聚吡咯-过渡金属-氧配合物储锂材料的结构与性能研究

目前锂离子电池电极材料主要使用无机材料.近年来有机物电极材料虽有报道,但这些材料大都比容量低、倍率性能差.本文介绍一类新型有机金属配合物聚吡咯-过渡金属-氧储锂材料的合成、结构及电化学性能.结合扩展X-射线吸收精细结构谱分析和密度泛函理论计算,发现这类材料呈现多层结构特征,层内稳定的过渡金属-吡咯N的配位作用及循环过程中层间过渡金属-氧键的可逆断裂和结合使该类材料具有很高的储锂容量和循环稳定性,且聚吡咯导电网络使得该材料具有良好的倍率性能.这类新材料将有望成为锂离子电池的高比容量负极材料.

从第13届国际插层化合物大会看插层化合物的最新发展趋势

This report briefly introduces the 13th intercalation symposium on intercalation compounds held in Clermont-Ferrand in France, 6-9 June, 2005. More than 170 experts from 23 nations presented 216 contributions of the updated development in the field of intercalation compounds. Presentations covered a wide range of issues, including graphite intercalation compounds (GICs), fullerenes, nanotubes, clays and modified clays, layered metal oxides and hydroxides, hybrid and nanocomposite materials, zeolites, phosphates and other related materials. Issues in nano-GICs, organic-inorganic nanocomposites, fullerene intercalations, lithium intercalation compounds and nanoscale hydrides for hydrogen storage represent future development for intercalation compounds.

Enhanced dehydrogenation kinetic properties and hydrogen storage reversibility of LiBH_4 confined in activated charcoal

LiBH4 was confined into activated charcoal（AC） by melt infiltration method（MI）, and its effects on the hydrogen sorption properties were investigated. The N2 adsorption results reveal that melt infiltration method can effectively incorporated LiBH4 into AC. It can maintain the structural integrity of the scaffold and ensure the confinement effect. The nano-confined LiBH4/AC starts to release hydrogen at around 190 °C, which is 160 °C lower than that of pure LiBH4, and reaches a hydrogen desorption capacity of 13.6% at 400 °C. When rehydrogenated under the condition of 6 MPa H2 and 350 °C, it has a reversible hydrogen storage capacity of 6%, while pure LiBH4 shows almost no reversible hydrogen storage capacity under the same condition. Mass spectrometry analysis（MS） results suggest that no diborane or other impurity gases are released in the decomposition process. The apparent activation energy of dehydrogenation of LiBH4 after confinement into AC decreases from 156.0 to 121.1 k J/mol, which leads to the eminent enhancement of dehydrogenation kinetics of LiBH4.

One-pot facile fabrication of carbon-coated Bi2S3 nanomeshes with efficient Li-storage capability

Layered bismuth sulfide （Bi2S3） has emerged as an important type of Li-storage material due to its high theoretical capacity and intriguing reaction mechanism. The engineering and fabrication of Bi2S3 materials with large capacity and stable cyclability via a facile approach is essential, but still remains a great challenge. Herein, we employ a one-pot hydrothermal route to fabricate carbon-coated Bi2S3 nanomeshes （Bi2S3/C） as an efficient Li-storage material. The nanomeshes serve as a highly conducting and porous scaffold facilitating electron and ion transport, while the carbon coating layer provides flexible space for efficient reduction of mechanical strain upon electrochemical cycling. Consequently, the fabricated Bi2S3/C exhibits a high and stable capacity delivery in the 0.01-2.5 V region, notably outperforming previously reported Bi2S3 materials. It is able to discharge 472 mA·h·g^-1 at 120 mA.g^-1 over 50 full cycles, and to retain 301 mA·h·g^-1 in the 40th cycle at 600 mA.g^-l, demonstrating the potential of Bi2S3 as electrode materials for rechargeable batteries.

Two-dimensional SnO_2/graphene heterostructures for highly reversible electrochemical lithium storage

The ever-growing market demands for lithium ion batteries have stimulated numerous research efforts aiming at the exploration of novel electrode materials with higher capacity and long-term cycling stability.Two-dimensional (2D)nanomaterials and their heterostructures are an intense area of study and promise great potential in electrochemical lithium storage owing to their unique properties that result from structural planar confinement.Here we report a microwave chemistry strategy to integrate ultrathin SnO2 nanosheets into graphene layer to construct surface-to-surface 2D heterostructured architectures,which can provide unique structural planar confinement for highly reversible electrochemical lithium storage.The as-synthesized 2D SnO2/graphene heterostructures can exhibit high reversible capacity of 688.5mAh g^-1 over 500cycles with excellent long-term cycling stability and good rate capability when used as anode materials for lithium ion batteries.The present work definitely reveals the advantages of 2D heterostructures featured with a surface-to-surface stack between two different nanosheets in energy storage and conversion devices.

Recent advancements in metal organic framework based electrodes for supercapacitors

Metal organic frameworks（MOFs） are considered as very promising candidates to build electrodes for electrochemical energy storage devices such as lithium ion batteries, fuel cells and supercapacitors, due to their diverse structure, adjustable aperture, large specific surface area and abundant active sites. Supercapacitor has been widely investigated in the past decades. Of critical importance in these devices is the electrode active materials, and this application has been intensively studied with the development of novel nanomaterials. In this review we summarize recent reports on MO Fs as electrode materials for super capacitors. Specifically,the synthesis of MOF materials for super capacitor electrodes and their performance in electrochemical energy storage are discussed. We aim to include supercapacitor electrode materials related to MOFs, such as carbon, metal and composite materials. It is proposed that MOFs play an important role in the development of a new generation of supercapacitor electrode materials. Finally, we discuss the current challenges in the field of supercapacitors, with a view towards how to address these challenges with the future development of MOFs and their derivatives.

Carbon-emcoating architecture boosts lithium storage of Nb_(2)O_(5)

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 CO_(2)activation treatment as demonstrated by the Nb_(2)O_(5)/C nanohybrid.Triple structure engineering of the carbon-emcoating Nb_(2)O_(5)/C nanohybrid is achieved in terms of porosity,composition,and crystallographic phase.The carbon-embedding Nb_(2)O_(5)/C nanohybrids show superior cycling and rate performance compared with the conventional carbon coating,with reversible capacity of 387 m A h g(-1)at 0.2 C and 92%of capacity retained after 500cycles at 1 C.Differential electrochemical mass spectrometry(DEMS) indicates that the carbon emcoated Nb_(2)O_(5)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.

Rapid CO_(2) exfoliation of Zintl phase CaSi_(2)-derived ultrathin free-standing Si/SiO_(x)/C nanosheets for high-performance lithium storage

Semiconducting silicon(Si)nanomaterials have great potential for the applications in electronics,physics,and energy storage fields.However,to date,it is still a challenge to realize the batch production of Si nanomaterials via efficient and low-cost approaches,owing to some long-standing shortcomings,e.g.,complex procedures and time and/or energy consumption.Herein,we report a green and inexpensive method to rapidly obtain two-dimensional(2D)free-standing Si/SiO_(x) nanosheets via the rapid thermal exfoliation of layered Zintl compound CaSi_(2).With the help of the rapid exfoliation reaction of CaSi_(2) in the atmosphere of greenhouse gas CO_(2),and the following mild sonication,2D free-standing Si/SiO_(x) nanosheets can be produced with very high yield.After applying the coating of a thin carbon outer layer,the electrodes of Si/SiO_(x)/C nanosheets serving as the anodes for lithium-ion batteries exhibit ultrahigh reversible capacity and outstanding electrochemical stability.We expect this study will provide new insights and inspirations for the convenient and batch production of nanostructural Si-based anode materials towards high-performance lithium-ion batteries.

Advances in flexible lithium metal batteries

Flexible energy storage devices are becoming indispensable new elements of wearable electronics to improve our living qualities.As the main energy storage devices,lithium-ion batteries(LIBs)are gradually approaching their theoretical limit in terms of energy density.In recent years,lithium metal batteries(LMBs)with metallic Li as the anode are revived due to the extremely high energy density,and are considered to be one of the ideal alternatives for the next generation of flexible power supply.In this review,key technologies and scientific problems to be overcome for flexible LMBs are discussed.Then,the recent advances in flexible LMBs,including the design of flexible Li metal anodes,electrolytes,cathodes and interlayers,are summarized.In addition,we have summed up the research progress of flexible device configurations,and emphasized the importance of flexibility evaluation and functionality integration to ensure the wearing safety in complex environment.Finally,the challenges and future development of flexible LMBs are summarized and prospected.

Boosting the lithium-ion storage performance of perovskite Sr_(x)VO_(3-δ) via Sr cation and O anion deficient engineering

Perovskite SrVO_(3) has been investigated as a promising lithium storage anode where the V cation plays the role of the redox center,combining excellent cycle stability and safe operating potential versus Li metal plating,with limited capacity.Here,we demonstrate the possibility to boost the lithium storage properties,by reducing the non-redox active Sr cation content and fine-tuning the O anion vacancies while maintaining a non-stoichiometric Sr_(x)VO_(3-δ) perovskite structure.Theoretical investigations suggest that Sr vacancy can work as favorable Li^(+) storage sites and preferential transport channels for guest Li^(+) ions,contributing to the increased specific capacity and rate performance.In contrast,inducing O anion vacancy in Sr_(x)VO_(3-δ) can improve rate performance while compromising the specific capacity.Our experimental results confirm the enhancement of specific capacities by fine adjusting the Sr and O vacancies,with a maximum capacity of 444 mAh g^(-1) achieved with Sr_(0.63)VO_(3-δ),which is a 37%increase versus stoichiometric SrVO_(3).Although rich defects have been induced,Sr_(x)VO_(3-δ) electrodes maintain a stable perovskite structure during cycling versus a LiFePO_(4) cathode,and the full-cell could achieve more than 6000 discharge/charge cycles with 80%capacity retention.This result highlights the possibility to use the cation defective-based engineering approach to design high-capacity perovskite oxide anode materials.