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The lithium–sulphur battery (Li–S battery) is a type of rechargeable battery, notable for its high energy density.〔Zhang, Sheng S. "Liquid electrolyte lithium/sulfur battery: Fundamental chemistry, problems, and solutions" Journal of Power Sources 2013, vol. 231, 153-162. 〕 The low atomic weight of lithium and moderate weight of sulfur means that Li–S batteries are relatively light (about the density of water). They were used on the longest and highest-altitude solar-powered airplane flight in August 2008.〔Amos, J. (24 August 2008) ("Solar plane makes record flight" ) ''BBC News''〕 Lithium–sulphur batteries may succeed lithium-ion cells because of their higher energy density and reduced cost from the use of sulfur.〔Arumugam Manthiram, Yongzhu Fu, Yu-Sheng Su "Challenges and Prospects of Lithium–Sulfur Batteries" Acc. Chem. Res., 2013, volume 46, pp 1125–1134. 〕 Currently the best Li–S batteries offer specific energies on the order of 500 W·h/kg, significantly better than most lithium-ion batteries which are in the 150 to 200 range. Li–S batteries with up to 1,500 charge and discharge cycles have been demonstrated. As of early 2014 none were commercially available.〔(【引用サイトリンク】title=New lithium/sulfur battery doubles energy density of lithium-ion )〕 ==Chemistry== Chemical processes in the Li–S cell include lithium dissolution from the anode surface (and incorporation into alkali metal polysulfide salts) during discharge, and reverse lithium plating to the anode while charging.〔Tudron, F.B., Akridge, J.R., and Puglisi, V.J. (2004) ("Lithium-Sulfur Rechargeable Batteries: Characteristics, State of Development, and Applicability to Powering Portable Electronics" ) (Tucson, AZ: Sion Power)〕 This contrasts with conventional lithium-ion cells, where the lithium ions are intercalated in the anode and cathodes. Each sulfur atom can host two lithium ions. Typically, lithium-ion batteries accommodate only 0.5–0.7 lithium ions per host atom.〔 〕 Consequently Li-S allows for a much higher lithium storage density. Polysulfides are reduced on the cathode surface in sequence while the cell is discharging: : → → → → Across a porous diffusion separator, sulfur polymers form at the cathode as the cell charges: : These reactions are analogous to those in the sodium–sulfur battery. Most use a carbon/sulfur cathode and a lithium anode. Sulfur is very cheap, but has practically no electroconductivity, 5 S cm−1 at 25 °C. A carbon coating provides the missing electroconductivity. Carbon nanofibers provide an effective electron conduction path and structural integrity, at the disadvantage of higher cost. One problem with the lithium–sulfur design is that when the sulfur in the cathode absorbs lithium, volume expansion of the LixS compositions happens, and predicted volume expansion of Li2S is nearly 80% of the volume of the original sulfur.〔Islam et al.,ReaxFF molecular dynamics simulations on lithiated sulfur cathode materials, Phys.Chem.Chem.Phys.,2015, 17, 3383, DOI:10.1039/C4CP04532G〕 This causes large mechanical stresses on cathode, which is a major cause of rapid degradation. This process reduces the contact between the carbon and the sulfur, and prevents the flow of lithium ions to the sulfur surface.〔Brian Dodson, ("New lithium/sulfur battery doubles energy density of lithium-ion" ), gizmag, 1 December 2013〕 Mechanical properties of the lithiated sulfur compounds are strongly contingent on the lithium content, and with increasing lithium content, the strength of lithiated sulfur compounds improves, although this increment is not linear with lithiation.〔Islam et al.,(ReaxFF molecular dynamics simulations on lithiated sulfur cathode materials ), Phys.Chem.Chem.Phys.,2015, 17, 3383, DOI:10.1039/C4CP04532G〕 One of the primary shortfalls of most Li–S cells is unwanted reactions with the electrolytes. While S and are relatively insoluble in most electrolytes, many intermediate polysulfides are not. Dissolving into electrolytes causes irreversible loss of active sulfur. Use of highly reactive lithium as negative electrode causes dissociation of most of the commonly used ether type electrolytes. Use of protective layer in the anode surface has been studied to improve cell safety, i.e., using Teflon coating showed improvement in the electrolyte stability,〔Islam, Md Mahbubul, Vyacheslav S. Bryantsev, and Adri CT van Duin. "(ReaxFF Reactive Force Field Simulations on the Influence of Teflon on Electrolyte Decomposition during Li/SWCNT Anode Discharge in Lithium-Sulfur Batteries )." Journal of The Electrochemical Society 161.8 (2014): E3009-E3014. doi:10.1149/2.005408jes〕 LIPON, Li3N also exhibited promising performance. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Lithium–sulfur battery」の詳細全文を読む スポンサード リンク
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