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

Abstract

Finding suitable electrode materials is one of the challenges for the commercialization of a sodium ion battery due to its pulverization accompanied by high volume expansion upon sodiation. Here, copper sulfide is suggested as a superior electrode material with high capacity, high rate, and long‐term cyclability owing to its unique conversion reaction mechanism that is pulverization‐tolerant and thus induces the capacity recovery. Such a desirable consequence comes from the combined effect among formation of stable grain boundaries, semi‐coherent boundaries, and solid‐electrolyte interphase layers. The characteristics enable high cyclic stability of a copper sulfide electrode without any need of size and morphological optimization. This work provides a key finding on high‐performance conversion reaction based electrode materials for sodium ion batteries.

Progress and Prospects of Transition Metal Sulfides for Sodium Storage

“…Figure 12j, m show the ex-situ SAED patterns of the full discharge and charge products. The results of ex-situ SAED patterns are [116] in accordance with the result of ex-situ XRD, confirming the discharge products are Na 2 S and Co and the charge product is Co 9 S 8 . Analysis of ex-situ XRD and SAED indicates a highly reversible conversion mechanism for the Co 9 S 8 during sodiation/desodiation.…”

“…On the other hand, Yuk et al revealed another sodiation mechanism of copper sulfide by ex-situ TEM and ex-situ HRTEM [116]. Figure 11i shows the structural evolution of CuS nanoplates upon charge/discharge.…”

A Selective Reduction Approach to Construct Robust Cu1.81S Truss Structures for High-Performance Sodium Storage

“…Based on the above results, the Na + -storage performance of the Cu 1.81 S MTs is superior to that of most of the previously reported Cu x S electrodes, 17,21,48,49,51,52 which can be ascribed to the fact that its unique triangular support structures accommodate volume changes during sodiation/desodiation, which effectively suppresses the pulverization of active materials ( Figure 5B). In addition, the hollow truss structure ensures the electrolyte rapid infiltration and shortens the diffusion length of electron/Na + ions for the acceleration of electrochemical kinetics as disclosed by electrochemical impedance spectroscopy (EIS) spectra (see Table S1 for details).…”

“…The electrode delivers an initial discharge/charge capacity of 563/487 mAh g À1 , corresponding to an initial Coulombic efficiency (CE) of 86.5%. The initial capacity loss of the MT electrode is much smaller than that of other Cu x S electrodes, 17,21,48,49,51,52 which may be due to the formation of a more stable solid electrolyte interphase film. Compared with the Cu x S HMCs, the Cu 1.81 S MTs illustrate a significant stability of 200 cycles at 0.1 A g À1 ( Figure 4C).…”

“…48 Meanwhile, the cathodic peaks at 1.47 V, 1.19 V, and 0.84 V are assigned to the multiple intercalation reactions of Na + ions into Cu 2Àx S lattices to form the intermediate phases Na x Cu y S z . 21,[49][50][51] Subsequently, a conversion reaction occurs in Na x Cu y S z to decompose into Na 2 S and Cu, corresponding to the cathodic peak at 0.41 V. For the anodic scan, the two peaks at 1.58 V and 2.12 V correspond to the conversion from Cu and Na 2 S to Na x Cu y S z and the deintercalation from Na x Cu y S z to Cu 2 S, 21,[49][50][51] respectively. These processes are further verified by in situ XRD and electrochemical measurements (see Figure S10 for details).…”