X-ray diffraction (XRD) was performed by Bruker D8 Advance diffractometer (Cu Kα radiation, λ = 1.54056 Å) at a scan rate of 5° min⁻¹. The morphology and microstructure measurements were carried out with a field emission scanning electron microscope (FE-SEM, HITACHI S4800) with energy-dispersive X-ray spectroscopy (EDS). X-ray photoelectron spectroscopy (XPS) analysis was performed through PHI 5000 VersaProbe II with Al Ka radiation. FTIR tests were conducted with Thermo Fisher Scientific FTIR spectrophotometer (Nicolet iS50). Nitrogen adsorption/desorption isotherms were obtained at 77 K by an automated adsorption apparatus (Micromeritics ASAP 2020). The surface area and pore size distribution were calculated based on the Brunauer–Emmett–Teller (BET) equation and density functional theory methods. Contact angle measurements were conducted using a drop shape analyzer (KRUSS DSA30S). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests were carried out on a VMP3 multichannel electrochemical station (Bio-Logic Science Instruments SA). Galvanostatic charge-discharge (GCD) tests were performed on a LAND CT 2001A battery test system.

The synthesis process of the PTCC substrate and Zn@PTCC electrode is shown in Figure 1A. The pristine carbon cloth sample was treated by oxygen plasma to obtain the PTCC sample. The surface morphology of CC and PTCC samples was characterized by scanning electron microscope (SEM). The SEM image of CC sample (Figure 1B) indicates that carbon cloth is made up of bundles of woven carbon fibers and the diameter of each carbon fiber is about 10 μm. The carbon fiber of CC sample has clean and relatively smooth surface morphology. As a comparison, numerous uniformly distributed tiny pits were observed on the carbon fiber surface of PTCC sample (Figure 1C). The appearance of these pits is related to the etching effect of carbon material induced by oxygen plasma treatment (Song et al., 2011; Chen et al., 2020). Nitrogen sorption isotherms of CC and PTCC samples (Supplymentary Figure S1) were measured to acquire the specific surface area information. The specific surface areas of CC and PTCC samples are calculated to be 0.3094 and 0.3138 m² g⁻¹, respectively. The results of the specific surface area tests indicate that the plasma treatment hardly changed the specific surface area of CC and PTCC samples. Zinc was then electrodeposited on CC and PTCC samples to form Zn@CC and Zn@PTCC electrodes (See Experimental Section). SEM images of Zn@CC and Zn@PTCC are shown in Figures 1D, E, respectively. After zinc deposition, zinc nanosheets with 10–100 nm in thickness were grown on the surface of CC and PTCC samples in a relatively uniform manner. The structure formed by stacking the zinc nanosheets can ensure a low-resistance path for electron transmission (Guo et al., 2020). The phase structure and phase evolution were measured by X-ray diffraction (XRD). Figure 1F shows the XRD spectroscopies of CC, PTCC, Zn@CC, and Zn@PTCC samples. Both CC and PTCC samples show the same peak at 2θ of 26.2°, which corresponds to the characteristic peak of amorphous carbon. The PTCC sample displays a similar XRD pattern with the CC sample, indicating that oxygen plasma treatment did not change the phase of the CC sample. The XRD patterns of the Zn@CC and Zn@PTCC samples after zinc deposition show clear diffraction peaks at 2θ of 36.3°, 39.0°, 43.2°, and 54.3°, which match well with metallic hexagonal zinc (JCPDS 04-0831), indicating that metallic hexagonal zinc was successfully deposited on CC and PTCC samples without other impurities.

X-ray photoelectron spectroscopy (XPS) characterization was performed to study the evolution in the surface chemical state of the samples. The XPS survey spectrums of CC and PTCC samples are shown in Supplymentary Figure S2. The survey scan proves the presence of carbon and oxygen core peaks in both CC and PTCC samples. The content of O element in the CC sample surface is 3.41%, which increases to 13.03% in the PTCC sample, demonstrating that oxygen plasma treatment has an oxidizing effect on CC samples. The de-convoluted high-resolution multiplex C 1s scan of CC and PTCC samples are displayed in Figures 2A,B. Compared to PTCC sample, only peaks of C-OH bond (285.5 eV) and C-C bond (284.7 eV) were observed on the C 1s spectrum of CC sample. The C 1s spectrum of the PTCC sample showed a novel peak at 288.5 eV, indicating that a novel chemical bond of C=O bond (carbonyl group) was created after plasma treatment. On the O 1s spectrum of CC sample (Figure 2D), just one peak of C-OH was observed at 532.3 eV, but a new peak of C=O appeared at 531.9 eV on the O 1s spectrum of PTCC sample (Figure 2E). The XPS analysis result reveals that carbonyl groups were effectively introduced to the surface of PTCC sample by oxygen plasma treatment, which is also verified by the corresponding FTIR analysis (Supplymentary Figure S3). The FTIR spectrum displays a peak around 1720 cm⁻¹, which corresponds to the C=O stretching bonds. In addition, the distribution of carbonyl groups in the PTCC sample was also analyzed by energy-dispersive X-ray spectroscopy. The EDS mapping images of PTCC sample (Supplymentary Figure S4) exhibit a homogeneous dispersion of oxygen element, indicating that the C=O functional groups were uniformly distributed on the PTCC surface. The abundant carbonyl groups on the surface of PTCC electrode can enhance the hydrophilicity of the sample surface and help to improve the wettability of the electrolyte to the electrode (Cho et al., 2000; Cha et al., 2019). Contact angle tests were performed to evaluate the electrolyte wettability of CC and PTCC electrodes. As shown in Figures 2C, F, PTCC sample exhibits significantly improved wettability of aqueous electrolyte (2 M ZnSO₄ aqueous solution) than CC sample. The contact angle of CC sample is measured to be 143.9°, which corresponds to a hydrophobic surface. For PTCC sample, the electrolyte droplet penetrates instantly into the PTCC after the droplet reaches its surface, which represents a near-zero contact angle. The optimized wettability of the electrolyte demonstrates a decrease in the interfacial free energy between the electrode surface and the electrolyte, which facilitates the uniform distribution of electrolyte flux towards the electrode (Liu M. et al., 2019). At the same time, owing to the high binding energy between C=O and Zn, the carbonyl groups can also act as nucleation sites to guide the uniform zinc deposition (Zhou et al., 2022).

The electrochemical performance of Zn@CC and Zn@PTCC anodes was investigated in symmetrical cells. To determine the long-term cycling stability, Zn@CC and Zn@PTCC symmetrical cells were cycled at various current densities with 2 M ZnSO₄ electrolyte. As shown in Figure 3A, the Zn@PTCC electrode presents stable voltage profile with a low voltage hysteresis of about 25 mV and more than 530 h lifespan at a current density of 0.5 mA cm⁻² with a limited capacity of 0.5 mAh cm⁻² (∼15% DOD). In contrast, the voltage profile of the Zn@CC electrode shows significant voltage fluctuation after 35 h of cycling, and then the cell fails, which is related to the short circuit caused by zinc dendrite growth (Li et al., 2022). The remarkable durability of Zn@PTCC anode can be validated by cycling at a higher current density of 2 mA cm⁻² and higher capacity of 2 mAh cm⁻² (Figure 3B). The Zn@PTCC anode enables the symmetric cell to be stably cycled at a lower voltage hysteresis (∼40 mV) without short circuits over 480 h with a very high DOD (∼60%). The rate performance of Zn@CC and Zn@PTCC electrodes at a variety of current densities is shown in Figure 3C. At various current densities, particularly at high current densities, the Zn@PTCC electrode exhibits significantly less voltage hysteresis than the Zn@CC electrode, indicating reduced polarization and enhanced stability. Electrochemical impedance spectroscopy (EIS) were used to further characterize the interfacial charge transfer resistance of symmetric cells. The EIS tests of Zn@CC and Zn@PTCC cells were recorded in the frequency range from 10 mHz to 300 kHz with an amplitude of 5 mV (Figure 3D). The Zn@PTCC symmetrical cell exhibits considerably lower charge transfer resistance than that of Zn@CC symmetrical cell in both pristine state and cycled state (after 10 h cycling), indicating the superior charge transfer kinetics in Zn@PTCC electrode. Asymmetric Zn|CC and Zn|PTCC cells were assembled to explore the zinc plating/stripping behaviors on CC and PTCC electrodes. As shown in Figure 3E, at a current density of 1 mA cm⁻², the Coulombic efficiency of the CC electrode first increases, then decreases, and decays to 81.57% after 30 cycles. As a comparison, the CE of the PTCC electrode can be maintained at about 93–95%. When the current density increases to 3 mA cm−2, the PTCC electrode exhibits an average CE of about 97.42%, exceeding that of the CC electrode (92.21%). The voltage profiles of zinc plating/stripping on CC and PTCC electrodes at a current density of 3 mA cm−2 are presented in Supplymentary Figure S5. The discharge curves of PTCC electrode exhibits higher capacities than that of CC electrode, which is in accordance with the higher CE. The stable and high CE of the PTCC electrode demonstrates enhanced reversibility of zinc plating/stripping on the surface of the PTCC electrode.

The deposition of zinc metal on the substrate usually consists of two stages: nucleation and deposition. The nucleation overpotentials of CC and CNT electrodes were compared to investigate the mechanism of PTCC electrodes in regulating zinc nucleation behavior. The PTCC electrode exhibits a reduced nucleation overpotential (97 mV) compared to the CC electrode (186 mV) at a current density of 1 mA cm⁻² (Figure 4A). Even at high current densities (2 and 5 mA cm⁻²), the PTCC electrodes still demonstrate lower nucleation overpotential (Figure 4B). The reduction in the nucleation overpotential manifests that the PTCC electrode has lower resistance of zinc nucleation, which is related to the improved electrolyte wettability and enhanced zincophilicity of the electrode. According to density functional theory (DFT) calculations (Supplymentary Figure S6), C=O bond (−0.38 eV) has higher binding energy to Zn atom than that of C-C (−0.20 eV) and C-OH (−0.25 eV) bonds, indicating that C=O has a good ability to capture Zn ions, thereby lowering the Zn ion transport barrier (Li et al., 2020). The uniformly distributed C=O functional groups on the surface of PTCC sample not only improve the wettability of the aqueous electrolyte but also acts as zincophilic active sites to promote uniform zinc nucleation and deposition, which leads to the improvement in the electrochemical performance of the PTCC electrode.

To demonstrate the significant differences in electrochemical properties between CC and PTCC electrodes, the zinc plating morphology on CC and PTCC electrodes after zinc deposition was characterized by SEM to evaluate their resistance to zinc dendrite growth. The SEM images of CC and PTCC electrodes before zinc deposition are shown in Figures 4C, D. It can be seen that CC and PTCC have similar fibrous textile morphology. After zinc deposition, Zn@CC and Zn@PTCC samples exhibit quite different morphologies. Zinc metal is uniformly deposited on the surface of each carbon fiber (Figure 4F). On the contrary, zinc aggregations in a small area of the electrode were observed on the surface of Zn@CC sample (Figure 4E). The aggregation is related to inhomogeneous zinc nucleation and deposition, which would evolve into zinc dendrite growth and lead to further safety problems. The substantial difference suggests that PTCC electrodes are more resistant to zinc dendrite growth, which correlates with their reduced nucleation overpotential and uniformly distributed nucleation sites.

The schematic comparison of zinc plating behaviors on the CC and PTCC electrodes is shown in Figure 5. Compared to the CC electrode, the PTCC electrode exhibit enhanced electrochemical performance and uniform zinc deposition without dendrite growth. Due to the improper electrolyte wettability and poor zincophilicity of the CC electrode, at the early nucleation stage, zinc cannot be nucleated uniformly on the electrode surface. As a result, zinc is nucleated and deposited in a small area. With further zinc deposition, zinc protrusions and aggregation will generate on the CC electrode surface. Once the zinc protrusions appear on the CC surface, the concentrated electric field will further lead to increased zinc dendrite growth and dead zinc (Xie et al., 2021). As a comparison, the PTCC electrode has better electrolyte wettability, enhanced zinc affinity and uniformly distributed zincophilic sites for zinc nucleation. Therefore, zinc would uniformly nucleate onto the PTCC surface at the early stage, and no dendrite growth was triggered during the subsequent deposition process.

As displayed in Figure 6A, full cells with vanadium-based oxide V₁₀O₂₄·12H₂O (VOH) as cathode were assembled to evaluate the practicability of the Zn@PTCC electrode. The VOH cathode material was synthesized via hydrothermal method. The morphology of the VOH material is depicted in Figure 6B, displaying that it is composed of micron-sized particles. The XRD diffraction analysis (Figure 6C) confirms the sample as V₁₀O₂₄·12H₂O (JCPDS No.25-1006) with extra-large layer spacing of 1.42 nm, stabilized by interlayer water molecules. Then, rate performance and long-term cycling stability tests were performed in full cells. The rate capabilities of Zn|VOH full cells with Zn@CC and Zn@PTCC anodes at different current densities are shown in Figure 6D. The rate capability was improved in the full cell with Zn@PTCC anode. Compared to the full cell with Zn@CC anode, the Zn@PTCC full cell exhibits higher capacity at all current densities. The long-term stability of Zn@CC|VOH and Zn@PTCC|VOH full cells at a current density of 1 A g⁻¹ is presented in Figure 6E. Both Zn@CC and Zn@PTCC cells exhibit a gradual increase in capacity during certain initial cycles. This phenomenon could be attributed to the activation process of vanadium-based oxides at the initial stage (Liu W. et al., 2019). The Zn@PTCC|VOH cell exhibits a reversible capacity of 216.0 mAh g⁻¹, which increases to the maximum value of 318.8 mAh g⁻¹ at the 25th cycle and remains 205.3 mAh g⁻¹ after 500 cycles, corresponding to a capacity retention of 95.0%. In contrast, the capacity retention of Zn@CC|VOH cell after 500 cycles is only 80.1% (Figure 6F). The improvement in reversible capacity and capacity retention confirms the enhanced cycling durability of the Zn@PTCC anode.