Electrochemical Intercalation Of Lithium Ions Research Articles

High-yield production of mono- or few-layer transition metal dichalcogenide nanosheets by an electrochemical lithium ion intercalation-based exfoliation method.

Transition metal dichalcogenide (TMD) nanomaterials, especially the mono- or few-layer ones, have received extensive research interest owing to their versatile properties, ranging from true metals (e.g., NbS2 and VSe2) and semimetals (e.g., WTe2 and TiSe2) to semiconductors (e.g., MoS2 and We2) and insulators (e.g., HfS2). Therefore, the reliable production of these nanomaterials with atomically thin thickness and laterally uniform dimension is essential for their promising applications in transistors, photodetectors, electroluminescent devices, catalysis, energy conversion, environment remediation, biosensing, bioimaging, and so on. Recently, the electrochemical lithium ion intercalation-based exfoliation method has emerged as a mature, efficient and promising strategy for the high-yield production of mono- or few-layer TMD nanosheets; monolayer MoS2 (yield of 92%), monolayer TaS2 (yield of 93%) and bilayer TiS2 (yield of 93%) with lateral dimensions of ~1 µm (refs. 1-3). This Protocol describes the details of experimental procedures for the high-yield synthesis of mono- or few-layer TMDs and other inorganic nanosheets such as MoS2, WS2, TiS2, TaS2, ZrS2, graphene, h-BN, NbSe2, WSe2, Sb2Se3 and Bi2Te3 by using the electrochemical lithium ion intercalation-based exfoliation method, which involves the electrochemical intercalation of lithium ions into layered inorganic crystals and a mild sonication process. The whole protocol takes 26-38 h for the successful production of ultrathin inorganic nanosheets.

Kinetics of electrochemical intercalation of lithium ion into Li[Li0.2Co0.3Mn0.5]O2 electrode from Li2SO4 solution

The kinetics of electrochemical lithium ion intercalation into Li[Li0.2Co0.3Mn0.5]O2 electrode in 2 M Li2SO4 aqueous electrolyte has been studied using two electroanalytical methods, namely, potentiostatic intermittent titration technique (PITT) and galvanostatic intermittent titration technique (GITT). The results are compared with those from nonaqueous electrolytes. Layered, lithium-rich Li[Li0.2Co0.3Mn0.5]O2 cathode material was synthesized by reactions under autogenic pressure at elevated temperature (RAPET) method. The effects of ohmic potential drop and charge-transfer resistance have been considered while predicting the current transients obtained with aqueous electrolyte. For PITT and GITT, we have defined their characteristic time-invariant functions, It1/2 and dE/dt1/2, respectively to present the diffusion time constant τ. Application of different theoretical diffusion models for treating the results obtained by the above-mentioned techniques allowed us to calculate the diffusion coefficient of lithium ions (D) at different potentials (E). The intercalation process is explained by considering the possible attractive interactions of the intercalated species in terms of Frumkin intercalation isotherm. We have observed a strictcorrespondence between the peaks of the intercalation capacitance and the minima in the corresponding log D vs. E curve.

Atom removal on the basal plane of layered MoS2 leading to extraordinarily enhanced electrocatalytic performance

Efficient utilization of sulfur atom in MoS2-based electrocatalysts on the basal plane is highly desirable and expectable to optimize the electrocatalytic performance for hydrogen evolution reaction (HER). Herein, removing atoms on the basal plane of layered MoS2 by Li-ion intercalation leading to extraordinarily enhanced electrocatalytic performance is newly reported, which provides a novel way to active the basal planes of layered transition metal sulfides towards hydrogen evolution. It is found that the desulfurization of layered MoS2 can bring atomic vacancies on the basal plane, which is confirmed to be active sites towards hydrogen evolution experimentally and theoretically. The first-principle calculations reveal that the desulfurization induced atomic vacancies not only reduce the free energy of hydrogen adsorption (ΔGH*), but also accelerate the electron transfer on the basal plane. Besides, the phase transformation from 2H to 1T during the electrochemical lithium-ion intercalation could reach higher electronic conductivity, thus further optimize the HER kinetics through phase engineering. For these reasons, the desulfurized MoS2 displays improved HER activity with lowered overpotential of 200 mV to obtain 10 mA cm−2, high stability, decreased Tafel slope of 65 mV dec−1 and enhanced TOF of 0.093H2 s−1 at overpotential of 250 mV, which are much better than that of the pristine MoS2 and other optimized MoS2-based catalysts.

Lithium-Ion Intercalation by Calcium-Ion Addition in Propylene Carbonate-Trimethyl Phosphate Electrolyte Solution

Electrochemical intercalation of lithium ions was investigated in propylene carbonate (PC)-trimethyl phosphate (TMP) electrolyte solution. Intercalation of lithium ions took place in 1 mol dm−3 lithium bis(trifluoromethanesulfonyl)amide (LiTFSA)/PC:TMP by adding a certain amount of calcium ions. When the molar ratio of PC:TMP:Li+ was 6:6:1, lithium-ion intercalation took place when the molar ratio of Ca2+/Li+ was 1.2. The criteria was Ca2+/Li+ = 0.8 when the molar ratio of the electrolyte was PC:TMP:Li+ = 2:10:1. It was suggested from Raman spectra that the solvation structure of lithium ions were altered from the four coordinated tetrahedral configuration in the case that intercalation reaction occurred. This change in the lithium-ion solvation structure was caused by adding calcium ions, which has stronger Lewis acidity than lithium ions. Different criteria of Ca2+/Li+ molar ratio for lithium-ion intercalation by the difference of PC:TMP:Li+ molar ratio shows that the lithium-ion solvation structure was also affected by the electrolyte composition.

Electrochemical Behavior of Graphitized Carbon Nanospheres in a Propylene Carbonate-Based Electrolyte Solution

Electrochemical lithium-ion intercalation and deintercalation at carbonaceous materials in propylene carbonate (PC)-based electrolyte solution depends on the graphitization degree of the material. In this study, graphitized carbon nanospheres (GCNSs) heat-treated at 2900°C (GCNS-2900) and 2600°C (GCNS-2600) showed the reversible lithium-ion intercalation and deintercalation in PC-based electrolyte solutions, despite their high graphitization degree. Moreover, in situ Raman spectroscopy and transmission electron microscopy (TEM) were performed to further understand the electrochemical behavior. According to the Raman spectra, the cointercalation of PC with lithium ions and partial exfoliation was observed only in GCNS-2900. The TEM images revealed that GCNS-2900 exhibited structural collapses due to the concentration of stress in the ridges of a polyhedron during the graphitization process. Such collapses were responsible for the cointercalation of PC with lithium ions and partial exfoliation in GCNS-2900. The control of the graphitization degree, including the stacking order, suppression of edges and structural collapses, and a suitable arrangement of graphene layers should effectively suppress the destruction of graphite and improve the first coulombic efficiency in PC-based electrolyte solutions.

Electrochemical lithium intercalation chemistry of condensed molybdenum metal cluster oxide: LiMo4O6

The electrochemical lithium-ion intercalation properties of molybdenum metal-cluster oxide LixMo4O6 (0.33 ≤ x ≤ 1.0) in an organic electrolyte of 1.0M LiPF6 in ethylene carbonate/dimethyl carbonate (1:2v/v) were characterized for the first time. Li0.66Mo4O6 (tetragonal, P4/mbm, a = 9.5914(3) Å, c = 2.8798(1) Å, V = 264.927(15) Å3, Z = 2) was prepared via ion-exchange of indium and lithium ions from InMo4O6 (tetragonal, P4/mbm, a = 9.66610(4) Å, c = 2.86507(2) Å, V = 267.694(2) Å3, Z = 2), which was first synthesized from a stoichiometric mixture of In, Mo, and MoO3 via a solid-state reaction for 11h at 1100°C. Then, Li0.33Mo4O6 was obtained via electrochemical charge of the electrode at 3.4V vs. Li. The electrochemical lithium-ion insertion into Li0.33Mo4O6 occurs stepwise: three separate peaks were observed in the cyclic voltammogram and three quasi-plateaus in the galvanostatic profile, indicating a complicated intercalation mechanism. However, examination of the structural evolution of LixMo4O6 during the electrochemical cycle indicated a reversible reaction over the measured voltage range (2.0–3.2V) and x range (0.33 ≤ x ≤ 1.00). Despite the excellent electrochemical reversibility, LixMo4O6 showed poor rate performance with a low capacity of 36.3mAhg−1 at a rate of 0.05C. Nonetheless, this work demonstrates a new structural class of lithium cathode materials with condensed metal clusters and 1D tunnels, and provides a host material candidate for multivalent-ion batteries.

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

Understanding the Abnormal Capacity of Metal Hydroxide Anode Material for Next Generation Lithium Rechargeable Batteries

Graphitic carbon is extensively used as anode material in most of the commercial lithium-ion batteries (LIBs) due to its low cost and high coulombic efficiency. However, capacity of carbon anode (372mAh/g and 830mAh/mL) is limited by the reversible electrochemical intercalation of lithium ions in its structure. So, alternative research directions and different anode materials are currently being investigated with an aim to achieve high capacity and cycling stability. Recently nano-material research has shed light on many high performing materials. Among these, cobalt hydroxide has been recognized as one of the potential candidates for anode materials because of its novel electric and electrochemical properties[1]. Co(OH)2 with a sheet-like structure tends to form a layered assembly, thus it has the benefit of improved ion transport and better contact of electro-active materials with electrolyte. Several methods have been used to synthesize the hexagonal β-Co(OH)2 nano sheets including facile hydrothermal and homogeneous precipitation with sodium hydroxide as the alkaline reagent. Co(OH)2-Graphene Nano Sheet (GNS) composite was reported in 2010[2] as anode material for LIBs with superior electrochemical performance and its reaction mechanism was suggested as: Co(OH)2 + 2Li+ +2e- → Co + 2LiOH (577mAh/g). GNS acted as synergistic effect to synthesized material for achieving higher capacity (1120mAh/g) because GNS could relieve the volume expansion during cycling and also, give excellent electronic conductivity. Co(OH)2-nanosheets/ Co3O4-nanoparticle hierarchical structure has also been reported[3] as anode material for LIB’s with enhanced capacity and performance. However, unlike the composite materials, bare Co(OH)2 anode material still has trouble with showing good electrochemical performance for lithium ion batteries, which may be due to insufficient electrolyte soaking between layers and severe volume expansion during the cycling. Herein, we successfully synthesized colloidal silica assisted sheet-like nano-structured Co(OH)2 using cobalt (Ⅱ) nitrate hexahydrate (Co(NO3)2∙6H2O, 97%, m.p. 55 ̊C, Aldrich) as precursor through simple synthetic strategy. Even though synthesized nano-structured Co(OH)2 is not a composite material, shows excellent reversible capacity (~1000 mAh/g) during the electrochemical cycling beyond the theoretical capacity after the first irreversible discharge process, and exhibits excellent rate capability with a good cycle performance. This research also included its novel reaction mechanism during electrochemical cycling with lithium. Structural and electrochemical properties of synthesized material were studied by electrochemical tests and combination of the synchrotron radiation based X-ray diffraction (XRD)/ X-ray absorption spectroscopy (XAS) techniques. Changes in the bulk structure were studied by XRD whereas local structure changes around Co during cycling were systematically investigated by recorded XAS data. Based on these results, novel reaction mechanism about the nano-structured Co(OH)2 anode material during electrochemical cycling was suggested specifically. This finding will not only be helpful in a more complete understanding of the reaction mechanism of metal oxide based anode materials but also will offer valuable guidance for developing new anode materials with abnormal high capacity for next generation rechargeable batteries. More detailed discussion will be presented at the time of meeting. [1]. Huang, X.-l et al., Journal of Materials Chemistry, 2012. 22(9): p. 3764. [2]. He, Y.-S et al., Electronbbn chemistry Communications, 2010. 12(4): p. 570-573. [3]. Dong, Q et al., Materials Research Bulletin, 2011. 46(8): p. 1156-1162.

Unveiling the Reaction Mechanism of Metal Oxide Based Anode Materials with High Abnormal Capacity for Lithium-Ion Batteries By Using Synchrotron X-Ray Techniques

Graphitic carbon is extensively used as anode material in most of the commercial lithium-ion batteries due to its low cost and high coulombic efficiency. However, capacity of carbon anode (372mAh/g and 830mAh/mL) is limited by the reversible electrochemical intercalation of lithium ions in its structure. So, alternative research directions and different anode materials are currently being investigated with an aim to achieve high capacity and cycling stability. Recently, nano-material research has shed light on many high performing materials. Among these, metal oxide based materials such as SnO2, MoO2, Co(OH)2 have been recognized as one of the potential candidates for anode material of lithium–ion batteries because of its higher specific lithium storage capacity [1, 2, 3]. But, their poor capacity retention over long-term charge-discharge cycling due to low electrical conductivity has prevented its use as commercial anode material in lithium-ion batteries. Furthermore, during the electrochemical cycling, metal oxides typically break into small metal clusters, resulting in a large volume expansion and a loss of capacity [4]. For improving the performance of metal oxide based materials, nanostructured materials have received much attention as battery electrodes due to the short transport lengths for both electrons and Li ions, higher electrode-electrode contact area, and better accommodation of the strain of Li insertion/extraction [5]. Although there have been reports in the electrochemical behavior and performance improvement on metal oxide based anode materials for lithium ion batteries, it is still difficult to prove the reaction mechanism and abnormal capacity clearly. For accurate explanation of reaction mechanism and abnormal capacity, it is important to analyze each region systematically. Herein, we successfully synthesized nano-structured metal oxide materials through simple synthetic strategy. This research also included its novel reaction mechanism during electrochemical cycling with lithium. Structure and electrochemical properties of synthesized material were studied by diverse electrochemical tests, combination of the synchrotron radiation XRD and XAS techniques. Especially, the changes in the local structures during cycling were investigated systematically on the basis of XAS analysis. Based on these results, novel reaction mechanism about the nano-structured metal oxide based anode material during electrochemical cycling was suggested specifically. This finding will not only be helpful in a more complete understanding of the reaction mechanism of metal oxide based anode materials but also will offer valuable guidance for developing new anode materials with abnormal high capacity for next generation rechargeable batteries. More detailed discussion will be presented at the time of meeting. [1]. Dong, Q et al., Materials Research Bulletin, 2011. 46(8): p. 1156-1162. [2]. I. A. Courtney and J. R. Dahn, J. Electrochem. Soc., 1997, 144, 2045 [3]. Wang, Z. Y et al., Chem. Commun. 2010, 46, 6906−6908 [4]. Poizot, P et al., Nature 2000, 407, 496−499 [5]. Maier, J et al., Nat. Mater. 2005, 4, 805−815.

Effect of the Addition of Bivalent Ions on Electrochemical Lithium-Ion Intercalation at Graphite Electrodes

Electrochemical lithium-ion intercalation/de-intercalation at a graphite electrode were studied in propylene carbonate-based electrolyte solutions containing both lithium bis(trifluoromethanesulfonyl)amide and magnesium bis(trifluoromethanesulfonyl)amide salts by using lithium/graphite cell, and the influence of the salt concentration was investigated. In the higher concentration electrolyte solutions, reversible lithium-ion intercalation/de-intercalation at the graphite electrodes occurred. In contrast, only the exfoliation of graphite occurred in the lower concentration electrolyte solutions. The threshold ratio of the magnesium salt (Mg2+/Li+ = 0.9) was lower than that of the calcium salt (Ca2+/Li+ = 1.1).

The Novel Study on the Reaction Mechanism and Structural Changes of Co(OH)2 By Using Synchrotron X-Ray Techniques

Graphitic carbon is extensively used as anode material in most of the commercial lithium-ion batteries (LIBs) due to its low cost and high coulombic efficiency. However, capacity of carbon anode (372mAh/g and 830mAh/mL) is limited by the reversible electrochemical intercalation of lithium ions in its structure. So, alternative research directions and different anode materials are currently being investigated with an aim to achieve high capacity and cycling stability. Recently nano-material research has shed light on many high performing materials. Among these, cobalt hydroxide has been recognized as one of the potential candidates for anode materials because of its novel electric and electrochemical properties[1]. Co(OH)2 with a sheet-like structure tends to form a layered assembly, thus it has the benefit of improved ion transport and better contact of electro-active materials with electrolyte. Several methods have been used to synthesize the hexagonal β-Co(OH)2 nano sheets including facile hydrothermal and homogeneous precipitation with sodium hydroxide as the alkaline reagent. Co(OH)2-Graphene Nano Sheet (GNS) composite was reported in 2010[2] as anode material for LIBs with superior electrochemical performance and its reaction mechanism was suggested as: Co(OH)2 + 2Li+ +2e- → Co + 2LiOH (577mAh/g). GNS acted as synergistic effect to synthesized material for achieving higher capacity (1120mAh/g) because GNS could relieve the volume expansion during cycling and also, give excellent electronic conductivity. Co(OH)2-nanosheets/ Co3O4-nanoparticle hierarchical structure has also been reported[3] as anode material for LIB’s with enhanced capacity and performance. However, despite diverse studies on Co(OH)2 material, pure Co(OH)2 nanosheets still have poor cycling performance, which may be due to insufficient electrolyte soaking between layers and large volume changes during the cycling process. Besides, pure Co(OH)2 nanosheets show higher reversibly capacity beyond the reported mechanism. In order to improve the Co(OH)2 electrode performance, primary research should first be focused on the study of pure Co(OH)2 to better understand its reaction mechanism.Herein, we successfully synthesized colloidal silica assisted sheet-like nano-structured Co(OH)2 using cobalt (Ⅱ) nitrate hexahydrate (Co(NO3)2∙6H2O, 97%, m.p. 55C, Aldrich) as precursor through simple synthetic strategy. This research also included its novel reaction mechanism during electrochemical cycling with lithium. Structural and electrochemical properties of synthesized material were studied by electrochemical tests and combination of the synchrotron radiation based X-ray diffraction (XRD)/ X-ray absorption spectroscopy (XAS) techniques. Changes in the bulk structure were studied by XRD whereas local structure changes around Co during cycling were systematically investigated by recorded XAS data. Based on these results, we propose novel reaction mechanism of the nano-structured Co(OH)2 material during electrochemical cycling. More detailed discussion will be presented at the time of meeting.[1]. Huang, X.-l et al., Journal of Materials Chemistry, 2012. 22(9): p. 3764.[2]. He, Y.-S et al., Electronbbn chemistry Communications, 2010. 12(4): p. 570-573. [3]. Dong, Q et al., Materials Research Bulletin, 2011. 46(8): p. 1156-1162.

The Newly Observed Reaction Mechanism of Mesoporous SnO2 Electrode Investigated by Synchrotron X-ray Techniques

Graphitic carbon is widely used as anode material due to its low cost, good cycle life, and very stable capacity in most commercial lithium-ion batteries (LIBs). However, capacity of carbon anode (372mAh/g and 830mAh/mL) is limited by the reversible electrochemical intercalation of lithium ions in its structure. So, the search of new anode material has been ongoing to achieve the higher capacity. SnO2 has been widely studied in the last decade as one of the potential candidates for anode materials due to its higher specific lithium storage capacity (783mAh/g). [1, 2] But, its poor capacity retention over long-term charge-discharge cycling has prevented its use as commercial anode material in LIBs. This problem has been associated with its alloying reaction which results in large volume changes of electrode material during electrochemical cycling. Also, an irreversible conversion reaction occurs prior to the alloying reaction, which results in the reduction of SnO2 to Sn and formation of a non-decomposable Li2O matrix. Although there have been reports in the electrochemical behavior and performance improvement on SnO2as anode materials for Li-ion batteries, it is still difficult to prove the reaction mechanism and abnormal capacity clearly. For accurate explanation of reaction mechanism and abnormal capacity, it is important to analyze each region systematically.We studied mesoporous SnO2 electrode material because of its higher abnormal capacity. Mesoporous SnO2 was synthesized by sol-gel method by using the KIT-6 template. SEM & EDS were used to confirm the successful synthesis of this electrode material. Additionally, we performed diverse electrochemical tests such as EIS, GITT and cyclic voltammetry. The first discharge capacity of mesoporous SnO2 was 2009.60mAh·g-1 and the charge capacity was 1048.43 mAh·g-1. Compared with the theoretical specific capacity, the extra discharge capacity was associated with the formation of a solid electrolyte interphase (SEI) layer generated by an irreversible insertion/extraction of Li-ions into host structures or Li alloying reactions and by possible interfacial Li storage. In this work, we have tried to explain the electrochemical reaction mechanism of meso-porous SnO2 by using ex situ X-ray Diffraction (XRD) and X-ray Absorption Spectroscopy (XAS) during cycles. Before the experiment, we were subdividing points in discharge/charge curves. Fig. 1 (a) shows ex-situ XRD patterns during first discharge of mesoporous SnO2 which clearly show that SnO2 structure changed into amorphous phase after point 4. Upon discharging below 0.2V amorphous SnO2 phase converts into metallic phases which are indicated by broad peaks around 22 and 38 degree. To further study the mechanism we carried out ex-situ XAS measurements on mesoporous SnO2 anode samples (Fig. 1 (b)). The peaks at 1.59Å and 2.60Å in the Fourier transform spectrum of extended X-ray absorption fine structure (EXAFS) represent Sn-O bond and Li-Sn bonds, respectively. [3] Irreversible capacity during first cycle of SnO2 is related to conversion reaction and Li4.4Sn is formed as a product of alloying reaction. Sn-O peak intensity was decreased gradually by progressing discharge and Li- Sn peak was revealed by alloying reaction after point 3. Moreover, through the EXAFS data of the first charge, we can verify the existence of Sn-O bond of conversion reaction at the last region and conversion reaction is associated with capacity of mesoporous SnO2after initial discharge. These results were related to high abnormal capacity of mesoporous SnO2 and more detailed discussion will be presented at the time of meeting.1. I. A. Courtney and J. R. Dahn, J. Electrochem. Soc., 144, 2045 (1997)2. I. A. Courtney and J.R. Dahn, J. Electrochem. Soc.,144, 2943 (1997) 3. A. N. Mansour, S. Mukerjee, X. Q. Yang and J. McBreen, J. Electrochem. Soc., 147, 869 (2000)

Mesoporous lithium vanadium oxide as a thin film electrode for lithium-ion batteries: comparison between direct synthesis of LiV2O5 and electrochemical lithium intercalation in V2O5

γ-LiV2O5 and α-V2O5 mesoporous thin films are prepared by a soft-templating route to compare the electrochemical performances of as-synthesized LiV2O5 with the in situ electrochemical intercalation of lithium ions in α-V2O5.

Electrochemical lithium ion intercalation into graphite electrode in propylene carbonate-based electrolytes with dimethyl carbonate and calcium salt

Electrochemical intercalation of Li+ ions into graphite electrodes in propylene carbonate (PC)-dimethyl carbonate (DMC)-based electrolytes containing Ca2+ ions was studied. The molar ratio of PC, Li+ ion, and Ca2+ ion was PC:Li+:Ca2+ = 12:1.0:0.5. Intercalation of Li+ ions became possible by adding DMC to the PC-based electrolytes containing Ca2+ ions: Li+ ion intercalation did not take place when the amount of DMC was DMC/PC = 6 (molar ratio) and below, and Li+ ions intercalated when the amount of DMC was above DMC/PC = 8. Intercalation of Li+ ions did not take place in PC-DMC-based electrolyte of no Ca2+ ions, and both Ca2+ ion and DMC were necessary for Li+ ion intercalation. Successful Li+ ion intercalation can be attributed to smaller solvation number of PC on Li+ ions by addition of DMC and Ca2+ ions to the PC-based electrolyte.

Synthesis and Electrochemical Behavior of LiTi2(PO4)3 as Anode Materials for Aqueous Rechargeable Lithium Batteries

Electrochemical intercalation of lithium ions into LiTi2(PO4)3 prepared by sol-gel method in 1 M Li2SO4 aqueous electrolyte solution was studied with cyclic voltammetry (CV), galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS). It was found that there was one step of intercalation for LiTi2(PO4)3 anode in the presence of aqueous electrolyte, corresponding to a pair of redox peak at ESCE = −0.67/−0.86 V. The initial discharge capacity of the LiTi2(PO4)3‖LiMn2O4 cell is 44.41 mAh g−1, the capacity retention of 67.3% after 60 cycles. The EIS for LiTi2(PO4)3 electrode consisted of two semicircles in the aqueous electrolyte, which were attributed to Schottky contact resistance and charge transfer process, respectively.

Electrochemical Intercalation of Lithium-Ion in Propylene Carbonate Based Electrolytes ― Effect of Addition of Bivalent-Ions ―

not Available.

Electrochemical lithium ion intercalation in Li0.5Ni0.25TiOPO4 examined by in situ X-ray diffraction

The complex structural transformations of Li0.5Ni0.25TiOPO4 during electrochemical lithiation have been examined by in situ X-ray diffraction. During the first lithiation two structural changes take place: first a transition to a second monoclinic phase (a=9.085(4), b=8.414(5), c=6.886(5), β=99.85(4)) and secondly a transition to a third phase with limited long-range order. The third phase is held together by a network of corner sharing Ti–O octahedra and phosphate ions with disordered Ni–Li channels. During delithiation the third phase is partially transformed back to a slightly disordered original phase, Li0.5Ni0.25TiOPO4 without formation of the second intermediate phase. These phase transitions correspond well to the different voltage plateaus that this material shows during electrochemical cycling.

Investigation of the Lithium Intercalation Behavior of Nanosheets of LiV3O8 in an Aqueous Solution

Nanosheets of lithium vanadium oxide (LiV3O8) are synthesized using a citrate sol–gel combustion route. The physical characterizations are carried out by scanning and transmission electron microscopies (SEM and TEM) and X-ray diffraction (XRD) measurements. Compact nanosheets of the active material are observed by SEM and TEM. XRD data indicate that the prepared nanosheets present pure phase of monoclinic LiV3O8 with p21/m symmetry. The kinetics of electrochemical intercalation of lithium ion into the nanosheets are investigated by cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) studies with special emphasis on the application potential as an anodic material for aqueous rechargeable lithium batteries. CV studies of the nanosheets at a slow scan rate of 0.3 mV s–1 between +250 and −700 mV vs Ag/AgCl demonstrate that nanosheets of LiV3O8 represent well-defined reversible peaks. The nonlinear chemical diffusion of lithium ion into the nanosheets is explored by EIS. The results are discussed on the basis of an equivalent circuit, distinguishing the kinetics of lithium intercalation. The fitting results are in good agreement with the experimental results, and the kinetic parameters of lithium intercalation are obtained with the proposed equivalent circuit. The changes of kinetic parameters of lithium intercalation with potential are also discussed in detail.

An aqueous rechargeable lithium-ion battery based on LiCoO2 nanoparticles cathode and LiV3O8 nanosheets anode

Nanoparticles of lithium cobalt oxide (LiCoO2) and nanosheets of lithium vanadium oxide (LiV3O8) were synthesized by a citrate sol–gel combustion route. The physical characterizations of the electrodic materials were carried out by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and also X-ray diffraction (XRD) measurements. Near spherical nanoparticles of ≈100 nm and compact nanosheets with a few nanometers thick were observed by SEM and TEM for LiCoO2 and LiV3O8, respectively. XRD data indicated that the as-prepared active materials presented pure phase of rhombohedral LiCoO2 with R-3m symmetry and monoclinic LiV3O8 with p21/m symmetry. The kinetics of electrochemical intercalation of lithium ion into the nanoparticles of LiCoO2 and nanosheets of LiV3O8 from 1.0 mol l−1 LiNO3 aqueous solution were investigated by cyclic voltammetry and chronoamperometry. An aqueous rechargeable lithium-ion battery consisting of LiCoO2 nanoparticles as positive and LiV3O8 nanosheets as negative electrode was assembled. This battery represented a discharge voltage of about 1 V with good cycling performance.

Role of Edge Orientation in Kinetics of Electrochemical Intercalation of Lithium-Ion at Graphite

A relation between the amount of edge orientations and the kinetics of lithium-ion intercalation at the basal plane of highly oriented pyrolytic graphite (HOPG) was studied. The fraction of edge orientations (f(edge)) exposed on the basal plane of HOPG was evaluated from the kinetics of heterogeneous electron transfer of Ru(NH(3))(6)(2+/3+). Obtained f(edge) values ranged from 0.025 to 0.067, which were in good agreement with those previously reported. The charge-transfer resistance (R(ct)) for lithium-ion intercalation at the same HOPG samples was evaluated by ac impedance spectroscopy in an electrolyte consisting of 1 mol dm(-3) LiClO(4) dissolved in a mixture of ethylene carbonate/dimethyl carbonate (1:1 by vol). A clear correlation was observed between the f(edge) and R(ct) values at the basal plane of 15 HOPG samples, and the edge-area specific resistance was evaluated to be ca. 200 Ω cm(2) at the electrode potential of 0.2 V versus Li/Li(+). These results indicate that the amount of edge orientations is one of the determining factors in the kinetics of lithium-ion intercalation at graphite.