鋰電池電解液發展現狀
鋰(li)電(dian)池(chi)憑借其自身的(de)(de)綜(zong)合優勢(shi)(shi)不斷滲透(tou)到一個個龐(pang)大的(de)(de)產(chan)業群汽車(che)、電(dian)動(dong)工(gong)具(ju)(ju)、電(dian)子(zi)產(chan)品等領(ling)域。為(wei)了適應這些(xie)龐(pang)大的(de)(de)產(chan)業群,鋰(li)電(dian)池(chi)電(dian)解(jie)液材料未來的(de)(de)發(fa)展(zhan)趨勢(shi)(shi)將主要(yao)集中在新(xin)型溶劑、離子(zi)液體、添加劑、新(xin)型鋰(li)鹽等方(fang)面,與新(xin)型正、負極材料相匹配,從而(er)使鋰(li)離子(zi)電(dian)池(chi)更(geng)安全,具(ju)(ju)有更(geng)高的(de)(de)功率、更(geng)大的(de)(de)容量,最(zui)終安全方(fang)便(bian)地應用于電(dian)動(dong)車(che)、儲(chu)能、航天以及更(geng)廣泛的(de)(de)領(ling)域。


為了滿足鋰離子電池產業未來發展的需要,必須開發出高安全性、高環境適應性更高的電解液材料。主要應從電解液的溶劑、溶質和添加劑的選擇上進行考量:
(1)盡量選擇工作溫度范圍寬的(de)溶劑,溶劑的(de)熔點最好(hao)能在(zai)-40℃以下(xia),沸點最好(hao)在(zai)150℃
以上或(huo)更高(gao),電(dian)化學窗口寬的(de)溶(rong)劑能更好地防止在荷電(dian)狀態下的(de)電(dian)解液的(de)氧化還原反應,同時可以提高(gao)電(dian)池的(de)循環穩定(ding)性(xing)。比如可以考慮(lv)使用(yong)離子液體、新型溶(rong)劑、多組分溶(rong)劑等,從而解決電(dian)池的(de)安全性(xing)和環境適應性(xing)。
(2)選擇合適的(de)(de)溶質,提高電池的(de)(de)環境(jing)適應性。目前(qian)通常所用的(de)(de)LiPF6(鋰(li)六(liu)氟磷(lin)酸鹽)分解溫度低,從60℃開始就有少量分解,在較高溫度或(huo)惡劣的(de)(de)環境(jing)下,分解的(de)(de)比(bi)例大(da)大(da)增(zeng)加,產生HF(氫氟酸)等游離酸,從而使電解液酸化,最(zui)終導致電極材(cai)料的(de)(de)損(sun)壞以及電池性能的(de)(de)急劇惡化。
(3)可(ke)以(yi)(yi)(yi)考慮(lv)添加(jia)(jia)適量(liang)的(de)(de)阻燃添加(jia)(jia)劑(ji)、氧化還(huan)原穿梭(suo)(suo)添加(jia)(jia)劑(ji)、保(bao)(bao)護(hu)正負極(ji)(ji)(ji)成(cheng)膜添加(jia)(jia)劑(ji)等。采用(yong)阻燃添加(jia)(jia)劑(ji)可(ke)以(yi)(yi)(yi)確(que)保(bao)(bao)電(dian)(dian)(dian)(dian)(dian)池(chi)內部熱失控時(shi),電(dian)(dian)(dian)(dian)(dian)解(jie)液不(bu)會(hui)燃燒起火,使(shi)電(dian)(dian)(dian)(dian)(dian)池(chi)安全(quan)性(xing)得以(yi)(yi)(yi)保(bao)(bao)證。采用(yong)氧化還(huan)原穿梭(suo)(suo)添加(jia)(jia)劑(ji)的(de)(de)作用(yong)是,防止當電(dian)(dian)(dian)(dian)(dian)池(chi)尤其是動力電(dian)(dian)(dian)(dian)(dian)池(chi)組由于在使(shi)用(yong)過(guo)程中出現異(yi)常的(de)(de)狀(zhuang)況,單體(ti)電(dian)(dian)(dian)(dian)(dian)池(chi)會(hui)經常性(xing)過(guo)充(chong)或過(guo)放(fang),從而(er)(er)導(dao)致電(dian)(dian)(dian)(dian)(dian)池(chi)性(xing)能(neng)的(de)(de)迅速惡化,進而(er)(er)影響整組電(dian)(dian)(dian)(dian)(dian)池(chi)的(de)(de)性(xing)能(neng)和使(shi)用(yong),甚至帶來(lai)安全(quan)隱(yin)患的(de)(de)發(fa)生。采用(yong)正負極(ji)(ji)(ji)成(cheng)膜添加(jia)(jia)劑(ji)的(de)(de)作用(yong)是可(ke)以(yi)(yi)(yi)有效地保(bao)(bao)護(hu)正負極(ji)(ji)(ji)材料在充(chong)電(dian)(dian)(dian)(dian)(dian)狀(zhuang)態(tai)下與電(dian)(dian)(dian)(dian)(dian)解(jie)液的(de)(de)接觸(chu)反應,通過(guo)成(cheng)膜的(de)(de)形式,將高度活性(xing)的(de)(de)正負極(ji)(ji)(ji)與電(dian)(dian)(dian)(dian)(dian)解(jie)液隔離開來(lai),從而(er)(er)防止電(dian)(dian)(dian)(dian)(dian)解(jie)液在電(dian)(dian)(dian)(dian)(dian)極(ji)(ji)(ji)表面(mian)的(de)(de)反應。
電解液(ye)主(zhu)要原材料為六(liu)氟磷(lin)酸鋰,占(zhan)電解液(ye)成本的50%左右,其生產(chan)(chan)成本為10萬(wan)(wan)元/噸(dun)(dun),售價(jia)為40萬(wan)(wan)元/噸(dun)(dun),毛利率高(gao)(gao)達75%。六(liu)氟磷(lin)酸鋰合成難度(du)較高(gao)(gao),整個生產(chan)(chan)過程涉(she)及高(gao)(gao)溫(wen)、低溫(wen)、真空、高(gao)(gao)壓、腐蝕性(xing)強、易(yi)燃易(yi)爆和(he)劇毒化學品,對(dui)設備和(he)人員要求高(gao)(gao)、工(gong)藝難度(du)極大。森田化工(gong)在張家(jia)港的建設年(nian)產(chan)(chan)300噸(dun)(dun)六(liu)氟磷(lin)酸鋰的工(gong)廠(chang),照(zhao)搬(ban)日本工(gong)廠(chang)的成熟設備和(he)工(gong)藝,仍然歷時3年(nian)才穩(wen)定達產(chan)(chan),可(ke)見工(gong)藝難度(du)之高(gao)(gao)。
難點在于雜質控(kong)制。電解液對(dui)六氟磷酸(suan)鋰的(de)純度要(yao)求(qiu)極(ji)高(gao)(gao),行業標準要(yao)求(qiu)水分小于30ppm,游離(li)酸(suan)小于10ppm。由于六氟磷酸(suan)鋰本(ben)身具(ju)有吸潮性,因此高(gao)(gao)純原(yuan)料的(de)獲取和(he)生產(chan)(chan)過程中雜質控(kong)制和(he)產(chan)(chan)品提純都是關鍵(jian)因素(su)。較高(gao)(gao)的(de)技術門檻,導致(zhi)極(ji)高(gao)(gao)的(de)市場(chang)集中度,市場(chang)主(zhu)要(yao)被(bei)關東電化學工業、STELLA、森田化學等(deng)幾家日本(ben)企業壟斷。
國內目(mu)前僅有天津金牛能(neng)實(shi)現工(gong)業化生產(chan)(chan),產(chan)(chan)量約(yue)80噸,產(chan)(chan)品全(quan)部自用不對外銷售(shou)。江蘇國泰和(he)多氟(fu)多正在進(jin)行中試生產(chan)(chan)。
發展趨(qu)勢:長期看(kan),新(xin)電(dian)(dian)(dian)(dian)解(jie)質(zhi)體(ti)(ti)系(xi)的(de)(de)(de)(de)開發將是大勢所趨(qu)。六氟(fu)磷酸(suan)(suan)(suan)(suan)鋰(li)材(cai)料(liao)的(de)(de)(de)(de)熱(re)穩(wen)(wen)定性(xing)較(jiao)(jiao)差,從(cong)60℃開始就有(you)少量(liang)分解(jie),在(zai)較(jiao)(jiao)高溫度(du)或惡劣(lie)的(de)(de)(de)(de)環境下(xia),分解(jie)的(de)(de)(de)(de)比(bi)(bi)例大大增加,產(chan)生(sheng)氫氟(fu)酸(suan)(suan)(suan)(suan)等游離酸(suan)(suan)(suan)(suan),會使電(dian)(dian)(dian)(dian)解(jie)液(ye)(ye)(ye)酸(suan)(suan)(suan)(suan)化,最終導(dao)致電(dian)(dian)(dian)(dian)極材(cai)料(liao)的(de)(de)(de)(de)損壞(huai)以及電(dian)(dian)(dian)(dian)池(chi)性(xing)能(neng)的(de)(de)(de)(de)急劇惡化。同時六氟(fu)磷酸(suan)(suan)(suan)(suan)鋰(li)易潮(chao)解(jie),而水分是電(dian)(dian)(dian)(dian)解(jie)液(ye)(ye)(ye)的(de)(de)(de)(de)大敵。近(jin)些(xie)年,草酸(suan)(suan)(suan)(suan)硼酸(suan)(suan)(suan)(suan)鋰(li)鹽在(zai)電(dian)(dian)(dian)(dian)解(jie)液(ye)(ye)(ye)中的(de)(de)(de)(de)應用逐漸引起(qi)關注。用草酸(suan)(suan)(suan)(suan)硼酸(suan)(suan)(suan)(suan)鋰(li)鹽配制(zhi)成的(de)(de)(de)(de)電(dian)(dian)(dian)(dian)解(jie)液(ye)(ye)(ye)有(you)抗過充、阻燃(ran)等功(gong)能(neng),形(xing)(xing)成的(de)(de)(de)(de)SEI膜非常穩(wen)(wen)定,滿足動(dong)力電(dian)(dian)(dian)(dian)池(chi)高安(an)全(quan)性(xing)的(de)(de)(de)(de)要求。更長遠(yuan)看(kan),聚合(he)物鋰(li)電(dian)(dian)(dian)(dian)池(chi)可能(neng)成為(wei)鋰(li)電(dian)(dian)(dian)(dian)池(chi)未來的(de)(de)(de)(de)發展方(fang)向(xiang)。由于用固體(ti)(ti)電(dian)(dian)(dian)(dian)解(jie)質(zhi)代(dai)替(ti)了液(ye)(ye)(ye)體(ti)(ti)電(dian)(dian)(dian)(dian)解(jie)質(zhi),與(yu)(yu)液(ye)(ye)(ye)態鋰(li)離子(zi)(zi)(zi)電(dian)(dian)(dian)(dian)池(chi)相比(bi)(bi),聚合(he)物鋰(li)離子(zi)(zi)(zi)電(dian)(dian)(dian)(dian)池(chi)具(ju)有(you)可薄(bo)形(xing)(xing)化、任意(yi)面積化與(yu)(yu)任意(yi)形(xing)(xing)狀化等優點,也不會產(chan)生(sheng)漏液(ye)(ye)(ye)與(yu)(yu)燃(ran)燒(shao)爆(bao)炸等安(an)全(quan)上的(de)(de)(de)(de)問題,因此外殼(ke)材(cai)質(zhi)可以更輕(qing),從(cong)而可以提高整個電(dian)(dian)(dian)(dian)池(chi)的(de)(de)(de)(de)比(bi)(bi)容量(liang)。此外,聚合(he)物鋰(li)離子(zi)(zi)(zi)電(dian)(dian)(dian)(dian)池(chi)在(zai)工(gong)作電(dian)(dian)(dian)(dian)壓、充放電(dian)(dian)(dian)(dian)循環壽命等方(fang)面都(dou)比(bi)(bi)普通鋰(li)離子(zi)(zi)(zi)電(dian)(dian)(dian)(dian)池(chi)有(you)所提高。

 




