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Title: | STRUCTURAL AND ELECTROCHEMICAL STUDIES OF NON-INTERCALATION TYPE ALTERNATIVE ANODE MATERIALS FOR LITHIUM-ION BATTERIES |
Authors: | RAJPUT, SHIVANGI |
Keywords: | ELECTROCHEMICAL STUDIES NON-INTERCALATION ANODE MATERIALS LITHIUM-ION BATTERIES |
Issue Date: | Jul-2024 |
Series/Report no.: | TD-7685; |
Abstract: | As the global economy advances and populations expand, pressing issues like climate change and the rapid depletion of fossil fuel reserves have spurred considerable global interest in renewable energy storage solutions. Recently, Lithium-ion Batteries (LIBs) have surged in prominence within electronic and energy storage sectors due to their remarkable characteristics, including high energy density, minimal maintenance, negligible memory effect, and extremely low self-discharge rates. Moreover, LIBs have proven to be among the most effective methods for storing energy across a spectrum of applications, ranging from small portable devices like mobile phones and laptops to larger-scale systems such as digital electronics and electric vehicles. The electrode material plays a pivotal role in batteries, dictating the movement of charges and the storage of energy. Consequently, enhancing electrochemical performance hinges on optimizing the electrode material. Since the commercial introduction of LIBs in 1990-91, graphite has been the prevalent choice for anodes. However, its usage is hindered by drawbacks such as low gravimetric and volumetric capacity, along with safety concerns, rendering graphite unsuitable for the next generation of LIBs. Conversely, carbonaceous electrode materials exhibit low theoretical capacity and are insufficient on their own to meet contemporary power demands. Hence, there is an urgent need to explore novel anode materials to enhance the storage capacity and safety of LIBs. Group IV elements such as Si, Ge, and Sn have emerged as promising candidates due to their superior specific capacities compared to carbon-based materials. Among these, Sn has garnered significant attention owing to its impressive theoretical capacity and safer thermodynamic potential when compared to carbon-based alternatives. Additionally, tin boasts a higher electrochemical potential compared to graphite, bolstering its security and reliability as an anode. Consequently, significant vii research efforts have focused on tin-based anodes. However, commercialization remains elusive due to the substantial volume expansion during cycling, resulting in particle cracking and capacity degradation. To address these obstacles, diverse strategies have been implemented, such as nano structuring and the use of composite materials instead of pure metal. Nanosized anode materials offer a compelling solution by providing improved strain accommodation, leading to enhanced specific capacity and rate capability due to augmented interfacial area and accelerated kinetics of Li-ion diffusion. Tin readily forms binary or ternary compounds like Sn-M, Sn-M-M’ by reacting with elements from groups VA and VI A elements. Consequently, one viable approach involves alloying tin with inert materials to mitigate volume expansion/shrinkage during charging or discharging, examples of which include Sn-Sb, Sn-Co, Sn-Ni, Sn-Cu, and similar alloys. Another strategy entails incorporating conductive materials like carbon, polypyrrole, or polyaniline into composites to enhance electrochemical performance. Moreover, conversion-based transition metal oxides (TMOs) have undergone extensive investigation in recent years due to their excellent theoretical capacities (ranging from 600 to 1200 mAhg-1 ). However, despite these promising attributes, TMOs have yet to be employed in commercial batteries due to issues such as capacity decay during cycling and inadequate conductivity. Consequently, there remains significant potential for further exploration of TMOs as anode materials for LIBs. Metal oxides with a binary composition (AxByOz, where A can be Zn, Mn, Fe, Co, Ni, or Cu; and B can be Zn, Mn, Fe, Co, Ni, or Cu) and operating via the conversion reaction mechanism possess two electrochemically active transition metal ions. These oxides exhibit promising electrochemical activity when used as anode materials for LIBs. When employed as anode in LIBs, AB2O4 type metal oxides are capable of delivering a very high theoretical specific capacity (nearly 1000 mAhg 1 ). In recent times, there has been a notable focus on AB2O4 type transition metal oxides viii (TMOs), owing to their attributes such as high energy density, environmental friendliness, and widespread availability Hence, the present research work mainly focuses on the synthesis, physicochemical and electrochemical analysis of tin-based alloy anodes and AB2O4 type transition metal oxides. The research work conducted within this thesis demonstrates that the non-intercalation type alloy anode (SnSe) and conversion based TMOs anodes (ZnFe2O4, CoFe2O4 and ZnCo2O4) would be potential anodes when employed as an anode in Lithium-ion batteries. To perform the research work, low-cost and simple synthesis methods are employed to enhance the structural and morphological properties, resulting in stable and advanced anode materials with superior electrochemical performance. These newly developed anode materials have the potential to replace commercialized materials in lithium-ion batteries (LIBs) The results of the current research work have been divided into seven chapters with the following brief details: Chapter 1 introduces rechargeable batteries and provides an overview of Lithium-ion batteries (LIBs), along with an explanation of various types of anode materials investigated for use in LIBs. This chapter presents an extensive literature review focusing on non intercalation types of anode materials, particularly alloy anodes and conversion-based anodes, proposed as alternative options for LIBs. Additionally, a succinct review comparing these materials and underscoring their advantages over other carbonaceous anode materials has been explored. Furthermore, the chapter delineates the objectives of the thesis, grounded in both current needs and the insights gleaned from the literature review. Chapter 2 outlines the synthesis and experimental characterization techniques employed for the production of SnSe, AFe2O4 (A=Zn,Co) and ZnCo2O4 as well as their composites. Specifically, the sol-gel route, urea assisted combustion route and planetary ball milling ix synthesis processes were primarily utilized for achieving pure phase of anode materials. This chapter provides concise details of experimental methodologies such as thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscopy/transmission electron microscopy/high-resolution transmission electron microscopy (SEM/TEM/HRTEM), Fourier-transform infrared spectroscopy (FTIR), DC conductivities, and Raman Spectroscopy. In addition, the cell fabrication and electrochemical measurement instruments used include an automatic coating unit, a calendaring machine, crimping machine in glove-box workstation for cell assembly, and an electrochemical analyser for cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge/discharge studies of the assembled coin cells. Chapter 3 presents the physical and electrochemical studies for SnSe/C and SnSe/MWCNT composites effectively synthesized through a high-energy ball milling process utilizing Sn and Se metal powder, Super P, and MWCNT as precursors. XRD results confirm the proper phase formation of SnSe/C and SnSe/MWCNT as an orthorhombic structure with space group, pnma. The morphological analysis was conducted using FESEM and TEM to examine the shape, size, and distribution of particles. Additionally, Energy Dispersive Spectroscopy (EDS) and Raman spectroscopy were employed to validate the uniform mixing of SnSe with Super P and MWCNT. When utilized as anodes in Li-ion batteries, both SnSe/C and SnSe/MWCNT composites demonstrated superior reversible capacity, cycle life, and rate performance as compared to pure SnSe. Initial discharge capacities of 1069 mAhg-1 and 1107 mAhg-1 were achieved by SnSe/C and SnSe/MWCNT, respectively. Chapter 4 reveals the effect of Mn doping on the physical and electrochemical properties of ZnFe2O4. Zn1-xMnxFe2O4 (x = 0.0, 0.01, 0.03, 0.05) was synthesized through a straightforward and efficient high-energy ball milling process. Analysis via X-ray Diffraction (XRD) confirmed the highly crystalline nature with spinel structures across all x prepared samples, devoid of impurities except for x = 0.05, which exhibited a trace of α Fe2O3. Morphological assessments conducted using SEM and TEM validated the shape and size of the prepared samples, with an average particle size ranging between 100 nm to 200 nm. Energy Dispersive Spectroscopy (EDS) analysis affirmed the uniform mixing of elements within the prepared samples. Electrochemical performance of the Mn-doped ZnFe2O4 was evaluated through Galvanostatic Charge-Discharge (GCD), Electrochemical Impedance Spectroscopy (EIS), and Cyclic Voltammetry (CV). The charge storage mechanisms, encompassing pseudocapacitive and diffusive contributions, were also investigated. Hence, the results demonstrated that the Zn1-xMnxFe2O4 (x = 0.03) electrode exhibited superior electrochemical behavior as compared to other prepared electrodes. Specifically, Zn1-xMnxFe2O4 (x = 0.03) showcased an initial charge-discharge capacity of 1405 mAhg-1 and 900 mAhg-1 with a coulombic efficiency of 64.2%. Zn1-xMnxFe2O4 (x=0.03) sample maintained a discharge capacity of 502 mAhg-1 , with a capacity retention of 35%. after 200 cycles. Moreover, the rate capability of Zn1-xMnxFe2O4 (x = 0.03) at a current density of 1000 mAg-1 was observed to be 434 mAhg-1 . Chapter 5 deals with the synthesis of ZnCo2O4 via two different routes viz urea-assisted combustion method and ball milling method. The physicochemical characterization has been carried out with the help of XRD, FESEM, and EDX to confirm the phase, morphology, and elemental composition, respectively. The average crystallite size of ZnCo2O4 via urea assisted combustion (ZCU) and the ball milled (ZCB) has been observed to be 57 nm and 70 nm as estimated from XRD. The average particle of ZnCo2O4 via urea combustion and the ball mill is 20 µm and 49 µm, respectively, as observed by FESEM. The diffusion coefficient calculated from EIS analysis for ZCB and ZCU has been estimated as 9.32 x 10−15 𝑐𝑚2 𝑠 −1 and 2.63 x 10−14 𝑐𝑚2 𝑠 −1 , respectively. xi Chapter 6 reveals the physical and electrochemical studies for CFO, CFO_MWCNT and CFO_rGO composites effectively synthesized through a sol gel auto combustion route. XRD results confirm the proper phase formation of CFO, CFO_MWCNT and CFO_rGO composites as inverse cubic spinel structure with space group, Fd3m. The morphological analysis was conducted using FESEM and TEM to examine the shape, size, and distribution of particles. Additionally, energy dispersive spectroscopy (EDS) and Raman spectroscopy were employed to validate the uniform mixing of CFO with rGO and MWCNT. When utilized as anodes in Li-ion batteries, both CFO_MWCNT and CFO_rGO composites demonstrated superior reversible capacity, cycle life, and rate performance compared to pure CFO. Initial discharge capacities of 1554 mAhg-1 and 1314 mAhg-1 were achieved for CFO_MWCNT and CFO_rGO, respectively. The Li-ion diffusion coefficient is calculated using EIS was found in the range of 0.26 x10-17 cm2 s -1 , 0.95 x10-17 cm2 s -1 and 1.00 x10-15 cm2 s -1 , for CFO, CFO_MWCNT and CFO_rGO sample, respectively. Chapter 7 encompasses the conclusion and summary of the research undertaken in this study. It outlines the findings of the optimized samples and discusses their implications. Additionally, this section delineates the potential avenues for future research based on the outcomes of the present investigation. |
URI: | http://dspace.dtu.ac.in:8080/jspui/handle/repository/21283 |
Appears in Collections: | Ph.D. Applied Physics |
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File | Description | Size | Format | |
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SHIVANGI RAJPUT pH.d..pdf | 10.11 MB | Adobe PDF | View/Open |
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