All-solid-state Batteries Research Articles

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.

Effects of Grain Boundaries and Surfaces on Electronic and Mechanical Properties of Solid Electrolytes

AbstractExtended defects, including exposed surfaces and grain boundaries (GBs), are critical to the properties of polycrystalline solid electrolytes in all‐solid‐state batteries (ASSBs). These defects can alter the mechanical and electronic properties of solid electrolytes, with direct manifestations in the performance of ASSBs. Here, by building a library of 590 surfaces and grain boundaries of 11 relevant solid electrolytes—including halides, oxides, and sulfides— their electronic, mechanical, and thermodynamic characteristics are linked to the functional properties of polycrystalline solid electrolytes. It is found that the energy required to mechanically “separate” grain boundaries can be significantly lower than in the bulk region of materials, which can trigger preferential cracking of solid electrolyte particles in the grain boundary regions. The brittleness of ceramic solid electrolytes, inferred from the predicted low fracture toughness at the grain boundaries, contributes to their cracking under local pressure imparted by lithium (sodium) penetration in the grain boundaries. Extended defects of solid electrolytes introduce new electronic interfacial states within bandgaps of solid electrolytes. These states alter and possibly increase locally the availability of free electrons and holes in solid electrolytes. Factoring effects arising from extended defects appear crucial to explain electrochemical and mechanical observations in ASSBs.

Multiphysics modeling of the influence of initial pressure on mechanical and electrochemical performance of all-solid-state batteries

All-solid-state batteries (ASSBs) are emerging as promising energy storage solutions owing to their enhanced safety and high energy density. However, the application of higher pressures is also required to improve electrochemical performance. This study employs a multiphysics approach by combining the discrete element method (DEM) and finite element method (FEM) to investigate the impact of the compression rate and initial pressure on electrochemical performance. To the best of the authors' knowledge, this is the first study to integrate the DEM and FEM methodologies for the prediction of electrochemical and mechanical responses, capitalizing on the advantages of both approaches. The DEM is used to investigate the compaction behaviors of solid electrolyte and electrode mixtures, yielding essential data on mechanical properties, which are subsequently incorporated into the FEM model. The FEM is utilized to systematically explore the electrochemical performance and mechanical responses. The findings highlight that elevated stress enhances geometric properties, including surface area and volume fraction, leading to improved electronic and ionic conductivity. Although higher compression ratios can enhance electrochemical performance, they also elevate stress levels, thereby increasing the potential for mechanical failure. Therefore, a well-balanced electrode design is crucial. This study provides valuable insights into the design of ASSBs.

Virtues of Cold Isostatic Pressing for Preparation of All-Solid-State-Batteries with Poly(Ethylene Oxide).

All-solid-state-batteries (ASSBs) necessitate the preparation of a solid electrolyte and an electrode couple with individually dense and compact structures with superior interfacial contact to minimize overall cell resistance. A conventional preparation method of solid polymer electrolyte (SPE) with polyethylene-oxide (PEO) generally consists in employing uni-axial hot press (HP) to densify SPE. However, while uni-axial press with moderate pressure effectively densifies PEO with Li salts, excessive pressure also unavoidably results in perpendicular elongation and deformation for polymer matrix. In this research, to overcome this limitation for the uni-axial press technique, a cold isostatic press (CIP) is applied to the fabrication of ASSB with PEO and LiFePO4 . CIP effectively and uniformly applies pressure as high as 500 MPa without deformation. Characterizations confirm that CIP treated SPE has enhanced mechanical puncture strength, increasing from 499.3±22.6 to 539.3±22.6 g, and ionic conductivity, increasing from 1.04×10-4 to 1.91×10-4 S cm-1 at 50 °C. ASSB treated by CIP demonstrates remarkably enhanced rate capability and cyclability compared with the cell processed by HP, which is further evidenced by improvement of the apparent Li ion diffusion constant based on Sand equation analysis. The improvement enabled by CIP treatment originates from the superior interface uniformity between electrodes and SPE and from the densification of the LiFePO4 and SPE composite electrode.

Interlayer Engineering and Prelithiation: Empowering Si Anodes for Low-Pressure-Operating All-Solid-State Batteries.

Silicon (Si) anodes, free from the dendritic growth concerns found in lithium (Li) metal anodes, offer a promising alternative for high-energy all-solid-state batteries (ASSBs). However, most advancements in Si anodes have been achieved under impractical high operating pressures, which can mask detrimental electrochemo-mechanical issues. Herein, we effectively address the challenges related to the low-pressure operation of Si anodes in ASSBs by introducing an silver (Ag) interlayer between the solid electrolyte layer (Li6PS5Cl) and anode and prelithiating the anodes. The Si composite electrodes, consisting of Si/polyvinylidene fluoride/carbon nanotubes, are optimized for suitable mechanical properties and electrical connectivity. Although the impact of the Ag interlayer is insignificant at an exceedingly high operating pressure of 70MPa, it substantially enhances the interfacial contacts under a practical low operating pressure of 15MPa. Thus, Ag-coated Si anodes outperform bare Si anodes (discharge capacity: 2430vs 1560mAhg-1). The robust interfacial contact is attributed to the deformable, adhesive properties and protective role of the in situ lithiated Ag interlayer, as evidenced by comprehensive ex situ analyses. Operando electrochemical pressiometry is used effectively to probe the strong interface for Ag-coated Si anodes. Furthermore, prelithiation through the thermal evaporation deposition of Li metal significantly improves the cycling performance.

Investigating the production of all-solid-state battery composite cathodes by numerical simulation of the stressing conditions in a high-intensity mixer

All-solid-state batteries (ASSB) are considered as attractive further development of conventional lithium-ion batteries, since they are expected to deliver higher energy and power densities. So far, ASSB with inorganic solid electrolytes have not been applied in large-scale due to difficulties in processing, insufficient overall ionic conductivities, and high interfacial resistances between active material and solid electrolyte. In this publication, the influence of stressing conditions on the scalable production of ASSB composite cathodes via a high-intensity mixer is investigated. The high-intensity mixer is supposed to circumvent the challenge of high interfacial resistances within an ASSB cathode consisting of submicron-sized active material LiFePO4, carbon black and solid electrolyte Li3InCl6. The mixing process is simulated employing the discrete-element-method, from which the stressing conditions acting on the particles are extracted and linked with microstructural observations and electrochemical data. These investigations show that the capacity of the ASSB increases with increasing specific energy input, which is, however, limited by a certain stress intensity determined by the rotational speed of the mixer. This examination of the influence of stressing conditions on the production and electrochemical performance of ASSB cathodes lays the foundation for further simulations and experimental investigations in the field of up-scaled ASSB cathode production.

State of Charge-Dependent Impedance Spectroscopy as a Helpful Tool to Identify Reasons for Fast Capacity Fading in All-Solid-State Batteries.

Thiophosphate-based all-solid-state batteries (ASSBs) are considered the most promising candidate for the next generation of energy storage systems. However, thiophosphate-based ASSBs suffer from fast capacity fading with nickel-rich cathode materials. In many reports, this capacity fading is attributed to an increase of the charge transfer resistance of the composite cathode caused by interface degradation and/or chemo-mechanical failure. The change in the charge transfer resistance is typically determined using impedance spectroscopy after charging the cells. In this work, we demonstrate that large differences in the long-term cycling performance also arise in cells, which exhibit a comparable charge transfer resistance at the cathode side. Our results confirm that the charge transfer resistance of the cathode is not necessarily responsible for capacity fading. Other processes, such as resistive processes on the anode side, can also play a major role. Since these processes usually depend on the state of charge, they may not appear in the impedance spectra of fully charged cells; i.e., analyzing the impedance spectra of charged cells alone is insufficient for the identification of major resistive processes. Thus, we recommend measuring the impedance at different potentials to get a complete understanding of the reasons for capacity fading in ASSBs.

A strategy involving the use of 3D self-supporting B·N co-doped carbon nanofiber composite solid polymer electrolytes to stabilize the interface between polymer electrolytes and lithium metal.

All-solid-state batteries (ASSBs) have gained significant attention in the field of energy storage owing to their enhanced safety features based on the nonflammable solid-state electrolyte (SSE). To achieve high energy density, lithium metal is commonly considered the best choice as an anode material. However, the compatibility issues at the interface between polymer electrolytes and lithium metal pose significant challenges to their practical implementation. In this work, we present a new strategy to protect the typical polymer electrolyte polyethylene oxide (PEO) from significant decomposition and puncture caused by lithium dendrites, which is achieved through the combination of PEO and B·N co-doped carbon nanofibers (B·N-CNF) to modify the surface of the lithium anode. The stable cycling performance of the symmetric battery can last over 900 h at a high current density of 1 mA cm-2. The ASSBs (LiFePO4 is used as the cathode and Li metal is employed as the anode) exhibit a high capacity close to 120 mA h g-1 at 2C and cycle for over 300 cycles at 0.2C stably. This work provides inspiration for the rational design of a modification layer on the Li anode, enabling the development of high-performance ASSBs based on polymer electrolytes.

Computational approach inspired advancements of solid-state electrolytes for lithium secondary batteries: from first-principles to machine learning.

The increasing demand for high-security, high-performance, and low-cost energy storage systems (EESs) driven by the adoption of renewable energy is gradually surpassing the capabilities of commercial lithium-ion batteries (LIBs). Solid-state electrolytes (SSEs), including inorganics, polymers, and composites, have emerged as promising candidates for next-generation all-solid-state batteries (ASSBs). ASSBs offer higher theoretical energy densities, improved safety, and extended cyclic stability, making them increasingly popular in academia and industry. However, the commercialization of ASSBs still faces significant challenges, such as unsatisfactory interfacial resistance and rapid dendrite growth. To overcome these problems, a thorough understanding of the complex chemical-electrochemical-mechanical interactions of SSE materials is essential. Recently, computational methods have played a vital role in revealing the fundamental mechanisms associated with SSEs and accelerating their development, ranging from atomistic first-principles calculations, molecular dynamic simulations, multiphysics modeling, to machine learning approaches. These methods enable the prediction of intrinsic properties and interfacial stability, investigation of material degradation, and exploration of topological design, among other factors. In this comprehensive review, we provide an overview of different numerical methods used in SSE research. We discuss the current state of knowledge in numerical auxiliary approaches, with a particular focus on machine learning-enabled methods, for the understanding of multiphysics-couplings of SSEs at various spatial and time scales. Additionally, we highlight insights and prospects for SSE advancements. This review serves as a valuable resource for researchers and industry professionals working with energy storage systems and computational modeling and offers perspectives on the future directions of SSE development.

In pursuit of all solid state batteries (ASSB): advances at the cathode–electrolyte interface for garnet-based ASSB

This review focuses on developments at the complex cathode–electrolyte interface (CEI) for garnet Li7La3Zr2O12 (LLZO)-based all solid state batteries.

3D current collector based on cellulose-carbon nanotube nanocomposites for all-solid-state batteries

We developed an eco-friendly conductive ink in water by dispersing nanocomposites using natural cellulose and SWCNTs (C-CNTs). The 3D hybrid current collector with the randomly entangled C-CNTs improved the electrochemical performance in an ASSB.

Revealing interfacial parasitic reactions of nitrile rubber binders in all-solid-state lithium batteries

The nitrile components in NBR lead to an irreversible side reaction during the initial charging process. However, the problematic chemical stability of NBR has been improved through coordination chemistry, resulting in enhanced battery performance.

Designing low-strain cathode materials for long-life all-solid-state batteries

This review provides valuable insights and suggestions for future research on designing low-strain cathode materials for long-life and high-energy-density all-solid-state batteries under low external pressure conditions.

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.

Co-sintering a cathode material and garnet electrolyte to develop a bulk-type solid-state Li metal battery with wide electrochemical windows

Co-sintering a cathode material and the Li7La3Zr2O12 (LLZ) electrolyte can assist in fabricating bulk-type all-solid-state batteries (ASSBs).

Interfacial degradation of the NMC/Li6PS5Cl composite cathode in all-solid-state batteries

Mitigating interfacial reactions in composite cathode materials remains a key challenge for high-performance all-solid-state batteries (ASSBs), particularly those employing argyrodite-based electrolytes coupled with high-voltage cathodes.

Sodium halide solid state electrolyte of Na3YBr6 with low activation energy.

Halide solid-state electrolytes (SSEs) are considered promising candidates for practical applications in all-solid-state batteries (ASSBs), due to their outstanding high voltage stability and compatibility with electrode materials. However, Na+ halide SSEs suffer from low ionic conductivity and high activation energy, which limit their applications in sodium all-solid-state batteries. Here, sodium yttrium bromide solid-state electrolytes (Na3YBr6) with a low activation energy of 0.15 eV is prepared via solid state reaction. Structure characterization using X-ray diffraction reveals a monoclinic structure (P21/c) of Na3YBr6. First principle calculations reveal that the low migration activation energy comes from the larger size and vibration of Br- anions, both of which expand the Na+ ion migration channel and reduce its activation energy. The electrochemical window of Na3YBr6 is determined to be 1.43 to 3.35 V vs. Na/Na+, which is slightly narrower than chlorides. This work indicates bromides are a good catholyte candidate for sodium all solid-state batteries, due to their low ion migration activation energy and relatively high oxidation stability.

Understanding the Stability of Copper Current Collector with Sulfide Electrolyte in All‐Solid‐State Batteries

AbstractSulfide‐based all‐solid‐state batteries (ASSBs) have attracted wide attention due to their notable advantages in energy density and enhanced safety. However, whether or not copper (Cu) current collectors can be adopted in sulfide‐based ASSBs remains unclear, as sulfide electrolyte (SE) may react with Cu, causing premature failure of the ASSBs. Herein it is reported that in the presence of traces amount of water, e.g. in a dry room with a dew point of −50 °C, the SE reacts with water to produce H2S, which corrodes Cu to produce Cu2S, causing serious performance degradation to the ASSBs. Conversely, in an anhydrous environment (such as within a glove box), SE is virtually inert to Cu, rendering Cu a valid current collector. This study establishes the conditions that Cu can be used as the current collectors for sulfide‐based ASSBs, which provides important guidance for the industrialization of ASSBs.

Frameworked Electrolytes: A Pathway Towards Solid Future of Batteries.

All-solid-state batteries (ASSBs) represent a highly promising next-generation energy storage technology owing to their inherently high safety, device reliability, and potential for achieving high energy density in the post-ara of lithium-ion batteries, and therefore extensive searches are ongoing for ideal solid-state electrolytes (SSEs). Though promising, there is still a huge barrier that limits the large-scale applications of ASSBs, where there are a couple of bottleneck technical issues. In this perspective, a novel category of electrolytes known as frameworked electrolytes (FEs) are examined, where the solid frameworks are intentionally designed to contain 3D ionic channels at sub-nano scales, rendering them macroscopically solid. The distinctive structural design of FEs gives rise to not only high ionic conductivity but also desirable interfaces with electrode solids. This is achieved through the presence of sub-nano channels within the framework, which exhibit significantly different ion diffusion behavior due to the confinement effect. This perspective offers a compelling insight into the potential of FEs in the pursuit of ASSBs, where FEs offer an exciting opportunity to overcome the limitations of traditional solid-state electrolytes and propel the development of ASSBs as the holy grail of energy storage technology.

SiSe2 for Superior Sulfide Solid Electrolytes and Li-Ion Batteries.

Among the various existing layered compounds, silicon diselenide (SiSe2) possesses diverse chemical and physical properties, owing to its large interlayer spacing and interesting atomic arrangements. Despite the unique properties of layered SiSe2, it has not yet been used in energy applications. Herein, we introduce the synthesis of layered SiSe2 through a facile solid-state synthetic route and demonstrate its versatility as a sulfide solid electrolyte (SE) additive for all-solid-state batteries (ASSBs) and as an anode material for Li-ion batteries (LIBs). Li-argyrodites with various compositions substituted with SiSe2 are synthesized and evaluated as sulfide SEs for ASSBs. SiSe2-substituted Li-argyrodites exhibit high ionic conductivities, low activation energies, and high air stabilities. In addition, when using a sulfide SE, the ASSB full cell exhibits a high discharge/charge capacity of 202/169 mAh g-1 with a high initial Coulombic efficiency (ICE) of 83.7% and stable capacity retention at 1C after 100 cycles. Furthermore, the Li-storage properties of SiSe2 as an anode material for LIBs are evaluated, and its Li-pathway mechanism is explored by using various cutting-edge ex situ analytical tools. Moreover, the SiSe2 nanocomposite anode exhibits a high Li- insertion/extraction capacity of 950/775 mAh g-1, a high ICE of 81.6%, a fast rate capability, and stable capacity retention after 300 cycles. Accordingly, layered SiSe2 and its versatile applications as a sulfide SE additive for ASSBs and an anode material for LIBs are promising candidates in energy storage applications as well as myriad other applications.