layered black phosphorus with fully exposed atoms and high sulfur affinity can be potential lithium–sulfur battery electrocatalysts, which, however, have limitations of restricted catalytic activity and poor electrochemical/chemical stability. To resolve these issues, we developed a multifunctional metal‐free catalyst by covalently bonding few layered black phosphorus nanosheets with nitrogen‐doped carbon‐coated multiwalled carbon nanotubes (denoted c‐FBP‐NC). The experimental characterizations and theoretical calculations show that the formed polarized P–N covalent bonds in c‐FBP‐NC can efficiently regulate electron transfer from NC to FBP and significantly promote the capture and catalysis of lithium polysulfides, thus alleviating the shuttle effect. Meanwhile, the robust 1D‐2D interwoven structure with large surface area and high porosity allows strong physical confinement and fast mass transfer. Impressively, with c‐FBP‐NC as the sulfur host, the battery shows a high areal capacity of 7.69 mAh cm−2 under high sulfur loading of 8.74 mg cm−2 and a low electrolyte/sulfur ratio of 5.7 μL mg−1. Moreover, the assembled pouch cell with sulfur loading of 4 mg cm−2 and an electrolyte/sulfur ratio of 3.5 μL mg−1 shows good rate capability and outstanding cyclability. This work proposes an interfacial and electronic structure engineering strategy for fast and durable sulfur electrochemistry, demonstrating great potential in lithium–sulfur batteries.

Highly Stable Lithium Metal Batteries Enabled by Tuning the Molecular Polarity of Diluents in Localized High-Concentration Electrolytes.

Electrolyte plays a crucial role in ensuring stable operation of lithium metal batteries (LMBs). Localized high-concentration electrolytes (LHCEs) have the potential to form a robust solid-electrolyte interphase (SEI) and mitigate Li dendrite growth, making them a highly promising electrolyte option. However, the principles governing the selection of diluents, a crucial component in LHCE, have not been clearly determined, hampering the advancement of such a type of electrolyte systems. Herein, the diluents from the perspective of molecular polarity are rationally designed and developed. A moderately fluorinated solvent, 1-(1,1,2,2-tetrafluoroethoxy)propane (TNE), is employed as a diluent to create a novel LHCE. The unique molecular structure of TNE enhances the intrinsic dipole moment, thereby altering solvent interactions and the coordination environment of Li-ions in LHCE. The achieved solvation structure not only enhances the bulk properties of LHCE, but also facilitates the formation of more stable anion-derived SEIs featured with a higher proportion of inorganic species. Consequently, the corresponding full cells of both Li||LiFePO4 and Li||LiNi0.8Co0.1Mn0.1O2 cells utilizing Li thin-film anodes exhibit extended long-term stability with significantly improved average Coulombic efficiency. This work offers new insights into the functions of diluents in LHCEs and provides direction for further optimizing the LHCEs for LMBs.

Exploring the Effect of Salinity as a Primary Cause of Teratology in Freshwater Diatoms

&lt;p&gt;Increased water conductivity levels have been proposed as a key factor to explain the occurrence of teratological forms in freshwater diatom assemblages. The current study aimed to carry out an experiment on a laboratory scale to assess the response of periphytic diatoms to artificially increased salinity levels. The obtained results show that: a) the proportion of aberrant cells increased in high conductivity treatments, b) developed teratologies were preserved in diatom populations even after being translocated to normal conditions, and c) the degree of valve outline deformation in the dominant species was proportional to the induced water conductivity. All these data support previous field observations that linked high electrolyte content and the abundance of aberrant cells among microalgal communities in continental aquatic ecosystems.&lt;/p&gt;&#x0D;

Interfacial polymerization mechanisms assisted flame retardancy process of low-flammable electrolytes on lithium anode

Thermal runaway is a hazardous risk, occurring more readily in high-energy–density lithium-ion batteries (LIBs), which leads to a rapid temperature rise and even combustion or explosion when using flammable electrolyte systems. Flame retardants (FRs), such as trimethyl phosphate (TMPa) and triethyl phosphate (TEP), are commonly utilized due to their effective flame suppression, low toxicity, and excellent thermal stability. However, the lack of in-depth understanding of the flame retardancy mechanism and solid electrolyte interphase (SEI) formation process has made the development of functional electrolytes difficult at present. In this study, we clarified the flame retardancy and interfacial reaction mechanisms of low-flammable TMPa localized high-concentration electrolytes (LHCE) using hybrid ab initio and reactive force field (HAIR) schemes. Long-term HAIR simulation reveals that phosphorous radicals produced by the decomposition of TMPa capture carbon radicals, encouraging their polymerization into low-flammable oligomers, while fluorine-containing solvents in the electrolyte capture hydrogen radicals and produce nonflammable hydrofluoric acid (HF). This synergistic flame retardancy mechanism provides essential atomic-level insights for the rational design of high-safety electrolytes in the future.