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隨著鋰離(li)子電(dian)池(chi)(chi)在手機、電(dian)腦、汽車(che)、儲能(neng)(neng)(neng)等領域的廣泛應(ying)用，人們對電(dian)池(chi)(chi)的安全(quan)性(xing)(xing)、能(neng)(neng)(neng)量密(mi)度(du)(du)和功率(lv)密(mi)度(du)(du)性(xing)(xing)能(neng)(neng)(neng)的需(xu)求(qiu)越來越高。為了(le)提高鋰離(li)子電(dian)池(chi)(chi)的能(neng)(neng)(neng)量密(mi)度(du)(du)和功率(lv)密(mi)度(du)(du)，一(yi)(yi)些鋰電(dian)新材料和新技術亟待開發(fa)。鋰離(li)子電(dian)池(chi)(chi)生(sheng)(sheng)產由多個工藝過(guo)程組成(cheng)，為了(le)得到安全(quan)可靠性(xing)(xing)高且性(xing)(xing)能(neng)(neng)(neng)一(yi)(yi)致(zhi)性(xing)(xing)好的電(dian)池(chi)(chi)，需(xu)要對每一(yi)(yi)個生(sheng)(sheng)產工藝制定嚴格的監控措施(shi)，確保(bao)不(bu)良品不(bu)流入市場。為了(le)節約生(sheng)(sheng)產成(cheng)本(ben)，提升生(sheng)(sheng)產效率(lv)，電(dian)池(chi)(chi)企(qi)業更加希望能(neng)(neng)(neng)在前工序(xu)階段就能(neng)(neng)(neng)快速識別出異常(chang)(chang)，及時做出相應(ying)改善措施(shi)。目前大多數(shu)(shu)電(dian)池(chi)(chi)企(qi)業在前工序(xu)常(chang)(chang)用的監控方法主要包括監控以(yi)下參數(shu)(shu)：漿(jiang)料黏度(du)(du)、漿(jiang)料固含量、涂(tu)布(bu)質量、壓實密(mi)度(du)(du)，這些方法雖然可以(yi)一(yi)(yi)定程度(du)(du)上監控出工序(xu)波動，但還不(bu)足以(yi)滿足監控成(cheng)品電(dian)芯一(yi)(yi)致(zhi)性(xing)(xing)的要求(qiu)。極(ji)(ji)片是電(dian)(dian)(dian)(dian)池前(qian)端工序的一個重要輸出，極(ji)(ji)片的電(dian)(dian)(dian)(dian)子電(dian)(dian)(dian)(dian)阻（電(dian)(dian)(dian)(dian)導率)影響全(quan)電(dian)(dian)(dian)(dian)池的功率性(xing)、可靠性(xing)及安全(quan)性(xing)，同時(shi)它(ta)又(you)與攪拌、涂布和輥(gun)壓工序息(xi)息(xi)相(xiang)關，因此(ci)，測量極(ji)(ji)片電(dian)(dian)(dian)(dian)阻的變化可以較好(hao)地評價(jia)極(ji)(ji)片制(zhi)(zhi)作(zuo)過程中電(dian)(dian)(dian)(dian)子導電(dian)(dian)(dian)(dian)網絡(luo)的性(xing)能，評估電(dian)(dian)(dian)(dian)極(ji)(ji)微觀結(jie)構的均勻性(xing)以及監控極(ji)(ji)片制(zhi)(zhi)作(zuo)工藝的穩定性(xing)，助力改(gai)進極(ji)(ji)片的配方(fang)以及攪拌、涂布和輥(gun)壓工藝的控制(zhi)(zhi)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(yong)的(de)方法(fa)是(shi)在兩探針法(fa)的(de)基礎上(shang)做(zuo)進(jin)一步改進(jin)，采用(yong)四線法(fa)加可(ke)控(kong)壓雙(shuang)圓(yuan)盤(pan)電(dian)極(ji)，測(ce)試極(ji)片電(dian)子電(dian)阻，監控(kong)涂布和輥壓工序極(ji)片電(dian)阻的(de)變(bian)化，將電(dian)芯的(de)風險(xian)控(kong)制提前至(zhi)極(ji)片端，從而(er)為(wei)鋰離(li)子電(dian)池研發和生產(chan)保駕護航。

1.1 極(ji)片批次穩定性監(jian)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)芯研發(fa)初期(qi)，通(tong)過(guo)對三元(yuan)極(ji)(ji)(ji)(ji)片(pian)電(dian)(dian)(dian)(dian)阻(zu)(zu)的大量(liang)測試(shi)和監(jian)控，初步(bu)制定正(zheng)常(chang)極(ji)(ji)(ji)(ji)片(pian)電(dian)(dian)(dian)(dian)阻(zu)(zu)范(fan)圍為0.2~0.4Ω，在電(dian)(dian)(dian)(dian)芯導(dao)入(ru)量(liang)產階段(duan)后(hou)，對不(bu)同批(pi)(pi)(pi)次極(ji)(ji)(ji)(ji)片(pian)進(jin)行電(dian)(dian)(dian)(dian)阻(zu)(zu)監(jian)控。如(ru)(ru)圖(tu)2（a）是對6個(ge)批(pi)(pi)(pi)次極(ji)(ji)(ji)(ji)片(pian)進(jin)行的極(ji)(ji)(ji)(ji)片(pian)電(dian)(dian)(dian)(dian)阻(zu)(zu)測試(shi)，黑(hei)色數(shu)據點代表單次測試(shi)電(dian)(dian)(dian)(dian)阻(zu)(zu)值，紅色數(shu)據點代表電(dian)(dian)(dian)(dian)阻(zu)(zu)均(jun)值，綠色數(shu)據點代表電(dian)(dian)(dian)(dian)阻(zu)(zu)COV。從電(dian)(dian)(dian)(dian)阻(zu)(zu)數(shu)據可(ke)(ke)發(fa)現(xian)有3個(ge)批(pi)(pi)(pi)次電(dian)(dian)(dian)(dian)芯極(ji)(ji)(ji)(ji)片(pian)電(dian)(dian)(dian)(dian)阻(zu)(zu)大于0.4Ω，明顯超出規(gui)格，進(jin)一(yi)步(bu)對正(zheng)常(chang)和異常(chang)批(pi)(pi)(pi)次的極(ji)(ji)(ji)(ji)片(pian)進(jin)行SEM形貌(mao)分(fen)析，如(ru)(ru)圖(tu)2（b）和2（c），正(zheng)常(chang)批(pi)(pi)(pi)次極(ji)(ji)(ji)(ji)片(pian)中導(dao)電(dian)(dian)(dian)(dian)碳(tan)(tan)的分(fen)布較均(jun)勻，而異常(chang)批(pi)(pi)(pi)次極(ji)(ji)(ji)(ji)片(pian)的導(dao)電(dian)(dian)(dian)(dian)碳(tan)(tan)出現(xian)明顯的團聚現(xian)象，由于測試(shi)極(ji)(ji)(ji)(ji)片(pian)電(dian)(dian)(dian)(dian)阻(zu)(zu)時是隨機選取極(ji)(ji)(ji)(ji)片(pian)不(bu)同位(wei)置，導(dao)電(dian)(dian)(dian)(dian)碳(tan)(tan)分(fen)布不(bu)均(jun)會導(dao)致無導(dao)電(dian)(dian)(dian)(dian)碳(tan)(tan)的位(wei)置處極(ji)(ji)(ji)(ji)片(pian)電(dian)(dian)(dian)(dian)阻(zu)(zu)明顯增大。因(yin)此(ci)，通(tong)過(guo)監(jian)控極(ji)(ji)(ji)(ji)片(pian)電(dian)(dian)(dian)(dian)阻(zu)(zu)的變(bian)化可(ke)(ke)在極(ji)(ji)(ji)(ji)片(pian)端快速識別異常(chang)極(ji)(ji)(ji)(ji)片(pian)，避免不(bu)良(liang)極(ji)(ji)(ji)(ji)片(pian)流入(ru)下一(yi)工序，節約生(sheng)產成(cheng)本。

1.2 極片(pian)涂布均勻性監控

為了提升電(dian)池能量密度，硅(gui)碳(tan)混(hun)(hun)合材(cai)(cai)料作為鋰離子(zi)電(dian)池負極材(cai)(cai)料的(de)(de)研究逐漸增多，如何控制硅(gui)碳(tan)混(hun)(hun)合材(cai)(cai)料在極片(pian)中的(de)(de)分(fen)布均(jun)勻性(xing)對負極的(de)(de)膨脹以及電(dian)位分(fen)布有顯(xian)著影(ying)響。監控不同工藝(yi)參數條件下(xia)極片(pian)電(dian)阻(zu)的(de)(de)變化可評估(gu)硅(gui)碳(tan)材(cai)(cai)料混(hun)(hun)合均(jun)勻性(xing)。

如圖3是兩種(zhong)混(hun)(hun)(hun)料(liao)(liao)工藝的(de)(de)(de)極(ji)片(pian)進(jin)行(xing)的(de)(de)(de)極(ji)片(pian)電(dian)(dian)阻(zu)測試和(he)(he)SEM形貌(mao)表征結果(guo)。由圖3（a）可(ke)看(kan)出(chu)混(hun)(hun)(hun)料(liao)(liao)1的(de)(de)(de)極(ji)片(pian)電(dian)(dian)阻(zu)均(jun)值和(he)(he)COV均(jun)明(ming)顯高于混(hun)(hun)(hun)料(liao)(liao)2組(zu)，說明(ming)混(hun)(hun)(hun)料(liao)(liao)1的(de)(de)(de)均(jun)勻性差于混(hun)(hun)(hun)料(liao)(liao)2 的(de)(de)(de)極(ji)片(pian)。結合(he)圖3（b）和(he)(he)3（c）SEM形貌(mao)分析可(ke)看(kan)出(chu)，混(hun)(hun)(hun)料(liao)(liao)1組(zu)極(ji)片(pian)中(zhong)硅碳(tan)(tan)的(de)(de)(de)混(hun)(hun)(hun)合(he)不均(jun)勻，有較(jiao)多單獨的(de)(de)(de)硅顆粒存(cun)在，因(yin)此導致(zhi)極(ji)片(pian)電(dian)(dian)阻(zu)均(jun)值增大(da)，且不同位置處的(de)(de)(de)極(ji)片(pian)電(dian)(dian)阻(zu)差異較(jiao)大(da)，從(cong)而(er)電(dian)(dian)阻(zu)COV較(jiao)大(da)，而(er)混(hun)(hun)(hun)料(liao)(liao)2組(zu)中(zhong)硅碳(tan)(tan)混(hun)(hun)(hun)合(he)相(xiang)對均(jun)勻，電(dian)(dian)阻(zu)的(de)(de)(de)均(jun)值和(he)(he)COV均(jun)較(jiao)小，進(jin)一步證明(ming)混(hun)(hun)(hun)料(liao)(liao)2對應(ying)的(de)(de)(de)混(hun)(hun)(hun)料(liao)(liao)工藝較(jiao)好。

      本(ben)文使(shi)用(yong)的(de)(de)四線法(fa)加可控壓雙圓盤電極(ji)的(de)(de)方(fang)法(fa)測試極(ji)片(pian)電阻，能(neng)較好的(de)(de)應(ying)用(yong)于監(jian)控極(ji)片(pian)工(gong)藝(yi)(yi)的(de)(de)穩定性和均(jun)勻性，且極(ji)片(pian)電阻數據(ju)可實時連(lian)接BIS或MES系統，實現(xian)數據(ju)的(de)(de)可記錄、可追溯。目前(qian)已(yi)有(you)多家(jia)材料和電池(chi)企業將該方(fang)法(fa)導入產(chan)線工(gong)藝(yi)(yi)監(jian)控，對工(gong)藝(yi)(yi)參數及(ji)工(gong)藝(yi)(yi)穩定性進行快速(su)有(you)效的(de)(de)評估，將電芯的(de)(de)風險控制提前(qian)至極(ji)片(pian)端，加速(su)鋰離子電池(chi)研發和生(sheng)產(chan)進度，滿足市場需(xu)求(qiu)。