Energy production and storage are critical research domains where the demands for improved energy devices and the requirement for greener energy resources are increasing. There is particularly intense interest in Lithium (Li)-ion batteries for all kinds of electrochemical energy storage. Li-ion batteries are currently the primary energy storage devices in the communications, transportation and renewable-energy sectors. However, scaling up the Liion battery technology to meet current increasing demands is still problematic and issues such as safety, costs, and electrode materials with higher performance are under intense investigation. The Li-sulphur (S) battery is a promising electrochemical system as a highenergy secondary battery, particularly for large-scale applications, due to its low cost, theoretically large specific capacity, theoretically high specific energy, and its ecofriendly footprint. The Li-S battery exhibits excellent potential and has attracted the attention of battery developers in large scale production in recent years. This review aims to highlight recent advances in the Li-S battery, providing an overview of the Li-ion battery applications in energy storage, then detailing the challenges facing Li-S battery and current applied strategies for improvement in its efficiency.

Experiments have been performed on specimens subjected to strain cycles similar to those experienced by sub-surface elements of material in rolling/sliding contact. It has been observed that if the strain cycle is closed then failure takes place by low cycle fatigue and the Coffin-Manson relationship may be used to predict the number of cycles to failure. If however, the strain cycle is open, so that the material accumulates unidirectional plastic strain (the situation known as "ratchetting") a different type of failure, which is termed ratchetting failure may occur. It occurs when the total accumulated plastic strain reaches a critical value which is comparable with the strain to failure in a monotonic tension test. The number of cycles to failure under these circumstances may be estimated by dividing this critical strain by the ratchetting strain per cycle. It is suggested that low cycle fatigue and ratchetting are independent and competitive mechanisms so that failure occurs by whichever of them corresponds to a shorter life. The results of both uniaxial and biaxial tests reported in the literature have been re-evaluated and these, together with new data on biaxial tests on copper, found to be consistent with this hypothesis. NOMENCLATUREC = constant 1 = length of gauge section of the specimen n =constant N = observed number of cycles to failure LCF = low cycle fatigueNf, N, = predicted number of cycles to failure by low cycle fatigue or ratchetting r =length and average radius of gauge section of the specimen RF = ratchetting failure AF&, A& = direct and shear strains of a material element in rolling/sliding E, = critical strain for failure by ratchetting E~ = strain to failure determined in a monotonic test E~, yT = total accumulated axial and shear strain A&, Ay = average ratchetting axial and shear strain per cycle A+, AyP = alternating plastic axial and shear strain per cycle Acr = equivalent ratchetting plastic strain per cycle 0, A0 = total twist and average twist per cycle

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Nanostructured materials such as nanocomposites and nanolaminates are currently of intense interest in modern materials research.

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