Rationally Designed ZnTe@C Nanowires with Superior Zinc Storage Performance for Aqueous Zn Batteries

Abstract

Te‐based materials with excellent electrical conductivity and ultra‐high volume specific capacity have attracted much attention for the cost‐efficient aqueous Zn batteries. However, the construction of functional structures with mild volume expansion and suppressed shuttle effects, enabling an expanded lifespan, is still a challenge for conversion‐type materials. Herein, the carbon‐coated zinc telluride nanowires (ZnTe@C NWs) are rationally designed as a high‐performance cathode material for aqueous Zn batteries. The carbon‐coated1D nanostructure could not only provide optimized transmission path for electrons and ions, but also help to maintain structure integrity upon volume variation and suppress intermediates dissolution, endowing the ZnTe@C NWs with improved cycling stability and reaction kinetics. Consequently, a reversible six‐electron reaction mechanism of ZnTe@C NWs based on Te2−/Te4+ conversion with excellent output capacity (586 mAh g−1 at 0.1 A g−1) and lifespan (>250 mAh g−1 retained for 400 cycles at 1 A g−1) is eventually achieved.

Offense‐Defense‐Balanced Strategy Escorting Tellurium Oxidation Conversion towards Energetic and Long‐Life Zn Batteries

“…All the pH values show a trend of first increasing and then decreasing with the prolonged soaking time when using different active materials, which could result from the dissolution of Te oxides and the inevitable Te oxidation by dissolved oxygen in the water. [15,24] The Nano-Te with a smaller diameter shows a more apparent pH drop than other samples, which could be caused by its larger contact area with water molecules. However, compared with that of ZS+ZC/ACN, the pH change of ZS+ZC/ACN/Glu is much smaller, especially in the first 10 min, implying the well-inhibited dissolution of Te oxides by Glu/Cl − co-additive.…”

“…In ZS+ZC/ACN/Glu, during the charging process, the pH value on the cathode side drops sharply from 5.12 (Dis-0.2V) to 4.8 (Cha-1.24V) and subsequently to 4.65 (Cha-1.35V), which can be attributed to proton generation during the conversion from Te 0 to Te 4+ ; while in ZS+ZC/ACN, the pH value on the cathode side slowly decreases from 5.13 (Dis-0.2V) to 5.04 (Cha-1.24V), which could be caused by the dissolution and/or shuttling of 𝛾-TeO 2 phase. [15,24] Figure 5f,g shows the top-view SEM image of cycled Zn anodes of Zn‖Te batteries in different electrolytes. In ZS+ZC/ACN/Glu, the Zn anode displays a relatively smooth surface; while in ZS+ZC/ACN, substantial loose substances appear on the surface of the Zn anode, which could be associated with the shuttling of active materials.…”

“…It is evident that at all current densities for the rate capability test, the Zn‖Te battery exhibits well‐kept discharge plateaus. Compared with the Zn‖Te batteries with other electrolytes reported elsewhere, [ 10,19,23–24 ] the Zn‖Te battery in ZS+ZC/ACN/Glu exhibits an obvious advantage in terms of volumetric capacity and cyclability (Figure 2f). In addition, the energy density and power density of Zn‖Te batteries in ZS+ZC/ACN/Glu are compared with other Zn batteries.…”

“…Nevertheless, proton-rich electrolytes usually aggravate the dissolution of active materials and/or oxidized products (TeO 2 ), resulting in poor cyclability (≤ 200 cycles). [22][23][24][25] Thus, activating a deep and reversible Te 0 /Te 4+ conversion in a relatively mild pH environment is conducive to reconciling the capacitycyclability conflict. Given this, additive-level nucleophiles (e.g., metal halides) could be appropriate to act as offensive reagents to activate the Te 0 /Te 4+ conversion, meanwhile, avoid a large pH fluctuation.…”

A Reversible Six‐Electron Transfer Cathode for Advanced Aqueous Zinc Batteries

“…It is therefore reasonable that the reversible formation and decomposition of zinc hydroxide sulfate hydrates is observed in the ex situ XRD patterns (Figure S11) and SEM images (Figure S12). The partial irreversibility of the pH value may be due to the fact that a small amount of Te was not converted to TeO 2 during the charging process (as evidenced by the XRD result), thus hindering the H + regeneration [11e] . To evaluate the effects of the partially increased pH on the device reversibility, the electrochemical performance of n‐TeO 2 /C in the electrolyte with a pH value of 4.77 is shown in Figure S13.…”