The SEM results of cycled electrodes also supported the preferential plane deposition shown in the XRD analysis. As shown in
Fig. 5a, protuberant Zn dendrites and resultant sharp structure were observed on the cycled bare Zn anode. Conversely, the cycled HPC@Zn anode obtained a very clean and uniform surface (
Fig. 5b), confirming the role of HPC in regulating Zn deposition and plane-oriented growth. After long-term Zn plating/stripping process, the preferential deposition of (002)
Zn planal-oriented Zn was still sustained (
Fig. 5c). The increased (002)
Zn plane and decreased (100)
Zn plane is illustrated by XRD patterns of cycled HPC@Zn anode. During the initial nucleation process, the salt-polymer complex on HPC@Zn further acts as zincophilic sites compared with the bare Zn surface to guide uniform Zn nucleation and deposition.
Fig. 5d shows CV curves of the symmetrical cells. During the cathodic scan, the Zn
2+ reduction overpotential of HPC@Zn is the lower than bare Zn, which indicates an effectively reduced energy barrier and regulates the distribution and migration Zn
2+ for deposition. CV profiles at different scan rates of the symmetrical HPC@Zn cell also demonstrate better electrochemical kinetics as indicated by smaller polarization and more intensive peak currents by virtue of higher interfacial charge transfer (Fig. S9 in Supporting information). Moreover, coulombic efficiency (CE) plots of Zn||Cu half-cells using HPC@Zn anodes showed stable cycling over 400 cycles with a high average CE of 99.65% (
Fig. 5e), indicating that HPC treatment mitigated dendrite growth and side reaction. In contrast, the bare Zn||Cu half-cell suffers from a short circuit at the 237
th cycle due to the dendrite penetrating the separator, resulting in cell failure. To demonstrate the practicality of Zn anodes, Zn||MnO
2 full cells have been assembled and tested using bare Zn and HPC@Zn anodes. As shown in
Fig. 5f, the cell with HPC@Zn anode exhibits a specific capacity of 261 mAh/g at 0.2 A/g. After 100 cycles, the HPC@Zn||MnO
2 cell still retains a remarkable specific capacity of 123.5 mAh/g, corresponding capacity retention of 47.3%). However, the cell with bare Zn as the anode behaves a rapid capacity decline at the 30 cycles, and the capacity is only 70.7 mAh/g with a low-capacity retention of 26.9% after 100 cycles, which can be ascribed to the formation of dendrites and accumulation of non-conductive byproducts. Long cycling tests for 250 cycles, HPC@Zn||MnO
2 cell still achieved capacity retention of 40%, showing excellent anodic protection and long-cycle stability. The rate performance of the HPC@Zn||MnO
2 and bare Zn||MnO
2 cells have been show in Fig. S10 (Supporting information), HPC@Zn||MnO
2 exhibits a better rate performance. The discharge capacity of the HPC@Zn cell is higher than that of bare Zn at different current densities.