Cobalt-free Cathode Materials Research Articles

Hydrothermal synthesis of Co-free NMA cathodes for high performance Li-ion batteries

Scalable and sustainable production of high voltage cathodes is required to meet the increasing demands for Li-ion batteries. Additionally, the anticipated scarcity of critical materials like cobalt necessitates demonstration of Co-free alternatives that can match the performance metrics of conventional cathodes. Herein, a hydrothermal synthesis route for production of a new class of high-capacity, cobalt-free cathode material, LiNi0.9Mn0.05Al0.05O2 (NMA9055) for next-generation Li-ion batteries is reported. The synthesized cathode material shows high crystallinity and purity with monodispersed spherical morphology. Extensive electrochemical, structural, and post-mortem characterization of this novel NMA material is carried out. NMA-Li half cells show an initial discharge capacity of 200 mAh/g with a 96% capacity retention over 100 cycles when cycled between 3.0 and 4.4 V. On the other hand, NMA full cells with Li4Ti5O12 (LTO) electrodes as the anode, show an initial discharge capacity of 186 mAh/g with 81% capacity retention over 200 cycles. Post-mortem structural and morphological characterization show that the NMA morphology and crystal structure do not degrade significantly over 200 charge/discharge cycles. This new class of cobalt free cathode material containing nickel, manganese and aluminum synthesized by an ammonia-free synthesis route is expected to provide a facile solution towards sustainable cathode production.

Ba0.95La0.05Fe0.8Ni0.2O3−δ perovskite as efficient cathode electrocatalysts for proton-conducting solid oxide fuel cells

The key issue that limits the electrochemical performance of proton-conducting solid oxide fuel cells (H+-SOFCs) is the sluggish kinetics of the oxygen reduction reaction (ORR) of cathode at intermediate and low temperatures. Herein, oxygen vacancy engineering is conducted on cobalt-free Ba0.95La0.05FeO3−δ (BLF) by nickel substitution, which is confirmed by density functional theory computations. Nickel-substituted BLF material (Ba0.95La0.05Fe1−xNixO3−δ (x = 0, 0.1, 0.2, 0.3)) can promote the generation of oxygen vacancies and improve catalytic activity, which is found to be in line with the experimental results of XPS. The phase structure, microstructure, and electrochemical performance of Ba0.95La0.05Fe0.8Ni0.2O3−δ (BLFNi0.2) are well-investigated. The single cells with the BLFNi0.2-BaCe0.7Zr0.1Y0.1Yb0.1O3−δ (BCZYYb) composite cathode achieve low polarization resistance (Rp) of 0.099 Ω cm2 and a peak power density of 631 mW cm−2 at 700 °C while maintaining good durability for 120 h with no observable degradation. The results demonstrate that Ni-doped BLF is a promising cobalt-free cathode material for H+-SOFCs.

LiNi<sub>0.7</sub>Mn<sub>0.3</sub>O<sub>2</sub> as a Cheap Cobalt Free Nickel Rich Cathode Material for High-Performance Li-Ion Batteries

A high-quality Lithium Nickel Manganese Oxide (LiNi0.7Mn0.3O2) material is successfully synthesized via co-precipitation. The precursors for lithium rechargeable batteries have been prepared using starting materials (NiCl2.6H2O and MnSO4.H2O) with precipitating agents of oxalic acid and sodium hydroxide, Ethylene diamine tetra acetic (EDTA) and sodium hydroxide, and sodium carbonate for oxalate co-precipitation, hydroxide co-precipitation, and carbonate co-precipitation, respectively. Then, the precursors were calcined at 500°C for 5 hours, mixed with Li2CO3, and sintered at 850°C for 15 hours under oxygen. X-ray Diffraction (XRD) analysis results show that the particles obtained by oxalate co-precipitation (LiNi0.7Mn0.3O2-C2O4) have higher crystallinity and more uniform particle shape than hydroxide co-precipitation and carbonate co-precipitation. The Fourier Transform Infrared (FTIR) spectroscopy characterization shows no carbonate group peak in the LiNi0.7Mn0.3O2-C2O4. Furthermore, electrochemical tests were analyzed by evaluating the charge/discharge curves and cycling performance. The highest specific discharge capacity of 122 mAh/g was achieved by the LiNi0.7Mn0.3O2-C2O4 sample, which also had a low capacity loss (22.7%), retaining 89.9% of its initial specific capacity at 0.5C between 2.5 and 4.25 V after 45 cycles. Based on these results, a cheap cobalt-free cathode material is promising for a new commercialized Li-ion battery.

A layered lithium nickel manganese oxide as environmentally friendly cathode material for secondary batteries

<p>Cobalt-free cathode material development is considered necessity to assure the sustainability of Li-ion batteries. Cobalt is always considered expensive and unsafe for both human and environment. LiNi<sub>0.5</sub>Mn<sub>0.5</sub>O<sub>2</sub> (LNMO) is a layer structured cathode material that has similar feature to LiCoO<sub>2</sub> (LCO). A simple and fast processing of LNMO is proposed. A precipitation of nickel manganese oxalate was obtained in a batch reactor under atmospheric condition. The as-obtained homogenous oxalate precursor was converted to LNMO via high temperature lithiation. Based on the XRD result, a crystalline product with layer structure is successfully obtained. The presence of impurities such as residual Li can be detected from the FTIR spectra. SEM Images confirmed quasi-spherical particles with grain size of less than 10 micrometer. The charge-discharge analysis of LNMO containing cell deliver a capacity of 42 mAh/g. In spite of its promising report, continuous improvement is necessary to obtain cell with better electrochemical performance.</p>

Recent Development of Nickel-Rich and Cobalt-Free Cathode Materials for Lithium-Ion Batteries

The exponential growth in the production of electric vehicles requires an increasing supply of low-cost, high-performance lithium-ion batteries. The increased production of lithium-ion batteries raises concerns over the availability of raw materials, especially cobalt for batteries with nickel-rich cathodes, in which these constraints can impact the high price of cobalt. The reliance on cobalt in these cathodes is worrisome because it is a high-cost, rare material, with an unstable supply chain. This review describes the need and feasibility of developing cobalt-free high-nickel cathode materials for lithium-ion batteries. The new type of cathode material, LiNi1−x−yMnxAlyO2 promises a completely cobalt-free composition with almost the same electrochemical performance as that of the conventional high-nickel cathode. Therefore, this new type of cathode needs further research for its commercial applications.

Comparative studies of tungsten and zirconium doping on single crystal cobalt-free cathode material

Comparative studies of tungsten and zirconium doping on single crystal cobalt-free cathode material

Understanding the Feasibility of Manganese Substitution for Cobalt in the Synthesis of Nickel-Rich and Cobalt-Free Cathode Materials

LiNi0.8Co0.15Al0.05O2 (LNCA) cathode materials have an extremely high energy density, which can greatly enhance the driving range of pure electric vehicles if they are used in on-board batteries. However, the development of the LNCA cathode material is restricted by the expensive transition metal cobalt (Co). Therefore, researchers are devoted to finding other metals to replace Co to synthesize nickel (Ni)-rich Co-free materials to reduce the cost. To investigate the feasibility of replacing Co with manganese (Mn) as a transition metal, this paper reports the synthesis and compares the properties of four Ni-rich materials with different Co–Mn contents by gradually adding Mn to LNCA materials and reducing the Co content in equal amounts using an oxalic acid coprecipitation method. The results show that Mn can compensate the effect of Co deficiency to a certain extent; it is feasible to use Mn to completely replace Co in the synthesis of Ni-rich ternary Co-free materials under the premise of sacrificing a certain initial specific capacity. The tetrameric material LiNi0.8Co0.1Mn0.05Al0.05O2 substituted with trace amounts of Mn exhibited the most excellent electrochemical properties among the four synthesized materials. Therefore, to synthesize satisfactory Ni-rich Co-free materials, it is suggested to develop and synthesize quaternary Co-free materials on the basis of LiNi0.8Co0.1Mn0.05Al0.05O2.

(Invited) Cobalt Free Li-Ion Battery Cathode Materials for Next Generation Electric Vehicles

The battery manufacturing industry has a cobalt problem! Over the recent years, rapid fluctuations in cobalt prices have created a drastic supply chain constraint that threatens to derail the burgeoning projections for electric vehicles over the next few decades. To reduce the cost of modern batteries to ~80$/kWh (to sustain the growing electric vehicle demands), it has become paramount that the amount of cobalt, the most expensive present-day battery cathode raw material, should be reduced to less than 50 mg at the cell level. Moreover, it is also important that any alternative cathode material developed, should facilitate a seamless integration into existing global battery manufacturing infrastructures to avoid a complete overhaul. The search for viable alternatives that address these challenges simultaneously is a continuing quest in today's battery research and development sectors. In this context, our team through a paradigm shifting approach has developed a new class of layered lithium ion battery cathode material with '0' cobalt in its composition. This new class of battery cathodes, termed the NFA class, has the general formula, LiNixFeyAlzO2 (where, x + y + z = 1)[1,2]. These layered cobalt-free cathodes are analogous in crystal structure and material properties to mainstream cobalt containing cathodes such as NCMs and NCAs while delivering comparable and in some cases better electrochemical performance. Here, I will present our efforts in the systematic development of these novel cathodes starting from compositional landscape investigations and advanced characterizations employing NFA material synthesized using the lab-scale sol-gel process. Through our approach, in-situ high temperature X-Ray and Neutron diffraction techniques were used to investigate the calcination and phase formation behavior while operando investigations using X-Ray diffraction and Mössbauer spectroscopy were employed to obtain a mechanistic understanding of the charge/discharge process of this new cobalt-free cathode material. Following these, the most promising compositional variants were upscaled using the co-precipitation process in continuous stirred tank reactors for obtaining kg levels of cathode material. Systematic optimization of reaction process variables ensured good particle morphologies, homogeneities and composition control. Electrochemical performance assessments performed in both half-cell and full-cell configurations tested in different voltage windows with upper cut-off voltages ranging from 4.1V to 4.5V demonstrated that the optimized NFA compositional variants deliver high capacities >200 mAh/g at 0.1C with good capacity retention >80% when cycled at C/3. Full pouch-cells (>1.5Ah) were then assembled using NFA electrodes fabricated using the slot-die coating technique with the upscaled cathode material demonstrating reasonable capacity retentions[3]. While the work presented here is still in an early stage of research, the immense potential that these NFA class of cathodes could have as viable candidates towards development of next generation cost effective lithium ion batteries is highlighted here. Overall, our research efforts in the development of this new class of cobalt-free cathodes aims to mitigate the battery industry's cobalt problem paving a promising pathway towards the wide adoption of electric vehicles in the coming decades.

Enhanced oxygen reduction reaction activity of BaCe0.2Fe0.8O3-δ cathode for proton-conducting solid oxide fuel cells via Pr-doping

BaCe0.2Fe0.8-xPrxO3-δ (x = 0–0.3) is studied as a cobalt-free cathode material for proton-conducting solid oxide fuel cells. The cathode is composed of a cubic BaFeO3-δ phase and an orthorhombic BaCeO3-δ phase, and Pr is doped in both phases. The partial substitution of Pr for Fe decreases the content of the BaFeO3-δ phase, leading to a lower electrical conductivity. BaCe0.2Fe0.6Pr0.2O3-δ has the most adsorbed oxygen and Fe3+ on the surface, resulting in the fastest oxygen surface exchange kinetics and the highest activity. The partial pressure of H2O shows a negligible effect on the polarization resistance of the cathode. In contrast, the polarization resistance increases remarkably with the decrease of oxygen partial pressure, indicating that the rate of the cathode process is controlled by the surface exchange of oxygen. At 700 °C, BaCe0.2Fe0.6Pr0.2O3-δ shows the lowest polarization resistance of 0.057 Ω cm2, and a single cell with that cathode exhibits the highest maximum power density of 562 mW cm−2. The results demonstrate that Pr doped BaCe0.2Fe0.8O3-δ is a promising cobalt-free cathode material for proton-conducting solid oxide fuel cells.

Novel cobalt-free Pr2Ni1-xNbxO4 (x = 0, 0.05, 0.10, and 0.15) perovskite as the cathode material for IT-SOFC

The cobalt-free cathode materials with high activity is critical to the commercial application of medium temperature solid oxide fuel cells (IT-SOFC). Herein, a series of cobalt-free Nb-doped Pr2Ni1-xNbxO4 (x = 0, 0.05, 0.10, and 0.15) perovskite oxides were successfully prepared, and the effects of Nb-doping on the structure, thermal stability and electrochemical properties of the cathode material are studied in detail. The Pr2Ni1-xNbxO4 exhibits a K2NiF4 type structure with Fmmm space group. The Nb5+ cations that doped into Pr2NiO4 replaces the Ni site, which increases the surface oxygen content, then effectively eliminates the phase transition of Pr2NiO4 and significantly improves the ORR catalytic activity. The Pr2Ni0.9Nb0.1O4 was found to occupy the lowest polarization resistance of 0.057 Ω cm2, and the peak power density of single cells supported by the electrolyte is 0.576 W cm−2 at 700 °C, which has good long-term stability.

Advanced cobalt-free cathode materials for sodium-ion batteries.

Attempts to utilize lithium-ion batteries (LIBs) in large-scale electrochemical energy storage systems have achieved initial success, and solid-state LIBs using metallic lithium as the anode have also been well developed. However, the sharply increased demands/costs and the limited reserves of the two most important metal elements (Li & Co) for LIBs have raised concerns about future development. Sodium-ion batteries (SIBs) equipped with advanced cobalt-free cathodes show great potential in solving both "lithium panic" and "cobalt panic", and have made remarkable progress in recent years. In this review, we comprehensively summarize the recent advances of high-performance cobalt-free cathode materials for advanced SIBs, systematically analyze the conflicts of structural/electrochemical stability with intrinsic insufficiencies of cobalt-free cathode materials, and extensively discuss the strategies of constructing stable cobalt-free cathode materials by making full use of non-cobalt transition-metal elements and suitable crystal structures, all of which aim to provide insights into the key factors (e.g., phase transformation, particle cracks, crystal defects, lattice distortion, lattice oxygen oxidation, morphology, transition-metal migration/dissolution, and the synergistic effects of composite structures) that can determine the stability of cobalt-free cathode materials, provide guidelines for future research, and stimulate more interest on constructing high-performance cobalt-free cathode materials.

Synthesis and Electrochemical Performance of a Homogenously Dispersed LiaMn1-x-y-ZFexCoyNizO2-DCld Lithium Ion Battery Cathode Material

Background: Lithium manganese oxide spinel is a strong candidate for lithium-ion battery cathodes due to its high operational voltage, three-dimensional network of lithium pathways within the structure, low toxicity, reasonable capacity, and low cost of raw materials. However, spinel suffers from diminished cycle life due to loss of crystallinity or fracturing of the structure either through the alternative phase formation or Jahn-Teller distortion. Historically, cycle life enhancements are achieved through stabilization of the spinel structure via transition metal doping on the B-site of the lattice; creating disorder necessary to stabilize the lattice structure during cycling. Previously, we have demonstrated a stabilization of this structure can also be achieved with a chlorine dopant on the oxygen site that results in enhanced performance at voltages below 3.0V when homogenously dispersed throughout the crystal, giving a desirable added capacity in a robust chemistry protected by this low voltage plateau. Single B-site dopants have been incorporated into these chlorinated spinels but rarely have several dopants been studied for optimizing and customizing cathode performance as well as anion dopant feasibility. Raw materials cost must be taken into to consideration when designing a novel cathode. An ideal cathode would limit scarce or unethically sourced materials like cobalt, and instead focus on considering inexpensive and available materials like iron. This effort focuses on the manganese substitution of up to three metals, iron, cobalt, and nickel, in order to stabilize the structure for further cycling while minimizing the need for cobalt incorporation. Several variations for LiaMn1-x-y-ZFexCoyNizO2-dCld will be presented that exhibit opportunities for 5.0+ V operation. Experimental: A wet chemical gel combustion method was used to synthesize metal-doped chlorinated lithium manganese oxide spinel. Stoichiometric amounts of Li(NO3), Mn(NO3)2∙4H2O, a metal-chloride salt appropriate for each metal, (Fe, Co, and/or Ni)(NO3)n, and a chelating agent (glycine or citric acid with ethylene glycol, Alfa Aesar/Sigma Aldrich) were dissolved into an aqueous or ethanol solution. The solution was heated to evaporate the water and form a gel, which was heated further to 250 °C when auto ignition occurs. The resultant ash was fired between 600 – 700°C for 2 to 12 hours to achieve the desired phase. Alternatively, an acetate-based synthesis is performed with metal acetate salts less a chlorine or lithium additive dissolved in distilled water. NH4OH is added to form a gel and is heated to evaporate the water. The gel is ignited above 200 °C and calcined at 400 °C in air. The resultant oxide is mixed with LiClO4 and LiOH and ground in solid state prior to a final calcination at 600 °C for 4 hours. Material characterization was performed using X-ray diffraction, X-ray fluorescence, thermogravimetric analysis, and scanning electron microscopy. Prepared active cathode materials were mixed with carbon black and polytetrafluoroethylene in a weight ratio of 85:10:5 of active to carbon to Teflon binder and calendared to 0.04 cm, punched into disks and pressed onto aluminum mesh opposite a Li metal anode. CR2025 button cells were filled with 1 M LiPF6 in a proportional mixture of diethyl carbonate, dimethyl carbonate, and ethylene carbonate. Electrochemical characterization was performed using electrochemical impedance spectroscopy (Solartron 1260) and cycling on an ARBIN MSTAT4 battery cycler system. Conclusion: Electrochemical data is presented for B-site dopants with two or more of the metals iron, cobalt and/or nickel. The results demonstrate an enhanced high voltage operation above 5.0 V coupled with a deep discharge capability below 3.0 V. In the case of LiaMn0.77Fe0.06Ni0.17O2-dCld, a cobalt-free cathode material exhibits a capacity of 210 mAh/g from 5.0V to 2.25V.An example electrochemical performance result is shown in the attached figure where LixMn0.945Fe0.05Co0.055O2-dCld is the active cathode material and lithium is the active anode material. For this example, the cell was cycled between 4.5 V and 3.5 V for the initial ten cycles. For the next three cycles, the cell was cycled between 5.25 V and 3.5 V. The next three cycles included a deep discharge between 5.25 V and 2.25 V before returning to cycling between 5.25 V and 3.5 V. The cycle plots indicate no loss of capacity when cycling between the aforementioned voltages. When discharging deep, there is a 50% increase in capacity and the return to high voltage charging without the deep discharge indicates the material is reversible and does not undergo permanent structural deformation. Importantly, a two-fold increase in capacity is shown when cycling to 4.5V (cycles 1-10) vs. 5.25V (cycles 11-13). Electrolytes with 5.0+ V stability will need to be studied further to enable the full potential of these presented cathodes. Figure 1

(Battery Division Student Research Award Sponsored by Mercedes-Benz Research & Development) Sustainable High-Performance Lithium-Ion Batteries: Aqueous Processing of Cobalt-Free High-Energy Cathodes

Increasing the environmental benignity of the lithium-ion battery (LIB) technology is one of the greatest challenges associated with their continuously increasing demand. At the same time, the performance metrics in terms of energy density, power capability and reliability have to be at least maintained to meet the requirements of the rapidly growing electric vehicle market.[1] Besides introducing cobalt-free high-performance active materials, such as the high-voltage spinel LiNi0.5Mn1.5O4 (LNMO),[2] the implementation of aqueous electrode processing strategies for lithium-ion cathodes, is a key step to realize environmentally benign battery production. To achieve this ambitious goal, the deployment of nature-derived, inexpensive polymers in combination with the use of water as dispersion agent provides the great possibility to spare energy-intensive drying procedures and costly dry-room conditions, and thus, will turn the whole battery fabrication more eco-efficient and abolish the need of harmful and rather costly N-methyl-2-pyrrolidone (NMP) as processing solvent for mutagenic and teratogenic fluorine-containing binders.[3,4] What could easily be established for graphite anodes, appears more complicated for transition metal oxide-based and imperatively cobalt-free cathode materials, which suffer from lithium leaching and transition metal dissolution when getting in contact with water, which has, so far, rendered the use of aqueous binders very challenging.[5,6] The strategies developed in our group enable the achievement of this desirable goal: The first one, i.e., the addition of phosphoric acid during electrode preparation, targets the prevention of the aluminum current collector corrosion and simultaneously stabilizes the LNMO particle surface, hence, avoiding the active material degradation in contact with water. The second one, i.e., the crosslinking of the binder by means of citric acid, provides an enhanced cycling stability of the aqueous processed electrodes.[ 6,7] Remarkably, these two complementary approaches can be easily adapted in the electrode preparation process without requiring any additional processing step. To achieve positive electrode tapes, readily available for large-scale high-energy lithium-ion batteries, a carbon-coated current collector is used. It provides functional groups to crosslink the positive electrode coating layer to the underlying aluminum foil. The resulting electrodes demonstrate significant improvements concerning the electrode to current collector adhesion and their capacity retention.[ 8] Through the further optimization of the initial formation cycles, these electrodes offer an electrochemical performance exceeding that of LNMO-based reference electrodes, comprising state-of-the-art poly(vinylidene difluoride) (PVdF) as binder. Transferring this knowledge to other modified biopolymers, such as chitosan and guar gum in combination with relations derived between structure and performance of electrodes made from these cheap, abundant and naturally available binders finally leads to the realization of entirely water-processed high-performance LIBs employing sustainable cobalt-free high-voltage LNMO cathodes and graphite anodes.[ 9,10] References D. Larcher and J. M. Tarascon, Nat. Chem., 7, 19–29 (2015).M. Kuenzel et al., Mater. Today, In Press (2020) https://doi.org/10.1016/j.mattod.2020.04.003.D. Bresser, D. Buchholz, A. Moretti, A. Varzi, and S. Passerini, Energy Environ. Sci., 11, 3096–3127 (2018).A. Kwade et al., Nat. Energy, 3, 290–300 (2018).Michael M. Thackeray, J. Am. Ceram. Soc., 82, 3347–3354 (1993).N. Loeffler et al., ChemSusChem, 9, 1112–1117 (2016).M. Kuenzel et al., ChemSusChem, 11, 562–573 (2018).M. Kuenzel et al., ACS Appl. Energy Mater., 3, 218–230 (2020).M. Kuenzel et al., Batter. Supercaps, 3, 155–164 (2020).M. Kuenzel et al., ChemSusChem, 13 (2020) https://doi.org/10.1002/cssc.201903483.

Breaking Free from Cobalt Reliance in Lithium-Ion Batteries.

SummaryThe exponential growth in demand for electric vehicles (EVs) necessitates increasing supplies of low-cost and high-performance lithium-ion batteries (LIBs). Naturally, the ramp-up in LIB production raises concerns over raw material availability, where constraints can generate severe price spikes and bring the momentum and optimism of the EV market to a halt. Particularly, the reliance of cobalt in the cathode is concerning owing to its high cost, scarcity, and centralized and volatile supply chain structure. However, compositions suitable for EV applications that demonstrate high energy density and lifetime are all reliant on cobalt to some degree. In this work, we assess the necessity and feasibility of developing and commercializing cobalt-free cathode materials for LIBs. Promising cobalt-free compositions and critical areas of research are highlighted, which provide new insight into the role and contribution of cobalt.

Advanced 18650 Lithium-Ion Batteries with LiMn2O4@Carbon Core-Shell Cathode and Si/Mcmb Anode

Nowadays, the 18650 cylindrical cells of lithium-ion batteries using cobalt-containing cathode materials have currently produced with a purpose of operating source of electric-powered application such as electric vehicle (EV), hybrid electric vehicle (HEV), and small-scale energy storage system (ESS). However, cobalt is not abundant and expensive. Thus, cobalt-free cathode materials are of interest. In this work, 18650 lithium-ion battery using LiMn2O4/Carbon core-shell (LMO@C) cathode and Si/MCMB anode. The LMO@C materials was synthesized bya sonvent-free mechanofusion method with a highly uniform coating. The LMO particles with fully covered by carbon nanoparticles can exhibit higher capacity ca. 10-15% as compared with the pristine LMO.In addition, the LMO@C also presents the superb rate capacity retention as well as cycling stability due to the improved intrinsic conductivity and mechanical property.

High capacity Li/Ni rich Ni-Ti-Mo oxide cathode for Li-ion batteries

With the rising cost and insufficient supply of cobalt, the thrust for cobalt-free cathode materials with the high specific capacity to build Li-ion batteries has increased significantly. Using nickel as the prime electrochemical active species, we have synthesized a new-class of materials with the combination of ordered and disordered phases. To obtain high capacity and electrical charge neutrality, stoichiometry of cations designed in a way that it forms Li/Ni rich Ni-Ti-Mo oxide materials. In addition to conventional capacity from redox activity of transition metals, partially reversible oxygen redox reaction also contributes to electrochemical activity and thus results in unusual high capacity. The resultant cathode materials of LiNi0.5Ti0.5O2-(Li4MoO5)0.8 and LiNiO2 mixture phases reach the specific capacity of 240 mAh/g. Detailed soft X-ray absorption spectroscopy and electron microscopy are used to reveal the crystal phases in this system and trace changes in the Ni2+/Ni4+ redox couple during charge-discharge processes. Such comprehensive analysis of ordered-disordered oxides suggesting potentiality to develop high-capacity cobalt-free cathodes.

(Invited) Towards the Realization of Sustainable High-Performance Lithium-Ion Batteries: Aqueous Processing of Cobalt-Free High-Energy Cathodes

The recently rising awareness for a more sustainable cell manufacturing can be expected to gain even more momentum in sight of the announcements from major car manufacturers across Europe and North America to entirely electrify their fleet within the next half-decade1,2. The implementation of aqueous electrode processing strategies for lithium-ion cathodes is a key step to realize the environmentally benign battery production. To achieve this ambitious goal, most studies focus on the development of non-toxic and abundant active materials and specifically, the implementation of nature-derived, inexpensive binders in combination with the use of water as dispersion agent and solvent provides the great possibility to spare energy-intensive drying procedures and costly dry-room conditions, and thus, will turn the whole battery fabrication more eco-efficient 3,4. What could easily be established for graphite anodes – employing water-soluble natural polymers as binder, thus, abolishing the need of toxic and rather costly N-methyl-2-pyrrolidone (NMP) as processing solvent3,5 – appears more complicated for transition metal oxide-based and imperatively cobalt-free cathode materials, which suffer from lithium leaching and transition metal dissolution when getting in contact with water, which has, so far, rendered the use of aqueous binders very challenging6,7. In our group we recently demonstrated the general feasibility for the aqueous processing of several lithium-ion cathode materials, such as high-voltage LiNi0.5Mn1.5O4, by introducing a complementary approach, of suitable processing additives to stabilize the active material surface as well as the electrode/electrolyte/current collector interface8. Moreover, we extended our investigations to various binder systems and cathode materials in order to advance the aqueous electrode preparation and move from the well-established lab-scale process towards the fabrication of commercial-scale lithium-ion batteries9. References C. J. Barnhart and S. M. Benson, Energy Environ. Sci., 6, 1083 (2013).D. Larcher and J. M. Tarascon, Nat. Chem., 7, 19–29 (2015).D. Bresser, D. Buchholz, A. Moretti, A. Varzi, and S. Passerini, Energy Environ. Sci. (2018) http://xlink.rsc.org/?DOI=C8EE00640G.A. Kwade et al., Nat. Energy, 3, 290–300 (2018) http://www.nature.com/articles/s41560-018-0130-3.S. F. Lux, F. Schappacher, A. Balducci, S. Passerini, and M. Winter, J. Electrochem. Soc., 157, A320 (2010).M. M. Thackeray, J. Am. Ceram. Soc., 82, 3347–3354 (1999).N. Loeffler et al., ChemSusChem, 9, 1112–1117 (2016).M. Kuenzel et al., ChemSusChem, 11, 562–573 (2018).A. Kazzazi et al., ACS Appl. Mater. Interfaces, 10, 17214–17222 (2018).

Structural, morphological, and electrochemical behavior of titanium-doped SrFe1-xTixO3-δ (x = 0.1–0.5) perovskite as a cobalt-free solid oxide fuel cell cathode

Abstract Titanium, Ti-doped SrFe1-xTixO3-δ (x = 0.1–0.5) perovskite-structured ceramics were synthesized via solution combustion. The structural, morphological, and electrochemical behaviors of the as-synthesized materials were investigated to determine the applicability of SrFe1-xTixO3-δ as a cobalt-free cathode material for intermediate-temperature solid oxide fuel cells. X-ray diffraction analysis confirmed the formation of a single-phase cubic perovskite structure. The unit volume of this perovskite structure increased as the amount of Ti dopant increased. Morphological analysis revealed that the porosity of the SrFe1-xTixO3-δ perovskite cathode film was inversely proportional to the amount of Ti dopant. The cathode SrFe0·9Ti0·1O3-δ film exhibited a high porosity of 24.74 ± 0.52%, a low but acceptable hardness value of 0.70 ± 0.01 GPa and an area specific resistance of 0.57 Ω cm2. These results suggested that cobalt-free SrFe1-xTixO3-δ cathode was still not good enough to be compared with the existing cobalt-containing cathode such as lanthanum strontium cobalt ferrite. But, the results obtained from this work can be considered as a major turning point as the literature works on SrFe1-xTixO3-δ cathode showed excellence electrochemical performance. The contradict result between the present and past studies proved that the use of SrFe1-xTixO3-δ cathode is worthy of being studied into details to confirm its capability.

Layered perovskite LnBa0.5Sr0.5Cu2O5+δ (Ln = Pr and Nd) as cobalt-free cathode materials for solid oxide fuel cells

Cobalt-free layered perovskite LnBa0.5Sr0.5Cu2O5+δ (Ln = Pr and Nd, PBSC and NBSC) powders are prepared using combined citrate and EDTA complexing method. The performance of PBSC and NBSC cathode materials are evaluated for solid oxide fuel cells (SOFCs). Two oxidation states (Cu2+/Cu+) for Cu ions exist in LnBa0.5Sr0.5Cu2O5+δ oxides. The main valence of Pr ions in PBSC is 3+. The average thermal expansion coefficients (TECs) of PBSC and NBSC are 14.2 and 14.6 × 10−6 K−1 between 30 and 950 °C, which are similar to the TECs of La0.9Sr0.1Ga0.8Mg0.2O3−δ (LSGM) intermediate-temperature electrolyte. The electrical conductivity of PBSC is slightly higher than that of NBSC. At 800 °C, the polarization resistance (Rp) values of the PBSC and NBSC cathodes on the LSGM electrolyte are 0.043 and 0.057 Ω cm2, respectively. The electrolyte-supported single cells were prepared by using PBSC and NBSC as cathode, LSGM as electrolyte (300 μm thickness), Ce0.9Sm0.1O1.95 (SDC) as interlayer and Ni/SDC as anode. At 850 °C, the maximal power densities are obtained as 681 and 651 mW cm−2 for PBSC and NBSC cathodes.

Novel, cobalt-free, and highly active Sr2Fe1.5Mo0.5−xSnxO6−δ cathode materials for intermediate temperature solid oxide fuel cells

One of the technical hurdles to commercialization of intermediate temperature solid oxide fuel cells (IT-SOFCs) is the requirement of highly efficient cathode materials. Herein, we report the evaluation of Sr2Fe1.5Mo0.5−xSnxO6−δ (x = 0, 0.1, 0.3 and 0.5, abbreviated as SFM, SFMS1, SFMS3, and SFS) oxides as cobalt-free cathode materials of IT-SOFCs. XPS analysis demonstrates the presence of variable valences among Fe, Mo and Sn elements, suggesting a small polaron hopping mechanism for electronic conduction. First principle calculations reveal that SFMS3 provides the lowest average formation energy of oxygen vacancy (EvacO*) among these perovskites. The relatively low area specific resistances are obtained with SFMS3 electrode based on La0.8Sr0.2Ga0.8Mg0.2O3−δ electrolytes, indicating its high activity for oxygen reduction reaction. Power density of the single cell using SFMS3 cathode as high as 618 mW cm−2 at 800 °C is achieved, and operation lasts for 200 h without obvious degradation. The encouraging results promise SFMS3 as an alternative cathode material for IT-SOFCs.