Cathode Material For Battery Applications Research Articles

Photo-assisted low temperature crystallization of solution-derived LiCoO2 thin film

LiCoO2 is one of the most successfully commercialized cathode materials for battery applications, owing to its excellent capacity and cycle performance. LiCoO2 exhibits two main crystallographic structures depending on the calcination temperature: low-temperature cubic spinel (Fd3m) structure, often called LT-LiCoO2, and high-temperature hexagonal layered structure (R3¯m), referred to as HT-LiCoO2. HT-LiCoO2, which generally requires a high processing temperature, shows a better battery performance than LT-LiCoO2. However, in the fabrication of thin film batteries, a low processing temperature is essential considering the thermal instability of the polymer substrates. Therefore, the low temperature fabrication of layered LiCoO2 is a primary concern for the development of thin film batteries. In this study, we observe that the ultraviolet (UV) treatment of sol-gel derived LiCoO2 precursors triggers the crosslinking of polyvinylpyrrolidone and impedes the phase crystallization of impurities, such as Co3O4. After the decomposition of the polymer during post-annealing above 350 °C, crystallites are found to exist in the metastable state, making them more efficiently oxidizable. Finally, with the UV treatment, the transition to the layered LiCoO2 is mostly completed at a low temperature of 400 °C.

The structural origin of enhanced stability of Na3.32Fe2.11Ca0.23(P2O7)2 cathode for Na-ion batteries

The storage of renewable energy depends largely on sustainable technologies such as sodium-ion batteries with high safety, long lifespan, low cost, and non-toxicity. Pyrophosphate Na3.32Fe2.34(P2O7)2 cathode could meet this requirement, however, its structural stability needs to be further enhanced for practical purposes. To overcome this problem, Na-deficient Na3.32Fe2.11Ca0.23(P2O7)2 with exceptional stability is prepared by Ca selective doping in this work. In operando synchrotron-based X-ray diffraction (SXRD) and in situ X-ray absorption near edge spectroscopy (XANES) results reveal that the prepared Na3.32Fe2.11Ca0.23(P2O7)2 is a single-phase solid-solution reaction with high reversibility. A strong correlation between the voltage curve and lattice parameters is deciphered for the first time. Additionally, the atomic-doping-engineering strategy could significantly enhance the thermal and electrochemical stability of the electrode materials, contributing to their good structural reversibility and enhanced operational safety. Specifically, after 1000 cycles at 1 C, the Ca doped electrode achieves a high capacity retention of 81.7%, which is much better than that of the un-doped electrode (15.5%). Our work may pave a new avenue for designing safe and low-cost cathode materials for battery applications with long cycle life.

Influence of Electrolyte Additives on the Degradation of Li2VO2F Li-Rich Cathodes

Li-rich disordered rock-salt structures have, because of their high theoretical capacity, gained a lot of attention as a promising class of cathode materials for battery applications. However, the ...

Cycling and Aging Studies of Li-Based Cathode Materials Via Aberration-Corrected STEM

The role of aberration-corrected scanning transmission electron microscopy (STEM) in materials characterization is examined with respect to layered-oxide cathode materials for battery applications. STEM-based methods are quickly becoming the most promising characterization tools for these materials, owed largely to the wide-range of techniques available on advanced STEM instruments, including the direct imaging of both heavy and light elements, and both energy-dispersive X-ray (EDX) and electron energy loss (EEL) spectroscopies. The current talk will focus on multiple Li-based, Mn-containing oxide cathode materials, for example, Li2MnO3 and Li(Ni0.5Co0.2Mn0.3)O2), characterized via STEM methods, in pristine, cycled, and in-situ irradiated states. The latter allows for single particle tracking of the dynamic processes occuring upon Li and O loss from the material, and is a form of accelerated ageing compared to the structural and electronic changes which occur upon electrochemical cycling. Various imaging modes, including high/low angle annular dark field (H/LAADF) and annular bright field (ABF), in conjunction with EELS/EDX, will be used extensively for this analysis, while parameters such as Mn valence, O presence, and light element occupation and intercalation will be discussed.

Advanced Characterization of Li- and Beyond Li-Ion Battery Cathode Materials Via Electron Microscopy

The role of aberration-corrected scanning transmission electron microscopy (STEM) in materials characterization is examined with respect to layered-oxide cathode materials for battery applications. STEM-based methods are quickly becoming the most promising characterization tools for these materials, owed largely to the wide-range of techniques available on advanced STEM instruments, including the direct imaging of both heavy and light elements, and both energy-dispersive X-ray (EDX) and electron energy loss (EEL) spectroscopies. The current talk will focus on multiple materials, including Li- and beyond Li-ion oxides, characterized via STEM methods, in pristine, cycled, and in-situ irradiated states. The latter allows for single particle tracking of the dynamic processes occuring upon Li and O loss from the material. Various imaging modes, including high/low angle annular dark field (H/LAADF) and annular bright field (ABF), in conjunction with EELS/EDX, will be used extensively for this analysis, while parameters such as Mn valence, O presence, and light element occupation and intercalation will be discussed.

Advanced Electron Microscopy of Layered-Oxide Cathode Materials

The role of aberration-corrected scanning transmission electron microscopy (STEM) in materials characterization is examined with respect to layered-oxide cathode materials for battery applications. STEM-based methods are quickly becoming the most promising characterization tools for these materials, owed largely to the wide-range of techniques available on advanced STEM instruments, including the direct imaging of both heavy and light elements, and both energy-dispersive X-ray (EDX) and electron energy loss (EEL) spectroscopies. The current talk will focus on multiple materials, including Li- and beyond Li-ion oxides, characterized via STEM methods, in pristine, cycled, and in-situ irradiated states. The latter allows for single particle tracking of the dynamic processes occuring upon Li and O loss from the material. Various imaging modes, including high/low angle annular dark field (H/LAADF) and annular bright field (ABF), in conjunction with EELS/EDX, will be used extensively for this analysis, while parameters such as Mn valence, O presence, and light element occupation and intercalation will be discussed.

High‐Voltage Pyrophosphate Cathodes

AbstractThe quest to explore and to discover novel cathode materials is key to sustaining the progress of Li‐ion rechargeable batteries. It has encouraged materials’ chemists to design and develop a variety of polyanionic compounds. This paper reports and summarizes recent progress in the development of alkali metal pyrophosphate based cathode materials for battery applications. It points out that the pyrophosphate‐based polyanionic‐framework materials offer a rich crystal chemistry, ease of synthesis and robust structure offering good alkali‐ion mobility. Thus, they can form a promising class of cathode materials both for lithium‐ and sodium‐ion secondary batteries. In the Perspectives section, it is speculated that keen study of the myriad of pyrophosphate phases, selective screening and design of key pyrophosphate compounds with open frameworks and optimizing those compounds with nanosizing and carbon coating can lead to breakthroughs in the realization of commercially viable high‐voltage Li‐ion and Na‐ion pyrophosphate cathodes.

Lithium intercalation into amorphous FePO 4 cathode in aqueous solutions

Amorphous iron phosphate (FePO 4) was investigated as a cathode material for battery applications using aqueous (lithium hydroxide or potassium hydroxide) electrolytes. Phosphate-based cathode materials are of great interest in lithium batteries which use non-aqueous electrolytes. In order for these materials to be used as cathodes in aqueous electrolytes it is important to understand their reduction/oxidation mechanisms. Potentiostatic and galvanostatic techniques are used to study these mechanisms. X-ray diffraction (XRD), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) have been used to gain insight into the reduction/oxidation behavior of FePO 4 cathodes. Our results show that FePO 4 undergoes reversible Fe 3+/ 2+ processes of reduction and oxidation in LiOH electrolyte, while using KOH electrolyte this process is found to be irreversible. The lithium intercalation mechanism is identified for LiOH while in the case of KOH electrolyte H reacts to form FeOOH. The Zn|LiOH|FePO 4 battery provides a reversible capacity of 65 mAh/g. The results indicate the trigonal FePO 4 as an attractive host intercalation compound.

The effect of B4C addition to MnO2 in a cathode material for battery applications

Boron carbide (B4C) added manganese dioxide (MnO2) used as a cathode material for a Zn–MnO2 battery using aqueous lithium hydroxide (LiOH) as the electrolyte is known to have higher discharge capacity but with a lower average discharge voltage than pure MnO2 (additive free). The performance is reversed when using potassium hydroxide (KOH) as the electrolyte. Herein, the MnO2 was mixed with 0, 5, 7 and 10 wt.% of boron carbide during the electrode preparation. The discharge performance of the Zn|LiOH|MnO2 battery was improved by the addition of 5–7 wt.% boron carbide in MnO2 cathode as compared with the pure MnO2. However, increasing the additive to 10 wt.% causes a decrease in the discharge capacity. The performance of the Zn|KOH|MnO2 battery was retarded by the boron carbide additive. Transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy analysis (EDS) results show evidence of crystalline MnO2 particles during discharging in LiOH electrolyte, whereas, manganese oxide particles with different oxygen and manganese counts leading to mixture of phases is observed for KOH electrolyte which is in agreement with X-ray diffraction (XRD) data. The enhanced discharge capacity indicates that boron atoms promote lithium intercalation during the electrochemical process and improved the performance of the Zn|LiOH|MnO2 battery. This observed improvement may be a consequence of B4C suppressing the formation of undesirable Mn(III) phases, which in turn leads to enhanced lithium intercalation. Too much boron carbide hinders the charge carrier which inhibits the discharge capacity.