New Insights into the Anchoring Mechanism of Polysulfides inside Nanoporous Covalent Organic Frameworks for Lithium–Sulfur Batteries

Abstract

The application prospects of lithium−sulfur (Li−S) batteries are constrained by many challenges, especially the shuttle effect of lithium polysulfides (Li 2 S x ). Recently, microporous covalent organic framework (COF) materials have been used to anchor electrodes in Li−S batteries, because of their preferable characteristics, such as self-design ability, suitable pore size, and various active groups.To identify the ideal anchoring materials that can effectively restrain the shuttle of Li 2 S x species, the anchoring mechanism between COF materials and Li 2 S x species should be investigated in depth. Therefore, we systematically investigated the anchoring mechanism between specific COF nanomaterials (consisting of boron and oxygen atoms and benzene group) and Li 2 S x (x = 1, 2, 4, 6, or 8) species on the surface and inside the pore using density functional theory methods with van der Waals interactions. The detailed analysis of the adsorption energy, difference charge density, charge transfer, and atomic density of states can be used to determine that the COF nanomaterials, with the structure of boroxine connecting to benzene groups and boroxine groups not constructed at the corner of the structure, can effectively anchor the Li 2 S x series. Accordingly, this study provides the theoretical basis for the molecular-scale design of ideal anchoring materials, which can be useful to improve the performance of the Li−S batteries.

Highly Interconnected Nanochannel and Silver, Nitrogen Co‐Doped Carbon Aerogel via Metal Organic Knot–Modifying as Active Polysulfide Immobilizer for Lithium–Sulfur Battery

“…The exchange correlation potentials between electrons were measured by Perdew–Burke–Ernzerhof method. [ 44 ] Then, the Ag 2 S (022) crystal model was established in the 3 × 3 supercell with the two‐layer slab, containing over 13 Å of vacuum space. The adsorption energy ( E ads ) of Ag 2 S to Li 2 S n species were calculated by…”

Covalent Organic Frameworks for Next‐Generation Batteries

“…Qiu's group verified that the boron and oxygen atoms in the boroxine ring and the nitrogen atom in the triazine ring have the function of limiting the shuttle effect of lithium polysulfides by density functional theory. [89,90] The TB-COF/S electrode maintains a reversible capacity of 663 mAh g À 1 after 800 cycles performed at 1672 mA g À 1 , with a capacity decay rate of 0.023 %. Threedimensional COFs have a unique pore structure and have been studied for use as a host material for sulfur.…”

“…Regarding the applications for next‐generation batteries, we first outline the application progress of COFs in sodium ion batteries (SIBs) and potassium ion batteries (PIBs) . Subsequently, the applications of COFs in lithium‐sulfur batteries (LSBs), lithium metal batteries (LMBs), and multivalent ion batteries (ZIBs, MIBs, AIBs) will be introduced. Finally, the challenges, prospects and improvement strategies of COF electrodes will be discussed and suggested.…”

Improved Performance and Immobilizing Mechanism of N‐doping Carbon Aerogel with Net Channel via Long‐Chain Directing for Lithium–Sulfur Battery

“…Lithium–sulfur (Li–S) battery gains great popularity for its high theoretical energy density, environment friendliness, cost effectiveness,and natural abundance of active sulfur element . In addition, elemental sulfur is deemed to be the most promising electrode material for its high theoretical specific capacity of 1675 mAh g −1 , and Li–S battery presents a high energy density of 2600 Wh kg −1 , being significantly higher than traditional lithium‐ion battery (<500 Wh kg −1 ) . Thus, it is considered to be the next generation of electrochemical devices providing high energy density …”