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).

     

Electrochemical Li insertion studies on WNb12O33—A shear ReO3 type structure

Electrochemical lithium insertion studies on WNb₁₂O₃₃ synthesized by solid state reaction (SSR) are carried out in the voltage range 1.0-3.2 V. During first discharge 15.6 Li are inserted with a specific capacity of 221 mAh/g. WNb₁₂O₃₃ is also synthesized by sol-gel (SG) technique with a view to enhance the rate capability and cycling properties. The SSR and SG samples are characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and galvanostatic cycling. Electrochemical cycling performance of SG samples is superior to that of the SSR sample at high ‘C’ rates. The sample synthesized by SG method exhibits high specific capacity of 142 mAh/g after 20 cycles at 20C rate.     

Preparation and electrochemical properties of V<Subscript>2</Subscript>O<Subscript>5</Subscript> submicron-belts synthesized by a sol–gel H<Subscript>2</Subscript>O<Subscript>2</Subscript> route

One-dimensional (1D) submicron-belts of V₂O₅ have been prepared by a sol–gel route using V₂O_5, H₂O₂ and aniline as starting materials. Thermogravimetric and differential thermal analysis, X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy were employed to characterize the samples. Electrochemical behaviors as cathode material in rechargeable lithium-ion batteries were investigated by galvanostatic charge–discharge measurement and cyclic voltammeter. The results showed that the synthesized V₂O₅ appeared to be submicron-belts and orthorhombic structure. The V₂O₅ submicron-belts exhibited a high initial discharge capacity of 346 mAh/g and stayed 240 mAh/g after 20 cycles at 0.1 C discharge rate in the potential region 1.8–4.0 V.     

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.     

煅烧温度对锂离子正极材料Li[Ni_(0.475)Mn_(0.475)Co_(0.05)]O_2结构和电化学性能的影响

应用高温固相合成法制备L i[N i0.475Mn0.475Co0.05]O2.XRD,SEM,循环伏安及充放电容量测试表明,在800℃下煅烧合成的样品具有较高的嵌锂容量和良好的循环稳定性,如在20 mA/g和2.3~4.6 V的电压范围内,其首次放电比容量为178.8 mAh/g,循环30周后放电比容量仍能达到150.2 mAh/g,容量损失16.0%.     

A hybrid nonaqueous electrochemical supercapacitor using nano-sized iron oxyhydroxide and activated carbon

A beta-iron oxyhydroxide (FeOOH) was synthesized via a hydrolyzing route and investigated as a lithium intercalation host. It delivers a capacity of about 170 mAh/g and exhibits good cycling performance when charged/discharged in the voltage range from 1.6 V to 3.3 V. For the first time we have confirmed that FeOOH is suitable for using it as a negative electrode for hybrid electrochemical supercapacitor assembled with an activated carbon positive electrode in 1.0 M LiPF₆ ethylene carbonate/dimethyl carbonate (EC/DMC, 1:2 in volume) solution. The cell reveals a slightly sloping voltage profile from 0 V to 2.8 V and gives an estimated specific energy of 45 Wh/kg based on the total weight of two electrode materials, approximately two times of carbon/carbon electrochemical double layer capacitors. The hybrid supercapacitor shows a good cycling performance, it remains approximately 96% of initial capacity after 800 cycles at a charge/discharge rate of 4 C. The capacitor also shows a desirable rate capability, even at 10 C discharge rate, it holds 80% of capacity compared with that at 1 C discharge rate.     

Synthesis and electrochemical properties of LiNi0.9-xCo0.1SnxO2 as cathode materials for lithium secondary batteries

LiNi_0.9-x Co_0.1Sn _x O₂ (x = 0.00, 0.02, and 0.03) were synthesized via the rheological phase reaction method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical tests. The sample of LiNi_0.9-x Co_0.1Sn _x O₂ (x = 0.02) not only shows good cycle performance but also exhibits an excellent discharge capacity of 188 mAh/g in the first cycle at a current density of 100 mA/g in the voltage range of 3.0–4.3 V. The tin doping results in reducing the resistance and increasing conductivity of LiNi_0.9-x Co_0.1Sn _x O₂. This composite oxide is promising as cathode material for lithium-ion battery.     

Electrochemical properties of Mg2Ni and Mg2Ni2 prepared by mechanical alloying

Crystallized Mg₂Ni and Mg₂Ni₂ amorphous alloys synthesized by mechanical alloying at room temperature were found to present first discharge capacities of 270 mAh/g and 500 mAh/g, respectively. These capacities decrease upon subsequent cycling to reach 30 mAh/g and 70 mAh/g after 60 charge/discharge cycles. The largest initial capacity, measured for the Mg₂Ni₂ composition, is ascribed to its amorphous nature, while its poor capacity retention upon cyding appears to originate from a fine Ni dispersion within the Mg/Ni matrix. This dispersion enables a better protection of the Mg against oxidation during cycling. We show, however, that this protection of Mg by Ni is not sufficient to avoid a strong corrosion of Mg in the KOH electrolyte during cycling, leading to the formation of Mg(OH)₂. Received: 8 October 1997 / Accepted: 20 January 1998     

High-performance thin-film Li4Ti5O12 electrodes fabricated by using ink-jet printing technique and their electrochemical properties

Li₄Ti₅O₁₂ thin-film anode with high discharge capacity and excellent cycle stability for rechargeable lithium ion batteries was prepared successfully by using ink-jet printing technique. The prepared Li₄Ti₅O₁₂ thin film were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, cyclic voltammograms, and galvanostatic charge–discharge measurements. It was found that the average thickness of 10-layer Li₄Ti₅O₁₂ film was about 1.7~1.8 μm and the active material Li₄Ti₅O₁₂ in the thin film was nano-sized about 50–300 nm. It was also found that the prepared Li₄Ti₅O₁₂ thin film exhibited a high discharge capacity of about 174 mAh/g and the discharge capacity in the 300th cycle retained 88% of the largest discharge capacity at a current density of 10.4 μA/cm² in the potential range of 1.0–2.0 V.     

Improved disordered carbon as high performance anode material for lithium ion battery

A sulfur-substituted disordered carbon is explored as anode material for lithium-ion battery. Its physical and electrochemical properties are characterized by a variety of techniques such as powder X-ray diffraction, element analysis, Fourier transform infrared spectrum, scanning electron microscopy, and typical electrochemical tests. Electrochemical tests show the activated carbon displays a first cycle discharge capacity of 1,216 mAh·g⁻¹. It also has a remarkable cycling stability with an average capacity fade of 0.92% per cycle from 11th to 100th cycle in the range of 0.01–3.00 V versus metallic lithium at a current density of 100 mA·g⁻¹. After 100 cycles, the electrode still maintained a capacity of 420 mAh·g⁻¹.     

Synthesis and characterization of core–shell F-doped LiFePO<Subscript>4</Subscript>/C composite for lithium-ion batteries

Core–shell LiFePO₄/C composite was synthesized via a sol–gel method and doped by fluorine to improve its electrochemical performance. Structural characterization shows that F⁻ ions were successfully introduced into the LiFePO₄ matrix. Transmission electron microscopy verifies that F-doped LiFePO₄/C composite was composed of nanosized particles with a ~3 nm thick carbon shell coating on the surface. As a cathode material for lithium-ion batteries, the F-doped LiFePO₄/C nanocomposite delivers a discharge capacity of 162 mAh/g at 0.1 C rate. Moreover, the material also shows good high-rate capability, with discharge capacities reaching 113 and 78 mAh/g at 10 and 40 C current rates, respectively. When cycled at 20 C, the cell retains 86% of its initial discharge capacity after 400 cycles, demonstrating excellent high-rate cycling performance.     

Carbon coated Na3V2(PO4)3 as novel electrode material for sodium ion batteries

A Na₃V₂(PO₄)₃ sample coated uniformly with a layer of 6 nm carbon has been successfully synthesized by a one-step solid state reaction. This material shows two flat voltage plateaus at 3.4 V vs. Na⁺/Na and 1.63 V vs. Na⁺/Na in a nonaqueous sodium cell. When the Na₃V₂(PO₄)₃/C sample is tested as a cathode in a voltage range of 2.7-3.8 V vs. Na⁺/Na, its initial charge and discharge capacities are 98.6 and 93 mAh/g. The capacity retention of 99% can be achieved after 10 cycles. The electrode shows good cycle performance and moderate rate performance. When it is tested as an anode in a voltage range of 1.0-3.0 V vs. Na⁺/Na, the initial reversible capacity is 66.3 mAh/g and the capacity of 59 mAh/g can be maintained after 50 cycles. These preliminary results indicate that Na₃V₂(PO₄)₃/C is a new promising material for sodium ion batteries.     

Synthesis of LiNi<Subscript>1/3</Subscript>Co<Subscript>1/3</Subscript>Mn<Subscript>1/3</Subscript>O<Subscript>2</Subscript> nanoparticles by modified Pechini method and their enhanced rate capability

Layered LiNi_1/3Co_1/3Mn_1/3O₂ nanoparticles were prepared by modified Pechini method and used as cathode materials for Li-ion batteries. The pyrolytic behaviors of the foamed precursors were analyzed by use of simultaneous thermogravimetric and differential thermal analysis (TG-DTA). Structure, morphology and electrochemical performance characterization of the samples were investigated by X-ray diffraction (XRD), field emission scanning electron macroscopy(SEM), Brunauer-Emmett-Teller (BET) specific surface area and charge–discharge tests. The results showed that the samples prepared by modified Pechini method caclined at 900 °C for 10 h were indexed to pure LiNi_1/3Co_1/3Mn_1/3O₂ with well hexagonal structure. The particle size was in a range of 100–300 nm. The specific surface area was larger than that of the as-obtained sample by Pechini method. Initial discharge capacity of 163.8 mAh/g in the range 2.8–4.4 V (vs. Li/Li⁺) and at 0.1C for LiNi_1/3Co_1/3Mn_1/3O₂ prepared by modified Pechini method was obtained, higher than that of the sample prepared by Pechini method (143.5 mAh/g). Moreover, the comparison of electrochemical results at different current rates indicated that the sample prepared by modified Pechini method exhibited improved rate capability.     

Polypyrrole-Fe2O3 nanohybrid materials for electrochemical storage

We report on the synthesis and electrochemical characterization of nanohybrid polypyrrole (PPy) (PPy/Fe₂O₃) materials for electrochemical storage applications. We have shown that the incorporation of nanoparticles inside the PPy notably increases the charge storage capability in comparison to the “pure” conducting polymer. Incorporation of large anions, i.e., paratoluenesulfonate, allows a further improvement in the capacity. These charge storage modifications have been attributed to the morphology of the composite in which the particle sizes and the specific surface area are modified with the incorporation of nanoparticles. High capacity and stability have been obtained in PC/NEt₄BF₄ (at 20 mV/s), i.e., 47 mAh/g, with only a 3% charge loss after one thousand cyles. The kinetics of charge–discharge is also improved by the hybrid nanocomposite morphology modifications, which increase the rate of insertion–expulsion of counter anions in the bulk of the film. A room temperature ionic liquid such as imidazolium trifluoromethanesulfonimide seems to be a promising electrolyte because it further increases the capacity up to 53 mAh/g with a high stability during charge–discharge processes.     

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.     

Synthesis and electrochemical properties of Zn3V3O8 as novel anode material

Zn₃V₃O₈ two-dimensional micro sheets are successfully synthesized by combination of solvothermal method and heat treatment. The Zn₃V₃O₈ has better electrochemical performances after calcinations.     

高比能LiFePO_4的制备及性能研究

应用液相沉淀法-固相烧结法制备高密度的LiFePO4/C及纯相LiFePO4.X射线衍射、扫描电镜、傅立叶红外光谱仪、电化学性能测试表明:该样品具有单一的橄榄石结构和3.4 V左右的放电平台,掺碳的LiFe-PO4具有更优良的性能,粒度较小粒径分布均匀,振实密度达1.46 g/cm3,0.1C首次放电比容量为144.6mAh/g,循环20次后容量保持率为93.2%,1C倍率首次放电比容量为133.5 mAh/g,循环20次后容量下降8.76%.     

纳米钴基氧化物锂离子电池负极材料的研究

采用流变相法合成Co3 O4 ,CoB1.3 6 O2 .8,CoB0 .5Al0 .1O1.5样品 ,并研究其作为锂离子电池负极材料的电化学性能 .当电池在 0 .0 1～ 3.0 0V的电压范围之间循环时 ,Li/Co3 O4 电池表现出最好的充放电性能 :循环 30周后 ,可逆比容量仍能保持为初始比容量 (931mAh/g)的 95 % .掺杂了B ,Al材料 ,其可逆比容量与未掺杂的相比明显降低 ,而且第 1周可逆容量随掺杂的B、Al量的增加而减少 .通过异位XRD方法研究了不同充放电态Co3 O4 电极材料结构的变化 .结果表明 ,Co3 O4 电极在充放电过程中与Li的反应机理不同于传统的过渡金属与Li的反应机理 ,即非Li+ 的嵌入 /脱出或合金的形成 ,而是Co3 O4 的可逆还原氧化以及Li2 O的可逆形成与分解机理     

钼掺杂Li3V2（PO4）3/C正极材料的制备及其电化学性能研究

以Li2CO3、NH4H2PO4、V2O5和MoO3为原料,柠檬酸为络合剂和碳源,采用溶胶-凝胶法制备了锂离子正极材料Li3MoxV2-x(PO4)3/C(x=0.01,0.02,0.03).X射线衍射(XRD)表明,合成的材料具有单一的单斜晶系结构,空间群为P21/n.扫描电镜(SEM)显示Li3Mo0.02V1.98(PO4)3/C具有均一的表面形貌.恒流充放电测试表明,当x=0.02时,掺杂后的Li3Mo0.02V1.98(PO4)3具有最佳的电化学性能.在1C倍率下,3.0～4.3 V电位区间,Li3Mo0.02V1.98(PO4)3/C的首次放电比容量达到122.3 mAh.g-1,循环50周之后,容量没有衰减的迹象;而当x=0、0.01和0.03时,首次放电比容量仅分别为117.1、115.1和116.0 mAh.g-1.在3C和5C倍率下,样品Li3Mo0.02V1.98(PO4)3/C仍能保持优异的循环稳定性.     

Synthesis and electrochemical characterizations of nano-crystalline LiFePO4 and Mg-doped LiFePO4 cathode materials for rechargeable lithium-ion batteries

Nano-crystalline LiFePO₄ and LiMg_0.05Fe_0.95PO₄ cathode materials were synthesized by sol–gel method in argon atmosphere using succinic acid as a chelating agent. Physico-chemical characterizations were done by thermogravimetric and differential thermal analysis, X-ray diffraction, scanning electron microscopy, transmittance electron microscopy, and Raman spectroscopy. Electrochemical behavior of the cathode materials were analyzed using cyclic voltammetry, and galvanostatic charge/discharge cycling studies were employed to characterize the reaction of lithium-ion insertion into and extraction from virginal and magnesium-doped LiFePO₄, in the voltage range 2.5 to 4.5 V (Vs Li/Li⁺) using 1 M LiPF₆ with 1:1 ratio of ethylene carbonate and dimethyl carbonate as electrolytes. LiMg_0.05Fe_0.95PO₄ exhibits initial charge and discharge capacities of 159 and 141 mAh/g at 0.2 C rate respectively, as compared to 121 and 107 mAh/g of pristine LiFePO₄. Furthermore, LiMg_0.05Fe_0.95PO₄ has retained more than 89% of the capacity even after 60 cycles. Hence, LiMg_0.05Fe_0.95PO₄ is a promising cathode material for rechargeable lithium-ion batteries.