题干

全固态锂硫电池能量密度高、成本低,其工作原理如图所示,其中电极a常用掺有石墨烯的S8材料,电池反应为:16Li+xS8=8Li2Sx(2≤x≤8).下列说法错误的是(  )


A:电池工作时,正极可发生反应:2Li2S6+2Li++2e=3Li2S4

B:电池工作时,外电路中流过0.02 mol电子,负极材料减重0.14 g

C:石墨烯的作用主要是提高电极a的导电性

D:电池充电时间越长,电池中的Li2S2量越多

上一题 下一题 0.0难度 选择题 更新时间:2019-02-06 10:31:32

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D

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    Feifei, an 11-year-old boy from Xuzhou, Jiangsu Province, suffered from a sudden acute eye disease which has almost led to blindness. The disease was caused by excessive(过度的)eye fatigue(疲劳)during the winter vacation, during which he played computer games for continuous 10 days and nights.

    Many youngsters in China nowadays are increasingly addicted to computer games and other electronic products. This is followed by a series of health problems, with the most typical case being myopia, or nearsightedness.

    According to the latest research report released by the World Health Organization (WHO), the myopia   rate among Chinese teenagers ranks first in the world—70 percent of high school and college students. The rate is nearly 40 percent in primary school students, while it is only 10 percent for their peers in the United States.

    There are at least 10 million people in China with severe myopia, and they are likely to get pathological(病理性的)myopia in middle age. Pathological myopia can't be treated with glasses or surgery, and it is one of the biggest factors that lead to blindness, Xu Xun, director of the ophthalmology(眼科学) department at Shanghai General Hospital, pointed out.

    Experts explain that two major factors lead to the high rate of myopia among Chinese people. One is high academic pressure, and the other one is excessive use of electronic devices over a long period of time. Genetics, on the other hand, are not the main reason, as only 20 percent of Chinese people had myopia in the 1960s.

    "Teenagers are now faced with severe academic pressure, which means they often study without natural light. This increases their risk of becoming nearsighted," Xu said.

    Experts suggest that youngsters maintain a proper balance between study and rest so as to protect their eyesight, and parents should play an active role in the process.