Porous Carbon-Based Composites for Lithium-Sulfur Batteries

In this dissertation, various porous carbons and their composites were developed and configurated in Li-S batteries. Considerable progresses including optimization of sulfur/carbon cathodes, configuration of carbon nanofibers (CNFs) interlayers, and stabilization of Li-metal anodes, have been developed to address the challenges of the Li-S cells and improve the performance. At first, aspect ratio of ordered mesoporous carbon-based sulfur host was tuned and the aspect ratio effect on electrochemical performance of S@OMCs cathodes was studied via systematic electrochemical measurements and characterizations. More impressive, the evolution of sulfur species in OMCs at different discharge state was explored. Next, to endow sulfur host with chemisorption toward polysulfides, cobalt/carbon spheres were introduced into CNTs. The hierarchical porous frameworks with large pore volume and high specific surface area alleviated the volume exchange and physically restricted the polysulfides. The partially remained cobalt nanoparticles were beneficial for the chemical adsorption and conversion of polysulfides. Further, the crystallinities of TiN coating on copper-embedded CNFs were tuned and the nanofibers were used as interlayers. Compared with highly-crystalline TiN, low-crystalline TiN not only strengthened chemical adsorption toward polysulfides, but also facilitated the redox conversions, contributing to impressive high-rate performance and remarkable cyclic stability. Finally, to achieve dendrite-free Li plating/stripping, nitrogen-doped CNFs with Cu/Cu3P decorations were developed. The lithiophilic nitrogen-doped carbon sites and the embedded functional Cu/Cu3P heterostructure endowed ultralow nucleation overpotential and small polarization. Thus, Cu/Cu3P-N-CNFs electrodes exhibited high Coulombic efficiency (~94%) after 500 cycles’ plating/stripping and the corresponding Li@ Cu/Cu3P-N-CNFs outperformed in symmetrical cells and Li-S full cells

Ordered mesoporous SiO₂ nanoparticles as charge storage sites for enhanced triboelectric nanogenerators

Triboelectric nanogenerators (TENGs) have demonstrated great prospects in energy harvesting and self-powered sensing. However, the surface triboelectric charges are very easy to dissipate in the air atmosphere, especially after the contact electrification stops. Here, we propose ordered mesoporous SiO2 (OMS) nanoparticles with a large specific surface area (SSA) as effective body charge storage sites inside polydimethylsiloxane (OMS-PDMS) to enhance the output performance of TENGs. With the addition of 1 wt% OMS nanoparticles, the transferred charges of the TENG showed a sharp enhancement, rising from 21 nC to 60 nC. The enhancement effect of OMS nanoparticles on the output increased linearly with SSA. In addition, the OMS-PDMS also demonstrated a superior charge retention ability, with 68 % of the voltage being retained over a long time after the contact separation motion stopped, while that of the pure PDMS quickly dropped to near zero. The instantaneous output power density of the TENG with OMS-PDMS reached 5.26 W/m2, which is a 25-fold enhancement. This work proposed OMS nanoparticles with a large SSA as effective charge storage sites to enhance the output performance of TENGs.</p

Enhanced triboelectric nanogenerators based on 2D smectite clay nanosheets with a strong intrinsic negative surface charge

Triboelectric nanogenerators (TENGs) have demonstrated their huge potential in micro/nano energy harvesting for self-powered systems. The output performance of TENGs is largely dependent on the surface charge density of the triboelectric materials. Here, for the first time, we propose 2D smectite clay (SC) nanosheets with a strong intrinsic negative surface charge for improving the charge density of traditional triboelectric-negative materials. A single-layer 2D SC nanosheet (∼1.1 nm thick) showed a strong negative surface potential (−14.3 mV), and the SC was confirmed to have a strong triboelectric negativity close to that of polytetrafluoroethylene (PTFE). 2D SC nanosheets were blended into polyvinylidene fluoride (SC-PVDF), based on which the SC-TENG demonstrated a significantly enhanced output performance, with the transferred charge increasing from 14 nC to 35 nC at the optimal SC concentration of 5 wt%. At higher SC concentrations, the influence of decreased effective contact area because of severe aggregation of SC nanosheets began to outperform the effect of increased interior charge. The instantaneous output power density of the SC-TENG was enormously improved to 1450 mW/m2 from that of the pristine TENG (15 mW/m2). This work proposed a new 2D material, SC, with a strong intrinsic negative surface charge, which has huge prospects in enhancing the output performance of TENGs.</p

Status and perspectives of hierarchical porous carbon materials in terms of high-performance lithium–sulfur batteries

Lithium–sulfur (Li–S) batteries, although a promising candidate of next-generation energy storage devices, are hindered by some bottlenecks in their roadmap toward commercialization. The key challenges include solving the issues such as low utilization of active materials, poor cyclic stability, poor rate performance, and unsatisfactory Coulombic efficiency due to the inherent poor electrical and ionic conductivity of sulfur and its discharged products (e.g., Li2S2 and Li2S), dissolution and migration of polysulfide ions in the electrolyte, unstable solid electrolyte interphase and dendritic growth on anodes, and volume change in both cathodes and anodes. Owing to the high specific surface area, pore volume, low density, good chemical stability, and particularly multimodal pore sizes, hierarchical porous carbon (HPC) materials have received considerable attention for circumventing the above problems in Li–S batteries. Herein, recent progress made in the synthetic methods and deployment of HPC materials for various components including sulfur cathodes, separators and interlayers, and lithium anodes in Li–S batteries is presented and summarized. More importantly, the correlation between the structures (pore volume, specific surface area, degree of pores, and heteroatom-doping) of HPC and the electrochemical performances of Li–S batteries is elaborated. Finally, a discussion on the challenges and future perspectives associated with HPCs for Li–S batteries is provided

Corrigendum to “Simultaneously suppressing the dendritic lithium growth and polysulfides migration by a polyethyleneimine grafted bacterial cellulose membrane in lithium-sulfur batteries” [Appl. Surf. Sci. 597 (2022) 153683]

The authors regret the error in the first author's name and the correct author list is updated as above. The authors would like to apologise for any inconvenience caused.</p

Simultaneously suppressing the dendritic lithium growth and polysulfides migration by a polyethyleneimine grafted bacterial cellulose membrane in lithium-sulfur batteries

Owing to the ultrahigh theoretical energy density and low-cost, lithium-sulfur (Li-S) batteries hold broad prospects as one of the promising substitutes for commercial lithium-ion batteries. The polysulfides shuttling originated from sulfur cathode and the lithium dendrite growth from lithium anode are the main challenges that hinder the commercial survival of Li-S batteries. Herein, thermal stable bacterial cellulose (BC) separator is successfully fixed with polyethyleneimine (PEI) by a scalable chemical grafting. The hydroxyl groups and amino groups in PEI grafted BC (PEI@BC) separator can participate in the formation of Li2O and Li3N, respectively, contributing to robust solid electrolyte interface with high ionic conductivity. Therefore, the lithium deposition is well regulated, resulting in a spherical and dendrite-free Li deposit pattern. The Li/Li symmetrical cell assembled with PEI@BC separator exhibits excellent cyclic stability, which can continuously plate/stripe for more than 820 h with an overpotential of ∼ 40 mV at 2 mA cm−2. Meanwhile, the polar amino group can restrain the polysulfides migration via chemosorption. As a consequence of these merits, ultrahigh initial capacity (1402 mAh g−1 at 0.1C) and excellent rate performance (440.5 mAh g−1 at 2C) for Li-S full cell are achieved, presenting new insights into the fabrication of multifunctional separators for Li-S batteries

Nitrogen-doped porous carbon nanofibers embedded with Cu/Cu₃P heterostructures as multifunctional current collectors for stabilizing lithium anodes in lithium-sulfur batteries

Among the various beyond-lithium-ion battery systems, lithium-sulfur batteries (Li-S) have been widely considered as one of the most promising technologies owing to their high theoretical energy density. However, the irregular Li plating/stripping and infinite volume change associated with low Coulombic efficiency and safety concerns of host-less lithium anode hinder the practical application of Li-S batteries. Herein, Cu/Cu3P heterostructure-embedded in carbon nanofibers (Cu/Cu3P-N-CNFs) are developed as multifunctional current collectors for regular lithium deposition. The 3D porous interconnected carbon skeleton endows effectively reduced local current density and volume expansion, meanwhile the Cu/Cu3P particles function as nucleation sites for uniform lithium plating. Consequently, the developed ion/electron-conducting skeleton delivers remarkable electrochemical performances in terms of high Coulombic efficiency for 500 cycles at 1 mA cm−2, and the accordingly symmetric cell exhibits long-term cyclic duration over 1500 h with a low voltage hysteresis of ∼ 80 mV at 1 mA cm−2. Moreover, Li-S full cells paired with the developed anode and S@CNTs cathode also show superior rate capability (568 mAh/g at 2C) and excellent stability of &gt;500 cycles at 0.2C, further demonstrating the great potential of Cu/Cu3P-N-CNFs as promising current collectors for advanced lithium-metal batteries.</p