Design of Roughened Current Collector by Bottom-up Approach Using the Electroplating Technique: Charge–Discharge Performance of a Sn Negative-Electrode for Na-Ion Batteries

ACS Appl. Energy Mater.

Yatsuzuka

Koya

et al. 2018

Self Cite

As one strategy for increasing energy density of K-ion batteries, electrochemical behavior of Sn oxides (SnO and SnO2) was studied as a negative electrode material. X-ray photoelectron spectroscopy and X-ray diffraction revealed followings: SnO underwent phase separation at the first charge (reduction) process to form metallic Sn and potassium oxide, and reversible alloying reactions between the resulting Sn and K proceeded up to a composition of KSn or more. In contrast, SnO2 showed little electrochemical reactivity to potassium. Interestingly, a reversible capacity obtained from SnO electrode at the initial cycle was comparable to that of Sn alone electrode. SnO electrode exhibited a reversible capacity of 183 mA h g −1 with a 80% capacity retention at the 30th cycle, whereas a capacity of Sn electrode rapidly decreased because of the electrode disintegration induced by the significant volume change during K−Sn alloying/dealloying reactions. No crack and peeling off of an active material layer were confirmed in SnO electrode. Scanning transmission electron microscope image of the SnO electrode after the first cycle displayed that Sn nanoparticles were dispersed in amorphous-like K2O matrices. The reason for the improved cycle stability of SnO electrode is probably that K2O suppressed Sn aggregation and/or play a role as a buffer to volumetric change in Sn. For achieving a further long cycle life of SnO electrode, the optimization of particle size and electrolyte solution, and elemental substitution of part of oxygen would be effective.

Section: Experimental Sectionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Tin Oxides as a Negative Electrode Material for Potassium-Ion Batteries

ACS Appl. Energy Mater.

Yatsuzuka

Koya

et al. 2018

Self Cite

“…The same is true for the popularization of autonomous vehicles. Li-ion batteries are still the most promising energy storage devices and have been widely used in portable devices as well as large-scale systems although Na ion, − K ion, − Mg ion, − Ca ion, − and Al ion − have been considered carrier ions from the perspective of not being free from resource constraints. As innovation in electrode materials is needed for the further improvement of energy density, Si has been attracting a great deal of attention as an alternative to graphite (LiC 6 : 372 mA h g –1 ) currently used as a negative electrode material for conventional Li-ion batteries. − This is motivated by the relatively low operation potentials and a significantly large theoretical capacity of 3580 mA h g –1 (Li 15 Si 4 ) based on lithiation and delithiation reactions. , However, Si has the disadvantage of a poor cycle life because the active material layer is isolated from an electrical network in the electrode due to the pulverization suffered from an extremely large volume change by 280% during alloying and dealloying with Li. − In addition to this, the low Li + diffusion coefficient (10 –15 to 10 –10 cm 2 s –1 ) , and the low electrical conductivity (∼10 5 Ω cm) disallow the exploitation of the potential high capacity, which is one of the bottlenecks in the practical application of Si negative electrodes.…”

Section: Introductionmentioning

confidence: 99%

Dopant Effect on Lithiation/Delithiation of Highly Crystalline Silicon Synthesized Using the Czochralski Process

ACS Appl. Energy Mater.

Kimoto

Kawai

et al. 2021

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The huge theoretical capacity of 3580 mA h g–1 based on alloying reactions with Li strongly motivates the use of Si as a negative electrode material in the construction of Li-ion batteries with high energy density. However, its poor electrical conductivity and low Li+ diffusion coefficients as well as the significant volume change in Si during lithiation/delithiation are the bottlenecks for practical application. As one typical method for improving their properties, impurity doping into Si has been considered; however, many of them were amorphous or the impurity concentration against depth direction was not homogeneous, which has complicated the understanding of the effect of impurities on the lithiation/delithiation of Si. In this work, we synthesized Si ingots heavily doped with P (2000 ppm) or B (1600 ppm) as a dopant using the Czochralski method, which overcomes the above issues. In galvanostatic charge/discharge conditions using slurry-type electrodes, the electrical conductivity increased by 108 times compared to that of the undoped Si. The P- (0.119 V) and B-doping (0.126 V) allowed the Li-insertion reaction to occur at higher potentials compared to undoped Si (0.113 V). Even when using 5 vol % fluoroethylene carbonate as a film-forming additive and suppressing an excess volume change in Si during lithiation by the limitation of a charge capacity of 1000 mA h g–1, the undoped Si showed poor cyclability. In contrast, the optimized condition maximized the effect of the improved electrical conductivity and the mechanical properties and thereby enabled the P-doped Si to achieve an excellent performance for more than 300 cycles. Considering the softer properties and the greater fracture toughness of the P-doped Si (1514 HV and P–Si: 363.6 kJ mol–1) than those of B-doped Si (1787 HV and B–Si: 317 ± 12 kJ mol–1), the mechanical properties and fracture toughness, rather than electrical conductivity, make a significant contribution.

“…For practical applications, a joining technology with a roughened plating film that does not rely on composite plating is desirable. We have already reported that a roughened electrodeposited copper film can be fabricated using a roughening agent [19], and that the roughened copper film acts as an effective current collector when applied to a lithium [20,21] or sodium [22] ion battery anode.…”

Section: Introductionmentioning

confidence: 99%

Fabrication of Roughened Electrodeposited Copper Coating on Steel for Dissimilar Joining of Steel and Thermoplastic Resin

Arai

Iwashita

et al. 2021

Metals

Self Cite

Electrodeposition of a roughened copper coating onto steel was carried out to produce a bonding surface for thermoplastic resin (polyphenylenesulfide). The roughened copper film was electrodeposited using a copper sulfate bath containing polyacrylic acid (PAA). Following injection molding of the resin, the bonding strength was evaluated in a tensile lap shear strength test, followed by durability testing at high temperature and humidity (85 ± 2 °C and 85 ± 2% relative humidity, respectively) for 2000 h, and a thermal shock test (−50 °C–150 °C) for 1000 cycles. An analysis of the boundary microstructure showed that the PAA concentration had a large effect on the surface morphology of the copper film. The shear strength of the joint between the coated steel substrate and the resin was more than 40 MPa, and the bonding strength also remained above 40 MPa throughout the durability test. During the thermal shock test, although the bonding strength gradually decreased with increasing number of cycles, it remained at over 20 MPa, even after 1000 cycles. This method achieves not only high initial bonding strength, but also durability for joints between dissimilar materials such as steel and resin.