基于第一性原理的Zr掺杂Li_(3)PS_(4)固态电解质的性能研究

Study on Properties of Zr-Doped Li_(3)PS_(4)Solid Electrolyte Based on First Principles

硫化物固态电解质是目前无机固态电解质的研究焦点之一。然而,当用于全固态电池时,硫化物固态电解质与电极材料的相容性较差,难以兼顾高电导率和高稳定性,因此通过元素取代或掺杂,以及结构调整来提高固态电解质的离子电导率获得了广泛的研究。基于第一性原理对Li_(3)PS_(4)进行Zr掺杂改性研究,研究思路即通过Zr掺杂取代Li原子,同时产生Li空位来增加锂离子的传输空位。通过计算Zr掺杂的Li_(3)PS_(4)的Li空位形成能,证明当Zr元素在Li_(3)PS_(4)晶体结构的Li_(2)位进行掺杂时具有较低的空位形成能,从而提高了Li_(3)PS_(4)固态电解质的结构稳定性。通过计算态密度和差分电荷密度,发现Zr掺杂可以改变其周围的电子态,不仅能提高Li_(3)PS_(4)的活性,还改善了Li_(3)PS_(4)的电化学稳定性。采用CI-NEB方法计算分析锂离子在Zr掺杂Li_(3)PS_(4)固态电解质体相中沿不同迁移路径的迁移能垒,发现锂离子沿Li_(2)→Li_(2)→Li_(2)路径进行迁移的迁移能垒最小,由此确定了锂离子在Zr掺杂Li_(3)PS_(4)晶体结构中的最优扩散通道。

Sulfide solid electrolyte is one of the research focuses of inorganic solid electrolytes at present.However,when used in all-solid-state batteries,sulfide solid electrolytes have poor compatibility with electrode materials,and it is difficult to balance high conductivity and high stability.Therefore,extensive studies have been carried out on improving the ionic conductivity of solid electrolytes by element substitution or doping as well as structural adjustment.Based on the first principles,Zr doping modification of Li_(3)PS_(4)is studied.The research idea is to increase the transport vacancy of lithium ion by replacing Li atom with Zr doping and generating Li vacancy at the same time.By calculating the Li vacancy formation energy of Zr-doped Li_(3)PS_(4),it is proved that Zr doped in the Li_(2) position of Li_(3)PS_(4)crystal structure has low vacancy formation energy,thus improving the structural stability of Li_(3)PS_(4)solid electrolyte.By calculating the density of states and the charge density difference,it is found that Zr doping can change the surrounding electronic states,improving not only the activity but also the electrochemical stability of Li_(3)PS_(4).The migration energy barriers of lithium ions along different migration paths in the Zr-doped Li_(3)PS_(4)solid electrolyte phase are calculated and analyzed by CINEB method.It is found that the migration energy barriers of lithium ions along the Li_(2)→Li_(2)→Li_(2) path are the smallest,and the optimal diffusion channel of lithium ions in the Zr-doped Li_(3)PS_(4)crystal structure is determined.