Metal–Metal Bonding as an Electrode Design Principle in the Low-Strain Cluster Compound LiScMo₃O₈

Abstract

Electrode materials for Li + -ion batteries require optimization along several disparate axes related to cost, performance, and sustainability. One of the important performance axes is the ability to retain structural integrity though cycles of charge/discharge. Metal-metal bonding is a distinct feature of some refractory metal oxides that has been largely underutilized in electrochemical energy storage, but that could potentially impact structural integrity. Here LiScMo 3 O 8 , a compound containing triangular clusters of metal-metal bonded Mo atoms, is studied as a potential anode material in Li + -ion batteries. Electrons inserted though lithiation are localized across rigid Mo 3 triangles (rather than on individual metal ions), resulting in minimal structural change as suggested by operando diffraction. The unusual chemical bonding allows this compound to be cycled with Mo atoms below a formally +4 valence state, resulting in an acceptable voltage regime that is appropriate for an anode material.Several characterization methods including potentiometric entropy measurements indicate two-phase regions, which are attributed through extensive first-principles modeling to Li + ordering. This study of LiScMo 3 O 8 provides valuable insights for design principles for structural motifs that stably and reversibly permit Li + (de)insertion.

Electrochemical Control of Magnetism on the Breathing Kagome Network of LixScMo3O8

“…At off-stoichiometric compositions, we expect electrons to remain localized and for there to be a mixture of oxidation states of the Mo 3 clusters. Indeed, analyzing the low-energy configurations considered previously reveals clear charge ordering, which can be inferred from both the average Mo–Mo bond length and total magnetic moment of each cluster …”

“…It has also been shown recently that Li insertion into the structure is highly stable and reversible, with minimal changes or expansion of the network. 27 The starting oxidation state of Mo in this structure is Mo 4+ , and previous electrochemistry of the compound shows that up to two additional Li can be inserted to achieve a total Li content of Li 3 ScMo 3 O 8 . The parent structure is very similar to the more studied Li 2 ScMo 3 O 8 (h.t.)…”

“…A more detailed procedure can be found elsewhere. 27 Li 2 ScMo 3 O 8 was prepared in a similar manner using identical precursor oxide powders in the appropriate stoichiometry. For this composition, the nitric acid wash was not necessary.…”

“…Indeed, analyzing the low-energy configurations considered previously reveals clear charge ordering, which can be inferred from both the average Mo−Mo bond length and total magnetic moment of each cluster. 27 One such configuration at x = 2.5, shown in Figure 11, serves as an example of the coupling between charge, spin, and Li ordering in this system. The Li are arranged in a row ordering, with rows of tetrahedrally coordinated Li between regions of octahedrally coordinated Li.…”

2D TaSe2 as a zero-strain and high-performance anode material for Li+ storage

“…Thus, in contrast to other zero-strain/quasizerostrain anode materials, such as Li 4 Ti 5 O 12 (B1.6 V), SrVO 3 (B0.9 V), V 3 Nb 17 O 50 (B1.7 V), Li 3.08 Cr 0.02 Si 0.09 V 0.9 O 4 (B1.0 V), and LiScMo 3 O 8 (B1.6 V), the average working voltage of the 2D/bulk TaSe 2 electrodes can result in higher energy density in full cells. 9,11,26,34 In addition, there are no plateaus in the discharge-charge curves, indicating that Li + reacts with TaSe 2 through a solidsolution reaction. 35 The cyclic voltammetry (CV) curves of 2D TaSe 2 (Fig.…”