1,721,002 research outputs found
Towards Realization of an Innovative Li-Ion Battery: Materials Optimization and System Up-Scalable Solutions
No full textThe optimisation of existing chemistries by the introduction of environmentally friendly materials and the simplification of the device production process are intriguing challenges to promote the future widespread diffusion of LIBs. Moreover, the recent development of the next-generation electronic devices promoted a new research field for the modification of the current systems into light, flexible and/or micro-sized device. The enhancement of mechanical properties through the introduction of flexible electrodes will enable LIBs to be embedded into various functional systems in a wide range of innovative products such as smart cards, displays and implantable medical devices. Moreover, the optimisation of the electrolyte by moving towards an all-solid-state configuration will offer adaptability to various designs and stressful mechanical handling, as well as enhance cell safety and reliability. During the three years of the Ph.D. course, the attention was focused on the optimisation of innovative materials for Li-ion batteries as well as the development of easily up-scalable procedures for the production of electrodes and polymer electrolytes. The basic idea was to start from eco-friendly materials to develop simple, low-cost and easily adaptable processes in order to propose innovative solutions for LIBs with a wide range of possible applications. Moreover, during my experimental activities, I considered the performances and the cycling stability of Li-ion batteries, by studying the mechanisms related to the capacity fade of lab-scale batteries and also by analysing commercial Li-ion batteries for automotive application. The results of the research work are presented in this thesis (Chapters 4-7) following an introductory section that provides the general information needed to follow the discussions (Chapters 1-3). The experimental research work presented in Chapter IV was carried out in collaboration with the Laboratory of Pulp and Paper Science and Graphic Arts (LGP2) in Grenoble (France). A well-known natural material such as cellulose was exploited for the production of innovative low-cost and easily recyclable electrodes for Li-ion batteries. A simple aqueous filtration process, based on a well-known industrialised paper-making technology, was developed and the electrodes (graphite-based anodes and LiFePO4-based cathodes) produced and partly characterized in Grenoble by Dr. Lara Jabbour were electrochemically studied in our Labs in Politecnico di Torino. In particular, cellulose fibres (FBs) were used as natural binder for the production of paper-like electrodes obtained without addition of any synthetic binder and/or solvent and showing electrochemical performance comparable to those produced with the same active materials by a standard process. In Chapter V, results are reported regarding a newly developed procedure where a methacrylic-based polymer electrolyte is directly formed in situ at the interface with the electrodes. Exploiting the versatile nature of UV-induced free-radical photo-polymerisation, novel ready-to-use multiphase electrode/electrolyte composites (MEEC) were developed in which the electrode is conformally coated by the polymer electrolyte. This "one-shot" process was successfully applied to enhance the cycling performances of two nanostructured materials conceived for microbattery application, such as Cu2O (in collaboration with CSHR@Polito IIT research institute in Torino) and V2O5 (in collaboration with Prof. Mustarelli's group in University of Pavia), prepared in the form of thin films and proposed respectively as anode and cathode. The proposed one-shot process, thanks to the intimate interfacial contact between electrodes surface and electrolyte obtained by in situ process, induced a huge effect of stabilization thus improving the cycling stability of both the nanostructures. All along Chapter VI, the problems related to the assembling of complete Li-ion cells, starting from two well performing electrodes, are progressively discussed and valuable solutions are proposed. A strong capacity fade was initially found, thus the possible causes were studied also considering the failure mechanisms proposed in the literature. Several measures were adopted to improve the cycling stability, considering the effect of all the different cell components as well as the effects of both charging protocol and cell apparatus. Moreover, due the knowhow progressively achieved on the intimate characteristics of complete Li-ion cells and their assembly, even thanks to a three months stage at ENEA Casaccia Research Centre of Rome, the installation of a 10 m2 dry room was personally followed at our Electrochemistry Research Group Labs in Politecnico di Torino and the results obtained are presented in the same Chapter VI. These results include the realisation of an all-paper Li-ion battery with the cellulose-based electrodes and paper hand-sheets as separator. Finally, the cycling stability and the failure prediction issue was studied for a 53 Ah commercial battery. The results obtained, by means of different standard reference tests, are reported in Chapter VII. The commercial battery was also disassembled in the controlled atmosphere of an Ar-filled dry box in order to study the system structure and characterise the various components. A testing protocol was personally developed and the results obtained allowed to evaluate the commercial battery based on the performances requested for HEV and EV application. In particular, an easy measure of the internal resistance was developed, by opportunely modulating the measured parameters, and the obtained results were found to be very useful in directly predicting the cell failure which is fundamental in practical applicatio
Inverse parameter determination in the development of an optimized lithium iron phosphate - Graphite battery discharge model
No full textBattery models are riddled with incongruous values of parameters considered for validation. In this work, thermally coupled electrochemical model of the pouch is developed and discharge tests on a LiFePO4 pouch cell at different discharge rates are used to optimize the LiFePO4 battery model by determining parameters for which there is no consensus in literature. A discussion on parameter determination, selection and comparison with literature values has been made. The electrochemical model is a P2D model, while the thermal model considers heat transfer in 3D. It is seen that even with no phase change considered for LiFePO4 electrode, the model is able to simulate the discharge curves over a wide range of discharge rates with a single set of parameters provided a dependency of the radius of the LiFePO4 electrode on discharge rate. The approach of using a current dependent radius is shown to be equivalent to using a current dependent diffusion coefficient. Both these modelling approaches are a representation of the particle size distribution in the electrode. Additionally, the model has been thermally validated, which increases the confidence level in the selection of values of parameters
Siloxane Diacrylate-based All-Solid Polymer Electrolytes for Lithium Batteries
Full text linkFully solid polymer electrolyte (SPE) membranes were prepared by UV induced free radical polymerisation (UV-curing) of acrylated siloxane polyalkyleneoxide copolymers in the presence of different lithium salts. The main chain contains locally mobile segments of ethoxy groups as part of the copolymer, and these moieties can provide coordination sites for the mobility of Li+ ions. The materials are produced through a solvent free procedure, and used as ion-conducting media as well as a separator in high temperature lithium-based batteries. The preparation process is easy, simple and versatile. The final product obtained demonstrates good mechanical integrity due to the highly cross-linked nature of the polymer network, and wide thermal stability. The membranes are also soft, easy to manage and transparent. They also exhibit acceptable ionic conductivity and wide electrochemical stability windo
A MODELLING APPROACH TO UNDERSTAND CHARGE DISCHARGE DIFFERENCES IN THERMAL BEHAVIOUR IN LITHIUM IRON PHOSPHATE GRAPHITE BATTERY
No full textLithium iron phosphate is a promising positive electrode material. It shows apparent asymmetry between charge and discharge affecting not only the electrochemical but also the thermal behaviour. Physics based models for batteries are usually parameterized for discharge behaviour, which can lead to inaccuracies in prediction of battery behaviour during charging or dynamic conditions, especially in the case of this battery chemistry. This has consequences for battery modelling and safety. A pseudo 2D electrochemical – 3D thermal model is parameterized for charging using experimental data. Substantial differences in parameters between charge and discharge are seen in the validated model. The model is used to quantify the thermal differences during charging and discharging and separate the contribution of the different battery layers. Reversible heat losses are seen to be the main cause for the difference between charge and discharge while graphite electrode are seen to have a much higher heat contribution compared to lithium iron phosphate electrode
Polymer Electrolytes for Green, Safe and Robust All-Solid Na-ion Batteries
No full textThe modern life style that we are enjoying depends on energy storage systems in which the role of Li-ion batteries (LiBs) is peerless. However, state-of-the-art LiBs are approaching the verge of possible technological imagination, particularly in terms of energy density. Some researchers argue that next-gen secondary batteries should switch to heavier elements such as sodium. Indeed, when it comes to gigantic energy storage systems for the electricity grid and/or other non-portable applications where size does not matter, Na-based systems can be an effective and intelligent choice. Nevertheless, research on NiBs' components is at the very beginning, particularly for what concerns the electrolyte, where standard organic liquid electrolytes are mainly used. Unfortunately, their flammable nature jeopardizes the safety of these large scale systems, which in case of failure may lead to thermal runaways. In this work, an overview is provided on quasi-solid polymer electrolytes specifically conceived and developed for Na-ion secondary cells, based on polyethylene oxide (PEO), acrylates/methacrylates and/or mixtures thereof. Eventually, pyranose ring based natural additives and/or low volatile plasticizers are added along with supporting sodium salts to improve specifically defined characteristics. All the sample are thoroughly characterized in the physic-chemical and electrochemical viewpoint. The performances in lab scale devices are presented, evaluated by means of cycling voltammetry and galvanostatic charge/discharge cycling exploiting different electrode materials (prepred by water-based procedures exploiting carboxymethylcellulose as binder). We also present preliminary aging resistance tests of the devices inherited by different solid electrolytes, as well as the cell response upon various temperatures and current regimes. So far, work on Na-ion polymer batteries for moderate temperature application is at an early stage, only lab-scale small battery cells are demonstrated. Nevertheless, with the appropriate choice and development of electrode/electrolyte materials, the overall characteristics of the SPEs here developed postulates the possibility of their effective implementation in safe, durable and high energy density secondary Na-based polymer devices conceived for green-grid storage and operating at ambient and/or sub-ambient temperature
Novel multipurpose polymer electrolytes for smart and efficient energy power sources
No full textPolymer electrolytes represent the ultimate in terms of desirable properties of energy storage/conversion devices, as they can offer an all-solid-state construction, a wide variety of shapes and sizes, light-weight, low costs, high energy density and safety. Here we present our recent results concerning a novel strategy for preparing efficient polymer membranes which are successfully demonstrated as suitable electrolytes for several energy conversion and storage devices (i.e., Li- and Na-based batteries and DSSCs). Highly ionic conducting polymer electrolytes containing PEO-based functionalities and different components (e.g., Li/Na salts, RTILs, natural biosourced and cellulosic fillers) are successfully prepared via a rapid process and, directly or subsequently, cross-linked via UV irradiation (patent pending, PCT/IT2014/000008). All the prepared materials are thoroughly characterised in terms of their physical, chemical and morphological properties and tested for their electrochemical performances and durability. The UV-curing process on such materials led to the production of elastic and resistant amorphous macromolecular networks. Noticeably increased ionic conductivities are registered (10-3 S cm-1 at RT), along with very stable interfacial and storage stability and wide electrochemical stability windows. The different lab-scale solid-state devices show remarkable performances even at ambient temperature, at the level of those using liquid electrolytes, respect to which demonstrate much greater durability and safety. The obtained findings demonstrate a new, easy and low cost approach to fabricate and tailor-make polymer electrolytes with highly promising prospects for the next generation of advanced flexible energy production and storage device
Facile fabrication of cuprous oxide nanocomposite anode films for flexible Li-ion batteries via thermal oxidation
No full textIn the present work, nanostructured Cu2O films are directly grown from a Cu metal foil by means of a rapid thermal oxidation process. The structural characteristics of the films are investigated by field emission scanning electron microscopy, X-ray diffraction and attenuated total reflectance Fourier-transformed infrared spectroscopy. The electrochemical behaviour is investigated in both lithium (liquid electrolyte) and all-solid lithium polymer cells. At a discharge/charge rate of C/5, the films can provide a specific capacity greater than 220 mAh g−1 in the all-solid configuration, with excellent cycling stability and capacity retention after prolonged cycling. High surface area, short diffusion path and good conduction of the Cu2O films are considered to be responsible for the good electrochemical performance, along with the use of the polymeric electrolyte which is directly formed in situ on the electrode film surface. The present findings can provide a new and easy approach to fabricate nanocomposite films with interesting performance as negative electrode particularly for the next generation of flexible all-solid-state Li-ion microbatteries
Towards large-scale energy storage systems: how industrially-scalable polymer electrolytes can be conceived
No full textThe modern life style that we are enjoying depends on energy storage systems in which the role of Li-ion batteries (LiBs) is peerless. However, state-of-the-art LiBs are approaching the verge of possible technological imagination, particularly in terms of energy density. Some researchers argue that next-gen secondary batteries should switch to heavier elements such as sodium. Indeed, when it comes to gigantic energy storage systems for the electricity grid and/or other non-portable applications where size does not matter, Na-based systems can be an effective and intelligent choice. Nevertheless, research on NiBs’ components is at the very beginning, particularly for what concerns the electrolyte, where standard organic liquid electrolytes are mainly used. Unfortunately, their flammable nature jeopardizes the safety of these large scale systems, which in case of failure may lead to thermal runaways.
In this work, an overview is provided on quasi-solid polymer electrolytes specifically conceived and developed for Na-ion secondary cells, based on polyethylene oxide (PEO), acrylates/methacrylates and/or mixtures thereof. Eventually, pyranose ring based natural additives and/or low volatile plasticizers are added along with supporting sodium salts to improve specifically defined characteristics. All the sample are thoroughly characterized in the physic-chemical and electrochemical viewpoint. The performances in lab scale devices are presented, evaluated by means of cycling voltammetry and galvanostatic charge/discharge cycling exploiting different electrode materials (prepared by water-based and industrially-scalable procedures exploiting carboxymethylcellulose as binder). We also present preliminary aging resistance tests of the devices inherited by different solid electrolytes, as well as the cell response upon various temperatures and current regimes.
So far, work on Na-ion polymer batteries for moderate temperature application is at an early stage, only lab-scale small battery cells are demonstrated. Nevertheless, with the appropriate choice and development of electrode/electrolyte materials, the overall characteristics of the materials here developed postulates the possibility of their effective implementation in safe, durable and high energy density secondary Na-based polymer devices conceived for green-grid storage and operating at ambient and/or sub-ambient temperatures
Cellulose-based novel hybrid polymer electrolytes for green and efficient Na-ion batteries
No full textIn the present work, a novel pyranose ring laden polymer electrolyte is proposed for all solid Na-ion secondary cells that can operate at moderate temperatures. The prepared fully solid polymer electrolyte film is based on a classic polyethylene oxide (PEO) backbone, homogeneously blended with sodium carboxymethyl cellulose (Na-CMC) and sodium perchlorate. The favourable use of Na-CMC as electrode binder as well as electrolyte additive is evaluated, which would enhance the pathways for forming an optimised electrode/electrolyte interface. The promising prospects of the newly elaborated hybrid electrolyte are investigated by means of galvanostatic charge/discharge cycling in lab-scale cell with TiO2-based or NaFePO4-based working electrode
- …
