Spinel compounds as multivalent battery cathodes: a systematic evaluation based on ab initio calculations

Abstract

contributed equally to this work. AbstractBatteries that shuttle multi-valent ions such as Mg 2+ and Ca 2+ ions are promising candidates for achieving higher energy density than available with current Li-ion technology. Finding electrode materials that reversibly store and release these multi-valent cations is considered a major challenge for enabling such multi-valent battery technology. In this paper, we use recent advances in high-throughput firstprinciples calculations to systematically evaluate the performance of compounds with the spinel structure as multivalent intercalation cathode materials, spanning a matrix of five different intercalating ions and seven transition metal redox active cation. We estimate the insertion voltage, capacity, thermodynamic stability of charged and discharged states, as well as the intercalating ion mobility and use these properties to evaluate promising directions. Our calculations indicate that the Mn2O4 spinel phase based on Mg and Ca are feasible cathode materials. In general, we find that multivalent cathodes exhibit lower voltages compared to Li cathodes; 2 the voltages of Ca spinels are ~ 0.2V higher than those of Mg compounds (versus their corresponding metals), and the voltages of Mg compounds are ~1.4 V higher than Zn compounds; consequently, Ca and Mg spinels exhibit the highest energy densities amongst all the multivalent cation species. The activation barrier for the Al 3+ ion migration in the Mn2O4 spinel is very high (~1400 meV for Al 3+ in the dilute limit); thus, the use of an Al based Mn spinel intercalation cathode is unlikely.Amongst the choice of transition metals, Mn-based spinel structures rank highest when balancing all the considered properties. Broader ContextThe high price and limited volumetric capacity of the lithium ion battery (LIB) challenges its application in electric vehicles and portable electronics. Multivalent batteries, such as those utilizing Mg 2+ or Ca 2+ as the working ions, are promising candidates for beyond LIB technology due to the increase in volumetric capacity and reduced cost. In the present work, we use first-principles calculations to systematically evaluate the theoretical performance of the spinel structure host with the general formula AB2O4 across a matrix of chemical compositions spanning A={Al, Y, Mg, Ca, Zn} and B={Ti, V, Cr, Mn, Fe, Co, Ni} for multivalent battery applications. The evaluation incorporates screening on voltage, capacity, thermodynamic structural and thermal stability as well as ion mobility and discusses the results in the context of available host structure sites, preference of the intercalating cation, and the oxidation state of the redox-active cation. Overall, the Mn2O4 spinel phases paired with Mg 2+ or Ca 2+ emerge as the most promising multivalent cathode materials. As the first comprehensive screening of multivalent intercalation compounds across size, valence, and redox-states of the involved cations, our work is intended to

Status and challenge of Mg battery cathode

“…The best candidate seems to be spinel MnO 2 , which has a barrier ∼ 650 meV. 48 Consistent with Liu et al's report, Kim et al reported the observation of reversible Mg intercalation into spinel-MnO 2 using aqueous Mg(NO 3 ) 2 eletrolyte (1 M) and Pt as the counter electrode. 49 The discharge delivered a capacity of 190 mAh/g.…”

“…48 All these compounds exhibit lower voltage than that of Li analogues. It is mainly a result of the high redox potential of Mg/Mg 2+ .…”

Fulfilling the promise of the materials genome initiative with high-throughput experimental methodologies

“…Multivalent intercalation cathodes can exhibit very high energy density compared to their Li-ion counterparts, creating the materials innovation challenge of identifying host structures with sufficient ionic mobility. Systematically searching through redox-active cations and mobile multivalent species, Liu et al 69,70 predicted reasonable overall performance for Mg and Ca in the Mn oxide spinel structure ( Fig. 3), as well as in the Cr, Ti, and Mn sulfide spinels.…”

Sponge-Like Porous Manganese(II,III) Oxide as a Highly Efficient Cathode Material for Rechargeable Magnesium Ion Batteries

“…4 This sluggish diffusion of Mg 2+ compared to Li + is presumed to be due to the strong Mg inter-actions with the anions and the cations of the hosts, giving rise to a low Mg intercalation level and a large difference between the charge and discharge potentials. The reasons behind the sluggish diffusion of Mg in spinel materials were recently further studied by Ceder et al and Persson et al 25,26 In order to improve this issue, reducing the particle size of the electrode material has been widely used, which significantly shortens the diffusion lengths of ions and electrons within the particles, resulting in more efficient and rapid access of the active cations. 27 Moreover, increased surface area ensures better contact between the electrolyte and active material.…”