作为一种高能量密度储能器件,锂离子电池不仅已经广泛应用于消费电子领域(如笔记本电脑、智能手机),而且也适合用于电动车中的动力电池.正极是锂电池最为重要的组成部分.在正极材料的研究中,当电子在空间上局域分布并与晶格耦合将形成极化子,极化子现象近些年逐渐引起人们更多关注,主要是因为其减弱电子导电性,不利于电子传导,是磷酸铁锂等正极材料电子导电性差的根本原因.极化子是一种晶格畸变束缚电子作整体运动的晶体缺陷.开展极化子现象的相关机理研究,将为设计高导电性正极材料提供理论指导,对锂离子电池电化学性能的进一步提升有着重要意义.基于第一性原理的理论计算方法己成为研究正极材料中极化子的重要研究手段,能够判断体系是否有极化子出现以及分析极化子的出现对正极材料的物理化学性能影响.本文主要从理论计算的角度出发,首先介绍了极化子的基本物理概念,其次结合我们的相关研究综述了极化子的理论计算判别方法、极化子对常见类型正极材料导电性能的影响与调控和当前研究方法的一些理论难题,最后从基础理论和实际应用两个角度对未来正极材料中的极化子研究进行展望.“,”In addition to their extensive commercial application in electronic devices such as cell phones and laptops,lithium-ion batteries(LIBs)are most suitable to fulfill the energy storage requirements of electric vehicles because of their recognized safety,portability,and high energy density.Cathodes are the most important part of LIBs,and various cathode materials have been widely investigated over the past decades.Polaron formation has been attracting increasing attention in the research of cathode materials,as it limits electron conduction.In particular,polarons are responsible for low electronic conductivity in cathode materials like olivine phosphate.Polaron is a typical crystal defect caused by the integrated motion of lattice distortion and its trapping electrons.Research on the mechanism of polaron formation will provide theoretical guidance for the design of high-electronic-conductivity cathode materials and improvement of the electrochemical performance of LIBs.Theoretical calculation is a direct and important method to study polaron formation in a specific crystal material,because the presence of polarons and their formation mechanisms can be effectively verified through this method.In this article,we first introduce the basic physical concept of polarons and their dynamical model according to the Marcus and Emin-Holstein-Austin-Mott theories.A comparison of the general properties of large and small polarons,summarized in this chapter,reveals that small polaron formation more likely occurs in cathode materials.Moreover,the theoretical characterization,electrical impact,control and challenges of polarons are reviewed.Although a universal necessary and suitable condition for the theoretical characterization of polarons has not yet been found,we still propose three criteria that are proven to be feasible and practical for the theoretical identification of polarons when applied in combination.Experimental characterizations are also introduced briefly for reference,because the comparison with the experiment is suggested to be necessary and mandatory.The electrical impact caused by polarons results in low electronic conductivity,which has been broadly reported in layered,olivine,and spinel cathode materials.Doping can weaken the influence of polarons and,thus,significantly enhance the electronic conductivity,thereby becoming the most prevalent strategy for tuning polarons.Although theoretical calculations have been widely and effectively conducted in the study of polarons,some challenges may still be faced because of the intrinsic shortcomings of the traditional density functional theory,which need to be addressed.Finally,further research on polarons from the perspective of basic theory and practical applications is prospected.