Advanced materials for stable Li-S and Li-organic batteries

Lithium ion batteries (LIBs) are playing an increasingly important role in our everyday life. LIBs are powering consumer electronics (e.g., cameras, smartphones, laptops), electric vehicles and large-scale industrial facilities. Also, LIBs are important energy storage systems for renewable energies like solar and wind. With respect to conventional LIBs, typically, the cathode material is LiCoO2 and the anode material is graphite. However, the upper limit of the conventional LIBs cannot meet the long-term needs of the rapidly developing society, for instance, extended-range of electric vehicles. In this regard, next-generation battery types are highly needed to build up a more sustainable society. Li-S batteries, with high theoretical capacity of 1675 mA h g–1 and high theoretical energy density of 2600 W h kg–1, is a promising candidate for next-generation high-energy batteries. Also, the low cost and abundance of sulphur is an attracting advantage for Li-S batteries. In order to achieve the high capacity and high energy density of Li-S batteries, two severe problems should be overcome, that is, the poor electrical conductivity, as well as the dissolution and shuttling of the intermediate products of lithium polysulphides

Improved cycling stability of lithium-sulphur batteries by enhancing the retention of active material with a sandwiched hydrothermally treated graphite film

A new lithium-sulphur battery with a hydrothermally treated graphite film sandwiched between the separator and the sulphur cathode shows increased capacity, enhanced cycling stability and improved coulombic efficiency. After 50 cycles, a high capacity of 631 mA h g-1 is maintained, compared to 203 mA h g-1 for the Li-S battery with conventional configuration. Moreover, the coulombic efficiency is increased to near 100% from around 94%. This improved electrochemical performance could be attributed to the new cell configuration, because the graphite film greatly retains the active material by alleviating the polysulphide shuttling problem and providing extra reaction sites for sulphur species

Ion selective separators based on graphene oxide for stabilizing lithium organic batteries

Ion selective membranes exist widely in the biological world and have been mimicked by scientists and engineers for the purpose of manipulating ion flow. For instance, polymers with sulfonate groups like Nafion are applied in proton exchange membrane fuel cells for facilitating proton transport whilst blocking other species. Herein, ion selective separators composed of graphene oxide (GO) and Super P (or graphene) are applied for stabilizing lithium organic batteries. The reconstructed GO sheets form numerous negatively charged nanochannels, which selectively allow the transport of lithium ions and reject the electroactive organic anions. Meanwhile, Super P (or graphene) on top of the coating layer functions as the upper current collector for reactivating the electroactive organic species. In this work, two typical carbonyl electrode materials with, respectively, two (anthraquinone, AQ) and four (perylene-3,4,9,10-tetracarboxylic dianhydride, PTCDA) carbonyl groups are applied as examples. Compared to the pristine Celgard separator, the ion selective separators enable significantly alleviated self-discharge, improved coulombic efficiency and cycling stability

Functional membrane separators for next-generation high-energy rechargeable batteries

The membrane separator is a key component in a liquid-electrolyte battery for electrically separating the cathode and the anode, meanwhile ensuring ionic transport between them. Besides these basic requirements, endowing the separator with specific beneficial functions is now being paid great attention because it provides an important alternative approach for the development of batteries, particularly next-generation high-energy rechargeable batteries. Herein, functional separators are overviewed based on four key criteria of next-generation high-energy rechargeable batteries: stable, safe, smart and sustainable (4S). That is, the applied membrane materials and the corresponding functioning mechanisms of the 4S separators are reviewed. Functional separators with selective permeability have been applied to retard unwanted migration of the specific species (e.g. polysulfide anions in Li-S batteries) from one electrode to the other in order to achieve stable cycling operation. The covered battery types are Li-S, room-temperature Na-S, Li-organic, organic redox-flow (RF) and Li-air batteries. Safe, smart and sustainable separators are then described in sequence following the first criterion of stable cycling. In the final section, key challenges and potential opportunities in the development of 4S separators are discussed

Improving the Li-S battery performance by applying a combined interface engineering approach on the Li2S cathode

This journal is © The Royal Society of Chemistry. Lithium sulfide (Li2S) has been a promising candidate for Li-S battery cathode materials due to its high theoretical specific capacity and ability to be paired with safer lithium metal-free anodes. However, the low active material utilization and the short cycle life, which stem from the poor conductivity and the polysulfide dissolution-diffusion problem, hinder the further application of Li-S batteries. Herein, a combined interface engineering approach, which includes an ion-selective sulfonated poly(ether ether ketone) (SPEEK) membrane and a freestanding single wall carbon nanotube (SWCNT)/reduced graphene oxide (rGO) interlayer, has been demonstrated successfully to enhance the performance of Li-S batteries with a Li2S cathode. The SPEEK membrane is integrated into the Li2S cathode, functioning as both a barrier of the polysulfides and a highway for Li+ ions, due to its negatively charged ionic nanochannels which have been proved to mediate high-speed ion transport. With SPEEK, the cell presents high rate performance (above 400 mA h g-1 at 10 A g-1). Furthermore, to balance the conductivity of ions and electrons, a SWCNT/rGO interlayer is inserted between the cathode and the separator to improve the electronic conductivity, block the polysulfides, and provide space for sustained electrochemical reactions, resulting in improved capacity and life. With the interlayer, a high capacity of 620 mA h g-1 is retained after 80 cycles

Small things make a big difference: binder effects on the performance of Li and Na batteries

Li and Na batteries are very important as energy storage devices for electric vehicles and smart grids. It is well known that, when an electrode is analysed in detail, each of the components (the active material, the conductive carbon, the current collector and the binder) makes a portion of contribution to the battery performance in terms of specific capacity, rate capability, cycle life, etc. However, there has not yet been a review on the binder, though there are already many review papers on the active materials. Binders make up only a small part of the electrode composition, but in some cases, they play an important role in affecting the cycling stability and rate capability for Li-ion and Na-ion batteries. Poly(vinylidene difluoride) (PVDF) has been the mainstream binder, but there have been discoveries that aqueous binders can sometimes make a battery perform better, not to mention they are cheaper, greener, and easier to use for electrode fabrication. In this review, we focus on several kinds of promising electrode materials, to show how their battery performance can be affected significantly by binder materials: anode materials such as Si, Sn and transitional metal oxides; cathode materials such as LiFePO4, LiNi1/3Co1/3Mn1/3O2, LiCoO2 and sulphur

Atomic layer-by-layer co3o4/graphene composite for high performance lithium-ion batteries

An atomic layer-by-layer structure of Co3O4/graphene is developed as an anode material for lithium-ion batteries. Due to the atomic thickness of both the Co3O4 nanosheets and the graphene, the composite exhibits an ultrahigh specific capacity of 1134.4 mAh g−1 and an ultralong life up to 2000 cycles at 2.25 C, far beyond the performances of previously reported Co3O4/C composites

Introducing ion-transport-regulating nanochannels to lithium-sulfur batteries

The ability of ion channels to facilitate the transport of some specific ions and meanwhile block other molecular or ionic species across the membranes of biological cells and intracellular organelles plays an important role in biological bodies for maintaining basic physiological activities. This feature is highly desirable in rechargeable lithium batteries because the electrochemical performances of some electrodes, such as sulfur cathodes, are greatly weakened by the dissolution of active material related anions into the electrolyte and the slow transport of lithium ions. Here, inspired by nature, a polymer membrane with negatively-charged nanochannels is applied to a sulfur-carbon cathode to overcome the poor cycling stability and rate capability of the lithium-sulfur battery. The polymer membrane possesses negatively charged nanochannels with a width dimension (ca. 2 nm) comparable to the Debye length, therefore is capable of regulating the ion transport by facilitating the transport of lithium ions and rejecting the migration of polysulfide anions. At 0.2 C and 1 C, the specific capacities keep at high levels of 1105 and 838 mA h g-1 after 100 cycles, respectively. Furthermore, at a high rate of 18 C, a high specific capacity of 612 mA h g-1 is retained over 250 cycles, with a high capacity retention of 91%

Characterization of a Mouse Model of Börjeson-Forssman-Lehmann Syndrome

Summary: Mutations of the transcriptional regulator PHF6 cause the X-linked intellectual disability disorder Börjeson-Forssman-Lehmann syndrome (BFLS), but the pathogenesis of BFLS remains poorly understood. Here, we report a mouse model of BFLS, generated using a CRISPR-Cas9 approach, in which cysteine 99 within the PHD domain of PHF6 is replaced with phenylalanine (C99F). Mice harboring the patient-specific C99F mutation display deficits in cognitive functions, emotionality, and social behavior, as well as reduced threshold to seizures. Electrophysiological studies reveal that the intrinsic excitability of entorhinal cortical stellate neurons is increased in PHF6 C99F mice. Transcriptomic analysis of the cerebral cortex in C99F knockin mice and PHF6 knockout mice show that PHF6 promotes the expression of neurogenic genes and represses synaptic genes. PHF6-regulated genes are also overrepresented in gene signatures and modules that are deregulated in neurodevelopmental disorders of cognition. Our findings advance our understanding of the mechanisms underlying BFLS pathogenesis. : Cheng et al. generated a mouse model of Börjeson-Forssman-Lehmann syndrome containing a patient-specific mutation of PHF6. PHF6 knockin mice display cognitive impairments, neuronal hyperexcitability, and seizure susceptibility. PHF6 promotes neurogenic and repressed synaptic genes in the cortex. This study advances understanding of the cellular and molecular underpinnings of BFLS. Keywords: PHF6, X-linked intellectual disability, mouse models, neuronal excitability, gene expressio