Activating the Stepwise Intercalation–Conversion Reaction of Layered Copper Sulfide toward Extremely High Capacity Zinc-Metal-Free Anodes for Rocking-Chair Zinc-Ion Batteries

Conventional zinc-ion batteries (ZIBs) are severely hindered by the inherent drawbacks of Zn metal anodes including dendrite growth, side reactions, and interface passivation. Developing intercalation-type anodes to fabricate rocking-chair ZIBs is a promising approach to overcome the above issues. However, the low capacity resulting from the limited transfer electron number of intercalation reactions impedes their practical applications. Herein, we report an effective strategy to break the capacity limit of layered CuS materials as a Zn-metal-free anode through activating its intrinsic conversion reaction. It is found that the preintercalation of cetyltrimethylammonium bromide in CuS (CuS@CTMAB) significantly lowers the energy barrier of the conversion reaction, thus realizing a record-breaking capacity (367.4 mAh g–1 at 0.1 A g–1) as a Zn-metal-free anode based on the reversible conversion of Cu2+/Cu0. Theoretical calculation, ex situ microscopy, and spectroscopy results verify that the characteristic stepwise intercalation–conversion reaction route occurred in CuS@CTMAB. Moreover, the moderate structure transformation and good electronic conduction during the phase evolution process led to excellent cycling stability and high rate performance. Consequently, the rocking-chair ZIB full battery system utilizing CuS@CTMAB and Zn2+-preintercalated MnO2 as the anode and cathode, respectively, exhibits exceptional capacity retention of 93.9% up to 8000 cycles at 2 A g–1. Besides, the CuS@CTMAB anode is also compatible with high-voltage Prussian blue cathodes, demonstrating its outstanding practicality.