(中南大學 冶金科學與工程學院，長沙 410083)
摘 要: 以FeC2O4∙2H2O、NH4H2PO4、Li2CO3和乙炔黑為原料，采用兩步固相反應(yīng)法制備了高密度LiFePO4/C正極復(fù)合材料。利用差熱(DSC)，熱重(TGA)和X射線衍射(XRD)等分析手段具體探討了第一步固相反應(yīng)中可能存在的反應(yīng)過程和中間產(chǎn)物。利用掃描電鏡表征了復(fù)合材料LiFePO4/C中LiFePO4微粒形貌和接觸狀態(tài)。結(jié)果表明，乙炔黑的含量是影響LiFePO4微粒尺寸和微粒間接觸界面的重要因素。在一次熱處理的基礎(chǔ)上，二次球磨和燒結(jié)有利于第二次固相反應(yīng)過程中反應(yīng)物質(zhì)的接觸和傳質(zhì)，較一步固相法提高了生成的LiFePO4的振實密度。當乙炔黑的含量(質(zhì)量分數(shù))為0.1%~1.5%時，兩步固相法所制正極材料LiFePO4/C的振實密度可達到1.7 g/cm3，初次放電容量達到105 mA∙h/g。
關(guān)鍵字: 鋰離子電池；LiFePO4/C復(fù)合材料；正極材料；高密度；兩步固相反應(yīng)
（School of Metallurgical Science and Engineering, Central South University,Changsha 410083, China）
Abstract: High density LiFePO4/C composite cathode material was synthesized by two-step solid state reaction using raw materials FeC2O4∙2H2O, NH4H2PO4, Li2CO3 and acetylene black. The possible reactions and middle products in the first calcining process were investigated in detail by means of DSC, TGA and XRD. SEM was used to characterize the morphology and contiguity of LiFePO4 particles in LiFePO4/C composite material. The results show that the content of acetylene black is an important factor to influence the particle size of LiFePO4 and the contiguity between grains. Based on the first heat treatment, the second ball milling and calcining favor the osculation and mass transfer of the reactants in the second solid state reaction, and compared with one-step method, the density of resultant LiFePO4/C is ameliorated. With the residual acetylene black content(mass fraction) of 0.1%−1.5%, the tap density of LiFePO4/C prepared by two-step process reaches 1.7 g/cm3, and its initial discharge capacity approximates 105 mA∙h/g.
Key words: lithium ion battery; LiFePO4/C composite material; cathode material; high density; two-step solid state reaction
