bluuebunny/crossref_metadata_2025 huggingface dataset:
Characteristics of Ionic Liquid/Li-Ion Conducting Hybrid Electrolytes for Graphene-Based Lithium-Ion Capacitors
Authors: Liu Mengxin , Yao Zhuo , Huang Hong
Published: February 2020

Lithium-ion capacitor (LICs), a novel electrochemical energy storage class combined the advantages of lithium-ion batteries and supercapacitor, are attractive for high energy densities, high power densities, and long cycle life. A typical LIC is made up of a Li-ion battery (LIB) anode, an electrochemical double-layer capacitor (EDLC) cathode, and the common Li-ion electrolyte. Graphene-based nanomaterials have been extensively studied as the electrodes for Li-ion or charge storage in LIBs and EDLCs, respectively. Recently, we have developed reduced graphene oxide (rGO) in composite with MnOx with reversible lithium storage capacity of 900 mA/h. Meanwhile, we have obtained charge storage capacitance up to 150F/g using rGO electrode with an ionic liquid (IL) electrolyte. In this work, we will report our studies on the conducting characteristics of the IL/Li-ion hybrid electrolyte and their compositional impacts on both Li-ion and charge storage in the graphene-based nanocomposites towards high-performance LICs operable in a broad temperature range.

The novel electrolyte series are a mixture of representative IL, e.g. EmimBF4, C8minBF4, C8mimPF6, and the common Li-ion electrolyte, e.g. 1M LiPF6-EC-DEC or 1M LiBF4-EC-DEC, with various preset volume ratios. The ionic conductivities of the hybrid electrolyte series were determined at temperatures from 25oC to 80oC, from which conduction activation energies were calculated. Further, the influences of the hybrid electrolyte composition on the ionic conductivity, activation energy, stability window, Li-ion and charge storage in the graphene-based nanocomposites were systematically studied.       

Results showed that ionic conductivities of the hybrid electrolytes increased in general with the addition of Li-ion electrolyte and the activation energies of the ionic conductance increased with the addition of IL. It is interesting to observe a secondary maxima point at around 1:1 volume ratio (IL: Li-ion electrolyte) and higher ionic conductivities of such hybrid electrolyte than that of the neat Li-ion electrolyte above 65oC. The hybrid electrolyte remains relatively stable up to 6V starting from the second cycle after the occurrence of the irreversible reactions corresponding to IL partial decomposition and SEI formation in the first charge/discharge cycle. The novel LIC consisting of the hybrid Li-conducting/IL electrolyte, rGO-MnOx anode, rGO cathode, is anticipated to have a high deliverable energy densities both gravimetrically and volumetricallyand operable in a broad temperature range.
Garnet-Based Electrolytes for All-Solid-State Lithium Batteries
Authors: Li Yiqiu , Zhao Ning , Du Fuming , Chen Cheng , Sun Jiyang , Guo Xiangxin
Published: February 2020

The lithium garnet has been considered as one of promising solid electrolytes for all solid state rechargeable lithium batteries. Under such circumstance, the Li7La3Zr2O12 (LLZO)-based powders and ceramics have been extensively studied in our lab. By elemental doping, liquid-phase sintering, atmosphere sintering, hot-pressing sintering technique and their combination, high-dense LLZO-based ceramics were obtained, showing the relative density above 99% and the ionic conductivity above 10-
3 S/cm at room temperature.

Based on these powders and dense ceramics, the solid electrolytes in form of hybrid membrane and thin plate were fabricated and used for the all solid state Li-ion and Li-air batteries. The batteries with LiFePO4 or Li(NMC)O2–based cathodes, the LLZO-based electrolytes and Li anodes exhibit good capacity and cycle performance. The Li-air batteries with the porous carbon-based air cathodes, the thin-plate electrolytes and Li anodes work for many cycles under ambient air, especially at elevated temperatures. In the presentation, the scientific and technical details for these batteries will be given. The fundamental issues and promising potential for application will be discussed.
High-Performance Anodes for Lithium-Ion Batteries Based on Nano-Porous Amorphous Silica
Authors: Vullum-Bruer Fride , Hasanuzzaman Muhammad
Published: February 2020

The high theoretical capacity and low discharge potential of silica (SiO2) draw major interest these days as a serious competitor to Si-based anodes. The drastic volume expansion of Si during cycling leads to capacity fading and pulverization and thus requires advanced treatment to make it a viable electrode in Li-ion batteries1-4. Abundantly available diatomaceous earth was explored as an anode which can substitute the existing graphite based anode, providing better electrochemical performance in terms of capacity, cyclability and stability.

As silica is an insulator, it is necessary to provide a conductive coating on the particles. Various amounts of corn-starch was added, followed by heat treatment in Ar atmosphere, to form a thin continuous conductive layer of carbon on the particles. Also, conventional binders are not compatible with Si or silica-based materials, hence other types of binders and binder additive must explored. Here we have used a naturally grown algae-based aqueous binder to prepare the electrodes, which is compatible with the diatomaceous earth and gives it increased stability during lithiation and de-lithiation. Specific discharge capacities of these materials have shown values of 600-800 mAhg-1, which is more than twice the value of the existing graphite based anodes.

Upon extended cycling the reversible capacity, for uncoated as well as coated silica, starts to increase from approximately the forth cycle due to chemical reactions causing a Si phase to form. The porous morphology and natural nano-structure of the diatomaceous earth anode can accommodate the volume expansion and preserve the solid electrolyte interface. The high reversible capacity, good cycle performance and simple processing of these electrodes make the diatomaceous earth a potential environmentally friendly anode material for lithium-ion batteries.

1. Favors, Z., et al. (2014). Sci. Rep. 4.

2. Yan, N., et al. (2013). Sci. Rep. 3.

3. Liu, X., et al. (2014). Nano Energy 4.

4. Epur, R., et al. (2012). Materials Science and Engineering: B 177(14).
Nickel Hexacyanoferrate-Modified LiFePO4 Cathodes with High-Rate and High-Pulse Current Charge-Discharge Capabilities
Authors: Chiu Kuo-Feng , Leu Hoang-Jyh , Su Shih-Hsuan , Chao Kuan-Yu
Published: February 2020

Nickel hexacyanoferrate (Prussian blue analogous, PBA) was synthesized by Reverse Micelle Method and was coated on LiFePO4 cathodes to improve the performances of high rate and pulse current charge-discharge. PBA consists of a structure of low strain open framework, and exhibits a redox potential (3.4 V v.s. Li/Li+) similar to LiFePO4. The PBA modified LiFePO4 cathodes show improved high-rate capability, with a 10 C discharge capacities of 15 % higher than pristine LiFePO4. It was found that the PBA modified LiFePO4 can endure high pulse current charge-discharge, which is well suited for green energy grids. The modified and pristine LiFePO4 cathodes were operated with alternate pulse currents of 0.01 C and 5 C introduced into a 0.2 C discharge/charge process to simulate the conditions of green grids. The modified LiFePO4 cathodes exhibited capacity retention of 92% under such conditions after 50 cycles, whereas the pristine sample showed capacity retention of  only 75%. The results can be attributed to the reduction of electrode/electrolyte interface resistances due to the PBA coatings, as characterized by electrochemical impedance spectroscopy.
Flexible High Energy Density Silicon Composite Anode for Structural Batteries
Authors: Nazri Gholam-Abbas , Nazri Maryam
Published: February 2020

The challenges of using high capacity metallic lithium foil as an anode for high energy density lithium battery are still remaining despite many years of research efforts, due to the intrinsic problems associated with the electrodeposition of reactive light metals such as lithium. In addition, the required excess lithium (3-5 times) to satisfy the battery long cycle life,  and the safety concern associated with the large format cells containing metallic lithium anode have force the battery community to search for other alternatives. Some of the alternative anodes may exceed the energy density of metallic lithium when the excess lithium is considered. We will present a new class of composite anode material for structural and conformal lithium batteries. Our new composite anode is based on an optimized free-standing silicon coated carbon nanofiber in the form of flexible thin-paper with capacity exceeding 1500Ah/kg for the electrode including the carbon fiber and the silicon, and with high capacity retention during extensive charge-discharge cycles. The electrode/electrolyte interface and the silicon/carbon interface have been engineered to minimize the initial irreversibility during lithiation and delithiation, to less than 10%.  In addition, the in-plan conductivity of the free standing composite anode has been optimized for high power battery application. We will report the performances of the silicon-carbon nanofiber composite anode in half cells and in full cells against high energy density lithium-rich layered oxide, and olivine based cathodes.
Impact of Nickel and Manganese Content on the Electrochemical Properties of Li1.13Mn0.54-X
Ni0.27+X
Co0.06O2 As Lithium Ion Battery Cathodes
Authors: Gao Min , Wang Zhenyao , Wang Zhong , Yin Yanping , Shao Zechao , Zhuang Weidong , Lu Shigang
Published: February 2020

Introduction

In recent years, Li-rich, Mn-based Li[Li1-x-y
Me
x
Mn
y
]O2 (Me=Co, Fe, Cr, Ni, etc.) cathode materials have received world-wide attention for their high capacity (>250 mAhg-1) when operating at high voltage [1]. However, the cathode materials still suffer from poor rate capability and gradual capacity degradation during cycling, accompanied with hysteresis and voltage fade [2]. In order to overcome those issues, extensive studies have been performed to improve the electrochemical performance of Li[Li1-x-yMexMny]O2 cathode materials. Among all the factors investigated, it was found that Mn/Ni content of Li[Li1-x-yMexMny]O2 could be an important factor that limits the rate capability and influences the capacity/voltage fade [3]. As such, in this paper, we study the effects of Mn/Ni content of Li1.13Mn0.54-x
Ni0.27+x
Co0.06O2on structure, morphology, rate capability, capacity degradation and voltage fade during cycling.

Fig.1. The cycle performance of Li1.13Mn0.54-x
Ni0.27+x
Co0.06O2in the voltage range of 2.5-4.6 V at 1.0 C after three formation cycles in the voltage of 2.0-4.8 V at 0.1 C, (a) discharge capacity and (b) median voltage of discharge

 

Results and Discussion

Fig. 1 shows the capacity cycling performance (Fig. 1 (a)) and median voltage of discharge (Fig. 1 (b) of Li1.13Mn0.54-x
Ni0.27+x
Co0.06O2 (x=0, 0.02, 0.04, 0.06) in the voltage range of 2.5-4.6 V at 1.0 C after three formation cycles in the voltage of 2.0-4.8 V at 0.1 C. As shown in Fig. 1(a), it can be seen that initial discharge capacities decrease with x value increasing in the voltage of 2.0-4.8 V at 0.1 C ,during the formation cycles. Meanwhile, Li1.13Mn0.54-x
Ni0.27+x
Co0.06O2 (x=0, 0.02, 0.04, 0.06) delivers the initial discharge capacity of 181.0, 178.4, 157.6, 142.7 mAhg-1 in the voltage of 2.5-4.6 V at 1.0 C and capacity retention are 75.0, 87.2, 90.0 and 88.9% of an initial discharge capacity after 200 cycles, respectively. Fig. 1(b) shows the variation of median voltage of discharge of Li1.13Mn0.54-x
Ni0.27+x
Co0.06O2 (x=0, 0.02, 0.04, 0.06) over 200 cycles. It is noted that Li1.13Mn0.54-x
Ni0.27+x
Co0.06O2 shows much smaller voltage fade with x value increasing. Our results indicate that the Li1.13Mn0.54-x
Ni0.27+x
Co0.06O2 with lower Mn content and higher Ni content demonstrates much better electrochemical performance with high capacity retention and small voltage fade comparing to Li1.13Mn0.54Ni0.27Co0.06O2.

References

[1]  M. M. Thackeray, S.-Ho Kang, C. S. Johnson, J. T. Vaughey, R. Benedek and S. A. Hackney, J. Mater. Chem., 17, 3112 (2007).

[2]  J.R. Croy, K. G. Gallagher, M. Balasubramanian, B. R. Long, and M. M. Thackeray, J. Electrochem. Soc., 161(3), A318 (2014).

[3]  E.-S. Lee, A. Manthiram, J. Mater. Chem. A, 2, 3932 (2014).

Figure 1
Applying Analytical Methods for Face Dependent Studies of LiCoO2
Authors: Slaymaker Laura E. , Jackson David H. K. , Kuech Thomas F. , Hamers Robert J
Published: February 2020

Surface reactions of electrode materials with electrolyte can be severely detrimental to performance and lifetime of a battery material. Coatings, such as Al2O3, facilitate lithium conduction and block electrolyte degradation. However, the mechanisms controlling how these coatings interact with the cathode surface and improve battery performance are not well understood. The role of the exposed crystal face of cathode materials may have a major impact on the ability of the coating material to bind with the cathode surface. By evaluating the effectiveness of coatings at different crystal planes, we can gain a better understanding of the surface reactivity of cathode materials such as LiCoO2. To accomplish this, we are investigating coating the surface of single crystal LiCoO2 with coating materials such as Al­2O3 and determining the amount of coating present on an edge or basal plane using XPS. We are extending this knowledge to future coating design to selectivity coat the LiCoO2 surface to improve battery performance.
A New Strategy to Mitigate the Initial Capacity Loss of Lithium Ion Batteries
Authors: Su Xin , Lin Chi-Kai , Wang Xiaoping , Maroni Victor A. , Ren Yang , Johnson Christopher , Lu Wenquan
Published: February 2020

Electrode materials and electrolyte choices largely dictate the design parameters and the type of lithium-ion battery (LIB) that can be optimized and eventually utilized.  Certainly all three components (anode, electrolyte, and cathode) must work in harmony to produce the highest possible energy density achievable for an LIB-based energy storage device. Balancing the electrochemical performance characteristics of the cathode and anode active materials is critical for maximizing the power/energy density of a LIB. Hard carbon (non-graphitizable) anode materials, like tin, tin oxide, silicon and silicon oxide, have a high theoretical capacity (>550 mAh/g depending on their structural and chemical properties) but unfortunately they also exhibit a large initial capacity loss (ICL), which overrides the true reversible capacity in a full cell.   Overcoming the large ICL of hard carbon in a full-cell lithium-ion  battery (LIB) necessitates a new strategy wherein a sacrificial lithium source additive such as Li5FeO4 (LFO) is used on the cathode side. Full batteries using hard carbon coupled with LFO/LiCoO2 (LCO) are currently under development at our laboratory. We find that the reversible capacity of a cathode  containing LFO can be increased by 24%. Furthermore, the cycle performance of full cells with LFO additive is improved from <90% to >95%. We believe that the LFO can not only address the irreversible capacity loss of the anode, but can also provide the additional lithium ion source required to mitigate the lithium loss caused by side reactions. In addition, we have explored the possiblity to achieve higher capacity on hard carbon, whereby the energy  density of full cells can be increased from ca. 300 Wh/kg to >400  Wh/kg .
Towards Improving the Practical Energy Density of Li-Ion Batteries: Optimization and Evaluation of Silicon:Graphite Composites in Full Cells
Authors: Abu-Lebdeh Yaser , Yim Chae-Ho , Niketic Svetlana , Salem Nuha , Naboka Olga
Published: February 2020

Increasing the energy density for Li ion batteries is very crucial for the success of EVs, grid-scale energy storage and next generation of power electronics.

A holistic approach is required where the performance of the electrodes and electrolyte needs to be improved simultaneously. On the anode side, Si has been considered as the best candidate to give much higher capacities reaching, in theory, 10 times those of graphite. [1,2] However, in practice Si alone cannot deliver this high capacity reversibly due to many problems associated with volume expansion/shrinking during lithiation/de-lithiation. Also, current cathode materials have limited specific capacity to 150-200 mAh/g and can only be coated up to certain thickness before fracture or polarization takes place. A composite of silicon and graphite with capacities between 500 and 1000 mAh/g has been considered as a transient and practical alternative. In this work we have conducted theoretical and experimental study of silicon, graphite, and binder composite electrodes. We have calculated the percentage of improvement in capacity of composites and in energy density of full cells. We have tested more than 50 compositions in half cells with different ratios, binder type and silicon (shape, size and surface chemistry). Also, we have tested full cells using NMC cathode, a carbonate solvent mixture and various additives.

We will show the result of our theoretical and experimental findings and demonstrate the actual parameters that need to be optimized in order to reach real improvements in practical energy density of Li-ion full cells.

[1] Chae-Ho Yim, Fabrice M Courtel, Yaser Abu-Lebdeh,Journal of Materials Chemistry, 1(28), 2013 8234.

[2] Nuha Salem, Matt Lavrisa and Yaser Abu-Lebdeh, 2015,  Energy Technology, DOI 10.1002/ente.201500250.
Structural Design and Electrochemical Performances of Hollow Metal Oxide/Carbon Core-Shell Fibers
Authors: Zhou Dan , Li Meng , Fan Li-Zhen
Published: February 2020

Transition metal oxide (MOx) offers great potential as anode for lithium ion batteries (LIBs) due to the high theoretical capacity compared with that of commercial graphite. However, several limitations, such as large volume variation during repeated cycling, slow kinetics and low electrical conductivity, have severely limited the practical performance in application. Here, we report a rational design of hollow metal oxide/carbon core-shell fibers (MOx/C, M= Sn, Ge) and the synthesis of the material via facile co-axial electrospinning process (Figure 1a). The unique hollow core-shell structure of MOx/C with MOx nanoparticles encapsulated into hollow carbon shells can provide a buffer layer to suppress the fracture of MOx nanoparticles caused by repeated volume changes, good conductivity and short diffusion paths for Li ions as well as stable solid electrolyte interphase (SEI) layer. Meanwhile, sufficient space between MOx nanoparticles and the carbon shell is contributed to accommodate the volume expansion of MOx during cycling process (Figure 1b–1c). As the anodes for LIBs, the as-prepared SnO2/C and GeOx/C electrodes exhibit excellent lithium storage performance, showing high reversible specific capacity of 833 mAh g−1 after 500 cycles at 600 mA g−1 and 875 mA h g−1 after 400 cycles at 160 mA g−1, respectively. The structural design in this paper can provide a novel strategy for the research of high-performance anode materials for LIBs.

References:

[1] Dan Zhou, Wei-Li Song, Li-Zhen Fan*. ACS Appl. Mater. Interfaces, 2015, 7, 21472−21478

[2] Meng Li, Dan Zhou, Wei-Li Song, Xiaogang Li, Li-Zhen Fan*. J. Mater. Chem. A, 2015, 3, 19907−19912.

Figure 1
Hard Carbon Coated Nano-Si/Graphite Composite As a High Performance Anode for Li-Ion Batteries
Authors: Jeong Sookyung , Li Xiaolin , Zheng Jianming , Yan Pengfei , Cao Ruiguo , Wang Chongmin , Liu Jun , Zhang Ji-Guang
Published: February 2020

With the ever increasing demands on Li-ion batteries with higher energy densities, alternative anode with higher reversible capacity is required to replace the conventional graphite anode.  Here, we demonstrate a cost-effective hydrothermal-carbonization approach to prepare the hard carbon coated nano-Si/graphite (HC-nSi/G) composite as a high performance anode for Li-ion batteries. In this hierarchical structured composite, the hard carbon coating layer not only provides an efficient pathway for electron transfer, but also alleviates the volume variation of silicon during charge/discharge processes. The HC-nSi/G composite electrode shows excellent electrochemical performances including a high specific capacity of 878.6 mAh g-1 based on the total weight of composite, good rate performance (398  mAh g-1 at 4C (2.4 mA g-1)) and a decent cycling stability (75.2% capacity retention over 150 cycles at 1.5 mAh cm-2 areal capacity loading), which is promising for practical applications.
Bulk and Surface Modifications in High Ni Cathode Materials
Authors: Pinedo Ricardo , Weber Dominik , Weldert Kai , Zeier Wolfgang , Janek Jürgen
Published: February 2020

High energy-density lithium ion batteries (LIBs) are in demand for portable electronic devices and electrical vehicles. Since the energy density of these batteries relies heavily on the cathode material, a great deal of attention is being focused on developing alternative materials with a higher degree of Li utilization and specific energy density [1]. In particular, layered Ni-rich oxides can deliver higher capacities at lower cost than the conventional LiCoO2(LCO). However, there are still several problems associated with their cycle life, thermal stability, and safety, which need to be solved [2]. In addition, these drawbacks increase with increasing Ni amount, and motivate major research efforts to understand, mitigate and overcome these effects. 

In stoichiometric layered lithium metal oxides, every vacant tetrahedral site is coordinated by either 3 lithium ions and 1 transition-metal (TM) ion, or 1 lithium ion and 3 TM ions. Effectively, only in the first case at least two Li sites are connected and can therefore sustain lithium migration. Hence, for each Li diffusion channel in the layered structure, exactly one gate site is a TM site, while the second one is a lithium site [3]. The barrier for lithium migration through such a 1-TM channel is correlated to the TM valence and the areal lithium-TM separation. The latter varies with the width of the Li layer (the distance between TM-O slabs), constraining the degree of local relaxation for the TM when lithium enters the activated state [4]. Nevertheless, the Li slab distance highly varies during discharge-charge processes and leads to cell volume fluctuation which is considered a potential source of electrode degradation, as it could favor the formation of microcracks [5]. Moreover, this fluctuation increases with increasing Ni amount.

One promising approach to control the Li slab distance in high Ni materials is anionic substitution [6]. In this work, the effect of N and F dopants is evaluated and a correlation between structural parameters and electrochemical performance was established. Moreover, the effect of N and F can be restricted to the materials surface. The stabilization of surfaces in high Ni materials is a fundamental challenge in order to control the aging processes of these materials.  

References

[1]. W. Liu et al., Angew. Chem. Int. Ed.
2015, 54, 4440.

[2]. L. Wu et al. Chem. Mater.
2011, 23, 3953.

[3]. A. Urban et al., Advanced Energy Materials
2014, 4, 1400478.

[4]. K. Kang et al. Phys.
Rev. B
2006, 74, 094105.

[5]. R. Hausbrand et al., Materials Science and Engineering: B
2015, 192, 3.

[6]. F. Kong et al., J. Mater. Chem. A
2015, 3, 8489.
Enhanced Rate Capability in Two Phase Reaction in LiFePO4 By Interfacial Modification Between Cathode and Electrolyte
Authors: Orikasa Yuki , Yoshinari Takahiro , Kato Eri , Mori Takuya , Nakanishi Koji , Uchimoto Yoshiharu
Published: February 2020

Olivine-type LiFePO4 is considered as a promising cathode material for high power density lithium-ion battery. Lithium-ion intercalation proceeds thorough a two-phase reaction divided into LiFePO4 and FePO4. During the phase transition between LiFePO4 and FePO4, the nucleation of a new phase occurs at the electrode / electrolyte interface, which is reported to be the rate determining reaction.1 To improve the rate capability of LiFePO4, Park et al performed the surface modification by nitrogen on LiFePO4 particles.2 However, their improved mechanism is not clearly understood due to the difficulty in the observation of electrode / electrolyte interface. In order to analyze the electrode / electrolyte interface, thin-film electrodes and surface sensitive X-ray absorption spectroscopy are powerful tool.3 In this study, we prepared LiFePO4thin-film model electrodes to clarify the reaction kinetics and applied the interfacial modification of nitrogen. Their reaction mechanism is discussed with the information of X-ray absorption spectroscopy.

LiFePO4 thin-film was prepared on a polycrystalline Au substrate by pulsed laser deposition method. The deposition was conducted under Ar atmosphere (0.0001 Pa) at 923K for 30 min. The prepared thin films were annealed under ammonia gas at 873 K. The obtained thin-film was characterized by X-ray diffraction and TEM. X-ray absorption spectroscopy at Co K-edge was performed at BL37XU, Spring-8. N K-edge X-ray absorption measurements were performed in Ritsumeikan SR-center. For the electrochemical analysis, three-electrode cells employing Li metal as a counter and a reference electrode, and 1 M LiClO4in propylene carbonate liquid electrolyte were prepared.

Annealing of ammonia gas introduces nitrogen into LiFePO4 surface, which is confirmed by N K-edge X-ray absorption spectra. The rate capability of the nitrogen modified LiFePO4 thin-film electrodes is improved. The surface sensitive Fe K-edge X-ray absorption spectra show the increasing of oxidation state in iron, which implies the lattice mismatch is decreased in surface of LiFePO4. Therefore, nucleation reaction is enhanced during two phase reaction between LiFePO4 and FePO4, which is the origin of surface modification effect.

References

[1] Delmas, C.; Maccario, M.; Croguennec, L.; Le Cras, F.; Weill, F., Nat. Mater.
2008,
7(8), 665.

[2] Park, K. S.; Xiao, P. H.; Kim, S. Y.; Dylla, A.; Choi, Y. M.; Henkelman, G.; Stevenson, K. J.; Goodenough, J. B., Chem. Mater.
2012,
24(16), 3212.

[3] Takamatsu, D.; Koyama, Y.; Orikasa, Y.; Mori, S.; Nakatsutsumi, T.; Hirano, T.; Tanida, H.; Arai, H.; Uchimoto, Y.; Ogumi, Z., Angew. Chem. Int. Edit.
2012,
51(46), 11597.

Acknowledgement

This work was supported by JSPS KAKENHI Grant Number 25249141.
Cus-Carbon Composite As Cathode Material for Lithium Secondary Batteries
Authors: Li Yong , Liu Wen , Guo Rui , Pei Haijuan , Xie Jingying
Published: February 2020

The Li/CuS battery was a promising high-energy battery system because of the good electronic conductivity of 103 S cm-1 and a high theoretical capacity of 560 mAh g-1 for CuS.[1-3]In this paper, S/C/nano-Cu composite was prepared by a fast deposit method in an aqueous solution. Then the S/C/nano-Cu composite was dried at 60℃ in a vacuum oven for 24h and the CuS/C composite was further in situ formed in the process of drying.

CuS/C composite cathode for a lithium rechargeable battery is tested with 1 M LiFSI/DOL-DME as electrolyte at room temperature. The cathode undergoes a two-step reaction during the initial discharge to 1.5 V with a specific capacity of 546.6 mAh g-1(see Figure 1a). Meanwhile, the composite also exhibits a good cycle behavior with 86.2% capacity retention after 30 cycles at 0.5 C (Figure 1b). These results suggest that the nano-size composite plays an important role during the charge-discharge process and the CuS/C composite is a promising cathode material for high-energy lithium secondary battery.

Figure 1. (a) Initial charge-discharge curves of the CuS/C composite cathode; (b) cycle performance of the CuS/C composite cathode at 0.5 C.

Acknowledgements

This work is supported by Shanghai Science and Technology Committee Rising-Star Program (15QB1402000).

 

Reference

[1] R.J. Jasinski, Electroanal. Chem. 26 (1970) 189.

[2] J.S. Chung, H.J. Sohn, J. Power Sources 108 (2002) 226.

[3] Y.R. Wang, X.W.Zhang, P.Chen, H.T.Liao, S.Q.Cheng, Electrochimica Acta 80 (2012) 264.

Figure 1
Post-Mortem Analysis of Commercial NMC/Graphite Li-Ion Pouch Cells within Mat4Bat European Project
Authors: Iturrondobeitia Amaia , Aguesse Frédéric , Waldmann Thomas , Kasper Michael , Wohlfahrt-Mehrens Margret , Bekaert Emilie
Published: February 2020

Li-ion batteries are good candidates for electric vehicles and stationary applications due to their high power and energy densities. It is well known that the lifetime of lithium ion batteries is limited by undesirable side reactions. Moreover, these side reactions can affect different parts of the battery including the electrolyte, the active material, binder, conducting agents, current collectors and the separator. Over time, this fact leads to a gradual capacity fade and the end of life of the battery. Thus, the understanding of degradation mechanisms in lithium ion batteries is considered to be of great importance.

In this work, the “post mortem analyses“ of NMC/graphite commercial pouch cells has been performed. For this, a standard procedure for cell opening and preparation of the samples has been defined. As safety plays an important role in the dissemination of batteries, full discharge of the investigated cells has been carried out [1,2,3]. Furthermore, a controlled environment such as an Ar-filled glove box has been used during cell opening in order to avoid material decomposition [4,5]. Once the electrodes have been separated, the conductive salt has been removed to prevent corrosion. Diagnostic evaluation of the first degradation mechanisms has been studied by ex-situ destructive physico-chemical and electrochemical analyses of the cell components. The crystallographic and morphological studies of the electrodes have been carried out by X-ray diffraction (XRD) and electron microscopy (SEM). Additionally, elemental analysis of the electrode composition has been determined by EDS and ICP techniques. In order to evaluate the electrochemical characterization of the harvested electrodes, galvanostatic testing in half-cell configuration has been performed.

The research leading to these results has been performed within the MAT4BAT project (http://www.mat4bat.eu)

[1] D. Aurbach, B. Markovsky, A. Rodkin, M. Cojocaru, E. Levi, H.-J. Kim, Electrochimica Acta 47 (2002) 1899.

[2] Y. Kobayashi, T. Kobayashi, K. Shono, Y. Ohno, Y. Mita, H. Miyashiro, Journal of the Electrochemical Society 160 (2013) A1181.

[3] T. Waldmann, M. Wilka, M. Kasper, M. Fleischhammer, M. Wohlfahrt-Mehrens, Journal of Power Sources 262 (2014) 129.

[4] H.-Y. Amanieu, D. Rosato, M. Sebastiani, F. Massimi, D.C. Lupascu, Materials Science and Engineering: A 593 (2014) 92.

[5] C. Wu, Y. Bai, F. Wu, Journal of Power Sources 189 (2009) 89.
Effects of Mesoscopic Microstructural Features on the Effective Ionic Diffusivity of Solid Electrolytes for Li Batteries
Authors: Heo Tae Wook , Wood Brandon C.
Published: February 2020

The kinetics of ion transport in solid electrolytes is known to be highly sensitive to the topological characteristics of ion conduction pathways. The conduction mechanisms usually involve concurrent ionic diffusion along a variety of mesoscopic features of internal microstructures such as bulk grain, structural domains, and associated boundaries as well as their network. Due to the complexity of these structural features of the solid electrolytes during operation, it is significantly challenging to characterize the microstructure-ionic diffusion property relationship. For better mechanistic understanding of relevant conduction mechanisms, it is necessary to thoroughly explore the impacts of individual microstructural factors on the overall kinetic properties and performances. In this presentation, we will present our development of an efficient mesoscopic computational method for extracting the effective diffusivity of the solid electrolyte containing arbitrarily distributed microstructural inhomogeneities such as differently oriented multiple grains, several structural variants of phase domains, and grain/domain boundaries. Using two- and three-dimensional digital microstructures generated by phase-field simulations as well as the fundamental diffusivity tensors of reference phases and boundaries derived from atomistic calculations as inputs, the method enable us to efficiently compute the effective diffusivity tensor of the entire system. We will then discuss the applications of this framework to investigating the relationship between relevant individual microstructural features and effective diffusivity of highly conductive solid electrolytes (e.g., LLTO and LLZO) focusing on the impacts of topological features of grains, internal mesoscopic structures of high- and low-temperature phase domains, and grain/phase boundary networks.

*This work of was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Evaluation of Commercial High Energy Lithium Primary Cells for Wide Temperature Range Aerospace Applications
Authors: Krause Frederick C. , Jones Simon C. , Brandon Erik J. , Ratnakumar Bugga V. , Jones John-Paul , West William C. , Pasalic Jasmina , Billings Keith J.
Published: February 2020

As NASA missions become increasingly demanding of robust, lightweight, and compact power sources, there is a need to develop long-life and high-energy battery systems. Lithium-ion batteries have been developed at JPL over the last two decades and have been successfully integrated into a number of NASA missions [1] in conjunction with solar arrays and radioisotope thermoelectric generator (RTG) power sources. In the case of short-term missions in extremely harsh conditions (i.e., thirty days or less and/or at temperatures reaching -40 °C) without an active thermal management system, lithium primary cells may be considered for their high specific energy, especially in environments where recharging secondary cells would be challenging [2]. The icy moons of the Jovian system, for example, offer little sunlight for photovoltaic power and Jupiter’s intense magnetosphere leads to constant potentially damaging radiation.

Many types of commercial lithium primary cells are available, reportedly offering high specific energies of ~500 Wh kg-1, with some designed specifically for low temperature operation. These commercial cells must be validated for space missions with extensive testing to demonstrate their performance, safety, reliability, and suitability for space environments. Radiation tolerance is also an important consideration, both as a method of sterilization for planetary protection and for survival in high radiation environments.

In the present study, we have evaluated a number of commercial lithium primary cells (ranging from AA to DD+ sizes) of varying chemistries (with CFx, MnO2, SOCl2, SO2, and FeS2 cathodes) and manufacturers for possible future use in NASA’s deep space missions. We have assessed various performance characteristics of these cells, including low temperature energy, rate capability, and tolerance to radiation exposure, which will be reported here.

Acknowledgement

The work described herein was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA) and supported by the NASA Space Technology Mission Directorate Game Changing Development Program.

References

[1] Ratnakumar, B. V., Smart, M. C., Huang, C. K., Perrone, D., Surampudi, S., & Greenbaum, S. G. (2000). Lithium ion batteries for Mars exploration missions.Electrochimica Acta, 45(8-9), 1513–1517. doi:10.1016/S0013-4686(99)00367-9

[2] J.F. Whitacre, W.C. West, M.C. Smart, R. Yazami, G.K. Surya Prakash, A. Hamwi, et al., Enhanced Low-Temperature Performance of Li – CF x Batteries, Electrochem. Solid-State Lett. . 10 (2007) A166–A170.doi:10.1149/1.2735823
System Theoretic Analysis of Battery Charging Optimization
Authors: Vincent Tyrone , Weddle Peter , Kee Robert J. , Tang Gongguo
Published: February 2020

Lithium-ion batteries have attractive features for many applications, and are widely used as high-energy density storage devices. The internal electrochemical and chemical reactions occurring during charge/discharge make Li-ion batteries sensitive to demand sequences and operating conditions. Battery management systems are necessary to keep cells within acceptable operating ranges to prolong life, reduce charging losses, and mitigate failure. One particular area of recent investigation is incorporating pulsed perturbations in charging protocols. Typical arguments for pulsed perturbations involve reduced chemical impedance and reduced electrode/electrolyte polarization which decrease losses, and electrode diffusion capabilities which can reduce losses and mitigate plating. However, published experimental and simulation evidence is contradictory, with some either arguing in favor pulsed charging and some indicating no effect or worse performance. While experimental results are useful, the measurable results are subtle enough that experimental conditions and uncertainty can be a plausible argument against both positive and negative results. In this work, we ask the following question: What are the features of a battery as a dynamic system that must appear in order for optimal charging sequences to include a periodic component? The answer to this question is then used to illuminate whether some of the physical, mechanistic explanations for the positive effects of perturbations are valid.

The analysis considers two cases: finding the current trajectory to minimize the energy required to supply a fixed amount of charge to a battery, and finding the current trajectory to maximize the charge supplied to the battery while meeting constraints on internal variables related to the deposition of lithium on the anode electrode. Under the assumption that the trajectories for the relevant battery parameters can be predicted using a linear time-invariant dynamic system, analytic solutions are obtained. Using these analytic solutions, we extract conditions on the battery model that must be satisfied in order for the solutions to contain a periodic component. In the case of energy minimization, it can be shown that the the electrochemical impedance must approach the imaginary axis, while in the case of meeting constraints, a necessary condition is developed involving the response of the internal variables to an impulse in charging current. By examining the impedance spectra and impulse responses of typical Li-ion batteries, these results indicate that that pulsed or sinusoidal perturbations do not appear in the optimal charging sequence. It should be emphasized that this analysis does not provide definitive arguments for or against pulse charging or any evidence against any particular experimental results. However, this study provides important guidance when considering a physical explanation for the benefits of pulsed or sinusoidal ripple charging.

Figure 1
Dual-Phase Li4Ti5O12/TiO2(B) Heteronanostructures As Anodes for High-Performance Lithium-Ion Batteries
Authors: Ho Ching-Kit , Li Chi-Ying Vanessa , Chan Kwong-Yu , Tay Yee-Yan
Published: February 2020

The synthesis of dual phase Li4Ti5O12/TiO2(B) composite remains a tremendous challenge due to the easy formation of anatase TiO2 instead of Li4Ti5O12 in the process. In this work, Li4Ti5O12/TiO2(B) heteronanostructures comprising porous TiO2(B) nanofibers integrated with Li4Ti5O12 nanocrystals are synthesized and applied as anode for lithium-ion batteries. Benefiting from the complementary advantages of higher theoretical capacity of TiO2(B) with favourable pseudocapacitive behaviour and excellent cyclability of Li4Ti5O12, this heteronanostructure demonstrates a superior lithium-ion storage performance in terms of high discharge capacity and remarkable long-term stability. As a result, Li4Ti5O12/TiO2(B) heteronanostructures manifest discharge capacity of 130 mAhg−1 and capacity retention of 93 % at high rate of 1.75 Ag-1, compared to those of TiO2(B) pristine of 90 mAhg−1 and 75 %. The superior electrochemical performance demonstrated by Li4Ti5O12/TiO2(B) heteronanostructure reveals a new direction of integration of Li4Ti5O12 into TiO2(B) to improve both the capacity performance and cyclability.

Acknowledgements

This project is financially supported by Innovation and Technology Fund (ITS/378/13) and Internship Programme (InP/299/14) from Innovation and Technology Commission, Hong Kong, HKU Strategic Research Theme on Clean Energy, University Development Fund for Initiative for Clean Energy and Environment, and our industry partner – Gold Peak (GP) Batteries Limited.

Figure 1
Breathable Polymer Encapsulation of Lithium Battery Electrode Materials Ensures Durable Cyclic Performance of Si Anode
Authors: Chu Peter Po-Jen , Tsai Minghan , Hsieh Y.S.
Published: February 2020

Silicon Anode is considered a most critical component for advanced lithium battery since it has about 10 folds higher theoretical capacity than that of conventional graphite anode. However, Si suffers from huge volume change during lithiation/ delithiation process has led to pulverization and the formation of unstable SEI layer with the electrolyte that quickly deteriorated the cyclic performance of lithium battery. In this study, smart polymer material bearing breathable network-like structure is employed to encapsulate the high energy anode material through photo polymerization. The monomers of the smart polymer in the solvent are adsorbed first to the surface of silicon particle, followed by photo-polymerization to form the dendrimer network-like structure which homogeneously encapsulated the active anode. During charging and discharging process, the flexible and breathable protection layer effectively retained the pulverized anode materials due to the huge volume change, and avoided a direct contact with the liquid electrolyte. Both functions are essential to inhibit the dissolution of active material and responsible for maintaining the cyclic performance of Si anode battery. NMR spectroscopy is used to follow the photo-polymerization identified, and the effect of the coating and the change of morphology after extensive charge and discharge cycle are identified by SEM and TEM. Current results show the coating of a network-like breathable polymer protection layer is effective in preserving the integrity and the structure of Si anode, leading to improved life cycle performance.
Interfacial Li-Ion Storage Between Graphene Layers
Authors: Liu Tianyuan , Park Jinho , Joiner Corey A , Lee Seung Woo , Navaei Milad , Stern Ilan
Published: February 2020

The ever increased development of portable devices and electrical vehicles demands the electrochemical energy storage devices with high energy and power densities. Graphite has been the most widely used anode materials for Li-ion batteries. However, because of its low theoretical capacity (372 mAh/g), there has been significant efforts in developing electrode materials with much higher energy densities. Graphene, a one-atom-thick carbon materials showed numerous advantages including superior electrical conductivity, thermal conductivity and high surface area; and is expected to be a good candidate as a high-power and high-energy electrode material for Li-ion batteries. Although, previous studies used graphene as anode materials, it showed significantly enhanced capacity >1000 mAh/g; the energy storage mechanism in graphene is still unclear. This is due to the high density of defects in chemically synthesized graphene. Few studies have been using chemical vapor deposition (CVD)-grown defect-free single layer graphene (SLG) on copper foil as anodes in Li-ion batteries.1 Despite this, the exact mechanism of Li ions storage in the SLG is still a subject of controversy. Theoretical study has shown that the absorption of Li-ions on defect-free SLG is energetically unfavorable.2 This is in controversy with the experiments which claims that CVD-grown SLG is promising electrode materials for Li anodes. In this study, we investigated the Li-ion storage in CVD-grown SLG graphene in comparison with Cu substrate, our results confirmed that the capacity obtained for SLG on Cu is mainly originated from the contribution of Cu substrate. However, by using bilayer or triple layer graphene which is prepared by a layer-by-layer transfer process, we found that the Li ion storage capacity will be significantly enhanced when additional layer graphene was placed on the top of initial SLG. The capacitance increased from 0.05 F/cm2 for Cu substrate to 0.08 F/cm2 for bilayer graphene on Cu and further increased to 0.129 F/cm2for triple layer graphene on Cu substrate. The areal capacity of the bilayer graphene is ~ 2 times of the capacity available for Cu substrate after 50 cycles. Our study indicates that the interfacial space between graphene layers plays a critical role for high performance Li-ion storage.

References:

1. D. Wei, S. Haque, P. Andrew, J. Kivioja, T. Ryhanen, A. Pesquera, A. Centeno, B. Alonso, A. Chuvilin and A. Zurutuza, Journal of Materials Chemistry A, 2013, 1, 3177-3181.

2. E. Lee and K. A. Persson, Nano Letters, 2012, 12, 4624-4628.
Probing the Growth and Ion Transport Properties of SEI Layers with NMR Using Novel 6Li/7Li Exchange Experiments
Authors: Ilott Andrew , Jerschow Alexej
Published: February 2020

Detecting and observing changes in the surface electrolyte interphase (SEI) is difficult due to the small size and amorphous nature of this layer, while its reactivity calls for characterization to be performed in situ, further limiting the applicability of many techniques. Nuclear Magnetic Resonance (NMR) can be performed in situ, but not in conjunction with magic angle spinning (MAS), which is often needed to enhance sensitivity and resolve the broad signal associated with the crystalline environments making up the SEI. It has therefore been necessary to devise alternative NMR approaches to probe the SEI.

Even in an isolated lithium metal electrode in contact with a standard electrolyte, an SEI forms and acts as an intermediary in the exchange between lithium ions in the electrolyte and the metal. Self-diffusion in the metal further complicates this picture, although its impact is only apparent when changes in the local 6Li/7Li isotopic concentration can be considered. This is possible with NMR and, coupled with the skin effect that limits the detected NMR signal to the micron-thickness surface region of the lithium metal, provides a unique, time resolved “window” into the lithium ion dynamics at the metal-SEI-electrolyte interfaces. We will describe how this “window” can be used to extract information about the growth of the SEI layer and measure the diffusion of lithium ions through it using NMR experiments on well-designed, isotopically-enriched systems (see Figure).

Figure caption: Model of the ion dynamics at the lithium metal electrode – SEI – electrolyte interface. Information about the diffusion, exchange and transport properties of the ions through the SEI can be accessed via carefully designed 6Li and 7Li NMR experiments.

Figure 1