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首页> 外文会议>Meeting of the Electrochemical Society;International Meeting on Chemical Sensors >Theoretical Study of the Charge Transport Mechanism in a Sodium Selenide (Na_2Se) Cathode for Sodium-Selenium Batteries
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Theoretical Study of the Charge Transport Mechanism in a Sodium Selenide (Na_2Se) Cathode for Sodium-Selenium Batteries

机译：硒电池硒化钠（Na_2Se）阴极电荷输送机制的理论研究

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Selenium (Se) is recognized as a promising cathode material for sodium-selenium (Na-Se) batteries because of its high electrical conductivity on the order of 10~(-3) S m~(-1) and facile sodiation kinetics. Although the terminal product, Na_2Se, could limit the overall battery conductivity, fundamental understanding of the charge transport mechanism and the formation of final product remains largely unexplored. Based on density functional theory, we evaluate the influence of each type of defect and strain on conductivity in Na_2Se by calculating the formation energy and mobility. We found that hole polaron (p~+) can stably form on Se ion upon initial distortion. Our calculations also show that the negatively charged sodium vacancy (V_(Na)~-) could be the major charge transport carrier with its lowest formation energy and fast mobility. While diffusion barrier of p~+ is considerably smaller than that of V_(Na)~-, the electronic transport related to p~+ is suggested to be negligible due to its high formation energy. Once the vacancy-polaron (V_(Na)~- - p~+) complex forms, the charge transport could be hindered mainly due to its charge neutrality and the relatively large binding strength of the complex. Lastly, we will also discuss the influence of compression which could be induced by significant volume change of Na-Se alloys on the conductivity of Na_2Se.
机译：硒（SE）被认为是亚硒（NA-SE）电池的有希望的阴极材料，因为其在10〜（3）S m〜（-1）的电导率高，并且容易调解动力学的高电导率。虽然终端产品NA_2SE可以限制整体电池电导率，对电荷运输机制的根本理解以及最终产品的形成仍然很大程度上是未开发的。基于密度函数理论，通过计算形成能量和迁移率，评估每种类型的缺陷和应变对NA_2SE中电导率的影响。我们发现在初始失真时，可以在SE离子上稳定地形成孔极化孔（P〜+）。我们的计算还表明，带负电的钠空位（V_（NA）〜 - ）可以是主要的电荷运输载体，其形成能量最低和快速移动性。虽然p〜+的扩散屏障远小于V_（NA）〜 - ，由于其高形成能量，建议与P〜+相关的电子传输忽略不计。一旦空位 - 极化子（V_（NA）〜 - - P〜+）复杂形式，电荷输送可能是由于其电荷中性和复合物的相对较大的粘合强度而受阻。最后，我们还将讨论压缩的影响，这可以通过Na-See对Na_2se电导率的显着体积变化来诱导。

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