Rechargeable Li-ion Batteries Research Articles

Synthesis of Reduced Graphene Oxide Through Microwave Irradiation of Graphene Oxide Derived from Vein Graphite for the Anode Application in Li-Ion Rechargeable Batteries

Journal of the Geological Society of Sri Lanka is a peer-reviewed and open access journal published by the Geological Society of Sri Lanka. It aims to publish the most topical and highest quality papers, summarizing the results of recent research across all sub-disciplines of the Earth Science. Papers are frequently interdisciplinary covering both pure and applied fields of Geology. Contributions often refer to local, regional and/or international studies and emphasize the development of the understanding of fundamental geological processes.

Correlative analysis of structure and chemistry of LixFePO4 platelets using 4D-STEM and X-ray ptychography

Lithium iron phosphate (LixFePO4), a cathode material used in rechargeable Li-ion batteries, phase separates upon de/lithiation under equilibrium. The interfacial structure and chemistry within these cathode materials affects Li-ion transport, and therefore battery performance. Correlative imaging of LixFePO4 was performed using four-dimensional scanning transmission electron microscopy (4D-STEM), scanning transmission X-ray microscopy (STXM), and X-ray ptychography in order to analyze the local structure and chemistry of the same particle set. Over 50,000 diffraction patterns from 10 particles provided measurements of both structure and chemistry at a nanoscale spatial resolution (16.6–49.5 nm) over wide (several micron) fields-of-view with statistical robustness. LixFePO4 particles at varying stages of delithiation were measured to examine the evolution of structure and chemistry as a function of delithiation. In lithiated and delithiated particles, local variations were observed in the degree of lithiation even while local lattice structures remained comparatively constant, and calculation of linear coefficients of chemical expansion suggest pinning of the lattice structures in these populations. Partially delithiated particles displayed broadly core–shell-like structures, however, with highly variable behavior both locally and per individual particle that exhibited distinctive intermediate regions at the interface between phases, and pockets within the lithiated core that correspond to FePO4 in structure and chemistry. The results provide insight into the LixFePO4 system, subtleties in the scope and applicability of Vegard’s law (linear lattice parameter-composition behavior) under local versus global measurements, and demonstrate a powerful new combination of experimental and analytical modalities for bridging the crucial gap between local and statistical characterization.

The Effects of the Binder and Buffering Matrix on InSb-Based Anodes for High-Performance Rechargeable Li-Ion Batteries.

C-decorated intermetallic InSb (InSb–C) was developed as a novel high-performance anode material for lithium-ion batteries (LIBs). InSb nanoparticles synthesized via a mechanochemical reaction were characterized using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and energy-dispersive X-ray spectroscopy (EDX). The effects of the binder and buffering matrix on the active InSb were investigated. Poly(acrylic acid) (PAA) was found to significantly improve the cycling stability owing to its strong hydrogen bonding. The addition of amorphous C to InSb further enhanced mechanical stability and electronic conductivity. As a result, InSb–C demonstrated good electrochemical Li-ion storage performance: a high reversible specific capacity (878 mAh·g−1 at 100 mA·g−1 after 140 cycles) and good rate capability (capacity retention of 98% at 10 A·g−1 as compared to 0.1 A·g−1). The effects of PAA and C were comprehensively studied using cyclic voltammetry, differential capacity plots, ex-situ SEM, and electrochemical impedance spectroscopy (EIS). In addition, the electrochemical reaction mechanism of InSb was revealed using ex-situ XRD. InSb–C exhibited a better performance than many recently reported Sb-based electrodes; thus, it can be considered as a potential anode material in LIBs.

Investigating on physical and electrochemical properties of high concentrated electrolytes based on LiBF4 salt for 5 V Li-ion rechargeable batteries

In this work, highly concentrated electrolytes were prepared by dissolving tetrafluoroborate (LiBF4) salt in the two solvents including tetramethylene sulfone (TMS) and trimethyl phosphate (TMP) with different mole ratios. The results indicated that the electrolyte LiBF4/TMS (1:3) (~3.4 M) possessed the highest oxidation stability of 6.2 V (vs. Li+/Li) and high ionic conductivity of 1.0 mS/cm that could be promising for high voltage Li-ion batteries operated in the voltage range of 3.5-4.9 V. The electrolyte compatibility with high voltage cathode Li || LiNi0.5Mn1.5O4 (LNMO) was evaluated in coin-cell configuration, which displayed high reversible discharge capacity of 113 mAh/g in the first cycle and high initial Coulombic efficiency >91% and remained >80% of the initial capacity at the 100th cycle. By using the cyclic voltammetry (CV) method, the diffusion coefficient was also calculated as about 4.51×10-11 cm2/s.

Photo Rechargeable Li-Ion Batteries Using Nanorod Heterostructure Electrodes.

New ways of directly using solar energy to charge electrochemical energy storage devices such as batteries would lead to exciting developments in energy technologies. Here, a two-electrode photo rechargeable Li-ion battery is demonstrated using nanorod of type II semiconductor heterostructures with in-plane domains of crystalline MoS2 and amorphous MoOx . The staggered energy band alignment of MoS2 and MoOx limits the electron holes recombination and causes holes to be retained in the Li intercalated MoS2 electrode. The holes generated in the MoS2 pushes the intercalated Li-ions and hence charge the battery. Low band gap, high efficiency photo-conversion and efficient electron-hole separation help the battery to fully charge within a few hours using solar light. The proposed concept and materials can enable next generation stable photo-rechargeable battery electrodes, in contrast to the reported materials.

Triggering anomalous capacity by nanoengineered ordered mesoporous structure for Co3O4 anode material in Li-ion rechargeable batteries

Nanostructured engineering is one of the strategies for optimizing transition metal oxides as anode materials in lithium-ion batteries. Among them, mesoporous structures have received significant attention due to their intrinsic properties which are related to porous structure. This structure provides short Li-ion diffusion pathways and acts as a buffer for volume changes during electrochemical reactions, affecting various electrochemical properties and performances. One of the intriguing aspects of the mesoporous structure effect is that it sometimes triggers a negative fading. Herein, we observed that ordered mesoporous Co3O4 exhibits a higher reversible capacity and anomalous cycle behavior that capacity increases during cycling, known as a negative fading, compared to bulk Co3O4. Moreover, the observed capacity is even higher than its theoretical capacity. Mesoporous Co3O4 exhibits stable and more reversible conversion reactions, and even gradually activated electrolyte-derived surface layer formation/decomposition during cycling. Based on combined synchrotron-based X-ray analyses and electrochemical tests, we found the weaker Co-O and Co-Co bond strength in mesoporous material than those in the bulk material, gives rise to a more reversible conversion reaction during cycling. In addition, the distinctive structural properties of mesoporous leads to the further formation/decomposition of electrolyte-derived surface layer, resulting in the negative fading.

Cooperative Conformational Change of Bio-Inspired Organic Molecule for Ultrafast Lithium-Ion Batteries

Biological energy transduction occurs through stepwise redox reactions of various organic molecules, such as adenosine triphosphate, quinone derivatives, nicotinamide and flavin cofactors.1,2 The redox reactions in the biological system have inspired the design of biomimetic materials for renewable energy and environmental science.3-5 Recently, the exploitation of biological redox reactions has provided a new approach to the design of organic electrode materials for rechargeable batteries.6,7 Redox-active bioorganic molecules led to the development of high-performance battery systems owing to their reversible redox activities.8 For examples, quinone and flavin derivatives, in which stable redox states exist during photosynthesis and cellular respiration, showed reversible battery operation at ~2.5 V vs. Li+/Li.9,10 Electron-withdrawing groups (e.g. N and O) in the vicinity of the redox active centers (e.g. C=O and C=N) in quinone and flavin derivatives further elevated the redox potential by attracting the electrons from the electron cloud around the redox active centers. Unfortunately, battery performance of organic-based electrodes is still lacking of energy and power density to be implemented into the practical energy storage system.11 To tackle this issue, the organic molecules with more redox moieties and higher conductivity have been explored.12,13 In addition, to improve the stability of organic molecules as well as inter-charge transfer, nano-dimensional networking between carbon conductor and organic molecules is of great interest so far.14,15 However, the organic-battery performance can be influenced by molecular geometry and molecular orbital structure according to the literature.16,17 Therefore, we envisage the cooperative conformational change of organic molecules during battery operation.Herein, as depicted in Figure 1, we unveiled that the proton-coupled redox reaction of single organic molecule in an aqueous solution can be translated to the lithium-coupled redox reaction of single organic molecule in a lithium-based organic electrolyte by using phenoxazin-3-one (i.e., resorufin) as a new bio-inspired redox-active molecule. In this report, we elaborate the cooperative conformational change of the single molecule during the redox reaction, which ultimately lead to the outstanding battery performance for the first time. Phenoxazin-3-one is selected as the model single organic molecule. Our analyses using operando Raman spectroscopy and DFT calculations confirmed the conformational flexibility in the molecular shape, enabling formation of strong p-p interactions between redox-active organic molecule and carbon. The strong p-p interaction of the single organic molecule with carbon resulted in the excellent battery performance (high discharge capacity, 298 mAhg-1, and outstanding rate capability, 65% retention at 10 C). Our work provides in-depth understanding about cooperative conformational change in the single molecule and its effect on the battery performance. Furthermore, we suggest a phenoxazin-3-one as a new redox-active molecules derived from biochemical redox reaction for energy storage materials in Li-ion rechargeable batteries.(1) B. B. Lowell, B. M. Spiegelman, Nature 2000, 404, 652.(2) H. Wang, Y. Yang, L. Guo, Adv. Energy Mater. 2017, 7, 1700663.(3) L. Que Jr, W. B. Tolman, Nature 2008, 455, 333.(4) U. G. K. Wegst, H. Bai, E. Saiz, A. P. Tomsia, R. O. Nat. Mater. 2014, 14, 23.(5) Y. J. Lee, H. Yi, W.-J. Kim, K. Kang, D. S. Yun, M. S. Strano, G. Ceder, A. M. Belcher, Science 2009, 324, 1051.(6) Y. Ding, Y. Li, G. Yu, Chem 2016, 1, 790.(7) B. Lee, Y. Ko, G. Kwon, S. Lee, K. Ku, J. Kim, K. Kang, Joule 2018, 2, 61.(8) J. Hong, M. Lee, B. Lee, D.-H. Seo, C. B. Park, K. Kang, Nat. Commun. 2014, 5, 5335.(9) M. Lee, J. Hong, D.-H. Seo, D. H. Nam, K. T. Nam, K. Kang, C. B. Park, Angew. Chem. Int. Ed. 2013, 52, 8322.(10) Z. Song, Y. Qian, X. Liu, T. Zhang, Y. Zhu, H. Yu, M. Otani, H. Zhou, Energy Environ. Sci. 2014, 7, 4077.(11) S. Lee, G. Kwon, K. Ku, K. Yoon, S.-K. Jung, H.-D. Lim, K. Kang, Adv. Mater. 2018, 30, 1704682.(12) B. Häupler, A. Wild, U. S. Schubert, Adv. Energy Mater. 2015, 5, 1402034.(13) Q. Zhao, Y. Lu, J. Chen, Adv. Energy Mater. 2017, 7, 1601792.(14) M. Lee, J. Hong, H. Kim, H.-D. Lim, S. B. Cho, K. Kang, C. B. Park, Adv. Mater. 2014, 26, 2558.(15) C. Luo, R. Huang, R. Kevorkyants, M. Pavanello, H. He, C. Wang, Nano Lett. 2014, 14, 1596(16) Y. Morita, S. Nishida, T. Murata, M. Moriguchi, A. Ueda, M. Satoh, K. Arifuku, K. Sato, T. Takui, Nat. Mater. 2011, 10, 947.(17) V. A. Mihali, S. Renault, L. Nyholm, D. Brandell, RSC Adv. 2014, 4, 38004. Figure 1

NMC811 Carbon Core Shell Materials for High-Performance 18650 Ni-Rich Li-Ion Batteries

Rechargeable Li-ion batteries (LIB) have been extensively studied and become one of the essential energy storage devices for many applications, especially for electric vehicles (EVs). To date, Ni-rich materials such as lithium nickel manganese cobalt oxide (LiNixMnyCo1-x-yO2; x ≥ 0.6) are believed to be the next-generation cathodes due to their low-cost, high capacity, and high operating voltage.2-4 However, the practical application of these materials has not yet been fully developed because of many intrinsic drawbacks. Herein, a surface coating approach using a green scalable solvent-free mechanofusion process is introduced to prepare an infusing thin layer carbon nanosphere shell to improve the intrinsic drawbacks of NMC811 including poor electrical conductivity, Li+/Ni2+ cation mixing, parasitic reactions with electrolytes, and micro-crack formation. The in operando XRD measurement confirms the fast and uniform phase transition with low Li diffusion/kinetics hindrance. The structural integrity of NMC811cs is not affected by the abrupt shrinkage in c-axis as it shows better cycling stability compared to the pristine NMC811 with less variation in c-direction. The formation of CO2 and H2 at high SOC over 4.0 V can also be minimized as observed by online DEMS. Finally, the practical application of the NMC811cs is demonstrated by the 18650 battery prototype which shows higher specific capacity and energy as well as excellent cycling stability compared to the pristine NMC811. This work provides both fundamental understanding and economical strategy towards highly stable and practical high-energy Li-ion batteries.

High Energy Density Li-Ion Capacitor for Use in Wearable Health Sensor Platforms

Lithium ion capacitors with their high energy density, high power density and good cycle life can offer potential standalone energy storage solution when combined with renewable energy harvesting technologies to power wearable health sensor or Internet of things platform. In this study, we demonstrate fabrication of 13 Wh/L packaged Li-ion capacitor 2016 coincell prototype that can be charged using harvested solar energy from indoor lighting to power wearable health sensor platforms. The capacitor with its extremely low self-discharge rate, high load carrying capability and cycle life can provide significant advantages relative to rechargeable batteries of similar form factor. The study provides a comparison of performance of Li-ion rechargeable battery against the fabricated capacitor to continuously power wearable heath sensor platform.

Forcespun and Coated SnO2/TiO2/C Composite Fibers as Anode Materials for Sodium Ion Batteries

Sodium-ion batteries (SIBs) are being demanded over the years due to profusion of Na in nature as well as the unavailability, expensiveness, and fragility of rechargeable Li-ion batteries (LIBs). Metal-oxide anode materials face various pitfalls such as volume expansion during charge/discharge cycles, high irreversible capacity, and conductivity-related issues. Porous structures aligned with amorphous carbon into the metal oxide is a novel technique that has been used to synthesize novel nanostructures for SIBs. Tin oxide has been recently used as a good anode material for SIBs, but SnO2 suffers from high volume change and low capacity retention after prolonged charge/discharge cycles. SnO2 coupled with Titanium oxide, has been proven as a good anode material due its good capacity retention and improved electrochemical performance and cyclability. The current work focuses on the processing of centrifugally spun PAN/PMMA/SnO2/TiO2 composite precursor fibers to fabricate SnO2/SnO2/C composite fibers for SIBs as anode materials in LIBs and SIBs. The electrochemical performance of the composite fibers was evaluated by galvanostatic charge/discharge, cyclic voltammetry (CV) and rate performance experiments. The SnO2/TiO2/C composite-fiber anode showed improved electrochemical performance when compared to SnO2/TiO2 composite fibers which was attributed to the synergetic effect of TiO2.

Lithium Potential Mapping Using Artificial Neural Networks: A Case Study from Central Portugal

The growing importance and demand of lithium (Li) for industrial applications, in particular rechargeable Li-ion batteries, have led to a significant increase in exploration efforts for Li-bearing minerals. To ensure and expand a stable Li supply to the global economy, extensive research and exploration are necessary. Artificial neural networks (ANNs) provide powerful tools for exploration target identification. They can be cost-effectively applied in various geological settings. This article presents an integrated approach of Li exploration targeting using ANNs for data interpretation. Based on medium resolution geological maps (1:50,000) and stream sediment geochemical data (1 sample per 0.25 km2), the Li potential was calculated for an area of approximately 1200 km2 in the surroundings of Bajoca Mine (Northeast Portugal). Extensive knowledge about geological processes leading to Li mineralisation (such as weathering conditions and diverse Li minerals) proved to be a determining factor in the exploration model. Furthermore, Sentinel-2 satellite imagery was used in a separate ANN model to identify potential Li mine sites exposed on the ground surface by analysing the spectral signature of surface reflectance in well-known Li locations. Finally, the results were combined to design a final map of predicted Li mineralisation occurrences in the study area. The proposed approach reveals how remote sensing data in combination with geological and geochemical data can be used for delineating and ranking exploration targets of almost any deposit type.

An Enhanced Method of Contactless Charging of Railway Signaling Torch Light

Wireless charging, also known as contactless charging (for shorter range), is a method of supplying energy to electrical devices by sending electricity via an air gap. Wireless charging methods have advanced recently, and commercial solutions have been developed, providing a potential option to overcome the energy bottleneck of typically portable battery-powered gadgets. Due to its simplicity and improved user experience, this technology is attracting a wide range of applications, from low-power gadgets to high-power electric cars. However, including wireless charging into the systems raises a number of difficult challenges in terms of implementation, scheduling, and power management. One such application is to convert the existing system of traditional battery powered railway signaling torchlight into a rechargeable type contactless charging system. This provides a better way of increasing the life time of the product and has better compactness. A rechargeable Li-ion battery must be installed in lieu of the old non-rechargeable battery. To achieve satisfactory efficiency, the magnetic resonance coupling technology of contactless charging can be utilized. Through a shorter air gap, electrical power is transmitted from the charging module (main coil) to the Torchlight (secondary coil). Overall, the present system's cost, size are reduced and lifetime is increased.

Ethylene Carbonate (EC)-Propyl Acetate (PA) Based Electrolyte for Low Temperature Performance of Li-Ion Rechargeable Batteries

Abstract Charge-discharge performance at −30 °C was studied by using low-viscosity ester solvents (propyl acetate (PA), propyl propionate (PP), and ethyl propionate (EP)) as electrolyte for improving the low-temperature performance of lithium-ion rechargeable batteries. Among the studied ester, PA based electrolyte shows the most superior cycle stability, and it was found that EC-PA based electrolyte increased the discharge capacity of the cell at −30 °C by 6% compared to the EC-DEC based electrolyte. Although the cell capacity at low temperature was increased, favorable solid electrolyte interface (SEI) may not be formed and the cycle stability was decreased in the cell using PA component as the electrolyte. By using an electrolyte additive for SEI formation in combination with PA based electrolyte, the low temperature discharge capacity and cycle stability were much increased which is strongly demanded for electric vehicle application.

Aramid nanofiber-based porous membrane for suppressing dendrite growth of metal-ion batteries with enhanced electrochemistry performance

Huge volume changes, uncontrolled side-reactions with electrolytes and irregular dendrite induced short-circuits have impeded practical application in rechargeable batteries based on metallic electrodes including lithium (Li), sodium (Na) and aluminum (Al). Separator with superior mechanical strength represent attractive alternatives to inhibit metal-dendrite growth while preventing capacity fading by stabilizing the solid electrolyte interphase (SEI). However, the challenge of simultaneous retaining high thermal resistance and good electrolyte wettability still have been not overcome in commonly used separators. Here we show that these key properties can be acquired in a porous membrane fabricated from Kevlar microfiber-derived aramid nanofibers (ANFs) prepared in a facile and scalable vacuum filtration method. The obtained ANFs membrane (ANFM), which yields mechanically strong that are markedly effective in inhibit dendrite growth as well as provides good electrolyte wettability to ensure excellent electrochemistry performance. Benefitting from these merits, ANFM guarantee stable cycling of Li-ion or Na-ion rechargeable batteries paired with conventional intercalating cathodes (LiCoO4 and Na2Ti3O7) even at a high operated temperature (150 ℃ for Li-ion battery). Replacing polyolefins-based separator with an ANFM appear to offer a major step towards dendrite-free Li /Na batteries and potentially other metal-ion batteries.

Enhancing the structural stability and capacity retention of Ni-rich LiNi0.7Co0.3O2 cathode materials via Ti doping for rechargeable Li-ion batteries: Experimental and computational approaches

The Ni-rich cathodes are considered as the next generation candidate cathode material of lithium-ion batteries due to their high-energy–density and environmentally friendly. In this study, the Ni-rich, LiNi0.7Co0.3O2 cathodes material was doped by titanium (Ti) via a self-propagating combustion method. The role of Ti species and its effects on the structural and electrochemical performance of the cathode materials were investigated through experimental and first principles studies. From the XRD results, all materials possessed a single phase with a hexagonal layered structure of the R-3m space group. The Rietveld refinement revealed that the lattice of the Ti-doped LiNi0.7Co0.3O2 sample was found to be expanded in the c-axis and has a lower cation mixing as compared to the pristine samples, which can ease the movement of Li-ions during the delithiation/lithiation process. After 70th cycle, the discharge capacity of the Ti-doped LiNi0.7Co0.3O2 sample possess an excellent capacity retention of 91.9% with a specific discharge capacity of 132.3 mAhg−1 as compared to the pristine sample with only has 86.2 mAhg−1. This can be explained by first-principles study where it was found that the Li-O distances for LNCT become expand after the delithiation process which ease the Li-ions diffusion during cycling. As a whole, the addition of Ti species into the Ni-rich layered cathode materials was found to stabilise the crystal structure of LiNi0.7Co0.3O2 and subsequently improved the lithium-ion kinetics of the layered cathode materials. Apart from lithium nickel manganese cobalt oxide (NMC) and lithium nickel cobalt aluminium oxide (NCA), this study demonstrated that LiNi0.6Co0.3Ti0.1O2 can also serve as potential cathode material for rechargeable Li-ion batteries.

Synchronized Operando Analysis of Graphite Negative Electrode of Li-Ion Battery

Since the rechargeable Li-ion battery was invented in the early 1990s, its performance has evolved continually and Li-ion batteries are now installed in most mobile devices. In these batteries, graphite is used as a negative electrode material. However, the detailed reaction mechanism between graphite and Li remains unclear. Here we apply synchrotron X-ray diffraction, 7Li-nuclear magnetic resonance and Raman spectroscopy to operando analysis of the charge/discharge mechanism of a graphite electrode. The spectrum of the graphite electrode is measured repeatedly during the reaction. The operando dataset obtained is then analyzed synchronously with the composition of x in LiCx estimated from the charge/discharge curves. We propose a synchronized operando analysis method that provides useful information about the behavior of the C–C bond vibration mode and the interactions between Li and carbon atoms due to structural change during the charge/discharge reaction. In addition, we determine details of the intercalation mechanism.

Combining Hyperbranched and Linear Structures in Solid Polymer Electrolytes to Enhance Mechanical Properties and Room-Temperature Ion Transport

Polyethylene oxide (PEO)-based polymers are commonly studied for use as a solid polymer electrolyte for rechargeable Li-ion batteries; however, simultaneously achieving sufficient mechanical integrity and ionic conductivity has been a challenge. To address this problem, a customized polymer architecture is demonstrated wherein PEO bottle-brush arms are hyperbranched into a star architecture and then functionalized with end-grafted, linear PEO chains. The hierarchical architecture is designed to minimize crystallinity and therefore enhance ion transport via hyperbranching, while simultaneously addressing the need for mechanical integrity via the grafting of long, PEO chains (M n = 10,000). The polymers are doped with lithium bis(trifluoromethane) sulfonimide (LiTFSI), creating hierarchically hyperbranched (HB) solid polymer electrolytes. Compared to electrolytes prepared with linear PEO of equivalent molecular weight, the HB PEO electrolytes increase the room temperature ionic conductivity from ∼2.5 × 10–6 to 2.5 × 10−5 S/cm. The conductivity increases by an additional 50% by increasing the block length of the linear PEO in the bottle brush arms from M n = 1,000 to 2,000. The mechanical properties are improved by end-grafting linear PEO (M n = 10,000) onto the terminal groups of the HB PEO bottle-brush. Specifically, the Young’s modulus increases by two orders of magnitude to a level comparable to commercial PEO films, while only reducing the conductivity by 50% below the HB electrolyte without grafted PEO. This study addresses the trade-off between ion conductivity and mechanical properties, and shows that while significant improvements can be made to the mechanical properties with hierarchical grafting of long, linear chains, only modest gains are made in the room temperature conductivity.

Fluorinated Carbons as Rechargeable Li-Ion Battery Cathodes in the Voltage Window of 0.5–4.8 V

Fluorinated carbon (CFx) cathodes have the highest theoretical energy density among lithium primary batteries. However, it is still a huge challenge to be reversible. Here, CFx is proposed as a high-performance cathode material for rechargeable lithium-ion batteries in the extended voltage window of 0.5-4.8 V. Specifically, the fluorinated graphite CF0.88 exhibits an initial specific discharge capacity of 1382 mAh g-1 (2362 Wh kg-1) and a specific discharge capacity of 782 mAh g-1 at the 2nd cycle and maintains a specific discharge capacity of 543 mAh g-1 (508 Wh kg-1) after the 20th cycle. This rechargeable behavior is associated with the conversion of CFx to LiF + C (>1.5 V) and then to Li1+xFC (0.5-1.5 V) during the initial discharge process; Li1+xFC is reversible to LiF + C in the following charge-discharge process (0.5-4.8 V). By extending the voltage window, CFx cathodes can show new electrochemical behaviors. Our research has provided new Li-free cathode materials for rechargeable batteries and insights for improving the performance of a Li/CFx secondary battery.

Enhanced performance of a Li‐ion rechargeable battery at low temperatures: Use of 3,3,3‐trifluoropropyl acetate as an electrolyte additive

AbstractThe addition of 3,3,3‐trifluoropropyl acetate (TFPA) to electrolyte in a Li‐ion rechargeable battery (LIB) provides a means for increasing the discharge performance at low temperatures as a result of the formation of a superior solid electrolyte interphase (SEI) on the graphite anode. For instance, the addition of 2 wt% TFPA to the electrolyte significantly increased the cycle stability and the discharge capacities at low temperatures (‐10°C) even at current rates of 3 C. The SEI films formed on the graphite anodes were characterized by electrochemical and spectroscopic techniques and by computational analysis. Although the formation of LiF on the anode has been recognized, present research revealed that the decomposition of TFPA on the anode surface resulted in the formation of an SEI layer consisting predominantly of organic fluorides. This layer suppressed the decomposition of the electrolyte resulting in a decreased anode impedance and an increase in cycle stability and discharge capacity at low temperatures.

Insights into Layered Oxide Cathodes for Rechargeable Batteries.

Layered intercalation compounds are the dominant cathode materials for rechargeable Li-ion batteries. In this article we summarize in a pedagogical way our work in understanding how the structure’s topology, electronic structure, and chemistry interact to determine its electrochemical performance. We discuss how alkali–alkali interactions within the Li layer influence the voltage profile, the role of the transition metal electronic structure in dictating O3-structural stability, and the mechanism for alkali diffusion. We then briefly delve into emerging, next-generation Li-ion cathodes that move beyond layered intercalation hosts by discussing disordered rocksalt Li-excess structures, a class of materials which may be essential in circumventing impending resource limitations in our era of clean energy technology.