Electrolyte Consumption Research Articles

Ultrathin CuF2 -Rich Solid-Electrolyte Interphase Induced by Cation-Tailored Double Electrical Layer toward Durable Sodium Storage.

Solid-electrolyte interphase (SEI) seriously affects battery's cycling life, especially for high-capacity anode due to excessive electrolyte decomposition from particle fracture. Herein, we report an ultrathin SEI (3-4 nm) induced by Cu+ -tailored double electrical layer (EDL) to suppress electrolyte consumption and enhance cycling stability of CuS anode in sodium-ion batteries. Unique EDL with SO3 CF3 -Cu complex absorbing on CuS in NaSO3 CF3 /diglyme electrolyte is demonstrated by in situ surface-enhanced Raman, Cyro-TEM and theoretical calculation, in which SO3 CF3 -Cu could be reduced to CuF2 -rich SEI. Dispersed CuF2 and F-containing compound can provide good interfacial contact for formation of ultrathin and stable SEI film to minimize electrolyte consumption and reduce activation energy of Na+ transport. As a result, the modified CuS delivers high capacity of 402.8 mAh g-1 after 7000 cycles without capacity decay. The insights of SEI construction pave a way for high-stability electrode.

Phosphorylation of Li-Rich Mn-Based Layered Oxides for Anion Redox and Structural Stability.

Li-rich Mn-based layered oxides are proposed to be candidates for high-energy Li-ion batteries. However, their large-scale production is still hampered by poor rate capability and severe voltage decay. It was mainly attributed to the irreversible oxygen loss, which induces transition metal ion migration, electrolyte consumption, and structural evolution. Herein, we propose an effective strategy of phosphorylation, in which the phosphate ion is induced to remove the surface labile oxygen. It urges the Li2MnO3 component to transform to the spinel-like structure and promotes the anionic redox process, thus facilitating lithium-ion diffusion and improving structural stability. As a result, the Li2MnO3 component is more prone to be activated, with the capacity increased by 18% in comparison with the pristine one. It also exhibits a superior capacity retention of 86.1% after 150 extended cycles and better rate performance delivering a capacity of 148.1 mA h g-1 even at 10 C. The effective phosphorylation opens a new way to tune anion redox chemistry and obtain structurally stable materials.

Effective SEI Formation via Phosphazene‐Based Electrolyte Additives for Stabilizing Silicon‐Based Lithium‐Ion Batteries

AbstractSilicon, as potential next‐generation anode material for high‐energy lithium‐ion batteries (LIBs), suffers from substantial volume changes during (dis)charging, resulting in continuous breakage and (re‐)formation of the solid electrolyte interphase (SEI), as well as from consumption of electrolyte and active lithium, which negatively impacts long‐term performance and prevents silicon‐rich anodes from practical application. In this work, fluorinated phosphazene compounds are investigated as electrolyte additives concerning their SEI‐forming ability for boosting the performance of silicon oxide (SiOx)‐based LIB cells. In detail, the electrochemical performance of NCM523 || SiOx/C pouch cells is studied, in combination with analyses regarding gas evolution properties, post‐mortem morphological changes of the anode electrode and the SEI, as well as possible electrolyte degradation. Introducing the dual‐additive approach in state‐of‐the‐art electrolytes leads to synergistic effects between fluoroethylene carbonate and hexafluorocyclotriphosphazene‐derivatives (HFPN), as well as enhanced electrochemical performance. The formation of a more effective SEI and increased electrolyte stabilization improves lifetime and results in an overall lower cell impedance. Furthermore, gas chromatography‐mass spectrometry measurements of the aged electrolyte with HFPN‐derivatives as an additive compound show suppressed ethylene carbonate and ethyl methyl carbonate decomposition, as well as reduced trans‐esterification and oligomerization products in the aged electrolyte.

Experimental research on thermal-electrical behavior and mechanism during external short circuit for LiFePO4 Li-ion battery

External short circuit is a common phenomenon triggering thermal runaway in Li-ion battery. In this research, the electrical and thermal characteristics of the Li-ion battery under different external short circuit current were analyzed combining with the failure characteristics of the electrodes. In addition, the performance of a short-circuited battery was evaluated as well as its potential thermal risks. Results showed that thermal runaway occurrence or not, the temperature rise and temperature rise rate of the battery significant related to the short-circuit current and initial SOC. The battery with 30% initial SOC had the fastest temperature rise rate, whereas higher SOC batteries (80% and 100%) have the maximum temperature rise. According to SEM images of the electrodes, the failure of the short-circuit electrodes was discovered to entail electrolyte consumption, metal deposition, electrode particle breaking, separator closure, and increased internal resistance. The capacity of the battery recovered in the cycle test after the short circuit, which was caused by a decrease in ohmic resistance and the elimination of the polarization effect. When the undamaged batteries in first short circuit process experienced a secondary short circuit, the batteries exhibited a larger voltage drop, faster temperature rise rate and a higher temperature rise than fresh one. It was concluded that although there was no thermal runaway occurred during first short circuit process, it would increase the potential thermal risk in the continuous applications.

High-loading polysulfide/cement cathode for the manufacture of dynamically and statically stable lean-electrolyte lithium–sulfur batteries

In order to design lithium-sulfur cells for practical viability in the high-density energy storage, the exploitation of the effective contribution of the large amount of active-material mass to the high specific capacity at a lean-electrolyte condition must be considered. However, this is limited by the insulating nature of solid-state sulfur/sulfide, and the diffusion loss of the liquid-state polysulfides. In this study, Portland cement is adopted as a reinforcement material to design a high-loading polysulfide/cement cathode with sulfur loading and content of 8.64 mg cm−2 and 60 wt%, respectively. The nonporous cement exhibits a high polysulfide-trapping capability and low electrolyte consumption, which enable the high-sulfur-loading cathode to achieve record low electrolyte-to-sulfur ratios of 7–3 μL mg−1, with high gravimetric capacity and areal capacity of the cathode (i.e., 768 mA h g−1 and 11.06 mA h cm−2, respectively) and dynamically/statically electrochemical stability with 90% capacity retention after 100 cycles and a 1-month rest.

Interfacial fluoride engineering enabled robust LiF-rich solid electrolyte interphase to reduce active lithium loss in rechargeable lithium battery

Active lithium loss, which is caused by parasitic reactions due to the instability of solid electrolyte interphase (SEI) on the anodes, results in fast capacity fade of batteries. Constructing robust SEI layer is an effective way to reduce active lithium loss. Herein, we propose a AgF-coated separator (AgF-CS) to facilitate robust LiF-rich SEI on the anode during initial cycle. Electrochemical analysis and microstructure investigations confirm the formation of the LiF-rich SEI on the anode induced by the fluoride-containing coating layer. The fluoride-containing interfacial layer not only effectively enhances the reversible capacity of the SiO anode even under lean electrolyte (14 μL mAh−1) condition, but also prolongs the cycling life of lithium metal batteries by reducing the consumption of electrolyte and active lithium. The initial Coulombic efficiency (ICE) of LiFePO4||SiO full cell is increased from 43.68 % to 84.18 % with pretreatment by AgF-CS. As a result, the reversible capacity of LiFePO4||SiO full cell is increased by ∼124 % in contrast with that of the unmodified one. The strategy proposed here, benefiting from the simple manufacture, provides a feasible way to alleviate active lithium loss and elevate energy density of rechargeable lithium batteries.

A facile integrated microfluidic chip based on Chitosan-Gold Nanoparticles-Anchored Three-Dimensional graphene fiber film for monitoring prostate specific antigen

Microfluidic electrochemical sensors are emerging as favorable platforms for rapid and precise detection of disease markers relying on their superiority of miniaturization, low electrolyte consumption, high precision and integration. Herein, an efficient and facile integrated microfluidic sensor with three-dimensional graphene fiber film/chitosan-gold nanoparticles (3D GF/CS-Au NPs) micro-nano composites as sensing interface was developed for the analysis of prostate specific antigen (PSA). The GF with 3D network structures modified by large amounts of CS-Au nanoparticles could facilitate the enhancement of electrochemical signals. The electrodes and microchannel were simply assembled and encapsulated by bolts, which made the microfluidic chip had excellent portability and operability. On the basis of this new microfluidic device and the 3D GF/CS-Au NPs composites, a sensitive determination of PSA could be realized with a low detection limit of 0.51 pg/mL and a wide response range from 0.001 − 200 ng/mL. Moreover, the proposed biosensor was further used to detect analytes in human blood samples, showing the satisfactory results. This novel microfluidic electrochemical immunosensor demonstrated superior performance for PSA detection, holding potential application in clinical diagnosis and personalized healthcare.

Is photocatalytic hydrogen production sustainable? – Assessing the potential environmental enhancement of photocatalytic technology against steam methane reforming and electrocatalysis

In the face of the burgeoning interests toward the utilization of nanomaterials in catalyzing solar-aided chemical processes, the doubts upon the capability of these emerging low-TRL technologies in offsetting the potential environmental impacts of conventional approaches have endured for years. Despite the scarcity of commercial-level data for low-TRL process route, an extensive life cycle study is necessitated to spotlight the demerit and potential enhancement of these systems, which would be beneficial for the future process upscaling. Therein, this study conducted a cradle-to-gate life cycle assessment (LCA) on electrocatalysis and photocatalysis, with steam methane reforming (SMR) simulated as the base case. With a functional unit of 1 kg hydrogen, the results demonstrated that electrocatalysis led to the greatest climate change (GWP100), exceeding that of photocatalysis and SMR by 7.04 and 56.63 kg CO2-Eq, respectively. In contrast to photocatalysis, which has its main impact released from the catalyst synthesis stage (95.87%), the reaction phase in the electrolyzer was revealed as the major contributor (96.10%) to the resulting GWP100 in electrocatalysis, attributed to the huge consumption of aqueous electrolyte. Solid polymer electrolyte has latterly been recognized as a potential candidate to replace liquid electrolyte. In view of the existing uncertainty in inventory data of both the emerging technologies, a significant fluctuation was observed in their resulting human toxicity (HTPinf), where the large reagent input for large-scale catalyst synthesis was raised as a contributing factor. In line with the promoted employment of renewables, power supply of the simulated system was varied from electricity mix to hydro and wind power, resulting in an improvement of 14% and 10% to the GWP100 level of photocatalysis, and 5.33% and 3.73% to that of electrocatalysis. Hence, this spotlights the potential of incorporating renewables-sourced electricity in the production plant, which lays a promising foundation for future carbon neutrality.

Solvating power regulation enabled low concentration electrolyte for lithium batteries

Li+ solvation structures have a decisive influence on the electrode/electrolyte interfacial properties and battery performances. Reduced salt concentration may result in an organic rich solid electrolyte interface (SEI) and catastrophic cycle stability, which makes low concentration electrolytes (LCEs) rather challenging. Solvents with low solvating power bring in new chances to LCEs due to the weak salt-solvent interactions. Herein, an LCE with only 0.25 mol L−1 salt is prepared with fluoroethylene carbonate (FEC) and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropylether (D2). Molecular dynamics simulations and experiments prove that the low solvating power solvent FEC not only renders reduced desolvation energy to Li+ and improves the battery kinetics, but also promotes the formation of a LiF-rich SEI that hinders the electrolyte consumption. Li||Cu cell using the LCE shows a high coulombic efficiency of 99.20%, and LiNi0.6Co0.2Mn0.2O2||Li cell also exhibits satisfying capacity retention of 89.93% in 200 cycles, which demonstrates the great potential of solvating power regulation in LCEs development.

Novel Electrolyte Development for in-Situ Formed Li-Metal Batteries Using Amplified SEI and Plating Investigations

The ubiquitous use of Li-ion batteries is hindered in part by limitations to achievable specific and volumetric energy. In addition to the physical constraints these properties address, they lead to higher cost per Wh. Replacing the intercalation or alloying based negative electrode leads to significant increases in both of the aforementioned energy related properties. In-situ formed or “anodeless” Li metal batteries, where Li is plated directly on the current collector, enable significant cost savings and improvement of energy of Li metal batteries relative to traditional Li metal which contain Li metal upon initial fabrication [1].Using anodeless configurations, we imparted on an effort to investigate the deleterious capacity consuming phenomena of the plating process by electrochemically isolating the key degradation and performance limiting phenomena. Using ultra low-capacity Li metal plating (0.08mAh/cm2) in Li-metal anodeless half cells, the formation and quality of the solid electrolyte interphase (SEI) can be investigated with amplification. The solid electrolyte interphase (SEI) is a protective and passivating layer formed during the initial reduction of electrolyte. A robust SEI protects against excess electrolyte consumption and allows for subsequent stable, high efficiency cycling while being electronically resistive and ionically conductive [2]. The composition and mechanical stability of this dynamic layer influences efficiency and cycle lifetime [2]. At higher lithium plating capacities however, the influence of the SEI is not easily observed. Instead, capacity fade attributed to dendrite formation and mechanical damage to the SEI can be more easily investigated. Using higher capacity lithium plating (2.5mAh/cm2) in anodeless cell configurations, dendrite formation and capacity fade over cycle lifetime can be observed. Dendrite formation, as the result of irregular lithium deposition, can hinder the amount of active lithium available as well as lead to battery failure through short circuiting and thermal runaway [3].In this work we have isolated the study SEI and dendrite formation electrochemically, using Li-metal and LiCoO2 counter electrode anodeless cell configurations, respectively. As a result, we developed novel non-aqueous, non-ionic liquid electrolytes that have achieved efficiency of 85% at 0.08mAh/cm2 where most of the capacity is associated with the formation of the SEI and 96% at 2.5mAh/cm2 at the more challenging initial cycles. In contrast, a standard electrolyte composition such as 1M LiPF6 EC/DMC shows poor initial efficiency of 52% at 0.08mAh/cm2 and 66% at 2.5mAh/cm2. High efficiencies were also achieved with optimized ionic liquid electrolytes. This work may provide insight into the initial stages of SEI formation and provide a systematic methodology for electrolyte optimization through SEI capacity loss and dendritic capacity fade observation.[1] S. H. Park, D. Jun, G. H. Lee, S. G. Lee, and Y. J. Lee, J. Materials Chemistry A 9 (2021) 14656-14681.[2] S. J. Park, J. Li, C. Daniel, D. Mohanty, S. Nagpure, and D. L. Wood, Carbon 105 (2016) 52-76.[3] J. B. Goodenough, J. Solid State Electrochem. 16 (2012) 2019-2029. Figure 1

The SEI on Lithium Metal Anodes: From Understanding to Enhancement

Lithium metal batteries (LMB) have risen back into focus of battery research in resent years, due to the high theoretical specific capacity of the lithium metal anodes (3860 mAh g-1).[1] However, the utilization of lithium metal as an anode material requires an in depth understanding of the solid electrolyte interphase (SEI) on lithium metal electrodes, since its formation, composition and electrochemical characteristics significantly impact important LMB lifetime parameters, e.g. lithium stripping/plating behaviour, dendrite growth and in operando electrolyte consumption.[2] Lithium metal electrode performance is influenced by a variety of different, however often overlooked factors, e.g. the native passivation layer, inevitably present on each lithium metal electrode surface, which has only recently gathered more attention as an influencing factor in respect to SEI characteristics.[3] The presented research utilizes the preformation of an uncontaminated SEI on the lithium metal electrode surface to circumvent the influence of native lithium metal passivation. A systematic study of different preformed SEIs resulted in a better understanding of the influence by different electrolyte components on relevant SEI characteristics, namely, selected conducting salts (LiFSI, LiPF6) and functional additives (VC, FEC). Analyses of the SEIs electrochemical properties, composition, morphology and dynamics were conducted via stripping/plating experiments as well as in operando EIS, SEM (incl. cryogenic cross section and post mortem) and XPS (post mortem) measurements. Finally, careful tailoring of the preformed SEI was shown to have an enhancing effect on NMC811||Li cells, increasing the LMB lifetime by up to 25%. Furthermore, the application of a tailored preformed SEI has also shown a positive impact on the performance of solid state LMBs.The presented results highlight the importance of an in depth understanding regarding the cause and effect of varying electrolyte components on the SEIs characteristics. This understanding will ultimately have a significant impact on the research towards enhanced and reliable LMB performance and future applicability.

High Current‐Density‐Charging Lithium Metal Batteries Enabled by Double‐Layer Protected Lithium Metal Anode

AbstractThe practical application of lithium (Li) metal anode (LMA) is still hindered by non‐uniformity of solid electrolyte interphase (SEI), formation of “dead” Li, and continuous consumption of electrolyte although LMA has an ultrahigh theoretical specific capacity and a very low electrochemical redox potential. Herein, a facile protection strategy is reported for LMA using a double layer (DL) coating that consists of a polyethylene oxide (PEO)‐based bottom layer that is highly stable with LMA and promotes uniform ion flux, and a cross‐linked polymer‐based top layer that prevents solvation of PEO layer in electrolytes. Li deposited on DL‐coated Li (DL@Li) exhibits a smoother surface and much larger size than that deposited on bare Li. The LiF/Li2O enriched SEI layer generated by the salt decomposition on top of DL@Li further suppresses the side reactions between Li and electrolyte. Driven by the abovementioned advantageous features, the DL@Li||LiNi0.6Mn0.2Co0.2O2 cells demonstrate capacity retention of 92.4% after 220 cycles at a current density of 2.1 mA cm–2 (C/2 rate) and stability at a high charging current density of 6.9 mA cm–2 (1.5 C rate). These results indicate that the DL protection is promising to overcome the rate limitation of LMAs and high energy‐density Li metal batteries.

A Magnesium/Lithium Hybrid-Ion Battery with Modified All-Phenyl-Complex-Based Electrolyte Displaying Ultralong Cycle Life and Ultrahigh Energy Density.

Magnesium/lithium hybrid-ion batteries (MLHBs) combine the advantages of high safety and fast ionic kinetics, which enable them to be promising emerging energy-storage systems. Here, a high-performance MLHB using a modified all-phenyl complex with a lithium bis(trifluoromethanesulfonyl)imide electrolyte and a NiCo2S4 cathode on a copper current collector is developed. A reversible conversion involving a copper collector with NiCo2S4 efficiently avoids the electrolyte dissociation and diffusion difficulties of Mg2+ ions, enabling low polarization and fast redox, which is verified by X-ray absorption near edge structure analysis. Such combination affords the best MLHB among all those ever reported, with a reversible capacity of 204.7 mAh g-1 after 2600 cycles at 2.0 A g-1, and delivers an ultrahigh full electrode-basis energy density of 708 Wh kg-1. The developed MLHB also achieves good rate performance and temperature tolerance at -10 and 50 °C with a low electrolyte consumption. The hybrid-ion battery system presented here could inspire a broad set of engineering potentials for high-safety battery technologies and beyond.

A versatile LiTFSI-like anchor for constructing robust interfacial layers with tailored structures for silicon anodes

To overcome the severe side reactions induced by the volume changes in silicon (Si) anodes, optimizing and constructing a robust solid electrolyte interphase (SEI) is a prerequisite for the construction of high-energy-density Si-based Li-ion batteries. This work combines the advantages of electrolyte design and surface modification, constructs a phenyl trifluoromethanesulfonimide (PTFSI, with a lithium bis (trifluoromethanesulfonyl) imide-like structure) interfacial layer with electrolyte additive function on the Si surface. The resultant PTFSI-customized interfacial layer modulates the solvation/desolvation reaction mechanism at the electrode interface, constructing an artificial SEI structure composed of oligomers and inorganic salts, which has fast ionic conductivity, and can depress the electrolyte consumption and maintain the integrity of electrode structure. Therefore, the optimized Si@PTFSI anode demonstrates significantly enhanced rate capability and cycling performance. After 300 cycles at 0.5 C, it delivers a capacity of 1241.9 mAh g–1, while the reference Si anode has almost no capacity. Furthermore, LiNi0.5Co0.2Mn0.3O2//Si@PTFSI full-cell delivers a high reversible capacity of 120.1 mAh g–1 at the 300th cycle.

锂硫电池非均相电催化剂

<p indent="0mm">With the rapid development of electronic transportation and portable electronics, commercial lithium-ion batteries would be unsatisfactory to meet the needs of future markets owing to the relatively low energy density. Seeking a reliable substitution system is becoming imperative. Lithium-sulfur (Li-S) battery has been recognized as a cutting-edge energy storage system because of its high theoretical capacity (1672 mAh g^–1) and cost-effectiveness of sulfur resources. Nevertheless, the severe shuttle effect and sluggish reaction kinetics significantly restrict its further commercialization. In the developing history of Li-S batteries, physical confinement and chemical adsorption have often been employed to achieve the anchoring of polysulfides. However, these strategies are still difficult to fully solve the problems of slow reaction kinetics and poor cycle performance. Recent years have witnessed the introduction of heterogeneous electrocatalysts into the Li-S system, which readily meets with great success in suppressing the shuttle effect and elevating the reaction kinetics. In this review, we introduce the basic reaction of Li-S battery and point out the main challenges in its current development stage, followed by summarizing the effects of electrocatalysts. Firstly, the polar electrocatalyst is able to effectively adsorb polysulfide and inhibit its diffusion in the electrolyte. Secondly, the electrocatalyst can effectively promote the conversion of polysulfide and improve the utilization rate of sulfur species. Thirdly, the uniform distribution of active sites in the electrocatalyst also contributes to the uniform deposition of short-chain polysulfides. In addition, the concepts and comparisons of homogeneous and heterogeneous electrocatalysts are presented, manifesting the essential significance of heterogeneous electrocatalysts in Li-S system. Homogeneous electrocatalysts usually refer to small soluble organic molecules with the same phase state as soluble polysulfides in the reaction system. Homogeneous electrocatalysts have more specific catalytic sites, whilst heterogeneous electrocatalysts have more diverse morphologies and higher possibility of multi-site synergistic catalysis. Then the common regulation strategies for heterogeneous electrocatalysts are classified, including vacancy regulation, doping regulation, heterostructure modulation, size control, and phase modulation. In further contexts, the underlying mechanisms of different regulation strategies for promoting polysulfide conversion are discussed. The introduction of heterogeneous electrocatalysts can effectively promote the reaction kinetics and improve their electrochemical performance. However, there are still many obstacles waiting to be solved in the practicability of Li-S batteries. For instance, there is a lack of highly selective and stable electrocatalysts. The identification of real catalytic sites in the electrocatalysts still remains unclear. Moreover, Li-S batteries have poor performance under lean electrolyte and low lithium consumption. In view of these issues, future development strategy is put forward from four aspects, encompassing material exploration, precise synthesis, characterization methods and practical application, aiming to bridge the gap between the reality and ideal in working Li-S batteries.

Single Component Protection Layers for Lithium Electrodes and Their Characterization in Lithium Metal Batteries

State-of-the art Lithium-ion batteries (LIBs) based on graphite intercalation compound (GIC) are reaching their theoretical energy density limits. Therefore, it has become prerequisite to implement active materials with higher specific energies.[1] In this direction, Lithium (Li) has reignited research interest mainly due to its high theoretical specific capacity (3860 mAh/g) and the lowest negative potential (-3.040 V vs. SHE). Many of the advantages are shadowed by its poor electrodeposition properties with the formation of high surface area lithium (HSAL) and continuous electrolyte consumption resulting in a solid electrolyte interphase (SEI) with inhomogeneous composition which still limits the practical application of Li metal electrodes in Lithium metal batteries (LMBs).[2] Overall, several published strategies can be summarized into improving the electrolyte with additives, development of 3D hosts or interface engineering by covering Li with a protective coating layer. An artificial protection layer on Lithium metal requires tuned characteristics to withstand the harsh conditions during cycling. Therefore, it is obligate for these coatings to fulfil several requirements, among many i) mechanical suppression of dendrites, ii) high Li-ion selectivity and conductivity and iii) chemical passivation against the liquid electrolytes, are mostly encountered with artificial SEI.[3],[4] In a recent study an in-situ generated lithium methyl carbonate (LMC) layer on the Li metal electrode was able to protect its surface by generating a homogeneous Li-ion flux and decreasing the electrolyte consumption process during cycling. This approach also enhanced the current distribution and effectively suppressed the lithium dendrite formation during the electrodeposition and -dissolution process. [5],[6] Herein, the LMC layer, synthesized and purified in order to exclude the presence of any halides, was coated on the surface of the Li metal electrode using an ex-situ procedure. Its characterization and the effect of LMC on the electrochemical performance of the coated Li metal electrode especially during the Li electrodeposition/dissolution process will be presented. Li metal electrodes coated with a dense LMC layer showed decreased overvoltages during the Li electrodeposition/dissolution process and reduced interfacial resistance as compared to uncoated Li metal electrodes. Beside its role as a protective layer, LMC was also employed as electrolyte additive due to its known solubility in carbonate-based electrolytes. Using ionic chromatography (IC) to investigate the electrolyte after cycling and cryo-SEM cross-section of the cycled Li metal electrodes, further characteristic properties of these LMC coating layers on Li metal electrodes will be revealed.[1] Placke, T.; Kloepsch, R.; Dühnen, S.; Winter, M., Journal of Solid State Electrochemistry 2017, 21, 1939-1964[2] Aurbach, D.; Zinigrad, E.; Cohen, Y.; Teller, H., Solid State Ionics 2002, 148, 405-416.[3] Kang, D.; Xiao, M.; Lemmon, J. P., Batteries & Supercaps 2021, 4, 445.[4] Yu, Z.; Cui, Y.; Bao Z., Cell Reports Physical Science, 2020 7, 100119.[5] Liu, H.; Zhou, H.; Lee, B., ACS Applied Materials and Interfaces 2017, 36, 30635-30642.[6] Liu, H.; Wang, X.; Zhou, H., ACS Applied Materials and Interfaces 2018, 5, 1864-1869.

Sustained Release of AgNO3 Additive in Carbonate Electrolytes for Stable Lithium Metal Anodes

With increasing energy storage demand, research on high energy density and stable battery became essential. Among different anode materials for lithium batteries, lithium metal is an ideal anode material as it has low redox potential and high specific capacity. Therefore, for post-lithium ion battery with high energy density cannot avoid using lithium metal as an anode. However, lithium metal anode has stability and safety issues due to dendritic growth. Lithium metal in contact with organic electrolyte reacts with the electrolyte to form solid electrolyte interface (SEI). SEI prevents further electrolyte consumption, however presence of unstable SEI causes uneven lithium ion diffusion through the SEI layer and induces lithium dendrite growth. Therefore, uniform deposition of lithium and stable SEI is important to operate lithium metal anode safely.The application of nitrate additives in carbonate electrolyte has been very limited due to poor solubility. However, nitrate containing polymer interlayer can release additive constantly enabling nitrate act as an electrolyte additive. Herein, AgNO3 synthesized with PAN nanofibers (AgPAN) is used as an additive to induce uniform lithium deposition and stable SEI formation. In the symmetric cell test, life time of 20 µm thick lithium foil enhanced from 140 hr to 300 hr with AgPAN. Lithium nucleation overpotential disappeared and overall overpotential is reduced. Originally, plane lithium foil had the sparsely deposited dendrite shaped lithium, but with AgPAN lithium was evenly deposited and grow in spherical shape. Ag+ reduces on lithium metal surface acting as a lithium nucleation seed helping uniform lithium deposition and NO3 - reacts with lithium to form stable inorganic SEI layer (Li2O, Li3N, LiNxOy, and etc) resulting in stable cycling of lithium metal anode.

Opportunities and Challenges of Li2 C4 O4 as Pre-Lithiation Additive for the Positive Electrode in NMC622||Silicon/Graphite Lithium Ion Cells.

Silicon (Si)‐based negative electrodes have attracted much attention to increase the energy density of lithium ion batteries (LIBs) but suffer from severe volume changes, leading to continuous re‐formation of the solid electrolyte interphase and consumption of active lithium. The pre‐lithiation approach with the help of positive electrode additives has emerged as a highly appealing strategy to decrease the loss of active lithium in Si‐based LIB full‐cells and enable their practical implementation. Here, the use of lithium squarate (Li2C4O4) as low‐cost and air‐stable pre‐lithiation additive for a LiNi0.6Mn0.2Co0.2O2 (NMC622)‐based positive electrode is investigated. The effect of additive oxidation on the electrode morphology and cell electrochemical properties is systematically evaluated. An increase in cycle life of NMC622||Si/graphite full‐cells is reported, which grows linearly with the initial amount of Li2C4O4, due to the extra Li+ ions provided by the additive in the first charge. Post mortem investigations of the cathode electrolyte interphase also reveal significant compositional changes and an increased occurrence of carbonates and oxidized carbon species. This study not only demonstrates the advantages of this pre‐lithiation approach but also features potential limitations for its practical application arising from the emerging porosity and gas development during decomposition of the pre‐lithiation additive.

Quantifying Absolute Amounts of Electrolyte Components in Lithium-Ion Cells Using HPLC

Capacity loss and solid electrolyte interphase (SEI) buildup are accompanied by continuous electrolyte consumption due to electrochemical decomposition reactions[1],[2],[3]. The quantitative analysis of electrolytes in battery cells usually consists in the determination of concentrations or quantity ratios. As the total electrolyte amount in the cell decreases during cell aging due to electrochemical decompositions, concentrations do not reveal reliable information about the dominant decomposition reactions. Hence, the total electrolyte mass and the absolute consumption of the electrolyte components need to be determined to get reliable insights into cell chemistry. For this purpose, a method for electrolyte extraction from pouch cells and subsequent analysis by high-performance liquid chromatography (HPLC) coupled to an electrospray ionization mass spectrometer (ESI/MS) and an ultraviolet/visible light (UV/Vis) detector is presented that enable a quantification of the absolute amounts of the electrolyte components in battery cells[4].The investigated pouch cells are initially filled with 1 M LiPF6 in ethylene carbonate (EC)/dimethyl carbonate (DMC) 1:1 by weight with 3 wt% vinylene carbonate (VC). For the electrolyte extraction, diethyl carbonate (DEC) is injected into the cell, followed by a sealing of the puncture and a storage of the cell for 8 days to enable an intermixing between DEC and the original electrolyte. Afterwards, the electrolyte is extracted through a puncture in the cell. The UV/Vis detector is used for the determination of the concentrations of EC, DMC, VC, and DEC in the extracts, while the quantification of Li+ and PF6 − is performed by the ESI/MS. Based on these concentrations and the weighed mass of the injected DEC, the total mass of the original electrolyte and the absolute amounts of EC, DMC, VC, Li+, and PF6 − in the cell is determined. The investigated electrolytes are extracted from fresh cells, cells after formation, 25 cycles, and about 2000 cycles (with a remaining capacity of 80%). Based on the absolute amounts of EC, DMC, VC, Li+, and PF6 − in the cells at different aging stages, the absolute consumption of the electrolyte components by electrochemical decomposition is eventually calculated.From the concentrations shown in Figure (a), only a VC decomposition during formation and cycling can be concluded. The consideration of the absolute, consumed amounts of substance during formation and long-term cycling in Figure (b), however, suggests that the EC decomposition is dominant and thus much more pronounced than the VC degradation. Besides, a slight salt and DMC decomposition during long-term cycling is observed. Simultaneously, the quantified electrolyte mass is diminished during formation and cycling, as can be seen in Figure (c).The pronounced VC consumption during formation and cycling is expected, as VC is an additive for the SEI buildup. As a high fraction of the initially present VC is decomposed, its decomposition can be identified by the concentrations. The decomposition of the other components cannot be detected based on the concentrations, as lower fractions of the initially present amounts are consumed and the total electrolyte amount in the cell decreases during formation and cycling. The strong EC degradation might be related to the tendency of EC to contribute to the Li+ solvation shell, which is associated with a preferential reduction[5]. These results demonstrate that only the determination of the absolute consumed amounts of substance allows for identification of the decompositions in battery electrolytes. Figure: (a) Overview of the average concentrations of EC, DMC, and VC (quantified by HPLC-UV/Vis), as well as the average concentrations of Li+ and PF6 − (quantified by HPLC-ESI/MS) in cells at different stages of electrochemical aging[4]. (b) The amounts of substance consumed during formation and prolonged cycling altogether determined by HPLC analyses[4]. (c) The electrolyte masses in the fresh cells, the cells after formation, and the cells after prolonged cycling determined by HPLC analyses related to the corresponding initial electrolyte masses[4].

Towards high-performance lithium metal batteries: sol electrolyte generated with mesoporous silica

High-energy lithium metal batteries are considered as a promising alternative for next-generation energy storage systems. However, the uncontrolled lithium-dendrite growth due to the inhomogeneous lithium electrochemical deposition prevents lithium batteries from commercial application. Herein, a sol electrolyte was prepared by the addition of mesoporous silica, SBA-15 to the liquid ester-based LiPF6 electrolyte to induce the formation of a dense protective layer on the lithium metal surface and inhibit the uncontrolled growth of lithium dendrites and the electrolyte consumption. Mesoporous silica with ordered hexagonal nanochannels and abundant surface silicon hydroxyl groups not only facilitates the formation of the sol electrolyte, but also adsorbs the electrolyte, leading to homogeneous lithium ion distribution. The sol electrolytes would generate a dense protective layer on the lithium metal and a robust CEI film on the surface of the cathode materials through an in situ gelation process, suppressing the uncontrolled lithium dendrite growth and improving the stability of the electrolyte. Consequently, high electrochemical performance was demonstrated with the Li||LiNi0.5Co0.2Mn0.3O2 (NCM523) full cells with the sol electrolyte. This work provides a new strategy for improving the performance of lithium metal batteries through the formation of sol electrolytes.