Space Charge Layer Research Articles

An Asymptotic Analysis of Space Charge Layers in a Mathematical Model of a Solid Electrolyte

An Asymptotic Analysis of Space Charge Layers in a Mathematical Model of a Solid Electrolyte

Interfacial ionic transportation in composite electrolyte induced by element segregation for low temperature fuel cells

Interfacial ionic conduction has been considered to play an important role in composite electrolyte of solid oxide fuel cell (SOFC). However, the contribution of interfacial conduction has not been well evaluated. In this study, interfacial conduction is evaluated in a composite electrolyte composed of (Na0.57K0.43)0.94Li0.06NbO3 (KNN) with ignorable electrical conductivity and ZnO with low bulk ionic conductivity. The dependence of power output on the ratio of KNN and ZnO as well as the size of particles is investigated to understand the influence of interfacial areas on cell performance. Additionally, the issues affecting cell performance is analyzed from the view of electric circuit model by focusing on the electrical property. A method is proposed to indirectly evaluate the existence of charge carriers at the interfaces. Moreover, the segregation of K at the interfaces of KNN and ZnO is confirmed, which is believed to play an important role in forming space charge layers at the interfaces and trigger the formation of high concentration of oxygen vacancies for improving interfacial ionic transportation. This study uncovers that element segregation at the interface of two phases maybe an important issue for ionic transportation at the hetero-interface of composite electrolyte for fuel cell application.

Surface-to-bulk synergistic modification enables stable interface of Ni-rich oxide cathode for all-solid-state lithium batteries

All-solid-state lithium batteries (ASSLBs) are supposed to a highly forward-looking battery technology by reason of their conspicuous energy density and excellent safety. Ni-rich layered oxide cathodes have been extensively studied in ASSLB systems with sulfide electrolytes owing to their high voltage and preeminent specific capacity. However, the electrochemical performance of ASSLBs is severely degraded due to the interfacial physical contact failure, space charge layer effect, and chemical/electrochemical side reactions between sulfide electrolytes and Ni-rich oxide cathodes. In this work, the surface of LiNi0.92Co0.04Mn0.04O2 (NCM92) is coated with a nano-level CeO2 buffer layer and is simultaneously doped with Ce element (NCM92–1%Ce) by one-step wet chemical method. Ce doping is beneficial for maintaining structural stability and suppressing irreversible phase transition. The CeO2 buffer layer can efficaciously avoid the oxidation and decomposition phenomenon at the interface between NCM92 and sulfide electrolyte. As expected, NCM92–1%Ce cathode shows the discharge specific capacity of 141.46 mAh g−1 after 80 cycles at 0.2C with 79.32% capacity retention rate, which is much higher than that of the unmodified NCM92 cathode. The results indicate that the surface-to-bulk synergistic modification strategy can successfully improve the structure toughness and interface stability of Ni-rich oxide cathode for ASSLBs with sulfide electrolytes.

Elucidating and Minimizing the Space‐Charge Layer Effect between NCM Cathode and Li6PS5Cl for Sulfide‐Based Solid‐State Lithium Batteries

AbstractThe electrochemical performance of all‐solid‐state lithium batteries (ASSLBs) can be significantly improved by addressing the challenges posed by space charge layer (SCL) effect, which plays a crucial role in determining Li+ ions transport kinetic at cathodic interface. Therefore, it is critical to realize the in situ inspection and visualization of SCL behaviors for solving sluggish Li+ ions transport issues, despite remaining grant challenges. Therewith, the well‐defined model of LiNbO3‐coated NCM (NCM@LNO) cathode is constructed and assembled for the representative Li6PS5Cl‐based ASSLBs, which not only ensures excellent cathodic compatibility, but also preferably enables the better monitoring of Li+ ions transport kinetics. Combining ex situ analysis with DFT calculation, the formation and evolution mechanism of SCL are comprehensively understood, and the relationship between well‐controlled SCL configuration and Li+ electrochemical behavior has been also further illustrated and established through the operando Raman spectroscopy. On these grounds, the preferred NCM@LNO cathodes acquire the enhanced discharge capacity of 90.6% (144.8 mAh g−1) after 100 cycles and it can still deliver the exceptional capacity of 136.2 mAh g−1 after 800 cycles in ASSLBs. Hence, the research will pave up a new perspective for fundamental scientific insight of the SCL and reasonable tailoring of cathodic interface for high‐efficiency ASSLBs.

Simulation comparison of the positive and negative surface discharges induced by metal particles in a plate–surface–plate structure under DC excitation in atmospheric air

Surface discharge induced by metal particles is a common insulation failure in many high-voltage equipment. In order to further understand the mechanisms of this surface discharge, a 2D simulation model of a plate–surface–plate structure with a pin is established and verified by experiments in this paper to simulate the actual discharge configurations, and the evolution characteristics of the positive and negative surface discharges are compared. The evolutions of both positive and negative discharges could be divided into two phases: the bridging phase and the expansion phase. As the electric field in the gap between the streamer and the dielectric surface is strengthened by the effect of the space charge, the ionization sources and the secondary electrons excited on the dielectric surface, the dielectric surface presents attraction to the streamer, and subsequently the two streamer routes first touch the dielectric surface and then arrive at the grounding electrode. However, the channel branching is the most distinctive characteristic of the positive and negative discharges. In the positive discharge, the channel first branches, then merges, and finally expands, and the gaps of pin to dielectric surface and pin to grounding electrode are broken down by two slender positive branches, respectively. The negative discharge presents a stout channel without branching, which develops and expands simultaneously. This is ascribed to the thinner space charge layer, the weaker shielding effect of the internal electric field and the more active movement of the internal charges in the positive discharge. Another important factor for the discharge branching is the appropriate matching of the sheath thickness and the curvature radius of the channel’s head.

Expulsion of hydrogen negative ions by the anode layer of negative space charge from Penning discharge with metal hydride cathodes

The method of expulsion of hydrogen negative ions in the axial direction by a negative space charge formed in the plasma of Penning discharge with metal hydride cathodes is discussed. The plasma is produced on hydrogen, which is stored in metal hydride cathodes and injected locally into the discharge cell without any external gas supply due to ion current impact from plasma. The process of nonequilibrium desorption resulted in high vibrational excitation of H2 molecules, which greatly increases the efficiency of H− ion production. The method of efficient expulsion of H− ions depends on the external magnetic field. At a high magnetic field, it is performed by the supply of negative electric bias of the opposite cathode, but at a low one, H− ions are pushed out by the negative space charge of the anode layer, which expands toward the axis. The impact of both methods is considered in the case of DC discharge and in pulsating regime implementation.

In Situ Polymerization Inhibiting Electron Localization in Hybrid Electrolyte for Room‐Temperature Solid‐State Lithium Metal Batteries

AbstractHybrid solid electrolytes (HSEs) have attracted much attention due to their advantages as both inorganic and organic polymer electrolytes. However, the organic/inorganic interfacial space charge layer has a great barrier to the transport of Li+ in the HSE. Here, an in situ polymerization layer is proposed on garnet‐type particles, working as the coherent region to eliminate the space charge layer at the organic/inorganic interfaces by inhibiting electron localization. The conjugate hybridization of fillers weakens the aggregation of particles, induces the dissociation of Li salt, and provides high‐throughput Li+ transport pathways at the ceramics/polymer interface. Furthermore, the continuous Li+ conduction networks are connected by the coherent region between inorganic fillers and polymer chains. The fabricated HSE exhibits a high ionic conductivity of 0.47 mS cm−1 and ion migration numbers of 0.78 at room temperature. The 3D Li//Li systematic battery assembled with the HSE delivers a high critical current density (CCD) of 2.0 mA cm−2. Meanwhile, the 4.5 V NCM811//Li batteries achieve a prolonged operation of 500 cycles at 0.5 C. The Li//LiFePO4 batteries demonstrate superior capacity retention of 96.4% at 1 C after 500 cycles.

Protonic and electronic hole conductivity of grain interior and grain boundaries in BaZr0.9Y0.1O3-δ: Effect from sample processing

BaZr0.9Y0.1O3-δ (BZY10) is a popular composition for the electrolyte in protonic ceramic cells, due to its relatively high proton conductivity, excellent chemical stability, and good compatibility with NiO negatrode substrate during high temperature co-sintering. The microstructure of BZY10 is highly dependent on sample processing, leading to large discrepancy of the electrochemical performance of BZY10 in literature. In this work, three BZY10 samples were prepared by different sample processing and sintering conditions, and the grain interior (bulk) and grain boundary partial conductivities of protons and holes were separated. The sintering processes influenced the transport properties of pristine BZY10 samples significantly, and longer sintering time at high temperature (1650 – 1700 °C) leads to lower proton conductivity in both bulk and grain boundary. However interestingly, longer sintering time resulted in higher ionic transport number of bulk conduction, but lower ionic transport number of grain boundary conduction, possibly due to increasing Ba-deficiency in bulk by longer annealing at high temperature. Besides, adding ZnO into BZY10 decreased the proton conductivity in both bulk and grain boundary, but its ionic transport number of bulk conduction increases. A further analysis based on the theory of space charge layer indicated that adding ZnO leaded to decreased Schottky barrier height in the grain boundary core, and the highest Schottky barrier height was observed in the pristine sample which was sintered for longer time. The results obtained in this work suggest a potential strategy to regulate the transport properties of BZY10 by choosing appropriate approaches for sample processing to control the microstructure and local composition of the polycrystalline BZY10 ceramic electrolyte.

Effect of Mixing Intensity on Electrochemical Performance of Oxide/Sulfide Composite Electrolytes

Despite the variety of solid electrolytes available, no single solid electrolyte has been found that meets all the requirements of the successor technology of lithium-ion batteries in an optimum way. However, composite hybrid electrolytes that combine the desired properties such as high ionic conductivity or stability against lithium are promising. The addition of conductive oxide fillers to sulfide solid electrolytes has been reported to increase ionic conductivity and improve stability relative to the individual electrolytes, but the influence of the mixing process to create composite electrolytes has not been investigated. Here, we investigate Li3PS4 (LPS) and Li7La3Zr2O12 (LLZO) composite electrolytes using electrochemical impedance spectroscopy and distribution of relaxation times. The distinction between sulfide bulk and grain boundary polarization processes is possible with the methods used at temperatures below 10 °C. We propose lithium transport through the space-charge layer within the sulfide electrolyte, which increases the conductivity. With increasing mixing intensities in a high-energy ball mill, we show an overlay of the enhanced lithium-ion transport with the structural change of the sulfide matrix component, which increases the ionic conductivity of LPS from 4.1 × 10−5 S cm−1 to 1.7 × 10−4 S cm−1.

High‐Capacity, Long‐Life Sulfide All‐Solid‐State Batteries with Single‐Crystal Ni‐Rich Layered Oxide Cathodes

AbstractSulfide all‐solid‐state battery (SASSB) with ultrahigh‐nickel layered oxide cathode (LiNixCoyMn1‐x‐yO2, NCM, x ≥ 0.9) offers the potential of high energy density and safety for superior energy storage systems. However, stable cycling is difficult to realize due to adverse interfacial reactions, space charge layer (SCL), and elemental diffusion. Herein, a straightforward solid‐phase coating strategy is exploited to synthesize Ni90‐S cathode, which greatly improves the charge transmission capability of the composite cathode and suppresses interfacial reactions in SASSB. The consequent SC‐Ni90‐0.2%S/Li6PS5Cl/Li4Ti5O12 SASSB exhibits enhanced electrochemical performance, including a long life of 500 cycles with 87% capacity retention at 1C, high areal capacity of 11.44 mAh cm−2, and excellent rate performance at 20 C. These results promise an efficient strategy for designing cathode materials for SASSBs.

Unraveling the evolution of Cathode–Solid electrolyte interface using operando X-ray Photoelectron spectroscopy

Understanding the evolution of the solid electrolyte-electrode interface is currently one of the most challenging obstacles in the development of solid-state batteries (SSBs). Here, we develop an X-ray Photoelectron Spectroscopy (XPS) that allows for operando measurement during cycling. Based on theoretical analysis and the modulated electrode and detector co-grounding mode, the displacement of binding energy can be correlated with the surface electrostatic potential of the material, revealing the charge distribution and composition evolution of the space charge layer between the cathode and the electrolyte. In the investigation of typical LiCoO2 (LCO)/Li6PS5Cl (LPSC)/Li–In batteries, we observed the static potential difference and oxidative decomposition between LPSC and LCO, and the effectiveness of the LiNbO3 coating in reducing potential difference and inhibiting the diffusion of Co and oxidation of S species. Furthermore, our study also revealed that the potential drop between LiNi0·8Co0·1Mn0·1O2 and LPSC is smaller than that of LCO, whilst that between Li3InCl6 and LCO remains near zero. The proposed operando XPS method offers a novel approach for real-time monitoring of interface potential and species formation, providing rational guidance for the interface engineering in SSBs.

A numerical study on applying ion concentration polarization in micropump design

This work focuses on applying the phenomenon of ion concentration polarization to design and investigate a micropump model that is a kind of electroosmotic micropump. Numerical study is conducted for ion concentration polarization in the manner that generates electro-osmosis flow and pumping effect. The formation of the extended space charge layer and the actions of the electric field upon this layer is applied to generate electro-osmosis flow to drive flow in the system. It is clarified that pumping effect can be enhanced by improving the geometry configurations. Multiple simulations are conducted to obtain an optimal micropump design.

A high-performance room-temperature NH3 gas sensor based on WO3/TiO2 nanocrystals decorated with Pt NPs.

In this work, a high-performance room-temperature ammonia (NH3) gas sensor based on Pt-modified WO3-TiO2 nanocrystals was synthesized via a two-step hydrothermal method. The structural properties were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The 10 at% Pt@WO3-TiO2 nanocrystals present the highest NH3 sensing performance at room temperature. Compared with the nanocrystals without Pt modification, the sensitivity of the Pt@WO3-TiO2 sensor is tenfold higher, with the lowest concentration threshold reaching the 75 ppb level. The response is approximately 92.28 to 50 ppm, and response and recovery times are 23 s and 8 s, respectively. The improved sensing was attributed to a synergetic mechanism involving the space charge layer effect and Pt metal sensitization, enhancing the electron transfer efficiency, oxygen vacancy and specific surface area. This study is expected to guide the development of high-performance room-temperature ammonia sensors for clinical breath testing.

Effect of monolithic photovoltaic-photoelectrochemical-integrated Cu(In, Ga)Se2-related co-planar device on water splitting reaction

This study presents the fabrication of a photovoltaic-photoelectrochemical-integrated (PV-PEC) (Cu(In, Ga)Se2 (CIGS)-related co-planar device (integrated CIGS co-planar water splitting device) that resulted in an onset potential (V onset) of over 1.23 V to achieve photoelectrochemical water splitting without external bias. Therefore, the utility of this device was indicated for unassisted water splitting reaction. Moreover, the effects of the open-circuit voltage of the CIGS solar cell part on the photocurrent density and V onset of the fabricated water splitting device were investigated. These results suggest that the applying the reverse bias owing to V oc of the CIGS solar cell part influences the space charge layer at the surface of the CIGS photoelectrode. This effect leads to the formation of an inversion layer, suppressing surface recombination on the CIGS photoelectrode and contributing to an increase in the photocurrent density. The results represent a preliminary step toward realizing potential applications of the CIGS PV-PEC device for the unassisted water splitting reaction.

The dynamic anti-corrosion of self-derived space charge layer enabling long-term stable seawater oxidation

Developing corrosion-resistant oxygen evolution electrocatalysts that can sustain seawater electrolysis is crucial but challenging for hydrogen production. Herein, we develop a bimetallic oxyhydroxide electrocatalyst with self-derived selenate space charge layer (SeO42− SCL) by in-situ electrochemically reconstructing cobalt-doped nickel diselenide (Co-NiSe2) pre-catalyst, enabling long-term stability for seawater electrolysis. In-situ experiments and theoretical results reveal the promoting effect of cobalt-doping on the reconstruction of NiSe2 and generation of dynamically stable oxygen vacancy sites. Importantly, the SeO42− SCL derived from the reconstruction process shows a dynamic anti-corrosion behavior, thus protecting metal species from dissolution and meanwhile without blocking the diffusion and adsorption of reactive species. Consequently, a two-electrode cell assembled by this Co-NiSe2 pre-catalyst as an anode, reaches an industrial current density (500 mA cm−2) at a cell voltage of 1.70 V, and that works stably for over 1500 h in alkaline seawater, which is of significance for promoting the practicality of low-cost catalysts.

A Novel, Efficient Approach to Simulate the 3D Resolved Spatial and Temporal Development of Space-Charge Layers in Solid Electrolytes

The role of space-charge layers (SCLs) on the overall battery performance of solid-state batteries is heavily discussed in the scientific community ranging from dominant to negligible [1]. Reasons for this are that direct measurements of SCLs in experiments are difficult and so far, simulation models that can efficiently resolve the transient development of the shape of SCLs while being thermodynamically consistent are missing. The different length scales of SCLs on the one hand and of the microstructure of a battery cell on the other hand make a spatial discretization of realistic microstructures with resolved SCLs infeasible. To date, this was circumvented by using phenomenological models that do not require a spatial discretization of the SCL, by applying thermodynamically consistent models to simplified one-dimensional geometries, or by performing simulations on the sub-continuum scale, e.g. DFT simulations or kinetic Monte Carlo simulations. As all models, the mentioned models have limitations. In this case, they are for example either thermodynamically not consistent or limited to small, not representative geometries.In this work [2], we propose a model that enables the prediction of the spatial and temporal development of SCLs within geometrically resolved microstructures while being thermodynamically consistent [3]. We exploit that effects in SCLs are predominantly one-dimensional. Furthermore, it can be shown, that SCLs develop orthogonal to the interface between the solid electrolyte and the electrode in the steady state. This allows to project the equations in the regions of the solid electrolyte where SCLs are expected in one dimension. In the remaining region of the solid electrolyte, the equations remain three-dimensional. A consistent coupling strategy between the three-dimensional and the one-dimensional region is derived and is irrevocably connected to the fulfilment of conservation properties. This modelling approach allows to drastically reduce the size of the numerical discretization required to resolve SCLs in space, as a fine discretization is only required in one direction embedded into a coarse three-dimensional discretization which represents the geometric microstructure. Thus, the required computational effort significantly reduces.The continuous equations are discretized in space using the finite element method. The obtained nonlinear system of equations is solved with the Newton-Raphson scheme using one monolithic system, i.e. the concurrent solution of the differently discretized regions to ensure robustness and efficiency of the solver. Tailoring an iterative solver by utilizing physical information of the system (similar to [4]), enables to apply the model to realistic microstructures with more than 10 million unknowns.With the proposed approach it is possible for the first time to quantify the influence of realistic microstructures on the transient and spatial formation process of SCLs. This work is the first to show that the formation process of SCLs at the interface between solid electrolyte and electrode is strongly influenced by the geometry of the microstructure (see Fig. 1): The dominating trend is a propagation of the SCL through the composite electrode, i.e. from the separator side to the current collector side of each electrode. Simultaneously, an inhomogeneity in the plane being orthogonal to the dominant direction is observed. This can be attributed to different conduction paths within this two-dimensional manifold due to the irregularity of the investigated microstructures and their geometric complexity. Furthermore, characteristic points in the microstructure can be identified where more charge is stored in the SCL during the transient development compared to the steady state. Again, this is attributed to the complex microstructures in interplay with the impedance of the bulk electrolyte and of the SCL. For these observations a modelling approach that resolves SCLs in realistic microstructures is mandatory.

Separating the Effects of Band Bending and Covalency in Hybrid Perovskite Oxide Electrocatalyst Bilayers for Water Electrolysis

Testing single crystalline epitaxial thin films as model systems for metal oxide electrocatalysts in the oxygen evolution reaction (OER) enables differentiating the OER descriptors such as crystal facet orientation, surface chemical composition, electronic structure and band bending at the interface to the electrolyte [1,2,3]. We designed single crystalline perovskite oxide bilayer structures to systematically tune the surface electronic structure and the band bending at the electrode/electrolyte interface to understand their role in the OER.The Co−O covalency in perovskite oxide cobaltites such as La1 − x SrxCoO3 is believed to impact the electrocatalytic activity during the OER. Additionally, space charge layers through band bending at the interface to the electrolyte may affect the electron transfer into the electrode, complicating the analysis and identification of true OER activity descriptors. Here, we separate the influence of covalency and band bending in hybrid epitaxial bilayer structures of highly OER-active La0.6Sr0.4CoO3 and undoped and less-active LaCoO3. Ultrathin LaCoO3 capping layers of 2−8 unit cells on La0.6Sr0.4CoO3 show intermediate OER activity between La0.6Sr0.4CoO3 and LaCoO3 evidently caused by the increased surface Co−O covalency compared to single LaCoO3 as detected by X-ray photoelectron spectroscopy. A Mott−Schottky analysis revealed low flat band potentials for different LaCoO3 capping layer thicknesses, indicating that no limiting extended space charge layer exists under OER conditions as all catalyst bilayer films exhibited hole accumulation at the surface [1].The combined X-ray photoelectron spectroscopy and Mott−Schottky analysis of atomically defined bilayer structures thus enables us to differentiate between the influence of the covalency and intrinsic space charge layers, which are indistinguishable in a single physical or electrochemical characterization. Our results emphasize the prominent role of transition metal oxygen covalency in perovskite electrocatalysts and introduce a bilayer approach to fine-tune the surface electronic structure [1].[1] L. Heymann, M. L. Weber, M. Wohlgemuth, M. Risch, R. Dittmann, C. Baeumer, F. Gunkel (2022) Separating the Effects of Band Bending and Covalency in Hybrid Perovskite Oxide Electrocatalyst Bilayers for Water Electrolysis, ACS Appl. Mater. Interfaces[2] M. Wohlgemuth, M. L. Weber, L. Heymann, C. Baeumer, F. Gunkel (2022) Activity-Stability Relationships in Oxide Electrocatalysts for Water Electrolysis, Front. Chem.[3] M. L. Weber, G. Lole, A. Kormanyos, A. Schwiers, L. Heymann, F. D. Speck, T. Meyer, R. Dittmann, S. Cherevko, C. Jooss, C. Baeumer, F. Gunkel, (2022) Atomistic Insights into Activation and Degradation of La0.6Sr0.4CoO3-δ Electrocatalysts under Oxygen Evolution Conditions Figure 1

Space Charges in Solid State Batteries: Friend, Foe or Fantasy?

Thermodynamics tells us that all materials have an internal energy that determines how they act and react with all matter in the universe. Furthermore, it forces all matter to strive towards equilibrium with its surroundings. For solid-state lithium-ion conductors, the chemical potential of lithium is an important parameter that determines stability and influences conductivity. However, it also implies something deeper. The chemical potential of an element in a solid is determined by the bonds that surround it as well as its concentration. Whereas the former is an intrinsic property of the material, the latter can be altered. When two solids with different chemical potentials are placed in contact, a driving force is created for atoms to migrate across the surface and establish thermodynamic equilibrium by altering their concentration. For semiconductors, in which either only a hole or electron can migrate, something interesting occurs. The migrating entity moves across but the counter-charge cannot, resulting in excess charge at the interface. The migrating partner, unable to return to its original material due to thermodynamics, is now unable to dissipate into the new material due to electrostatics. The result is a thin, charged layer across the interface. Because solid electrolytes conduct lithium cations but no anions or electrons, this ‘space-charge layer’ is also thought to occur in solid-state batteries between electrolyte and electrode. Whereas its size is thought to only be a few nanometres, its (negative) influence could be very large as it can act as barrier for lithium transport across the surface. Yet experimental evidence of its existence is rare and investigation of its behaviour even more so. The space charge between two materials is very thin and chemically almost identical to the bulk. But just like how water can carve the stone, we employ liquids to crack a solid-state problem.We find that when mixing an argyrodite solid electrolyte (Li6PS5Cl) with an ionic liquid (1-Ethyl-3-methylimidazolium bis(trifluoromethyls ulfonyl) imide or EMIN TFSI) , we observe a new chemical environment with NMR (see figure) that cannot be attributed to dissolved precursors. We see an increase in the mobility of lithium ions in the solid electrolyte itself with NMR and an increase in conductivity of the mixture with EIS. Furthermore, exchange of lithium has been confirmed between argyrodite and the mystery environment. What does this all mean? Are we observing the illusive space charge layer? Or are we just staring at an empty promise in the well-known shape of a mysterious peak in a spectrum? Figure 1

Electro-Chemo-Mechanical Study of Cathode-Interface-Engineered All-Solid-State Lithium Batteries

All-solid-state lithium batteries (ASSLBs) have been regarded as one of the most promising next-generation batteries in terms of their superior safety and great potential to meet the requirements of high energy and power density.1 However, the performance of ASSLBs based on even state-of-the-art solid electrolytes (SEs) with a high room-temperature ion conductivity of 10−2 S·cm−1 is still inferior to that of commercially available LIBs, because fast solid electrode/electrolyte interfacial lithium-ion transport remains a vital challenge in ASSLBs.2 The sluggish lithium-ion transport across the solid electrode/electrolyte interface mainly results from the electro-chemo-mechanical degradation, such as the space charge layer (SCL), interface reaction generating ionically resistive products, and poor physical contact.3,4 On the cathode side, coating high-voltage cathodes with chemically compatible and stable buffering layers with high ionic conductivity but low electronic conductivity has been widely confirmed to be an effective approach to overcome these problems.However, a mechanistic understanding of the coating functionality remains unresolved, and there is still much room for improvement regarding the methodology and associated material properties.5 Here, from electro-chemo-mechanical perspectives, we have fully studied the improvement mechanism of cathode interface engineering for ASSLBs based on the complementary analyses including calculations (e.g., first-principles, finite element methods), in-situ (e.g., differential phase contrast scanning transmission electron microscopy (DPC-STEM), Raman, electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), galvanostatic intermittent titration technique (GITT)) and ex-situ (X-ray absorption spectra (XAS), X-ray photoelectron spectroscopy (XPS), focused-ion beam scanning electron microscopy (FIB-SEM)) characterizations. We find that discontinuous ferroelectric BaTiO3 coating can effectively suppress the SCL formation and lead to fast continuous interfacial lithium-ion conduction pathways, thus significantly improving the interfacial migration kinetics between cathode materials and the sulfide SEs.6 The bidirectionally compatible NASICON-type LixZr2(PO4)3 (LZPO) buffering layer enables the high-voltage cathode interface (4.5 V LiCoO2/Li6PS5Cl) with high chemical/electrochemical stability and fast Li-ion transport dynamics.7 Additionally, the high Young’s modulus of the coating layer (e.g., LZPO) can remarkably decrease stress inside cathodes and prevent cathode/SE interface separation, which is beneficial to mitigate microcracks in cathodes and cathode/SE interface contact loss, respectively.8 We believe these findings will help advance the fundamental scientific understanding of the coating functionality and the interfacial lithium-ion transport mechanism in ASSLBs, thus shed light on rational electrode/electrolyte interface design for high-rate performance ASSLBs.References Janek, J. & Zeier, W. G. A solid future for battery development. Nat. Energy 1, 16141 (2016).Janek, J. & Zeier, W. G. Challenges in speeding up solid-state battery development. Nat. Energy, doi:10.1038/s41560-023-01208-9 (2023).Banerjee, A., Wang, X., Fang, C., Wu, E. A. & Meng, Y. S. Interfaces and Interphases in All-Solid-State Batteries with Inorganic Solid Electrolytes. Chem. Rev. 120, 6878–6933 (2020).Chen, R., Li, Q., Yu, X., Chen, L. & Li, H. Approaching Practically Accessible Solid-State Batteries: Stability Issues Related to Solid Electrolytes and Interfaces. Chem. Rev. 120, 6820–6877 (2020).Culver, S. P., Koerver, R., Zeier, W. G. & Janek, J. On the functionality of coatings for cathode active materials in thiophosphate-based all-solid-state batteries. Adv. Energy Mater. 9, 1900626 (2019).Wang, L. et al. In-situ visualization of the space-charge-layer effect on interfacial lithium-ion transport in all-solid-state batteries. Nat. Commun. 11, 5889 (2020).Wang, L. et al. Bidirectionally compatible buffering layer enables highly stable and conductive interface for 4.5 V sulfide-based all-solid-state lithium batteries. Adv. Energy Mater. 11, 2100881 (2021).Sun, X. et al. A Bifunctional Chemomechanics Strategy To Suppress Electrochemo-Mechanical Failure of Ni-Rich Cathodes for All-Solid-State Lithium Batteries. ACS Appl. Mater. Interfaces 14, 17674–17681 (2022).

Synthesis and Characterization of Vitrimer-like Self-Healing Polymer Electrolytes for Lithium Metal Batteries

Solid-polymer electrolytes have become crucially significant with the fast-expanding energy requirements in both the academic and industrial spheres due to their better safety and energy density compared to liquid electrolytes. Despite these encouraging possibilities, a few obstacles are associated with these electrolytes, chief among them being the limited charge transport via the solid electrode-electrolyte interface. Due to the difference in electrochemical potential between the electrode and the electrolyte, this obstruction initiates electrode-electrolyte interactions through electrode volumetric changes, interface reactions, and space charge layers.One possible way to enhance the LIB performance could be by integrating a new class of covalent adaptable networks called vitrimers.The self-healing, shape memory, recyclability, and reprocessibility properties of vitrimers, a class of covalent adaptable networks (CANs), are derived from a covalent molecular network that can change its topology through molecular rearrangements while maintaining the overall number of network bonds. In this manner, Li dendrites that might develop during battery cycling could be eliminated and the electrolyte-electrode contact could be restored by vitrimers. Figure 1