Ordered Vacancies as Sodium Ion Micropumps in Cu‐Deficient Copper Indium Diselenide to Enhance Sodium Storage

Abstract

Unordered vacancies engineered in host anode materials can't well maintain the uniform Na+ adsorbed and possibly render the local structural stress intense, resulting in electrode peeling and battery failure. Here, we firstly introduce the indium into Cu2Se to achieve the formation of CuInSe2. Next, ion extraction strategy is employed to fabricate Cu0.54In1.15Se2 enriched with ordered vacancies by the spontaneous formation of defect pairs. Such ordered defects, compared with unordered ones, can serve as myriad sodium ion micropumps evenly distributing in crystalline host to homogenize the adsorbed Na+ and the generated volumetric stress during the electrochemistry. Furthermore, Cu0.54In1.15Se2 is indeed proved by the calculations to exhibit smaller volumetric variation than the counterpart with unordered vacancies. Thanks to the distinct ordered vacancy structure, the material exhibits a highly reversible capacity of 428 mAh g−1 at 1 C and a high−rate stability of 311.7 mAh g−1 at 10 C after 5,000 cycles when employed as an anode material for SIBs. This work presents the promotive effect of ordered vacancies on the electrochemistry of SIBs and demonstrates the superiority to the unordered vacancies, which is expected to extend it to other metal−ion batteries, not limited to SIBs to achieve high capacity and cycling stability.This article is protected by copyright. All rights reserved