Rationally Tailoring Superstructured Hexahedron Composed of Defective Graphitic Nanosheets and Macropores: Realizing Durable and Fast Potassium Storage

Abstract

Multipores engineering composed of micro/mesopores is an effective strategy to improve potassium storage performance via providing enormous adsorption sites and shortened ions diffusion distance. However, a detailed exploration of the role played by macropores in potassium storage is still lacking and has been barely reported until now. Herein, a superstructure carbon hexahedron (DGN‐900) is synthesized using poly tannic acid (PTA) as precursor. Due to the spatially confined two‐step local contraction of PTA along different directions and dimensions during pyrolysis, defective nanosheets with macropores are formed, while realizing a balance between defects content and graphitization degree by regulating temperature. The presence of macropores is conducive to accelerating electrolyte ions rapid infiltration within electrode, and its pore volume can accommodate electrode structure fluctuation upon cycling, while the most suitable ratio of defects to graphitic provides rich ions adsorption sites and sufficient electrons transfer channels, simultaneously. These advantages enable a prominent electrochemical performance in DGN‐900 electrode, including high rate (202.9 mAh g −1 at 2 A g −1 ) and long cycling stability over 2000 cycles. This unique fabrication strategy, that is, defects engineering coupled with macropores structure, makes fast and durable potassium storage possible.

Graphene Oxide Block Derived Edge‐Nitrogen Doped Quasi‐Graphite for High K+ Intercalation Capacity and Excellent Rate Performance

“…[51,52] The NQG anode performs a high charge capacity below 0.5 V of 180 mAh g −1 at 0.05 A g −1 , which is much higher than that of the recently reported hard carbon anodes (Figure S20a, Supporting Information). [18,[53][54][55][56][57][58][59][60] Even at high current densities of 0.1, 0.2, and 0.5 A g −1 , high charge capacities of 170, 158, and 133 mAh g −1 can also be obtained. When compared with LG, RGO, and graphite, NQG still shows the highest charge capacity below 0.5 V, fully demonstrating the advantage of local graphite domain structure (Figure S20b, Supporting Information).…”

A comprehensive review of carbon anode materials for potassium-ion batteries based on specific optimization strategies

“…Moreover, Li and co-workers 100 used SeO 2 powder as a self-sacrificing template to elaborately develop an interconnective macroporous structure, resulting in an extraordinary rate (145 mA h g −1 at 20 A g −1 ) and long cyclability (214 mA h g −1 at 2 A g −1 exceeding 5000 cycles). Recently, our group also explored the influence of macropores on the potassium-storage performance, and in depth demonstrated that the temperature plays a vital role in forming macropores; namely, it is hard for a lower temperature to create macropores due to the partial decomposition of large radicals, 21 while a higher temperature will cause the structural shrinkage associated with pore collapse. Only a suitable temperature can make the macropore configurations reach the best, thus enabling an excellent rate (188.2 mA h g −1 at 2 A g −1 ) and cyclability (over 1800 cycles) in K half-cells.…”

“…According to the pore size distribution, it is illustrated that the micropores (d p < 2 nm) can provide abundant sites for K-ion uptake, while the mesopores (2 nm < d p < 50 nm) can shorten the ion diffusion distance for fast reaction kinetics. 16,29,97,98 As for macropores (d p > 50 nm), these can function as a buffering space and electrolyte reservoir, 21,99,100 considerably resulting in an improved structure stability and capacity. Accordingly, rationally tailoring hierarchical-porous structure in carbon anode is highly attractive for realizing an excellent potassium-storage performance.…”

“…At present, carbonaceous anodes have been demonstrated to be an effective host material for storing K-ions because of their cost-effectiveness, good conductivity, and flexible architecture. [18][19][20] Unfortunately, the larger ionic radius of K + (1.38 Å) compared with its Li + counterpart (0.76 Å) can easily cause significant volume change and inevitably encounter sluggish kinetics in the solid-state diffusion stage, [21][22][23][24] thus eventually leading to inferior cycling stability and poor rate capability. To solve these issues, some optimization strategies have been proposed and proved to be feasible, such as heteroatom-doping (N, S, P, and O, e.g.…”

“…[30][31][32][33][34] To be specific, the introduction of heteroatoms into the carbon matrix not only can expand the interlayer spacing to accelerate K-ion diffusion and alleviate volume fluctuation, but induces more defect sites to adsorb potassium, 35 all of which are favorable for realizing excellent rate, cycling, and capacity. Moreover, the existence of micropores can provide active sites for K-ion adsorption storage, 29 while mesopores and macropores are able to reduce the diffusion distance and improve the structural stability, 21,29 respectively. In addition, a stable SEI film can inhibit the exposure of a fresh active surface and simultaneously avoid the excessive consumption of electrolytes, 30 benefiting the capacity and cyclability.…”