Fast Intercalation in Locally Ordered Carbon Nanocrystallites for Superior Potassium Ions Storage

Abstract

Hard carbons (HCs) have great potential as anode material for high‐performance potassium ion batteries (PIBs). However, due to the complexity of HCs, the relationship between their structures and potassium (K) storage behaviors is still not quite clear. Here, three types of HCs with different structures are designed for further understanding the electrochemical storage processes. Among them, the carbon spheres (CS) exhibit impressive rate performance (161.6 mAh g−1 at 2 A g−1) and cycle stability (140.2 mAh g−1 at 2 A g−1 after 500 cycles). The superior performance of CS can be mainly ascribed to the intercalation into its locally‐ordered carbon nanocrystallites, and the charge/discharge processes are further characterized with significant pseudocapacitive dominating. Suitable nanocrystalline size and the ratio of defects with proper morphology are the key factors to improve K storage efficiency. This work will contribute to understanding the role of these factors in the K storage performance of carbon materials.

Noncrystalline Carbon Anodes for Advanced Sodium‐Ion Storage

“…In addition to defects caused by heteroatom doping and surface groups, NCC itself has many inherent defects. [ 26,93 ] Yu et al. [ 23 ] designed ultrathin 2D nanosheets into 3D mesoporous carbon nanosheets by the MgO template method (Figure 7e), which have a hierarchical pore structure and expanded interlayer spacing.…”

“…In addition to defects caused by heteroatom doping and surface groups, NCC itself has many inherent defects. [26,93] Yu et al [23] designed ultrathin 2D nanosheets into 3D mesoporous carbon nanosheets by the MgO template method (Figure 7e), which have a hierarchical pore structure and expanded interlayer spacing. These morphological engineering can expose more active surfaces to the electrolyte and shorten the diffusion length of ions and electrons, thereby increasing the storage rate of sodium ions.…”

Integrated Design from Microstructural Engineering to Binder Optimization Enabling a Practical Carbon Anode with Ultrahigh ICE and Efficient Potassium Storage

“…16,17 Compared to graphite, hard carbon exhibits excellent rate capability and stability due to large interlayer spacing and high disorder. 18 However, the disadvantages are equally obvious and intolerable. A large number of pores and functional groups lead to extremely low initial Coulombic efficiency (ICE, even <40%) and low energy density, seriously hindering the application of hard carbons.…”

“…Although the most commonly used anode graphite for LIBs can form stable intercalation compounds with potassium, its theoretical capacity is only 279 mAh g –1 . , Worse, since the K + size is much larger than Li + (1.33–0.68 Å), the (de)­intercalation leads to severe volumetric deformation, making the stability and rate capability of graphite very poor. , Compared to graphite, hard carbon exhibits excellent rate capability and stability due to large interlayer spacing and high disorder . However, the disadvantages are equally obvious and intolerable.…”

Discrete Graphitic Crystallites Promise High‐rate Ion Intercalation for KC8 Formation in Potassium Ion Batteries

“…[3b,4a,5] Identifying a superior carbon anode to commercial graphite for K + storage is the major challenge in developing high-energy and high-power PIBs.Two approaches to solving this problem have been developed: modifying the microstructure of graphite and developing other non-graphitic carbons as anodes. For the former, strategies such as increasing the interlayer spacing, [6] modifying morphology, [7] and disordering graphitic crystallites [8] have been explored to facilitate K + diffusion and precisely tune the void space to buffer the expansion of electrodes. These modified graphitic anodes generally exhibit high slope capacity due to additional defects or surfaces introduced for K + adsorption, excellent rate performance, and cycle stability.…”