High-capacity Lithium Batteries Research Articles

Reversible Three-Electron Redox Behaviors of FeF3 Nanocrystals as High-Capacity Cathode-Active Materials for Li-Ion Batteries

Three types of FeF3 nanocrystals were synthesized by different chemical routes and investigated as a cathode-active material for rechargeable lithium batteries. XRD and TEM analyses revealed that the as-synthesized FeF3 samples have a pure ReO3-type structure with a uniformly distributed crystallite size of ∼10 to 20 nm. Charge−discharge experiments in combination with cyclic voltammetric and XRD evidence demonstrated that the FeF3 in the nanocomposite electrode can realize a reversible electrochemical conversion reaction from Fe3+ to Fe0 and vice versa, enabling a complete utilization of its three-electron redox capacity (∼712 mAh·g−1). Particularly, the FeF3/C nanocomposites can be well cycled at very high rates of 1000−2000 mA·g−1, giving a considerably high capacity of ∼500 mAh·g−1. These results seem to indicate that the electrochemical conversion reaction can not only give a high capacity but also proceed reversibly and rapidly at room temperature as long as the electroactive FeF3 particles are sufficiently downsized, electrically wired, and well-protected from aggregation. The high-rate capability of the FeF3/C nanocomposite also suggests its potential applications for high-capacity rechargeable lithium batteries.

Control of the carbon shell thickness in Sn 70Ge 30@carbon core–shell nanoparticles using alkyl terminators: Its implication for high-capacity lithium battery anode materials

This paper describes the synthesis and electrochemical characterization of Sn 70Ge 30@carbon core–shell nanoparticles prepared by vacuum annealing of the alkyl-capped Sn 70Ge 30 nanoparticles obtained from the reaction of SnCl 4 and GeCl 4 with sodium naphthalide in ethylene glycol dimethyl ether (glyme) and RLi (R = butyl, ethyl, methyl). The Sn 70Ge 30@carbon core–shell nanoparticles have different core sizes and shell thicknesses depending on the alkyl terminator. The annealed nanoparticles that terminate with butyl and ethyl groups have core sizes of ∼14 and ∼17 nm with carbon shell thicknesses of ∼16 and ∼8 nm, respectively. On the other hand, annealed nanoparticles that terminate with methyl groups have core sizes of 40 nm with a very thin carbon shell without uniform coverage of the core. Electrochemical characterization shows that nanoparticles prepared using butyl terminators have the highest capacity retention out to 40 cycles (95%) and a first charge capacity of 1040 mAh/g. On the other hand, ethyl- and methyl-capped nanoparticles show 82 and 64% capacity retention after 40 cycles.

Size effect of tin oxide nanoparticles on high capacity lithium battery anode materials

Tin oxide anode materials have a high reversible capacity for secondary lithium ion batteries. However, the volume expansion of tin oxide is known to reduce the battery cycle life. Nanocomposite anode materials were thus synthesized using a sol–gel method to solve this problem. The nanocomposite materials (SnO 2/C) have a core–shell structure. The core is made of commercial graphite (∼ 10 μm) and the shell is made of the tin oxide nanoparticles. The morphology and the nanostructure were characterized by SEM (JSM-6500F) and the results of electrochemical tests were analyzed using an Arbin BT2400 battery tester. The tin oxide nanoparticles (∼ 20 nm) uniformly dispersed on the surface of commercial graphite. The tin oxide nanoparticles had a markedly greater cyclability than the micro-tin oxide particles. The tin oxide nanoparticles are believed to reduce the effect of volume expansion. It is apparent that the nanocomposite structure (SnO 2/C) inhibits the volume expansion of the tin oxide anode materials.

Synthesis of Spherical Nano- to Microscale Core−Shell Particles Li[(Ni0.8Co0.1Mn0.1)1-x(Ni0.5Mn0.5)x]O2 and Their Applications to Lithium Batteries

Spherical nano- to microscale core−shell Li[(Ni0.8Co0.1Mn0.1)1-x(Ni0.5Mn0.5)x]O2 was successfully synthesized via a coprecipitation route. The structure, chemical composition, and morphology of the core−shell powders can be tailored by tuning the reaction conditions. The core−shell-structured material provides a significant breakthrough in the development of high-capacity lithium batteries with respect to energy density, cycle life, and safety.

Synthesis and Characterization of Li[(Ni0.8Co0.1Mn0.1)0.8(Ni0.5Mn0.5)0.2]O2 with the Microscale Core−Shell Structure as the Positive Electrode Material for Lithium Batteries

The high capacity of Ni-rich Li[Ni(1-x)M(x)]O(2) (M = Co, Mn) is very attractive, if the structural instability and thermal properties are improved. Li[Ni(0.5)Mn(0.5)]O(2) has good thermal and structural stabilities, but it has a low capacity and rate capability relative to the Ni-rich Li[Ni(1-x)M(x)]O(2). We synthesized a spherical core-shell structure with a high capacity (from the Li[Ni(0.8)Co(0.1)Mn(0.1)]O(2) core) and a good thermal stability (from the Li[Ni(0.5)Mn(0.5)]O(2) shell). This report is about the microscale spherical core-shell structure, that is, Li[Ni(0.8)Co(0.1)Mn(0.1)]O(2) as the core and a Li[Ni(0.5)Mn(0.5)]O(2) as the shell. A high capacity was delivered from the Li[Ni(0.8)Co(0.1)Mn(0.1)]O(2) core, and a high thermal stability was achieved by the Li[Ni(0.5)Mn(0.5)]O(2) shell. The core-shell structured Li[(Ni(0.8)Co(0.1)Mn(0.1))(0.8)(Ni(0.5)Mn(0.5))(0.2)]O(2)/carbon cell had a superior cyclability and thermal stability relative to the Li[Ni(0.8)Co(0.1)Mn(0.1)]O(2) at the 1 C rate for 500 cycles. The core-shell structured Li[(Ni(0.8)Co(0.1)Mn(0.1))(0.8)(Ni(0.5)Mn(0.5))(0.2)]O(2) as a new positive electrode material is a significant breakthrough in the development of high-capacity lithium batteries.

Investigation of possible superstructure and cation disorder in the lithium battery cathode material LiMn 1/3Ni 1/3Co 1/3O 2 using neutron and anomalous dispersion powder diffraction

A study has been conducted to discover whether the recently reported high-capacity lithium battery material LiMn 1/3Ni 1/3Co 1/3O 2 possesses a superstructure due to ordering of the transition metal cations. A recent paper in the literature concluded from ab initio calculations that, if a superstructure exists, it would likely take the form of a [√3×√3]R30° type superlattice rather than an ordered stacking of Co–O 2, Ni–O 2, and Mn–O 2 slabs. A suitable technique to detect the presence or otherwise of a superstructure in this material is neutron diffraction due to the contrast between Mn, Ni, and Co neutron scattering lengths. An alternative method to enhance the contrast between elements close in the periodic table is to use resonant diffraction techniques. The beneficial contrasts afforded by each method may be retained by conducting a simultaneous refinement using both neutron and X-ray data. It was found that LiMn 1/3Ni 1/3Co 1/3O 2 did not appear to possess either of the proposed types of supercell and that the data were consistent with a random distribution of Mn, Ni, and Co over the R-3m 3a sites. Simultaneous Rietveld analysis showed that some nickel displaced lithium from the 3b site, whilst the manganese and cobalt remained solely on the transition metal 3a site.

X‐Ray Absorption Spectroscopy Study of Cu0.25V2O5 and Zn0.25V2O5 Aerogel‐Like Cathodes for Lithium Batteries.

AbstractFor Abstract see ChemInform Abstract in Full Text.

X-ray Absorption Spectroscopy Study of Cu0.25V2O5 and Zn0.25V2O5 Aerogel-Like Cathodes for Lithium Batteries

Vanadium pentoxide materials prepared through sol−gel processes (xerogel, aerogel, and aerogel-like) act as excellent intercalation hosts for lithium as well as polyvalent cations. The large lithium insertion capacity of these materials makes them attractive for use as cathodes in high-capacity lithium batteries. The local structural modifications resulting from low dopant concentration (copper and zinc) in V2O5 aerogel-like material have been investigated by X-ray absorption spectroscopy (XAS). To study the structural sites of the polyvalent ions, extended X-ray absorption fine structure (EXAFS) spectra have been recorded at the vanadium, zinc, and copper K edges. The EXAFS analysis shows that the vanadium atomic environment is almost the same for Cu0.25V2O5 and Zn0.25V2O5. Furthermore, the doping metals (Cu and Zn) are found to be in the same site. Copper and zinc are 4-fold coordinated by almost-coplanar oxygens. This suggests a preferred site for the doping metal (M) and the same interaction between t...

Absorption of polarized X-rays by V 2O 5-based cathodes for lithium batteries: an application

Vanadium pentoxide materials prepared through sol–gel processes (xerogel, aerogel and aerogel-like) act as excellent intercalation hosts for lithium as well as for polyvalent cations. The large lithium insertion capacity of these materials makes them attractive for use as cathodes in high capacity lithium batteries. This paper describes the utility of X-Ray absorption spectroscopy (XAS) for the investigation of gel-based V 2O 5 materials. In particular, X-ray near edge structure (XANES) and polarized EXAFS experiments are highlighted.

Evidence for Reversible Formation of Metallic Cu in Cu0.1 V 2 O 5 Xerogel Cathodes during Intercalation Cycling of Li + Ions as Detected by X-Ray Absorption Spectroscopy

Vanadium pentoxide materials prepared through sol-gel processes (xerogel, aerogel, and aerogel-like) act as excellent intercalation hosts for lithium as well as polyvalent cations. The large lithium insertion capacity of these materials makes them attractive for use as cathodes in high-capacity lithium batteries. Copper-doped cathodes have excellent properties in terms of high intercalation rate and very good reversibility upon cycling with no capacity fading after more than 450 cycles. This paper reports in situ X-ray absorption spectroscopy (XAS) investigations of copper-doped xerogel. The K-edge X-ray absorption thresholds of V and Cu were studied. The local structure around copper is found to change dramatically during individual insertion/release cycles for ions. The XAS analysis indicates that the lithiation of the xerogel cathode proceeds with concurrent formation of copper metal. However, the starting compound is regenerated upon releasing the inserted lithium (charging the cathode), thus revealing the foundation for excellent structural and electronic reversibility of the material. © 2001 The Electrochemical Society. All rights reserved.