Developing batteries with energy densities comparable to internal combustion technology is essential for a worldwide transition to electrified transportation. Li-O2 batteries are seen as the 'holy grail' of battery technologies since they have the highest theoretical energy density of all battery technologies. Current lithium-oxygen (Li-O2) batteries suffer from large charge overpotentials related to the electronic resistivity of the insulating lithium peroxide (Li2O2) discharge product. One potential solution is the formation and stabilization of a lithium superoxide (LiO2) discharge intermediate that exhibits good electronic conductivity. However, LiO2 is reported to be unstable at ambient temperature despite its favorable formation energy at -1.0 eV per atom. In this paper - based on our recent work on the development of cathode materials for aprotic lithium oxygen batteries including two intermetallic compounds, LiIr3 and LiIr, that are found to form good template interfaces with LiO2 - a simple goodness of fit R factor to gauge how well a template surface structure can support LiO2 growth, is developed. The R factor is a quantitative measurement to calculate the geometric difference in the unit cells of specific Miller Index 2D planes of the template surface and LiO2. Using this as a guide, the R factors for LiIr3, LiIr, and La2NiO4+delta, are found to be good. This guide is attested by simple extension to other noble metal intermetallics with electrochemical cycling data including LiRh3, LiRh, and Li2Pd. Finally, the template concept is extended to main group elements and the R factors for LiO2 (111) and Li2Ca suggest that Li2Ca is a possible candidate for the template assisted LiO2 growth strategy. A simple goodness of fit R factor to gauge how well a template surface structure can support LiO2 growth is developed. The R factor may be extended to other transition and main group element LiMx catalysts, as potential LiO2 growth supports.

Li-O-2 batteries suffer from large charge overpotentials due to the high charge transfer resistance of Li2O2 discharge products. A potential solution to this problem is the development of LiO2-based batteries that possess low charge overpotentials due to the lower charge transfer resistance of LiO2. In this report, IrLi nanoparticles were synthesized and implemented for the first time as a LiO2 battery cathode material. The IrLi nanoparticle synthesis was achieved by a temperature-and time-optimized thermal reaction between a precise ratio of iridium nanoparticles and lithium metal. Li-O-2 batteries employing the IrLi-rGO cathodes were cycled up to 100 cycles at moderate current densities with sustained low cell charge potentials (< 3.5 V). Various characterization techniques, including SEM, DEMS, TEM, Raman, and titration, were used to demonstrate the LiO2 discharge product and the absence of Li2O2. On the basis of first-principles calculations, it was concluded that the formation of crystalline LiO2 can be stabilized by epitaxial growth on the (111) facets of IrLi nanoparticles present on the cathode surface. These findings demonstrate that, in addition to the previously studied Ir3Li intermetallic, the IrLi intermetallic also provides a means by which LiO2 discharge products can be stabilized and confirms the importance of templating for the formation process.

Redox mediators (RMs) are solution-based additives that have been extensively used to reduce the charge potential and increase the energy efficiency of Li-oxygen (Li-O2) batteries. However, in the presence of RMs, achieving a long cycle-life operation of Li-O2 batteries at a high current rate is still a major challenge. In this study, we discover a novel synergy among InX3 (X = I and Br) bifunctional RMs, molybdenum disulfide (MoS2) nanoflakes as the air electrode, dimethyl sulfoxide/ionic liquid hybrid electrolyte, and LiTFSI as a salt to achieve long cycle-life operations of Li-O2 batteries in a dry air environment at high charge-discharge rates. Our results indicate that batteries with InI3 operate up to 450 cycles with a current density of 0.5 A g-1 and 217 cycles with a current density of 1 A g-1 at a fixed capacity of 1 A h g-1. Batteries with InBr3 operate up to 600 cycles with a current density of 1 A g-1. These batteries can also operate at a higher charge rate of 2 A g-1 up to 200 cycles (for InBr3) and 160 cycles (for InI3). Our experimental and computational results reveal that while X3- is the source of the redox mediator, LiX at the MoS2 cathode, In3+ reacts on the lithium anode side to form a protective layer on the surface, thus acting as an effective bifunctional RM in a dry air environment. This evidence for a simultaneous improvement in the current rates and cycle life of a battery in a dry air atmosphere opens a new direction for research for advanced energy storage systems.

This paper presents the first comprehensive study of a propagation mechanism referred to as 'current dumping', which has been identified as a dominant cause for thermal runaway in Lithium-ion battery packs. Baseline nail penetration tests were performed on commercial, fully charged lithium-ion battery packs with 18650 nickel-manganese-cobalt cells and Phase Change Composite to study the propagation of thermal runaway in packs with both electrically connected and disconnected cells. This study showed that packs with electrically connected cells experience thermal runaway propagation due to neighboring cell current dumping. Packs with electrically disconnected cells did not propagate and maximum neighboring cell temperatures were less than 85 degrees C, below the cell thermal runaway threshold temperatures characterized by accelerating rate calorimetry tests. Cell-to-cell current dumping tests were performed on 18650 and 21700 cells at 60, 80 and 100% state-of-charge. These tests demonstrated that cell current interrupt device activation times vary over several minutes, and trigger cell short resistance vary between 17 and 62 mO. Along with neighboring cell internal resistance data obtained from hybrid pulse power characterization testing, the current dumping study allowed accurate prediction of the magnitude of current dumping for various battery designs. This enabled the first battery design with individual cell fusing integrated into battery current collectors. Nail penetration tests performed on commercial 18650 battery packs incorporating the engineered fuse did not propagate and current dumping was prevented. Practical insights from this study can play a critical role in solving the thermal runaway propagation problem plaguing lithium-ion battery manufacturers globally.

Developing promising solid-state Li batteries with capabilities of high current densities have been a major challenge partly due to large interfacial resistance across the electrode/electrolyte interfaces. This work represents an integrated network of self-standing polymer electrolyte and active electrode materials with in situ UV cross-linking. This method provides a uniform morphology of composite polymer electrolyte with low thickness of 20-40 mu m. This modification leads to promising cycling results with 85% specific capacity retention in Li||LiFePO4 cell over 100 cycles at high current densities of 170 mA g(-1) (similar to 25 mu A cm(-2), 1 C)(.) By applying this method, the interfacial resistance decreases as high as seven folds compared to noncross-linked interfaces. The following work introduce a facile and cost-effective method in developing fast-charging self-standing polymer batteries with enhanced electrochemical properties.

Li-O-2 batteries have recently emerged to meet nowadays elevated electric energy demands. Redox mediators (RMs) for solution-inducing decomposition of discharge products are one approach to increase energy efficiency and reduce high overpotentials in these batteries. However, multiple obstacles hinder their usage such as redox shuttling, capacity fading, electrolyte degradation, etc. Herein, we present a new chemistry based on a combination of LiNO3, TEGDME and an ionic liquid that enables LiI (1 M) to lower the charge potential (3.5V) with a long cycle life of 270 cycles. 0.1 M LiI increases the cyclability up to 500 with a slightly increased charge potential (similar to 4V) for a fixed capacity of 1000 mAh/g. Up to 100 cycles, this battery system retained similar to 95% Li2O2 capacity with a similar to 0.8 V charge-discharge polarization gap. The addition of LiNO3 to the electrolyte provides a protective solid electrolyte interface (SEI) on anode that works in synergy with the LiI RM. Moreover, we found that this electrolyte blend results in domain formation of ionic and neutral species enhancing the discharge and charge processes. Finally, DFT calculations provide a better understanding of the role of the anode SEI layer and the Li2O2 decomposition promoted by the LiI during charge on the cathode.

Current lithium-oxygen (Li-O-2) batteries suffer from large charge overpotentials related to electronic resistivity of the insulating lithium peroxide (Li2O2) discharge product. One potential solution to this challenge is the stabilization of the lithium superoxide (LiO2) discharge intermediate, which has much higher electronic conductivity compared to Li2O2. Cathodes based on small iridium (Ir) nanoparticles have been recently used in a LiO2 battery to successfully stabilize the LiO2 product, however, the LiO2 had a short lifetime. In the previous study, researchers found that the LiO2 was stabilized on Ir3Li surfaces which were formed from Ir nanoparticles during battery operation. Little is known about the electronic properties of Ir3Li and its role in stabilizing LiO2 product formation. This work provides the first study of the electronic properties of Ir3Li, which was thermally synthesized in bulk prior to implementation on the reduced graphene oxide (rGO) cathode of a Li-O-2 cell. The bulk Ir3Li was found to have comparable electrical conductivity to Ir metal, possess metal-like magnetic properties, and has an affinity towards O-2 adsorption. The LiO2 discharge product formed from the Li-O-2 battery discharge was characterized using Raman spectroscopy, titration, along with a comprehensive transmission electron microscopy (TEM) study. This analysis revealed the formation of ultra-nanocrystalline LiO2 particles greater than 200 nm. This result was attributed to the use of large micron sized Ir3Li particles, which could stabilize larger LiO2 particles compared to previous cathodes that utilized Ir nanoparticles that partially converted to Ir3Li during cycling. These results demonstrate that cathode properties can be modified to stabilize the bulk LiO2 discharge product, which can be useful for the further development of LiO2-based Li-O-2 batteries.

In recent years, Lithium-ION (LI-ION) battery packs have been the dominant energy storage system (ESS) in electrified transportation applications such as material handling, robotics, and electric vertical takeoff and landing aircraft. These applications prefer a high-energy-density and lightweight ESS owing to size and weight limitations. However, they are often equipped with an oversized battery pack to mitigate the long downtime due to the low charging rates (1C) of high-energydensity Li-ion batteries. Fast charging is a potential solution to create a "filling a tank" experience that has recently drawn tremendous interest from researchers and the industry.

The theoretical energy density of lithium-oxygen (Li-O-2) batteries is extremely high, although there are many challenges that must be overcome to achieve high energy density in a manufactured cell. For example, little is known about the properties of one of the key intermediates, lithium superoxide (LiO2), which until recently had not been stabilized in bulk form. In this work, lithium superoxide was deposited onto iridium-reduced graphene oxide (Ir-rGO) cathodes in a Li-O-2 system under a flow of O-2. Lithium peroxide (Li2O2) was subsequently produced on the cathode surface in an inert Ar atmosphere. Based on a detailed analysis of electrochemical impedance spectroscopy data, it was demonstrated experimentally for the first time that the charge transport resistance through LiO2 was much lower than for Li2O2 and correlated with lower LiO2 charge overpotentials. This result indicates that LiO2 has good electronic conductivity and confirms previous theoretical predictions that bulk LiO2 has better charge transport properties than Li2O2. In addition, impedance and other characterization of Li2O2 formation from LiO2 in an Ar atmosphere revealed that when surface-mediated Li2O2 formation occurs, it has a significantly lower discharge potential than when it forms through a solution-phase-mediated process. These significant findings will contribute to the development of Li-O-2 batteries through better understanding of LiO2 properties and formation mechanisms.

Electrochemical performance of nanostructured carbon electrodes was evaluated using cyclic voltammetry and a simple simulation model. The electrodes were prepared from soluble precursors by anodic electrodeposition of two sizes of graphene quantum dot assemblies (hexabenzocoronene (HBC) and carbon quantum dot (CQD)) onto a conductive support. Experimental and simulated voltammograms enabled the extraction of the following electrode parameters: conductivity of the electrodes (a combination of ionic and electronic contributions), density of available electrode states at different potentials, and tunneling rate constant (Marcus Gerischer model) for interfacial charge transfer to ferrocene/ferrocenium (Fc/Fc(+)) couple. The parameters indicate that HBC and CQD have significant density of electronic states at potentials more positive than -0.5 V versus Ag/Ag+ Enabled by these large densities, the electron transfer rates at the Fc/Fc(+) thermodynamic potential are several orders of magnitude slower than those commonly observed on other carbon electrodes. This study is expected to accelerate the discovery of improved synthetic carbon electrodes by providing fast screening methodology of their electrochemical behavior.

Nail penetration of a cell situated in a Lithium ion battery pack constructed of PCC material populated with commercial cells has been conducted. The thermal and voltage response of the trigger and neighboring cells was recorded. Characterization of a new design employing loosely-fitted cells with an air layer between each cell and the surrounding PCC was performed and compared to previous designs with tightly-fitted cells. Packs with tightly-fitted cells did not experience thermal runaway propagation however neighboring cells experienced temperatures previously observed to initiate thermal runaway. Severe thermal runaway propagation occurred in the loosely-fitted pack design resulting in excessive damage to the pack. Proposed mechanisms for propagation were cell ejecta ignition and radiation through the added air-film. Thermal and voltage responses, along with post-mortem analysis revealed several cell and pack safety mechanism failures that will be investigated in future work.