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Sodium superionic conductor (NASICON)-type materials are widely explored as Li- and Na-ion cathodes and solid-state electrolytes but are largely ignored as anodes due to their lower capacities and higher intercalation voltages, which reduce the overall energy densities of Li- and Na-ion batteries (LIBs and SIBs).

We find that the addition of PC co-solvent suppresses parasitic reactions at both electrodes, and improves the cycling stability and coulombic efficiency of Zn-ion batteries.

P2-type Na0.67[Ni0.33Mn0.67]O2 layered oxide cathode is attractive for practical Na-ion battery application due to its high voltage Ni4+/Ni2+ redox and good air-stability. However, it suffers from rapid capacity decay originating from high voltage P2-O2 transformation. To alleviate this issue, herein we explore optimum Li-substitution into the transition metal layer of Na0.67[Ni0.33Mn0.67]O2 to tailor a series of high Na-content P2-type cathodes. Among them, Na0.85[Li0.14Ni0.29Mn0.57]O2 cathode with optimal Li-substitution exhibits reversible capacities of ∼168 mAh g−1 at 0.1C rate and good cycling stability (82% of retention after 100 cycles at 1C rate). In-situ XRD measurement reveals the formation of complete solid-solution and X-ray absorption spectroscopy studies confirm the participation of Ni4+/Ni2+ and Mn4+/Mn3+ redox couples during Na (de)intercalation of the Na0.85[Li0.14Ni0.29Mn0.57]O2. A full Na-ion cell (Na0.85[Li0.14Ni0.29Mn0.57]O2||hard carbon) is demonstrated with an energy density of 420 Wh kg−1.

Chemical lithiation using lithium metal dissolved in liquid ammonia is introduced for the first time as a viable, potentially scalable method to overlithiate cathode materials, in this case, the 5 ...

The continuous pursuit on building low cost and sustainable batteries to efficiently harvest renewable energy from intermittent sources is ever expanding. The research on Na-ion technology has gained significant interest due to inexpensive and broad availability of precursor materials. Until now, various Na-ion anodes including carbonaceous materials such hard carbon, alloy-based materials such as Bi, Pb, Sb and Sn based systems and conversion materials have been explored1. Along this line, the recent chase on two dimensional (2D) materials such as chalcogenides, MXenes and van der Waals types oxyhalide heterostructures, have become more intense due to their excellent electrical and structural properties 2. Among them, 2D Sillén-type metal oxyhalide heterostructures (MOX), due to their unique layered structure consisting of anionic sheets interleaved with cationic layers have gain particular interest as electrode materials. BiOCl is one such candidate with fluorite-like layers, [Bi2O2]2+ intergrown with halide Cl– anions, have been studied as anode in rechargeable batteries. However, its application is mainly challenged by rapid capacity decay originating from particle pulverization and unstable solid electrolyte interphase (SEI). In this work, 2D layered mixed lead bismuth oxychloride nanosheets (BiOCl4 and PbBiO2Cl 3) were synthesized by new rapid room temperature chemical precipitation route. In former anode, the electrolyte engineering approach has been used to enhance the cycling stability of BiOCl and at the same time, its electrochemical (de)sodiation mechanism is also clarified through in-operando XRD studies, which reveals the reversible formation of Bi ↔ NaBi ↔ cubic-Na3Bi phases. On the other hand, the later anode, i.e., 2D-PbBiO2Cl was further investigated with the combined in-operando XRD and ex-situ TEM, XPS studies, which reveal a distinct (de)sodiation process of the 2D-PbBiO2Cl in comparison with reported Na-(Pb/Bi) phase diagram. This 2D heterostructure demonstrated stable sodium storage performance (~250 mAh g–1 for 250 cycles at 100 mA g–1). Henceforth, the detailed understanding of formation process of these two structures (BiOCl and PbBiO2Cl) at room temperature using material characterizations and electrochemical studies combined with operando findings will be discussed to comprehend the reversible storage mechanism of 2D-MOX type heterostructures as anodes in SIBs. References: Y. Hwang, S.T. Myung, Y.K. Sun, Chem. Soc. Rev. 2017, 46, 3529–3614. Zeng, Y. Xiao, J. Liu, K. Yang, L. Fu, Chem. Rev. 2018, 118, 6236–6296. Ahuja, S. Singh, R. Vengarathody, P. Senguttuvan, J. Phys. Chem. C 2021, 125, 17622 Ahuja, S. Singh, R. Vengarathody, P. Senguttuvan, J. Power Sources 2022, 529, 231227

The development of low-cost and sustainable rechargeable batteries is attractive for storing energy from renewable sources. At present, the expansion of Na-ion batteries (NIBs) serves as an appealing solution from the perspective of both raw material abundance as well as the cost in comparison with the existing Li-ion batteries.1 However, the energy densities of NIBs are lower compared to their Li-ion counterparts due to thermodynamic reasons. To address this issue, researchers have turned their attention towards the development of high energy density cathodes, such as Na3V2(PO4)2F3 and Na3V2(PO4)3-type materials,2 in which the operation of multi-redox couples render high storage capacities. Moving forward, the replacement of PO4 3- by SO4 2- provides higher intercalation voltages (due to inductive effect), thereby further improving the overall energy density of cathode. 3 The inclusion of fluoride into the sulphate based polyanionic frameworks will help to increase the operating voltage through inductive effects.4 This will enhance cationic mobility by reducing electrostatic interactions along conduction channels, thereby, lead to increase in cell capacity. Herein, we report synthesis, structural and electrochemical properties of two classes of sodium transition metal fluorosulfates, namely Na3MF2(SO4)2 and jarosites NaM3(SO4)2(OH/F)6 (M= V and Mn etc.,). The Na2VF3(SO4)2 framework consists of chains of trans-VO2F4 octahedra linked to each other via vertex sharing of F atoms and bridged by SO4 tetrahedron as adjacent pairs. 5 Jarosite is a natural mineral to be found in acidic and sulfate-rich environments with a general formula of AM3(SO4)2(OH)6, where A = K+, Na+, and NH4 + and M = Fe3+, Cr3+, V3+, Ga3+, Al3+, and In3+. Jarosite crystals stabilize in a trigonal system with space group R3m. The structure is composed of 2D uneven layers formed by linkage of transition metal octahedra [MO2(OH)4] and sulfate tetrahedra (SO4), that are stacked along the c direction. 6 We unveil the details of growth mechanism of these materials in hydro- and solvo-thermal conditions using X-ray diffraction and microscopy techniques. Further, the mechanism of electrochemical (de)sodiation reactions in these materials will be presented using galvanostatic cycling and in-operando XRD measurements. References: Hwang, J. Y.; Myung, S. T.; Sun, Y. K. Sodium-Ion Batteries: Present and Future. Soc. Rev. 2017, 46 (12), 3529–3614. Lalère, F.; Seznec, V.; Courty, M.; David, R.; Chotard, J. N.;Masquelier, C. Mater. Chem. A. 2015, 3, 16198-16205 Lander, L.; Tarascon, J. M.; Yamada, A. Chem. Rec. 2018, 18, 1394–1408 Senthilkumar, B.; Murugesan, C.; Sharma, L.; Lochab, S.; Barpanda, P. Small methods 2019, 3, 1800253 Wang, Q.; Madsen, A.; Owen, J. R.; Weller, M. T. Commun. 2013, 49 (21), 2121–2123. Gnanavel, M.;Pralong, V.; Lebedev, I.; Caignaert, V.; Bazin, P.; Raveau, B.Chem. Mater. 2014, 26, 15, 4521–4527

Spinel LiMn2O4 is a popular cathode material in lithium-ion batteries due to its high operating voltage and reversible specific capacity. Synthesizing analogous NaMn2O4 in the spinel structure, for sodium-ion batteries, is challenging due to the thermodynamic instability of the compound, mostly arising due to Jahn–Teller distortion of the Mn3+ centre. However, post-spinel NaMn2O4 (named as such because the compounds were initially achieved by subjecting a spinel phase to high pressure) could be synthesized at a high temperature and pressure (1373 K and 4.5 GPa, respectively) and is found to be stable at standard conditions. Also, these compounds have a lower ion diffusion barrier than their respective spinels. In this work, an attempt has been made to induce chemical pressure within the system by the use of a heavy cation, i.e., Sn4+ in the framework, to synthesize post-spinel NaMnSnO4 at ambient pressure conditions. The as-prepared NaMnSnO4 samples are characterized with scanning electron microscopy, X-ray diffraction, inductively coupled plasma-atomic emission spectroscopy and galvanostatic cycling with potential limitation measurements.

Sodium superionic conductor (NASICON)-Na

Antimony based anode materials are attractive for alkali-ion battery applications due to their high theoretical capacity and lower insertion voltage. Herein, Sb/hard carbon composites are fabricated using a simple and scalable high-energy ball-milling approach and have been investigated as anodes for alkali-ion batteries. The structural and morphological studies reveal that Sb nanoparticles are embedded into hard carbon matrix, which provide mechanical buffer and conductive network to improve alkali-ion insertion kinetics. In sodium cells, the composite (HS5050) with optimized Sb loading delivers capacities of 250 mAh g −1 at 100 mA g−1 with excellent cycle life up to 800 cycles, compared to other composite and individual anodes. Remarkably, the same HS5050 provides higher capacities of 572 and 380 mAh g−1 in lithium and potassium cells, respectively with impressive cycle life. The enhanced alkali-ion charge storage performances of composite anode are attributed to the synergistic effect of Sb and hard carbon.

Author(s): Ghosh, Subham; Barman, Nabadyuti; Gonzalez-Correa, Eliovardo; Mazumder, Madhulika; Zaveri, Aryan; Giovine, Raynald; Manche, Alexis; Pati, Swapan K; Clement, Raphaele J; Senguttuvan, Premkumar

Electrochemical energy storage devices, particularly rechargeable batteries, are attractive solution to balance energy production of intermittent natural sources such as wind and solar. Despite its success in portable electronics market, Li-ion technology faces serious hurdle for grid storage application due to scarcity and geographical access of lithium sources. From the viewpoint of cost and abundance of raw materials, sodium ion batteries are appealing for grid storage application.1 Various classes of Na-ion electrode and electrolyte materials have been developed recently based on the know-how knowledge gained from Li-ion chemistry. However, the commercialization of NIBs has been impeded by the lack of high energy density cathodes. To this end, multi-electron based polyanionic cathodes are attractive, because of their high insertion voltages and storage capacities.2 Among the cathode materials, NASICON type cathodes with a general chemical formula NaxMM’(PO4)3(x= 2-4; M=V, Ti, Fe, Cr; Mʹ =Mn, Co, Mg, Fe) have garnered significant interest due to higher sodium ion conductivities as well as enhanced chemical and thermal stabilities.3 In this talk, we will present our recent studies on the impact of Mg2+ and Al3+ cationic substitution into the Na3V2(PO4)3 framework.4,5 The Mg- and Al-substituted NVMP cathodes exhibit smoother voltage profiles, facile sodium (de)intercalation, enhanced rate performances (80 mA h g-1 at 5C rate) and better capacity retention (~96% after 100 cycles) compared to the unsubstituted sample. Their improved performances are attributed to suppressed Jahn-Teller effect, enhanced covalent character and Na-ion vacancies created in the NASICON framework. References: N. Yabuuchi, K. Kubota, M. Dahbi, S. Komaba, Chem. Rev. 2014, 114, 11636. C. Masquelier, L. Croguennec, Chem. Rev. 2013, 113, 6552. R. Liu, Z. Liang, Z. Gong, Y. Yang, small methods 2019, 3, 1800221. S. Ghosh, N. Barman, M. Mazumder, S. K. Pati, G. Rousse, P. Senguttuvan, Adv. Energy Mater. 2020, 10, 1902918. S. Ghosh, N. Barman, P. Senguttuvan, Small 2020, 16, 2003973. Figure 1

The successful realization of sustainable energy technologies is nested into the incorporation of resilient storage technologies in grid due to their intermittent nature of energy production. Among these technologies, rechargeable batteries are ubiquitous due to their low cost, easy maintenance, high round trip efficiency and durability. Recently, Na-ion batteries have garnered significant interest for their potential grid application due to inexpensive and earth abundant raw materials. However, their successful commercialization faces several hurdles at both material and cell levels. In particular, the development of high voltage and capacity Na-ion cathodes is one of the key challenges for the successful realization of high energy density sodium ion batteries.1 Whilst layered Na-ion transition metal oxides are the frontrunners for practical application, their poor air stability and cycling stability are still required to be addressed.2 On other hand, phosphate cathodes offer high structural stability and insertion voltages as well rich structural diversity.3 Among them, NASICON-Na3V2(PO4)3 cathode is attractive because of its high intercalation voltage (3.45 V vs. Na+/Na0), moderate capacity (~120 mAh g-1) and excellent rate capability.4 The sodium (de)intercalation process in the NVP cathode proceeds via a two-phase mechanism and the corresponding redox activity is ascribed to the operation of V4+/V3+ couple. Further, other cations are substituted in the place of vanadium of the NVP lattice to seek the participation multiple redox centers, thereby enhancing intercalation capacities. Particularly, the NASICON end member Na4VMn(PO4)3 has garnered significant attention due to its reduced cost, improved insertion voltage and the participation of V5+/V4+, V4+/V3+ and Mn3+/Mn2+ redox couples.5,6 Herein, we will present a comprehensive study on the structural and electrochemical properties of Na3+xV2-xMnx(PO4)3 series. We will show how it is important to modulate electronic and crystal structures of the NASICON framework to attain high capacity and high-rate performances.7 Further, we will also discuss about the impact of alio-/iso-valent cationic substitutions into the NVP framework, which enhances their rate performances and cycle life.8 References Yabuuchi, K. Kubota, M. Dahbi and S. Komaba, Chem. Rev. 2014, 114, 11636. F. Wang, Y. You, Y. X. Yin, Y. G. Guo, Adv. Energy Mater. 2017, 8, 1701912. Masquelier, L. Croguennec, Chem. Rev. 2013, 113, 6552. Chen, C. Wu, L. Shen, C. Zhu, Y. Huang, K. Xi, J. Maier, Y. Yu, Adv. Mater. 2017, 29, 1700431. Zhou, L. Xue, X. Lü, H. Gao, Y. Li, S. Xin, G. Fu, Z. Cui, Y. Zhu, J. B. Goodenough, Nano Lett. 2016, 16, 7836. Chen, V. M. Kovrugin, R. David, O. Mentré, F. Fauth, J. Chotard, C. Masquelier, Small Methods 2019, 3, 1800218. Ghosh N. Barman, M. Mazumder, S. K. Pati, G. Rousse, P. Senguttuvan, Adv. Energy Mater. 2020, 10, 1902918. Ghosh, N. Barman, P. Senguttuvan, Small 2020, 16, 2003973.

The endless pursuit on building low cost and sustainable batteries to effectively harvest renewable energy from intermittent sources is ever increasing. The research on Na-ion technology has gained significant interest due to inexpensive and broad availability of precursor materials. Until now, various Na-ion anodes have been explored including carbonaceous materials such hard carbon, alloy-based materials such as Bi, Pb, Sb and Sn based systems and conversion materials [1]. Along this line, the recent chase on two dimensional (2D) materials such as chalcogenides, MXenes and van der Waals types oxyhalide heterostructures, have become more intense due to their excellent electrical and structural properties [2]. Among them, 2D Sillén-type metal oxyhalide heterostructures (MOX), due to their unique layered structure consisting of anionic sheets interleaved with cationic layers have gain particular interest as electrode materials. BiOCl is one such candidate with fluorite-like layers, [Bi2O2]2+ intergrown with halide Cl– anions, have been studied as anode in rechargeable batteries. For instance, the 2D-(Bi1-xFex)OCl have increased insertion kinetics in Li-ion storage performances [3] in comparison with unsubstituted BiOCl, whereas 2D-(Bi1-xSbx)OCl heterostructures have shown synergetic effect of (Bi/Sb) alloys on with improved K-ion storage capacity [4]. However, in continuation, the further assessment of other mixed cationic Sillén heterostructures with the crystal structures of [BixM1-xO2]n+ (M = Na+/Ca2+/Pb2+/Fe3+/Sb3+; n = +1, +2 and +3) layers intergrown with single/double/triple halide anionic layers, remain unexplored. This is mainly challenged by their current synthesis strategies which demand high temperature, longer reaction durations, toxic chemicals, and complex reaction setup. In this work, 2D layered lead bismuth oxychloride (PbBiO2Cl) heterostructure nanosheets were synthesized by new rapid room temperature chemical precipitation route within ~45 mins. The stepwise reaction intermediates were harvested and investigated further with XRD and SEM mechanistic studies. The formation proceeds through topotactic ion exchange route from analogous PbBiO2NO3 intermediate. When employed as an anode material in Na half-cell configurations (as presented in Figure 1), this 2D heterostructure demonstrated stable sodium storage performance (~250 mAh g–1 for 250 cycles at 100 mA g–1). Surprisingly, the electrochemical profile of the 2D-PbBiO2Cl significantly differs from those of its individual counterparts Pb, Bi anodes. This was further investigated with the combined in-operando XRD and ex-situ TEM, XPS studies, which reveal a distinct (de)sodiation process of the 2D-PbBiO2Cl in comparison with reported Na-(Pb/Bi) phase diagram. Henceforth, the detailed understanding of formation process of 2D-PbBiO2Cl at room temperature using non-operando material characterizations and electrochemical studies combined with operando findings will be discussed to comprehend the reversible storage mechanism of 2D-PbBiO2Cl type heterostructures as anodes in SIBs. References: Y. Hwang, S.T. Myung, Y.K. Sun, Chem. Soc. Rev. 2017, 46, 3529–3614. Zeng, Y. Xiao, J. Liu, K. Yang, L. Fu, Chem. Rev. 2018, 118, 6236–6296. Myung, J. Choi, F. Wu, S. Banerjee, E. H. Majzoub, J. Jin, S. U. Son, P. V. Braun, P. Banerjee, ACS Appl. Mater. Interfaces 2017, 9, 14187–14196. Wang, B. Wang, B. Lu, Adv. Energy Mater. 2020, 10, 2000884. Figure 1

The intermittent nature of renewable sources demands the utilization of resilient storage systems, which can smoothen their energy production and distribution to consumer utilities. Among the storge systems, rechargeable batteries offer easy maintenance, low cost, high round trip efficiency and durability. At present, sodium-ion batteries (SIBs) have garnered widespread interest for grid storage application due to inexpensive and earth abundant raw materials. Their practical realization is nested in successful exploration of suitable electrode and electrolyte materials. So far, various Na-ion cathodes have been discovered including layered oxides, polyanionic compounds and Prussian blue frameworks, whose energy densities are slightly inferiro to their Li-ion counterparts. Polyanionic frameworks consists of tetrahedral anions (XO4)n– (X= S, P) and MeOx (Me= 3d transition metal) polyhedral. In sulfate based polyanionic systems, the presence of SO4 2– anions will ensure rapid and better pathway for alkali conduction along with structural stability to metal redox. The inclusion of fluoride anion into the sulphate frameworks increases their operating voltages through inductive effect.2 It can also enhance cationic mobility by reducing electrostatic interactions along conduction channels, thereby, lead to increase in cell capacity.3 Recently, metal fluorosulfates such as NaMSO4F, Na3MF2(SO4)2 (M=3d transition metals) have been reported as promising high voltage cathode materials for sodium-ion batteries. In this work, we have explored a new family of Na2MF3SO4 (M= V, Cr, and Mn) fluorosulfates as potential Na-ion cathode materials. They were synthesized through hydrothermal route at ~200 °C. These compounds are isostructural with the reported Na2FeF3(SO4)2 as depicted in X-ray diffraction refinement (Figure 1a).4 The Na2VF3(SO4)2 crystallizes as light green needle like particles (Figure 1b and inset of Figure 1a), as single phase. The framework consists of chains of trans-VO2F4 octahedra linked to each other via vertex sharing of F atoms and bridged by SO4 tetrahedron as adjacent pairs (Figure 1c). Furthermore, its growth mechanism is studied with microscopy techniques to comprehend its formation kinetics and evolution of morphology with respect to time. Upon first desodiation, the Na2VF3SO4 structure showed a plateau at ~4.5 V Na+ (de)insertion where it exceeds the capacity beyond ~100 mAh g–1. Its subsequent sodiation profile showed two-step flat voltage with voltage at 4.0 and 3.2 V. Detailed reaction kinetics, electrochemical performances and sodium (de)intercalation mechanism will be presented. References: Dunn, B.; Kamath, H.; Tarascon, J.-M. Science 2011, 334 (6058), 928-935. Senthilkumar, B.; Murugesan, C.; Sharma, L.; Lochab, S.; Barpanda, P. small methods 2019, 3, 1800253. Masquelier, C.; Croguennec, L. Rev. 2013, 113, 6552–6591. Wang, Q.; Madsen, A.; Owen, J. R.; Weller, M. T. Commun. 2013, 49 (21), 2121–2123. Figure 1

NASICON-Na3V2−xMx(PO4)3 (M = Al3+, Cr3+, Fe3+ & Ga3+) cathodes are attractive for sodium-ion battery application due to their high voltage multi-redox (V5+/V4+/V3+) couples and faster sodium-ion diffusivity. However, they suffer from rapid capacity decay due to irreversible structural changes occurring at high voltages. Herein, we present the structural and electrochemical sodium (de)intercalation properties of NASICON-Na3VIn(PO4)3 (NVIP) cathode. Although, this In3+-substituted cathode also undergoes similar high voltage structural degradation, but its structure is rejuvenated through the following low voltage deep-sodiation process, resulting in reversible capacities of ∼145 mA h g−1 (i.e., equivalent to ∼2.82 moles of Na per vanadium). Our combined electrochemical, in-operando X-ray diffraction and exsitu X-ray absorption spectroscopy analyses reveal asymmetric sodium (de)intercalation pathways of the NVIP cathode in the window of 4.2–1.2 V vs Na+/Na0 that is driven by multi-redox (V5+/V4+/V3+/V2+) couples.

Phosphate compounds are one of the attractive classes of cathodes for their potential application in rechargeable Na-ion batteries (NIBs) due to their high insertion voltages and stabilities. Unlike olivine-LiMPO4 (M ​= ​Fe, Mn, Co, Ni) cathodes, maricite-NaMPO4 phases are electrochemically inactive due to lack of sodium diffusion channels. Interestingly, cobalt bearing compounds exhibit rich polymorphism (α-, β-, ABW- and Red-NaCoPO4). However, the preparation of NaCoPO4 single phases is challenging due to their closer enthalpies of formation. In this study, we have attempted to understand the formation mechanism of NaCoPO4 polymorphs during solid state reaction using two different cobalt precursors (Co(OH)2 and CoCO3). The temperature dependent in-situ powder X-ray Diffraction (PXRD) studies showed the formation of β-NaCoPO4 at a much lower temperature compared to the one reported in the literature, whilst we have discovered a new high temperature polymorph γ-NaCoPO4. The choice of precursors was also found to be important for the preparation of ABW-NaCoPO4, i.e., the rapid decomposition of Co(OH)2 has resulted in its formation whilst the high stability of CoCO3 prohibited the same. The order of the formation of the NaCoPO4 polymorphs during heating was found to be ABW→ β → α → γ. During normal cooling, γ-NaCoPO4 transformed primarily into α-polymorph whilst quenching in liquid N2 resulted in the formation of β-NaCoPO4. The as-synthesized β- and ABW-NaCoPO4 phases exhibited high sodium (de)-intercalation voltages (~4.2 and 4.5 ​V vs. Na+/Na0, respectively), albeit with limited reversible capacities. This study is expected to open new avenues to harvest metastable polymorphs based on other transition metals (Fe, Mn and Ni).

Sodium superionic conductor (NASICON)-Na4 VMn(PO4 )3 (NVMP) cathode is attractive for sodium-ion battery application due to its reduced cost and toxicity, and high energy density (≈425 Wh kg-1 ). However, it exhibits significant polarization, limited rate and cycling performances due to its lower electronic conductivity and formation of Jahn-Teller active Mn3+ during cycling. In this report, a chemical approach is presented to partially replace Mn2+ of the NVMP framework by Mg2+ and Al3+ substitutions. The Mg- and Al-substituted NVMP cathodes present smoother voltage profiles, facile sodium (de)intercalation, enhanced rate performances (80 mA h g-1 at 5C rate) and capacity retention (≈96% after 100 cycles) in comparison with the unsubstituted sample. Their enhanced performances are attributed to suppressed Jahn-Teller effect, increased covalent character and sodium ion vacancies of the NASICON framework. These results highlight the significance of fine tuning the chemical compositions to attain high performance NASICON cathodes.

Na2Ti3O7 is an interesting negative electrode material for sodium ion batteries given its electrochemical capacity and low operation potential. Unfortunately its prospects of practical application are hindered by an unacceptable capacity fading upon cycling. In this work we combine experiments and DFT calculations to investigate the origin of such a phenomenon. Different electrode technologies and different electrolytes have been targeted for electrochemical testing while the stability of Na2Ti3O7 and the fully reduced Na4Ti3O7 has been studied. The calculated elastic constants and vibrational modes support the mechanical and dynamical stability of the Na4Ti3O7 structure. In situ XRD measurements corroborate the reversibility of the insertion reaction as no structural damage is detected after 50 cycles. An intriguing reactivity of Na2Ti3O7 with the electrolyte upon storage is observed, which coupled to electrochemical measurements points to this being the main factor behind capacity fading.

Na2Ti3O7 was recently reported to be highly promising as a negative electrode material for Na-ion batteries, thanks to its very low intercalation voltage (0.3 V vs Na+/Na0) and high capacity (200 mAh/g). The investigation of the redox mechanism in A2Ti3O7 (A = Li, Na) upon additional alkali ion intercalation concomitant to reduction of titanium is reported in this paper. Even if the low stability of the reduced phases (A2+xTi3O7) precluded a direct study, density functional theory (DFT) calculations allowed us to propose structural models for the reduced phases (A2+xTi3O7), which were further successfully confronted to the available experimental data. The alkali atoms are octahedrally coordinated in the reduced A2+xTi3O7 phase, so that the whole resulting structure can be considered rocksalt type. The very different potentials at which ion insertion is observed for A = Li or A = Na clearly prove that analogies between lithium and sodium systems cannot be taken for granted. In this case, such findings can ...

NaMnMoO3F3·H2O was precipitated at low temperature from aqueous dissolutions of Na2MoO4·2H2O in aqueous HF (or NaHF2) using either Mn(CH3COO)2·4H2O or MnF2 as manganese precursors. Chemical analysis, IR spectra, and effective paramagnetic moment are in agreement with the proposed formula. Electron microscopy studies indicate that the sample is constituted of very thin plate-like microcrystals. The average crystal structure (a = 3.5947(1), b = 21.246(1), and c = 7.3893(2) Å and Cmcm (No. 63) SG) has been elucidated through powder diffraction methods (synchrotron and neutron). Tiny superstructure peaks are observed that can be indexed with the space group Pbca and cell parameters a = 7.1894(2), b = 21.246(1), and c = 7.3893(2) Å. Electron diffraction confirms the doubling of a parameter. Ordering of O and F is proposed in agreement with Pauling's second crystal rule and bond strength sums for each anionic position. The structure that is formed has a layered stacking arrangement along the b-axis of the MnO4F2 octahedra layers that share corners along a- and c-directions. The large interlayer space contains MoO4F2 octahedra (connected to the layer) together with sodium ions and water molecules, tentatively forming hydrogen bonding with fluorine anions. The origin of the superstructure could not be fully elucidated, but it is presumably related to slight distortions within the MnO4F2 octahedra.

A straightforward synthesis of Ti2(SO4)3 and reversible intercalation of 1.7 sodium ions via a two step process with formation of an intermediate phase was reported. The product was then washed with ethyl acetate and dried at 80°C overnight under vacuum. Electrochemical measurements were carried out in Swagelok cells using sodium metal as counter electrode and Whatman GF/D borosilicate glass fiber soaked in the electrolyte as separator. For the sample manually milled, a pseudo-plateau is observed at ca. 1.5 V vs Na+/Na followed by a sloping region to 1.0 V and another pseudo-plateau at ca. 1.0 V. Ball-milled samples exhibit similar profiles but with substantially enhanced capacity, even above 1.5 V. Upon oxidation, two well-defined plateaus at 1.10 and 1.64 V are observed in all samples. The number of electrons exchanged per mol of Ti2(SO4)3 increases with milling time to reach 3.4, which is above the theoretical expected capacity, but only 1.7 are reversible.

Na2Ti3O7, a potential negative electrode for Na batteries, is investigated by combining experiments and first-principles calculations at the Density Functional Theory (DFT) level. A structural model is proposed for the reduced phases (A2+xTi3O7), with all alkali ions in octahedral coordination, leading to a distorted rocksalt type structure. The calculated elastic constants support the mechanical stability of the proposed Na4Ti3O7 structure. Calculated average intercalation potentials are 0.37 V for Na insertion in Na2Ti3O7 and 1.46 V for Li insertion in Li2Ti3O7, being in very good agreement with the values observed experimentally (0.3 V and 1.6 V respectively). The higher polarizing character of Li ions vs Na ions acts as a key-factor to bring the Li intercalation voltage 0.7 V above that of Na intercalation in layered-A2Ti3O7 materials.

Recently, new energy storage chemistries based on nonaqueous electrolytes and multivalent metals (e.g., Mg, Zn, Ca and Al) have drawn the attention of the researchers as a promising advanced energy storage technology due to their higher theoretical volumetric capacity, limited dendrite formation and low cost.1 A major developmental need for these systems is the identification of electrolytes compatible with both electrodes while showing reversible deposition/dissolution on an anode and multivalent intercalation into a cathode.1,2 In the case of nonaqueous Mg or Ca ion-based systems, electrolyte compatibility issues (e.g., low Coulombic efficiency, a high overpotential and corrosion) have held back the development of Mg or Ca metal batteries.3 However, the nonaqueous Zn2+ ion chemistry utilized in a Zn metal cells with a reversible intercalation cathode is an exception with a number of promising features including highly-efficient reversible Zn deposition/dissolution on a Zn metal anode with a wide electrochemical window,3 similar ionic radius compared with Li+ and Mg2+ ions,4 relatively lower activation barrier energy for diffusion in cathode materials (e.g., FePO4, CoO2 and V2O5)5 and high volumetric capacity.1 Considering these advantages, a nonaqueous Zn system provides an opportunity to delve into the mechanisms in multivalent-ion cell chemistry and solve the present issues in multivalent cell design and prototyping.3 In this study, the intercalation chemistry on a variety of cathodes materials (e.g., V2O5, Mn2O4 and FePO4) have been investigated in various nonaqueous Zn electrolytes. The electrochemical and transport properties of the electrolytes (e.g., reversible Zn deposition, anodic/cathodic stability, ionic conductivity and diffusion coefficient) were characterized utilizing the experimental and computational analysis.3 Among various Zn metal cells, a Zn/nanostructured bilayered V2O5 cell with a selected acetonitrile(AN)-Zn(TFSI)2 electrolyte demonstrates good reversibility and stability for 120+ cycles with nearly 100% Coulombic efficiency and ~170 mAhg-1 of gravimetric capacity, albeit operating at a cell voltage of 0.7 V vs. Zn/Zn2+.6 A Zn/nanostructured layered δ-MnO2 cell with an AN-Zn(TFSI)2 electrolyte also shows good reversibility (~100% Coulombic efficiency) and stability for 50+ cycles with ~100 mAhg-1 capacity with an operating voltage of 1.2 V vs. Zn/Zn2+.7 By utilizing a combination of analytical tools, we address numerous factors affecting capacity fade, and issues associated with the second phase formation including Mn dissolution in Zn/δ-MnO2 cells that have been extensively cycled.7 References 1. J. Muldoon, C. B. Bucur and T. Gregory, Chem. Rev. 2014, 114, 11683-11720. 2. H. D. Yoo, I. Shterenberg, Y. Gofer, G. Gershinsky, N. Pour and D. Aurbach, Energy Environ. Sci. 2013, 6, 2265-2279. 3. S.-D. Han, N. N. Rajput, X. Qu, B. Pan, M. He, M. S. Ferrandon, C. Liao, K. A. Persson and A. K. Burrell, ACS Appl. Mater. Inter. 2016, 8, 3021-3031. 4. R. D. Shannon, Acta Cryst. 1976, A32, 751-767. 5. Z. Rong, R. Malik, P. Canepa, G. Gautam, M. Liu, A. Jain, K. Persson and G. Ceder, Chem. Mater. 2015, 27, 6016-6021. 6. P. Senguttuvan, S.-D. Han, S. Kim, A. L. Lipson, S. Tepavcevic, T. T. Fister, I. D. Bloom, A. K. Burrell and C. S. Johnson, Adv. Energy Mater. 2016, 6, 1600826. 7. S.-D. Han, S. Kim, D. Li, V. Petkov, H. D. Yoo, P. J. Phillips, H. Wang, J. J. Kim, K. L. More, B. Key, R. F. Klie, J. Cabana, V. Stamenkovic, T. T. Fister, N. M. Markovic, A. K. Burrell, S. Tepavcevic, J. T. Vaughey, 2017, in revision.

The new title compound is precipitated from solutions of Na2MoO4 and Mn(OAc)2 in aqueous HF (80 °C, 10 h, 60% yield).

We report the direct synthesis of powder Na3Ti2(PO4)3 together with its low-potential electrochemical performance and crystal structure elucidation for the reduced and oxidized phases. First-principles calculations at the density functional theory level have been performed to gain further insight into the electrochemistry of Ti(IV)/Ti(III) and Ti(III)/Ti(II) redox couples in these sodium superionic conductor (NASICON) compounds. Finally, we have validated the concept of full-titanium-based sodium ion cells through the assembly of symmetric cells involving Na3Ti2(PO4)3 as both positive and negative electrode materials operating at an average potential of 1.7 V.

For applications involving transportation and the electricity grid, future energy storage systems will require high energy density, fast charge/discharge times, increased safety, and low cost compared to current Li-ion batteries. Non-aqueous multivalent metal (Mg, Zn, Ca, Al) based cells are a promising advanced energy storage technology due to their higher theoretical volumetric capacity, limited dendrite formation, and low cost. A major need for these systems is the development of compatible electrolytes for both electrodes that show reversible multivalent intercalation cathodes.1,2 In the case of non-aqueous Mg or Ca ion systems the electrolyte compatibility issues (e.g., low Coulombic efficiency, a high overpotential, and corrosion) hold back the development of Mg or Ca metal batteries.3 However, non-aqueous Zn2+ ion chemistry in Zn metal cells with a reversible intercalation cathode is an exception among multivalent metals with a number of promising features including high volumetric capacity,1 similar ionic radius compared with Li+ and Mg2+ ions,4 relatively lower activation barrier energy for diffusion in cathode materials (e.g., FePO4, CoO2 and V2O5)5 and highly-efficient reversible Zn deposition behavior on a Zn metal anode with wide electrochemical window.3 Considering these advantages, a non-aqueous Zn system provides an opportunity to delve into the mechanisms in multivalent-ion cell chemistry and solve the present issues in multivalent cell design and prototyping.3 In this study, the intercalation chemistry on a variety of cathodes materials (e.g., V2O5 and Mn2O4) and reversible deposition/dendritic growth issues on a Zn metal anode have been investigated in various non-aqueous Zn electrolytes. The electrochemical and transport properties―reversible Zn deposition behavior, Coulombic efficiency, anodic stability, ionic conductivity and diffusion coefficient―were characterized utilizing the experimental and computational analysis. Among various Zn metal cells, a hydrated Zn/nanostructured bilayered V2O5 cell with an acetonitrile(AN)-Zn(TFSI)2 electrolyte demonstrates good reversibility and stability for 120+ cycles with nearly 100% Coulombic efficiency and ~170 mAhg-1 of gravimetric capacity, albeit operating at a cell voltage of 0.7 V.6 A low crystalline Zn/Nanostructured δ-MnO2 cell with an AN-Zn(TFSI)2 electrolyte also shows good reversibility (~100% Coulombic efficiency) and stability for 50+ cycles with ~100 mAhg-1 capacity and relatively higher operating voltage of 1.2 V. On the other hand, Zn dendrite growth studies on a Zn metal anode in non-aqueous Zn electrolytes have been performed under various conditions, including various current densities (0.1, 1.0, and 10 mA cm-2) and time (0.2 and 2.0 h cycle-1). The cycled Zn metal anodes were characterized using SEM-EDX and X-ray tomography to analyze morphological changes and dendritic growth in both selected regions and overall samples. References J. Muldoon, C. B. Bucur and T. Gregory, Chem. Rev. 2014, 114, 11683-11720. H. D. Yoo, I. Shterenberg, Y. Gofer, G. Gershinsky, N. Pour and D. Aurbach, Energy Environ. Sci. 2013, 6, 2265-2279. S.-D. Han, N. N. Rajput, X. Qu, B. Pan, M. He, M. S. Ferrandon, C. Liao, K. A. Persson and A. K. Burrell, ACS Appl. Mater. Inter. 2016, 8, 3021-3031. R. D. Shannon, Acta Cryst. 1976, A32, 751-767. Z. Rong, R. Malik, P. Canepa, G. Gautam, M. Liu, A. Jain, K. Persson and G. Ceder, Chem. Mater. 2015, 27, 6016-6021. P. Senguttuvan, S.-D. Han, S. Kim, A. L. Lipson, S. Tepavcevic, T. T. Fister, A. K. Burrell and C. S. Johnson, 2016, submitted.

Polyanion compounds are attractive for use as cathode materials because they generally have higher potentials for a given Mn+/(n+1)+ redox couple in comparison to the oxide analogue.1 In addition, the strong bonding within the polyanion group provides similar safety characteristics to oxides even though they exhibit higher working potentials.2 The phospho-olivine LiFePO4 has been thoroughly investigated as a cathode material for use in lithium-ion batteries since its introduction in 1997.3 It has been determined that NaMPO4 (M = Fe and Mn) compounds prefer the electrochemically inactive maricite structure and not the olivine structure when using conventional synthesis methods,4 which has left the research community seeking unorthodox methods to access the olivine phase.5 , 6 Herein we report on a NaCoPO4 (NCP) polymorph (Red-phase) that has previously only been observed as an impurity while attempting to synthesize other polymorphs.7 The Red-phase was synthesized by a microwave-assisted solvothermal process using tetraethylene glycol as the solvent. Ex-situ XRD and XANES measurements indicate that during cycling the structure undergoes reversible changes and the Co2+/3+ redox couple is partially active near 4.4 V vs. Na. The silicate family of cathode materials is rich in polymorphism8 and has also been thoroughly investigated for use in lithium-ion batteries. Among the polymorphs investigated is Pn­-Li2MnSiO4 9 that was accessed by ion-exchange of the parent Pn­-Na2MnSiO4 compound. Yet, minimal work has been reported on the sodium analogue.9 , 10 Considering the air sensitivity reported of the lithium version,11 herein we report preliminary results on the effect of air exposure on the electrochemistry of Pn­-Na2MnSiO4. § cjohnson@anl.gov Acknowledgements Work supported by U. S. DOE, Office of Science under Contract No. DE-AC02-06CH11357. We also thank the Argonne LDRD program office for additional support. References: (1) Gutierrez, A.; Benedek, N. A.; Manthiram, A. Chemistry of Materials 2013, 25, 4010. (2) Hautier, G.; Jain, A.; Ong, S. P.; Kang, B.; Moore, C.; Doe, R.; Ceder, G. Chemistry of Materials 2011, 23, 3495. (3) Padhi, A. K.; Nanjundaswamy, K. S.; Goodenough, J. B. Journal of the Electrochemical Society 1997, 144, 1188. (4) Bridson, J. N.; Quinlan, S. E.; Tremaine, P. R. Chemistry of Materials 1998, 10, 763. (5) Lee, K. T.; Ramesh, T. N.; Nan, F.; Botton, G.; Nazar, L. F. Chemistry of Materials 2011, 23, 3593. (6) Fang, Y.; Liu, Q.; Xiao, L.; Ai, X.; Yang, H.; Cao, Y. ACS Applied Materials & Interfaces 2015, 7, 17977. (7) Feng, P.; Bu, X.; Stucky, G. D. Journal of Solid State Chemistry 1997, 131, 160. (8) Armstrong, A. R.; Sirisopanaporn, C.; Adamson, P.; Billaud, J.; Dominko, R.; Masquelier, C.; Bruce, P. G. Z Anorg Allg Chem 2014, 640, 1043. (9) Duncan, H.; Kondamreddy, A.; Mercier, P. H. J.; Le Page, Y.; Abu-Lebdeh, Y.; Couillard, M.; Whitfield, P. S.; Davidson, I. J. Chemistry of Materials 2011, 23, 5446. (10) Murphy, D. T.; Schmid, S. In The 17th International Meeting on Lithium Batteries 2014. (11) Muraliganth, T.; Stroukoff, K. R.; Manthiram, A. Chemistry of Materials 2010, 22, 5754.

As the lithium ion battery technology matures, it becomes apparent that the energy density is more limited by the materials used. Beyond-Li ion battery technology is now garnering more interest, and, as such, the search for new greater energy storage materials is underway. For us we are pursuing multivalent batteries [1] and are investigating new cathode materials, in hopes of discovering and designing new (de)intercalation hosts, or possibly cathodes that hold multivalent cations (Mg2+, Zn2+, Ca2+) by other storage mechanisms as well at high voltages. In particular, oxide cathodes, for example bilayer-V2O5 (BL-V2O5) [2]or alpha-MnO2(hollandite, 2x2 tunnel structure) [3], have been explored for high voltage intercalation. Unfortunately many problems abound, such as poor diffusion of multivalent cations due to strong electrostatic interactions with the oxide lattice. The development of multivalent ion electrolytes is also at its infancy and it is required to exhibit high voltage stability, compatibility with cathode and inactivity towards cell components. Viable electrolytes for this battery task are hard to find, and thus limit our productivity. Nevertheless, the search and evaluation and synthesis will require the means to chemically cycle the materials. A few reagents like di-n-butyl magnesium, di-ethyl zinc have been reported to intercalate Mg2+ and Zn2+ions [4],[5]. In this work and poster, we will discuss and demonstrate a new method of utilizing novel reagents to intercalate multivalent cations into a variety of host materials. References [1] J. Muldoon et al., Chem. Rev. 114 (2014) 11683–11720. [2] S. Tepavcevic et al., ACS Nano. 9 (2015) 8194–8205. [3] R. Zhang et al., Electrochem. Commun. 23 (2012) 110–113. [4] P.G. Bruce et al., Solid State Ionics 53–56, Part 1 (1992) 351–355. [5] H. Wang et al., ECS Electrochem. Lett. 4 (2015) A90–A93. Acknowledgments This work was supported as part of the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the U. S. Department of Energy, Office of Science, Basic Energy Sciences. Work done at Argonne and use of the Advanced Photon Source, an Office of Science User Facility operated for the U.S. Department of Energy Office of Science by Argonne National Laboratory, were supported by the U.S. Department of Energy under Contract No. DE-AC02-06CH11357.

A non-aqueous multivalent metal cell, one of the potential candidates for a post-lithium-ion battery, provides an attractive opportunity in energy storage research due to higher theoretical volumetric capacity of a metal anode coupled with the limited dendrite formation at the metal anode.1 The development of compatible electrolytes and reversible multivalent intercalation cathodes, however, is a significant challenge:1 in the case of Ca metal cells there is recently developed electrolytes possibly compatible with reversible chemistry at a Ca metal anode, which need much more improvement.2 In Mg metal cells various halide, BH4 and their derivatives electrolytes are known to be compatible with Mg metal anode, but correlation between speciation and functionality is still under debate.3-7 The compatibility of glyme-Mg(TFSI)2 electrolyte with Mg metal is also controversial and generally low Coulombic efficiency and high overpotential are observed in cell cycling.6,7 However, it appears that non-aqueous Zn2+ ion chemistry in Zn metal cells with a reversible intercalation cathode provides an exception among multivalent metals with a number of promising features: high volumetric capacity,1 similar ionic radius compared with Li+ and Mg2+ ions,8 relatively lower activation barrier energy for diffusion in cathode materials (e.g., FePO4, CoO2 and V2O5)9 and highly-efficient reversible Zn deposition behavior on a Zn metal anode with wide electrochemical window.7 In addition, the non-aqueous Zn system provides an opportunity to delve into the mechanisms in multivalent cell chemistry (e.g., reversible deposition on a metal anode and (de)intercalation into(from) a cathode material) and furthermore possibly solve the present issues in multivalent cell design and prototyping.7 In this study, the electrochemical and transport properties (e.g., reversible Zn deposition behavior, Coulombic efficiency, anodic stability, ionic conductivity and diffusion coefficient) of a variety of non-aqueous Zn electrolytes have been examined in detail.7 Classical molecular dynamics and DFT calculations have been utilized to complement the experimental work and to provide insights into the molecular-level solvation structure and dynamics of the bulk electrolytes and a prediction of the electrochemical stability window.7 Based upon the experimental analysis and the simulation studies of the range of different electrolytes, we have selected promising electrolytes and instituted electrochemically testing with a cell consisting of a Zn metal anode and a variety of cathodes materials. Among them, the Zn metal cell consisting of an acetonitrile-Zn(TFSI)2 electrolyte and a synthesized nanostructured bilayered-hydrated V2O5 10 demonstrates good reversibility and stability for 120 cycles with nearly 100% coulombic efficiency and ~180 mAhg-1 of gravimetric capacity, albeit operating at a relatively low cell voltage of 0.9 V. On the other hand, λ-MnO2 (spinel) host material represents no intercalation behavior even in all selected electrolytes, while nanostructured and low crystalline α-, γ-, and δ-MnO2(tunnel or layer) show possible intercalation behavior. Acknowledgments This work was supported as part of the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. The submitted abstract has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract no. DE-AC02-06CH11357. References 1 J. Muldoon, C. B. Bucur and T. Gregory, Chem. Rev. 2014, 114, 11683-11720. 2 A. Ponrouch, C. Frontera, F. Bardé and M. R. Palacín, Nat. Mater.2015, doi:10.1038/nmat4462. 3 J. Muldoon, C. B. Bucur, A. G. Oliver, T. Sugimoto, M. Matsui, H. S. Kim, G. D. Allred, J. Zajicek and Y. Kotani, Energy Environ. Sci. 2012, 5, 5941-5950. 4 H. D. Yoo, I. Shterenberg, Y. Gofer, G. Gershinsky, N. Pour and D. Aurbach, Energy Environ. Sci. 2013, 6, 2265-2279. 5 C. J. Barile, R. Spatney, K. R. Zavadil and A. A. Gewirth, J. Phys. Chem. C 2014, 118, 10694-10699. 6 C. B. Bucur, T. Gregory and J. Muldoon, In Rechargeable Batteries: Materials, Technologies and New Trends, Z. Zhang and S. S. Zhang, Eds., Springer International Publishing: Switzerland, 2015, Chapter 22, 611-635. 7 S.-D. Han, N. N. Rajput, X. Qu, B. Pan, M. He, M. S. Ferrandon, C. Liao, K. A. Persson and A. K. Burrell, ACS Appl. Mater. Inter.2016, accepted. 8 R. D. Shannon, Acta Cryst. 1976, A32, 751-767. 9 Z. Rong, R. Malik, P. Canepa, G. Gautam, M. Liu, A. Jain, K. Persson and G. Ceder, Chem. Mater. 2015, 27, 6016-6021. 10 S. Tepavcevic, X. Xiong, V. R. Stamenkovic, X. B. Zou, M. Balasubramanian, V. B. Prakapenka, C. S. Johnson and T. Rajh, ACS Nano 2012, 6, 530.

Na2Ti3O7 is prepared from milled mixtures of anatase TiO2 and anhydrous Na2CO3 in 10% excess (800 °C, 40 h).

International audience; Due to its success in the domain of power electronics, the lithium ion battery technology is currently being considered for electric vehicle propulsion and even electric grid storage.1,2 However, the implementation of a lithium based technology on a large scale faces controversial debates on lithium availability and cost. Alternative lower cost and sustainable chemistries would be specially suited for large scale applications even if they involve a penalty in energy density. The most appealing alternative is to use sodium, instead of lithium. Indeed, it exhibits a rich intercalation chemistry3,4 and its resources are in principle unlimited (high concentrations in seawater) being very easy to recuperate. Sodium technology has already been successfully implemented in today's commercialized high-temperature Na/S cells for MW storage and for Na/NiCl2 ZEBRA-type systems for electric vehicles, both of which take advantage of the highly conducting solid beta-alumina ceramics at temperatures of ca. 300 C. Mindful of these considerations, and within the current knowledge gained in Li-ion technology, a room temperature analogous Na-ion cell is a realistic target. If achieved, it would bring about a radical decrease in cost with respect to lithium ion technology while ensuring sustainability.

Multivalent-ion chemistries such as Mg-ion are emerging as alternative battery systems to Li-ion. Current Mg-ion chemistries are limited to relatively low voltages and relatively low reversible specific capacities (1-2). Recent research on potential high voltage Mg-ion cathode materials and alternative anode materials such as transition metal oxides and metal alloys have highlighted the urgent need to understand structure activity relationships and insertion/intercalation phenomenon for development of such systems (3). Solid state NMR is a powerful tool to investigate local structure and insertion/intercalation phenomena, particularly for batteries as shown for Li-ion chemistries with 6Li and 7Li NMR (4, 5). However, the low natural abundance (10%) of the NMR active Mg isotope (25Mg), highly quadrupolar nuclear spin of 25Mg (spin 5/2) and very low gyromagnetic ratio (i.e 30.6 MHz Larmor frequency relative to 1H = 500 MHz) limits the effective use of 25Mg NMR for solid Mg-ion battery materials (6). In this work, despite the challenges of 25Mg NMR, our recent efforts to characterize Mg environments in cathode materials such as MgMn2O4 spinels, MgV2O5, in anode materials such as h-TiO2 and Mg alloys will be presented. Chemical magnesiation using dibutylmagnesium and preliminary electrochemical (de)magnesiation and the structural changes induced will be discussed. The results will summarize the effectiveness of the method in distinguishing side reactions or undesirable conversion reactions, including amorphous phases, from intercalation phenomenon. 1. D. Aurbach, Z. Lu, A. Schechter, Y. Gofer, H. Gizbar, R. Turgeman, Y. Cohen, M. Moshkovich, and E. Levi, Nature, 407 (6805), 724-727 (2000). 2. H. D. Yoo, I. Shterenberg, Y. Gofer, G. Gershinsky, N. Pour, and D. Aurbach, Energ Environ Sci, 6 (8), 2265-2279 (2013). 3. Magnesium Batteries 1 and 2, 224th Electrochemical Society Meeting, San Francisco CA, 2013 4. C. P. Grey and N. Dupre, Chem. Rev. (Washington, DC, U. S.), 104, 4493 (2004). 5. B. Key, R. Bhattacharyya, M. Morcrette, V. Seznec, J. M. Tarascon and C. P. Grey, Journal of the American Chemical Society, 131, 9239 (2009). 6. R. Dupree and M. E. Smith, Journal of the Chemical Society-Chemical Communications, 1483 (1988).

A non-aqueous multivalent (e.g., Mg2+, Ca2+ and Zn2+) metal cell is one of the potential candidates for a post-lithium-ion battery. The theoretical volumetric capacity of a metal anode coupled with the lack of dendrite formation at a multivalent metal anode provide an attractive opportunity in energy storage.1 However, the development of multivalent cathodes and electrolytes is a significant challenge. For example, with Ca metal cells there is no known electrolyte compatible with reversible chemistry at a metal anode. In the Mg systems only diglyme-Mg(TFSI)2 and various halide and pseudohalide electrolytes are known to be compatible with Mg metal where an unknown passivation layer on a Mg metal anode induces low Columbic efficiency in the cell chemistry. However, it appears that Zn2+ maybe an exception in the multivalent metals. Zn metal anodes coupled with a reversible intercalation cathodes chemistry have a number of promising features: 1) high volumetric capacity (much higher than Mg and Ca);1 2) similar ionic radius compared with Li+ and Mg2+ ions;2 3) relatively lower activation barrier energy for diffusion in cathode materials (e.g., FePO4, CoO2 and V2O5)3 and 4) reversible Zn deposition and higher anodic stability in non-aqueous Zn electrolytes. Most of the previous rechargeable Zn cell studies have been performed using an aqueous Zn electrolyte system,4-6and very little information is available about non-aqueous Zn battery, in particular non-aqueous Zn electrolytes. In this study, the general electrochemical and transport properties of non-aqueous Zn electrolytes—consisting of mixtures of Zn salts (e.g., Zn(PF6)2, Zn(TFSI)2, Zn(BF4)2 and Zn(CF3SO3)2) and organic solvents (e.g., diglyme, propylene carbonate, acetonitrile and dimethylformamide)—have been examined in detail. The ionic conductivity of the electrolytes was determined as a function of salt concentration and temperature, and their diffusion coefficient was estimated by the chronocoulometry technique.7 The anodic stability of each electrolyte was studied by linear sweep voltammetry, while reversible Zn deposition behavior of the electrolytes on a Zn metal anode was investigated by cyclic voltammetry. Classical molecular dynamics and DFT calculations have been utilized to complement the experimental work and to provide insights into the molecular-level solvation structure (ion solvation and ionic association behavior) and dynamics of the bulk electrolytes. In particular, a prediction of the electrochemical stability window via adiabatic ionization potential/electron affinity calculations was undertaken. Based on our experimental analysis and the simulation studies of the range of different electrolytes, we have selected promising electrolytes and performed electrochemical testing with cells consisting of a Zn metal anode and a variety of cathodes materials. Among them, the Zn metal cell consisting of an acetonitrile-Zn(TFSI)2 electrolyte and an electrochemically synthesized nanostructured V2O5 8 demonstrates good reversibility and stability for 120 cycles with nearly 100% coulombic efficiency and ~180 mAhg-1of gravimetric capacity, albeit operating at a relatively low cell voltage of 0.9 V. Acknowledgments This work was supported as part of the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. The submitted abstract has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract no. DE-AC02-06CH11357. References 1) J. Muldoon, C. B. Bucur and T. Gregory, Chem. Rev. 2014, 114, 11683. 2) R. D. Shannon, Acta Cryst. 1976, A32, 751. 3) Z. Rong, R. Malik, P. Canepa, G. Gautam, M. Liu, A. Jain, K. Persson and G. Ceder, submitted. 4) C. Xu, B. Li, H. Du and F. Kang, Angew. Chem. Int. Ed. 2012, 51, 933. 5) J. Lee, J. B. Ju, W. I. Cho, B. W. Cho and S. H. Oh, Electrochimica Acta 2013, 112, 138. 6) B. Lee, C. S. Yoon, H. R. Lee, K. Y. Chung, B. W. Cho and S. H. Oh, Scientific Reports 2014, 4, 6066. 7) A. Benmayza, M. Ramanathan, T. S. Arthur, M. Matsui, F. Mizuno, J. Guo, P. Glans and J. Prakash, J. Phys. Chem. C 2013, 117, 26881. 8) S. Tepavcevic, X. Xiong, V. R. Stamenkovic, X. B. Zou, M. Balasubramanian, V. B. Prakapenka, C. S. Johnson and T. Rajh, ACS Nano 2012, 6, 530.

not Available.

A new TiP2O7 form has been prepared by low temperature synthesis, which does not exhibit the superstructure reported when TiP2O7 is prepared via a conventional ceramic route. This LT-TiP2O7 polymorph presents linear P2O7 pyrophosphate groups, connected through a pivotal oxygen which ensure the flexibility of the structure. Therefore it can reversibly take up both Li and Na ions, contrary to the high temperature polymorph that can only take up Li.