Li-ion Conductivity Research Articles

Co-Intercalation-Free Graphite Anode Enabled by an Additive Regulated Interphase in an Ether-Based Electrolyte for Low-Temperature Lithium-Ion Batteries.

Graphite (Gr) anode, which is endowed with high electronic conductivity and low volume expansion after Li-ion intercalation, establishes the basis for the success of rocking-chair Li-ion batteries (LIBs). However, due to the high barrier of the Li-ion desolvation process, sluggish transport of Li ions through the solid electrolyte interphase (SEI) and the high freezing points of electrolytes, the Gr anode still suffers from great loss of capacity and severe polarization at low temperature. Here, 1,2-diethoxyethane (DEE) with an intrinsically wide liquid region and weak solvation ability is applied as an electrolyte solvent for LIBs. By rationally designing the additives of electrolytes, an intact SEI with fast Li-ion conductivity is constructed, enabling the co-intercalation-free Gr anode with long-term stability (91.8% after 500 cycles) and impressive low-temperature characteristics (82.6% capacity retention at -20 °C). Coupled with LiFePO4 and LiNi0.8Mn0.1Co0.1O2 cathodes, the optimized electrolyte also demonstrates low polarization under -20 °C. Our work offers a feasible approach to enable ether-based electrolytes for low-temperature LIBs.

Unlocking Li superionic conductivity in face-centred cubic oxides via face-sharing configurations.

Oxides with a face-centred cubic (fcc) anion sublattice are generally not considered as solid-state electrolytes as the structural framework is thought to be unfavourable for lithium (Li) superionic conduction. Here we demonstrate Li superionic conductivity in fcc-type oxides in which face-sharing Li configurations have been created through cation over-stoichiometry in rocksalt-type lattices via excess Li. We find that the face-sharing Li configurations create a novel spinel with unconventional stoichiometry and raise the energy of Li, thereby promoting fast Li-ion conduction. The over-stoichiometric Li-In-Sn-O compound exhibits a total Li superionic conductivity of 3.38 × 10-4 S cm-1 at room temperature with a low migration barrier of 255 meV. Our work unlocks the potential of designing Li superionic conductors in a prototypical structural framework with vast chemical flexibility, providing fertile ground for discovering new solid-state electrolytes.

Amorphous Oxyhalide Matters for Achieving Lithium Superionic Conduction.

The recently surged halide-based solid electrolytes (SEs) are great candidates for high-performance all-solid-state batteries (ASSBs), due to their decent ionic conductivity, wide electrochemical stability window, and good compatibility with high-voltage oxide cathodes. In contrast to the crystalline phases in halide SEs, amorphous components are rarely understood but play an important role in Li-ion conduction. Here, we reveal that the presence of amorphous component is common in halide-based SEs that are prepared via mechanochemical method. The fast Li-ion migration is found to be associated with the local chemistry of the amorphous proportion. Taking Zr-based halide SEs as an example, the amorphization process can be regulated by incorporating O, resulting in the formation of corner-sharing Zr-O/Cl polyhedrons. This structural configuration has been confirmed through X-ray absorption spectroscopy, pair distribution function analyses, and Reverse Monte Carlo modeling. The unique structure significantly reduces the energy barriers for Li-ion transport. As a result, an enhanced ionic conductivity of (1.35 ± 0.07) × 10-3 S cm-1 at 25 °C can be achieved for amorphous Li3ZrCl4O1.5. In addition to the improved ionic conductivity, amorphization of Zr-based halide SEs via incorporation of O leads to good mechanical deformability and promising electrochemical performance. These findings provide deep insights into the rational design of desirable halide SEs for high-performance ASSBs.

Pendulum-swing coordination boosting “liquid-like” Li-ion conduction within asymmetric lamellar fillers for solid polymer electrolytes

Solid polymer electrolytes have shown great prospect in high-energy lithium-metal batteries, yet the most critical challenge is their unsatisfactory ionic conductivity. A common strategy involves the incorporation of symmetric lamellar fillers with ions/molecules fixed in interlayers. However, because of strong fixation, it sacrifices “liquid-like” flow properties as small-molecular solvents in polymer matrices. Herein, a novel concept of pendulum-swing coordination within interlayers is proposed to integrate advantages from both scenarios, based on the design of one-side fixation of solvents in asymmetric lamellar fillers. This delicate modulation of the coordination environment ensures the weakened Li+-solvent interaction and the strengthened anion-cation dissociation of lithium salts. More importantly, it enhances dynamic motion of the “hanged” solvents in highly-confined space, activating “liquid-like” Li-ion conduction. Meanwhile, the confined solvent does not plasticize polymer matrices, thus excellent mechanical property maintains. As a result, the developed electrolyte exhibits an impressive ionic conductivity of 1.35 × 10−4 S/cm at room temperature and exceptional anodic stability with stable Li stripping/platting cycles for over 2000 h. Solid-state Li-LiFePO4 batteries exhibit good rate behavior and remarkable capacity retention of 85.4% after 400 cycles at 0.5C. This work provides enlightening ideas for continuous development of high-performance polymer electrolytes towards real applications of lithium-metal batteries.

Design of interfacial Li-ion transfer channels for practical improvement of a multicomponent high-voltage olivine cathode

The development of a high-voltage olivine cathode is of great interest to increase the energy density of Li-ion batteries. Focusing on the multicomponent LiFe0·4Mn0·3Co0·3PO4 (LFMCP) olivine material, in which the involvement of Co is necessary to extend the operating voltage range of the olivine materials up to 5.0 V despite having many critical issues, our research shows that the construction of Li-ion transfer channels on the particle surface is a key factor for the practical realization of the high-voltage cathode. A systematic electrochemical investigation reveals that the weakening and disappearance of the Mn activity due to the redox shift and overlap during cycling are responsible for the poor capacity delivery and capacity retention of the multicomponent LFMCP material. Surface coating of the LFMCP material with either carbon (LFMCP@C) or with a combination of carbon and LATP (LFMCP@C_LATP) helps to identify and stabilize the redox regions of the Fe, Mn, and Co components. The presence of LATP as a Li-ion conductor and an electrochemically active component on the LFMCP particle surface can induce the formation of the Li-ion concentration gradient between the core and the shell to facilitate the Li-ion diffusion during cycling. As a result, the LFMCP@C_LATP has faster Li-ion diffusion in all redox regions, more stable operating plateaus, and can therefore provide better capacity and retention than the conventional LFMCP@C. The LFMCP@C_LATP can provide a discharge capacity of 139.2 mA h g−1 with 80.5 % retention after 50 cycles, while the LFMCP@C provides a discharge capacity of 135.1 mA h g−1 with 68.4 % retention under the same cycling conditions, using a common electrolyte without the addition of any high-voltage additive.

Novel design of high elastic solid polymer electrolyte for stable lithium metal batteries

Li metal anodes have high specific capacity and low electrode potential, and have always been considered as one of the most promising anode materials. However, the growth of Li dendrites, unstable solid electrolyte interface layer (SEI), severe side reactions at the Li/electrolyte interface, and infinite volume expansion of the Li anode seriously hinder the practical application of solid-state Li metal batteries (LMBs). Herein, we report a polyurethane elastomer (TPU) material with high elasticity and interfacial stability as a solid polymer electrolyte (SPE) for LMBs. The synergistic effects of its designed soft chain forging (PEO) and hard chain segments (IPDI) can enhance Li ion conductivity, elastic modulus and flexibility of the SPE to settle the challenges of the Li metal anodes. Moreover, Li2S, as a solid-state electrolyte additive, is able to effectively inhibit the occurrence of side reactions at the interface between Li metal and SPE, promote the decomposition of N(CF3SO2)2− and in-situ generation of LiF with low Li+ diffusion barrier and excellent electronic insulation, achieving rapid Li ion transport and uniform Li deposition. As a result, stable cycle of up to 1400 h has been achieved for a Li||TPU-Li2S||Li battery at 0.1 mA/cm2 at 50 ℃, accompanied with a stable cycling performance of 350 h at a higher current density of 0.5 mA/cm2. Finally, the LiFePO4||TPU-Li2S||Li full battery exhibits an excellent cycling performance with a capacity retention rate of 80 % after 500 cycles at 1C. This simple and low-cost strategy provides novel design thoughts for practical application of high-performance SPEs in stable and long-life LMBs.

Deciphering the Origin of Interface‐Induced High Li and Na Ion Conductivity in Nanocomposite Solid Electrolytes Using X‐Ray Raman Spectroscopy

AbstractSolid‐state electrolytes (SSEs) with high ionic conductivities are crucial for safer and high‐capacity batteries. Interface effects in nanocomposites of SSEs and insulators can lead to profound increases in conductivity. Understanding the composition of the interface is crucial for tuning the conductivity of composite solid electrolytes. Herein, X‐ray Raman Scattering (XRS) spectroscopy is used for the first time to unravel the nature of the interface effects responsible for conductivity enhancements in nanocomposites of complex hydride‐based electrolytes (LiBH4, NaBH4, and NaNH2) and oxides. XRS probe of the Li, Na, and B local environments reveals that the interface consists of highly distorted/defected and structurally distinct phase(s) compared to the original compounds. Interestingly, nanocomposites with higher concentrations of the interface compounds exhibit higher conductivities. Clear differences are observed in the interface composition of SiO2‐ and Al2O3‐based nanocomposites, attributed to differences in the reactivity of their surface groups. These results demonstrate that interfacial reactions play a dominant role in conductivity enhancement in composite solid electrolytes. This work showcases the potential of XRS in investigating interface interactions, providing valuable insights into the often complex ion conductor/insulator interfaces, especially for systems containing light elements such as Li, B, and Na present in most SSEs and batteries.

Influence of oxygen distribution on the Li-ion conductivity in oxy-sulfide glasses - taking a closer look.

Lithium thiophosphates are a promising class of solid electrolyte (SE) materials for all-solid-state batteries (ASSBs) due to their high Li-ion conductivity. Yet, the practical application of lithium thiophosphates is hindered by their chemical instability, which remains a prevalent challenge in the field. Oxygen substitution has been discussed in the literature as a promising strategy to enhance stability. Nevertheless, the lack of understanding of the role of synthesis strategy on the resulting structure-property relationship makes it difficult to predict and control the material's behaviour, limiting our ability to fully utilize oxygen substitution as a viable solution. Here, we show that not only the total oxygen content but also the oxygen distribution within the material affects the ion conductivity. By carefully analysing the local structure of oxy-sulfide glasses, we find that few highly oxygenated structural units like [PO4]3- and [PO3S]3- are more detrimental to the ionic conductivity than a larger amount of less substituted units like [POS3]3-. Further, we demonstrate how the oxygen distribution is connected to the synthesis in high-energy ball milling by comparing two different sets of precursor materials. The results may explain the deviations in the past literature. The findings should be transferable to other Li-thiophosphate materials and enable more directed design of new materials.

Optimizing ionic transport in argyrodites: a unified view on the role of sulfur/halide distribution and local environments.

Understanding diffusion mechanisms in solid electrolytes is crucial for advancing solid-state battery technologies. This study investigates the role of structural disorder in Li7-x PS6-x Br x argyrodites using ab initio molecular dynamics, focusing on the correlation between key structural descriptors and Li-ion conductivity. Commonly suggested parameters, such as configurational entropy, bromide site occupancy, and bromine content, correlate with Li-ion diffusivity but do not consistently explain conductivity trends. We find that a uniform distribution of bromine and sulfur ions across the 4a and 4d sublattices is critical for achieving high conductivity by facilitating optimal lithium jump activation energies, anion-lithium distances, and charge distribution. Additionally, we introduce the ionic potential as a simple descriptor that predicts argyrodite conductivity by assessing the interaction strength between cations and anions. By analyzing the correlation between ionic potential and conductivity for a range of argyrodite compositions published over the past decade, we demonstrate its broad applicability. Minimizing and equalizing ionic potentials across both sublattices enhances conductivity by reducing the strength of anion-lithium interactions. Our analysis of local environments coordinating Li jumps reveals that balancing high and low-energy pathways is crucial for enabling macroscopic diffusion, supported by investigating percolating pathways. This study highlights the significance of the anionic framework in lithium mobility and informs the design of solid electrolytes for improved energy storage systems.

Melt-casted Li1.5Al0.3Mg0.1Ge1.6(PO4)3 glass ceramic electrolytes: A comparative study on the effect of different oxide doping

The development of Li-ion conducting solid-state electrolytes (SSEs) is crucial to achieve increased energy density, operative reliability, and unprecedented safety to replace the state-of-the-art Li-ion battery (LIB). In this regard, we here present the successful melt-casting synthesis of a MgO-added NASICON-type LAGP glass-ceramic electrolyte with composition Li1.5Al0.3Mg0.1Ge1.6(PO4)3, namely LAMGP. The effects of three different additional oxides are investigated, with the aim to improve grain cohesion and consequently enhance Li-ion conductivity. Specifically, yttrium oxide (Y2O3, 5 mol%), boron oxide (B2O3, 0.7 mol%) and silicon oxide (SiO2, 2.4 %mol) are added, yielding LAMGP-Y, LAMGP-B and LAMGP-Si, respectively. Their effects are exhaustively compared in terms of thermal, crystalline, structural/morphological and ion conducting features. Among the three oxides, B2O3 is able to positively act on grain boundaries without bringing along grains deformation and insulating secondary phases formation, achieving enhanced ionic conductivity of 0.21 mS cm−1 at 20 °C as compared to 0.08 mS cm−1 for a commercial LAGP subjected to the same thermal treatment. A remarkable anodic oxidation stability up to 4.8 V vs Li+/Li is assessed by LAMGP-B system, which accounts for promising prospects for its use in combination with high-energy (high-V) cathodes.

Elucidating the local structure of Li1+xAlxTi2−x(PO4)3 and Li3AlxTi2−x(PO4)3 (x = 0, 0.3) via total scattering

We have used a combination of X-ray and neutron total scattering in order to elucidate the local structure of the Li-ion conductor family Li1+xAlxTi2−x(PO4)3 and Li3AlxTi2−x(PO4)3 (x = 0, 0.3), revealing it structure–property relationships.

Reducing the environmental footprint of solid-electrolytes - a green synthesis route for LATP

We present a simplified, CO2-free and energy efficient synthesis to produce high-purity LATP with competitive electrochemical properties.

Overcoming the interfacial challenges of Ni-rich layered oxide cathodes for all-solid-state batteries through an ultrathin and amorphous Al2O3 coating

An ultrathin and amorphous Al2O3 coating on Ni-rich layered oxide cathodes in all-solid-state batteries significantly enhanced the cycle life by mitigating interfacial degradation while maintaining Li-ion conductivity.

Advancing solid-state lithium phosphate electrolyte: Synthesis and characterization of Li2NaPO4–ZrO2 nanocomposites for solid-state batteries

Lithium phosphates are one of the most promising groups of inorganic solid electrolytes under investigation owing to their excellent Li-ion conductivity. A series of compositions with different weight percentages of (1-x) Li2NaPO4-(x) ZrO2 samples have been prepared by the solid-state technique and characterized by FT-IR, XRD, SEM-EDS, TEM, and Impedance Spectroscopy. Among the various compositions, 20 wt % ZrO2 exhibits the highest ionic conductivity, i.e., σ = 4.5 × 10−3 Scm−1, and the lowest activation energy 0.0759 eV at 298 K. XRD analysis reveals that the addition of ZrO2 nano-filler up to the optimum value of 20 wt % suggests the formation of the amorphous phase. SEM micrographs reveal that the introduction of ZrO2 nanofiller reduces the crystallinity of the Li2NaPO4 and enhances the ionic conductivity compared with pure Li2NaPO4. Our study marks substantial advancement in the synthesis of innovative nanocomposite solid electrolytes for batteries with superior energy storage capacities.

Morphology-controlled synthesis of novel nanostructured Li4P2O7 with enhanced Li-ion conductivity for all-solid-state battery applications.

Mechanical stiffness of oxide-type solid-electrolytes is a major drawback which has hindered their practical application in all-solid-state Li-ion batteries to date. Despite their enhanced structural and electrochemical stabilities, lack of deformability of fast-ion conducting oxides impedes the integration of these materials in bulk-type solid-state cells. Deformable solid-electrolytes such as sulfides, on the other hand, lack sufficient electrochemical stability in contact with conventional cathodes. This has recently triggered a search for new materials that combine high ion-conductivity, deformability and sufficient electrochemical stability. Here, we report the synthesis of a novel form of Li4P2O7 that can be densified by cold-pressing and possesses an ion conductivity that is two orders of magnitude higher than conventional Li4P2O7 phases. The material is synthesized by a combination of microwave synthesis and chemical lithiation and adopts a nanostructured morphology with a small amorphous component. The material is electrochemically stable at voltages >5 V vs. Li+/Li, which suggests safe use with high-voltage cathodes. The newly-synthesized material is therefore a bulk, deformable analogue of LiPON, with comparable ion conductivity and phase stability. This research highlights the potential of using novel low-temperature synthetic routes to control the morphology and enhance the electrochemical performance of conventional functional materials.

Improvement of the Li-ion conductivity and air stability of the Ta-doped Li7La3Zr2O12 electrolyte via Ga co-doping and its application in Li–S batteries

The co-doping of Ga in LLZT has expedited the densification of the garnet electrolyte, leading to a reduction in the sintering temperature required for densification and an enhancement in the stability of the electrolyte.

Improved structure stability and performance of a LiFeSO4F cathode material for lithium-ion batteries by magnesium substitution.

Tavorite LiFeSO4F with high Li-ion conductivity has been considered a promising alternative to LiFePO4. However, its poor cycle stability and low electronic conductivity limit the practical application of Tavorite LiFeSO4F. In the present study, we employ a solvothermal method to produce magnesium-substitution LiMgxFe1-xSO4F (x = 0, 0.02, 0.04) cathode materials in which the Mg substitutes the Fe(2) sites. The first-principles calculations demonstrate that Mg-substitution could reduce the bandgap of LiFeSO4F and increase its electronic conductivity to 2.5 × 10-11 S cm-1. Meanwhile, CI-NEB and BV calculations reveal that the diffusion energy barrier of lithium along the (100) direction after Mg substitution is lower than the pristine sample, and the electrochemical inactive Mg2+ could improve the structure stability. The results show that the Mg-substituted LiFeSO4F exhibits enhanced cycle stability and rate performance compared with the pristine LiFeSO4F, suggesting that the use of electrochemically inactive ion substitution may be critical for the development of high-performance LiFeSO4F cathode materials for lithium-ion batteries.

Effect of synthesis process on the Li-ion conductivity of LiTa2PO8 solid electrolyte materials for all-solid-state batteries

Tailoring grain boundary resistivity in LiTa2PO8 for improved ionic conductivity, offering insights into enhancing the performance of oxide solid electrolytes for safer all-solid-state batteries.

High ionic conductivity of a flexible solid-state composite electrolyte for a lithium-ion battery

A solid composite electrolyte (PLC SCE) with PEG/PEO/LATP/CNF enhances Li-ion conductivity (1.31 × 10−4 S cm−1 at 30 °C) and prevents dendrite growth. A symmetrical Li-ion battery with PLC SCE remains stable for 300 hours, even under stress.

An interweaving 3D ion-conductive network binder for high-loading and lean-electrolyte lithium–sulfur batteries

A waterborne multifunctional 3D network binder is elaborately developed for lithium–sulfur batteries to accommodate the volume expansion, adsorb lithium polysulfides, and provide satisfactory Li-ion conductivity under lean electrolyte conditions.