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Behavior of Lithium Metal Anodes under Various Capacity Utilization and High Current Density in Lithium Metal Batteries
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Maximizing neutron yields by scaling hollow diameter of a dense plasma focus anode [Neutron yield maximization and anode surface damage characterization by scaling hollow diameters of a DPF anode]
Experiments were performed to maximize the neutron yield from a 2 kJ dense plasma focus (DPF) and characterize the amount of copper sputtered from the surface of an anode by varying the diameter of the anodes’ on-axis hollow. The hollow is a void in the copper material along the longitudinal axis of the anode. All the anodes had an outer diameter of 1.2 in. and the diameter of the hollow varied from 0 in. (no hollow) to 1 in. The anodes with a hollow produced a greater number of neutrons per discharge than the anode without a hollow. Over 40 discharges, the hollow anode that yielded the most neutrons (9.1±0.4×10 6 neutrons per discharge produced with the 0.75 in. hollow) produced >6 times more neutrons than the anode with no hollow. A qualitative observation of the anodes after 130 discharges showed less surface damage on anodes with a larger hollow. Quantitative sputter measurements were performed by characterizing the amount of copper sputtered onto on-axis quartz targets for three newly machined anodes, each with a particular hollow diameter. The quantitative results matched the qualitative observations: the copper sputter was reduced using larger hollows. Finally, the largest hollow sputtered 17±1.0 nm/sr/discharge of copper, a reduction of 69% compared to the anode with the most damage.
Effect of TiO{sub 2} Addition on Grain Growth, Anodic Bubble Evolution and Anodic Overvoltage of NiFe{sub 2}O{sub 4}-Based Composite Inert Anodes
A two-step powder compaction and sintering process was employed to fabricate TiO{sub 2}-doped NiFe{sub 2}O{sub 4} ceramic-based inert anodes. Grain growth during isothermal sintering was analyzed using Brook grain growth model. The bubble behavior of NiFe{sub 2}O{sub 4} ceramic-based inert anodes was investigated in a two-compartment see-through quartz cell for aluminum electrolysis process. Anodic overvoltage and potential decay curves of the inert anodes were measured by using the steady state and current interruption technique. The results showed that the kinetic index of grain growth decreased with an increase in temperature. The average activation energy of grain growth for 1.0 wt.% TiO{sub 2}-doped NiFe{sub 2}O{sub 4} ceramic samples with a sintering temperature range from 1373 to 1673 K dropped from 675.30 to 183.47 kJ/mol. The diameter size of bubbles before releasing from the bottom surface of the anodes was reduced with increasing the current density, and the larger average releasing bubble size for carbon anode at the same current density could be obtained, which was compared to the NiFe{sub 2}O{sub 4} inert anodes. Besides, the cell voltage of carbon anodes fluctuated much more violently under the same experimental conditions. After adding small amount of TiO{sub 2}, a minor reduction in anodic overvoltage of NiFe{sub 2}O{sub 4}-based anodes can be observed.
Unraveling the convoluted and dynamic interphasial mechanisms on Li metal anode
Accurate understanding of the chemistry of solid-electrolyte interphase (SEI) is key to developing new electrolytes for high-energy batteries using lithium metal (Li-0) anodes(1). SEI is generally believed to be formed by the reactions between Li-0 and electrolyte(2,3). However, our new study shows this is not the whole story. Through synchrotron-based X-ray diffraction and pair distribution function analysis, we reveal a much more convoluted formation mechanism of SEI, which receives considerable contributions from electrolyte, cathode, moisture and native surface species on Li-0, with highly dynamic nature during cycling. Using isotope labelling, we traced the origin of LiH to electrolyte solvent, moisture and a new source: the native surface species (LiOH) on pristine Li-0. When lithium accessibility is very limited as in the case of anode-free cells, LiOH develops into plate-shaped large crystals during cycling. Alternatively, when the lithium source is abundant, as in the case of Li||NMC811 cells, LiOH reacts with Li-0 to form LiH and Li2O. While the desired anion-derived LiF-rich SEI is typically found in the concentrated electrolytes or their derivatives, we found it can also be formed in low-concentration electrolyte via the crosstalk effect, emphasizing the importance of formation cycle protocol and opening up opportunities for low-cost electrolyte development.
Surface Coating Constraint Induced Self-Discharging of Silicon Nanoparticles as Anodes for Lithium Ion Batteries
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Order–disorder transition in nano-rutile TiO 2 anodes: a high capacity low-volume change Li-ion battery material
Li-Intercalation in nano-rutile TiO 2 -anodes induces loss of long-range order with the formation of ∼5 nm layered Li x TiO 2 domains with ∼1 nm columbite-like grain boundaries.
Investigating anode off-gas under spark-ignition combustion for SOFC-ICE hybrid systems
Solid oxide fuel cell – internal combustion engine (SOFC-ICE) hybrid systems are an attractive solution for electricity generation. The system can achieve up to 70% theoretical electric power conversion efficiency through energy cascading enabled by utilizing the anode off-gas from the SOFC as the fuel source for the ICE. Experimental investigations were conducted with a single cylinder Cooperative Fuel Research (CFR) engine by altering fuel-air equivalence ratio (φ), and compression ratio (CR) to study the engine load, combustion characteristics, and emissions levels of dry SOFC anode off-gas consisting of 33.9% H 2 , 15.6% CO, and 50.5% CO 2 . The combustion efficiency of the anode off-gas was directly evaluated by measuring the engine-out CO emissions. The highest net-indicated fuel conversion efficiency of 31.3% occurred at φ = 0.90 and CR = 13:1. These results demonstrate that the anode off-gas can be successfully oxidized using a spark ignition combustion mode. The fuel conversion efficiency of the anode tail gas is expected to further increase in a more modern engine architecture that can achieve increased burn rates in comparison to the CFR engine. NO x emissions from the combustion of anode off-gas were minimal as the cylinder peak temperatures never exceeded 1800 K. This experimental study ultimately demonstrates the viability of an ICE to operate using an anode off-gas, thus creating a complementary role for an ICE to be paired with a SOFC in a hybrid power generation plant.
Yolk-shell structured Sb@C anodes for high energy Na-ion batteries
Despite great advances in sodium-ion battery developments, the search for high energy and stable anode materials remains a challenge. Alloy or conversion-typed anode materials are attractive candidates of high specific capacity and low voltage potential, yet their applications are hampered by the large volume expansion and hence poor electrochemical reversibility and fast capacity fade. Here, we use antimony (Sb) as an example to demonstrate the use of yolk-shell structured anodes for high energy Na-ion batteries. The Sb@C yolk-shell structure prepared by controlled reduction and selective removal of Sb2O3 from carbon coated Sb2O3 nanoparticles can accommodate the Sb swelling upon sodiation and improve the structural/electrical integrity against pulverization. It delivers a high specific capacity of ~554 mAh•g-1, good rate capability (315 mhA•g-1 at 10C rate) and long cyclability (92% capacity retention over 200 cycles). Full-cells of O3-Na0.9[Cu0.22Fe0.30Mn0.48]O2 cathodes and Sb@C-hard carbon composite anodes demonstrate a high specific energy of ~130 Wh•kg-1 (based on the total mass of cathode and anode) in the voltage range of 2.0-4.0 V, ~1.5 times energy of full-cells with similar design using hard carbon anodes.
Consumable anode and anode assembly for electrolytic reduction of metal oxides
An anode assembly is provided having a pair of channels; anodes in slidable communication with the channels; conduit to direct carrier gas to the anode; and conduit to remove reaction gas from the anode. Also provided is a method for continuously feeding anodes into a electrolytic bath, the method having the steps of stacking the anodes such that all of the anodes reside in the same plane and wherein the stack includes a bottom anode; contacting the bottom anode with the electrolytic bath for a time and at a current sufficient to cause the bottom anode to be consumed during an electrolytic process; using gravity to replace the bottom anode with other anodes defining the stack.
Mechanical and tribological properties of anodic Al coatings as a function of anodizing conditions
Enhanced wear and corrosion resistance properties are vital for numerous functional and decorative applications. Anodizing is a process frequently used to generate stable oxide coatings on metal surfaces, including aluminium (Al). In this work, we present an evaluation of process variables for optimized anodized coating properties using existing methods and as a baseline for novel coating development. A representative relatively pure Al alloy was chosen as a model system with a goal of finding conditions to achieve high wear coatings with retained ductility. AA5052 alloy coupons were anodized in two different electrolytes (sulfuric and phosphoric acid) to study the effects of anodizing conditions on the mechanical and tribological properties of the anodic coatings. Porosity was evaluated with microscopy, coating hardness was determined via nanoindentation, and tribological properties were characterized using a pin-on-disk tribometer. These measurements were correlated and a loading evaluation was performed to assess the optimum nanoindentation parameters for the use of representative coupons without the need for special processing prior to anodizing. The porosity and coating thickness were found to depend on the anodizing time and the type of electrolyte. Thicker and harder anodic coatings were generated in sulfuric acid compared to phosphoric acid. Porosity studies of the anodic coatings generated in phosphoric acid revealed that coating porosity decreased as the anodizing time increased. Both electrolytes generated anodic coatings with improved tribological properties (friction coefficient and dimensional wear rate), and an optimum processing time was identified for best wear properties.
TiO2 Nanocrystal-Framed Li 2 TiSiO 5 Platelets for Low-Voltage Lithium Battery Anode
Titanium-based anode materials are attracting considerable attention for use in high-performance lithium-ion batteries, but the compromised energy density caused by high voltage plateaus and unsatisfactory capacities severely retards their practical applications. Herein, a molten-salt synthesis of Li 2 TiSiO 5 crystalline platelets and a subsequent selective facet modification by in situ growth of TiO 2 nanocrystal frames are facilely achieved. The discharge voltage plateau at around 0.5 V renders the Li 2 TiSiO 5 anode safe compared with graphite and confers a high energy density compared with zero-strain Li 4 Ti 5 O 12 anode. With the optimized size, structure, and content of modified TiO2 nanocrystals associated with the exposed (001) plane of Li 2 TiSiO 5 , the Li 2 TiSiO 5 -based anodes can deliver a capacity of above 300 mAh g -1 , enhanced rate performance, and a capacity retention of 66% after 10 000 cycles. In situ X-ray diffraction and ex situ transmission electron microscopy have demonstrated the structural stability of the anodes upon charge/discharge. Further theoretical calculation reveals 3D migration paths of Li + ions in Li 2 TiSiO 5 . The selective modification of in situ grown TiO2 nanocrystals on certain facets of crystallites opens a new door for the development of electrode materials possessing superior electrochemical properties.
High-performance silicon anodes enabled by nonflammable localized high-concentration electrolytes
Silicon (Si) anode is regarded as one of the most promising alternatives to graphite for high energy density lithium ion batteries (LIBs), but their practical applications have been hindered by high volume change, limited cycle life and safety concerns. In this work we developed nonflammable localized high concentration electrolytes (LHCEs) for Si-based anodes. The LHCEs enabled the Si anodes with significantly enhanced electrochemical performances comparing to the conventional carbonate electrolytes with high content of fluoroethylene carbonate (FEC). The LHCE with only 1.2 wt% FEC can further improve the long-term cycling stability of Si-based anodes. When coupled with a LiNi0.3Mn0.3Co0.3O2 cathode, the full cells using this nonflammable LHCE could maintain >90% capacity after 600 cycles at C/2 rate, demonstrate excellent rate capability and cycling stability at elevated temperatures and high loadings. This work casts new insights in electrolyte development from the perspective of in-situ Si/electrolyte interphase protection for high energy density LIBs with Si anodes.
Enhanced Stability of Li Metal Anodes by Synergetic Control of Nucleation and the Solid Electrolyte Interphase
Use of a protective coating on a lithium (Li) metal anode (LMA) is an effective approach to enhance its coulombic efficiency and cycling stability. Here we report a facile approach to produce uniform silver (Ag) nanoparticle-decorated LMAs for high-performance Li metal batteries (LMBs). This effective treatment can lead to well controlled nucleation and the formation of a stable solid electrolyte interphase (SEI). Ag nanoparticles embedded in the surface of Li anodes induced uniform Li plating/stripping morphologies with reduced overpotential. More importantly, cross-linked lithium fluoride (LiF) networks formed during Ag+ reduction enabled a highly stable SEI layer. Based on the Ag-LiF decorated anodes, LMBs with LiNi1/3Mn1/3Co1/3O2 cathode (~1.8 mAh cm-2) can retain >80% capacity over 500 cycles. The similar results were also obtained when the same approach was applied to the design of stable sodium (Na) anodes. These results indicate that synergetic control of the nucleation and SEI is an efficient approach to stabilize rechargeable metal batteries.
Essential distinction between one-step anodization and two-step anodization of Ti
Highlights: • One-step anodization (OSA) and two-step anodization (TSA) of Ti are compared. • Constant current anodizations were designed to control charge transfer. • Essential distinction between the OSA and the TSA was analyzed for the first time. • The distinction was clarified by oxygen bubble mould and plastic flow model. • The concaves contribute to the growth of highly-ordered ATNTs during TSA. - Abstract: One-step anodization (OSA) and two-step anodization (TSA) have been widely used to fabricate anodic TiO{sub 2} nanotubes (ATNTs). It has been reported that TSA can fabricated more ordered nanotubes, as compared to OSA. However, the essential distinction between OSA and TSA of Ti has never been clarified. Here, constant current anodizations were designed to study the effects of TSA and OSA on the morphology of ATNTs. The significant differences between nanotubular architecture (length, diameter, porosity) of ATNTs fabricated by OSA and TSA were observed and analyzed for the first time. For TSA, the relationship between the nanotube length (y) and anodizing current (x) corresponds to the liner equation y = 0.259x-2.3, and the relationship between nanotube outside diameter (Y) and anodizing current (x) corresponds to the linear equation Y = 3.352x+65.73. However, no similar linear relationships were found for OSA. The essential distinction between OSA and TSA was clarified by oxygen bubble mould combined with plastic flow model.
Investigation of mechanism of anode plasma formation in ion diode with dielectric anode
The results of investigation of the anode plasma formation in a diode with a passive anode in magnetic insulation mode are presented. The experiments have been conducted using the BIPPAB-450 ion accelerator (350–400 kV, 6–8 kA, 80 ns) with a focusing conical diode with B{sub r} external magnetic field (a barrel diode). For analysis of plasma formation at the anode and the distribution of the ions beam energy density, infrared imaging diagnostics (spatial resolution of 1–2 mm) is used. For analysis of the ion beam composition, time-of-flight diagnostics (temporal resolution of 1 ns) were used. Our studies have shown that when the magnetic induction in the A-C gap is much larger than the critical value, the ion beam energy density is close to the one-dimensional Child-Langmuir limit on the entire working surface of the diode. Formation of anode plasma takes place only by the flashover of the dielectric anode surface. In this mode, the ion beam consists primarily of singly ionized carbon ions, and the delay of the start of formation of the anode plasma is 10–15 ns. By reducing the magnetic induction in the A-C gap to a value close to the critical one, the ion beam energy density is 3–6 times higher than that calculated by the one-dimensional Child-Langmuir limit, but the energy density of the ion beam is non-uniform in cross-section. In this mode, the anode plasma formation occurs due to ionization of the anode material with accelerated electrons. In this mode, also, the delay in the start of the formation of the anode plasma is much smaller and the degree of ionization of carbon ions is higher. In all modes occurred effective suppression of the electronic component of the total current, and the diode impedance was 20–30 times higher than the values calculated for the mode without magnetic insulation of the electrons. The divergence of the ion beam was 4.5°–6°.
Controlled Fabrication of Nanoporous Anodic Titania Films on Ti-6Al-4V Alloy for Enhanced Self-Lubricating Properties by Combining Spark Anodization and Electropulse-Assisted Ultrasonic Rolling
We report the fabrication of self-lubricating nanoporous anodic titania films through spark anodization in an aqueous ammonia sulfate electrolyte on a hardened nanocrystalline layer of Ti-6Al-4V rods after electropulse-assisted ultrasonic surface rolling process (EP-USRP). The spark anodization with an optimum anodizing voltage of 130 V produced sponge-like nanoporous anodic titania films with stable crystalline structure of rutile-phase TiO{sub 2}, and the EP-USRP resulted in a nanocrystalline layer with a higher surface hardening depth (> 220 µm) through severe plastic deformation. The combinatorial technique resulted in excellent tribological properties, with lower friction coefficient of ~ 0.72 (compared to EP-USRP of ~ 0.80), smoother wear scar with less adhesion and less wear loss (maximum depth of 12 nm, 33.3% lower than the EP-USRP sample). These enhancements are attributed to the synergetic effect of the self-lubricating nanoporous anodic titania films formed by spark anodization (which acted as transition layer and prevented direct contact between the counter materials and the substrate) and the hardened nanocrystalline layer formed by EP-USRP (which slowed down the consumption of the anodic powder).
Understanding the Origin of the Nonpassivating Behavior of Si-Based Anodes during the Initial Cycles
In this contribution, we combined electrochemical cycling and X-ray photoelectron spectroscopy (XPS) to understand the nonpassivating behavior of the solid electrolyte interphase (SEI) on Si anodes during the first cycles. Based on galvanostatic measurements, we show that the irreversible capacity loss is reduced after the first cycle, and it stays almost constant from the second cycle onwards. XPS was used to determine the root causes of the Coulombic inefficiency, showing that the rate of decomposition of the organic solvents strongly decreased after the first cycle, whereas the rate of salt decomposition is almost unchanged between cycles. We determine that the inhibition of the decomposition reaction of the organic solvent is responsible for the lower Coulombic loss during the second electrochemical cycle in comparison to the first, whereas the nonpassivating behavior toward the salt decomposition is one of the main causes of capacity loss upon cycling. Here, we further revisit the role of cracking in contributing to capacity loss. Whereas high volumetric expansion remains an issue plaguing the performance of Si anodes, our chronoamperometry studies reveal that the SEI formed on Si anodes does not passivate even when the electrode is fully expanded, and no additional surface is exposed. Overall, our work establishes the need to address the chemical and electrochemical instability of the SEI on the Si anode in addition to the more notorious issue of cracking.