Controllable Substitution of S Radicals on Triazine Covalent Framework to Expedite Degradation of Polysulfides

Abstract

Lithium–sulfur (Li–S) batteries are facing a significant barrier due to the diffusion of intermediate redox species. Although some S doped covalent framework cathodes have been reported with outstanding reversibility, the low content of sulfur (less than 30%) limits the practical applications. To overcome the issue, the sulfur and nitrogen co‐doped covalent compounds (S‐NC) as a host‐type cathode have been developed through the radical transfer process during thermal cracking amino groups on the precursor, and then plentiful positively charged sulfur radicals can be controllably introduced. The experimental characterization and DFT theoretical calculation certificate that the sulfur radicals in S‐NC/S can expedite redox reactions of intermediate polysulfides to impede their dissolution. Moreover, the energy barriers during ions transfer also obviously decreased after introducing S radicals, which lead to improved rate performance.

Tubular CoFeP@CN as a Mott–Schottky Catalyst with Multiple Adsorption Sites for Robust Lithium−Sulfur Batteries

“…[60] However, CoFeP@CN exhibited the lowest Gibbs free energy changes (0.47 eV) than CoFeP and t-CN (0.61 and 0.75 eV, respectively), and this value is much lower than previously reported graphene or N-doped graphene (above 1 eV), which suggested that the composite CoFeP@CN was a relatively excellent catalyst to promote the LiPS conversion kinetics. [57,61,62] The lowest Gibbs free energy change in the reduction of Li 2 S 2 measured for CoFeP@CN was consisted of Li 2 S nucleation test and overall, these results demonstrated that CoFeP@CN Mott-Schottky heterostructure catalyst plays a catalytic role to accelerate the Li 2 S formation.…”

Interfacial Engineering of Binder‐Free Janus Separator with Ultra‐Thin Multifunctional Layer for Simultaneous Enhancement of Both Metallic Li Anode and Sulfur Cathode

“…These comparisons validate that the CTP-PAN-LLZTO separator can reduce the polarization and suppress the shuttle effect to enhance sulfur cathode. [47] The rate performance of a cell is a measurement showing its ability to charge and discharge at a high current density. As shown in Figure 4f, the discharge specific capacity of different separators decreased noticeably with the increase in current density in general.…”

The Synergy of La2O3 Nanoparticles and Graphene for Advanced Li‐S Batteries

“…The oxidation peak represents the conversion from Li 2 S to S 8 (peak iii). [40] The current of La 2 O 3 /Graphene modified layer is also much higher than that of PP and graphene (Figure S8, Supporting information). As shown in the inset of Figure 6b, the battery with La 2 O 3 /Graphene coating separator shows the highest potential value of the second cathodic peak located at 2.06 V, higher than that of graphene (2.02 V) and bare separator (1.99 V), suggesting that La 2 O 3 could reduce electrochemical polarization and expedite the reaction kinetics process.…”