软包装锂离子动力电池关键工艺及电化学性能研究

环125次后，容量保持率由

15．8％增加至86．6％；但0．2C放电电压平台降低，高倍率放电能力降低。电化

学阻抗谱研究表明，在保持正极容量不变的情况下，随着负极容量的增加电极表

面SEI界面膜引起的阻抗‰1。以及电极表面表面电化学反应阻抗RcT先减小

(N／P=0．8～1．6)然后再增大(N／P=I．8)。

SEM形貌照片表明，随着充放电的进行，电极表面的裂纹逐渐增多并生成

白色絮状物质。通过对白色生成物的EXAF能谱分析，发现C和O的含量分别

为56．97％，43．03％，说明有机电解质溶液在嵌锂碳负极表面被还原，大量含氧

物质生成，在负极电极表面沉积并消耗电解液，使电极电阻增大，电化学极化增

II

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大，放电电压降低，放电容量减小。FTIR分析表明，在EC—DEC—DMC—EMC／LiPF6

溶液中形成的碳负极表面SEI膜主要成分为Li2C03和(CH20C02Li)2等物质。

关键词：锂离子电池，软包装，高倍率放电，化成制度，正负极容量匹配，衰退

行为

IIl

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ABSTRACT

Lithium secondary bakeries are the new types of cleanliness and recyelable

energy source．They have high voltage and hi曲energy density．Recently they are

widely used in digital products，e．g．，mobile phone，notebook，bluetooth headset，MP3，

digital camera，et a1．Soft-packed lithium-ion battery is a new type of the lithium

secondarybatteries，which has excellent characteristics including safety,light weight，

flexible．but its lowrate ofdischargeability makes it Can not compete wim Ni-MH and

Ni—Cd batteries at the liRle-scaled hi曲power battery markets．

At the alms of the improvement of the hi曲rate discharge ability of the

soft-·packed lithium-·ion battery,the production processes of the soft-packed

lithium—ion battery,including the selection of the raw materials of the electrode and

the fabrication techniques．were optimized in this thesis．The electrochemical

properties of the lithium—ion battery were tested by the electrochemical impedance

spectra(EIS)，etc．The microstructure and the composite of the solid—electrolyte

interphase(SEI)were analyzed by scanning electron microscopy(SEM)，energy

dispersive analysis of x—rays fEDAX)and Fourier transform infrared spectroscopy．

Thedecaymechanism ofthe negatives electrodewas also discussed．

The results

show that the bonding of active materials of the cathode and the

copper foil was enhanced when the raw materials used for fabricating soft-p