Reversible lithium uptake by CoP3 at low potential: role of the anion

Although various transition metal compounds in Group V (nitrides and antimonides) have been reported to act as low potential Li insertion hosts, the phosphides have remained unexplored to date. We show here that lithium uptake and extraction in the metal phosphide, CoP₃, provides a reversible capacity of 400 mAh/g at an average potential of 0.9 V vs Li/Li⁺, via a novel mechanism. The latter was revealed using a combination of X-ray diffraction, electron microscopy, and potentiodynamic and galvanostatic intermittent measurements coupled with X-ray photoelectron spectroscopy (XPS). Initial uptake of Li forms highly dispersed cobalt clusters embedded in a matrix of Li₃P; extraction of Li from this ion-conductive matrix on charge yields nano-particles of LiP, with little change evident in the oxidation state of the Co site. This shows that contrary to the case of metal oxides here the anion plays the major role in reduction and oxidation. We expect this is a general phenomenon for phosphides, and to be of fundamental interest and future importance in the search for new negative electrode materials.     

Electrochemical lithium extraction from β-lithium nitride

In this paper we report the electrochemical characterization of mixtures of ball-milled lithium nitride and iron metal. Several samples were prepared with different lithium nitride to iron molar ratios. X-ray diffraction (XRD) spectra showed the presence of iron metal in all the samples and β-lithium nitride in the samples with higher Li₃N/Fe ratio. No evidence of other phases was detected. The milled powders were used to prepare composite cathodes for the electrochemical characterization. It was found that lithium can be extracted from the materials at a flat potential of 1.2 V vs. Li. The sample with Li₃N/Fe molar ratio 8:1 showed the highest specific capacity (1125 mAh g⁻¹) corresponding to the extraction of 1.8 Li equivalents per mole of lithium nitride. Only a fraction of the lithium extracted was re-inserted in the following discharge cycle. A drastic reduction of the capacity was observed for all the samples on further cycling. An enhancement of the cyclability was obtained by lowering the end-charge voltage that resulted in a reduction of the lithium extracted. The lithium extraction/insertion process was characterized by a large voltage difference indicating that the reaction is largely irreversible.     

Electrochemical lithium and sodium insertion studies in 3D metal oxy-phosphate framework MoWO3(PO4)2 for battery applications

A new type of three-dimensional (3D) oxy-phosphate materials are explored for the application of Li and Na batteries. The molybdenum tungsten oxy phosphate, MoWO₃(PO₄)₂, was synthesized by solid-state method and evaluated for Li/Na insertion/de-insertion electrode material for the first time. The cell at charged state (vs. Li⁺/Li) showed a discharge capacity of 786 mAh g⁻¹ within the voltage window of 0.3 V with amorphization of crystalline MoWO₃(PO₄)₂ as observed from ex-situ powder XRD analysis. The structural integrity was revealed in this material, even with nearly more than 5 Li⁺ ions into the lattice, leading to the discharge capacity of 250 mAh g⁻¹. The reversible charge/discharge behavior with insertion/de-insertion of 2.4 Li⁺ ions in the voltage range of 1.65 − 3.5 V resulted in 110 and 95 mAh g⁻¹ at C/10 and C/5 rates, respectively. On the other hand, poor cycling performance was noticed for Na ion insertion and desertion, with a discharge capacity of 250 mAh/g within the voltage range of 0.3 − 3.5 V (vs. Na⁺/Na).

     

Comparison of the electrochemical properties of metallic layered nitrides containing cobalt,nickel and copper in the 1 V–0.02 V potential range

We report the first example of an intercalation compound based on the nitrogen framework in which lithium can be intercalated and deintercalated. A comparison of the structural and electrochemical properties of the ternary lithium cobalt, nickel and copper nitrides is performed. Vacancy layered structures of ternary lithium nitridocobaltates Li_3−2xCo_xN and nitridonickelates Li_3−2xNi_xN with 0.10 ⩽ x ⩽ 0.44 and 0.20 ⩽ x ⩽ 0.60, respectively, are proved to reversibly intercalate Li ions in the 1 V–0.02 V potential range. These host lattices can accommodate up to 0.35 Li ion par mole of nitride. Results herein obtained support Li insertion in vacancies located in Li₂N⁻ layers while interlayer divalent cobalt and nickel cations are reduced to monovalent species. No structural strain is induced by the insertion–extraction electrochemical reaction which explains the high stability of the capacity in both cases. For the Li_1.86Ni_0.57N compound, a stable faradaic yield of 0.30 F/mol, i.e. 130 mAh/g, is maintained at least for 100 cycles. Conversely, the ternary copper nitrides corresponding to the chemical composition Li_3−xCu_xN with 0.10 ⩽ x ⩽ 0.40 do not allow the insertion reaction to take place due to the presence of monovalent copper combined with the lack of vacancies to accommodate Li ions. In the latter case, the discharge of the lithium copper nitrides is not reversible.     

Electrochemical performance of LiMSnO4 (M=Fe, In) phases with ramsdellite structure as anodes for lithium batteries

LiMSnO₄ (M=Fe, In) compounds were synthesized by high temperature solid-state reaction method and the electrochemical studies were carried out vs. lithium metal. Lithium is reversibly intercalated and deintercalated in LiFeSnO₄ with a constant capacity of ∼90 mAh/g. In situ X-ray diffraction data show that ramsdellite structure is stable for lithium intercalation and deintercalation in LiFeSnO₄. Galvanostatic discharge/charge of LiFeSnO₄ in the voltage window 0.05-2.0 V shows a reversible capacity of ∼100 mAh/g. The observed capacity in LiFeSnO₄ is due to the two processes involving alloying/dealloying of Li_4.4Sn and formation/decomposition of Li₂O. In contrast, the new isotypic oxide LiInSnO₄ does not exhibit any lithium intercalation due to the absence of mixed valence for indium. Its reversible capacity is strongly dependent on the voltage window. LiInSnO₄ exhibits severe capacity fading on cycling in the voltage window 0.05-2.0 V, but shows a stable capacity of ∼90 mAh/g in the voltage range 0.75-2.0 V.     

New NASICON type oxyanion high capacity anode, Li2Co2(MoO4)3, for lithium-ion batteries: preliminary studies

We describe in this paper the lithium insertion/extraction behavior of a new NASICON type Li₂Co₂(MoO₄)₃ at a low potential and explored the possibility of considering this new oxyanion material as anode for lithium-ion batteries for the first time. Li₂Co₂(MoO₄)₃ was synthesized by a soft-combustion glycine-nitrate low temperature protocol. Test cells were assembled using composite Li₂Co₂(MoO₄)₃ as the negative electrode material and a thin lithium foil as the positive electrode material separated by a microporous polypropylene (Celgard® membrane) soaked in aprotic organic electrolyte (1 M LiPF₆ in EC/DMC). Electrochemical discharge down to 0.001 V from OCV (～3.5 V) revealed that about 35 Li⁺ could ^possibly be inserted into Li₂Co₂(MoO₄)₃ during the first discharge (reduction) corresponding to a specific capacity amounting to 1,500 mAh g^?1. This is roughly fourfold higher compared to that of frequently used graphite electrodes. However, about 24 Li⁺ could be extracted during the first charge. It is interesting to note that the same amount of Li⁺ could be inserted during the second Li⁺ insertion process (second cycle discharge) giving rise to a second discharge capacity of 1,070 mAh g^?1. It was also observed that a major portion of lithium intake occurs below 1.0 V vs Li/Li⁺, which is typical of anodes being used in lithium-ion batteries.     

Li2MTi6O14 (M=Sr,Ba): new anodes for lithium-ion batteries

Isostructural Li₂MTi₆O₁₄ (M=Sr, Ba) materials, prepared by a solid state reaction method, have been investigated as insertion electrodes for lithium battery applications. These titanate compounds have a structure that consists of a three-dimensional network of corner- and edge-shared [TiO₆] octahedra, 11-coordinate polyhedra for the alkali-earth ions, and [LiO₄] tetrahedra in tunnels that also contain vacant tetrahedral and octahedral sites. Electrochemical data show that these compounds are capable of reversibly intercalating four lithium atoms in a three-stage process between 1.4 and 0.5 V vs. metallic lithium. The electrodes provide a practical capacity of approximately 140 mAh/g; they are, therefore, possible alternative anode materials to the lithium titanate spinel, Li₄Ti₅O₁₂. The lithium intercalation mechanism and crystal structure of Li₂MTi₆O₁₄ (M=Sr, Ba) electrodes are discussed and compared with the electrochemical and structural properties of Li₄Ti₅O₁₂. The area-specific impedance (ASI) of Li/Li₂SrTi₆O₁₄ cells was found to be significantly lower than that of Li/Li₄Ti₅O₁₂ cells.     

Sol–gel processing and electrochemical characterization of monoclinic Li3FeF6

To find new cathode materials for future applications in lithium-ion batteries, lithium transition metal fluorides represent an interesting class of materials. In principle the Li intercalation voltage can be increased by replacing oxygen in the cathode host structure with the more electronegative fluorine. A facile pyrolytic sol–gel process with trifluoroacetic acid as fluorine source was established to synthesize monoclinic Li₃FeF₆ using nontoxic chemicals. The acicular Li₃FeF₆ powder was characterized with X-ray diffraction and a detailed structure model was calculated by Rietveld analysis. For the preparation of cathode films to cycle versus lithium monoclinic Li₃FeF₆ was ball milled with carbon and binder down to nanoscale. After 100 cycles galvanostatic cycling (C/20) 47 % fully reversible capacity of the initial capacity (129 mAh/g) could be retained. To the best of our knowledge the results presented in this work include the first rate performance test for monoclinic Li₃FeF₆ up to 1 C maintaining a capacity of 71 mAh/g. The redox reaction involving Fe³⁺/Fe²⁺ during Li insertion/extraction was confirmed by post-mortem XPS and cyclic voltammetry.     

锂钛复合氧化物锂离子电池负极材料的研究

采用 3种化学方法合成锂钛复合氧化物 .应用X -射线衍射分析对其结构进行表征以及电化学性能测试 ,结果表明 :由Li2 CO3、TiO2 高温合成的锂钛复合氧化物为尖晶石结构的Li4Ti5 O12 .Li4Ti5 O12 电极在 1 .5V左右有一放电平台 ,充放电可逆性良好 ,即充电电压平台与此接近 ,且电极的比容量较大 ,循环性能良好 .以 0 .30mA·cm- 2 充放电时 ,首次放电容量可达 30 0mAh·g- 1,可逆比容量为 1 0 0mAh·g- 1,经多次充放电循环后 ,其结构仍保持稳定性 .试验电池测试表明 ,Li4Ti5 O12 可选作Li4Ti5 O12 /LiCoO2 锂离子电池的负极材料 .     

High capacity silicon/carbon composite anode materials for lithium ion batteries

Silicon/carbon composite materials are prepared by pyrolysis of pitch embedded with graphite and silicon powders. As anode for lithium ion batteries, its initial reversible capacity is 800–900 mAh/g at 0.25 mA/cm² in a voltage range of 0.02/1.5 V vs. Li. The material modification by adding a small amount of CaCO₃ into precursor improves the initial reversibility (η₁=84%) and suppresses the capacity fade upon cycling. A little higher insertion voltage of the composites than commercial CMS anode material improves the cell safety in the high rate charging process.     

Low-Temperature Synthesis of Honeycomb CuP2@C in Molten ZnCl2 Salt for High-Performance Lithium Ion Batteries

Phosphorus-rich metal phosphides have very high lithium storage capacities, but they are difficult to prepare. A low-temperature phosphorization method based on Mg reducing PCl₃ in ZnCl₂ molten salt at 300 °C is developed to synthesize phosphorus-rich CuP₂@C from a Cu-MOF derived Cu@C composite. Abnormal oxidation of Cu by Zn²⁺ in the molten salt is observed, which leads to the porous honeycomb nanostructure and homogeneously distributed ultrafine CuP₂ nanocrystals. The honeycomb CuP₂@C exhibits excellent lithium storage performance with high reversible capacity (1146 mAh g⁻¹ at 0.2 A g⁻¹) and superior cycling stability (720 mAh g⁻¹ after 600 cycles at 1.0 A g⁻¹), showing the promising application of P-rich metal phosphides in lithium ion batteries.     

A novel anode material of antimony nitride for rechargeable lithium batteries

Antimony nitride thin film has been successfully fabricated by magnetron sputtering method and its electrochemistry with lithium was investigated for the first time. The reversible discharge capacity of Sb₃N/Li cells cycled between 0.3 V and 3.0 V was found above 600 mAh/g. By using transmission electron microscopy and selected area electron diffraction measurements, the conversion reaction of Sb₃N into Li₃Sb and Li₃N was revealed during the lithium electrochemical reaction of Sb₃N thin film electrode. The high reversible capacity and the good cycleability made Sb₃N one of promising anode materials for future rechargeable lithium batteries.     

Low‐Temperature Synthesis of Honeycomb CuP2@C in Molten ZnCl2 Salt for High‐Performance Lithium Ion Batteries

Phosphorus‐rich metal phosphides have very high lithium storage capacities, but they are difficult to prepare. A low‐temperature phosphorization method based on Mg reducing PCl₃ in ZnCl₂ molten salt at 300 °C is developed to synthesize phosphorus‐rich CuP₂@C from a Cu‐MOF derived Cu@C composite. Abnormal oxidation of Cu by Zn²⁺ in the molten salt is observed, which leads to the porous honeycomb nanostructure and homogeneously distributed ultrafine CuP₂ nanocrystals. The honeycomb CuP₂@C exhibits excellent lithium storage performance with high reversible capacity (1146 mAh g^?1 at 0.2 A g^?1) and superior cycling stability (720 mAh g^?1 after 600 cycles at 1.0 A g^?1), showing the promising application of P‐rich metal phosphides in lithium ion batteries.     

Preparation of Li2SnO3 and its application in lithium‐ion batteries

Tin‐based oxide Li₂SnO₃ has been synthesized by a hydrothermal route as negative material for lithium‐ion batteries. The microstructure and electrochemical properties of the as‐synthesized materials were investigated by some characterizations means and electrochemical measurements. The as‐synthesized Li₂SnO₃ is a porous rod, which is composed of many uniform and regular nano‐flakes with a size of 50–60 nm. Li₂SnO₃ also displays an electrochemical performance with high capacity and good cycling stability (510.2 mAh g^?1 after 50 cycles at a current density of 60 mA g^?1 between 0.0 V and 2.0 V verusus Li/Li⁺). Copyright © 2013 John Wiley & Sons, Ltd.     

Layered manganese oxide with O2 structure,Li(2/3)+x(Ni1/3Mn2/3)O2 as cathode for Li-ion batteries

Using LiI as the reducing agent, the compound O2-Li_(2/3)+x(Ni_1/3Mn_2/3)O₂, x∼1/3 (O2(Li+x)) has been prepared from the O2-Li_2/3(Ni_1/3Mn_2/3)O₂ (O2(Li)). Cyclic voltammetry and voltage-capacity profiles of the O2(Li+x) phase are qualitatively different from that of O2(Li) phase. The first extraction capacity of O2(Li+x) at C/10 rate is 190 mAh/g corresponding to the removal of 2/3 mole of Li from the compound. At C/5 rate it delivers a reversible capacity of 158 mAh/g at 25 °C and 184 mAh/g at 50 °C (vs Li metal; voltage window 2.5–4.6 V). In Li-ion cells, with MCMB anode and O2(Li+x) as cathode, a discharge capacity of 140 mAh/g was obtained at C/5 rate in the voltage window 2.5–4.5 V (25 °C). The charge–discharge cycling performance and the cyclic voltammograms reveal that O2(Li) and O2(Li+x) do not convert to the spinel structure.     

Poly(3,4-ethylenedioxythiophene)V2O5 hybrids for lithium batteries

A series of hybrid electrode materials, poly(3,4-ethylenedioxythiophene)/V₂O₅, has been synthesized using an oxidative insertion and polymerization reaction. FTIR, X-ray diffraction and transmission electron microscopy studies have shown that the incorporation of polymer between V₂O₅ slabs leads to an enhanced bidimensionality. The electrochemical lithium capacity has been increased up to ∼330 mAh/g at the second discharge in the range of 2.0–4.4 V vs. Li. This improvement of electrochemical performance compared to pristine V₂O₅ is attributed to the higher electric conductivity and enhanced bidimensionality.     

Electrochemical lithium insertion in two polymorphs of a reduced molybdenum oxide (γ and γ′- Mo4O11)

A study of the electrochemical lithium insertion in two polymorphs of a reduced molybdenum oxide, Mo₄O₁₁, is presented in this work. When used as active materials in cells discharged down to 1 V vs. Li⁺/Li, both forms, the orthorhombic γ-Mo₄O₁₁ and the monoclinic γ′-Mo₄O₁₁, incorporated a similar number of lithium atoms per metal atom (Li/Mo=2.12 and 2.25, respectively). Step potential electrochemical spectroscopy experiments proved that the insertion reaction proceeds in both cases through different mechanisms. In situ X-ray diffraction studies showed an almost complete loss of crystallinity of both compounds after the first discharge, leading to amorphous materials with different electrochemical behaviour on cycling. When discharged to low potentials (0.5 V vs. Li⁺/Li), the γ′-Mo₄O₁₁ polymorph showed very good cycling behaviour for at least five lithium atoms per formula unit, corresponding to a specific capacity of 230 Ah/kg after seven complete charge-discharge cycles. Received: 20 April 1999 / Accepted: 20 June 1999     

Full structural and electrochemical characterization of Li2Ti6O13 as anode for Li-ion batteries

A detailed structural and electrochemical study of the ion exchanged Li(2)Ti(6)O(13) titanate as a new anode for Li-ion batteries is presented. Subtle structural differences between the parent Na(2)Ti(6)O(13), where Na is in an eightfold coordinated site, and the Li-derivative, where Li is fourfold coordinated, determine important differences in the electrochemical behaviour. While the Li insertion in Na(2)Ti(6)O(13) proceeds reversibly the reaction of lithium with Li(2)Ti(6)O(13) is accompanied by an irreversible phase transformation after the first discharge. Interestingly, this new phase undergoes reversible Li insertion reaction developing a capacity of 170 mAh g(-1) at an average voltage of 1.7 V vs. Li(+)/Li. Compared with other titanates this result is promising to develop a new anode material for lithium ion rechargeable batteries. Neutron powder diffraction revealed that Na in Na(2)Ti(6)O(13) and Li in Li(2)Ti(6)O(13) obtained by Na/Li ion exchange at 325 °C occupy different tunnel sites within the basically same (Ti(6)O(13))(2-) framework. On the other hand, electrochemical performance of Li(2)Ti(6)O(13) itself and the phase released after the first full discharge is strongly affected by the synthesis temperature. For example, heating Li(2)Ti(6)O(13) at 350 °C produces a drastic decrease of the reversible capacity of the phase obtained after full discharge, from 170 mAh g(-1) to ca. 90 mAh g(-1). This latter value has been reported for Li(2)Ti(6)O(13) prepared by ion exchange at higher temperature.     

Mixed-phase WO3 Cocatalysts on Hierarchical Si-based Photocathode for Efficient Photoelectrochemical Li Extraction

Photoelectrochemical lithium (Li) extraction can be expected to provide a useful recycle of Li⁺ from waste Li-containing battery, but the process is limited by the photocathodes with poor Li⁺ absorption and low yield rate. Here, we have designed a hierarchical silicon (Si)-based photocathode with mixed-phase tungsten oxide (WO₃) cocatalysts for photoelectrochemical Li extraction under 1 sun illumination, achieving a high Li yield rate of ≈223.0 μg cm⁻² h⁻¹ and an excellent faradaic efficiency of 91.9 % at 0.0817 V versus Li^0/+ redox couple. The WO₃ cocatalysts with the mixture of amorphous and crystalline phase accelerates the Li⁺ insertion and precipitation and enriches the concentration of Li⁺ at the photocathode surface. This robust photoelectrochemical Li extraction system provides a new insight on designing green and efficient route for cyclic utilization of Li resources in the sustainable energy field.     

Low Temperature Synthesis and Characterization of Li1.2-y NayV3O8(0≤y≤1.2) from V2O5 Gel

Without overnight heating and stirring,Li1.2V3O8 and its analogs Li1.2-y NayV3O8(0≤y≤1.2) were successfully synthesized by adding mixed solution of LiOH and NaVO3 to V2O5 gel and dehydrating the prepared gel in 150-350℃.The simplicity awards this synthesis process superiority over other low temperature synthesis routes when mass production is concerned.TG-DTA,XRD and TEM experiments were carried out for physical characterization.By galvanostatic charge-discharge and cyclic voltammetry tests,these products showed better electrochemical performance than high temperature products as cathode active materials in secondary lithium batteries.After treatment of Li1.2V3O8 at 250℃,it exhibited a capacity of 350mAh/g when cycled at current rate of about 60 mA/g over the voltage range of 3.8-1.7V vs,Li^ /Li.The influence of partial substitution of Li by Na was also extensively studied.