2.3 退役電池容量衰減突變現(xiàn)象

在隨機循環(huán)測試的12支退役單體電池中， #1電池在循環(huán)過程中出現(xiàn)容量衰減突變?yōu)? mAh的現(xiàn)象。#1電池的初始放電容量為17.7 Ah，與新電池比，剩余容量為80.5%。在1243次循環(huán)之前，電池充放電容量與循環(huán)次數(shù)出現(xiàn)很好的線性關(guān)系，與#2～#4電池一樣，每發(fā)生一次容量衰減突變，都會伴隨有較為明顯的容量下降趨勢。在循環(huán)至1243次時，放電容量突然降至0.12 Ah，與新電池比，剩余容量為0.55%。此后繼續(xù)衰減至接近0 Ah，如圖8所示。

圖6 #4退役單體電池的容量循環(huán)曲線

Fig.6 Capacity fading acteristic for #4 retired power cell in ging/disging condition

圖7 #2～#4退役單體電池的容量衰減率曲線

Fig.7 Capacity fading rates for #2～#4 retired power cells in disging condition

圖8 #1退役單體電池循環(huán)容量衰減曲線

Fig.8 Capacity fading and it’s mutation acteristic for #1 retired power cell in ging/disging condition

#1退役電池的容量衰減率曲線見圖9，在循環(huán)至1242次之前，其衰減率平均為4.4%，且在1242次之前，容量衰減率與循環(huán)次數(shù)間保持較好的線性關(guān)系。循環(huán)至1243次及以后，容量衰減率突然增大近100%。

在本次抽樣實驗研究中，12支單體電池循環(huán)2000次左右后，僅#1電池出現(xiàn)了上述衰減突變現(xiàn)象，發(fā)生概率為8.3%。由此可見，退役電池性能衰減在2000次內(nèi)突變是不可預(yù)測的現(xiàn)象，但存在發(fā)生可能性，且發(fā)生概率不低。這種容量衰減突變現(xiàn)象對梯次利用儲能系統(tǒng)可靠運行是較大的挑戰(zhàn)，一方面需要研究電池容量跳水等性能衰減、突變預(yù)警技術(shù)，另一方面應(yīng)設(shè)計靈活的儲能系統(tǒng)電氣拓撲結(jié)構(gòu)，以便可以隔離突然失效電池所在支路，保證尚未失效支路可以正常工作。

圖9 #1退役單體電池容量衰減率曲線

Fig.9 Capacity fading rate for #1 retired power cell in disging condition

3 結(jié)論

(1)純電動大巴和純電動出租汽車兩類退役磷酸鐵鋰電池模塊容量測試結(jié)果表明，退役電池模塊間容量差均較為明顯，離散性突出，不利于電池重組。

(2)以退役單體電池為研究對象，抽樣測試了12支單體電池的循環(huán)性能，2000次充放電循環(huán)試驗數(shù)據(jù)表明，絕大多數(shù)退役電池仍具有較好的循環(huán)性能，其容量衰減與循環(huán)次數(shù)呈現(xiàn)明顯的線性關(guān)系，其容量衰減率不超過8%，具有較理想的梯次利用價值。

(3)退役單體電池2000次充放電循環(huán)試驗數(shù)據(jù)表明，個別退役電池存在容量突變?yōu)榱愕默F(xiàn)象，本文研究抽樣樣本中，其發(fā)生概率為8.3%。為保證退役電池儲能系統(tǒng)可靠性，應(yīng)針對性開展容量跳水預(yù)警技術(shù)研究。

作者：

趙光金1,2，邱武斌1,2

(1. 國網(wǎng)河南省電力公司電力科學(xué)研究院，河南省 鄭州市 450052;2. 國家電網(wǎng)公司電網(wǎng)廢棄物資源化處理技術(shù)實驗室，河南省 鄭州市 450052)

國家電網(wǎng)公司科技項目(52170217000L)。

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原標題:退役磷酸鐵鋰電池容量一致性及衰減特征研究