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This work was supported by the Faraday Institution (Grant number—FIRG018). The authors also acknowledge the Engineering and Physical Sciences Research Council (EPSRC) Light Element Facility Grant (EP/T019298/1) and the EPSRC Strategic Equipment Resource Grant (EP/R023751/1). D.N.R. acknowledges the EPSRC (grant: EP/N509759/1) for funding. Sodium-ion batteries are commanding increasing attention owing to their promising electrochemical performance and sustainability. Organic electrode materials (OEMs) complement such technologies as they can be sourced from biomass and recycling them is environmentally friendly. Organic anodes based on sodium carboxylates have exhibited immense potential, except the limitation of current synthesis methods concerning upscaling and energy costs. In this work, a rapid and energy efficient microwave-assisted synthesis for organic anodes is presented using sodium naphthalene-2,6-dicarboxylate as a model compound. Optimizing the synthesis and electrode composition enables the compound to deliver a reversible initial capacity of ≈250 mAh g–1 at a current density of 25 mA g–1 with a high initial Coulombic efficiency (≈78%). The capacity is stable over 400 cycles and the compound also exhibits good rate performance. The successful demonstration of this rapid synthesis may facilitate the transition to preparing organic battery materials by scalable, efficient methods. Publisher PDF

Recent work has highlighted the possibility that through the introduction of metals into the one-dimensional channels of zeolite L, it may be feasible to engineer charge transport along the channels to produce a unique compound comprising a precise, assembled array of ultrafine, atomic-scale conducting wires embedded within the aluminosilicate framework. Using electron spin resonance (ESR), and microwave cavity perturbation measurements, we examine the properties of these remarkable materials as a function of composition as they approach the insulator to metal transition.

As a result of their high energy density lithium-ion batteries have been widely applied in the fields of portable electronic, implantable organs, power tools, and more recently electric vehicles. Typically carbon is widely used as a conductive additive in electrode fabrication due to the low conductivity of the active materials, which has a negative effect on the volumetric and gravimetric energy density. As a result, exploration of new materials with high conductivity as electrodes for Li-ion batteries is highly desirable. Titanium-based materials as lithium-ion battery negative electrode have been widely studied. The zero strain insertion leads to excellent reversibility (>10,000 times) and capacity retention rate; [1] the combination of high lithium mobility results in high rate ability of the batteries; [2] higher working potential (>1.2 V vs Li+/Li) brings better safety with no lithium metal deposition during discharging compared to the carbon anodes. [3] But the relatively low electric conductivity (e.g. Li4Ti5O12 is only 10-9 S·cm-1 at 20 ℃) limits their ability and low temperature applications. LiTi2O4 adopting the ramsdellite structure was firstly fabricated by D.C. Johnston. [4] This structure consists of distorted TiO6 octahedra which connect together by sharing edges resulting in double linked columns. These columns form an open framework structure in which Li+ occupies 50% of the tetrahedral channel sites. Hence the remaining tetrahedral sites are available for Li+ insertion delivering a theoretical specific capacity of 161 mAh g-1 for complete reduction to Ti3+ and all tetrahedral sites occupied and presumably lithium could be extracted. For titanium ramsdellite series capabilities of 180 mAh·g-1 (theoretical 298 mAh·g-1) for Li2Ti3O7, 113 mAh·g-1 for LiTi2O4 and 320 mAh·g-1 (theoretical 335 mAh·g-1) for TiO2 under 0.25 mA·cm-2 has been obtained by Gover. [5] Titanium oxycarbide, TiOxC1-x, with a rocksalt structure formed by TiC and TiO, with O and C atoms sharing the anion sites, has a high metallic conductivity. [6] Thus partial replacement of O by C in transition metal oxides opens up a range of new compositions that might be expected to yield important functional properties. In this work a novel carbon doping strategy was used to successfully fabricate LiTi2O4-xCx with the Ramsdellite structure. Initially TiOxC1-x and Li2Ti3O7 were made as raw materials by solid reaction ans then the LiTi2O4-xCx was fabricated in Ar under specific temperature. After that its structure was characterised and electrochemical property was tested. Based on refiment of X-ray diffraction patterns, increased levels of carbon substitution led to an increase in a and b parameters with a contraction in c. The incorporation of carbon was further confirmed by mass spectroscopy/thermal analysis. The performance as a negative electrode material for lithium-ion batteries was enhanced by carbon substitution with increased rate capability and improved cycle ability. Especially for LiTi2O3.925C0.075 capacities of 151 mAh·g-1 and 67 mAh·g-1 could be obtained under discharging current densities of 100 mA·g-1 and 2000 mA·g-1 and capacity decreased by 5.57% after 100 cycles. This results from increased conductivity and reduced cell polarization. Keywords: titanium carbide, lithium ion battery, carbon doping Reference [1] T. Ohzuku, A. Ueda, N. Yamamoto, Journal of the Electrochemical Society, 142, 1431(1995). [2] K. Ariyoshi, R. Yamato, T. Ohzuku, Electrochimica acta, 51, 1125(2005). [3] D. Peramunage, K. Abraham, Journal of the Electrochemical Society, 145, 2615(1998). [4] D. Johnston, Journal of Low Temperature Physics, 25, 145(1976). [5] R. K. Gover, J. R. Tolchard, H. Tukamoto, T. Murai, J. T. Irvine, Journal of the Electrochemical Society, 146, 4348(1999). [6] D. N. Miller, A. K. Azad, H. Delpouve, L. Quazuguel, J. Zhou, A. Sinha, P. Wormald, J. T. Irvine, Journal of Materials Chemistry A, 4, 5730(2016).

There is intensive research activity targeted on developing new electrode materials for the next generation of rechargeable lithium batteries, particularly for large-scale use in future hybrid electric or pure electric vehicles and in stationary energy storage of solar/wind power [1-3]. Polyoxyanion compounds are receiving considerable interest as cathodes since the strong binding of the oxygen enhances stability and thus safety, compared with transition metal oxides. The electronic inductive effect shifts the d-states of the transition metal ions and hence the redox potentials, providing a means of tuning the latter. Phosphate materials, particularly LiFePO4, have been extensively studied and continue to be important [2,3]. Recent work on oxalates by Tarascon and co-workers [4,5] has demonstrated the possible use of oxalate materials as a new class of polyoxyanion. Here we report the synthesis and characterization of hitherto-unknown alkali metal iron compounds in the oxalate system with new compositions and structures. The three dimensional framework structures were determined by single crystal X-ray diffraction, with an example shown in Fig. (a). All the materials displayed redox activity vs. either Li or Na, depending on the compound with stable cycling as shown in Fig. (b). (1) B. L. Ellis, K. T. Lee and L. F. Nazar, Chem. Mater., 2010, 22, 691; (2) J. B. Goodenough and Y. Kim, Chem. Mater., 2010, 22, 587. (3) A. K. Padhi, K. S. Nanjundaswamy, and J. B. Goodenough, J. Electrochem. Soc. 1997, 144, 1188. (4) H. Ahouari, G. Rousse, Y. Klein, J.N. Chotard, M.T. Sougrati, N. Recham, J.M. Tarascon. Solid State Sci. 2015, 42(6), 13. (5) H. Ahouari, G. Rousse, J.R. Carvajal, M.T. Sougrati, M. Saubanere, M. Courty, N. Recham, J.M. Tarascon. Chem. Mater., 2015, 27, 1631. Figure 1

X-Ray Absorption Spectroscopy (XAS) is a powerful tool, which can be used to study the atomic local structure as well as oxidation state during battery cycling. Hence, XAS can be used to provide detailed atomic information for improvement of materials design. Here we present in situ XAS results for Li2FeSiO4 and Li2.2Fe0.9SiO4, promising cathode materials for lithium-ion batteries. It provides a low cost solution and is considered as a safe electrode material for future electric transportation, as the Si–O bond provides stability similar to the P – O bond in LiFePO4 compounds. In theory, it is possible to remove two Li ions from Li2FeSiO4, by utilizing both Fe+2/Fe+3 and the Fe+3/Fe+4 redox couples and, thus, producing a higher capacity than 166 mAhg-1 for one Li ion. Although capacities greater than 200 mAhg-1 it has yet to be clarified whether it was due to Fe+4 formation or electrolyte degradation. The aim was to establish the valence and local structure of Fe during charge and discharge. The valence state changes between Fe+2 and Fe+3, with no evidence of Fe+4 before the onset of electrolyte degradation. There is a reversible contraction and extension of the Fe–O bond lengths during cycling while the Fe-Si distance remains constant, which underlines the stability of the Li2FeSiO4 material. The same observations apply to Li2.2Fe0.9SiO4 cathode material indicating that changing the stoichiometry does not provide any additional structural stability.1 1. A.W. Brownrigg, G. Mountjoy, A.V. Chadwick, M. Alfredsson, W. Bras, J. Billaud, A.R. Armstrong, P.G. Bruce, R. Dominko and E.M. Kelder, J. of Mater. Chem. A, 2015, 3, 7314-7322

Graphite has proved a highly successful anode for lithium ion batteries; however it is not without its limitations. There is intensive research to perfect silicon based anodes but important challenges still remain in the quest for high cycling efficiency and high cycle numbers. As a result, there remains much need for investigation of alternative anodes for lithium-ion batteries. Recently we investigated anodes based on LiVO2 1,2. Intercalation into this compound, which is isostructural with LiCoO2, occurs in a two phase process with the formation of hexagonal Li close packed Li2VO2.1 We have now extended these studies to related compounds, and solid solutions, and have identified anodes with a capacity of over 205 mAh/g at C rate, Fig. 1. The density of these materials is 3.34 g/cm3 resulting in a volumetric capacity of 718 mAh/cm3 at 1C. Volumetric capacity is important for applications such as electric vehicle. Detailed results of these investigations will be presented in the meeting. References: 1) A.R. Armstrong, C. Lyness, P.M. Panchmatia, M.S. Islam, P.G. Bruce, Nat. Mater. 10 (2011) 223-228. 2) F.d.r. Pourpoint, X. Hua, D.S. Middlemiss, P Adamson, D Wang, P.G Bruce, C.P. Grey, Chem. Mater. 2012, 24, 2880−2893. Figure 1

Lithium ion batteries have dominated the world of portable electronic devices over the past two decades and are making their way into the electric vehicle market due to their high energy density. However, recently sodium ion batteries have regained the interest of the scientific community due to the high and uniform abundance of sodium across the world and consequent low cost compared to lithium, making them attractive for grid storage. Various electrode materials have been studied for sodium ion batteries. Layered oxides, NaMO2, where M is one or more transition metals, represent an attractive class of cathodes for Na batteries. Here we show that Na0.67MnO2 with the P2 structure, Figure 1 a), exhibits a high capacity (175 mAhg-1), close to the best reported for a Na cathode, and with good capacity retention, in contrast to previous studies of Na0.67MnO2 where the capacity faded rapidly. [1] Due to the presence of Jahn–Teller active Mn3+ in Na0.67MnO2, the structure undergoes various structural transitions during sodiation/desodiation leading to many voltage steps in the charge/discharge profile. [2], [3] We have investigated reducing the phase transitions by substituting Mn3+ ions with electrochemically inactive dopant ions, which have a strong preference for octahedral sites in the layered oxide framework. This leads to the formation of a highly stable framework that shows a smooth charge/discharge profile with very low polarization even for a substitution level as low as 5%, Figure 1 b) and a capacity of ~ 175 mAhg-1. Such an observation is significant for the future development of sodium ion battery cathode materials. References: [1] A. Caballero, L. Hernán, J. Morales, L. Sánchez, J. Santos Peña, and M. A. G. Aranda, J. Mater. Chem., 12, 1142–1147. [2] N. Yabuuchi, M. Kajiyama, J. Iwatate, H. Nishikawa, S. Hitomi, R. Okuyama, R. Usui, Y. Yamada, and S. Komaba, Nat. Mater., 11, 512-517. [3] X. Wang, M. Tamaru, M. Okubo, and A. Yamada, J. Phys. Chem. C, 2013, 117, 15545. Figure 1

Lithium transition metal silicates, Li2MSiO4(M=Fe, Mn, Co)[1], have attracted a lot of interest recently as positive electrodes for Li-ion batteries due to their potentially high theoretical capacities and to their rich crystal chemistry as they undergo complex polymorphism. One of the drawbacks of the silicates is their modest rate capability, particularly at room temperature. The present work addressed this problem. The polymorphs of Li2MSiO4can be classified into low (β) and high (γ) temperature forms, which differ in the ordering/distribution of cations within tetrahedral sites of an hcp based packing of oxygen. β forms exhibit only corner sharing and γ polymorphs both corner and edge sharing. It has been shown by us and by others that Li2FeSiO4 exists in at least 3 different polymorphic forms and that. in the case of Li2MnSiO4two stable polymorphs are observed [1-3]. The silicates are analogous to the LISICON materials (Lithium SuperIonic Conductors), of the form Li2+2xZn1-xGeO4, which adopt the γ structure with interstitial and highly mobile lithium. Therefore, stabilization of the γ polymorph to room temperature represents a potentially attractive route to enhancing the rate performance thus overcoming one of the major barriers to adoption of Li2MSiO4 cathodes. With appropriate substitutions we have been able to stabilise the γ polymorph for both Li2FeSiO4 and Li2MnSiO4systems. We will report the effects on structure and electrochemistry of the various substitutions. In the iron system good cycling stability and improved rate capability are observed (fig. 2). References [1] a) A. Nytén, A. Abouimrane, M. Armand, T. Gustafsson and J.O. Thomas, Electrochem. Comm., 7, (2005) 156; b) M. S. Islam, R. Dominko, C. Masquelier, C. Sirisopanaporn, A. R. Armstrong and P. G. Bruce, J. Mater. Chem., 21 (2011) 9811. [2] S. I. Nishimura, S. Hayase, R. Kanno, M. Yashima, N. Nakayama, A. Yamada, J. Am. Chem. Soc., 130 (2008) 13212. [3] C. Sirisopanaporn, A. Boulineau, D. Hanzel, R. Dominko, B. Budic, A. R. Armstrong, P. G. Bruce, C. Masquelier, Inorg. Chem., 49 (2010) 7446.

Lithium ion batteries have dominated the world of portable electronic devices over the past two decades and are making their way into the electric vehicle market due to their high energy density. However, recently sodium ion batteries have regained the interest of the scientific community due to the high and uniform abundance of sodium across the world and consequent low cost compared to lithium, making them attractive for grid storage. Various electrode materials have been studied for sodium ion batteries. Layered oxides, NaMO2, where M is one or more transition metals, represent an attractive class of cathodes for Na batteries. Here we show that Na0.67MnO2 with the P2 structure, Fig 1, exhibits a high capacity (175 mAhg-1), close to the best reported for a Na cathode, and with good capacity retention, in contrast to previous studies of Na0.67MnO2 where the capacity faded rapidly.1 Due to the presence of Jahn–Teller active Mn3+ in Na0.67MnO2, the structure undergoes various structural transitions during sodiation/desodiation leading to many voltage steps in the charge/discharge profile.1-3 We have investigated reducing the phase transitions by substituting Mn3+ ions with electrochemically inactive dopant ions, which have a strong preference for octahedral sites in the layered oxide framework. This leads to the formation of a highly stable framework that shows a smooth charge/discharge profile with very low polarization even for a substitution level as low as 5%, Fig. 2, and a capacity of ~ 175 mAhg-1. Such an observation is significant for the future development of sodium ion battery cathode materials. Lattice parameters of all the substituted compositions could be refined using hexagonal (P63/mcm) and orthorhombic (Cmcm) space group symmetries, whilst the situation pertaining to Na0.67MnO2 samples proved more complex. References [1] A. Caballero, L. Hernan, J. Morales, L. Sanchez, J. Santos Pena and M. A. G. Aranda, J. Mater. Chem., 2002, 12, 1142. [2] N. Yabuuchi, M. Kajiyama, J. Iwatate, H. Nishikawa, S. Hitomi, R. Okuyama, R. Usui, Y. Yamada and S. Komaba, Nature Mater., 2012, 11 512. [3] X.F. Wang, M. Tamaru, M. Okubo and A. Yamada, J. Phys. Chem. C, 2013, 117, 15545.