Lithium is the smallest and most acti影鐵ve metal on the ch他現emical periodic tab煙路le. Small volume, high volume 我視density, widely welcomed by consumers 了理and engineers. However,劇家 the chemical character吧物istics are too active, which brin生呢gs great danger. When exposed to air文報, lithium metal will explode wi計科th intense oxidation of oxygen. 計弟To improve safety and voltage, scient體子ists have invente討刀d materials such as graphi錯麗te and lithium cobalt to stor相妹e lithium atoms. The molecula很木r structure of these materials 歌月forms tiny nanoscale storage l短議attices that can be used 也好to store lithium atoms. In this way他著, even if the batter民內y shell ruptures, oxygen enters, becau到亮se the oxygen molecule is 中跳too big to enter these small物數 storage cells, so that lithium at低站oms will not contact with oxyge醫學n and avoid explosion. This principle 問妹of lithium-ion batteries e坐到nables people to obtain high月讀 capacity density, but also to ac呢要hieve safety purposes通爸.

When lithium ion bat日員teries are charged, the lithium他兵 atoms of positiv會鄉e electrodes will林還 lose electrons and become lithium i不這ons. Lithium ions swim through th自離e electrolyte to the anode, enter th這妹e anode cell, and obtain an electr木離on, which is reduced to 費花lithium atoms. When discharging, 林也the whole procedure is場術 reversed. In order to prevent the bat就見tery's positive and negat你東ive electrodes from directly touching a一多nd short-circuiting, 到術the battery will be coupled with a務的 diaphragm paper with many holes黑一 to prevent short-circuiting. Go請吃od diaphragm paper can 內但also be in the battery temp玩拿erature is too high, 什業automatically cl多快ose the pores, so that li錯數thium ions can not penet學綠rate, to self-waste martial arts電村, to prevent danger.

protective measures

The lithium battery core will 務看start to produce side effects對著 when the charge exceeds 4.2V. The 作了higher the overcharging volt日可age, the higher the光照 risk. When the lit時和hium cell voltage is higher than 4機小.2V, the number 河時of lithium atoms left i路體n the cathode material is les樂北s than half, and the cell oft自劇en collapses, causing a permanent decli跳土ne in battery capacity. If the 從熱charge continues, subse睡著quent lithium metal w雜作ill accumulate on the 學開surface of the an視事ode material becau煙做se the cell of the ano綠木de is already filled 問聽with lithium atoms. These lithium文區 atoms will grow dendrites fro不商m the surface of the negative electrode些內 to lithium ions. These lithium me路票tal crystals will pass 頻師through the separa放街tor paper to make the p子少ositive and negative poles shor女舞t circuited. Sometimes the bat器東tery explodes before the short間好 circuit occurs, because during th商間e overcharge proce亮長ss, materials such as electrol就影yte will crack to produce gas,說白 causing the batte睡服ry shell or pressure valve to swell a風花nd rupture, allowing oxygen to煙紅 react with lithium atoms deposited 但務on the negative surface, and then exp遠服lode. Therefore, wh暗妹en charging lithium batterie市秒s, it is necessary to set the vol作煙tage limit, so as to take into acc笑低ount the battery life,民些 capacity, and safety. The i河會deal charge voltage limi們醫t is 4.2V.

The discharge voltage of the lit就業hium core should also have a lower volt秒子age limit. When the core voltage is lo男頻wer than 2.4V, some 內玩materials will start to be靜老 destroyed. And b不你ecause the battery will s司近elf-discharge, the空短 longer the discharge v金嗎oltage will be lower, 學嗎therefore, it is better not理件 to discharge 2.4 V before stoppi鐵道ng. The lithium battery 師做releases only about 3% of the ba在見ttery capacity during t不如he period from 這路3.0V to 2.4V. Therefore, 3.0V is an id近河eal discharge cut-off voltage.

In addition to vo放哥ltage limitation, current lim資她itation is also necessary. When店腦 the current is too large, the說刀 lithium ion will not enter the s但來torage cell and will aggregate o視黃n the surface of the material. W老年hen these ions get electrons, th舞報ey produce lithium atom crystals on金頻 the surface of the ma老吧terial, which, like over門服charging, can be dangerous. I呢都f the battery shell breaks, it will ex紅電plode.

Therefore, the protection of lit業習hium-ion batteries should 是器include at least thr木器ee items: charge voltag校我e upper limit, discharge voltage lower業能 limit, and current uppe冷飛r limit. In general, in addition 什電to lithium battery batte玩拿ries, there will be a服雨 protective plate,區海 this plate is mainly to provide t開對hese three protections. Howeve得睡r, the protection of these 歌劇three protection is obvi熱吃ously not enough, and the global lit我歌hium battery explo裡匠sion is still fre有微quent. To ensure t報男he safety of the bat是弟tery system, we must make a more 謝路careful analysis of the站在 cause of the battery explosion.了理