The storage of electrical energy at high charge and discharge rate is an important technology in today's society, and can enable hybrid and plug-in hybrid electric vehicles and provide back-up for ...wind and solar energy. It is typically believed that in electrochemical systems very high power rates can only be achieved with supercapacitors, which trade high power for low energy density as they only store energy by surface adsorption reactions of charged species on an electrode material. Here we show that batteries which obtain high energy density by storing charge in the bulk of a material can also achieve ultrahigh discharge rates, comparable to those of supercapacitors. We realize this in LiFePO4 (ref. 6), a material with high lithium bulk mobility, by creating a fast ion-conducting surface phase through controlled off-stoichiometry. A rate capability equivalent to full battery discharge in 10-20 s can be achieved.
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Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Aqueous precipitation of transition metal oxides often proceeds through non-equilibrium phases, whose appearance cannot be anticipated from traditional phase diagrams. Without a precise understanding ...of which metastable phases form, or their lifetimes, targeted synthesis of specific metal oxides can become a trial-and-error process. Here, we construct a theoretical framework to reveal the nanoscale and metastable energy landscapes of Pourbaix (E-pH) diagrams, providing quantitative insights into the size-dependent thermodynamics of metastable oxide nucleation and growth in water. By combining this framework with classical nucleation theory, we interrogate how solution conditions influence the multistage oxidation pathways of manganese oxides. We calculate that even within the same stability region of a Pourbaix diagram, subtle variations in pH and redox potential can redirect a non-equilibrium crystallization pathway through different metastable intermediates. Our theoretical framework offers a predictive platform to navigate through the thermodynamic and kinetic energy landscape towards the rational synthesis of target materials.
In the past several years, Materials Genome Initiative (MGI) efforts have produced myriad examples of computationally designed materials in the fields of energy storage, catalysis, thermoelectrics, ...and hydrogen storage as well as large data resources that are used to screen for potentially transformative compounds. The bottleneck in high-throughput materials design has thus shifted to materials synthesis, which motivates our development of a methodology to automatically compile materials synthesis parameters across tens of thousands of scholarly publications using natural language processing techniques. To demonstrate our framework’s capabilities, we examine the synthesis conditions for various metal oxides across more than 12 thousand manuscripts. We then apply machine learning methods to predict the critical parameters needed to synthesize titania nanotubes via hydrothermal methods and verify this result against known mechanisms. Finally, we demonstrate the capacity for transfer learning by using machine learning models to predict synthesis outcomes on materials systems not included in the training set and thereby outperform heuristic strategies.
Solid-state batteries (SSBs) using a solid electrolyte show potential for providing improved safety as well as higher energy and power density compared with conventional Li-ion batteries. However, ...two critical bottlenecks remain: the development of solid electrolytes with ionic conductivities comparable to or higher than those of conventional liquid electrolytes and the creation of stable interfaces between SSB components, including the active material, solid electrolyte and conductive additives. Although the first goal has been achieved in several solid ionic conductors, the high impedance at various solid/solid interfaces remains a challenge. Recently, computational models based on ab initio calculations have successfully predicted the stability of solid electrolytes in various systems. In addition, a large amount of experimental data has been accumulated for different interfaces in SSBs. In this Review, we summarize the experimental findings for various classes of solid electrolytes and relate them to computational predictions, with the aim of providing a deeper understanding of the interfacial reactions and insight for the future design and engineering of interfaces in SSBs. We find that, in general, the electrochemical stability and interfacial reaction products can be captured with a small set of chemical and physical principles.The reliable operation of solid-state batteries requires stable or passivating interfaces between solid components. In this Review, we discuss models for interfacial reactions and relate the predictions to experimental findings, aiming to provide a deeper understanding of interface stability.
A unifying theory is presented to explain the lithium exchange capacity of rocksalt‐like structures with any degree of cation ordering, and how lithium percolation properties can be used as a ...guideline for the development of novel high‐capacity electrode materials is demonstrated. The lithium percolation properties of the three most common lithium metal oxide phases, the layered α‐NaFeO2 structure, the spinel‐like LT‐LiCoO2 structure, and the γ‐LiFeO2 structure, are demonstrated and a strong dependence of the percolation thresholds on the cation ordering and the lithium content is observed. The poor performance of γ‐LiFeO2‐type structures is explained by their lack of percolation of good Li migration channels. The spinel‐like structure exhibits excellent percolation properties that are robust with respect to off‐stoichiometry and some amount of cation disorder. The layered structure is unique, as it possesses two different types of lithium diffusion channels, one of which is, however, strongly dependent on the lattice parameters, and therefore very sensitive to disorder. In general it is found that a critical Li‐excess concentration exists at which Li percolation occurs, although the amount of Li excess needed depends on the partial cation ordering. In fully cation‐disordered materials, macroscopic lithium diffusion is enabled by ≈10% excess lithium.
A simple model based on percolation theory
can explain the relationship between structure, composition, and specific capacity of rocksalt‐type lithium battery electrodes. Numerical percolation simulations therefore allow identification of concrete design guidelines regarding the crystal structure, the lithium content, and the degree of cation disorder for the development of novel high‐capacity electrode materials.
Layered Na–metal oxides can form in different crystal structures, each with different electrochemical behavior. As a prototype system to better understand how each phase can be formed, we present the ...conditions under which different layered phases of Na x CoO2 can be stabilized in solid-state synthesis. Using a novel combination of ex situ XRD on as-synthesized samples, with in situ XRD to monitor the relation between Na content and lattice parameters, we are able to construct a phase diagram of Na x CoO2 between 450 to 750 °C in air and for Na:Co sample ratios ranging from 0.60 to 1.05. Four single phase domains of O3, O′3, P′3, and P2 are revealed based on the XRD analysis. In contrast to previous reports it is found that pure O3, O′3 and P′3 phase can only form at a fixed stoichiometry of x = 1.00, 0.83, and 0.67, respectively, while the P2 phase forms in a slightly larger composition range from 0.68 to 0.76. Galvanostatic charging of O3–Na1.00CoO2 shows several flat and sloping regions on the voltage profile, which follows the sequence of O3–O′3–P′3–P3–P′3, with increasing interslab distances. Our results indicate that the electrochemically important P2 structure is likely stabilized by entropy.
Sustained growth in lithium-ion battery (LIB) demand within the transportation sector (and the electricity sector) motivates detailed investigations of whether future raw materials supply will ...reconcile with resulting material requirements for these batteries. We track the metal content associated with compounds used in LIBs. We find that most of the key constituents, including manganese, nickel, and natural graphite, have sufficient supply to meet the anticipated increase in demand for LIBs. There may be challenges in rapidly scaling the use of materials associated with lithium and cobalt in the short term. Due to long battery lifetimes and multiple end uses, recycling is unlikely to provide significant short-term supply. There are risks associated with the geopolitical concentrations of these elements, particularly for cobalt. The lessons revealed in this work can be relevant to other industries in which the rapid growth of a materials-dependent technology disrupts the global supply of those materials.
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The key conclusions of this perspective have shown that the supply of most materials contained within lithium-ion batteries will likely meet the demand for the near future. However, there are potential risks associated with the supply of cobalt. Furthermore, if there is rapid adoption of electric vehicles (incentivized by policy interventions including a carbon tax, higher fuel taxes, and more aggressive Corporate Average Fuel Economy targets), demand could outpace supply for some battery-grade materials (even for lithium in the very near term). The implications for research based on this perspective span many scales. First, continued research into cathode materials that alleviate some of these supply issues is of interest, particularly those that are cobalt free. Supply chain research and investigations in the policy domain may also help uncover ways to address materials availability in the future. Future investigations should provide a dynamic analysis with sufficient detail to map technological and operational changes to their impact on cost and to map performance to market value.
There has been continued growth in lithium-ion battery-powered electric vehicles. This puts new pressure on the supply of materials used in these products. We present an analysis of supply chain issues for lithium, manganese, cobalt, nickel, and natural graphite focused first on their potential supply concerns and then the scaled demand for these materials. This contribution provides practical considerations that should factor into sustainable energy research, particularly as it relates to global impact on materials supply chains.
Structure plays a vital role in determining materials properties. In lithium ion cathode materials, the crystal structure defines the dimensionality and connectivity of interstitial sites, thus ...determining lithium ion diffusion kinetics. In most conventional cathode materials that are well-ordered, the average structure as seen in diffraction dictates the lithium ion diffusion pathways. Here, we show that this is not the case in a class of recently discovered high-capacity lithium-excess rocksalts. An average structure picture is no longer satisfactory to understand the performance of such disordered materials. Cation short-range order, hidden in diffraction, is not only ubiquitous in these long-range disordered materials, but fully controls the local and macroscopic environments for lithium ion transport. Our discovery identifies a crucial property that has previously been overlooked and provides guidelines for designing and engineering cation-disordered cathode materials.
Cation disorder is an important design criterion for technologically relevant transition-metal (TM) oxides, such as radiation-tolerant ceramics and Li-ion battery electrodes. In this Letter, we use a ...combination of first-principles calculations, normal mode analysis, and band-structure arguments to pinpoint a specific electronic-structure effect that influences the stability of disordered phases. We find that the electronic configuration of a TM ion determines to what extent the structural energy is affected by site distortions. This mechanism explains the stability of disordered phases with large ionic radius differences and provides a concrete guideline for the discovery of novel disordered compositions.
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