Nonignorable Influence of Oxygen in Hard Carbon for Sodium Ion Storage

Abstract

As an effective method, heteroatom doping is widely used to improve the electrochemical performance of carbon materials. However, the influence of oxygen-containing functional groups in carbon materials is often neglected. Therefore, we use buckwheat hulls as the precursor to prepare oxygen-doped hard carbon by simple carbonization. The buckwheat hull at a pyrolysis temperature of 1100 °C has the highest reversible capacity of 400 mA h g–1 at 50 mA g–1, and the capacity can maintain 96% of the initial capacity after 3000 cycles at 2A g–1. These results confirm that the natural pore structure and proper interlayer spacing of the BPC-1100 contribute to the transport and insertion of sodium ions. In addition, the first principle proves that the role of oxygen atoms cannot be ignored in the storage of sodium ions. In particular, the improvement of the CO bond is helpful to improve the adsorption capacity of hard carbon to sodium ions and enhance the reversible capacitance.

Multi-heteroatom doped porous carbon derived from insect feces for capacitance-enhanced sodium-ion storage

“…The thermogravimetric process shown in Fig. 2 is similar with other biochar materials and can be divided into three stages depending on the heating process [24][25][26]. In the first stage (25-220°C), the slight weight loss is basically because the evaporation of water adsorbed on the material surface as the temperature increases [21].…”

Potassium‐Ion Storage in Cellulose‐Derived Hard Carbon: The Role of Functional Groups

“…[49] This behaviour is similar to that observed for lithiumion or sodium-ion adsorption onto the heteroatom-containing carbon materials. [43][44][45] A small sloping plateau-like trend is seen in the charge-discharge curve, that can be attributed to the potassium insertion into the turbostratic nanodomains and micropores. The random orientations of crystallites in the hard carbons produce micropores that provide considerable storage capacities at low voltages close to 0 V.…”

“…This presence of oxygen on the edge or surface functional groups (C=O) appears to improve the cation adsorption capacity and eventually enhance the reversible capacitance. [43][44][45] Moreover, the influence of pyrolysis temperature was observed on the surface area of carbon samples. The BET surface area of CL-1000, CL-1300 and CL-1400 were 552, 153 and 19 m 2 g À 1 , respectively, indicating the decreasing trend of porosity upon pyrolysis.…”

A Stable Biomass‐Derived Hard Carbon Anode for High‐Performance Sodium‐Ion Full Battery

“…They mainly contain sp 3 -C along with broadened signals on the low energy side associated with the presence of C─C, which may lead to fewer side effects during charging and discharging ( Figure 1g,h,i). [59][60][61][62] Compared with HC-900 and HC-1100, HC-1000 delivers favorable electrochemical performance because of its moderate specific area.…”