Research on gas generation of polymer Li-ion battery with LiFePO ₄ cathode material

When "a" and "b" two commercial LiFePO₄ sample materials were used in polymer Li-ion batteries as cathode, the "b" sample polymer batteries swollened after storing for some days, and this didn't happen in "a" sample polymer batteries. The "a" and "b" LiFePO₄ sample materials were charactered by X-ray diffraction(XRD), scanning electron microscope (SEM) and electrichemical property test, there was no obvious difference between them. The result of gas chromatography with mass spectrometry(GC-MS) indicated that the main gas composition in "b" sample polymer batteries was DMC, CH ₃CH₂CH₂CH₃ and CH₃CH ₂OCH₂CH₂OH.The generation of C ₃CH₂CH₂CH₃ and C₃CH ₂OCH₂CH₂OH may have some relationships with too much water in the polymer batteries.