Pore Structure Modification of Pitch‐Derived Hard Carbon for Enhanced Pore Filling Sodium Storage

Abstract

The pore structure of hard carbon has an important influence on its sodium storage performance. Herein, pitch‐derived hard carbons with different pore structures have been prepared via the combination of physical activation and vapor carbon coating. It reveals that the open pores favor the slope capacity while the closed pores can promote the plateau capacity, which consolidates the pore‐filling mechanism of hard carbon during the sodium storage in the plateau region. HC1400‐5 h@PP with rich closed micropores can deliver a reversible specific capacity of 299.1 mAh g−1 with initial Coulombic efficiency of 81.1%. The plateau capacity accounts for 66.6% of the total capacity. Ex situ Raman and galvanostatic intermittent titration investigations show that there exists an energy barrier for the Na deposition in the closed pores, leading to the rapid decay of plateau capacity at a high current density.

Laser Etching Post‐Processing to Create Low‐Tortuosity Structured Electrodes for Advanced Sodium‐Ion Batteries

“…As shown in Figure 2a, both the electrodes show two broad peaks in the range of 20°-25.5°(002 crystal plane) and one broad peak at about 43°( 100 crystal plane), indicating the disordered structure of HC in the electrodes. [26,27] The peak intensity of the laser-etched electrode becomes sharper near 25°, showing a tendency of graphitization. [28,29] However, there is no new peak and only a minor variation in peak intensity, indicating that the materials of the electrode did not undergo obvious crystal structure change during the laser etching process.…”

NaF Modification of Open/Closed Pores Enhancing the Sodium Storage in Hard Carbon

“…Furthermore, the average pore diameters of NaF@HC and PP@NaF@HC are slightly increased while the pore volume and true density are decreased, indicating that NaF can be infilled into micropores and lead to the increase of closed pores. The closed pore volume is calculated by the equation [33] of…”

“…The plateau capacity of HC mainly originates from the Na þ filling in closed pores, where sodium exists in the form of pseudometallic atomic clusters. [33,34] Therefore, it can be reasonably conjectured that the sodium deposition in the closed pores is also DOI: 10.1002/ente.202301597 Hard carbon (HC) is one of the most promising anode materials in sodium-ion batteries, and its sodium-storage performance is closely related to its open/ closed pore structures. However, modification of the inner pore structure of HC still remains a challenge.…”

“…[ 19 ] Zhang et al used vapor carbon to seal the open pores in HC into closed pores and found that the plateau capacity was significantly improved. [ 33 ] It can be seen that the pore structure in HC is important for its sodium‐storage properties. From the current research, although various methods have been applied to regulate the pore structures in HC, the modification of the inner pore structure remains a challenge.…”

Closed pore structure engineering from ultra-micropores with the assistance of polypropylene for boosted sodium ion storage

“…13 Currently, several strategies have been proposed for the fabrication of closed pores in hard carbon, 26 such as shrinking the open pores of biomass-derived hard carbon into closed pores via high-temperature treatment, 27–29 the introduction of pore-forming agents (ethanol and nano-sized MgO particles) 30,31 and the transformation of open pores into closed pores through carbon coating. 25,32,33 However, the instability of precursor sources and the non-uniform porous structure of activated carbon present challenges for precise regulation of closed pores, restricting the comprehensive understanding of their intrinsic sodium storage mechanism. Therefore, it is crucial to select a carbon source with regular and uniform porosity and precisely construct a closed pore structure to realize an advanced hard carbon anode.…”