context: Long cyclic lifespan under high-current density is an important factor to assess the possibility of practical application. Fig. 3e presents the GCD result at a high current density of 2.0 A g−1. Approximately 85% retention of the capacity over 1000 cycles (the initial capacity was 183 mA h g−1) and CEs of the NV NSs@ACC electrode more than 99% were measured, demonstrating the outstanding stability and efficacy of rapid electron transfer during the charge/discharge processes. By contrast, the NV-ACC electrode only shows a capacity of 45 mA h g−1 with obvious long-time active phenomenon (Fig. S3c†). The worsening performance of the NV-ACC electrode is mainly caused by the loose binding force between the active materials and the ACC substrate as well as the non-active binder, resulting in low conductivity and instability. This kind of traditional electrode needs more cycles to activate the cathode materials, which could be attributed to the inefficient electronic and mechanical contact between the active materials and the electrolyte, compared with the binder-free 2D ultrathin nanosheets grown on the ACC. To better verify this hypothesis, electrochemical impedance spectroscopy (EIS) was employed to investigate the ion transport property within the NV NSs@ACC electrode, as shown in Fig. S4a,† where a lower charge-transfer resistance (Rct) can be clearly observed compared to that of NV-ACC.