Origin of initial capacity loss in Ni-rich cathodes for sulfide-based all-solid-state batteries

We propose a strategy to mitigate both the initial capacity loss and long-term capacity degradation in Ni-rich cathodes by leveraging internal Li-ion transfer through blending with LiFePO 4 .

All-solid-state lithium metal batteries promise a specific energy >500 Wh/kg. A solid-state electrolyte (SSE) plays an irreplaceable role in reaching such an energy density goal. Among different SSE types, the sulfide and thiophosphate-based SSE has emerged as a prominent class of soft ionic conductors. Compared to their ceramic and oxide SSE counterparts, sulfide SSEs provide several favorable advantages, including a) high room temperature ionic conductivity up to 10 mS/cm that is comparable to liquid-based electrolytes; b) ductile and mechanically soft SSE that enables better processible and intimate contact with electrodes; and c) scalability with solution-based low-temperature synthesis route.However, when paring with a high voltage cathode, such as lithium nickel manganese cobalt oxide (NMC), the (electro)chemical instability of the sulfide SSE at the electrode/SSE interfaces becomes a major challenge to tackle with. The interfacial instability can result in up to 50% initial capacity loss in a Li/sulfide SSE/NMC battery, thereby keeping the sulfide SSEs from commercialization. Herein, by using neutron computed tomography, we trace in situ lithium displacement in an all-solid-state battery composed of a 7Li anode, natLi3PS4(LPS) electrolyte, and a natLiNi0.8Mn0.1Co0.1O2 (NMC811) cathode. We show that after the first galvanostatic charge/discharge cycle, lithium accumulates at the LPS/NMC811 interface and preferably fills in the pre-formed cracks in the cold-pressed LPS SSE pellet. Such irreversible lithium displacement contributes to the initial capacity loss of the Li/LPS/NMC battery. Our findings suggest that to achieve high-capacity retention of an all-solid-state sulfide-based battery using an NMC cathode, the cathode/sulfide interface should be better engineered and the defects of the LPS pellet should be suppressed.AcknowledgmentThis research was conducted at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) and is supported by Asst. Secretary, Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (VTO) through the Advanced Battery Materials Research (BMR) Program. This research used resources at High Flux Isotope Reactor, a DOE Office of Science User Facilities operated by the Oak Ridge National Laboratory.

The rapid development of mobile electronics, electric-vehicles and intermittent power generation relies on the availability of advanced electrochemical energy storage systems such as high capacity lithium ion batteries (LIBs). Although the state-of-the-art commercial LIBs have impressive electrochemical performance, they are suffering from relative low capacities due to the usage of host materials for storing lithium ions safely and reproducibly. The host material for LIB anode is dominated by graphite with a theoretical capacity of 372 mAh g-1. To further improve the capacity and energy density of LIBs, revolutionary changes in electrode materials, electrolytes, additives, binders and cell design are much needed. Alloying anode materials like Si, Ge and Sn have much higher theoretical capacities (4200, 1600 and 990 mAh g-1 for Si, Ge and Sn, respectively) as compared to graphite. However, a high capacity inevitably leads to a large electrode volume change during lithiation and de-lithiation process (e.g. 300% for Si-based anodes). Such a huge volume change can cause electrode pulverization, detachment of active materials from conductive additives, unstable solid-electrolyte interphase, and eventually result in a rapid, permanent capacity loss. Although Si-based anode has caught much research attention, formidable challenges remain to develop an electrode fabrication method that is efficient, low-cost, scalable, highly reproducible, and self-assembled, thus boosting the commercialization potential of Si-based anodes. As inspired by the hollow fiber membrane technology that has been successfully commercialized in the last decades to provide billions of gallons of purified drinking water worldwide, we report the use of carbonized asymmetric membrane electrodes (fiber and thin film types) that contain silicon, silicon monoxide, germanium, tin dioxide or vanadium (V) oxide to significantly increase LIB electrode capacity while maintaining a long cycling life and an excellent rate performance. These asymmetric membrane electrodes are fabricated using a modified reverse-osmosis membrane technology, the phase-inversion method combined with dip-coating and carbonization. The asymmetric membrane electrodes have a thin, nanoporous top layer (up to several microns) and a thick, macroporous bottom layer (up to 200 µm). The top layer can prevent fractured anode materials from falling away, while the bottom layer can efficiently accommodate the large volume changes of high capacity alloying anodes. 90% capacity of thin film asymmetric membrane at 1000 mAh g-1 containing Si nanoparticles can be retained after 200 cycles with an initial capacity loss of ~ 30%. Combining phase inversion with sol-gel chemistry, this method can be extended to obtain SnO2 and V2O5 asymmetric membranes. Thin film SnO2 asymmetric membrane electrode demonstrates a specific capacity of 500 mAh g-1 a current density of 280 mA g-1 (~0.5C) with >96% capacity retention after 400 cycles. When the current density is increased from 28 to 560 mA g-1, more than 65% capacity can be retained. The V2O5 electrode can be cycled at 0.5C with a capacity of 160 mAh g-1 for 380 times with ~100% capacity retention. The same method can be employed to stabilize micron-size Ge and Si alloying anodes with >80% capacity retention in 100 cycles. Most recently, our group has successfully fabricated various fibrous Si and Sn asymmetric membrane electrodes whose electrochemical performance is compared to thin film Si and Sn asymmetric membrane electrodes. e.g. ~90 % initial capacity at ~1,200 mAh g-1 can be maintained in 300 cycles applying a current density of 400 mA g-1 with an initial capacity loss less than 15%. These asymmetric membrane electrodes have been systematically characterized using extensive instruments spanning from scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS), Raman spectroscopy, powder X-ray diffractometer (PXRD), thermogravimetric analyzer (TGA), surface area analyzer (BET method) to X-ray photoelectron spectroscopy (XPS), as well as various electrochemical tests such as cycling and rate performance, cyclic voltammetry, and electrochemical impedance spectroscopy, purposing to understand the relationship between structure, chemical composition and electrochemical properties for these asymmetric membrane electrodes.

Electrode materials and electrolyte choices largely dictate the design parameters and the type of lithium-ion battery (LIB) that can be optimized and eventually utilized. Certainly all three components (anode, electrolyte, and cathode) must work in harmony to produce the highest possible energy density achievable for an LIB-based energy storage device. Balancing the electrochemical performance characteristics of the cathode and anode active materials is critical for maximizing the power/energy density of a LIB. Hard carbon (non-graphitizable) anode materials, like tin, tin oxide, silicon and silicon oxide, have a high theoretical capacity (>550 mAh/g depending on their structural and chemical properties) but unfortunately they also exhibit a large initial capacity loss (ICL), which overrides the true reversible capacity in a full cell. Overcoming the large ICL of hard carbon in a full-cell lithium-ion battery (LIB) necessitates a new strategy wherein a sacrificial lithium source additive such as Li5FeO4 (LFO) is used on the cathode side. Full batteries using hard carbon coupled with LFO/LiCoO2 (LCO) are currently under development at our laboratory. We find that the reversible capacity of a cathode containing LFO can be increased by 24%. Furthermore, the cycle performance of full cells with LFO additive is improved from <90% to >95%. We believe that the LFO can not only address the irreversible capacity loss of the anode, but can also provide the additional lithium ion source required to mitigate the lithium loss caused by side reactions. In addition, we have explored the possiblity to achieve higher capacity on hard carbon, whereby the energy density of full cells can be increased from ca. 300 Wh/kg to >400 Wh/kg .

Synthesis and electrochemical properties of La-doped Li4Ti5O12 as anode material for Li-ion battery

Keywords: solid-liquid interface, solid-state battery, surface-enhanced Raman spectroscopy (SERS), tip-enhanced Raman spectroscopy (TERS), neutron tomography, sulfide solid-state electrolyte, Raman imagingThe ever-growing needs for energy storage systems require batteries with even higher power and energy density with extended life and enhanced safety beyond the current Li-ion battery technologies. Fulfilling these needs requires new battery chemistries, including high-energy-density electrode materials, solid-state electrolytes, and efficient interphases to mitigate the side reactions between the electrodes and the electrolytes.Charge transport across the electrode and electrolyte interface is believed to be one of the charge/discharge rate-limiting steps. Although the composition, morphology, and structure of solid-electrolyte interphase (SEI) have been extensively studied, probing its evolution at the nanoscale is challenging to a large extent. Plasmon-enhanced Raman spectroscopy (PERS) is promising to solve this challenge. PERS is the resonant oscillation of conduction electrons at the interface between negative and positive permittivity molecules stimulated by incident light. It includes surface-enhanced Raman spectroscopy (SERS) and tip-enhanced Raman spectroscopy (TERS). In the first part of this talk, I will show that gap-mode SERS is ideal to probe salt solvation structure in the immediate vicinity (< 20 nm) of the electrode/electrolyte interface. SERS lacks the nanoscale resolution in the sample plane. This can be compensated by TERS. TERS analysis on cycled high-energy silicon anodes indicates that the nanometer scale SEI "islands" are unevenly distributed. Even for the same SEI "island", the composition is different from point to point with inter-point distance smaller than 10 nm.All-solid-state lithium metal batteries (SSBs) promise specific energy >500 Wh/kg. A solid-state electrolyte (SSE) plays an irreplaceable role in reaching such an energy-density goal. Sulfide-based SSEs have emerged as a prominent class of soft ionic conductors that have comparable room-temperature ionic conductivity to their liquid electrolyte counterparts. However, when paring with a high voltage cathode, such as lithium nickel manganese cobalt oxide (NMC), the (electro)chemical instability of the sulfide SSE at the electrode/SSE interfaces becomes a major challenge. The interfacial instability can result in >50% initial capacity loss in a Li/sulfide SSE/NMC battery, thereby keeping the sulfide SSEs from commercialization. In the second part of this talk, I will show how we synergistically use neutron computed tomography and in situ Raman imaging, with clustering analysis to track lithium displacement at the interface of a sulfide-based SSB. Acknowledgment This research was conducted at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) and is supported by Asst. Secretary, Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (VTO) through the Advanced Battery Materials Research (BMR) Program. This research used resources at High Flux Isotope Reactor, a DOE Office of Science User Facilities operated by the Oak Ridge National Laboratory.

As demand for energy storage expands, securing reliable supply-chains for raw battery materials is critical in mitigating the threats of delayed manufacturing and inflated manufacturing costs. These issues have pushed researchers and industry to consider alternative sources for traditional lithium-ion battery materials, such as graphite. Commonly available sources of graphite for Li-ion anodes include natural graphite and petroleum coke derived synthetic graphite. While many carbon sources have been studied, most require complicated processing and result in sub-par graphite anode materials. This talk highlights raw coal and coal derived materials as promising graphite sources thanks to their abundance of sp2 hybridized carbon, resulting in simpler processing, and low material costs.We show that coal derived graphite can be implemented as a lithium-ion anode, however, many chemical, microstructural, and morphological considerations are necessary to compare with commercial graphite performance. Key topics of this talk include i) the processing steps necessary for achieving high-performing coal-derived graphite, ii) chemical, microstructural, and morphological graphite characterization, and iii) comparative performance of coal-derived graphites and commercial graphite as lithium-ion anodes. Characterization of the anodes’ performance includes gravimetric capacity, initial capacity loss, coulombic efficiency, internal resistance, intercalation energetics, and pseudo-open circuit potential characterization. Emphasis is placed on the careful consideration and effects of fundamental anode properties (particle size, surface area, etc.) because they are crucial in determining the viability of alternative graphite sources for lithium-ion battery anodes.

The increasing demand for energy storage systems such as Li-ion batteries requires an increasing supply of critical minerals such as graphite. Graphite is the predominant anode material due to its high theoretical capacity, electrochemical stability and long cycle life. In an effort to develop sustainable supply chains to meet the increasing demand, alternative carbon feedstocks for synthetic graphite are needed. One emerging feedstock is coal, owing to its abundance and cost.A comprehensive study of several coal-derived graphites synthesized from anthracite, bituminous and coal pitch will be presented in this work. Material properties such as BET surface area, morphology and microstructure are examined through SEM imaging, XRD and RAMAN spectroscopy. The electrochemical performance in half cells such as initial capacity loss and gravimetric capacity will be presented for all of the coal-derived graphites investigated. Single layer pouch cell data will be discussed for selected materials and compared to a commercial MesoCarbon, MicroBead (MCMB) graphite.The White Forest bituminous coal shows the most promise as a feedstock for synthetic graphite production. It has been demonstrated that this material has comparable performance to the MCMB graphite used in this study and has superior capacity retention. Commentary will also be provided on the future steps needed to optimize the coal-derived graphites presented in this work.

As the shift to renewables continues, new sources of critical materials such as graphite are needed. One potential feedstock being investigated is coal. Coal-derived graphite shows promise as an anode material for Li-ion batteries1. In this work, a white forest coal-derived graphite will be studied, and its physical and electrochemical properties will be presented. In an effort to reduce the particle size and modify the coal-derived graphite, ball milling is used. Through this additional processing, the physical and electrochemical properties of the graphite are changed. These differences will be presented in this work.The physical properties that will be examined for the milled and unmilled graphites include microstructure such as d-spacing and crystallite size, BET surface area and morphology through SEM imaging. The electrochemical performance of the materials will also be discussed. The performance will be measured through initial capacity loss (ICL), gravimetric capacity, rate capability and cycle life.

2D materials are emerging materials for energy storage and among these layered double hydroxides (LDHs) seem particularly promising due to their structure, easily adjustable composition, and cheapness. This study marks the first reported application of an LDH, specifically NiFe‐NO3, as anode material in a sodium half‐cell, to the best of our knowledge. Despite an initial loss in capacity, the material demonstrates notable stability, retains a high specific capacity even after 50 discharge/charge cycles (~ 500 mAh/g). The intricate reaction mechanism was explored using various ex‐situ techniques such as DC magnetometry and FTIR, as well as in‐operando X‐ray Absorption Spectroscopy (XAS). The proposed Na‐storage mechanism in NiFe‐NO3 involves an initial irreversible "activation" during the first sodiation, characterized by a phase change reaction that leads to the formation of NiOx and Fe3O4, followed by a reversible mechanism involving both intercalation and conversion in subsequent cycles.

Tin (Sn) is a promising anode material for sodium-ion batteries (SIBs) due to its high theoretical specific capacity (847 mAh g-1) and volumetric capacity (6238 mAh cm-3). In addition, Sn is a commodity and can be readily sourced. However, alloy anodes tend to suffer from a low initial Coulombic efficiency (ICE) and severe capacity loss due to extensive volume expansion (~420% for Sn) during electrochemical cycling. In this work, commodity-sourced Sn is used (with an electrode active material composition of &gt;99% Sn) to demonstrate how these traditional challenges can be overcome without major modifications. When paired with a NaCrO2 (NCrO) cathode in a full cell, a high specific energy of 178 Wh/kg and volumetric energy density of 417 Wh/L can be achieved. This work highlights the opportunities for alloy materials such as Sn to enable high energy density SIBs.

IntroductionThe past few years have seen an increasing interest in the development of wireless sensor networks. But the limited available energy source is one of the major bottlenecks, which are limiting the wireless sensor technology from mass deployment. Micro energy harvesting is the most promising solution towards autonomous sensor nodes by providing low cost, permanent, and maintenance-free energy source to wireless sensor nodes. Because many harvesting devices could only capture low levels of ambient energy, very small batteries are required for energy storage and intermittent use. Compared to liquid electrochemical batteries with limitation of life span, thin film batteries with flexible charging models and excellent cycle life are very promising for paring with a variety of energy harvesting devices. Thin-film rechargeable lithium or Li-ion batteries have been investigated extensively. So far, positive-negative electrode combinations of LiCoO2-Li, LiMn2O4-Li, TiS2-Li, LiCoO2-SnO and LiMn2O4-V2O5 have been reported. Active Li requires an extra-protective layer to exclude entry of open air. Further, the voltage of the batteries containing Li electrode during charge-discharge processes is restricted to prevent degradation by over-charge or over-discharge. In the electrochemical conversion of oxides system, the initial Li2O formation is irreversible and a significant initial capacity loss is observed. On the other hand, V2O5 is toxic and moisture-sensitive. For practical applications, Nb2O5 displayed relatively good charge-discharge performance and stability although the poor crystallinity of films fabricated through low-temperature processes. In this study, we report on electrochemical properties of amorphous Nb2O5thin film and its application to rechargeable thin film batteries. Experimental. Nb2O5 thin films are deposited using an RF magnetron sputtering equipment (ISP-400, ULVAC) and the thicknesses of these thin films were controlled by the sputtering time. During the deposition, the substrate temperature, the sputtering pressure and the RF power were kept at room temperature, 1 Pa and 100 W, and the sputtered gas (O2/Ar) composition of 1:9 was maintained to minimize the loss of Oxygen. The electrochemical properties of Nb2O5 thin film electrodes were investigated in a liquid electrolyte (1 M LiPF6 in EC + DMC (EC/DMC = 1/1 v/v) )using head-type cells. A Li foil and 20 μm PBS separator were used as the counter electrode and separator. These half-cells were assembled in an Ar-filled glove box. The charge and discharge measurements were carried out using a source-meter (Keithley 2400) with the applied various charge-discharge currents and the cutoff voltages of between 1.0 and 3.0 V. In addition, thin-film batteries were fabricated on 30 μm SUS304 substrates. Charge–discharge properties of these thin-film batteries were measured at room temperature with charge-discharge currents of 50 μA and cutoff voltages of between 3.2 V and 0.5V by using a charge–discharge measuring instrument (ACD-01, Asuka). The surface area of thin film batteries was 4.2 x 4.2 cm2. Results and discussion. Figure 1 shows charge-discharge curves of Nb2O5 thin films in the voltage window 1.0-3.0 V (vs. Li/Li+) at a rate of 5 μAh/cm2 up to 10 cycles. The open circuit voltage of the cell lies at 2.46 V. The discharge capacities in the 1st, 3rd, 5th, and 10th cycles are 59.4, 56.8, 56.1, and 56.8 μAh/cm2μm, respectively; the corresponding charge capacities are 79.2, 56.1, 55.4, and 56.2 μAh/cm2μm for 1st, 3rd, 5th, and 10th cycles, respectively. After first few cycles, the coulombic efficiency reaches to 100%. Such irreversible capacity loss during first few cycles was also observed with other nanoparticle. Figure 2a shows charge-discharge cycling curves of a flexible thin-film battery based on Li2Mn2O4 thin films of 720 nm and Nb2O5 thin films of 800 nm at a charge-discharge current of 50 μA. The charge-discharge curve consists of smooth S-shape profiles at any cycle without any plateau having average voltage of about 1.7 V and the voltage may vary in broad voltage range of 3.2-0.5V with cycling. As shown in Fig. 2b, an initial irreversible capacity was observed, which is due to irreversible Li ions trapped in the negative electrode. The coulombic efficiency at the first cycle was only 26.3%, which is due to a large internal resistance of the battery when no Li ion was inserted into Nb2O5 thin films. After 20 cycles, the cycle performance of the thin-film battery showed steady cycling behaviors and the coulombic efficiency was all over 95% except for the first few cycles. The maximium discharge capacity (30.9 μAh/cm2μm) of the thin-film battery based on the negative electrode volume is about half of the negative capacity of the liquid battery (56.8 μAh/cm2μm), which may originate from Li ions partly being inserted into the negative electrode. Figure 1

The phenomenon of increasing bactericidal activity of N-chlorotaurine in the presence of chlorine-consuming material has been investigated both on a chemical-analytical and microbiological basis using plasma as substrate and chloramine T for comparison. Chlorine consumption assessed by iodometric titration showed a biphasic time-course with a very fast loss of oxidation capacity within one minute (N-chlorotaurine: -9.3%, chloramine T: -16.8%) followed by a slow loss which could still be detected after 24 h (total loss -61.7% and -74.1%, respectively). Killing curves revealed that an increase in bactericidal activity, in spite of improved consumption, did not occur with all strains, and could be detected only at a certain degree of consumption. Escherichia coli and Pseudomonas aeruginosa showed the most pronounced effect, Streptococcus pyogenes and Proteus mirabilis a medium-sized one, while it was absent in Staphylococcus aureus. With chloramine T, an increase in bactericidal activity could not be proved. The chemical basis of these consumption effects can be reduced to four reaction types: oxidation of thiols; chlorine substitution of activated C-H compounds; transhalogenation; and hydrolytic degradation of N-chloro-alpha-amino acids and -peptides emerging by transhalogenation. The initial fast loss of oxidation capacity can be attributed mainly to oxidation of thiols, while the subsequent slower decrease is caused by the other types of reaction. The increase in bactericidal activity, on the other hand, can be explained by transhalogenation, leading to the formation of more bactericidal N-chloro compounds by which the loss of N-chlorotaurine is over-compensated.

Purpose – The purpose of this study is to develop a numerical framework to predict the time-dependent probability of failure of a bridge subjected to multiple vehicle impacts. Specially, this study focuses on investigating the inter-relationship between changes in life-cycle parameters (e.g., damage size caused by vehicle impact, loss of initial structural capacity, and threshold intervention) and bridges probability of failure. Design/Methodology/Approach – The numerical procedure using MATLAB program is developed to compute the probability failure of a bridge. First, the importance and characteristics of life-cycle analysis is described. Then, model for damage accumulation and life cycle as a result of heavy vehicle impacts is discussed. Finally, the probability of failure of a bridge subjected to vehicle impacts as a result of change in life-cycle parameters is presented. Findings – The results of study show that damage size caused by both vehicle impacts and loss of initial structural capacity have a great impact on the long-term safety of bridges. In addition, the probability of failure of a bridge under different threshold limits indicates that the structural intervention (e.g., repair or maintenance) should be undertaken to extend the service life of a bridge. Research Limitations/Implications – The damage sizes caused by heavy vehicle impacts are based on simple assumptions. It is suggested that there would be a further study to estimate the magnitude of bridge damage as a result of vehicle impact using the full-scale impact test or computational simulation. Practical Implications – This will allow much better predictions for residual life of bridges which could potentially be used to support decisions on health and maintenance of bridges. Originality/Value – The life-cycle performance for assessing the time-dependent probability of failure of bridges subjected to multiple vehicle impact has not been fully discussed so far.

The graphite/silicon‐based diffusion‐dependent electrodes (DDEs) are one of the promising electrode designs to realize high energy density for all‐solid‐state batteries (ASSBs) beyond conventional composite electrode design. However, the graphite/silicon‐based electrode also suffers from large initial irreversible capacity loss and capacity fade caused by significant volume change during cycling, which offsets the advantages of the DDEs in ful‐cell configuration. Herein, a new concept is presented for DDEs, dry pre‐lithiated DDEs (PL‐DDEs) by introducing Li metal powder. Since Li metal powder provides Li ions to graphite and silicon even in a dry state, the lithiation states of active materials is increased. Moreover, the residual Li within PL‐DDE further serves as an activator and a reservoir for promoting the lithiation reaction of the active materials and compensating for the active Li loss upon cycling, respectively. Based on these merits, ASSBs with PL‐DDE exhibit excellent cycling performance with higher columbic efficiency (85.2% retention with 99.6% CE at the 200th cycle) compared to bare DDE. Therefore, this dry lithiation process must be a simple but effective design concept for DDEs for high‐energy‐density ASSBs.