Cobalt-doped Hollow Carbon Framework as Sulfur Host for the Cathode of Lithium Sulfur Battery

Abstract

Lithium-sulfur batteries are deemed to be next generation of cost-effective and high energy density systems for energy storage. However, low conductivity of active materials, shuttle effect and sluggish kinetics of redox reaction lead to serious capacity fading and poor rate performance. Herein, a sodium citrate derived three-dimensional hollow carbon framework embedded with cobalt nanoparticles is designed as the host for sulfur cathode. The introduced cobalt nanoparticles can effectively adsorb the polysulfides, enhance the kinetics of conversion reaction and further improve the cyclic and rate performance. The obtained cathode delivered a high initial discharge capacity of 1280 mAh•g-1 at 0.5C(1C=1672 mAh•g-1), excellent high-rate performance up to 10C and stable cyclic capacity of 770 mAh•g-1 at 1C for 200 cycles with high Columbic efficiency.

Acetylation Strategy for Unzipping Carbon Nanotubes in High-Performance Lithium-Ion Batteries

“…49 The four components of the C 1s XPS spectrum of UCNTs are assigned to the carboxyl group O− C�O (288.2 eV), the hydroxyl group C−O (286.0 eV), sp 3 hybridized C−C (284.8 eV), and sp 2 -hybridized C�C (284.1 eV), respectively. 50,51 These four components can also be found in the C 1s spectrum of AcUCNTs. However, the band at 286.0 eV is attributed to C−O of hydroxyl and C−O−C after acetyl substitution whereas the band at 288.1 eV is assigned to C�O of acetyl, providing evidences for the strong chemical modification.…”

Reduced Graphene Oxide Embedded with ZnS Nanoparticles as Catalytic Cathodic Material for Li-S Batteries

“…In particular, the SN-rGO/ZnS sample shows good reversibility and facile polysulfide conversion considering the distinct peaks at −0.092, 0.087, 0.342 V in reduction and 0.079, −0.086, −0.291 V in oxidation which are visible in Figure 4 and even more in the scan performed at 1 mV , reported in Figure S9b . More specifically, the peaks in the cathodic scan are indicative of the step-by-step reduction from original Li S to insoluble Li S on the working electrode and oxidation of Li S on the counter electrode (see Table S3 in supporting information for the Equations (S1)–(S9) describing the reaction path during the scan) [ 57 , 58 ]. Furthermore, the current response in the symmetrical CVs turns out to be in the order SN-rGO/ZnS > SN-rGO > KjB, thus corroborating the hypothesis that the kinetic of the conversion of polysulfides is primarily increased by the ZnS nanoparticles but also partially by the heteroatomic doping process of graphene by N and S.…”

A conductive framework embedded with cobalt-doped vanadium nitride as an efficient polysulfide adsorber and convertor for advanced lithium–sulfur batteries

“…In contrast, the Co-VN/NC and VN/NC electrodes with Li 2 S 6 both clearly display three pairs of redox peaks, and the peaks around −0.05/0.05V, −0.27/0.27V and −0.07/0.07V represent the reversible stepwise redox reactions of Li 2 S 6 ⇋ Li 2 S 4 , Li 2 S 4 ⇋ Li 2 S 2 /Li 2 S, and S 8 ⇋ Li 2 S 6 , respectively. 49,50 Moreover, the Co-VN/NC cell exhibits smaller peak separation and higher current intensity relative to VN/NC, implying the significantly boosted conversion kinetics between LiPSs and Li 2 S, which is ascribed to the catalytic effects of the dopant cobalt element. To gain insight into the catalytic processes of the 3D Co-VN/NC framework for polysulfide conversion, the calculation of the Li ion diffusion pathways on both the Co-VN and VN surfaces was further implemented and the results are shown in Fig.…”