María C. López

Improving the performance of titania nanotube battery materials by surface modification with lithium phosphate.

Self-organized TiO2 nanotubes ranging from amorphous to anatase structures were obtained by anodization procedures and thermal treatments at 500°C. Then electrolytic Li3PO4 films were successfully deposited on the nanotube array by an electrochemical procedure consisting in proton reduction with subsequent increase in pH, hydrogen phosphate dissociation and Li3PO4 deposition on the surface of the cathode. The Li3PO4 polymorph (γ or β) in the deposit could be tailored by modifying the electrodeposition parameters, such as time or current density, as determined by X-ray patterns. The morphological analysis evidenced the formation of a 3D nanostructure consisting of Li3PO4 coating the TiO2 nanotube array. The anode-solid electrolyte stacking was tested in lithium half cells. Interestingly, the electrochemical performances revealed a better cycling stability for samples containing low amount of lithium phosphate, which is deposited for short times and low current densities. These results suggested the possibility of fabricating 3D Li-ion batteries. nt-TiO2/γ-Li3PO4/LiFePO4 full cells were cycled at different rates in the C/5-5C range. This cathode-limited microbattery delivered a reversible gravimetric capacity of 110 mA h g(-1) and a capacity retention of 75 % after 190 cycles at 5C.

Enhancing the energy density of safer Li-ion batteries by combining high-voltage lithium cobalt fluorophosphate cathodes and nanostructured titania anodes

Recently, Li-ion batteries have been heavily scrutinized because of the apparent incompatibility between safety and high energy density. This work report a high voltage full battery made with TiO2/Li3PO4/Li2CoPO4F. The Li2CoPO4F cathode and TiO2 anode materials are synthesized by a sol–gel and anodization methods, respectively. X-ray diffraction (XRD) analysis confirmed that Li2CoPO4F is well-crystallized in orthorhombic crystal structure with Pnma space group. The Li3PO4-coated anode was successfully deposited as shown by the (011) lattice fringes of anatase TiO2 and (200) of γ-Li3PO4, as detected by HRTEM. The charge profile of Li2CoPO4F versus lithium shows a plateau at 5.0 V, revealing its importance as potentially high-voltage cathode and could perfectly fit with the plateau of anatase anode (1.8–1.9 V). The full cell made with TiO2/Li3PO4/Li2CoPO4F delivered an initial reversible capacity of 150 mA h g−1 at C rate with good cyclic performance at an average potential of 3.1–3.2 V. Thus, the full cell provides an energy density of 472 W h kg−1. This full battery behaves better than TiO2/Li2CoPO4F. The introduction of Li3PO4 as buffer layer is expected to help the cyclability of the electrodes as it allows a rapid Li-ion transport.

An Unnoticed Inorganic Solid Electrolyte: Dilithium Sodium Phosphate with the Nalipoite Structure

Solid electrolytes are crucial in the development of advanced lithium batteries and related technologies. Orthorhombic Li2NaPO4 (nalipoite) was synthesized, and its ionic conductivity compared very favorably with that of Li3PO4. The potential applicability of Li(3-x)Na(x)PO4 as a lithium ion solid electrolyte was investigated for first time. First-principles DFT calculations were used to evaluate the possibilities of preparing other crystal structures.

High Performance Full Sodium-Ion Cell Based on a Nanostructured Transition Metal Oxide as Negative Electrode.

A novel design of a sodium-ion cell is proposed based on the use of nanocrystalline thin films composed of transition metal oxides. X-ray diffraction, Raman spectroscopy and electron microscopy were helpful techniques to unveil the microstructural properties of the pristine nanostructured electrodes. Thus, Raman spectroscopy revealed the presence of amorphous NiO, α-Fe2 O3 (hematite) and γ-Fe2 O3 (maghemite). Also, this technique allowed the calculation of an average particle size of 23.4 Å in the amorphous carbon phase in situ generated on the positive electrode. The full sodium-ion cell performed with a reversible capacity of 100 mA h g(-1) at C/2 with an output voltage of about 1.8 V, corresponding to a specific energy density of about 180 W h kg(-1) . These promising electrochemical performances allow these transition metal thin films obtained by electrochemical deposition to be envisaged as serious competitors for future negative electrodes in sodium-ion batteries.

Can We Be Friends Here? Visitation and Hospitality in J.M. Coetzee's Disgrace

In his 1999 novel, Disgrace, J.M. Coetzee deals with both the perspicuous and subtle ways in which personal relationships in post-apartheid South Africa are conditioned by the persistent and entrenched legacy of apartheid and of centuries of racial inequality and oppression. However, and it is here that my analysis differs from those racialised readings the novel has received, Disgrace points to the fallacies of post-1994 ‘rainbowism’ by showing that inter-racial conflict is just one among the many others at work in South African society: the novel is pervaded by acts of violent intrusion that highlight the hostility and lack of understanding not only between blacks and whites, but also between different social groups such as landowners and tenants, country people and people from the city, men and women, parents and children, the old and the young, religious and non-religious people, and between human beings and animals. Simultaneously, we encounter acts of friendly visitation and hospitality that, on a more optimistic note, point to the possibility of creating a new community on the land in South Africa. Since unequal power relations in South Africa have been very much dependent on an unfair distribution and zealous possession of the land, Disgrace also suggests that the right relation to the land is that of the person who, instead of creating bonds of rooted attachment with it, adopts the stance of the visitor or guest. In order to justify my arguments, I will be often appealing to the textual immanence of the novel, in particular to over-lexicalisation and lexical repetition, central devices to which critics have not paid enough attention and which constitute explicit clues as to how to read this intensely self-reflexive novel.

Foe: A Ghost Story

This article argues that J.M. Coetzee’s Foe (1986) may be read as a ghost story, in which Coetzee writes back to Daniel Defoe’s “A True Relation of the Apparition of One Mrs. Veal”. The ghostly character of Coetzee’s novel derives from the silences and secrets pervading the narrator Susan’s story, among which Friday’s mute and enigmatic presence is the most overwhelming, and from the presence of strange creatures that seem to come from various Defoe’s literary works. Hence Susan begins to doubt her own ontological status and to consider herself, and also Friday and Foe, as ghosts, a notion which is explored in relation to Freud’s analysis of the uncanny and the double. Foe, thus, highlights an intimate relation between literature and secrecy, an idea that is developed in relation to the thinking of Jacques Derrida, J. Hillis Miller and Frank Kermode, this secret and indecipherable dimension of the literary work demanding, in turn, a position of blindness and lack of authority from both writer and critic.