Synthesis and investigation of electrochemical properties of carbon reinforced innovative cathode electrode for sodium ion batteries

Energy storage has become a growing global concern over the past decade as a result of the massive increases in the price of refined fossil fuels and the environmental consequences of their use, as well as increased energy demand. This has increased calls for environmentally sound alternative sources for both energy production and storage. Sustainable energy alternatives have become a global demand in the last decade due to the ever-increasing energy demand, increasing fossil fuel consumption and environmental degradation. Although wind and solar-generated electricity is becoming increasingly popular in many industrialized countries, these sources provide intermittent energy; therefore, energy storage systems are required for load (charge) balancing. Secondary batteries are renewable, environmentally friendly, safe and economical and are the most researched sources as energy storage systems. Lithium-ion batteries are the most studied as secondary batteries. The main reason why lithium-ion batteries used in energy storage are most preferred is their long life, recyclability, high capacity and light weight. In this context, lithium-ion batteries (LIBs) with high gravimetric and volumetric energy densities are widely used in portable electronic devices and are generally considered the best candidates for electric vehicles, hybrid electric vehicles. However, the increasing demand for lithium-ion batteries causes lithium prices to increase due to the limited lithium reserves in the world and its uneven distribution in the earth's crust. The lithium market is not only volatile due to the geographic concentration of the metal, but also comes under severe criticism from its extraction due to heavy water use and other aspects of its environmental footprint. Compared to lithium, it offers an economical energy storage potential due to the abundance of sodium reserves and its low cost. Sodium, the second lightest and smallest alkali metal with chemical properties similar to lithium, has been recognized as an ideal alternative to meet sustainable energy storage needs. To advance the electrochemical performance of sodium-ion batteries, many researchers have made extensive efforts on high-performance electrode materials. The electrochemical performance of sodium ion batteries in terms of specific energy, specific power and cycle life is closely related to the cathode materials. So far, a number of cathode materials such as layered transition metal oxides, Prussian blue compounds and polyanionic compounds have been extensively studied for sodium ion batteries. Among the various cathode materials, multilayer oxides (NaMO2, M=Cr, Co, Fe, Ti, V, Mn, Ni and a mixture of 2 or 3 elements) are suitable for sodium ion batteries due to their simple structure and high performance capacity and ease of synthesis is a candidate. Among many cathode materials, Na0.5Ni0.25Mn0.75O2, which has the layered P2 type, has advantages such as abundant manganese in the soil and low cost. Ni+2 ion contribution, which is another element in the structure, is expected to stabilize the layered structure and increase the total cell voltage by preventing the dissolution of Mn+3 ions at high voltages (>4V). It is also known that the serious capacity reduction caused by Jahn-Teller distortion of Mn+3 ions can be minimized by Ni+2 contribution to layered P2 type Na0.5MO2 compounds. In this master's study, both the electrochemical and structural properties of the Ni+2 doped Na0.5Ni0.25Mn0.75O2 cathode material were improved by adding graphene. In this context, Na0.5Ni0.25Mn0.75O2 cathode material was produced by sol-gel method and graphene used as reinforcement material by Hummers method. X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential thermal analysis (DTA), field emission scanning electron microscopy (FE-SEM), elemental distribution spectroscopy (EDS) and point mapping analyzes were used for the characterization of the produced products. materials. In electrochemical analysis, impedance spectroscopy (EIS), cyclic voltammetry (CV) and galvanostatic charge/discharge tests were performed. The synthesized P2 type layered Na0.5Ni0.25Mn0.75O2 cathode active material retained 80% of its total capacity after 250 cycles in the potential range of 2.2 to 4 V at 0.5°C. The P2 type electrode exhibited a capacitance value of 130 mAh g-1 in the first cycle. Charge-discharge tests of the cathode active electrode material at the end of 250 cycles also showed that the P2 type electrode is a very promising electrode.