Lithium can be reversibly intercalated into layered Li 1+x V 1−x O 2 (LiCoO 2 structure) at ∼0.1 V, but only if x > 0. The low voltage combined with a higher density than graphite results in a higher theoretical volumetric energy density; important for future applications in portable electronics and electric vehicles. Here we investigate the crucial question, why Li cannot intercalate into LiVO 2 but Li-rich compositions switch on intercalation at an unprecedented low voltage for an oxide? We show that Li + intercalated into tetrahedral sites are energetically more stable for Li-rich compositions, as they share a face with Li + on the V site in the transition metal layers. Li incorporation triggers shearing of the oxide layers from cubic to hexagonal packing because the Li 2 VO 2 structure can accommodate two Li per formula unit in tetrahedral sites without face sharing. Such understanding is important for the future design and optimization of low-voltage intercalation anodes for lithium batteries.R ecent reports that Li can be reversibly intercalated into the layered compound Li 1+x V 1−x O 2 (with the LiCoO 2 structure) at a potential of ∼0.1 V versus Li + /Li represent an important milestone in lithium-ion battery research 1-4 . For almost twenty years graphite has remained the dominant anode in rechargeable lithium-ion batteries; operating by intercalation of Li between the graphene sheets. Efforts to improve on the energy storage of graphite have concentrated on reactions other than intercalation, including silicon and tin anodes that form alloys with Li, conversion/displacement reactions such as Li + CoO and extrusion reactions . Although work on these alternatives to intercalation has made important progress, and Sn-Co-C alloys are in use, in general, problems of large volume expansion or large voltage hysteresis remain to be solved. As a result, intercalation remains an attractive mechanism for lithium-ion batteries.Oxide intercalation hosts are attractive because their density is twice that of graphite, leading to double the volumetric energy density, something that is crucial for future applications in electronics and electric vehicles. The lowest voltage oxide intercalation hosts have been the titanates, but their potential is still relatively high at ∼1.6 V versus Li + /Li, compared with graphite at ∼0.1 V, thus halving the overall cell voltage and negating the benefits of using a dense oxide. This is why recent reports that Li can be intercalated into the layered transition metal oxide Li 1+x V 1−x O 2 , at ∼0.1 V and with a theoretical volumetric capacity of 1,360 mA h cm −3 compared to graphite at 790 mA h cm −3 , are so significant 1-4 . Also, intercalation into an oxide at such a low voltage is unprecedented as usually conversion/displacement reactions dominate in this voltage region 20,21 .Given the significance of Li intercalation into Li 1+x V 1−x O 2 , an important question that arises is why Li can only be intercalated into lithium-rich Li 1+x V 1−x O 2 , that is for x > 0 (refs 1,2). Here...

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The electrochemical behaviour of 3 polymorphs of the lithium intercalation compound Li2CoSiO4, betaI, betaII and gamma0, as positive electrodes in rechargeable lithium batteries is investigated for the first time.

Electric vehicle (EV) manufacturers are employing cylindrical format cells in the construction of the vehicles' battery systems. There is evidence to suggest that both the academic and industrial communities have evaluated cell degradation due to vibration and other forms of mechanical loading. The primary motivation is often the need to satisfy the minimum requirements for safety certification. However, there is limited research that quantifies the durability of the battery and in particular, how the cells will be affected by vibration that is representative of a typical automotive service life (e.g., 100,000 miles). This paper presents a study to determine the durability of commercially available 18,650 cells and quantifies both the electrical and mechanical vibration-induced degradation through measuring changes in cell capacity, impedance and natural frequency. The impact of the cell state of charge (SOC) and in-pack orientation is also evaluated. Experimental results are presented which clearly show that the performance of 18,650 cells can be affected by vibration profiles which are representative of a typical vehicle life. Consequently, it is recommended that EV manufacturers undertake vibration testing, as part of their technology selection and development activities to enhance the quality of EVs and to minimize the risk of in-service warranty claims.

Li2CoSiO4 was prepared in three polymorphic forms. The βII (Pmn21) polymorph was obtained by hydrothermal synthesis (150 °C), and subsequent heat treatments yielded the βI (Pbn21) form (700 °C) and the γ0 (P21 /n) form (1100° then quenching from 850 °C). Rietveld refinement of X-ray and neutron powder diffraction patterns reveal considerable Li/Co mixing for βII, very moderate mixing for βI, and no mixing for γ0. 7Li MAS NMR spectra have been recorded for the three forms. The mechanism of the Fermi contact interaction that leads to negatively shifted signals is as yet unexplained, but the nature and the number of signals were analyzed in relation to the site occupancies for each compound. The agreement is good for βII, although the extent of disorder leads to very poorly defined NMR signals; it is reasonable (although not fully quantitative) for βI, where well-defined NMR signals can be assigned to definite environments; finally, the γ0 sample surprisingly leads to a single rather broad NMR signal, whereas two well-defined and rather different environments are present in the structure deduced from diffraction.