Reliable development of Li-ion Batteries requires a good understanding of the correlation between electrochemical performances and accurate aging interfaces phenomena. The present study focuses on the SEI characterization formed at both electrodes surface in LiMn₂O₄/Li₄Ti₅O₁₂ (LMO/LTO) cells, depending on the cycling temperature, which is one of the major stress factors for batteries. LMO/LTO cells were cycled at 25 °C, 40 °C and 60 °C over 100 cycles and the chemical composition of surface layers was investigated by XPS, SAM and ToF-SIMS at the end of the 100th cycles. LTO electrodes are covered by surface layers since the first cycle (inducing an irreversible capacity loss) and the SEI thickness increases with the cycling temperature; moreover, organic (alkyl-carbonates, polyethylene oxides, oxalates) and inorganic species (LiF and (fluoro)-phosphates) of the solid interphase are present in different proportions depending on the temperature; more fluorophosphates are especially observed at 60 °C due to a higher chemical degradation of LiPF₆ salt. Finally, small amounts of manganese, heterogeneously spread over the LTO electrode surface, are found at different oxidation states at higher temperatures; for the first time, metallic Mn⁰ was detected at the LTO surface after cycling at 60 °C which could explain the important capacity loss of the system at this temperature.

锂离子电池的可靠开发需要对电化学性能与准确的老化界面现象之间的相关性有充分的了解。本研究的重点是在LiMn ₂ O ₄ / Li ₄ Ti ₅ O _12的两个电极表面形成的SEI表征。（LMO / LTO）电池，取决于循环温度，这是电池的主要压力因素之一。LMO / LTO细胞在100个循环中分别在25°C，40°C和60°C下循环，并在第100个循环结束时通过XPS，SAM和ToF-SIMS研究了表面层的化学组成。由于第一个循环（导致不可逆的容量损失）和SEI厚度随循环温度而增加，因此LTO电极被表面层覆盖。此外，取决于温度，固体相的有机物（碳酸烷基酯，聚环氧乙烷，草酸酯）和无机物（LiF和（氟）-磷酸盐）以不同的比例存在。由于LiPF _6的化学降解更高，在60°C时尤其观察到更多的氟磷酸盐盐。最后，在较高的温度下，在不同的氧化态下会发现少量锰异质分布在LTO电极表面。首次在60°C循环后在LTO表面检测到金属Mn ⁰，这可以解释该系统在该温度下的重要容量损失。