132 research outputs found

    Synthesis of LiFePO4 (Lithium Iron Phosphate) with Several Methods: A Review

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    Olivine-type LiFePO4 these days is being observed by many researchers as a promising alternative cathode material in lithium-ion batteries since it was relatively cheaper, lower toxicity, and high safety. A few methods to synthesize LiFePO4 were used. However, it needs a review to find out which one is more effective. From the cost, process, or the end synthesis product aspect. This review contained 60 articles from the year 2002 to 2020. The discussed synthesis method is freeze-drying, hydrothermal, microwave heating, polyol process, supercritical water synthesized, co-precipitation, solid-state reaction, three steps calcination, solvothermal, sol-gel, rheological, and combustion process. From those methods, the most efficient way to synthesize LiFePO4 is the hydrothermal method. Because this method was cheaper, using relatively low temperature, rapid reaction time, reproducible, homogeneous particle size distribution, and larger electrochemical performance.

    Development of Nanostructured LiMPO4 (M=Fe, Mn) as Cathodes for High Performance Lithium-Ion Batteries

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    Olivine LiFePO4 has garnered the most interest because of its environmental benignity, high safety and theoretical capacity. However, the major limitation for LiFePO4 is the intrinsically poor electronic conductivity and ionic conductivity. The sluggish kinetics for LiFePO4 could be overcome by reducing the size, coating with conductive carbon, or doping with isovalent ions. The decrease of the size to nanoscale could shorten the diffusion time of Li ions in LiFePO4 during intercalation/deintercalation process, but the nano-size active material usually accompanies with low tap density. Carbon coating and carbon addition could alleviate the poor electronic conductivity. However, simple or nonuniform carbon coating cannot obtain an ideal electrochemical performance due to the fact that the electrons could not reach some positions where Li ions charge/discharge takes place. The research in this thesis aims at developing high electrochemical performance of the LiFePO4 composite. In this research, we proposed as follows: (1) three dimensional (3D) porous LiFePO4 in microscale. The porous strategy could allow efficient percolation of the electrolyte through the electrode, favoring the electrolyte access to active materials via the pores, then make full use of electrode material; (2) the nanosized LiFePO4 anchors in the 3D conducting network. This could achieve fast electronic and ion conduction, leading to high performance of the composites. Therefore, we first reported 3D porous LiFePO4 with N-CNTs, CNTs and graphene fabricated by using sol-gel approach. The highly conductive and uniformly dispersed N-CNTs and graphene nanosheets incorporated into 3D interlaced porous LiFePO4, which could facilitate the electric and lithium ion diffusion rate, thus resulting in high performance of LiFePO4 electrodes. We also reported the nanosized and unfolded graphene modified LiFePO4 composites.The LiFePO4 nanoparticles anchored to 3D conducting unfolded graphene network resulted in almost theoretical capacity (171 mAh g-1). One-dimensional LiFePO4@CNTs nanowires have been prepared, while 3D CNTs conducting network structure was also obtained simultaneously. The LiFePO4@CNTs nanowires can give excellent cycling stability and rate capability. The effect of Mn concentration on the morphology of LiFePO4 and the electrochemical performance have been investigated In summary, the discoveries in this thesis contribute to a better understanding and design on LiFePO4 candidate and provide novel hierarchical nanostructured materials as electrodes applied in LIBs as power sources for EVs or HEVs

    LiFePO4 spray drying scale-up and carbon-cage for improved cyclability

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    The growing market for electrical vehicles requires inexpensive, long-lasting batteries. LiFePO4 (LFP) melt-synthesized from ore concentrate fits this role, but the manufacturing process requires additional steps that includes grinding large ingots into a nanoparticle suspension followed by a dessication step. Spray drying, rather than tray drying, creates a mesopomus powder that enhances wettability. Adding lactose and high-Mw polyvinyl alcohol (PVA) to the suspension of nanostructures followed by pyrolysis, creates a carbon-cage that interconnects the cathode nanoparticles, imparting better capacity (LiFePO4/C: 161 mA h g(-1) at 0.1C), discharge rate (flat plateau, 145 mA h g(-1) at 5C), and cyclability (91% capacity retention after 750 cycles at 1C). Particle size affects battery stability; PVA increases the suspension's viscosity and alters the powder morphology, from spherical to hollow particles. A model describes the non-Newtonian suspension's rheology changing: shear, temperature, LFP and PVA loading. Carbon precursors prevent the nanoparticles from sintering during calcination but lactose gasifies 50% of the carbon, according to the chemical and allotropic composition measurements (CS analyzer, XPS, and Raman). The carbon-cage imparts micmporosity and we correlate the SEM and TEM powder's morphology with N2 physisorption porosimetry. Ultrasonication of the suspension fragments the PVA chain, which is detrimental to the final cathode performance

    Facile Fabrication Of Mesostructured Zn2sno4 Based Anode Materials For Reversible Lithium Ion Storage

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    Increase in all electric and hybrid car sales from Electric drive transportation association show that Lithium-ion batteries stands as a promising option for these vehicles. Hence improving these batteries is the objective of this thesis. We try to improve the electrode material by using unique structures and coating carbon layers on the material. We chose Zinc tin oxide (ZTO) as it has been shown in literature to be a good oxide for batteries. We tried improving it by making new Rubik-cube like microstructure of it and more interestingly coating a layer of carbon on it. We could show from our experiments that the carbon layer is around 10nm and has an effect on the battery performance. The ZTO/SnO2 has a capacity of 400mAh/g after 20 cycles and the same material after carbon coating layer has around 550mAh/g after 20 cycles which shows a clear improvement in the one with carbon coating. Then we were able to discover a unique structure of ZTO which to our knowledge has been produced first time. This has a capacity of around 400mAh/g after 20 cycles

    High Energy Density Cathode for Lithium Batteries: From LiCoO_(2) to Sulfur

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    Lithium batteries are receiving increasing interest worldwide due to the urgent demand for higher energy density, longer cycling life, cheaper price, and better safety, so that long-distance electric vehicles and stationary energy storages can be viable. This dissertation, motivated with these aims, investigated both Li-ion batteries and Li-S batteries. LiCoO_(2), though it has been commercialized in Li-ion batteries, still has the potential to achieve higher energy density, since its practical capacity is limited to half of its theoretical capacity due to the overcharge problem. Surface coatings of lithium vanadate (Li_(3)VO_(4)) on LiCoO_(2) nanoparticles were employed to overcome this issue. With 3.4-wt.% and 5.5-wt.% Li_(3)VO_(4) coatings, both the cyclability and high-rate capability of LiCoO_(2) cells were greatly improved when overcharged to voltages as high as 4.5 V and 4.7 V. The improvement was attributed to the structurally protective and Li-ion conductive Li_(3)VO_(4) coating, which can suppress the side reaction and structure damage of LiCoO_(2) nanoparticles, as indicated by TEM images after the cycling test. Li-S batteries, promising due to the high energy density and low price, face two challenges that have not been well addressed, i.e. the safety hazard resulted from the Li dendrite formation on the Li metal anode and the poor cyclability arising from the polysulfides shuttle. Firstly, to overcome the safety issue, this dissertation reported a lithiated Si-S (LSS) battery that replaced the Li metal with a pre-lithiated Si anode. Due to the high theoretical capacity of Si, no sacrifice of the energy density was made. Stable cycling performances with capacity retention up to 80% were achieved in the organic electrolyte. The better safety of the LSS battery in terms of external and internal short-circuits was also demonstrated. Secondly, to suppress the polysulfides shuttle, a novel semi-liquid Li-S battery was designed with carbon nanotubes (CNT) sponges soaked by liquid polysuflides as the cathode. Stable cycling performances were achieved over 300 cycles. Due to the absence of the polymer binder and metal current collector in this design, the energy density of the total electrode was improved significantly

    Electrospun one dimensional composite materials as durable anode for efficient energy storage

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    Ph.DDOCTOR OF PHILOSOPH

    Development and Characterization of Nano-Structured LiFePO4 Cathode and Li4Ti5O12 Anode Materials for High-Performance Li-Ion Battery

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    Lithium-ion batteries with high power density and long lifetime is becoming the leading energy storage technologies for applications such as electric vehicles and large-scale electricity storage. But the state-of-the-art batteries based on current cathode and anode material can hardly meet the requirements of the large-scale applications due to the limitations on power density and safety characteristics. My research has been dedicated to the development and characterization nano-cathode and nano-anode material for new-generation high power lithium-ion batteries. The selected material candidates for cathode is LiFePO4 and that for anode is Li4Ti5O12. The effective combination of solid-state reaction and hydrothermal method has been used to synthesize both LiFePO4 cathode and Li4Ti5O12 anode because of its low cost and availability of the precursors. The goal for my project is to elucidate the fundamental processes for controllable synthesis of stable LiFePO4 cathode and Li4Ti5O12 anode nanomaterials. The first part of my thesis is the controllable synthesis and performance characterizations of carbon-coated LiFePO4 nanomaterials. A variety of analytical techniques such as x-ray diffraction, scanning and transmission electron microscopy (TEM, HRTEM), electron diffraction, and X-ray photoelectron spectroscopy are applied to investigate LiFePO4 morphologies and phase structures on the nanometer scale. Well-ordered olivine LiFePO4 crystal with a homogenous carbon coating of ~ 3 nm thickness is clearly revealed. The state-of-the-art structural characterization techniques provide a comprehensive view of the correlation between structure and performance of these LiFePO4 cathode nanomaterials. The nanostructures characteristics and the amorphous carbon-coating has been demonstrated to improve the electrical conductivity by reducing the path of both electron transfer and lithium ions diffusion, thereby is beneficial to improve electrochemical performance of these LiFePO4 nanomaterials. The excellent performance in terms of enhanced rate capability, good cycling performance, and high discharge capacity, should enable the development of high power LiFePO4 batteries. More importantly, the practical performance of these carbon-coated LiFePO4 nanomaterials as cathode was performed with a prototype of 18650-type battery cell manufactured by using the commercial graphite as the anode active materials. The remarkable rate capability and cycling performance are clearly demonstrated in the prototype of LiFePO4 battery cell. The second part of my thesis is the facile synthesis and performance evaluation of carbon-coated spinel Li4Ti5O12 nanomaterials. Spinel Li4Ti5O12 has been regarded as an attractive anode material for the development of high-power lithium-ion batteries because of its unique attributes of high safety and rate capability. Carbon-coating has been proved to be an effective method to improve electronic conductivity of Li4Ti5O12 anode materials. It is critically important to investigate in depth the influence of the carbon-coating on the electrochemical performance. Comparative nanostructure analyses and various electrochemical testing demonstrated that these Li4Ti5O12 anode nanomaterials have the improved capacitive, high-rate, and enhanced cycling performance. These improved lithium storage properties can be attributed to the combination of uniform thin carbon-coating and high-purity spinel Li4Ti5O12 nanocrystal, which increases electron transport and facilitates lithium-ion insertion/extraction simultaneously throughout the electrode, making it a highly promising anode material for use in the development of high power density lithium-ion batteries. The practical comparison of the carbon-coated Li4Ti5O12 nanomaterial and the commercial Li4Ti5O12 sample was evaluated in half cells with lithium as the negative electrode. More interestingly, the improved cycling performance is demonstrated in the Li4Ti5O12 battery cell. Finally, the future outlook of the research directions and key developments of spinel Li4Ti5O12 anode and olivine LiFePO4 cathode are proposed from view of scientific project and industrial demand. The practical attempt is to investigate the effective combination of Li4Ti5O12 anode and LiFePO4 cathode to design the leading nano-battery of Li4Ti5O12/LiFePO4 with a high degree of safety, long cycle life and rapid charge for various potential applications. In addition, the prospect of newly development of graphene-Li4Ti5O12 anode and graphene-LiFePO4 cathode hybrid nanocomposite materials for next-generation of green and sustainable lithium-ion batteries is also presented in the last Chapter
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