Indiana University-Purdue University Indianapolis (IUPUI) / Lithium-Ion Batteries (Li-ion batteries or LIBs) have been extensively used in a wide variety of industrial applications and consumer electronics. Additive Manufacturing (AM) or 3D printing (3DP) techniques have evolved to allow the fabrication of complex structures of various compositions in a wide range of applications. The objective of the thesis is to investigate the application of 3DP to fabricate a LIB, using a modified process from the literature [1]. The ultimate goal is to improve the electrochemical performances of LIBs while maintaining design flexibility with a 3D printed 3D architecture. In this research, both the cathode and anode in the form of specifically formulated slurry were extruded into filaments using a high-temperature pellet-based extruder. Specifically, filament composites made of graphite and Polylactic Acid (PLA) were fabricated and tested to produce anodes. Investigations on two other types of PLA-based filament composites respectively made of Lithium Manganese Oxide (LMO) and Lithium Nickel Manganese Cobalt Oxide (NMC) were also conducted to produce cathodes. Several filaments with various materials ratios were formulated in order to optimize printability and battery capacities. Finally, flat battery electrode disks similar to conventional electrodes were fabricated using the fused deposition modeling (FDM) process and assembled in half-cells and full cells. Finally, the electrochemical properties of half cells and full cells were characterized. Additionally, in parallel to the experiment, a 1-D finite element (FE) model was developed to understand the electrochemical performance of the anode half-cells made of graphite. Moreover, a simplified machine learning (ML) model through the Gaussian Process Regression was used to predict the voltage of a certain half-cell based on input parameters such as charge and discharge capacity. The results of this research showed that 3D printing technology is capable to fabricate LIBs. For the 3D printed LIB, cells have improved electrochemical properties by increasing the material content of active materials (i.e., graphite, LMO, and NMC) within the PLA matrix, along with incorporating a plasticizer material. The FE model of graphite anode showed a similar trend of discharge curve as the experiment. Finally, the ML model demonstrated a reasonably good prediction of charge and discharge voltages.

The increasing demand for Li-ion batteries requires moving away from cobalt-containing cathode materials because Co is scarce, expensive, and geographically strongly localized. Co-free Ni-rich cathodes and their derivatives are, in principle, an excellent alternative, as Ni is more abundant, less expensive, and environmentally friendlier than Co. LiNiO₂, the parent of Ni-rich cathode materials, is structurally identical and chemically similar to LiCoO₂, offering almost the same theoretical capacity. However, LiNiO₂ and related materials often degrade rapidly during electrochemical cycling, with degradation modes including Li/Ni mixing, stacking faults, and surface reconstructions, making them unsuitable for battery applications. In this thesis, we used first-principles calculations to investigate the origin of Li/Ni mixing and stacking-fault formation, and we explored if entropy stabilization can be exploited to stabilize cobalt-free cathode materials. At half Li concentration, layered Li₀.₅NiO₂ is metastable, and the ground state is the spinel phase. The phase transformation from the layered to the spinel structure involves Ni migration and leads to Li/Ni mixing but only occurs at high temperatures. To better understand Li/Ni mixing in LiNiO₂, we determined the layered-to-spinel transformation in Li₀.₅NiO₂. We found the mechanism determined by electronic-structure symmetries, leading to a different route and intermediates from other well-studied lithium transition-metal oxides, such as Li₀.₅MnO₂. One important complication in LiNiO₂ is that it forms stoichiometry defects in which Ni atoms replace Li atoms, yielding off-stoichiometric Li₁₋zNi₁₊zO₂. Li/Ni mixing, a process in which Li and Ni interchange sites, can occur during synthesis or electrochemical cycling, and it reduces the capacity by impeding the intercalation of Li ions during battery operation. We unraveled the Li/Ni-mixing mechanism and explained the impact of off-stoichiometry on Li/Ni mixing from an electronic and geometric perspective. We also determined the role of the Li concentration and the Ni oxidation state on the driving force for Li/Ni cation mixing. At low Li contents, stacking faults can form in LiNiO₂, a process in which Ni layers glide relative to each other. These planar glides can alter the particle morphology, create new surfaces, and accelerate degradation. Stacking faults form unfavorable sites for Li, which impedes intercalation and lowers the capacity. We investigated the role of off-stoichiometry in planar glides and Ni migration in the presence of stacking faults. We determined how the distribution of Ni across the Li layers affects planar glides and explained how Li/Ni mixing may prevent the formation of stacking faults. Finally, to provide alternatives to the Ni-rich family of Co-free cathodes, we investigated if entropic stabilization can be exploited to stabilize layered cathode materials and prevent their degradation. We computationally assessed equimolar layered high-entropy oxides, a new class of layered materials that exhibits substitutional disorder in the transition-metal layer. We found that the general strategy of entropic stabilization is viable and identified four candidate compositions with good predicted energy density as a starting point for further studies. The research conducted as part of this thesis advances the understanding of degradation in Co-free cathode materials and identifies a direction for developing stable Co-free layered cathode materials with high energy density.

Yes / Ultrasmall SnO2 nanocrystals as anode materials for lithium-ion batteries (LIBs) have been synthesized by bubbling an oxidizing gas into hot surfactant solutions containing Sn-oleate complexes. Annealing of the particles in N2 carbonifies the densely packed surface capping ligands resulting in carbon encapsulated SnO2 nanoparticles (SnO2/C). Carbon encapsulation can effectively buffer the volume changes during the lithiation/delithiation process. The assembled SnO2/C thus deliver extraordinarily high reversible capacity of 908 mA.h.g(-1) at 0.5 C as well as excellent cycling performance in the LIBs. This method demonstrates the great potential of SnO2/C nanoparticles for the design of high power LIBs. / National Natural Science Foundation of China (21103039), Anhui Province Natural Funds for Distinguished Young Scientists, https://bradscholars.brad.ac.uk/browse?order=ASC&rpp=20&sort_by=-1&etal=-1&offset=6150&type=authorResearch Fund for the Doctoral Program of Higher Education of China (20110111120008), Beijing National Laboratory for Molecular Sciences (BNLMS), and Deutsche Forschungsgemeinschaft Grant (DFG): H1113/3-5. C.Y. acknowledges the support from the “Thousand Talents Program” and the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD).

The experimental data presented in this thesis demonstrates the preparation and characterization of TiO₂ polymorphs (anatase and TiO₂-(B)) in the form of nanomaterials. The reduced dimension of the nanomaterials amplifies the properties compared to the bulk TiO₂; however, this is often at the cost of the tapped density. The anatase nanomaterials with pseudo-spherical nanoparticles of 5 to 70 nm in size were synthesized and their volumetric capacities compared. Both the gravimetric and volumetric capacity is higher for nanoparticles of less than 10 nm in diameter. The volumetric capacity is also dependent on the agglomerate size. For example at the very lowest rate of 50 mA/g, the agglomerate larger than 50 μm leads to the highest volumetric capacity; while at a rate higher than 600 mA/g the smaller agglomerates are preferred. Following this, we reported the synthesis of mesoporous TiO₂-(B) with the particle size along the [010] direction ranged from 3 to 300 nm, and the pore size increasing from 2.5 to more than 20 nm. By comparing the volumetric capacity of these TiO₂-(B) mesoporous materials, the optimal morphology for an improved volumetric capacity was identified. TiO₂-(B) with a novel microstructure was synthesized via a hydrothermal reaction. The primary particles are brick-like in shape with the shorter dimensions (4 - 10 nm) in parallel to the [100] and [010] directions, facilitating the Li⁺ ion diffusion in the particle. This TiO₂-(B) offers a superior rate capability compared to many other titanate anodes reported in the literature. In addition, it exhibits a great cycleability due to its exceptional structural stability and minimal SEI layer. Surface treatments could reduce its first cycle irreversible capacity to ~10%.

Indiana University-Purdue University Indianapolis (IUPUI) / Due to the drastic increase in the cost of fossil fuels and other environmental issues, the demand for energy and its storage has risen globally. Rather than being dependent on intermittent energy sources like wind and solar energy, focus has been on alternative energy sources. To eliminate the need for fossil fuels, advances are being made to provide energy for hybrid electric vehicles (HEV), plug-in hybrid vehicles (PHEV) and pure electric vehicles (EV) thus providing scope for much greener environment. Hence, focus has been on development in lithium ion batteries to provide with materials that have high energy density and voltage. Ortho olivine lithium transitional metals are known to be abundant and inexpensive; these compounds are less noxious than other cathode materials. Advancement in research is being done in finding iron and manganese compounds as cathode materials for advanced technologies. However, Lithium manganese phosphates are known to suffer with poor electrochemical performances due the manganese dissolution in the organic liquid electrolyte due to Jahn-Teller Lattice distortion. This problem was tried to endorse in this thesis. In the second chapter by synthesizing nano sized cathode particles with good electronic conductivity, good performance was achieved. In the third chapter additive olivine cathode was synthesized my modified sol gel process. A wt. % of TMSP was added as an additive in the organic liquid electrolyte. By comparing the properties between the two kinds of electrolytes it was observed that by the addition of the additive in the organic electrolyte good electrochemical properties could be achieved hindering the Mn dissolution in the electrolyte. In the final chapter, a composite solid electrolyte was fabricated by using NASICON-type glass ceramic of Lithium aluminum titanium phosphate (LATP) with organic binder of Polyethylene oxide. The flexible solid electrolyte exhibited good ionic conductivity. An all solid state cell was fabricated using the composite solid electrolyte using LiMn2O4 as the symmetric electrodes. At different pressures, the performance of the solid state cell was studied.

Indiana University-Purdue University Indianapolis (IUPUI) / Heat generation is a major safety concern in the design and development of Li ion batteries (LIBs) for large scale applications, such as electric vehicles. The total heat generation in LIBs includes entropic heat, enthalpy, reaction heat, and heat of mixing. The main objective of this study is to investigate the influence of heat of mixing on the LIBs and to understand whether it is necessary to consider the heat of mixing during the design and development of LIBs. In the previous research, Thomas and Newman derived methods to compute heat of mixing in LIB cells. Their results show that the heat of mixing cannot be neglected in comparison with the other heat sources at 2 C rate. In this study, the heat of mixing in different materials, porosity, particle sizes, and charging/discharging rate was investigated. A COMSOL mathematical model was built to simulate the heat generation of LIBs. The LIB model was based on Newman’s model. LiMn2O4 and LiCoO2 were applied as the cathode materials, and LiC6 was applied as the anode material. The results of heat of mixing were compared with the other heat sources to investigate the weight of heat of mixing in the total heat generation. The heat of mixing in cathode is smaller than the heat of mixing in anode, because of the diffusivity of LiCoO2 is 1 ×10-13 m2/s, which is larger than LiC6's diffusivity 2.52 × 10-14 m2/s. In the comparison, the heat of mixing is not as much as the irreversible heat and reversible heat, but it still cannot be neglected. Finally, a special situation will be discussed, which is the heat of mixing under the relaxation status. For instance, after the drivers turn off their vehicles, the entropy, ix enthalpy and reaction heat in LIBs will stop generating, but the heat will still be generated due to the release of heat of mixing. Therefore, it is meaningful to investigate to see if this process has significant influence on the safety and cycle life of LIBs.

Crystalline polymer/salt complexes can conduct, in contrast to the view held for 30 years. The alpha-phase of the crystalline poly(ethylene oxide)₆:LiPF₆ is composed of tunnels formed from pairs of (CH₂-CH₂-O)ₓ chains, within which the Li⁺ ions reside and along which the latter migrate.¹ When a polydispersed polymer is used, the tunnels are composed of 2 strands, each built from a string of PEO chains of varying length. It has been suggested that the number and the arrangement of the chain ends within the tunnels affects the ionic conductivity.² Using polymers with uniform chain length is important if we are to understand the conduction mechanism since monodispersity results in the chain ends occurring at regular distances along the tunnels and imposes a coincidence of the chain ends between the two strands.² Since each Li⁺ is coordinated by 6 ether oxygens (3 oxygens from each of the two polymeric strands forming a tunnel), monodispersed PEOs with the number of ether oxygen being a multiple of 3 (NO = 3n) can form either “all-ideal” or “all-broken” coordination environments at the end of each tunnel, while for both NO = 3n-1 and NO = 3n+1 complexes, both “ideal” and “broken” coordinations must occur throughout the structure. A synthetic procedure has been developed and a series of 6 consecutive (increment of EO unit) monodispersed molecular weight PEOs have been synthesised. The synthesis involves one end protection of a high purity glycol, functionalisation of the other end, ether coupling reaction (Williamson's type ether synthesis³), deprotection and reiteration of ether coupling. The parameters of the process and purification methods have been strictly controlled to ensure unprecedented level of monodispersity for all synthesised samples. Thus obtained high purity polymers have been used to study the influence of the individual chain length on the structure and conductivity of the crystalline complexes with LiPF₆. The results support the previously suggested model of the chain-ends arrangement in the crystalline complexes prepared with monodispersed PEO² over a range of consecutive chain lengths. The synthesised complexes constitute a series of test samples for establishing detailed mechanism of ionic conductivity. Such series of monodispersed crystalline complexes have been studied and characterised here (PXRD, DSC, AC impedance) for the first time. References: 1. G. S. MacGlashan, Y. G. Andreev, P. G. Bruce, Structure of the polymer electrolyte poly(ethylene oxide)₆:LiAsF₆. Nature, 1999, 398(6730): p. 792-794. 2. E. Staunton, Y. G. Andreev, P. G. Bruce, Factors influencing the conductivity of crystalline polymer electrolytes. Faraday Discussions, 2007, 134: p. 143-156. 3. A. Williamson, Theory of Aetherification. Philosophical Magazine, 1850, 37: p. 350-356.

Thesis (M.Sc. (Physics)) -- University of Limpopo, 2021 / The stead-fast demand for sustainable lithium-ion batteries (LIB) with competitive electrochemical properties, safety, reduced costs, and long-life cycle, calls for intensive efforts towards the development of new battery cathode materials. The layered transition metal oxides formulated LiMO2 (M: Mn, Ni and Co) have attracted considerable attention due to their capability to optimize the discharge capacity, cycling rate, electrochemical stability and lifetime. The transition metals Mn, Ni and Co (NMC) have been reported to contribute towards enhancement of the performance of NMC based lithium-ion batteries. In this work, the electronic properties of transition metal oxides LiMO2 (M: Mn, Ni and Co) as individual crystal structures are studied using density functional theory (DFT+U) in the local density and generalized gradient approximation (LDA and GGA). The Hubbard U values together with the low spin transition metal in 3+ charge state (Mn3+, Ni3+ and Co3+) predicts the electrical conductivity of the materials. The conductivity is associated predominantly with 3d states of the transition metals (Mn, Ni and Co) and 2d character in oxygen. The LiNiO2 material is high in conductivity, while both LiMnO2 and LiCoO2 are low in electrical conductivity. All independent elastic constants satisfy the mechanical stability criterion of orthorhombic materials implying stability of the materials. However, the phonon dispersion curves display imaginary vibration along high symmetry direction for LiCoO2. The heats of formations predict that the LiNiO2 is the most thermodynamically stable material while the LiMnO2 is the least thermodynamically stable material. The derived interatomic potentials produced NiO and CoO structures with a difference of less than 1% and 9% respectively, from the experimental structures. The structures were melted at temperatures close to their experimental values from molecular dynamics. The radial distribution curves and Nano architectures presented the melting point of NiO and CoO at 2250K and 2000K respectively. All independent elastic constants satisfy the mechanical stability criterion of cubic materials implying stability of the materials. The high electrical conductivity and thermodynamic favourability LiNiO2 suggests that the material can be the most recommendable material as a cathode material and further improved through doping. This will add the overall enhancement of the electrochemical performance while stabilizing structural stability of the cathode material in high energy density Li-ion batteries. / National Research Foundation (NRF)

Temperature is one of the most important parameters for the performance, safety, and aging of lithium-ion batteries and has been linked to all main barriers for widespread commercial success of electric vehicles. The aim of this thesis is to highlight the importance of temperature effects, as well as to provide engineering tools to study these. The mass transport phenomena of the electrolyte with LiPF6  in EC:DEC was fully characterized in between 10 and 40 °C and 0.5 and 1.5 M, and all mass transport properties were found to vary strongly with temperature. A superconcentrated electrolyte with LiTFSI in ACN was also fully characterized at 25 °C, and was found to have very different properties and interactions compared to LiPF6  in EC:DEC. The benefit of using the benchmarking method termed electrolyte masstransport resistivity (EMTR) compared to using only ionic conductivity was illustrated for several systems, including organic liquids, ionic liquids, solid polymers, gelled polymers, and electrolytes containing flame-retardant additives. TPP, a flame-retardant electrolyte additive, was evaluated using a HEV load cycle and was found to be unsuitable for high-power applications such as HEVs. A large-format commercial battery cell with a thermal management system was characterized using both experiments and a coupled electrochemical and thermal model during a PHEV load cycle. Different thermal management strategies were evaluated using the model, but were found to have only minor effects since the limitations lie in the heat transfer of the jellyroll. / Temperatur är en av de viktigaste parametrarna gällande ett litiumjonbatteris prestanda, säkerhet och åldring och har länkats till de främsta barriärerna för en storskalig kommersiell framgång för elbilar. Syftet med den här avhandlingen är att belysa vikten av temperatureffekter, samt att bidra med ingenjörsverktyg att studera dessa. Masstransporten för elektrolyten LiPF6  i EC:DEC karakteriserades fullständigt i temperaturintervallet 10 till 40 °C för LiPF6-koncentrationer på 0.5 till 1.5 M. Alla masstransport-egenskaper fanns variera kraftigt med temperaturen. Den superkoncentrerade elektrolyten med LiTFSI i ACN karakteriserades även den fullständigt vid 25 °C. Dess egenskaper och interaktioner fanns vara väldigt annorlunda jämfört med LiPF6  i EC:DEC. Fördelen med att använda utvärderingsmetoden elektrolytmasstransportresistivitet (EMTR) jämfört med att endast mäta konduktivitet illustrerades för flertalet system, däribland organiska vätskor, jonvätskor, fasta polymerer, gellade polymerer, och elektrolyter med flamskyddsadditiv. Flamskyddsadditivet TPP utvärderades med en hybridbils-lastcykel och fanns vara olämplig för högeffektsapplikationer, som hybridbilar. Ett kommersiellt storformatsbatteri med ett temperatur-kontrollsystem karakteriserades med b.de experiment och en kopplad termisk och elektrokemisk modell under en lastcykel utvecklad för plug-inhybridbilar. Olika strategier för kontroll av temperaturen utvärderades, men fanns bara ha liten inverkan på batteriets temperatur då begränsningarna för värmetransport ligger i elektrodrullen, och inte i batteriets metalliska ytterhölje. / <p>QC 20150522</p> / Swedish Hybrid Vehicle Center

This thesis investigates several approaches to the development of high-performance batteries. A general background to the field and an introduction to the experimental methods used are given in Chapters 1 and 2 respectively. Chapter 3 presents a study of ordered and disordered LiNi₀.₅Mn₁.₅O₄ materials produced using an optimised resorcinol-formaldehyde gel (R-F gel) synthetic technique. Both materials exhibited good electrochemical properties and minimal side reaction with the electrolyte. Structural analyses of the materials in various states of discharge and charge were undertaken, and from these the charge / discharge processes were elucidated. In chapter 4 R-F gel synthesised Li(Ni₁/₃Mn₁/₃Co₁/₃)O₂ is studied and found to exhibit a high degree of structural stability on cycling, as well as excellent capacity, cyclability and rate capability. Photoelectron spectroscopy studies revealed that the R-F gel derived particles have highly stable surfaces. A discussion of the results and their significance, with particular regard to the outstanding electrochemical performance observed, is also presented. Chapter 5 sets out an investigation into the nature of R-F gel synthesised 0.5Li₂MnO₃:0.5LiNi₁/₃Mn₁/₃Co₁/₃O₂. The electrochemical data revealed that, after an initial activation stage, the R-F gel derived material exhibited a high capacity, good cyclability and exceptional rate capability. This chapter also considers some initial structural investigations and the electrochemical processes occurring on charge. In chapter 6 the use of ether-based electrolytes, combined with various cathode materials, in lithium-oxygen batteries is examined. The formation of decomposition products was observed, and a scheme suggesting probable reaction pathways is given. It was noted that significant quantities of the desired discharge product, lithium peroxide, were formed on the 1st cycle discharge, implying some electrolyte / cathode combinations do demonstrate a degree of stability. A summary of the results and a discussion of their significance are also included.