【作者】 刘鹏；

【导师】 李成超； 周沛；

【作者基本信息】 广东工业大学 ， 化学工程（专业学位）， 2021， 硕士

【摘要】 目前可充电锂离子电池（LIBs）因为具备较高的比能量和输出电压,在电动汽车和移动电子设备领域得到了广泛的运用,并主导了可充电电池市场。但锂资源在地壳中的含量低、在世界范围内分布不均匀以及锂盐的价格不断上涨,使得可充电LIBs的前景令人担忧。近年来,钠离子电池（NIBs）的快速发展引起了人们的关注,由于Na资源天然储量丰富、容易获得、价格不高、绿色安全,并且Na和Li属于同族元素,其物理和化学的相关特性非常类似,所以NIBs技术认为是非常有潜力的代替技术。然而Na⁺的半径（1.02（?））大于Li⁺的（0.76（?））,以及Na⁺迟缓的扩散能力,导致电池性能不佳。因而亟待探索新的NIBs材料。现在研究的负极材料有很多,锑基材料是目前研究的热点之一,因为金属锑（Sb）具有较高的理论比容量(660 m Ah g^-1)以及合适的工作电压（0.5-0.8 V vs.Na/Na⁺）。但是,在脱嵌钠过程中,Sb基材料的体积会发生剧烈膨胀（393%）,致使锑基材料和集流体之间的接触变得不再那么严密,容易脱离导电网络,损失大量的电池容量,极大的降低了材料的寿命。因此本论文通过水热反应和表面包覆碳的方法引入了磷酸根离子和碳材料,合成了复合材料SbPO₄-C,其中SbPO₄纳米粒子被导电碳包覆。首先,体积较大的磷酸根离子作为缓冲层缓解了SbPO₄-C复合材料在嵌钠脱钠过程中的体积膨胀问题。第二,碳保护层可以有效的防止SbPO₄-C复合材料的结构坍塌,同时还能增加材料的导电性。由于以上这些优点,在钠离子电池中,SbPO₄-C表现出优秀的电池性能。在电流密度为0.5 A g^-1时,循环200次后,SbPO₄-C电极展现出248 m Ah g^-1的容量。在电流密度为1A g^-1下,SbPO₄-C电极仍能够展现出180 m Ah g^-1的容量,循环次数为1000次,具有78.3%的保留率。即便处于5 A g^-1时,也有159 m Ah g^-1的容量。Na₃V₂（PO₄）₂O₂F||SbPO₄-C全电池也展现出3.2 V的高放电电压,表现出潜在的实际应用价值。更重要的是,导电碳涂层的策略为其他纳米电极材料的高性能可充电储能装置的设计提供了思路。更多还原

【Abstract】 At present,rechargeable lithium-ion batteries are widely used in electric vehicles and mobile electronic devices because of their high higher specific energy and output voltage,and occupy the rechargeable battery market.However,the prospect of rechargeable lithium-ion batteries is worrying due to the low content of lithium resources in the earth’s crust,different distribution around the world,and rising prices of lithium salts.In recent years,the rapid development of sodium-ion batteries has made many people pay attention to sodium-ion batteries.Because sodium resources are abundant in natural reserves,easy to obtain,low-priced,green and safe,and sodium and lithium are in the same main group.The related physical and chemical properties are very similar,so sodium ion batteries are considered to be a very potential alternative technology.However,the radius of Na⁺is 1.02（?）,the radius of Li⁺is 0.76（?）,the radius of Na is larger than that of Li,and the slow diffusion kinetics of Na⁺,resulting in poor battery performance.Therefore,it is urgent to explore new sodium ion battery materials.There are many anode materials currently being studied.Antimony-based materials are one of the hottest topics for researchers,because the metal antimony（Sb）has a high theoretical specific capacity of 660 m Ah g^-1 and a suitable working voltage（0.5-0.8 V vs.Na/Na⁺）.However,during the charging and discharging process,the volume of the antimony-based material will change drastically（393%）,causing the contact between the antimony-based material and the current collector to become less tight,easily detaching from the conductive network,and losing a lot of battery capacity,which greatly reduces the life of the material.Therefore,phosphate ions and carbon materials were introduced through the method of hydrothermal reaction and surface coating carbon to synthesize composite SbPO₄-C,in which SbPO₄ nanoparticles were coated with conductive carbon.First of all,the larger volume of phosphate ion as a buffer layer alleviates the volume expansion problem of the SbPO₄-C composite material during the sodium insertion and removal process.Second,the carbon protective layer can effectively prevent the structure of the SbPO₄-C composite from collapsing,and at the same time can increase the electronic conduction of the material.Due to the above advantages,the SbPO₄-C composite material exhibits excellent battery performance in sodium ion batteries.At a current density of 0.5 A g^-1,the SbPO₄-C electrode exhibits a capacity of 248 m Ah g^-1 after 200 cycles.the SbPO₄-C electrode can still exhibit a capacity of180 m Ah g^-1 at 1 A g^-1 after 1000 cycles,and its retention rate is 78.3%.Even at 5 A g^-1,there is a capacity of 159 m Ah g^-1.The Na₃V₂（PO₄）₂O₂F||SbPO₄-C full battery also exhibits a high discharge voltage of 3.2 V,showing potential practical application value.More importantly,the conductive carbon coating strategy provides ideas for the design of high-performance rechargeable energy storage devices for other nano-electrode materials.更多还原