Browsing by Subject "Anodes"

Now showing 1 - 5 of 5

Cell modification strategies for high-energy lithium-sulfur batteries
(2020-01-31) Luo, Liu; Manthiram, Arumugam
Lithium-sulfur (Li-S) batteries have drawn tremendous interest in the next-generation energy-storage field due to the high theoretical capacity (1675 mA h g⁻¹) and low cost of the eco-friendly sulfur. Nevertheless, the practical realization of Li-S technology is still challenging. The major bottleneck lies in the insulating nature of sulfur and its redox products, together with the shuttling of intermediate polysulfides (Li₂S [subscript x], 4 ≤ x ≤ 8) during cycling, leading to low active-material utilization and fast capacity fade. This dissertation focuses on the development of advanced cell configurations with novel modification strategies to improve the electrochemical performance of Li-S cells. First, a multi-layer-coated separator is established to suppress the polysulfide migration. The functional coating films act as net-like filters to intercept the diffusing polysulfides by both physical and chemical interactions, contributing to enhanced cycling stability and capacity retention. Second, a new sulfur cathode configuration with a poached-egg-shaped architecture is proposed to improve the cyclability of Li-S cells. The carbon shell not only achieves an effective physical encapsulation of the "sulfur yolk" to localize active material, but also serves as interlinked electron pathways to favor the active-material reactivation, greatly enhancing the electrochemical utilization and reversibility. Third, in addition to the physical polysulfide-entrapment, the chemical adsorbent is also introduced into the sulfur cathode substrate. By coupling the sulfiphilic metal compounds (e.g., NiS₂ and SnS₂) with a conductive carbon framework to construct a hybrid sulfur host, the polysulfide adsorptivity is significantly improved due to the physical confinement and chemical anchoring, further limiting the active-material loss and polysulfide diffusion. Fourth, another novel cathode design with electrocatalyst incorporation is presented to enhance the rate capability and cycle life of Li-S cells. The electrocatalysts (e.g., Ni and B₄C) function as efficient redox mediators to accelerate the reaction kinetics of polysulfide transformation, leading to highly promoted active-material utilization and rate performance. Finally, an advanced Li-metal host is also designed with a three-dimensional lithiophilic architecture. The lithiophilic seeds (e.g., Mo₂N) substantially lower the Li nucleation overpotential, thus spatially guiding the uniform Li deposition in the conductive matrix and suppressing the Li-dendrite formation as well as Li anode degradation.
Controlled prelithiation of PbS to Pb/Li₂S for high initial Coulombic efficiency in lithium ion batteries
(2018-12) Guo, Yong, M.A.; Mullins, C. B.
PbS nanoparticle aggregates were synthesized in a simple aqueous reaction at room temperature, and were tested as a lithium ion anode material, with a gravimetric capacity of 374 mAh/g at C/2, and a 0.15% capacity loss per cycle. However, its half cell initial Coulombic efficiency (ICE) was only 40%, due to a combination of irreversible Li₂S and solid electrolyte interface (SEI) formations. A custom controlled prelithiation technique was then applied to the PbS electrodes, converting the active material to Pb/Li₂S, and consolidating the SEI prior to coin cell assembly. This brought the ICE from 40% to >97%, and allowed for immediate cycling of the electrode at high Coulombic efficiency, without further formation cycles. Upon construction of prelithiated Pb/Li₂S vs NCM full cells, an 82% ICE was observed, with the majority of the lithium loss from the NCM. The full cells had a combined electrode capacity of 100 mAh/g at C/2
Design of composite foil anodes for lithium-ion batteries
(2021-08-23) Heligman, Brian Theodore; Manthiram, Arumugam; Goodenough, John B; Taleff, Eric M; Hwang, Gyeong S.
In this work, multi-phase metallic foils are developed for use as high-capacity lithium-ion battery anodes. The core of the approach relies upon using severe plastic deformation to generate dense nanostructures containing multiple metallic phases with differing electrochemical activity. In the first chapter, a historical context is provided both for the development of lithium-ion battery technology broadly and alloying anode materials specifically. This introduction serves to outline the motivation for the work that follows. In the second chapter, the experimental methods utilized to develop this new class of alloying anode materials are outlined. The third chapter entails a detailed investigation of the zinc-tin binary metal system to understand its operation as a battery anode. In this work, we highlight the unmatched volumetric capacity realized by the foil form factor. The fourth chapter investigates the electrochemical reactions of alloying metals more broadly and develops a generalized framework for understanding the implementation of metallic foil anodes in the modern battery system. This work provides a robust foundation for the design and implementation of foil anodes, highlighting the viable materials systems and contextualizing their performance in a modern cell architecture. The fifth chapter represents an investigation of how the electrochemical cycling of a metallic foil anode alters its microstructure and impacts performance. We investigate the processes associated with electrochemical cycling that transform the bulk metallic foil into a porous electrode in-situ. The sixth chapter introduces a new technique for the manufacturing of foil anodes broadly that greatly expands the nanostructured composite foil anode design space. In this work, we investigate the performance and degradation mechanisms of a model Sn/Cu system, highlighting the elimination of active material loss enabled by the inactive matrix. The final chapter is a summary of the work carried out for this dissertation.
Structural engineering of lithium-ion battery electrodes for the production of stable, energy-dense storage
(2023-04-17) Weeks, Jason Alexander; Mullins, C. B.; Ren, Hang; Rose , Michael J.; Yu, Guihua; Mitlin, David
Lithium-ion batteries (LIBs) have revolutionized many facets of our everyday life, enabling devices such as cell phones, laptops, and, most recently, electric vehicles to become everyday commodities for consumers. However, as the demands of consumers and the energy requirements of these devices continue to grow, so must the storage capabilities of LIBs. Unfortunately, the chemistry and design space of these devices has remained stagnant over the technology’s lifespan. Several energy-dense density chemistries, such as lithium metal, silicon, and tin, are highly regarded for their lithium storage capabilities,. Yet, the non-advantageous side effects of their lithiation/delithiation (dendrite formation, particle fracturing, excessive SEI growth, etc.) have prevented the practical implementation of these materials. As such, an investigation was conducted to determine how structural engineering can be used to help enable next-generation chemistries and electrode designs for higher energy-density LIBs. Lithium metal touts any anode's highest theoretical capacity and power density; however, the safety risks from dendrite formation, such as electrical short-circuiting and explosions, prevent its utilization. Employing a systematic approach to the characterization of the solid electrode interphase (SEI) displays how electrolyte composition influences the chemical makeup of the SEI and its resulting properties. These results demonstrate how the subsequent modulation of the SEI structure and composition can influence the electrochemical performance and lithium deposition morphology. Similarly, the purposeful design of alloying anode materials, like tin and lead, and their host structures can tune their performance and electrochemistry. Typically, the large mechanical stress from the volumetric expansion during lithiation causes severe capacity fade in these materials; however, implementing a carbonaceous scaffold can drastically increase the stability of these materials. In addition to examining new active materials, the structural engineering of the overall electrode is explored. Metal foil current collectors comprise approximately 15% of the total cell weight in traditional batteries. Implementing a templated slurry casting process using camphene enables the formation of free-standing electrodes with enhanced flexibility and rate capabilities. Compared to classical electrode designs, an increase of 25% in energy density can be achieved by eliminating the gravimetrically dense current collector and increasing lithiation site accessibility.
Tin-based nanocomposite alloy anodes for lithium-ion batteries
(2014-05) Leibowitz, Joshua Abel; Manthiram, Arumugam
Lithium-alloying anode materials have attracted much attention as an alternative to carbon due to their high theoretical gravimetric capacities (e.g. Li4.4Si: 4200 mAh g-1, Li4.4Sn: 990 mAh g-1, and Li3Sb: 660 mAh g-1). An additional benefit of lithium alloying metals is that some of the react at a higher potentials vs. Li/Li+ than carbon, which can mitigate safety issues caused by solid-electrolyte interface layer formation and lithium plating. One of the most promising lithium -alloying anode materials that are being pursued are Sn-based materials due to their high capacity and tap density. This thesis investigates the synthesis and characterization of Sn-based lithium-ion battery anodes. SnSb-TiC-C and FeSn2-TiC nanocomposite alloy anodes for lithium-ion batteries have been synthesized by a mechanochemical process involving high-energy mechanical milling of Ti/Sn, Ti/M (M = Fe or Sb), and C. Characterization of the nanocomposites formed with x-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) reveals that these alloys are composed of crystalline nanoparticles of FeSn2 and SnSb dispersed in a matrix of TiC and carbon. The SnSb-TiC-C alloy shows an initial gravimetric capacity of 653 mAh g-1 (1384 mAh cm-3), an initial coulombic efficiency of 85%, and a tap density of 1.8 g cm-3. The FeSn2-TiC alloy shows an initial gravimetric capacity of 510 mAh g-1 (1073 mAh cm-3), an initial coulombic efficiency of 71%, and a tap density of 2.1 g cm-3. The TiC-C buffer matrix in the nanocomposite alloy anodes accommodates the large volume change occurring during the charge-discharge process and leads to good cyclability compared to pure FeSn2 and SnSb anodes.