1、直流內阻對磷酸鐵鋰電池的soc影響

在1C、5C、8C充(chong)電和放電情(qing)況下(xia)、持續(xu)5s測(ce)試(shi)的(de)(de)(de)(de)電池(chi)直流內(nei)(nei)(nei)阻(zu)(zu)隨soc的(de)(de)(de)(de)變化情(qing)況。可以看出，在較(jiao)低的(de)(de)(de)(de)sOc下(xia)（30%以下(xia)），電池(chi)直流內(nei)(nei)(nei)阻(zu)(zu)比(bi)較(jiao)高，在30~80%期間(jian)保持比(bi)較(jiao)平穩，之后，充(chong)電測(ce)試(shi)的(de)(de)(de)(de)直流內(nei)(nei)(nei)阻(zu)(zu)又(you)逐漸(jian)上升(sheng)，而放電測(ce)試(shi)的(de)(de)(de)(de)直流內(nei)(nei)(nei)阻(zu)(zu)仍保持比(bi)較(jiao)平穩。充(chong)電測(ce)試(shi)的(de)(de)(de)(de)直流內(nei)(nei)(nei)阻(zu)(zu)在sOC中間(jian)階段有(you)逐漸(jian)下(xia)降的(de)(de)(de)(de)趨勢，而放電測(ce)試(shi)的(de)(de)(de)(de)直流內(nei)(nei)(nei)阻(zu)(zu)有(you)逐漸(jian)上升(sheng)趨勢，與(yu)某(mou)些報道的(de)(de)(de)(de)情(qing)況并不相符(fu)，與(yu)采用的(de)(de)(de)(de)電池(chi)、實驗電流、持續(xu)時間(jian)以及(ji)測(ce)量誤差等有(you)關。

無論是放(fang)電(dian)(dian)(dian)(dian)還是充電(dian)(dian)(dian)(dian)，在30~80%sOC范(fan)圍(wei)內，電(dian)(dian)(dian)(dian)池(chi)的(de)(de)直流(liu)內阻(zu)相差不(bu)大(da)(da)。所(suo)以對(dui)對(dui)磷酸鐵鋰電(dian)(dian)(dian)(dian)池(chi)或電(dian)(dian)(dian)(dian)源系統的(de)(de)直流(liu)內阻(zu)的(de)(de)評價，應當選取此SOC范(fan)圍(wei)進行比(bi)較。而(er)30%、80%SOC作(zuo)為內阻(zu)變化的(de)(de)臨界點(dian)，可以為混合電(dian)(dian)(dian)(dian)動汽車(che)的(de)(de)控制作(zuo)為參考（混合電(dian)(dian)(dian)(dian)動車(che)電(dian)(dian)(dian)(dian)源系統應用SOC范(fan)圍(wei)一般在30~80%）。由于在此范(fan)圍(wei)內對(dui)磷酸鐵鋰電(dian)(dian)(dian)(dian)池(chi)直流(liu)內阻(zu)變化比(bi)較小，并且受電(dian)(dian)(dian)(dian)流(liu)、溫度等(deng)其(qi)他因素影響比(bi)較大(da)(da)，不(bu)適宜作(zuo)為soC判斷的(de)(de)依(yi)據。超(chao)出此范(fan)圍(wei)，電(dian)(dian)(dian)(dian)池(chi)放(fang)電(dian)(dian)(dian)(dian)/充電(dian)(dian)(dian)(dian)的(de)(de)極化電(dian)(dian)(dian)(dian)阻(zu)比(bi)較大(da)(da)，引起(qi)的(de)(de)電(dian)(dian)(dian)(dian)池(chi)內阻(zu)增大(da)(da)。

2、時間與直流內阻的關系

4C充電(dian)情況下0.1~0.9s內(nei)(nei)和1~10s內(nei)(nei)測(ce)試(shi)計算直流(liu)(liu)內(nei)(nei)阻。可(ke)以看出，無論充電(dian)還是放電(dian)測(ce)試(shi)，直流(liu)(liu)內(nei)(nei)阻對測(ce)試(shi)持續(xu)時間(jian)有強烈的(de)(de)依賴(lai)性，隨著持續(xu)時間(jian)的(de)(de)增(zeng)(zeng)加，直流(liu)(liu)內(nei)(nei)阻明(ming)顯(xian)加大(da)(da)(da)，但(dan)(dan)在不同(tong)時間(jian)段內(nei)(nei)，其增(zeng)(zeng)加的(de)(de)速率不同(tong)。在1s以內(nei)(nei)，直流(liu)(liu)內(nei)(nei)阻與測(ce)試(shi)持續(xu)時間(jian)呈良好的(de)(de)線(xian)性關系，不同(tong)SOC下（30~80%）的(de)(de)擬合曲線(xian)的(de)(de)斜(xie)(xie)率相(xiang)差不大(da)(da)(da)；但(dan)(dan)在1~10s內(nei)(nei)，隨著SOC的(de)(de)增(zeng)(zeng)大(da)(da)(da)，雖然曲線(xian)也呈較好的(de)(de)線(xian)性關系，但(dan)(dan)斜(xie)(xie)率的(de)(de)變化隨soc的(de)(de)增(zeng)(zeng)大(da)(da)(da)而(er)增(zeng)(zeng)大(da)(da)(da)。

4C放電(dian)情況(kuang)下0.1~0.9s和1~10s內(nei)測(ce)試(shi)的直流(liu)內(nei)阻(zu)，直流(liu)內(nei)阻(zu)隨測(ce)試(shi)時間也呈現較好(hao)的線性關系。在0.1~0.9s內(nei)，隨著sOC增大(da)，擬(ni)合曲線的斜率逐漸減(jian)小，1~10s內(nei)，斜率變化不大(da)。

這(zhe)種變(bian)(bian)化(hua)(hua)(hua)與(yu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)內(nei)(nei)部(bu)的(de)(de)反應有關。對電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)施(shi)加(jia)(jia)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)流后(hou)，引起(qi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓變(bian)(bian)化(hua)(hua)(hua)的(de)(de)首先是電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的(de)(de)歐姆(mu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)阻，瞬間(jian)使電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓上升（充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)）或(huo)下降（放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)），然后(hou)是電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)轉(zhuan)移阻抗引起(qi)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓降，最后(hou)是傳質(zhi)阻抗。在充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)測試(shi)過程中，隨著(zhu)SOC的(de)(de)增(zeng)(zeng)大(da)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)轉(zhuan)移阻抗增(zeng)(zeng)大(da)，所以擬合(he)曲線(xian)(xian)的(de)(de)斜(xie)率(lv)逐(zhu)漸增(zeng)(zeng)大(da)。在放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)過程中，隨著(zhu)SOC增(zeng)(zeng)大(da)，放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)的(de)(de)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)荷(he)轉(zhuan)移阻抗逐(zhu)漸減小，所以放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)期間(jian)的(de)(de)斜(xie)率(lv)隨SOc增(zeng)(zeng)加(jia)(jia)而逐(zhu)漸邊小。隨著(zhu)測試(shi)持續時間(jian)的(de)(de)增(zeng)(zeng)加(jia)(jia)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)內(nei)(nei)部(bu)傳質(zhi)阻抗逐(zhu)漸增(zeng)(zeng)加(jia)(jia)，并占據主導(dao)，內(nei)(nei)阻變(bian)(bian)化(hua)(hua)(hua)也(ye)不(bu)呈線(xian)(xian)性(xing)變(bian)(bian)化(hua)(hua)(hua)了。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)1C充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)和(he)放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)情況下6min內(nei)(nei)測試(shi)計(ji)算的(de)(de)直(zhi)流內(nei)(nei)阻（測試(shi)前后(hou)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)SOC增(zeng)(zeng)加(jia)(jia)或(huo)減小了10%）。其(qi)直(zhi)流內(nei)(nei)阻的(de)(de)變(bian)(bian)化(hua)(hua)(hua)曲線(xian)(xian)與(yu)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)的(de)(de)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)、放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓曲線(xian)(xian)非常接近。

由于對(dui)磷酸鐵鋰電(dian)池(chi)的(de)(de)(de)直流內阻(zu)(zu)對(dui)測(ce)試(shi)(shi)(shi)(shi)持續時(shi)(shi)間(jian)比(bi)較敏感(gan)，在(zai)(zai)進行電(dian)池(chi)或電(dian)池(chi)組(zu)直流內阻(zu)(zu)的(de)(de)(de)評價時(shi)(shi)，應根據實(shi)際應用(yong)情況來選擇測(ce)試(shi)(shi)(shi)(shi)的(de)(de)(de)持續時(shi)(shi)間(jian)。如對(dui)于混合電(dian)動車(che)來說，起(qi)啟動、加速時(shi)(shi)間(jian)一般在(zai)(zai)10s左(zuo)右，所(suo)以(yi)可以(yi)選擇10s的(de)(de)(de)持續時(shi)(shi)間(jian)進行比(bi)較。測(ce)試(shi)(shi)(shi)(shi)時(shi)(shi)間(jian)越短，越能體(ti)(ti)現(xian)電(dian)池(chi)或電(dian)池(chi)組(zu)的(de)(de)(de)歐姆電(dian)阻(zu)(zu)，但(dan)短的(de)(de)(de)測(ce)試(shi)(shi)(shi)(shi)持續時(shi)(shi)間(jian)受測(ce)試(shi)(shi)(shi)(shi)設備和數據采集響應誤差的(de)(de)(de)影(ying)響，也(ye)不能完全(quan)體(ti)(ti)現(xian)電(dian)池(chi)組(zu)的(de)(de)(de)實(shi)際應用(yong)性能，不宜作(zuo)為評價的(de)(de)(de)標(biao)準。但(dan)在(zai)(zai)實(shi)際應用(yong)中，利用(yong)較短時(shi)(shi)間(jian)內直流內阻(zu)(zu)的(de)(de)(de)測(ce)試(shi)(shi)(shi)(shi)可以(yi)判(pan)斷電(dian)池(chi)組(zu)內的(de)(de)(de)歐姆阻(zu)(zu)抗變化情況，進行故障診斷。

3、對(dui)磷(lin)酸鐵鋰(li)電(dian)池的電(dian)流與直流內(nei)阻的關系

在不(bu)同電(dian)流(liu)下(xia)測試對(dui)磷酸鐵鋰電(dian)池的充電(dian)和放電(dian)情況(kuang)下(xia)的直流(liu)內(nei)阻(zu)。隨著電(dian)流(liu)的增加，電(dian)池直流(liu)內(nei)阻(zu)有明顯的下(xia)降趨(qu)勢，當電(dian)流(liu)達到一定程度后(hou)，又會隨著電(dian)流(liu)的增加而上升(sheng)，主(zhu)要是由于(yu)電(dian)池內(nei)部的極化形(xing)式(shi)發生了變化。增大電(dian)流(liu)，電(dian)池內(nei)部傳質過程成(cheng)為控(kong)制步(bu)驟(zou)，電(dian)池內(nei)阻(zu)將開始增大。

對于對磷酸鐵鋰(li)電(dian)(dian)池或電(dian)(dian)源系(xi)統的(de)不同(tong)，應采(cai)用(yong)不同(tong)的(de)測試電(dian)(dian)流(liu)進(jin)(jin)行(xing)比較(jiao)(jiao)與評價，或者根據實際(ji)應用(yong)特征(zheng)進(jin)(jin)行(xing)電(dian)(dian)流(liu)的(de)選(xuan)擇，對于大容(rong)量(liang)動力(li)電(dian)(dian)池（混(hun)合電(dian)(dian)動客(ke)車(che)應用(yong)），適宜選(xuan)擇5C左右(you)的(de)電(dian)(dian)流(liu)，而混(hun)合電(dian)(dian)動轎車(che)應用(yong)的(de)小容(rong)量(liang)動力(li)電(dian)(dian)池，較(jiao)(jiao)適宜選(xuan)取10C左右(you)的(de)電(dian)(dian)流(liu)甚(shen)至更高。

4、電流(liu)與時間的(de)交互(hu)作用對對磷(lin)酸(suan)鐵(tie)鋰電池(chi)直(zhi)流(liu)內阻的(de)影響(xiang)

電(dian)(dian)流(liu)(liu)與時(shi)間的(de)(de)交(jiao)(jiao)(jiao)(jiao)互作用對(dui)對(dui)磷酸鐵鋰電(dian)(dian)池直流(liu)(liu)內(nei)(nei)阻(zu)的(de)(de)影響(xiang)非常明顯。1C、2C、充電(dian)(dian)情(qing)況下1~10s內(nei)(nei)直流(liu)(liu)內(nei)(nei)阻(zu)隨測(ce)試(shi)時(shi)間的(de)(de)變化(hua)情(qing)況，隨測(ce)試(shi)持續時(shi)間的(de)(de)延長，直流(liu)(liu)內(nei)(nei)阻(zu)逐漸加大(da)(da)，但變化(hua)幅度明顯不同。在(zai)1C情(qing)況下，不同SOC下的(de)(de)曲(qu)線(xian)無交(jiao)(jiao)(jiao)(jiao)叉點，同一(yi)測(ce)試(shi)時(shi)間下soc越(yue)大(da)(da)，直流(liu)(liu)內(nei)(nei)阻(zu)越(yue)低(di)，2C充電(dian)(dian)就有了較(jiao)明顯的(de)(de)交(jiao)(jiao)(jiao)(jiao)叉點，交(jiao)(jiao)(jiao)(jiao)叉點大(da)(da)約在(zai)7~8s左右。4C充電(dian)(dian)的(de)(de)交(jiao)(jiao)(jiao)(jiao)叉點就更(geng)為明顯了，約在(zai)4s。低(di)于(yu)4s，在(zai)同一(yi)測(ce)試(shi)時(shi)間下，隨sOC增(zeng)(zeng)大(da)(da)，電(dian)(dian)池直流(liu)(liu)內(nei)(nei)阻(zu)降低(di)，而(er)在(zai)此點之后，變化(hua)相反，sOC增(zeng)(zeng)大(da)(da)，直流(liu)(liu)內(nei)(nei)阻(zu)變大(da)(da)。即各(ge)曲(qu)線(xian)的(de)(de)斜率隨soc的(de)(de)增(zeng)(zeng)加而(er)增(zeng)(zeng)大(da)(da)。

這種(zhong)原因(yin)應(ying)當是對(dui)磷(lin)酸鐵(tie)鋰(li)電(dian)池(chi)內(nei)(nei)部的極化(hua)變(bian)化(hua)引起的。充電(dian)情況(kuang)下，sOC越(yue)大(da)，極化(hua)及極化(hua)變(bian)化(hua)率也越(yue)大(da)，因(yin)此曲線的斜率也越(yue)大(da)，反(fan)(fan)映到電(dian)池(chi)性能上就是sOC越(yue)大(da)電(dian)池(chi)充電(dian)接受能力越(yue)低(di)。這種(zhong)情況(kuang)也解釋了某些(xie)研究者測(ce)試(shi)直流內(nei)(nei)阻(zu)時出(chu)現(xian)隨SOC增大(da)直流內(nei)(nei)阻(zu)出(chu)現(xian)相反(fan)(fan)變(bian)化(hua)的原因(yin)。時間(jian)和電(dian)流的交(jiao)互作用引起的變(bian)化(hua)點與(yu)對(dui)磷(lin)酸鐵(tie)鋰(li)電(dian)池(chi)的類型、結構、設計(ji)、材(cai)料等各方(fang)面(mian)有關。