Electrodeposition Stability Research Articles

Charging dependent electro-chemo-mechanical coupling behavior of polymer electrolytes containing immobilized anions

Theoretical models have been developed to explore the electrodeposition stability between Li metal and salt-doped polymer electrolytes. However, there is still limited investigation on the coupling behavior between mechanics and electrochemistry in those novel nano-structured polymers with immobilized anions. In this work, we employ a multiphysics modeling framework to predict the electro-chemo-mechanical behavior of polymer electrolytes containing immobilized anions. We analyze the impacts of charging conditions, stress coupling and the immobilization of anions on their ion transport, electrical and mechanical properties during charging. Strengthening stress coupling is demonstrated to improve the diffusion-driven stability of electrodeposition, by enhancing limiting applied current densities. Compared with stress coupling, immobilizing anions surprisingly sustains the non-zero interfacial Li+-ion concentrations even at high applied currents, thereby mitigating the potential diffusion-driven instability of electrodeposition. Both stress/strain and overpotentials also get reduces with increasing the concentrations of immobilized anions. This theoretical work provides insights into the strategy of redesigning polymer electrolytes, and also lays foundation for the multiphysics modeling of electrodes and full-cell battery systems.

Flotation-assisted electrodeposition process to recover copper from waste printed circuit boards

Electrodeposition is an attractive method to recover copper from waste printed circuit boards (WPCBs), which preferably requires metal-rich concentrate as raw material. In this study, a metal-rich route for WPCBs was established to assist copper electrodeposition by using flotation method. Different from aqueous disperse medium in conventional flotation, we proposed ethanol as a disperse medium to improve dispersivity and sustainability. An H-type electrolytic cell with a cation exchange membrane was used to electrolyze copper in metal-rich concentrate at the anode and recover pure copper on the cathode. The experiments were conducted to investigate the effect of grade on the proportion of metal-rich concentrate after flotation and the electrodeposition rate of copper, and the key factors (solid-to-liquid ratio and applied voltage) affecting copper electrodeposition were evaluated. The results show that the flotation with ethanol can greatly enrich copper, and the copper content in metal-rich concentrate can be increased by 182.3 %, with a copper recovery rate of 85.1 %. Increasing the solid-to-liquid ratio and applied voltage can increase the deposition rate of copper, but affects the stability of electrodeposition. The optimized electrodeposition parameters are: electrolyte temperature of 50℃, solid-to-liquid ratio of 25 g/L, and applied voltage of 10 V. The purity of copper in electrodeposits can reach over 99 %.

Heterogeneous Solid Electrolyte Interphase Interactions Dictate Interface Instability in Sodium Metal Electrodes.

Sodium (Na) metal batteries have attracted recent attention due to their low cost and high abundance of Na. However, the advancement of Na metal batteries is impeded due to key challenges such as dendrite growth, solid electrolyte interphase (SEI) fracture, and low Coulombic efficiency. This study examines the coupled electro-chemo-mechanical interactions governing the electrodeposition stability and morphological evolution at the Na/electrolyte interface. The SEI heterogeneities influence transport and reaction kinetics leading to the formation of current and stress hotspots during Na plating. Further, it is demonstrated that the heterogeneity-induced Na metal evolution and its influence on the stress distribution critically affect the mechanical overpotential, contributing to a faster SEI failure. The analysis reveals three distinct failure mechanisms-mechanical, transport, and kinetic-that govern the onset of instabilities at the interface. Finally, a comprehensive comparative study of SEI failure in Na and lithium (Li) metal anodes illustrates that the electrochemical and mechanical characteristics of the SEI are crucial in tailoring the anode morphology and interface stability. This work delineates mechanistic stability regimes cognizant of the SEI attributes and underlying failure modes and offers important guidelines for the design of artificial SEI layers for stable Na metal electrodes.

Electrodeposition Stability Landscape for Solid–Solid Interfaces

AbstractAs solid‐state batteries (SSBs) with lithium (Li) metal anodes gain increasing traction as promising next‐generation energy storage systems, a fundamental understanding of coupled electro‐chemo‐mechanical interactions is essential to design stable solid‐solid interfaces. Notably, uneven electrodeposition at the Li metal/solid electrolyte (SE) interface arising from intrinsic electrochemical and mechanical heterogeneities remains a significant challenge. In this work, the thermodynamic origins of mechanics‐coupled reaction kinetics at the Li/SE interface are investigated and its implications on electrodeposition stability are unveiled. It is established that the mechanics‐driven energetic contribution to the free energy landscape of the Li deposition/dissolution redox reaction has a critical influence on the interface stability. The study presents the competing effects of mechanical and electrical overpotential on the reaction distribution, and demarcates the regimes under which stress interactions can be tailored to enable stable electrodeposition. It is revealed that different degrees of mechanics contribution to the forward (dissolution) and backward (deposition) reaction rates result in widely varying stability regimes, and the mechanics‐coupled kinetics scenario exhibited by the Li/SE interface is shown to depend strongly on the thermodynamic and mechanical properties of the SE. This work highlights the importance of discerning the underpinning nature of electro‐chemo‐mechanical coupling toward achieving stable solid/solid interfaces in SSBs.

Novel Theories for Modeling the Surface Stabilization and Dendrite Suppression for Lithium-Metal Anode Based on Piezoelectric Effect

During electrodeposition, a small perturbation can cause the metal surface to lose its stability and form dendrite. Lithium dendrite is a key barrier that has impeded the commercialization of lithium metal batteries as well as fast charging. We find a piezoelectric mechanism to suppress dendrites, whose effect measured by over-potential can easily be 106 stronger than mechanically blocking dendrite with a stiff film. We first expanded the classical electrochemical reaction kinetics by incorporating the effect of stress and thin film piezoelectricity. We then developed a novel theory that couples the fields of electrochemistry, piezoelectricity and thin film mechanics. We then developed a rigorous stability analysis approach to reveal the effect of surface tension, mechanical blocking and piezoelectric mechanism on the stability of electrodeposition. We finally developed a theoretical expression of the critical wavelength, which provides useful guidance on achieving stable electrodeposition for various systems [1].We further developed a theory for a bulk porous piezoelectric medium which couples electrochemistry, piezoelectricity, and mechanics. Specifically, we derived a piezoelectric overpotential, which reveals a fundamental relation to surface charge density, dielectric property of the medium, electrolyte concentration and diffusivity, and the reaction coefficient. Our simulation results show that piezoelectric medium can effectively suppresses electrodeposition on any protrusion, leading to a flat, dendrite-free surface [2].

Role of Mechanics-Driven Kinetic Interactions in Electrodeposition Stability

Solid-state batteries (SSBs) show a promise to boost energy density, power density and thermal safety of lithium-ion batteries. Even though solid electrolytes (SEs), owing to their mechanical rigidity, have enabled the use of Li-metal anodes, growth of filaments within the SE still remains a major challenge. Internal stresses and molar volumes of interacting species strongly influence both reaction kinetics at the anode-SE interface and ionic transport within the SE and thus, play an important role in dictating the stability of the solid-solid interfaces during electrodeposition. In this work, we examine the role of mechanics in altering the underlying reaction and transport processes by analyzing various electrochemical and mechanical parameters involved such as molar volumes, shear moduli, applied current density and ionic conductivity. We present a non-dimensional formulation to demarcate regimes of stable/unstable growth. The effects of interface morphology and molar volume variation at the interface have also been studied.

Critical Role of Pits in Suppressing Li Dendrites Revealed by Continuum Mechanics Simulation and In Situ Experiment

Dendrite growth and surface pitting are critical factors hindering the development of ultra-high energy density rechargeable lithium battery. However, the mechanism of dendrite growth promoted by pits on the surface of lithium metal remains unclear. In this study, we propose a combination of continuum mechanics simulations and develop an in situ experimental observation device to investigate the effects of pit size, curvature of pit edge, overpotential, and lithium-ion concentration gradient on dendrite growth. Results show that a larger size and curvature of pits can reduce the deposition rate of lithium and dendrite morphology significantly. Larger overpotential can aggravate dendritic nucleation and thereby promotes dendrite growth. Uneven lithium-ion concentration gradient distribution significantly influences the direction of the dendrite growth and leads to the formation of branches. The lithium deposition behavior near the ideal pit predicted by continuum mechanics is consistent with that observed in the in situ experiments. These results lay the basis for future studies to determine the effect of the surface morphology of lithium metal electrodes on the electrodeposition stability and performance of lithium metal batteries.

Directional controllable electrodeposition growth of homogeneous Au nano-rampart arrays and its reliable SERS applications

High-yield large-area uniform metal nanoarrays have shown attractive application potential in many fields. Electrodeposition growth has unique advantages in the construction of metal nanostructures due to its high efficiency. However, the uniformity and stability of electrodeposition are still remain challenging. Here, an efficient, stable and cost-effective directional electrodeposition route was proposed to construct large-scale uniform metal nanoarrays, which could be further used as reliable SERS substrates. Assisted with uniform porous anodized aluminum oxide (AAO) templates, a series of homogeneous Au nano-rampart arrays (Au-NRAs) were prepared controllably by directional electrodeposition growth technology. Using the prepared Au-NRAs as SERS substrates, the results showed that the optimal electrodeposition growth is 600 s. At this time, Au-NRAs showed highest SERS activity and the low relative standard deviation (RSD) value of Raman intensity at 619 cm−1 mode of R6G (with concentration of 10-5 M) was 2.08%, which indicated excellent SERS stability. This method integrated not only cost-effectiveness, but also good directional controllability and repeatability, showing great potential in constructing large-area uniform metal nanostructures.

A theory that couples electrochemistry and thin film piezoelectricity with stability analysis for electrodeposition

During electrodeposition, a small perturbation can cause the metal surface to lose its stability and form dendrite. Lithium dendrite is a key barrier that has impeded the commercialization of lithium metal batteries as well as fast charging. We find a piezoelectric mechanism to suppress dendrites, whose effect measured by over-potential can easily be 106 stronger than mechanically blocking dendrite with a stiff film. We first expand the classical electrochemical reaction kinetics by incorporating the effect of stress and thin film piezoelectricity. We then develop a theory that couples the fields of electrochemistry, piezoelectricity and thin film mechanics. Such a fundamental framework is expected to help analyze various new phenomena and material innovation that involves electrochemistry and thin film piezoelectricity. A rigorous stability analysis approach is developed to reveal the effect of surface tension, mechanical blocking and piezoelectric mechanism on the stability of electrodeposition. A theoretical expression of the critical wavelength is derived, which provides useful guidance on achieving stable electrodeposition for various systems.

Ultrafast Metal Electrodeposition Revealed by In Situ Optical Imaging and Theoretical Modeling towards Fast-Charging Zn Battery Chemistry.

Metallic Zn is a preferred anode material for rechargeable aqueous batteries towards a smart grid and renewable energy storage. Understanding how the metal nucleates and grows at the aqueous Zn anode is a critical and challenging step to achieve full reversibility of Zn battery chemistry, especially under fast-charging conditions. Here, by combining in situ optical imaging and theoretical modeling, we uncover the critical parameters governing the electrodeposition stability of the metallic Zn electrode, that is, the competition among crystallographic thermodynamics, kinetics, and Zn2+ -ion diffusion. Moreover, steady-state Zn metal plating/stripping with Coulombic efficiency above 99 % is achieved at 10-100 mA cm-2 in a reasonably high concentration (3 M) ZnSO4 electrolyte. Significantly, a long-term cycling-stable Zn metal electrode is realized with a depth of discharge of 66.7 % under 50 mA cm-2 in both Zn||Zn symmetrical cells and MnO2 ||Zn full cells.

Ultrafast Metal Electrodeposition Revealed by In Situ Optical Imaging and Theoretical Modeling towards Fast‐Charging Zn Battery Chemistry

AbstractMetallic Zn is a preferred anode material for rechargeable aqueous batteries towards a smart grid and renewable energy storage. Understanding how the metal nucleates and grows at the aqueous Zn anode is a critical and challenging step to achieve full reversibility of Zn battery chemistry, especially under fast‐charging conditions. Here, by combining in situ optical imaging and theoretical modeling, we uncover the critical parameters governing the electrodeposition stability of the metallic Zn electrode, that is, the competition among crystallographic thermodynamics, kinetics, and Zn2+‐ion diffusion. Moreover, steady‐state Zn metal plating/stripping with Coulombic efficiency above 99 % is achieved at 10–100 mA cm−2 in a reasonably high concentration (3 M) ZnSO4 electrolyte. Significantly, a long‐term cycling‐stable Zn metal electrode is realized with a depth of discharge of 66.7 % under 50 mA cm−2 in both Zn||Zn symmetrical cells and MnO2||Zn full cells.

Mesoscale Analysis of Interfacial Stability in Solid-State Batteries

The utilization of lithium metal anodes along with inorganic solid electrolytes holds the potential to enhance the energy density, power density and safety of conventional lithium-ion batteries. Despite the theoretical promise of solid electrolytes, the morphological instability of lithium metal anodes during electrochemical operation continues to pose major challenges for the advancement of solid-state batteries. Electrodeposition stability at the solid-solid interface is governed by a wide range of factors including the surface roughness, microstructural arrangement, transport and mechanical properties, relevant to the solid electrolyte and lithium metal. In addition, the competing kinetics of vacancy diffusion and electrochemical reaction alters the metal morphology during discharge and governs the interfacial contact. In this work, a mechanistic understanding of the electrochemical-mechanical interactions underlying the electrodeposition and dissolution stability of lithium metal anodes during fast charge and discharge operation of solid-state batteries will be presented.

Mesoscale Interfacial Interactions in All-Solid-State Lithium Batteries

All-solid-state batteries comprising of a lithium metal anode are promising next-generation energy storage systems, capable of providing enhanced safety and delivering high power and energy densities. Despite the inherent mechanical rigidity of solid electrolytes, the irregular nature of electrodeposition at the metal anode remains unresolved and thereby necessitates a detailed description of the mechanisms underlying the interfacial instability. The morphological evolution of the metal anode is influenced by various factors including the mechanical properties of lithium and solid electrolyte, presence of interfacial roughness, grain boundaries in the solid electrolyte microstructure and external operating conditions. In this work, the fundamental electrochemical-mechanical interactions governing the electrodeposition stability at the solid-solid interface, especially the role of grain boundaries will be examined in detail.

Microstructure and Pressure-Driven Electrodeposition Stability in Solid-State Batteries

Interfacial deposition stability at the Li-metal-solid electrolyte interface in all solid-state batteries is governed by the stress-transport-electrochemistry coupling in conjunction with the polycrystalline/amorphous solid electrolyte architecture. In this work, we delineate the optimal solid electrolyte microstructure comprising grains, grain boundaries, and voids possessing desirable ionic conductivity and elastic modulus for superior transport and strength. An analytical formalism is provided to discern the impact of external “stack” pressure-induced mechanical stress on electrodeposition stability; the stress magnitudes obtained are in the megapascal range, considerably diminishing the stress-kinetics effects. For experimental stack pressures ranging up to 10 MPa, the impact of stress on reaction kinetics is negligibly small, and electrolyte transport overpotentials dictate electrodeposition stability. High current density operation with stable deposition can be ensured with ample external pressure, high temperature, and low surface roughness operation for a low shear modulus ratio of the solid electrolyte to Li-metal. Solid electrolyte architecture is screened via virtual generation and characterization Large grain size, low void size, and porosity provide favorable conduction and stiffness Stack pressure <10 MPa has negligible impact on stress-kinetics coupling High operating pressure, temperature, and low roughness can aid stable deposition Lithium electrodeposition is dependent on solid electrolyte microstructure, stack pressure, and operating temperature. Verma et al. suggest a method to delineate the architecture and operating conditions that lead to stable deposition.

Mesoscale Elucidation of Electrodeposition in All-Solid-State Lithium Batteries

Lithium metal anodes, owing to their theoretical promise have been considered decisive towards the development of next-generation battery systems with higher power and energy densities. Compared to the liquid counterparts, solid electrolytes proffer enhanced safety and dendrite suppression features due to the non-flammability and mechanical stiffness. However, the electrodeposition dynamics at a solid-solid interface is quite intricate, involving coupled transport, mechanical and kinetic processes, which are closely related to the interfacial heterogeneities. Furthermore, the mechanical properties of the solid electrolyte, lithium metal and externally applied pressure influence the mechano-electrochemical interaction and hence the interfacial stability. In this work, a mechanistic understanding of the mesoscale underpinnings in the electrodeposition stability at solid-solid interfaces for all-solid-state lithium batteries will be presented.

A Multiscale View on Li+ Transport in Li Metal Solid-State-Batteries

The fast-expanding sector of portable electronics and electric vehicles looks for new solutions to overcome the safety and performance limitations of liquid electrolyte-based Li-ion batteries. A promising new technology is the so-called Li metal Solid State Battery (SSB), which aims to replace the flammable liquid electrolyte by solid electrolyte materials, such as ceramics or polymers. Ceramic electrolytes are the best candidates for SSB in terms of high Li+ conductivity, though they are strongly limited by their mechanical properties and the limited interfacial contact with Li metal anode. On the other hand, polymer electrolytes present good mechanical properties with a high degree of processability, whereas a low ionic conductivity limits them at RT. An alternative is to combine the desirable properties of ceramic and polymeric electrolytes into a composite concept. Generating knowledge about interactions between composite components and their influence on Li-ion mobility, electrochemical stability, and Li electrodeposition properties is thus, essential to progress towards practical applications.This work attempts to give suitable solutions to overcome the main constraints of solid-state batteries, necessary to implement metallic lithium anode into the solid-state battery concept. Primarily, the intimate and stable contact between electrolyte and electrodes, continuous and fast lithium ions mobility across the membrane and interfaces were targeted. In this contribution, we focused on the Li-metal SSB with a composite solid electrolyte system based on PEO-LiTFSI polymeric matrix enriched with Li6.55Ga0.15La3Zr2O12 garnet filler [1]. To accurately investigate the Li-ion transport properties and avoid the typical segregation issues of these immiscible mixtures. We apply a new processing method that ensures the high degree of structural and chemical homogeneity, even at the local scale, and across a broad range of ceramic filler content. Solid-state NMR and Electron microscopy were used to characterize the structure of the composites locally. The local mobility of Li-ion was investigated by 2D NMR to understand and propose possible transport mechanisms. The effect of garnet filler on salt dissociation, ions interactions, and a correlation between local and global ion mobilities was reconsidered. The impact of the garnet filler content on the macroscopic Li-ion conductivity will be discussed as well as their influence on Li metal stripping/plating and Li dendrite suppression. Finally, the implementation of these composite electrolytes in the Li metal all-solid-state full cell device will be presented.All in all, this work shows how the combination of hard-soft electrolyte materials can enhance the interfacial stability with Li metal anode upon cycling, offering new opportunities to prevent Li dendrite formation in solid-state batteries.[1] J. Zagorski, J.M. Lopez del Amo, M.J. Cordill, F. Aguesse, L. Buannic, A. Llordes. Garnet-Polymer Composite Electrolytes: New Insight on Local Li-Ion Dynamics and Electrodeposition Stability with Li Metal Anodes. ACS Applied Energy Materials 2019 2(3), 1734-1746 DOI: 10.1021/acsaem.8b01850

(Invited) Electrodeposition at Solid-Solid Interfaces

The development of next generation batteries is predicated on utilization of lithium metal anodes with solid electrolytes. Solid electrolytes offer attractive features of improved safety and reduced predilection for dendritic lithium growth through mechanical rigidity. However, the inherent solid-solid interfaces in these systems are not always stable necessitating fundamental understanding of the electrodeposition characteristics at solid-solid interfaces. In particular, coupled transport-kinetics-mechanics complexations arise with dependence on solid electrolyte structure, and interfacial stochasticity dependent on chemical and mechanical wettabilities. Furthermore, the formation of interphase layer complicates the phase-interface pairs with varying kinetic, transport and mechanical properties. In this presentation, the mechanistic underpinnings of the electrodeposition stability at the solid-solid interface for solid electrolyte and lithium metal systems will be examined.

A functionalized metal organic framework-laden nanoporous polymer electrolyte for exceptionally stable lithium electrodeposition.

A nanoporous all-solid-state MOF-laden polymer electrolyte that is simply mediated by an electronic effect shows remarkably high lithium electrodeposition stability of hundreds of charge-discharge cycles and over 1500 operating hours, while maintaining a very small voltage polarization. This result is a significant improvement relative to conventional PEO and, when used in an all-solid-state battery (ASSB), this electrolyte enabled enhanced cycle life. This new all-solid-state electrolyte shows a promising rational design for the emerging microporous polymeric materials as novel SPEs in ASSBs.

Microstructure Ramifications on Electrodeposition for Solid-State Electrolytes

Safe Li-ion batteries with enhanced energy and power density rely on utilization of lithium metal anodes in conjunction with non-flammable solid electrolytes that inhibit dendritic growth through mechanical rigidity. The kinetics, transport, mechanics complexations are strongly dependent on the microstructure of the solid electrolyte. In particular, garnet type electrolytes exhibit crystalline structure consisting of grain, grain boundaries and voids while glassy sulfide type electrolytes exhibit an amorphous structure with voids; with prominent dependence of the transport properties (ionic conductivity) and mechanical properties (shear modulus, fracture toughness) on the structural arrangement. The Li metal-solid electrolyte interface also shows a wide degree of stochasticity due to the imperfect solid-solid contact delineating the importance of surface roughness effects on kinetics and interlayer design to promote surface uniformity. In this work, we investigate these coupled interactions and delineate electrodeposition stability for aforementioned class of inorganic solid electrolytes cognizant of microstructural considerations.

Electrodeposition stability of metal electrodes

Rechargeable battery chemistries, with high energy densities, are particularly desirable in order to meet the burgeoning demand for energy storage. In this regard, metal electrodes have recently drawn extensive research interest due to the intrinsic energy density boost, while a fundamental study is needed to reveal the underlying mechanisms governing the electrodeposition stability. Here, we explore the mesoscale interactions in nucleation and growth of electrodeposition, with a focus on the competition of ion transport in the electrolyte, electrochemical reactions at the electrolyte-electrode interface, and surface self-diffusion. It is found that lithium (Li) and sodium (Na) metal anodes have the tendency to form dendrites at high local reaction rates, whereas magnesium (Mg) and aluminum (Al) do not, because of the low intrinsic self-diffusion barriers. Nonuniform electrodeposition at low reaction rates is observed, which could be attributed to the spatial inhomogeneities due to separator wetting, solid electrolyte interphase (SEI) formation, and electrode surface roughness. This work provides a fundamental understanding of the mesoscale underpinnings on the electrodeposition stability of various metal electrodes, especially shedding light on pathways toward potentially dendrite-free electrodeposition morphology.