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In all-solid-state batteries (ASSB), increasing the thickness of electrodes is essential for increasing the energy density. However, this limits the C-rate performance, particularly for electrodes with a large volume fraction of active materials (AMs), transport of ions in the electrode is hindered, leading to poor utilization of AMs in ASSBs. To accelerate the development of ASSBs, it is highly desirable to develop analytical methods for understanding the utilization of AMs in thick electrodes. In this paper, we propose a novel impedance analysis method using the transmission line model (TLM) for estimating the utilization of AMs in an electrode in terms of effective electrode thickness. In the TLM model, electrode thickness is treated as a variable instead of a fixed parameter in the conventional sequence. Hence, the modified C-rate performance considering the TLM-calculated thickness exhibits an identical trend regardless of the actual electrode thickness, suggesting the calculated electrode thickness reflects the effective electrode thickness. This indicates effective utilization of AMs for electrochemical reactions. We also demonstrate the versatility of this method by using different electrode specifications.

In lithium–sulfur (Li–S) batteries, the impregnation of sulfur into electrically conductive materials of porous carbon plays a significant role in preventing the dissolution of lithium polysulfide (LiPS) into an electrolyte solution and improving cycling performance. However, this strategy does not render high-energy density to Li–S cells because of the limited amount of sulfur in porous carbon. Once the sulfur overflows out of porous carbon because of the significant volume change occurring during charge–discharge cycling, the LiPS formed outside porous carbon probably diffuses toward the anode, leading to poor cycling performance. In this study, the poly-2-acrylamido-2-methylpropanesulfonic acid (AMPS)-based polymer incorporated into the sulfur/porous carbon composite cathode in a Li–S cell effectively suppresses LiPS dissolution even when sulfur is present outside porous carbon, achieving good cycling performance with a capacity retention of 72% at the 100th cycle. Herein, the polymer used is poly-AMPS with a crosslinker of N-[tris(3-acrylamidopropoxymethyl)methyl]acrylamide, which is synthesized using 2-hydroxy-2-methylpropiophenone as the photoinitiator. The characteristics of the as-synthesized AMPS-based polymer and sulfur–carbon composite cathode are meticulously investigated by scanning electron microscopy–energy-dispersive X-ray spectrometry, transmission electron microscopy, dynamic light-scattering analysis, thermogravimetric analysis, and X-ray diffraction.

The dissolution of lithium polysulfide (Li2Sx, 4 ≤ x ≤ 8, LiPS) during charge/discharge testing is a critical issue hindering the practical application of lithium-sulfur batteries (LSBs). To suppress LiPS dissolution, we propose a facile method to fabricate a Li-ion-conductive polymer layer by photopolymerization. The electrochemical performance of LSBs was investigated by preparing small pouch cells containing a three-dimensional (3D) structured sulfur-based cathode that either was or was not layered with the new polymer. Analysis of the electrolyte in the LSB pouch cell by UV-Vis spectroscopy revealed that a 3D S cathode with polymer layer shows a good discharge capacity of 535 mA h g−1 and a coulombic efficiency (CE) of over 96% after 40 cycles. In comparison, the 3D S cathode without a polymer layer has a poor discharge capacity of 389 mA h g−1 and a CE of over 22% after 40 cycles. The dissolution suppressing ability of our new polymer layer demonstrates promise for the practical application of LSBs.

Cycle life of series-connected lithium-ion battery (LIB) modules in the presence or absence of an overcharged cell is reported, and degradation behavior is characterized by electrochemical impedance spectroscopy (EIS) and differential voltage analysis (DVA). Three-stage capacity decay is solely observed in modules in the presence of an overcharged cell, which is exposed to a state of charge (SoC) of ≥105% during cycling. The module without overcharged cells or with an overcharged cell at an SoC of

A solvate ionic liquid (SIL) of highly concentrated 4.0 M lithium nitrate (LiNO3) in a dimethylsulfoxide solution is introduced for lithium-oxygen batteries. As a redox mediator (RM), highly concentrated LiNO3 in the SIL works more effectively than the lower concentrated one to decompose lithium peroxide (Li2O2) on the cathode with an extremely low charging voltage of 3.6 V. In addition, X-ray photoelectron spectroscopy analysis confirms that side products during discharging and charging are markedly restricted in the SIL. The low solubility of Li2O2 intermediate (LiO2) in the SIL may be an important reason for the restriction of side products.

An anionic polymer coating produced by ultraviolet curing and thermosetting to suppress polysulfide dissolution of the sulfur cathode for lithium-sulfur batteries was investigated. An sulfur/Ketjenblack cathode with a high sulfur loading of 10 mg cm−2 was prepared using a three-dimensional foam current collector. From the current rate and cycle characteristics, the cross-linked polymer coating suppressed the polysulfide dissolution, and the discharge capacities were 1031 and 414 mAh g−1-sulfur at 0.1 and 1.0C, respectively. In a long-term cycle test of 300 cycles, a capacity retention rate was 41%. An average coulombic efficiency was 91% throughout the cycles.

Addressing the reuse of lithium ion batteries (LIBs) extracted from used battery packs is an option for addressing environmental concerns. To guarantee their safety, the development of non-destructive analysis to identify LIBs exposed to over-discharge is mandatory. In this study, over-discharge-induced degradation in graphite/nickel cobalt aluminum oxide (NCA) lithium ion cells was investigated using differential voltage analysis (DVA) and electrochemical impedance spectroscopy (EIS). Two-stage cell capacity decay was solely observed in the deep over-discharge cycling at a lower cutoff voltage (LCV) of 1.00 V; in the first stage, the capacity gradually decreased similar to that at LCV ≥ 2.50 V, and then decreased steeply. In the over-discharge cycling, the DVA results confirmed that the electrode balancing between the anode and cathode contribute to increasing the cell capacity, whereas the cathode capacity decreased as cycling progressed, suggesting that electrode degradation induced by over-discharge is difficult to assess using the cell capacities. EIS analysis revealed that the charge-transfer resistance and interfacial capacitance of the NCA cathode changed markedly in the first stage under over-discharge. This study reports a meticulous characterization of over-discharge of LIBs using non-destructive electrochemical analysis and introduces a critical aspect for their detection before serious cell deterioration.

A Lithium-ion capacitor (LIC) is composed of an electrochemical capacitor-like cathode and battery-like anode which store charge based on non-faradaic and faradaic processes, respectively. As an anode material for LIC, graphite is widely used because of its physical and electrochemical advantages. In the LIC system, stable cyclability at the high rate conditions is essential for bridging the gap between lithium-ion batteries and supercapacitors. However, there have been reported that the low working potential of graphite (close to 0.05 V vs Li/Li+) causes Li plating on the graphite surface and non-unity coulombic efficiency at high current charge/discharge results in degradation of cycle performance. To overcome this issue, stacked reduced graphene oxide-tin (SrGO-Sn) composite by co-reduction of graphene oxide and Sn2+ are studied in this work. The LIC consisting of SrGO-Sn anode shows good long-term cyclability with a remarkable capacity retention of 85, 77, and 60% at 10,000, 50,000, and 100,000th cycle and coulombic efficiency of 98% after 120,000 cycles. We believe that this study presents a new approach to the design of the high-performance LIC using an alternative to conventional graphite-based anode materials.

Lithium sulfide (Li2S) is considered to be a promising cathode material for safer energy storage cells due to its compatibility with Li metal-free anodes. However, challenges remain regarding the insulating nature of Li2S, which leads to poor electrochemical performance, currently making Li2S electrodes far from practical in real-world applications. Herein we present a chemical method to synthesize Li2S nanoflake wrapped carbon material, Ketjenblack (LS@KB) composite, which can be coated on different current collectors without the addition of a binder. The high contact area between KB nanoparticles and Li2S nanoflakes effectively improves the cathode's conductivity, which contributes to a high Li2S weight ratio (83%). In addition, we prove that the well wrapped LS@KB structure enhances the physical confinement of polysulfides, leading to improved cyclability. As a result, the synthesized LS@KB cathode delivers stable cyclability (1000 cycles) with a fading rate of 0.03% per cycle at 0.5 C-rate. This room temperature fabrication strategy conquers the major drawbacks existing in Li2S fabrication, such as high temperature, hazardous gas release, complex and high-cost production process, making it a promising cathode material for light and safe portable electronic devices.

Electrochemical impedance spectroscopy (EIS) can be utilized to characterize battery features, because it allows the dynamics of each elemental process of the battery reaction to be sensitively and separately determined without destruction of the cell. In addition, EIS is expected to be utilized for premonitory diagnosis of onboard batteries in electric vehicles. Here, an overview of the recent diagnosis technologies for determining the health of commercial lithium-ion batteries (LIB) using EIS is provided. We describe equivalent circuit design techniques while explaining and investigating physical and chemical phenomena for a wide range of measured impedance spectra, which are obtained using commercial LIBs. Attention is then focused on separation of the frequency responses of each electrode with or without a reference electrode, symmetric cell, and temperature control. Additionally, a square-current EIS (SC-EIS) technique, which we have proposed, is introduced for monitoring of large-scale LIB systems as a promising future technique.

Experimental Specimens.— As starting materials, four kinds of commercial alu- minum sheets (20 × 50 mm; anodized area: 20 × 40 × 2 mm) with purities of 99.0% (A1100, Kanto Chemicals Co. Ltd.), 99.3% (1N30, Japan Foil Co. Ltd.), 99.56% (A1050, Nippon Light Metal Co. Ltd.), and 99.999% (5N, Nilaco Co. Ltd.) were used as received, the ele- mental compositions of which are given in Table I.

The microstructure of electrodeposited nano-crystalline Au-Ni film was investigated by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning transmission electron microscopy (STEM). Carbon was found to be included in the deposit, and the state of bonding and dispersion of the carbon and its effect on the microstructure of Au-Ni film were studied. Nano-crystalline films were found to be composed of Au-rich crystalline phase and Ni-rich phase, and the latter consisted of crystalline and amorphous phases. The amorphous phase contained a large number of carbon particles measuring 5–20 nm. TEM and STEM examinations showed that the large carbon particles possess a graphite-like structure with some of the particles being arranged in arrays. Mechanism of the carbon inclusion was discussed based on the results of XRD and the composition analysis of Au-free Ni film electrodeposited from a cyanide-containing bath. These results showed that carbon is co-deposited with Ni as nickel carbide and also as carbon particles. It is concluded that the inclusion of carbon and the coexistence of Au and Ni are the conditions necessary for the formation of amorphous structure of the electrodeposited Au-Ni alloy film.

In this work, the co-continuous polymer blend was synthesized for use as the electrolyte in lithium batteries. Such electrolytes were characterized by a co-continuous morphology consisting of two three-dimensionally interpenetrated polymer networks simply formed by hot-mixing two nonmiscible polymers. A preliminary electrochemical characterization of the gelified co-continuous polymer blend as electrolyte for lithium batteries is also reported. © 2004 The Electrochemical Society. All rights reserved.

During the course of our recent work performed to develop an electroplated CoNiFe ternary alloy with high saturation magnetic flux density and low coercivity for use in magnetic recording heads, it was observed that two common sulfur‐containing additives, saccharin and thiourea, behave differently with respect to the dependence of sulfur inclusion and coercivity of the alloy film on the additive concentration in the plating bath. To understand the cause of this difference, scanning tunneling microscopy (STM) was performed, using Au(111) as the substrate, to examine the structure of the adsorbed layers of the additive molecules. The result revealed that the nature of adsorption is fundamentally different for the two different additives; i.e., the adsorption of saccharin is physical and reversible, whereas thiourea undergoes irreversible chemisorption. This finding is consistent with the known behaviors of the two additives in the electroplating of nickel. In this paper the different effects of saccharin and thiourea in the electrodeposition of CoNiFe alloy are interpreted based on the STM results and relevant information available in the literature on the electrodeposition of nickel. © 1999 The Electrochemical Society. All rights reserved.