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Sn-based alloy compounds have been considered as possible alternatives for carbon in lithium-ion batteries and attract great attentions because of their large electrochemical capacity compared with that of carbon. In this work, a multilayered Sn–Zn/Zn/Cu alloy thin-film electrode has been prepared by electroplating method. The structure and performance of the electrode before and after heat treatment have been investigated. It is found that Cu 6 Sn 5 phase and multilayered structure in electrode are formed after heat treatment. This optimized structure of the heat-treated electrode results in enhanced cycle life. The capacity of the electrode is over 320 mA h g −1 after 100 cycles; though it is 83 mA h g −1 after 20 cycles for as-plated electrode. The Sn–Cu and Zn–Cu alloy formed a network in the electrode is considered to strengthen the electrode and reduce the effect of volume expansion and phase transition during cycling. Experimental results also reveal that lower cut-off potential (0.05 V) for charging and higher one (1.2 V) for discharging result in long cycle life and high discharge capacity, respectively. The reason of capacity decay of the heat-treatment electrode during cycling has also been investigated. All these results show that the electroplated Sn–Zn-based alloy film on Cu foil would be a promising negative material with high capacity and low cost for Li secondary batteries.

スズ-亜鉛共晶合金は, 融点が現行のスズ-鉛共晶合金のそれに近いことから, 鉛フリーはんだの候補として期待されている。ポリオキシエチレン-α-ナフトール (POEN) を添加剤とするスルホコハク酸浴から, カソード電流密度0.5～3A/dm2において, 共晶組成 (亜鉛9mass%) を有する合金皮膜が得られた。POENの添加は, スズ析出の分極を増大し, 低電流密度領域におけるスズの優先析出を抑制することにより, 亜鉛の共析を可能にした。めっき浴は極めて安定であり, 6カ月経過後においてもSn4+化合物の沈殿形成は認められなかった。スズ-亜鉛共晶合金皮膜は, β-スズ相と亜鉛相からなり, その融点は198℃であった。銅素地上のスズ-亜鉛共晶合金皮膜には, 1年間の室温経時後においてもウイスカの発生は認められなかった。

Sn-based compounds have attracted great attentions because of their larger specific capacity for Li secondary batteries. An electroplating method has been developed to prepare a Sn-Zn based alloy. The structure and electrochemical performance of as-plated and heat-treated electrodes have been investigated in detail. Experimental results show that phase and many voids were formed in plated film after heat-treatment. At the same time, the component of Zn was segregated, forming two Zn layers. This multilayer structure in electrode was beneficial to strengthen the contact between the plated film and Cu foil, and to relax the volume expansion during cycling, which improved the cyclability of electrode. The discharge capacity of the heat-treated electrode remained over after 50 cycles, while that of as-plated anode decreased seriously to The charge-discharge reaction mechanism of a heat-treated anode also changed due to the formation of phase in the plated film. These results show that electroplated Sn-Zn alloy film on Cu foil is a promising anode material with larger specific capacity and long cycle life for Li secondary batteries. © 2003 The Electrochemical Society. All rights reserved.

Tin-zinc alloys of low zinc content are believed to have high corrosion resistance when they are used for protective films on steel surface. This paper describes the following studies: an optimum composition for protective films was selected by electrochemical measurements of the cast alloys; and, zincate-stannate baths and gluconate baths were investigated to obtain such alloy deposits from baths free from cyanides and fluorides. The following results were obtained: (1) The static potential of tinzinc alloys was base enough to act as a sacrificial film for steel, and the potential of an alloy containin more than about 10% of zinc showed almost the same value as that of single zinc. (2) The anodic dissolution in NaCl solution and the formation of white precipitate on the alloy surface in a salt spray test more readily occurred with the increase in zinc content of the alloy. (3) It was difficult to obtain alloy deposits of lower zinc content from zincate-stannate baths under normal plating conditions. (4) A semi-bright zinc alloy deposit of lower zinc content was obtained from the bath containing 0.25mol/l of metal and 0.50mol/l of Na-gluconate with an additive such as 0.25mol/l of triethanolamine, 2.5-5g/l of polyethyleneglycolnonylphenylether (PEGNPE), 0.2-1g/l of peptone, and 0.04-0.06g/l of o-vanillin at pH=5. It was observed that a deposit of fine luster was apt to be obtained at a composition of nearly equi-molecular ratio between tin and zinc. (5) It was further observed that a deposit of highest zinc content was obtained from gluconate baths containing 20 and 35% of zinc at pH=5, and the zinc content of deposit was almost equal to that of the bath when the plating was conducted at a current density of 1-2Amp/dm2.