Lithium Mobility Research Articles

Enhancing the Cycle Performance of Lithium-Sulfur Batteries by Coating the Separator with a Cation-Selective Polymer Layer.

Lithium-sulfur batteries are believed to possess the feasibility to power electric vehicles in the future ascribed to the competitive energy density. However, soluble polysulfides continuously shuttle between the sulfur electrode and lithium anode across the separator, which dramatically impairs the battery's capacity. Herein, the surface of a polypropylene separator (PP film) is successfully modified with a delicately designed cation-selective polymer layer to suppress the transport of polysulfides. In principle, since bis-sulfonimide anions groups on the backbone of the polymer are immobilized, only cations can pass through the polymer layer. Furthermore, plenty of ethoxy chains in the polymer can facilitate lithium-ion mobility. Consequently, in addition to obstructing the movement of negatively charged polysulfides by the electrostatic repulsive force of fixed anions, the coated multi-functional layer on the PP film also guarantees the smooth conduction of lithium ions. The investigations demonstrate that the battery with the pristine PP film only delivers 228.5 mAh g-1 after 300 cycles at 2 C with a high capacity fading rate of 60.9 %. By contrast, the polymer-coated sample can release 409.4 mAh g-1 under the identical test condition and the capacity fading rate sharply declines to 43.2 %, illustrating superior cycle performance.

Lithium mobility along conduction channels of ceramic LiTa2PO8

Lithium mobility along conduction channels of ceramic LiTa2PO8

Revealing the Equilibrium of Lithium Cations Across a Solid–Electrolyte Interface by T_1 NMR Relaxation

Battery fast charging is pivotal for broader acceptance of electric mobility. While demonstrated for lithium titanate (text {Li}_4text {Ti}_5text {O}_{12}, LTO) anodes, the underlying mechanisms are still poorly understood. Recently, NMR T_1 relaxation time constants of {}^7text {Li} in the bulk of LTO were found to change if the surrounding electrolyte was altered. It was explained by interdiffusion of mobile lithium ions between the two phases, facilitated by unpinning of polarons from surface defects and leading to a pseudocapacitive effect that potentially influences fast charging. This effect is explored further by systematically varying the lithium salt concentration in an aprotic electrolyte in contact with LTO. Spectrally resolved {}^7text {Li}T_1 NMR relaxation times were used as a measure for bulk concentration changes of paramagnetic polaronic charges in LTO. Correlation of electrolyte concentration and {}^7text {Li}T_1 showed qualitatively different behavior above and below a salt concentration of about 5 mM, leading to a relaxation dispersion maximum in the LTO bulk. At intermediate concentrations, relaxation was consistent with a {}^7text {Li} exchange equilibrium between LTO and electrolyte. Upon contact of the two phases, yet without insertion into an electrochemical cell or applying an external potential, lithium ions redistributed between LTO bulk and liquid electrolyte. The results can be understood analogously to the distribution of mobile lithium ions between two phases separated by a text {Li}^{+} permeable membrane. This is the first demonstration of such an equilibrium for non-faradaic lithium exchange at an interface between a solid ceramic electrode and a liquid electrolyte outside an electrochemical cell, substantiating our previous hypothesis of a polaron-supported mechanism. This study provides a basis for more quantitative (surface)-defect engineering, which is key to optimize battery fast-charging properties.

(Invited) Ion Transport and Interface Resistance in Polymer-Based Composite Electrolytes and Composite Cathode

Solid-state electrolytes are promising to enable the next generation batteries with higher energy density and improved safety. However, each major class of solid electrolytes has intrinsic weaknesses. By combining different classes of solid electrolytes, such as a polymer electrolyte and an oxide ceramic electrolyte, one can potentially overcome the intrinsic weaknesses of each component and develop a composite electrolyte to achieve high ionic conductivity, good mechanical properties, good chemical stability, and adhesion with the electrodes.In this presentation, we show that the interfacial resistance strongly affects the ionic conductivity of polymer/oxide ceramic composite electrolytes, in both the ceramic-in-polymer design where ceramic particles are dispersed within the polymer electrolyte matrix as well as the polymer-in-ceramic design where a three dimensionally interconnected ceramic scaffold is developed. The quantification of the interfacial resistance, the origin of this resistance, as well as the strategies to minimize it are discussed.In a second case, we examine the effect of interfaces on ion transport in a polymer based composite cathode consisting of LiFePO4 (LFP), carbon and poly(ethylene oxide) (PEO) with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). The structure and dynamics of PEO and lithium ion mobility are studied by small angle neutron scattering and quasi-elastic neutron scattering. The results show that Li ion mobility in PEO/LiTFSI in the composite cathode is only 30% of the bulk electrolyte. This suggests a key bottleneck that limits the rate performance of polymer-based solid-state batteries originates from the sluggish ion transport in the polymer electrolyte confined in the cathode.

Enabling the Production of Homogeneous High-Load Positive Electrodes by Tailoring the Electrode Formulation – a Conductive Additive and Solvent Approach

The automotive industry experiences a substantial change due to electrification of major parts of the transportation system by using lithium ion batteries (LIBs). To facilitate this transition, low cost and high energy density LIBs produced under the most sustainable conditions possible are required. These objectives are amongst others strongly related with the positive electrode. Thus, in order to achieve enhanced energy densities on cell level, the application of high-load positive electrodes for various cell systems ranging from lithium ion to lithium metal batteries is inevitable. However, to ensure high lithium ion mobility within thick composite electrodes and to obtain maximized capacity utilization, it is crucial to tailor the electrode microstructure. With regard to the production, detrimental effects like binder-migration can occur upon drying of thick electrodes inducing inhomogeneous distribution of binder and conductive additive within the electrode coating. Beyond that, the effect of lateral coating shrinkage resulting in electrode cracking during drying plays an increasingly significant role with increasing electrode thickness.The application of high solid contents (SC) during electrode paste processing can widely suppress the effects of binder migration and crack formation.[1,2] However, elevated SCs result in increasing paste viscosities leading to practical limitations for homogeneous electrode coating. By using nano-scale and micro-scale spherical, linear and three-dimensional conductive additives like carbon microfibers (CMF) or conductive graphite (CG) in addition to carbon black (CB), the adjustment of an appropriate paste viscosity can be facilitated. The addition of more carbonaceous additives acting as conductive additive as well as processing additive resolves the rheological requirements for an electrode paste with 80% SC and significantly influences the pore structure of the electrode. Thus, tailoring active and inactive components is crucial to enable processing of high SC electrode pastes with an appropriate viscosity in conjunction with the production of thick electrodes exhibiting an optimized pore structure benefiting the electrochemical performance. The additional introduction of carbon nanotubes (CNTs) leads to the formation of segregated networks providing more stability within the electrode and a favorable electrode microstructure. Moreover, the use of CNTs benefits the electrochemical performance by immensely boosting electronic conductivity resulting in higher rate capability and increased capacity retention. The various electrode formulations containing up to three different conductive additives were compared to the benchmark formulation without further additives in terms of electronic conductivity, adhesion, pore structure and electrochemical performance. Different electrode formulations were investigated and compared regarding the composite electrode adhesion strength, electronic conductivity, microstructure and electrochemical performance over 400 cycles in a coin cell setup with a graphitic negative electrode. However, the optimized formulation containing CNTs enables the production of thick positive electrodes exhibiting significantly higher areal capacities up to 8 mAh cm-2 with superior electrochemical properties and higher content of active material in the formulation resulting in higher energy densities on cell level. In a next step, the state-of-art processing solvent N-Methyl-2-pyrrolidon (NMP) was targeted with the goal of replacing NMP with a non-toxic solvent. The influence of a co-solvent on the electrode paste viscosity was investigated to further increase the SC, lower production costs and enable improved environmental benignity.A comprehensive study on tailoring the rheological, structural and electrochemical properties by processing additives is presented. The increase of the SC to 80% is a first step towards the reduction of the ecologic and economic footprint for LIB production while simultaneously enabling electrodes with high areal capacities exhibiting increased rate capability and capacity retention enabled by the addition of CNTs.[1] J. Seeba, S. Reuber, C. Heubner, A. Müller-Köhn, M. Wolter, A. Michaelis, Chemical Engineering Journal Volume 402, 2020, 125551. [2] L. Ibing, T. Gallasch, P. Schneider, P. Niehoff, A. Hintennach, M. Winter, F. M. Schappacher, Journal of Power Sources 423, 2019, 183–191.

Tailoring Binder Systems for LiNi0.6Mn0.2Co0.2O2-Based Positive Electrode by Investigating Various Polyvinylidene Difluorides for Different Active Material Morphologies

Polyvinylidene difluoride (PVdF) is the state-of-the-art binding agent for positive electrodes (cathodes) consisting of Ni-rich materials such as LiNi0.6Mn0.2Co0.2O2 (NMC622) and a conductive additive, which are processed with the organic solvent N-methyl-pyrrolidone. Processing and composition of the positive electrode strongly influence the specific energy and electrochemical performance of the corresponding lithium ion batteries (LIBs). Various binder systems were studied for state-of-the-art positive electrodes, however, a deeper understanding of the impact on the electrode properties is yet to be acquired.1,2 Besides the electronical and mechanical properties of the positive electrode, the binding agent additionally affects the charge/discharge cycling stability and rate capability of the battery cell. An important factor is the ratio of binder content to surface area of the solid components.3 For instance, using a low binder coverage (ratio of binding agent to solid components) can lead to weak adhesion between composite electrode and current collector, resulting in a decrease in cycling stability. This is due to mechanical degradation upon prolonged charge/discharge cycling, as altering volume extension and reduction leads to mechanical stress and therefore in particle cracking and contact loss. On the contrary, extensive binder coverage leads to high internal resistance, due to hindered lithium mobility and potentially reduced electronical conductivity of the composite electrode.The properties of binding agents vary depending on chain length and the degree of polymerization, hence affecting intermolecular stability, swelling rate, and adhesion to the current collector. While the morphologies of active materials are predetermined (primary/secondary particles) and the variation of the conductive additive can influence the pore structure and conductivity of the electrode, the binding agent is essential for the distribution of the conductive additive and the adhesion to the current collector. Binding agents make up a comparably small part in the electrode composition, however, it is the electrode component that can essentially enhance the lifetime of a battery.Thus, it is crucial to understand the influence of the binder characteristics on the electronical, mechanical, and electrochemical properties of the cathode. To understand how binder coverage can enhance or impair these properties, primary particles (high surface area) and secondary particles (comparably low surface area) of NMC622 were processed with various polyvinylidene difluoride binding agents differing in molecular weight. Experiments regarding the physical electrode properties such as adhesion and electronic through-plane conductivity, as well as the electrochemical properties concerning rate capability and long-term charge/discharge cycling were compared and evaluated for the two active material variants. Additionally, aging studies with one of the binding agents were carried out to investigate the influence of the active material surface on the aging products found in the electrolyte and by that gaining a deeper understanding for the aging mechanisms in different NMC622 cell set ups. The combination of the mentioned experimental techniques enables the determination of a tailored binder system for a specific active material morphology and the associated electrode composition for the intended LIB application.[1] Gordon, R.; Kassar, M.; Willenbacher, N., ACS omega 2020, 5 (20), 11455–11465.[2] Chen, H.; Ling, M.; Hencz, L.; Ling, H. Y.; Li, G.; Lin, Z.; Liu, G.; Zhang, S., Chemical reviews 2018, 118 (18), 8936–8982.[3] Weichert, A.; Göken, V.; Fromm, O.; Beuse, T.; Winter, M.; Börner, M., Journal of Power Sources 2022, 551, 232179.

Unlocking the chemical space in anti-perovskite conductors by incorporating anion rotation dynamics

Anti-perovskite compounds have drawn significant research interest as promising next-generation electrolytes for solid-state batteries, due to the high chemical stability against Li-metal, the negligible electronic conductivity and low cost. However, the low ionic conductivity, and the deficient fundamental understandings of ion transports impede the further optimization of the lithium anti-perovskite electrolytes. Herein, we reveal that exchanging anion lattice sites in the anti-perovskite could promote the structure stabilities and ionic conductivities simultaneously, by incorporating the rotational dynamics of anion clusters and strengthening the coupling between Li migrations and cluster rotations. Based on high-throughput calculations by density functional theory (DFT), twelve new anti-perovskite materials are predicted to exhibit superionic conductivity, among which the highest ionic conductivity of 10.9 mS/cm in Li3BrSO4 can be achieved (hundreds of times higher than the ionic conductivity of typical Li3OCl antiperovskite, 0.021 mS/cm). Furthermore, the local difference frequency center is proposed to quantitatively characterize the coupled degree of Li migration and cluster rotation, revealing the contribution of paddlewheel effect to the ionic conductivity. Our proposed cation-anion dynamics coupling in site-exchanged and cluster-based antiperovskites not only open a new avenue for understanding the key role played by rotational dynamics on fast lithium mobility, but also can be generally applied to develop other fast ionic conductors with cluster dynamics.

A new type of LATP doped PVDF-HFP based electrolyte membrane with flame retardancy and long cycle stability for solid state batteries

Lithium ion batteries are a widely used high-density energy storage device due to their low self-discharge rate and lack of memory effect. However, their use in liquid electrolyte systems poses a significant safety risk due to issues such as lithium dendrite growth and toxic electrolytes that are also prone to leakage. Therefore, the development of gel polymer electrolytes (GPE) with high ionic conductivity and elevated lithium ion migration numbers is crucial to addressing these concerns. This work focuses on the preparation of flexible microporous composite gel polymer electrolytes (L-GPE) based on Polyvinylidene fluoride-Hexafluoropropylene (PVDF-HFP) and Li1.3Al0.3Ti1.7P3O12 (LATP) as a filler and on testing its performance as an electrolyte in applications of lithium ion battery. The L-GPE demonstrated an ionic conductivity of 8.13 × 10−4 S·cm−1 at 40 °C, with a lithium ion mobility number of 0.58, indicating high ionic mobility. Notably, in all-solid-state lithium ion battery applications, the L-GPE demonstrated excellent long-cycle stability, with a capacity retention of 90.3 % after 1000 cycles at 0.5C. These results demonstrate that the interaction force between LATP and anions enhances lithium ion mobility in composite gel polymer electrolytes, which is favorable for the regulation of lithium ion deposition and the control of lithium dendrite growth. Besides, the performance of this L-GPE membrane is significantly improved due to its suitable porosity, gratifying mechanical properties, and excellent flame retardancy. In summary, this strategy provides a valuable contribution to the development of safe and long-lasting energy storage systems by presenting a novel L-GPE membrane with enhanced mechanical, high ionic conductivity, excellent flame retardant property and thermal stability.

Designing Electrolytes With Controlled Solvation Structure for Fast‐Charging Lithium‐Ion Batteries

AbstractRecharging battery‐powered electric vehicles (EVs) in a similar timeframe as those used for refueling gas‐powered internal combustion vehicles is highly desirable for rapid penetration of the EV market. It is well known that the electrolyte in a battery plays a critical role in fast‐charging capability of the battery because it determines the rate of ion transport together with its derived electrode/electrolyte interphases on both cathode and anode of the battery. In this study, the effects of contents of salt, coordinating solvent, and noncoordinating diluent on salt dissociation degree and electrolyte ionic conductivity are investigated, and a controlled solvation structure electrolyte is developed to improve the lithium ion mobility and conductivity in the electrolyte and to enhance the kinetics and stability of the electrode/electrolyte interphases in the battery. This electrolyte enables fast‐charging capability of high energy density lithium‐ion batteries (LIBs) at up to 5 C rate (12‐min charging), which significantly outperforms the state‐of‐the‐art electrolyte. The controlled solvation structure sheds light on the future electrolyte design for fast‐charging LIBs.

Toward High-Performance Metal-Organic-Framework-Based Quasi-Solid-State Electrolytes: Tunable Structures and Electrochemical Properties.

Metal-organic frameworks (MOFs) have been reported as promising materials for electrochemical applications owing to their tunable porous structures and ion-sieving capability. However, it remains challenging to rationally design MOF-based electrolytes for high-energy lithium batteries. In this work, by combining advanced characterization and modeling tools, a series of nanocrystalline MOFs is designed, and the effects of pore apertures and open metal sites on ion-transport properties and electrochemical stability of MOF quasi-solid-state electrolytes are systematically studied. It isdemonstrated that MOFs with non-redox-active metal centers canlead to a much wider electrochemical stability window than those with redox-active centers. Furthermore, the pore aperture of MOFs is found to be a dominating factor that determines the uptake of lithium salt and thus ionic conductivity. The ab initio molecular dynamics simulations further demonstrate that open metal sites of MOFs can facilitate the dissociation of lithium salt and immobilize anions via Lewis acid-base interaction, leading to good lithium-ion mobility and high transference number. The MOF quasi-solid-state electrolyte demonstrates great battery performance with commercial LiFePO4 and LiCoO2 cathodes at 30°C. This work provides new insights into structure-property relationships between tunable structure and electrochemical properties of MOFs that can lead to the development of advanced quasi-solid-state electrolytes for high-energy lithium batteries.

Polymer-coated silica dual functional fillers to improve the performance of poly(ethylene oxide)-based solid electrolytes

The application of solid polymer electrolytes (SPEs) is mainly hindered by their low ionic conductivity and the limited mechanical properties. Adding functional small molecules and inorganic fillers are two of the simplest and most effective ways to improve the performance of SPEs. However, most of the time, both methods cannot be implemented concomitantly, and may even inhibit each other. Here, an original dual functional filler, consisting of hollow porous SiO2 nanospheres three-dimensionally wrapped by poly(2,2,6,6-tetramethylpiperidin-4-yl methacrylate) (PTMPM), is blended with poly(ethylene oxide) (PEO) and LiClO4 to obtain a composite solid electrolyte (CSE). Compared to the reference PEO SPE, the room-temperature ionic conductivity of the synthesized CSE is improved by 4 orders of magnitude reaching 1.3 × 10−4 S cm−1. Moreover, a lithium ion transference number value as high as 0.81 is obtained. The CSE membrane is further assembled with a Li anode and a standard LiFePO4 cathode to obtain an all-solid-state battery showing high capacity (149.3 mAh g−1 at 0.1 C) and long-term stability (0.68‰ loss of capacity per cycle, over 100 cycles). The peculiar structure of the PEO/PTMPM interface is thought to be at the origin of the enhanced LiClO4 dissociation and mobility of lithium ions. Remarkably, the well-known toughening effect of SiO2 fillers is preserved in the CSE.

High-resolution isotopic analysis of lithium by micro laser-induced breakdown self-reversal isotopic spectrometry (LIBRIS) for isotopic labelling of lithium in solid-state electrolyte of lithium batteries

In order to improve the safety of Li-ion batteries, solid-state electrolytes have been studied for many years. However, lithium is known to have lower diffusion coefficients in these materials. Various methods can be used to investigate lithium transport mechanisms; one of them relies on isotopic tracing. This method often used in environmental sciences, medicine and biology has been developed since 2011 by Lu et al. in the battery field. In addition to the techniques commonly used for isotopic analysis of lithium in battery materials, such as nuclear magnetic resonance (NMR) and mass spectrometry techniques, a new complementary method for determining the spatial distribution of the lithium isotopic ratio in solid electrolytes has been developed: laser induced self-reversal isotopic spectrometry (LIBRIS) proposed by Touchet et al. in 2020. In this paper, a proof of concept of LIBRIS analysis of a solid electrolyte composed of poly(ethylene oxide) (POE) containing 6Li enriched lithium bis(trifluoromethylsulphonyl)imide (LiTFSI) was first achieved. Then, the lateral resolution of LIBRIS measurements was improved from 250 μm down to 7 μm. Such lateral resolution is well adapted to future studies of lithium transport mechanisms in a solid electrolyte composed of a dispersion of ceramic microparticles in a polymer matrix. This material design is used as a trade-off to improve Li diffusion compared to polymer-based electrolytes. The sources of signal fluctuations were discussed, and a calibration curve of the 6Li isotopic abundance in POE/LiTFSI samples was finally obtained, with a relative uncertainty of 25%. The results demonstrate the feasibility of high resolution isotopic analysis by the LIBRIS technique and could be applied in the future to the characterization of the lithium mobility in battery materials.

Visualizing Lithium Ion Transport in Solid‐State Li–S Batteries Using 6Li Contrast Enhanced Neutron Imaging

AbstractThe elucidation of lithium ion transport pathways through a solid electrolyte separator is a vital step toward development of reliable, functional all‐solid‐state batteries. Here, advantage has been taken of the significantly higher neutron attenuation coefficient of one of the most abundant stable isotopes of lithium, 6Li, with respect to that of naturally occurring lithium isotope mixture, to perform neutron imaging on a purpose built all‐solid‐state lithium–sulfur battery. Increasing the 6Li content in the anode while using natural lithium in the solid electrolyte separator and the cathode enhances the contrast such that it is possible to differentiate, during the initial discharge, between the mobile lithium ions diffusing through the cell from the anode and those that are initially located in the solid electrolyte. The sensitivity of neutrons to the different lithium isotopes means that operando neutron radiography allows demonstration of the lithium ion diffusion through the cell while in situ neutron tomography has permitted presentation, in three dimensions, of the distribution of the trapped lithium ions inside the cell in charged and discharged states.

Synchronous Light Harvesting and Energy Storing Organic Cathode Material 1,4-Dihydroxyanthraquinone for Lithium-Ion Batteries

The electrode materials for lithium-ion batteries which offer integrated conversion of light and storage of electricity are auspicious for compact and stand-alone energy systems. Herein, coin-cell lithium batteries based on organic compound 1,4-dihydroxyanthraquinone coupling porous carbon derived from MOFs (1,4DHAQ&ZIF-8C) are demonstrated. The proposed material simultaneously acts as lithium storing and photoactive electrode. Along with the electrochemical lithium-ion reactivity, 1,4DHAQ&ZIF-8C offers notable photoelectric properties, its specific capacity increases to 285mAh g-1 (1.58 times of the specific capacity without light) when illuminated, and the lithium-ion mobility improves to 0.313cm2 s-1 (up by 55%), meanwhile its charge transfer resistance decreases to 95.6Ω (down to 39%). Moreover, theoretical excited state analysis and microsecond measurements reveal the existence states of photogenerated carriers, demonstrating obvious intramolecular charge transfer and nanosecond-scale exciton lifetime (∼5ns). Our findings suggest valuable directions to advance the current strategies for the assembly of efficient photo-rechargeable lithium-ion batteries.

Understanding Lithium-Ion Dynamics in Single-Ion and Salt-in-Polymer Perfluoropolyethers and Polyethyleneglycol Electrolytes Using Solid-State NMR

Lithium metal batteries with high energy densities can enable a revolution in energy storage and accelerate shifts in electric transportation and electricity generation. However, several morphological and electro-chemo-mechanical challenges impede their development. Solid-state electrolytes such as those based on polymers show great promise in replacing liquid electrolytes in lithium metal batteries. Polyether-based polymer electrolytes are the most investigated but are plagued by low room-temperature ionic conductivity and poor oxidative stability. Hence, there is great need for the development and understanding of ion transport in new classes of polymer electrolytes. Perfluoropolyether (PFPE)-based electrolytes have shown improved oxidative stability, but little is understood about their lithium solvation and transport mechanism. In this work, we use multinuclear solid-state magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy to investigate the lithium cation environment and mobility in crosslinked single-ion and salt-in-polymer PFPE electrolytes and compare it directly to that of well-known polyethylene glycol (PEG) electrolytes. We show that the interaction of the lithium cation with the polymer backbone is weaker in PFPE systems compared to PEG, likely resulting in stronger ion pairing in the PFPE systems. Line shape analyses show lower lithium mobility in PFPE electrolytes despite lower activation energies being derived from spin-lattice relaxation (T1) measurements as compared to those for the PEG systems. The rapid relaxation is instead ascribed to the local fluctuations caused by polymer backbone mobility. By studying different modes of ion binding (single-ion vs salt-in-polymer), we show that differences across polymer backbones (PFPE vs PEG) have a greater effect on mobility than differences in ion binding modes within each polymer class (especially when single-ion conducting site density is not high). Our ability to use MAS NMR to study polymer electrolytes in their native state opens new opportunities to develop and understand novel polymer or hybrid solid-state electrolytes for next-generation lithium metal batteries.

Probing lithium mobility at a solid electrolyte surface

Solid-state electrolytes overcome many challenges of present-day lithium ion batteries, such as safety hazards and dendrite formation1,2. However, detailed understanding of the involved lithium dynamics is missing due to a lack of in operando measurements with chemical and interfacial specificity. Here we investigate a prototypical solid-state electrolyte using linear and nonlinear extreme-ultraviolet spectroscopies. Leveraging the surface sensitivity of extreme-ultraviolet-second-harmonic-generation spectroscopy, we obtained a direct spectral signature of surface lithium ions, showing a distinct blueshift relative to bulk absorption spectra. First-principles simulations attributed the shift to transitions from the lithium 1 s state to hybridized Li-s/Ti-d orbitals at the surface. Our calculations further suggest a reduction in lithium interfacial mobility due to suppressed low-frequency rattling modes, which is the fundamental origin of the large interfacial resistance in this material. Our findings pave the way for new optimization strategies to develop these electrochemical devices via interfacial engineering of lithium ions.

Properties of Bacterial Cellulose/Polyvinyl Composite Membrane for Polymer Electrolyte Li ion Battery

High ionic conductivity and porous properties of material play important role as a solid polymer electrolyte in Li ion battery application. In this study, a bacterial cellulose (BC)- based polymer was modified with polyvinyl pyrrolidone (PVP) and polyvinyl alcohol (PVA). Blending the polymer host is one more approach to work on the morphology pore and electrochemical properties of polymer electrolytes. The slurry of BC is rich of fibers that contribute to forming of the pore template for solid electrolyte membrane. Polyvinyl act as material to creating pore and increases the polymer segmental ion lithium mobility. Pore morphology of BC-PVA and -PVP composite membrane homogeneously distributed by SEM observations. The presence of many pores makes the tensile strength of the BC PVA membrane lower. For solid electrolytes purposes, it does not affect battery performance but has a greater possibility for battery lifetime. The presence of pores contributes to the absorption of electrolytes membranes. In addition, enhancement of the conductivity upon addition of salt is correlated to the enhancement of pores from solid polymer electrolyte. The conductivity of BC-PVA composite is reported 8.7 x 10-5 Scm-1 , and this ion conductivity is slightly higher than conductivity in BC-PVP 8.4 x 10-7 Scm-1 at room temperature. In the future, BC-PVA can be applied for solid electrolyte membranes material based on cellulose.

Modulating Entropic Driving Forces to Promote High Lithium Mobility in Solid Organic Electrolytes

Modulating Entropic Driving Forces to Promote High Lithium Mobility in Solid Organic Electrolytes

Lithium‐ion Mobility in Li6B18(Li3N) and Li Vacancy Tuning in the Solid Solution Li6B18(Li3N)1−x(Li2O)x

AbstractAll‐solid‐state batteries are promising candidates for safe energy‐storage systems due to non‐flammable solid electrolytes and the possibility to use metallic lithium as an anode. Thus, there is a challenge to design new solid electrolytes and to understand the principles of ion conduction on an atomic scale. We report on a new concept for compounds with high lithium ion mobility based on a rigid open‐framework boron structure. The host–guest structure Li6B18(Li3N) comprises large hexagonal pores filled with Li7N] strands that represent a perfect cutout from the structure of α‐Li3N. Variable‐temperature 7Li NMR spectroscopy reveals a very high Li mobility in the template phase with a remarkably low activation energy below 19 kJ mol−1 and thus much lower than pristine Li3N. The formation of the solid solution of Li6B18(Li3N) and Li6B18(Li2O) over the complete compositional range allows the tuning of lithium defects in the template structure that is not possible for pristine Li3N and Li2O.

Lithium-ion Mobility in Li6 B18 (Li3 N) and Li Vacancy Tuning in the Solid Solution Li6 B18 (Li3 N)1-x (Li2 O)x.

All-solid-state batteries are promising candidates for safe energy-storage systems due to non-flammable solid electrolytes and the possibility to use metallic lithium as an anode. Thus, there is a challenge to design new solid electrolytes and to understand the principles of ion conduction on an atomic scale. We report on a new concept for compounds with high lithium ion mobility based on a rigid open-framework boron structure. The host-guest structure Li6 B18 (Li3 N) comprises large hexagonal pores filled with Li7 N] strands that represent a perfect cutout from the structure of α-Li3 N. Variable-temperature 7 Li NMR spectroscopy reveals a very high Li mobility in the template phase with a remarkably low activation energy below 19 kJ mol-1 and thus much lower than pristine Li3 N. The formation of the solid solution of Li6 B18 (Li3 N) and Li6 B18 (Li2 O) over the complete compositional range allows the tuning of lithium defects in the template structure that is not possible for pristine Li3 N and Li2 O.