Pistachio Shell-Derived Carbon Activated with Phosphoric Acid: A More Efficient Procedure to Improve the Performance of Li-S Batteries.

Almudena Benítez,Julián Morales,Álvaro Caballero

doi:10.3390/nano10050840

Abstract

A sustainable and low-cost lithium–sulfur (Li–S) battery was produced by reusing abundant waste from biomass as a raw material. Pistachio shell was the by-product from the agri-food industry chosen to obtain activated carbon with excellent textural properties, which acts as a conductive matrix for sulfur. Pistachio shell-derived carbon activated with phosphoric acid exhibits a high surface area (1345 m2·g−1) and pore volume (0.67 cm3·g−1), together with an interconnected system of micropores and mesopores that is capable of accommodating significant amounts of S and enhancing the charge carrier mobility of the electrochemical reaction. Moreover, preparation of the S composite was carried out by simple wet grinding of the components, eliminating the usual stage of S melting. The cell performance was very satisfactory, both in long-term cycling measurements and in rate capability tests. After the initial cycles required for cell stabilization, it maintained good capacity retention for the 300 cycles measured (the capacity loss was barely 0.85 mAh·g−1 per cycle). In the rate capability test, the capacity released was around 650 mAh·g−1 at 1C, a higher value than that supplied by other activated carbons from nut wastes.

Highlights

Current energy challenges involve overcoming growing energy needs, climate change, and the increasing scarcity of resources
We previously reported the use of H3PO4 to activate carbon derived from cherry pits and its application in a Li–S battery [45]
To prepare the activated carbon, a temperature of 800 ◦C was selected according to the thermogram registered for the fresh pistachio shell in inert atmosphere (Figure 1a)

Summary

Introduction

Current energy challenges involve overcoming growing energy needs, climate change, and the increasing scarcity of resources. The active material of the battery, has the following advantages: (i) It is very abundant in the earth’s crust, is an enormous residue from the petrochemical industry, and is a cheap material; (ii) it is non-toxic and environmentally friendly due to the fact that its production process is well-controlled industrially; and (iii) it is highly energetic in its reversible reaction with lithium [2], being able to supply a theoretical specific capacity of 1675 mAh·g−1 (corresponding to an energy density of ~2500 Wh·kg−1). Li–S batteries must overcome different obstacles to avoid capacity fading during cycling, such as the following [3]: (a) Sulfur and solid reduction products (Li2S2 and Li2S) are insulators, leading to poor electrochemical utilization of the element; (b) formation of intermediate polysulfide, causing severe changes in the volume on the cathode; and (c) dissolution in the electrolyte of some formed polysulfides (Li2Sx, 2 ≤ x ≤ 8), giving rise to the shuttle phenomenon that causes loss of active material and coulombic efficiency. Most synthetic procedures for these materials are complex and require expensive and non-renewable raw materials, a drawback for large-scale applications

Methods

Results

Conclusion