Fluorinated electrolytes for li-ion batteries: the lithium difluoro(oxalato)borate additive for stabilizing the solid electrolyte interphase

Fluorinated electrolytes based on fluoroethylene carbonate (FEC) have been considered as promising alternative electrolytes for high-voltage and high-energy capacity lithium-ion batteries (LIBs). However, the compatibility of the fluorinated electrolytes with graphite negative electrodes is unclear. In this paper, we have systematically investigated, for the first time, the stability of fluorinated electrolytes with graphite negative electrodes, and the result shows that unlike the ethylene carbonate (EC)-based electrolyte, the FEC-based electrolyte (EC was totally replaced by FEC) is incapable of forming a protective and effective solid electrolyte interphase (SEI) that protects the electrolyte from runaway reduction on the graphite surface. The reason is that the lowest unoccupied molecular orbital energy levels are also lowered by the introduction of fluorine into the solvent, and the FEC solvent has poorer resistance against reduction, leading to instability on the graphite negative electrode. To tackle this problem, two lithium salts of lithium bis(oxalato)borate and lithium difluoro(oxalato)borate (LiDFOB) have been investigated as negative-electrode film-forming additives. Incorporation of only 0.5 wt % LiDFOB to a FEC-based electrolyte [1.0 M LiPF6 in 3:7 (FEC?ethyl methyl carbonate)] results in excellent cycling performance of the graphite negative electrode. This improved property originates from the generation of a thinner and better quality SEI film with little LiF by the sacrificial reduction of the LiDFOB additive on the graphite negative electrode surface. On the other hand, this additive can stabilize the electrolyte by scavenging HF. Meanwhile, the incorporated LiDFOB additive has positive influence on the interphase layer on the positive electrode surface and significantly decreases the amount of HF formation, finally leading to improved cycling stability and rate capability of LiNi0.5Mn1.5O4 electrodes at a high cutoff voltage of 5 V. The data demonstrate that the LiDFOB additive not only exhibits a superior compatibility with graphite but also improves the electrochemical properties of high-voltage spinel LiNi0.5Mn1.5O4 positive electrodes considerably, confirming its potential as a prospective, multifunctional additive for 5 V fluorinated electrolytes in high-energy capacity lithium-ion batteries (LIBs)

Impact of CO2 activation on the structure, composition, and performance of Sb/C nanohybrid lithium/sodium-ion battery anodes

Antimony (Sb) has been regarded as one of the most promising anode materials for both lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs) and attracted much attention in recent years. Alleviating the volumetric effect of Sb during charge and discharge processes is the key point to promote Sb-based anodes to practical applications. Carbon dioxide (CO2) activation is applied to improve the rate performance of the Sb/C nanohybrid anodes caused by the limited diffusion of Li/Na ions in excessive carbon components. Based on the reaction between CO2 and carbon, CO2 activation can not only reduce the excess carbon content of the Sb/C nanohybrid but also create abundant mesopores inside the carbon matrix, leading to enhanced rate performance. Additionally, CO2 activation is also a fast and facile method, which is perfectly suitable for the fabrication system we proposed. As a result, after CO2 activation, the average capacity of the Sb/C nanohybrid LIB anode is increased by about 18 times (from 9 mA h g−1 to 160 mA h g−1) at a current density of 3300 mA g−1. Moreover, the application of the CO2-activated Sb/C nanohybrid as a SIB anode is also demonstrated, showing good electrochemical performance

Carbon-emcoating architecture boosts lithium storage of Nb2O5

Intercalation transition metal oxides (ITMO) have attracted great attention as lithium-ion battery negative electrodes due to high operation safety, high capacity and rapid ion intercalation. However, the intrinsic low electron conductivity plagues the lifetime and cell performance of the ITMO negative electrode. Here we design a new carbon-emcoating architecture through single CO2 activation treatment as demonstrated by the Nb2O5/C nanohybrid. Triple structure engineering of the carbon-emcoating Nb2O5/C nanohybrid is achieved in terms of porosity, composition, and crystallographic phase. The carbon-embedding Nb2O5/C nanohybrids show superior cycling and rate performance compared with the conventional carbon coating, with reversible capacity of 387 mA h g−1 at 0.2 C and 92% of capacity retained after 500 cycles at 1 C. Differential electrochemical mass spectrometry (DEMS) indicates that the carbon emcoated Nb2O5 nanohybrids present less gas evolution than commercial lithium titanate oxide during cycling. The unique carbon-emcoating technique can be universally applied to other ITMO negative electrodes to achieve high electrochemical performance

PERK-Mediated Cholesterol Excretion from IDH Mutant Glioma Determines Anti-Tumoral Polarization of Microglia

Isocitrate dehydrogenase (IDH) mutation, a known pathologic classifier, initiates metabolic reprogramming in glioma cells and has been linked to the reaction status of glioma-associated microglia/macrophages (GAMs). However, it remains unclear how IDH genotypes contribute to GAM phenotypes. Here, it is demonstrated that gliomas expressing mutant IDH determine M1-like polarization of GAMs, while archetypal IDH induces M2-like polarization. Intriguingly, IDH-mutant gliomas secrete excess cholesterol, resulting in cholesterol-rich, pro-inflammatory GAMs without altering their cholesterol biosynthesis, and simultaneously exhibiting low levels of tumoral cholesterol due to expression remodeling of cholesterol transport molecules, particularly upregulation of ABCA1 and downregulation of LDLR. Mechanistically, a miR-19a/LDLR axis-mediated novel post-transcriptional regulation of cholesterol uptake is identified, modulated by IDH mutation, and influencing tumor cell proliferation and invasion. IDH mutation-induced PERK activation enhances cholesterol export from glioma cells via the miR-19a/LDLR axis and ABCA1/APOE upregulation. Further, a synthetic PERK activator, CCT020312 is introduced, which markedly stimulates cholesterol efflux from IDH wild-type glioma cells, induces M1-like polarization of GAMs, and consequently suppresses glioma cell invasion. The findings reveal an essential role of the PERK/miR-19a/LDLR signaling pathway in orchestrating gliomal cholesterol transport and the subsequent phenotypes of GAMs, thereby highlighting a novel potential target pathway for glioma therapy

Dental resin monomer enables unique NbO2/carbon lithium‐ion battery negative electrode with exceptional performance

Niobium dioxide (NbO2) features a high theoretical capacity and an outstanding electron conductivity, which makes it a promising alternative to the commercial graphite negative electrode. However, studies on NbO2 based lithium-ion battery negative electrodes have been rarely reported. In the present work, NbO2 nanoparticles homogeneously embedded in a carbon matrix are synthesized through calcination using a dental resin monomer (bisphenol A glycidyl dimethacrylate, Bis-GMA) as the solvent and a carbon source and niobium ethoxide (NbETO) as the precursor. It is revealed that a low Bis-GMA/NbETO mass ratio (from 1:1 to 1:2) enables the conversion of Nb (V) to Nb (IV) due to increased porosity induced by an alcoholysis reaction between the NbETO and Bis-GMA. The as-prepared NbO2/carbon nanohybrid delivers a reversible capacity of 225 mAh g−1 after 500 cycles at a 1 C rate with a Coulombic efficiency of more than 99.4% in the cycles. Various experimental and theoretical approaches including solid state nuclear magnetic resonance, ex situ X-ray diffraction, differential electrochemical mass spectrometry, and density functional theory are utilized to understand the fundamental lithiation/delithiation mechanisms of the NbO2/carbon nanohybrid. The results suggest that the NbO2/carbon nanohybrid bearing high capacity, long cycle life, and low gas evolution is promising for lithium storage applications

A novel fluorocyclophosphazene as bifunctional additive for safer lithium-ion batteries

A high-efficiency flame-retarding additive, (Ethoxy)pentafluorocyclotriphosphazene (N3P3F5OCH2CH3, PFPN), has been synthesized and explored as a safer protection additive for rechargeable lithium batteries. The flammability tests indicate that only the addition of 5 wt% PFPN can make the electrolyte be totally non-flammable. As far as we know, the PFPN additive is the most efficient one of any flame-retarding additive ever synthesized and reported in the literature. The charge discharge results demonstrate that the PFPN additive shows a good electrochemical compatibility on the graphitic anode and LiCoO2 cathode. Meanwhile, the incorporated PFPN additive can greatly improve the cyclic performance of LiCoO2 electrode at a high cut-off voltage of 4.5 V, showing a prospective flame-retarding additive for the applications in high-voltage lithium ion batteries. (C) 2014 Elsevier B.V. All rights reserved

Thiophene derivatives as novel functional additives for high-voltage LiCoO2 operations in lithium ion batteries

Thiophene derivatives (THs) are examined as novel functional additives for improving the cycling performance of high-voltage LiCoO2. Our investigation reveals that 2,2'-Bithiophene (2TH) and 2,2': 5',2 ''-Terthiophene (3TH) can be electrochemically polymerize prior to the electrolyte solvent decomposition to form a protective layer of conducting polymer film on the cathode surface, which blocks off severe electrolyte decomposition at high voltages and, therefore, improves the cycling stability of high voltage LiCoO2 cathode. After 100 cycles at a high cutoff voltage of 4.4 V, the discharge capacity retention is 50% in the base electrolyte, in contrast, the LiCoO2 cathode cycled in the electrolyte containing 0.1 wt% 3TH displays a high capacity retention of 84.8% at 0.25 C rate. This work demonstrates that these thiophene derivatives have considerable potential as functional additives for the applications in high-voltage lithium-ion batteries. (C) 2014 Elsevier Ltd. All rights reserved

Synthesis of Three-Dimensional Nanoporous Li-Rich Layered Cathode Oxides for High Volumetric and Power Energy Density Lithium-Ion Batteries

As rechargeable Li-ion batteries have expanded their applications into on-board energy storage for electric vehicles, the energy and power must be increased to meet the new demands. Li-rich layered oxides are one of the most promising candidate materials; however, it is very difficult to make them compatible with high volumetric energy density and power density. Here, we develop an innovative approach to synthesize three-dimensional (3D) nanoporous Li-rich layered oxides Li[Li-0.144Ni0.136Co0.136Mn0.544]O-2, directly occurring at deep chemical delithiation with carbon dioxide. It is found that the as-prepared material presents a micrometer sized spherical structure that is typically composed of interconnected nanosized subunits with narrow distributed pores at 3.6 nm. As a result, this unique 3D micro-/nanostructure not only has a high tap density over 2.20 g cm(-3) but also exhibits excellent rate capability (197.6 mA h g(-1) at 1250 mA g(-1)) as an electrode. The excellent electrochemical performance is ascribed to the unique nanoporous micro-nanostructures, which facilitates the Li+ diffusion and enhances the structural stability of the Li-rich layered cathode materials. Our work offers a comprehensive designing strategy to construct 3D nanoporous Li-rich layered oxides for both high volumetric energy density and power density in Li-ion batteries

New perspective to understand the effect of electrochemical prelithiation behaviors on silicon monoxide

Electrochemical prelithiation is a facile, effective and extensively used method to improve the initial coulombic efficiency of SiO. However, much less research attention has been devoted to prelithiation effect on initial several cycles. Here, we introduce a new perspective to evaluate the prelithiation behaviors, which could understand in depth the electrochemical prelithiation behaviors and their effects on the following two cycles. Then X-ray photoelectron spectroscopy was further performed to pinpoint the reaction products. It has been found that the quantity of irreversible Li4SiO4, Li2O and SEI (Li2CO3 and LiF) and reversible LixSi are increasing as the prelithiation time extending. When the prelithiation time extending over 20 min, only alloy reaction of Si has been revealed. The regeneration of SEI discloses at least 7% capacity loss in the first cycle which depends on the prelithiated time. However, the reformation of SEI in the second cycles reveals 3% capacity loss. Because the coulombic efficiencies are independent on prelithiated time in the second cycle which indicates only one discharge/charge cycle is enough to form integrated SEI and adequate irreversible Li4SiO4 and Li2O except part of unreactive SiOx

Recent development in two-dimensional material-based membranes for redox flow battery

Funding Information: This work was supported by the National Natural Science Foundation of China (Grant no. 21636007 ), the Start-up Foundation offered by Ningbo University of Technology to J.S. Yuan, and the Start-up Package of T10108 Professorship offered by Aalto University to Y.D. Li. Publisher Copyright: © 2022 Elsevier LtdRedox flow battery (RFB) has been widely considered to be one of the most promising grid-scale energy-storage technology. The membrane, namely separator, serves as preventing the crossover of the positive and negative active species, while facilitating the transport of the supporting electrolyte ions, is crucial to achieve a high performance and a long-term stability for an RFB. Advances in RFBs require high-performance and low-cost membranes with high ion-selective transport for the application of large-scale energy storage. Two-dimensional (2D) materials have emerged as promising functional materials owing to their atomic-scale thickness and unique physical/chemical properties, which have great potential in the application of RFB membrane. Focusing on the recent state-of-the-art of 2D materials, in this mini review, various 2D materials applied in the membrane for RFB are briefly introduced. A perspective on the near-future developments of 2D materials in RFB membranes is presented.Peer reviewe