CAJ | 학술논문

橄榄石型LiFePO_4正极材料具有对环境友善、资源丰富、价格便宜和安全性能好等优点,被认为是非常具有发展前景的锂离子电池正极材料,然而由于自身晶体结构的本征特性,LiFePO_4的电导率低,高倍率充放电性能较差是限制其应用的最大障碍,通过碳包覆或金属离子掺杂等改性方法提高这种材料的电子导电率成为锂离子电池材料领域的研究热点.以提高电化学性能和更好的实现产业化为主要目的,对LiFePO_4材料的碳包覆和合成条件等进行了研究.以氧化铁为原料,采用碳热还原法合成锂离子电池正极材料LiFePO_4/C,利用扫描电镜和电化学性能测试方法对磷酸铁锂材料的表面形貌以及电性能进行分析研究,讨论了不同的煅烧温度、煅烧时间和掺碳量对材料电性能的影响.实验结果表明最佳合成工艺为:碳的包覆量为6%(质量分数),合成温度为720 ℃,保温时间为12 h,合成过程在惰性气氛下完成,合成的LiFePO_4/C复合正极材料在2.0～4.3 V,0.2 C倍率下的放电比容量可达160.56 mAh/g,0.5 C放电比容量可稳定在143 mAh/g左右,循环性能较好.
감람석형LiFePO_4정겁재료구유대배경우선、자원봉부、개격편의화안전성능호등우점,피인위시비상구유발전전경적리리자전지정겁재료,연이유우자신정체결구적본정특성,LiFePO_4적전도솔저,고배솔충방전성능교차시한제기응용적최대장애,통과탄포복혹금속리자참잡등개성방법제고저충재료적전자도전솔성위리리자전지재료영역적연구열점.이제고전화학성능화경호적실현산업화위주요목적,대LiFePO_4재료적탄포복화합성조건등진행료연구.이양화철위원료,채용탄열환원법합성리리자전지정겁재료LiFePO_4/C,이용소묘전경화전화학성능측시방법대린산철리재료적표면형모이급전성능진행분석연구,토론료불동적단소온도、단소시간화참탄량대재료전성능적영향.실험결과표명최가합성공예위:탄적포복량위6%(질량분수),합성온도위720 ℃,보온시간위12 h,합성과정재타성기분하완성,합성적LiFePO_4/C복합정겁재료재2.0～4.3 V,0.2 C배솔하적방전비용량가체160.56 mAh/g,0.5 C방전비용량가은정재143 mAh/g좌우,순배성능교호.
Olivine-structured LiFePO_4 is considered as a promising cathode material for lithium-ion batteries, due to its advantages such as environmentally friendliness, abundant raw materials, inexpensive price and high safety. However, it suffers from low conductivity and poor rate performance, which prevents it from commercial use. To improve the electrochemical performances of LiFePO_4 material, the synthesis condition, carbon coating, electrochemical behavior of LiFePO_4 as cathode materials were studied. The cathode material LiFePO_4 was synthesized by carbothermal method, using Fe_2O_3 as materials. The morphology and electrochemical performances were investigated by scanning electro microscope and electrochemical tests. The effects of synthesis time, temperature and carbon contents on electrochemical performances of LiFePO_4 material were discussed. In the experiment, the optimized synthesis condition was obtained. The amount of carbon in precursor compound was 6%, and the material was synthesized at 720 ℃ for 12 h under a flowing inert gas in the process. The results showed that the initial discharge capacity of LiFePO_4 was 160.56 mAh/g in 2.0-4.2 V and at 0.1C rate and 143 mAh/g at 0.5 C rate.