Copper Thiophosphate (Cu₃PS₄) as Electrode for Sodium‐Ion Batteries with Ether Electrolyte

Abstract

Lithium and sodium thiophosphates (and related compounds) have recently attracted attention because of their potential use as solid electrolytes in solidstate batteries. These compounds, however, exhibit only limited stability in practice as they react with the electrodes. The decomposition products partially remain redox active hence leading to excess capacity. The redox activity of thiophosphates is explicitly used to act as electrode for sodium-ion batteries. Copper thiophosphate (Cu 3 PS 4 ) is used as a model system. The storage behavior between 0.01 and 2.5 V versus Na + /Na is studied in half cells using different electrolytes with 1 m NaPF 6 in diglyme showing the best result. Cu 3 PS 4 shows highly reversible charge storage with capacities of about 580 mAh g −1 for more than 200 cycles @120 mA g −1 and about 450 mAh g −1 for 1400 cycles @1 A g −1 . The redox behavior is studied by operando X-ray diffraction and X-ray photoelectron spectroscopy. During initial sodiation, Cu 3 PS 4 undergoes a conversion reaction including the formation of Cu and Na 2 S. During cycling, the redox activity seems dominated by sulfur. Interestingly, the capacity of Cu 3 PS 4 for lithium storage is smaller, leading to about 170 mAh g −1 after 200 cycles. The results demonstrate that thiophosphates can lead to reversible charge storage over several hundred cycles without any notable capacity decay.

CoPSe: A New Ternary Anode Material for Stable and High‐Rate Sodium/Potassium‐Ion Batteries

“…[21][22][23] It is noted that ternary metal phosphorus chalcogenides (MPX, X = S, Se) typically containing two different anions show the modulated electronic structure and enhanced activity for various energy applications compared with conventional TMS/ TMSe. [24][25][26][27][28][29][30][31][32][33][34][35][36] For example, ternary metal phosphorus sulfides (MPS) have been intensively synthesized and investigated in batteries, such as 2D MPS 3 (M = Fe, Co, Ni) nanosheets, [26] 2D SnP 2 S 6 nanosheets/graphene hybrid, [28] and Cu 3 PS 4 /C composite. [36] However, scarcely studied in batteries were ternary metal phosphorus selenides (MPSe) due to their difficulty in synthesis despite a set of characteristics desirable for batteries including higher conductivity and lower shuttle effect derived from Se atoms relative to MPS 3 .…”

“…[ 24–36 ] For example, ternary metal phosphorus sulfides (MPS) have been intensively synthesized and investigated in batteries, such as 2D MPS 3 (M = Fe, Co, Ni) nanosheets, [ 26 ] 2D SnP 2 S 6 nanosheets/graphene hybrid, [ 28 ] and Cu 3 PS 4 /C composite. [ 36 ] However, scarcely studied in batteries were ternary metal phosphorus selenides (MPSe) due to their difficulty in synthesis despite a set of characteristics desirable for batteries including higher conductivity and lower shuttle effect derived from Se atoms relative to MPS 3 . [ 37 ] The development of new ternary MPSe materials with combined intrinsic advantages for long‐life and high‐rate SIBs/PIB is highly desirable.…”

Na‐Ion Batteries—Approaching Old and New Challenges

“…The strong and weak points of all these materials can be found in these references and herein. [ 19,20 ] A possible approach to mitigate the limitations shown by all these anode materials consists on the use of additives such as graphene. Optimal use of graphene as additive should entail increasing the low FCCE caused by its high surface area.…”

Fluoro(Phosphates,Sulfates) or (Phosphate,Sulfate) Fluorides: Why Does It Matter?

“…In contrast, as an example, the battery community is correctly naming thiophosphate compounds containing the tetrathiophosphate anion PS 4 3− . Thiophosphates are recently highly investigated in the field of solid state electrolytes [ 17–19 ] and also as electrode materials, [ 20 ] but as far as we know are always referred correctly.…”

“…. Thiophosphates are recently highly investigated in the field of solid state electrolytes [17][18][19] and also as electrode materials, [20] but as far as we know are always referred correctly.…”