The global energy transition, involving the widespread adoption of electric vehicles and grid-scale energy storage, demands energy storage devices made up of abundant, inexpensive minerals. For this to be achieved, the large Co content in conventional Li-ion battery cathodes (e.g., LiCoO₂) must be replaced while also maintaining or improving the energy density of the battery. Alternative low-Co and Co-free materials (e.g., layered LiNixMnyCozO₂, spinel LiNi₀.₅Mn₁.₅O₄, and olivine LiFePO₄) are promising alternatives due to their theoretically higher energy densities or improved safety properties from the industry standards. However, in practice, these materials exhibit both bulk and interfacial instabilities that limit their practical energy density and cycle lifetime. It is well known that reactions between the delithiated (charged) cathode surface with the electrolyte generates electrolyte decomposition species that form an interphase layer called the cathode electrolyte interphase (CEI), where such reactions are concomitant with a crystallographic reconstruction of the surface of the bulk material. The CEI is air sensitive, disordered, nanometers thick and evolves as a function of state of charge and cycle number, making it difficult to fully understand its composition and effect on device performance. The dynamic nature of the CEI necessitates development of chemical characterization tools that can analyze surface reactivity during battery operation. Commercial cathode films are also composites including not just the electrochemically active material but also conductive carbon additive and polymer binder, meaning we need spatially resolved tools to study CEI composition across the film to isolate reactivity by film component. In this thesis, we have developed and applied spatially resolved and operando characterization tools to study the CEI of low-Co and Co-free cathode materials and use these data to pinpoint the degradation reactions at play during battery operation. In the first chapter, we introduce the three most prevalent types of cathode materials (layered, spinels, and olivines) used in Li-ion batteries. We then highlight recent progress in the analytical characterization tools that have been developed to elucidate CEI composition, spatial arrangement, and formation pathways during battery operation while discussing the difference in surface reactivity between each cathode active material as revealed by these techniques. Major findings from my own thesis work, detailed in following chapters, are discussed in parallel within this broader context. Finally, equipped with a deeper understanding of the CEI and the processes that lead to its formation, we discuss what remains to be discovered and enabled by optimizing these complex interfaces. The second chapter investigates the composition of the CEI formed by the Li-rich layered cathode material, Li₂RuO₃, to better understand performance decline in this class of materials. To bridge this gap in understanding, we use solid-state NMR (SSNMR) and surface-sensitive dynamic nuclear polarization (DNP) NMR to achieve high resolution compositional assignment of the CEI. We show that the CEI that forms on Li₂RuO₃, when cycled in carbonate-containing electrolytes, is similar to the solid electrolyte interphase (SEI) that has been observed on anode materials, containing components such as polyethylene oxide (PEO) structures, Li acetate, carbonates, and LiF. The CEI composition deposited on the cathode surface on charge is chemically distinct from that observed upon discharge, supporting the notion of crosstalk between the SEI and the CEI, with Li+-coordinating species leaving the CEI during delithiation. We use electrochemical impedance spectroscopy (EIS) to assess the impedance of the CEI on Li₂RuO₃ as a function of state of charge in connection with the migration of CEI species as identified with NMR. Migration of the outer CEI combined with the accumulation of poor ionic conducting components on the static inner CEI may contribute to the loss of performance over time in Li-excess cathode materials. This work demonstrates the utility of SSNMR for studying electrolyte decomposition at the cathode-electrolyte interface which is then applied in the following chapter to more commercially relevant materials. In the third chapter, we study the CEI and surface reactivity of the Ni-rich layered material LiNi₀.₈Mn₀.₁Co₀.₁O₂ (NMC811). The high specific capacities of Ni-rich transition-metal oxides have garnered immense interest for improving the energy density of Li-ion batteries. However, Ni-rich cathodes suffer from interfacial instabilities that lead to formation of electrochemically inactive phases at the cathode particle surface as well as the formation of a CEI layer on the composite surface during electrochemical cycling. We use a combination of ex situ SSNMR spectroscopy and X-ray photoemission electron microscopy (XPEEM) to provide chemical and spatial information, on the nanometer length scale, on the CEI deposited on NMC811 composite cathode films. XPEEM elemental maps offer insight into the lateral arrangement of the electrolyte decomposition products that comprise the CEI and paramagnetic interactions (assessed with electron paramagnetic resonance (EPR) and relaxation measurements) in 13C SSNMR provide information on the radial arrangement of the CEI from the NMC811 particles outward. Using this approach, we find that LiF, Li₂CO₃, and carboxy-containing structures are directly appended to NMC811 active particles, whereas soluble species detected during in situ 1H and 19F solution NMR experiments (e.g., alkyl carbonates, HF, and vinyl compounds) are randomly deposited on the composite surface. We show that the combined approach of ex situ SSNMR and XPEEM, in conjunction with in situ solution NMR, allows spatially resolved, molecular-level characterization of paramagnetic surfaces and new insights into electrolyte oxidation mechanisms in porous electrode films. The in situ solution NMR cell developed here is one of the first of its kind developed specifically for studying electrolyte decomposition products during or directly after battery operation, which is further developed in the next chapter. The fourth chapter focuses on studying the surface reactivity of the high-voltage LiNi₀.₅Mn₁.₅O₄ (LNMO) spinel cathode material. Unfortunately, LNMO-containing batteries suffer from poor cycling performance because of the intrinsically coupled processes of electrolyte oxidation and transition metal dissolution that occurs at high voltage. In this work, we use operando EPR and NMR spectroscopies to study these high voltage reactions, applying the in situ cell design from the previous chapter to operando conditions (characterization during battery charging). We demonstrate that transition metal dissolution in LNMO is tightly coupled to HF formation (and thus, electrolyte oxidation reactions as detected with operando and in situ solution NMR), indicative of an acid-driven disproportionation reaction that occurs during delithiation (battery charging). Leveraging the temporal resolution (s-min) of magnetic resonance, we find that the LNMO particles accelerate the rate of LiPF6 decomposition and subsequent Mn²⁺ dissolution, possibly due to the acidic nature of terminal Mn-OH groups and protic species generated upon oxidizing the solvents. X-ray photoemission electron microscopy (XPEEM) provides surface-sensitive and localized X-ray absorption spectroscopy (XAS) measurements, in addition to X-ray photoelectron spectroscopy (XPS), that indicate disproportionation is enabled by surface reconstruction upon charging, which leads to surface Mn³⁺ sites on the LNMO particle surface that can disproportionate into Mn²⁺(dissolved) and Mn⁴⁺(s). During discharge of the battery, we observe high quantities of metal fluorides (in particular, MnF₂) in the cathode electrolyte interphase (CEI) on LNMO as well as the conductive carbon additives in the composite. Electronic conductivity measurements indicate that the MnF₂ decreases film conductivity by threefold compared to LiF, suggesting that this CEI component may impede both the ionic and electronic properties of the cathode. Ultimately, to prevent transition metal dissolution and the associated side reactions in spinel-type cathodes (particularly those that operate at high voltages like LNMO), the use of electrolytes that offer improved anodic stability and prevent acid byproducts will likely be necessary. In the fifth chapter, we conduct an in situ X-ray spectroscopy, electron microscopy, and electron diffraction experiment to study the oxidation of the surface of Li metal, which is of critical importance for next generation Li metal batteries. Elemental Li is one of the most promising anode materials for high energy density Li batteries if it can replace graphite because it increases the specific capacity by an order of magnitude. However, Li metal is extremely reactive and is easily oxidized by air and moisture, even under inert conditions (e.g., in argon-filled gloveboxes, ultrahigh vacuum chambers). The industrial production of Li metal anodes, their surface evolution upon contact with the electrolyte, and electrodeposition behavior upon battery cycling all rely on the initial oxidative processes that take place prior to cell assembly. To better understand Li metal oxidation, we deposit pure Li on a Cu substrate and dose the Li deposit with various amounts of oxygen gas. During this experiment, we monitor the surface composition in situ using low-energy electron microscopy (LEEM), low-energy electron diffraction (LEED), and XPS measurements. We show that by evaporating Li onto Cu substrates, we can bypass long sputtering times needed to study commercial Li foils that usually exhibit alkali metal impurities and thick contamination layers from their external environment. Combined insights from LEED, LEEM and DFT calculations indicate that upon oxygen dosing of this ultrapure Li film, oxygen adsorbs to Li, forming a disordered layer, followed by (111) oriented polycrystalline Li₂O growth. DFT was particularly instrumental in elucidating the precise work function of the surface for the intermediate oxide phases (timescale of seconds) to correlate with trends observed via in situ LEEM imaging experiments. To conclude, we reflect on the overarching insight on cathode degradation that we have learned from these studies and discuss remaining knowledge gaps in the field. We highlight promising future avenues to study for stabilizing the cathode-electrolyte interface of these materials, such as adapting the characterization methods developed here for more high throughput study of next generation electrolyte formulations.

<p dir="ltr">This dissertation addresses the significant challenge of enhancing the performance of lithium-ion batteries (LIBs) in extremely low-temperature environments, which is critical for applications in defense and space exploration. By innovating both electrolyte formulations and electrode materials, this research extends the operational boundaries of LIBs to temperatures below -100 ℃. </p>

<p dir="ltr">Lithium-ion (Li-ion) batteries are promising electrochemical energy storage and conversion systems to drive the rechargeable world toward a sustainable future. Following the breakthrough of material innovations, advanced Li-ion batteries have significantly mitigated the range and lifetime anxieties of electric vehicles (EVs) and consumer electronics. Nevertheless, state-of-the-art Li-ion chemistries still suffer from several defects, such as rapid degradations under abusive or fast-charge scenarios and unfavorable high thermal instabilities. Essentially, aging mechanisms and safety hazards of Li-ion cells are strongly coupled events. The cell safety factors are most likely to be deteriorated as degradation progresses, making the cell less safe after a long-term deployment. In this thesis, we comprehensively investigate thermo-electrochemical interactions on the safety of Li-ion batteries. Fundamental principles of Li-ion batteries, basic knowledge about material-level thermal instabilities at electrode-electrolyte interphases, thermal characterization approaches, and thermal runaway mechanisms under abusive scenarios are fully overviewed. Thermally unstable characteristics of key cell components, including inter-electrode crosstalk as a result of oxygen liberation from cathode lattice structures, significant electric energy release from massive internal short circuit due to separator collapse, anode-centric lithium-plating-induced early exotherm, and silicon-dopant-driven thermal risks of composite anodes, are specifically discussed to understand their critical role in accelerating cell-level thermal runaway catastrophes. Aging pathways of Li-ion cells under off-normal conditions, particularly overdischarge and fast charging, are thoroughly elucidated using a promising reference electrode architecture, which effectively deconvolutes the electrode behaviors from the complex full-cell performance for precise identification of the root causes in cell failure. Given the profound revelation of degradation-safety sophistication in various Li-ion chemistries, corresponding mitigation and prevention strategies are proposed to maximize cell lifetime and reliability. This thesis provides new insights into aging and safety diagnostics of cutting-edge Li-ion batteries, taking one step further in the online monitoring of battery state of health to develop adaptive battery management systems.</p>

Indiana University-Purdue University Indianapolis (IUPUI) / Lithium-ion batteries are widely used for portable electronics due to high energy density, mature processing technology and reduced cost. However, their applications are somewhat limited by safety concerns. The lithium-ion battery users will take risks in burn or explosion which results from some internal components failure. So, a practical method is required urgently to find out the failures in early time. In this thesis, a new method based on temperature difference between internal point and surface (TDIS) of the battery is developed to detect the thermal failure especially the thermal runaway in early time. A lumped simple thermal model of a lithium-ion battery is developed based on TDIS. Heat transfer coefficients and heat capacity are determined from simultaneous measurements of the surface temperature and the internal temperature in cyclic constant current charging/discharging test. A look-up table of heating power in lithium ion battery is developed based on the lumped model and cyclic charging/discharging experimental results in normal operating condition. A failure detector is also built based on TDIS and reference heating power curve from the look-up table to detect aberrant heating power and bad parameters in transfer function of the lumped model. The TDIS method and TDIS detector is validated to be effective in thermal runaway detection in a thermal runway experiment. In the validation of thermal runway test, the system can find the abnormal heat generation before thermal runaway happens by detecting both abnormal heating power generation and parameter change in transfer function of thermal model of lithium ion batteries. The result of validation is compatible with the expectation of detector design. A simple and applicable detector is developed for lithium ion battery catastrophic failure detection.

Silicon (Si) has been considered as a promising negative electrode material for lithium ion batteries (LIBs) because of its high theoretical capacity, low discharge voltage, and low cost. However, the utilization of Si electrode has been hampered by problems such as slow ionic transport, large stress/strain generation, and unstable solid electrolyte interphase (SEI). These problems severely influence the performance and cycle life of Si electrodes. In general, ionic conduction determines the rate performance of the electrode, while electron leakage through the SEI causes electrolyte decomposition and, thus, causes capacity loss. The goal of this thesis research is to design Si electrodes with high current efficiency and durability through a fundamental understanding of the ionic and electronic conduction in Si and its SEI. Multi-scale physical and chemical processes occur in the electrode during charging and discharging. This thesis, thus, focuses on multi-scale modeling, including developing new methods, to help understand these coupled physical and chemical processes. For example, we developed a new method based on ab initio molecular dynamics to study the effects of stress/strain on Li ion transport in amorphous lithiated Si electrodes. This method not only quantitatively shows the effect of stress on ionic transport in amorphous materials, but also uncovers the underlying atomistic mechanisms. However, the origin of ionic conduction in the inorganic components in SEI is different from that in the amorphous Si electrode. To tackle this problem, we developed a model by separating the problem into two scales: 1) atomistic scale: defect physics and transport in individual SEI components with consideration of the environment, e.g., LiF in equilibrium with Si electrode; 2) mesoscopic scale: defect distribution near the heterogeneous interface based on a space charge model. In addition, to help design better artificial SEI, we further demonstrated a theoretical design of multicomponent SEIs by utilizing the synergetic effect found in the natural SEI. We show that the electrical conduction can be optimized by varying the grain size and volume fraction of two phases in the artificial multicomponent SEI.

There is an intense, worldwide effort to develop durable lithium ion batteries with high energy and power densities for a wide range of applications, including electric and hybrid electric vehicles. For improvement of battery technology understanding the capacity fading mechanism in batteries is of utmost importance. Novel electrode material and improved electrode designs are needed for high energy- high power batteries with less capacity fading. Furthermore, for applications such as automotive applications, precise cycle-life prediction of batteries is necessary. One of the critical challenges in advancing lithium ion battery technologies is fracture and decrepitation of the electrodes as a result of lithium diffusion during charging and discharging operations. When lithium is inserted in either the positive or negative electrode, there is a volume change associated with insertion or de-insertion. Diffusion-induced stresses (DISs) can therefore cause the nucleation and growth of cracks, leading to mechanical degradation of the batteries. With different mathematical models we studied the behavior of diffusion induces stresses and effects of electrode shape, size, concentration dependent material properties, pre-existing cracks, phase transformations, operating conditions etc. on the diffusion induced stresses. Thus we develop tools to guide the design of the electrode material with better mechanical stability for durable batteries. Along with mechanical degradation, chemical degradation of batteries also plays an important role in deciding battery cycle life. The instability of commonly employed electrolytes results in solid electrolyte interphase (SEI) formation. Although SEI formation contributes to irreversible capacity loss, the SEI layer is necessary, as it passivates the electrode-electrolyte interface from further solvent decomposition. SEI layer and diffusion induced stresses are inter-dependent and affect each-other. We study coupled chemical-mechanical degradation of electrode materials to understand the capacity fading of the battery with cycling. With the understanding of chemical and mechanical degradation, we develop a simple phenomenological model to predict battery life. On the experimental part we come up with a novel concept of using liquid metal alloy as a self-healing battery electrode. We develop a method to prepare thin film liquid gallium electrode on a conductive substrate. This enabled us to perform a series of electrochemical and characterization experiments which certify that liquid electrode undergo liquid-solid-liquid transition and thus self-heals the cracks formed during de-insertion. Thus the mechanical degradation can be avoided. We also perform ab-initio calculations to understand the equilibrium potential of various lithium-gallium phases.

Solid state lithium ion electrolytes are important to the development of next generation safer and high power density lithium ion batteries. Perovskite-structured LLT is a promising solid electrolyte with high lithium ion conductivity. LLT also serves as a good model system to understand lithium ion diffusion behaviors in solids. In this thesis, molecular dynamics and related atomistic computer simulations were used to study the diffusion behavior and diffusion mechanism in bulk crystal and grain boundary in lithium lanthanum titanate (LLT) solid state electrolytes. The effects of defect concentration on the structure and lithium ion diffusion behaviors in LLT were systematically studied and the lithium ion self-diffusion and diffusion energy barrier were investigated by both dynamic simulations and static calculations using the nudged elastic band (NEB) method. The simulation results show that there exist an optimal vacancy concentration at around x=0.067 at which lithium ions have the highest diffusion coefficient and the lowest diffusion energy barrier. The lowest energy barrier from dynamics simulations was found to be around 0.22 eV, which compared favorably with 0.19 eV from static NEB calculations. It was also found that lithium ions diffuse through bottleneck structures made of oxygen ions, which expand in dimension by 8-10% when lithium ions pass through. By designing perovskite structures with large bottleneck sizes can lead to materials with higher lithium ion conductivities. The structure and diffusion behavior of lithium silicate glasses and their interfaces, due to their importance as a grain boundary phase, with LLT crystals were also investigated by using molecular dynamics simulations. The short and medium range structures of the lithium silicate glasses were characterized and the ceramic/glass interface models were obtained using MD simulations. Lithium ion diffusion behaviors in the glass and across the glass/ceramic interfaces were investigated. It was found that there existed a minor segregation of lithium ions at the glass/crystal interface. Lithium ion diffusion energy barrier at the interface was found to be dominated by the glass phase.

Le travail de thèse, présenté dans ce mémoire, est consacré à l'étude de nouveaux matériaux d'électrode pour batterie lithium-ion pour le stockage d'énergie photovoltaïque. Ce type de production d'énergie impose de nombreuses intermittences de charge, des non synchronisations entre les périodes de production et de consommation, etc. L'objectif est d'évaluer le comportement de différents types de matériau d'électrode dans des batteries soumises à des profils de charge photovoltaïque pour ensuite sélectionner les plus adaptés à ce stockage spécifique d'énergie. Les matériaux choisis, Li4Ti5O12, Li2Ti3O7, NiP3, TiSnSb, présentent tous des mécanismes de réaction vis-à-vis du lithium très différents. Afin d'améliorer la durée de vie de ces matériaux d'électrodes, un travail d'optimisation des performances électrochimiques a été effectué en travaillant sur leur synthèse puis sur la formulation des électrodes. La formulation d'électrode en utilisant la carboxymethylcellulose sodique a notamment donné d'excellents résultats. La caractérisation de leurs propriétés physico-chimiques a été réalisée par diffraction des rayons X, in situ et en température, MEB, ATD, cyclage galvanostatique, etc.). Afin de reproduire des profils représentatifs de la production photovoltaïque à l'échelle des accumulateurs expérimentaux de laboratoire, un banc de simulation a été élaboré et validé avec un accumulateur de référence à base de Li4Ti5O12. Après cette étape de validation, les différents matériaux d'électrode ont été testés en condition photovoltaïque. Cette étude a permis de montrer que les intermittences de courte de durée (passages nuageux) et les régimes variables qu'impose ce type de production n'ont pas que peu d'influence sur les propriétés électrochimiques de l'ensemble de ces matériaux. Cependant, les périodes d'absence de production (nuit, journée pluvieuse, etc.) correspondant à une relaxation pour le matériau peuvent avoir un impact important. Les matériaux de conversion (NiP3, TiSnSb) ont montré de surprenants bons résultats. Enfin, les observations montrent que chaque type de matériau (mécanisme électrochimique différent) pourrait convenir i) à un type de production photovoltaïque, c'est à dire à une zone géographique et ii) à un type d'application particulière. / The thesis work, presented in this manuscript, is devoted to the study of new materials for lithium-ion battery for storing solar energy. This type of energy production imposes intermittent loading, non-synchronization between periods of production and consumption, etc. The objective is to evaluate the behavior of different types of electrode material in batteries under photovoltaic (PV) charge profiles and then to select the most suitable for this specific energy storage. The chosen materials, Li4Ti5O12, Li2Ti3O7, NiP3, TiSnSb, follow all very different reaction mechanisms versus lithium. To improve the cycling life of these electrode materials, a work on electrochemical performance optimization was performed by working on the synthesis and the electrode formulation. The electrode formulation, using in particular carboxymethyl cellulose, presented excellent results. Characterization of their physico-chemical properties was carried out by X-ray diffraction, in situ and as function of temperature, SEM, DTA, galvanostatic cycling, etc.). To reproduce representative profiles of the photovoltaic production at the experimental batteries scale, a test bench has been developed and validated with reference batteries (Li4Ti5O12). After this step of validation, different electrode materials were tested under photovoltaic conditions. This study shows that both intermittences with short duration (clouds) and variable rates of current imposed by this type of production don't strong influence on the electrochemical properties of all these materials. However, periods of no production (night, rainy day, etc.), corresponding to a relaxation for the material, can impact significantly. Materials following conversion mechanism (NiP3, TiSnSb) showed surprising good results. Finally, the observations indicated that each type of material (with different electrochemical mechanism) could be adapted to i) a type of photovoltaic production, ie to a geographical area and ii) a type of application.

Ce mémoire est consacré à l'étude de nouveaux matériaux composites de type Si/Sn-Ni/Al/C pour former des électrodes négatives de batteries lithium ion. La microstructure de ces matériaux se présente sous la forme de nanoparticules de Si enrobées dans une matrice conductrice constituée de carbone et d'un composé intermétallique Ni3,4Sn4. La nanostructure et la composition du matériau composite lui confèrent de très bonnes performances en termes de capacité réversible, de stabilité électrochimique, et de cinétique de réaction. La mécanosynthèse a été choisie comme méthode d'élaboration. Les propriétés structurales et chimiques du composite ont été déterminées par analyses DRX, par microscopies électroniques MET et MEB, par analyses EDX et EFTEM et par spectroscopie Mössbauer de 119Sn. La caractérisation électrochimique a été réalisée par cyclage galvanostatique et par voltamétrie cyclique. La réactivité de ces matériaux envers le lithium a été étudiée par analyses DRX et spectroscopie Mössbauer de 119Sn in-situ. Ce mémoire détaille les résultats structuraux et électrochimiques obtenus pour différents matériaux composites basés sur Ni3,4Sn4 en ajoutant les éléments C, Al et Si. Une étude des mécanismes réactionnels lors du broyage mécanique ainsi que pendant le cyclage électrochimique a été effectuée et le rôle des différents éléments a été mis en évidence. Enfin, une discussion sur l'influence de la microstructure sur les performances électrochimiques des matériaux composites est donnée. Les meilleures performances électrochimiques sont obtenues pour le composite de composition nominale Ni0,14Sn0,17Si0,32Al0,04C0,35. Il présente une capacité réversible de 920 mAh/g avec une très bonne stabilité sur 280 cycles. Le matériau possède une excellente cinétique de délithiation : 90% de la capacité peut être délivrée en moins de 5 minutes. La capacité irréversible (20%) reste toutefois élevée et doit être encore améliorée en stabilisant l'interface solide/électrolyte (SEI) / This study is devoted to a new Si/Sn-Ni/Al/C composite material usable as negative electrode for lithium-ion batteries. The composite microstructure is made from Si nanoparticles embedded in a matrix, consisting of conductive carbon and Ni3.4Sn4 intermetallic compound. The nanostructure and composition of the composite material give excellent properties regarding reversible capacity, electrochemical stability, and reaction kinetics. Mechanical alloying has been chosen as synthesis method. The material structural and chemical properties have been determined by XRD analysis, by electron microscopy TEM and SEM, by EDX and EFTEM analysis and 119Sn Mössbauer spectroscopy. The electrochemical characterization was carried out by galvanostatic cycling and cyclic voltammetry. Lithium reactivity of these materials was studied by in-situ XRD analysis and 119Sn Mössbauer spectroscopy. This manuscript details the structural and electrochemical results obtained from various composite materials based on Ni3.4Sn4 by adding C, Al and Si elements. Reaction mechanisms during mechanical alloying and during electrochemical cycling have been investigated and the role of the different elements has been demonstrated. Finally, a discussion of the microstructure influence on the electrochemical performance of the composite materials is given. The best electrochemical properties are obtained for the composite material with nominal composition Ni0.14Sn0.17Si0.32Al0.04C0.35, which has a reversible capacity of 920 mAh/g with a very good stability of 280 cycles. Excellent kinetics during délithiation are obtained : 90% of capacity can be delivered in less than 5 minutes. However, the irreversible capacity (20 %) remains high and should be improved by stabilizing the solid/electrolyte interface (SEI)

Materiais auto-organizados constituídos de V2O5 xerogel, poli(etilenoimina) (PEI) e nanopartículas de carbono (NpCs) foram obtidos por meio da técnica camada-por-camada (LbL). A metodologia aplicada permitiu a obtenção de filmes finos com elevado controle de espessura além de permitir um crescimento linear dos filmes, denominados neste trabalho V2O5/PEI e V2O5/PEI/NpCs. Além disso, o desempenho eletroquímico dos materiais auto-organizados foi comparado a um eletrodo de V2O5. Análises de FTIR mostraram que interações específicas entre os grupos amina do PEI e os grupos carboxila do V2O5 são responsáveis pelo crescimento do filme. Estas interações permitem a formação de um campo eletrostático capaz de blindar as interações entre os íons lítio e os oxigênios da vanadila (V=O) e, por consequência, são responsáveis pelo aumento na mobilidade iônica dos íons lítio no interior da matriz hospedeira e, portanto, um aumento na capacidade de armazenamento de carga. Resultados obtidos através de medidas de carga/descarga mostram que o V2O5/PEI/NpCs apresenta uma melhor desempenho do que os demais materiais estudados neste trabalho. Estes resultados mostram que a capacidade específica do V2O5/PEI/NpCs foi de 137 mA h g-1 para a menor densidade de corrente aplicada e aproximadamente 1,6 vezes maior do que os valores de capacidade específica para os outros materiais para a maior densidade de corrente aplicada. Além disso, estas medidas permitiram a observação de uma menor variação na razão estequiométrica máxima (xmáx) em função das densidades de corrente aplicadas para os filmes auto-organizados, fato este relacionado a uma maior mobilidade iônica dos íons lítio no interior dessas matrizes. Os resultados obtidos a partir de espectroscopia de impedância eletroquímica (EIS) mostraram que a difusão dos íons lítio no interior das matrizes auto-organizadas é maior do que no caso do V2O5, cujos valores do coeficiente de difusão foram de 1,64 x 10-15, 1,21 x 10-14 e 2,26 x 10-14 cm2 s-1 para os filmes V2O5, V2O5/PEI e V2O5/PEI/NpCs, respectivamente. Sendo assim, o polímero e as NpCs promoveram novos caminhos condutores e permitiram a conexão elétrica entre camadas isoladas da matriz V2O5. Dessa forma, novos nanocompósitos foram obtidos visando demonstrar o método de auto-organização empregado para melhorar o transporte de carga em matrizes hospedeiras. / Self-assembled materials constituted of V2O5 xerogel, poly (ethyleneimine) (PEI), and carbon nanoparticles (CNPs) were obtained by the layer-by-layer (LbL) technique. The applied methodology permitted the obtainment of thin films with high thickness control and also permitted a linear growth of the films, which will be named V2O5/PEI and V2O5/PEI/CNPs. Besides, the electrochemical performance of the self-assembled materials was compared to a V2O5 electrode. FTIR analyses showed that the specific interactions between the amine groups of PEI and the vanadyl groups of the V2O5 are responsible for the film growth. These interactions permitted the formation of an electrostatic shield capable of hindering the interactions between the lithium ions and the vanadyl oxygen atoms (V=O) and are consequently responsible for the enhancement on the ionic mobility of the lithium ions within the host matrix, leading to a higher energy storage capability. Results obtained by the charge/discharge measurements showed that V2O5/PEI/CNPs presents a better performance than the other materials studied for this research. These results demonstrated that the specific capacity of the V2O5/PEI/CNPs was 137 mA h g-1 under the lowest current density applied and approximately 1.6 times higher than the specific capacity values obtained for the other materials under the highest current density applied. Moreover, it was observed that the variation of the maximum stoichiometric ratio (xmax) as a function of the current density is lower for the self-assembled materials than for the V2O5 electrode, which can be related to the higher ionic mobility of the lithium ion within the self-assembled materials. Electrochemical Impedance Spectroscopy (EIS) data demonstrated that the diffusion of the lithium ions within the self-assembled materials is higher than within the V2O5 electrode, and the diffusion coefficients were 1.64 x 10-15, 1.21 x 10-14 e 2.26 x 10-14 cm2 s-1 for V2O5, V2O5/PEI and V2O5/PEI/CNPs, respectively. Thus, the polymer and the CNPs provided new conducting pathways and connected isolated V2O5 chains in the host matrix. Therefore, novel spontaneous nanocomposites were formed, aiming to demonstrate the self-assembled method adopted for improving charge transport within host matrices.