Formation Of Solid Layer Research Articles

In Situ Formation of Stable Dual-Layer Solid Electrolyte Interphase for Enhanced Stability and Cycle Life in All-Solid-State Lithium Metal Batteries.

All-solid-state lithium metal batteries have emerged as a promising solution to overcoming the energy density and safety challenges associated with conventional lithium-ion batteries. Solid polymer electrolytes, particularly those based on poly(vinylidene fluoride) (PVDF) and dimethylformamide (DMF), demonstrate significant potential. However, interfacial side reactions between residual DMF solvents and lithium metal present substantial challenges. In this study, we investigate the in situ formation of solid electrolyte interphase protective layers to mitigate these side reactions. By incorporating F-rich additives, such as fluoroethylene carbonate and lithium difluorophosphate, we successfully establish a dual-layer inorganic SEI structure characterized by an outer LiF layer and an inner Li2O layer. Consequently, our approach extends the cycle life of lithium symmetric batteries to 3000 h. Additionally, the Li||LiFePO4 solid-state battery demonstrates exceptional stability, enduring 400 cycles at a 1C rate with an impressive capacity retention of 84%. This strategic methodology effectively leverages the benefits of residual solvents, ensuring both enhanced battery efficiency and long-term operational stability for PVDF-based all-solid-state lithium metal batteries.

Organic montmorillonite modified polyethylene oxide based polymer electrolyte for dendrite-free flexible solid-state lithium metal batteries

Polyethylene oxide (PEO) based solid-state electrolytes are known for the low manufacturing cost and excellent processability, but their practical application is paved with thorns including the inferior ionic conductivity, low Li+ transfer number and insufficient Li dendrite blocking ability. Herein, we propose organic montmorillonite (OMMT) with expanded layer spacing (1.97 nm) as versatile fillers to construct PEO-OMMT electrolyte, in which OMMT not only increases Li+ transfer number (0.56) and ionic conductivity (7.15 × 10−4 S cm−1), providing fast ionic transport channels, but also endows PEO with high mechanical strength, resulting remarkable Li dendrite blocking ability (>2100 h). Additionally, the high dielectric constant and Lewis-rich polar sites of OMMT facilitate the dissociation of lithium salts and the rapid formation of LiF and Li3N-rich solid electrolyte interface layers. Impressively, the LiFePO4|PEO-OMMT|Li cell shows a high initial capacity (154.4 mAh g−1 at 0.5C) with ultralong cycling lifespan (>1200 cycles). Similarly, the LiNi0.83Mn0.05Co0.12O2|PEO-OMMT|Li cell retains a high discharge capacity of 151.5 mAh g−1 after 100 cycles at 0.2C. This work highlights the indelible contributions of OMMT functionalized fillers in improving the interfacial stability of PEO based solid-state electrolytes, paving a feasible avenue for the practical application of solid-state lithium metal batteries.

Open-atmosphere laser nitriding of austenitic steels to form wear-resistant surfaces

This study presents an interesting result based on the laser beam irradiation of austenitic steels in an open atmosphere, which enables the formation of a surface layer comprising a nitrogen solid solution rather than an oxide. First, a focused nanosecond pulsed Nd:YAG laser beam with a laser energy of 400 mJ·pulse−1 was used to irradiate an AISI 316 stainless steel. This formed a surface layer of ~3 μm thickness with ~12 at.% nitrogen solid solution, thereby enhancing the hardness of the AISI 316 stainless steel surface to ~380 HV, nearly twice that of the untreated surface. Consequently, wear resistance was improved by preventing plastic deformation and abrasive wear. Thereafter, similar laser beam irradiation of Inver42® and Kovar® steels resulted in the formation of nitrogen solid solution layers with a thickness of ~1.5 μm, which is lower than that of AISI 316 steel. Furthermore, their nitrogen contents were reduced to ~6 at.%. Consequently, the improvement in the surface hardness of the Inver42® and Kovar® steels was less than that of the AISI 316 stainless steel. These differences were attributed to their alloy compositions; for instance, Cr, which has a high affinity for nitrogen, might trap the available nitrogen, thereby contributing to an increase in the nitrogen content.

A tailorable and stable lithium-oxygen battery with close to theoretical charge-discharge overpotential

Rechargeable lithium-Oxygen batteries (LOBs) are attractive alternatives to lithium ion batteries due to their high theoretical energy density. However, a large charge-discharge overpotential is usually accompanied, which reduces the energy efficiency and the cycling life. Redox mediators can be introduced in LOBs to reduce the overpotential by effectively decomposing the discharged product, lithium peroxide. Here, we propose 10-ethylphenoxazine as an active additive in the electrolyte to reduce the overpotential to 0.3 V and increase the energy efficiency to 90.4%. The 10-ethylphenoxazine is believed to favor the formation of stable solid electrolyte interface layer on the lithium anode, which benefits the even accumulation of the Li+ on the anode surface to prevent the formation of dendrite and improve the stability of Li foil against the attack of soluble species in the electrolyte. In addition, by utilizing a self-supporting graphene aerogel as the cathode, the LOB can be tailored to different sizes and shapes. The tailorable LOB features the low charging-discharging overpotential of 0.3 V and can be stably cycled for 93 times. With its excellent tailorability and stable electrochemical performance, the current LOB holds a promising future to power portable electronic devices with individualized sizes and shapes.

In-Built Fabrication of MOF Assimilated Porous Hollow Carbon from Pre-Hydrolysate for Supercapacitor.

With the fast consumption of traditional fossil fuels and the urgent requirement for a low-carbon economy and sustainable development, supercapacitors are gaining more and more attention as a clean energy storage and conversion device. The research on electrode materials for supercapacitors has become a hot topic nowadays. An electrode material for a supercapacitor, comprising the ZIF-67 in-built carbon-based material, was prepared from a biomass pre-hydrolysate via a hydrothermal process. As a by-product of dissolving slurry, the pre-hydrolysate is rich in carbon, which is an excellent biomass resource. The utilization of pre-hydrolysate to prepare carbon energy materials could realize the high value utilization of pre-hydrolysate and the efficient energy conversion of biomass. Meanwhile, the cobalt-based MOF (such as ZIF-67), as a porous crystalline material, has the advantages of having a regular order, high specific surface area and controllable pore size, as well as good thermal and chemical stability. The addition of ZIF-67 modified the morphology and pore structure of the carbon, and the obtained samples showed outstanding electrochemical performance. One- and two-step synthetic processes generated specimens with a coral-like cross-linked structure and a new type of rough, hollow, dandelion-like structure, respectively, and the pore size was in the range of 2.0–5.0 nm, which is conducive to ion transport and charge transfer. In C2-ZIF-67, the hollow structures could effectively prevent the accumulation of the electrochemical active center, which could provide enough space for the shrinkage and expansion of particles to protect them from the interference of electrolytes and the formation of solid electrolyte interphase film layers. Additionally, the plush tentacle structure with low density and a large specific surface area could expose more active sites and a large electrolyte electrode contact area, and short electron and charge transport paths. Importantly, active, free electrons of small amounts of Co-MOF (1 wt%) could be stored and released through the redox reaction, further improving the electrical conductivity of Carbon-ZIF-67 materials in this work. Consequently, C2-ZIF-67 exhibited superior specific capacitance (400 F g−1, at 0.5 A g−1) and stability (90%, after 10,000 cycles).

Conductive metal organic framework mediated Sb nanoparticles as high-capacity anodes for rechargeable potassium-ion batteries

The natural abundance of K in the earth crust and ocean and its low redox potential make potassium-ion batteries (PIBs) a feasible substitute for lithium-ion batteries. However, PIB anodes are still limited by slow reaction kinetics due to a large K-ion radius. Herein, for the first time, Sb@Ni3(HHTP)2 (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) composites are utilised as high-capacity anodes for rechargeable PIBs. In the composites, Sb nanoparticles are homogenously enveloped by a conductive metal–organic-framework (MOF), namely, Ni3(HHTP)2. The empirical results demonstrate that the composites undergo a consecutive reversible phase transformation from Sb to KSb2, KSb, K5Sb4, and K3Sb at different potentials during the potassiation–depotassiation phenomenon. An optimised Sb@Ni3(HHTP)2–10 electrode delivers high reversible capacities of 590 and 431 mAh g−1 at specific currents of 100 and 1000 mA g−1 after 100 and 300 cycles, respectively. The full cell, which is composed of the Sb@Ni3(HHTP)2 anode and a potassium ferrous ferricyanide cathode, provides a reversible capacity of 514 mAh g−1 at a specific current of 500 mA g−1. The excellent capacity performances of the Sb@Ni3(HHTP)2 anode prove that it is among the best PIB anodes reported until now. The exceptional performance of Sb@Ni3(HHTP)2 is attributed to the efficient coating of Sb nanoparticles by the conductive Ni3(HHTP)2 MOF as well as the formation of a strong KF-rich solid electrolyte interphase layer on the Sb@Ni3(HHTP)2 electrode in a concentrated electrolyte of 3 M potassium bis(fluorosulfonyl)imide in ethylene carbonate/diethyl carbonate.

Stability of intermediate states in the surface lithiation process of silicene

We have studied using density functional theory the Li-silicene system, mainly in the saturated region (0.11>X(Li)<1.0) which is critical to understand the solid electrolyte interface layer (SEI) formation. The electronic and vibrational properties of the intermediate states of lithiated silicene were calculated. Two models were used for the Li atoms on the silicene surface: Li on top of Si (perpendicular) and Li on top of the hexagon center (centered). The centered configurations have lower Eb values up to X(Li) = 0.33. However, the vibrational properties showed instabilities for lithium in the hexagon center. An intermediate state at X(Li) = 0.38 was found to be dynamically stable. A metallic to semiconductor transition is observed at X(Li) = 0.33, and X(Li) = 0.46. Few ordered vacancies or vacancies in the dilute region exhibit vibrational stability and gap opening. Elastic stiffness tensor for different concentrations of Li in the silicene-Li system were calculated, a critical concentration of X(Li)=0.333 was determined for the change of the mechanical properties behavior. silicel has a slightly higher 2D Young‘s moduli than silicene. However, vacancies in silicel produce a substantial decrement in mechanical properties.

Effects of soluble products decomposed from chelato-borate additives on formation of solid electrolyte interface layers

The prevailing account attributes the positive effects of boron-based additives on solid electrolyte interface (SEI) layers to its solid products by prior decomposition. However, this study proves the BOF2− anion, a soluble product of film formation additive of lithium difluoro(oxalato)borate, plays a crucial role in improving the SEI layer. Specifically, BOF2− suppresses the excessive decomposition of salt anions by aggregating on the electrode surface. Meanwhile, it catalyzes the reduction of ethylene carbonate, leading to improving the stability of the interface. In the end, ultrasound shaking is used to generate more BOF2− anion and increase the cycle performance of cells at a high rate as excepted. This work helps to understand the effects of soluble products on the SEI forming process and provides new insights for improving the stability of electrode electrolyte interfaces.

Investigation of the Anode‐Electrolyte Interface in a Magnesium Full‐Cell with Fluorinated Alkoxyborate‐Based Electrolyte

AbstractMagnesium (Mg) anode‐electrolyte interaction is not trivial and investigation of the interfacial process can be helpful for the development of Mg batteries. In this work, we studied the Mg metal anode cycled in a chloride (Cl)‐free magnesium tetrakis (hexafluoroisopropyloxy) borate electrolyte using a full‐cell configuration with TiS2 model cathode. Electrochemical measurements and structural analysis of the cathode showed reversible de‐/magnesiation of TiS2 with some entrapment of irreversibly bound Mg2+. Electrochemical impedance spectroscopy (EIS) was applied to analyze the Mg‐electrolyte interaction in a three‐electrode system. The results showed a rapid increase in charge transfer resistance on the anode side with increasing resting time. In contrast, we observed a significant drop in the charge transfer impedance upon cycling along with the appearance of an additional semi‐circle, which suggested to the development of a solid interphase. X‐ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) corroborated the EIS results and confirmed the solid interphase layer formation, in which MgF2 was identified as the primary species contributing to its formation. The current study provides fundamental insights into the interfacial phenomena between the metallic Mg anode and Cl‐free electrolyte by highlighting the role played by the formed interphase on the reversible Mg stripping and plating in a Mg full‐cell.

Lithiophilic Mo3N2/MoN as multifunctional interlayer for dendrite-free and ultra-stable lithium metal batteries

The formation of lithium dendrite and the unstable electrode/electrolyte interface, especially at high rates, are the dominant obstacles impeding the implementation of lithium metal batteries (LMBs). To tackle these fundamental challenges, here we propose a lithiophilic Mo3N2/MoN heterostructure (designated as MoNx) interlayer for dendrite-free and ultra-stable lithium metal anodes for the first time. The MoNx interlayer presents excellent electrolyte wettability, fast lithium diffusion kinetics and strong mechanical strength, which function synergistically to inhibit lithium dendrite growth. During cycling, an in-situ formation of Li3N-rich solid electrolyte interphase layer and metallic Mo phase can regulate the Li-ion conductivity and Li metal deposition, thus indicating uniform and compact Li plating. Above ameliorating features accompany an ultra-long-life of 2000 h at a high current density of 5 mA cm−2 for the MoNx-Li anode. The feasibility of the MoNx-Li anode in LMB is further confirmed in conjunction with LiFePO4 cathodes. The full cells deliver exceptionally high-capacity retentions of above 82.0% after 500 cycles at 1C and 425 cycles at 3C, which are among the best thus far reported for LMBs. This work provides both new insights towards functional interlayer design and effective transition-metal nitrides for practical LMBs.

Properties and Kinetics of Selective Zinc Leaching with Choline Chloride and Urea

A choline chloride-urea (ChCl-urea) deep eutectic solvent (DES) was used to experimentally investigate the secondary recovery of zinc from zinc-bearing dust sludge via a leaching process. The effects of varying the liquid–solid ratio, leaching temperature, stirring speed, and leaching time on the zinc leaching efficiency were determined, and the optimum values of these parameters were found to be 15:1, 90 °C, 400 rpm, and 600 min, respectively, at which a leaching efficiency of 86.87% was achieved. XRF and EDS analyses confirmed that the zinc content in the sludge decreased noticeably after leaching, while those of other elements did not, indicating the selective and efficient leaching of zinc. A study of the leaching kinetics showed that the reaction conforms to the nuclear shrinkage model without solid product layer formation, and the calculated apparent activation energy is 22.16 kJ/mol.

Challenges of Formation of Thin-Film Solid Electrolyte Layers on Non-Conductive Substrates by Electrophoretic Deposition

In this work, the challenges associated with the formation of single and bilayer coatings based on Ce0.8Sm0.2O1.9 (SDC) and CuO modified BaCe0.5Zr0.3Y0.1Yb0.1O3−δ (BCZYYbO-CuO) solid state electrolytes on porous non-conducting NiO-SDC anode substrates by the method of electrophoretic deposition (EPD) are considered. Various approaches that had been selected after analysis of the literature data in order to carry out the EPD, are tested: direct deposition on a porous non-conductive anode substrate and multiple options for creating the conductivity of the anode substrate under EPD conditions such as the reduction of the NiO-SDC substrate and the creation of a surface conducting sublayer via synthesizing a polypyrrole (PPy) film. New effective method was proposed based on the deposition of a platinum layer on the front side of the substrate. It was ascertained that, during the direct EPD on the porous NiO-SDC substrate, the formation of a continuous coating did not occur, which may be due to insufficient porosity of the substrate used. It was shown that the use of reduced substrates leads to cracking and, in some cases, to the destruction of the entire SDC/NiO-SDC structure. The dependence of the electrolyte film sinterability on the substrate shrinkage was studied. In contrast to the literature data, the use of the substrates with a reduced pre-sintering temperature had no pronounced effect on the densification of the SDC electrolyte film. It was revealed that complete sintering of the SDC electrolyte layer with the formation of a developed grain structure is possible at a temperature of 1550 °C.

Electrocatalytic-driven compensation for sodium ion pouch cell with high energy density and long lifespan

The content of cyclable sodium ions in the sodium ion pouch cell can determine the energy density and cycling lifespan directly and efficiently by alleviating the sodium ion loss in the initial formation process and following cycling period. The method of electrocatalytic-driven compensation sodium ions was explored, and the cell fabrication process was proposed as well. High sodium content (88%) sodium oxide (Na2O) can provide sufficient cyclable sodium ions electrocatalytic-driven by high active Ruthenium@graphene (Ru@G) electrocatalyst to compensate the sodium loss during the initial solid electrolyte layer formation and following consumption. This electrocatalytic-driven compensation can provide numerous cyclable sodium, but also be no adverse effects on the stability of electrode materials, electrolyte, and the whole battery. Meanwhile, the industrial feasibility of this cell fabrication process can accelerate the practical application. Based on this technology, the initial coulombic efficiency of pouch cell can reach up to 90%, while the 295 Wh Kg−1 materials energy density is much superior and promising for future energy storage system application.

Simple Designed Micro-Nano Si-Graphite Hybrids for Lithium Storage.

Up to now, the silicon-graphite anode materials with commercial prospect for lithium batteries (LIBs) still face three dilemmas of the huge volume effect, the poor interface compatibility, and the high resistance. To address the above challenges, micro-nano structured composites of graphite coating by ZnO-incorporated and carbon-coated silicon (marked as Gr@ZnO-Si-C) are reasonably synthesized via an efficient and convenient method of liquid phase self-assembly synthesis combined with annealing treatment. The designed composites of Gr@ZnO-Si-C deliver excellent lithium battery performance with good rate performance and stable long-cycling life of 1000cycles with reversible capacities of 1150 and 780 mAh g-1 tested at 600 and 1200mA g-1 , respectively. The obtained results reveal that the incorporated ZnO effectively improve the interface compatibility between electrolyte and active materials, and boost the formation of compact and stable surface solid electrolyte interphase layer for electrodes. Furthermore, the pyrolytic carbon layer formed from polyacrylamide can directly improve electrical conductivity, decrease polarization, and thus promote their electrochemical performance. Finally, based on the scalable preparation of Gr@ZnO-Si-C composites, the pouch full cells of Gr@ZnO-Si-C||NCM523 are assembled and used to evaluate the commercial prospects of Si-graphite composites, offering highly useful information for researchers working in the battery industry.

Intercalation of graphene formed on silicon carbide with iron, cobalt and silicon atoms

Intercalation of graphene formed on silicon carbide surface with iron, cobalt and silicon has been used to form the graphene/silicides/SiC interfaces. The experiments were carried out in situ in ultrahigh vacuum conditions. The elemental composition and chemical state of the sample surfaces, as well as their atomic structure, were controlled by high-energy-resolution photoelectron spectroscopy and low-energy electron diffraction. The nominal thicknesses of the deposited iron, cobalt and silicon layers varied in the range of 2-20 Å, and the temperature of the sample annealing was changed from room temperature to 600°C. It is shown, that the intercalation of graphene/Fe/SiC with Si leads to the formation of Fe-Si solid solution layer covered with surface silicide Fe3Si, while intercalation of graphene/Co/SiC with Si results in the formation of a Co-Si solid solution and CoSi silicide covered with Co3Si surface phase. The obtained silicide layers are reliably protected by graphene, making it compatible for nanoscale applications at ambient conditions.

Optimal Fast Charging Method for a Large-Format Lithium-Ion Battery Based on Nonlinear Model Predictive Control and Reduced Order Electrochemical Model

Design of an appropriate charging protocol is a challenging issue. Recent emerging charging methods have employed electrochemical models to determine charging protocols. However, these protocols are not otimized considering reduction of charging time and minimization of reaction rates of solid electrolyte phase layer (SEI) formation and lithium plating simultaneously. In this paper, we proposed an optimal fast charging method that simultaneously considers the charging time and the two aging effects in addition to lithium stripping. The optimization is performed using nonlinear model predictive control, where variables in the objective function are the charging time and ion loss caused by SEI layer and constraints are cutoff voltage and lithium ion concentrations. In addition, the charging protocol consists of not only constant currents, but also pulse discharging currents that can recover ions from the lithium metal by lithium stripping, which can further reduce the charging time by allowing increased currents. The designed charging method is verified using Battery-In-The-Loop system and compared with CC/CV charging protocols under a constant temperature. Experimental results have shown significant minimization of capacity fade and the associated extension of cycle life, and effective suppression of the lithium plating.

Si and Ge-Based Anode Materials for Li-, Na-, and K-Ion Batteries: A Perspective from Structure to Electrochemical Mechanism.

Silicon and germanium are among the most promising candidates as anodes for Li-ion batteries, meanwhile their potential application in sodium- and potassium-ion batteries is emerging. The access of their entire potential requires a comprehensive understanding of their electrochemical mechanism. This Review highlights the processes taking place during the alloying reaction of Si and Ge with the alkali ions. Several associated challenges, including the volumetric expansion, particle pulverization, and uncontrolled formation of solid electrolyte interphase layer must be surmounted and different strategies, such as nanostructures and electrode formulation, have been implemented. Additionally, a new approach based on the use of layered Si and Ge-based Zintl phases is presented. The versatility of this new family permits the tuning of their physical and chemical properties for specific applications. For batteries in particular, the layered structure buffers the volume expansion and exhibits an enhanced electronic conductivity, allowing high power applications.

Mechanism of lithium electrodeposition in a magnetic field

Lithium metal anode is a promising anode for next-generation lithium-based batteries. However, the lithium dendrite growth due to uneven Li-ion deposition could cause safety problem, and the unceasing formation of solid electrolyte interphase layer leads to capacity fading of anode. Here, we report a mechanism of Li electrodeposition under a magnetic field with the direction perpendicular or parallel to electric field in the cell systematically. We for the first time observe that at the initial nuclei stage the deposited Li metal is needlelike; for the later growth stage, a very compact deposits with dendrite-free structure can be obtained. Compared with perpendicular magnetic field, the parallel one can facilitate more uniform and dense lithium growth. The Lorentz force and the electric field force during Li platting are calculated and compared. It also indicates that the magnetic field can contribute to a smooth Li deposits after cycling at various current densities and deposited capacities. The polarization of the Li symmetrical cells is reduced in the magnetic field resulting in more stable cycling performance. In addition, improved electrochemical performance of the Li|LiCoO2 half cells can be achieved by applying a magnetic field. The study demonstrates that the electromagnetic environment is critical to stabilizing Li-metal anode in high-energy-rechargeable batteries.

Hollow Boron-Doped Si/SiOx Nanospheres Embedded in the Vanadium Nitride/Nanopore-Assisted Carbon Conductive Network for Superior Lithium Storage.

SiOx-based anode materials with high capacity and outstanding cycling performance have gained numerous attentions. Nevertheless, the poor electrical conductivity and non-negligible volume change hinder their further application in Li-ion batteries. Herein, we propose a new strategy to construct a hollow nanosphere with boron-doped Si/SiOx decorated with vanadium nitride (VN) nanoparticles and embedded in a nitrogen-doped, porous, and partial graphitization carbon layer (B-Si/SiOx@VN/PC). Benefiting from such structural and compositional features, the B-Si/SiOx@VN/PC electrode exhibits a stable cycling capacity of 1237.1 mA h g-1 at a current density of 0.5 A g-1 with an appealing capacity retention of 87.0% after 300 cycles. Additionally, it delivers high-rate capabilities of 1139.4, 940.7, and 653.4 mA h g-1 at current densities of 2, 5, and 10 A g-1, respectively, and ranks among the best SiOx-based anode materials. The outstanding electrochemical performance can be ascribed to the following reasons: (1) its hollow structure makes the Li+ transportation length decreased. (2) The existing nanopores facilitate the Li+ insertion/desertion and accommodate the volume variation. (3) The nitrogen-doped partial graphitization carbon enhances the electrical conductivity and promotes the formation of stable solid electrolyte interface layers during the repetitive Li+ intercalation/extraction process.

Inhibition of Hydrogen Entry into Pure Iron By Formation of Nitrogen Solid Solution Layer in the Surface

Hydrogen embrittlement is a serious problem for steels such as high strength steels. In order to prevent hydrogen embrittlement, the inhibition of hydrogen entry into the steel matrix is one of important subjects. The formation of surface layers with low hydrogen diffusivity is thought to be effective in inhibiting the hydrogen entry into the steel matrix. In this study, we formed nitrogen solid solution layers containing iron-nitrogen martensite and retained austenite phases on the surface of pure iron specimens by plasma-nitriding and subsequent quenching, and investigated the hydrogen permeation behavior. Pure iron sheets of 1 mm in thickness were used as the specimens. Prior to the nitriding treatment, the specimen surfaces were polished using a diamond past down to 1 μm. The plasma nitriding treatments were carried out in a nitrogen-hydrogen atmosphere at 370 Pa for 600 s. The temperature of the specimen surface was kept at 873 K by controlling the supplied DC voltage. After the plasma nitriding, the specimens were quenched from 1073 or 1273 K for 180 s. In the case of the quenching from 1273 K, an iron-nitrogen martensite phase was formed in the surface. The thickness of the surface layer was over 100 µm. Iron-nitrogen martensite and retained austenite phases were formed in the surface of the specimen quenched from 1073 K. The thickness was ca. 50 µm. To investigate the effect of the nitrogen solid solution layers on the hydrogen permeation behavior through the specimens, a hydrogen permeation test using a conventional Devanathan-Stachurski cell was carried out for 3.6 ks. The nitrided surface was arranged in the hydrogen entry side. Pd of 200 nm in thickness was deposited on the specimen in the hydrogen detection side. The hydrogen detection side was polarized at 0.2 V vs. SHE in 0.1 M NaOH fully deaerated by pure Ar gas. The specimen in the hydrogen entry side was polarized at −0.8 V vs. SHE in 0.1 M H2SO4. The hydrogen permeation tests reveal that the permeation current of the specimen quenched from 1273 K was smaller than that of as-polished one. The surface martensite phase seems to suppress the hydrogen permeation. In addition, no permeation current of the specimen quenched at 1073 K was detected. This is because the hydrogen diffusivity in the austenite phase is much lower than the ferrite phase due to high solubility limit in the austenite phase. The surface layer containing the austenite phase is found to be effective in inhibiting the hydrogen entry into the matrix.