"D", were observed, which can be attributed to the formation of solid electrolyte interphase (SEI) layers on the cathode and similar has been reported for nitrogen rich COF material. Three consecutive CV cycles were then performed, showing two reversible redox couples. The overlapped CV cycles with two reduction peaks at 3.5 V and 2.8 V indicate lithiation at two redox sites corresponding to N-H and C=N bonds in HAT-DAB COF. Also, the charge derivative (dq/dv) plot against potential given in supplementary compliments the findings in CV scans (Figure ). As the presence of one strong derivative peak around 2.8 V and a diminished peak at around 3.5 V suggests redox activity is more favourable around 2.8 V as compared to 3.5 V. This might be due to the decreases in total energies of COF structures as the no. of lithiation increases and thus more lithium ion is accommodated in the second discharge plateau (2.8 V), which is more than 75% of the overall capacity and a similar mechanism has been reported. Correspondingly, two distinct discharge plateaus were observed at approximately 3.36-3.12 V and 2.47-2.12 V in the galvanostatic charge/discharge plot depicted in Figure . After stabilizing the SEI layers, the highest galvanostatic discharge capacity achieved was up to 265 mAh/g at a current density of 0.02 A/g. Interestingly, HAT-DAB COF exhibits a higher average discharge voltage plateau of ~2.3 V, further improving the overall energy density of the cell. In Figure , plausible mechanism for Li + ion insertion/desertion and possible sites have been shown. Based on previously reported literature, up to 6 Li + ions can initially insert into the available sites, followed by an additional six Li + ions, totalling 12 Li + ion insertion sites throughout the HAT-DAB COF structure. This high capacity for Li + ion accommodation makes HAT-DAB COF a promising candidate for cathode materials in Li-ion batteries, offering a high theoretical capacity. The rate capabilities of HAT-DAB COF were investigated at various current densities, ranging from 0.02 A/g to 0.14 A/g as shown in Figure . The HAT DAB COF exhibits a high specific capacity of ~264 mAh/g at a current density of 0.02 A/g, demonstrating excellent performance under low current conditions. However, at a current density of 0.04 A/g, a sudden drop in capacity to 119 mAh/g is observed, corresponding to a 44% capacity loss. The specific capacities achieved were 119, 75, 58, 52, and 55 mAh/g at current densities of 0.04, 0.06, 0.08, 0.1, and 0.14 A/g, respectively. Notably, when the capacity was re-evaluated at a current density of 0.02 A/g, a significant decrease in capacity up to 146 mAh/g was observed compared to the initial values, with a 55 % capacity loss and suggesting structural instability at a higher discharge current rate. Thus, a minimal current of 0.04 A/g (at 0.3C) was chosen to evaluate the cycling performance for the cell as shown in Figure . It is worth mentioning that HAT-DAB COF exhibited superior long-term cycling stability, as depicted in Figure , maintaining a capacity of ~90.94 mAh/g with ~75% capacity retention even after 216 cycles. Further to investigate the 25% capacity loss during stability testing, we examined the voltage profile and differential capacity (dQ/dV) vs voltage plot (Figure ). In the initial cycle, three reduction peaks and one oxidation peak were observed, indicating the presence of multiple redox-active sites in the HAT-DAB COF cathode material. However, after several cycles, two reduction peaks disappeared, attended by slight peak shifting. This performance can be attributed to increased resistance at the electrode/electrolyte interphase and structural changes in the electrode (Figure ). The deactivation of two redox-active sites resulted in only one reversible peak remaining after 216 cycles leading to reduced cyclic stability and serving as the cause of the observed capacity fade. Interestingly, the Coulombic efficiency remained approximately 98% throughout stability cycling, which signifies no loss of charge during charging/discharging. Electrochemical impedance spectroscopy (EIS) and CV spectra were collected before and after cycling to explore the plausible mechanism of capacity fading, as shown in Figure . In EIS measurements, the starting point of the semicircle at the higher frequency region corresponds to the solution resistance (Rs), and the endpoint of the semicircle is used to calculate the charge transfer resistance (Rct). EIS spectra were fitted using EC Lab's Z-fit software (fitted circuit in the inset of Figure ), and it was observed that the solution resistance (Rs) increased from 0.28 Ω to 37.80 Ω. The Rct value increased drastically from 744.9 Ω to 2000 Ω over cycling, possibly due to the decline of Li⁺ ion diffusion through the SEI layer to the cathode material. EIS was also measured after the charging and discharging cycles. The charge-transfer resistance was lower when measured after discharging, likely due to the presence of Li+ ions on the electrode surface (Figure ). The inset of Figure shows the CV spectra collected before and after cycling, where the sharp reversible redox peaks diminished after cycling, likely due to the degradation of Li⁺ redox sites over cycling leading to the less utilization of redox sites. This less utilization of redox site could be another possible reason for the capacity fading after cycling. Also, we performed the post-mortem analysis, and the morphology of the cathode material surface is almost intact with some minimal crack observed after cycling shown in Figure , proves the mechanical strength and suitability of the material as cathode material.