Interfacial Issues Research Articles

Isolating the Oxygen Adsorption Defects on Sputtered Tin Oxide for Efficient Perovskite Solar Cells

Tin oxide (SnO2) is the most commonly used electron transport material for perovskite solar cells (PSCs). Various techniques have been applied to deposit tin dioxide, including spin-coating, chemical bath deposition, and magnetron sputtering. Among them, magnetron sputtering is one of the most mature industrial deposition techniques. However, PSCs based on magnetron-sputtered tin oxide (sp-SnO2) have a lower open-circuit voltage (Voc) and power conversion efficiency (PCE) than those prepared by the mainstream solution method. This is mainly due to the oxygen-related defects at the sp-SnO2/perovskite interface, and traditional passivation strategies usually have little effect on them. Herein, we successfully isolate the oxygen adsorption (Oads) defects located on the surface of sp-SnO2 from the perovskite layer using a PCBM double-electron transport layer. This isolation strategy effectively suppresses the Shockley-Read-Hall recombination at the sp-SnO2/perovskite interface, which results in an increase in the Voc from 0.93 to 1.15 V and an increase in PCE from 16.66 to 21.65%. To our knowledge, this is the highest PCE achieved using a magnetron-sputtered charge transport layer to date. The unencapsulated devices maintain 92% of their initial PCE after storage in air with a relative humidity of 30-50% after 750 h. We further use the solar cell capacitance simulator (1D-SCAPS) to confirm the effectiveness of the isolation strategy. This work highlights the application prospect of magnetron sputtering in the field of perovskite solar cells and provides a simple yet effective way to tackle the interfacial defect issue.

Perspective on powder technology for all-solid-state batteries: How to pair sulfide electrolyte with high-voltage cathode

Sulfide solid electrolytes (SEs) have attracted ever-increasing attention due to their superior room-temperature ionic conductivity (∼10−2 S cm−1). Additionally, the integration of sulfide SEs and high-voltage cathodes is promising to achieve higher energy density. However, the incompatible interfaces between sulfide SEs and high-voltage cathodes have been one of the key factors limiting their applications. Therefore, this review presents a critical summarization of the interfacial issues in all-solid-state lithium batteries based on sulfide SEs and high-voltage cathodes and proposes strategies to stabilize the electrolyte/cathode interfaces. Moreover, the future research direction of electrolyte/cathode interfaces and application prospects of powder technology in sulfide-based ASSLBs were also discussed.

Anode Interfacial Issues in Solid‐State Li Batteries: Mechanistic Understanding and Mitigating Strategies

All‐solid‐state Li metal batteries (ASSLBs) using inorganic solid electrolyte (SE) are considered promising alternatives to conventional Li‐ion batteries, offering improved safety and boosted energy density. While significant progress has been made on improving the ionic conductivity of SEs, the degradation and instability of Li metal/inorganic SE interfaces have become the critical challenges that limit the coulombic efficiency, power performance, and cycling stability of ASSLBs. Understanding the mechanisms of complex/dynamic interfacial phenomena is of great importance in addressing these issues. Herein, recent studies on identifying, understanding, and solving interfacial issues on anode side in ASSLBs are comprehensively reviewed. Typical issues at Li metal/SE interface include Li dendrite growth/propagation, SE cracking, physical contact loss, and electrochemical reactions, which lead to high interfacial resistance and cell failure. The causes of these issues relating to the chemical, physical, and mechanical properties of Li metal and SEs are systematically discussed. Furthermore, effective mitigating strategies are summarized and their effects on suppressing interfacial reactions, improving interfacial Li‐ion transport, maintaining interfacial contact, and stabilizing Li plating/stripping are highlighted. The in‐depth mechanistic understanding of interfacial issues and complete investigations on current solutions provide foundations and guidance for future research and development to realize practical application of high‐performance ASSLB.

Dynamic Supramolecular Polymer Electrolyte to Boost Ion Transport Kinetics and Interfacial Stability for Solid‐State Batteries

AbstractThe key hurdle to the practical application of polymeric electrolytes in high‐energy‐density solid lithium‐metal batteries is the sluggish Li+ mobility and inferior electrode/electrolyte interfacial stability. Herein, a dynamic supramolecular polymer electrolyte (SH‐SPE) with loosely coordinating structure is synthesized based on poly(hexafluoroisopropyl methacrylate‐co‐N‐methylmethacrylamide) (PHFNMA) and single‐ion lithiated polyvinyl formal. The weak anti‐cooperative H‐bonds between the two polymers endow SH‐SPE with a self‐healing ability and improved toughness. Meanwhile, the good flexibility and widened energy gap of PHFNMA enable SH‐SPE with efficient ion transport and superior interfacial stability in high‐voltage battery systems. As a result, the as‐prepared SH‐SPE exhibits an ionic conductivity of 2.30 × 10−4 S cm−1, lithium‐ion transference number of 0.74, electrochemical stability window beyond 4.8 V, and tensile strength up to 11.9 MPa as well as excellent adaptability with volume change of the electrodes. In addition, no major electrolyte decomposition inside batteries made from SH‐SPE and LiNi0.8Mn0.1Co0.1O2 cathode can be observed in the in situ differential electrochemical mass spectrometry test. This study provides a new methodology for the macromolecular design of polymer electrolytes to address the interfacial issues in high‐voltage solid batteries.

Directly Using Li2CO3 as a Lithiophobic Interlayer to Inhibit Li Dendrites for High-Performance Solid-State Batteries

Garnet solid electrolytes have attracted great interest due to their wide electrochemistry window and high ion conductivity. However, the lithiophobic Li2CO3 generated on the garnet surface results in a huge interfacial resistance and interface incompatibility. Herein, different from the extensive removal or conversion strategies, the Li2CO3 on the surface of Li6.5La3Zr1.5Ta0.5O12 (LLZTO) is directly used as a lithiophobic layer to suppress Li dendrite growth, and the lithophilic Li-In-F composite is used as the anode. The Li symmetrical half-cell with a Li2CO3 interlayer is stably cycled for 6500 h without Li dendrite formation, a much longer time than for the half-cell without a Li2CO3 interlayer (2334 h), showing a much higher interfacial stability. Moreover, the full cell based on LiFePO4 and LiNi0.8Co0.1Mn0.1O2 cathode shows a stable cycling performance and high rate capability (LiNi0.8Co0.1Mn0.1O2, 94%@100th cycle@1C; LiFePO4, 90%@500th cycle@2C). This study provides a distinct way of converting disadvantages into advantages and solving the Li|LLZTO interfacial issues.

Recent advances and interfacial challenges in solid-state electrolytes for rechargeable Li-air batteries.

Among the promising batteries for electric vehicles, rechargeable Li-air (O2) batteries (LABs) have risen keen interest due to their high energy density. However, safety issues of conventional nonaqueous electrolytes remain the bottleneck of practical implementation of LABs. Solid-state electrolytes (SSEs) with non-flammable and eco-friendly properties are expected to alleviate their safety concerns, which have become a research focus in the research field of LABs. Herein, we present a systematic review on the progress of SSEs for rechargeable LABs, mainly focusing on the interfacial issues existing between the SSEs and electrodes. The discussion highlights the challenges and feasible strategies for designing suitable SSEs for LABs.

In-situ construction of multifunctional interlayer enabled dendrite-free garnet-based solid-state batteries

Garnet-based Li6.5La3Zr1.5Ta0.5O12 (LLZTO) is a prospective solid-state electrolyte with fast ionic mobility and distinguished chemical/electrochemical stabilities toward Li metal. However, Li dendrite propagated within LLZTO bulk is one of the main obstacles to the practical application of solid-state batteries. Herein, we propose to inhibit Li dendrite growth through in-situ construction of a multifunctional interlayer of Li2S/LiSn alloy achieved via a conversion reaction of SnS layer coated on the surface of the LLZTO pellet. DFT calculation reveals that the interfacial contact of LLZTO and Li is considerably improved via Li2S/LiSn interlayer, consequently contributing to a low interfacial impendence (5.1 Ω cm2). Furthermore, the electronic insulativity of LLZTO is also meliorated to suppress electron tunneling. As a result, with effectively restraining the Li dendrite, the Li|LLZTO@Li2S/LiSn|Li symmetrical battery exhibits a superb long-term Li plating/stripping performance over 1500 h and 700 h under 0.2 and 0.4 mA cm−2, respectively. Furthermore, the LFP|LLZTO@Li2S/LiSn|Li full battery displays notable cycling performance (99.8% capacity retention after 100 cycles at 1 C) and rate properties (160.6 mAh g−1 at 0.1 C and 116.3 mAh g−1 at 1 C). This facile and effective method may provide a feasible strategy for eliminating the interfacial issue and achieving dendrite-free solid-state Li metal batteries.

Water absorption in alkaline-treated coir pith – For use as reinforcement material in polymer matrix composites

Green composites, made of sustainable materials and manufacturing, have been attractive owing to their low cost, renewability, and biodegradability. Coir pith is one of the agrowaste based products available in huge quantities in tropical countries and has superior properties compared to many other natural agrowaste based materials. Due to its sponginess, fluffiness, high porosity, high water absorption, and retention capacity, coir pith poses a significant challenge in its use as a reinforcement material due to interfacial adhesion issues with the polymer matrix phase in composite making. This interfacial adhesion is associated with the high-water absorption capacity of coir. Chemical treatment of natural fibers is one of the methods that have been applied to alter the morphology and chemistry of fibers. In the current study, coir pith was treated using 2% sodium hydroxide (NaOH) concentration for 20, 40, and 60 min, washed, and oven dried for 72 h. The dried samples were used for the water absorption studies by immersing the samples in distilled water for 2 h and measuring the weight changes every 15 min. The results show that treated coir pith absorbs more water than raw untreated coir pith, and detailed observation of the surface of coir pith after treatment indicates increased surface roughness compared to the surface of a raw particle.

A promising composite solid electrolyte of garnet-type LLZTO and succinonitrile in thermal polyurethane matrix for all-solid-state lithium-ion batteries

For solid-state electrolyte in lithium-ion batteries, high crystal boundary impedance leads to tough electrolyte-electrode interfacial issues. Here, we introduce garnet Li6.4La3Zr1.4Ta0.6O12 (LLZTO) nanoparticles and succinonitrile (SN) into thermal polyurethane (TPU) to fabricate a composite solid-state electrolyte (TPU/LLZTO/SN), achieving high ionic conductivity of 6.452 × 10−4 S cm−1. The TPU polymer with specific soft and hard segments allows lithium ions fast transport and holds good mechanical strength as the electrolyte matrix. The ionic conductor LLZTO further improves the ionic conductivity and mechanical property of the composite electrolyte membrane. Additional SN supplies the electrolyte’ wide electrochemical stabilization window, and enhances the metallic lithium compatibility of the TPU matrix. As a result, the as prepared TPU/LLZTO/SN electrolyte presents high lithium ions transference number of 0.64, and also good mechanical property.

An integrated study on the ionic migration across the nano lithium lanthanum titanate (LLTO) and lithium iron phosphate-carbon (LFP-C) interface in all-solid-state Li-ion batteries

A major challenge for the development of all-solid-state lithium-ion batteries (ASS-LIBs) relay on the development of an ideal electrolyte material and solving the interfacial issues at the electrode-electrolyte interface. Nano-crystalline lithium lanthanum titanate (LLTO) and lithium iron phosphate-carbon (LFP/C) has been prepared as electrolyte and cathode material for a solid-state lithium ion cell (LIBs). Prepared lithium lanthanum titanate, lithium iron phosphate-carbon and the composite powders were subjected to structural, optical, morphological and electrochemical characterizations. The high ionic conductivity of lithium lanthanum titanate (1.06 × 10−4), carbon coated lithium iron phosphate (5.01 × 10−5) and their interface (6.00 × 10−5) designate the pertinence of their full cell configurations. The full cell assembly has been characterized electrochemically to evaluate the performance of the interface. The assembled ASSBs show cyclability up to 55 initial cycles, with the nano-LLTO/LFP-C interface. The line scan analysis has been performed to identify the cation movement and accumulation of ions towards and across the cathode-electrolyte interface after cycling. The present study provides new direction and methodology for the detailed interface analysis across the nano-electrode- nano-solid electrolyte layer in all solid-state assemblies.

Interfacial Issues and Modification of Solid Electrolyte Interphase for Li Metal Anode in Liquid and Solid Electrolytes

AbstractThe high energy density required for the next generation of lithium batteries will likely be enabled by a shift toward lithium metal anode from the conventional intercalation‐based anode such as graphite. However, several critical challenges for Li metal originate from its highly reactive nature and the hostless reaction of deposition and stripping impede the practical use of Li metal as an anode. The role of the solid electrolyte interphase (SEI) is very important for the Li metal anode where the SEI must protect the dynamically changing surface of the Li metal. Since the SEI‐generating reaction mechanisms for the two different electrolyte systems, liquid and solid, are considerably different, the SEI layers formed between the Li metal and the electrolytes in the two electrolyte systems have substantially different properties, causing different interfacial issues. Inhibition of the interfacial problems requires different strategies to reinforce the SEI layer for each of the electrolyte systems. However, the differences in the two electrolyte systems have not been clearly compared in the prior literature. In this report, the interfacial issues for the two different electrolyte systems are compared and different strategies for SEI modification are provided to overcome the issues.

Multifunctional Mesoporous Carbonaceous Materials Enable the High Performance of Lithium-Sulfur Batteries.

Focusing on multifunctional mesoporous carbonaceous materials (MCMs) is one of the hot research topics due to increasing demand in the high-energy-density devices of lithium-sulfur (Li-S) batteries (2600 Wh kg-1). On the premise of applying MCMs as a porous framework to load elemental sulfur, to improve the electronic conductivity of the cathode, and to trap the in situ-formed electrolyte-soluble intermediates of lithium polysulfides (LiPSs), the commercialization of MCMs-based energy storage devices still needs to solve solid/solid and solid/liquid interfacial issues such as the chemical anchoring of the electrically insulating active substances, the sluggish redox kinetics of intermediate LiPSs, and so on. Through the permutation of multifunctional MCMs serving as the primary sulfur-loading carrier of the cathode, as the secondary surface-coating layers of the separator, the cathode, and the anode separately, this Perspective highlights research challenges to clarify a comprehensive high-performance mechanism of MCM-based Li-S batteries and provides new chemical insight for potential application purposes.

Stabilizing cathodes and interphases for next-generation Li-ion batteries

The past-30-year advances enable lithium (Li)-ion batteries to reshape our daily life from living, work and entertainment to transportation. Yet current Li-ion batteries cannot fulfill the boosting market needs. To build higher performance and lower-cost batteries, it is crucial to comprehend the fundamentals of battery chemistries and consider both electrodes, electrolyte, as well as their interphases, namely anode solid-electrolyte interphase (SEI) and cathode solid electrolyte interphase (CEI). While many prior articles have focused on anodes and their SEIs, few reviews and analyses covered the materials and interfacial issues on the cathode side. Here we offer a critical overview of the current status and challenges for Li-ion battery cathodes and their CEIs. We discuss the impact of the CEI on both the intercalation and conversion-type cathode performance characteristics, summarize various strategies used for the CEI and cathode stabilizations, offer design guidelines and outline promising future directions for the development and applications for next-generation Li-ion batteries.

Practical Application of Li-Rich Materials in Halide All-Solid-State Batteries and Interfacial Reactions between Cathodes and Electrolytes

Benefiting from the advanced solid-state electrolytes (SSEs), conventional cathodes have been widely applied in all-solid-state lithium batteries (ASSLBs). However, Li-rich Mn-based (LRM) cathodes, which possess enhanced discharge capacities beyond 250 mA h g-1, have not yet been studied in ASSLBs. In this work, the practical application of LRM cathodes in ASSLBs using a high-voltage-stability halide SSE (Li3InCl6, LIC) is reported for the first time. Furthermore, we decipher that the active oxygen released from LRM cathodes at a high operation voltage seriously oxidizes the LIC electrolytes, thus resulting in the large interfacial resistance between cathodes and electrolytes and hindering their industrialized application in ASSLBs. Therefore, surface chemistry engineering of LRM cathodes with an ionic conductive coating material of LiNbO3 (LNO) is employed to stabilize the LRM/LIC interface. Consequently, the LRM-based ASSLBs deliver a high specific capacity of 221 mA h g-1 at 0.1 C and a decent cycle life of 100 cycles. This contribution gives insights into studying the interfacial issues between LRM cathodes and halide electrolytes and sheds light on the application of LRM cathode materials in ASSLBs.

In-situ constructed SnO2 gradient buffer layer as a tight and robust interphase toward Li metal anodes in LATP solid state batteries

Li1.3Al0.3Ti1.7(PO4)3 (LATP), of much interest owing to its high ionic conductivity, superior air stability, and low cost, has been regarded as one of the most promising solid-state electrolytes for next-generation solid-state lithium batteries (SSLBs). Unfortunately, the commercialization of SSLBs is still impeded by severe interfacial issues, such as high interfacial impedance and poor chemical stability. Herein, we proposed a simple and convenient in-situ approach to constructing a tight and robust interface between the Li anode and LATP electrolyte via a SnO2 gradient buffer layer. It is firmly attached to the surface of LATP pellets due to the volume expansion of SnO2 when in-situ reacting with Li metal, and thus effectively alleviates the physical contact loosening during cycling, as confirmed by the mitigated impedance rising. Meanwhile, the as-formed SnO2/Sn/LixSn gradient buffer layer with low electronic conductivity successfully protects the LATP electrolyte surface from erosion by the Li metal anode. Additionally, the LixSn alloy formed at the Li surface can effectively regulate uniform lithium deposition and suppress Li dendrite growth. Therefore, this work paves a new way to simultaneously address the chemical instability and poor physical contact of LATP with Li metal in developing low-cost and highly stable SSLBs.

Interfacial design for detection of a few molecules.

Major advances in molecular detection are being driven by goals associated with the development of methods that are amenable to miniaturization and automation, and that have high sensitivity and low interference. The new detection methods are confronted by many interfacial issues, which when properly addressed can lead to improved performance. One interfacial property, special wettability, can facilitate precise delivery and local enrichment of molecules to sensing elements. This review summarizes applications of unique features of special wettability in molecular detection including (1) chemical and electrochemical reactions in anchored microdroplets on superwetting surfaces, (2) enrichment of analytes and active materials at low contact areas between droplets and superwetting surfaces, (3) complete opposite affinities of superwetting surfaces toward nonpolar/polar solutes and oil/water phases, and (4) directional droplet transportation on asymmetric superwetting surfaces. The challenges and opportunities that exist in design and applications of special wettability in interfacial delivery and enrichment for detection of a few molecules are also discussed.

Interfacial Challenges and Strategies toward Practical Sulfide-Based Solid-State Lithium Batteries

All-solid-state lithium batteries are considered as the priority candidates for next-generation energy storage devices due to their better safety and higher energy density. As the key part of solid-state batteries, solid-state electrolytes have made certain research progress in recent years. Among the various types of solid-state electrolytes, sulfide electrolytes have received extensive attention because of their high room-temperature ionic conductivity and good moldability. However, sulfide-based solid-state batteries are still in the research stage. This situation is mainly due to the fact that the application of sulfide electrolytes still faces challenges in particular of interfacial issues, mainly including chemical and electrochemical instability, unstable interfacial reaction, and solid–solid physical contact between electrolyte and electrode. Here, this review provides a comprehensive summary of the existing interfacial issues in the fabrication of sulfide-based solid-state batteries. The in-depth mechanism of the interfacial issues and the current research progress of the main coping strategies are discussed in detail. Finally, we also present an outlook on the future development of sulfide-based solid-state batteries to guide the rational design of next-generation high-energy solid-state batteries.

Reactive boride as a multifunctional interface stabilizer for garnet-type solid electrolyte in all-solid-state lithium batteries.

All-solid-state batteries are one of the most important game changers in electrochemical energy storage since they are free from the risk of leakage of hazardous flammable liquid solvents. Among the various types of solid-state electrolytes, Li7-xLa3Zr2-xTaxO12 garnets possess many desirable advantages to be considered a suitable candidate for lithium-ion batteries. However, their practical application has been hindered by premature short-circuits due to lithium dendrite growth, nonnegligible electronic conductivity and interfacial air sensitivity issues. Herein, we propose a multifunctional layer strategy to simultaneously address both the interface and electronic conductivity issues. With the help of a facile chemical process based on reactive cobalt boride, electron leakage was effectively blocked and the electrochemical performance/stability could be well maintained over extended cycles. The cobalt boride-coating layer also possessed an impressive Li metal wetting ability while sustaining a low interfacial resistance. A full cell paired with a commercialized cathode showed satisfactory performance with low overpotentials and a high specific capacity over 150 mA h g-1. Moreover, first-principle calculations further revealed the status of the rearrangement of the electron cloud behind the charge-density difference, and the nature of the low diffusion energy barrier of the reactive cobalt boride protective layer. Our strategy highlights the necessity of designing proper multifunctional layers in the garnet-type solid-state lithium-ion battery system.

Orientated growth the 3D diamond/graphene hybrid arrays and the application in thermal interface materials

Diamond and graphene are considered to be one of the most promising thermal interface materials (TIMs) for electronic devices benefited from their highest thermal conductivity in the natural world. However, orientated fabrication of high thermal conductivity diamond and graphene hybrid arrays with three dimensions (3 D) thermal conductive networks are still problematic. Here, we used a unique one-step microwave plasma chemical vapor deposition, n-butylamine, as the liquid source to prepare a novel high thermal conductivity 3 D vertical diamond/graphene (VDG) hybrid arrays films. The orientated 3 D thermal conduction path of the VDG is regulated by the growth temperature, and the through-plane thermal conductivity value of the VDG700 films up to 97 W m−1 K−1. In the actual TIM performance measurement, the system cooling efficiency with our VDG as TIM is higher than the state-of-the-art commercial TIM, demonstrating the superior ability to solve the inter-facial heat transfer issues in electronic systems.

In situ induced crosslinking highly conductive solid polymer electrolyte with intimated electrodes interfacial compatibility for safe Li-ion batteries

Nowadays, lower ionic conductivity and interfacial issue are hindering industrial development of solid-state lithium batteries. Herein, we prepare cross-linking solid polymer electrolytes (CSPEs) with a certain amount of additive fluorosulfonamide (FSA) by employing lithium bis(fluorosulfonyl)imide (LiFSI) as an initiator for catalyzing cationic ring-opening polymerization (CROP) via an in-situ thermal strategy. a series of technologies have used to investigate the physiochemical properties and electrochemical performances of as-prepared CSPEs. The ionic conductivity of as-prepared CSPE-2 is 1.46 mS/cm at 25 °C. Its electrochemical anodic oxidation potential is stable up to 5.2 V. Its lithium transference number (tLi+) reaches to 0.61 at room temperature (RT). Furthermore, the assembled half-cell of LiFePO4/CSPE-2/Li delivers an excellent initial discharge capacity of 165 mAh/g at 0.1C and shows Coulombic efficiency (CE) of 96.7%. It retains its capacity at 136 mAh/g after 200 cycles. Full cell configuration of LiFePO4/CSPE-2/graphite shows an initial discharge capacity of 142 mAh/g at 0.1C, retains its capacity at 122 mAh/g, and achieves a CE of 90.2% after 200 cycles. Field emission scanning electron microscope (FE-SEM) reveals an intimate interface compatibility with additive FSA. This study may provide a strategy to design and fabricate solid-state electrolytes for lithium-ion batteries.