Electrolyte Volume Research Articles

On the Volume Expansion of Lithium Ion Battery Electrodes (I) after Wetting, and (II) Selection of the Right Amount of Electrolyte

The electrolyte is necessary for transport of lithium ions between the negative and positive electrode within the battery cell. The lower the amount of electrolyte, the higher the energy density and specific energy. Hence, it is important to understand which cell parameters are relevant to determine the right amount of electrolyte. Here, three different cell designs in 1 to 5 Ah pouch cells where investigated for cell impedance after filling, cell capacity after formation, C-rate performance, and capacity retention for up to 3,000 full cycles. Wetting the cell with electrolyte, the cell pore volume changed between 25%–35% due to changes of 6%–16% in the thickness of the anode and cathode. Although electrolyte volumes >0.85 times the wet cell pore volume showed minimal resistance before formation, only electrolyte volumes of 1.08 times the wet cell pore volume were sufficient for a successful formation process. For long-term cycling, a minimum electrolyte volume of 1.19 times the wet cell pore volume was required to improve long-term cycling performance. Future experiments will investigate the correlation of capacity fade with electrolyte consumption for different electrolytes.

Reversible Li-ion trade-off in ultrathick sulfur cathodes for practical lean Li–S batteries

The use of low electrolyte volume is beneficial to improve energy density but severely limits access over obscured sulfur, along with sluggish ion kinetics and aggravated polarization, as the ion imbalance across the multicomponent interface of thick sulfur cathodes at a lean electrolyte viciously dominates the sulfur electrokinetics. Herein, we demonstrate that an ion imbalance at the interfaces of a thick electrode with a lean electrolyte can be compensated by the ion trade-off strategy utilizing a cationic ion conductive active binder. It ensures sustained lithium-ion donation/release over the vicinity of slow electrolyte percolation to realize an ion-enriched sulfur–binder–electrolyte interface. The in-situ evolved ionic interface essentially activates the inaccessible sulfur, bringing about additional capacity and low ion and charge transfer resistances. The active binder adopts sulfur cathodes housing 8.1 mg cm–2 with an E/S ratio of 6 µL mg–1 electrochemically utilized 60.89 % sulfur, corresponding to a 1020 mAh g–1 capacity. The lean Li–S pouch cell delivers an energy density of 324 Wh kg–1, demonstrating the efficacy of ion trade-off to ease the interfacial barrier. This study would open up a new paradigm in potentially designing thick electrodes for multiple high energy density batteries.

Analyzing the Effect of Electrolyte Quantity on the Aging of Lithium-Ion Batteries.

Despite a substantial impact on various economic and cell technology factors, the influence of electrolyte quantities is rarely addressed in research. This study examines the impact of varying electrolyte quantities on cell performance and aging processes using three different electrolytes: LP57 (1 M LiPF6 in ethylene carbonate:ethyl methyl carbonate (EC:EMC 3:7 w/w), LP572 (LP57+2 wt.% vinylene carbonate (VC)) and LP57 + absVC (18.351 mg VC). Comprehensive analytical post mortem investigations revealed that continuous excessive electrolyte decomposition determines the performance of cells using LP57, leading to enhanced irreversible lithium-ion loss and interphase thickening with increasing electrolyte volume. Impedance rise due to the growth of the interphase was also identified as the cause of degrading cell performance with rising amounts of LP572, attributed to an increasingly pronounced consumption of VC rather than electrolyte aging effects. By varying the electrolyte quantity while maintaining a constant amount VC within the cell system, the differences in cell performance were minimized, and observed deteriorating effects were suppressed. This study demonstrates the sensitive interdependence of electrolyte volume and additive concentration, practically affecting aging behavior. Comprehensively understanding the characteristics of each individual electrolyte component and tailoring the electrolytes to cell-specific cell properties proves to be crucial to optimize cell performance.

Concerted Formation of Reversibly Precipitated Sulfur Species and Its Importance for Lean Electrolyte Lithium-Sulfur Batteries.

Achieving high energy densities for lithium-sulfur batteries remain elusive. Largely limited by the volume of electrolyte used, lean electrolyte conditions (electrolyte/sulfur mass ratio <3) present enormous challenges that have led to very poor specific capacity and rate performance. Previous studies have identified that the high concentration of polysulfide is responsible for the poor discharge voltage. However, there still lacks sufficient understanding of the processes occurring at lean electrolyte conditions. In this work we uncovered a polysulfide concentration regulating mechanism that operates through the precipitation and redissolution of solid sulfur-based species (reversibly precipitated sulfur species, RPSS). This occurs in a concerted manner in a global sense through the cathode and can be measured using impedance spectroscopy. It was found that the more RPSS that is formed, the higher the energy density of discharge. We propose that high concentration of polysulfide tends to supersaturate, which impeded the formation of RPSS. Employing an electrolyte with low Li ion concentration along with using poorly dissociating lithium salts allowed for more RPSS formation and ultimately enabled discharge at >2.0 V at 0.05 C, at E/S = 2.5, and at room temperature without the use of an engineered cathode.

Anion-Dominated Solvation in Low-Concentration Electrolytes Promotes Inorganic-Rich Interphase Formation in Lithium Metal Batteries.

While the formation of an inorganic-rich solid electrolyte interphase (SEI) plays a crucial role, the persistent challenge lies in the formation of an organic-rich SEI due to the high solvent ratio in low-concentration electrolytes (LCEs), which hinders the achievement of high-performance lithium metal batteries. Herein, by incorporating di-fluoroethylene carbonate (DFEC) as a non-solvating cosolvent, a solvation structure dominated by anions is introduced in the innovative LCE, leading to the creation of a durable and stable inorganic-rich SEI. Leveraging this electrolyte design, the Li||NCM83 cell demonstrates exceptional cycling stability, maintaining 82.85% of its capacity over 500 cycles at 1 C. Additionally, Li||NCM83 cell with a low N/P ratio (≈2.57) and reduced electrolyte volume (30µL) retain 87.58% of its capacity after 150 cycles at 0.5 C. Direct molecular information is utilized to reveal a strong correlation between solvation structures and reduction sequences, proving the anion-dominate solvation structure can impedes the preferential reduction of solvents and constructs an inorganic-rich SEI. These findings shed light on the pivotal role of solvation structures in dictating SEI composition and battery performance, offering valuable insights for the design of advanced electrolytes for next-generation lithium metal batteries.

Influence of electrolyte to silicon electrode volume ratio on the capacity of next generation lithium ion cells at low temperature

Silicon electrodes are being investigated as potential high-capacity replacements for graphite electrodes in lithium-ion batteries. Various factors affecting silicon electrodes need to be understood to maintain increased capacity and high performance at subzero temperatures. This work investigates electrode thickness and volume of electrolyte used that can affect performance of a copper modified silicon electrode at −20 °C. When electrolyte volume is large compared to electrode volume (20:1 ratio), the performance of these cells at low temperature is noticeably improved, retaining approximately 400 mAh/g capacity at −20 °C after 50 cycles.

A correlated multi-observable assessment for vanadium redox flow battery state of charge estimation — Empirical correlations and temperature dependencies

The efficient operation of vanadium redox flow batteries requires the half cell specific monitoring of the state of charge (SOC). Monitoring of the SOC is affected by temperature fluctuations, which need to be distinguished from the SOC signal. Several SOC monitoring approaches have been proposed in the literature and either been evaluated individually or compared to one other approach. The aim of this study is to contribute to SOC sensor development for VRFB by providing a first correlated assessment of several established and new SOC monitoring methods. We perform multi observable measurements of: half cell electrolyte potentials, electrolyte densities, electrolyte volumes, electrolyte viscosity related pressure drops, pH related potentials and UV/Vis absorbances. We determine SOC correlations of these observables in full charge/discharge cycles at constant temperature and derive temperature corrections in additional measurements over a range of 12°C to 32°C at 25%, 50% and 75% SOC. We compare the SOC and temperature sensitivity as well as the accuracy of these monitoring methods at constant and varied temperature. We find that the established half cell electrolyte potentials and UV/Vis absorbances can estimate the SOC at constant temperature with measurement errors of 1.7% and 4%, respectively and with slightly higher errors at varying temperatures. The viscosity related pressure drop and electrolyte density are both suitable for SOC estimation if temperature corrections are included. The pH related potentials for the positive half cell and both half cell electrolyte volumes could be used for a rough SOC estimate, but need accurate temperature corrections and further long term stability evaluation.

An experimentally validated model for anodic H2O2 production in alkaline water electrolysis and its implications for scaled-up operation

The anodic co-production of hydrogen peroxide (H2O2) during alkaline water electrolysis has gained interest as a sustainable alternative for anthraquinone oxidation. However, electrochemical H2O2 production is often studied with idealized laboratory setups to determine the H2O2 formation kinetics. In this work, we perform the reaction with industrially relevant operating principles using a flow cell with separately recirculating anolyte and catholyte. We then fit the data to an analytical model that we derive based on mole balances that accounts for anodic generation, anodic oxidation, and bulk disproportionation of H2O2, as well as electrolyte volumes and electrode surface area. We performed experiments at 100, 200, and 300 mA cm-2 to derive values for the reaction system. At 200 mA cm-2, we found a generation rate of 0.037 mmol min-1 cm-2 (FEH2O2 = 59%) and an anodic decomposition rate constant of 0.304 cm min-1, with a bulk disproportionation rate constant of 1.85 × 10-3 min-1. We successfully applied our model to two sources in literature to derive values for their systems as well. In all cases, the contribution of anodic oxidation of H2O2 was found to be the larger loss mechanism in comparison to bulk disproportionation. Using the analytical model, we show that decreasing the reservoir volume is a simple way to increase the H2O2 concentration over time. Further refinement of the model can be achieved through the use of mass transfer relationships based on electrolyzer geometries to describe the anodic oxidation of H2O2 in the mole balance equations.

In vivo Assessment of a Manual Single Lumen Alternating Micro-Batch Hemodiafiltration System

Introduction: The manual single lumen alternating micro-batch hemodiafiltration (mSLAMB) system is a closed-loop dialysis system designed to provide kidney support in emergency situations (e.g., fluid overload, hyperkalemia, acidemia). If done repeatedly in small batches and at high flow rates, this system was found to achieve clearance levels comparable to traditional renal replacement therapy. Methods: Using a porcine model, uremic toxins and exogenous fluorescent tracer concentrations were successfully lowered within just 1 h of treatment. Results: With a maximal dialysate flow, mSLAMB can achieve decreases in serum potassium concentration of >0.5 mmol/L/h. With the mSLAMB hemodiafiltration system, micro-batch processing was also successful in removing up to 250 mL of ultrafiltrate in 8 cycles. Conclusion: This process could create a better fluid balance allowing for administering therapeutic fluids such as sodium bicarbonate in the clinic. Electrolyte imbalance and volume overload remain severe life-threatening emergencies in low resource settings; therefore, mSLAMB should be explored further due to its modest vascular access requirements, low cost, and ability to be performed without electricity or batteries.

Exploring the Voltage Stability of Birnessitic Bi-MnO2 Cathodes Formed In Situ in NaOH and KOH-Based Electrolytes

MnO2, in its many phases, is abundant, non-flammable, non-toxic, reliable, made with abundant materials using simple manufacturing methods, and can have a high theoretical capacity for some phases (up to 617 mAh g−1). Here we have investigated the sensitivity of the performance ofbirnessite—produced in situ—to the presence of Bi2O3, depth-of-discharge, electrolyte salt type, and relative electrolyte volume. We prepared cathodes composed of 45 wt% MnO2, 22.5 wt% Bi2O3, and 22.5 wt% carbon additives, and compared cycling stability in two electrolytes—6.6 M KOH (27 wt%) and 6.6 M NaOH (21 wt%), and two types of 3-electrode test fixtures (flooded beaker or electrolyte-lean T-cell). Our results showed that birnessite can be synthesized electrochemically in NaOH, and cycling the cathode in NaOH improves its stability when compared to cycling in KOH. We tested the cathode in electrolyte-lean environments and found a drastic improvement in cycling stability in NaOH. The cathode exhibited higher initial capacity in lean amounts of KOH, but capacity retention plummeted after the first 20 cycles. In contrast, the cathode in NaOH delivered 65% of the theoretical capacity for over 400 cycles.

Investigation of lead-acid battery water loss by in-situ electrochemical impedance spectroscopy

Understanding the chemical reactions that occur during lead-acid battery aging is useful for predicting battery life and repairing batteries for reuse. Current research on lead-acid battery degradation primarily focuses on their capacity and lifespan while disregarding the chemical changes that take place during battery aging. Motivated by this, this paper aims to utilize in-situ electrochemical impedance spectroscopy (in-situ EIS) to develop a clear indicator of water loss, which is a key battery aging process and could be repaired, through unique water loss experiments. These experiments were designed to ensure that the percentage of water in the electrolyte or the volume of electrolyte was the only factor that affected in-situ EIS in each experiment, and these values were regularly changed to simulate water loss in a specially designed transparent lead-acid battery. Through an improved equivalent circuit model (ECM) and grey relation analysis (GRA), this work shows that the variation of double-layer capacity and internal resistance can indicate added water content and electrolyte volume. The developed method is simple and can be applied to identify and respond to battery water loss effectively.

Anion-Involved Solvation Structure of Lithium Polysulfides in Lithium-Sulfur Batteries.

Lithium polysulfides (LiPSs) are pivotal intermediates involved in all the cathodic reactions in lithium-sulfur (Li-S) batteries. Elucidating the solvation structure of LiPSs is the first step for rational design of electrolyte and improving Li-S battery performances. Herein, we investigate the solvation structure of LiPSs and find that Li salt anions tend to enter the first solvation sheath of LiPSs and form contact ion pairs in electrolyte. The anion-involved solvation structure of LiPSs significantly influences the intrinsic kinetics of the sulfur redox reactions. In particular, the LiPS solvation structure modified by lithium bis(fluorosulfonyl)imide endows Li-S batteries with reduced polarization and enhanced rate performances under high sulfur areal loading and lean electrolyte volume conditions. This work updates the fundamental understanding of the solvation chemistry of LiPSs and highlights electrolyte engineering for promoting the performances of Li-S batteries.

Anion‐Involved Solvation Structure of Lithium Polysulfides in Lithium–Sulfur Batteries

AbstractLithium polysulfides (LiPSs) are pivotal intermediates involved in all the cathodic reactions in lithium–sulfur (Li−S) batteries. Elucidating the solvation structure of LiPSs is the first step for rational design of electrolyte and improving Li−S battery performances. Herein, we investigate the solvation structure of LiPSs and find that Li salt anions tend to enter the first solvation sheath of LiPSs and form contact ion pairs in electrolyte. The anion‐involved solvation structure of LiPSs significantly influences the intrinsic kinetics of the sulfur redox reactions. In particular, the LiPS solvation structure modified by lithium bis(fluorosulfonyl)imide endows Li−S batteries with reduced polarization and enhanced rate performances under high sulfur areal loading and lean electrolyte volume conditions. This work updates the fundamental understanding of the solvation chemistry of LiPSs and highlights electrolyte engineering for promoting the performances of Li−S batteries.

Study of the wear resistance of composite coatings modified with h-BN particles on AZ31 magnesium alloy

A low wear resistance is a significant disadvantage of magnesium-based alloys widely used in industry. The results of plasma electrolytic oxidation (PEO) carried out in an aqueous-alkaline phosphate electrolyte with the addition of hexagonal boron nitride (h-BN) powder to obtain coatings with greater wear resistance on the surface of AZ31 magnesium alloy are presented. The PEO method is one of the most promising for surface treatment of magnesium alloys, since oxidation is carried out in alkaline aluminate, silicate or phosphate electrolytes with various functional additives. The addition of nanocrystalline hexagonal h-BN powder in the form of a suspension into the electrolyte volume does not affect the electrical parameters of PEO, and h-BN particles are incorporated into the structure of the formed composite coating, increasing the wear resistance. It is shown that the resulting coatings have a relief typical of PEO with developed morphology and porosity, which change depending on the oxidation time. In this case, the incorporation of h-BN particles into the coating occurs by an inert mechanism, since they do not undergo chemical transformations with the formation of new phases. Composite coatings obtained on the surface of the AZ31 magnesium alloy by the PEO method consist of crystalline phases of MgO and Mg3(PO4)2, regardless of the addition of h-BN particles to the electrolyte. The wear resistance of coatings is 6 – 8 times higher compared to the untreated alloy. The results obtained can be used to produce PEO coatings with increased wear resistance and use them in various sectors of the economy.

In-situ Crosslinked Gel Polymer Electrolytes Based on Ionic Monomers as Charge Carriers for Lithium-Ion Batteries

Abstract In-situ polymerization is a method for fabricating lithium-ion batteries to contain solid or gel electrolytes without major manufacturing changes. Gel polymer electrolytes (GPEs) wherein some polymer in incorporated, decreasing the volume of liquid electrolyte, have been pursued as they may be safer. One challenge with GPEs is reduced ion transport properties. In this work, macromonomers with different chain chemistry and ionic monomers are crosslinked on electrospun polyvinylidene difluoride (PVDF) in the presence of solvents, without conventional salt, to in-situ fabricate GPEs with elevated transference number within coin cells. These GPEs would be single-ion conductors in the case of complete ionic monomer polymerization to the crosslinked network. The effect of chain chemistry and the percentage of macromonomers and ionic monomers in the GPEs on conductivity are investigated. It is found that poly(siloxane) diacrylate (PDMSDA)- and perfluoropolyether tetra-acrylate (PFPETA)-based GPEs outperform the poly(propylene glycol) diacrylate (PPGDA)- and poly(tetrahydrofuran) diacrylate (PTHFDA)-based GPEs in terms of ionic conductivity. The highest ionic conductivity was achieved for a PDMSDA-based GPE at 4.2 × 10-4 S/cm at 23°C. Graphite/NMC-811 full cells prepared with the in-situ polymerized PDMSDA-based GPEs show capacity retention of 82.6% after 100 cycles, albeit with limited electrode utilization due to ion transport limitations.

Stability Criterion for Electrodeposition in Solid-State Batteries with Metallic Anodes

We establish an analytical criterion for stable electrodeposition by combining electrochemistry and mechanics. experiments combined with molecular simulations are performed to validate the robustness of the theoretical predictions. Our analysis shows that stable electrodeposition is intimately linked with the interfacial defect size, fracture toughness, and molar volume of solid electrolytes. We find an exponential scaling law between the critical current density and the interfacial defect size, and the inherent softening in strength of grain boundaries lowers the critical current density in polycrystalline solid electrolytes. Modeling and analyses provide roadmaps to design solid electrolytes with metallic anodes for achieving stable electrodeposition. Published by the American Physical Society 2024

Neuropilin-1 regulates renin synthesis in juxtaglomerular cells.

Renin is the key enzyme of the systemic renin-angiotensin-aldosterone system, which plays an essential role in regulating blood pressure and maintaining electrolyte and extracellular volume homeostasis. Renin is mainly produced and secreted by specialized juxtaglomerular (JG) cells in the kidney. In the present study, we report for the first time that the conserved transmembrane receptor neuropilin-1 (NRP1) participates in the development of JG cells and plays a key role in renin production. We used the myelin protein zero-Cre (P0-Cre) to abrogate Nrp1 constitutively in P0-Cre lineage-labelled cells of the kidney. We found that the P0-Cre precursor cells differentiate into renin-producing JG cells. We employed a lineage-tracing strategy combined with RNAscope quantification and metabolic studies to reveal a cell-autonomous role for NRP1 in JG cell function. Nrp1-deficient animals displayed abnormal levels of tissue renin expression and failed to adapt properly to a homeostatic challenge to sodium balance. These findings provide new insights into cell fate decisions and cellular plasticity operating in P0-Cre-expressing precursors and identify NRP1 as a novel key regulator of JG cell maturation. KEY POINTS: Renin is a centrepiece of the renin-angiotensin-aldosterone system and is produced by specialized juxtaglomerular cells (JG) of the kidney. Neuropilin-1 (NRP1) is a conserved membrane-bound receptor that regulates vascular and neuronal development, cancer aggressiveness and fibrosis progression. We used conditional mutagenesis and lineage tracing to show that NRP1 is expressed in JG cells where it regulates their function. Cell-specific Nrp1 knockout mice present with renin paucity in JG cells and struggle to adapt to a homeostatic challenge to sodium balance. The results support the versatility of renin-producing cells in the kidney and may open new avenues for therapeutic approaches.

Heterostructured nickel–cobalt metal alloy and metal oxide nanoparticles as a polysulfide mediator for stable lithium–sulfur full batteries with lean electrolyte

AbstractBatteries that utilize low‐cost elemental sulfur and light metallic lithium as electrodes have great potential in achieving high energy density. However, building a lithium–sulfur (Li–S) full battery by controlling the electrolyte volume generally produces low practical energy because of the limited electrochemical Li–S redox. Herein, the high energy/high performance of a Li–S full battery with practical sulfur loading and minimum electrolyte volume is reported. A unique hybrid architecture configured with Ni–Co metal alloy (NiCo) and metal oxide (NiCoO2) nanoparticles heterogeneously anchored in carbon nanotube‐embedded self‐standing carbon matrix is fabricated as a host for sulfur. This work demonstrates the considerable improvement that the hybrid structure's high conductivity and satisfactory porosity promote the transport of electrons and lithium ions in Li–S batteries. Through experimental and theoretical validations, the function of NiCo and NiCoO2 nanoparticles as an efficient polysulfide mediator is established. These particles afford polysulfide anchoring and catalytic sites for Li–S redox reaction, thus improving the redox conversion reversibility. Even at high sulfur loading, the nanostructured Ni–Co metal alloy and metal oxide enable to have stable cycling performance under lean electrolyte conditions both in half‐cell and full‐cell batteries using a graphite anode.

Multiple protective layers for suppressing Li dendrite growth and improving the cycle life of anode-free lithium metal batteries

Anode-free lithium metal batteries (AFLMBs) have sparked considerable attention in recent years because of their potential for high energy density; however, they suffer from severe Li dendrite growth and unstable solid electrolyte interphase (SEI), which typically result in rapid capacity decay. Herein, we demonstrate a long-life anode-free pouch cell by designing a dual-coating protective layer (Cu-Sn@SFPH) electrode with Sn-coated Cu (denoted as Cu-Sn) as the bottom layer and SrF2 nanoparticles strengthened by poly (vinylidene fluoride)-co-hexafluoropropylene (PVDF-HFP) as the top layer. The in-situ formed LiF-rich SEI enables fast Li+ transfer, while the lithiophilic Li-Sn and Li-Sr alloy layers serve as nucleation seeds for uniform Li deposition. The dual-coated Cu electrode in the Cu-Sn@SFPH||Li cell exhibits remarkable cycling stability for more than 3,200 h at a capacity of 2 mAh cm−2. The NCM111||Cu-Sn@SFPH pouch cell demonstrates outstanding performance with a capacity retention of 72.1 % and an average Coulombic efficiency (CE) of 99.9 % for 120 cycles. Under practical conditions, with NCM cathodes and a lean electrolyte volume, this design strategy opens a new approach to AFLMBs.

Impact of Electrolyte Volume on the Cycling Performance and Impedance Growth of 18650 Li-ion Cells

We provide compelling evidence that the cycling performance of 18650 Li-ion cells is adversely affected by excessive amounts of electrolyte volume, with a noticeable decline observed within the initial 30 cycles, particularly at higher discharge rates. This “high-volume effect” imposes additional constraints on the optimization of cell manufacturing, highlighting the importance of identifying its underlying causes. The electrochemical impedance of 3.5 Ah 18650 cylindrical cells with varying levels of electrolyte volume was extensively measured using PEIS and GEIS techniques. The results indicate that, in general, the ohmic and charge transfer resistance(s) of the cells increase at a faster rate when excess electrolyte volume (9% and 18%) is present. During high discharge rate cycling, relaxation periods can effectively recover the lost capacity, but when high discharge rate cycling resumes, the trend in the capacity loss reappears. We hypothesize that a salt segregation effect in the electrolyte may contribute to the growth of both ohmic and charge transfer resistance, leading to capacity loss when excess electrolyte is present.