LiODFP在锂离子电池正极氧化分解的DFT研究

DFT study on the oxygenolysis of LiODFP in cathode of Li-ion battery

使用密度泛函理论(DFT),研究锂盐二氟二草酸磷酸锂(LiODFP)作为成膜添加剂在锂离子电池正极的作用机理。各研究体系的氧化电势理论计算值的排列顺序为:碳酸酯(包括EC、PC、EMC和DMC)>ODFP^(-)(单分子)≈碳酸酯-ODFP^(-)配合物。ODFP^(-)优先于碳酸酯发生氧化反应,ODFP^(-)结构分解的路径比EC分子分解的路径更容易进行。EC+ODFP^(-)-e体系可能发生的分解反应路径是ODFP^(-)结构开环,生成CO、CO_(2)和自由基R1。R1可能进一步发生自由基终止反应,生成含有氟代磷酸盐单体的低聚物,从而抑制碳酸酯溶剂分子的氧化分解。

The mechanism of lithium difluoro(dioxalato) phosphate(LiODFP) as a film-forming additive in the cathode of Li-ion battery is studied by density functional theory(DFT).The theoretical calculation values of oxidation potential in each system are in the following order:carbonate(including EC,PC,EMC and DMC) > ODFP~-(single molecule) ≈ carbonate-ODFP~- complex.It can be concluded that ODFP~- is preferentially oxidized over carbonate,the path of ODFP~- structure decomposition is easier than the path of EC molecular decomposition.The most likely decomposition reaction path of EC+ODFP~--e is an ODFP~- structure ring-opening which results in the formation of CO,CO_(2) and R1.R1 may undergo further radical termination reactions to produce oligomers containing fluorophosphates,thereby inhibiting the oxidative decomposition of carbonate solvent molecules.