# Macroporous Activated Carbon Derived from Rapeseed Shell for Lithium-Sulfur Batteries
## 1 Introduction  
Given the rapid development of portable electronics, electric vehicles, and smart grids, advanced electrochemical energy storage systems have been investigated extensively [1; 2; 3; 4; 5; 6; 7; 8; 9; 10; 11]. Lithium-sulfur (Li-S) batteries are expected to perform a significant role in the field of energy storage owing to its ultrahigh theoretical energy density of 2500 Wh kg\({}^{-1}\), environmental friendliness, and low cost [12; 13; 14; 15; 16; 17; 18; 19]. However, in practical applications, Li-S batteries are usually hindered by problems originating from the sulfur cathode, metallic lithium anode, and electrolyte [20; 21; 22; 23]. For the sulfur cathode, key problems mainly comprise three aspects: the low conductivity of sulfur and its discharge products, the diffusion of polysulfide ions, and the expansion of active material during electrochemical reaction [12; 13; 14; 15; 16; 17; 18; 19; 20; 21; 22; 23]. To solve the abovementioned problems, one of the most effective methods is loading sulfur into electronically conductive frameworks with good structural stability [24; 25; 26; 27; 28; 29; 30; 31; 32]. Various nanoporous carbon materials, such as mesoporous carbon [33], porous graphene [34; 35], porous carbon nanofibers [36; 37], hollow carbon spheres [38], and activated carbon (AC) [39], have been widely studied as loading frameworks for sulfur. During electrochemical reaction, the carbon framework can not only provide a stable and conductive network for both sulfur and discharge products, but can also efficiently restrain the diffusion of polysulfides. Among porous carbon materials, AC, which features a large specific surface area, high pore volume, and small-size nanopores, is a highly promising framework for sulfur [39]. The large specific surface area and high pore volume can yield high mass loading and enhance the utilization of sulfur in electrochemical reactions, and nanopore structures with a small pore size can suppress the diffusion of polysulfide more efficiently [39].  
The utilization and development of biomass resources are some of the most important research topics at present [40; 41]. Biomass materials are rich in resources, widely available, renewable, and environmentally friendly. In recent years, considerable attention has been focused on AC prepared from biomass materials as a loading support for sulfur applied to the cathode of Li-S batteries [40; 41; 42]. [PERSON] et al. reported an AC material made from fish scale for sulfur loading [43]. The resulting nanocomposite cathode showed a discharge capacity of 1039 mA h g\({}^{-1}\) at the first cycle and a reversible discharge capacity of 1023 mA h g\({}^{-1}\) over 70 cycles at 1 C. [PERSON] et al. reported an AC material by the utilization of coconut shell as a raw material [44]. The obtained AC/sulfur composite material possessed an initial capacity of 878 mAh g\({}^{-1}\) and a reversible capacity of 774 mAh g\({}^{-1}\) over 50 cycles at 0.1 C. In our previous works, AC materials were prepared from waste litch shells and mango stones [45; 46]. As-prepared AC/sulfur composite cathodes exhibited good electrochemical performance.  
In this work, a series of AC materials was prepared using waste rapeseed shells as raw materials. Influences of KOH amount, activated temperature, and activated time on pore structure parameters of AC materials were studied. The AC sample with the maximum specific surface area (2090 m\({}^{2}\) g\({}^{-1}\)) and pore volume (1.28 cm\({}^{3}\) g\({}^{-1}\)) was applied as a loading framework for sulfur. When used as a cathode of a Li-S battery, the AC/sulfur composite exhibited high specific capacity and good capacity retention.