Li Distribution Research Articles

The chemical origin of temperature-dependent lithium-ion concerted diffusion in sulfide solid electrolyte Li10GeP2S12

Solid-state batteries have received increasing attention in scientific and industrial communities, which benefits from the intrinsically safe solid electrolytes (SEs). Although much effort has been devoted to designing SEs with high ionic conductivities, it is extremely difficult to fully understand the ionic diffusion mechanisms in SEs through conventional experimental and theoretical methods. Herein, the temperature-dependent concerted diffusion mechanism of ions in SEs is explored through machine-learning molecular dynamics, taking Li10GeP2S12 as a prototype. Weaker diffusion anisotropy, more disordered Li distributions, and shorter residence time are observed at a higher temperature. Arrhenius-type temperature dependence is maintained within a wide temperature range, which is attributed to the linear temperature dependence of jump frequencies of various concerted diffusion modes. These results provide a theoretical framework to understand the ionic diffusion mechanisms in SEs and deepen the understanding of the chemical origin of temperature-dependent concerted diffusions in SEs.

Mixed Ionic–Electronic Conduction and Magnetoelectric Coupling in Li0.5Fe2.5–xCrxO4(x= 1.0, 1.1, 1.3, 1.5, and 1.6) Involving Magnetization Compensation Phenomenon

The correlations between the crystal structural, magnetic, and electrical properties of Li0.5Fe2.5–xCrxO4 (x = 1.0, 1.1, 1.3, 1.5, and 1.6) have been investigated by neutron diffraction, DC magnetization, and impedance spectroscopy. Crystal structural analysis reveals mixed cation (Li, Fe, and Cr) distributions over both tetrahedral and octahedral crystallographic sites and an enhancement of the site disorder with increasing Cr concentration. The magnetization study yields ferrimagnetic ordering for all the compounds below the respective TC (640 K for x = 1.0 to 470 K for x = 1.6), and magnetization compensation at the respective TComp (540 K for x = 1.0 to 290 K for x = 1.6). The comprehensive analyses of the frequency and temperature-dependent impedance data in terms of DC and AC conductivities reveal the presence of mixed ionic and electronic conductions. The ionic conduction in the compounds is anticipated due to the presence of Li+ ions over the tetrahedral and octahedral crystallographic sites, whereas electron migration through a small polaron hopping mechanism is responsible for electronic conductivity. The relative contributions of electronic and ionic conductions are determined by charge transference number analysis. Almost equal fractions of the ionic and electronic conductivities for the composition x = 1.5 over the entire temperature range of 300 to 600 K reveal the character of a nearly ideal mixed conductor. We have shown highly tunable relative contributions of the ionic and electronic conductions with Cr substitution at room temperature. In addition, a strong coupling between magnetic and electric degrees of freedoms has been demonstrated by the changes in the slopes of the temperature-dependent DC and AC conductivities at both the ferrimagnetic ordering temperature TC and at the magnetization compensation temperature TComp. The role of cation distributions over the tetrahedral and octahedral sites on the conduction as well as magnetic properties has been discussed.

MnO2 nanosheet modified N, P co-doping carbon nanofibers on carbon cloth as lithiophilic host to construct high-performance anodes for Li metal batteries

Lithium (Li) metal batteries have attracted much attention owing to its ultra-high energy density. However, as important part of Li metal batteries, Li anodes still face many challenges, mainly including uncontrolled dendritic Li formation, dramatical volume variation and serious pulverization. Herein, manganese dioxide (MnO2) nanosheet modified nitrogen (N), phosphorus (P) co-doping carbon nanofibers (NPC) on carbon cloth (CC) (MnO2@NPC-CC) is successfully fabricated through electrodeposition approach and further treated with Li by the molten-infusion method to prepare Li based Mn@NPC-CC (Li-Mn@NPC-CC) electrode. The synergy of MnO2 and NPC obviously increases the reaction rate between MnO2@NPC-CC and Li and guides even Li distribution over infusion process. Additionally, theoretical calculation, simulation and experimental results further indicate that N, P, Mn multi-doping effectively improves the superior lithiophilicity of Li-Mn@NPC-CC, which induces uniform Li deposition/dissolution to suppress dendrite growth over cycles. Moreover, conductive and porous NPC matrix not only effectively improves the stability of Li-Mn@NPC-CC, but also provides abundant spaces to accelerate the transfer of ion/electron and buffer electrode dimension variation during cycling. Hence, Li-Mn@NPC-CC-based symmetric cells exhibit extra-long cycling life (over 2200 h) with small hysteresis of 20 mV. When the Li-Mn@NPC-CC anode couples with air, Li iron phosphate (LiFePO4), or hard carbon (C) cathode, the assembled full cells exhibit outstanding performance with low hysteresis and stable cycling properties. Especially, the corresponding pouch-typed Li–air cells also exhibit good performance at different bending angles and even power a series of electronic devices.

Considerations in applying neutron depth profiling (NDP) to Li-ion battery research

Li distribution within the battery electrode material is quantified using neutron depth profiling (NDP) as a function of depth in real-time.

The bi-modal 7Li distribution of the Milky Way’s thin-disk dwarf stars

Context. The lithium abundance, A(Li), in stellar atmospheres suffers from various enhancement and depletion processes during the star’s lifetime. While several studies have demonstrated that these processes are linked to the physics of stellar formation and evolution, the role that Galactic-scale events play in the galactic A(Li) evolution is not yet well understood. Aims. We aim to demonstrate that the observed A(Li) bi-modal distribution, in particular in the FGK-dwarf population, is not a statistical artefact and that the two populations connect through a region with a low number of stars. We also want to investigate the role that Galactic-scale events play in shaping the A(Li) distribution of stars in the thin disk. Methods. We use statistical techniques along with a Galactic chemical evolution model for A(Li) that includes most of the well-known 7Li production and depletion channels. Results. We confirm that the FGK main-sequence stars belonging to the Milky Way’s thin disk present a bi-modal A(Li) distribution. We demonstrate that this bi-modality can be generated by a particular Milky Way star formation history profile combined with the stellar evolution’s 7Li depletion mechanisms. We show that A(Li) evolution can be used as an additional proxy for the star formation history of our Galaxy.

Application of high-spatial-resolution secondary ion mass spectrometry for nanoscale chemical mapping of lithium in an Al-Li alloy

High-spatial-resolution secondary ion mass spectrometry offers a method for mapping lithium at nanoscale lateral resolution. Practical implementation of this technique offers significant potential for revealing the distribution of Li-containing nanoscale precipitates in Al-Li alloys with exceptional lateral resolution and elemental sensitivity. Here, two state-of-the-art methods are demonstrated on an aluminium-lithium alloy to visualise nanoscale Li-rich phases by mapping the 7 Li + secondary ion. NanoSIMS 50L analysis with a radio frequency O − plasma ion source enabled visualisation of needle-shaped T 1 (Al 2 CuLi) phases as small as 75 nm in width. A compact time-of-flight secondary ion mass spectrometry detector added to a focused ion beam scanning electron microscope facilitated mapping of the T 1 phases down to 45 nm in width using a Ga + ion beam. Correlation with high resolution electron microscopy confirms the identification of T 1 precipitates, their sizes and distribution observed during SIMS mapping. • High-lateral-resolution SIMS was used to characterise Li distribution in nanoscale. • The observations from SIMS were validated using correlative electron microscopy. • NanoSIMS visualises Li-rich T 1 (Al 2 CuLi) phases as small as 75 nm in size. • FIB ToF-SIMS visualises intergranular T 1 precipitates as small as 45 nm in size. • STEM-EDX analysis provides complementary information of phase chemistry.

Use of Pulsed RF Glow Discharge Optical Emission Spectroscopy for the Study of Elemental Distribution of Li-NMC Cathode at Various State of Charge in Li-Ion Batteries

Glow discharge optical emission spectroscopy (GDOES) is an analytical technique that provides both a surface and depth profile of the elemental composition and distribution of solid or porous samples. Although GDOES is a destructive technique, it provides the advantage of being a high throughput technique that is highly sensitive to all elements from H to U and can provide high resolution (from nm to µm) depth profiles of elemental distributions in practically any sample. Previous works have investigated and optimized the operating parameters of using GDOES to study negative electrode materials and from the data gathered therein [1] we used 5% H2 in Ar gas in this study to increase sputtering rate of Li-NMC cathode materials and to increase sensitivity to Li in the sample to provide a more detailed elemental distribution. This study investigates the use of GDOES as a method for analyzing elemental and specifically lithium distribution in Li-NMC cathode materials in extreme depth and with validation from other techniques such as x-ray photoelectron spectroscopy (XPS) and x-ray fluorescence (XRF) and with additional morphological analysis of cells using x-ray computed tomography (X-ray CT).In this study coin cells were assembled in an Ar filled glovebox using a 15 mm diameter double sided graphite anode coated on a Cu current collector, 14 mm double sided NMC 111 cathode coated on an Al current collector, either a Celgard 3401 or 5550 separator, and 75 µL of 1M LiPF6–EC:EMC (3:7) electrolyte. The coin cells were then brought outside and EIS data was taken on the freshly made cells. They were then allowed to rest for 12 hours before going through a formation cycle at a C-rate of C/20. After the formation cycle, all cells went through 10 charge/discharge cycles at a C-rate of C/5. After these cycles EIS data was taken again and the cells were then charged to different states of charge (SOC) of 0, 25, 75, and 100% and again EIS data was taken after this. The cells were then brought back into the glovebox where they were de-crimped and disassembled. The electrodes were then rinsed in DMC and dried. They were then analyzed using XPS for surface analysis, XRF for elemental mapping, and X-ray CT for analysis of electrode morphology. Finally, they were analyzed using GDOES and the through thickness Li atomic distribution was plotted for the SOCs listed. An example of atomic concentration distribution of various elements for a SOC of 0% is shown by Figure 1. This study aims to validate the use of GDOES to generate accurate Li distribution profiles and elemental distributions in Li-NMC cathode materials.[1] H. Takahara, A. Kojyo, K. Kodama, T. Nakamura, K. Shono, Y. Kobayashi, M. Shikano, and H. Kobayashi, J. Anal. At. Spectrom., 29, 95–104 (2014). Figure 1

Suppressing High-Current-Induced Phase Separation in Ni-Rich Layered Oxides by Electrochemically Manipulating Dynamic Lithium Distribution.

Understanding the cycling rate-dependent kinetics is crucial for managing the performance of batteries in high-power applications. Although high cycling rates may induce reaction heterogeneity and affect battery lifetime and capacity utilization, such phase transformation dynamics are poorly understood and uncontrollable. In this study, synchrotron-based operando X-ray diffraction is performed to monitor the high-current-induced phase transformation kinetics of LiNi0.6 Co0.2 Mn0.2 O2 . The sluggish Li diffusion at high Li content induces different phase transformations during charging and discharging, with strong phase separation and homogeneous phase transformation during charging and discharging, respectively. Moreover, by exploiting the dependence of Li diffusivity on the Li content and electrochemically tuning the initial Li content and distribution, phase separation pathway can be redirected to solid solution kinetics at a high charging rate of 7 C. Finite element analysis further elucidates the effect of the Li-content-dependent diffusion kinetics on the phase transformation pathway. The findings suggest a new direction for optimizing fast-cycling protocols based on the intrinsic properties of the materials.

Evidence of lithium mobility under neutron irradiation

Understanding compositional and microstructural changes in functional intermetallic coatings is of great importance for fusion energy and nuclear materials applications. Tritium ( 3 H) and lithium ( 6 Li, 7 Li) transport within a neutron irradiated target rod employing an aluminide-coated austenitic stainless-steel cladding was investigated using state-of-the-art multimodal imaging. Specifically, a scanning electron microscope augmented with focused ion beam (SEM-FIB) was used to prepare lift-out samples of the irradiated coating for microanalysis. Scanning transmission electron microscopy (STEM) was used to acquire atomic-scale information on the coating surface microstructure, morphology, and composition. Atomic force microscopy (AFM) was used to determine lift-out dimensions nondestructively. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) revealed the presence of carbonaceous species and unexpected lithium isotopic distributions in the irradiated tubing, suggesting light isotope mobility between internal target components during irradiation. SIMS chemical mapping of aluminide coatings at core midplane and lower core locations of the cladding shows that light isotopic (e.g., 3 H, 6 Li, 7 Li) distributions are different in the irradiated coating. Advance correlative imaging results suggest lithium transport during the tritium production process and give new insights into the fundamental transport mechanism within the target during irradiation and non-equilibrium conditions.

Cycling Rate-Induced Spatially-Resolved Heterogeneities in Commercial Cylindrical Li-Ion Batteries.

Synchrotron high-energy X-ray diffraction computed tomography has been employed to investigate, for the first time, commercial cylindrical Li-ion batteries electrochemically cycled over the two cycling rates of C/2and C/20. This technique yields maps of the crystalline components and chemical species as a cross-section of the cell with high spatiotemporal resolution (550 × 550 images with 20 × 20 × 3 µm3 voxel size in ca. 1 h). The recently developed Direct Least-Squares Reconstruction algorithm is used to overcome the well-known parallax problem and led to accurate lattice parameter maps for the device cathode. Chemical heterogeneities are revealed at both electrodes and are attributed to uneven Li and current distributions in the cells. It is shown that this technique has the potential to become an invaluable diagnostic tool for real-world commercial batteries and for their characterization under operating conditions, leading to unique insights into "real" battery degradation mechanisms as they occur.

Effect of Li and Li-RE co-doping on structure, stability, optical and electrical properties of bismuth magnesium niobate pyrochlore

New Bi1.5Mg0.9-xLixNb1.5O7–δ (x = 0.25; 0.40) and Bi1.4RE0.1Mg0.5Li0.4Nb1.5O7–δ (RE – Eu, Ho, Yb) compounds with the pyrochlore structure were synthesized. The displacements of the A-site atoms (96g) and O' ones (32e) as well as the Li and RE atoms distribution in the A-sites were determined. The dopant distribution was proven by ab initio calculations. The most preferable (Bi1.5Li0.5)(Nb1.5Mg0.5)O7 model was predicted with a direct band gap of 3.18 eV corresponding to the experimental Eg for Bi1.5Mg0.5Li0.4Nb1.5O7–δ. The thermal stability of the compounds in air up to 1100–1220 °C and the reducing atmosphere up to 400 °C was determined. The charge disbalance in the A2O' sublattice and the oxygen vacancies predetermine the dielectric behavior of the ceramics up to 200 °C, the mixed conductivity at high temperatures (T > 200 °C), and the proton transport up to 400 °C.

In-situ growth of Ag particles anchored Cu foam scaffold for dendrite-free lithium metal anode

Metallic lithium is considered to be the potential anode for high energy density rechargeable Li batteries. Yet the growth of lithium dendrites impedes the industrial production of lithium metal batteries. Herein, we fabricate a dendrite-suppressed composite Li metal anode via introducing Ag particles as lithiophilic layer on the 3D copper foam (Cu-Ag). The Li ion prefers deposit on the surface of Cu-Ag foam, which is beneficial to the better adsorption of the Cu-Ag hierarchical heterojunction structure by the first-principles calculations. The heterojunction structure can further reduce the nucleation overpotential and surface current density of the composite Cu-Ag-Li anode to realize the homogeneous Li distribution for stable Li deposited/stripped. Thus, the Cu-Ag-Li composite electrode (CAL) presents better electrochemical performance in the symmetric battery and excellent rate performance in the full cell with a greatly enhanced capacity retention of 83% after 500 cycles. This strategy presents a general approach to suppress the growth of lithium dendrites and regulate the volume changes for long-life span lithium metal batteries.

Intrinsic Li Distribution in Layered Transition-Metal Oxides Using Low-Dose Scanning Transmission Electron Microscopy and Spectroscopy

Understanding Li distribution in layered lithium transition-metal oxide (LiTMO) cathodes in Li-ion batteries has been a major challenge at the atomic scale and nanoscale. Li is extremely difficult to study by transmission electron microscopy (TEM) because the high-energy electrons impart significant energy and cause massive migration. Here, we directly map the intrinsic spatial distribution and bonding of Li in LiNiO2-layered cathode materials using low-dose and low-loss electron energy loss spectroscopy (EELS). EELS spectra of the Li–K edge are measured simultaneously with O–K and Ni–L, M3,2 edges from layered, cation-mixed, and rock-salt phases and directly matched with atomic-resolution scanning TEM images to correlate the changes in peak intensities and positions to the stoichiometry changes with continual loss of Li and O. Changes in the Li content in the LiNiO2 particles as a function of electron beam dose are studied by sequential Li spectroscopic mapping. We show that the “intrinsic” Li distribution can be observed using a total dose of less than ∼1.5 × 108 e– nm–2 at an accelerating voltage of 80 kV. The method of nanoscale mapping of Li distribution introduced in this study is applicable to high-Ni LiTMO cathode materials (>89% of Ni) as well as LiNiO2. Further study on the extra peaks of the Li–K edge reveals that the peak at ∼59 eV is from the Li ions intercalated in between NiO2 layers barely interacting with each other with less Li K shell electrons pulled to the L shell electrons in NiO2. The results shown here provide improved low-loss TEM characterization approaches that can be used to understand the intrinsic fundamental behaviors in Li-ion batteries.

Determination of the Li Distribution in Synthetic Recycling Slag with SIMS

The recovery of technically important elements like lithium from slag of pyrometallurgical recycling of lithium traction batteries will be very important in future due to the expected increasing demand of this element with the upcoming world-wide implementation of electro mobility. Therefore, the investigation of possibilities to recover lithium from pyrometallurgical slag from the recycling of lithium traction batteries is mandatory. In this context, the EnAM (engineered artificial mineral) approach is very promising. Solidified melt of synthetic recycling slag with the compounds Li2O-MgO-Al2O3-SiO2-CaO-MnO contains various Li-bearing phases including spinel solid solution, Li-aluminate and eucryptite-like Li-alumosilicate. Most probably, the Ca-alumosilicate matrix (melilite-like solid solution) incorporates lithium as well. These compounds can be determined and calculated to an acceptable approximation with electron probe microanalysis (EPMA). Nevertheless, an adequate precise measurement of lithium is virtually impossible due to the extremely low fluorescence yield and long wavelength of Li Kα. Secondary mass spectrometry (SIMS) can be used to fill this gap in the analytical assessment of the slag. Therefore, the combination of these two analytical methods can distinctively improve the mineralogical and chemical characterization of lithium-containing solidified (slag) melt.

Lithiophilic NiO Nanoarrays-Modified Ni Skeletons with Vertical Channels for High-Loading Li Metal Batteries

Li metal has been a promising anode material for high-energy-density batteries because of its ultrahigh theoretical capacity, but its practical application is hindered by serious dendrite growth and volume change. Herein, NiO nanoarrays are grown on a porous Ni skeleton derived from phase inversion method for stabilizing Li metal. The lithiophilic NiO nanoarrays decrease Li nucleation barrier and local current density, and provide abundant sites for nucleation. The Ni skeleton with vertical channels and interconnected small pores, not only provides Li storage space and ion channels, but also alleviates top-surface deposition and improved uniformity of Li distribution. As a result, the half cells comprising the NiO nanoarrays-modified Ni skeletons demonstrate a high Coulombic efficiency of 98.8% under 4 mAh cm−2 over 210 cycles (>1700 h), and the symmetric cells show much reduced voltage hysteresis and prolonged lifespan (>2000 h) under a capacity of 5 mAh cm−2 and a current density of 2 mA cm−2. Full cells with LiFePO4 as cathodes delivered a capacity retention of 79.4% after 500 cycles at 2 C and excellent rate capability at 10 C, shedding a fresh light on an effective strategy for the practical application of Li metal batteries.

WIYN Open Cluster Study. LXXXV. Li in NGC 2243: Implications for Stellar and Galactic Evolution

AbstractHigh-dispersion spectra in the Liλ6708 region have been obtained and analyzed in the old, metal-deficient cluster NGC 2243. From Hydra spectra for 29 astrometric and radial velocity members, we derive rotational velocities, as well as [Fe/H], [Ca/H], [Si/H], and [Ni/H] based on 17, 1, 1, and 3 lines, respectively. Using ROBOSPECT, an automatic equivalent width measurement program, we derive [Fe/H] = −0.54 ± 0.11 (MAD), for an internal precision for the cluster [Fe/H] below 0.03 dex. Given the more restricted line set, comparable values for [Ca/H], [Si/H], and [Ni/H] are −0.48 ± 0.19, −0.44 ± 0.11, and −0.61 ± 0.06, respectively. WithE(B−V) = 0.055, appropriate isochrones imply (m−M) = 13.2 ± 0.1 and an age of 3.6 ± 0.2 Gyr. Using available VLT spectra and published Li abundances, we construct an Li sample of over 100 stars extending from the tip of the giant branch to 0.5 mag below the Li dip. The Li dip is well populated and, when combined with results for NGC 6819 and Hyades/Praesepe, implies a mass/metallicity slope of 0.4M⊙/dex for the high-mass edge of the Li dip. The A(Li) distribution among giants reflects the degree of Li variation among the turnoff stars above the Li dip, itself a function of stellar mass and metallicity and strongly anticorrelated with avrotdistribution that dramatically narrows with age. Potential implications of these patterns for the interpretation of Li among dwarf and giant field populations, especially selection biases tied to age and metallicity, are discussed.

Engineering the Site‐Disorder and Lithium Distribution in the Lithium Superionic Argyrodite Li6PS5Br

AbstractLithium argyrodite superionic conductors, of the form Li6PS5X (X = Cl, Br, and I), have shown great promise as electrolytes for all‐solid‐state batteries because of their high ionic conductivity and processability. The ionic conductivity of these materials is highly influenced by the structural disorder of S2−/X− anions; however, it is unclear if and how this affects the Li distribution and how it relates to transport, which is critical for improving conductivities. Here it is shown that the site‐disorder once thought to be inherent to given compositions can be carefully controlled in Li6PS5Br by tuning synthesis conditions. The site‐disorder increases with temperature and can be “frozen” in. Neutron diffraction shows this phenomenon to affect the Li+ substructure by decreasing the jump distance between so‐called “cages” of clustered Li+ ions; expansion of these cages makes a more interconnected pathway for Li+ diffusion, thereby increasing ionic conductivity. Additionally, ab initio molecular dynamics simulations provide Li+ diffusion coefficients and time‐averaged radial distribution functions as a function of the site‐disorder, corroborating the experimental results on Li+ distribution and transport. These approaches of modulating the Li+ substructure can be considered essential for the design and optimization of argyrodites and may be extended to other lithium superionic conductors.

Visualizing Lithium Distribution and Degradation of Composite Electrodes in Sulfide-based All-Solid-State Batteries Using Operando Time-of-Flight Secondary Ion Mass Spectrometry.

Understanding the electrochemical reactions taking place in composite electrodes during cell cycling is essential for improving the performance of all-solid-state batteries. However, comprehensive in situ monitoring of Li distribution, along with measurement of the evolution of degradation, is challenging because of the limitations of the characterization techniques commonly used. This study demonstrates the observation of Li distribution and degradation in composite cathodes consisting of LiNi0.8Co0.15Al0.05O2 (NCA) and 75Li2S·25P2S5 (LPS) during cell operation using operando time-of-flight secondary ion mass spectrometry. The evolution of the nonuniform reaction of NCA particles during charge and discharge cycles was successfully visualized by mapping fragments containing Li. Furthermore, degradation of the NCA/LPS interface was investigated by mapping POx- and SOx- fragments, which are related to the solid electrolyte interphase. We found that during the charge-discharge cycle and application of a high-voltage stress to the composite electrodes, the PO2- and PO3- fragments increased monotonically, whereas the SO3- fragment exhibited a reversible increase-decrease behavior, implying the existence of a redox-active component at the NCA/LPS interface. The demonstrated technique provides insights into both the optimized structures of composite electrodes and the underlying mechanisms of interfacial degradation at active material/solid electrolyte interfaces.

Can carbon sponge be used as separator in Li metal batteries?

The high theoretical specific capacity and low redox potential endow lithium (Li) great promise to be used in the next generation rechargeable batteries. However, the safety issues and cycling degradation that are caused by dendrite growth and high reactivity of Li, impede the practical application of Li metal batteries. Herein, a strategy is reported to confine electrolyte in a nitrogen- and carboxyl-rich hollow carbon sponge reservoir. The hollow structure and its lithiophilicity help to mitigate the side reactions by containing the electrolyte. The carboxyl groups in the carbon sponge that can form hydrogen bond with 1,2-dimethoxyethane and thus alleviate the Li solvation and enhance the Li mobility, along with the lithiophilicity that controls Li distribution, substantially suppress dendrite growth. The limited Li solvation also reduces the parasitic reactions of solvent molecules on Li anode. With such carbon sponge electrolyte reservoir, the Li-Li cells can operate stably for over 4000 hours and Li-Cu cells exhibit Coulombic efficiency of ~99.3% after at least 800 cycles. The practical application of such reservoir is also demonstrated in Li-LiCoO2 and Li-S batteries.

Interfacial Potentials in a Thin Film All-Solid-State Li-Ion Battery Probed By in Operando KPFM

Designing smaller, safer, cheaper, and more stable batteries necessitates thorough understanding of the electrochemical processes governing their operation at multiple length scales. In all-solid-state power sources the electrolyte is no-flammable and can be made ultimately thin, making them safer and more compact. Yet, experimental evidence suggests that the multiple internal interfaces in their layered structure give rise to high impedances, limiting their performance. Studying these nanoscopic interfaces requires microscopic tools. Here, we employ in operando Kelvin Probe Force Microscopy (KPFM) to quantitatively measure the potential distribution in a solid-state Li-ion battery as a function of its state of charge. The battery was fabricated by sequentially depositing thin layers of Pt (110-130 nm), LiCoO2 (280-420 nm), LIPON (1100-1200 nm), Si (50-240 nm) Cu or Pt (150-200 nm) onto a Si/SiO2 wafer (oxide thickness 100 nm). The fabricated battery was cleaved in an Ar atmosphere to expose the stacked layers, mounted on a holder, wired, and safely transferred without exposing to air into a dual-beam instrument that combines a scanning electron microscope (SEM), a Ga-ion focused ion beam (FIB) and an atomic force microscope (AFM) in one vacuum chamber (residual pressure of 10-4 Pa). The stacked battery was milled to expose a cross-section of the layers, and imaged using SEM and KPFM, while cycling the battery. The acquired potential maps reveal a highly non-uniform interelectrode potential distribution, with most of the potential drop occurring at the electrolyte-Si anode interface in the pristine battery. During the first charge, the potential distribution gradually changes, revealing complex polarization within the LIPON layer due to Li-ion redistribution. Cycling the battery at high rate significantly decreased its capacity, although the capacity loss can be recovered. KPFM imaging allowed the detection of the interface responsible for this capacity loss. Li distribution in the battery was also measured using Neutron Depth Profiling as a function of the state of charge. The acquired data was compared to first principles calculations shedding light onto the interfacial Li-ion transport in the battery and its reversibility.ES acknowledges support under the Cooperative Research Agreement between the University of Maryland and the National Institute of Standards and Technology Center for Nanoscale Science and Technology, Award 70NANB14H209, through the University of Maryland.