S‐Decorated Porous Ti3C2 MXene Combined with In Situ Forming Cu2Se as Effective Shuttling Interrupter in Na–Se Batteries. Issue 33 (9th July 2021) - Lu, Chengxing
Abstract : Given natural abundance of Na and superior kinetics of Se, Na–Se batteries have attracted much attention but still face the problem of shuttling effect of soluble intermediates. The first‐principle calculations reveal the S‐decorated Ti3 C2 exhibits increased binding energy to sodium polyselenides, suggesting a better capture and restriction on intermediates. The obtained Se@S‐decorated porous Ti3 C2 (Se@S‐P‐Ti3 C2 ) exhibits a high reversible capacity of 765 mAh g −1 at 0.1 A g −1 (calculated based on Se), ≈1.2, 1.3, and 1.7 times of Se@porous Ti3 C2 (Se@P‐Ti3 C2 ), Se@Ti3 C2, and Se, respectively. It gives considerable capacity of 664 mAh g −1 at 20 A g −1 and impressive cycling stability over 2300 cycles with an ultralow capacity decay of 0.003% per cycle. The excellent electrochemical performance can be ascribed to the S‐modified porous Ti3 C2, which provides effective immobilization toward polyselenides, makes full use of nanosized Se, and alleviates volume expansion during sodiation/desodiation. Additionally, in situ forming Cu2 Se can generate Cu nanoparticles through discharge process and then transform polyselenides into solid‐phase Cu2 Se, further suppressing the shuttling effect. This work provides a practical strategy to immobilize and transform sodium polyselenides for high‐capacity and long‐life Na–Se batteries. Abstract : S‐decorated porous Ti3 C2 MXene is used as effective selenium host, giving high capacity, rate capability, and long lifespan of Na–Se batteries. The S‐decorated interfaces combined with in situ forming Cu2 Se facilitate the immobilization and transformation of polyselenides and thus lead to efficient surface‐dominated capacitive behavior.