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隨著鋰(li)(li)離(li)子(zi)電(dian)(dian)(dian)(dian)池(chi)(chi)在(zai)手(shou)機(ji)、電(dian)(dian)(dian)(dian)腦、汽(qi)車、儲能(neng)等領(ling)域(yu)的廣泛應用，人們對電(dian)(dian)(dian)(dian)池(chi)(chi)的安全性(xing)(xing)、能(neng)量密(mi)度(du)(du)和(he)功率(lv)密(mi)度(du)(du)性(xing)(xing)能(neng)的需求(qiu)越來越高(gao)。為了提高(gao)鋰(li)(li)離(li)子(zi)電(dian)(dian)(dian)(dian)池(chi)(chi)的能(neng)量密(mi)度(du)(du)和(he)功率(lv)密(mi)度(du)(du)，一些鋰(li)(li)電(dian)(dian)(dian)(dian)新(xin)材料和(he)新(xin)技術亟(ji)待開(kai)發。鋰(li)(li)離(li)子(zi)電(dian)(dian)(dian)(dian)池(chi)(chi)生(sheng)產(chan)由多(duo)個工(gong)(gong)藝過程組(zu)成(cheng)，為了得到(dao)安全可(ke)靠(kao)性(xing)(xing)高(gao)且性(xing)(xing)能(neng)一致(zhi)性(xing)(xing)好的電(dian)(dian)(dian)(dian)池(chi)(chi)，需要(yao)對每一個生(sheng)產(chan)工(gong)(gong)藝制(zhi)定嚴格的監(jian)控(kong)措(cuo)施，確保(bao)不(bu)良品不(bu)流(liu)入市場。為了節約生(sheng)產(chan)成(cheng)本，提升生(sheng)產(chan)效(xiao)率(lv)，電(dian)(dian)(dian)(dian)池(chi)(chi)企業更(geng)加希望能(neng)在(zai)前工(gong)(gong)序階(jie)段就(jiu)能(neng)快速識別(bie)出異常，及時(shi)做出相應改善措(cuo)施。目前大多(duo)數電(dian)(dian)(dian)(dian)池(chi)(chi)企業在(zai)前工(gong)(gong)序常用的監(jian)控(kong)方法主(zhu)要(yao)包括監(jian)控(kong)以下參數：漿(jiang)(jiang)料黏(nian)度(du)(du)、漿(jiang)(jiang)料固含(han)量、涂布(bu)質量、壓實密(mi)度(du)(du)，這些方法雖(sui)然可(ke)以一定程度(du)(du)上監(jian)控(kong)出工(gong)(gong)序波動，但(dan)還(huan)不(bu)足(zu)(zu)以滿足(zu)(zu)監(jian)控(kong)成(cheng)品電(dian)(dian)(dian)(dian)芯一致(zhi)性(xing)(xing)的要(yao)求(qiu)。極(ji)片(pian)(pian)(pian)(pian)是電(dian)(dian)池前端工(gong)序的(de)(de)(de)一個重(zhong)要(yao)輸出，極(ji)片(pian)(pian)(pian)(pian)的(de)(de)(de)電(dian)(dian)子(zi)電(dian)(dian)阻（電(dian)(dian)導率)影響全電(dian)(dian)池的(de)(de)(de)功率性(xing)(xing)、可靠性(xing)(xing)及安全性(xing)(xing)，同時它(ta)又與攪(jiao)拌、涂布和輥壓(ya)工(gong)序息息相關，因(yin)此，測量極(ji)片(pian)(pian)(pian)(pian)電(dian)(dian)阻的(de)(de)(de)變化(hua)可以較(jiao)好(hao)地評價極(ji)片(pian)(pian)(pian)(pian)制作過程(cheng)中電(dian)(dian)子(zi)導電(dian)(dian)網絡(luo)的(de)(de)(de)性(xing)(xing)能(neng)，評估電(dian)(dian)極(ji)微(wei)觀結構的(de)(de)(de)均勻性(xing)(xing)以及監(jian)控極(ji)片(pian)(pian)(pian)(pian)制作工(gong)藝(yi)的(de)(de)(de)穩定性(xing)(xing)，助(zhu)力改進極(ji)片(pian)(pian)(pian)(pian)的(de)(de)(de)配方以及攪(jiao)拌、涂布和輥壓(ya)工(gong)藝(yi)的(de)(de)(de)控制參數。

目前，測試極片電子電阻主要有兩種原理：四探針法和兩探針法。四探針法只能表征極片表面涂層的電阻，忽略了涂層和集流體的界面電阻，與極片在電池中的實際使用情況不符，因此不用于測試鋰離子電池極片電阻^1-2。兩探針法能表征極片的整體穿透內阻，包含涂層電阻、涂層與集流體界面電阻以及集流體本身電阻，測試時的電子傳導路徑與極片在電池中實際使用時的電子傳導路徑相同，大多數企業和科研工作者采用該方法進行極片電阻表征^2-4。本文使用的(de)方法(fa)是在兩(liang)探針法(fa)的(de)基礎(chu)上做進一步(bu)改進，采(cai)用四線法(fa)加可控壓(ya)雙圓盤電極，測試極片(pian)電子電阻(zu)，監控涂布和輥壓(ya)工序極片(pian)電阻(zu)的(de)變化，將電芯(xin)的(de)風(feng)險(xian)控制提前(qian)至(zhi)極片(pian)端(duan)，從而(er)為鋰離子電池研發和生產(chan)保駕護航。

1.1 極片批次穩定(ding)性監控

極片電阻受導電劑分散、涂布重量、冷壓參數等多種因素影響，其中導電劑對電阻的影響非常顯著³。正極導電劑的分散情況與漿料配方、攪拌條件、涂布/烘干條件等眾多復雜工藝控制參數有關，導電劑分散不均將極大惡化電池動力學性能，但不均勻性很難通過極片外觀、粘接力等常規監控手段發現，往往容易被忽略，造成不可挽回的損失。

在電(dian)(dian)(dian)(dian)(dian)(dian)芯(xin)(xin)研(yan)發初期，通過對(dui)三元極(ji)(ji)(ji)片(pian)(pian)(pian)(pian)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)的(de)大量測試和(he)(he)監(jian)(jian)控(kong)，初步(bu)制定正常(chang)極(ji)(ji)(ji)片(pian)(pian)(pian)(pian)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)范圍(wei)為0.2~0.4Ω，在電(dian)(dian)(dian)(dian)(dian)(dian)芯(xin)(xin)導(dao)入量產(chan)階段后，對(dui)不同(tong)批次(ci)極(ji)(ji)(ji)片(pian)(pian)(pian)(pian)進行(xing)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)監(jian)(jian)控(kong)。如圖2（a）是對(dui)6個(ge)批次(ci)極(ji)(ji)(ji)片(pian)(pian)(pian)(pian)進行(xing)的(de)極(ji)(ji)(ji)片(pian)(pian)(pian)(pian)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)測試，黑(hei)色數(shu)(shu)據(ju)點(dian)代(dai)表單(dan)次(ci)測試電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)值，紅(hong)色數(shu)(shu)據(ju)點(dian)代(dai)表電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)均(jun)值，綠色數(shu)(shu)據(ju)點(dian)代(dai)表電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)COV。從(cong)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)數(shu)(shu)據(ju)可(ke)發現有3個(ge)批次(ci)電(dian)(dian)(dian)(dian)(dian)(dian)芯(xin)(xin)極(ji)(ji)(ji)片(pian)(pian)(pian)(pian)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)大于0.4Ω，明(ming)顯超出規格(ge)，進一(yi)步(bu)對(dui)正常(chang)和(he)(he)異常(chang)批次(ci)的(de)極(ji)(ji)(ji)片(pian)(pian)(pian)(pian)進行(xing)SEM形貌分(fen)析(xi)，如圖2（b）和(he)(he)2（c），正常(chang)批次(ci)極(ji)(ji)(ji)片(pian)(pian)(pian)(pian)中導(dao)電(dian)(dian)(dian)(dian)(dian)(dian)碳(tan)(tan)的(de)分(fen)布較均(jun)勻，而異常(chang)批次(ci)極(ji)(ji)(ji)片(pian)(pian)(pian)(pian)的(de)導(dao)電(dian)(dian)(dian)(dian)(dian)(dian)碳(tan)(tan)出現明(ming)顯的(de)團(tuan)聚現象，由于測試極(ji)(ji)(ji)片(pian)(pian)(pian)(pian)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)時是隨機選取極(ji)(ji)(ji)片(pian)(pian)(pian)(pian)不同(tong)位置，導(dao)電(dian)(dian)(dian)(dian)(dian)(dian)碳(tan)(tan)分(fen)布不均(jun)會導(dao)致無導(dao)電(dian)(dian)(dian)(dian)(dian)(dian)碳(tan)(tan)的(de)位置處(chu)極(ji)(ji)(ji)片(pian)(pian)(pian)(pian)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)明(ming)顯增大。因此，通過監(jian)(jian)控(kong)極(ji)(ji)(ji)片(pian)(pian)(pian)(pian)電(dian)(dian)(dian)(dian)(dian)(dian)阻(zu)(zu)(zu)的(de)變化(hua)可(ke)在極(ji)(ji)(ji)片(pian)(pian)(pian)(pian)端快速識別異常(chang)極(ji)(ji)(ji)片(pian)(pian)(pian)(pian)，避免不良極(ji)(ji)(ji)片(pian)(pian)(pian)(pian)流入下(xia)一(yi)工序，節約生產(chan)成本。

1.2 極片涂(tu)布(bu)均勻性監控

為(wei)了提(ti)升電池能量密度(du)，硅(gui)(gui)碳(tan)混合材料作為(wei)鋰(li)離子電池負極(ji)(ji)材料的(de)研究逐漸增多，如何控(kong)制硅(gui)(gui)碳(tan)混合材料在(zai)極(ji)(ji)片中的(de)分布(bu)(bu)均(jun)勻性對負極(ji)(ji)的(de)膨脹以及電位分布(bu)(bu)有(you)顯(xian)著影響(xiang)。監控(kong)不同工藝參數條件下極(ji)(ji)片電阻的(de)變化可評估硅(gui)(gui)碳(tan)材料混合均(jun)勻性。

如圖(tu)3是兩種混(hun)(hun)料工(gong)藝的(de)(de)極(ji)(ji)片(pian)進(jin)行(xing)的(de)(de)極(ji)(ji)片(pian)電(dian)(dian)(dian)阻(zu)(zu)測試和(he)SEM形貌表征結果。由圖(tu)3（a）可看(kan)出混(hun)(hun)料1的(de)(de)極(ji)(ji)片(pian)電(dian)(dian)(dian)阻(zu)(zu)均值和(he)COV均明(ming)顯(xian)高于混(hun)(hun)料2組(zu)，說明(ming)混(hun)(hun)料1的(de)(de)均勻性(xing)差于混(hun)(hun)料2 的(de)(de)極(ji)(ji)片(pian)。結合(he)圖(tu)3（b）和(he)3（c）SEM形貌分析可看(kan)出，混(hun)(hun)料1組(zu)極(ji)(ji)片(pian)中硅(gui)碳(tan)的(de)(de)混(hun)(hun)合(he)不(bu)均勻，有較(jiao)多單(dan)獨的(de)(de)硅(gui)顆粒存(cun)在(zai)，因此導(dao)致極(ji)(ji)片(pian)電(dian)(dian)(dian)阻(zu)(zu)均值增大，且不(bu)同位(wei)置處的(de)(de)極(ji)(ji)片(pian)電(dian)(dian)(dian)阻(zu)(zu)差異較(jiao)大，從而(er)電(dian)(dian)(dian)阻(zu)(zu)COV較(jiao)大，而(er)混(hun)(hun)料2組(zu)中硅(gui)碳(tan)混(hun)(hun)合(he)相對均勻，電(dian)(dian)(dian)阻(zu)(zu)的(de)(de)均值和(he)COV均較(jiao)小，進(jin)一步(bu)證明(ming)混(hun)(hun)料2對應的(de)(de)混(hun)(hun)料工(gong)藝較(jiao)好。

      本文使用的(de)四線(xian)法(fa)加可控(kong)壓(ya)雙圓盤電(dian)極的(de)方法(fa)測試極片(pian)(pian)電(dian)阻(zu)，能較好的(de)應用于(yu)監控(kong)極片(pian)(pian)工藝的(de)穩定(ding)性和(he)均勻性，且極片(pian)(pian)電(dian)阻(zu)數(shu)(shu)據(ju)(ju)可實(shi)(shi)時(shi)連接BIS或MES系(xi)統，實(shi)(shi)現數(shu)(shu)據(ju)(ju)的(de)可記(ji)錄(lu)、可追溯。目(mu)前已有(you)多家材料和(he)電(dian)池企(qi)業將(jiang)該(gai)方法(fa)導入(ru)產線(xian)工藝監控(kong)，對工藝參數(shu)(shu)及工藝穩定(ding)性進(jin)行快速有(you)效的(de)評估，將(jiang)電(dian)芯的(de)風險(xian)控(kong)制提前至極片(pian)(pian)端，加速鋰(li)離子電(dian)池研發(fa)和(he)生產進(jin)度(du)，滿足市(shi)場需(xu)求。