2022-11-17
电(dian)(dian)(dian)池形(xing)(xing)(xing)成(cheng)的(de)过(guo)程(cheng)(cheng),实际上就(jiu)是次给(ji)锂离子电(dian)(dian)(dian)池充电(dian)(dian)(dian)的(de)过(guo)程(cheng)(cheng)。为了保证在负极表面(mian)形(xing)(xing)(xing)成(cheng)均匀致密的(de)SEI薄膜(mo),在形(xing)(xing)(xing)成(cheng)过(guo)程(cheng)(cheng)中(zhong)通常会使用非常小(xiao)的(de)电(dian)(dian)(dian)流给(ji)电(dian)(dian)(dian)池充电(dian)(dian)(dian),以降低界(jie)(jie)面(mian)薄膜(mo)的(de)成(cheng)膜(mo)速度(du),从而使形(xing)(xing)(xing)成(cheng)的(de)界(jie)(jie)面(mian)薄膜(mo)更加致密。
渗透(tou)和化成完成后,为(wei)(wei)了消(xiao)除漏(lou)(lou)电(dian)流(liu)(liu)较大的(de)(de)电(dian)池,通常需要对电(dian)池进行1-2周的(de)(de)老化筛选(xuan)。在(zai)电(dian)池形(xing)成结束时,锂离子电(dian)池内部(bu)的(de)(de)泄漏(lou)(lou)电(dian)流(liu)(liu)通常为(wei)(wei)20-50ua/cm2。稳定数小时后,漏(lou)(lou)电(dian)流(liu)(liu)将(jiang)降(jiang)至2-5uA/cm2,数周后,电(dian)池内部(bu)的(de)(de)漏(lou)(lou)电(dian)流(liu)(liu)将(jiang)降(jiang)至1uA/cm2以下。但是,由于制造缺陷和电(dian)解(jie)质(zhi)杂质(zhi)等因素(su),某(mou)些锂离子电(dian)池的(de)(de)泄漏(lou)(lou)电(dian)流(liu)(liu)将(jiang)继(ji)续很高(gao)。一(yi)旦(dan)它们(men)进入(ru)组(zu)(zu)合,单(dan)个电(dian)池之间的(de)(de)电(dian)压(ya)偏差(cha)将(jiang)太(tai)大,这将(jiang)影响电(dian)池组(zu)(zu)的(de)(de)性能。为(wei)(wei)了保证电(dian)池的(de)(de)一(yi)致性,这部(bu)分电(dian)池需要通过筛选(xuan)来(lai)消(xiao)除。
为(wei)了压缩形(xing)成(cheng)时(shi)间(jian),首(shou)先(xian)以(yi)较大的(de)(de)(de)电(dian)(dian)流(liu) (1C) 将(jiang)锂离子电(dian)(dian)池充(chong)(chong)电(dian)(dian)至3.9V,然后以(yi)3.9-4.2V范围(wei)内的(de)(de)(de)C/5速(su)(su)率对(dui)锂离子电(dian)(dian)池进(jin)行充(chong)(chong)放电(dian)(dian),后将(jiang)电(dian)(dian)池放电(dian)(dian)至3.0V。与(yu)0.05C速(su)(su)率下的(de)(de)(de)三个循环相比,该系(xi)统下电(dian)(dian)池的(de)(de)(de)形(xing)成(cheng)时(shi)间(jian)仅为(wei)14h,形(xing)成(cheng)速(su)(su)度提高了8.5倍。以(yi)这种方式,尽管形(xing)成(cheng)时(shi)间(jian)被大大压缩,但(dan)电(dian)(dian)池的(de)(de)(de)容量(liang)降低(di)(di)了,并且快速(su)(su)性使(shi)电(dian)(dian)池的(de)(de)(de)容量(liang)降低(di)(di)了13%。如果(guo)我们将(jiang)用于在低(di)(di)电(dian)(dian)压范围(wei)内快速(su)(su)充(chong)(chong)电(dian)(dian)的(de)(de)(de)电(dian)(dian)流(liu)降低(di)(di)到0.2C或0.33C,则与(yu)0.05C相比,电(dian)(dian)池的(de)(de)(de)正极的(de)(de)(de)比容量(liang)将(jiang)降低(di)(di)12 mAh/g(7%)。
一(yi)些先(xian)进(jin)的(de)(de)电(dian)池技术(shu),例(li)如原(yuan)子(zi)层(ceng)(ceng)沉(chen)积技术(shu) (ALD),使进(jin)一(yi)步(bu)的(de)(de)压缩(suo)(suo)润(run)湿和形(xing)成(cheng)(cheng)时(shi)(shi)间(jian)成(cheng)(cheng)为可能。研究表明,通过在正负极(ji)材(cai)料表面添加原(yuan)子(zi)层(ceng)(ceng)沉(chen)积层(ceng)(ceng),甚至直接采用原(yuan)子(zi)层(ceng)(ceng)沉(chen)积技术(shu),可以将形(xing)成(cheng)(cheng)时(shi)(shi)间(jian)进(jin)一(yi)步(bu)压缩(suo)(suo)至10h以下正极(ji)和负极(ji)指示SEI薄膜的(de)(de)形(xing)成(cheng)(cheng),取代(dai)了(le)传统(tong)的(de)(de)SEI薄膜,从(cong)而(er)进(jin)一(yi)步(bu)减少了(le)锂离(li)子(zi)电(dian)池的(de)(de)化成(cheng)(cheng)所需时(shi)(shi)间(jian)。
研究表明,高电(dian)位相(xiang)的负极使用较(jiao)大的电(dian)流,在(zai)(zai)较(jiao)低电(dian)位下使用较(jiao)小(xiao)的电(dian)流进行形成(cheng),可有(you)效压缩成(cheng)时(shi)间(jian),该方法在(zai)(zai)形成(cheng)相(xiang)时(shi)可部(bu)分形成(cheng)SEI薄膜(mo),终完(wan)成(cheng)SEI薄膜(mo)在(zai)(zai)锂离子电(dian)池(chi)使用过程(cheng)中(zhong)的构(gou)建,对终锂离子电(dian)池(chi)循环性(xing)能无显(xian)著影响。
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