Unveiling Oxygen Redox Activity in P2-Type NaxNi0.25Mn0.68O2 High-Energy Cathode for Na-Ion Batteries

Na-ion batteries are emerging as convenient energy-storage devices for large-scale applications. Enhanced energy density and cycling stability are key in the optimization of functional cathode materials such as P2-type layered transition metal oxides. High operating voltage can be achieved by enabling anionic reactions, but irreversibility of O2–/O2n–/O2 evolution still limits this chance, leading to extra capacity at first cycle that is not fully recovered. Here, we dissect this intriguing oxygen redox activity in Mn-deficient NaxNi0.25Mn0.68O2 from first-principles, by analyzing the formation of oxygen vacancies and dioxygen complexes at different stages of sodiation. We identify low-energy intermediates that release molecular O2 at high voltage, and we show how to improve the overall cathode stability by partial substitution of Ni with Fe. These new atomistic insights on O2 formation mechanism set solid scientific foundations for inhibition and control of this process toward the rational design of new anionic redox-active cathode materials

Process Scale-up for Production of Water-based Lithium-ion Pouch Cell

With the aim to promote technology transfer to small and medium-sized enterprises, a scale-up process to synthesize kilos of LiFePO4 is described. The process allowed the production of a material with a specific capacity of to 150 mAh g-1. Furthermore, a water-based manufacturing process to produce LiFePO4 electrodes was described. The experimental conditions were widely investigated to obtain homogeneous slurries and cracking free electrode coating, which resulted in flexible electrodes with good mechanical characteristics. These electrodes have been coupled with graphite base anodes to build 50 mAh Li-ion batteries and their electrochemical performance evaluated by galvanostatic cycles

X‐ray microscopy. A non‐destructive multi‐scale imaging to study the inner workings of batteries

X-ray microscopy (XRM) is a non-destructive characterization technique that provides quantitative information regarding the morphology/composition of the specimen and allows to perform multiscale and multimodal 2D/3D experiments exploiting the radiation-matter interactions. XRM is particularly suitable to afford in situ images of inner parts of a battery and for the early diagnosis of its degradation in a non-invasive way. Since traditional characterization techniques (SEM, AFM, XRD) often require the removal of a component from the encapsulated device that may lead to non-desired contamination of the sample, the non-destructive multi-scale potential of XRM represents an important improvement to batteries investigation. In this work, we present the advanced technical features that characterize a sub-micron X-ray microscopy system, its use for the investigation of hidden and internal structures of different types of batteries and to understand their behavior and evolution after many charge/discharge cycles

Crystal Group Prediction for Lithiated Manganese Oxides Using Machine Learning

This work aimed to predict the crystal structure of a compound starting only from the knowledge of its chemical composition. The method was developed to select new materials in the field of lithium-ion batteries and tested on Li-Fe-O compounds. For each testing compound, the correspondence with respect to the training compounds was evaluated simply by calculating the Euclidean distance existing between the stoichiometric coefficients of the elements constituting the two compounds. At the compound under test was assigned the crystal structure of the training compound for which the distance value was minimum. The results showed that the model can predict the crystalline group of the test compound with an accuracy higher than 80% and a precision higher than 90%, for a cut-off distance higher than four. The method was then used to predict the crystalline group of manganese-based compounds (Li-Mn-O). The analysis conducted on twenty randomly selected compounds showed an accuracy of 70%. Out of ten valid predictions, nine were true positives, with a precision of 90%

Crystal Group Prediction for Lithiated Manganese Oxides Using Machine Learning

This work aimed to predict the crystal structure of a compound starting only from the knowledge of its chemical composition. The method was developed to select new materials in the field of lithium-ion batteries and tested on Li-Fe-O compounds. For each testing compound, the correspondence with respect to the training compounds was evaluated simply by calculating the Euclidean distance existing between the stoichiometric coefficients of the elements constituting the two compounds. At the compound under test was assigned the crystal structure of the training compound for which the distance value was minimum. The results showed that the model can predict the crystalline group of the test compound with an accuracy higher than 80% and a precision higher than 90%, for a cut-off distance higher than four. The method was then used to predict the crystalline group of manganese-based compounds (Li-Mn-O). The analysis conducted on twenty randomly selected compounds showed an accuracy of 70%. Out of ten valid predictions, nine were true positives, with a precision of 90%

Electrochemical characterization of titanium oxide nanotubes

To evaluate the possibility of using nanosized TiO2to replace the carbonaceous materials usuallyemployed as the negative electrode of lithium-ion batteries, we studied and compared the electrochem-ical performance of TiO2nanotubes with a commercial material (P25 Degussa). TiO2nanotubes wereprepared by electrochemical anodization of titanium sheets. The nanotubes were characterized by usingSEM and XRD. Composite electrode tapes were made by roll milling the TiO2nanotubes and the TiO2P25 Degussa with carbon and Teflon. The electrodes were electrochemical characterized in lithium cellby charge/discharge cycles. The electrochemical tests comprised low rate cycling, cycling at C/rate andcycling at different rates

Lithium-ion batteries based on titanium oxide, nanotubes and LiFePO4

In this paper, the morphology, the conformation, and the electrochemical performance of TiO2 nanotubes and LiFePO4 have been studied by using scanning electron microscope, XRD, and charge/discharge cycles. The electrochemical tests comprised low rate cycling, cycling at C rate, and cycling at different rates. This work was finalized to the fabrication of lithium-ion batteries based on the TiO2/LiFePO4 redox couple. Battery cells were assembled and electrochemical tests were performed to evaluate cell capacity, power, and energy. Further tests were carried out to evaluate the capacity retention as a function of cycle number and discharge curren

TyzorTM-LA used as a precursor for the preparation of carbon coated TiO2

In this paper the preparation, the morphology, the structure and the electrochemical performance of carbon coated TiO2 produced by using Tyzor®-LA as a precursor have been studied by using SEM, XRD and electrochemical methods. The electrochemical methods included low rate cycling, cycling at C-rate and cycling at different rates. At the same time the physical and electrochemical properties of LiFePO4 were investigated by using the same methods. Lithium-ion batteries were prepared by sandwiching a glass fiber between a TiO2 electrode used as the anode and a LiFePO 4 electrode used as the cathode and tested to evaluate cell performance

Synthesis of microcrystalline LiFePO4 in air

In this paper a method for the synthesis of nano-sized microcrystalline LiFePO4, which is particularly suitable for the production of high energy density electrodes, was developed. The method is characterized by the fact that it provides for the solid state reaction of anhydrous FePO4 with lithium acetate. The method is easy to implement and, above all, does not involve the need to operate in a controlled environment, since the material may be syn- thesized directly in air by mixing anhydrous FePO4 with lithium acetate. This latter is simultaneously used as a reducing and lithiating agent. Anhydrous FePO4 is prepared by dehydrating iron phosphate hydrate, which is in turn prepared by means of the spontaneous precipitation thereof from a solution of FeSO4 and NaH2PO4, using H2O2 as the oxidizing agent. The FePO4 used as the precursor is characterized by thermogravimetry and its morphology is investigated by SEM microscopy. The structure of LiFePO4 is characterized by X-Ray diffraction and its morphology investigated by SEM microscopy. Finally, the LiFePO4 is used to fabricate composite elec- trodes that are electrochemical tested in lithium cells