Li-ion Secondary Batteries Research Articles

Lithium isotopic records of anthropogenic activity in the Xiaoqing River basin, eastern China

The environmental impact of the discharge of lithium (Li) by anthropogenic activity has been overlooked. By analyzing Li concentrations and isotope compositions (δ7Li) of water and sediment samples, this study evaluates the influence of anthropogenic Li discharge on the Xiaoqing River and Laizhou Bay, which are heavily polluted areas in China. High Li concentrations of the river water (up to 7.8 μmol/L) should be linked to anthropogenic Li discharge. However, no profound δ7Li anomalies were observed, preventing identification of the exact discharge sources. In the river sediments, Li concentrations (19.0–45.0 μg/g) were weakly correlated with Zn, Cu, and Cr concentrations, whereas δ7Li values ranged from 0.6 ‰ to 13.9 ‰ with high values being accompanied by high contents of total organic carbon and heavy Cr isotope compositions (δ53Cr). All these point to significant influence of anthropogenic activity on the Li budget of river sediments. A simple mass balance calculation indicates that smelters, Li-bearing therapeutic drugs, and secondary Li-ion batteries are the main anthropogenic Li sources. In contrast to river sediments, marine sediments in the Laizhou Bay were broadly homogeneous at both spatial and temporal scales, indicating no significant influence of anthropogenic Li discharge. Overall, our data indicate that Li isotope systematics in river sediments, especially sediments near intense anthropogenic activity, are effective at tracing potential Li pollution and can help obtain accurate results for environmental inspection.

(Invited) Design of Specific Polymer Binders for Stabilization of Si Based Anode in Lib

In recent years, intense efforts have been focused on stabilization of silicon-based anode in Li ion secondary batteries due to their remarkably high theoretical capacity. At the same time, strategy has not yet been established on how to stabilize the silicon based anode sufficiently during long cycles so that it will be feasible for practical use. In this talk, several different approaches on stabilization of silicon-based anode will be introduced both in terms of polymer binders design and active materials design. Our group synthesized several self-healing polymer binder and polymer coating material which are efficient for the use in silicon-based anode. Poly(borosiloxane) (PBS)1 was prepared by dehydrocoupling polymerization between mesitylborane and diphenylsilanediol in the presence of transition metal catalyst. PBS was found to show self-healing property at 45oC when coated onto Si electrode. When PBS coated Si electrode was employed for anodic half cell (Si/EC:DEC (1/1=v/v)/Li), it showed much improved durability when compared with PVDF coated Si based cell or bare Si based cell. We also reported a design of BIAN (bis-imino-acenaphthene) based conjugated polymer (P-BIAN) /Poly(acrylic acid) (PAA) composite binder for Si based anode2,3. Due to combination of n-type imine-based conjugated polymer (H-bonding acceptor) and PAA (H-bonding donor), synergistic effect in stabilization of Si/C composite anode was observed due to both of desirable electronic structure of P-BIAN and H-bonding based self-healing properties. In this system, anodic half cell delivered specific discharging capacity of above 2000 mAhg-1 for 600 cycles. As alternative approaches, we are also working on preparation of specific Si based anodic active materials which showed extremely high durability. b-SiC/N-doped carbon4 was found to show excellent durability even in the presence of conventional binder materials due to restricted volumetric changes of b-SiC during lithiation/delithiation. We also report coating of mechanically highly robust silicon oxycarbide on micro silicon5, which was also found to be quite effective.References1) Patnaik, S. G.; Jayakumar, T. P.; Sawamura, Y. Matsumi, N. ACS Appl. Ener. Mater. 2021, 4, 2241.2) Gupta, A.; Badam, R.; Matsumi, N. ACS Appl. Ener. Mater. 2022, 5, 7977.3) Gupta, A.; Badam, R.; Nag, A.; Kaneko, T.; Matsumi, N. ACS Appl. Ener. Mater. 2021, 4, 22314) Nandan, R.; Takamori, N.; Higashimine, K.; Badam, R.; Matsumi, N. J. Mater. Chem. A. 2022, 10, 5230.5) Nandan, R.; Takamori, N.; Higashimine, K.; Badam, R.; Matsumi, N. J. Mater. Chem. A. 2022, 10, 15960.

(Invited) Electrochemical and Postmortem Analyses of 18650-Type Li-Ion Secondary Battery Degraded at High and Low Temperature Environments

Lithium-ion secondary batteries have been widely used as small-size and lightweight energy sources for applications of laptops, robots and electric vehicles. For realizing a high performance, the energy sources are required to have high energy density with high reliability. The batteries are charged and discharged repeatedly based on anode and cathode reactions, which both accompany side reactions to a greater or less extent. The battery degradation phenomena are well explained by kinetics of chemical reactions evaluated by non-destructive examination.1 To understand the battery degradation mechanism for developing a durable one, it is indispensable to clarify the side reactions occurred to cause the degradation. For that purpose, differential capacity curves (dQ/dV vs. V) and electrochemical impedance spectroscopy (EIS) were employed as electrochemical measurements.2 To support the mechanism estimated by the measurements, postmortem analyses were conducted using SEM, XPS and XRD. These investigations were performed to the commercially available 18650 cell consisting of Li(Ni, M)O2 (M: metal elements to partially replace Ni) as the cathode material and graphite as the anode material. The employed loads were calendar deterioration and charge/discharge cycle deterioration.3,4 Firstly, the calendar deterioration behavior of the 18650-type battery was evaluated by storing them at 80 °C for different durations. The results indicate that the battery capacity decreased with the increasing number of storage days in a high-temperature environment. From the differential capacity curves, we found that the change in the overvoltage, which was caused by the electrode reaction, that appeared at approximately 4.2 V was most significant. To analyze this phenomenon, EIS of the deteriorated battery was measured at 4.2 V, and it was confirmed that the cathode-based resistance of the battery increased significantly at this potential. Furthermore, postmortem analysis revealed that the cathode active material of the tested batteries clearly deteriorated; however, no significant change in the active material in the anode was observed. Therefore, it is considered that the cathode materials of nickel-based lithium-ion secondary batteries deteriorate by storing at 80 °C, thereby resulting in reduced battery capacity and increased cathode component resistance after storing at high temperatures.Secondly, cycle deterioration behaviors of the lithium-ion batteries in different operating temperature were studied. Compared with the deterioration in the high-temperature range, the degree of decrease in battery capacity at the low temperature was greater, and the more severe the deterioration was shown at temperatures far from the safe temperature range. From the differential capacity analysis, the peaks corresponding to the anode was significantly reduced at the voltage of the initial charging stage after cycle deterioration at low temperature. This means that the lithium ions intercalated into/deintercalated from the graphite layer decreased. In addition, EIS of the batteries before and after cycle deterioration was measured at each deteriorated temperature. Based on these, postmortem analysis was conducted with a major focus on the anode after 20-cycle deterioration at low temperature. From the SEM observation, the anode can be known to grow thicker with generating cracks and gas pockets. According to the XPS measurements, it is found that Li2CO3 and LiF are generated by decomposition of electrolytic solution at the anode surface.Overall, it was clarified that the deterioration at high temperature affected the cathode and that at low temperature affected the anode.

Transport in Ion-Exchange Membranes with Ternary Solutions of Salt, Water and Alcohol Relevant for (Reverse) Electrodialysis

Leaching of Li-ion battery components in sulfuric acid followed by precipitation with ethanol has been proposed as a route for material recycling [1]. Cobalt, copper and lithium were then recovered as sulphate salts. The final mixture of dilute salts, water and ethanol may be further processed using ion-exchange membranes and electrodialysis to separate salts and water from ethanol, with the aim of increasing salt recovery and allowing for the re-use of the spent ethanol. We investigate the effect of alcohol on the transport numbers, resistance and the thermodynamic properties of the membrane and the aqueous solutions of alcohol, water and salt. This has implications for the electrodialysis of alcohol-containing mixtures, as well as for the application of this working fluid to a power-producing reverse electrodialysis system.[1] S. Aktas, D. J. Fray, O. Burheim, J. Fenstad & E. Açma, Recovery of metallic values from spent Li ion secondary batteries.

Data-driven direct diagnosis of Li-ion batteries connected to photovoltaics

Photovoltaics supply a growing share of power to the electric grid worldwide. To mitigate resource intermittency issues, these systems are increasingly being paired with electrochemical energy storage devices, e.g., Li-ion batteries, for which ensuring long and safe operation is critical. However, in this operation framework, secondary Li-ion batteries undergo sporadic usage, which prevents the application of standard diagnostic methods. Here, we propose a diagnostic methodology that uses machine learning algorithms trained directly on data obtained from photovoltaic charging of Li-ion batteries. The training is carried out on synthetic voltage data at various degradation conditions calculated from clear sky model irradiance data. The method is validated using synthetic voltage responses calculated from plane of array irradiance observations for a photovoltaic system located in Maui, HI, USA. We report an average root mean square error of 2.75% obtained for more than 10,000 different degradation paths with 25% or less degradation on the Li-ion cells.

Chemical lithiation methodology enabled Prussian blue as a Li-rich cathode material for secondary Li-ion batteries

Prussian blue analogues (PBAs) have been attracting intense attention owing to its two-electron storage capability and considerable cost advantage, especially in Na-ion and K-ion batteries. However, things are quite different when it comes to Li-ion batteries, because lithium-containing Li4Fe(CN)6 precursor is not commercially available and thus the traditionally prepared Li-deficient FeFe(CN)6 products fail to couple with commercial graphite anode for full cells. Herein, we put forward a potential matching principle to guide the chemical pre-lithiation of FeFe(CN)6 into a Li-rich LixFeFe(CN)6 (x varies from 0 to 2) cathode. The potential matching principle was convincingly confirmed by theoretical analysis and over-lithiation experiments. Perylene-Li reagent was elaborately screened to serve as both Li+ and electron donor for controllable chemical lithiation reaction while preserving the host framework stable. Our work provided a general guiding principle and effective methodology for controllable synthesis of Prussian blue analogues in gradient lithiation depth, which could be served as a platform for in-depth, systematic and comprehensive research on the properties of PBAs materials.

2-dimensional biphenylene monolayer as anode in Li ion secondary battery with high storage capacity: Acumen from density functional theory

Energy storage methods are cardinal for the mitigation of intermittency of renewable energy and among many technologies available, Li-ion batteries (LIBs) dominate the market on the account of their significant attributes. However, there is still room for improvement in their performance for high-end applications. Modifying the anode material can significantly affect the overall battery performance. It becomes necessary to discover a satisfactory negative electrode for more productive Li ion batteries. The present density functional theory based work examines the potential of a novel, experimentally fabricated 2D monolayer, Biphenylene having sp2 carbon atoms arranged periodically in four, six, and eight-membered rings, for its application in LIBs as adequate anode. Phonon spectrum and ab initio molecular dynamics (AIMD) signify the dynamic and thermal stability of the nanosheet. The band structures and density of states reveal the metallic nature which is maintained after the Li (adatom) adsorption as well. The mean adsorption energies for subsequent loading of Li over the sheet vary from -0.44 to -0.15 eV. The appreciative interactions between the adatom and the monolayer are well authenticated by charge transfer analysis. The Biphenylene monolayer is observed to offer a low diffusion barrier of 0.23 eV for the Li atoms. High storage capacity of 1302 mAhg−1 (almost 3.5 times higher than that of marketable Graphite), a low voltage of 0.34 V, and low volume changes (less than 3%) are noticed. This comprehensive study authenticates the capability of the 2D carbonous Biphenylene sheet as a suitable LIB negative electrode.

Lithiation and Delithiation Behavior of Porous Li-Cu Anode in Li-ion Battery Systems

Li-metal anodes exhibit the potential to increase the efficiencies of Li-ion battery systems. However, the commercialization of Li metal is hindered by several inherent challenges, such as the formation of inhomogeneous Li dendrites and considerable volume expansion during deposition and dissolution. Fabrication of 3D porous structures is a promising technique that resolves these problems, however, no attempts to replace graphite anodes with porous Li-Cu anodes in Li-ion secondary battery systems are reported. Moreover, the charging/discharging behaviors of porous Li-Cu anodes are not yet completely understood. In this study, the changes in a porous Li-Cu anode in a symmetric cell during lithiation and delithiation are investigated. The porous Li-Cu anode suppresses dendrite growth and volume changes via the filling and evacuation of the pores around the Li particles within and on the surface of the anode, and thus, the higher porosity results in a larger capacity. The Li-Cu anode displays a stable cyclability at 1 mA cm–2 with a capacity of 1 mA h cm–2 over 700 h. The porous Li-Cu anode exhibits promise in replacing graphite in Li-ion secondary battery systems.

Hollow nanostructured NiO particles as an efficient electrode material for lithium-ion energy storage properties.

This work has developed a straightforward approach to obtaining NiO hollow structures by using Li2O2 as an easily removable template. The easy availability and electrochemically active nature of NiO have attracted researchers' attention as an anode electrode for Li-ion storage applications, including Li-ion secondary batteries (LIBs) and for Li-ion hybrid supercapacitors (LiHSCs; which offer higher power densities than LIBs without compromising energy density). However, NiO usage has been limited to its low reaction reversibility, poor conductivity, and conversion reaction capability. Recently, hollow nanostructured materials have attracted attention as efficient battery materials due to their fascinating structural features. This study presents a modified Li2O2-assisted method to obtain porous open 3D architectures of NiO nanostructures. The resultant hollow structures are electrochemically studied as an anode for a LIB, exhibiting excellent stability over hundreds of cycles. The result is recognized as one of the finest among NiO anodes reported. Also, NiO hollow structures studied as anodes for LiHSC devices fabricated with activated carbon cathodes exhibit an outstanding comprehensive electrochemical performance which is better than the typical LIB and supercapacitors.

Eldfellite NaV(SO4)2 as a versatile cathode insertion host for Li-ion and Na-ion batteries

Eldfellite NaV(SO4)2 has been shown to be a versatile cathode insertion host for secondary Li-ion and Na-ion batteries.

Preparation of size-controlled LiCoPO4 particles by membrane emulsification using anodic porous alumina and their application as cathode active materials for Li-ion secondary batteries.

Membrane emulsification using anodic porous alumina is an effective method for preparing monodisperse droplets with controlled sizes. In this study, membrane emulsification using anodic porous alumina was applied to the preparation of size-controlled particles composed of composite metal oxides. To obtain size-controlled composite metal oxide particles, membrane emulsification was performed using an aqueous solution containing a water-soluble monomer and metal salts as a dispersed phase. After the membrane emulsification, composite metal oxide particles were obtained by solidifying the droplets in a continuous phase and subsequent heat treatment. Here, as a demonstration of this process, the fabrication of size-controlled LiCoPO4 particles, which are considered high-potential cathode active materials for Li-ion secondary batteries (LIBs), was investigated. The application of the obtained LiCoPO4 particles as cathode active materials for LIBs was also investigated. The results of this study showed that LiCoPO4 particles with controlled sizes could be fabricated on the basis of this process and that their cathode properties could be improved by optimizing the heat treatment conditions and particle sizes. According to this process, size-controlled particles composed of various metal oxides can be fabricated by changing the metal salt in the dispersed phase, and the resulting size-controlled particles are expected to be applied not only as cathode active materials for LIBs but also as components of various functional devices.

Valorizing the carbon byproduct of methane pyrolysis in batteries

While low-cost natural gas remains abundant, the energy content of this fuel can be utilized without greenhouse gas emissions through the production of molecular hydrogen and solid carbon via methane pyrolysis. In the absence of a carbon tax, methane pyrolysis is not economically competitive with current hydrogen production methods unless the carbon byproducts can be valorized. In this work, we assess the viability of the carbon byproduct produced from methane pyrolysis in molten salts as high-value-added anode or conductive additive for secondary Li-ion and Na-ion batteries. Raman characterization and electrochemical differential capacity analysis demonstrate that the use of molten salt mixtures with catalytically-active FeCl3-or MnCl2 result in more graphitic carbon co-products. These graphitic carbons exhibit the best electrochemical performance (up to 272 mAh/g of reversible capacity) when used as Li-ion anodes. For all carbon samples studied here, disordered carbon domains and retained salt species trapped and/or intercalated into the carbon structure were identified by X-ray photoelectron and multinuclear solid-state nuclear magnetic resonance spectroscopy. The latter lead to reduced electrochemical activity and reversibility, and poorer rate performance compared to commercial carbon anodes. The electronic conductivity of the pyrolyzed carbons is found to be highly dependent on their purity, with the purest carbon exhibiting an electronic conductivity nearly on par with that of commercial carbon additives. These findings suggest that more effective removal of the salt catalyst could enable applications of these carbons in secondary batteries, providing a financial incentive for the large-scale implementation of methane pyrolysis for “low-carbon” hydrogen production.

Analysis of Mechanical Properties and Electrochemical Behavior of Li-Ion Secondary Batteries According to Particle Size of Silicon Anode

Li-ion secondary batteries have been applied to various electronic devices since Sony released a lithium secondary battery using hard carbon as an anode in 1991. The market for large secondary batteries is gradually expanding and moving forward. And although high energy density, cyclability, and stability are required for use in various applications at this time, the currently commercialized graphite anode is facing the limit of theoretical capacity (LiC6, 372 mAh/g).While research on next-generation anode materials is underway to increase the energy density of lithium secondary batteries, silicon has a high theoretical capacity close to 4000 mAh/g, attracting attention as an anode for next-generation lithium-ion batteries. However, the capacity retention rate is low due to the huge volume change and low electrical conductivity that occur during charging and discharging of silicon.In order to solve this problem, many studies are being conducted, such as a) making a silicon-sized structure into a nano-scale and porous structure, b) oxidizing silicon, and c) a composite with a carbon material. Among them, much attention has been paid to improving the electrochemical performance of a silicon-based anode by designing a structure by fabricating silicon in a nano size. Compared to conventional silicon materials, nano-sized silicon was able to better withstand the stress caused by volume expansion during charging/discharging in the nano-surface-to-volume ratio. As a result, intergranular cracking can be limited, thereby improving cycle stability and maintaining high capacity. The particles can shorten the diffusion path of lithium by providing a stable electron and Li-ion transport path, and can provide increased rate-limiting properties and reduced resistance.In this study, the effect of the manufactured silicon grain size on the mechanical and electrochemical properties of the Li-ion secondary battery was studied by various analytical methods.

Quantifying the Thermo-Electrochemical Sensitivity of Li-Ion Batteries to Modulating Interelectrode Thermal Gradients

Li-ion secondary batteries are used in many applications and technologies as energy storage devices because of their relatively high Coulombic efficiency and energy and/or power density. However, Li-ion batteries (LIBs) are prone to safety concerns (e.g., thermal runaway), which limit their application [1]. Thermal conditions are one of the major parameters that influence the safety and performance of LIBs due to temperature-dependent electrochemistry. Low temperatures [2] and high temperatures [3] have distinct effects on LIB electrochemistry and are well-reported in the literature. Although non-uniform thermal conditions are more practical during use, the effect of various non-uniform thermal conditions is not fully understood. A non-uniform temperature distribution can easily develop inside Li-ion cells by surface cooling, and the resulting thermal gradient can have adverse effects. Moreover, the direction of the thermal gradient can dictate local transport mechanisms and can cause different degradation modes [4]. Thus, further assessment of the impact of thermal gradients is needed to fully understand the fundamental electrochemical mechanisms, performance, and safety implications. In this work, we quantify the thermo-electrochemical sensitivity of LIBs to modulating interelectrode thermal gradients in synchronization with electrochemical cycling using a custom test facility. Instrumented single-layer pouch cells are fabricated using NMC cathodes and graphite anodes. The internal temperature of each electrode is obtained in real-time using a thin thermistor. Electrochemical impedance spectroscopy is performed before and after galvanostatic cycling at C/5, and the magnitude and the direction of the thermal gradient in synchronization with cell cycling is varied.AcknowledgmentsThe authors thank Dr. Michele Anderson (Office of Naval Research, grant N00014-21-1-2307) for financial support of this work. The authors also acknowledge Dr. Corey Love and Dr. Rachel Carter (U.S. Naval Research Laboratory) for technical discussion of this work.

Comparative Study on the Electrochemical Properties of Cylindrical and Pouch-Type Lithium Ion Battery

As the field expands from portable electronic devices to large energy storage devices such as electric vehicles, more reliable and innovative battery technologies are more important than ever.Currently, there are three types of lithium battery packaging: cylindrical, prismatic and pouch. Cylindrical batteries with a cylindrical shape and structure were one of the first mass-produced battery types and are still mass-produced and dominate in some applications. On the other hand, prismatic batteries are gaining popularity due to their high capacity, thin form, and efficient use of space. Due to the angular shape, multiple cells can be easily connected to form larger packs. Finally, pouch batteries are known for their lighter construction, using a sealed flexible foil as the packaging material.Each of these battery types offers a set of advantages and disadvantages. There is no clear winner, but the battery you choose can influence your product design in many ways. For example, each of these battery form factors can have a different temperature distribution and heat transfer model.In this study, a cylindrical battery and a pouch-type battery of the same capacity were manufactured using the same four major materials (positive electrode, negative electrode, separator, and electrolyte), respectively, to study the cell chemical characteristics of Li-ion secondary batteries. In particular, it is intended to provide a field to which each type of lithium ion secondary battery can be applied by understanding the characteristics of thermal and deterioration.

Update on Systematic Cycle and Calendar Aging of NMC and NCA 18650 Li-Ion Batteries

The true useful life of secondary Li-ion batteries is currently not well characterized. 80% of initial capacity, a decades old metric for vehicle applications, is a common endpoint in literature cycling studies and commercial cell specification sheets. As such, much is not known about cell performance beyond this metric. The 80% cutoff may not be applicable for non-vehicle applications, like grid energy storage, where there are different requirements for performance. Degradation data beyond the 80% capacity threshold is needed to make these evaluations.To address this, we have been conducting a multi-year study of both cycling and calendar aging of 18650 cells. During this study, LiNixCoyAl1-x-yO2/NCA, and LiNixMnyCo1-x-yO2/NMC cells have been cycled at systematically varied temperature, state of charge (SOC) ranges, and cycling rates. Cells were cycled at different state of charge (SOC) ranges (0-100%, 20-80%, and 40-60%), temperatures (15, 25, and 35 °C) and discharge rates (0.5C, 1C, 2C, and 3C). Additionally, we present data from a concurrent calendar aging study at different temperatures (15, 25, and 35 °C) and SOCs (25, 50, and 90%). Our group has previously reported on trends for cycle aging down to 80% capacity [1]. Here, we present an update on performance of cells cycled beyond 80% capacity to an end of life (EOL) of 40% capacity and cells undergoing calendar aging.Results so far suggest that SOC range continues to be the largest factor in capacity fade rate for both chemistries. Combining stress factors (NMC at high SOC and low temperature) causes rapid capacity fade beyond what would be expected by simple addition of degradation rates from the individual stress factors. Depending on the conditions of cycling, so called knee points do not always appear when a cell is cycled beyond 80%. When a knee point occurs varies by cycling conditions. We also consider additional metrics by which battery performance can be measured such as round-trip efficiency (RTE), total discharged energy, and internal resistance (IR). And find that IR increases generally matches well with capacity fade and appear to increase dramatically at observed knee points. For the calendar aging study, we find that holding cells at higher SOCs and temperatures generally increases the rate of fade. This study represents the broadest public report of post 80% capacity cycling across multiple chemistries. It will inform cell lifetime prediction and allow for better utilization of battery systems.Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. SAND2022-5089 A

Nonflammable Sulfone-Based Electrolytes for Achieving High-Voltage Li-Ion Batteries Using LiNi0.5Mn1.5O4 Cathode Material

High voltage Li-ion batteries have been expected a forward technology designed for vehicles, marines and other high power and energy density applications 1–3. Among high voltage cathodes, LiNi0.5Mn1.5O4 is considered a promising cathode to reduce the battery cost as well as environmental hazard issues4,5. However, a high operation potential and Mn dissolution brings the most critical challenges for achieving the long cycle-life of Li-ion cell6,7.In this study, we report a rational design of nonflammable electrolyte based on LiBF4 and sulfolane (TMS) mixed with a dimethyl carbonate (DMC) as co-solvent to enhance conductivity. Among different molar ratios, the electrolyte LiBF4: TMS: DMC =1:2:1 in mol. exhibited the highest electrochemical stability (~ 6.1 V vs. Li+/Li) and ionic conductivity up to 1.57 mS.cm-1 at 30 oC. Cycling performance of LNMO/Li half-cell and LNMO/graphite full-cell cycled were carried out using the optimized electrolyte. While half-cells LNMO//Li display a high initial capacity of 118 mAh.g-1 and remain 56.48 % of initial value after 100 cycles, a full cell LNMO//Graphite with an areal loading of 1.0 mAh.cm-2 and low N/P ratio (~1.2) exhibited a better cycling stability than the one using commercial electrolyte 1M LiPF6/EC-DMC, 1:1 in vol (with initial capacity of 87 mAh.g-1 and capacity retention of 18% after 100 cycles8). References Goodenough JB, Kim Y. Challenges for Rechargeable Li Batteries. Chem Mater. 2010;22(3):587-603.Etacheri V, Marom R, Elazari R, Salitra G, Aurbach D. Challenges in the development of advanced Li-ion batteries: a review. Energy Environ Sci. 2011;4(9):3243.Amine K, Kanno R, Tzeng Y. Rechargeable lithium batteries and beyond: Progress, challenges, and future directions. MRS Bull. 2014;39(5):395-401.Kim J-H, Myung S-T, Sun Y-K. Molten salt synthesis of LiNi0.5Mn1.5O4 spinel for 5 V class cathode material of Li-ion secondary battery. Electrochim Acta. 2004;49(2):219-227.Patoux S, Daniel L, Bourbon C. High voltage spinel oxides for Li-ion batteries: From the material research to the application. J Power Sources. 2009;189(1):344-352.Jang DH, Shin YJ, Oh SM. Dissolution of Spinel Oxides and Capacity Losses in 4 V Li / LixMn2O4 Cells. J Electrochem Soc. 1996;143(7):2204-2211.Du Pasquier A, Blyr A, Courjal P. Mechanism for Limited 55°C Storage Performance of Li1.05Mn1.95 O 4 Electrodes. J Electrochem Soc. 1999;146(2):428-436.Wang J, Yamada Y, Sodeyama K, Chiang CH, Tateyama Y, Yamada A. Superconcentrated electrolytes for a high-voltage lithium-ion battery. Nat Commun. 2016;7(1):12032. Acknowledgement This work is supported by Ho Chi Minh city - Department of Science and Technology (DOST) under grant number 54/2020/HĐ-QPTKHCN.

Lowering the sintering temperature of Li<sub>7</sub>La<sub>3</sub>Zr<sub>2</sub>O<sub>12</sub> electrolyte for co-fired all-solid-state batteries via partial Bi substitution and precise control of compositional deviation

Li7La3Zr2O12 (LLZ) has great potential as a solid electrolyte for co-fired all-solid-state Li-ion secondary batteries. However, to realise a solid-state battery using LLZ, the sintering temperature of LLZ should be reduced to one that can suppress the formation of a high-resistance reaction layer at the interface between LLZ and the electrode. In this study, we demonstrate an effective method for reducing the sintering temperature of Li6La3ZrTaO12 by combining partial Bi-substitution for Ta and precise control of the compositional deviation. The intentional tuning of the La deficiency in Li6La3ZrTa0.8Bi0.2O12 (LLZTB0.2) promoted the formation of a liquid phase based on Li2O–Bi2O3 at the grain boundary, resulting in its densification at 775 °C. Furthermore, we fabricated a co-fired all-solid-state half-cell based on an LLZTB0.2 electrolyte attached to a LiCoO2 + LLZTB0.2 composite electrode and a half-cell operated at 60 °C. From these results, it was found that the proposed concept is effective in reducing the sintering temperature of LLZ and is applicable for co-firing an all-solid-state battery.

An Exploration of Sulfur Redox in Lithium Battery Cathodes.

Secondary Li-ion batteries have enabled a world of portable electronics and electrification of personal and commercial transportation. However, the charge storage capacity of conventional intercalation cathodes is reaching the theoretical limit set by the stoichiometry of Li in the fully lithiated structure. Increasing the Li:transition metal ratio and consequently involving structural anions in the charge compensation, a mechanism termed anion redox, is a viable method to improve storage capacities. Although anion redox has recently become the front-runner as a next-generation storage mechanism, the concept has been around for quite some time. In this perspective, we explore the contribution of anions in charge compensation mechanisms ranging from intercalation to conversion and the hybrid mechanisms between. We focus our attention on the redox of S because the voltage required to reach S redox lies within the electrolyte stability window, which removes the convoluting factors caused by the side reactions that plague the oxides. We highlight examples of S redox in cathode materials exhibiting varying degrees of anion involvement with a particular focus on the structural effects. We call attention to those with intermediate anion contribution to redox and the hybrid intercalation- and conversion-type structural mechanism at play that takes advantage of the positives of both mechanistic types to increase storage capacity while maintaining good reversibility. The hybrid mechanisms often invoke the formation of persulfides, and so a survey of binary and ternary materials containing persulfide moieties is presented to provide context for materials that show thermodynamically stable persulfide moieties.

Structure and electrochemical properties of CNT-supported Li-Ti-O anode material for Li-ion battery

We investigated the structural and electrochemical properties of Li-Ti-O (LTO) and carbon nanotube (CNT)-added LTO for anode material in secondary Li-ion batteries using various techniques. The study focused on elucidating the effects of the microstructural evolution in LTO and the CNT addition on battery functionality. For all the tested compositions of LTO ([Li]/[Ti] = 0.9, 1.0 and 1.22), the system is fully oxidized to comprise a mixed-phase having Li4+2δTi5O12+δ (δ’s are approximately 0.14, 0.25, and 0.65, respectively) and Li2TiO3 structures. The results of the half-cell tests show a decrease in charge/discharge capacity with increasing [Li]/[Ti] ratio, and the detailed structural and chemical analyses unequivocally reveal that the such degradation in the electrochemical property originates mainly from the increase of Li content (δ). Meanwhile, after adding CNT, the Li capacity becomes greatly increased while the LTO composition and the redox kinetics do not change significantly. The origin of the improved specific capacity is associated with the formation of micron-sized structures at the surface of the LTO particles. Thereby we demonstrate that surface engineering via the CNT addition is a promising way to improve the performance of the LTO-based anode material.