湿法合成LiNi_(0.8)Co_(0.2)O_2及其性能表征

Characterization of Wet-Chemistry Synthesized LiNi_(0.8)Co_(0.2)O_2

LiNi0.8Co0.2O2是极为看好的下一代锂离子电池正极材料,以湿法合成可得到成分均匀、颗粒尺寸一致的材料,有效提高电池性能,所以采用共沉法与微粒溶胶凝胶法(PSG)合成锂离子电池正极材料LiNi0.8Co0.2O2。共沉法先形成-β(Ni,Co)(OH2),然后与计量比的锂混匀,煅烧获得材料。PSG法在制得凝胶的同时发生酯化反应,将当中的镍与钴还原为金属,锂则以碳酸锂形态存在;随后煅烧得到LiNi0.8Co0.2O2。两种方法所得材料进行红外光谱、X射线衍射及XRD精修结构分析、电化学阻抗谱、循环性能等检测。其中X射线衍射鉴定出这两种方法合成物相结晶都良好,XRD精修结构分析、电化学阻抗谱、循环性能测试都表明PSG结构比较优良。

LiNi0.8Co0.2O2 is one of the potential cathode material for Li-ion battery. The materials with homogeneous phase, narrow distribution of particle size and enhanced performance of Li-ion battery can be achieved by wet-chemistry. Coprecipitation and particulate sol-gel （PSG） were used to synthesize LiNi0.8Co0.2O2. The precursor β-（Ni, Co） （OH2） was firstly prepared by coprecipitation method, then it was calcined with lithium in the stoichiometric amount to form LiNi0.8Co0.2O2. In PSG, the gel was formed when an esterification happened. Both nickel and cobalt were reduced as metals, while lithium carbonate was remained. LiNi0.8Co0.2O2 was also produced after calcining. In PSG, the synthesized materials were examined by using Infrared spectroscopy （IR）, X-ray diffratometry （XRD）, Rietveld refinement, electrochemical impedance spectroscopy （EIS） and cycleability measurements. The LiNi0.8Co0.2O2 produced by both methods is well-crystallized, which is confirmed through XRD. However, all the results of Rietveld refinement, EIS and cycleability measurements indicate that the PSG method is better by which the product has better layered structure, smaller charge transfer resistance and better cycleability.