Unusual Na⁺ Ion Intercalation/Deintercalation in Metal-Rich Cu_1.8S for Na-Ion Batteries

Abstract

A key issue with Na-ion batteries is the development of active materials with stable electrochemical reversibility through the understanding of their sodium storage mechanisms. We report a sodium storage mechanism and properties of a new anode material, digenite CuS, based on its crystallographic study. It is revealed that copper sulfides (Cu S) can have metal-rich formulas ( x ≥ 1.6), due to the unique oxidation state of +1 found in group 11 elements. These phases enable the unit cell to consist of all strong Cu-S bonds and no direct S-S bonds, which are vulnerable to external stress/strain that could result in bond cleavage as well as decomposition. Because of its structural rigidness, the CuS shows an intercalation/deintercalation reaction mechanism even in a low potential window of 0.1-2.2 V versus Na/Na without irreversible phase transformation, which most of the metal sulfides experience through a conversion reaction mechanism. It uptakes, on average, 1.4 Na ions per unit cell (∼250 mAh g) and exhibits ∼100% retention over 1000 cycles at 2C in a tuned voltage range of 0.5-2.2 V through an overall solid solution reaction with negligible phase separation.

Synthesis of CuS@CoS2 Double‐Shelled Nanoboxes with Enhanced Sodium Storage Properties

“…And the peaks at 0.85 and 0.50 V are ascribed to the conversion of Na x CoS 2 to Co and Na 2 S and the formation of a solid‐electrolyte interphase (SEI) film . In the second cathodic scan, two new peaks at 1.91 and 1.49 V emerge, which are ascribed to the Na + ion intercalation processes of CuS x and CoS x , respectively . During the anodic scans, two peaks at about 1.58 and 2.15 V are associated with deintercalation of Na + ions from the Na x CuS structure, and three peaks at 1.87, 1.96 and 2.07 V represent the reverse processes from Co and Na 2 S to the CoS x .…”

Synthesis of Cobalt Sulfide Multi‐shelled Nanoboxes with Precisely Controlled Two to Five Shells for Sodium‐Ion Batteries

“…The as-obtained cobalt sulfide multi-shelled nanoboxes exhibit enhanced sodium-storage properties when evaluated as anodes for sodium-ion batteries. [9,[14][15][16][17][18] In particular,h ollow structures with complex interiors have drawn significant attention owing to their structure-dependent merits.A sf or sodium storage applications,i ntricate hollow structures exhibit great advantages over simple hollow architectures. [1][2][3] Besides lithium-ion batteries (LIBs), sodium-ion batteries (SIBs) have been considered as one promising energy storage alternative because sodium is abundantly available.…”

“…[9,[14][15][16][17][18] In particular,h ollow structures with complex interiors have drawn significant attention owing to their structure-dependent merits.A sf or sodium storage applications,i ntricate hollow structures exhibit great advantages over simple hollow architectures. [9,[14][15][16][17][18] In particular,h ollow structures with complex interiors have drawn significant attention owing to their structure-dependent merits.A sf or sodium storage applications,i ntricate hollow structures exhibit great advantages over simple hollow architectures.…”

Pulverization‐Tolerance and Capacity Recovery of Copper Sulfide for High‐Performance Sodium Storage

“…As a promising alternative for LIBs, thus, sodium ion batteries (SIBs) have been suggested owing to natural abundance and low cost of sodium, and its similar chemical nature to lithium. [5,9,12] There have been numerous reports on conversion reaction materials that show the capacity recovery after its initial degradation, [13][14][15] which is counter-intuitive since conversion reaction typically induces pulverization, which translates directly into capacity degradation. [1][2][3][4][5][6][7] Unlike intercalation reaction, conversion and alloying reactions generally involve abrupt crystallographic changes and huge volume expansion rate over 100% leading to capacity degradation by active materials destruction.…”

“…[1][2][3][4][5][6][7] Unlike intercalation reaction, conversion and alloying reactions generally involve abrupt crystallographic changes and huge volume expansion rate over 100% leading to capacity degradation by active materials destruction. [5,9,12] There have been numerous reports on conversion reaction materials that show the capacity recovery after its initial degradation, [13][14][15] which is counter-intuitive since conversion reaction typically induces pulverization, which translates directly into capacity degradation. [5,9,12] There have been numerous reports on conversion reaction materials that show the capacity recovery after its initial degradation, [13][14][15] which is counter-intuitive since conversion reaction typically induces pulverization, which translates directly into capacity degradation.…”