3.3.2　Nickel-Based Batteries

Text（课文）

Nickel is a lighter metal than lead and has very good electrochemical properties desirable for battery applications.There are four different nickel-based battery technologies:nickel-iron，nickel-zinc，nickel-cadmium，and Ni-MH.

Ni-MH battery

The Ni-MH battery has been on the market since 1992.Its characteristics are similar to those of the nickel/cadmium battery.The principal difference between them is the use of hydrogen，absorbed in a metal hydride，for the active negative electrode material in place of cadmium.Because of superior specific energy to Ni-Cd and since it is free from toxicity or carcinogenicity，such as cadmium，the Ni-MH battery is superseding the Ni-Cd battery.

At present，Ni-MH battery technology has a nominal voltage of 1.2V and attains a specific energy of 65（W·h）/kg and a specific power of 200 W/kg.A key component of the Ni-MH battery is the hydrogen storage metal alloy，which should be formulated to obtain a material that is stable over a large number of cycles.

Because the Ni-MH battery is still under continual development，its advantages based on present technology are summarized as follows:it has the highest specific energy［70-95（W·h）/kg］and highest specific power（200-300W/kg）of nickel-based batteries；environmental friendliness（cadmium free）；a flat discharge profile（smaller voltage drop）；and rapid recharge capability.However，this battery still suffers from its high initial cost.It may also have a memory effect and be exothermic during charging.

The Ni-MH battery has been considered as an important near-term choice for EV and HEV applications.A number of battery manufacturers，such as GM Ovonic，GP，GS，Panasonic，SAFT，VARTA，and YUASA，have actively engaged in the development of this battery technology，especially for powering EVs and HEVs.Since 1993，Ovonic has installed its Ni-MH battery in the Solectric GT Force EV for testing and demonstration.A 19-kW·h battery has delivered over 65（W·h）/kg，134 km/h，acceleration from zero to 80 km/h in 14s，and a city driving range of 206 km.Toyota and Honda have used the Ni-MH battery in their HEVs—Prius and Insight，respectively.

New words and expressions（单词和短语）

1.New words（单词）

2.Expressions（短语）

Notes to the text（难点解析）

★1.Because of superior specific energy to Ni-Cd and since it is free from toxicity or carcinogenicity，such as cadmium，the Ni-MH battery is superseding the Ni-Cd battery.

当与镍-镉蓄电池相比较时，因其占优的比能量，及其免除于毒性或致癌性的性能，Ni-MH蓄电池正在取代镍-镉蓄电池。

★2.A key component of the Ni-MH battery is the hydrogen storage metal alloy，which should be formulated to obtain a material that is stable over a large number of cycles.这类Ni-MH蓄电池的关键组成是贮氢合金，它被配制以获得在大量循环中稳定反应的物质。

Exercises（练习）

◆1.Translate the following passages（expressions）into Chinese（英译汉）

（1）However，this battery still suffers from its high initial cost.It may also have a memory effect and be exothermic during charging.

（2）environmental friendliness

（3）metal hydride

★2.Translate the following passages（expressions）into English（汉译英）

（1）记忆效应

（2）行程范围

（3）Ni-MH蓄电池正在取代镍-镉蓄电池。

★3.Directions:Answer the following questions briefly according to the text

What are the advantages of Ni-MH batteries？

Reading material（阅读材料）

The operating voltage of Ni-MH is almost the same as that of Ni-Cd，with flat discharge characteristics.The capacity of the Ni-MH is significantly higher than that of Ni-Cd，with specific energy ranging from 60 to 80（W·h）/kg.The specific power of Ni-MH batteries can be as high as 250 W/kg.

The Ni-MH batteries have penetrated the market in recent years at an exceptional rate.The Chrysler electric minivan“Epic”uses a Ni-MH battery pack，which gives a range of 150 km.Ni-MH battery packs are being used in Toyota HEV Prius.

The components of Ni-MH are recyclable，but a recycling structure is not yet in place.Ni-MH batteries have a much longer life cycle than lead-acid batteries and are safe and abuse tolerant.The disadvantages of Ni-MH batteries are the relatively high cost，higher self-discharge rate compared to Ni-Cd，poor charge acceptance capability at elevated temperatures，and low cell efficiency.Ni-MH is likely to survive as the leading rechargeable battery in the future for traction applications，with the strong challenge coming only from lithium-ion batteries.