结构掺杂型Li_(1.12)K_(0.05)Mn_(0.57)Ni_(0.24)Nb_(0.02)O_(2)正极材料的合成及其性能提升机制研究

Preparation and Characterization of the Li_(1.12)K_(0.05)Mn_(0.57)Ni_(0.24)Nb_(0.02)O_(2)Cathode Material with Highly Improved Rate Cycling Performance for Lithium Ion Batteries

多元掺杂结构型富锂材料被广泛应用于合成高性能锂电池正极材料.本文采用高温固相方法,合成了K和Nb元素共掺杂Li_(1.12)K_(0.05)Mn_(0.57)Ni_(0.24)Nb_(0.02)O_(2)(2 LMN–K/Nb)材料,并进行相关结构表征,同时应用于锂离子电池的正极材料开展相关研究.结构分析表明,微量的元素K^(+)和Nb^(5+)分别掺入了富锂正极材料锂层和过渡金属(TM)层,并对富锂材料的动力学行为、电化学性能产生了明显影响.LMN–K/Nb在5C倍率的放电容量为145 mAh·g^(-1),在10C倍率放电容量达112 mAh·g^(-1),并在400次循环后保持83.1%的容量.在充放电循环过程中,微量元素掺杂起到了抑制富锂材料不可逆的副反应作用.该工作证实:为了提高LLO基锂电池正极材料的性能,在锂层和TM层中的进行多元元素取代是一种可行的策略.

Multi-doped structured lithium rich materials are widely used in the synthesis of high-performance cathode materials for lithium-ion batteries.In this paper,Li_(1.12)K_(0.05)Mn_(0.57)Ni_(0.24)Nb_(0.02)O_(2)(LMN–K/Nb)as a novel high energy density cathode material was successfully synthesized and applied in lithium ion batteries by using a high-temperature solid-state method.Related structural characterization was carried out,too.Structural analysis shows that K^(+)and Nb^(5+)were doped into the lithium layer and transition metal(TM)layer of lithium-rich cathode materials,respectively,and had a significant impact on the dynamic behavior and electrochemical performance of the lithium-rich materials.LMN–K/Nb delivers an initial capacity of 145 mAh·g^(-1)at 5C rate and 112 mAh·g^(-1)at 10C rate,and maintains 83.1%after 400 cycles at 5C rate and 82.5%at 10C rate.By post-mortem analysis of long-term cycled LMN–K/Nb,K^(+)and Nb^(5+)are recognized to play a role in suppressing the irreversible side reactions in LLOs during cycling.This work demonstrates that dual elemental substitution into the lithium layer and TM layer is a feasible strategy to enhance the performance of LLO cathode materials.