Mixed Polyanion Glass Cathodes: Glass-State Conversion Reactions

Abstract

Mixed polyanion glasses can undergo glass-state conversion (GSC) reactions to provide an alternate class of high-capacity cathode materials. GSC reactions have been demonstrated in phosphate/vanadate glasses with Ag, Co, Cu, Fe, and Ni cations. These mixed polyanion glasses provided high capacity and good high power performance, but suffer from moderate voltages, large voltage hysteresis, and significant capacity fade with cycling. Details of the GSC reaction have been revealed by X-ray absorption spectroscopy, electron microscopy, and energy dispersive X-ray spectroscopy of ex situ cathodes at key states of charge. Using the Open Quantum Materials Database (OQMD), a computational thermodynamic model has been developed to predict the near-equilibrium voltages of glass-state conversion reactions in mixed polyanion glasses.

A Reconstructed Cu2P2O7 Catalyst for Selective CO2 Electroreduction to Multicarbon Products

“…Figure 2f displays the Cu K‐edge X‐ray absorption near edge structure (XANES) spectra of the as‐prepared Cu 2 P 2 O 7 electrode and the same sample under CO 2 RR condition at −0.8 V vs. RHE, along with Cu foil, CuO and Cu 2 O as references. The spectrum of the as‐prepared electrode shows an absorption edge similar to that of Cu 2 P 2 O 7 [12] . The spectrum of the reconstructed Cu 2 P 2 O 7 during CO 2 RR conditions shows a close absorption edge with Cu foil, indicative of a complete reduction into metallic Cu.…”

“…The spectrum of the as-prepared electrode shows an absorption edge similar to that of Cu 2 P 2 O 7 . [12] The spectrum of the reconstructed Cu 2 P 2 O 7 during CO 2 RR conditions shows a close absorption edge with Cu foil, indicative of a complete reduction into metallic Cu. The Fourier transformation of the extended Xray absorption fine-structure (EXAFS) spectra present a characteristic CuÀ Cu peak at 2.3 Å but with lower intensity compared to that of a Cu foil, and the fitting results show that the CuÀ Cu coordination number in the reconstructed Cu 2 P 2 O 7 under CO 2 RR conditions is about 9.9, confirming the formation of low-coordinated Cu sites under the electrochemical reduction reaction (Supporting Information, Figure S16, Table S4).…”

Mixed Polyanion Glass Cathodes: Mixed Alkali Effect

“…The high-capacity electrochemical reactions below ∼2.5 V are a Cu-based conversion reaction and a vanadium-based intercalation reaction (occurring concurrently or sequentially). 9 The plateau voltages of the first discharge curves were similar for all Li x CuPV glasses ( Figure 2a); the Li 1 CuPV glass only had a slightly lower plateau voltage (2.3 V versus 2.4 V). However, Na x CuPV & K x CuPV with x ≥ 0.5 had significantly lower plateau voltages (Na 1 CuPV 2.0 V, K 1 CuPV 1.75 V) for the first cycle.…”

“…8 Phosphovanadate glasses with Ag, Cu, Co, Fe, and Ni cations have previously been demonstrated to be electrochemically active. 9 Mixed polyanion glasses, however, typically have the same fundamental electrochemical problems as other conversion cathodes i.e. : large hysteresis (typical ∼55% cycling efficiency), capacity fade during 10's of cycles, and a large 1 st -cycle irreversible loss (∼25%).…”

Research Progresses on Interfaces in Solid‐State Sodium Batteries: A Topic Review

“…The amorphous materials have the additional stable sites for cations due to their open and random structures. [ 118–122 ] Therefore, the SSSBs using amorphous TiS 3 (α‐TiS 3 ) electrode with AB showed a reversible capacity of over 300 mAh g −1 for 5 cycles (Figure 7h), which is three times higher than that of the cell using TiS 2 crystal. [ 104 ] The shape of inorganic fillers can also influence the ion conduction of the composite electrolytes.…”