bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Keynote) A Path Forward to Low-Cobalt or Cobalt-Free Cathodes for Lithium-Ion Batteries
Authors: Manthiram Arumugam 
Published: February 2020

Lithium-ion batteries have become the choice of power source for portable electronics as they offer much higher energy density than other rechargeable systems. They are also in the process of transforming the transportation sector and beginning to penetrate the utility industry for grid storage of electricity produced from renewable sources like solar and wind. The lithium-ion battery industry is now based on layered LiMO2 cathodes with fractions of M = Mn, Co, and Ni as each of them has its own advantages and disadvantages. For example, Mn offers good chemical stability without oxygen release, while Co suffers from oxygen release on charging LiCoO2 beyond ~ 50% as the Co3+4+: t2g band overlaps with the top of the O2-:2p band. In contrast, Co offers good structural stability without migrating from the transition-metal layer to the lithium layer via the neighboring tetrahedral sites due to the high octahedral-site stabilization energy, while Mn migrates readily to the lithium layer resulting in a layered to spinel-like phase transition due to the low octahedral-site stabilization energy. Also, Mn is abundant, environmentally benign, and less conductive, while Co has limited abundance, is relatively toxic, and becomes metallic on charging. Ni is in between Co and Mn in all these criteria. To make use of the best out of each of these three ions, the industry is now based on LiNi1-y-zMnyCozO2 with (1-y-z) < 0.6 and a significant fraction of Co (z > 0.2). There is a significant drive to reduce the fraction of Co or eliminate it altogether and increase the fraction of Ni. However, LiMO2 cathodes with a high fraction of Ni suffer from a few serious issues: capacity fade, thermal instability, and air-reactivity due to (i) a series of phase transitions causing internal stress, (ii) high surface reactivity with the electrolyte resulting in the formation of thick solid-electrolyte interphase, and (iii) high surface reactivity with ambient air resulting in a significant amount of LiOH and LiHCO3 on the surface.
This presentation will first focus on a fundamental understanding of the bulk and surface instability of layered LiMO2 cathodes, employing advanced characterization tools, such as time-of-flight secondary ion mass spectrometry, x-ray photoelectron spectroscopy, and aberration-corrected transmission electron microscopy, to probe both the layered oxide cathode and graphite anode subjected in full lithium-ion cells to extended cycling (up to 1,500 cycles). The presentation will then focus on developing LiMO2 cathodes with a cobalt content of as low as 6% with appropriate cationic doping and surface stabilization. Finally, it will also present a path forward to develop cobalt-free LiMO2 cathodes. Based on the strategies, cathodes with capacities of as high as 220 mAh/g with good cycle life and air stability will be presented.
(Invited) Identification of Cathode Materials for Ca Batteries
Authors: Torres Arturo , Luque Javier , Tortajada José , Arroyo-de Dompablo M. Elena 
Published: February 2020

In the last years, concerns on Li availability have aroused the search for suitable alternatives to rechargeable Li-ion batteries. An attractive alternative is to combine sustainability with prospects of high energy density and develop metal anode technologies based on multivalent abundant elements such as Ca. The development of the Ca-ion technology requires technical advances to overcome the existing hurdles concerning electrolytes, electrodes and cell design1-3. Identifying cathode materials enabling effective diffusion of Ca2+ ions is far from being evident and, to the date, none of the investigated materials develops a stable high specific capacity with cycling 1-3.
In order to identify potential cathode materials for the Ca batteries, we have carried out a Density Functional Theory investigation to quickly screen a variety of structures and compositions. The screening started with a pre-selection of candidate compounds from the Inorganic Crystal Structure Database (ICSD). For the selected compounds, the general strategy is firstly to calculate average voltage and volume changes associated to the redox reaction. In a second step, DFT calculations for the promising materials are performed to gain information of electronic and ionic conductivities, crystal structure of reduced/oxidized phases and possible phase transformations. Fifty Ca-transition metal compounds including oxides, sulphides, nitrides, carbonates and phosphates were preselected from the ICSD. Out of this set, 25 ternary oxides and the minerals belonging to the pyroxene, garnet and double carbonates groups have been analysed in deep. The results will be discussed in this communication.
Acknowledgments: Authors are grateful for financial support from European Union H2020-FETOPEN funded project CARBAT-766617.
References:

A. Ponrouch and M. R. Palacin, Current Opinion in Electrochemistry, 2018, 9, 1-7.

R. J. Gummow, G. Vamvounis, M. B. Kannan and Y. He, Advanced Materials, 2018, 30, e1801702.

P. Canepa, G. S. Gautam, D. C. Hannah, R. Malik, M. Liu, K. G. Gallagher, K. A. Persson and G. Ceder, Chemical Reviews, 2017, 117, 4287-4341.
(Invited) Understanding Interfacial Reaction of LiCoO2 Positive Electrode in Aqueous Lithium-Ion Batteries
Authors: Byon Hye Ryung , Oh Hyunjung , Yamagishi Hirona , Yamanaka Keisuke , Ohta Toshiaki 
Published: February 2020

Since the risk of catch fire using non-aqueous electrolyte solution, aqueous solution-based rechargeable lithium batteries (ARLB) have been highlighted. However, the conventional positive electrodes of lithium transition-metal oxide such as LiCoO2 (LCO) and LiNi1/3Mn1/3Co1/3O2 (NMC) have suffered from poor cyclability in aqueous medium. Representatively, the layered two-dimensional structure of LCO shows notably poor stability, possibly due to the surface degradation from water [1] and proton [2]. The understanding of interfacial reaction of LCO in the aqueous electrolyte solution is still superficial however.
Here we present degradation phenomena of LCO electrode in aqueous medium using various X-ray measurement techniques, and suggest the solution to avoid such an irreversible electrochemical reaction. The aqueous solution was prepared with 0.5 M lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and pH was controlled to ~6.8 and 10. In both cases, there was no evidence for the formation of cathode-electrolyte interphase (CEI) on LCO in contrast to the one with non-aqueous electrolyte solution. The direct contact of aqueous electrolyte solution to LCO surface results in the short-range disorder of LCO structure such as the distortion of octahedral CoO6, and irreversible Li+ desertion during 10 cycles. To improve electrochemical reversibility and structural stability of LCO, we prepared the organic protection layer that opened the Li+ mass transport route while inhibiting H2O contact from hydrophobic surface. As a result, the capacity retention was improved to ~85% during 30 cycles at pH ~ 6.8. Furthermore, we developed the way to protect LCO surface by anion engineering and in the absence of protection layer, which give insight into the inner Helmholtz plane (IHP) structure and its effect for LCO degradation in aqueous medium.
Direct Liquid Fuel Cells By Using Hypophosphites
Authors: Wang Ren-He , Wu Meng-Jia , Haller Servane , Metivier Pascal , Wang Yong-Gang , Xia Yong-Yao 
Published: February 2020

Direct liquid fuel cells (DLFCs) are promising power sources for future portable, wearable or implantable electronic devices owing to their high energy density and low emissions. Large efforts have been given for the development of DLFCs since 1990s, however the wide spread commercialization of DLFCs is still limited by the high cost coming from the expensive noble metal catalysts and proton exchange membranes. Furthermore, the safety risks related to organic fuels (methanol, ethanol and formic acid), such as toxicity and flammability, bring up tremendous consideration in fuel cell design, fuel distribution and transportation [1]. Finally, the emission of CO2 is inevitable by using organic fuels, which escalates to Green House Effect.
In this work, we proposed a new category of inorganic fuels for DLFCs. Hypophosphite is a type of food additive, therefore no safety hazards at all, and is also a strong reductant whose electrochemical oxidation reactivity is strongly correlated to metallic palladium [2]. Moreover, the inorganic fuels could realize “Zero Emission” after “Burning”. From thermodynamic calculations, the theoretical cell voltage and volumetric energy density at 1M are 2.05 V and 188 Wh/L at standard conditions, which are comparable and even better than the data of DMFCs (Direct Methanol Fuel Cells).
The unique electrochemical oxidation behavior of hypophosphites on Pd catalyst brings advantages in simplifying fuel cell structure and broadening our selections of cathodic catalysts for ORR (Oxygen Reduction Reaction). Herein, we report the investigation of catalyst design and cell design of a novel membrane-free Direct Hypophosphite Fuel Cell (DHPFC), which showed an open circuit voltage of 1.0 V and a maximum power density of 32 mW cm-2 under air flow at 25 oC. The oxidation mechanism of hypophosphites on Pd was also studied in this work.
This work is financially sponsored by Solvay and “Shanghai Rising-Star Program” (16QB1404600).

Reference:

[1] G. L. Soloveichik, Beilstein J. Nanotechnol.
2014, 5, 1399-1418.
[2] N. Fujiwara, Z. Siroma, T. Ioroi, K. Yasuda, J. Power Sources
2007, 164, 457-463.
Surface Modulation of PdCu Nanocatalysts Via the Crystal Structure Change for Lithium-Oxygen Battereis
Authors: Park Mihui , Liang Chaoping , Adjei Agyeman Daniel , Cho Kyeongjae , Kang Yong-Mook 
Published: February 2020

Palladium-copper (PdCu) alloys have two representative crystal structures; one is body-centered cubic (bcc), the other is face-centered cubic (fcc) even though both Pd and Cu originally have fcc crystal. The fcc PdCu alloys have disordered structure within which Pd and Cu have solid-solution in fcc lattice, whereas the bcc PdCu alloys have ordered structure which consists of alternative layers with either Pd or Cu atoms.
In particular, bcc PdCu alloys have occasionally shown superior performance to fcc PdCu alloys since the unique ordered structure of bcc has isolated Pd on the surface. Most of bcc PdCu alloys have been synthesized for structural transformation by annealing or seed-growth method of fcc PdCu alloys with inevitable grain growth, uneven surface structure and particle size distribution. Despite these limitations, the Pd on the bcc surface which is provided charge flow from Cu serves as an active site for catalytic reaction, which is highly favorable for lithium-oxygen battery. However, the same size of fcc and bcc PdCu alloys is quite difficult to be obtained since the crystallites larger than 20 nm favor the ordered bcc structure with lower symmetry. Thus, bcc PdCu alloys in nanoscale have been rarely reported, consequently fcc and bcc PdCu nanoparticles (NPs) have never been properly compared until now.
In this study, we successfully synthesize fcc and bcc PdCu alloys in nanoscale through precisely adjusting the driving force for reducing organometallic complex. The bcc PdCu NPs with higher surface energy govern the growth thermodynamics of discharge product and greatly improved battery performance based on density functional theory calculation and experimental proof. This study provides critical descriptor on material design in the perspective of modulating surface structure via crystal structure to tune its intrinsic properties.
Thermal-Runaway-Free Lithium Ion Battery Cell
Authors: Qiao Yu , Wang Meng , Yi Haozhe 
Published: February 2020

For large-format high-energy lithium-ion battery (LIB), formation of internal short circuit (ISC) often results in catastrophic thermal runaway, leading to fire and/or explosion. It imposes touch challenges to system safety and robustness for electric vehicles, personal electronics, large-scale energy storage systems, to name a few. It is desirable to prevent thermal runaway at the electrodes level, through cell engineering.
Recently, we developed “super-safe” LIB cells with functional current collectors (FCC). Independent of the active materials layers, FCC contains physical features that can favorably control the damage mode of electrodes. Once ISC is formed, FCC works as an effective “fuse” that shuts down the internal short current immediately, before heat generation even begins.
The advantages of FCC include:

FCC is highly effective. Our experiments on FCC-based pouch cells showed only mild temperature increase upon severe impact penetration of metal; reference cells exploded instantaneously under the same abuse testing condition.

FCC does not affect the cell cycle life, since the thermal runaway mitigation process is non-chemical and decoupled from the electrochemical reactions.

FCC does not affect the mass production of active materials and other cell components. The failsafe mechanisms are carried entirely by the current collectors.

Similar FCC technique can be applied to a wide variety of battery chemistries, including future high-energy batteries.

FCC adds little mass or volume to battery cell, and is cost efficient.

FCC can be produced through a roll-to-roll procedure.
Studies of Rollover Failure in Lithium-Ion Cells
Authors: Ma Xiaowei , Harlow Jessie , Keefe Alison S , Li Jing , Glazier Stephen , Ma Lin , Hall David S , Aiken Connor P , Genovese Matthew , Cormier Marc , Dahn Jeff R 
Published: February 2020

Sometimes lithium-ion cells show a very insidious type of failure where they display close to 100% of their capacity for about 1000 charge-discharge cycles and then lose most of their capacity in only 100 cycles or so with very little warning to the user. This is called “rollover failure” [1]. Experimental observations show that the likelihood of rollover failure increases with upper cut-off potential of lithium-ion cells and decreases with LiPF6 concentration in a reasonable range.
Since increasing the upper cut-off potential is essential to increase the energy density of lithium-ion cells, a full understanding of the causes of rollover failure is essential, but this is proving very difficult to attain.
The phenomenon of rollover failure during long-term cycling will be discussed based on a comparison among Li(Ni0.5Mn0.3Co0.2)O2/graphite pouch cells with different electrolyte and electrode designs undergoing different testing protocols. A few facts can be gleaned from the data:

For cells charged to the same upper cut-off potential, those showing the highest rates of electrolyte oxidation at the positive electrode (due to electrolyte or cell chemistry changes) are most prone to rollover failure.

Any cell is more prone to rollover failure if charged to a higher potential. This increases the rate of electrolyte oxidation at the positive electrode.

When rollover occurs, the impedance at the positive electrode always increases significantly while the impedance at the negative electrode side is relatively stable.

Lithium metal plating at the negative graphite electrode surface is not always observed during the initial stages of rollover failure.

Increasing the LiPF6 concentration properly can delay the occurrence of rollover failure. For example Figure 1 shows the impact of increasing salt concentration from 1.2 M to 1.5 M.

Based on these and other observations, some simple models that integrate electrolyte oxidation, impedance growth and lithium ion diffusion can be postulated but further experimental studies using a variety of methods are required for full understanding.
[1] J. C. Burns, A. Kassam, N. N. Sinha, L. E. Downie, L. Solnickova, B. M. Way, J. R. Dahn, J. Electrochem. Soc., 160, A1451-A1456 (2013).
Figure 1. Capacity (top panels), normalized capacity (middle panels) and ΔV (bottom panels) versus cycles of Li[Ni0.5Mn0.3Co0.2]O2/graphite pouch cells filled with 1.2 M LiPF6 or 1.5 M LiPF6 in EC:EMC:DMC (25:5:70 vol.%) and 2 wt.%VC+1 wt.%DTD. Cycling was performed between 3V and 4.1V or 4.3V at 20 oC with charging/discharging rates at 1C/1C.

Figure 1
Effect of Processing Route and Dopant on Capacity/Fading of Layered Oxide Cathode
Authors: Fung Kuan-Zong , Fung Kenneth , Yang Hui-Ju , Chang Chia Chin , Tsai Shu-Yi 
Published: February 2020

Although several crystal structures have been demonstrated and shown reversible capabilities during lithiation/delithiation processes in cathode of Li ion batteries; oxides with layered structure still remain the ones that provide higher capacities.
However, higher charging capacity means the creation of more ionic/electronic defects in both cation and/or anion sublattices of layered structure. Higher defect concentration in either cation or anion sublattices tend to destabilize its crystal structure. As a result, the phase change is frequently observed in repeatedly cycled cathode. Furthermore, the phase-changing layered cathode tends to show the capacity fading after cycling tests. Based on defect consideration, the stability of highly defective materials may be enhanced by using dopant and/or better processing control. In this study, the electrical/electrochemical/structural properties of NMC 811 and LiNi0.8Co0.15Al0.05 will be investigated. Since Ni content is fixed at 80% in the transition metal ion layers in these cathode materials, the variation in electrochemical properties will be caused by the minor elements/dopants such as Mn and Al. First, the electrical measurement of NMC 811 and LiNi0.8Co0.15Al0.05 are conducted using sintered disc. Assembled cells using above-mentioned cathode and Li anode with desired liquid electrolyte will be tested and cycled. XPS, SEM and XRD analyses will be conducted on as-assembled as well as cycled cells. The analyzing results will be illustrated based on the chemical characteristics of doping ions and the accompanying defects created.
Three-Dimensional Porous Si with in Situ Decorated Carbon Nanotubes As Anode Materials for Li-Ion Batteries
Authors: Su Junming , Huang Tao , Yu Aishui 
Published: February 2020

Rechargeable Li-ion Batteries have been widely used as energy storage devices for portable electronics owing to their higher energy density and long cycle life. However, higher capacity cathode and anode materials are required for their large-scale application in electrical vehicles (EVs)[1-3]. Currently, commercialized Li-ion batteries with graphite as an anode material are still far from practical use in EVs because of their limited capacity and unsatisfactory cycling performance. Many anode materials with higher theoretical capacities have been proposed. Among them, silicon is more attractive because of its highest theoretical specific capacity (~4200 mAh/g), low redox potential (< 0.5 V versus Li/Li+), and abundance as a mineral resource[4-5]. However, silicon has two main defects: low electronic conductivity and very large volume changes (~300%) during lithiation/delithiation. In this work, we prepared three-dimensional porous Si with in situ decorated carbon nanotubes. Si clusters were obtained from commercial Al-Si alloy spheres by pickling aluminum component. Then, carbon nanotubes were in situ grown on Si cluster by a chemical vapor deposition (CVD) process using toluene as a carbon source and Ni particles as a catalyst. The obtained material was denoted as Si cluster/CNTs. For comparison, Si cluster coated with carbon layers by the same CVD process without Ni catalyst was also prepared, denoted as Si cluster/C. The electrochemical results demonstrated that Si cluster/CNTs had longer life and higher rate cycling performance (2000 mAh g-1 at 0.5 A g-1 after 250 cycles) than Si cluster and Si cluster/C. The cluster structure could effectively relieve the volumetric change during charge-discharge process. The carbon nanotubes could improve the electronic conductivity and stabilize the structure of Si cluster in Si cluster/CNTs.
References
[1] Park, M.-H.; Kim, M. G.; Joo, J.; Kim, K.; Kim, J.; Ahn, S.; Cui, Y.; Cho, J. Nano Lett. 2009, 9, 3844−3847.
[2] Goodenough, J. B.; Kim, Y. Challenges for Rechargeable Li Batteries. Chem. Mater. 2010, 22, 587−603.
[3] Zuo, X.-X, Zhu, J., Muller-Buschbaum, P., Cheng, Y.-J., Nano Energy, 2017, 31, 113-143
[4] Zhou, M.; Cai, T.; Pu, F.; Chen, H.; Wang, Z.; Zhang, H.; Guan,S. ACS Appl. Mater. Interfaces 2013, 5, 3449−3455.
[5] Szczech, J. R.; Jin, S., Energy Environ. Sci. 2011, 4, 56−72.
(Invited) Generation and Evolution of Materials in the Anode Solid Electrolyte Interphase (SEI) of Lithium Ion Batteries
Authors: Lucht Brett 
Published: February 2020

A solid electrolyte interphase is generated on the anode of lithium ion batteries during the first few charging cycles. The presence and stability of the solid electrolyte interphase (SEI) is critical to the performance of the battery. Despite thorough investigation of the SEI for over 20 years, the mechanism of formation and function are still relatively poorly understood. We have investigated the structure of the initial SEI on graphite and silicon electrodes along with changes which occur to the SEI upon additional cycling via a combination of ex-situ surface analysis techniques. The investigation of SEI provides significant insight into the structure and properties of the anode SEI.
The one electron reducing agent, lithium napthalenide has been used to independently prepare the reduction products which constitute the SEI. The initial reduction product of ethylene carbonate is lithium ethylene dicarbonate (LEDC). However, the thermal decomposition of LEDC and related lithium alkyl carbonates in the presence of LiPF6 generates a intricate mixture of compounds which greatly complicates the structure of the SEI. The reduction products and their subsequent thermal decomposition products have been thoroughly investigated via a combination of NMR, XPS, IR-ATR, TGA, and GC-MS. Mechanisms for the generation of the complicated mixture of products will be discussed.
Thermal behavior of the SEI on a silicon electrode for Lithium ion batteries has been investigated by TGA. In order to provide a better understanding of the thermal decomposition of the SEI on silicon, the thermal decomposition behavior of independently synthesized lithium ethylene dicarbonate (LEDC) was investigated as a model SEI. The model SEI (LEDC) has three stages of thermal decomposition. Over the temperature range of 50~300oC, LEDC decomposes to evolve CO2 and C2H4 gasses leaving lithium propanoate (CH3CH2CO2Li) and Li2CO3 as solid residues. The lithium propanoate decomposes over the temperature range of 300~600oC to evolve pentanone leaving Li2CO3 as a residual solid. Finally, the Li2CO3 decomposes over 600oC to evolve CO2 leaving Li2O as a residual solid. A very similar thermal decomposition process is observed for the SEI generated on cycled silicon electrodes. However, two additional thermal decomposition reactions were observed characteristic of LixPOyFz at 300oC and the polyimide binder at 550oC. TGA measurements of Si electrodes after various numbers of cycles suggest that the LEDC on Si electrodes thermally decomposes during cycling to form lithium propanoate and Li2CO3, resulting in increased complexity of the SEI.