锂离子电池Li-Mn-O系正极材料的制备和改性研究
发布时间：2018-11-27 15:19
【摘要】：锂离子电池由于其具备较高的比能量、较宽的工作温度、较长的储存寿命等特点,在各能源板块已经得到广泛的应用,如手机、便携式计算机、照相机、汽车、离微网及分布式电站等。本文主要聚焦于尖晶石型Li-Mn-O锂离子电池正极材料的研究,从合成工艺、包覆、掺杂材料的包覆等方面改善极具市场前景的锰基高电压正极材料的电化学性能,提升其市场竞争性,制备了球形多孔锰酸锂、磷酸锰锂包覆锰酸锂、磷酸钴锂包覆镍锰酸锂,并对其结构性能进行了测试表征,获得了有一定的创新性意义和价值的研究结论。具体内容如下:1、采用简单快速的乳液法结合沉淀破乳法和高温固相法制备了球形多孔锰酸锂,并通过多种手段对其结构、形貌、电化学性能进行了表征。通过XRD和SEM表明了合成前驱、中间体和成品的物相和形貌,探究了不同水相浓度对产物形貌的影响,再通过CV、EIS和电池循环性能测试探究了不同浓度水相对产物电化学性能的影响,得出如下结论:乳液中水相的Mn离子浓度会对成品的微观形貌和性能有一定的影响,水相离子浓度越高,得到的组成球形颗粒的纳米粒子越小,比表面积越大,对于材料的倍率性能有极大的改善,但是因为电解液与电极材料的接触面积变大,使得Mn2+的溶出变得严重,从而使得其循环性能不佳。低水相离子浓度的产物虽然倍率性能不佳,但是其容量和循环性能有不错的表现。2、通过常规沉淀法结合高温固相制备了球形锰酸锂,再通过一步水热法对LiMn_2O_4进行表面LiMnPO_4材料的包覆,得到了一种富含Mn2+包覆层的LMO覆合材料。该包覆层能有效的阻止Mn2+溶出到电解液中,抑制了LiMn_2O_4中Mn~(3+)的歧化反应,从而有效的改善了LMO材料的循环性能。从电化学测试数据中可以看出,不同包覆比例的LiMn_2O_4@3wt%LiMnPO_4和LiMn_2O_4@10wt%LiMnPO_4在不同倍率循环测试的电化学性能都要优于纯的LiMn_2O_4。此外,由于低价锰在电极表面的存在,LiMn_2O_4的离子和电子导通能力得到改善,从而导致了材料的倍率性能得到改善。因此,稳定的富含Mn2+的材料作为LiMn_2O_4的包覆层能有效的改善LiMn_2O_4的电化学性能。3、通过共沉淀结合高温固相法制备球形多孔LiNi_(0.5)Mn_(1.5)O_4颗粒,再通过常规水热法将LiCoPO_4生长在LiNi_(0.5)Mn_(1.5)O_4颗粒表面,借助SEM和HRTEM确定了材料的形貌及包覆结构的形成,通过XRD和XPS确定了包覆层为LiCoPO_4。通过对四个样品的XPS、CV和电池充放电分析,证实了包覆层LCP能在LCP和LNM界面上激发出Mn~(3+),Mn~(3+)含量随着LCP量的增加而增加。而EIS和GITT测试则进一步说明了出现的Mn~(3+)对于材料导电性和锂离子迁移能力的作用,其增加了LNM中Ni/Mn混排度从而极大的改善LNM的导电性和锂离子迁移能力。从电池循环性能上看,Mn~(3+)的出现对于材料的倍率性能有着重要的提高。LCP作为包覆层的作用还体现在两点:一是有效的阻止了Mn~(3+)歧化反应生成的可溶性Mn2+溶出到电解液中,二是有效的减少了电解液中LiPF6的分解和在电极表面的副反应,这两点确保了复合材料的循环性能得到了显著的提高。在实验中发现,适量包覆层的LNM@5%LCP样品呈现出最佳的电化学性能,在0.5C充放电倍率下,初始放电容量为128mAh g-1,循环100圈后,容量保持率为初始容量的96%。在20C的充放电倍率下,初始充放电容量为115 mAh g-1,远远高于纯LNM的57 mAh g-1。
[Abstract]:As a result of its high specific energy, wide operating temperature and long storage life, Li-ion battery has been widely used in various energy sectors, such as mobile phone, portable computer, camera, automobile, off-grid and distributed power station. The paper mainly focuses on the research of the cathode material of the spinel Li-Mn-O lithium ion battery, and improves the electrochemical performance of the manganese-based high-voltage cathode material with the market prospect from the aspects of the synthesis process, the coating, the coating of the doping material and the like, improves the market competitiveness, and prepares the spherical porous lithium manganate, Lithium manganese phosphate, lithium nickelate and lithium cobalt phosphate are used to coat the lithium manganate, and the structural properties of the lithium manganese phosphate are tested and characterized, and the research conclusion with certain innovative significance and value is obtained. The following contents are as follows: 1. The spherical porous lithium manganate is prepared by a simple and rapid emulsion method in combination with a precipitation demulsification method and a high-temperature solid phase method, and the structure, the morphology and the electrochemical performance of the spherical porous lithium manganate are characterized by a plurality of means. The influence of different water phase concentration on the product morphology was investigated by means of XRD and SEM. The effects of different water phase concentration on the product morphology were investigated. The effects of different concentrations of water on the electrochemical performance of the product were investigated by CV, EIS and battery cycle performance test. The following conclusions were drawn: The Mn ion concentration of the water phase in the emulsion has a certain influence on the micro-morphology and the performance of the finished product, the higher the ion concentration of the water phase, the smaller the nano-particles of the obtained spherical particles, the larger the specific surface area, and greatly improves the rate performance of the material, However, because the contact area of the electrolyte and the electrode material becomes large, the dissolution of the Mn2 + becomes severe, so that the cycle performance thereof is not good. Although the product of low water phase ion concentration is not good, its capacity and cycle performance are good. 2. The spherical manganese acid lithium is prepared by conventional precipitation method in combination with high-temperature solid phase, and the surface LiMn _ 2O _ 4 is coated with LiMn _ 2O _ 4 by one-step hydrothermal method. and a LMO cladding material rich in Mn2 + cladding layer is obtained. The coating layer can effectively prevent Mn2 + from being dissolved in the electrolyte, and the disproportionation reaction of Mn to (3 +) in the LiMn _ 2O _ 4 is inhibited, so that the cycle performance of the LMO material is effectively improved. It can be seen from the electrochemical test data that the electrochemical performance of the LiMn_2O_4@3wt% LiMnPO _ 4 and the LiMn_2O_4@10wt% LiMnPO _ 4 with different coating ratios is better than that of the pure LiMn _ 2O _ 4. In addition, because of the presence of low-cost manganese on the electrode surface, the ion and electron-conduction ability of the LiMn _ 2O _ 4 is improved, resulting in an improvement in the rate performance of the material. Therefore, the stable Mn 2 +-rich material can effectively improve the electrochemical performance of LiMn _ 2O _ 4 as the coating of LiMn _ 2O _ 4. 3. The spherical porous LiNi _ (0.5) Mn _ (1.5) O _ 4 particles are prepared by co-precipitation and high-temperature solid phase method, and the LiCoPO _ 4 is grown on the surface of LiNi _ (0.5) Mn _ (1.5) O _ 4 particles by conventional hydrothermal method. The morphology of the material and the formation of the coating structure were determined by means of SEM and HRTEM, and the cladding layer was LiCoPO _ 4 by XRD and XPS. The content of Mn ~ (3 +) and Mn ~ (3 +) in the LCP and LNM interface can be increased with the increase of the LCP, by analyzing the XPS, CV and charge-discharge of the four samples. The EIS and GITT test further illustrate the effect of Mn ~ (3 +) on the conductivity of the material and the capacity of the lithium ion mobility, which increases the mixed degree of Ni/ Mn in the LNM so as to greatly improve the conductivity and the lithium ion mobility of the LNM. The appearance of Mn ~ (3 +) has an important effect on the rate performance of the material from the battery cycle performance. The effect of the LCP as the cladding layer is also shown at two points: one is effective to prevent the soluble Mn2 + dissolved in the Mn-(3 +) disproportionation reaction to be dissolved in the electrolyte, and the second is to effectively reduce the decomposition of the LiPF6 in the electrolyte and the side reaction on the surface of the electrode, These two points ensure a significant improvement in the cycle performance of the composite. In the experiment, the optimum electrochemical performance of the LNM@5% LCP sample was found, and the initial discharge capacity was 128mAh g-1 at the charge/ discharge rate of 0.5C, and the capacity retention rate was 96% of the initial capacity after 100 cycles. At the charge/ discharge rate of 20C, the initial charge/ discharge capacity was 115 mAh g-1, much higher than that of the pure LNM of 57 mAh g-1.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912
本文编号：2361267
[Abstract]:As a result of its high specific energy, wide operating temperature and long storage life, Li-ion battery has been widely used in various energy sectors, such as mobile phone, portable computer, camera, automobile, off-grid and distributed power station. The paper mainly focuses on the research of the cathode material of the spinel Li-Mn-O lithium ion battery, and improves the electrochemical performance of the manganese-based high-voltage cathode material with the market prospect from the aspects of the synthesis process, the coating, the coating of the doping material and the like, improves the market competitiveness, and prepares the spherical porous lithium manganate, Lithium manganese phosphate, lithium nickelate and lithium cobalt phosphate are used to coat the lithium manganate, and the structural properties of the lithium manganese phosphate are tested and characterized, and the research conclusion with certain innovative significance and value is obtained. The following contents are as follows: 1. The spherical porous lithium manganate is prepared by a simple and rapid emulsion method in combination with a precipitation demulsification method and a high-temperature solid phase method, and the structure, the morphology and the electrochemical performance of the spherical porous lithium manganate are characterized by a plurality of means. The influence of different water phase concentration on the product morphology was investigated by means of XRD and SEM. The effects of different water phase concentration on the product morphology were investigated. The effects of different concentrations of water on the electrochemical performance of the product were investigated by CV, EIS and battery cycle performance test. The following conclusions were drawn: The Mn ion concentration of the water phase in the emulsion has a certain influence on the micro-morphology and the performance of the finished product, the higher the ion concentration of the water phase, the smaller the nano-particles of the obtained spherical particles, the larger the specific surface area, and greatly improves the rate performance of the material, However, because the contact area of the electrolyte and the electrode material becomes large, the dissolution of the Mn2 + becomes severe, so that the cycle performance thereof is not good. Although the product of low water phase ion concentration is not good, its capacity and cycle performance are good. 2. The spherical manganese acid lithium is prepared by conventional precipitation method in combination with high-temperature solid phase, and the surface LiMn _ 2O _ 4 is coated with LiMn _ 2O _ 4 by one-step hydrothermal method. and a LMO cladding material rich in Mn2 + cladding layer is obtained. The coating layer can effectively prevent Mn2 + from being dissolved in the electrolyte, and the disproportionation reaction of Mn to (3 +) in the LiMn _ 2O _ 4 is inhibited, so that the cycle performance of the LMO material is effectively improved. It can be seen from the electrochemical test data that the electrochemical performance of the LiMn_2O_4@3wt% LiMnPO _ 4 and the LiMn_2O_4@10wt% LiMnPO _ 4 with different coating ratios is better than that of the pure LiMn _ 2O _ 4. In addition, because of the presence of low-cost manganese on the electrode surface, the ion and electron-conduction ability of the LiMn _ 2O _ 4 is improved, resulting in an improvement in the rate performance of the material. Therefore, the stable Mn 2 +-rich material can effectively improve the electrochemical performance of LiMn _ 2O _ 4 as the coating of LiMn _ 2O _ 4. 3. The spherical porous LiNi _ (0.5) Mn _ (1.5) O _ 4 particles are prepared by co-precipitation and high-temperature solid phase method, and the LiCoPO _ 4 is grown on the surface of LiNi _ (0.5) Mn _ (1.5) O _ 4 particles by conventional hydrothermal method. The morphology of the material and the formation of the coating structure were determined by means of SEM and HRTEM, and the cladding layer was LiCoPO _ 4 by XRD and XPS. The content of Mn ~ (3 +) and Mn ~ (3 +) in the LCP and LNM interface can be increased with the increase of the LCP, by analyzing the XPS, CV and charge-discharge of the four samples. The EIS and GITT test further illustrate the effect of Mn ~ (3 +) on the conductivity of the material and the capacity of the lithium ion mobility, which increases the mixed degree of Ni/ Mn in the LNM so as to greatly improve the conductivity and the lithium ion mobility of the LNM. The appearance of Mn ~ (3 +) has an important effect on the rate performance of the material from the battery cycle performance. The effect of the LCP as the cladding layer is also shown at two points: one is effective to prevent the soluble Mn2 + dissolved in the Mn-(3 +) disproportionation reaction to be dissolved in the electrolyte, and the second is to effectively reduce the decomposition of the LiPF6 in the electrolyte and the side reaction on the surface of the electrode, These two points ensure a significant improvement in the cycle performance of the composite. In the experiment, the optimum electrochemical performance of the LNM@5% LCP sample was found, and the initial discharge capacity was 128mAh g-1 at the charge/ discharge rate of 0.5C, and the capacity retention rate was 96% of the initial capacity after 100 cycles. At the charge/ discharge rate of 20C, the initial charge/ discharge capacity was 115 mAh g-1, much higher than that of the pure LNM of 57 mAh g-1.
【学位授予单位】：江苏大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM912
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