Odyssey of Multivalent Cathode Materials: Open Questions and Future Challenges

Abstract

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.

On the viability of Mg extraction in MgMoN2: a combined experimental and theoretical approach

“…1,2 Indeed, for divalent charge carriers, the number of ions that must react to achieve a certain electrochemical capacity should diminish by a factor of two when compared to monovalent ions such as lithium or sodium, or, for the same number of reacted ions there would be a concomitant two-fold increase in the energy density of the cells. Furthermore, the exploitation of naturally abundant elements, such as Ca, Mg and Al in replacement of conventional Li-ion battery chemistry would bear substantial environmental and cost benefits.…”

Magnesium-sulfur battery: its beginning and recent progress

“…So far, only a few types of conventional intercalation materials have been identified that are capable of storing Mg 2+ ions reversibly. [8][9][10][11][12][13][14][15] Thus, the challenges to realize the rechargeable Mg battery technology are not only the improvement of the electrolyte toward high oxidative stability, but also the discovery of cathode materials enabling high performance of Mg batteries.…”

“…The research work on Mg batteries in general has been timely reviewed and thoroughly discussed, [8][9][10][11][12][13][14][15][18][19][20] so that we will focus on the properties of Mg electrolytes in view of the application to S cathodes. Thereafter, we will illustrate the progress that is being made on Mg-S battery and discuss future prospects for high-energy Mg and Mg-S batteries.…”

“…The electrochemical performance, e.g., cycling ability, cell voltage, and achievable capacity of the common intercalation compounds in Mg batteries falls far behind from that of in Li-ion batteries. [15] So far, Mo 6 S 8 is still the most successful cathode enabling effectively reversible Mg 2+ ion insertion/ extraction owing to its unique crystallographic structure. [6] However, the high molecular weight and the relatively low discharge voltage (<1.5 V versus Mg/Mg 2+ ) leads to the low gravimetric energy density of the Mg cell.…”

Fast Mg2+ diffusion in Mo3(PO4)3O for Mg batteries

“…This low barrier is verified by ab initio molecular dynamics and kinetic Monte Carlo simulations. The voltage and specific energy are predicted to be B1.98 V and B173 W h kg A promising strategy to increase the energy density of rechargeable batteries is to transition from monovalent to multivalent batteries, such as Mg batteries, [1][2][3] Fig. 1), we also investigated other possible sites for Mg to reside in the empty host structure Mo 3 (PO 4 ) 3 O.…”