Anode Interface Research Articles

Ion Redistribution Gel Electrolyte Dissipates Interfacial Turbulence for Aqueous Zinc‐Ion Batteries

AbstractAqueous zinc‐ion batteries (AZBs) degrade under a high current density due to the existence of interfacial turbulence with severe concentration polarization. Herein, an ion redistribution gel electrolyte is introduced to stabilize the electrode‐electrolyte interface by regulating the ion density gradient. Negatively charged carboxymethyl groups in carboxymethyl starch ether polymer (PCMS) electrolytes can preferentially regulate the ion concentration at the anode interface. The quasi‐solid PCMS gel electrolytes can dissipate the charge accumulation caused by ion concentration differences, which is beneficial for achieving excellent electrochemical stability at high current densities. As a result, the symmetric Zn cells with PCMS gel electrolyte can be cycled for more than 2000 h at a high current density of 40 mA cm−2. Furthermore, the Zn//I2 cell using PCMS gel electrolyte also sustained cycling for over 8000 cycles, and the pouch cell with PCMS gel electrolyte exhibited practical deformable applications in flexible devices. This work highlights an effective gel electrolyte approach for enhancing interfacial stability, potentially advancing the development of highly reversible AZBs.

High Hydrophilic/Zincophilic Interpenetrating Double-Network Hydrogel Electrolyte Constructing Stable Organic–Inorganic Anode Interface toward Nickel–Zinc Batteries

High Hydrophilic/Zincophilic Interpenetrating Double-Network Hydrogel Electrolyte Constructing Stable Organic–Inorganic Anode Interface toward Nickel–Zinc Batteries

Zn2+ flux regulator to modulate the interface chemistry toward highly reversible Zn anode

The persistent challenges of diminished coulombic efficiency (CE) and the formation of Zn dendrites at the Zn anode interface substantially hinder the cycle life of aqueous Zn-ion batteries (AZIBs), thereby impeding their widespread deployment. To address these issues, multifunctional 2-amino-5-guanidino-pentanoic acid (AGPA) additive is introduced into the electrolyte, as a novel Zn2+ flux regulator (ZFR) to improve the reversibility and durability of Zn anodes. The distinctive zincophilicity of amino groups empowers such ZFR with a higher adsorption energy, enabling the construction of a multifunctional molecular adsorption layer on Zn electrode surface. Simultaneously, leveraging the exceptional nucleophilic characteristics of polar carboxyl groups, AGPA molecules tend to form chelating bonds with Zn2+ for manipulating the interface chemistry and solvation chemistry. The functional groups in ZFR work in synergy to attract zinc ions for homogenizing Zn2+ flux and suppress the interfacial side reactions, resulting in uniform dendrite-free Zn deposition. Consequently, the Zn//Zn symmetrical cell achieves an extended cycle life of 5500 h. Moreover, the ZFR enables stable operation of the full batteries with an ultra-long cycling lifespan of 6000 cycles at 5 A/g, showcasing the effectiveness of ZFR in advancing the commercialization of AZIBs.

Regulated solvation structure and solid electrolyte interfaces via imidazolium ionic gel electrolytes with high Li-ion transference number for Li-metal batteries

Solid lithium metal batteries (LMBs) are faced with problems such as the solvation structure of lithium ion and the instability of solid electrolyte interface (SEI), which lead to poor cycling stability and anode interface damage. Here, the introduced 1-ethyl-3-methylimidazolium bis(fluorosulfonyl)imide ([EMIM][FSI]) ionic liquid (IL) interacts strongly with Lithium salt to form a new ionic gel electrolyte (IGE) based on the poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), which facilitates the excellent Li-ion transference number up to 0.506 and improves the mechanical properties. The reconstruction of Li-ion solvation environment by [EMIM][FSI] and PVDF-HFP functional groups, as well as the formation of SEI protective layer rich in LiF and Li3N, make the IGE with excellent electrochemical properties and interfacial stability. As a result, the Li||Li symmetric batteries demonstrate outstanding cycle stability, while the LiFePO4||Li batteries exhibit a superior capacity of 154.04 mAh/g at 0.2 C, maintaining a capacity retention rate as high as 94.5 % even after 200 cycles. The results not only demonstrate a new approach to improve Li-ion transference number in IGEs, but also open a potential avenue to achieve LMBs with high performance.

Achieving Uniform Deposition of Zn with Amide Additives for Metal Anodes Stabilization.

The practical applications of aqueous zinc-ion batteries (AZIBs) are hindered by detrimental effects such as dendrites formation at the Zn metal anode interface and parasitic side reactions induced by H2O. Hence, we propose adding amide additives to the Zn sulfate electrolyte (ZSO) to regulate the composition and properties of the electrolytes, thereby stabilizing the Zn anode interface. Different amide molecules containing formamide (FA), acetamide (AA), or trifluoroacetamide (TFA) are discussed. The polar C═O group shared by amide molecules can interact with Zn2+, forming their solvation shells. The molecules can also facilitate the transport of Zn2+ and increase the conductivity of the electrolytes. Additionally, amide molecules can interact with H2O through hydrogen bonds to limit the erosion of active H2O on the Zn anode. The unique -H, -CH3, and -CF3 groups of the molecules result in different polarities and varying numbers of interaction sites with H2O and Zn2+, leading to some differences in the protective effects of the Zn anode. The stability and lifespan of Zn||Zn batteries assembled with amide electrolytes have significantly improved, especially those with TFA. Moreover, the Zn||NH4V4O10 full cells demonstrate remarkable capacity retention, and the overall performance of the batteries has also been enhanced.

Suppressing the Dark Current Under Forward Bias for Dual‐Mode Organic Photodiodes

AbstractTremendous research efforts are developed to suppress the reverse dark current (Jd) and enhance the responsivity of organic photodiodes (OPDs). The functional layers of traditional OPDs usually follow the principle of energy level alignment to make unobstructed photo‐carriers transport under reverse bias, but this inevitably leads to a large forward Jd. Herein, a universal strategy is proposed to manipulate the carrier dynamics and effectively suppress the forward Jd of OPDs, that is, tuning the energy level and electron traps of the anode interface layers (AILs). The bandgap and electron traps of typical organometallic chelate AIL (PEIE‐Co) can be well controlled by adjusting the component ratio of PEIE and metal ions. The wide bandgap increases the carrier injection barrier under reverse and forward bias, endowing OPD with a much lower Jd; the electron traps induce hole tunneling injection by capturing photo‐generated electrons under forward bias, thereby enabling the photomultiplication effect. The obtained OPD exhibits photoconductive/photomultiplication working mode at reverse/forward bias and the specific detectivity approaches ≈1013/1012 Jones, showing promise for adaptively detecting faint and strong light. This study presents an intelligent strategy to achieve dual‐mode OPDs, paving the way for the multifunctional development of photodetectors.

Research Progress on Solid-state Electrolyte Interface Problems in Lithium-ion Batteries

Nowadays, compared with traditional liquid batteries, solid-state batteries have the superiorities of higher energy density, power density and safety due to their solid electrolytes. However, a series of interfacial problems at solid-solid interface have always hindered the further development of solid-state batteries. Based on these problems, this paper firstly introduces the types of solid-state batteries and interface, secondly describes the mechanical failure principles of cathode interface and anode interface, and finally elaborates the corresponding modification strategies for cathode interface and anode interface. By adopting various improved measures for these interfacial problems, the progress of wider commercialization of solid-state batteries can be facilitated.

Engineering Molecule‐Designed In Situ Polymerization on Al‐Doped Molecular‐Sieve Framework Enables Robust Quasi‐Solid‐State Lithium Batteries

AbstractAchieving fast Li+ transport kinetics and stable electrode/electrolyte interfaces is of paramount importance, yet extremely challenging for the practical success of solid‐state lithium metal batteries, which requires the rational design of the structure and composition of solid‐state electrolytes. Herein, a composite quasi‐solid‐state electrolyte is fabricated through in situ polymerization of a molecule‐designed polymer chain within the functionalized molecular sieve framework (Al‐MCM41). In this design, the robust Brønsted/Lewis acid–base interactions between Al‐MCM41 and TFSI− facilitate the dissociation of lithium salt, leading to a Li+ transference number as high as 0.81. Meanwhile, the well‐ordered mesopores of Al‐MCM41 act as the “reservoir” of the polymer chain, creating continuous ionic migration pathways to offer an excellent Li+ conductivity of 1.09 × 10−3 S cm−1 at 30 °C. Furthermore, the polymer with fluorinated and nitrided functional groups guarantees a dual‐reinforced anode and cathode interface. Such an integrated electrolyte with simultaneous unimpeded Li+ transport and robust interfaces delivers extraordinary capacity retention of 84.6% over 600 cycles at 5 C when coupled with LiFePO4 cathode and remarkable reversible capacity of 129.0 mAh g−1 after 200 cycles with high‐voltage NCM622 cathode. This work provides a significant avenue for enhancing the practical feasibility of solid‐state lithium metal batteries.

The Impact of Lithium Anode Interface on Capacity Fade in Polymer Electrolyte-Based Solid-State Batteries

The Impact of Lithium Anode Interface on Capacity Fade in Polymer Electrolyte-Based Solid-State Batteries

Anodic Dissolution Behavior of DD6 Nickel-Based Single Crystal Superalloy for Electrochemical Machining Applications

Nickel-based single crystal superalloys have been widely used in turbomachinery components. Electrochemical machining (ECM) is an essential method for shaping such high-performance alloys. Understanding the fundamentals of ECM for these alloys is crucial for the design and optimization of the process. This study investigated the anodic dissolution of DD6 nickel-based single crystal superalloy in concentrated NaCl and NaNO3 electrolytes under ECM conditions. Polarization curves showed a passive-transpassive transition behavior in both electrolytes. Galvanostatic experiments demonstrated unique current efficiency characteristics contradicting the empirical ECM knowledge. Surface analysis revealed that the anomalous current efficiency of >100% in the NaNO3 electrolyte results from the falling of γ' phases from anodic surfaces due to the preferential dissolution of the γ matrix phase. The transition from selective to uniform dissolution with increased current density and reduced electrolyte flow velocity leads to decreased current efficiency in NaNO3 electrolyte. The removal of both γ and γ' phases depends entirely on electrochemical dissolution in NaCl electrolyte, ensuring that current efficiency maintains a normal value. A schematical anodic interface model was proposed to describe the dissolution behavior.

Outer Helmholtz plane adsorption regulation to achieve low-concentration of pure propylene carbonate solvent electrolytes compatible with graphite anode

The low melting point and high polarity of propylene carbonate (PC) make it an ideal solvent for electrolytes of lithium-ion batteries (LIBs), but the incompatibility with graphite anode hinders the application. In the present study, a new method is developed to solve this problem from a new viewpoint. Introduction of saturated LiNO3 (0.14 mol L‒1) into pure PC electrolyte containing lithium salt with normal concentration (1.38 mol L‒1) leads to a perfect compatibility with graphite anode. Li/Graphite cell using this pure PC electrolyte shows a reversible capacity of 350.0 mAh g‒1 and a 200-cycle capacity retention of 96.3 %. Further mechanism study and theoretical computation indicate that the NO3‒ anions are adsorbed to outer Helmholtz plane of the electric double layer at the graphite anode interface. This changes the Li+ solvation structure in the electric double layer, facilitating the Li+ desolvation process hence resulting in high compatibility with the graphite anode. The most prominent advantage of the present strategy is that, because of the adsorption of NO3‒ anions to the outer Helmholtz plane, the compatibility with graphite anode could be improved by introduction of tiny amount of Li salt without large change of the bulk phase properties of the electrolyte. This work provides a new understanding of the compatibility from the viewpoint of outer Helmholtz plane, which might deliver new insights for the optimization of electrolytes for LIBs.

Machine learning descriptors for crystal materials: applications in Ni-rich layered cathode and lithium anode materials for high-energy-density lithium batteries

Lithium batteries have revolutionized energy storage with their high energy density and long lifespan, but challenges such as energy density limitations, safety, and cost still need to be addressed. Crystalline materials, including Ni-rich cathodes and lithium anodes, play pivotal roles in the performance of high-energy-density lithium batteries. Understanding the micro-scale behavior and degradation mechanisms of these materials is crucial for improving macro-scale battery performance. Simulation methods, particularly machine learning (ML) techniques, have become indispensable tools in elucidating these intricate processes because of great efficiency and acceptable accuracy. ML methods depend on descriptors, which bridge the gap between crystal structures and input matrices of models. These descriptors encode essential atomic-level details in crystal structures, enabling predictions of material properties and behaviors relevant to lithium batteries. This paper reviews and discusses the diverse array of descriptors employed in the simulation of crystalline materials for lithium batteries with high energy density. Case studies highlight the effectiveness of different descriptors in simulating cathode behaviors such as Li/Ni disordering, screening of stable LiNi0.8Co0.1Mn0.1O2 (NMC811) configurations, and lithium deposition behaviors at the anode interface. The discussed descriptors can also be applied to other crystalline cathode, anode, and electrolyte materials in lithium batteries and advance the development of lithium batteries with superior energy density.

A Clay-Based Quasi-Solid-State electrolyte with high cation selective channels for High-Performance aqueous Zinc-Ion batteries

A clay-based quasi-solid-state electrolyte was prepared using dimethyl sulfoxide (DMSO) intercalated kaolinite as the raw material to suppress the adverse effects of free water molecules on aqueous zinc-ion batteries (AZIBs). Based on the inherent water absorption and retention properties of clay kaolinite, as well as the interlayer modification, this clay-based quasi-solid-state electrolyte not only achieved a low water content but also exhibited a strong water binding effect, which restricted the HER and side reactions involving water participation. Furthermore, the intercalation of DMSO increased the number of negative charges on the surface of kaolinite, resulting in the formation of a continuous spatial electrostatic field area around the kaolinite particles, which played a role in cation selectivity. The ionic transference number of the quasi-solid-state electrolyte reached 0.91. Additionally, the intercalation of DMSO broadened the interlayer ionic transport channels of kaolinite, further enhancing the transport efficiency of Zn2+ in the quasi-solid-state electrolyte, achieving uniform deposition of Zn2+ on the surface of the Zn anode, and suppressing dendrite growth to maintain a stable quasi-solid-state electrolyte/Zn anode interface. Zn||MnO2 battery assembled with this electrolyte demonstrated a discharge specific capacity of 301 mAh/g at a current density of 60 mA g−1. The Zn||MnO2 battery could be stably cycled for 1000 cycles at a current density of 150 mA g−1, and after 1000 cycles, the battery still maintained a discharge specific capacity of 248.2 mAh/g with a capacity retention rate of 84.8 %, showing excellent capacity performance and cycle stability. The Zn||MnO2 pouch battery could still provide stable power under heavy pressure, bending, and continuous tapping and had the potential for use in flexible batteries.

Sieving-type Electric Double Layer with Hydrogen Bond Interlocking to Stable Zinc Metal Anode.

The stability of aqueous zinc metal batteries is significantly affected by side reactions and dendrite growth on the anode interface, which primarily originate from water and anions. Herein, we introduce a multi H-bond site additive, 2, 2'-Sulfonyldiethanol (SDE), into an aqueous electrolyte to construct a sieving-type electric double layer (EDL) by hydrogen bond interlock in order to address these issues. On the one hand, SDE replaces H2O and SO4 2- anions that are adsorbed on the zinc anode surface, expelling H2O/SO4 2- from the EDL and thereby reducing the content of H2O/SO4 2- at the interface. On the other hand, when Zn2+ are de-solvated at the interface during the plating, the strong hydrogen bond interaction between SDE and H2O/SO4 2- can trap H2O/SO4 2- from the EDL, further decreasing their content at the interface. This effectively sieves them out of the zinc anode interface and inhibits the side reactions. Moreover, the unique characteristics of trapped SO4 2- anions can restrict their diffusion, thereby enhancing the transference number of Zn2+ and promoting dendrite-free deposition and growth of Zn. Consequently, utilizing an SDE/ZnSO4 electrolyte enables excellent cycling stability in Zn//Zn symmetrical cells and Zn//MnO2 full cells with lifespans exceeding 3500 h and 2500 cycles respectively.

Sieving‐type Electric Double Layer with Hydrogen Bond Interlocking to Stable Zinc Metal Anode

AbstractThe stability of aqueous zinc metal batteries is significantly affected by side reactions and dendrite growth on the anode interface, which primarily originate from water and anions. Herein, we introduce a multi H‐bond site additive, 2, 2′‐Sulfonyldiethanol (SDE), into an aqueous electrolyte to construct a sieving‐type electric double layer (EDL) by hydrogen bond interlock in order to address these issues. On the one hand, SDE replaces H2O and SO42− anions that are adsorbed on the zinc anode surface, expelling H2O/SO42− from the EDL and thereby reducing the content of H2O/SO42− at the interface. On the other hand, when Zn2+ are de‐solvated at the interface during the plating, the strong hydrogen bond interaction between SDE and H2O/SO42− can trap H2O/SO42− from the EDL, further decreasing their content at the interface. This effectively sieves them out of the zinc anode interface and inhibits the side reactions. Moreover, the unique characteristics of trapped SO42− anions can restrict their diffusion, thereby enhancing the transference number of Zn2+ and promoting dendrite‐free deposition and growth of Zn. Consequently, utilizing an SDE/ZnSO4 electrolyte enables excellent cycling stability in Zn//Zn symmetrical cells and Zn//MnO2 full cells with lifespans exceeding 3500 h and 2500 cycles respectively.

Achieving High Doping Density in pH-neutral Conjugated Polyelectrolyte Toward Effective Hole-Transporting Materials for Organic Solar Cells.

The lack of effective and non-corrosive hole-transporting layer (HTL) materials has remained a long-standing issue that severely restricts the performance of organic solar cells (OSCs). Most pH-neutral conjugated polyelectrolytes (CPEs) exhibit inferior performance to the acid-doped HTL materials due to their low doping density. In this study, a series of pH-neutral CPEs is designed and synthesized with high doping density as HTL materials. Through an elaborate synthetic route, two sulfonate-terminating alkoxyl side chains can be introduced into thiophene, by which the electron-rich, highly soluble, and chemically stable thiophene monomer is synthesized to enable the subsequent polymerization. The CPE PTT-F exhibit a remarkable self-doping property with an enhanced doping density from 2.01 × 1017 to 7.02 × 1018 cm-3. The high work function and the increased doping density of PTT-F-based HTL decrease the depletion region width from 38.4 to 8.1nm at the anode interface, which minimized the energy loss in hole transport. Consequently, a binary OSC modified by PTT-F-based HTL achieve a high PCE of 18.8%. To the best of the knowledge, this is the highest PCE for OSC employing CPE-based HTL. The results from this work demonstrate an encouraging achievement of realizing exceptional hole collection ability in pH-neutral CPEs.

Boosting Li-Ion Conductivity of Fluoride Solid Electrolyte by Low-Temperature Molten Salt Ablation and Particle Boundary Doping.

Halide solid electrolytes (SEs) are attracting great attention, owing to their high ionic conductivity and excellent high-voltage compatibility. However, severe moisture sensitivity, poor thermal stability, and instability at the lithium metal anode interface with chloride and bromide SEs retard their applications in solid-state lithium metal batteries. Fluoride SEs are expected to solve these problems, but they are now plagued by inadequate room-temperature (RT) ionic conductivity. Herein, a low-temperature molten salt (LiCl+1.33AlCl3) ablation method is proposed to enhance the ionic conductivity of monoclinic Li3GaF6 by particle boundary doping. The RT ionic conductivity of Li3GaF6 is correspondingly increased by 2 orders of magnitude, and the conductivity reaches 10-4 S cm-1 at 60 °C. The improved ionic conductivity benefits from the enhancement of interfacial ion transport, with the formation of more conductive chlorine-doped Li3GaF6-xClx and in situ binder LiAlCl4 to cement surrounding nanoparticles. The as-synthesized Li3GaF6 demonstrates outstanding humidity tolerance without conductivity degradation after exposure to a relative humidity of up to 35%. It also exhibits the widest electrochemical stability window experimentally (close to 6 V) compared with other state-of-the-art SEs. The solid-state Li/Li3GaF6/LiFePO4 cell with a stable Li+-conductive polymer interface is successfully driven for at least 200 cycles at 0.5C. Our study provides a solution to various chemical and electrochemical stability issues encountered by the halide SE family.

Self-forming Na3P/Na2O interphase on a novel biphasic Na3Zr2Si2PO12/Na3PO4 solid electrolyte for long-cycling solid-state Na-metal batteries

A novel biphasic Na3Zr2Si2PO12/Na3PO4 solid electrolyte is proposed to effectively address critical anode interface challenges for solid-state Na-metal batteries (SSSMBs). The Na3PO4 phase, at an optimal composition of ∼20 mol%, transforms the interface chemistry throughout the NZSP electrolyte, which results in dense electrolytes with high Young's modulus, rapid ion transport (6.2 × 10−4 S cm-1) at low activation barrier (0.19 eV), negligible electronic conductivity, and excellent sodiophilicity. The AIMD/DFT calculations and XPS analysis reveal a self-formed, (electro)chemically stable mixed Na+/electron-conducting interphase, comprising Na3P and Na2O, at the Na anode interface. The interphase not only homogenizes the Na+ flux distribution and accelerates the interfacial charge transport, but prevents continuous interfacial reactions, thereby stabilizing the anode interface against dendrite formation. Benefiting from the low-impedance, dendrite-free anode interface, Na symmetric cells demonstrate a low interface resistance of 12.7 Ω cm2 and exceptional cyclability of 3000 h. Additionally, full cells with Na3V2(PO4)3 cathodes achieve 93 % capacity retention after 550 cycles at 0.5 C. This research comprehensively elucidates and leverages the critical advantages of Na3PO4 in enhancing the bulk and interface properties of Na3Zr2Si2PO12 solid electrolytes. The design strategy of biphasic solid electrolytes presented here offers new insights into the developing high-performance solid electrolytes for advanced SSSMBs.

Dual-Seed Strategy for High-Performance Anode-Less All-Solid-State Batteries.

Interest in all-solid-state batteries (ASSBs), particularly the anode-less type, has grown alongside the expansion of the electric vehicle (EV) market, because they offer advantages in terms of their energy density and manufacturing cost. However, in most anode-less ASSBs, the anode is covered by a protective layer to ensure stable lithium (Li) deposition, thus requiring high temperatures to ensure adequate Li ion diffusion kinetics through the protective layer. This study proposes a dual-seed protective layer consisting of silver (Ag) and zinc oxide (ZnO) nanoparticles for sulfide-based anode-less ASSBs. This dual-seed-based protective layer not only facilitates Li diffusion via multiple lithiation pathways over a wide range of potentials, but also enhances the mechanical stability of the anode interface through the in situ formation of a Ag-Zn alloy with high ductility. The capacity retention during full-cell evaluation is 80.8% for 100 cycles when cycled at 1mA cm-2 with 3 mAh cm-2 at room temperature. The dual-seed approach provides useful insights into the design of multi-seed concepts in which, from a mechanochemical perspective, various lithiophilic materials synergistically impact upon the anode-less interface.

The Effect of Bi Addition on the Electromigration Properties of Sn-3.0Ag-0.5Cu Lead-Free Solder

As electronic packaging technology advances towards miniaturization and integration, the issue of electromigration (EM) in lead-free solder joints has become a significant factor affecting solder joint reliability. In this study, a Sn-3.0Ag-0.5Cu (SAC305) alloy was used as the base, and different Bi content alloys, SAC305-xBi (x = 0, 0.5, 0.75, 1.0 wt.%), were prepared for tensile strength, hardness, and wetting tests. Copper wire was used to prepare EM test samples, which were subjected to EM tests at a current density of approximately 0.6 × 104 A/cm2 for varying durations. The interface microstructure of the SAC305-xBi alloys after the EM test was observed using an optical microscope. The results showed that the 0.5 wt.% Bi alloy exhibited the highest ultimate tensile strength and microhardness, improving by 33.3% and 11.8% compared to SAC305, respectively, with similar fracture strain. This alloy also displayed enhanced wettability. EM tests revealed the formation of Cu6Sn5 and Cu3Sn intermetallic compounds (IMCs) at both the cathode and anode interfaces of the solder alloy. The addition of Bi inhibited the diffusion rate of Sn in Cu6Sn5, resulting in similar total IMC thickness at the anode interface across different Bi contents under the same test conditions. However, the total IMC thickness at the cathode interface decreased and stabilized with increasing EM time, with the SAC305-0.75Bi alloy demonstrating the best resistance to EM.