In the critical area of sustainable energy storage, solid-state batteries have attracted considerable attention due to their potential safety, energy-density and cycle-life benefits. This Review describes recent progress in the fundamental understanding of inorganic solid electrolytes, which lie at the heart of the solid-state battery concept, by addressing key issues in the areas of multiscale ion transport, electrochemical and mechanical properties, and current processing routes. The main electrolyte-related challenges for practical solid-state devices include utilization of metal anodes, stabilization of interfaces and the maintenance of physical contact, the solutions to which hinge on gaining greater knowledge of the underlying properties of solid electrolyte materials. Solid-state batteries are attractive due to their potential safety, energy-density and cycle-life benefits. Recent progress in understanding inorganic solid electrolytes considering multiscale ion transport, electrochemical and mechanical properties, and processing are discussed.

Fundamentals of inorganic solid-state electrolytes for batteries

All-solid-state batteries (ASSBs) have attracted enormous attention as one of the critical future technologies for safe and high energy batteries. With the emergence of several highly conductive solid electrolytes in recent years, the bottleneck is no longer Li-ion diffusion within the electrolyte. Instead, many ASSBs are limited by their low Coulombic efficiency, poor power performance, and short cycling life due to the high resistance at the interfaces within ASSBs. Because of the diverse chemical/physical/mechanical properties of various solid components in ASSBs as well as the nature of solid-solid contact, many types of interfaces are present in ASSBs. These include loose physical contact, grain boundaries, and chemical and electrochemical reactions to name a few. All of these contribute to increasing resistance at the interface. Here, we present the distinctive features of the typical interfaces and interphases in ASSBs and summarize the recent work on identifying, probing, understanding, and engineering them. We highlight the complicated, but important, characteristics of interphases, namely the composition, distribution, and electronic and ionic properties of the cathode-electrolyte and electrolyte-anode interfaces; understanding these properties is the key to designing a stable interface. In addition, conformal coatings to prevent side reactions and their selection criteria are reviewed. We emphasize the significant role of the mechanical behavior of the interfaces as well as the mechanical properties of all ASSB components, especially when the soft Li metal anode is used under constant stack pressure. Finally, we provide full-scale (energy, spatial, and temporal) characterization methods to explore, diagnose, and understand the dynamic and buried interfaces and interphases. Thorough and in-depth understanding on the complex interfaces and interphases is essential to make a practical high-energy ASSB.

/pdf/interfaces-and-interphases-in-all-solid-state-batteries-with-1oqa3azz6p.pdf

Interfaces and Interphases in All-Solid-State Batteries with Inorganic Solid Electrolytes.

https://cyberleninka.org/article/n/403409.pdf

A review of numerical analysis of friction stir welding

DOI: 10.1002/aenm.202002689 lightweight, and compact and allow for versatile device geometries. They must also be scalable and offer high energy density to provide improved packing efficiency and longer device operation. Although both Ni–MH batteries and LIBs have been commercialized since the 1990s,[1] LIBs possess twice the gravimetric/volumetric energy density (250 Wh kg−1/700 Wh L−1 vs 170 Wh kg−1/350 Wh L−1),[2] higher battery voltage (3.7 V vs 1.2 V), and longer cycle life with lower self-discharge,[3] contributing tremendously to the proliferation of portable electronic devices (e.g., mobile phones, laptops, cameras, tablets) as well as emerging new technologies such as wearable electronic devices (e.g., smart watches and sport-related tracking devices). Their high gravimetric/ volumetric energy density,[2] excellent cycle life (thousands of cycles), and lack of the memory effect have positioned LIBs as state-of-the-art power sources and one of the greatest successes of modern electrochemistry, revolutionizing the way we acquire, process, transmit, and share information globally. Nevertheless, advances in battery energy density, safety, costs, and flexibility in shape and size are still needed to keep up with the rapidly growing demand for devices with even longer runtime as well as real-time data collection and transmission capabilities in addition to increasingly energy-demanding applications such as electric vehicles (EVs) and electricity grid storage. Even though LIBs were first commercialized in all electric vehicles (EVs) in 2010 and also emerged for grid application in the same time frame, the low energy density (≈250 Wh kg−1) and high average cost (≈$156 kWh−1 in 2019) of conventional LIBs do not meet the requirements for advanced EVs and grid-scale energy storage.[4–6] Specifically, the driving range per charge (miles), which is related to the energy density of each cell, and the cost are important parameters for EVs. For example, one 85 kWh battery pack in a Tesla Model S requires 7104 LIB cells, with an energy density of 265 Wh kg−1, providing an average range of 250 miles, which is ahead of the range of other EVs but still behind the target of 375 miles.[4] In grid-scale applications, LIBs can be used for various tasks: frequency regulation, peak shaving, load leveling, and large-scale integration of renewable energies, with specific properties generally required for each task. For frequency regulation, LIBs need to provide a fast response, high rate performance, and high-power capability, The introduction of new, safe, and reliable solid-electrolyte chemistries and technologies can potentially overcome the challenges facing their liquid counterparts while widening the breadth of possible applications. Through tech-historic evolution and rationally analyzing the transition from liquidbased Li-ion batteries (LIBs) to all-solid-state Li-metal batteries (ASSLBs), a roadmap for the development of a successful oxide and sulfide-based ASSLB focusing on interfacial challenges is introduced, while accounting for five parameters: energy density, power density, longterm stability, processing, and safety. First taking a strategic approach, this review dismantles the ASSLB into its three major components and discusses the most promising solid electrolytes and their most advantageous pairing options with oxide cathode materials and the Li metal anode. A thorough analysis of the chemical, electrochemical, and mechanical properties of the two most promising and investigated classes of inorganic solid electrolytes, namely oxides and sulfides, is presented. Next, the overriding challenges associated with the pairing of the solid electrolyte with oxide-based cathodes and a Li-metal anode, leading to limited performance for solid-state batteries are extensively addressed and possible strategies to mitigate these issues are presented. Finally, future perspectives, guidelines, and selective interface engineering strategies toward the resolution of these challenges are analyzed and discussed.

Solid-State Li–Metal Batteries: Challenges and Horizons of Oxide and Sulfide Solid Electrolytes and Their Interfaces

A review on modeling of electro-chemo-mechanics in lithium-ion batteries

Progressive damage, which eventually leads to failure, is ubiquitous in biological and synthetic polymers. The simplest case to consider is that of elastomeric materials which can undergo large reversible deformations with negligible rate dependence. In this paper we develop a theory for modeling progressive damage and rupture of such materials. We extend the phase-field method, which is widely used to describe the damage and fracture of brittle materials, to elastomeric materials undergoing large deformations. A central feature of our theory is the recognition that the free energy of elastomers is not entirely entropic in nature — there is also an energetic contribution from the deformation of the bonds in the chains. It is the energetic part in the free energy which is the driving force for progressive damage and fracture.

Progressive damage and rupture in polymers

Rupture of polymers by chain scission

The interfacial contact between active material and solid electrolyte in a composite electrode limits the kinetics of all-solid-state batteries (ASSB). Despite the progress in processing techniques to improve cohesion in composite electrodes, the electrochemical reactions and mechanical stresses developed during battery operation affects interface properties. Here, we propose a one-dimensional radially symmetric analytical model based on the cohesive theory of fracture, to investigate the mechanical stability of interfaces in ASSB microstructures. Using the cohesive-energy approach, we analyze the delamination criterion and derive a stability condition for fracture propagation. Furthermore, we investigate the role of particle size and material properties on delamination, and we explore the effect of delamination on area-specific impedance. We report that delamination is induced when electrode particles undergo a volumetric change of about $7.5%$ during (de)intercalation. Compliant electrolytes $(El25\phantom{\rule{4pt}{0ex}}\mathrm{GPa})$ are found to accommodate up to $25%$ of particle volume change and delay the onset of delamination. The study identifies geometric regimes for mechanical stability. Such regimes are based on the relative size of the damage zone with respect to the particle radius. Finally, we demonstrate that delamination can significantly influence the total charge/discharge time if highly conductive electrolytes are employed. Overall, the analyses provide guidelines for engineering electrode-electrolyte interfacial properties by controlling particle size, material stiffness, and adhesive strength and length scale.

https://link.aps.org/accepted/10.1103/PhysRevMaterials.2.105407

Mechanical instability of electrode-electrolyte interfaces in solid-state batteries

Wet-sand impulse loading of metallic plates and corrugated core sandwich panels

Experimental studies in the literature show that the fracture of ferritic steels in the presence of hydrogen occurs primarily perpendicular to the direction of the maximum principal tensile stress, is transgranular in nature, and has fracture surfaces which show “quasi-cleavage” features. Such features are cleavage-like but not along any known cleavage plane or grain boundaries. While the precise micromechanisms which lead to a transition from regular plastic deformation of the steel to “quasi-brittle” fracture are at present unclear, in this paper we have formulated a continuum theory for the diffusion of hydrogen coupled with the elastic-viscoplastic response of metals, together with a simple model which leads to quasi-brittle fracture in the presence of hydrogen. We assume that when an internal variable φ of the theory reaches a critical value φcr, then the inelastic deformation transitions from (a) a volume-preserving plastic stretching which occurs in the direction of the stress deviator — as in standard Mises-type plasticity, to (b) a different form of inelastic stretching which occurs in the direction of the maximum principal stress, and which is dilational in nature. We call this latter form of inelastic deformation craze inelasticity. We view the strain produced due to crazing as a “quasi-brittle” form of inelastic deformation. We allow only a small amount of inelastic craze-strain before the process of craze-breakdown and fracture sets in. To model craze-breakdown we introduce a damage variable d ∈ [ 0 , 1 ] ; if d = 0 at a point then that point is intact, while if d = 1 at some point then that point is fractured. With the aim of “regularizing” the strain-softening behavior during craze-breakdown, and to avoid mesh-dependency related issues during finite element simulations, we develop a damage theory which depends not only on d but also its gradient ∇ d , which is considered to be a measure of the spatial inhomogeneity of the damage during the craze-breakdown process. We have numerically implemented our coupled diffusion-deformation-damage theory in a finite element program, and we present representative numerical examples which show the ability of the simulation capability to qualitatively replicate the process of fracture due to hydrogen embrittlement in some technically relevant geometries.

Brandon Talamini

Papers

Progressive damage and rupture in polymers

Rupture of polymers by chain scission

Mechanical instability of electrode-electrolyte interfaces in solid-state batteries

Wet-sand impulse loading of metallic plates and corrugated core sandwich panels

On modeling fracture of ferritic steels due to hydrogen embrittlement