|DNA has a high concentration of heteroatoms, including oxygen, nitrogen and phosphorus, that can anchor soluble polysulfides to improve the cycling performance of Li/S batteries. Li et al. Click to enlarge.|
A team from the China University of Geosciences has taken a novel approach to stabilizing Lithium-sulfur batteries by functionalizing the carbon-sulfur cathode with DNA.
Experimental results reported in a paper accepted for publication in the RSC Journal of Materials Chemistry A showed that adding a fine adding amount of DNA into a carbon/sulfur composite enables a significant improvement to cyclic performance by anchoring the soluble polysulfides that lead to performance degradation. The DNA-decorated electrode offered a discharge capacity of 771 mAh·g-1 at 0.1 C after 200 cycles (retention 70.7% of the initial)—a three-fold enhancement in capacity retention over 200 cycles.
Rechargeable lithium/sulfur battery promises an appealing candidate for energy storage to power portable devices and electric vehicles. However, sulfur electrode encounters several vital intrinsic disadvantages, including low conductivity, volume expansion during discharge and dissolution of polysulfides to organic electrolyte. In particular, the shuttle-effect resulted from severe dissolution of polysulfides leads to low active materials utilization, low Coulombic efficiency and unaffordable performance decay, which inhibits the Li/S cells from being practically deployed.
In recent years, many strategies have been attempted to confront these challenges, especially the polysulfides dissolution problem. … It is not difficult to envision that, for those efforts, the relatively large loading amount of third-party agents, either polymers or oxides, implies not only higher internal resistance but capacity penalty. Enlarging the anchoring role of third-party additives brought by the interactions hereby becomes a promising approach. To balance the energy density and the polysulfide adsorption, the candidate agents should be light-weighted, rich of functional groups and can be easily dispersed homogeneously in the C/S composite.
Based on these understanding, we selected DNA as a model additive to conduct the proof-of-concept studies. DNA strains own high concentration of heteroatoms including O, N, and P, which may serve as absorbent for anchoring polysulfides. Upon integration with certain substrate which allows a well- dispersion of DNA, the quasi-linear structure of DNA implies that the heteroatoms are mostly disposed to the target adsorbates, which should maximize the anchoring function.—Li et al.
The team first performed first-principles density functional theory calculations on the adsorption behaviors of polysulfides on DNA strains, and demonstrated that −P=O and =N− sites of the constituent deoxyribonucleotides of DNA are capable of anchoring polysulfides.
To create the DNA-decorated electrode materials, they first prepared different concentrations of aqueous DNA solution by dissolving salmon sperm DNA powder in deionized water. CMK-3 carbon was then ultrasonically dispersed into the solution. The resulting mixture was slowly evaporated at 50 °C to ensure all DNA strains were uniformly absorbed by the CMK-3 substrate. After drying, the substrate was coupled with sulfur using a typical melting-diffusion procedure.
They found that a moderate DNA loading rate (14 mg∙g−1 S, 0.83 wt% of total active components) gave the best cyclic performance under two different loading strategies.
The DNA-decoration strategy for C/S electrodes can be facilely implemented in industry and provides a commercially feasible choice for pursuing high-performance lithium-sulfur batteries.—Li et al.
Battery researcher Shizhao Xiong from the National University of Defense Technology in China told RSC’s Chemistry World that even though other studies have experimented with trapping polysulfides in the cathode host material, the idea of loading DNA into it is “extraordinarily brilliant and impressive. Even if we ignore the improved performance of lithium–sulfur batteries, we will find that this work builds a brand-new bridge between traditional materials and biological materials fields.”
Qiyang Li, Chenggang Zhou, Zhuan Ji, Bo Han, Liang Feng and Jinping Wu (2015) “High-Performance Lithium/Sulfur Batteries by Decorating CMK-3/S with Fine-amount DNA” J. Mater. Chem. A, doi: 10.1039/C4TA06083K