Insights and Perspectives on Graphene-PVDF Based Nanocomposite Materials for Harvesting Mechanical Energy

The evolution of energy storage technology that can deliver high energy density with excellent rate performance is desirable all around. The scientific community putting their efforts together to solve this...

Phosphate-based Cathode Materials to boost the electrochemical performance of Sodium-ion Battery

The essential requirement to harness well-known renewable energy sources like wind energy, solar energy, etc. as a component of an overall plan to guarantee global power sustainability will require highly efficient, high power and energy density batteries to collect the derived electrical power and balance out variations in both supply and demand. Owing to the continuous exhaustion of fossil fuels, and ever increasing ecological problems associated with global warming, there is a critical requirement for searching for an alternative energy storage technology for a better and sustainable future. Electrochemical energy storage technology could be a solution for a sustainable source of clean energy. Sodium-ion battery (SIB) technology having a complementary energy storage mechanism to the lithium-ion battery (LIB) has been attracting significant attention from the scientific community due to its abundant resources, low cost, and high energy densities. Layered transition metal oxide (TMO) based materials for SIBs could be a potential candidate for SIBs among all other cathode materials. In this paper, we discussed the latest improvement in the various structures of the layered oxide materials for SIBs. Moreover, their synthesis, overall electrochemical performance, and several challenges associated with SIBs are comprehensively discussed with a stance on future possibilities. Many articles discussed the improvement of cathode materials for SIBs, and most of them have pondered the use of NaxMO2 (a class of TMOs) as a possible positive electrode material for SIBs. The different phases of layered TMOs (NaxMO2; TM = Co, Mn, Ti, Ni, Fe, Cr, Al, V, and a combination of multiple elements) show good cycling capacity, structural stability, and Na+ ion conductivity, which make them promising cathode material for SIBs. This review discusses and summarizes the electrochemical redox reaction, structural transformations, significant challenges, and future prospects to improve for NaxMO2. Moreover, this review highlights the recent advancement of several layered TMO cathode materials for SIBs. It is expected that this review will encourage further development of layered TMOs for SIBs.

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Transition metal oxides as a cathode for indispensable Na-ion batteries

Fast ionic conduction and rectification effect of NaCo0.5Fe0.5O2-CeO2 nanoscale heterostructure for LT-SOFC electrolyte application

Polyimide-Al2O3 membranes are developed as a direct alternative to current polyolefin separators by the electrospinning technique and their chemical structures confirm the carbonyl group with the presence of asymmetric and symmetric stretching and bending vibrations at 1778, 1720, and 720 cm-1 and stretching vibration at 1373 cm-1 for the imide group. Porous nanofiber architecture morphology is realized with a nanofiber thickness of ∼200 nm and shows an ultrasmooth surface and >1 μm pore size in the architecture, built with the chemical constituents of carbon, nitrogen, aluminum, and oxygen elements. The galvanostatic cycling study of the Li/PI-Al2O3/LiFePO4 lithium cell delivers stable charge-discharge capacities of 144/143 mAh g-1 at 0.2 C and 110/100 mAh g-1 at 1 C for 1-100 cycles. The fabricated MCMB/PI-Al2O3/LiFePO4 lithium-ion full-cell reveals less charge transfer resistance of Rct ∼ 25 Ω and yields stable charge-discharge capacities of 125/119 mAh g-1. The thermogravimetric curve for the PI-Al2O3 separator discloses thermal stability up to 525 °C, and the differential scanning calorimetric curve shows a straight line until 300 °C and depicts high thermal stability than the PP separator. In situ multimode calorimetry analysis of the MCMB/PP/LiFePO4 full-cell showed a pronounced exothermic peak at 225 °C with a higher released heat energy of 211 J g-1 at the thermal runaway event, while the MCMB/PI-Al2O3/LiFePO4 full-cell revealed an almost 8-fold less exothermic released heat energy of 25 J g-1 than the Celgard polypropylene separator, which was because the MCMB anode and LiFePO4 cathode can be mechanically isolated without any additional separator's melting and burning reactions, as a fire-suppressant separator for lithium-ion batteries.

In Situ Thermal Safety Aspect of the Electrospun Polyimide-Al2O3 Separator Reveals Less Exothermic Heat Energies Than Polypropylene at the Thermal Runaway Event of Lithium-Ion Batteries.

Despite the multiple phase transitions that occur during Na+ ion intercalation and deintercalation, an enhanced charge–discharge rate and a long cycle life are achieved with a hexagonal shaped P2-type NaCoO2 cathode for sodium-ion batteries (SIBs). The hysteresis abated crystalline phase was obtained by tuning the calcination temperature/time factors for the citric acid assisted sol–gel technique precursor. Powder X-ray diffraction data confirmed that the studied material belongs to a hexagonal crystal system and that, among the materials, the material synthesized at 750 °C/28 h in an air atmosphere in particular showed pure phase formation with an ordered structure. Furthermore, the local atomic arrangement of the synthesized NaCoO2 cathodes was monitored using a Raman spectroscopy technique, revealing five active vibration modes of E1g(O), E2g(O), 2 E2g (Na), and A1g(O), in NaCoO2 to confirm the existence of the hexagonal crystal structure. The surface morphology of the designed materials exhibited a hexagonal shape with a size of 2–5 μm. By tuning the calcination temperature/time factors, the optimized critical parameters of the P2-type NaCoO2 cathode were 750 °C and 28 h, resulting in a well-ordered structure, which enhances Na+ ion storage capacity at a high-rate. Thus, a hysteresis abated P2-type NaCoO2 cathode demonstrated high-rate, stable charge–discharge cycles with 79 mA h g−1 capacity at a rate of 1C with a retention of 99% coulombic efficiency for the 100th cycle.

Hysteresis abated P2-type NaCoO2 cathode reveals highly reversible multiple phase transitions for high-rate sodium-ion batteries

A sol-gel process followed by heat treatment derived a layered P2-type NaCoO2 cathode, which depicted unit cell parameters values of a = 2.8389 A, c = 10.9899 A, and V = 76.71 A3 in powder X-ray diffraction pattern. The synthesized cathode exhibited hexagonal, 2D platelets with an ∼300 nm thickness. During the anodic and cathodic sweeps, the cyclic voltammograms revealed multiple redox peaks with the same current densities, shapes, and peak positions, associated with the highly reversible phase transition mechanism of the layered P2-type NaCoO2 cathode. The sodium cells yielded the capacities of 93/92 mAh g-1 at 0.5 C and 87/87 mAh g-1 at 1 C for the 50th charge-discharge cycles. The in situ multimode calorimetry (MMC) studies of sodium cells demonstrated a thermal explosion event, which occurred by sodium melting, short-circuit, electrode decomposition reaction, gas generation, exothermic reaction, released heat energy ,and cell gasket melting. Ultimately, the calculated released total heat energies of ∼550/740 J g-1 for in situ MMC studies and ∼312/594 J g-1 for ex situ DSC analyses (charge state at 4 V and discharge state at 2 V) show that the discharged state of sodiated layered P2-type NaCoO2 cathode material is more unsafe than the charge state. Furthermore, the ex situ differential scanning calorimetry (DSC) spectrum of a discharge state at 2 V of layered P2-type NaCoO2 revealed a decreased onset temperature (DOT) at 141 °C with two pronounced exothermic peaks at 197 and 266 °C with a released higher total heat energy of 594 J g-1 than the charge state heat energy at 312 J g-1, attributed to the higher charge onset temperature (COT) at 191 °C. Thus, the observed higher heat energy and decreased onset temperature for the discharge state at 2 V is associated with the higher Na+ ion in the discharge state of the layered P2-type NaxCoO2 cathode than that of the pristine cathode, showcasing that the layered P2-type NaCoO2 cathode is unsafe at the discharged condition for sodium-ion batteries.

Discharge State of Layered P2-Type Cathode Reveals Unsafe than Charge Condition in Thermal Runaway Event for Sodium-Ion Batteries.

Global interest in the development of sodium-ion batteries (SIBs) continues, largely due to the advantage of the affordable cost of sodium resources (compared to lithium), which could produce cost-effective rechargeable batteries for large-scale applications. However, the discovery of reliable cathodes, tailored amorphous carbon anodes, and compatible electrolytes is required to yield safer, longer lasting SIBs with wide operating temperature. Among various cathodes systems, layered oxide cathodes are of great interest due to 230–245 mAhg−1 theoretical capacity with facile structure forming ability. Among the various phases of NaxCoO2 cathode, the P2 is the most favored, because of low polarization with enhanced structural stability and high theoretical capacity of 183 mAhg−1 for the empirical formula of Na0.74CoO2. Charge/discharge profiles of these systems exhibit plateaus, continuous changes in voltage and voltage drop, which impacts the electrochemical performance. This review discusses recent advancement in NaxCoO2 cathode in terms of the effect of particle morphology, size, crystal structure, electronic structure, cation and anion doping, sacrificial salt, Na deficiency, effect of electrolyte salts and solvents, and thermal safety. We present a comprehensive analysis of the recent developments in NaxCoO2 and its derivative cathode materials and propose various approaches to mitigate the challenges for the near future successful commercialization of SIBs.

Venkata Rami Reddy Boddu

Papers

Hysteresis abated P2-type NaCoO2 cathode reveals highly reversible multiple phase transitions for high-rate sodium-ion batteries

Discharge State of Layered P2-Type Cathode Reveals Unsafe than Charge Condition in Thermal Runaway Event for Sodium-Ion Batteries.

Layered NaxCoO2-based cathodes for advanced Na-ion batteries: review on challenges and advancements