This review provides a personal account of career‐long efforts, interwoven with the contributions of others, to exploit the B2O4 framework of an AB2O4 spinel structure for lithium‐ion battery ...applications, where A = Li, and B is one or more metal cations. The narrative starts at the Council for Scientific and Industrial Research (CSIR) in South Africa in the mid‐1970s when, in response to the Middle East oil crisis, worldwide efforts were turned to develop high‐temperature sodium and lithium batteries to power electric vehicles. In 1981, results in CSIR's program on a high‐temperature lithium battery led to a collaborative project on room‐temperature lithium cells with Prof. John B. Goodenough at Oxford University, where studies of Fe3O4, Mn3O4, and LiMn2O4 cathodes led to the recognition of the broad utility of the B2O4 spinel framework as an anode, cathode, or solid electrolyte for rechargeable lithium cells. This finding has had a profound and lasting impact, influencing further ideas and discoveries at the CSIR, Argonne National Laboratory, and elsewhere. The narrative emphasizes the compositional versatility of the spinel structure and the opportunities to tailor the electrochemical potential and stability of a Li‐ion cell.
This personal and historical review highlights the unique and versatile properties of the B2O4 framework of a LiB2O4 spinel as an electrode for lithium‐ion batteries, which, with its 3D network of channels, has been exploited both as an anode and a cathode. Minimal disorder between the lithium and metal (B) cations can modify the electrochemical signature of the electrode.
The escalating and unpredictable cost of oil, the concentration of major oil resources in the hands of a few politically sensitive nations, and the long-term impact of CO
2
emissions on global ...climate constitute a major challenge for the 21
st
century. They also constitute a major incentive to harness alternative sources of energy and means of vehicle propulsion. Today's lithium-ion batteries, although suitable for small-scale devices, do not yet have sufficient energy or life for use in vehicles that would match the performance of internal combustion vehicles. Energy densities 2 and 5 times greater are required to meet the performance goals of a future generation of plug-in hybrid-electric vehicles (PHEVs) with a 40-80 mile all-electric range, and all-electric vehicles (EVs) with a 300-400 mile range, respectively. Major advances have been made in lithium-battery technology over the past two decades by the discovery of new materials and designs through intuitive approaches, experimental and predictive reasoning, and meticulous control of surface structures and chemical reactions. Further improvements in energy density of factors of two to three may yet be achievable for current day lithium-ion systems; factors of five or more may be possible for lithium-oxygen systems, ultimately leading to our ability to confine extremely high potential energy in a small volume without compromising safety, but only if daunting technological barriers can be overcome.
Confining extremely high potential energy in a small volume without compromising safety or lifetime is the grand challenge of lithium batteries.
Autogenic reactions, based on the decomposition of one or more precursors at elevated temperatures with self generated pressures can be used to prepare a wide range of materials with interesting ...structural, morphological and technological properties. Recent reports that spherical carbon particles and carbon nanotubes can be prepared by this technique from waste products, such as used plastic bags, have highlighted this environmentally-attractive approach to synthesize new or modified carbon-based materials. In this paper, we report the synthesis of spherical carbon particles and carbon nanotubes and their evaluation as negative electrodes (anodes) in lithium electrochemical cells. A steady reversible capacity of approximately 240 mAh/g for hundreds of cycles was achieved from both types of carbon, when cycled at a 1C rate between 1.5 V and 5 mV. A reversible capacity of 372 mAh/g, i.e., the theoretical value for graphite, was obtained from the carbon nanotube electrodes by raising the upper voltage limit to 3 V. To increase the graphitic order in the carbon spheres, the particles were heated to 2400 degreeC in an inert atmosphere. This treatment reduced the first cycle irreversible capacity loss of Li/C half cells from 60 to 20%, the spherical carbon electrodes yielding a stable 252 mAh/g discharge capacity for numerous cycles. Structural and morphological information about the parent and cycled carbon electrodes, obtained by powder X-ray diffraction, Raman spectroscopy, high-resolution scanning electron microscopy, and electron dispersive analysis of X-rays is provided.
Crystalline defects are commonly generated in lithium-metal-oxide electrodes during cycling of lithium-ion batteries. Their role in electrochemical reactions is not yet fully understood because, ...until recently, there has not been an effective operando technique to image dynamic processes at the atomic level. In this study, two types of defects were monitored dynamically during delithiation and concomitant oxidation of oxygen ions by using in situ high-resolution transmission electron microscopy supported by density functional theory calculations. One stacking fault with a fault vector b/6110 and low mobility contributes minimally to oxygen release from the structure. In contrast, dissociated dislocations with Burgers vector of c/2001 have high gliding and transverse mobility; they lead to the formation, transport and release subsequently of oxygen related species at the surface of the electrode particles. This work advances the scientific understanding of how oxygen participates and the structural response during the activation process at high potentials.
Lithium-ion batteries (LIBs) have been used widely in portable electronics, and hybrid-electric and all-electric vehicles for many years. However, there is a growing need to develop new cathode ...materials that will provide higher cell energy densities for advanced applications. Several candidates, including Li2MnO3-stabilized LiM'O2 (M' = Mn/Ni/Co) structures, Li2Ru0.75Sn0.25O3 (i.e., 3Li2RuO3–Li2SnO3), and disordered Li2MoO3–LiCrO2 compounds can yield capacities exceeding 200 mA h g-1, alluding to the constructive role that Li2MO3 (M4+) end-member compounds play in the electrochemistry of these systems. Here in this paper, we catalog the family of Li2MO3 compounds as active cathodes or inactive stabilizing agents using high-throughput density functional theory (HT-DFT). With an exhaustive search based on design rules that include phase stability, cell potential, resistance to oxygen evolution, and metal migration, we predict a number of new Li2MIO3–Li2MIIO3 active/inactive electrode pairs, in which MI and MII are transition- or post-transition metal ions, that can be tested experimentally for high-energy-density LIBs.
The cathode in rechargeable lithium-ion batteries operates by conventional intercalation; Li+ is extracted from LiCoO2 on charging accompanied by oxidation of Co3+ to Co4+; the process is reversed on ...discharge. In contrast, Li+ may be extracted from Mn4+-based solids, e.g., Li2MnO3, without oxidation of Mn4+. A mechanism involving simultaneous Li and O removal is often proposed. Here, we demonstrate directly, by in situ differential electrochemical mass spectrometry (DEMS), that O2 is evolved from such Mn4+-containing compounds, LiNi0.2Li0.2Mn0.6O2, on charging and using powder neutron diffraction show that O loss from the surface is accompanied by diffusion of transition metal ions from surface to bulk where they occupy vacancies created by Li removal. The composition of the compound moves toward MO2. Understanding such unconventional Li extraction is important because Li−Mn−Ni−O compounds, irrespective of whether they contain Co, can, after O loss, store 200 mAhg-1 of charge compared with 140 mAhg-1 for LiCoO2.
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