發(fā)布時(shí)間：2018-02-10 03:03

  本文關(guān)鍵詞： 快充 極化 電池制作工藝 改性 L333三元材料　出處：《江西理工大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：本文擬開發(fā)一種快充型鋰離子電池,以LiCoO2為正極材料,石墨為負(fù)極材料,設(shè)計(jì)400mAh的軟包電池,并分析了大電流充電條件下電池的電化學(xué)性能、電極材料結(jié)構(gòu)與形貌的變化規(guī)律、電池?zé)嵝?yīng)等。研究了電池制作工藝參數(shù)對(duì)快充性能的影響規(guī)律。另外,對(duì)L333-石墨的快充體系進(jìn)行了初步研究,重點(diǎn)研究了L333晶體形貌對(duì)快充性能的影響。通過充放電測(cè)試、交流阻抗(EIS)及電化學(xué)循環(huán)測(cè)試研究了鋰離子電池在大電流充電條件下的電化學(xué)性能變化規(guī)律,發(fā)現(xiàn)鋰離子電池在大電流充電過程中正負(fù)極存在較大的極化,嚴(yán)重影響電池的快充性能,減小極化能夠提高電池大電流充電性能,降低電池內(nèi)阻能夠有效減少電池電極極化現(xiàn)象,為此,研究了不同導(dǎo)電劑及其摻入比例、電池制作工藝等的對(duì)電池快充性能的影響。結(jié)果顯示:正負(fù)極配料制漿過程中,導(dǎo)電劑與電極活性物質(zhì)的均勻性與加入比例對(duì)電極電阻有影響,當(dāng)導(dǎo)電劑加入比例加入量在4%時(shí),電池綜合性能最佳。在0.2C電流作用下形成的SEI膜內(nèi)阻相對(duì)較小且穩(wěn)定,在一定程度上改善了極化程度,性能穩(wěn)定的SEI膜對(duì)后期循環(huán)性能具有很大的影響。電極材料的面密度越小,大電流充電時(shí)電池的極化越小,循環(huán)穩(wěn)定性較好,正極面密度為153g/m2時(shí),6C倍率充電循環(huán)1700次后容量保持率仍有80%。當(dāng)正極材料的壓實(shí)比為3.6g/cm3時(shí),電池的極化及內(nèi)阻最小,循環(huán)穩(wěn)定性能好。通過絕熱量熱測(cè)試儀(ARC)測(cè)試了大倍率充電情況電池的熱量變化及電池的比熱容,結(jié)果表明電池?zé)崛轂?.02J/(K*g),在6C充電時(shí)電池表面溫升為5℃±0.1℃,受溫度效應(yīng)影響,此時(shí)電池內(nèi)熱能夠提高電化學(xué)反應(yīng)效率,并無安全性影響。對(duì)循環(huán)前后電池電極材料進(jìn)行了X射線衍射(XRD)譜,掃描電子顯微分析,場(chǎng)發(fā)射透射電子顯微分析,結(jié)果表明,大電流充電作用下,循環(huán)1000次后,正極材料晶體結(jié)構(gòu)發(fā)生變化,(001)晶面間距變大,晶胞體積增大,結(jié)構(gòu)中存在鋰離子的缺失,產(chǎn)生晶格缺陷,晶化程度變低。負(fù)極材料的晶面間距變小,且循環(huán)后晶格條紋模糊,出現(xiàn)部分非晶化現(xiàn)象。正極材料粒度分布對(duì)電池影響電池快充性能。對(duì)比分析了不同粒徑正極材料的快充性能,結(jié)果表明減小正極材料顆粒粒度有利于提高電池倍率充電性能。負(fù)極材料的結(jié)構(gòu)特點(diǎn)也影響電池快充效率,研究了層狀石墨、球形石墨及中間相碳微球的快充性能。通過KOH溶液對(duì)層狀石墨負(fù)極處理改性后,電池在大電流(6C)充電時(shí)能量密度提高至128Wh/kg,循環(huán)1000次后容量保持率為80.3%。另外,研究了三元正極材料L333的快充性能,結(jié)果表明,顆粒較小的正極材料具有更好的倍率性能,使用改性后的石墨作為負(fù)極,6C充放條件下,將快充電池的能量密度提高至130wh/kg時(shí),循環(huán)1000次后容量保持80mAh/g。
[Abstract]:In this paper, a fast charging lithium-ion battery with LiCoO2 as cathode material and graphite as negative electrode material is developed, and a 400mAh soft-clad battery is designed. The electrochemical performance, structure and morphology of electrode material are analyzed under the condition of high current charging. The influence of battery fabrication process parameters on the rapid charging performance was studied. In addition, the effect of L333 crystal morphology on the rapid charge performance was studied, with emphasis on the effect of L333 crystal morphology on the rapid charge performance. Ac impedance spectroscopy (EIS) and electrochemical cycle measurements were used to study the electrochemical performance of lithium ion batteries under high current charging conditions. It was found that the positive and negative electrodes of lithium ion batteries were highly polarized during high current charging. The rapid charging performance of the battery is seriously affected, and the polarization reduction can improve the charging performance of the battery with high current and reduce the internal resistance of the battery, which can effectively reduce the polarization phenomenon of the battery electrode. Therefore, different conductive agents and their mixing ratios are studied. The results show that the homogeneity of conductive agent and electrode active material and the proportion of electrode active material have influence on electrode resistance in the process of batching process of positive and negative electrode. When the ratio of conductive agent is 4, the overall performance of the battery is the best. The internal resistance of SEI film formed under the action of 0.2C current is relatively small and stable, and the polarization degree is improved to a certain extent. The lower the surface density of the electrode material, the smaller the polarization of the battery under high current charge, and the better the cycle stability. When the positive electrode surface density is 153g / m ~ 2, the capacity retention rate is still 80 when the charge cycle is 1700 times. When the compaction ratio of the cathode material is 3.6 g / cm ~ 3, the polarization and internal resistance of the battery are minimum. The cycle stability is good. The heat change of the battery and the specific heat capacity of the battery are measured by the adiabatic calorimeter ARC. the results show that the heat capacity of the battery is 2.02J / L KG, and the surface temperature of the battery rises to 5 鈩，

本文編號(hào)：1499506