预嵌锂硬碳和软碳用于锂离子电容器负极的比较研究

锂离子电容器是一种应用前景广阔的电化学储能器件. 目前,活性炭作为锂离子电容器正极被广泛使用. 然而,锂离子电容器负极却有多种不同选择,如硬碳和软碳等碳材料. 本文使用两种具有不同结构和电化学特性的硬碳和软碳材料作为锂离子电容器负极,进行了对比研究. 研究表明,软碳相比于硬碳有更好的电子导电性和更高的可逆容量. 通过在电流范围0.1 ~ 12 A·g^-1下进行充放电测试,分别研究了两种碳基电极在不同涂覆厚度下的倍率性能. 结果显示,硬碳电极在大电流下有更好的倍率特性. 然后,以活性炭为正极,预嵌锂的硬碳和软碳为负极,锂片为锂源和参比电极,分别组装了三电极软包锂离子电容器. 根据三电极充放电测试,分别研究了不同预嵌锂量的硬碳和软碳所组装的锂离子电容器的电化学性能. 结果表明,合适的负极预嵌锂容量可以提升锂电容的能量密度、功率密度和循环稳定性. 最后,大容量硬碳和软碳基软包锂离子电容器被分别组装,软碳基锂电容实现了最高的能量密度21.2 Wh·kg^-1（基于整个器件质量）,硬碳基锂电容实现最高的功率密度5.1 kW·kg^-1.     

C/C composite anodes for long-life lithium-ion batteries

The research of anodic materials which could improve the performance and reduce the cost of graphite-based materials in lithium-ion batteries leads to a considerable effort for creating novel carbons. In this work, special attention has been paid to investigating the possibility of improving the electrochemical behavior of graphite anode by application of composite materials with carbon materials coming from agro-wastes. For that, different carbons coming from agro-wastes have been synthesized and characterized in order to study the effect of their properties on the electrochemical performance of C/C composites with graphite. It has been established that introduction of hard carbon obtained from olive stones into the active mass of anode based on graphite allows one to increase the reversible capacity up to 405 mAh g^?1 for the total mass of graphite/carbon content of electrode, and also to improve stability of characteristics during cycling. We suggested that such a binary carbon mixture (graphite and hard carbon) would be a better choice for development of the anode for lithium-ion battery.     

Carbon-coated Li3VO4 with optimized structure as high capacity anode material for lithium-ion capacitors

Due to the high capacity, moderate voltage platform, and stable structure, Li₃VO₄ (LVO) has attracted close attention as feasible anode material for lithium-ion capacitor. However, the intrinsic low electronic conductivity and sluggish kinetics of the Li⁺ insertion process severely impede its practical application in lithium-ion capacitors (LICs). Herein, a carbon-coated Li₃VO₄ (LVO/C) hierarchical structure was prepared by a facial one-step solid-state method. The synthesized LVO/C composite delivers an impressive capacity of 435 mAh/g at 0.07 A/g, remarkable rate capability, and nearly 100% capacity retention after 500 cycles at 0.5 A/g. The superior electrochemical properties of LVO/C composite materials are attributed to the improved conductivity of electron and stable carbon/LVO composite structures. Besides, the LIC device based on activated carbon (AC) cathode and optimal LVO/C as anode reveals a maximum energy density of 110 Wh/kg and long-term cycle life. These results provide a potential way for assembling the advanced hybrid lithium-ion capacitors.     

A high performance solid-state asymmetric supercapacitor based on Anderson-type polyoxometalate-doped graphene aerogel

The manufacture of single-atom transition metal-doping carbon nanocomposites as electrode materials is crucial for electrochemical energy storage with high energy and power density. However, the simple strategy for preparation of such active materials with controlled structure remains a great challenge. Here, cobalt-doped carbon nanocomposites (Co-POM/rGO) were synthesized successfully by deposition of Anderson-type polyoxometalate (POM) on the surface of reduced graphene oxide (rGO) aerogel via one-pot hydrothermal treatment. The resulting Co-POM/rGO possesses three-dimensional graphene-based frameworks with hierarchical porous structure, high surface area and uniform single-atom metal doping. These intriguing features render Co-POM/rGO to be a promising electrode for applications in electrochemical energy storage. As an electrode material of a supercapacitor, Co-POM/rGO shows high-performance electrochemical energy storage (211.3 F g^?1 at 0.5 A g^?1). Furthermore, the solid-state asymmetric supercapacitor (ASC) device, using Co-POM/rGO as a positive electrode, exhibits the outstanding energy density of 37.6 Wh kg^?1 at a power density of 500 W kg^?1, and high capacitance retention of 95.2% after 5000 charge–discharge cycles. These results indicate that the proposed strategy for rational design of single-atom-metal doped carbon nanocomposites for flexible ASC devices with excellent capacitive properties.

     

A high-performance potassium-ion capacitor based on a porous carbon cathode originated from the Aldol reaction product

Potassium-ion capacitors (KICs) emerge as a promising substitute for the well-developed lithium-ion capacitors (LICs), however, the energy density of KICs is below expectations because of lacking a suitable electrical double-layer positive electrode. Using chemical activation of the Aldol reaction product of acetone with KOH, we synthesized a porous carbon with a Brunauer-Emmett-Teller surface area of up to 2947 m²/g and a narrow pore size distribution ranging from 1 nm to 3 nm. Half-cell (versus potassium metal) test demonstrates that this porous carbon has high capacitive performance in K⁺ based organic electrolytes. Furthermore, a novel KIC fabricated by this porous carbon as the cathode, yields high values of energy density and power density. The processes used to make this porous carbon are readily low-cost to fabricate metal-ion capacitors.     

A high-performance asymmetric supercapacitor achieved by surface-regulated MnO2 and organic-framework–derived N-doped carbon cloth

It is possible to achieve high energy density and power density simultaneously for asymmetric supercapacitors by using pseudocapacitive materials with abundant ion intercalation/de-intercalation sites on the surface. Herein, a positive electrode based on feather-like MnO₂ anchored on the activated carbon cloth is prepared, in which oxygen-enriched MnO₂ nanorods with a radial sheet-like structure (OMO@AC) further form via electrochemical oxidation. Because of the large contact area with electrolyte and abundant oxidation functional groups on its surface, the OMO@AC displays excellent capacitance of 3,160 mF/cm² at 1 mA/cm². For the nitrogen-doped active carbon negative electrode, the capacitance is up to 1,875 mF/cm² at 4 mA/cm² due to the increase in disorder and defect on the carbon surface by N-doping. Furthermore, we verify the good electrochemical activity on the OMO@AC electrode surface by first-principles calculations and confirm the good matching degree between the positive and negative electrodes by CV testes. The aqueous oxygen-enriched MnO₂// nitrogen-doped active carbon asymmetric supercapacitor exhibits an ultrahigh energy density of 8.723 mWh/cm³ at a power density of 14.248 mW/cm³ and display excellent cycle stability maintaining 95.5% after 10,000 cycles. The facile synthesis method and excellent performance provide a feasible way for the preparation of high-performance electrode materials for energy storage devices.     

Ionic Liquid Assisted Electrospinning of Porous LiFe0.4Mn0.6PO4/CNFs as Free-Standing Cathodes with a Pseudocapacitive Contribution for High-Performance Lithium-Ion Batteries

In pursuit of high-performance cathode materials for lithium-ion batteries with high energy and power densities, porous LiFe_0.4Mn_0.6PO₄/CNF free-standing electrodes have been successfully prepared through a facile ionic liquid (IL) assisted electrospinning method. Owing to the hierarchical porosity and N-doped carbon layer derived from the ionic liquid, the resulting electrodes exhibited superior electrochemical performances with an improvement of conductivity and pseudocapacitive contribution, delivering a discharge capability of 162.7, 133.5, 114.5, and 102.6 mAh g⁻¹ at the current rates of 0.1, 1, 5, and 10 C, respectively. It is highly expected that this facile IL-assisted electrospinning method will lead to further developments for other phosphate-based free-standing electrodes, which offers a new route in designing polyanionic cathodes for high-performance Li-ion batteries.     

Superior storage performance of carbon nanosprings as anode materials for lithium-ion batteries

Carbon nanosprings (CNSs) with spring diameter of ～140 nm, carbon ring diameter of ～100 nm and pitch distance of ～150 nm, synthesized by using a catalytic chemical vapor deposition technology, have been investigated for potential applicability in lithium batteries as anode materials. The electrochemical results demonstrate that the present CNSs are superior anode materials for rechargeable lithium-ion batteries with high-rate capabilities, as well as long-term cycling life. At a current density as high as 3 A g^?1, CNSs can still deliver a reversible capacity of 160 mA h g^?1, which is about six times larger than that of graphite and three times larger than that of multi-wall carbon nanotubes under the same current density. After hundreds of cycles, there is no significant capacity loss for CNSs at both low and high current densities. The much improved electrochemical performances could be attributed to the nanometer-sized building blocks as well as the unusual spring-like morphology.     

Direct synthesis of self-assembled ferrite/carbon hybrid nanosheets for high performance lithium-ion battery anodes

Extensive applications of rechargeable lithium-ion batteries (LIBs) to various portable electronic devices and hybrid electric vehicles result in the increasing demand for the development of electrode materials with improved electrochemical performance including high energy, power density, and excellent cyclability, while maintaining low production cost. Here, we present a direct synthesis of ferrite/carbon hybrid nanosheets for high performance lithium-ion battery anodes. Uniform-sized ferrite nanocrystals and carbon materials were synthesized simultaneously through a single heating procedure using metal-oleate complex as the precursors for both ferrite and carbon. 2-D nanostructures were obtained by using sodium sulfate salt powder as a sacrificial template. The 2-D ferrite/carbon nanocomposites exhibited excellent cycling stability and rate performance derived from 2-D nanostructural characteristics. The synthetic procedure is simple, inexpensive, and scalable for mass production, and the highly ordered 2-D structure of these nanocomposites has great potential for many future applications.     

《能源电化学材料》专辑序言

以电化学能量储存和转化为特点的电池、电容器等储能技术,正在信息通讯、新能源汽车、微电网、分布式发电、大型电力储能、智能电网等领域得到广泛应用,将有力推动能源互联网的快速发展. 作为储能核心技术之一的锂电池、钠电池与超级电容器,更加受到重视. 这些电化学储能装置的性能依赖于所使用的电极材料与结构等. 发展高能量密度、高功率密度和长循环寿命的低成本储能体系成为能源电化学材料研究的核心. 本专辑围绕锂离子电池、钠离子电池、锂硫电池、超级电容器等,收录了在该领域具有丰富研究经验的团队所撰写的8篇相关综述和研究论文. 其中,围绕下一代锂离子电池负极硅材料,邀请了3篇综述和研究论文;鉴于丰富的钠资源,在钠离子电池研究方面也邀请了3篇综述论文;同时在高能量密度的锂硫电池和高功率密度的超级电容器方面各邀请1篇论文. 从这些论文中,可以部分看出锂离子电池、钠离子电池、锂硫电池、超级电容器等能源电化学材料的研究进展. 希望借助此专辑的出版,能使广大读者更好地了解上述几类电池、电容器的研究现状,研究趋势和存在问题及挑战,为更深入地开展该领域研究提供参考,以推动我国能源电化学材料研究的进一步发展. 在此,对专辑的所有作者、审稿人及编辑部工作人员的辛勤劳动,表示最衷心的感谢！     

Li-ion charge storage performance of wood-derived carbon fibers@MnO as a battery anode

Wood-derived carbons have been demonstrated to have large specific capacities as the anode materials of lithium-ion batteries(LIBs). However, these carbons generally show low tap density and minor volumetric capacity because of high specific surface area and pore volume. Combination with metal oxide is one of the expected methods to alleviate the obstacles of wood-derived carbons. In this work, the composites of Mn O loaded wood-derived carbon fibers(CF@Mn O) were prepared via a simple and envir...     

Electrochemical performance of pre-lithiated graphite as negative electrode in lithium-ion capacitors

Electrochemical performance of the pre-lithiated graphite and the as-assembled lithium-ion capacitors (LICs) were investigated within the Li/graphite two-electrode cell and activated carbon (AC)/graphite two-electrode cell, respectively. The morphologies of the electrodes were characterized by scanning electron microscopy (SEM). The Li intercalation of Li/graphite two-electrode cell was performed using short circuiting and galvanostatic charging techniques. The Li pre-doping process was characterized by electrochemical impedance spectroscopy (EIS). The cycle performance of the LICs were investigated at the rates of 1–20 C between the cut-off voltage at 2 to 4 V. The results demonstrated that the LIC cells with 8 h pre-doping time have the best cycle performance at the high rate of 10 C. Li pre-doping methodology plays a crucial role in the electrochemical performance of the graphite electrode and the as-assembled LICs.     

In Situ Polymerized 1,3-Dioxolane Electrolyte for Integrated Solid-State Lithium Batteries

Solid-state lithium batteries are promising and safe energy storage devices for mobile electronics and electric vehicles. In this work, we report a facile in situ polymerization of 1,3-dioxolane electrolytes to fabricate integrated solid-state lithium batteries. The in situ polymerization and formation of solid-state dioxolane electrolytes on interconnected carbon nanotubes (CNTs) and active materials is the key to realizing a high-performance battery with excellent interfacial contact among CNTs, active materials and electrolytes. Therefore, the electrodes could be tightly integrated into batteries through the CNTs and electrolyte. Electrons/ions enable full access to active materials in the whole electrode. Electrodes with a low resistance of 4.5 Ω □⁻¹ and high lithium-ion diffusion efficiency of 2.5×10⁻¹¹ cm² s⁻¹ can significantly improve the electrochemical kinetics. Subsequently, the batteries demonstrated high energy density, amazing charge/discharge rate and long cycle life.     

Fluorinated carbon nanofibres for high energy and high power densities primary lithium batteries

The electrochemical performances of fluorinated carbon nanofibres have been tested for a use as cathode material in primary lithium battery using LiBF₄ PC:DME 1M as electrolyte. For a very narrow fluorination range (420–450 °C), the fluorine content in the carbon nanofibres increases up to CF_0.78 and so do both the energy and the power densities. A maximum of 8057 W kg⁻¹ power density has been reached. Moreover, a current density of 6C can be used for such fluorinated carbon nanofibres. Such high electrochemical values can be correlated to the amount of unfluorinated carbon located in the core of the carbon nanofibres. Owing to solid state ¹³C NMR which can accurately evaluated this fraction, a minimum of 10% of unfluorinated carbon nanofibre is necessary in order to insure a good conducting behaviour.     

用于超级电容器的锰钴氧化物/碳纤维材料

The development of high-performance supercapacitor electrode materials is imperative to alleviate the ongoing energy crisis. Numerous transition metals (oxides) have been studied as electrode materials for supercapacitors owing to their low cost, environmental-friendliness, and excellent electrochemical performance. Among the developed binary transition metal oxides, manganese cobalt oxides typically show high theoretical capacitance and stable electrochemical performance, and are widely used in the electrode materials of supercapacitors. However, the poor conductivity and active material utilization of manganese cobalt oxide-based electrode materials limit their potential capacitance application. Cotton is mainly composed of organic carbon-containing materials, which can be transformed to carbon fibers after calcination. The resultant carbonaceous material exhibits a large specific surface area and good conductivity. Such advantages could potentially suppress the negative effects caused by the poor conductivity and small specific surface area of manganese cobalt oxides, thereby improving the electrochemical performance. Herein, we firstly deposited manganese cobalt oxides on cotton by a simple hydrothermal method, yielding a composite of manganese cobalt oxides and carbon fibers via subsequent calcination, to improve the electrochemical performance of the electrode material. X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET), thermogravimetric analysis (TGA), and electrochemical characterizations were used to investigate the physical, chemical, and electrochemical properties of the prepared samples. The fabricated manganese cobalt oxides in the composite were uniformly dispersed on the carbon fiber surface, which increased the contact between the interface of the electrode material and electrolyte, and enhanced electrode material utilization. The electrode material was confirmed to have well contacted with the electrolyte during a contact angle test. Hence, a pseudo-capacitance reaction completely occurred on the manganese cobalt oxide material. Moreover, the addition of carbon fibers reduced the resistance of the material, resulting in excellent capacitive performance. The capacitance of the prepared composite was 854 F∙g^-1 at a current density of 2 A∙g^-1. The capacitance was maintained at 72.3% after 2000 cycles at a current density of 2 A∙g^-1. These results indicate that the manganese cobalt oxide and carbon fiber composite is a promising electrode material for high-performance supercapacitors. The findings presented herein provide a strategy for coupling with carbon materials to enhance the performance of supercapacitor electrode materials based on manganese cobalt oxides. Thus, novel insights into the design of high-performance supercapacitors for energy management are provided.     

Platelike CoO/carbon nanofiber composite electrode with improved electrochemical performance for lithium ion batteries

Platelike CoO/carbon nanofiber (CNF) composite materials with porous structures are synthesized from the thermal decomposition and recrystallization of β-Co(OH)₂/CNF precursor without the need for a template or structure-directing agent. As negative electrode materials for lithium-ion batteries, the platelike CoO/CNF composite delivers a high reversible capacity of 700 mAh g⁻¹ for a life extending over hundreds of cycles at a constant current density of 200 mA g⁻¹. More importantly, the composite electrode shows significantly improved rate capability and electrochemical reversibility. Even at a current of 2 C, the platelike CoO/CNF composite maintain a capacity of 580 mAh g⁻¹ after 50 discharge/charge cycles. The improved cycling stability and rate capability of the CoO/CNF composite electrodes may be attributed to synergistic effect of the porous structural stability and improved conductivity through CNF connection.     

锂离子电池3d 过渡金属氧化物负极微/纳米材料

与传统的碳材料相比,锂离子电池3d 过渡金属氧化物(M_xO_y,M = Co、Fe、Cu、Ni) 负极材料具有更高的容量、倍率及安全性能,更适于锂离子电池在移动电子设备、电动汽车、备用储能和智能电网等领域的应用,因此备受关注。本文介绍了M_xO_y 负极材料的充放电机理,并以零维、一维、二维、三维等纳米结构及空心、核壳等多种微/纳米结构为出发点,详细讨论了过渡金属氧化物电极材料的电化学性能与结构特征之间的关系,分析了具有不同结构特征的负极材料的合成方法;展望了3d 过渡金属氧化物负极微/纳米材料的研究趋势和发展前景。     

Scalable Synthesis of Porous SiFe@C Composite with Excellent Lithium Storage

Utilizing cost-effective raw materials to prepare high-performance silicon-based anode materials for lithium-ion batteries (LIBs) is both challenging and attractive. Herein, a porous SiFe@C (pSiFe@C) composite derived from low-cost ferrosilicon is prepared via a scalable three-step procedure, including ball milling, partial etching, and carbon layer coating. The pSiFe@C material integrates the advantages of the mesoporous structure, the partially retained FeSi₂ conductive phase, and a uniform carbon layer (12–16 nm), which can substantially alleviate the huge volume expansion effect in the repeated lithium-ion insertion/extraction processes, effectively stabilizing the solid–electrolyte interphase (SEI) film and markedly enhancing the overall electronic conductivity of the material. Benefiting from the rational structure, the obtained pSiFe@C hybrid material delivers a reversible capacity of 1162.1 mAh g⁻¹ after 200 cycles at 500 mA g⁻¹, with a higher initial coulombic efficiency of 82.30 %. In addition, it shows large discharge capacities of 803.1 and 600.0 mAh g⁻¹ after 500 cycles at 2 and 4 A g⁻¹, respectively, manifesting an excellent electrochemical lithium storage. This work provides a good prospect for the commercial production of silicon-based anode materials for LIBs with a high lithium-storage capacity.     

Nitrogen-doped carbon nanotubes by multistep pyrolysis process as a promising anode material for lithium ion hybrid capacitors

Lithium-ion hybrid capacitors (LIHCs) is a promising electrochemical energy storage devices which combines the advantages of lithium-ion batteries and capacitors. Herein, we developed a facile multistep pyrolysis method, prepared an amorphous structure and a high-level N-doping carbon nanotubes (NCNTs), and by removing the Co catalyst, opening the port of NCNTs, and using NCNTs as anode material. It is shows good performance due to the electrolyte ions enter into the electrode materials and facilitate the charge transfer. Furthermore, we employ the porous carbon material (APDC) as the cathode to couple with anodes of NCNTs, building a LIHCs, it shows a high energy density of 173 Wh/kg at 200 W/kg and still retains 53 Wh/kg at a high power density of 10 kW/kg within the voltage window of 0–4.0 V, as well as outstanding cyclic life keep 80% capacity after 5000 cycles. This work provides an opportunity for the preparation of NCNTs, that is as a promising high-performance anode for LIHCs.     

Optimization of preparing LiFePO<Subscript>4</Subscript> for lithium-ion batteries via carbothermal reduction route

Lithium iron phosphate olivines (LiFePO₄) have been considered as very promising cathode for lithium-ion batteries due to their energy storage capacity combined with electrochemical and thermal stability. A key issue in synthesizing this materials is to optimize the synthetic conditions for obtain materials with excellent electrochemical properties. Here, we report full studies that investigate the synthesis of the LiFePO₄ by promising carbothermal reduction methods to prepare LiFePO₄ coated with pyrolytic carbon. Variation of the synthesis parameters showed that the materials synthesized at 700°C for 12 h have appropriate particles size and electronically conductive carbon. This makes it have better performances than others prepared at different temperature.