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Abstract: Lithium-ion battery cathode material Li1+ x V3O8 is synthesized by a citric acid/tartaric acid assisted sol–gel method and sintered at 350 °C, 450 °C and 550 °C for 3 h for the formation of Li1+ x V3O8 phase. The synthesized samples were fully characterized by FTIR, TG/DTA, XRD, SEM, EIS and charge–discharge tests. Li1+ x V3O8 material synthesized by tartaric acid assisted route and sintered at 450 °C for 3 h shows best electro-chemical performance. It shows a high initial capacity of 249 mAh g−1 and still reserves a discharge capacity of 260 mAh g−1 after 50 cycles. Moreover, in the case of tartaric assisted products, no capacity decadence is observed in 50 cycles. XRD together with TG/DTA measurements reveal that compared with citric acid assisted products, the adoption of tartaric acid as chelating agent effectively lowers the crystallization temperature of amorphous Li1+x V3O8. Therefore, precursors obtained by tartaric acid route calcinated at 450 °C for 3 h exhibit lower crystallinity and smaller grain size, which contributes to the better electrochemical performance of the cathode electrodes. From EIS measurements, the bulk resistance is reduced, which favors the intercalation and de-intercalation of lithium ions while cycling. [Copyright &y& Elsevier]

The overdischarge behaviors of LiFePO, LiNiO, and LiMnO are thoroughly studied in different overlithiation voltage limitations. The results showed that LiFePO and LiMnO cathode materials show high structure stability under the overdischarge process to 1.0 V. The microstructure of LiNiO is vulnerable to breakdown under the same testing condition. Fe-based olivine and Mn-based spinel cathode materials show better cyclic calendar life than that of Ni-based layered material. When an extreme overdischarge parameter (down to 0.0 V) is applied, all three samples experience an electrochemically driven irreversible solid-state amorphization process. Due to this overlithiation reaction, the host structure is totally destroyed. Therefore, it is harmful to experience deep overdischarge behaviors for most cathode materials. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, Nano-sized hard carbon spherule (HCS) is prepared from the distilled water/ethylene glycol mixed solution by hydrothermal technique. Due to the addition of ethylene glycol, the as-prepared sample is a kind of nano-sized HCS and the particle size of nano-sized HCS is 50–100nm. Furthermore, nano-sized HCS displays larger specific surface area attributed to the well-dispersed property. As a result, it shows lower charge transfer impedance than that of micro-sized HCS owing to the huge contact area between particles and electrolyte. However, the initial coulombic efficiency of nano-sized HCS is a little lower than that of micro-sized HCS due to the large specific surface area for electrolyte irreversible decomposition. Charge-discharge cycling tests demonstrate that nano-sized HCS samples have high capacity retention ratio (92.7%) and high reversible lithium storage performance (525mAhg−1). Therefore, it is a potential anode material for lithium–ion batteries. [Copyright &y& Elsevier]

Abstract La 2 (MoO 4) 3 is a kind of transition metal molybdate. It has been proved to be a possible anode material for lithium ion batteries due to the high theoretical capacity. In this work, molybdenum-based La 2 (MoO 4) 3 material is successfully synthesized through a traditional solid-state reaction method. Carbon-coated La 2 (MoO 4) 3 is designed by using glucose as carbon source. By comparing the carbon-coated La 2 (MoO 4) 3 with the carbon-free La 2 (MoO 4) 3 , carbon-coated La 2 (MoO 4) 3 delivers better cyclic stability and rate performance. Carbon-coated La 2 (MoO 4) 3 obtains a reversible charge capacity of 525.9 mA h g−1 at 100 mA g−1 after 100 cycles, corresponding to capacity retention of 75.2%. However, the capacity retention of carbon-free La 2 (MoO 4) 3 is only 33.4%. The results indicate that carbon layer can evidently alleviate the irreversibility of structure and improve capacity retention of La 2 (MoO 4) 3. It demonstrates that the carbon-coated La 2 (MoO 4) 3 composite can be a possible anode candidate for high capacity lithium ion batteries. In addition, in-situ X-ray diffraction investigation (XRD), ex-situ X-ray photoelectron spectroscopy (XPS), and ex-situ transmission electron microscopy (TEM) are employed to analyze the electrochemical behavior during process of cycling. These experimental results indicate that the conversion behavior of La 2 (MoO 4) 3 upon lithiation/delithiation is a process of structural pulverization. Based on that, our work provides guidance for the research of molybdenum-based electrode materials. [ABSTRACT FROM AUTHOR]

Isostructural LiMTiO 4 (M = Mn, Fe, Co) have been successfully synthesized by a facile sol-gel route and evaluated their possibility as an anode materials for lithium ion batteries (LIBs). All the samples exhibit high operating potential plateaus (>1.7 V vs. Li + /Li), which can prevent the formation of the solid electrolyte interphase (SEI) film on the electrode surface effectively. In addition, electrochemical investigations show that LiCoTiO 4 has a superior cycling performance, better rate capability, lower charge transfer resistance and higher lithium-ion diffusion coefficient than those of LiMnTiO 4 and LiFeTiO 4 . These electrochemical results indicate that LiCoTiO 4 is the most promising lithium storage material among all the examined spinel-type LiMTiO 4 samples. [ABSTRACT FROM AUTHOR]

In this work, Na 2 Ti 3 O 7 is fabricated as lithium storage material via one-step solid state reaction. Worked as anode material, Na 2 Ti 3 O 7 delivers a stable electrochemical performance with good lithium storage capability. Structural analyses show that Na 2 Ti 3 O 7 anode experiences slight volume change during electrochemical lithiation/delithiation process. Moreover, the reversibility of structural evolution is further demonstrated by in-situ X-ray diffraction technique. All these evidences prove the cycling stability of Na 2 Ti 3 O 7 as lithium storage material. Besides, the kinetic properties of the Li + ion storage in Na 2 Ti 3 O 7 are systematically investigated. The observed results reveal that Na 2 Ti 3 O 7 delivers the lithium ions diffusion coefficient in the range of 10 − 14 –10 − 12 cm 2 s − 1 during the discharge process and 10 − 15 –10 − 12 cm 2 s − 1 during the recharge process. It suggests that Na 2 Ti 3 O 7 has good lithiation/delithiation kinetics in rechargeable batteries. [ABSTRACT FROM AUTHOR]

Spinel LiCrTiO 4 is synthesized via sol-gel pretreatment and subsequent solid state reaction at different calcining temperatures. Structural observation and electrochemical evaluation show that 800 °C is a suitable calcining temperature for LiCrTiO 4 preparation. Compared with samples prepared at other temperatures, LiCrTiO 4 formed at 800 °C exhibits better electrochemical performance with the capacity retention of 92.2% at 100 mA g −1 after 80 cycles. Even cycled at a higher current density of 500 mA g −1 in 0.0-3.0 V, LiCrTiO 4 prepared at 800 °C still shows excellent cycling performance with a reversible capacity of 226.7 mAh g −1 after 80 cycles. Ex-situ valence analysis reveals that the high lithium storage capacity in LiCrTiO 4 between 0.0 and 3.0 V is attributed to the reversible redox process of Ti 4+ /Ti 3+ and Cr 3+ /Cr 2+ couples. In addition, quasi zero-strain characteristic of LiCrTiO 4 during lithiation is also demonstrated by in-situ and ex-situ structural observations. Therefore, LiCrTiO 4 exhibits high structural stability and electrochemical reversibility as anode material for rechargeable lithium-ion batteries. [ABSTRACT FROM AUTHOR]

In this work, a novel lithium storage material Li 5 Cr 9 Ti 4 O 24 is reported as anode material for rechargeable lithium-ion batteries. We prepare Li 5 Cr 9 Ti 4 O 24 by two different routes, sol-gel method and solid state reaction. Li 5 Cr 9 Ti 4 O 24 nanocrystalline can be achieved by sol-gel method, while solid state reaction delivers micro-sized product. Electrochemical results show that Li 5 Cr 9 Ti 4 O 24 nanocrystalline exhibits reduced charge transfer resistance, decreased redox polarization and improved lithium-ion diffusion coefficient compared with micro-sized product. As a result, Li 5 Cr 9 Ti 4 O 24 nanocrystalline shows excellent lithium storage capability with 100% capacity retention after 200 cycles. Cycled at 600 mA g −1 , it still can deliver a charge specific capacity of 110.3 mAh g −1 . In contrast, micro-sized Li 5 Cr 9 Ti 4 O 24 only reveals the reversible capacity of 66.8 mAh g −1 at the same current density. In addition, Li 5 Cr 9 Ti 4 O 24 nanocrystalline also shows outstanding structural stability for repeated lithium storage. In-situ structural observation reveals that the entire volume expansion of Li 5 Cr 9 Ti 4 O 24 is only 0.62% during the charge/discharge process, which is similar with the zero-strain Li 4 Ti 5 O 12 . Therefore, Li 5 Cr 9 Ti 4 O 24 nanocrystalline can be used as high performance anode material for lithium-ion batteries. [ABSTRACT FROM AUTHOR]

A series of Li 3− x Na x V 2 (PO 4 ) 3 /C (0≤ x ≤3) materials are successfully prepared by a simple solid-state reaction method and used for the first time as anode materials for Na-ion batteries. Powder X-ray diffraction (XRD) results show that the phase structures of Li 3− x Na x V 2 (PO 4 ) 3 /C evolve along with the change of Li/Na atomic ratio (0≤x≤3). With increasing x in Li 3− x Na x V 2 (PO 4 ) 3 /C from 0.0 to 3.0, the main phase in as-prepared sample transforms from monoclinic Li 3 V 2 (PO 4 ) 3 to rhombohedral Li 3 V 2 (PO 4 ) 3 , and finally to rhombohedral Na 3 V 2 (PO 4 ) 3 , which results in different sodium storage behavior and performance between Li 3− x Na x V 2 (PO 4 ) 3 /C (0≤ x ≤3) materials. Electrochemical results show that Li 3− x Na x V 2 (PO 4 ) 3 /C ( x =0.0, 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0) can deliver the initial charge capacities of 21.1, 35.9, 33.8, 41.7, 43.3, 43.9 and 47.7 mAh g −1 at a current density of 10 mA g −1 , respectively. After 45 cycles, the reversible capacities can be kept at 16.9, 45.1, 32.6, 44.6, 43.7, 37.8 and 27.3 mAh g −1 for Li 3 V 2 (PO 4 ) 3 /C, Li 2.5 Na 0.5 V 2 (PO 4 ) 3 /C, Li 2 NaV 2 (PO 4 ) 3 /C, Li 1.5 Na 1.5 V 2 (PO 4 ) 3 /C, LiNa 2 V 2 (PO 4 ) 3 /C, Li 0.5 Na 2.5 V 2 (PO 4 ) 3 /C and Na 3 V 2 (PO 4 ) 3 /C, respectively. Furthermore, the structural reversibility of Li 3− x Na x V 2 (PO 4 ) 3 /C ( x =1.0, 2.0, and 3.0) is also observed by in-situ XRD observation during sodiation/de-sodiation process. All these observed evidences indicate that only some of Li 3− x Na x V 2 (PO 4 ) 3 /C (0≤ x ≤3) can be used as possible sodium storage materials. [ABSTRACT FROM AUTHOR]

Due to the characteristics of an electronic insulator, Na 2 Li 2 Ti 6 O 14 always suffers from low electronic conductivity as anode material for lithium storage. Via Ag coating, Na 2 Li 2 Ti 6 O 14 @Ag is fabricated, which has higher electronic conductivity than bare Na 2 Li 2 Ti 6 O 14 . Enhancing the Ag coating content from 0.0 to 10.0 wt%, the surface of Na 2 Li 2 Ti 6 O 14 is gradually deposited by Ag nanoparticles. At 6.0 wt%, a continuous Ag conductive layer is formed on Na 2 Li 2 Ti 6 O 14 . While, particle growth and aggregation take place when the Ag coating content reaches 10.0 wt%. As a result, Na 2 Li 2 Ti 6 O 14 @6.0 wt% Ag displays better cycle and rate properties than other samples. It can deliver a lithium storage capacity of 131.4 mAh g −1 at 100 mA g −1 , 124.9 mAh g −1 at 150 mA g −1 , 119.1 mAh g −1 at 200 mA g −1 , 115.8 mAh g −1 at 250 mA g −1 , 111.9 mAh g −1 at 300 mA g −1 and 109.4 mAh g −1 at 350 mA g −1 , respectively. [ABSTRACT FROM AUTHOR]

In this work, Na 2 Ti 6 O 13 nanorods are prepared by a traditional solid state reaction and reported as anode materials for advanced lithium-ion batteries. The effect of calcining temperature on the size and electrochemical behavior of nanorodes is thoroughly described and compared within the temperature range of 800-1000 °C. It can be found that the size of nanorodes increases with the enhancing of calcining temperature. At 1000 °C, Na 2 Ti 6 O 13 nanorodes melt into big bulks, which exhibit poor ionic conductivity and low lithium storage capacity. Although Na 2 Ti 6 O 13 nanorodes with smaller size can be formed at 800 °C, its capacity retention is poor. In contrast, Na 2 Ti 6 O 13 nanorodes obtained at 900 °C reveal high reversible capacity, rapid lithium ion diffusion behavior and outstanding rate property. In-situ and ex-situ analyses reveal that the structural evolution of Na 2 Ti 6 O 13 during lithiation and delithiation process is quasi-reversible, which ensures the excellent electrochemical performance of Na 2 Ti 6 O 13 nanorods for repeated lithium storage. [ABSTRACT FROM AUTHOR]

A range of Al doped Li 2 Na 2 Ti 6 O 14 anode materials are synthesized by a simple solid state method at 800 °C. Structure and morphology investigations show that Li 2-x Al x Na 2 Ti 6 O 14 (0.0 ≤ x ≤ 0.2) are well crystallized with a particle size in the range of 100 to 300 nm, and Al doping can slightly reduce the particle size of Li 2 Na 2 Ti 6 O 14 . Electrochemical evaluation indicates that Li 1.95 Al 0.05 Na 2 Ti 6 O 14 reveals the highest reversible capacity of 245.1 mAh g −1 after 40 cycles at a current density of 100 mA g −1 among all the as-prepared samples. For comparison, the reversible charge capacities for Li 2 Na 2 Ti 6 O 14 , Li 1.9 Al 0.1 Na 2 Ti 6 O 14 , Li 1.85 Al 0.15 Na 2 Ti 6 O 14 and Li 1.8 Al 0.2 Na 2 Ti 6 O 14 are only 225.6, 200.0, 206.7 and 216.9 mAh g −1 , respectively. Rate performance shows that Li 1.95 Al 0.05 Na 2 Ti 6 O 14 also delivers the best electrochemical property with the charge capacities of 224.8 mAh g −1 at 200 mA g −1 , 204.7 mAh g −1 at 300 mA g −1 and 192.4 mAh g −1 at 400 mA g −1 . The excellent electrochemical performance of Li 1.95 Al 0.05 Na 2 Ti 6 O 14 is attributed to the decreased electrochemical resistance and the improved chemical diffusion coefficient induced by Al doping. Besides, the zero-strain characteristic as proved by in-situ structure analysis should also be responsible for the enhanced cycling and rate properties. [ABSTRACT FROM AUTHOR]

Three Li 3-x Na x V 2 (PO 4 ) 3 (x=0.5, 1.5 and 2.0) samples are synthesized by a traditional solid-state reaction method in this work. Their phase composition, surface morphology and electrochemical property are described and compared by using various physical/chemical methods. Phase analysis results reveal that Li 2.5 Na 0.5 V 2 (PO 4 ) 3 consists of monoclinic Li 3 V 2 (PO 4 ) 3 , rhombohedral Li 3 V 2 (PO 4 ) 3 and rhombohedral Na 3 V 2 (PO 4 ) 3. While, both Li 1.5 Na 1.5 V 2 (PO 4 ) 3 and LiNa 2 V 2 (PO 4 ) 3 are the two-phase mixture consisted of rhombohedral Li 3 V 2 (PO 4 ) 3 and rhombohedral Na 3 V 2 (PO 4 ) 3 . Electrochemical testing results reveal that LiNa 2 V 2 (PO 4 ) 3 and Li 1.5 Na 1.5 V 2 (PO 4 ) 3 can deliver the initial discharge capacities of 101.4 mAh g −1 and 108.6 mAh g −1 with a long potential plateau at 3.69 V, respectively. In contrast, Li 2.5 Na 0.5 V 2 (PO 4 ) 3 presents an initial discharge capacity of 111.7 mAh g −1 with four potential plateaus. High lithium ion diffusion coefficient in Li 2.5 Na 0.5 V 2 (PO 4 ) 3 indicates that the existence of monoclinic Li 3 V 2 (PO 4 ) 3 phase can improve the ionic conductivity and then be responsible for good electrochemical performance. Besides, in-situ X-ray diffraction observation of LiNa 2 V 2 (PO 4 ) 3 demonstrates that the phase transition is not fully reversible but quasi-reversible during the lithiation-delithiation process. The partial irreversibility of structural evolution for LiNa 2 V 2 (PO 4 ) 3 induces the capacity loss upon repeated cycles. [ABSTRACT FROM AUTHOR]

In this work, triclinic structured LiVPO 4 F is prepared by a simple two-step carbothermal reduction method and subsequently exposed to water under different storage conditions. The impact of exposure on the structure, morphology and electrochemical performance of LiVPO 4 F is investigated in detail. It is found that the effect of exposure at room temperature (20 °C) is slight. In contrast, exposure at 80 °C has great effect on the structure and electrochemical properties of LiVPO 4 F. Li, P and V dissolution into aqueous solution at 80 °C results in the formation of a yellowish solution. Electrochemical tests show that LiVPO 4 F samples aged in water at 80 °C for 3 and 5 days show poorer electrochemical properties than the pristine sample. LiVPO 4 F aged in water at 80 °C for 15 days exhibits higher initial reversible capacity compared with the pristine sample. However, it deteriorates rapidly in the following cycles due to the moisture-sensitive surface, which induces the formation of thick Li 2 CO 3 /Li 3 PO 4 film on the surface and leads to a high charge transfer resistance and the degradation of electrochemical performance. [ABSTRACT FROM AUTHOR]

Delafossite-type CuCrO 2 is prepared by a citric acid-assisted sol–gel method and used as anode material for lithium ion batteries. Electrochemical results demonstrate that CuCrO 2 has a good reversibility for lithium storage. As anode material, the initial charge capacity of CuCrO 2 is 157.6 mA h g −1 . After 17 cycles, a maximum reversible charge capacity of 346.4 mA h g −1 can be observed for CuCrO 2 anode, and then the charge capacity shows a gradual decrease upon further cycles. It indicates that an electrochemical activation process takes place in the initial several charge/discharge cycles. With an investigation by electrochemical impedance spectroscopy, it is found that the gradual decrease of charge transfer resistance and the gradual increase of lithium ion diffusion coefficient may induce the initial electrochemical activation process of CuCrO 2 anode. [ABSTRACT FROM AUTHOR]

To improve the electrochemical performance of Na 2 Li 2 Ti 6 O 14 , carbon black (CB), graphene (GN) and carbon nanotube (CNT) are introduced to fabricate high conductive Na 2 Li 2 Ti 6 O 14 /CB, Na 2 Li 2 Ti 6 O 14 /GN, Na 2 Li 2 Ti 6 O 14 /CNT and Na 2 Li 2 Ti 6 O 14 /CB/GN/CNT by a solid state method. It can be found that only CNT forms a complete three-dimensional conductive network which embeds the randomly distributed Na 2 Li 2 Ti 6 O 14 particles, leading to an improvement of electronic conductivity. The results of cyclic voltammetry, electrochemical impedance spectroscopy and charge–discharge tests reveal that Na 2 Li 2 Ti 6 O 14 /CNT obtains the lowest redox polarization and the highest peak current among all the five samples. As a result, Na 2 Li 2 Ti 6 O 14 /CNT shows the best cycling and rate performances among all the five samples. It reveals a charge capacity of 111.4 mAh g −1 at 100 mA g −1 , 110 mAh g −1 at 200 mA g −1 , 103.9 mAh g −1 at 300 mA g −1 and 98.9 mAh g −1 at 400 mA g −1 . For comparison, bare Na 2 Li 2 Ti 6 O 14 only displays a charge capacity of 89.9 mAh g −1 at 100 mA g −1 , 79.7 mAh g −1 at 200 mA g −1 , 73.7 mAh g −1 at 300 mA g −1 and 69.4 mAh g −1 at 400 mA g −1 . It indicates that the introduction of CNT is more effective to improve the performance of Na 2 Li 2 Ti 6 O 14 than CB, GN and CB/GN/CNT. [ABSTRACT FROM AUTHOR]

By using multi-wall carbon nanotube (MWCNT), a well-dispersed composite of Cu(NO 3 ) 2 · xH 2 O/MWCNT (2.5

Abstract: In this paper, Cr2O3@Ag2O composite is prepared by a simple chemical decomposition method and then used as anode material for lithium-ion batteries. It can be found that Ag2O coating can effectively enhance the electrochemical property of Cr2O3. For bare Cr2O3, a discharge capacity of 1123.5mAhg−1 can be delivered during the first lithiation process. After Ag2O coating, the initial discharge capacity of Cr2O3@Ag2O is improved to 1357.8mAhg−1. The reversible lithium storage capacity of Cr2O3@Ag2O is 694.5mAhg−1 after 80 cycles with a capacity retention of 98.5%, which is also much higher than that (139.6mAhg−1, 21.7%) of Cr2O3. It indicates that Cr2O3@Ag2O shows good cycling stability with high reversible capacity as anode material for lithium-ion batteries. [Copyright &y& Elsevier]

Three basic carnobates, (PbCO3)2·Pb(OH)2, NiCO3·2Ni(OH)2·4H2O, and CuCO3·Cu(OH)2, are prepared and used for the first time as anode materials for lithium-ion batteries. Electrochemical results show that (PbCO3)2·Pb(OH)2, NiCO3·2Ni(OH)2·4H2O and CuCO3·Cu(OH)2 can deliver high initial discharge capacities of 1175.8, 1742.6 and 1356.2mAhg−1, respectively. The lithium storage mechanisms of basic metal carbonates are observed by various electrochemical, ex-situ and in-situ methods during the initial charge–discharge cycle. It can be found that basic metal carbonates decompose into metal (M=Pb, Ni or Cu), Li2CO3, LiOH and H2O upon the preliminary discharge. With further lithiation, the active metal can alloy with Li to form several Li x M phases. During the reverse charge process, Li extraction from the de-alloying reaction, M/Li2CO3 and M/LiOH mixtures can be observed. However, the cycling efficiency is low. Electrochemically inactive particles generated from pulverization, structural collapse and electronic contact loss result in the large irreversible capacity and low initial cycling efficiency. By using carbon black as conductive additive and buffer layer, the electrochemical properties of composite can be greatly improved. Carbon black–(PbCO3)2·Pb(OH)2 composite shows a reversible charge capacity of 244.7mAhg−1 after 20 cycles, which is much higher than the value (77.2mAhg−1) of the pristine sample. [ABSTRACT FROM AUTHOR]

Abstract: Spherical LiNi0.5Co0.3Mn0.2O2 samples with the particle size distribution between 10 and 20 μm are prepared by a hydroxide co-precipitation method and subsequent high temperature solid state calcination. Electrochemical results show that the reversible lithium storage capacities of spherical LiNi0.5Co0.3Mn0.2O2 cathode after 20 cycles are 121.5, 154.2 and 99.3 mAh g−1 in 2.0–4.3 V, 2.0–4.6 V and 2.0–4.9 V, respectively. The structural evolutions of layered materials in different working potential ranges are carefully studied by homemade in-situ X-ray diffraction techniques. It is found that the formation of hexagonal phase H3 is the main source resulting in poor electrochemical properties, where the hexagonal phase H2 to hexagonal phase H3 transition occurs at about 4.7 V in the charge process. As a result, it is expected that the suppression of hexagonal phase H3 can achieve a long-term cyclability and high reversible capacity for LiNi0.5Co0.3Mn0.2O2. Therefore, spherical LiNi0.5Co0.3Mn0.2O2 cathode shows the highest reversible lithium storage capacity of 154.2 mAh g−1 in 2.0–4.6 V after 20 cycles among all the three electrochemical working windows. [Copyright &y& Elsevier]