第33卷第4期湖南大學(xué)學(xué)報(bào)(自然科學(xué)版)Vol 33, No 42006年8月Journal of Hunan University( Natural Sciences)Ar文章編號(hào):10002472(2006)04-009403LiFePo4合成工藝的優(yōu)化韓紹昌’,薄紅志,陳晗,于文志,范長(zhǎng)嶺,徐仲榆(湖南大學(xué)新型碳材料研究所,湖南長(zhǎng)沙410082)摘要:利用正交實(shí)驗(yàn)方法優(yōu)化固相反應(yīng)法制備 LiFePO的合成工藝.考察合成溫度、鋰鐵磷摩爾比、成型壓強(qiáng)及保溫時(shí)間等因素對(duì)材料電化學(xué)性能的影響.得到最佳工藝組合鋰鐵磷摩爾比1.05:1:1,合成溫度650℃,保溫時(shí)間18h,成型壓強(qiáng)0MPa.按最佳工藝合成樣品的首次放電容量為131.45mAh/g,庫(kù)侖效率為96.78%關(guān)鍵詞:正極; LiFePO;正交實(shí)驗(yàn);合成工藝中圖分類號(hào):TM911.1;O614.111文獻(xiàn)標(biāo)識(shí)碼:AOptimization of the Synthesis Technology of liFePO4haN Shao-chang, BO Hong-zhi, CHEN Han, YU Wen-zhi, FAN Chang-ling, XU Zhong-yuInstitute of New Carbon Material Research, Hunan Univ, Changsha, Hunan 410082, China)Abstract: The synthesis technology of LiFePO4 prepared through the solidnized with orthogonal tests. The influencing on the electrochemical properties of the material by four main factors( the synthesis temperature, molar ratio of lithium/iron/phosphorus, briquetting pressure and homothermaltime) was investigated. In the optimized synthesis technology, the molar ratio of lithium/iron/phosphorus was1. 05: 1: 1, the synthesis temperature was 650C, the homothermal time was 18 hours and no briquetting pressure was applied. The first discharge capacity of the optimized sample was 131 45mAh/, and its Coulombic ef-ficiency was 96.78%Key words: cathodes material; LiFePO4; orthogonal test; synthesis technology1997年 Goodenough小組1首先報(bào)道了一種具壓強(qiáng)等因素對(duì)材料電化學(xué)性能的影響;優(yōu)化出最佳有優(yōu)異的電化學(xué)性能、良好的環(huán)境相容性以及資源的合成工藝,合成出結(jié)晶良好、電化學(xué)性能優(yōu)異的豐富等突出優(yōu)點(diǎn)的新型鋰離子電池正極材料LiFe- LiFePOPO4.隨后人們對(duì) LiFePO4的合成及其工藝進(jìn)行了廣泛的實(shí)驗(yàn)研究2-6). Yamada等7發(fā)現(xiàn),在LFe實(shí)驗(yàn)部分PO4的合成過(guò)程中,合成溫度低于500℃時(shí)會(huì)殘存Fe3雜相,而溫度超過(guò)600℃時(shí)顆粒則很容易長(zhǎng)1.1正交實(shí)驗(yàn)表的選擇大迄今為止,尚未找到一種合成具有優(yōu)異電化學(xué)性以材料的首次充放電容量為考核指標(biāo),考察合能 LiFePo4的最佳工藝成工藝對(duì) LiFePO4容量的影響.以鋰鐵磷摩爾比本文通過(guò)固相反應(yīng)法合成 LiFePO4,以正交實(shí)合中國(guó)煤化T等4個(gè)對(duì)材料充放驗(yàn)法考察鋰鐵磷摩爾比、合成溫度保溫時(shí)間及成型電性CNMHG察對(duì)象每個(gè)因素收稿日期:2005-10-17課題資助項(xiàng)目作者簡(jiǎn)介:韓紹昌(1951-),男,湖南常德人,湖南大學(xué)教授博士生導(dǎo)師十通訊聯(lián)系人E-mail:hanse@hnu.cn第4期韓紹昌等: LiFePO4合成工藝的優(yōu)化設(shè)置3個(gè)水平(見(jiàn)表1)鐵磷摩爾比為1.00:1:1時(shí),因Li的損失而在材料表1因素水平表中會(huì)存在含F(xiàn)e雜相;當(dāng)鋰鐵磷摩爾比為1.10:1:1Tab 1 Factors and levels of orthogonal test時(shí),過(guò)多的鋰鹽會(huì)在材料中存留Li1O等雜相因而水平鋰鐵磷摩合成溫度/保溫時(shí)間/成型壓強(qiáng)/鋰鐵磷摩爾比為A2最好.合成溫度對(duì)材料容量的D爾比℃MPa影響最大.溫度過(guò)低不利于合成反應(yīng)進(jìn)行,材料中易1.00:1:1殘存雜相,溫度過(guò)高,顆粒容易長(zhǎng)大.根據(jù)Gode1.05:1:160nough小組11的容量損失假設(shè)及A.S. Andersson1.10:1:1750等9的容量損失模型,顆粒過(guò)大不利于得到優(yōu)異的電化學(xué)性能因而選擇合成溫度B2最好合成的保1.2材料制備高溫固相法合成 LiFePO4·稱取一定量的溫時(shí)間直接關(guān)系到材料顆粒的生長(zhǎng)時(shí)間過(guò)短,顆粒生長(zhǎng)不完善,缺陷多;時(shí)間過(guò)長(zhǎng),顆粒過(guò)于長(zhǎng)大;因而Li2CO3,FeC2O4·2H2O和NHH2PO,用瑪瑙研缽于確定保溫時(shí)間為C2最好合成材料之前將原料進(jìn)充Ar的手套箱內(nèi)研磨均勻,于管式爐內(nèi)Ar氣保護(hù)行一定程度的壓型,會(huì)使各原料間充分接觸,有利于下350℃預(yù)分解5h,再次研磨均勻后按L(34)正合成反應(yīng)的充分進(jìn)行;然而同時(shí)也會(huì)促進(jìn)顆粒的進(jìn)交實(shí)驗(yàn)表進(jìn)行合成熱處理一步長(zhǎng)大由圖1可以看出成型壓強(qiáng)選擇D1最好1.3結(jié)構(gòu)表征從而確定最佳工藝組合為A2B2C2D1,即鋰鐵磷摩采用西門子D500X射線衍射儀(CuKn,35爾比為105:1:1,合成溫度為650℃,保溫時(shí)間為kV,30mA)對(duì)樣品進(jìn)行物相及結(jié)構(gòu)分析掃描范圍18h,成型壓強(qiáng)為0MPa15°~45°,步長(zhǎng):0.02°,步進(jìn)時(shí)間:0.2s表2實(shí)驗(yàn)結(jié)果及極差分析1.4電化學(xué)測(cè)試Tab 2 Result and range analysis of the orthogonal test將 LiFePO4,乙炔黑和PTFE按質(zhì)量比75:2實(shí)驗(yàn)混合均勻后滾壓成厚度為0.1mm的薄片,取∮121.00:1:1105.54mm圓片為電極膜,以鋁網(wǎng)為集流體,金屬鋰片為對(duì)1.00:1:16501860122電極和參比電極, Celgard2400為隔膜,1mol·L100:11LiP6/EC+DMC為電解液,在充Ar手套箱內(nèi)組裝1.05:1:155018120105.631.05:1:1成三電極模擬電池.采用 Arbin bt2000電化學(xué)測(cè)1.05:1:16047,69試儀進(jìn)行充放電測(cè)試充放電電壓范圍為2.5~4.11.10:1:1V,充放電電流密度為10mA/g1.10:1:165012120111.72i1.10:1:1K1270.42311.85264.95279.962結(jié)果與討論K2273.54270.K3258.07136.00272.07259.99K190.14103.9583293.322.1正交實(shí)驗(yàn)結(jié)果的統(tǒng)計(jì)分析8K2120.9091.1890.20K386.02表2為正交試樣的電化學(xué)性能測(cè)試及極差分析R8.0075572.86結(jié)果.本實(shí)驗(yàn)的考核指標(biāo)D1(首次放電容量)越大越好.從表2中可以看出實(shí)驗(yàn)方案e具有最好的結(jié)果22驗(yàn)證實(shí)驗(yàn)利用極差R可以直觀地判斷各工藝因素對(duì)考察指按最佳工藝組合A2BCD1制備 LiFePO4(標(biāo)記標(biāo)的影響程度,并確定出最佳工藝組合.R越大因?yàn)闃悠稯)圖2為樣品O的XRD圖譜如圖所示,其素對(duì)容量的影響越大;反之亦然本實(shí)驗(yàn)中各因素對(duì)晶體結(jié)構(gòu)完整,結(jié)晶度高,不含雜相;其晶胞參數(shù)為a容量的影響程度大小順序?yàn)锽>A>D>C,不難發(fā),c=0.46908mm,V現(xiàn),合成溫度為最關(guān)鍵的工藝因素,原料配比和成型中國(guó)煤化工組的結(jié)果接近壓強(qiáng)次之,保溫時(shí)間對(duì)容量的影響程度最小樣品CNMH棋顆粒大小均勻,在對(duì)各因素不同水平測(cè)試結(jié)果的平均值做趨勢(shì)圖1m以下圖4為樣品O的第一循環(huán)充放電曲線,其(見(jiàn)圖1),可以直觀地找出各因素的最佳水平,并確首次放電容量為131.45mAh/g,庫(kù)侖效率為定最佳工藝組合.在合成過(guò)程中,L容易揮發(fā).當(dāng)鋰96.78%,與正交實(shí)驗(yàn)分析吻合湖南大學(xué)學(xué)報(bào)(自然科學(xué)版)2006年八3 BI2e/(圖1各因素不同水平測(cè)試結(jié)果均值趨勢(shì)圖圖2樣品O的XRD圖譜ig. 1 The tendency charts of the average values ofFig.2 The XRd pattern of samplehe test result from various factors and levels2.8150200250300容量/(mAhg-)圖4樣品O的第一循環(huán)充放電曲線ig. 4 The first charging-discharging curve of sample o圖3樣品O的SEM像Fig 3 The SEM of sample Oprecipitation and microwave heating[J].Electrochem. 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