bluuebunny/crossref_metadata_2025 huggingface dataset:
Increase in Cycling Stability of Doped Lithium Nickel Manganese Oxide Spinels during Charging Between 2.0 and 5.0 V
Authors: Höweling Andres , Stoll Andreas , Geßwein Holger , Binder Joachim R.
Published: February 2020

The increase in batteries energy is one of the main issues in current battery research and mandatory for the development of electric vehicles with long ranges. The energy of a battery is determined by the capacity and the potential difference of the active materials. Thus, both parameters offer the ability for an increase in energy.

In many studies high capacity cathode materials are analyzed. One of the most promising materials is a Li-rich layered oxide. Other studies use high voltage cathode materials (e.g. LiMxMn2-xO4, with M = e.g. Ni, Co) in order to increase the operational voltage of the cell. Cells with high voltage cathodes suffer from unwanted side reactions with the electrolyte. This is because the operational voltage is higher than the stability window (ca. 1.0 – 4.3 V vs. Li+/Li0 in the presence of transition metal ions like Ni4+ and Mn4+) of current organic electrolytes. The reactions consume active lithium and a severe capacity fade occurs. On the other side, the increase of energy of high capacity cathode materials is limited due to the relatively low voltages of ca. 3.5 V vs. Li+/Li0 of these materials and the need for balancing of anode capacity.

In principle the high voltage spinel (LiNi0.5Mn1.5O4) offers the ability to increase the voltage and the capacity compared with other cathode materials. This can be reached when a metallic lithium anode is used. The spinel lattice can host a second lithium and therefore the theoretical capacity is increased from 147 to 294 mAh g-1. The increase in capacity during cycling between 2.0 and 5.0 V and the high operational voltage lead to a theoretical specific energy of more than 1000 Wh kg-1 based on the active materials. During intercalation of the second lithium, the spinel undergoes a phase transition from cubic to tetragonal because of a cooperative Jahn-Teller-distortion of Mn3+in the low voltage area. This is associated with material degradation and capacity loss.

Here we use different LiNi0.5Mn1.5O4-spinels doped with transition metals and treated with different temperature programs in order to increase the cycling stability. It is found that the stability and the initial capacities are directly dependent on the treatment and doping elements. At a rate of C/2 a capacity of 190 mAh g-1 is achieved with 92 % of the initial capacity retained after 100 cycles. The difference in the discharge behavior of the materials is analyzed based on electrochemical data, particle morphology and in-situ XRD analysis. A model, which can explain the different behaviors is introduced and will be discussed.
Stability of Ni-Rich NMC Cathode Materials in Water and Electrolyte Solutions during Aqueous Electrode Processing
Authors: Wood Marissa , Sheng Yangping , Keever Tamara J. , Li Jianlin , Wood David L
Published: February 2020

Despite recent advances in lithium-ion battery technology, further energy density improvements and cost reductions are necessary to achieve widespread adoption of electric vehicles. Nickel-rich formulations of lithium nickel manganese cobalt oxide (NMC) have been developed as promising high-energy, high-voltage cathode materials capable of significantly increasing the energy density of lithium-ion batteries. Aqueous processing of these cathodes offers significant environmental benefits and lower production expenses compared to traditional processing using N-methylpyrrolidone (NMP). However, Ni-rich NMC materials can react with water during electrode preparation, and with electrolyte during battery assembly and cycling, resulting in metal leaching that can cause structural changes and performance degradation. We investigated the effect of aqueous processing on the structure and electrochemical behavior of these cathode materials by exposing four NMC powders with varying nickel contents (NMC 333, NMC 532, NMC 622, NMC 811) to water and electrolyte for different time durations meant to simulate electrode processing and battery assembly conditions. The resulting metal dissolution was then measured using inductively coupled plasma mass spectrometry (ICP-MS). Since the pH of aqueous slurries can differ depending on composition, and pH variation may lead to additional reactions, the effect of pH was also explored.

We found that lithium dissolution increases with increasing nickel content at all pH values, and slurries made with all four powders become basic during typical processing times. Dissolution of Ni, Mn, and Co in water was minimal for all formulations. In order to gain a better fundamental understanding of the structural changes taking place during these reactions, a subset of the NMC powders was characterized by SEM and X-ray photoelectron spectroscopy (XPS) before and after exposure to water and electrolyte. In addition, the effect of aqueous processing on battery performance was evaluated by comparing the rate performance of pouch cells made using cathodes processed with different water exposure durations. Correlating processing conditions with performance could lead to the design of new approaches to mitigate metal leaching from Ni-rich NMC materials and enable the use of these cathodes for high energy density lithium-ion batteries.

Acknowledgment

This research at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) under contract DE-AC05-00OR22725, was sponsored by the Office of Energy Efficiency and Renewable Energy (EERE) Vehicle Technologies Office (VTO) (Deputy Director: David Howell) Applied Battery Research subprogram (Program Manager: Peter Faguy).

Figure 1
Advanced Sodium-Ion Battery Anode Constructed Via Chemical Bonding Between Phosphorus, Conducting Polymer and Crosslinked Polymer Binder
Authors: Song Jiangxuan , Zhang Li
Published: February 2020

Maintaining structural stability is a great challenge for high-capacity conversion electrodes with large volume change, but is necessary for the development of high-energy-density, long-cycling batteries.[1-3]Here, we report a stable phosphorus anode for sodium-ion batteries by the synergistic use of chemically bonded phosphorus-conducting polymer hybrid and cross-linked polymer binder. The phosphorus-conducting polymer hybrid was synthesized through ball-milling of red phosphorus and functionalized polyacrylonitrile. The P-O(S)-C bonds formed in this process help maintain contact between phosphorus and CNTs, leading to a durable hybrid. As a result, this anode delivers a high initial capacity and excellent cycling stability, along with a high Coulombic efficiency of ~99%. The unique electrode framework through chemical bonding strategy reported here is potentially inspirable for other electrode materials with large volume change in use.

References

[1] W. Luo, F. Shen, C. Bommier, H. Zhu, X. Ji, L. Hu, Acc. Chem. Res.
2016, 49, 231.

[2] J. Song, Z. Yu, M. L. Gordin, S. Hu, R. Yi, D. Tang, T. Walter, M. Regula, D. Choi, X. Li, A. Manivannan, D. Wang, Nano Lett.
2014, 14, 6329.

[3] J. Song, Z. Yu, M. L. Gordin, X. Li, H. Peng, D. Wang, ACS Nano
2015.
Comparision and Characterization of Carbon-Coated LiMnxFe1-XPO4 (x= 0.4) Between Different Synthesis Routes
Authors: Penumaka Rani v , Lastres Miguel P , Bhattacharya Indranil
Published: February 2020

LiMnxFe1-xPO4 (x=0.4) (LMFP) solid solution system of olivine transition metal phosphates are considered to be very attractive cathode materials owing to their high redox couple and high theoretical capacity of 170mAh/g .With inherent low cost, stability at high temperatures, high energy density and non-toxic nature these materials are highly suitable for plug-in hybrid vehicles. Nevertheless, due to the low electrical conductivity and low Li ion diffusion kinetics makes these materials unsuitable for practical applications. In this research, carbon coated LMFP was synthesized by a modified solid state and a surfactant based sol-gel technique. The cathode materials obtained were characterized and performance was compared and evaluated. The materials obtained by both the processes showed similar morphologies and excellent cycle stability. The cathode materials prepared by sol-gel process delivered the best electrochemical performance when compared to solid state process.
Low Temperature Synthesis and Characterization of Carbon-Coated LiMnPO4 for Lithium-Ion Batteries
Authors: Penumaka Rani v , Lastres Miguel P , Bhattacharya Indranil
Published: February 2020

LiMnPO4 based phospho olivines are considered to be environmentally friendly, and low cost potential cathode material for the next generation of Li-ion secondary batteries to meet the huge market of electric and hybrid vehicles [1, 2]. The relatively higher operation voltage at around 4 V makes the theoretical specific energy of LiMnPO4 (684 Wh/kg) 20% greater than that of LiFePO4 (578 Wh/kg) while still compatible with most conventional electrolytes [3]. However, due to the low electrical conductivity and poor Li ion diffusion kinetics these materials are unsuitable for practical applications [4]. In here, carbon coated LiMnPO4 was synthesized by both solid state and modified sol-gel technique using a low temperature synthesis techniques. The cathode materials obtained were characterized and performance was compared and evaluated. Results of the electrochemical tests show that the prepared LiMnPO4/C (around 10 wt. % carbon) composites by both the routes exhibits not only a high initial discharge capacity but also good cycling stability. Although highly crystalline phase pure cathode materials could be obtained by both the processes, the materials prepared by sol-gel process delivered slightly better electrochemical performance when compared to solid state process.

References:

[1] C. Delacourt, P. Poizot, M. Morcrette, J. M. Tarascon and

C. Masquelier, Chem. Mater., 2004, 16, 93.

[2] J. Xiao, W. Xu, D. Choi and J.-G. Zhang, J. Electrochem. Soc.,

2010, 157, A142.

[3] Xiao, Jie, et al. Physical Chemistry Chemical Physics 13.40 (2011): 18099-18106.

[4] J. Yang, J.J, Journal of The Electrochemical Society 153 (4) (2006) A716–A723
A Novel Li-Metal Alloy Battery with Ultra-Long Cycles at High Rates
Authors: Niu Junjie
Published: February 2020

Carbon emission from non-renewable energy sources such as gasoline due to the drastically increasing energy demand becomes a critical issue in the world. This necessitates researchers to develop an environmental friendly energy storage that can meet the requirement for large devices particularly EVs. However, the current LIBs can’t provide sufficient energy density due to a limiting capacity of 372 mAh/g from graphite anode. Therefore, searching novel electrode materials for large energy storage that can deliver much higher capacity becomes very urgent. Sn has a 3 times greater capacity of ~1000 mAh/g that poses one of primary candidates for the next-generation LIBs. Sony released the first commercial amorphous Sn based battery called Nexelion that shows a 30% improved capacity than conventional graphite based battery in 2005. Scientists have made numerous attempts to stabilize the Sn alloy geometry by constructing nano-structures with carbon nanotubes, graphene, nanorods, nanocores, metal forms and metal alloy scaffold.

Here we present a novel Sn cage (Sn-NC) configuration comprising an industrially available, pure metal Sn and an oxide surface (not SnOx). Through the in-situ TEM study on 3D Sn matrix, we found a well-designed space can accommodate the morphology change during the charging/discharging process (Liu, Nano Lett 2016). The protection of the rigid oxide surface and the adjustable interspace can prevent the pulverization and oxidation of the metal while supplying a fast Li+/e- pathway. The coin/punch cells using Sn-NCs as anode provide a high capacity up to >600 mAh/g after ultra-long 5000 cycles at a high charge/discharge rate. The mass production of this anode material opens an avenue for industrial applications.
Mechanistic Insights into Oxygen Reduction and Evolution Reactions in Non-Aqueous Metal-Air Batteries
Authors: Zhang Yelong , Zhang Xinmin , Wang Jiawei , Ma Shunchao , Guo Limin , Rawal Saurin , McKee William C. , Xu Ye , Peng Zhangquan
Published: February 2020

Non-aqueous metal-air batteries have generated strong research interest because they possess much greater theoretical gravimetric energy storage density than today’s rechargeable battery technologies.1-4 This has re-kindled research into the fundamentals of oxygen reduction and evolution reactions (ORR and OER) in non-aqueous electrolytes because they are the central electrochemical processes at metal-air cathodes. Understanding the reaction mechanisms is critical to improving cycling efficiency and making rechargeable metal-air batteries a reality.

We will present the results of a series of electrochemical studies of the ORR/OER on a gold electrode in strictly dry, non-aqueous dimethyl sulfoxide (DMSO) electrolytes containing different cations, including H+, Li+, and Na+,5,6 using in situ spectroelectrochemistry and first-principles calculations and theoretical modeling. Significantly the ORRs share a common characteristic, namely the superoxide anion (O2
-), the one-electron reduction product of O2, is the first O2 reduction product to form. It has several important consequences: O2
- thus controls the onset potential of the ORR, and its solubility in the electrolyte makes solution-phase reactions involving O2
- an integral part of the electrode processes at low overpotentials, including the formation of superoxides and peroxides (via disproportionation of the superoxides) away from the cathode. On the other hand, there is a clear contrast between Li+ and Na+: Whereas the main reduction product is Li2O2 for Li+, which requires a high overpotential to be oxidized, the reduction product for Na+ is predominantly NaO2, whose high solubility in DMSO alleviates solid buildup on the electrode and also facilitates the oxidation of NaO2. Consequently the Na+ O2 cathode is much more reversible than its Li+ counterpart. The energetic factors controlling the formation of O2
-, solution vs. surface reaction pathways, and the lack of Na2O2 formation will be discussed. Overall, our studies reveal that the ORR/OER mechanisms depend intimately on the cation, potential, and electrolyte, and contribute new mechanistic understanding to the eventual realization of reversible metal-air battery technologies.

1. P.G. Bruce, S.A. Freunberger, L.J. Hardwick, J.-M. Tarascon, Nat. Mater. 2012, 11, 19.

2. J. Lu, L. Li, J.-B. Park, Y.-K. Sun, F. Wu, K. Amine, Chem. Rev.
2014, 114, 5611.

3. A.C. Luntz, B.D. McCloskey, Chem. Rev.
2014
, 114, 11721.

4. R. Black, B. Adams, L.F. Nazar, Adv. Energy Mater.
2012, 2, 801

5. Z. Peng, Y. Chen, P.G. Bruce, Y. Xu, Angew. Chem. Int. Ed.
2015, 54, 8165.

6. Y. Zhang, X. Zhang, J. Wang, W.C. McKee, Y. Xu, Z. Peng, J. Phys. Chem. C
2016, 120, 3690.
Three-Dimensional Lithium-Iodine Microbatteries for Implantable Devices
Authors: Citrin Michael A , Greer Julia R
Published: February 2020

Conventional batteries use thick electrodes that provide high energy density, but have large ion transport lengths that limit their current densities. Thin film batteries utilize thin layers of material and small transport lengths for higher power, but are limited in their total energy due to low mass loading. Three-dimensional batteries combine both high mass loading and small ion transport lengths due to their architected design, allowing for both high energy and power densities over a small footprint area. Accessing height in battery design permits much more active material than a planar thin film battery. Modern nanofabrication techniques, such as two-photon lithography, can fabricate 3D structures at the micro and nano scale that can be incorporated into a small-scale architected 3D cell. This type of battery could power the next generation of bio-implantable devices and miniaturized wearable sensors.

We demonstrate the fabrication of architected anodes using two-photon lithography to form a polymer scaffold. A gold layer on the nickel current collector alloys with lithium, creating an adhesion layer that assists lithium electrodeposition. The cathode used is iodine mixed with poly(2-vinylpyridine) (P2VP), which forms a lithium iodide solid electrolyte in situ when the anode and cathode come in contact and can be poured into the structure in its molten state. The geometry of the anode is determined by surface area and the pore size is determined to accommodate the thickness of the lithium iodide layer and infiltration of cathode. The increase in surface area and decrease in ion transport lengths from the 3D architecture provide improved performance of the primary battery over planar cells with the same footprint area. Other battery chemistries could be investigated with such a battery design to enhance performance.
Investigation of Oxidizing Graphene Halides for Li/S Batteries
Authors: Pardo Eduardo , Thai Edward , Dunham Nathanael , Alonso Josue , Garcia Jonathan , Dinh Andrew , Yu Ted H.
Published: February 2020

Lithium-sulfur batteries1 are a potential game-changer in rechargeable lithium battery technology. In addition to being very low cost due to the abundance of sulfur, it also has a higher theoretical specific capacity (1674 mAh/g-sulfur) than traditional lithium-ion batteries. In the last five years, incorporating graphene oxide2
,
3 (GO) has been an effective strategy to prolong the life of lithium-sulfur batteries, which improves overall performance and battery stability. However, current methods of GO synthesis, such as the Hummers method2, are not cost-effective. New research explores the use of graphene halides4to replace GO. The graphene halides used in this study can be produced through a simple ball-mill process which is easily scalable. Our studies show that out of the halides, graphene-iodide (GI) has performed remarkably well in cycle performance with its ability to retain capacity after subsequent charge/discharge cycles when compared to graphene bromide and graphene chloride.

We attempted to increase the cycle life and performance of our cathodes by using a technique to reintroduce oxygen functional groups on the GI basal planes. Through NO2 adsorption followed by UV treatment, we have been able to create carbon-oxygen functional groups to synthesize epoxidic, hydroxyl, and carbonyl carbon-oxygen bonds on graphene halides. This alternative method to oxidation uses fewer resources than the traditional Hummers method, which will reduce cost and environmental impact. The oxidized GI outperformed the non-oxidized GI based cathodes in its ability to maintain discharge capacity over time as seen in Figure 1.

Figure 1
Comparative Studies of Ti Doped LiNi0.7Co0.3O2 and LiNi0.7Co0.3O2 Nano Cathode Material for High Energy Density Li-Ion Battery
Authors: Rusdi Roshidah , Kamarulzaman Norlida , Rusdi Hashlina
Published: February 2020

Ti doped LiNi0.7Co0.3O2 materials were investigated for their electrochemical characteristics. LiNi0.7Co0.3O2 and LiNi0.6Co0.3Ti0.1O2 materials were prepared using a self-propagating combustion method. The structure and morphology of the materials were characterized using X-Ray Diiffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM) and Energy Dispersive X-Ray Spectroscopy (EDX). The oxidation state of elements and their chemical environments were studied using X-Ray Photoelectron Spectroscopy (XPS). XRD results showed that the materials were all single phase with hexagonal layered structure of R-3m space group. The discharge capacities are between 135.5 and 151.1 mAhg-1. The LiNi0.7Co0.3O2 compound exhibits the highest first cycle capacity of 151.1 mAhg-1 over the voltage range of 2.5 to 4.2 V compared to the Ti doped sample LiNi0.6Co0.3Ti0.1O2, showing a capacity of 146 mAhg-1. However, at the 30th cycle, the Ti doped material shows the highest specific discharge capacity of 137.8 mAhg-1. The capacity fading is only about 5.6 % compared to 38.2% for undoped LiNi0.7Co0.3O2. Therefore, eventhough the undoped LiNi0.7Co0.3O2 material has a higher first cycle capacity, the doped compounds exhibits much better capacity retention over 30 cycles
Novel Lithium Manganese Silicate with Stable Structure upon Cycling As Positive Electrode for Lithium-Ion Batteries
Authors: Lefèvre Guillaume , Ducros Jean-Baptiste , Boulineau Adrien , Benayad Anass , Martinet Sebastien
Published: February 2020

Lithium manganese silicate Li2MnSiO4 is theoretically one of the most interesting polyanionic material for lithium-ion batteries positive electrode. Its theoretical capacity reaches 333mAh/g thanks to the possible exchange of two lithium ions per formula unit which happens below the organic electrolyte degradation voltage. Indeed, the first lithium ion is calculated to be exchanged at 4.1V vs Li+/Li and the second one at 4.4V [1]. The high energy density combined with the thermal stability of the Si-O bond make Li2MnSiO4 in theory one of the best choice to equip the next generation of electrified transportation [2].

1st studied in 2006 by Dominko et al. [3], lithium manganese silicate still shows severe limitations. Both its ionic and electronic conductivities are low [4] and Li2MnSiO4 structure cannot accommodate large Li+ extraction without amorphization. Thus, it leads to high polarization and capacity fading during cycling, impeding its practical interest. Despite this trend, manganese-based silicate polyanions are essentially interesting because of their high abundance, low cost and environmental friendliness.

Here we propose an unreported manganese silicate material that we recently patented. This new material, usable as a positive electrode for lithium ion batteries, showed remarkable cycling stability. 100 mAh/g were obtained in half-cells versus lithium metal counter-electrode (Figure 1). Ex-situ X-Ray Diffraction showed that the structure was maintained during cycling, demonstrating that the material can accommodate reversible extraction of Li+ ions. To limit particle growth careful attention was paid on the synthesis route. Primary particles of 50 nanometers were obtained by a sol-gel process (Figure 2). Rate capabilities of the material, studied by galvanostatic cycling, will also be presented. Deeper characterization by X-Ray Photoelectron Spectroscopy (XPS), Transmission Electron Microscopy-Selected Area Electron Diffraction (TEM-SAED) and Differential Scanning Calorimetry (DSC) will be shown to assess the redox process, structure and thermal stability of this material.

[1] Arroyo-de Dompablo et al., Electrochem. Commun., 2006, 8, 1292–1298

[2] Andre et al., J. Mater. Chem. A, 2015, 3, 6709–6732

[3] Dominko et al., Electrochem. Commun., 2006, 8, 217–222

[4] Dominko et al., J. Power Sources, 2008, 184, 462–468

Figure 1
Optimizing the Electrolyte for Glucose-Derived Carbon Based Na-Ion Battery
Authors: Väli Ronald , Thomberg Thomas , Jänes Alar , Lust Enn
Published: February 2020

Sodium-ion batteries have attracted great deal of attention due to sodium’s abundance and lower price compared to lithium and cobalt. A major obstacle that prevents sodium-ion batteries going to a mass-scale is the negative electrode (anode during discharge). Graphite is currently the safest negative electrode material for lithium-ion batteries, but does not intercalate sodium reversibly, because sodium ions prefer prismatic or octahedral coordination sites [1].

Our previous work [2] focused on the synthesis and electrochemical characterization of glucose-derived hard carbon negative electrodes for sodium-ion batteries. Unfortunately, the tested electrochemical half-cell showed high capacity fade during cycling. At the time, we thought it was due to material’s spherical morphology (Fig. 1a). But when we substituted the previously used electrolyte (1M NaClO4 in PC) with 1M NaPF6 in PC:EC (9:1) capacity fade was significantly reduced. The discharge capacity for the 100th discharge cycle was only 177 mAh g-1 when using NaClO4 in PC, but remained at 267 mAh g-1 when using NaPF6 in PC:EC (9:1) (Fig. 1d - e).

The results of full cell testing with NVP-type cathode [3] will also be discussed.

Acknowledgements

This research was supported by the EU through the European Regional Development Fund TK141 “Advanced materials and high-technology devices for energy recuperation systems”, Estonian target research project IUT20–13 and personal research grant PUT55. Mr. Väli thanks Estonian Students Fund in USA and University of Tartu Foundation for financial support.

References

1. J. Qian, X. Wu, Y. Cao, X. Ai, and H. Yang, Angew. Chem. Int. Ed., 52, 4633 (2013).

2. R. Väli, A. Jänes, T. Thomberg, and E. Lust, J. Electrochem. Soc., 163, A1619 (2016).

3. R. Väli, P. Möller, and A. Jänes, ECS Trans., 69, 27 (2015).

Figure 1
Application of Ordered Intermetallic Nanoparticles to Polymer Electrolyte Fuel Cells
Authors: Liu Yubin , Gunji Takao , Tsuda Takashi , Tanabe Toyokazu , Kaneko Shingo , Ohsaka Takeo , Matsumoto Futoshi
Published: February 2020

Our recent investigations of electrocatalysts for low temperature fuel cells have shown that ordered intermetallic compounds such as PtBi and PtPb have lower oxidation onset potentials and higher current densities for formic acid oxidation than pure Pt and Pd electrodes1
,2). In this presentation, carbon black (CB)-supported Pt3Pb NPs was synthesized as catalysts for the formic acid oxidation and oxygen-reduction reaction. Atomically disordered and ordered intermetallic Pt3Pb NPs were prepared at room temperature using the polyol method. The Pt/carbon black (CB) and Pb(CH3COO)2•3H2O were dissolved in ethylene glycol. The mixture was sonicated and then treated in the flask under reflux for 1 min with 300-W microwave radiation. The mixture in the flask was cooled to room temperature with water. The mixture was again treated with microwave radiation (focused microwave instrument, CEM) at 300 W for 9 min. After the mixture cooled, Pt3Pb NPs/CB was collected by centrifugation, washed sequentially with methanol and dried under vacuum. The formation of ordered intermetallic Pt3Pb after annealing was confirmed by X-ray photoemission spectroscopy, powder X-ray diffraction, and a scanning transmission electron microscope with an electron-probe microanalyser (STEM). The surface structure of atomically disordered and ordered intermetallic Pt3Pb NPs was analyzed with high-resolution STEM. The relationship between the electrocatalytic activity and the surface structure was examined.

(1) Fuma Ando, Takao Gunji, Hikaru Fujima, Tsuyoshi Takeda, Toyokazu Tanabe, Shingo Kaneko, Futoshi Matsumoto, Preparation of PtPb/TiO2/Cup-Stacked Carbon Nanotube Composite for Enhancement of Electrocatalytic Reaction of Oxygen Reduction Reaction, Chem Lett., 44(12), 1741-1743(2015).

(2) Takao Gunji, Toyokazu Tanabe, Arockiam John Jeevagan, Sho Usui, Takashi Tsuda, Shingo Kaneko, Govindachetty Saravanan, Hideki Abe, Futoshi Matsumoto, Facile Route for the Preparation of Ordered Intermetallic Pt3Pb-PtPb Core-Shell Nanoparticles and Its Enhanced Activity for Alkaline Methanol and Ethanol Oxidation, J. Power Sources, 273, 990-998(2014).
(Invited) Freestanding Nanoscale SWCNT Films: Durability, Transport and Applications
Authors: Hobbie Erik K.
Published: February 2020

Single-wall carbon nanotube (SWCNT) films are ideal components for thin, flexible coatings in solar cells and electronic devices. In this context, we will examine the precise role of the nanotube in SWCNT-silicon heterojunctions, with a particular focus on the impact of purity, doping and alignment. Through an analysis of the light and dark transport characteristics of the junctions as a function of bias and temperature, we extract a coarse picture of the width and location of the depletion layer. We also consider specific examples where SWCNT type or chirality plays a critical role in the response. Finally, we will consider some examples of true nanoscale heterojunctions made entirely from colloidal nanomaterials.
(Invited) Polymer Wrapped Carbon Nanotubes As Highly Effective Hole Transporting Layers for New Perovskite and Quantum Dot Photovoltaic Devices
Authors: Nicholas Robin J , Habisreutinger Severin N , Noel Nakita K , Snaith Henry J , Watt Andrew , Tazawa Yujiro , Zhang Nanlin
Published: February 2020

Our recent work (1) has shown that polymer wrapped carbon nanotubes can be used to transform the properties of the hole transporting layer in a number of different perovskite based solar cell configurations. This presentation will report on two examples where the CNT hole transporter produces enhanced device performance, firstly for tin oxide/perovskite alloy/CNT devices and secondly in PbS colloidal quantum dots (CQD) where improved charge extraction by the CNT is particularly important.

Halide perovskite solar cells remain to generate a lot of interest and enthusiasm among researchers, largely due to the prospect of readily transitioning from a purely lab based technology to real-world scales. This expectation is largely based on the rapid increase in efficiency over the past few years to values above 22%. An essential component of this device architecture are the two charge selective contacts. The n-type contact in the majority of all devices is TiO2, either as a thin compact layer, or a mesostructured configuration, but recently, SnO2 has moved into the spotlight as n-type contact with recent studies reporting excellent steady-state performances.

The p-type contact on the other side of the absorber has been investigated even more intensively. The best-performing devices still use the “original” hole-transport material, spiro-OMeTAD, which provided the crucial breakthrough for the perovskite solar cell in 2012, but which suffers from the fact that it is not sufficiently conductive for efficient charge-transport, and requires extrinsic doping, typically with Li-TFSI, which has been shown to detrimentally impact the device stability. This presentation will demonstrate that for FA0.83MA0.117Pb(I0.87Br0.17)3 based solar cells we can achieve steady-state efficiencies of up to 18.8%, by using polymer-wrapped single-walled carbon nanotubes (SWNTs) as an inert conductive element in undoped spiro-OMeTAD, exceeding the performance of their fully doped counterparts.

In a completely different example we can use the same polymer wrapped SWNTs as a hole collection electrode for PbS based CQD photodetectors which are capable of operating over a spectral range extending beyond one micron. We find that the use of a polymer wrapped CQD combined with PMMA filler more than doubles the current collection in such devices and enables efficiencies of over 7%. In addition the SWNT layer produces a substantial improvement in long term device stability in normal ambient conditions.

(1) Habisreutinger, S. N.; Leijtens, T.; Eperon, G. E.; Stranks, S. D.; Nicholas, R. J.; Snaith, H. J. Nano Lett.
2014, 14, 5561–5568.
(Invited) Less Is More: Thermoelectric Performance Enhancements in Polymer-Free Semiconducting Single-Walled Carbon Nanotube Networks
Authors: Ferguson Andrew John , Norton-Baker Brenna , Ihly Rachelle , Gould Isaac E. , Stanton Noah J. , MacLeod Bradley A. , Avery Azure D. , Owczarczyk Zbyslaw R. , Blackburn Jeffrey L.
Published: February 2020

There is a growing interest in the use of carbon nanostructures for a variety of electronic and optoelectronic technologies, including energy harvesting applications such as photovoltaics (PV) and thermoelectrics (TE). We will present a series of studies aimed at improving the TE performance of semiconducting single-walled carbon nanotube (s-SWCNT) thin film networks.

The optical and electrical performance of SWCNT ensembles is often limited by the presence of metallic single-walled carbon nanotube (m-SWCNT). We will demonstrate a polymer-based purification strategy that effectively eliminates these, and other impurities, from the raw material, leaving s-SWCNTs in extremely high purity. Modification of this extraction process produces s-SWCNT thin film networks where the polymer can be completely removed, resulting in close tube-tube contacts in a dense s-SWCNT network. Removal of the polymer in the solid state, rather than in solution, also minimizes nanotube bundling during network formation. By controlling the bundle size and extent of polymer remaining in the s-SWCNT network we demonstrate TE power factors that almost double the performance of s-SWCNT networks previously demonstrated. We trace the improved performance to an enhanced electrical conductivity, resulting from improved doping and strongly enhanced charge carrier mobility, and analyze our data within the framework of a recently developed thermoelectric transport model. Finally, we demonstrate that the removal of the polymer from the s-SWCNT network has negligible impact on the thermal conductivity, which appears to be limited by dopant-induced phonon scattering processes.

These observations demonstrate the ability to exert exquisite control of the thermoelectric performance by controlling the composition of the s-SWCNT network and tuning the carrier density (i.e., Fermi energy), and touts SWCNTs as an avenue for realizing thermally stable room temperature thermoelectric devices fashioned from inexpensive and abundant organic constituents.
Thermally Chargeable All-Solid-State Flexible Supercapacitor for Waste Heat Harvesting and Storage
Authors: Kundu Arpan , Fisher Timothy
Published: February 2020

Low-grade thermal energy is an abundantly available, sustainable and clean energy source. Its source includes waste heat from power plants, ocean thermal energy, geo-thermal energy, distributed solar energy among others. Conventional solid-state thermoelectric devices are limited in application due to their high cost, intrinsically low Seebeck coefficient (10-100 μV/K) and inflexible nature. Thermogalvanic systems, also known as thermocells have recently been found to be a promising alternative. These devices using the temperature dependence of electrochemical potential of redox electrolytes such as aqueous ferri/ferrocyanide possess the advantages of simple design, direct thermal-to-electric energy conversion, continuous operation, low mainte­nance, zero carbon emissions and low cost. However, these devices need to be connected to energy storage devices (battery or capacitor) by a power management circuit in order to store energy. This leads to complexity in system design and operation. Here, we demonstrate an integrated thermal energy harvesting supercapacitor device that can convert a temperature gradient applied over a short period of time, into stored charge. The stored electrical energy can be used to power an external load long after the temperature gradient is disengaged. Furthermore, it is flexible, thin, lightweight and all-solid-state which makes it ideal for powering portable and wearable devices. Electrodes consisting of graphene petals (GP) grown on conductive carbon cloth by microwave plasma chemical vapor deposition (MPCVD) are sandwiched onto a polyvinyl alcohol (PVA)/potassium ferrocyanide/ferricyanide gel electrolyte film to build a supercapacitor device. The device exhibits a Seebeck coefficient of -1.21 mV/K, a high areal capacitance near 9 F cm-2 at a current density of 0.1 mA cm-2 and excellent charge retention capability.
Fullerene Nanostructures As High-Performance Supercapacitors and Beyond
Authors: Zheng Shushu , Lu Xing
Published: February 2020

During the past two decades, the self-assembly of organic crystals have been a hot topic widely studied by material chemists.[1] Among the potential candidate molecules, the spherical fullerene molecules are particularly attracting for their definite structures, high electronic affinity and three-dimensional (3D) electron transporting property.[2-4] In this presentation, we first systematically investigate the self-assembly behavior of various C60 polyhedron microstructures and also their extraordinarily enhanced luminescence properties. Moreover, C60 well-aligned arrays are readily prepared by a simple dip-coating process, which present excellent UV-photoresponse performances. Furthermore, a solution-processible co-assembly strategy taking advantage of charge-transfer interaction is developed to prepare needle-like fullerene (C70)/cobalt porphyrin supramolecular architectures, which possess excellent electrical conductivity and high thermal resistance. More interestingly, three-dimensional porous carbon structures with abundant functionalities are readily obtained by KOH activation of fullerene (C70) microtubes, exhibiting excellent supercapacitor performances which are much better than that of the original microtubes.[5]

References

[1] O. Ostroverkhova, 
Chem. Rev. 2016, 116, 13279.

[2] D. M. Guldi, Chem. Soc. Rev.
2002, 31, 22.

[3] S. Babu, H. Möhwald, T. Nakanishi, Chem. Soc. Rev. 2010, 39, 4021.

[4] C. Park, J. Park, H. Choi, Acc. Chem. Res. 2014, 47, 2353.

[5] S. Zheng, H. Ju, X. Lu, Adv. Energy Mater. 2015, 1500871.
The Modification of the Pore Characteristics of Activated Carbon, for Use in Electrical Double Layer Capacitors, through Plasma Processing
Authors: Muriel Marcelis L. , Narayanan Rajaram , Bandaru Prabhakar R
Published: February 2020

An important issue related to energy harness concerns obtaining high capacitance and related energy density in electrochemical capacitors (ECs), which have been mostly noted for high power density. In this paper, we address the possibility of obtaining enhanced capacitance in activated carbon based electrodes in ECs through the plasma processing, which has been hypothesized to introduce additional charge states in the electrode.

It was determined, based on extensive electrochemical experimentation and correlation of all the standard testing procedures (including constant current charge/discharge, cyclic voltammetry, and electrochemical impedance spectroscopy) that there is an optimal plasma processing at which both an increased capacitance as well as reduced resistance were observed, promising an enhancement in both energy and power density. For instance, while an increase of up to 35% of the gravimetric capacitance, along with ~ 20% decrease in resistance, was obtained through optimal plasma processing, increased plasma exposure yielded a drastic reduction (/increase) in the capacitance (/resistance).

It was also found that the capacitance and resistance modulation was a sensitive function of sample processing as well as electrochemical testing procedure. Considering the complexity of modeling realistic porous matrices, a metric to parameterize the reach of an electrolyte into the matrix has been posited.

Considering the difficulty of representing actual porous matrices, and as an alternative to relatively simplified lumped parameter models, we propose, for the first time in this paper, a new parameter indicating the reach of the electrolyte into the porous electrode, and which considers the extent to which a given testing procedure may be considered complete.  We expect that our method of analysis and experimental demonstrations will have a major impact, through providing insight into understanding how the energy and power capacity of electrochemical capacitors may be enhanced.
Electrochemical Lithiation-Delithiation of Sulfur in Single-Walled Carbon Nanotubes
Authors: Fu Chengyin , Li Guanghui , Haddon Robert C , Guo Juchen
Published: February 2020

Lithium-sulfur (Li-S) batteries are one of the most promising energy storage technologies because of the high theoretical capacity of sulfur as cathode. However, the high electrical resistivity of sulfur and the dissolution of lithium polysulfides into electrolytes are greatly limiting the performance of Li-S batteries. Interestingly, when the sulfur confinement size is smaller than 1 nm, different electrochemical behaviors and excellent cycle stabilities have been observed. However, the mechanism of sub-nano confinement of sulfur has not been investigated in details. Single-walled carbon nanotubes (SWCNTs) with their various pore size, uniform pore size distribution, and excellent electron conductivity are ideal hosts for studying the effect of different sulfur confinement sizes. In this study, we investigate the effect of sulfur confinement size by incorporating sulfur into both EA- (electric arc) and HiPco- (high-pressure carbon monoxide) SWCNTs with diameter of 1.55 ± 0.1 and 1.0 ± 0.2 nm, respectively. Interestingly, when sulfur is incorporated into HiPco-SWCNTs, the polymerized long chain sulfur molecules inside the tubes largely changes the Raman spectra. The giant Raman response from the sulfur provides an ideal opportunity to perform in situ studies on the lithiation-delithiation reactions of the confined sulfur. High-resolution TEM images confirm the chain structure of sulfur in EA- and HiPco-SWCNTs. Cyclic voltammetry and galvanostatic charge–discharge are performed by using different electrolytes, and sulfur in EA- and HiPco-SWCNTs show distinctively different electrochemical behaviors. In situ Raman spectra and ex situ XPS are measured during galvanostatic charge–discharge to investigate the lithiation-delithiation mechanism. A solid-state reaction mechanism was proposed when sulfur is in sub-nano confinement.
Carbon Nanotube-Based Non-Noble Metal Catalyst for Oxidation Reduction Reaction
Authors: Nakashima Naotoshi , Yang Jun
Published: February 2020

Development of non-platinum electrocatalyst for fuel cells and batteries with high performance, durablity, and scalability is a strong social demand for next-generation eco-friendly energy society. We here report a pristine multi-wall carbon nanotube/iron phthalocyanine (MWNT/FePc) hybrid catalyst with a well-defined nanostructure for oxygen reduction reaction (ORR) in alkaline media that meets this demand. By carefully tuning the thickness of the FePc stack layer deposited on the highly crystallized graphitic surface of the MWNT support, an ultra-high ORR activity and excellent durability were obtained. Moreover, a power density of 185 mW cm-2 at 0.8 V was obtained for a zinc-air battery using the MWNT/FePc cathode[1].

Reference

[1] J. Yang, F. Toshimitsu, T. Fujigaya, N. Nakashima, J. Mater. Chem. A, in press.
(Invited) Diameter-Dependent Thermal Defunctionalization of Single-Walled Carbon Nanotubes
Authors: Ghosh Saunab , Wei Fang , Bachilo Sergei M. , Hauge Robert , Billups W. E. , Barron Andrew R , Weisman R. Bruce
Published: February 2020

Covalent sidewall functionalization of single-walled carbon nanotubes (SWCNTs) is an important tool for tailoring their properties for research purposes and applications. In this study, SWCNT samples were first functionalized by reductive alkylation using metallic lithium and 1-iodododecane in liquid ammonia. Samples of the alkyl-functionalized SWCNTs were then pyrolyzed under an inert atmosphere at selected temperatures between 100 and 500 °C to remove the addends. The extent of defunctionalization was assessed using a combination of thermogravimetric analysis, Raman measurements of the RBM, D, and G bands, absorption spectroscopy of the first- and second-order van Hove peaks, and near-IR fluorescence spectroscopy of (n,m)-specific emission bands. These measurements all indicate a substantial dependence of defunctionalization rate on nanotube diameter, with larger diameter nanotubes showing more facile loss of addends. The effective activation energy for defunctionalization is estimated to be a factor of ~1.44 greater for 0.76 nm diameter nanotubes as compared to those with 1.24 nm diameter. The experimental findings also reveal the quantitative variation with functionalization density of the Raman D/G intensity ratio and the relative near-IR fluorescence intensity. Pyrolyzed samples show spectroscopic properties that are equivalent to those of SWCNTs prior to functionalization. The strong structure-dependence of defunctionalization rate suggests a new approach for diameter-sorting of mixed SWCNT samples on relatively large scales without ultrasonic agitation. In addition, properties of a new reactor designed for large-scale functionalization of SWCNTS will be presented.

Figure 1
(Invited) Excited-State Dynamical Studies of Positively and Negatively Charged Excitons in Polymer-Wrapped Single-Walled Carbon Nanotube Superstructures
Authors: Bai Yusong , Olivier Jean-Hubert , Bullard George , Therien Michael J.
Published: February 2020

Conjugated, highly charged aryleneethynylene polymers exfoliate, individualize, and disperse single-walled carbon nanotubes (SWNTs) via a single-chain helical wrapping mechanism. These semiconducting polymer-SWNT superstructures are robust in a wide range of aqueous and organic solvents, maintaining a fixed polymer helical pitch length on the SWNT surface; importantly, this single chain polymer wrapping of the SWNT surface solubilizes the nanotube at a minimal polymer:SWNT molar ratio, and provides a facile means to organize functional organic moieties at predefined intervals along the SWNT surface. We have investigated the transient absorptive and dynamical properties of positively and negatively charged excitons (i.e., hole- and electron-trions) in these semiconducting polymer-wrapped SWNT superstructures. This work exploits redox titration experiments that fix SWNT electron or hole polaron concentrations, and ultrafast pump-probe transient spectroscopic measurements that determine trion transient absorptive signatures and dynamics as functions of absolute electron- or hole-doping levels. Global analysis of these data over the entire vis-NIR spectral domain, where these systems display characteristic transient absorptive spectral signatures, provide fundamental new understanding of trion formation and decay mechanisms in semiconducting SWNTs essential for developing electro-optic and photonic materials.

Figure. (A) Structural schematic of a chiral aryleneethynylene polymer-wrapped SWNT. (B) Molecular structure of the binaphthalene-based conjugated, polyanionic semiconducting polymer,
S-PBN(b)-Ph5
. (C) Schematic illustration highlighting semiconducting SWNT hole polaron, exciton, positively charged exciton (hole-trion) states.

Figure 1
Field Deployment of Printed Carbon Nanotube Gas Sensor Arrays for Natural Gas Leak Detection
Authors: Smith Clinton J. , Kim Beomseok , Iftime Gabriel , Wei Austin , Cocker Eric , Zhang Yong , Meyyappan M. , Schwartz David Eric
Published: February 2020

PARC and NASA Ames have developed part-per-million level sensitivity room-temperature printed gas sensors based on arrays of modified single-walled carbon nanotubes (SWNTs). The SWNT sensors change resistance in response to reversible electro-chemical interactions between target analytes and the modifications on the SWNTs. The ultra-low power (microwatt level) ability to measure trace-gas concentrations through changes in SWNT resistance has enabled us to build an autonomous, off-the-grid, distributed gas sensing network to be deployed to the ARPA-E natural gas leak testing facility in Ft. Collins, CO during the spring of 2017. During this deployment, the leak detection network will be subjected to tests of its accuracy and precision in locating the sources of leaks on a mock natural gas well-pad. The key enablers of this technology are the SWNTs which we have modified with coatings, chemical functionalization, and nanoparticles, to achieve sensitivity to a wide selection of gases including CH4, NH3, CO, H2S, etc., in the presence of real-world environmental conditions. We will report on the results of this field deployment, along with a discussion of the SWNT modifications made to create the sensor arrays.