Progress of enhancing the safety of lithium ion battery from the electrolyte aspect

The ever-increasing demands for batteries with high energy densities to power the portable electronics with increased power consumption and to advance vehicle electrification and grid energy storage have propelled lithium battery technology to a position of tremendous importance. Carbon nanotubes (CNTs) and graphene, known with many appealing properties, are investigated intensely for improving the performance of lithium-ion (Li-ion) and lithium-sulfur (Li-S) batteries. However, a general and objective understanding of their actual role in Li-ion and Li-S batteries is lacking. It is recognized that CNTs and graphene are not appropriate active lithium storage materials, but are more like a regulator: they do not electrochemically react with lithium ions and electrons, but serve to regulate the lithium storage behavior of a specific electroactive material and increase the range of applications of a lithium battery. First, metrics for the evaluation of lithium batteries are discussed, based on which the regulating role of CNTs and graphene in Li-ion and Li-S batteries is comprehensively considered from fundamental electrochemical reactions to electrode structure and integral cell design. Finally, perspectives on how CNTs and graphene can further contribute to the development of lithium batteries are presented.

The Regulating Role of Carbon Nanotubes and Graphene in Lithium‐Ion and Lithium–Sulfur Batteries

The support plays an important role for supported metal catalysts by positioning itself as a macromolecular ligand, which conditions the nature of the active site and contributes indirectly but also sometimes directly to the reactivity. Metal species such as nanoparticles, clusters, or single atoms can be deposited on carbon materials for various catalytic reactions. All the carbon materials used as catalyst support constitute a large family of compounds that can vary both at textural and at structural levels. Today, the recent developments of well-controlled synthesis methodologies, advanced characterization techniques, and modeling tools allow one to correlate the relationships between metal/support/reactant at the molecular level. Based on these considerations, in this Review article, we wish to provide some answers to the question "How and why anchoring metal nanoparticles, clusters, or single atoms on carbon materials for catalysis?". To do this, we will rely on both experimental and theoretical studies. We will first analyze what sites are available on the surface of a carbon support for the anchoring of the active phase. Then, we will describe some important effects in catalysis inherent to the presence of a carbon-type support (metal-support interaction, confinement, spillover, and surface functional group effects). These effects will be commented on by putting into perspective catalytic results obtained in numerous reactions of thermal catalysis, electrocatalysis, or photocatalysis.

A Theory/Experience Description of Support Effects in Carbon-Supported Catalysts.

Combining theory and experiment in lithium–sulfur batteries: Current progress and future perspectives

J.Y. and W.L.Z. contributed equally to this work. The research reported in this publication was supported by the King Abdullah University of Science and Technology – King Abdulaziz University (KAUST–KAU) Initiative (Grant # OSR-2018 KAUST-KAU-3903).

/pdf/synthesis-strategies-of-porous-carbon-for-supercapacitor-4eiw8xptxd.pdf

Synthesis Strategies of Porous Carbon for Supercapacitor Applications

Phosphorus-doped 3D hierarchical porous carbon for high-performance supercapacitors: A balanced strategy for pore structure and chemical composition

Carbon materials have attracted considerable attention as the hosts for lithium-sulfur batteries, especially the 3D structural carbon matrix. Herein, novel 3D interconnected porous carbon nanosheets/carbon nanotubes (denoted as PC/CNT) as a polysulfide reservoir are synthesized by a simple one-pot pyrolysis method. In the designed hybrid carbon matrix, porous carbon nanosheets exhibit hierarchical porous structures for high sulfur loading and effectively strengthen the physical confinement to trap soluble polysulfides, while carbon nanotubes provide a highly robust conductive pathway which can facilitate electron transport and maintain structural integrity. Moreover, the 3D interconnected structure combining 1D carbon nanotubes and 2D porous carbon nanosheets is beneficial for rapid electrical/ionic transport and favorable electrolyte infiltration. As a result, the S-PC/CNT composite exhibits outstanding electrochemical performance, with a high active-sulfur utilization, high specific capacity (1485.4, 1300.3 and 1138 mA h g-1 at 0.5, 1 and 2 C, respectively), superior cycling stability (only 0.1% capacity decay per cycle over 400 cycles at 2 C) and excellent rate capability (the reversible capacity of 749 mA h g-1 even at 4 C).

3D interconnected porous carbon nanosheets/carbon nanotubes as a polysulfide reservoir for high performance lithium–sulfur batteries

Supercapacitance of nitrogen-sulfur-oxygen co-doped 3D hierarchical porous carbon in aqueous and organic electrolyte

Pyrrole as a promising electrolyte additive to trap polysulfides for lithium-sulfur batteries

Lithium cathode materials have been considered as promising candidates for energy storage applications because of their high power/energy densities, low cost, and low toxicity. However, the Li/Ni cation mixing limits their application as practical electrode materials. The cation mixing of lithium transition-metal oxides, which was first considered only as the origin of performance degeneration, has recently been reconsidered as a way to stabilize the structure of active materials. Here we find that as the duration of the post-synthesis thermal treatment (at 500 °C) of LiNi1/3Co1/3Mn1/3O2 (NCM) was increased, the Li/Ni molar ratio in the final product was found to decrease, and this was attributed to the reduction in nickel occupying lithium sites; the cation mixing subtly changed; and those subtle variations remarkably influence their cycling performance. The cathode material with appropriate cation mixing exhibits a much slower voltage decay and capacity fade during long-term cycling. Combining X-ray diffraction, Rietveld analysis, the Fourier transform infrared technique, field-emission scanning electron microscopy, and electrochemical measurements, we demonstrate that an optimal degree of Ni2+ occupancy in the lithium layer enhances the electrochemical performance of layered NMC materials and that this occurs through a “pillaring” effect. The results provide new insights into “cation mixing” as a new concept for material design utilization of layered cathodes for lithium-ion batteries, thereby promoting their further application in lithium-ion batteries with new functions and properties.

Ailing Song

Papers

Phosphorus-doped 3D hierarchical porous carbon for high-performance supercapacitors: A balanced strategy for pore structure and chemical composition

3D interconnected porous carbon nanosheets/carbon nanotubes as a polysulfide reservoir for high performance lithium–sulfur batteries

Supercapacitance of nitrogen-sulfur-oxygen co-doped 3D hierarchical porous carbon in aqueous and organic electrolyte

Pyrrole as a promising electrolyte additive to trap polysulfides for lithium-sulfur batteries

The effect of cation mixing controlled by thermal treatment duration on the electrochemical stability of lithium transition-metal oxides.