Generation Li-ion Batteries Research Articles

Understanding Mechanisms of Ethylene Carbonate Gassing and Gas-Reducing Additives Using Isotopically Labeled Solvents

Gas generation during Li-ion battery operation remains a problem that can affect both safety and operational lifetime of the battery. Electrolyte solvents are a key source of gas generation1 and while gas-reducing additives have been identified, the underlying mechanisms require more study to fully understand the role between solvent structure and gas generation. Understanding of these gassing mechanisms can lead to optimized electrolyte systems with reduced gassing for the next generation of Li-ion batteries. Previous studies in the literature2 have detailed the use of 13C-labeled EC and DEC to identify the proportions of CO2 and CO that are derived from solvent sources, which in turn can help inform mechanistic understanding on gas generation in Li-Ion Batteries.As previously studied by Silatronix®, electrolytes containing organosilicon (OS) materials show significantly reduced gas generation during high temperature storage and cycling in pouch cells primarily through CO2 reduction.3 Studies utilizing simple carbonate blends indicated that EC was the primary source of CO2; therefore, it was hypothesized that OS materials reduce gassing by preventing EC decomposition during high temperature testing. In this work, 13C-labeling was used to identify the sources of gas species in ternary carbonate electrolytes after both first charge (SEI formation4) and high temperature storage (extended aging) to allow the effects of electrolyte additives gas reduction to be elucidated.Gas component analysis was performed using a calibrated GC-MS, providing identification and quantification of each gas species (labeled and unlabeled). These data give insight into how the labeled carbonate solvent may decompose into the observed gas phase products during the first charge (i.e., during SEI layer formation) and high temperature storage. Ethylene carbonate (EC) is found to be the primary source of ethylene generation, as well as a significant source of CO2 and CO. With the addition of OS, the most notable effect is that the previously seen reduction in all gas components is due to not only reduction of EC-related sources, but reduction in non-EC gas sources as well. 1 Rowden, B.; Garcia-Araez, N., A Review of Gas Evolution in Lithium-Ion Batteries. Energy Rep. 2020, 6, 10-18. 2Onuki, M.; Kinoshita, S.; Sakata, Y.; Yanagidate, M.; Otake, Y.; Ue, M.; Deguchi, M., Identification of the Source of Evolved Gas in Li-Ion Batteries using 13C-labeled Solvents. Journal of the Electrochemical Society 2008, 155, A794. 3 Guillot, S.L.; Usrey, M.; Peña-Hueso, A.; Kerber, B.; Zhou, L.; Du, P.; Johnson, T., Reduced Gassing In Lithium Ion Batteries With Organosilicon Additives. Journal of the Electrochemical Society 2021, 168, 030533. 4 Ktristiina Heiskanen, S.; Kim, J.; Lucht, B., Generation and Evolution of the Solid Electroyte Interphase of Li-Ion Batteries. Joule 2019, Volume 3 Issue 10, 2322.

Negating Crosstalk in High Voltage Spinel (LiNi0.5Mn1.5O4)/ Graphite Full Cellsby Electrode Modifications

Since its discovery, the high-voltage spinel oxide LiNi0.5Mn1.5O4 (LNMO, sg: Fd-3m) has been widely pursued as a promising cathode for next generation Li-ion batteries due to advantages that include the following: high operating voltage, excellent rate capability and low manufacturing cost (1, 2). However, the LNMO cathode when paired with graphite shows poor capacity retention and increased cell impedance due to oxidation of the organic liquid electrolyte and Mn2+ migration onto the anode (2, 3). Herein, we aim to understand the causes of poor capacity retention in LNMO/graphite full cells and systematically address those issues with various electrode modification strategies. Cycling performance of cells with carbon-nanotube (CNTs) in the LNMO electrode (LNMO-CNT), and with a thin layer of Al2O3 on the graphite electrode (Gr-Al2O3), is examined in half, full and three-electrode cell configurations. The cells with LNMO-CNT electrode show significantly lower cell impedance than cells with LNMO electrodes (without the CNT). Additionally, cells with the Al2O3-coated graphite electrode show improved capacity retention compared to cells with the uncoated graphite. Furthermore, cells containing Li4Ti5O12 anodes display the best capacity retention. We investigate and compare the physiochemical changes in electrodes and electrolyte using various diagnostic techniques; data from these experiments will be reported during the presentation. References : M. M. Thackeray, W. I. F. David, P. G. Bruce and J. B. Goodenough, Materials Research Bulletin, 18, 461 (1983).S. Patoux, L. Daniel, C. Bourbon, H. Lignier, C. Pagano, F. Le Cras, S. Jouanneau and S. Martinet, J Power Sources, 189, 344 (2009).F. Zou, H. C. Nallan, A. Dolocan, Q. Xie, J. Y. Li, B. M. Coffey, J. G. Ekerdt and A. Manthiram, Energy Storage Materials, 43, 499 (2021). Acknowledgements: This document has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357.

One-step construction of oxygen vacancies and coating to improve lithium storage performance of Li-rich layered oxides

With the advantages of higher capacity and lower price, Li-rich layered oxides have tremendous potential to become an advanced cathode material in the next generation Li-ion batteries (LIBs). Nevertheless, the commercialization of Li-rich layered oxides is seriously hindered by the large initial non-reversible capacity loss, inferior rate performance, capacity and voltage decay. Herein, a multi-strategy synergistic Li1.2Ni0.13Co0.13Mn0.54O2 (LRNCM) sample was prepared by the simultaneous establishment of oxygen vacancies and Nb2O5/C coating by C10H5NbO20·xH2O pyrolysis. The oxygen vacancies on the surface inhibit irreversible O2 release and promote the diffusion of Li+ ions, while the well-stabilized Nb2O5/C coating alleviates the corrosion of electrolytes. As a result, the initial coulombic efficiency (ICE) is increased from 60.41% to 76.95%. The capacity retention is improved from 80.6% to 86.8% after 100 cycles at 0.5 C, and the high-rate performance increases from 87 mAh g−1 to 144.6 mAh g−1 at 10 C. This work shows that the synergistic effect of oxygen vacancies and Nb2O5/C coating on LRNCM can effectively improve the charge/discharge reversibility, cycle stability and rate performance.

(Invited) John B. Goodenough's Centenarian : Success Story of LiFePO4 (LFP) As Cathode Material for Rechargeable Lithium Batteries

Lithium-ion and solid-state battery (SSB) are now playing a central role in consumer electronic, energy storage and electric vehicles thanks to their excellent cycle life and high energy density. One of the key components that have paved the way for this success story in the past 27 years is LiFePO4 (LFP) which has served as a lithium-ion host structure for the cathode electrode. Today only LFP is used in both commercial Li-ion and SSB batteries, due their safety, low cost (cobalt free), fast charge and discharge, and over 20 years of calendar life.In this presentation, we will show the progress of the physical chemistry of the olivine compounds since the pioneering work of Prof. John B. Goodenough. This major improvement has positioned LiFePO4 as the active cathode element of a new generation of Li-ion batteries from cell to pack, hence making a breakthrough in the technology of energy storage and electric transportation. This achievement is the fruit of about 27 years of intensive research in the electrochemical community during which chemists, electrochemists, physicists, and engineers added their efforts to understand the properties of the material, to overcome the obstacles that were met on the way, and finally to reach the state of the art enabling its ubiquitous use in technology today and in the future.

(Invited, Digital Presentation) Fundamental Understanding and Challenges in Cathode Materials for Next Generation Li-Ion Batteries

Introducing high-performance Li-ion batteries in current energy storage technologies has great hope in achieving decarbonization goals for sustainable future. The impact of Li-ion batteries in current energy sector is huge, especially portable electronics to electric vehicles. With this energy demand, recently, researchers have been exploring the so-called “Li-rich anion redox” cathode chemistry, in which electrons stored on oxide anions are reversibly utilized during redox reaction along with conventional transition metal redox to obtain high energy storage capability.1-2 Compared to conventional cathodes, the anion redox cathode chemistry is not straightforward as it goes through a complex redox reaction pathway, leading to fundamental issues such as voltage fade, voltage hysteresis and irreversible oxygen release. However, these anionic redox reactions in transition metal oxide-based cathodes attained by extracting excess lithium ions have resulted in stability issues due to weak metal (M) – oxygen(O) ligand covalency.1 In order to increase the tightness between metal–ligand, an alternative strategy was investigated by replacing M–O framework with M–X (X- S, Se) ligands. Based on the experimental studies, it is found that the metal-ligand tunability is the key to achieve highly reversible chalcogen anion redox reactions in various Li based chalcogen cathode materials.3 Further, the lithiation delithiation reactions of cathodes are investigated using in-depth electrochemical analysis and the electronic as well as structural changes during electrochemical reactions are understood using detailed spectroscopy and microscopy characterization. Findings from this research will inspire Ni and Co free chalcogen cathode design and various functional materials in the pursuit of next-generation cathode materials. In parallel, this presentation will also focus on fundamental understanding and importance of fabricating rechargeable high-temperature Li-ion batteries for various demanding applications such as military applications, sensor applications, oil and gas industry drilling applications. In this work, high temperature compatible electrode materials are identified, and their electrode/electrolyte interfacial stability issues at different depth levels are understood using energy tunable X-ray photon electron spectroscopy and further visualized with advanced microscopy imaging. This proof-of-concept study will lead to a new paradigm for transforming ambient temperature Li-ion battery technology to high-temperature applications.

Passive Components in Next Generation Li-Ion Batteries

Most of the research in development of next generation and high-performance Li-ion batteries has focused on active materials (either in the cathode or anode side). This might sound obvious as active materials are the main component responsible for storing charge in batteries, and therefore, any improvement in them, will directly impact the overall performance of the battery. However, when looking at the cell level, passive components such as current collectors, conductive additives, binders, and separators constitute around 20 wt.% of each battery cell. These so-called passive components while do not directly contribute to the charge storage, their ratio, composition, and structure has a profound effect on the overall performance of the active material and therefore the battery cell. This is mainly due to their importance in charge transport inside the electrode, processing of electrodes, and also cycle life the battery cells. Despite this, they usually receive less attention in development of high power and energy density batteries. If these components are engineered properly or substitute with alternative new materials, potentially, one can improve the performance (energy and power metrics) of a Li-ion battery cell by up to 20%; a number that industry still strives to achieve through modification of active materials which usually is a more complex issue with slower development timeframes. In this talk, we take a closer look at the role of passive components in Li-ion batteries and discuss the possibilities that novel nanomaterials can offer as next generation passive components, both from the standpoint of improvements in metrics of battery cells as well as electrode processing and manufacturing in Li-ion batteries. We will also discuss the cost and safety advantages these materials can offer when used as passive components of the cells and present results and give examples that demonstrate how nanomaterials can in fact act as semi-passive components where they can substitute multiple conventionally used passive components and serve multiple purposes even if directly do not contribute to charge storage. Taking such an approach in development of battery electrodes/cells can potentially pave the way for development of batteries with higher power and energy densities using the current commercially available active materials, and further enable the use of high-capacity materials that degrade quickly and therefore, cannot be used in commercial cells using current technologies.

(Digital Presentation) Sol-Gel Based Synthesis Route for High Capacity Disordered Rocksalt (DRX) Oxyfluoride Cathodes

The cost and energy density of commercial Li-ion batteries (LIBs) are largely limited by the cathode. Currently, the LIB cathode market is dominated by intercalation type layered transition metal oxides of the general form LiNixMnyCo1-x-yO2 (NMC). As the LIB market continues to grow, there is an increasing risk of over-reliance on cobalt and nickel, which not only leads to increased cost and resource depletion, but also raises ethical concerns related to the cobalt mining industry. Hence, there is an urgent need to develop new cathodes based on earth abundant materials. Disordered rocksalt (DRX) oxides and oxyfluorides have emerged as a promising candidate for next generation LIB cathodes due to their high energy density and ability to utilize low-cost, earth abundant elements such as Mn and Ti. Studies have shown that anionic substitution of oxygen with fluorine enhances electrochemical performance and cycling stability of DRX cathodes. DRX cathodes are traditionally synthesized using high temperature solid-state and high energy mechanochemical routes. While these methods have yielded promising cathodes, they face challenges with fluorine substitution and process scalability. Keeping this in mind, the goal of this research is to develop alternate synthesis routes to prepare DRX oxyfluoride cathodes and identify key structure – property correlations to optimize cathode performance. Our team recently developed a sol-gel based approach to synthesize Li1.2MnxTi0.8-xO2-yFy (y=0-0.2; x=0.4-0.6) DRX oxides and oxyfluorides. This presentation will discuss recent development related to the synthesis, structure, and performance of these cathodes Acknowledgements This research was conducted at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) and is sponsored by the Office of Energy Efficiency and Renewable Energy (EERE) through the Vehicle Technologies Office (VTO).

Internally inflated core-buffer-shell structural Si/EG/C composites as high-performance anodes for lithium-ion batteries

A watermelon-like internally inflated core-buffer-shell structural Si/electrochemically exfoliated graphene/C (Si/EG/C) composite is designed and prepared by the industrially established ball milling and spray drying method. Owing to numerous folds and voids in the EG filled between nano silicon and carbon shell, the volume fluctuations of silicon inside the Si/EG/C particles are buffered and lithium ions also could transport fast through the channels. With these advantages, the core-buffer-shell structural Si/EG/C composite demonstrates excellent electrochemical performance. The Si/EG/C anodes in half cells exhibit no degradation of the initial capacity (834 mA h g−1) after 100 cycles. Moreover, the Si/EG/C//LiCoO2 full cells retain almost 100% of the initial discharge capacity after 500 cycles. These results highlight the potential applications of Si/EG/C in the next generation of Li-ion batteries.

Al–Li alloys as bifunctional sacrificial lithium sources for prelithiation of high-energy-density Li-ion batteries

The low initial Coulombic efficiency of anodes such as Si@C can seriously affect the capacity of high-energy-density Li-ion batteries (LIBs). Supplement the initial irreversible lithium loss in the anode through prelithiation technology is the only way to realize the next generation of LIBs. In this work, we report the study of Al–Li alloy (ALA) as a prelithiation additive for LIBs cathodes. As a bifunctional sacrificial lithium source, ALA can not only provide an additional capacity of 1068 mAhg−1 to supplement the initial active lithium consumption, but also form aluminum and aluminum oxide to stabilize the cathode interface after the delithiation to improve the battery cycling stability. Therefore, the initial charge capacity of LiCoO2 (LCO) and LiNi0.6Co0.2Mn0.2O2 (NCM622) electrodes can be increased to 12.5%–18.5% by adding 2%–4% ALA. In addition, the energy density of the NCM811/Si@C pouch cell prelithiated by ALA can reach 541 Wh kg−1, which means that the cathode can maximize the capacity (from 189 mAh g−1 to 205 mAh g−1). In conclusion, this work develops a more inexpensive and efficient cathode prelithiation additive for next-generation LIBs.

Silicon nanowire growth on carbon cloth for flexible Li-ion battery anodes

Binder and conductive additive-free Si nanowires (NWs) grown directly on the current collector have shown great potential as next generation Li-ion battery anodes. However, low active material mass loadings and consequentially low areal capacities have remained a challenge in their development. Herein, we report the high-density growth of Si NWs on carbon cloth (CC) for use as Li-ion battery anodes. The NW growth reactions were carried out using a modified, glassware-based solvent vapor growth (SVG) process. Optimized growth conditions were applied to CC substrates to generate flexible Si NW anodes for Li-ion batteries. Battery testing revealed high areal charge and discharge capacities (>2 mAh/cm2) compared to Si NWs grown on stainless steel (SS) substrates (∼0.3 mAh/cm2) and stable long-term cycling with 80% capacity retention after 200 cycles. The findings reported herein represent a significant advancement in the field in terms of achievable areal capacity enabled by a low-cost glassware-based system.

Facilitating Reversible Cation Migration and Suppressing O2 Escape for High Performance Li-Rich Oxide Cathodes.

High-capacity Li-rich Mn-based oxide cathodes show a great potential in next generation Li-ion batteries but suffer from some critical issues, such as, lattice oxygen escape, irreversible transition metal (TM) cation migration, and voltage decay. Herein, a comprehensive structural modulation in the bulk and surface of Li-rich cathodes is proposed through simultaneously introducing oxygen vacancies and P doping to mitigate these issues, and the improvement mechanism is revealed. First, oxygen vacancies and P doping elongates OO distance, which lowers the energy barrier and enhances the reversible cation migration. Second, reversible cation migration elevates the discharge voltage, inhibits voltage decay and lattice oxygen escape by increasing the Li vacancy-TM antisite at charge, and decreasing the trapped cations at discharge. Third, oxygen vacancies vary the lattice arrangement on the surface from a layered lattice to a spinel phase, which deactivates oxygen redox and restrains oxygen gas (O2 ) escape. Fourth, P doping enhances the covalency between cations and anions and elevates lattice stability in bulk. The modulated Li-rich cathode exhibits a high-rate capability, a good cycling stability, a restrained voltage decay, and an elevated working voltage. This study presents insights into regulating oxygen redox by facilitating reversible cation migration and suppressing O2 escape.

Effect of lithium salt type on silicon anode for lithium-ion batteries

Silicon (Si) is one of the most promising anode materials in the next generation of Li-ion batteries. However, the application of Si is restricted by its unsatisfactory electrochemical performance. This work investigates the influence of lithium salt type on the electrochemical performance of Si anode, and shows that lithium salt type plays an importing role in determining the electrochemical performance of Si anode. Through investigation and optimization, lithium hexafluorophosphate (LiPF6)-lithium bis(fluorosulfonyl)imide (LiFSI)-lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) ternary composite lithium salt with a mole ratio of 7:1:2 exhibits the best cycling stability and rate capability. It retains a high capacity of 1879.8 mAh g−1 after 400 cycles at 0.5 C charge and discharge, and still maintains 1851.4 mAh g−1 at 30 C; which are significantly higher than the 583.3 and 316.4 mAh g−1 of the LiPF6-based electrolyte under the same conditions. The underlying mechanism is investigated, and the results indicate that the lithium type has an effect on both the Si anode and the lithium counter electrode, and the synergistic effect of LiPF6-LiFSI-LiTFSI enables high-rate and long-cycle Si anodes.

Building a stabilized structure from surface to bulk of Ni-rich cathode for enhanced electrochemical performance

Nickel-rich layered oxides are considered to be one of the most promising candidates of cathode material for the next generation Li-ion batteries (LIBs) due to their high specific capacity. However, the capacity fading and poor rate capability caused by the interface instability and structure degradation hinder their commercial applications. Herein, we propose a one-step strategy to stabilize the nickel-rich cathode material through a synergistic effect of surface engineering and lattice doping. The interfacial structure stability is improved by a uniform nano-coating of Gd2O3&LiGdO2 with an ultra-high electronic conductivity, the lattice degradation and grain cracks have been suppressed by gradient Gd-doping. It exhibits a distinguish discharge capacity of 62.68 mAh g − 1 at a super high rate of 50 C within the voltage range of 2.7 - 4.5 V, as well as suppresses the capacity decay at high temperature.

V6O13 nanosheets self-assembled into 3D hollow microflowers for long-life and high-rate Li-ion batteries

Among vanadium-based materials, V6O13 is considered to be an ideal cathode candidate material due to its high theoretical capacity and energy density. However, as mixed-valence vanadium oxide, it faces the challenge of controllable synthesis, and suffers unsatisfactory cycle performance due to the unstable structure. Constructing 3D micro/nano-structures is a very effective method to solve the above problems. Herein, we report a simple template-free solvothermal method to controllably synthesize 3D hollow microflowers structure formed by self-assembly of thin nanosheets. The growth mechanism of the hollow microflowers is revealed by changing the solvothermal reaction time and the content of ethylene glycol. As a cathode material for Li-ion batteries, the V6O13 hollow microflowers exhibit an initial discharge specific capacity of 326 mAh/g at a current density of 0.1 A/g. Even at a high current density of 1 A/g, the V6O13 hollow microflowers still deliver a discharge capacity of 183.2 mAh/g, and display high capacity retention of 75.6% after 500 cycles. The excellent electrochemical performance benefits from the unique advantages of 3D hollow microflowers structure, that is, large specific surface area, abundant mesopores, and robust structure. These results indicate that the V6O13 hollow microflowers have great potential as the long-life and high-rate cathode materials for the next generation of Li-ion batteries.

Determination of Si/graphite anode composition for new generation Li-ion batteries: a case study.

Silicon with the properties of high capacity capability, moderate working potential, environmental sensitivity, and existence are the highly promising anode materials for lithium-ion batteries. Silicon anodes have disadvantageous properties and advantages like 300% volume change during lithium insertion and extraction process that can result in capacity fading and a shorter lifetime of the battery. In the literature, different optimizations of Silicon with different nanomaterials or composite materials, in different ratios, and with different binders and different procedures have been studied. The physical mixing of silicon with carbon provides a good performance by combining the high lithium storage capacity of the silicon and the good mechanical and conductive properties of carbon. Binders are one of the other factors affecting the performance of the Si/C anodes. In this study, different ratios of silicon/graphite combinations were tested. The Si/C hybrid material provides an advantageous and efficient use for innovative lithium-ion anodes and available lithium-ion battery technology when the Si/C match performs a suitable combination of two material properties, such as the high lithium storage capacity of silicon and the conductive properties of carbon. This study is aimed to improve the performance of the cell by changing the amount of active material and polymer in the electrode by finding the most appropriate amount of active substance and binder polymer ratio in the electrode. The electrochemical result of the composition, which compensates for the problems caused by the volume expansion of the silicon by using less silicon, showed higher capacitive properties, as it exhibits better adhesion among these compositions with a higher binder ratio. This study resulted in more than 1000 mAh/g specific capacity after 100 cycles at C/3 rate and structural characterization of the samples before and after cycling provided information about the electrode content.

Aqueous processing based novel composite electrode for Li-ion batteries using an environmentally benign binder

Along with the high energy density and safer battery materials, easy and environment benign electrode processing is also one of the major concerns for the battery manufacturing industries. Therefore, herein, water-based electrode processing is used which reduces manufacturing cost and makes easy and cost-effective recycling of discarded batteries. In addition, the increasing use of Li-ion batteries from portable electronics to electric vehicles has imposed a threat to the environment due to hazardous materials used. The present study also focuses on the replacement of polyvinylidene difluoride (PVDF) non-conducting binder dissolves in toxic solvent N-methyl 2-pyrrolidone with water-soluble poly (3,4-ethylene dioxythiophene): poly (styrene sulfonate) (PEDOT:PSS) conducting binder. The entire study is performed on the synergistic effect of PEDOT:PSS with multi-walled carbon nanotubes (MWCNTs or MC) and carbon black (CB) on Li-ion battery performance using LiFePO 4 cathode active material. The discharge capacities were found 144 mAh g −1 and 160 mAh g −1 at 0.1C for composite electrodes LFP/CB-9P and LFP/MC-9P, respectively having 9 wt% PEDOT:PSS. Whereas the composite electrodes LFP/CB-10PV and LFP/MC-10PV having 10 wt% PVDF binder show only capacities 117 mAh g −1 and 134 mAh g −1 , respectively. The composite electrode LFP/MC-9P shows the highest capacities up to 20C rate and maximum retention capacity of 84% at 5C after 500 cycles among all samples studied. Whereas electrodes prepared with PVDF binder could not perform well at more than 5C current rate, capacity retention is also found nearly 0% after 500 cycles. Therefore, superior results of PEDOT:PSS and MWCNTs with LiFePO 4 propose an environmentally benign composite electrode of next generation Li-ion batteries for electric vehicles. Aqueous processed composite electrode for environmentally benign Li-ion battery .

Na doping into Li-rich layered single crystal nanoparticles for high-performance lithium-ion batteries cathodes

Lithium-rich layered manganese-based cathodes (LRLMOs) with first-class energy density (∼1000 W h kg−1) have attracted wide attention. Nevertheless, the weak cycle stability and bad rate capability obstruct their large-scale commercial application. Here, single crystal Li1.2−x Na x Ni0.2Mn0.6O2 (x = 0, 0.05, 0.1, 0.15) nanoparticles are designed and successfully synthesized due to the single crystal structure with smaller internal stress and larger ionic radius of Na. The synergistic advantages of single crystal structure and Na doping are authenticated as cathodes for Li ion batteries (LIBs), which can consolidate the crystallographic structure and be benefit for migration of lithium ion. Among all the Na doping single crystals, Li1.1Na0.1Ni0.2Mn0.6O2 cathode possesses supreme cycling life and discharge capacity at large current density. To be more specific, it exhibits a discharge capacity of 264.2 mAh g–1 after 50 charge and discharge cycles, higher than that of undoped material (214.9 mAh g–1). The discharge capacity of Li1.1Na0.1Ni0.2Mn0.6O2 cathode at 10 C (1 C = 200 mA g−1) is enhanced to 160.4 mAh g−1 (106.7 mAh g–1 for x = 0 sample). The creative strategy of Na doping single crystal LRLMOs might furnish an idea to create cathode materials with high energy and power density for next generation LIBs.

Li-rich layered oxide single crystal with Na doping as a high-performance cathode for Li ion batteries

Although Li-rich layered oxides (LLOs) have high specific capacity over 250 mAh g−1, their large scale applications are hindered because of the release of oxygen and structural change during cycling. In this paper, Na-doped LLOs single crystal, Li1.1Na0.1Ni0.13Co0.13Mn0.54O2 (N-LLNCMO), has been prepared to combine the advantages of Na doping and single crystal structure. As cathode in Li ion batteries, N-LLNCMO shows a higher discharge capacity of 278.5 mAh g–1 at 0.2 C and capacity retention of 87.0% after 100 charge and discharge cycles. More importantly, N-LLNCMO cathode delivers a superior rate capability (150.1 mAh g–1 at 10 C) and the discharge capacity of undoped analog is only 122.4 mAh g–1. The improved electrochemical performances are closely related to single crystal structure and Na doping which possess more stable structure, pinning effect and enlargement of the channels for Li ions diffusion. This strategy with synergistic effect of single crystal structure and Na doping can be developed to next generation Li ion batteries with high performance.

Towards a 3D-resolved model of Si/Graphite composite electrodes from manufacturing simulations

Composite graphite/silicon (Si) electrodes with low Si weight percentages are considered as a promising anode for next generation Li-ion batteries. In this context, understanding the mesostructural changes due to Si volume expansion and the complex electrochemical interplay between graphite and Si becomes crucial to unlock real-life applications of such composite electrodes. This work presents, for the first time, a three-dimensional (3D) physics-based model for graphite/Si composite electrodes, coupling electrochemistry and mechanics, using as input electrode mesostructures obtained from manufacturing-related Coarse-Grained Molecular Dynamics models. The slurry and dried electrode mesostructure are first generated by considering graphite and additives only, while the Si is included in an additional step. The model herein presented is a step further into obtaining a fundamental understanding of the complex processes happening in graphite/Si composite electrodes, paving the way towards their optimization. • A graphite/Si composite electrode mesostructural model was generated. • Coupled electrochemical and mechanical simulations are performed. • Complicated electrochemical interplay between Graphite and Si is analyzed. • Pressure and stresses acting on the CBD phase are studied.

Development of Silicon-Graphite-Reduced Graphene Oxide Anode for Lithium-Ion Batteries

Silicon (Si) anode was recently studied to overcome the storage capacity of graphite anode for lithium-ion (Li-ion) batteries. Si performs best as one of the candidates for anode material since its storage capacity is higher than that of graphite anode roughly ten times. However, due to its drastic volume expansion, prevention of capacity loss requires a support material such as carbon-based materials. Herein, Si-Graphite composite with the addition of reduced graphene oxide (RGO) was prepared and studied. The electrochemical evaluation of the prepared anode versus Li chip suggests a higher capacity than conventional graphite. The initial discharge capacity of Si-Graphite with RGO is ca. 740 mAh g-1 at 0.3 A cm-2. Also, as a full-cell with lithium nickel manganese cobalt oxides (NMC811) cathode, capacity was achieved up to ca. 160 mAh g-1 at 0.1C. The prototype of the 18650 cells also delivered a high storage capacity of up to 2.0 Ah at 0.1C. The result suggests the possibility of up-scaling Si-Graphite with RGO composite for higher storage capacity and cycling stability for the next generation of Li-ion batteries.