Protective coating on silicon particles is a strategy reported in literature to improve capacity retention of Si-containing lithium ion batteries. Up to date, the impact of the coating on the cell energy density and specific energy is not considered and guidelines for coating design are missing. In this paper a model is proposed to fill this gap. The model depicts how energy density and specific energy of lithium ion cells based on a Si-graphite composite electrode change in function of coating type, thickness and silicon weight fraction in the negative electrode. Volume changes during lithiation-delithiation and corresponding electrolyte displacement are also considered. Energy density depends on the ratio of coating thickness to silicon particle dimension and weight fraction of silicon in the electrode. Specific energy depends - marginally - also on the coating type. As a case study silicon spherical particles of 200 nm diameter are considered. For a 10 nm coating, the maximum energy density gain vs. state of art graphite negative electrodes is 13%, obtained with 40% weight fraction of silicon in the negative electrode. Above 60 nm thickness no improvement can be obtained vs. state of art graphite negative electrodes.

硅颗粒上的保护涂层是文献中报道的一种改善含硅锂离子电池容量保持率的策略。迄今为止，尚未考虑涂层对电池能量密度和比能的影响，并且缺少涂层设计指南。本文提出了一个模型来填补这一空白。该模型描绘了基于Si-石墨复合电极的锂离子电池的能量密度和比能如何随负极的涂层类型，厚度和硅重量分数的变化而变化。还考虑了锂化-脱锂期间的体积变化和相应的电解质位移。能量密度取决于涂层厚度与硅颗粒尺寸的比值以及电极中硅的重量分数。比能量在某种程度上取决于涂层类型。作为案例研究，考虑了直径为200 nm的硅球形颗粒。对于10 nm的涂层，相对于现有技术的石墨负极，最大能量密度增益为13％，这是负极中硅含量为40％的重量百分比。与现有技术的石墨负极相比，超过60 nm的厚度无法获得改善。