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鋰離子電池的不一致性會影響電池組的使用壽命，降低了電池成組后的性能。鋰電池成組不一致性是指單體電池的容量、電壓、內阻、自放電速率等參數存在差異，是由電池組的組合結構、使用工況、使用環境、電池管理不同所致。

單(dan)體(ti)電(dian)(dian)池(chi)成組(zu)后，循(xun)環壽(shou)命會(hui)有(you)所(suo)降低。選(xuan)用(yong)(yong)(yong)較長使(shi)用(yong)(yong)(yong)壽(shou)命的單(dan)體(ti)電(dian)(dian)池(chi)組(zu)合成電(dian)(dian)池(chi)組(zu)，會(hui)增加電(dian)(dian)池(chi)組(zu)循(xun)環使(shi)用(yong)(yong)(yong)次數，但為提升電(dian)(dian)池(chi)組(zu)整體(ti)性(xing)能(neng)，獲得更長使(shi)用(yong)(yong)(yong)壽(shou)命，還應(ying)重視單(dan)體(ti)電(dian)(dian)池(chi)匹配一(yi)致性(xing)，提供適宜的工作條件和(he)采用(yong)(yong)(yong)妥當熱管理(li)措(cuo)施，進(jin)行及時修復與保養。在分析鋰離子電(dian)(dian)池(chi)組(zu)不(bu)一(yi)致性(xing)成因基礎(chu)上，提出電(dian)(dian)池(chi)不(bu)一(yi)致性(xing)的改(gai)進(jin)措(cuo)施和(he)優化方法。

一、不一致性機理

1 單體電池之間參數差異

單(dan)體電(dian)(dian)池(chi)之間(jian)的(de)狀(zhuang)態差異(yi)主要包括單(dan)體電(dian)(dian)池(chi)初(chu)始(shi)差異(yi)和使用過程(cheng)中產生的(de)參(can)數(shu)差異(yi)。電(dian)(dian)池(chi)設計、制造、存(cun)儲以及使用過程(cheng)中存(cun)在多種不(bu)可控(kong)制的(de)因素，會影(ying)響(xiang)電(dian)(dian)池(chi)的(de)一致性(xing)。提(ti)高單(dan)體電(dian)(dian)池(chi)的(de)一致性(xing)是提(ti)升電(dian)(dian)池(chi)組(zu)性(xing)能的(de)先(xian)決(jue)條(tiao)件。單(dan)體電(dian)(dian)池(chi)參(can)數(shu)的(de)相互影(ying)響(xiang)，當前的(de)參(can)數(shu)狀(zhuang)態受初(chu)始(shi)狀(zhuang)態和時間(jian)累積作用的(de)影(ying)響(xiang)。

電池容量、電壓和自放電速率
電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)容(rong)量(liang)不(bu)一(yi)(yi)致(zhi)會使電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)組各(ge)單體電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)深度不(bu)一(yi)(yi)致(zhi)。容(rong)量(liang)較小、性(xing)能(neng)(neng)(neng)較差的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)將(jiang)(jiang)提(ti)前達到(dao)滿充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)狀態，造成容(rong)量(liang)大、性(xing)能(neng)(neng)(neng)好的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)不(bu)能(neng)(neng)(neng)達到(dao)滿充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)狀態。電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓的不(bu)一(yi)(yi)致(zhi)將(jiang)(jiang)導致(zhi)并聯電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)組中單體電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)互充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓較高的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)將(jiang)(jiang)給(gei)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓較低的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)充(chong)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)，這會加快電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)性(xing)能(neng)(neng)(neng)的衰減，損(sun)耗整(zheng)個電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)組的能(neng)(neng)(neng)量(liang)。自放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)速(su)率大的電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)容(rong)量(liang)損(sun)失大，電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)自放(fang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)速(su)率的不(bu)一(yi)(yi)致(zhi)將(jiang)(jiang)導致(zhi)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)荷電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)狀態、電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)壓產生差異(yi)，影響(xiang)電(dian)(dian)(dian)(dian)(dian)(dian)(dian)(dian)池(chi)(chi)(chi)(chi)組的性(xing)能(neng)(neng)(neng)。

電池內阻

串聯系統中，單體電池內阻差異將導致各個電池的充電電壓不一致，內阻大的電池提前達到電壓上限，此時其他電池可能未充滿電。內阻大的電池能量損耗大，產生的熱量高，溫度差異進一步增大內阻差異，導致惡性循環。

并聯系統中，內阻差異將導致各個電(dian)(dian)池電(dian)(dian)流(liu)的(de)不(bu)一致，電(dian)(dian)流(liu)大的(de)電(dian)(dian)池電(dian)(dian)壓(ya)變化快，使各個單體電(dian)(dian)池的(de)充放電(dian)(dian)深度不(bu)一致，造(zao)成系統的(de)實際容量值難以達到設(she)計值。電(dian)(dian)池工作電(dian)(dian)流(liu)不(bu)同(tong)，其性能在使用過程(cheng)中會產生差異，最終會影響整個電(dian)(dian)池組的(de)壽(shou)命。

2 充放電工況
充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)方(fang)(fang)式(shi)(shi)影響(xiang)鋰(li)電(dian)(dian)(dian)(dian)(dian)池組(zu)的(de)(de)(de)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)效(xiao)率和(he)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)狀(zhuang)態，過充(chong)(chong)(chong)(chong)(chong)(chong)過放(fang)都會(hui)(hui)損壞電(dian)(dian)(dian)(dian)(dian)池，多次充(chong)(chong)(chong)(chong)(chong)(chong)放(fang)電(dian)(dian)(dian)(dian)(dian)后電(dian)(dian)(dian)(dian)(dian)池組(zu)會(hui)(hui)顯露不一致(zhi)性。目前，鋰(li)離子(zi)電(dian)(dian)(dian)(dian)(dian)池充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)方(fang)(fang)式(shi)(shi)有(you)(you)數種，但(dan)常見(jian)的(de)(de)(de)有(you)(you)分(fen)段(duan)恒(heng)(heng)流(liu)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)方(fang)(fang)式(shi)(shi)和(he)恒(heng)(heng)流(liu)恒(heng)(heng)壓(ya)(ya)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)方(fang)(fang)式(shi)(shi)。恒(heng)(heng)流(liu)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)是(shi)較(jiao)為理(li)想的(de)(de)(de)方(fang)(fang)式(shi)(shi)，能夠進行(xing)安全(quan)、有(you)(you)效(xiao)的(de)(de)(de)滿充(chong)(chong)(chong)(chong)(chong)(chong)；恒(heng)(heng)流(liu)恒(heng)(heng)壓(ya)(ya)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)有(you)(you)效(xiao)結(jie)合了恒(heng)(heng)流(liu)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)和(he)恒(heng)(heng)壓(ya)(ya)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)的(de)(de)(de)優點，解決了一般恒(heng)(heng)流(liu)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)方(fang)(fang)式(shi)(shi)難(nan)以(yi)精準滿充(chong)(chong)(chong)(chong)(chong)(chong)的(de)(de)(de)問題，避(bi)免了恒(heng)(heng)壓(ya)(ya)充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)方(fang)(fang)式(shi)(shi)在充(chong)(chong)(chong)(chong)(chong)(chong)電(dian)(dian)(dian)(dian)(dian)初期電(dian)(dian)(dian)(dian)(dian)流(liu)過大對電(dian)(dian)(dian)(dian)(dian)池造成的(de)(de)(de)影響(xiang)，操作簡單方(fang)(fang)便(bian)。

3 溫度
鋰電(dian)(dian)池在高(gao)溫(wen)和高(gao)放電(dian)(dian)倍(bei)率下(xia)(xia)的性能會有(you)明顯衰減。這是因為鋰離(li)子電(dian)(dian)池在高(gao)溫(wen)條件下(xia)(xia)和大電(dian)(dian)流使(shi)用時(shi)，會造(zao)成(cheng)(cheng)正極活(huo)性物(wu)質和電(dian)(dian)解(jie)(jie)液的分解(jie)(jie)，這是放熱(re)過程，短時(shi)間(jian)放出等熱(re)量能導致電(dian)(dian)池自(zi)身溫(wen)度進(jin)一步升高(gao)，溫(wen)度升高(gao)又加速了分解(jie)(jie)現象，形成(cheng)(cheng)惡性循環，加速分解(jie)(jie)使(shi)電(dian)(dian)池性能進(jin)一步下(xia)(xia)降(jiang)。所(suo)以，如果電(dian)(dian)池組熱(re)管(guan)理不(bu)當，會帶來不(bu)可(ke)逆性能損(sun)降(jiang)。

電池組設計和使用環境差異會造成單體電池所處溫度環境不一致。由Arrhenius定律可知，電池的電化學反應速度常數與度呈指數關系，不同溫度下電池電化學特性不同。溫度會對電池電化學系統的運行、庫侖效率、充放電能力、輸出功率、容量、可靠性以及循環壽命產生影響。目前，主要開展的是溫度對電池組不一致性影響定量化研究。

4 電池外電路

連接方式
在規模儲能系統中，電池將以串并聯的方式組合在一起，因此在電池和模塊之間會有許多連接電路和控制元件。由于每個結構件或元器件的性能和老化速度不同，以及每個連接點消耗的能量不一致，不同器件對電池的影響不一樣，造成電池組系統的不一致。并聯電路中電池衰減速度的不一致會加速系統的惡化。
連接片阻抗也會對電池組的不一致性產生影響，連接片阻值不盡相同，極柱到各單體電池支路的阻值不同，遠離極柱的電池因連接片較長而阻值較大，電流則較小，連接片會使得與極柱相連的單體電池最先達到截止電壓，造成能量利用率降低，影響電池性能，而且該單體電池提前老化會導致與其相連的電池過充，造成安全隱患。
隨著電池循環次數增多，將造成歐姆內阻增加，容量衰減，歐姆內阻與連接片阻值的比率將發生變化。為保證系統安全性，必須考慮連接片阻值的影響。

BMS輸入電路
電池管理系統(BMS)是電池組正常運行的保障，但BMS輸入電路會對電池的一致性產生不利影響。電池電壓的監測方法有精密電阻分壓、集成芯片采樣等，這些方法由于電阻與電路板通路的存在，無法避免采樣線外載漏電流，電池管理系統電壓采樣輸入阻抗將增加電池荷電狀態(SOC)的不一致性，影響電池組的性能。

5 SOC估算誤差
SOC不一致產生的原因有單體電池初始標稱容量不一致和工作中單體電池標稱容量衰減速度不一致。對于并聯電路，單體電池的內阻差異會造成電流分配不均，進而導致SOC的不一致。SOC算法包括安時積分法、開路電壓法、卡爾曼濾波法、神經網絡法、模糊邏輯法、放電測試法等。
安時積分法在起始荷電狀態SOC0比較準確時有較好的精度，但是庫侖效率受電池荷電狀態、溫度和電流等狀態的影響較大，難以準確測量，因此安時積分法很難達到荷電狀態估計的精度要求。開路電壓法在較長時間靜置之后，電池的開路電壓與 SOC 存在確定的函數關系，通過測量端電壓來獲得SOC的估計值。開路電壓法具有估算精度高的優點，但是靜置時間長的缺點也限制了其使用范圍。


二、成組不一致性優化方法

1 單體電池制造技術

鋰電池材料
鋰離子電池的正極材料有三元材料、磷酸鐵鋰、鈷酸鋰和錳酸鋰等，負極材料有石墨、硅和鈦酸鋰等。同批次原材料對電池性能的一致性十分重要，在生產過程中，需要對原材料的粒徑分布、比表面積和雜質含量等參數進行嚴格的控制，保證原材料的批次一致性。

鋰離子電池生產工藝
電池的生產工藝由多個工序組成，每個工序過程都可能會影響電池的一致性。生產單體性能要一致，必須對每一個工序進行合理的設計和管控，使之平行重復。根據電池的性能要求設計電池生產工序，分析原材料、電極和電解液等參數對電池一致性的影響，從而合理控制各個工序參數的閾值。生產線減少人為干預，實現自動化也能提高電池的一致性。

2 分選制度
為了降低初始狀態差異對電池組的不利影響，通常需要對單體電池進行篩選，將狀態參數較為一致的電池組合在一起。電池成組方法主要有單參數配組法、多參數配組法和動態特性曲線配組法。動態特性曲線配組法通過比較同一倍率下不同電池間充放電曲線的差異，能夠很好地反映電池特性，分選效果理想。

3 電池組外電路

電池串并聯方式　　
電池組的連接方式影響電池一致性。目前有兩種較好的連接方式：先并聯兩個相同的電池為一個模塊，再將模塊串聯起來(PSB)；先串聯兩個不同的電池為一個模塊，再將模塊并聯起來(SPA)。

電池管理系統
為了提高電池的性能和使用壽命需要對單體電池進行管理和維護。電池管理系統是電池系統正常運行的重要保障，主要任務是保證電池組的性能，防止電池損壞，避免安全事故，使電池在適宜的區域內工作，延長壽命。BMS由傳感器、執行器、控制器和信號線等部分組成，主要功能有：數據采集、狀態估計、充放電控制、均衡充電、熱量管理、安全管理和數據通信等。
雖然電池管理技術已經被廣泛運用，但還需要繼續完善，尤其是在SOC的估算和數據采集精確度、均衡電路、電池快充等方面。由于不同類型的電池特性具有差異，適用于所有電池的BMS是目前的主要研究方向。

均衡控制
為了緩解甚至消除電池組中各單體電池間的不一致性，提高電池組的性能、壽命和安全性，通過均衡電路和均衡控制策略能夠有效地改善電池組的不一致性。
均衡電路拓撲結構：均衡電路拓撲結構的研究主要是對均衡電路結構進行設計與改進，提高均衡效率，降低成本。根據均衡電路在均衡過程中電路是否消耗能量可以分為能耗式均衡和非能耗式均衡。能耗式均衡電路采用耗能元件消耗電池組中電壓較高的電池電量，從而實現單體電池一致性，電路簡單，均衡速度快，效率高，但會導致電池組能量利用率不高；非能耗式電路利用儲能元件和均衡外電路來實現電池間的能量轉移，能量利用效率高，非能耗式均衡有開關電容式、變換器式和變壓器式。
均衡控制策略：均衡控制策略主要是確定均衡模塊的工作方式。目前，工作方式有最大值均衡法、平均值比較法和模糊控制法。均衡能力的提升是電池一致性研究的重要方向。均衡技術需進一步提高，包括：
(1)SOC 作為最理想的判斷標準，實時估測精度還需進一步提高；(2)優化均衡電路的拓撲結構，提升均衡速度，縮短均衡時間；(3)均衡控制策略還需要優化，確定最佳的均衡參數，根據均衡電路尋找合適的均衡路徑來達到快速均衡的目的。
現階段均衡控制策略的研究大多聚焦于均衡硬件電路設計與實現。但均衡電路參數會影響均衡效果。另外，均衡啟動時電池荷電狀態、均衡閾值、充放電電流、均衡電流與充放電電流比值以及充放電工況切換方式也會影響均衡效果。

4 充放電策略
科學、合理的充放電策略能夠提高電池能量利用效率。目前綜合性能最好的充電方法是電池管理系統和充電機協調配合串聯充電，通過BMS對電池組的環境溫度、單體電池的電壓和電流、一致性和溫升等狀態監控，與充電機實現數據共享，實時改變輸出電流，能夠防止電池過充和優化充電。這種充電方式是目前的主流，可一定程度消除鋰電池組充電時一致性差、充電效率低和無法滿充等問題。

5 電池熱管理
電池組中各單體電池的產熱量和散熱量在空間上分布不均，會造成電池自身、電池組部分區域及所處環境的溫度不一致，如不加以控制，電池組內部的溫差會持續擴大，進而加快電池性能衰降。因此，需要對電池組進行熱管理。
熱管理系統通常要求結構緊湊，質量輕，易于包裝，可靠，成本低，易于維護。它的功能有：使電池在最適宜的溫度范圍內運行；減小電池間、模組內和模組間的溫度差。熱管理分主動和被動兩種方式。系統中使用導熱介質可以分為三類，分別是空氣、液體和相變材料。
目前(qian)，電(dian)池(chi)組熱(re)管理研(yan)究(jiu)有局限性(xing)，比如電(dian)池(chi)熱(re)模型過于(yu)簡化，電(dian)池(chi)單體(ti)常采用零維(wei)的生熱(re)模型，電(dian)池(chi)各部(bu)分生熱(re)率(lv)相同(tong)，缺少(shao)基于(yu)非均勻內(nei)熱(re)源對(dui)不同(tong)熱(re)管理系(xi)統的性(xing)能對(dui)比。對(dui)鋰離子(zi)電(dian)池(chi)低溫特性(xing)研(yan)究(jiu)及(ji)低溫熱(re)管理技術研(yan)究(jiu)較少(shao)。