The rapidly expanding field of nonaqueous multivalent intercalation batteries offers a promising way to overcome safety, cost, and energy density limitations of state-of-the-art Li-ion battery ...technology. We present a critical and rigorous analysis of the increasing volume of multivalent battery research, focusing on a wide range of intercalation cathode materials and the mechanisms of multivalent ion insertion and migration within those frameworks. The present analysis covers a wide variety of material chemistries, including chalcogenides, oxides, and polyanions, highlighting merits and challenges of each class of materials as multivalent cathodes. The review underscores the overlap of experiments and theory, ranging from charting the design metrics useful for developing the next generation of MV-cathodes to targeted in-depth studies rationalizing complex experimental results. On the basis of our critical review of the literature, we provide suggestions for future multivalent cathode studies, including a strong emphasis on the unambiguous characterization of the intercalation mechanisms.
A major bottleneck for the development of Mg batteries is the identification of liquid electrolytes that are simultaneously compatible with the Mg-metal anode and high-voltage cathodes. One strategy ...to widen the stability windows of current nonaqueous electrolytes is to introduce protective coating materials at the electrodes, where coating materials are required to exhibit swift Mg transport. In this work, we use a combination of first-principles calculations and ion-transport theory to evaluate the migration barriers for nearly 27 Mg-containing binary, ternary, and quaternary compounds spanning a wide chemical space. Combining mobility, electronic band gaps, and stability requirements, we identify MgSiN2, MgI2, MgBr2, MgSe, and MgS as potential coating materials against the highly reductive Mg metal anode, and we find MgAl2O4 and Mg(PO3)2 to be promising materials against high-voltage oxide cathodes (up to ∼3 V).
The diffusion of ions in solid materials plays an important role in many aspects of materials science such as the geological evolution of minerals, materials synthesis, and in device performance ...across several technologies. For example, the realization of multivalent (MV) batteries, which offer a realistic route to superseding the electrochemical performance of Li-ion batteries, hinges on the discovery of host materials that possess adequate mobility of the MV intercalant to support reasonable charge and discharge times. This has proven especially challenging, motivating the current investigation of ion mobility (Li+, Mg2+, Zn2+, Ca2+, and Al3+) in spinel Mn2O4, olivine FePO4, layered NiO2, and orthorhombic δ-V2O5. In this study, we not only quantitatively assess these structures as candidate cathode materials, but also isolate the chemical and structural descriptors that govern MV diffusion. Our finding that matching the intercalant site preference to the diffusion path topology of the host structure controls mobility more than any other factor leads to practical and implementable guidelines to find fast-diffusing MV ion conductors.
Cu2ZnSnS4-based solar cells, which constitute an inexpensive, beyond-Si photovoltaic technology, often suffer from low open-circuit voltage and efficiency. This drawback is often attributed to ...disorder in the Cu–Zn sublattice of the kesterite structure. While previous experiments have reported improved performances with isovalent substitution of Cd and Ag for Cu and Zn, respectively, the fundamental driving force for such improvements remains unclear. Here, we use density functional theory to study bulk stability, defect, and surface energetics, as well as the electronic structure of these dopants in Cu2ZnSnS4. We find that Cd and Ag can increase efficiencies, depending on the dopant concentration and Cu content used during synthesis. Most importantly, we find that a low level of Cd doping can suppress disorder in the kesterite phase across all Cu concentrations, while a low level of Ag doping can do so only when Zn- and Sn-rich conditions are employed. A higher Ag content is beneficial as it stabilizes the kesterite structure, whereas a higher Cd content is detrimental as it stabilizes the lower-gap stannite structure. Cd does not significantly influence the surface energetics of kesterite Cu2ZnSnS4. Ag, on the other hand, decreases the surface energies significantly, which would favor smaller particle sizes. We thus attribute the coarsening of particle size and changes in morphology observed during Cu2ZnSnS4 synthesis to annealing conditions during sulfurization and selenization, instead of any effect of Cd or Ag. Finally, we suggest the exploration of abundant, nontoxic, isovalent dopants, i.e., different from the attributes of Cd and Ag, to improve the performance of Cu2ZnSnS4.
Cointercalation is a potential approach to influence the voltage and mobility with which cations insert in electrodes for energy storage devices. Combining a robust thermodynamic model with ...first-principles calculations, we present a detailed investigation revealing the important role of H2O during ion intercalation in nanomaterials. We examine the scenario of Mg2+ and H2O cointercalation in nanocrystalline Xerogel-V2O5, a potential cathode material to achieve energy density greater than Li-ion batteries. Water cointercalation in cathode materials could broadly impact an electrochemical system by influencing its voltages or causing passivation at the anode. The analysis of the stable phases of Mg-Xerogel V2O5 and voltages at different electrolytic conditions reveals a range of concentrations for Mg in the Xerogel and H2O in the electrolyte where there is no thermodynamic driving force for H2O to shuttle with Mg during electrochemical cycling. Also, we demonstrate that H2O shuttling with the Mg2+ ions in wet electrolytes yields higher voltages than in dry electrolytes. The thermodynamic framework used to study water and Mg2+ cointercalation in this work opens the door for studying the general phenomenon of solvent cointercalation observed in other complex solvent–electrode pairs used in the Li- and Na-ion chemical spaces.
For the transition into a sustainable mode of energy usage, it is important to develop photovoltaic materials that exhibit better solar-to-electricity conversion efficiencies, a direct optimal band ...gap, and are made of non-toxic, earth abundant elements compared to the state-of-the-art silicon photovoltaics. Here, we explore the non-redox-active pnictide chemical space, including binary A
3
B
2
, ternary AA′
2
B
2
, and quaternary AA′A′′B
2
compounds (A, A′, A′′ = Ca, Sr, or Zn; B = N or P), as candidate beyond-Si photovoltaics using density functional theory calculations. Specifically, we evaluate the ground state configurations, band gaps, and 0 K thermodynamic stability for all 20 pnictide compositions considered, besides computing the formation energy of cation vacancies, anion vacancies, and cation anti-sites in a subset of candidate compounds. Importantly, we identify SrZn
2
N
2
, SrZn
2
P
2
, and CaZn
2
P
2
to be promising candidates, exhibiting optimal (1.1-1.5 eV) hybrid-functional-calculated band gaps, stability at 0 K, and high resistance to point defects (formation energies >1 eV), while other possible candidates include ZnCa
2
N
2
and ZnSr
2
N
2
, which may be susceptible to N-vacancy formation. We hope that our study will contribute to the practical development of pnictide semiconductors as beyond-silicon light absorbers.
A first principles screening study of pnictides as candidate photovoltaics.
Fluoride frameworks as potential calcium battery cathodes Tekliye, Dereje Bekele; Sai Gautam, Gopalakrishnan
Journal of materials chemistry. A, Materials for energy and sustainability,
07/2024, Letnik:
12, Številka:
30
Journal Article
Recenzirano
Calcium batteries (CBs) are potential next-generation energy storage devices, offering a promising alternative to lithium-ion batteries due to their theoretically high energy density, better safety, ...and lower costs associated with the natural abundance of calcium. However, the limited availability of positive electrode (cathode) materials has constrained the development of CBs so far. Given the similar ionic radii of Na + and Ca 2+ , structures that are effective at reversibly intercalating Na + may be able to reversibly intercalate Ca 2+ as well. In this context, transition metal fluorides (TMFs) exhibiting weberite and perovskite structures that are known for intercalating Na + form an interesting set of possible CB cathode frameworks. Thus, we use first principles calculations to explore weberite and perovskite TMFs as CB cathodes, of compositions Ca x M 2 F 7 and Ca x MF 3 , respectively, where M = Ti, V, Cr, Mn, Fe, Co, or Ni. We systematically evaluate key cathode properties, including the ground state structure, average Ca-intercalation voltage, thermodynamic stability (at 0 K), theoretical capacity, and Ca 2+ migration barriers. Importantly, we identify Ca x Cr 2 F 7 and Ca x Mn 2 F 7 weberite frameworks as promising Ca-cathodes. Our study not only unveils potential CB cathodes but also paves the way for further advancement in TMF-based intercalation cathodes, diversifying the chemical space for next-generation energy storage systems.
A crucial ingredient in lithium (Li) and sodium (Na)-ion batteries (LIBs and NIBs) is the electrolyte. The use of Li metal (Na metal) as the anode in liquid electrolyte LIBs (NIBs) is constrained by ...several issues including thermal runaway, flammability, electrolyte leakage, and limited chemical stability. Considerable effort has been devoted toward the development of solid electrolytes (SEs) and all-solid-state batteries, which are presumed to mitigate some of the issues of Li metal (Na metal) in contact with flammable liquid electrolytes. However, most SEs, such as Li
3
PS
4
, Li
6
PS
5
Cl and Na
3
PS
4
readily decompose against the highly reducing Li-metal and Na-metal anodes. Using first-principles calculations we elucidate the stability of more than 20 solid|solid interfaces formed between the decomposition products of Li
3
PS
4
, Li
6
PS
5
Cl (and Na
3
PS
4
) against the Li-metal (Na-metal) electrode. We suggest that the work of adhesion needed to form a heterogenous interface is an important descriptor to quantify the stability of interfaces. Subsequently, we clarify the atomistic origins of the resistance to Li-ion transport at interfaces of the Li-metal anode and selected decomposition products (Li
3
P, Li
2
S and LiCl) of SEs,
via
a high-fidelity machine learning potential. Utilising an machine learning potential enables nano-second-long molecular dynamics simulations on 'large' interface models (here with 8320 atoms), but with similar accuracy to first-principles approaches. Our simulations demonstrate that the interfaces formed between Li metal and argyrodite (
e.g.
, Li
6
PS
5
Cl) decomposition products are resistive to Li-ion transport. The implications of this study are important since binary compounds are commonly found in the vicinity of the Li(Na) metal anode upon chemical and/or electrochemical decomposition of ternary and quaternary SEs.
A crucial ingredient in lithium (Li) and sodium (Na)-ion batteries (LIBs and NIBs) is the electrolyte.
Magnesium batteries appear a viable alternative to overcome the safety and energy density limitations faced by current lithium-ion technology. The development of a competitive magnesium battery is ...plagued by the existing notion of poor magnesium mobility in solids. Here we demonstrate by using ab initio calculations, nuclear magnetic resonance, and impedance spectroscopy measurements that substantial magnesium ion mobility can indeed be achieved in close-packed frameworks (~ 0.01-0.1 mS cm
at 298 K), specifically in the magnesium scandium selenide spinel. Our theoretical predictions also indicate that high magnesium ion mobility is possible in other chalcogenide spinels, opening the door for the realization of other magnesium solid ionic conductors and the eventual development of an all-solid-state magnesium battery.
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