摘要:【目的】為了制備環(huán)保型的石墨烯基水性導(dǎo)電油墨,印刷高性能柔性電阻加熱器(flexible resistive heaters,F(xiàn)RHs),實(shí)現(xiàn)鋰離子電池的低溫?zé)峁芾?。【方法】采用球磨法制備石墨烯基水性?dǎo)電油墨;采用掃描電子顯微鏡和透射電子顯微鏡表征石墨烯及印刷圖案的形貌和結(jié)構(gòu);采用平板流變儀和四探針電阻儀表征炭黑含量對石墨烯基水性油墨流變性能和印刷圖案導(dǎo)電性能的影響;探討石墨烯基FRHs的響應(yīng)速率、熱穩(wěn)定性和力學(xué)性能,以及其在鋰離子電池低溫?zé)峁芾碇械膽?yīng)用。【結(jié)果】油墨的靜態(tài)黏度和黏度恢復(fù)率隨著炭黑含量的增加而增大,印刷圖案的電導(dǎo)率在炭黑質(zhì)量分?jǐn)?shù)為15%時(shí)達(dá)到最大,為20383 S/m;石墨烯基FRHs在8 V的低電壓下30 s快速達(dá)到150℃,能夠?qū)崿F(xiàn)120次的重復(fù)開關(guān)循環(huán),在72 h的持久運(yùn)行后溫度僅增加2. 54%,并且在2000次的彎折后溫度變化小于2. 1%。在電壓為6 V時(shí)將鋰離子電池從-30℃預(yù)熱至20℃,并在30 min內(nèi)實(shí)現(xiàn)80%的充電容量?!窘Y(jié)論】射流空化法產(chǎn)生的高剝離度、完好晶體結(jié)構(gòu)和較大橫向尺寸(1 μm)的石墨烯與填充于其中的炭黑使油墨具有合適的流變性,并在印刷圖案中構(gòu)建致密的導(dǎo)電通道,賦予FRHs優(yōu)異的性能。
關(guān)鍵詞:石墨烯;水性油墨;絲網(wǎng)印刷;柔性電阻加熱器;熱管理
中圖分類號(hào):TB34;TQ152文獻(xiàn)標(biāo)志碼:A
引用格式:
王友昌,張曉靜,朱宇薇,等. 石墨烯基水性導(dǎo)電油墨的制備及其在低溫?zé)峁芾碇械膽?yīng)用[J]. 中國粉體技術(shù),2024,30
(6):15-26.
WANG Youchang,ZHANG Xiaojing,ZHU Yuwei,et al. Preparation of graphene-based water-based conductive ink and its application in low-temperature thermal management[J]. China Powder Science and Technology,2024,30(6):15?26.
鋰離子電池因具有能量密度高、自放電率低、無記憶效應(yīng)和循環(huán)壽命長等優(yōu)點(diǎn)而成為便攜式電子產(chǎn)品和電動(dòng)汽車的主要電源[1-2],但低溫會(huì)導(dǎo)致其性能降低,甚至可能因充電引起的鋰枝晶造成內(nèi)部短路而導(dǎo)致熱失控,進(jìn)而引發(fā)火災(zāi)[3-4]。電阻加熱膜預(yù)熱是改善鋰離子低溫性能的有效方法[5-7],但是目前常用的金屬加熱膜因柔性差、密度大和不耐腐蝕而使其應(yīng)用受到限制[8-11]。石墨烯作為一種具有優(yōu)異的導(dǎo)電性、熱穩(wěn)定性、化學(xué)穩(wěn)定性和質(zhì)量輕等特點(diǎn)的納米材料,在制造柔性電阻加熱器(flexible resistive heaters,F(xiàn)RHs)方面具有巨大的應(yīng)用前景[12-13]。
絲網(wǎng)印刷通過使導(dǎo)電油墨透過圖案化的網(wǎng)版而沉積在基底上,而形成與圖案一樣的導(dǎo)電線路,是一種可規(guī)?;⒌统杀旧a(chǎn)FRHs的工藝,該工藝可以與各種柔性基底兼容,并適用于卷對卷工藝[14]。該工藝前提是設(shè)計(jì)出具有合適流變性能的高濃度石墨烯基導(dǎo)電油墨[15]。強(qiáng)疏水特性和π-π鍵的吸引,使石墨烯易于團(tuán)聚,因此常使用氧化石墨烯(graphene oxide,GO)和有機(jī)溶劑,如N-甲基吡咯烷酮(NMP)、N,N-二甲基甲酰胺(DMF)、丙酮和二甲基亞砜(DMSO)等制備石墨烯基導(dǎo)電油墨[16]。由于低電導(dǎo)率GO的后續(xù)還原過程有有毒物質(zhì)的參與,而且高沸點(diǎn)有機(jī)溶劑的使用也增加了后處理的時(shí)間和對人體的危害,因此,亟須開發(fā)石墨烯基水性導(dǎo)電油墨。
本文中采用水-乙醇-乙二醇三元混合溶劑制備石墨烯基水性導(dǎo)電油墨,使用乙醇和乙二醇作為助溶劑調(diào)節(jié)水的表面張力和沸點(diǎn),改善石墨烯的分散性,添加炭黑作為輔助導(dǎo)電填料,減小石墨烯之間的接觸電阻,深入探討炭黑對油墨的流變性和導(dǎo)電性能的影響,采用絲網(wǎng)印刷方法制備了石墨烯基FRHs,并研究了其電熱性能。
1材料與方法
1.1試劑材料和儀器設(shè)備
試劑材料:乙醇、乙二醇(分析純,上海阿拉丁生化科技股份有限公司);去離子水(一級(jí),北京科奧生物科技有限公司);濃硫酸(sulfuric acid,H2SO4,純度98%,北京藍(lán)弋化工產(chǎn)品有限責(zé)任公司);天然石墨薄片(純度≥99.8%,阿法埃莎化學(xué)有限公司);炭黑EC-600JD(純度≥98.4%,阿克蘇諾貝爾中國公司);水性聚氨酯(聚氨酯質(zhì)量分?jǐn)?shù)(32±5)%,深圳吉田化工有限公司);分散劑Disper 850(質(zhì)量分?jǐn)?shù)50%,深圳同泰化工科技有限公司);消泡劑NXZ(質(zhì)量分?jǐn)?shù)99%,圣諾普科);聚乙烯醇(polyvinyl alcohol,PVA,水解度為87.0%~89.0%,上海麥克林生化科技有限公司);羧甲基纖維素(carboxymethyl cellulose,CMC,相對分子質(zhì)量約為250000,分子取代度=0.7,1500~3100 mPa?s,上海麥克林生化科技股份有限公司);聚對苯二甲酸乙二醇酯薄膜(polyethylene terephthalate,PET,美國DuPont公司)。
儀器設(shè)備:LEO 1530VP型掃描電子顯微鏡(SEM,德國Zeiss公司);JEM-2010F型透射電子顯微鏡(TEM,日本JEOL公司);MCR92型流變儀(奧地利Anton Parr公司);KE-0.4L型行星式球磨機(jī)(啟東市宏宏儀器設(shè)備廠);LTA 6080型半自動(dòng)絲網(wǎng)印刷機(jī)(菱鐵(廈門)機(jī)械有限公司);Zennium Pro型電化學(xué)工作站(德國Zahner公司);HSV型拉力試驗(yàn)機(jī)(樂清市艾德堡儀器有限公司);CT2001A型藍(lán)電電池測試系統(tǒng)(武漢市藍(lán)電電子股份有限公司);eTM3060C型直流電源(北京北穩(wěn)電氣有限公司);Compact Pro型紅外熱成像相機(jī)(美國Seek Thermal公司)。
1.2石墨烯基水性油墨和FRHs的制備
1.2.1油墨的合成
石墨烯通過射流空化法制備[17]。將天然石墨薄片以初始質(zhì)量濃度為1 g/L分散到體積比為1:1的異丙醇和水的混合溶劑中,在射流空化裝置中處理1 h后,在轉(zhuǎn)速為500 r/min的條件下離心分離45min,然后將離心分離得到的上清液真空過濾,并在溫度為80℃下干燥24 h,即得到石墨烯。油墨制備示意圖如圖1所示。將黏合劑即水性聚氨酯以及包括分散劑Disper 850和消泡劑NXZ在內(nèi)的添加劑溶解在去離子水-乙醇-乙二醇的溶劑混合物中,得到聚合物溶液。然后將混合填料即石墨烯和炭黑以一定的比例加入到聚合物溶液中,在行星式球磨機(jī)中以575 r/min的轉(zhuǎn)速研磨10 h,得到均勻的分散體。最后,在分散體中加入增稠劑CMC,繼續(xù)研磨30 min,即可得到適合絲網(wǎng)印刷的高濃度石墨烯基水性油墨。其中溶劑、黏結(jié)劑(按有效成分計(jì))、導(dǎo)電填料、助劑在油墨中的質(zhì)量分?jǐn)?shù)分別為77.6%、4.8%、12%、5.6%,其中助劑為分散劑3.6%、消泡劑0.5%、CMC 1.5%。油墨中石墨烯和炭黑的質(zhì)量比見表1。
1.2.2FRHs的制備
在LTA6080絲網(wǎng)印刷機(jī)進(jìn)行絲網(wǎng)印刷。聚酯亞胺基底在真空抽吸的作用下緊貼在印刷機(jī)的基座上,帶有設(shè)計(jì)圖案的網(wǎng)版固定在基底上方約5 mm處。聚氨酯刮刀傾斜,與網(wǎng)版成60°夾角,并在速度為40 mm/s的條件下印刷。聚酯亞胺基底在印刷前經(jīng)電暈處理以增加印刷圖案的黏附力。干燥后的印刷薄膜在輥壓機(jī)上在溫度為60℃、速度為24 mm/s的條件下經(jīng)過輥壓后,裁剪成所需形狀,并在其兩端涂以導(dǎo)電銀漿用作電極,然后在100℃下干燥15 min。
1.3表征
采用SEM和TEM表征石墨烯的形貌和結(jié)構(gòu)。油墨的穩(wěn)態(tài)流變特性在25℃下使用MCR92流變儀表征,平行板的直徑為50 mm,間距為1 mm。平行板間的油墨在所有測試前都靜置5 min,以消除預(yù)剪切,并用一薄層硅油覆蓋油墨的邊緣,以防止水分蒸發(fā)。在0.1~1000 s-1的剪切速率下測量切變黏度。在3個(gè)區(qū)間(剪切速率為0.1 s-1測試60 s,剪切速率為100 s-1測試50 s,剪切速率為0.1 s-1測試200 s)內(nèi)進(jìn)行三區(qū)間觸變試驗(yàn)(three-interval thixotropy tests,3ITT)模擬絲網(wǎng)印刷過程以研究油墨的觸變行為。采用紅外熱成像相機(jī)和直流電源對石墨烯基RFHs進(jìn)行電熱測試和預(yù)熱鋰離子電池測試。
2結(jié)果與分析
2.1石墨烯表征
石墨烯的尺寸和質(zhì)量影響導(dǎo)電油墨及印刷圖案的性能。射流空化法制備石墨烯的SEM和TEM圖像如圖2所示。圖2(a)的SEM圖像表明,石墨烯的橫向尺寸在1~2 μm左右。圖2(b)中TEM圖像的透明性表明石墨烯的厚度較小。石墨烯層數(shù)通過高分辨率TEM圖像中片層的邊緣進(jìn)一步確定。如圖2(c)所示,圖2(b)方框區(qū)域的HRTEM圖像顯示石墨烯僅在邊緣處有一個(gè)條紋,因此是單層石墨烯[18]。從圖2(d)可以看出,石墨烯的電子衍射圖像呈規(guī)則的六角形對稱結(jié)構(gòu),表明石墨烯的結(jié)晶性在剝離過程中完整地保存下來[19]。這種剝離程度較高、晶體結(jié)構(gòu)保存完好、橫向尺寸較大的石墨烯表現(xiàn)出更加優(yōu)異的導(dǎo)電性能[17]。
2.2石墨烯基水性導(dǎo)電油墨的制備
首先研究炭黑含量對油墨流變性能的影響。油墨的黏度和觸變性隨炭黑含量的變化如圖3所示。從圖3(a)可以看出,所有油墨的黏度隨著剪切速率的增加而減小,表現(xiàn)出假塑性流體的性質(zhì),這有利于印刷的進(jìn)行。印刷前當(dāng)油墨靜置在網(wǎng)版上時(shí),較大的黏度阻止了油墨的流動(dòng),從而避免油墨透過網(wǎng)孔而污染基底;而印刷過程中高剪切速率使油墨的黏度減小,使其易于透過網(wǎng)孔而沉積在基底上,形成預(yù)期的圖案。另外,油墨的黏度隨著炭黑含量的增加而增大,這是因?yàn)閷?dǎo)電炭黑EC-600JD的比表面積大,含有大量的微孔,因此增加了分散的難度[20-21]。由圖3(b)可以看出,盡管所有油墨在剪切速率為100 s-1時(shí),黏度差異不大(1.1~1.2 Pa·s),然而當(dāng)印刷停止后黏度的恢復(fù)速率隨著炭黑含量的增加而增大。黏度的恢復(fù)速率決定了印刷停止后油墨的流平性能,恢復(fù)速率較小時(shí)流平性更好,能夠彌補(bǔ)印刷圖案中的缺陷,但恢復(fù)速率過小也會(huì)導(dǎo)致油墨在基底上暈染。當(dāng)恢復(fù)速率過大時(shí),油墨的流平性能不佳,造成印刷圖案的缺陷無法彌補(bǔ),降低圖案的導(dǎo)電性能。
其次研究炭黑含量對印刷圖案導(dǎo)電性能的影響。印刷圖案的電導(dǎo)率隨炭黑含量的變化如圖4所示。從圖中可以看出,油墨G-ink-15的電導(dǎo)率最大,約為2.04×104 S/m。
不同炭黑含量油墨印刷圖案的SEM圖像如圖5所示。由圖可知,未添加炭黑時(shí),石墨烯之間的剛性連接導(dǎo)致相鄰片層之間的間距較大,從而增大了接觸電阻。當(dāng)添加炭黑時(shí),炭黑納米粒子附著在石墨烯的邊緣,縮短了導(dǎo)電填料之間的距離。當(dāng)炭黑含量(質(zhì)量分?jǐn)?shù),下同)為15%時(shí),炭黑粒子恰好填充了石墨烯之間的孔隙,形成了完整的導(dǎo)電路徑,這也是油墨G-ink-15印刷圖案導(dǎo)電性能最佳的原因。當(dāng)炭黑含量繼續(xù)增加至25%時(shí),團(tuán)聚的炭黑粒子增大了石墨烯之間的距離,破壞了導(dǎo)電路徑,從而使電導(dǎo)率降低。
2.3石墨烯基柔性電阻加熱器的性能
絲網(wǎng)印刷可以在一次印刷中沉積厚膜,因此在大面積柔性電子設(shè)備的制造方面具有低成本和規(guī)?;膬?yōu)勢[22-23]。使用具有合適的流平性和最佳的電導(dǎo)率的G-ink-15印刷了石墨烯薄膜,經(jīng)過熱壓后組裝成FRHs。FRHs在不同電壓下的紅外圖像如圖6所示。從圖6(b)—(e)看出,F(xiàn)RHs在不同電壓下的熱圖像呈現(xiàn)出均勻的溫度分布,表明了印刷薄膜厚度的一致性和缺陷程度小,這是因?yàn)镚-ink-15合適的黏度恢復(fù)速率允許沉積在基底上的油墨有充分的時(shí)間流平、消除氣泡和填充孔洞。均勻性是FRHs的重要標(biāo)準(zhǔn),可以避免局部溫度過熱而導(dǎo)致其失效。
FRHs表面溫度與電壓的關(guān)系如圖7所示。從圖7(a)中看出,不論供應(yīng)電壓的大小,F(xiàn)RHs僅在30 s內(nèi)達(dá)到穩(wěn)態(tài)飽和溫度Tm。這種加熱時(shí)間不依懶于供應(yīng)電壓的快速響應(yīng)特征,源于FRHs較小的比熱容[12,24]。由于輸入電壓的增加,隨之輸入功率增加,因此FRHs的飽和溫度Tm也升高。當(dāng)輸入電壓(或功率密度)分別為2 V(0.06 W/cm2)、4 V(0.21 W/cm2)、6 V(0.45 W/cm2)、8 V(0.82 W/cm2)和9 V(1.05 W/cm2)時(shí),該柔性電阻加熱器的最高溫度分別約為39、64、103、150、191℃?;贕-ink-15絲網(wǎng)印刷制造的FRHs在低電壓下表現(xiàn)出的高穩(wěn)態(tài)飽和溫度和高響應(yīng)速率的特征,原因是它具有較大的電導(dǎo)率,這歸功于石墨烯與炭黑形成的致密導(dǎo)電路徑。此外,由圖7(b)可知,輸入電壓低于9 V時(shí),Tm與輸入的功率密度平方呈現(xiàn)良好的線性關(guān)系。而輸入電壓大于9 V時(shí)線性關(guān)系的偏離說明達(dá)到同樣的Tm需要更低的功率密度(或電壓),原因可能是薄膜中的聚合物在較高溫度下分解降低了FRHs的電阻[25],
這也體現(xiàn)在圖7(a)中電壓為9 V時(shí)FRHs飽和溫度的波動(dòng),以及圖6(f)的紅外圖像更高的中心溫度。
不同加熱條件下FRHs的附著強(qiáng)度如圖8所示。與未經(jīng)加熱的FRHs和在輸入電壓為8 V下加熱5h的FRHs相比,在輸入電壓為9 V下工作5 h的FRHs的附著強(qiáng)度明顯降低。雖然FRHs沒有被從基底上完全撕脫,但膠帶上黏附大量的導(dǎo)電填料,證實(shí)上文對聚合物分解的猜測。盡管如此,8 V的安全電壓(小于12 V)下實(shí)現(xiàn)150℃的穩(wěn)態(tài)溫度已經(jīng)可以滿足大多數(shù)的應(yīng)用場景。
為了充分理解石墨烯基的FRHs的溫度變化機(jī)制,對基于G-ink-15印刷的石墨烯基FRHs傳熱過程進(jìn)行了熱力學(xué)分析。時(shí)間依賴性的溫度曲線的3個(gè)階段,即溫度增長、穩(wěn)態(tài)、溫度衰減,遵循如下的方程式[11]:
式中:T0、Tm、Tf和Tt分別為FRHs的初始溫度、穩(wěn)態(tài)溫度、最終溫度和實(shí)時(shí)溫度;t為時(shí)間;Pd為FRHs的輸入功率密度;τg、τ d分別為特征增長時(shí)間常數(shù)、特征衰減時(shí)間常數(shù);h為對流及輻射傳熱系數(shù)。
環(huán)境溫度為25℃時(shí)FRHs的表面溫度的實(shí)驗(yàn)和擬合結(jié)果如圖9所示。溫度增長階段和溫度衰減階段擬合曲線與實(shí)驗(yàn)結(jié)果的高度一致,證明了理論預(yù)測的準(zhǔn)確性。擬合得到的特征參數(shù)列于表2中,較小的τg和τd值表明石墨烯基FRHs對輸入電壓的快速響應(yīng),即通電時(shí)的快速加熱和斷電時(shí)的快速冷卻行為。而較大的h值表明需要相對較高的輸入功率才能維持溫度的穩(wěn)定,這可能與石墨烯的輻射系數(shù)較高有關(guān)。
FRHs的耐用性和機(jī)械可靠性是決定其長期使用和不同場景適應(yīng)性的關(guān)鍵因素。FRHs的長期循環(huán)和力學(xué)性能如圖10所示。從圖10(a)看出,F(xiàn)RHs在重復(fù)2 h的120次開關(guān)循環(huán)過程中,表面溫度快速上升和下降,證明了其具有足夠的可重復(fù)性。為了進(jìn)一步表征FRHs的熱穩(wěn)定性,在電壓為8 V時(shí)連續(xù)監(jiān)測FRHs穩(wěn)態(tài)飽和溫度的變化,如圖10(b)所示,Tm在持續(xù)運(yùn)行約35 h后緩慢增加了1.47%,即使長達(dá)72 h時(shí)變化率也僅為2.54%。由圖10(c)可知,在角度為120°時(shí)重復(fù)彎曲2000次,F(xiàn)RHs表面溫度的時(shí)間依賴性曲線表現(xiàn)出了高度的重疊,而圖10(d)顯示穩(wěn)態(tài)溫度的波動(dòng)小于2. 1%。這些結(jié)果都表明,基于G-ink-15絲網(wǎng)印刷制造的石墨烯基柔性電熱器件具有良好的循環(huán)穩(wěn)定性和力學(xué)性能,擁有廣闊的應(yīng)用前景。
2.4石墨烯基FRHs在鋰離子電池低溫?zé)峁芾碇械膽?yīng)用
作為例證,石墨烯基FRHs被用于在低溫下預(yù)熱商用26650磷酸鐵鋰電池(額定容量為2.5 A·h)。
FRHs預(yù)熱鋰離子電池前后對比如圖11所示。由圖11(a)、(b)可知,電池在-30℃時(shí)的性能嚴(yán)重下降,當(dāng)以2 C(1 C表示電池1 h完全放電時(shí)的電流強(qiáng)度)的倍率采用恒流恒壓模式充電時(shí),電壓很快達(dá)
到3.6 V從而轉(zhuǎn)入涓流充電模式,最終充電容量只達(dá)到了額定容量的36%(0.9 A·h);而當(dāng)電池以5 C的倍率放電時(shí),瞬間達(dá)到截止電壓(2.0 V),這也說明-30℃時(shí)電池的功率能力受到嚴(yán)重限制。
如圖11(c)所示,當(dāng)使用FRHs在電壓分別為6、7、8 V時(shí)對電池進(jìn)行預(yù)熱,電池的表面溫度從-30℃升高到20℃分別用時(shí)為800、400、240 s,對應(yīng)的升溫速率是3.75、7.5、12.5℃/min。從圖11(d)中可以看出,預(yù)熱后的電池性能得以恢復(fù),能夠分別以2、5 C的倍率充電和放電,而且如圖11(e)所示,在6 V的預(yù)熱電壓下,電池在24.2 min(lt;30 min)實(shí)現(xiàn)了80%的充電容量(2.02 A·h),表現(xiàn)了快速充電的能力;而在預(yù)熱電壓為7 V時(shí)也實(shí)現(xiàn)了30 min內(nèi)達(dá)到64.8%的充電容量。二者的不同主要是因?yàn)榈偷念A(yù)熱速率有助于減小電池內(nèi)部的溫度梯度。如圖11(f)所示,與目前的常規(guī)預(yù)熱方法相比,基于G-ink-15絲網(wǎng)印刷的石墨烯基FRHs的加熱速率優(yōu)于其他文獻(xiàn)中報(bào)道的外部預(yù)熱方法,且能夠與內(nèi)部預(yù)熱方法媲美,因此有廣闊的低溫?zé)峁芾砬熬啊?/p>
3結(jié)論
1)以水-乙醇-乙二醇為三元混合溶劑成功制備了石墨烯基水性導(dǎo)電油墨。
2)炭黑的引入,增大了油墨的靜態(tài)黏度和恢復(fù)速率。當(dāng)炭黑含量為15%時(shí),印刷圖案的電導(dǎo)率達(dá)到最大,約為2.04×104S/m。此時(shí)石墨烯與炭黑形成致密導(dǎo)電通道,賦予其優(yōu)異的導(dǎo)電性能。
3)石墨烯基FRHs具有高影響速率,優(yōu)異的熱穩(wěn)定性和力學(xué)穩(wěn)定性。在電壓為8 V時(shí)的升溫速率為5℃/s,實(shí)現(xiàn)了120次的重復(fù)開關(guān)循環(huán)和長達(dá)72 h的持久運(yùn)行,并且在2000次的彎折后溫度變化僅小于2. 1%。
4)石墨烯基FRHs表現(xiàn)出了在低溫?zé)峁芾碇袘?yīng)用的廣闊前景,其在電壓為6 V時(shí)將鋰離子電池從-30℃預(yù)熱至20℃,并使其在30 min實(shí)現(xiàn)了80%的充電容量。
利益沖突聲明(Conflict of Interests)
所有作者聲明不存在利益沖突。
All authors disclose no relevant conflict of interests.
作者貢獻(xiàn)(Authors’Contributions)
王友昌和張曉靜進(jìn)行了方案設(shè)計(jì),王友昌、朱宇薇和李筱璐參與了樣品合成和表征,王友昌、張曉靜、劉宇航和沈志剛參與了論文的寫作和修改。所有作者均閱讀并同意了最終稿件的提交。
The study was designed by WANG Youchang and ZHANG Xiaojing. Sample synthesis and characterization were completed by WANG Youchang,ZHU Yuwei,and LI Xiaolu. The manuscript was written and revised by WANGYouchang,ZHANGXiaojing,LiuYuhang,andSHENZhigang. Allauthorshavereadthefinal version of the paper and consented to its submission.
參考文獻(xiàn)(References)
[1]申健,李麗,段廣彬. Ti3C2Tx基納米復(fù)合材料的制備及其鋰離子電池負(fù)極性能的改進(jìn)作用[J]. 中國粉體技術(shù),2021,27(5):134-140.
SHEN J,LI L,DUAN GB,et,al. Preparation of Ti3C2Tx-nanocomposites and its improvement of anode performance of lith-iumion battery:a review[J]. China Powder Science and Technology,2021,27(5):134-140.
[2]BOSE B,GARG A,PANIGRAHI BK,etal. Study on Li-ion battery fast charging strategies:review,challenges and pro-posed charging framework[J]. Journal of Energy Storage,2022,55:105507.
[3]曹賀,聞雷,郭震強(qiáng),等. 炭材料在低溫型磷酸鐵鋰材料中的應(yīng)用分析及展望[J]. 新型炭材料,2022,37(1):46-58. CAO H,WEN L,GUOZQ,etal. Application and prospects for using carbon materials to modify lithium iron phosphate materials used at low temperatures[J]. New Carbon Materials,2022,37(1):46-58.
[4]OSMANI K,ALKHEDHER M,RAMADAN M,et al. Recent progress in the thermal management of lithium-ion batteries[J]. Journal of Cleaner Production,2023,389:136024.
[5]WANGY,ZHANGX,CHENZ. Lowtemperature preheating techniquesforlithium-ion batteries:recent advances and future challenges[J]. Applied Energy,2022,313:118832.
[6]HU X,ZHENG Y,HOWEY DA,et al. Battery warm-up methodologies at subzero temperatures for automotive applications:recent advances and perspectives[J]. Progress in Energy and Combustion Science,2020,77:100806.
[7]LEI Z,ZHANG C,LIJ,et al. Preheating method of lithium-ion batteries in an electric vehicle[J]. Journal of Modern Power Systems and Clean Energy,2015,3(2):289-296.
[8]ZHANGJ,SUNF,WANGZ. Heating character of aLiMn2O4battery pack at low temperature based on PTC and metallic resistance material[J]. Energy Procedia,2017,105:2131-2138.
[9]HE F,LI X,ZHANG G,et al. Experimental investigation of thermal management system for lithium ion batteries module with coupling effect by heat sheets and phase change materials[J]. International Journal of Energy Research,2018,42(10):3279-3288.
[10]HUANGH,ZHOUZ,GAO L,et al. Investigation and optimization of fast cold start of 18650 lithium-ion cell by heating film-based heating method[J]. Energies,2023,16(2):750.
[11]WANG ZX,DU PY,LI WJ,et al. Highly rapid-response electrical heaters based on polymer-infiltrated carbon nano?tube networks for battery thermal management at subzero temperatures[J]. Composites Science and Technology,2023,231:109796.
[12]HUANG Z,LI S,GUO H,et al. Multi-scale GO/CNT/AlN nanocomposites for high-performance flexible electrothermal film heaters[J]. Journal of Materials Chemistry C,2023,11(29):9925-9936.
[13]童乾峰,劉清海,彭文聯(lián),等. 摻雜石墨烯粉末的靜電紡納米纖維薄膜的制備[J]. 中國粉體技術(shù),2023,29(2):130-138.
TONG QF,LIU QH,PENG WL,et,al. Preparation of electrospun nanofiber films doped with graphene powder[J]. China Powder Science and Technology,2023,29(2):130-138.
[14]LIANG J,JIANG C,WU W. Printed flexible supercapacitor:ink formulation,printable electrode materials and applica?tions[J]. Applied Physics Reviews,2021,8(2):021319.
[15]CHEN H,ZHANG Y,MA Y,et al. Sand-milling exfoliation of structure controllable graphene for formulation of highly conductive and multifunctional graphene inks[J]. Advanced Materials Interfaces,2021,8(1):2000888.
[16]TRAN TS,DUTTA NK,CHOUDHURY NR. Graphene inks for printed flexible electronics:graphene dispersions,ink
formulations,printing techniques and applications[J]. Advances in Colloid and Interface Science,2018,261:41-61.
[17]WANG Y,ZHANG X,LIU L,et al. A high-yield and size-controlled production of graphene by optimizing fluid forces[J]. Journal of Materials Science,2023,58(35):13946-13956.
[18]ZHAO Y,SHEN Z,ZHANG X. Exploring graphene and graphene/nanoparticles as fillers to enhance atomic oxygen corro?sion resistance of polyimide films[J]. Colloids and Surfaces A:Physicochemical and Engineering Aspects,2021,629:127398.
[19]MA H,SHEN Z,YI M,et al. Direct exfoliation of graphite in water with addition of ammonia solution[J]. Journal of Col?loid and Interface Science,2017,503:68-75.
[20]PANTEA D,DARMSTADT H,KALIAGUINE S,et al. Electrical conductivity of conductive carbon blacks:influence of surface chemistry and topology[J]. Applied Surface Science,2003,217(1/2/3/4):181-193.
[21]LIU L,SHEN Z,ZHANG X,et al. Highly conductive graphene/carbon black screen printing inks for flexible electronics[J]. Journal of Colloid and Interface Science,2021,582:12-21.
[22]KJAN S,LORENZELLI L,DAHIYA RS. Technologies for printing sensors and electronics over large flexible substrates:a review[J]. IEEE Sensors Journal,2015,15(6):3164-3185.
[23]PARK S,BAN S,ZAVANELLI N,et al. Fully screen-printed PI/PEG blends enabled patternable electrodes for scalablemanufacturing of skin-conformal,stretchable,wearable electronics[J]. ACS Applied Materialsamp;Interfaces,2023,15(1):2092-2103.
[24]CHANG H,JIA Y,XIAO L,et al. Three dimensional cross-linked and flexible graphene composite paper with ultrafast electrothermal response at ultra-low voltage[J]. Carbon,2019,154:150-155.
[25]LIU L,ZHANG X,MA H,et al. CuCl2-doped graphene-based screen printing conductive inks[J]. Science China Materials,2022,65(7):1890-1901.
Preparation of graphene-based water-based conductive ink and its application in low-temperature thermal management
WANG Youchanga,b,ZHANG Xiaojinga,b,ZHU Yuweia,b,LI Xiaolua,b,LI Yuhanga,SHEN Zhiganga,b a. School of Aeronautic Science and Engineering,b. Beijing Key Laboratory for Powder Technology Research and Development,Beihang University,Beijing 100191,China
Abstract
ObjectiveTraditional metal heating films used for preheating lithium-ion batteries are often inflexible,dense,and susceptible to corrosion. In contrast,graphene-based flexible resistive heaters(FRHs),produced through screen printing,demonstrate great potential due to their outstanding conductivity,stability,and lightweight properties. However,replacing toxic,high-boiling-point organic solvents with water remains asubstantial challenge. To address this,this paper prepares an environmen?tally friendly graphene-based ink using aternary mixed solvent composed of water,ethanol,and ethylene glycol.
MethodsHigh-quality graphene was initially prepared using the jet cavitation method,with its morphology and structure charac?terized by scanning electron microscopy(SEM)and transmission electron microscopy(TEM). A simple sand-milling method was then employed to produce graphene-based water-based ink with varying ratios of graphene and carbon black. A parallel-platerheometer and afour-probe resistivity meter were utilized to assess the rheological properties of the ink and the conductivity of the printed patterns. SEM was used to explore the mechanism by which carbon black influenced the conductivity of the printed patterns. Finally,graphene-basedFRHswerefabricatedthroughscreenprinting,andtheirelectrothermalpropertieswere tested. These FRHs were applied to low-temperature thermal management in lithium-ion batteries.
Results and DiscussionThe size and quality of graphene had asignificant impact on the rheological properties of the ink andthe conductivity of the printed patterns. Graphene produced through jet cavitation method exhibited large lateral sizes(~1 μm)and ahigh degree of exfoliation,as observed in TEM images. The symmetrical hexagonal patterns in electron diffraction imagesconfirmed its excellent crystallinity. These characteristics contributed to its superior conductivity due to minimal obstruction tocarrier mobility. However,the rigid connections between two-dimensional graphene sheets created numerous line contacts,lim?iting the full utilization of graphene’s specific surface area. Introducing zero-dimensional carbon black particles filled the voidsbetween graphene sheets,constructing adense conductive network that significantly enhanced conductivity by approximatelyseven times,from~3. 2×103S?m-1to~2. 04×104S?m-1. Additionally,the large specific surface area and structure of carbonblack increased the static viscosity of the ink while maintaining its viscosity(1. 1~1. 2 Pa·s)at ahigh shear rate(100 s-1),mak?ing it highly suitable for screen-printing process. Moreover,carbon black enhanced the post-printing viscosity recovery rate,optimizing leveling properties on the substrate. Results indicated that at 15%carbon black content,the ink exhibited optimalrheological properties,and the printed patterns achieved maximum conductivity of 20,383 S/m. FRHs prepared through screenprinting showed rapid voltage-independent response time,reaching 150℃within 30 seconds at alow voltage of 8 V,while main?taining uniform temperature distribution. The prepared FRHs could undergo120 repeated switching cycles,with only a 2. 54%temperatureincreaseafter72hoursof continuousoperationand less than2. 1%temperature variationafter2000bendingcycles. Theseresultsdemonstratedexcellentreliability,long-termstability,andmechanicalperformanceoftheprintedgraphene-based FRHs. When using FRHs to preheat lithium-ion batteries at voltages of 6 V,7 V,and 8 V,the battery surfacetemperature rose from-30℃to 20℃in 800,400,and 240 s,corresponding to heating rates of 3. 75,7. 5,and 12. 5℃·min-1,respectively. Preheated lithium-ion batteries could be charged and discharged at rates of 2 C and 5 C,respectively. At 6 V,thebattery achieved 80%state of charge(SOC)within 24. 2 minutes,and at 7 V,64. 8%SOC within 30 minutes. Graphene-basedFRHs screen-printed with G-ink-15 outperformed conventional external preheating methods and showed comparable perfor?mance to internal preheating methods.
ConclusionIn this paper,an environmentally friendly graphene-based water-based ink was successfully prepared using ater?nary mixed solvent of water,ethanol,and ethylene glycol. The ink exhibits excellent rheological properties and produces highly conductive printed patterns. The prepared FRHs demonstrate afast response time and outstanding stability,indicating signifi?cant potential for thermal management applications in lithium-ion batteries.
Keywords:graphene;water-based ink;screen printing;flexible resistive heater;thermal management
(責(zé)任編輯:王雅靜)