基于分子轨道杂化的高电压钠离子电池层状氧化物正极材料  

Layered oxide cathode materials based on molecular orbital hybridization for high voltage sodium-ion batteries

作　　者：胡海燕 侴术雷 肖遥 HU Haiyan;CHOU Shulei;XIAO Yao(Technology Innovation Institute for Carbon Neutralization,College of Chemistry and Materials Engineering,Wenzhou University,Wenzhou 325035,Zhejiang,China;School of Materials Science and Engineering,Nanyang Technological University,Singapore 639798,Singapore)

机构地区：[1]温州大学化学与材料工程学院,碳中和技术创新研究院,浙江温州325035 [2]南洋理工大学材料科学与工程学院,新加坡639798

出　　处：《储能科学与技术》2022年第4期1093-1102,共10页Energy Storage Science and Technology

基　　金：国家自然科学基金项目(51971124);国家博士后创新人才项目(BX20200222);博士后科学基金项目(2020M682878)。

摘　　要：O3型层状过渡金属氧化物NaNi_(0.5)Mn_(0.5)O_(2)是目前最有应用前景的钠离子电池正极材料之一。然而,由于在充放电过程中过渡金属层的滑移,O3型正极材料伴随着多重不可逆的复杂相变,所以其应用受到了限制。另外,O3-NaNi_(0.5)Mn_(0.5)O_(2)正极的容量主要集中在3 V左右的低电压区域,在充放电过程中这一区域很容易发生O3-P3相变,所以限制了其能量密度。本研究提出了一种精准的化学元素取代策略来解决这些问题。通过Sn^(4+)掺杂来抑制过渡金属层的滑移,从而抑制循环过程中的不可逆相转变。同时,由于Sn^(4+)具有独特的外层电子结构,在d轨道上没有单电子,无法与O 2p轨道发生杂化,所以O 2p轨道就只与Ni eg轨道发生杂化,增大了Ni—O键的离子度,提高了Ni的氧化还原电势。因此,NaNi_(0.5)Sn_(0.5)O_(2)正极材料的中值电压高达3.28 V。同时,该电极材料表现出较为优异的电化学性能和动力学性质。本工作基于分子轨道杂化对O3型正极材料的氧化还原电势实现了可控调制,从而获得了具有高电压的钠离子电池层状氧化物正极材料。O3-type sodium-layered transition-metal oxides,NaNi_(0.5)Mn_(0.5)O_(2),are one of the most promising cathode materials.However,the application of O3-NaNi_(0.5)Mn_(0.5)O_(2) cathode material is limited due to the transition metal layer's slip during charge and discharge processes,with multiple irreversible complex phase transitions.In addition,its energy density is limited due to the capacity of O3-NaNi_(0.5)Mn_(0.5)O_(2) electrode,which is mainly concentrated in the low voltage region around 3 V,and O3-P3 phase transition easily occurred in this region.This study proposes a precise chemical element substitution strategy for successfully solving these problems Doping with Sn^(4+)inhibits the transition metal layer's slip and the irreversible multiphase transformation.Meanwhile,Sn^(4+)cannot be hybridized with the O 2p orbital due to the unique outer electronic structure,which lacks a single electron in its d orbital.The O 2p orbital only hybridized with the Ni eg orbital,increasing the ionic degree of Ni-O bond and Ni's redox potential.Therefore,O3-NaNi_(0.5)Mn_(0.5)O_(2) can display a high midpoint voltage of 3.28 V.Meanwhile,the electrode material exhibits excellent electrochemical performance and kinetic properties.The controllable redox potential of O3-type cathode material was realized based on molecular orbital hybridization theory to obtain the high-voltage layered oxide cathode materials sodium-ion batteries.

关 键 词：钠离子电池 层状正极材料 分子轨道杂化 高电压 相变机制 

分 类 号：TM911.14[电气工程—电力电子与电力传动]