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Surface-modified LiNi0.8Co0.1Mn0.1O2 cathode with different coating amounts of SiO2 (0.25–1 wt%) is successfully synthesized and its electrochemical performances are investigated. Compared to bare LiNi0.8Co0.1Mn0.1O2, the 0.25 wt% SiO2 coated LiNi0.8Co0.1Mn0.1O2 delivers an initial capacity of 200.7 mAh g−1 as well as the excellent cyclability (capacity retention of 87.3% after 100 cycles at 0.5C) and rate capability (82.2% at 2C). Furthermore, 0.25 wt% SiO2 coated LiNi0.8Co0.1Mn0.1O2 exhibits the stable cycle performance at 55 °C (84.5% after 100 cycles at 0.5C). Such improvements are attributed to the SiO2 coating, which can suppress the irreversible phase transformation and play a role in obstacle to protect the LiNi0.8Co0.1Mn0.1O2 from electrolyte.

The realisation of fast-charging lithium-ion batteries with long cycle lifetimes is hindered by the uncontrollable plating of metallic Li on the graphite anode during high-rate charging. Here we report that surface engineering of graphite with a cooperative biphasic MoOx–MoPx promoter improves the charging rate and suppresses Li plating without compromising energy density. We design and synthesise MoOx–MoPx/graphite via controllable and scalable surface engineering, i.e., the deposition of a MoOx nanolayer on the graphite surface, followed by vapour-induced partial phase transformation of MoOx to MoPx. A variety of analytical studies combined with thermodynamic calculations demonstrate that MoOx effectively mitigates the formation of resistive films on the graphite surface, while MoPx hosts Li+ at relatively high potentials via a fast intercalation reaction and plays a dominant role in lowering the Li+ adsorption energy. The MoOx–MoPx/graphite anode exhibits a fast-charging capability (, Fast-charging of lithium-ion batteries is hindered by the uncontrollable plating of metallic Li on the graphite anode during cycling. Here, the authors demonstrate the fast chargeability and long cycle lifetimes via surface engineering of graphite with a cooperative biphasic MoOx–MoPx promoter.

Li-metal has steadily gained attention as one of the promising next-generation anode materials because of its exceptional specific capacity and low operating potential that can significantly increase the energy density of batteries beyond those of the state-of-the-art Li-ion batteries. Nevertheless, the use of Li-metal is still faced with the challenge of uncontrollable dendrite growth that ceaselessly causes parasitic reactions, further impeding the practical use of Li-metal batteries. To circumvent this limitation by using a structural approach, herein, we report a 1D hollow carbon fiber incorporating lithiophilic Au nanoparticles (Au@HCF) as a promising Li host that is fabricated by scalable dual-nozzle electrospinning. Due to its well-defined 1D electronic conducting pathways for reducing the effective current density as well as the hollow core for confining Li-metal, Au@HCF can mitigate Li dendrite growth on the top surface and stabilize the solid-electrolyte interphase layer, thereby achieving a high Coulombic efficiency of 99–99.9% under 1 mA cm−2 and 2 mAh cm−2. Moreover, the LiFePO4 full cell combined with the Au@HCF anode containing predeposited 2 mAh cm−2 Li showed considerably improved cycle life of over 380 cycles, indicating that the design concept for the Li-confinable structure can be an excellent option for realizing emerging Li-metal batteries.

Polycrystalline tetragonal and cubic with garnet related type structured Li 7 La 3 Zr 2 O 12 (LLZO) has been successfully synthesized at 700 °C (tetragonal) and 1100 °C (cubic), respectively by modified polymer complex synthesis. Citric acid was used for a chelating agent and ethylene glycol was applied for polymer complex agent. Thermal analysis indicated that the crystallization has been completed at the low temperature in case of applying high energy ball-milling process. It is presumed that applied mechano-chemical energy promotes the earlier crystallization at lower temperature, which induces the reduction of particle size effectively. LLZOs with tetragonal and cubic phase showed ionic conductivities of 6.2 × 10 −7 Scm −1 and 1.4 × 10 −4 Scm −1 , respectively. Prepared LLZO powders, having relatively small size, are expected to provide the large surface area for Li-ion conducting path in the design of all solid electrodes.

Mo 0.8 Si 0.2 P 2 was synthesized via a simple mechanical milling method to improve the electrochemical properties of MoP 2 . It was found that Si ion was successfully doped and well dispersed on pristine MoP 2 layered structure without any structure changes. The electrochemical properties of Mo 0.8 Si 0.2 P 2 anode were increasingly improved. It showed a higher initial charge capacity of 783 mA h g −1 and better cycle retention rate of 93.2% compared with the MoP 2 alloy anode, respectively. When lithium uptake in Mo 0.8 Si 0.2 P 2 anode during the first discharge process, silicon was partially decomposed and well dispersed in sustained Mo 0.8 Si 0.2 P 2 structure. Partially decomposed Si in Mo 0.8 Si 0.2 P 2 act as electrochemically alloying material for increasing the reversible capacity, whereas sustained Mo 0.8 Si 0.2 P 2 serve as host material with lithium intercalation reaction and prevent to aggregation of decomposed silicon.

Sn 3.95 Fe 0.05 P 3 alloy was synthesized via a solvothermal method, using tin metal, iron metal and amorphous red phosphorous. The XRD and TEM results showed that Fe ion was successfully substituted on original the Sn 4 P 3 layered structure without any structure changes. The Sn 3.95 Fe 0.05 P 3 alloy anode showed a higher initial charge capacity and coloumbic efficiency of 1304 mAh g −1 and 73% compared with the Sn 4 P 3 alloy anode, respectively. Additionally, a relatively large capacity of about 420 mAh g −1 after 100th cycles was achieved in the Sn 3.95 Fe 0.05 P 3 anode, whereas the capacity of the Sn 4 P 3 anode remained at only about 100 mAh g −1 after 100 cycles. Fe atoms as an inactive matrix could be dispersed between the tin atoms, resulting in the suppression of tin agglomeration in Sn 3.95 Fe 0.05 P 3 during cycling. It is confirmed from the voltage profile and differential capacity plots that the Fe ion in the Sn 3.95 Fe 0.05 P 3 structure could stabilize the structure and improve the electrochemical properties during cycling.

Recently, there is a growing demand for high-energy lithium ion batteries in order to apply to electric vehicles, hybrid electric vehicle, uninterruptible power supplies and portable devices. The cathode active material of three component layered LiNixCoyMnzO2 (NCM, 0≤x, y, z In this paper, we prepared SiO2 coated LiNi0.8Mn0.1Co0.1O2 cathode and investigated the effect of SiO2 coating layer on the electrochemical performances and thermal behavior. The SiO2 coated LiNi0.8Mn0.1Co0.1O2 cathode delivers outstanding electrochemical performances. Therefore, we believe that SiO2 coated LiNi0.8Mn0.1Co0.1O2 cathode is beneficial approach for high performance and reliability lithium ion batteries. SiO2 coated LiNi0.8Mn0.1Co0.1O2 delivers high initial capacity of 200.7 mAh g-1 as well as the excellent cycleability (capacity retention of 87.3 % after 100 cycles at 0.5 C) and rate capability (82.2% at 2C). Such improvements are attributed to the SiO2 coating, which can suppress the irreversible phase transformation and play a role in obstacle to protect the LiNi0.8Mn0.1Co0.1O2 from electrolyte.

To enhance the electrochemical properties of the Sn3.95Fe0.05P3 anode, we focus on reducible additives to mitigate damage to the anode by electrolyte decomposition. It is found that the the electrochemical performance of the anode is significantly improved when formulated with an FEC-added electrolyte. Ex-situ X-ray photoelectron spectroscopy (XPS) reveals that the FEC additive builds an LiF-based solid electrolyte interphase (SEI) with less organic species on the anode upon cycling. Keywords: Lithium-ion batteries, Tin phosphide, Solid electrolyte interphase, Electrolyte additive

A novel energy storage system employing a KS-6 graphite cathode and niobium (V) oxide (Nb 2 O 5 ) anode was developed with a 1:1 weight ratio of cathode to anode. The cell, with a voltage range of 1.5–3.5 V, showed higher capacity and better cycle performance than those of cells with other voltage ranges. At 1C and 35C rates, this cell delivered 57 and 26 mAh g −1 , respectively. A graphite cathode can be increased to approximately 5.2 V, which is well above the LIB cathode material, without causing safety issues, and the operating voltage of the Nb 2 O 5 anode was greater than that of the lithium deposition voltage. In situ X-ray diffraction results at various states of charge indicated that the mechanism of this energy storage system was intercalation and de-intercalation of PF 6 − and Li + in the KS-6 graphite cathode and in the Nb 2 O 5 anode. This novel energy storage system was inherently safe because 1) no oxygen is released from cathode materials, 2) no lithium dendrite is used at the anode, and 3) there was no possibility of overcharge from the electrode/electrolyte reaction.

The performance of a lithium-ion battery (LiB) fabricated with a tin-phosphate glass anode was studied as well as the characteristics of the anode. It was confirmed that the total positive charge of Sn2+ ions in the glass anode is compensated by a reaction with lithium during the first charge by forming tin crystals. It was observed after the first charge that the glass is converted into a nanocomposite in which the metallic crystals are embedded in an amorphous lithium phosphate matrix. A half-cell fabricated with the glass anode showed a reproducible capacity of 550 mAh/g at room temperature, which was much higher than that of the cell with a graphite anode. The cell also showed a steady capacity of 160 mAh/g even at −20°C with no deposition of lithium dendrites. A full-cell fabricated with the glass anode and LiMn2O4 cathode showed a good life cycle performance at 60°C along with no degradation in its life cycle performance. The tin-phosphate glass is a promising candidate as a new anode material that realizes LiBs with a high energy density that can be used over a wide temperature range.

a b s t r a c t The performance of the graphite (KS-6)/MoO3 full cell has been studied at different cut-off voltages, rates, temperatures and cathode to anode mass ratios. It was found that cathode to anode weight ratio and charging potential are the most influential parameters which determine the cycle life of this device. Under optimized condition (graphite:MoO3 weight ratio 1 and operation voltage window 1.5-3.3 V), the capacity retention of the cell between the 5th and 500th cycles was found to be 91%. At 0.3 C and 10 C rates this device delivers 88.9 mAh g −1 and 35.5 mAh g −1 , respectively. High and low temperature performance of this device is superior to that of the conventional EDLCs. The charge/discharge mechanism of the full cell was elucidated by ex situ XRD data and analyzing the voltage profiles of each electrode by 4-electrode cell. Partial amorphization of the MoO3 anode was confirmed by XRD and SEM data. These results indicate that the electrolyte could be used as the sole source of lithium ions to develop a novel type of energy storage devices which do not contain traditional lithium rich cathode materials. © 2011 Elsevier B.V. All rights reserved.

The electrochemical properties of graphite with various degrees of graphitization, contents of rhombohedral phase, and surface areas were electrochemically investigated at 25 °C and −5 °C. The degree of graphitization and the amount of rhombohedral phase affected the samples’ lithium intercalation/deintercalation and surface deposition. The reductions of electrolyte conductivity and lithium ion diffusion in the graphite interlayer at −5 °C lowered the graphite's capacity. Lithium deposition also occurred on the graphite's surface. Highly graphitized samples were affected greatly by temperature, showing large capacity loss at low temperature. Increased rhombohedral phase facilitated lithium deposition on the graphite's surface as lithium ions did not insert into the graphite interlayers and accumulated at its edged planes. Increasing the pathways for lithium ion intercalation could facilitate lithium intercalation and reduce lithium deposition.

Glass-ceramic LiFePO 4 was synthesized through the crystallization of glass powder prepared by melting low-cost raw materials in ambient air. To obtain the homogeneous precursor glass, the addition of a small amount of Nb 2 O 5 was effective. Ferric ions in the precursor glass were reduced and precipitated as LiFePO 4 through the heat treatment of a mixture of the glass powder and a carbon source. The obtained glass-ceramic particles contained a LiFePO 4 crystalline phase and a carbon-containing surface amorphous layer with a thickness of about 20 nm. A lithium-ion rechargeable battery fabricated with the glass-ceramic powder showed better high-rate performance than that of a battery made using commercial LiFePO 4 ceramic powder. The better performance of the battery with the glass-ceramic is attributed to the existence of the surface amorphous layer. This synthesis process, consisting of glass melting in air and the subsequent crystallization of glass powder, has the potential to be used for the large-scale continuous production of high-performance LiFePO 4 .

10 wt.% carbon-coated natural graphite (NC-10) is prepared by thermal vapor deposition. The carbon coating is electrochemically investigated at −5 °C; it improves lithium intercalation in the graphite's interlayer spacing. NC-10 graphite clearly shows 3 voltage plateaus and a higher capacity during the first charge/discharge cycle at −5 °C than uncoated natural graphite. XRD study of the electrode after the first charging shows increased lithium intercalation into the graphite layers and also suppression of lithium deposition on the graphite's surface. Due to the homogeneous potential profile on the graphite surface, carbon coating enhance lithium intercalation at −5 °C. In addition, NC-10 shows less lithium deposition on the surface than bare natural graphite.

A novel electrode of nickel-doped mesoporous carbon (NMC) is prepared from furfuryl alcohol and firstly developed for use in electrochemical capacitors. The electrochemical performance of NMC/AC capacitor is systematically investigated and characterized by BET and BJH methods for determining surface area and pore size distribution, respectively. This new NMC/AC shows a high specific capacitance, high energy and power density due to its large surface area and bulk conductivity. Its electrochemical characteristics are investigated through cyclic voltammetry (CV), electrochemical impedance spectroscopy and charge–discharge (C/D) tests. The NMC/AC has a specific capacitance of 144.3 Fg−1, higher than that of a pure activated carbon (AC)-based EDLC (ca. 105 Fg−1). It can be a promising candidate for a new energy storage material for supercapacitor.

A cell employing a graphite cathode and a molybdenum (VI) oxide (MoO3) anode is investigated as a possible energy storage device. Graphite cathode allows raising the voltage well above the cathode materials of LIBs without causing safety issues. The bottom potential of this anode is 2.0 V vs. Li/Li+, which is well above the lithium plating potential. Pulse polarization experiment reveals that no lithium deposition occurs, which further enhances the safety of the graphite/MoO3 full cell. Charge/discharge mechanism of this system results from intercalation and de-intercalation of the PF6− in the cathode (KS-6) and Li+ in the anode (MoO3). This mechanism is supported by in situ X-ray diffraction data of the graphite/MoO3 cell recorded at various states of charge.

Transition metal oxides in the nano size region are enormous attention as a new generation of anode materials for high energy density Li-ion batteries. MgFe2O4 is used for the first time as active electrode vs. lithium metal in test cells. The research has been focused on the effect of grain size of MgFe2O4 and their electrochemical performance studied. In this studies, nanostructured milled MgFe2O4 (grain size 19 nm) sample have been compared with relatively large-sized as-prepared sample (grain size 72 nm). From the result, the 19 nm grain size sample delivered an improved discharge capacity of around 850 mAh/g, whereas it is only 630 mAh/g for as-prepared sample (72 nm). These values are two times higher than that of a carbon anode (372 mAh/g). The anomalous capacity may be associated with the formation of oxygen rich MgFe2O4 samples.

A graphite/TiO2 full cell has been developed as a new safety energy storage system using a highly safety process. The crystal structures of the anatase TiO2 electrode have been investigated with respect to the performance of the electrodes. Due to the large anion intercalation into the graphite positive electrode. the possible charging potential can be raised to around 5 3 V against the Li/Li+ electrode, which is a higher charging voltage than lithium-ion batteries (maximum voltage is around 43 V vs Li/Li+). In situ XRD measurements have been carried out on both the cathode and anode electrodes of the graphite/TiO2 cell during the charge process to elucidate the intercalation mechanism. (C) 2010 Elsevier Ltd All rights reserved

Nanoscale carbon-coated Li2MnSiO4 powder is prepared using a conventional solid-state method and can be used as the negative electrode in a Li2MnSiO4/activated carbon (AC) hybrid supercapacitor. Carbon-coated Li2MnSiO4 material presents a well-developed orthorhombic crystal structure with a Pmn21 space group, although there is a small impurity of MnO. The maximum specific capacitance of the Li2MnSiO4/AC hybrid supercapacitor is 43.2 F g−1 at 1 mA cm−2 current density. The cell delivers a specific energy as high as 54 Wh kg−1 at a specific power of 150 W kg−1 and also exhibits an excellent cycle performance with more than 99% columbic efficiency and the maintenance of 85% of its initial capacitance after 1000 cycles.

To meet the high current load requirement from the high energy density realized by metal oxide and high power density graphite, we propose a novel hybrid supercapacitor consisting of Nb2O5 and KS6 graphite in 1.0 M LiPF6-EC:DEC (1:2). This new system exhibits a sloping voltage profile from 2.7 to 3.5 V during charging and presents a high operating voltage plateau between 1.5 and 3.5 V during discharging. The cell was tested at a current density of 100 mA/g with a cut-off voltage between 3.0 and 1.0 V. This novel energy storage system delivers the highest initial discharge capacity of 55 mAh/g and exhibits a good cycle performance.

1,3-Propane sultone (PS) additive for graphite electrodes was studied for propylene carbonate (PC) and ethylene carbonate (EC)-based electrolytes in lithium batteries. Decomposition of solvents with graphite electrodes could be remarkably suppressed by addition of the PS additive in the PC-based electrolyte, leading to improvement of electrochemical performances of the cells. The 1,3-propane sultone additive showed very interesting properties for the graphite electrode. It is predicted to give a solid electrolyte interphase (SEI) on the surface of the graphite prior to solvent decomposition and bring about effects that not only suppress lithium deposition on the graphite electrode surface, but also accelerate lithium intercalation, leading to formation of LiC 6 onto graphite electrode.

Lithium deposition on graphite anodes is considered as a main reason for failures and safety for lithium ion batteries (LIB). Different amounts of carbon coating on the surface of natural graphite are used in this work to suppress the amount of lithium deposited at −10 °C. Pulse polarization experiments reveal relative polarization of graphite anodes at various temperatures and show that lithium deposition is accelerated at lowered temperatures. Electrochemical experiments, along with photographs, scanning electron microscopy (SEM) images and ex-situ X-ray diffraction (XRD) data suggest that carbon coating not only suppresses the lithium deposition but also enhances the formation of LiC6 at −10 °C. The homogeneous potential profile on the graphite surface attained by the carbon coating explains such an improved low temperature performance, as it allows efficient Solid Electrolyte Interface (SEI) film formation, which is a prerequisite for safety LIB. Keywords: Safety of graphite anode, Carbon coating, Lithium deposition, Pulse polarization

LiFePO4 material was synthesized at 670 °C in an Ar atmosphere using a sol–gel method. This material showed a well developed XRD pattern (orthorhombic structure, Pnma) without any peaks at 2θ = 41°, indicating the absence of FeP or metallic Fe2P impurities. The Li/LiFePO4 cell showed a high initial discharge capacity of more than 150 mA h/g and no capacity decrease until the 70th cycle (>99.9%). This cell also exhibits excellent cycle performance at high current densities of over 30C, without any surface treatment or carbon coating onto the LiFePO4 particles. Keywords: LiFePO4, High rate capability, Sol–gel, Cathode material, Lithium secondary battery

The electrochemical behavior of nanocrystalline MgFe2O4 as anode material for lithium ion batteries is characterized by electrochemical impedance spectroscopy and cyclic voltammetry.

The current level of performances of Lithium Ion Batteries (LIBs) is not enough to meet commercial demands for new applications(xEV, ESS), in particular, with respective to energy density. Graphite and hard carbons are commonly used as a negative electrode material for LIBs, but higher-capacity alternatives are being consistently sought due to their limited capacity as an anode material of next generation LIBs for large-scale power applications. Recently, various Si, and Sn based compound including transition metal oxide, multiphase alloy, and intermetallic compounds have been extensively studied as alternatives to the existing carbon based anode material. These materials show much higher capacities than those of carbonaceous material. However, they are suffering from huge lattice volume change (4.4Li+Si ® Li4.4Si, ΔV>300%) through conversion reaction mechanism during Li insertion, which results in poor cycle life of LIBs. In this respect, metal phosphides have been alternatively suggested as a promising anode material for their reversibility, and large amount of lithium uptake at relatively low potential. It is not clarified yet until now, but the electrochemical reaction in metal phosphides with lithium might be classified into two reaction mechanisms, depending on electronegativity difference between metal and phosphorous atoms. Obviously, the large difference in electronegativity between constituting elements inevitably brings about decomposition of host composition (structure) with lithium intercalation, which can be readily understood by considering the Gibbs formation free energy. Even if being composed of elements with the very small difference in electronegativity, however, the reaction mechanisms are different with chemical stoichiometry of metal phosphides (MPx). In case of SnPx (Electronegativity : Sn=1.96, P=2.19) intermetallic compounds, the SnP0.75 equilibrium phase shows typical conversion reaction mechanism, on the other hand, SnP0.94metastable phase has been observed to be on intercalation reaction mechanism during lithiation process [1,2]. In this work, we have investigated the reaction mechanism of MoPx(Electronegativity : Mo=2.16, P=2.19) with various stoichiometry, relating with electrochemical properties. We finally propose newly designed metal phosphide with ternary composition showing topotatic reation. References [1] Young-Ugk Kim, Churl Kyung Lee, Hun-Joon Sohn, and Tak Kang, Journal of The Electrochemical Society, 151 (2004) A933-A937 [2] Youngsik Kim, Haesuk Hwang, Chong S. Yoon, Min G. Kim, and Jaephil Cho, Adv. Mater.19 (2007) 92–96

Introduction Recently, metal phosphides have received much attention as anode material for lithium ion batteries due to high reversible capacity at relatively low potential.[1] However, most MPx suffers from a relatively large irreversible capacity due to the decomposition of LixM, LixP, and metal during cycling. In order to improve the electrochemical properties, ternary M-M’-P system have been suggested and some of them prove to be effective in improving the cycle performance. [2] Cho et. al. reported the electrochemical properties and reaction mechanism of nanoparticle cluster MoP2 anode. [3] It showed high reversible capacity and good cycle performance at limited voltage range. However, upon increasing voltage, the capacity decreases rapidly, suggesting that MoP2 decomposed to Mo and LiPnphase. Here, we developed a novel Si-substituted MoP2 (Mo0.8Si0.2P2) alloy to increase the reversible capacity and enhance the cycle performance. We investigated the differences in physical and electrochemical properties between MoP2 and Mo0.8Si0.2P2 anode, examined using powder X-ray diffraction, SEM, and TEM, and galvanostatic charge-discharge test. We also investigated the volume expansion of MoP2 and Mo0.8Si0.2P2 alloys during cycling, considering the influence of substitution of Si into MoP layers in MoP2alloy. Experimental Orthorhombic Molybdenum Phosphide (MoP2) and Si-substituted Molybdenum Phosphide (Mo0.8Si0.2P2) were synthesized by mechanical-ball milling method. The physical properties were examined by powder XRD, SEM, HR-TEM and EDX. The electrochemical characterizations were performed using a CR2032 coin-type cell. The electrodes were prepared by mixing 75 wt% active material, 10 wt% Super P conducting agent, and 15 wt% PAA binder dissolved in NMP. The cells were made of a lithium metal anode separated by polypropylene film. The electrolyte was a mixture of 1M LiPF6-ethylene carbonate (EC)/diethylene carbonate (DEC)/dimethyl carbonate (DMC) (3:5:2 by vol) with 10 wt% fluroethylene carbonate (FEC). The charge and discharge rate was both 0.1C (0.3 mA/cm2) with a cut-off voltage of 5 ~ 1200 mV. Results and Discussion Fig. 1 shows the typical XRD results of MoP2 and Mo0.8Si0.2P2 alloy powders prepared by mechanical milling method. All peaks of MoP2 and Mo0.8Si0.2P2 could be indexed as the Orthorhombic MoP2 phase of Cmc21 (JCPDS#00-016-0499). The lattice constants of Mo0.8Si0.2P2 show smaller than those of pristine MoP2 because of substitution of smaller Si ion. The broad peak at 2θ = 22oindicated the residue amorphous red P. Fig. 2 shows the cycle performance of the Li/MoP2 and Li/Mo0.8Si0.2P2 half cells at 0.1C rate with voltage region from 1200 to 5 mV. The Mo0P2 anode showed a specific capacity of 655 mAhg-1 in the first charge process and showed a capacity retential rate of 88 % after 100 cycles. Conversely, the Mo0.8Si0.2P2exhibited much higher initial capacity of 783 mAhg-1better cyclic retention rate of 93.2 % after 100 cycles. Acknowledgement This study was supported by a National Research Foundation of Korea Grant funded by the Korean Government (MEST) (NRF-2011-C1AAA001-0030538). References 1. D. C. S. Souza, V. Pralong, A. J. Jacobson, L. F. Nazar, Science 296, 2012 (2002). 2. G. Park, C. Lee, J. Lee, J. Choi, Y. Lee, S. Lee, J. Alloys compd. 585, 534 (2014). 3. M. Kim, S. Lee, C. Cho, J. Electrochem. Soc. 156, A89 (2009).

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LiCoPO4 and Li1.02(Co0.9Fe0.1)0.98PO4 were prepared by conventional solid state reactions. The surface modification of Li1.02(Co0.9Fe0.1)0.98PO4 particulates by LiFePO4 was successfully carried out by a dry coating procedure. TEM analysis confirmed the presence of a LiFePO4 coating layer of about 20 nm on the surface of the Li1.02(Co0.9Fe0.1)0.98PO4 particles. All three cells delivered high initial discharge capacities of 122, 130 and 128 mA h g−1 for LiCoPO4, Li1.02(Co0.9Fe0.1)0.98PO4, and LiFePO4 modified Li1.02(Co0.9Fe0.1)0.98PO4, respectively. However, these cells presented quite different cycle retention rates after 20 cycles, 21, 22 and 70% for LiCoPO4, Li1.02(Co0.9Fe0.1)0.98PO4, and LiFePO4 modified Li1.02(Co0.9Fe0.1)0.98PO4, respectively. The improved cycle retention of the LiFePO4-modified Li1.02(Co0.9Fe0.1)0.98PO4 resulted from its reduced reactivity towards the electrolyte and the effective prevention of resistive layer formation on the LiCoPO4 surface during high voltage cycling.

A novel energy storage system was developed using graphite and Nb2O5 for cathode and anode materials, respectively. This system exhibited a sloping voltage profile from 2.7 to 3.5 V during charging and presented a high operating voltage plateau between 1.5 and 3.5 V during discharging process. The adsorption of anions to the edge plane regions in graphite happened in the voltage region between 0.0 and 2.7 V, but anion intercalation into graphite occurred between 2.9 and 3.5 V.