非平衡分子動力學分析鋰電池固態電解質界面熱傳導係數

Abstract

鋰離子電池在電池儲能領域當中佔據極為重要的地位，然而，隨著科技發展，人們對儲能設備續航力的要求日益月滋，傳統以石墨作為主要負極材料的鋰離子電池 (lithium ion battery, LIB) 已逐漸難以負荷。而設備的性能往往取決於材料的選擇，而這在鋰電池當中同樣適用，因此，更換電極材料或者電解液系統是電池效能提昇的主要研究方向。 影響鋰電池效能的原因除了材料本身，溫度也是一個影響電池效能的主要原因，過低的溫度會導致鋰電池性能下降，而過高的溫度則會造成電池老化，甚至有引發爆炸的風險，因此，了解電池內部材料的熱性能可以有效的幫助鋰電池的設計。因此，本研究選用非平衡分子動力學 (non-equilibrium molecular dynamics,NEMD) 模擬多種電極材料以及固態電解質界面的熱傳導係數。 將研究結果與實驗比對後發現，我們所使用的 ReaxFF 力場所搭配的勢能函數對於熱傳導係數的估計都略有所低估，而後使用相同力場對由 EC 以及 DEC 組成的電解液系統與鋰金屬負極反應而成的 SEI 進行熱傳導係數的模擬，而經過計算所得 SEI 的熱傳導係數為 1.12 W/m · K。

Lithium-ion battery (LIB) hold a crucial position in the field of battery energy storage. However, with the advancement of technology, the demand for the endurance of energy storage devices has been increasing. Traditional lithium-ion batteries, which mainly use graphite as the anode material, are gradually struggling to meet these demands. The performance of devices often depends on the materials, and this is equally applicable to lithium-ion batteries. Therefore, replacing electrode materials or the electrolyte system is a primary research direction for improving battery performance. Besides the battery materials, temperature is also a major factor affecting battery performance. Extremely low temperatures can lead to a decline in lithium battery performance, while excessively high temperatures can cause battery aging and even pose a risk of explosion. Hence, understanding the thermal properties of the materials of the battery can aid in the design of lithium batteries. In this study, we use non-equilibrium molecular dynamics (NEMD) to simulate the thermal conductivity of various electrode materials and solid electrolyte interphases (SEI). Comparing the simulation results with experiments, we found that the potential parameters paired with the ReaxFF force field tend to slightly underestimate the thermal conductivity. Subsequently, using the same force field, we simulated the thermal conductivity of the SEI formed by the reaction between an electrolyte system composed of EC and DEC and a lithium metal anode. The calculated thermal conductivity of the SEI is 1.12 W/m · K.