Electrochemical Synthesis of a Lithium-Rich Rock-Salt-Type Oxide Li₅W₂O₇ with Reversible Deintercalation Properties

Abstract

Starting from the ribbon structure Li2W2O7, the lithium-rich phase Li5W2O7 with an ordered rock-salt-type structure has been synthesized, through a topotactic irreversible reaction, using both electrochemistry and soft chemistry. In contrast to Li2W2O7, the lithium-rich oxide Li5W2O7 shows reversible deintercalation properties of two lithium molecules per formula unit: a stable reversible capacity of 110 mAh/g at 1.70 V is maintained after 10 cycles. The exploration of the lithium mobility in this system shows that Li2W2O7 is a cationic conductor with σ = 4.10(-4) S/cm at 400 °C and Ea = 0.5 eV.

A disordered rock salt anode for fast-charging lithium-ion batteries

“…Lithium-rich disordered rock salt (DRS) oxides are known to be promising cathode materials, with fast lithium (Li) diffusion that is due to a perco-lating network of octahedrontetrahedron-octahedron pathways 4,10 . However, although the formation of DRS such as Li3MoO4 and Li5W2O7 oxides during electrochemical reactions is known 11,12 , there have been no investigations of further insertion of Li into DRS oxides to form potential anode materials. Delmas showed that three Li ions could intercalate into V2O5 to form Li3V2O5 when the discharge cut-off voltage is extended to 1.9 V, with the proposed structure to be a rock salt phase with crystallo-graphic formula Li0.6V0.4O (refs.…”

New Insights into Alkali Metal Tungstates: The High Temperature Polymorphism of Na2WO4, the New Polymorph Li2WO4‐V and the Redetermined Crystal Structure of Li2W2O7

“…The anion features two crystallographically distinct sets of WO 6 octahedra sharing three and two edges with adjacent ones according to the Niggli formalism (W1O 1/1 O 3/2 O 2/3 )(W2O 2/1 O 3/2 O 1/3 ) 2− resulting in [W 2 O 7 ] 2− double chains along [100]. These [W 2 O 7 ] ∞ ribbons exhibit rock salt type configuration [17] . Further, there are two crystallographically distinct tetrahedrally coordinated lithium sites, Li1 (Figure 6b) and Li2 (Figure 6c).…”

“…High ionic conductivity is reported for Li 2 W 2 O 7 . [17] This was attributed to the ribbon-type structure. Recently, Xu et al investigated the ionic conductivity of Li 2 W 2 O 7 extensively.…”

Wet-Chemical Synthesis of 3D Stacked Thin Film Metal-Oxides for All-Solid-State Li-Ion Batteries

“…This is confirmed by additional analysis of the lower diffraction angles, revealing that minor amounts of Li 2 W 2 O 7 are present due to a solid-state reaction as a result of lithium diffusion from the LLT layer to the WO 3 underneath. Although Li 2 W 2 O 7 is known as an electrode material with a larger storage capacity than WO 3 [ 54 ], the intercalation voltage (1.55 V vs. Li + /Li) is too low to be compatible with the LLT electrolyte, which suffers from a Ti 4+ reduction at lower voltages [ 3 ]. Hence, for this study, the Li 2 W 2 O 7 is regarded as an undesirable but unavoidable secondary phase for the LLT-WO 3 half-cell.…”