bluuebunny/crossref_metadata_2025 huggingface dataset:
Kinetic Surface Control for Improved Magnesium−Electrolyte Interfaces for Magnesium Batteries
Authors: Masse Robert , Cao Guozhong , Li Bin
Published: February 2020

Magnesium (Mg) metal is a compelling battery anode material for Mg batteries because of its high volumetric energy density, good operational safety and abundance. The metal promises extremely high energy density without the safety risks posed by lithium (Li) metal dendrite formation. However, most conventional battery electrolytes react with Mg to form blocking layers. Much attention has been dedicated to synthesizing electrolytes that are thermodynamically stable with respect to Mg metal. Here we report a new approach to improving the (electro)chemical compatibility of the Mg-electrolyte interface by exerting kinetic control instead. A chemically inert magnesium fluoride (MgF2) layer is formed through controlled reaction of Mg surface with hydrofluoric acid. The tailored surface layer improves the voltage stability, Coulombic efficiency, and cycling performance of full-cell Mg batteries compared to cells using bare Mg metal as an anode. Remarkably, unlike almost all other Mg surface films, the MgF2 passivating layer not only suppresses side reactions with the electrolyte but also allows for Mg2+ transport between the electrode and electrolyte. This result reinforces the importance of controlling Mg surface chemistry for the successful development of high-energy magnesium ion batteries.
Si Nanoparticles: Its Stability in Aqueous Slurries and the Optimization of Oxide Layer Thickness for Optimal Electrochemical Performance
Authors: Zhang Linghong , Liu Yuzi , Key Baris , Trask Stephen E. , Yang Zhenzhen , Lu Wenquan
Published: February 2020

For the silicon particles used as anode for lithium ion batteries, there is always a native oxide layer on the surface, whose role on electrochemical performance of silicon electrode need to be understood. The actual thickness of the oxide layer may also vary due to the manufacturing processes. As the size of the silicon particle becomes smaller, this oxide layer will play a more important role as it takes up a larger volume and weight percentage. Previous study suggests that the presence of oxide layer harms the initial performance of the silicon anodes in a non-aqueous system. However, the effect of the oxide layer on the long cycling performance of the electrodes has not been well studied.

Here we investigated the effect of oxide layer on the electrochemical performance of silicon anodes by growing the oxide layer of Si nanoparticles in a controlled manner. Si nanoparticles with an average size of 80 nm was used. LiPAA and carbon black was used to fabricate the electrodes. Brunauer-Emmett-Teller (BET) surface analysis, transmission electron microscopy as well as Fourier-transform infrared spectroscopy were performed to characterize the silicon nanoparticles. The stability of the silicon nanoparticles with different oxide layer thickness during electrode fabrication process was compared. Electrochemical performance of the silicon electrodes of different thicknesses was also analyzed and compared.

Acknowledgement

We gratefully acknowledge the support from the U.S. Department of Energy’s (DOE) office of Energy Efficiency & Renewable Energy (EERE) Vehicle Technologies Office. This work is performed at Argonne National Laboratory, a U.S. Department of Energy Office of Science Laboratory operated under Contract No. DE-AC02-06CH11357
Facile and Cost Effective Directly Electrosprayed Graphene/Silicon Nanocomposites for High-Rate Lithium-Ion Battery Anodes
Authors: Shoorideh Ghazal , Park Sang Mok , Berry Adam , Joo Yong Lak
Published: February 2020

Silicon is in the research spotlight for the next generation of Li-ion battery anodes due to its high specific capacity of 4200 mAh/g for lithium storage at room temperature. However, it has a few serious shortcomings that prevent its commercialization. In the present work, we explored a facile and environmentally friendly process based on electrospraying to directly deposit active material on the current collector and remedy silicon problems in one step. Instead of graphene-oxide or other derivatives, direct employment of a graphene suspension in the deposition process which does not require heat treatment to increase its conductivity enables usage of a polymeric binder in the system. As a result, the sprayed composite layer has a uniform morphology with an excellent dispersion of nanoparticles between graphene layers and an electrode density above 0.7 g/cc was prepared. Graphene sheets provide conductivity and keep the silicon nanoparticles in place during constant volume expansion/contraction. Nevertheless, existence of polymeric binder greatly increases the life of the electrodes with minimal capacity fading of about 15% after 300 cycles with a specific capacity of 2100 mAh/g. In addition, electrodes prepared with this technique have a noticeably high first cycle columbic efficiency up to 92%, which makes them desirable for full cell fabrication. These electrodes also have a great electrochemical performance at high rates (1200 mAh/g at 2C and 1000 at 5C), due to the highly conductive network of dispersed graphene sheets. In this presentation, the innovative and facile electrode preparation technique will be introduced and underlying phenomena responsible for the outstanding electrochemical performance of the fabricated electrodes will be discussed.
Highly Stretchable Conductive Binder Based on PEDOT:PSS for High Performance Si Anode
Authors: Wang Lei , Fu Huo Kai
Published: February 2020

Silicon (Si) is a promising anode material in advanced high-energy-density lithium-ion batteries (LIBs) due to its large theoretical capacity of 4200 mAh g-1, however, the high volume change cause the pulverization and unstable solid-state interface layer. How to maintain the structural integrity and high electronic conductivity during cycling is the major challenge for high-capacity Si anodes. Binder plays a key role in maintaining the mechanical integrity of electrodes in lithium-ion batteries. However, the existing binders typically exhibit poor stretchability or low conductivity at large strains, which are not suitable for high rate and high-capacity silicon (Si)-based anodes undergoing severe volume changes during cycling. Herein, we report a novel stretchable conductive polymer that possesses inherent high conductivity, excellent stretchablity and ductility. The polymer can be stretched up to 400% in volume and 250% in length without conductivity loss and mechanical fracture. The Si anode composed of the polymer and Si nanoparticles exhibited excellent cycle performance with a high discharge capacity (1500 mAh g-1 for over 700 cycles) as well as high areal capacity (5.13 mAh cm-2). The highly stretchable conductive binder provides a new perspective for designing next-generation high-capacity and high-power batteries.

References:

[1] L. Wang, T. Liu, et al. Adv. Funct. Mater. DOI: 10.1002/adfm.201704858.

[2] L. Wang, K. Huo et al. Nanoscale 7 (2015) 13840.

[3] K. Huo, L. Wang et al. J. Mater. Chem. A 4 (2016) 7585.

[4] W. Zeng, L. Wang et al. Adv. Energy Mater. DOI: 10.1002/aenm.201702314.
Effects of Local Tortuosity and Porosity Heterogeneities on Charge and Discharge Performance of Li-Ion Batteries
Authors: Forouzan Mehdi M , Wheeler Dean R , Mazzeo Brian A
Published: February 2020

Local variations of mechanical, structural, transport, and kinetic properties, referred to as heterogeneity (generated by a non-optimized manufacturing process [1]), can detrimentally affect battery life and performance, especially at high cycling rates and low temperatures, in a number of manners. The distribution of current density across an electrode surface can be non-uniform as a consequence of electrode heterogeneity. A high local charging rate (especially at local low temperature) may lead to local lithium plating, resulting in capacity fade and shorter cycle life. Additionally, deviation of local charging-discharging rate from the average rate results in variation in local state of charge (SOC, Li concentration in active material). For a given chemistry and application, there is an SOC operation range (lower and upper bounds) beyond which capacity loss and damage occur. Therefore, highly heterogeneous electrodes may cause “hot” and “cold” spots, in terms of SOC, leading to non-uniform aging within the cell. Another negative effect of local inhomogeneity is non-uniform utilization of active materials, resulting is decreased volumetric and gravimetric energy density of a Li-ion battery.

In this work, we introduce a computationally efficient Newman-type model to further understand and quantify the effects of local inhomogeneities, particularly non-uniform ionic and electronic impedance. As shown in Fig. 1, we imitate the real heterogeneity of the cell by a system consisting of three localized Li-ion domains, each with specific properties ion-transport associated with “cold” (high tortuosity and low porosity [2]), “middle” (moderate tortuosity and porosity), and “hot” (low tortuosity and high porosity) spots. The properties for each of the domains are obtained experimentally through a combination of SEM/FIB and localized conductivity measurements. The three simulated domains are treated as separate cells electrically connected in parallel. This approach can simplify mathematical treatment and significantly reduces intensive computation requirements needed for true 3D modeling.

[1] M.M. Forouzan, C.-W. Chao, D. Bustamante, B.A. Mazzeo, D.R. Wheeler, Journal of Power Sources, 312 (2016) 172-183.

[2] M.M. Forouzan, M. Wray, L. Robertson, D.R. Wheeler, J. Electrochem. Soc., 164 (2017) A3117-A3130.

Figure 1: Heterogeneity of the NMC electrode using SEM/FIB images and equivalent circuit used in the Newman-type model.

Figure 1
Improvement of Thermal Stability of Lithium Ion Pouch Type Cell
Authors: Sung Changhun , Kim Hyejung , Kim Cheon-Soo , Kim Min Gyu , Jeong Kyeong-Min
Published: February 2020

Thinner design of smart phone continuously would need to the high energy density lithium-ion batteries. Lithium-ion batteries are composed of four major component, cathode, anode, electrolyte and separator. Each components’s reaction by pyrolysis and interaction between components are causative of exothermic reaction of lithium ion batteries.

We investigated causes of exothermic reaction of lithium ion batteries having thermal analysis, surface analysis and structure analysis by dismantling two kinds of 3.2Ah lithium-ion batteries composed of most commercialized LiCoO2 cathode material and Graphite anode material.

In LiCoO2 cathode material, Li ions are oxidized by charge process, it exists as Li0.5CoO2. Near 230oC, structure of Li0.5CoO2 is changed, it causes exothermic reaction. EXAFS, structure analysis, showed change of two kind of Li0.5CoO2 structure according to temperature change. By investigating Co-Co and Co-O bond, we can find that structure stability as temperature increasing is different as status of LiCoO2 such as Mg doping.

Surface analysis showed surface status of cathode material and distribution of anode SEI layer. Especially, in case of anode, Alkyl Carbonate is considered as important factor of thermal stability because it makes exothermic reactions as it decomposed. We identified how thick the alkyl carbonates were deposited and we found difference of exothermic value by DSC thermal analysis between two kinds of graphite of lithium ion batteries.

These analysis data indicate which part is important for thermal stability and investigate exothermic reaction mechanism of Cell components. We made sure structure change of cathode material and distribution of Alkyl carbonate in anode SEI layer is important for thermal runaway of Cell. These results suggest improvement direction for increasing of thermal stability.
Strategies to Stabilize the Cathode/Electrolyte Interface in Ni-Rich NMC Based Li-Ion Batteries
Authors: Zhao Wengao , Zheng Jianming , Zou Lianfeng , Patel Rajankumar L. , Wang Xiaofeng , Liang Xinhua , Wang Chongmin , Yang Yong , Zhang Ji-Guang
Published: February 2020

Lithium ion batteries (LIBs) have been widely used in consumer electronics and electric vehicles due to their high energy density, high voltage, and environmental friendly nature, etc. Ni-rich layered cathode, LiNixMnyCo1-x-yO2 (NMC) has been considered as one of the most promising cathodes for high energy LIBs considering its high capacity (> 200 mAh g-1), high energy density (> 800 Wh kg-1), and reasonable cost comparing with other commercial cathodes. However, Ni-rich NMC-based batteries still exhibit significant capacity fade, especially under high voltage cycling conditions. This fade is related to the instability of cathode/electrolyte interface (CEI) and structure degradation induced by the continuous oxidation of electrolyte and dissolution of transition metal. To address aforementioned issues, some effective strategies including Atomic Layer Deposition (ALD) and usage of B-containing electrolyte additives have been presented in this work to suppress the interface reaction/transition metal dissolution. More details regarding to the interface stabilization in Ni-rich NMC-based LIBs using these strategies will be discussed in this work.
Correlating the Effects of Processing Conditions to Cation Mixing and Performance of an NMC 111 Cathode Material for Lithium Ion Batteries
Authors: Gates Byron D. , Ovens Jeffrey , Taylor Audrey K. , Feng Yingzi , Talebi-Esfandarani Majid , Campbell Stephen
Published: February 2020

Lithium ion batteries have been utilized in a wide range of applications. On-going research and development efforts are expanding the application of these materials for use in electric vehicles and household energy storage solutions. Much of these efforts have focused on improving the performance of lithium ion battery materials through achieving alterations to the composition of the cathode material, which has been seen as the limiting factor in terms of capacity and overall battery lifetime. For example, LiNi1/3Mn1/3Co1/3O2 (often referred to as NMC 111) is becoming a material of focus for commercial-scale production. A significant challenge in synthesizing this material is the propensity for Ni/Li based cation mixing in the octahedral sites of the product. While several studies have correlated the synthetic and processing methods with observations for cation mixing and electrochemical performance of the final material, these studies have not performed an in-depth analysis of the cation mixing phenomenon in situ on a mechanistic level. A detailed investigation is presented on the correlations between the processing conditions (e.g., thermal and compositional) for NMC 111 using a pre-lithiated precursor material. The relationship between cation mixing, sintering temperature and sintering time, as well as potential methods for the reversal of cation mixing were investigated through the use of in situ, variable temperature XRD methods. The importance of this knowledge and determining the ideal processing conditions for NMC 111 (and by extension, cathode materials in general) is further demonstrated through a final analysis of the quality of Li+ distribution in these materials as assessed by microscopy techniques and electrochemical coin cell tests.
In-Situ STM Studies on Li- and Na- Intercalation Batteries
Authors: Seidl Lukas , Schneider Oliver , Stimming Ulrich
Published: February 2020

The processes of SEI formation and of intercalation are still not well understood on the molecular level. Scanning probe techniques are capable of analysing these processes under in-situ conditions.

The SEI-formation on graphitic electrodes operated as an Li+-ion battery anode in a standard 1 M LiPF6 EC/DMC (1 : 1) electrolyte has been studied using in-situ electrochemical scanning tunnelling microscopy (EC-STM)1. Two different modes of in situ study were applied, one, which allowed to follow topographic and crystallographic changes (solvent co-intercalation, graphite exfoliation, SEI precipitation on the HOPG basal plane) of the graphite electrode during SEI-formation, and the second, which gave an insight into the SEI precipitation on the HOPG basal plane in real time. From the in situ EC-STM studies, not only conclusions about the SEI-topography could be drawn, but also about the formation mechanism and the chemical composition, which strongly depend on the electrode potential. It was shown that above 1.0 V vs. Li/Li+ the SEI-formation is still reversible, since the molecular structure of the solvent molecules remains intact during an initial reduction step. During further reduction, the molecular structures of the solvents are destructed, which causes irreversible charge losses.

The reversible intercalation of solvated Na-ions into graphite and the concomitant formation of ternary Na-graphite intercalation compounds (GICs) is studied by EC-STM and other in-operando techniques2. Linear ethylene glycol dimethyl ether homologes (“glymes”) Gx with x+1 O-atoms were used as solvents, where x is 1-4. The intercalation mechanism of Na+(Gx)y-complexes was investigated with the focus on phase transitions and diffusion rates of the Na+(Gx)y-complexes inside the graphite lattice. For the four shortest glymes (G1 to G4), it is found by XRD that an intermediate stage 2 Na-GIC (NaC48) is formed upon partial sodiation of the graphite electrode. At full sodiation a stage 1 Na-GIC (NaC18, 112 mAh g-1) is obtained for G1, G2 and G4, while the G3-system is also forming a stage 1 Na-GIC but with less Na incorporated (NaC30, 70 mAh g-1). Phase transitions of a battery electrode upon ion-intercalation are visualised by STM on the atomic scale for the first time. In addition, local diffusion rates of the intercalated species inside the electrode were determined, a unique approach to determining kinetic effects in batteries on the atomic scale. The formation of a solid electrolyte interphase (SEI) is observed in EC-STM.

Lukas Seidl, Sladjana Martens, Jiwei Ma, Ulrich Stimming, Oliver Schneider "In-Situ Scanning Tunneling Microscopy of the SEI Formation on Graphite Electrodes for Li-Ion Batteries" Nanoscale, 2016, 8, 14004;

Seidl, N. Bucher, E. Chu, S. Hartung, S. Martens, O. Schneider and U. Stimming, "Intercalation of solvated Na-ions into graphite", Energy Environ. Sci.,2017, 10, 1631.
One Step Soft-Chemical Approach Towards the Synthesis of Na3V2O2(PO4)2f and Its Electrochemical Properties in Na- and Li-Ion Batteries
Authors: Manna Subal , Sandineni Prashanth , Choudhury Amitava
Published: February 2020

The great concern about the availability of lithium is leading to an increasing interest in sodium ion batteries. Sodium is very abundant and widely available throughout the world, which make sodium-ion technology an attractive candidate for the development of large battery systems. Currently, the lack of well-performing cathode has been a limiting factor in the successful implementation of Na-ion technology. Therefore, there is a need to develop cathode materials in sodium ion batteries that can sustain long cycle life and display reasonable gravimetric capacity that can potentially challenge the lithium ion battery technology. In this regard one of the polyanion-based cathodes, Na3V2O2(PO4)2F, is emerging as a viable candidate due to its high gravimetric capacity and long cycle-life. Recently it has been shown that Na3V2O2(PO4)2F can be cycled between NaV2O2(PO4)2F and Na4V2O2(PO4)2F leading to the possibility of achieving a theoretical energy density of 600 Wh Kg–1. However, there is a challenge in the synthesis of phase pure composition of Na3V2O2(PO4)2F. The unwanted by-product and the tendency of solid solution formation between the full fluoro and the oxo-fluoro derivatives, Na3V2O2x
(PO4)2F3-2x
(0 ≤ x ≤ 1), have created some confusion about the optimum performance of this material. In this presentation we will report a one-step soft chemical approach for the synthesis of phase pure Na3V2O2(PO4)2F and their single-crystal X-ray structure determination. There is some new insights in terms of location of Na ion as emerged from single-crystal solution of this compound in tetragonal system and I4/mmm space group. The detail electrochemical activities of this material towards Na- and Li-ion batteries along with other spectroscopic and magnetic characterization will be presented.
Surface Layer Effects Synergism with Electrolytes for Li Nucleation and Growth
Authors: Lochala Joshua Andrew , Wu Bingbin , Tarverne Tyler , Xiao Jie
Published: February 2020

Li metal has been considered the “holy grail” anode materials. Li metal has the most negative potential with an extremely high theoretical specific capacity of 3860 mA h g−1.[1] It is, however, plagued with multiple challenges which need solutions before the realization of this material. Li metal has two main failure mechanisms, one is the random growth of detrimental dendrites, which can lead to rapid thermal runoff, i.e. Galaxy Note 7.[2] The other issue that arises upon cycling is pulverization of lithium metal through none uniform plating, leading to an increase in solid electrolyte formation(SEI) and thereby the increase in voltage polarization within the cell.[3] Both Li failure mechanisms are rooted in the uneven distribution of SEI layers whose properties vary depending on the location of SEI formed.[4] The initial surface chemistry on Li metal influences SEI formation in the very beginning. In this work, electrochemical deposition of Li metal on different substrates with bare oxides has been performed to understand the nucleation and growth of Li crystals. Electrolyte and surface modification give rise to differing SEI properties/composition which leads to improved Li deposition morphology. The fundamental mechanisms that dictates the smooth Li deposition will be discussed.

References:

Xu, W., Wang, J., Ding, F., Chen, X., Nasybulin, E., Zhang, Y. and Zhang, J.G., 2014. Lithium metal anodes for rechargeable batteries.Energy & Environmental Science, 7(2), pp.513-537.

Cohen, Y.S., Cohen, Y. and Aurbach, D., 2000. Micromorphological studies of lithium electrodes in alkyl carbonate solutions using in situ atomic force microscopy.The Journal of Physical Chemistry B, 104(51), pp.12282-12291.

Lu, D., Shao, Y., Lozano, T., Bennett, W.D., Graff, G.L., Polzin, B., Zhang, J., Engelhard, M.H., Saenz, N.T., Henderson, W.A. and Bhattacharya, P., 2015. Failure mechanism for fast‐charged lithium metal batteries with liquid electrolytes.Advanced Energy Materials, 5(3).

Aurbach, D., Zinigrad, E., Cohen, Y. and Teller, H., 2002. A short review of failure mechanisms of lithium metal and lithiated graphite anodes in liquid electrolyte solutions.Solid state ionics, 148(3), pp.405-416.
Free-Standing Binder-Free Multi-Wall Carbon Nanotube/Silicon Anodes for Lithium-Ion Batteries
Authors: Luanwuthi Santamon , Babenko Vitaliy , Naylor Andy , Roberts Matthew R. , Hong Jindui , Kasemchainan Jitti , Bruce Peter G. , Grobert Nicole
Published: February 2020

Silicon is of interest owing to its high theoretical capacity (4200 mAh/g). However, its enormous volume expansion of silicon during cycling is one of the main reasons for the rapid capacity fading and pulverisation of the anode commonly observed.

Here, freestanding multi-wall carbon nanotube (MWCNT)/silicon anodes were prepared using so-called MWCNT buckypapers (BPs) as current collectors instead of the traditional metallic foils. To prepare the anodes, silicon was deposited on these MWCNT BPs to form silicon nanoparticles (SiNPs) and subsequent annealing resulted in the formation of a connecting SiC interface preventing the SiNPs from detaching. An amorphous carbon coating was applied in order to enhance electrical conductivity and overall integrity of these hierarchical anode materials.

The morphology and chemical composition of the Si-BP anodes were characterised by means of SEM, TEM, EDX, STEM, XRD, RAMAN, etc. Cycling tests of these binder and additive-free anodes revealed an areal capacity of 0.55 mAh/cm2 after 300 cycles with 99.7% of Columbic efficiency and showed that the presence of the SiC interface and a-C coating played a crucial role in improving their rate capability and stability.
Core-Shell Structured SiOx-TiO2@C Nanocomposites As High-Rate and Long-Cycle Anode for Lithium Ion Batteries
Authors: Li Zhaolin , Zhao Hailei , Lv Pengpeng
Published: February 2020

Silicon suboxide (SiOx, 0˂x˂2) is one of the promising anode materials for lithium-ion batteries (LIBs) due to its high specific capacity, low operating voltage (˂0.4 V) and rich abundance [1]. SiOx produces inert components (lithium oxide and lithium silicate) and nano-Si particles during initial lithiation/delithiation process. The former can act as buffer matrix to significantly reduce the volume change of nano-sized Si. Therefore, compared to pure Si, SiOx electrode shows relatively good cycling stability and thus appears promising for high energy density Li-ion batteries. Nevertheless, the poor intrinsic electronic and ionic conductivity of SiOx often leads to a low specific capacity and inferior rate capability [2]. In addition, the SiOx electrode cannot withstand long-period cycling due to the inevitable volume variation of SiOx.

In this work, we prepared core-shell SiOx-TiO2/C nanoparticles with unique watermelon-like structured by a simple sol-gel combined with a following carbon coating process. Ultrafine TiO2 nanocrystals are homogeneously distributed inside SiOx particles, forming SiOx-TiO2 dual-phase cores, which are coated with outer carbon shells. The incorporation of TiO2 component can effectively enhance the electronic and lithium ionic conductivities, release the structure stress caused by alloying/dealloying of Si component and maximize the capacity utilization by decreasing the O/Si ratio (x value). The synergetic combination of these advantages enables the synthesized SiOx-TiO2@C nanocomposite to have outstanding electrochemical performances, including high specific capacity, excellent rate capability and stable long term cycleability. A stable specific capacity of ~910 mAh g-1 is achieved after 200 cycles at the current density of 0.1 A g-1 . These results suggest the synthesized SiOx-TiO2/C composite is a promising high performance anode material for lithium ion batteries.
Improvement of Nickel-Rich Lithium Transition-Metal Oxide By Surface Modifications
Authors: Son You-Hwan , Hong Suk-Gi , Yu Byoungyong
Published: February 2020

Nickel-rich lithium transition-metal oxides for Li-ion batteries have been interested under intense commercialization as high-energy cathode materials because of their high specific capacity and relatively low cost. However, it still demands the necessities of higher energy density and more improved thermal stability to compete with requirements of smart mobile applications and x-EVs (extended electric vehicles). Accordingly, further research to increase both Ni content over 60 mol% and the cut off voltage to more than 4.5 V are being carried out to increase the energy density of Li-ion cells. However, two critical problems (structural instability both at >60 °C cycling and fast exothermic oxygen evolution at >200 °C) affecting such Ni contents should be solved. Here, we present electrochemical performance of a nickel-rich lithium transition-metal oxide (Ni content from 60 mol% to 91 mol %. Furthermore, by employing various surface chemistry on the cathode materials such as dry powder mixing, direct precipitation, colloidal deposition, Improvement of structural instability have been studied. The degradation of LiMO2 (M = Co, Ni, and Mn) cathode materials was strongly related to their surface chemistry. Among the proposed degradation mechanisms, the irreversible formation of inactive di- or tri-valant Ni species, particularly those localized in surface regions, are the products of such reactions. In other words, when the cathode materials are charged above 4.3 V, the cathodes could be partially transformed into an electrochemically inactive NiO-like phase or spinel structure with volumetric changes due to the migration of the Ni cations from the original transition metal (TM) layers. Our surface treatment cathode materials suppressed formation of NiO-like phase or spinel structure over 5% compared with bare cathode materials. The experimental results suggest one of way for applications that require high energy, long maintain life and excellent safety.
MOF-Derived Carbons As Ordered Isoreticular Structures for High Performance Sodium-Ion Battery Anode
Authors: Ingersoll Nolan , Underwood Robert , Warren Roseanne
Published: February 2020

Sodium-ion batteries present many advantages over lithium-ion batteries for large-scale, stationary energy storage, including higher abundance, lower cost, and simpler processing procedures of sodium compared to lithium. To date, the low energy density and long-term instability of sodium-ion batteries have prevented them from being commercially viable. One of the main research challenges for sodium-ion batteries is finding high capacity anode materials with good voltage window and cycle life when combined with sodium electrolytes. Early research on sodium-ion battery anodes strived to mimic electrode materials from lithium-ion batteries such as graphitic carbons; other simple structured carbons were then studied including hard carbons, petroleum cokes and carbon black1. However, these structures do not allow the larger sodium ion to diffuse and intercalate as easily as the smaller lithium ion. Research efforts have since broadened to structured carbons such as pyrolized glucose2, carbon microspheres3, silica templated carbon4, and others. These structures moderately improve performance but still face limitations including low available surface area, poor cycle performance, and complex fabrication.

We propose the application of metal organic framework-derived carbons (MOFDCs) as a large surface area, highly porous, and electrochemically stable material for the sodium-ion battery anode. MOF material is a tunable sacrificial template that, when carbonized, produces ordered, porous structures highly conducive to diffusion and intercalation of sodium ions. Here, we present two MOF structures that are used as sacrificial templates for carbonization, MOF-5 and ZIF-8. After carbonization, the materials were characterized via scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) (Figure 1) to confirm complete carbonization and structural consistency with the starting MOF material. Open cell charge-discharge tests (Figure 2) were performed using a sodium metal cathode and NaClO4 electrolyte to provide initial confidence in cycle stability and capacity. This work will present detailed characterization of MOF-5 and ZIF-8-derived carbons as sodium-ion battery anode materials, including charge-discharge measurements, cycle performance testing, rate performance testing, and electrochemical impedance spectroscopy measurements.

[1] M. M. Doeff, Y. P. Ma, S. J. Visco, L. C. Dejonghe, J. Electrochem. Soc. 1993, 140, L169.

[2] R. Alcantara, P. Lavela, G. F. Ortiz, J. L. Tirado, Electrochem. Solid-State Lett. 2005, 8, A222.

[3] Kun Tang et. al., Adv Energy Mater. 2012, 2, 873-877.

[4] S. Wenzel, T. Hara, J. Janek, P. Adelhelm, Energy Environ. Sci. 2011, 4, 3342.

Figure 1
In-Situ Diagnostics of Coupled Electrochemical-Mechanical Failures of Solid Electrolyte Interphases on Lithium Metal for Rechargeable Batteries
Authors: Xiao Xingcheng , Xu Jiagang , Li Binsong , Zhang Qinglin
Published: February 2020

Low cycle efficiency and dendrite growth are two critical barriers for rechargeable batteries using Li metal as negative electrodes. Current research efforts are mostly focused on how to suppress dendrite growth to improve the abuse tolerance, while the low cycle efficiency is temporally fixed by using large amount of extra lithium. However, the low cycle efficiency remains a significant technical challenge to achieve the high energy density (>350 Wh/kg) for Li-S or Li metal rechargeable batteries, and in new systems based on solid electrolytes, where the amount of excess Li must be minimized. we have developed a comprehensive set of in-situ diagnostic techniques and a model SEI/Li electrode system to understand the coupled mechanical/chemical degradation of SEI layer during Li cycling at different material level with controlled Li capacity. Based on those fundamental understanding, we developed some coating design strategies to achieve high cycle efficiency and extend the cycle life of high energy density batteries for EV application.
First-Principles Approach to Lithium Diffusion in Silicon
Authors: Kumar Vishank , Di Stefano Davide , Rignanese Gian-Marco , Gonze Xavier
Published: February 2020

Silicon has drawn a strong interest for its possible application as anode material for the next generation Li-ion batteries. The capacity of silicon is 10 times higher than graphite, however the kinetics of lithiation and delithiation of Si has not yet been fully understood. In this work, the temperature dependent diffusion coefficient of Li has been calculated, in bulk Si and LiSi phase, in the transition state theory framework. The energy barriers and pre-exponential factors have been obtained from total energy and phonon calculations, respectively, using the density functional theory (DFT). In LiSi case with multiple vacancy mediated diffusion pathways, kinetic monte carlo (KMC) simulations were used to calculate the effective diffusion coefficient.

Our results are in good agreement with the experimental data and suggest that in Li-Si system, quantum mechanical effects are only marginally significant. The current study shows a theoretical approach, which is computationally efficient and quantitatively accurate, to fill the gap due to limited studies of Li diffusion in lithiated LixSi phases.
Low Temperature Carbon and Glass Coating of SiO as Anode Material for High Performance Lithium-Ion Batteries
Authors: Liu Gao , Fang Shan
Published: February 2020

The carbon coating on silicon oxide (SiO) was designed to have both high conductivity and elastic polymeric properties. By sintering a pyrene-based homopolymer poly (1-pyrenemethyl methacrylate) at temperatures between 400–600° C and avoiding carbonization at temperatures >800 °C, we obtain a carbon coating which have some residue polymer properties and graphite-like structure, which effective improves the electrochemical performance of SiO for applications as the anode materials for Li-ion batteries. This anode electrode made with full carbon coated SiO materials achieves a high gravimetric specific capacity ~2000 mAh/g, areal capacity above 3 mAh/cm2, first cycle Coulombic efficiency of ∼62% during C/20 rate formation process. The Coulombic efficiency is above 99.8% when cycles at C/3 cycling rate after formation. We will report the carbon coating process, the coating properties at different coating and sintering conditions, and their electrochemical performances.
Amorphous Nanoporous Niobium Oxide Electrodes for Lithium-Ion Batteries
Authors: Barnes Pete , Dixon Kiev , Rill Laura , Karsann Devan , Xiong Claire
Published: February 2020

Lithium-ion batteries (LIB) are the leading technology in energy storage systems, however, they are plagued with several limitations including safety and stability. Metal oxide electrodes could provide a safer battery while maintaining high reversible capacity. When compared to the commonly used graphite, metal oxides provide a chemically inert anode with lithiation voltages well above that of Li plating. In addition, nanostructured metal oxides could enhance the performance of the battery by facilitating fast electron- and ion-transport to the active sites. One remarkable material yet to be fully researched by the battery community is nanostructured niobium oxides (Nb2O5). Recent studies have indicated that the electrochemical properties of crystalline Nb2O5 exhibit high capacitance and high rate capability. For example, orthorhombic niobium oxide (T-Nb2O5) has shown to participate in a two-dimensional Li+ transport within the crystal structure that causes no phase changes during the electrochemical reaction. This behavior causes the oxide to exhibit a high stability and power density. Moreover, nanostructuring of this oxide has proven to further increase the power and stability of the electrode material. We report here the results of our investigation into anodically grown nano-channeled niobium oxide (NCNO) as electrodes for LIBs. Through our conditions, it is possible to obtain a uniform amorphous oxide on the surface of niobium metal with the ability to control pore diameter. In a lithium half-cell, this amorphous material undergoes an irreversible phase transition driven by electrochemically cycling with Li. In addition, long-range order can be observed after discharge via structural characterization. Remarkably, the crystalline NCNO has exhibited dramatic improvements in stability compared to the amorphous oxide. This work aims to gain a fundamental understanding about the structural evolution of the metal oxide and charge transport mechanism.
Surface Chemical Modification of Si Nanoparticles for Application in Si-Based Anode
Authors: Jiang Sisi , Hu Bin , Tornheim Adam , Zhang Lu , Zhao Bin , Zhang Zhengcheng
Published: February 2020

Silicon (Si), with its extremely high theoretical specific capacity (up to 4200 mAhg−1), natural abundance and low toxicity, is considered as one of the most promising anode material candidates for next generation high energy density lithium-ion batteries. However, large volume expansion (~300 %) upon lithiation/delithiation makes it difficult for Si-based anode to maintain its capacity over extended cycles. Several possible mechanisms have been proposed to explain the rapid capacity fade in Si-based anode such as pulverization of the active materials, loss of electrical pathways caused by rearrangement of electrode structure, instability of the electrode/electrolyte interface or some combinations of these. While application of nano-structured Si (nanoparticles, nanowires) as anode largely resolved the pulverization issue, the use of nano-silicon inevitably increases the reactive surface between active materials and the electrolyte. Additionally, the continuous growth of solid-electrolyte-interphase (SEI) on the particle surface remains a significant cause for performance deterioration. Therefore, an increasing number of research has focused on the correlation between surface functionality of Si NPs and their electrochemical performance. Previous studies in this area mainly focused on the study of the inherent SiOx layers on Si NPs or the effect of electrolyte additives on the surface properties of Si NPs.

We take a different strategy to address the Si anode issue. We propose to chemically modify the surface of Si NPs and study how the chemical modification would affect the electrochemical performance of the Si-based anode. Commercially available Si NPs usually bear a native layer of silicon oxide on the surface of the particle. The first step in the surface modification of Si NPs is to enrich the surface silanol (Si-OH) groups as the new working platform. The silanol enriched surfaces will be converted to a variety of functional groups on the Si NPs. (Scheme 1). In this paper, we will present some preliminary results on the surface-modified Si NPs with methacrylate group and amine group and discuss the effects of the functional groups on the electrochemical performance of the Si anode.

Scheme 1. Chemical surface modification of Si NPs via silane chemistry.

Figure 1
Synthesis of Li-Ion Conducting Garnet Li7La3Zr2O12 Powders in Molten Salt Media: Implications for Future Li-Ion Batteries
Authors: Weller Jon Mark , Chan Candace K.
Published: February 2020

Recently, solid-state electrolytes have been a highly active area of research for future Li-ion batteries due to the potential for drastically improved energy density and safety. Among these materials, garnet structured lithium lanthanum zirconate (Li7La3Zr2O12, LLZO) shows particular promise owing to the high ionic conductivity of its cubic polymorph, inertness, and electrochemical stability against metallic lithium. Herein we report the facile preparation of phase-pure cubic LLZO via molten salt synthesis at temperatures substantially lower than conventional solid-state reactions. Fine powders of cubic LLZO were obtained with primary particle sizes in the submicron range. Depending on the consolidation conditions, dense ceramics with Li+ conductivity values above 0.371 mS cm-1 could be obtained. It is also observed that the effect of hydration has a profoundly deleterious effect on sintering and densification, and that this effect can be mitigated by the simple addition of LiOH before sintering to reverse hydration and aid densification. Qualitative discussions on the mechanisms of LLZO formation in the molten salt medium are discussed, in addition to implications for future scalable processing of LLZO electrolytes.
Investigation of CO2 Reduction Products in Lithium Ion Batteries Using Model Systems
Authors: Heiskanen Satu Kristiina , Lucht Brett L
Published: February 2020

Lithium ion batteries (LIBs) are essential to renewable energy development and are presently being utilized in more numerous applications including but not limited to consumer electronics and larger scale energy storage for backup residential power as well as electric vehicles. It is known that during cycling and especially at elevated temperatures, LIBs form gaseous reduction and degradation products which cause performance fade as well as unsafe intracellular pressure which can contribute to cell rupture. With cycling, carbonate based electrolytes decompose into CO2 and various other SEI components and vary in concentration dependent on the construction of the cell. Here, we present preliminary NMR, IR, and GC-MS results of studies performed on model systems consisting of lithium napthalenide, and solid sodium and lithium reacted with CO2 gas. We confirm here that the fate of evolved CO2 is to react with metallic lithium to form simple lithium carbonate and not more complex products such as lithium oxalate or lithium alkyl carbonates.
An Asymmetric Boron-Centered Ionic Additive Enables High-Energy Density Lithium-Ion Batteries
Authors: Han Jung-Gu
Published: February 2020

To cater for drastically growing demands for batteries with high energy density and long-term cycle life in transportation sector and large-scale energy storage systems, advancement of energy storage technologies is urgently required. Because ultimate energy density of batteries can be realized through developing high-capacity electrode materials, structural optimization of electrode materials that are capable of storing high energy has been intensively addressed. In this study, we demonstrate the significant roles of artificially constructed surface on high-capacity Li-rich cathodes preventing mechanical fracture of the cathode particles, mitigating the exposure of inner surface of the cathode toward electrolytes by intergranular cracking, and alleviating voltage decay of the cathode by phase transformation and vulnerable interface. Newly synthesized asymmetric boron-centered ionic additive with partially fluorinated malonate bonded to a central boron core is employed as a functional additive ensuring interfacial stability of high-capacity SGC anodes and Li-rich cathodes. The action of the protective surface layer created by asymmetric boron-centered ionic additive on intergranular cracking of Li-rich cathode particles synthesized via co-precipitation is explored using field emission scanning electron microscopy (FE-SEM). The unique feature of asymmetric boron-centered ionic additive -induced interfacial structure scavenging the oxygen species derived by Li2MnO3 and mitigating undesirable phase transformation of Li-rich cathodes are elucidated through in situ differential electrochemical mass spectrometry (DEMS) and high-resolution transmission electron microscopy (HR-TEM) analyses, respectively. Furthermore, we examine the chemistry of the surface of both electrodes evolved by asymmetric boron-centered ionic additive using ex situ X-ray photoelectron spectroscopy (XPS) and demonstrate the possible mechanisms of asymmetric boron-centered ionic additive constructing stable electrolyte-electrode interface.
Fabrication of Li-Polymer/Silica Aerogel Nanocomposite Electrolyte for an All-Solid-State Lithium Battery
Authors: Lim Ye Sol , Yoon Mi Young , Hwang Hae Jin
Published: February 2020

The demand for solid-state lithium ion electrolytes has increased owing to the safety concerns regarding the use of lithium ion batteries, which contain flammable organic solvent electrolytes. The liquid electrolyte can give rise to serious problems such as leakage and gas explosions when the operating temperature rises. The use of an organic or inorganic solid electrolyte not only results in improved safety, but also facilitates the fabrication of miniature batteries using thin films.

A solid electrolyte is required to have high lithium ion conductivity, mechanical strength, and transference number for lithium ions as well as good thermal/electrochemical stability and compatibility with the electrodes. Recently, polymer-based solid electrolytes have been widely studied for a possible replacement for liquid electrolytes. Various types of polymer-based solid electrolytes for lithium ion batteries exist, such as polyethylene oxide (PEO), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), and polyvinylidene fluoride (PVDF). Among them, the PEO-based polymer has attracted considerable attention, owing to its flexible skeleton and good interfacial stability with lithium electrodes. The mechanism of lithium ion conduction in the PEO-based solid-polymer electrolyte involves the coordination of the lithium ion from the Li-salt by the ether oxygen from the PEO, which moves according to the polymer segmental motion.

In this study, a polymer blend of PEO and PVDF, containing fluorine as a polar element, was fabricated to improve the dissociation degree of the Li-salt. In addition, we anticipate that the addition of ultra-porous silica aerogels, which has a high porosity and specific surface area, would increase the lithium ion conductivity. The silica aerogel was fabricated from water glass using the emulsion polymerization method, as was previously described by our research group. We also investigated the effects of the PEO:PVDF molar ratio, polymer:Li-salt molar ratio, and silica aerogel content on the structural, thermal, and electrical properties.