Commercial Cathode Materials Research Articles

Surface Design Engineering of LiTaO3 Coating on Li-Excess Li2NiO2 Cathode Additive for Lithium-Ion Batteries

The latest research has mainly focused on enhancement in the energy density of lithium-ion batteries (LIBs) to satisfy the rigorous industrial demands. As the most common approach for improving the energy density of LIBs, the utilization of high capacity anode materials, such as silicon suboxide (SiOx), has been highlighted, instead of graphite. SiOx anodes are known to have a high specific capacity and low operating voltage (< 0.5 V vs. Li/Li+). However, the severe initial capacity loss induced by the formation of solid electrolyte interphase (SEI) limits their commercial use in LIBs. To compensate for the initial loss of available Li+, the application of Li-excess cathode additives has been considered as the most practical strategy for supplying surplus Li+ during the initial charge process. In this respect, Li2NiO2 is a suitable cathode additive because it offers a high initial charge capacity (≥ 320 mAh g-1) and a compatible operating voltage with commercial cathode materials. Surface protection of Li2NiO2 is still required, however, due to its vulnerability to moisture (H2O) and carbon dioxide (CO2) in the ambient atmosphere. Moreover, Li2NiO2 becomes more structurally unstable during cycle due to oxygen (O2) gas evolution, leading to the formation of microcracks. To overcome these obstacles, we suggest a functional LiTaO3 coating layer onto the surface of Li2NiO2 for structural stabilization. In practice, the LiTaO3 coating layer can effectively suppress the production of impurities (i.e., LiOH and Li2CO3) at the surface of Li2NiO2 after air exposure. Furthermore, the gas evolution and microcracks can be minimized by enhancing the structural stability of Li2NiO2 during cycling. These synergetic effects of the LiTaO3 coating layer can provide clear insights for the development of Li-excess cathode additives for achieving advanced LIBs.

Alternating Current Electrolytic Extraction of Transition Metals from NMC532 using Rotating Disc Cyclic Voltammetry in Dilute Chloride Solution

The rising application of portable electric devices has led to the rapid accumulation of electronic wastes such as lithium-ion batteries. These wastes pose significant environmental threats when improperly disposed of and contain valuable metals that could supplement the supply chain and reduce the need for certain conflict minerals. Recycling methods that limit the potential for environmental damage and improve separation of transition metals are vital to the sustainability of battery based electrical storage. Conventional aqueous recycling of lithium battery electrode materials utilizes oxidizing acids and a chemical reducing agent. This study investigates if chemical oxidizing and reducing agents may be aided or replaced by the application of an alternating electric field to reduce surface metal oxides and subsequently accelerate reoxidation with a solubilizing anion. The electrolytic leaching mechanics of commercial battery cathode material (NMC532) in dilute hydrochloric acid were investigated using rotating disc cyclic voltammetry (RDE-CV), solution analysis with inductively coupled plasma mass spectrometry (ICP-MS), and residue analysis with scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS). We found evidence that applying an alternating electric field allows for adjustment of leaching rates for different transition metals based on electrochemical cell parameters. By applying up to one volt oscillating between reducing and oxidizing polarity, the relative molar leaching rate of nickel and manganese drastically increased while that of cobalt slightly decreased. Future research will be required to determine how this effect translates to different leaching systems and its applicability to an industrial scale process.The authors acknowledge financial support from the NSF IUCRC program for the “Center for solid-state electric power storage” (#2052631) and support from the South Dakota Board of Regents for the “Governor’s Research Center (GRC) for electrochemical energy storage”.

(Invited) Using Synchrotron Techniques to Pry into Lithium-Ion Batteries Limitations

Li-ion batteries have been highly successful since they were introduced commercially some 30 years ago. However, there are still improvement to be made to reduce cost, charging times, energy density etc. In this talk, we will present the some of our recent synchrotron radiation-based work on the sub-processes that must work in unison for lithium battery operation, in particular at high current densities. Specifically, we will present work at the particle level on high power charging, illustrating how under favorable conditions some commercial cathode materials may be fully charged within tens of seconds. Moving towards the electrode scale, our latest technique development include an x-ray fluorescence technique that permits the determination of the electrolyte concentration within the electrode during battery operation. As such, this represent a major step forward towards validating mesoscale modeling as well as testing novel electrode architectures specifically designed for improved electrolyte transport. The importance of the electrode design is that in theory it can provide higher active material loading per area without losss of power capabilities. As such, the mass and volume of separator as well as current collector could be minimized improving both energy density and cost.

Regenerated Ni-Rich Cathode Materials from Spent Li-Ion Batteries by a Closed Loop Process

The demand for rechargeable lithium-ion batteries (LIBs) has increased exponentially since they were first commercialized by Sony in 1991.[1] Due to the high energy density and excellent cycle stability, LIBs have been widespread utilized in electric vehicles and other applications. However, the lifespan of LIBs is limited. Thus, tons of spent LIBs are generated during the recent decades. More importantly, the price of raw materials, including lithium and cobalt salts, for producing LIBs grows significantly.[2, 3] Therefore, recycling these End-of-Life LIBs becomes a non-negligible part in the whole manufacturing process and hydrometallurgical process is the most common recycling method. Here, our group has demonstrated a closed loop recycling process, combining inorganic acid etching and coprecipitation reaction, to produce regenerated Ni-rich cathode materials. The regenerated LiNi0.83Mn0.06Co0.11O2 shows excellent performance: the first cycle discharge capacity is 214.1mAh/g at 0.05C in the voltage range of 2.8 - 4.3V and the initial columbic efficiency is 90.9%. The performance of our regenerated cathode materials is comparable to commercial cathode materials. In order to further optimize the properties of the regenerated LiNi0.83Mn0.06Co0.11O2, different elements, like Al, with various doping or coating methods will be utilized. Manthiram A. A reflection on lithium-ion battery cathode chemistry. Nature Communications 2020; 11(1):1550.Li W, Lee S, Manthiram A. High‐Nickel NMA: A Cobalt‐Free Alternative to NMC and NCA Cathodes for Lithium‐Ion Batteries. Advanced materials (Weinheim) 2020; 32(33):2002718-n/a.Hou J, Ma X, Fu J, Vanaphuti P, Yao Z, Liu Y, et al. A green closed-loop process for selective recycling of lithium from spent lithium-ion batteries. Green Chemistry 2022; 24(18):7049-7060.

Enhanced Cycling Performance by Transition Metal Substitution on Li2CuO2 Cathode Additive for Advanced Lithium-Ion Battery

Lithium-Ion batteries (LIBs) have made remarkable progress in the last decade and have been employed so far as the most popular power source for electric vehicles (EVs). However, the energy density issue still remains a drawback for LIBs on long-range driving of EVs for the reason of significant irreversible Li+ loss in the initial charging process of LIBs, induced by a spontaneous formation of solid electrolyte interphase (SEI) on the anode surface. Therefore, strategic studies are required to maximize the energy density of LIBs as compensation of the initial loss of Li+ during cell operation. The utilization of a Li-excess cathode additive in commercial cathodes is an ideal approach to minimize the loss of energy density of LIBs. Recently, Li2CuO2 has been proposed as a potential cathode additive with many advantages over other candidates, including the following: (i) high charge capacity (~ 490 mAh g-1), (ii) comparable operating voltage window (2.5 ~ 4.3 V vs. Li/Li+) to commercial cathode materials, and (iii) abundance of copper (Cu) on the earth. But, its practical use is still restricted by the structural instability and spontaneous oxygen (O2) evolution (> 3.8 V vs. Li/Li+), which results in loss of reversibility during subsequent cycling. It is thus crucial to reinforce the structure of Li2CuO2 to make it more reliable as a cathode additive for charge compensation. In a pursuit of improving the structural stability of Li2CuO2, herein, we demonstrate structural modification via co-substitution by heteroatoms, such as nickel (Ni) and manganese (Mn), for improving the structural stability and electrochemical performance of Li2CuO2. Such an approach effectively enhances the reversibility of Li2CuO2 by suppressing continuous structural degradation and O2 gas evolution during cycling. Our findings provide new conceptual pathways for developing advanced cathode additives for high-energy LIBs.

An advanced CoNb2O6 anode material with in-situ interstitial doping for high-rate lithium-ion batteries

Niobium-based bimetallic oxide, as a potential anode material for fast-charging lithium-ion batteries, has attracted much attention owing to its unique lithium intercalation channel. However, the poor conductivity and structural instability of such material severely limit its further application. In this paper, CoNb2O6 was prepared by a molten-salt method and was in-situ doped with high-valence V5+ ion in different proportions. Different from conventional substitutional doping, a small amount of interstitial doping is more conducive to the entry of V5+ into the gap, which leads to lattice expansion. With the increase of doping amount, elemental Nb5+ was gradually replaced by V5+, which then hinders the Li+ intercalation/de-intercalation to a certain extent. Based on the DFT and electrochemical tests, the interstitial-doped CNO-V0.005 nanoparticles has not only faster Li+ diffusion kinetics and lower energy barrier, but also delivers high discharge capacity with long cycling stability at high current density of 2000 mA g−1 (≈ 8C). After assembling the full cell with CNO-V0.005 and commercial LiFePO4 cathode material, the reversible capacity of 150.6 mAh g−1 could be achieved after 200 cycles at the current density of 1000 mA g−1, demonstrating its application potential in fast- charging lithium-ion batteries.

Enhancing of long cycle and high rate performance of LiNi0.8Co0.15Al0.05O2 by Li1.5Al0.5Zr1.5(PO4)3 surface coating and Zr4+ doping

Layered LiNi0.8Co0.15Al0.05O2 (NCA) is a potential cathode material for the next generation of lithium-ion batteries due to its high energy density. However, the rapid attenuation of capacity caused by harmful phase change (H2-H3) and the side reaction between the active material and the electrolyte during the cycle have hindered its further development. In order to solve these problems, the side reaction can be alleviated by fast lithium-ion conductor Li1.5Al0.5Zr1.5(PO4)3 (LAZP) coating on the surface of NCA. At the same time, the doping of Zr4+ also inhibits the generation of harmful phase transition, which improves the cycle life and rate performance of NCA. After 300 cycles at 1C, the capacity loss rate of 1.0 wt% LAZP-NCA is 13.4%, and even at 5C, the capacity loss rate is only 16.3% after 200 cycles. In addition, the full cell composed of 1.0 wt% LAZP-NCA and graphite still has 72.1% capacity retention after 300 cycles at 1C. Therefore, this work provides a new idea for turning NCA into a commercial cathode material for lithium-ion batteries.

Temperature-Driven Anisotropic Mg2+ Doping for a Pillared LiCoO2 Interlayer Surface in High-Voltage Applications.

High-voltage lithium cobalt oxide (LiCoO2) has the highest volumetric energy density among commercial cathode materials in lithium-ion batteries due to its high working voltage and compacted density. However, under high voltage (4.6 V), the capacity of LiCoO2 fades rapidly due to parasitic reactions of high-valent cobalt with the electrolyte and the loss of lattice oxygen at the interface. In this study, we report a temperature-driven anisotropic doping phenomenon of Mg2+ that results in surface-populated Mg2+ doping to the side of the (003) plane of LiCoO2. Mg2+ dopants enter the Li+ sites, lower the valence state of Co ions with less hybridization between the O 2p and Co 3d orbitals, promote the formation of surface Li+/Co2+ anti-sites, and suppress lattice oxygen loss on the surface. As a result, the modified LiCoO2 demonstrates excellent cycling performance under 4.6 V, reaching an energy density of 911.2 Wh/kg at 0.1C and retaining 92.7% (184.3 mAh g-1) of its capacity after 100 cycles at 1C. Our results highlight a promising avenue for enhancing the electrochemical performance of LiCoO2 by anisotropic surface doping with Mg2+.

Advanced Sustainable Trilayer Cellulosic "Paper Separator" Functionalized with Nano-BaTiO3 for Applications in Li-Ion Batteries and Supercapacitors.

In the quest of developing a sustainable, low-cost and improved separator membrane for application in energy storage devices like lithium-ion batteries (LIBs) and supercapacitors (SCs), here we fabricated a trilayer cellulose-based paper separator engineered with nano-BaTiO3 powder. A scalable fabrication process of the paper separator was designed step-by-step by sizing with poly(vinylidene fluoride) (PVDF), thereafter impregnating nano-BaTiO3 in the interlayer using water-soluble styrene butadiene rubber (SBR) as the binder and finally laminating the ceramic layer with a low-concentration SBR solution. The fabricated separators showed excellent electrolyte wettability (216-270%), quicker electrolyte saturation, increased mechanical strength (43.96-50.15 MPa), and zero-dimensional shrinkage up to 200 °C. The electrochemical cell comprising graphite|paper separator|LiFePO4 showed comparable electrochemical performances in terms of capacity retention at different current densities (0.05-0.8 mA/cm2) and long-term cycleability (300 cycles) with coulombic efficiency >96%. The in-cell chemical stability as tested for 8 weeks revealed a nominal change in bulk resistivity with no significant morphological changes. The vertical burning test as performed on a paper separator showed excellent flame-retardant property, a required safety feature for separator materials. To examine the multidevice compatibility, the paper separator was tested in supercapacitors, delivering a comparable performance to that of a commercial separator. The developed paper separator was also found to be compatible with most of the commercial cathode materials such as LiFePO4, LiMn2O4, and NCM111.

Low-Cost Mn-Based Cathode Materials for Lithium-Ion Batteries

Due to a high energy density and satisfactory longevity, lithium-ion batteries (LIBs) have been widely applied in the fields of consumer electronics and electric vehicles. Cathodes, an essential part of LIBs, greatly determine the energy density and total cost of LIBs. In order to make LIBs more competitive, it is urgent to develop low-cost commercial cathode materials. Among all cathode materials, Mn-based cathode materials, such as layered LiNi0.5Mn0.5O2 and Li-rich materials, spinel LiMn2O4 and LiNi0.5Mn1.5O4, olivine-type LiMnPO4 and LiMn0.5Fe0.5PO4, stand out owing to their low cost and high energy density. Herein, from the perspective of industrial application, we calculate the product cost of Mn-based cathode materials, select promising candidates with low cost per Wh, and summarize the structural and electrochemical properties and improvement strategies of these low-cost Mn-based cathode materials. Apart from some common issues for Mn-based cathode materials, such as Jahn–Teller distortions and Mn dissolution, we point out the specific problems of each material and provide corresponding improvement strategies to overcome these drawbacks.

Enhanced Cycling Performance of a Li-Excess Li2CuO2 Cathode Additive by Cosubstitution Nanoarchitectonics of Ni and Mn for Lithium-Ion Batteries.

The adoption of Li2CuO2 has drawn interest as a Li-excess cathode additive for compensating irreversible Li+ loss in anodes during cycling, which would move forward high-energy-density lithium-ion batteries (LIBs). Li2CuO2 provides a high irreversible capacity (>200 mAh g-1) in the first cycle and an operating voltage comparable with commercial cathode materials, but its practical use is still restricted by the structural instability and spontaneous oxygen (O2) evolution, resulting in poor overall cycling performance. It is thus crucial to reinforce the structure of Li2CuO2 to make it more reliable as a cathode additive for charge compensation. Pursuing the structural stability of Li2CuO2, herein, we demonstrate cosubstitution by heteroatoms, such as nickel (Ni) and manganese (Mn), for improving the structural stability and electrochemical performance of Li2CuO2. Such an approach effectively enhances the reversibility of Li2CuO2 by suppressing continuous structural degradation and O2 gas evolution during cycling. Our findings provide new conceptual pathways for developing advanced cathode additives for high-energy LIBs.

Improving the Electrochemical Performance of LiNi1/3Co1/3Mn1/3O2 Cathode Material by LiF Modification

LiNi1/3Co1/3Mn1/3O2 is a widely used commercial cathode material in the fields of consumer electronics and electric vehicles. However, its energy density still falls short of the standard and needs to be improved. The most effective method is to increase the cut-off voltage, but this will result in a drop in capacity. In this study, a LiF layer is coated on the surface of LiNi1/3Co1/3Mn1/3O2 via an in situ method. It is found that the LiF layer may protect materials from side reactions with electrolytes, improve the interfacial stability, and enhance the cyclic performance. The bare sample shows relatively poor cycling stability, with capacity retention rates of 65.9% (0.2 C) and 12.8% (5 C) after 100 cycles, while 1% LiF-coated NCM has higher cycling stability with capacity retention rates of 83.4% (0.2 C) and 73.3% (5 C) after 100 cycles, respectively. Our findings suggest that a LiF surface layer could be a useful means of boosting the electrochemical performance of NCM cathode materials.

Insight into the decay mechanism of non-ultra-thin silicon film anode for lithium-ion batteries

Silicon thin-film is one of the most promising silicon anode materials for lithium-ion batteries, with the advantages of high cycle stability and initial coulombic efficiency. The excellent performance of silicon thin-films is due to their ultra-thin thickness (< 200 nm), but this results in their areal capacity too low to be compatible with commercial cathode materials, and only films thicker than 500 nm are practical. However, frequent volume changes in non-ultra-thin silicon films during cycling may cause layer misalignment and separation of the film from substrate. In this paper, silicon films with a thickness of ∼700 nm are prepared by magnetron sputtering on the inhomogeneous surface of a copper foil. The properties of the silicon films and mechanisms involved in the cycling process is investigated by combining experimental means during cycling with calculations of the atomic-scale amorphous lithium-silicon Zintl Phases’ structural volumes before and after cycling. The results show that the volume of silicon doesn't recover after delithiation and there is still significant swelling. The cyclic process causes a superimposed expansion of the volume, but the non-uniform film substrate causes the lateral expansion stresses to offset each other, thereby retaining a relatively stable structure. At the end of 100 cycles, the specific capacity of the silicon film electrode is 1461.5 mAh g −1 (areal capacity 0.242 mAh cm−2), with a capacity retention of 64.35%, and the silicon film thickness becomes 8.5 μm. We believe that by reducing the longitudinal expansion volume or stress of the silicon film, the cycle life of the silicon film can be further optimized.

Facile Deposition of the LiFePO4 Cathode by the Electrophoresis Method.

Lithium iron phosphate (LiFePO4, LFP) is one of the most advanced commercial cathode materials for Li-ion batteries and is widely applied as battery cells for electric vehicles. In this work, a thin and uniform LFP cathode film on a conductive carbon-coated aluminum foil was besieged by the electrophoretic deposition (EPD) technique. Along with the LFP deposition conditions, the impact of two types of binders, poly(vinylidene fluoride) (PVdF) and poly(vinylpyrrolidone) (PVP), on the film quality and electrochemical results has been studied. The results revealed that the LFP_PVP composite cathode had a highly stable electrochemical performance compared with the LFP_PVdF counterpart due to the negligible influence of the PVP on the pore volume and size and retaining high surface area of LFP. The LFP_PVP composite cathode film unveiled a high discharge capacity of 145 mAh g-1 at 0.1C and performed over 100 cycles with capacity retention and Coulombic efficiency of 95 and 99%, respectively. The C-rate capability test also revealed a more stable performance of LFP_PVP compared to LFP_PVdF.

Facile preparation of regular truncated octahedral LiMn2O4 cathode with high rate cyclability and stability for Li-ion batteries

Spinel LiMn2O4, as a mainstream commercial cathode material for lithium-ion batteries, is still suffered from severe capacity fading caused by Mn dissolution and Jahn-Teller distortion during the cycle process, which can be solved by developing selectively exposed crystal planes. Herein, a perfect monocrystal LiMn2O4 with regular truncated octahedral structure has been synthesized via a facile and low-cost carbon template sol-gel method. The phase composition and morphology of LiMn2O4 can be regulated by carbon template content, ranging from irregular micro-aggregates to nanoporous network structure composed of truncated nano-octahedrons with high crystallinity. The high crystallinity suppresses Jahn-Teller distortion and the large presence of {111} surfaces inhibit Mn dissolution can both improve its cycle stability, the unique nanoporous network structure facilitates shortening the Li+ diffusion path and the truncated {100} and {110} surfaces promote Li+ diffusion can increase the discharge capacity and rate capability. Accordingly, the as-obtained LMO-0.5 sample achieves remarkable discharge specific capacity (135.8 mA h/g at 0.1 C), excellent rate capability (91.2 mA h/g even at 20 C) and prominent cycle stability (a capacity retention of 91.7 % after 2000 cycles at 20 C), which will be an ideal cathode material for developing long-lifespan lithium-ion batteries.

New Avenues for Organic Redox Materials as Sustainable Lithium-ion Battery Cathodes

As the demand for electrification of means of transportation and storage of electrical energy for later use is skyrocketing, rechargeable Li-ion batteries (LIBs) are at the heart of this revolution. Acknowledging the carbon footprints, environmental concerns and cost of the commercial cathode materials, this is the high time to advocate sustainable alternatives. This review aims at establishing the potential of organic redox-active molecules as a burgeoning class of sustainable solid cathode materials for LIBs. The materials are classified according to their structural features (molecules, metallo-organic complexes, and organic/metal–organic frameworks) and electrochemical performance to lay emphasis on practical applications and bottlenecks in commercialization. However, these materials are still in early stages of development, and new frontiers have been explored in the last five years.

Synthesis of high-nickel and high-performance ternary cathode materials through spent lithium-ion batteries recycling system

In order to minimize the effect of energy consumption and environment risk, the ternary nickel-cobalt-manganese metals from existing spent lithium-ion batteries (LIBs) recycling system need for higher value-added utilization, such as synthesis for commercial high-nickel cathode materials. In this study, the nickel-cobalt-manganese mixed solution obtained from spent LIBs recycling system was used as raw material for the synthesis. After secondary precipitation, the precursors with different nickel contents were synthesized by the same equipment, and the cathode material was synthesized by calcination. This method has good adaptability for different nickel contents in the same equipment. The optimized conditions are listed as follows: (2 M mixed salt solution, 5 M NaOH, 15 wt% NH3·H2O, 65 °C, 1000 rpm speed, and 24 h aging time). The stable crystal forms of LiNixCoyMn(1-x-y)O2(NCM) (x = 0.50, 0.55, 0.60 and 0.80) with an average particle size of 5 μm was synthesized after secondary precipitation, thus the cation mixing degree reduced and the tap density increased. The electrochemical characterization of the four materials shows that the first discharge specific capacity of NCM811, NCM622, NCM551530 and NCM523 are 203.0 mAh/g, 188.5 mAh/g, 188.3 mAh/g, and 150.5 mAh/g at 0.1 C, respectively. Moreover, the capacity retention rate of NCM523 is 100.0% after 100 cycles at 1 C under high temperature of 50 °C.

High-voltage superionic and humidity-tolerant Li2.5Sc0.5Zr0.5Cl6 conductor for lithium batteries via preferred orientation

Chloride solid electrolytes (CSEs) have good compatibility with commercial oxide cathode materials and show great potential for application in all-solid-state Li metal batteries (ASSLMBs). However, achieving simultaneously low cost, high ionic conductivity, excellent moisture tolerance, and robust electrochemical stability with >4 V-class cathodes for CSEs remains challenging. Herein, we report a facile Zr substitution strategy to increase the degree of preferred orientation and lower the Li+ diffusion barrier of the (001) plane, i.e. the ab plane, of Li3ScCl6, thus boosting the ion conduction kinetics and framework stability. As such, Li2.5Sc0.5Zr0.5Cl6 exhibits a high conductivity of 2.23 mS cm−1 and low activation energy of 0.26 eV at room temperature (RT). ASSLMBs are constructed using a LiNi0.8Co0.1Mn0.1O2cathode, Li2.5Sc0.5Zr0.5Cl6 electrolyte, and Li-In anode, and deliver an exceptional initial Coulombic efficiency of 89.6 % at RT and can run stably over 200 cycles with 90 % capacity retention at 0.2C. In-situ electrochemical impedance inspection of the battery further reveals a high interfacial stability between Li2.5Sc0.5Zr0.5Cl6 and LiNi0.8Co0.1Mn0.1O2. Moreover, Li2.5Sc0.5Zr0.5Cl6 demonstrates high wet fatness with a preserved structure stability and high ionic conductivity after exposure to atmosphere with 5 % relative humidity. Such humidity tolerance and cost-effectiveness solve two major obstacles for the application of CSEs.

Using innovative FeF3 cathode materials in Li batteries working under spacecraft applications

The discovery of new cathode materials for lithium batteries is a slow process yet crucial task to develop advanced LIBs, and almost all known commercial cathode materials are still based on those identified in the 1990s. Thus, searching for new cathode materials is crucial for increasing the performance of Lithium batteries especially in the spacecraft industry as storage devices used in this domain need to be as small and light as possible to ease their integration in the spacecraft as well as minimizing the energy required for take-off. Conversion materials such as iron trifluoride (FeF3) are of particular interest as they exhibit high specific capacity (237 mAh.g−1 in intercalation for anhydrous FeF3 versus 200 mAh.g−1 for typical NCA or NMC) and high voltage. This study focuses on using innovative gaseous fluorination with F2 gas to prepare anhydrous FeF3 while favoring the formation of a porous structure to maximize electrochemical performances. We were able to tune the crystalline structure, composition, and morphology of the fluorination product obtained by selecting the precursor as well as tailoring the fluorination treatment. After a complete electrochemical characterization of all fluorination products obtained, FeSi2 appeared as the best precursor to maximize the performances of FeF3 in lithium batteries. Electrochemical tests were performed on our homemade FeF3 and the results were compared to a commercial product, namely NCA. Both cells were cycled at a current density of C/10, and a DoD of 80%. Those conditions were chosen because they are close to those found in geostationary satellites batteries. Electrochemical tests demonstrated that anhydrous FeF3 synthesized by gaseous fluorination exhibits an increased performance compared to NCA when these 2 materials are used as a cathode material in lithium batteries on a short-term cycling analysis.

Photocatalytic Evaluation of TiOx Films Produced by Cathodic Arc-PVD with Silver Addition by UVC Photo-Reduction Method

A titanium (Ti) commercial cathode material and high purity Ar and O2 were used in the cathodic arc physical vapor deposition (arc-PVD) process. The TiOx coating was deposited on the three sets of Raschig rings using decreasing ratios of Ar/O2:440/60, 400/100 and 300/100. The cross sections of the TiOx PVD coating were analyzed using field emission scanning electron microscopy (FE-SEM), X-ray energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). A homogeneous layer of Ti with small O content was observed, and the data suggest that a thin TiOx oxide film was deposited. For this reason, a thermal treatment was applied to the coating to oxidize it and form the rutile phase of TiO2 in the coating, which was demonstrated by grazing incidence XRD. In addition, the TiOx coatings absorb radiation, which was observed by diffuse reflectance band gap energy measurement. Silver (Ag) was added by the photo-reduction method, using UVC light to activate the TiO2 coating, and the band gap energy was analyzed by diffuse reflectance. The photocatalytic activities of the films were evaluated by degradation of the model dye rhodamine B and in the removal of fecal coliforms using two matrices, water from a secondary treatment effluent, and synthetic water.