Abstract: Introduction Among the available energy-storage technologies, lithium batteries will play an increasingly important role because of their high specific energy and energy density. Since their introduction in 1991, Li-ion batteries have transformed portable electronic devices. New generations of such batteries will transform transport and find use in stationary electricity storage. Extensive research in lithium-ion anode technologies have made it possible to obtain 1,950 mAh/g anode capacities with stable performance (1-3). However the current cathodes plays a limiting role with a maximum achieved capacity five folds lower than that of the anode (4). Reaching beyond the horizon of Li-ion batteries is a serious challenge and requires the exploration of new chemistries, especially related to the electrochemistry, and new materials development. Li-S battery which works on the ‘conversion’ principle is a promising candidate for this purpose. Sulfur has a theoretical capacity of 1672 mAh/g, representing to nearly 6, 11 and 10 fold improvement in capacity as compared to LiCoO 2 , LiMn 2 O 4 and LiFePO 4 respectively. Since the first demonstration of LiS batteries, research has burgeoned at an alarming rate in this exciting field. However, this technology still has many challenges due to the poor conductivity of sulfur and more importantly, the polysulfide dissolution. Polysulfide originally dissolves as short chain and grows into a longer chain, eventually resulting in the loss of active material and capacity fade. Polysulfide dissolution is a serious issue yet to be addressed economically. Previous work from our group(5) demonstrates a very effective method to prevent polysulfide dissolution by coating a thin layer of Lithium Ion Conductor (LIC) over nano-sulfur anode in a multilayer architecture. This approach resulted in a stable capacity of ~600mAh/g for over 60 cycles with minimal fade. In this work, we attempt to enhance the capacity and stability by altering the size of the active sulfur nanomaterials and engineering the porosity of LIC layer on the performance of the battery. Figure 1 depicts an LIC coated sulfur electrode with tailored porosity and pore volume. Using dynamic light scattering the size of nanoparticles is analyzed and porosity and pore volume are studied using mercury porosimetry, envelope density measurement and BET surface area analysis. Results of these studies will be presented and discussed.  Captions Figure 1: SEM image of the LIC coated sulfur electrodes(5). References 1.         M. K. Datta, J. Maranchi, S. J. Chung, R. Epur, K. Kadakia, P. Jampani and P. N. Kumta, Electrochimica Acta , 56 , 4717 (2011). 2.         R. Epur, M. K. Datta and P. N. Kumta, Electrochimica Acta , 85 , 680 (2012). 3.         W. Wang, R. Epur and P. N. Kumta, Electrochemistry Communications , 13 , 429 (2011). 4.         J. Chen, Materials , 6 , 156 (2013). 5.         P. J. Hanumantha, B. Gattu, O. Velikokhatnyi, M. K. Datta, S. S. Damle and P. N. Kumta, Journal of The Electrochemical Society , 161 , A1173 (2014). Figure 1

Abstract: Silicon based anode systems have attracted considerable attention as alternative materials to replace graphite as a high energy density anode for lithium ion batteries due to silicon’s high theoretical capacity (~4200mAh/g). However, the material suffers from colossal volumetric expansion (~400%) associated with the formation of Li 4.4 Si phase during the lithiation reaction. Over the past few years, different approaches have been developed to address this issue which causes mechanical degradation and results in rapid loss in capacity of silicon anodes. These approaches involve the use of silicon nanoparticles [1], composite structures of amorphous silicon [2] , active-inactive matrices [3], electrodeposited thin films and VACNT-Si heterostructures [4-6] . Nanostructures of silicon have been shown to withstand the mechanical pulverization by providing stress – strain relaxation mechanisms thus, showing improved cycling stability. However, most of the synthesis methods used to generate these Si nanostructures involve high processing costs, complex machinery/equipment, utilization of expensive templates and large number of processing steps. Additionally these materials show higher first cycle irreversible (FIR) loss and have poor areal loading densities. In the present work, Si nanostructures are generated using a simple two-step procedure employing a low-cost recyclable template. The template was generated using a high throughput high energy mechanical milling process (HEMM) utilizing an abundant, cheap and water soluble material. Si nanoflakes and Si nanorods (deposited using low pressure chemical vapor deposition) were obtained by varying the template synthesis conditions. The template is then recovered and reused by washing in water making the procedure amenable for commercialization. Slurry based electrodes of these nanostructures mixed with binder and conductive additives were then fabricated and tested in a half cell configuration against lithium foil between the voltage range 0.01V – 1V vs. Li/Li + in 1M LiPF 6 (dissolved in EC:DEC:FEC=45:45:10) electrolyte. Fig. 1a shows the XRD patterns of the two different morphologies of silicon obtained using this simple two-step procedure. It can be seen therein that the procedure can be tailored to obtain either amorphous (Si flakes) or nanocrystalline (Si rods) silicon materials. The aim of this study is to understand the effect of the synthesis conditions on the morphology, crystal structure and subsequent electrochemical performance of low-cost template-derived silicon nanostructures.  It can be seen in Fig. 1b that both morphology and crystallinity affect the silicon capacity and cycling behavior of both silicon morphologies. Though Si rods show a superior first cycle discharge capacity (~2790 mAh/g at current rate of 50mA/g; FIR loss ~12%-13%) as compared to Si flakes (~2930 mAh/g at current rate of 50mA/g; FIR loss ~17%-20%), the long term cycling behavior is in stark contrast,  with Si nanoflakes  and nanorods showing a fade rate of ~0.03% and ~0.4% loss per cycle, respectively, due to the differences in morphology and crystallinity. Additionally, electrodes with areal loading density of ~1.3 – 1.5mg/cm 2 were obtained independent of the morphology of the silicon nanostructures. Furthermore, Si nanoflakes and nanorods showed a specific discharge capacity of ~1150mAh/g and ~1025mAh/g, respectively (at a current rate of 1A/g), at the end of 150 cycles. Results of these studies will be presented and discussed. Acknowledgement: The authors gratefully acknowledge financial support of DOE contract administered through PNNL and NSF-CBET 1511390. The authors also acknowledge the Edward R. Weidlein Chair Professorship funds and the Center for Complex Engineered Multifunctional Materials (CCEMM) for support of this research. References: [1] I. Kim, P.N. Kumta, G.E. Blomgren, Electrochemical and Solid State Letters 3 (2000) 493-496. [2] X.H. Liu, L. Zhong, S. Huang, S.X. Mao, T. Zhu, J.Y. Huang, Acs Nano 6 (2012) 1522-1531. [3] M.K. Datta, J. Maranchi, S.J. Chung, R. Epur, K. Kadakia, P. Jampani, P.N. Kumta, Electrochimica Acta 56 (2011) 4717-4723. [4] W. Wang, R. Epur, P.N. Kumta, Electrochemistry Communications 13 (2011) 429-432. [5] W. Wang, P.N. Kumta, Acs Nano 4 (2010) 2233-2241. [6] R. Epur, M.K. Datta, P.N. Kumta, Electrochimica Acta 85 (2012) 680-684. Figure 1

Abstract: Silicon based anode has attracted considerable attention to replace graphite as a high-energy density anode material for the next generation lithium ion batteries due to the high theoretical specific capacity of silicon (~4200 mAh/g). However, bulk crystalline silicon exhibits poor performance due to colossal volumetric expansion (~400%) following reaction with lithium. The past decade has witnessed different approaches to address and counter the issue of mechanical degradation of silicon anodes. These approaches involve the use of silicon nanoparticles [1], composite structures of amorphous silicon [2] , active-inactive matrix [3], electrodeposited thin films and VACNT-Si hetero-structures [4-6] . On the other hand, the cathode systems are restricted due to low capacities (160-190mAh/g) and sulfur has been shown as a promising alternative with a theoretical capacity of ~1600mAh/g. However, sulfur cathode suffers from polysulfide dissolution and electrode passivation which results in poor performance, high capacity fade and subsequent failure of the electrodes. [7-10] In the present work, a promising anode material for Li-ion batteries consisting of active material deposited on carbon nanotubes (CNT) has been synthesized as a viable electrode generated by a commerically viable facile electrodeposition (ED) process. At first, a thin layer of catalyst M on Cu substrate (denoted as M-Cu) has been developed using a high throughput solution based coating technique. The SEM image and EDAX mapping ( Fig 1a ) of M-Cu confirms that a distinct layer ( 〈 1µ) of catalyst M is coated on the Cu foil. Subsequently, a forest of carbon nanotubes (CNTs)is grown on the M-Cu substrate by CVD technique using a mixture of cost effective carbon precursors and argon at varying temperatures and times. The SEM image of the CNT/M-Cu ( Fig 1b ) shows the formation of CNTs well adhered to the M/Cu substrate. The thickness of the CNT layer varies from ~30µ to ~200µ depending on the deposition time. Amorphous Si is deposited on the CNT/M-Cu by a commerically viable electrodeposition process using a non aqueous ionic electrolyte consisiting of silicon containing precursors. The SEM analysis of the Si deposited CNT/M-Cu ( Fig 1c and Fig 1d ) shows a uniform film of Si deposited on the CNTs with the size of the silicon particles being 〈 100nm. Furthermore, the CNT/Cu substrate was used to develop S/CNT nanostructured composite on Cu substrate as the cathode. The electrodes of these nanocomposites (Si/CNT and S/CNT) were initially tested in a half cell configuration within the voltage range of 0.01V – 1V vs. Li/Li + in their respective electrolyte system without addition of any binder. The electrodeposited Si on CNT/M-Cu (denoted as ED-Si/CNT) was tested as an anode in Li/Li + electrochemical cell without any further addition of additives. The ED-Si/CNT electrodes show a first cycle discharge and charge capacity of ~ 3435 mAh/g and ~2050 mAh/g, respectively, with a first cycle irreversible (FIR) loss of ~35-45% (Fig 1e) at a charge/discharge current rate of ~300mA/g. The ED-Si/CNT also shows an excellent capacity retention with a stable capacity of ~1870 mAh/g up to 70 cyles (Fig. 1e) . The electrochemical performance of S/CNT binderless electrode shall be reported and discussed along with complete characterization of the electrodes using Raman Spectroscopy, X-ray Diffraction, TEM and XPS to understand the behavior of these respective electrode system with respect to Li/Li + system. Acknowledgement: The authors gratefully acknowledge financial support of the DOE-BATT (DE-AC02-05CHl1231), DOE-PNNL and NSF (CBET-1511390) programs. The authors also acknowledge the Edward R. Weidlein Chair Professorship funds and the Center for Complex Engineered Multifunctional Materials (CCEMM) for support of this research. References: [1] I. Kim, P.N. Kumta, G.E. Blomgren, Electrochemical and Solid State Letters 3 (2000) 493-496. [2] X.H. Liu, L. Zhong, S. Huang, S.X. Mao, T. Zhu, J.Y. Huang, ACS Nano 6 (2012) 1522-1531. [3] M.K. Datta, J. Maranchi, S.J. Chung, R. Epur, K. Kadakia, P. Jampani, P.N. Kumta, Electrochimica Acta 56 (2011) 4717-4723. [4] W. Wang, R. Epur, P.N. Kumta, Electrochemistry Communications 13 (2011) 429-432. [5] W. Wang, P.N. Kumta, ACS Nano 4 (2010) 2233-2241. [6] R. Epur, M.K. Datta, P.N. Kumta, Electrochimica Acta 85 (2012) 680-684. [7] J. R. Akridge, Y. V. Mikhaylik and N. White, Solid State Ionics, 2004, 175, 243-245. [8] X. Ji and L. F. Nazar, Journal of Materials Chemistry, 2010, 20, 9821-9826. [9] G. C. Li, J. J. Hu, G. R. Li, S. H. Ye and X. P. Gao, Journal of Power Sources, 2013, 240, 598-605. [10] C.-N. Lin, W.-C. Chen, Y.-F. Song, C.-C. Wang, L.-D. Tsai and N.-L. Wu, Journal of Power Sources, 2014, 263, 98-103. Figure 1

Abstract: Introduction Lithium sulfur and lithium-air batteries hold much promise for the future of batteries on account of their theoretical capacities of 2567 and 3505 Wh/kg respectively(1). The dissolution of sulfur through the formation of soluble polysulfides and the poor electronic conductivity of sulfur are however, major problems hindering Li-S battery progress (1-3). In addition, particle fracture and delamination as a result of repeated volumetric expansion and contraction have also been identified as factors responsible for poor long term performance(4, 5). In our previous work on lithium-sulfur batteries, we have shown the effectiveness of using a thin Li-ion conducting barrier layer in improving the cycling characteristics(6). In this work, we develop a unique strategy to directly prepare sulfur wire mattes ( Figure 1 ) capable of being spun as yarn and thereupon being used directly in the form of ‘textile fabric batteries’. Using these wires, we generate two other morphologies to specifically tackle fade and conductivity issues existing in sulfur cathodes. This results in sulfur cathodes with high electronic conductivity, minimal volumetric expansion and improved rate capabilities and cyclability. In addition, the electrodes that we use in this study allow us to obtain high areal capacities.  Figure 1 shows SEM and EDAX map of the same. Results of these studies will be presented and discussed. Captions Figure 1: (a) Scanning electron microscopy image of the sulfur wires (b) EDAX map indicating the Sulfur distribution. References 1.         P. G. Bruce, S. A. Freunberger, L. J. Hardwick and J.-M. Tarascon, Nature Materials , 11 , 19 (2012). 2.         J. Cabana, L. Monconduit, D. Larcher and M. Rosa Palacin, Advanced Materials , 22 , E170 (2010). 3.         B. Scrosati and J. Garche, Journal of Power Sources , 195 , 2419 (2010). 4.         L. Ji, M. Rao, S. Aloni, L. Wang, E. J. Cairns and Y. Zhang, Energy & Environmental Science , 4 , 5053 (2011). 5.         Z. Wei Seh, W. Li, J. J. Cha, G. Zheng, Y. Yang, M. T. McDowell, P.-C. Hsu and Y. Cui, Nat Commun , 4 , 1331 (2013). 6.         P. J. Hanumantha, B. Gattu, O. Velikokhatnyi, M. K. Datta, S. S. Damle and P. N. Kumta, Journal of The Electrochemical Society , 161 , A1173 (2014). Figure 1

Abstract: The global demand for energy storage systems for portable consumer devices such as cell phone, laptop including electric vehicles is clearly on the rise. To date, lithium ion batteries are considered the flagship battery system due to its high volumetric/gravimetric energy and power densities. Current lithium ion batteries exhibit a power density of 100-260 Whkg -1 when layered spinel and olivine cathode material such as LiCoO 2 , LiNiO 2 , LiMnO 4 , and LiFePO 4 are coupled with a graphite anode. With the recent demand for higher energy storage capacities for use in electric vehicles research has been focused on replacing graphite with Li metal as anode material owing to its high theoretical capacity of ~3800mAh/g. However, lithium anode suffers from growth of dendritic morphology and low columbic efficiency which leads to failure of the battery. The dendrite formation is caused by the non-uniform current density at the surface of the solid electrolyte interphase (SEI) which results in a high-surface area lithium (HSAL). A solution to prevent the HSAL formation is using uniform low current density and by increasing the active surface area, the actual current density can be kept low during plating/deplating process. Li electroplating is a well-studied phenomenon. However, the effect of electrode surface features on the resultant electrocrystallization process of Li from nucleation and growth perspective is not yet defined and well understood. In the present work, patterning of Li electrode surface was implemented and their effect on the the nucleation and growth process is studied. Various patterned Li electrodes (plain Li, Li-300, Li-2500) were assembled in CR2025 coin cell using commercial Li foil as counter electrode and tested at different areal current densities for plating and deplating. Fig 1a-c shows the evolution of voltage of plain Li foil, patterned Li-300 and Li-2500, respectively, on repeated plating and deplating at 0.5mA/cm 2 . The voltage profile can be identified as two distinct regions of nucleation overpotential (E N ) and growth overpotential (E G ) in the electrocrystallization process of Li. Depending on the Li surface, a noticeable change in the nucleation and growth overpotential is observed. Plain Li surface shows a very high E N (0.45V) as compared to the Li-300 (0.32V) indicating the formation of higher nucleation sites which results in HSAL. Li-300 and Li-2500 on the other hand, show rapid decrease in E N on cycling with similar nucleation and growth potential ( 〉 10 th cycle) indicating growth of preexisting nucleation sites instead of creating fresh nucleation sites. For full cell testing, electrodes were made from slurry consisting of 90% Lithium Manganese Oxide (LiMn 2 O 4 ) with 5% Carbon (Super P) and 5% Polyvinylidene difluoride (PVDF) cast on aluminum current collector and assembled in a CR2025 coin cell with different patterned Li electrodes. Long term cycling and rate capability tests were conducted at different current rates and their performance evaluated in terms of stability, columbic efficiency and charge/discharge capacities. Subsequently, electrical impedance spectroscopy and SEM analysis were carried out to understand the evolution of Li plating morphology and variation of electrochemical performance with different surface patterns. Results of these studies will be presented and discussed. Figure 1

Abstract: Silicon based anode has attracted considerable attention to replace graphite as a high energy density anode material for lithium ion batteries due to the high theoretical specific capacity of silicon (~4200 mAh/g). However, bulk crystalline silicon exhibit poor performance due to colossal volumetric expansion (~400%) on reaction with lithium. The past decade has witnessed different approaches to address and counter the issue of mechanical degradation of silicon anodes. These approaches involve the use of silicon nanoparticles [1], composite structures of amorphous silicon [2] , active-inactive matrix [3], electrodeposited thin films and VACNT-Si heterostructures [4-6] . However, the systems developed are either based on high cost synthesis approaches or utilize pre synthesized silicon nano particles and still suffer from poor capacity retention. Silica and silicon oxides are commercially cheap sources to synthesize silicon and high energy mechanical milling (HEMM) is also a well-known commercial processing technology to generate nano particles/nano-composites. In the present work, nanocrystalline Si, nc-Si/metal oxide/carbon composite (nc-Si/MO/C) has been synthesized and studied as a promising anode material for Li-ion batteries. Reduction of commercially available silicon monoxide has been carried out with suitable metal based reducing agents using an in-situ high energy mechanochemical reduction (HEMR) followed by low temperature heat treatment to enable completion of the reduction reaction. This directly generates silicon and metal oxide based nanocomposite which acts as an electrochemically active/inactive composite for use in lithium ion batteries. The obtained nanocomposite material was embedded in different carbon (C) based matrices to further improve the performance of the system. Slurry based electrodes of these nanocomposites mixed with binder and conductive additives were then fabricated and tested in a half cell configuration within the voltage range of 0.01V – 1V vs. Li/Li + in 1M LiPF 6 (dissolved in EC:DEC:FEC=45:45:10) electrolyte. XRD pattern (Fig 1a) shows the evolution of the nanocrystalline silicon ( nc -Si) and decrease in intensity of SiO amorphous broad peak with the increase in milling time from 20h to 40h, hence, indicating the reduction of SiO by the metal based reducing agent to form nc -Si. The heat treatment of the material obtained after 40h HEMR (Fig 1a) increases the crystalline nature of silicon and improves the formation of Si by completing the reaction. The XRD pattern (Fig 1a) after heat treatment shows no unreacted SiO phase indicating the completion of reduction process. FTIR, Raman spectroscopy, SEM and TEM analysis has been conducted on the material at different stages of reduction and heat treatment process to study the evolution of the phases in the nanocomposite. The nanocomposite embedded in carbon (nc-Si-MO/C) system shows a first and second cycle discharge capacity ~1500mAh/g and ~1340mAh/g at a current rate of ~50mA/g with a first cycle irreversible (FIR) loss of ~25%-35% (Fig 1b). The obtained capacities are in agreement with theoretical calcluated specific capacity of the composite. Following long term cycling, the system shows a stable specific capacity of ~730mAh/g after 120 cycles at a charge/discharge rate of ~500mA/g with a columbic efficiency of ~99.65-99.82% and a fade rate of ~0.15% capacity loss per cycle. Retention of the MO matrix in the HEMR generated composite coupled with the interconnected carbon acts as an efficient buffer to relieve the stresses generated during alloying/dealloying and also maintains the electrical continuity during expansion of the nc-Si. Results of these studies combined with the extensive electrochemical characterization including electrochemical impedance, rate capability and SEM analysis of the electrodes before and after electrochemical cycling will be presented and discussed. Acknowledgement: The authors gratefully acknowledge financial support of the DOE-BATT (DE-AC02-05CHl1231), DOE-PNNL and NSF (CBET-0933141) programs. The authors also acknowledge the Edward R. Weidlein Chair Professorship funds and the Center for Complex Engineered Multifunctional Materials (CCEMM) for support of this research. References: [1] I. Kim, P.N. Kumta, G.E. Blomgren, Electrochemical and Solid State Letters 3 (2000) 493-496. [2] X.H. Liu, L. Zhong, S. Huang, S.X. Mao, T. Zhu, J.Y. Huang, ACS Nano 6 (2012) 1522-1531. [3] M.K. Datta, J. Maranchi, S.J. Chung, R. Epur, K. Kadakia, P. Jampani, P.N. Kumta, Electrochimica Acta 56 (2011) 4717-4723. [4] W. Wang, R. Epur, P.N. Kumta, Electrochemistry Communications 13 (2011) 429-432. [5] W. Wang, P.N. Kumta, ACS Nano 4 (2010) 2233-2241. [6] R. Epur, M.K. Datta, P.N. Kumta, Electrochimica Acta 85 (2012) 680-684. Figure 1

Abstract: Identification of low cost, highly active, durable completely noble metal-free electro-catalyst for oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells, oxygen evolution reaction (OER) in PEM based water electrolysis and metal air batteries remains one of the major unfulfilled scientific and technological challenges of PEM based acid mediated electro-catalysts. In contrast, several non-noble metals based electro-catalysts have been identified for alkaline and neutral medium water electrolysis and fuel cells. Herein we report for the very first time, F doped Cu 1.5 Mn 1.5 O 4 , identified by exploiting theoretical first principles calculations for ORR and OER in PEM based systems. The identified novel noble metal-free electro-catalyst showed similar onset potential (1.43 V for OER and 1 V for ORR vs RHE) to that of IrO 2 and Pt/C, respectively. The system also displayed excellent electrochemical activity comparable to IrO 2 for OER and Pt/C for ORR, respectively, along with remarkable long term stability for 6000 cycles in acidic media validating theory, while also displaying superior methanol tolerance and yielding recommended power densities in full cell configurations.