Electronically conductive phospho-olivines as lithium storage electrodes

Doping-induced memory effect in Li-ion batteries: the case of Al-doped Li4Ti5O12

A memory effect in Li-ion batteries can be induced and tailored by element doping, such as Al-doping in spinel Li₄Ti₅O₁₂.

In Li-ion batteries (LIBs), a memory effect has been revealed in two-phase electrode materials such as olivine LiFePO₄ and anatase TiO₂, which complicates the two-phase transition and influences the estimation of the state of charge. Practical electrode materials are usually optimized by the element doping strategy, however, its impact on the memory effect has not been reported yet. Here we firstly present the doping-induced memory effect in LIBs. Pristine Li₄Ti₅O₁₂ is free from the memory effect, while a distinct memory effect could be induced by Al-doping. After being discharged to a lower cutoff potential, Al-doped Li₄Ti₅O₁₂ exhibits poorer electrochemical kinetics, delivering a larger overpotential during the charging process. This dependence of the overpotential on the discharging cutoff leads to the memory effect in Al-doped Li₄Ti₅O₁₂. Our discovery emphasizes the impact of element doping on the memory effect of electrode materials, and thus has implications for battery design.

Role of PO4 tetrahedron in LiFePO4 and FePO4 system

Using high resolution transmission electron microscopy with image simulation and Fourier analysis, the Li1- x FePO4 (x < 0.01), Li1- x FePO4 (x ∼ 0.5), and FePO4 particles, prepared by charging or discharging the 053048 electrochemical cells (thickness: 5 mm, width: 30 mm, height: 48 mm) and dismantled inside an Ar-filled dry box, were investigated. The high resolution images reveal: (1) the solid solution of Li1- x FePO4 (x < 0.01) contains some missing Li ions leading PO4 group distorted around M1 tunnel of the unit cell; (2) the texture of the particles of Li1- x FePO4 (x ∼0.5) has homogeneously distributed compositional domains of LiFePO4 and FePO4 resulting from spinodal decomposition which promote Li ion easily getting into the particle due to uphill diffusion, (3) the particles of FePO4 formed in charging have heavily distorted lattice and contain some isolated LiFePO4 , (4) interface between LiFePO4 and FePO4 and between amorphous and crystal region provides the lattice distortion of small polarons.

Fabricating high performance lithium-ion batteries using bionanotechnology

Designing, fabricating, and integrating nanomaterials are key to transferring nanoscale science into applicable nanotechnology. Many nanomaterials including amorphous and crystal structures are synthesized via biomineralization in biological systems. Amongst various techniques, bionanotechnology is an effective strategy to manufacture a variety of sophisticated inorganic nanomaterials with precise control over their chemical composition, crystal structure, and shape by means of genetic engineering and natural bioassemblies. This provides opportunities to use renewable natural resources to develop high performance lithium-ion batteries (LIBs). For LIBs, reducing the sizes and dimensions of electrode materials can boost Li(+) ion and electron transfer in nanostructured electrodes. Recently, bionanotechnology has attracted great interest as a novel tool and approach, and a number of renewable biotemplate-based nanomaterials have been fabricated and used in LIBs. In this article, recent advances and mechanism studies in using bionanotechnology for high performance LIBs studies are thoroughly reviewed, covering two technical routes: (1) Designing and synthesizing composite cathodes, e.g. LiFePO4/C, Li3V2(PO4)3/C and LiMn2O4/C; and (2) designing and synthesizing composite anodes, e.g. NiO/C, Co3O4/C, MnO/C, α-Fe2O3 and nano-Si. This review will hopefully stimulate more extensive and insightful studies on using bionanotechnology for developing high-performance LIBs.

Storing energy in plastics: a review on conducting polymers & their role in electrochemical energy storage

This review article on conducting polymers discusses the background & theory behind their conductivity, the methods to nano-engineer special morphologies & recent contributions to the field of energy (e.g.supercapacitors, batteries and fuel cells).

Advances in high-capacity Li2MSiO4 (M = Mn, Fe, Co, Ni, …) cathode materials for lithium-ion batteries

This review highlights the high-capacity Li₂MSiO₄ (M = Mn, Fe, Co, Ni, …) cathode materials for lithium-ion batteries.

Very high power and superior rate capability LiFePO4 nanorods hydrothermally synthesized using tetraglycol as surfactant

Small polarizations, i.e. sufficiently good electronic and ionic conductivity is indispensible for high power lithium iron phosphate, especially for its applications to large current power supplies.

Fabrication and properties of polybutadiene rubber-interpenetrating cross-linking poly(propylene carbonate) network as gel polymer electrolytes for lithium-ion battery

Novel polybutadiene rubber interpenetrating cross-linking poly(propylene carbonate) network has been synthesized as GPEs with excellent electrochemical performances for lithium-ion batteries.

Porous micro-spherical LiFePO4/CNT nanocomposite for high-performance Li-ion battery cathode material

Although many routes have been developed that can efficiently improve the electrochemical performance of LiFePO₄ cathodes, few of them meet the urgent industrial requirements of large-scale production, low cost and excellent performance.

Synthesis, and crystal and electronic structure of sodium metal phosphate for use as a hybrid capacitor in non-aqueous electrolyte

A mixed sodium transition metal phosphate served as an active electrode material for a hybrid supercapacitor, offering new possibilities for sodium hybrid devices.

Nitrogen-doped carbon coated LiFePO4/carbon nanotube interconnected nanocomposites for high performance lithium ion batteries

High performance conductive networks, which were fabricated from a nitrogen-doped carbon layer and 3D CNT networks, have been prepared.

High performance (1 − x)LiMnPO4·xLi3V2(PO4)3/C composite cathode materials prepared by a sol–gel method

A series of (1 − x)LiMnPO₄·xLi₃V₂(PO₄)₃/C (x = 0, 0.1, 0.3, 0.5, 0.7, 0.9 and 1) composite nanoparticles are synthesized as cathode materials for lithium-ion batteries by the sol–gel method, using N,N-dimethyl formamide as a dispersing agent.

Synthesis and electrochemical investigation of novel phosphite based layered cathodes for Li-ion batteries

Reversible lithium storage has been demonstrated in novel phosphite containing cathode materials, A₂[(VO)₂(HPO₃)₂(C₂O₄)]; A = Li, Na and K.

A Mo-doped TiNb2O7 anode for lithium-ion batteries with high rate capability due to charge redistribution

High rate capability of TiNb₂O₇ due to charge redistribution upon doping with Mo⁶⁺.

Hydrothermal synthesis, evolution, and electrochemical performance of LiMn0.5Fe0.5PO4 nanostructures

Composition and crystallographic structural evolution of the intermediate involved in the organic free hydrothermal synthesis of LiMn_0.5Fe_0.5PO₄ nanostructures.

Materials for suspension (semi-solid) electrodes for energy and water technologies

Conducting suspension electrodes for novel flow-assisted electrochemical systems such as grid energy storage, water deionization, and water treatment.

Crystal structures and luminescence properties of Eu2+-activated new NaBa0.5Ca0.5PO4 and Na3Ba2Ca(PO4)3

In the NaBa_1−xCa_xPO₄ system, three kinds of crystal structure were observed at x = 0, 1/3 and 0.5. New crystal structures were formed rather than the formation of solid solutions. Eu-doped samples exhibited an emission maximum between 435 nm and 460 nm, depending on the amount of Ca.

High-rate performance of a mixed olivine cathode with off-stoichiometric composition

By controlling off-stoichiometry, LiFe_0.6Mn_0.4PO₄ with non-crystalline surface phases is formed, enabling the material to achieve high power density.

Large-scale preparation of Mg doped LiFePO4@C for lithium ion batteries via carbon thermal reduction combined with aqueous rheological phase technology

A uniform distribution of doped metal and coated carbon in the as-prepared LiFePO₄material is obtained. The LiFePO₄delivers a discharge capacity of 166 mA h g⁻¹at 0.1C and presents excellent rate capacity and a high potential plateau at 1C.

Etched colloidal LiFePO4 nanoplatelets toward high-rate capable Li-ion battery electrodes

LiFePO4 has been intensively investigated as a cathode material in Li-ion batteries, as it can in principle enable the development of high power electrodes. LiFePO4, on the other hand, is inherently "plagued" by poor electronic and ionic conductivity. While the problems with low electron conductivity are partially solved by carbon coating and further by doping or by downsizing the active particles to nanoscale dimensions, poor ionic conductivity is still an issue. To develop colloidally synthesized LiFePO4 nanocrystals (NCs) optimized for high rate applications, we propose here a surface treatment of the NCs. The particles as delivered from the synthesis have a surface passivated with long chain organic surfactants, and therefore can be dispersed only in aprotic solvents such as chloroform or toluene. Glucose that is commonly used as carbon source for carbon-coating procedure is not soluble in these solvents, but it can be dissolved in water. In order to make the NCs hydrophilic, we treated them with lithium hexafluorophosphate (LiPF6), which removes the surfactant ligand shell while preserving the structural and morphological properties of the NCs. Only a roughening of the edges of NCs was observed due to a partial etching of their surface. Electrodes prepared from these platelet NCs (after carbon coating) delivered a capacity of ∼ 155 mAh/g, ∼ 135 mAh/g, and ∼ 125 mAh/g, at 1 C, 5 C, and 10 C, respectively, with significant capacity retention and remarkable rate capability. For example, at 61 C (10.3 A/g), a capacity of ∼ 70 mAh/g was obtained, and at 122 C (20.7 A/g), the capacity was ∼ 30 mAh/g. The rate capability and the ease of scalability in the preparation of these surface-treated nanoplatelets make them highly suitable as electrodes in Li-ion batteries.

Morphology-controlled synthesis of self-assembled LiFePO4/C/RGO for high-performance Li-ion batteries

Novel architectured LiFePO4 (LFP) that consisted of ordered LFP nanocubes was prepared through a facile hydrothermal method using polyethylene glycol (PEG) as a surfactant. The micro/nanostructured LFP with various morphologies ranging from cube cluster to rugby-like structure was synthesized via controlling the pH values of the precursor. A reasonable assembly process elucidating the formation of the hierarchical structure is also provided based on the experimental results. After a combination of carbon (C) coating and reduced graphene oxide (RGO) wrapping, the obtained LFP/C/RGO composites exhibit enhanced electrochemical performance compared to that of blank LFP synthesized under the same condition. Among as-synthesized cube-cluster-like, dumbbell-like, rod-like, and rugby-like composites, the rugby-like LFP/C/RGO reveal the best electrochemical properties with the discharge specific capacity of ∼150 mA h g(-1) after 100 cycles and a high reversible specific capacity of 152 mA h g(-1) at 0.1 C. The prepared LFP/C/RGO composite can be a promising cathode material for high energy, low cost, and environmentally friendly lithium-ion batteries.

Mechanical force-driven growth of elongated bending TiO2 -based nanotubular materials for ultrafast rechargeable lithium ion batteries

A stirring hydrothermal process that enables the formation of elongated bending TiO2 -based nanotubes is presented. By making use of its bending nature, the elongated TiO2 (B) nanotubular crosslinked-network anode electrode can cycle over 10 000 times in half cells while retaining a relatively high capacity (114 mA h g(-1)) at an ultra-high rate of 25 C (8.4 A g(-1)).

A XANES study of LiVPO4F: a factor analysis approach

Evolving factor analysis (EFA) of X-ray absorption near-edge spectroscopy (XANES) data is shown to be a useful tool to understand the phase relationships and compositional ranges of stability in the LiVPO4F-VPO4F system. EFA was used to calculate the concentration of phases versus state-of-charge in a lithium-ion battery and true XANES spectra. The results of EFA showed that, indeed, three phases were present during cycling of a LiVPO4F∥Li cell: LiVPO4F, LixVPO4F, and VPO4F. In contrast to what was reported by others, the second phase was not a fixed composition with x = 0.67, but, instead, existed over a range of lithium stoichiometry, x = 0.25 to 0.80. EFA results also showed that the reactions leading to these phases are reversible.