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對比等溫量熱及絕熱量熱用于鋰電池充放電產熱測量

  • 發布時間:2023-01-11
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等溫(wen)(wen)量(liang)熱儀和(he)絕(jue)熱加速量(liang)熱儀是研(yan)究鋰電(dian)(dian)池(chi)充放電(dian)(dian)產熱的兩種主流(liu)儀器。本文利用仰儀科技BIC-400A電(dian)(dian)池(chi)等溫(wen)(wen)量(liang)熱儀以及BAC-420A電(dian)(dian)池(chi)絕(jue)熱量(liang)熱儀在不(bu)同溫(wen)(wen)度和(he)不(bu)同倍率條件(jian)下(xia)對(dui)電(dian)(dian)池(chi)充放電(dian)(dian)產熱進(jin)行測試,總結(jie)了(le)兩種方法量(liang)熱結(jie)果對(dui)比的一般性(xing)規律。

前言

鋰離子(zi)電(dian)(dian)(dian)(dian)池在充(chong)放電(dian)(dian)(dian)(dian)過程中存在明顯(xian)的(de)熱(re)(re)效(xiao)(xiao)應,包括電(dian)(dian)(dian)(dian)極(ji)反應熱(re)(re)、極(ji)化熱(re)(re)、焦耳(er)熱(re)(re)和(he)副反應熱(re)(re)等[1]。這(zhe)些熱(re)(re)量(liang)(liang)(liang)(liang)使電(dian)(dian)(dian)(dian)池內部溫(wen)(wen)度(du)上(shang)升,一旦(dan)溫(wen)(wen)度(du)過高將影響電(dian)(dian)(dian)(dian)池性能(neng)和(he)壽命,甚至會導致電(dian)(dian)(dian)(dian)池發生(sheng)熱(re)(re)失控。因此,電(dian)(dian)(dian)(dian)池充(chong)放電(dian)(dian)(dian)(dian)產(chan)(chan)熱(re)(re)數據是(shi)進(jin)行(xing)電(dian)(dian)(dian)(dian)池熱(re)(re)管理(li)設計(ji)的(de)必要參數。目前,基于功率(lv)補(bu)償等溫(wen)(wen)量(liang)(liang)(liang)(liang)熱(re)(re)原理(li)的(de)等溫(wen)(wen)量(liang)(liang)(liang)(liang)熱(re)(re)儀(yi)和(he)基于絕(jue)(jue)(jue)熱(re)(re)追蹤原理(li)的(de)絕(jue)(jue)(jue)熱(re)(re)加速量(liang)(liang)(liang)(liang)熱(re)(re)儀(yi)是(shi)測(ce)量(liang)(liang)(liang)(liang)電(dian)(dian)(dian)(dian)池充(chong)放電(dian)(dian)(dian)(dian)產(chan)(chan)熱(re)(re)的(de)主要儀(yi)器(qi)。如圖(tu)1所(suo)示(shi),等溫(wen)(wen)量(liang)(liang)(liang)(liang)熱(re)(re)儀(yi)能(neng)夠控制電(dian)(dian)(dian)(dian)池溫(wen)(wen)度(du)保(bao)持恒定,并(bing)利用電(dian)(dian)(dian)(dian)功率(lv)對電(dian)(dian)(dian)(dian)池產(chan)(chan)熱(re)(re)功率(lv)進(jin)行(xing)等效(xiao)(xiao)補(bu)償;絕(jue)(jue)(jue)熱(re)(re)量(liang)(liang)(liang)(liang)熱(re)(re)儀(yi)能(neng)夠進(jin)行(xing)電(dian)(dian)(dian)(dian)池溫(wen)(wen)度(du)追蹤,獲得電(dian)(dian)(dian)(dian)池在充(chong)放電(dian)(dian)(dian)(dian)過程中的(de)絕(jue)(jue)(jue)熱(re)(re)溫(wen)(wen)升曲線和(he)比熱(re)(re)容數據,并(bing)計(ji)算產(chan)(chan)熱(re)(re)量(liang)(liang)(liang)(liang)。本文重點比較了兩種方法(fa)在量(liang)(liang)(liang)(liang)熱(re)(re)結果(guo)上(shang)的(de)差(cha)別性。

圖1 (a)等溫量熱儀和(b)絕熱加速量熱儀檢測原理

實驗部分

1. 樣品準備

18650電池(NCM,2000mAh)*2

方形電池(LFP,50Ah)*2
6061標準鋁塊

2. 實驗(yan)條件

絕熱量熱電池起始溫度:30°C;
等溫量熱電池溫度:30°C、50°C;
電池充放電方式:恒壓恒流充電、恒流放電;
充放電倍率:0.33C、0.5C、1C;
比熱容溫升速率(lv):0.2°C/min。

實驗結果

1. 電池比熱容實驗

圖2 電池比熱容測量結果

利用(yong)差式功率補(bu)償原(yuan)理,絕熱(re)量(liang)熱(re)儀可(ke)測(ce)(ce)定電(dian)池(chi)比熱(re)容的數據,本文根據電(dian)池(chi)充放(fang)電(dian)過程的溫度變化范圍,測(ce)(ce)定該(gai)溫區內的平(ping)均比熱(re)容,用(yong)于計算電(dian)池(chi)放(fang)熱(re)量(liang),測(ce)(ce)試結(jie)果如圖(tu)2所(suo)示(shi)。


2. 18650電池量熱結果

圖(tu)3 18650電(dian)池(chi)在(a,b)0.5C和(c,d)1C倍率下電(dian)池(chi)(a,c)充電(dian)和(b,d)放電(dian)產熱(re)功率測量(liang)結果對比


如(ru)圖3所示,等(deng)溫(wen)與(yu)絕(jue)熱(re)兩(liang)種儀器(qi)測(ce)(ce)定(ding)(ding)的(de)(de)產熱(re)功(gong)率變化趨勢基本一(yi)致,說(shuo)明上述兩(liang)種測(ce)(ce)試方法(fa)均能(neng)夠(gou)反映充放(fang)(fang)電過程中電池內阻和熵變系數變化規律(lv)。另外(wai),可(ke)以發現(xian)等(deng)溫(wen)量(liang)(liang)(liang)熱(re)測(ce)(ce)定(ding)(ding)熱(re)流的(de)(de)滯后性略大,這與(yu)等(deng)溫(wen)相(xiang)對復雜的(de)(de)裝樣(yang)方式有(you)關(guan)。30℃起始溫(wen)度(du)下充放(fang)(fang)電產熱(re)量(liang)(liang)(liang)的(de)(de)測(ce)(ce)量(liang)(liang)(liang)結(jie)果如(ru)表(biao)1所示,4種工步(bu)下等(deng)溫(wen)量(liang)(liang)(liang)熱(re)值(zhi)均高(gao)于(yu)絕(jue)熱(re)。0.5C和1C下電池的(de)(de)絕(jue)熱(re)溫(wen)升分別(bie)為15°C和30°C左右,在該范(fan)圍內,溫(wen)度(du)升高(gao)有(you)利于(yu)降(jiang)低電池極化內阻,減(jian)少電池產熱(re)。通過圖3也可(ke)以看出(chu),絕(jue)熱(re)法(fa)測(ce)(ce)定(ding)(ding)的(de)(de)功(gong)率曲線都介于(yu)30°C和50°C兩(liang)個溫(wen)度(du)條件下測(ce)(ce)定(ding)(ding)的(de)(de)等(deng)溫(wen)量(liang)(liang)(liang)熱(re)曲線之(zhi)間。


表1 18650電池充放電產(chan)熱量數據統計

3. 方形電池量熱結果

圖4  0.33C倍率下方形電池在(a)充電和(b)放電過程產熱功率測量結果對比

表2 0.33C倍率下等溫與絕熱測定的產熱量對比