CO₂ Etching Modulates Lithium and Sodium Storage Performance of Hard–Soft Carbon Composite-Based Freestanding Thick Electrodes

Abstract

Carbon-based materials are the most prospective anodes. Typically, a single carbon-based material is applied to different energy storage systems (EESs) without modification. However, the microcrystal structure of carbon plays a decisive role in the energy storage performance, and therefore, it should be adjusted when applied to different EESs. Here, a hierarchical porous carbon monomer monolith (HPCM) embedded with carbon nanotubes blooming on ZIF-67 was designed as a soft–hard carbon-based freestanding thick electrode for achieving high-energy lithium-ion and sodium-ion batteries. HPCM is resorcinol–formaldehyde (RF) resin-derived carbon, mainly composed of hard carbon, which has outstanding mechanical properties, a high surface area, and high porosity. Carbon nanotubes (CNTs) derived from ZIF-67 have extraordinary electronic conductivity, which provides soft carbon. High-temperature CO2 etching was performed to adjust the microcrystal structure, and the lithium/sodium storage performance of the electrode was evaluated. After CO2 etching, the materials lose almost half their weight (mainly hard carbon), and pseudocapacitive contribution decreases for both lithium-ion and sodium-ion batteries, whereas the specific capacity increases for lithium-ion batteries and decreases for sodium-ion batteries. Capacities of 5.96 mAh cm–2 (areal) and 132.48 mAh cm–3 (volumetric) were achieved for lithium storage, and those for sodium storage were 2.31 and 51.24 mAh cm–3, respectively. In summary, it is significant to adjust the microcrystal structure of carbon-based electrodes, and this study provides related experience for lithium and sodium storage.

Flexible Precursor Modulation toward Selective Heteroatom Doping in a Hard-Carbon Anode for Sodium-Ion Batteries

“…As shown in the charge–discharge curves of the N/S-HC electrode at different current densities (Figure b), the N/S-HC electrode realizes the smallest polarization at each current density compared with these of the HC and N-HC electrodes (Figures S6a and S7a), reflecting a stable and reversible storage response even at a high rate. , Moreover, to the best of our knowledge, the N/S-HC electrode shows rate capabilities comparable to those of the recently reported HC materials (Figure S8). ,,,− …”

Tuning Nanopore Structure of Hard Carbon Anodes by Zinc Gluconate for High Capacity Sodium Ion Batteries

“…[1][2][3] Alternatively, sodium has the benefit of being inexpensive and possessing significant reserves. [4][5][6] Hard carbon materials, [7][8][9][10][11][12] soft carbon material, [13][14][15][16][17] nano-carbon material, [18][19][20][21][22][23] alloy material, [24][25][26][27][28] oxide material, [29][30][31] and organic compound materials show own advantages when using in sodium-ion batteries. [32][33][34][35] Among them, hard carbon hold great promise because of the disordered structure and large layer spacing, providing higher reversible capacity.…”

Liquid Template Assisted Activation for “Egg Puff”‐Like Hard Carbon toward High Sodium Storage Performance

“…[21][22][23][24][25] Advanced hard carbon anodes can be obtained due to the increase of the reaction contact area and the shortening of the Na + transfer path, through increasing the specific surface area via template or activation methods to regulate the capacitance ratio. [26][27][28] In addition, doping the carbon matrix with heteroatoms such as N, S, P, can increase the defects in the graphene sheets, change the electronic conductivity properties of carbon materials, and provide the additional adsorption sites for Na + , thus improving the reversible capacity and rate performance of hard carbon. [29,30] Therefore, based on the capacitive sodium storage mechanism, promising hard carbon materials with high reversible capacity and high-rate performance can be fabricated, decreasing unexpected security concerns of longplateaus induced sodium plating at low potential.…”