Correlation between Microstructure and Potassium Storage Behavior in Reduced Graphene Oxide Materials

Abstract

Potassium-ion batteries (PIBs) are considered to be potential alternatives to the conventional lithium-ion batteries (LIBs) due to the similar working mechanism and abundant potassium (K) resource. However, it still remains challenging to directly apply commercial graphite anodes for PIBs owing to the large K ions, which may impede the electrochemical intercalation of K ions into the graphite interlayer and result in a poor cyclic stability and rate capability. Reduced graphene oxide (rGO) has shown remarkable electrochemical performance as an anode material for PIBs due to the fact that rGO possesses more active sites with an enlarged interlayer distance. Understanding the microstructure of rGO is crucial for optimizing its K-ion storage capabilities. Herein, it is revealed that the K-ion storage behavior of rGO is strongly dependent on the thermal treatment temperature on account of the difference in microstructure. rGO graphitized at 2500 °C exhibits a superior long-term cyclic stability for 2500 cycles due to the expanded interlayer distance and the unique graphite-like structure in a long range, enabling it to endure the huge volume change during uninterrupted K-ion intercalation/deintercalation processes.

Ultrathin carbon nanosheets for highly efficient capacitive K-ion and Zn-ion storage

“…Similarly, the b values can be extracted from the CV curves at various potentials (Fig. 6b), which are undoubtedly higher than that of PIBs, indicating the capacitive inherence of ZHSs 34 . The contribution of capacitive behavior was plotted in Fig.…”

Recent Advances in Stability of Carbon‐Based Anodes for Potassium‐Ion Batteries

“…Compared with graphite, rGO has the natural advantages of larger interlayer spacing [47] . Our group systematically studied the effect of heat treatment temperature on the microstructure of rGO (Figure 4d), proving that increasing the interlayer spacing is beneficial to store more K + ions and alleviate the volume change of K‐GICs [26] . The rGO‐2500 (heat treatment at 2500 °C) delivered high cycle stability as 88.4 mAh/g at 100 mA/g after 2500 cycles.…”

“…However, K + ions along with solvation sheath intercalate into graphite in the low concentrated ether electrolyte. Such co‐intercalation behavior forms a ternary GICs and the corresponding specific capacity can only reach 110 mAh/g [26] …”

“…The storage mechanism mainly involves K + ions adsorption in the pores and defect locations. According to the GCD curves, the intercalation process shows a voltage platform related to phase change (Figure 2e), and the capacitance contribution (adsorption process) shows a slope‐like feature, as shown in Figure 2f [26] …”

Boosting Fast and Stable Potassium-ion Storage by Synergistic Interlayer and Pore-structure Engineering

“…As concluded and depicted in Figure 3e and Table S1, based on the selected crucial electrochemical parameters, KC electrode overmatches most of the reported carbonaceous materials. 17,23,[52][53][54] Especially, the rate capability of KC is at the apex, which indicates a smooth and fast K ion diffusion process enabled by the synergistic interlayer and pore-structure engineering.…”