## 3 Results and Discussion
### The Performance of Activated Coal Gangue in LOBs  
The 2032-coin-type LOBs were assembled to examine the actual electrocatalytic performance of the activated coal gangue. As shown in Figure 5a, the battery configuration is composed of a gangue-based cathode, a diaphragm, and a lithium anode. The gangue-based cathode plays a dual role as the electrochemical reaction area and the storage area of the discharge product lithium peroxide (Li\({}_{2}\)O\({}_{2}\)) in the cycling process of LOBs. The activity of the gangue-based cathode has been the key to the development of LOBs. The full charging-discharging curve in Figure 5b shows that activated coal gangue delivers a superior specific discharge capacity (9156 mAh g\({}^{-1}\)) and a small discharge overvoltage  
Figure 4: (a) XPS surveys for as-prepared samples; High-resolution Si 2p (b), C 1s (c), O 1s (d) spectra for activated coal gangue and crushed coal gangue. (0.17 V) at median discharge capacity. Impressively, the activated coal gangue showed a low charge overvoltage (0.95 V) at median charge capacity, which contributed to preventing the side decomposition of the organic electrolyte, thus improving the durability of LOBs. The existence of the SiC\({}_{\mathrm{X}}\)/SiO\({}_{\mathrm{X}}\)-activated layer could facilitate the catalytic stability of coal gangue, resulting in large, specific capacities in LOBs. Moreover, the activated coal gangue cathode demonstrated an outstanding rate performance in the long cycling process under different current densities, ranging from 200 to 2000 mA g\({}^{-1}\) (Figure 5c). Notably, the activated coal gangue kept a discharge-charge voltage gap from \(\sim\)1.51 V (200 mA g\({}^{-1}\)) to \(\sim\)1.96 V (2000 mA g\({}^{-1}\)). In addition, the activated coal gangue maintained little numerical difference in the discharge-charge overvoltage (\(\sim\)1.54 V) when returning to 200 mA g\({}^{-1}\). Amazingly, the activated coal-gangue-based cathode could still circulate stably for more than 300 h at 200 mA g\({}^{-1}\), implying that the activated coal-gangue-based LOBs delivered a splendid practical application in fast charging. In terms of the cycling stability of LOBs, the activated coal gangue could be maintained for more than 400 h, without evident degradation, at 200 mA g\({}^{-1}\). To sum up, the coal gangue activated by the simple acid-alkali treatment was a promising cathode catalyst for the LOBs. The electrochemical performance of activated coal gangue-based cathode in this work and those of reported typical other catalyst-based cathodes are summarized in Table S2 (Supporting Information). By comparison, the discharge capacity and cycling stability of activated coal gangue-based cathode in this work is the best among the catalysts in LOBs. To totally clarify the intrinsic mechanisms of the activated coal gangue and understand the potential influence of amorphous SiC\({}_{\mathrm{X}}\)/SiO\({}_{\mathrm{X}}\) on the cycling efficiencies of LOBs, electrochemical impedance spectra (EIS) and XPS were applied (Figure 6). As shown in Figure 6a, the activated coal gangue demonstrated ohmic resistance (Ro, \(\sim\)20 \(\Omega\)), with an evident  
Figure 5: (**a**) Configuration of 2032-coin LOBs. (**b**) initial full discharge/charge curves of gangue-based LOBs at 100 mA g\({}^{-1}\); (**c**) rate performances of gangue-based LOBs; (**d**) cycling stability of gangue-based LOBs with a cut-off capacity of 1000 mAh g\({}^{-1}\). change in all states, but showed distinctly different values in charge transfer resistance (Rct). In detail, the activated coal-gangue-based LOBs showed a bigger discharge Rct (208.40 \(\Omega\)) than that of the charged (145.70 \(\Omega\)) and pristine states (126.43 \(\Omega\)). The equivalent circuit (right in Figure 6a) made it clear that a new interface was formed on the surface of the gangue-based cathode after the 1 st discharge, relating to the formation and loading of the discharge products.