Anode For Lithium-ion Capacitors Research Articles

Sulfur covalently bonded to porous graphitic carbon as an anode material for lithium-ion capacitors with high energy storage performance

Sulfur covalently bonded to porous graphitic carbon is utilized as an anode for lithium-ion capacitors with high energy storage performance.

3D Hierarchically Structured CoS Nanosheets: Li+ Storage Mechanism and Application of the High-Performance Lithium-Ion Capacitors.

Lithium-ion capacitors possess excellent power and energy densities, and they can combine both of those advantages from supercapacitors and lithium-ion batteries, leading to novel generation hybrid devices for storing energy. This study synthesized one three-dimensional (3D) hierarchical structure, self-assembled from CoS nanosheets, according to a simple and efficient manner, and can be used as an anode for lithium ion capacitors. This CoS anode, based on a conversion-type Li+ storage mechanism dominated by diffusion control, showed a large reversible capacity, together with excellent stability for cycling. The CoS shows a discharge capacity ≈434 mA h/g at 0.1 A/g. The hybrid lithium-ion capacitor, which had the CoS anode as well as the biochar cathode, exhibits excellent electrochemical performance with ultrahigh energy and power densities of 125.2 Wh/kg and 6400 W/kg, respectively, and an extended cycling life of 81.75% retention after 40 000 cycles. The CoS with self-assembled 3D hierarchical structure in combination with a carbon cathode offers a versatile device for future applications in energy storage.

Application of Sn-Ni Alloy as an Anode for Lithium-Ion Capacitors with Improved Volumetric Energy and Power Density

Lithium-ion capacitors (LIC) constructed by combining a supercapacitor-like cathode and battery-like anode are expected to bridge a gap between low power density from lithium-ion batteries (LIB) and low energy density from the supercapacitors. In this study, we synthesize the Sn-Ni alloy by electrodeposition in the aqueous solution as an anode for LIC. The lower volume expansion rate of Sn-86 than pure Sn anode can be confirmed by in-operando investigation using an optically transparent cell during the 1st charging process. This is attribute to the co-deposited Ni can act as a buffer matrix to restrain volume expansion. For the full-cell test, the pre-lithiation condition of Sn-Ni was investigated with different depth of discharge levels. As a result, a LIC consisting of activated carbon (AC) cathode and Sn-86 exhibits a good cyclability for 3000 cycles with a capacity retention of 80% and coulombic efficiency of 98% at 3000th cycle. The Sn-Ni//AC LIC shows improved volumetric energy and power density than graphite//AC LIC. This study presents a new possibility of Sn-Ni alloy as an anode for the improved electrochemical performance of LIC.

Influence of sintering temperature and graphene additives on the electrochemical performance of porous Li4Ti5O12 anode for lithium ion capacitor

Porous L4Ti5O12 (LTO) nanoparticles were prepared by a precursor directed hydrothermal method followed by sintering. The influence of sintering temperature and graphene additives on the microstructure evolution and electrochemical properties of LTO for lithium ion capacitors (LICs) was investigated. Bare LTO with fine particle and porous microstructure can be obtained under low temperature sintering (600°C), which can deliver a specific capacity of 65.2mAhg−1 at the current rate of 20C. With increasing temperature, the LTO particles are inclined to grow with coarse particle and the agglomerate state, deteriorating the electrochemical performances (14.3mAhg−1 at 20C). After introduction of graphene additives, LTO can be prepared with increased surface area, pore volume and electrical conductivity, which are beneficial for LTO to contact with electrolyte, shorten the lithium diffusion length and facilitate the electron and ion transport during lithiation/delithiation process, leading to the greatly improved electrochemical performances (102mAhg−1 at 20C). The LICs full cell using the LTO/graphene anode and activated carbon cathode was also evaluated. The decent energy/power densities (maximum energy/power densities are 44.0 Wh kg−1 and 7200Wkg−1, respectively) with excellent cycling stability (capacitance retention of 80% at a current density of 3.2Ag−1 after 10000 cycles) show the promising application perspective.

High-Energy Electrochemical Capacitors Utilizing Chemically Reduced Graphite Oxide As Negative Electrode Material

Taking into account power needs for portable devices, the energy storage through electrochemical reactions seems to be a crucial technology, especially due to the growing technological advances requirements. Electrochemical capacitors have attracted great attention as promising energy storage devices because of their high power density and cycle life noticeably longer than batteries [i],[ii]. Recently, extensive works have been focused on enhancing both the energy and power density accompanied by reasonable cost of device production as well as its environment-friendly character. One of the approaches is idea initiated in 2001 [iii], of improving capacitors performance by merging advantages of capacitors and lithium-ion batteries. This procedure was aimed to increase the energy of the capacitor while maintaining the level of supplied power. Starting from 2001 till now in the literature we can find examples of different methods involving various electrode materials [iv],[v],[vi],[vii],[viii],[ix],[x]. Asymmetric supercapacitors composed of battery-type electrode and a high surface area carbon electrode [xi] combine the advantages and reduces the drawback of redox and capacitive based systems. Therefore, the asymmetric design offers the advantages of supercapacitors (power rate, cycle life) and batteries (energy density) [xii]. This work is focused on high-energy electrochemical capacitors utilizing chemically reduced graphite oxide (CRGO) as a negative electrode material and activated carbon (AC) with the well-developed surface area as a positive electrode material. For comparison, electrochemical characteristic of capacitors utilizing graphite negative electrode was also performed. The pre-lithiation process, made by electrochemical intercalation of lithium ions into graphite, has been chosen as the main method of negative electrode material preparing. Performed electrochemical measurements, i.e., cyclic voltammetry and galvanostatic charging/discharging presented improved energy efficiency compared with results for symmetric cells (i.e. AC/AC capacitor). All measurements were performed in the organic electrolyte to provide a wide range of operating voltage. In the case of the hybrid system energy density has been improved and exceed 90 Wh kg-1 accompanied by good power profile. Additionally, good cycle performance was also achieved. Chemically reduced graphite oxide (CRGO) displays excellent performance at current densities up to 8 A g-1and, therefore, it can be considered as a very promising material for high energy Lithium-ion capacitors (LICs). Moreover, for more detailed analysis, measurements in three-electrode cells were also conducted. Fig. 1 shows an example of cyclic voltammetry curves for two systems composed of activated carbon cathode and graphite or CRGO anode. For graphite anode, Faradaic reactions can be observed in very narrow working range (134 mV) comparing to the positive electrode (1266 mV). CRGO characteristics merge two mechanisms of lithium storage, namely, Faradaic and capacitive one. In result, the quite good proportion of working potentials between positive and negative electrodes (772 mV vs. 628 mV, respectively) can be seen. The intercalation of lithium ions into graphite material occurs relatively slowly, hence the difference in power between the electrochemical capacitors and lithium-ion batteries. The electrode with the slowest sweep of potential will determine the power of the device. In this case chemically reduced graphite oxide seems to be promising material as an anode in lithium ion capacitors due to the merged lithium insertion movement, that’s why the energy storage can take place comparatively fast, as in the positive electrode. Financial support from the project DEC-2013/09/D/ST5/03886 is gratefully acknowledged. Fig. 1. Comparison of working potentials positive and negative electrodes in hybrid systems AC/G(Li) and AC/CRGO(Li), obtained from cyclic voltammetry measurements. [i] A. Burke, J. Power Sources 91 (2000) 37 [ii] P. Simon, Y. Gogotsi, Nat. Mater. 7 (2008) 845 [iii] G.C. Amatucci, F. Badway, A.D. Pasquier, T. Zheng, J. Electrochem. Soc. 148 (2001) A930 [iv] D. Cericola, R. Kötz, Electrochimica Acta 72 (2012) 1 [v] W.J. Cao, J. Shih, J.P. Zheng, T. Doung, J. Power Sources 257 (2014) 388 [vi] S.R. Sivakkumar, A.G. Pandolfo, J. Appl. Electrochem. 44 (2014) 105 [vii] X. Sun, X. Zhang, H. Zhang, N. Xu, K. Wang, Y. Ma, J. Power Sources 270 (2014) 318 [viii] S. Dsoke, B. Fuchs, E. Gucciardi, M. Wohlfahrt-Mehrens, J. Power Sources 282 (2015) 385 [ix] J. Zhang, Z. Shi, J. Wang, J. Shi, J. Electroana. Chem. 747 (2015) 20 [x] K. Naoi, P.Simon, Electrochem. Soc. Interface 17 (1) (2008) 34 [xi] J.W. Long, D. Belanger, T. Brousse, W. Sugimoto, M.B. Sassin, O. Crosnier, MRS Bull. 36 (2011) 513 [xii] Z.J. Fan, J. Yan, T. Wei, L.J. Zhi, G.Q. Ning, T.Y. Li, F. Wei, Adv. Funct. Mater. 21 (2011) 2366 Figure 1

Unveiling TiNb2O7 as an Insertion Anode for Lithium Ion Capacitors with High Energy and Power Density

This is the first report of the utilization of TiNb2 O7 as an insertion-type anode in a lithium-ion hybrid electrochemical capacitor (Li-HEC) along with an activated carbon (AC) counter electrode derived from a coconut shell. A simple and scalable electrospinning technique is adopted to prepare one-dimensional TiNb2 O7 nanofibers that can be characterized by XRD with Rietveld refinement, SEM, and TEM. The lithium insertion properties of such electrospun TiNb2 O7 are evaluated in the half-cell configuration (Li/TiNb2 O7 ) and it is found that the reversible intercalation of lithium (≈3.45 mol) is feasible with good capacity retention characteristics. The Li-HEC is constructed with an optimized mass loading based on the electrochemical performance of both the TiNb2 O7 anode and AC counter electrode in nonaqueous media. The Li-HEC delivers very high energy and power densities of approximately 43 Wh kg(-1) and 3 kW kg(-1) , respectively. Furthermore, the AC/TiNb2 O7 Li-HEC delivers a good cyclability of 3000 cycles with about 84% of the initial value.