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The lead-acid battery has been a successful commercial product for over a century and is still widely used as the electrical energy storage in the automotive field and other applications.Its advantages are its low cost，mature technology，and relatively high-power capability.These advantages are attractive for application in HEVs，where high power is the first consideration.The materials involved（lead，lead oxide，and sulfuric acid）are rather low cost when compared with their more advanced counterparts.Lead-acid batteries also have several disadvantages.The energy density is low，mostly because of the high molecular weight of lead.The temperature characteristics are poor.Below 100C，specific power and specific energy are greatly reduced.This aspect severely limits the application of lead-acid batteries for the traction of vehicles operated in cold climates.

The presence of highly corrosive sulfuric acid is a potential safety hazard for vehicle occupants.The hydrogen released by the self-discharge reactions is another potential danger，since this gas is extremely flammable even in tiny concentrations.The hydrogen emission is also a problem for hermetically sealed batteries.Indeed，in order to provide a good level of protection against acid spills，it is necessary to seal the battery，thus trapping the parasitic gases in the casing.As a result，pressure may build up in the battery，causing swelling and mechanical constraints on the casing and sealing.The lead in the electrodes is an environmental problem because of its toxicity.The emission of lead consecutive to the use of lead-acid batteries may occur during the fabrication of the batteries，in the case of vehicle wreck（spill of electrolyte through cracks），or during their disposal at the end of battery life.

Different lead-acid batteries with improved performance are being developed for EVs and HEVs.Improvements of the sealed lead-acid batteries in specific energy over 40（W·h）/kg，with the possibility of rapid charge，have been attained.Advanced lead-acid batteries have been developed to remedy their disadvantages.The specific energy has been increased through the reduction of inactive materials such as the casing，current collector，separators，and so on.The lifetime has been increased by over 50%—at the expense of cost，however.The safety issue has been improved，with electrochemical processes designed to absorb the parasitic releases of hydrogen and oxygen.

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.This aspect severely limits the application of lead-acid batteries for the traction of vehicles operated in cold climates.这一状况严格地限制了铅酸蓄电池在冷气候下的车辆牵引中的应用。

★2.The specific energy has been increased through the reduction of inactive materials such as the casing，current collector，separators，and so on.由于减少了不活泼物质，例如壳体、集电极和隔膜等，比能量已经提高。

Exercises（练习）

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

（1）Its advantages are its low cost，mature technology，and relatively high-power capability.

（2）The presence of highly corrosive sulfuric acid is a potential safety hazard for vehicle occupants.

（3）self-discharge

（4）lead-acid batteries

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

（2）在冷气候下

（3）因铅具有毒性，电极上的铅涉及环境问题。

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

Let's discuss the advantages and disadvantages of the lead-acid batteries.

Reading material（阅读材料）

Lead-acid batteries had ever been the most popular choice of batteries for EVs.Lead-acid batteries can be designed to be high powered and are inexpensive，safe，and reliable.A recycling infrastructure is in place for them.However，low specific energy，poor cold temperature performance，and short calendar and cycle life are among the obstacles to their use in EVs and HEVs.

The lead-acid battery has a history that dates to the middle of the 19th century，and it is currently a mature technology.The first lead-acid battery was produced as early as in 1859.In the early 1980s，over 100，000，000 lead-acid batteries were produced per year.The long existence of the lead-acid battery is due to the following: