本文選題：鋰離子電池 + 真空燒結(jié)法��； 參考：《昆明理工大學(xué)》2017年碩士論文

【摘要】：鋰離子電池不僅在各相關(guān)領(lǐng)域中得到廣泛應(yīng)用,在商業(yè)上也獲得了巨大的成功。本文采用真空燒結(jié)法合成LiFePO4/C正極材料,采用XRD、SEM以及室溫恒流充放電和交流阻抗等測試方法進(jìn)行表征,對比了不同的反應(yīng)條件對合成LiFePO4/C正極材料的形貌特征和電化學(xué)性能的影響。本文用碳酸鋰(Li2CO3)、草酸亞鐵(FeC2O4 2H2O)、磷酸二氫銨(NH4H2PO4)為原料,蔗糖作為碳源,經(jīng)過高能機(jī)械球磨,在氬氣和真空狀態(tài)的不同組合方式下,采用兩段式高溫固相燒結(jié)法,首先對比了合成LiFePO4/C復(fù)合正極材料的區(qū)別;然后通過改變碳源加入方式,預(yù)燒結(jié)時間,以及不同碳源包覆等因素,探討了合成LiFePO4/C的最佳條件。實驗結(jié)果表明:兩段燒結(jié)均在真空狀態(tài)下合成的LiFePO4/C正極材料比氬氣氣氛保護(hù)下合成的LiFePO4/C正極材料形貌規(guī)則顆粒細(xì)小,倍率和循環(huán)性能更好,并且減少了保護(hù)氣的消耗,降低生產(chǎn)成本。采用真空狀態(tài)下兩段固相燒結(jié)法,在前驅(qū)體中加入蔗糖作為碳源,經(jīng)350℃燒結(jié)5 h,再升溫到650℃燒結(jié)6 h合成的LiFePO4/C材料電化學(xué)性能最佳。該材料在0.2 C放電倍率下放電比容量為156.2 mAh g-1，，在1 C放電倍率下循環(huán)100次后有98.9%的容量保持率。為了進(jìn)一步減小能耗,采用真空狀態(tài)下一段高溫固相燒結(jié)法合成了 LiFePO4/C正極材料,分別討論燒結(jié)溫度,燒結(jié)時間以及碳包覆量對合成材料性能的影響。實驗結(jié)果表明:在真空狀態(tài)下用碳含量為7 wt%的前驅(qū)體,經(jīng)過650℃燒結(jié)6h合成的LiFePO4/C材料電化學(xué)性能最好,0.2 C放電倍率下放電比容量為154.5 mAh g-1,即使在1 C放電倍率下放電比容量為123.6 mAh g-1,且循環(huán)100次后具有98.3%的容量保持率。真空高溫?zé)Y(jié)法合成正極材料的過程含氧量很少,可以避免材料表面氧化問題。真空燒結(jié)法也具有燒結(jié)溫度低,燒結(jié)時間短,耗氣少等諸多優(yōu)點(diǎn),使之成為合成電極材料的有效方法。
[Abstract]:Lithium ion batteries have not only been widely used in various fields, but also achieved great commercial success. LiFePO4/C cathode materials were synthesized by vacuum sintering and characterized by room temperature constant current charge-discharge and AC impedance measurements. The effects of different reaction conditions on the morphology and electrochemical properties of synthesized LiFePO4/C cathode materials were compared. In this paper, lithium carbonate Li _ 2CO _ 3, FeC _ 2O _ 4 H _ 2O _ 4 H _ 2O _ 4, NH _ 4H _ 2PO _ 4) were used as raw materials, sucrose as carbon source, high energy mechanical ball milling, two-stage high temperature solid-state sintering method in argon and vacuum state. The differences of LiFePO4/C composite cathode materials were compared at first, and then the optimum conditions of LiFePO4/C synthesis were discussed by changing the carbon source addition mode, pre-sintering time, and different carbon source coating. The experimental results show that the LiFePO4/C cathode materials synthesized in vacuum state by two-stage sintering are smaller in shape, smaller in size and better in cycling performance than those synthesized in argon atmosphere, and the consumption of protective gas is reduced. Reduce production costs. The best electrochemical properties of LiFePO4/C were obtained by two-stage solid-state sintering in vacuum state, adding sucrose to the precursor as carbon source, sintering at 350 鈩

本文編號：1867344