Dual‐Functional Atomic Zinc Decorated Hollow Carbon Nanoreactors for Kinetically Accelerated Polysulfides Conversion and Dendrite Free Lithium Sulfur Batteries

Abstract

The continuously growing demand for clean, sustainable power systems for consumer electronics, electric vehicles, and national grid storage is driving the research interest for electrochemical energy storage systems with better safety, lower cost, and higher energy density beyond current Li-ion battery. [1] Among alternative competitors, lithium sulfur (Li-S) battery has been considered as outstanding representative considering its high theoretical capacity (S: 1675 mAh g −1 and Li: 3860 mAh g −1), sustainability of S, and lowest reduction potential of Li (−3.04 V vs SHE). [2] Despite intensive efforts over decades, the Li-S battery still suffers from several detrimental issues associated with both cathode and anode. For S cathode, the diffusion of intermediates lithium polysulfides (LiPS) and sluggish S redox conversion kinetic cause unsatisfactory specific capacity, inferior rate performance, and rapid capacity degradation. [3] For Li anode, the uncontrollable dendrite growth and infinite volume expansion result in safety risk and low Coulombic efficiency (CE). [4] Therefore, it is highly urgent to design the kinetically advanced Li-S battery system with well-designed configuration for both LiPSsuppressed cathode and dendrite-free anode. Hollow carbon sphere nanoreactors with good electrical conductivity, large surface area, and enhanced structural stability have been widely applied as the host for secondary batteries to improve their electrochemical performance. [5] For example, as S cathode, a hollow porphyrin organic framework was designed for long cycling stability Li-S battery resulting from the physical confinement of LiPS. [6] Besides, double-shelled hollow carbon sphere was explored as a free-standing S host for highenergy-density Li-S battery. [7] As for Li anode, encapsulation of Li into the hollow carbon sphere was designed for high stable Li metal anode. [8] However, the shuttle effect and Li dendrite has not substantially been resolved because the physical effect only addresses the surface issue and not the root. To overcome this, integrating bare carbon nanostructures with catalysts, such as The lithium sulfur (Li-S) battery is a preferential option for next-generation energy storage technologies, but the lithium polysulfide shuttling, sluggish redox kinetics, and uncontrollable lithium dendrite growth hamper its commercial viability. Herein, well-dispersed single atom Zn-decorated hollow carbon spheres (Zn 1-HNC) are developed as dual-functional nanoreactors for polysulfides-suppressed sulfur cathodes (Zn 1-HNC-S) and dendrite-free lithium anodes (Zn 1-HNC-Li) simultaneously for high-capacity, high-rate, and long-cycling Li-S batteries with fast redox kinetics. Benefiting from its excellent electronic conductivity, high surface area (370 m 2 g −1), highly-effective active sites and protective carbon shell, the resultant nanoreactor possesses strong physical confinement, chemical anchoring, and exceptional electrocatalysis for polysulfides. Meanwhile, the nanoreactor with excellent lithiophilic ab...

A flexible metallic TiC nanofiber/vertical graphene 1D/2D heterostructured as active electrocatalyst for advanced Li–S batteries

“…Most of them, however, have poor electronic conductivity, which will result in sluggish reaction kinetics during the charge and discharge cycles 29–35 . The sluggish conversion kinetics in a battery cell will cause the accumulation of LiPS in its cathode and consequently gives rise to seriously uneven electrodeposition of Li 2 S, which in turn results in inhomogeneity in the transfer of electrons, being detrimental to electrochemical processes over charging and discharging 36–38 . The electrically insulating Li 2 S film is also of poor conductivity to Li + ions, and the formation of uneven Li 2 S film is therefore considered to be the main factor to greatly aggravates the mass transfer in cells over cycling, which finally leads to termination of the liquid/solid conversion reactions in the discharge/charge processes.…”

Defect Engineering for Expediting Li–S Chemistry: Strategies, Mechanisms, and Perspectives

“…To verify the superb adsorption effect of SACs, Shi et al performed a visual observation by immersing PS-adsorbed cathodes into transparent solution. [162] As is illustrated in Figure 11a, the initially transparent solution turns yellow quickly (1 h) due to the overflow of PS intermediates in hollow carbon sphere (HNC)based cathode, in sharp contrast to the almost unchanged electrolyte color (8 h) around the Zn atoms-decorated hollow carbon sphere (Zn-HNC)-based counterpart, implying that Zn-SACs can enable the strong immobilization with PS. In addition, the high-resolution Zn 2p XPS spectrum of Zn-HNC exhibits obvious shift to a lower binding energy after adsorbing Li 2 S 4 (Figure 11b), again indicative of the intense chemical interaction between isolated atomic Zn sites with PS intermediates.…”

“…[171] It is worth noting that reaction pathway and energy barrier for Li 2 S decomposition were, respectively, simulated and calculated. Figure 12c [162] Copyright 2020, Wiley-VCH. c) Current curves under discharge PITT.…”

Single-atom catalysts for high-energy rechargeable batteries

“…Various SACs, such as carbon materials with Fe, Co, Zn, and Ni single atoms, have been prepared for cathodes and separators for Li-S and RT-Na-S batteries. 11,[70][71][72] By promoting polysulde conversion, SACs can effectively decrease the polarization and suppress shuttle effects, leading to the enhancement of rate and cycling performance.…”