| Lithium-ion batteries with the advantages of high working voltage, high energy density, low self-discharge rate and excellent cycle performance, have widely applied in the field of portable devices, such as laptops, mobile phone and camera. In recent years, the BYD, YUTONG and other motor enterprises from china, together with international famous enterprises have further pushed lithium-ion power battery toward the large-scale commercialization. Among them, researching and developing anode materials which have high energy density and good cycle stability, is a key step for producing advanced energy storage system. As it is well known that, the conjugated carbonyl compounds as green organic negative electrode materials, which have high specific capacity, low cost and easy to extract, are regarded as one of the best electrode material candiates. It is a pity that organic conjugated carbonyl compound electrode materials which are easy to dissolve in the organic electrolyte, show low intrinsic conductivity, which is the reason why the poor rate capability and cycle performance are observed. As a consequence, these drawbacks limit their application in power lithium-ion battery. This thesis has reported the synthesis of nano-sized pure phase Li2C8H4O4 or LiTPA material through anti-solvent method in one-step. Then LiTPA was complexed with Carbon nano-tube(CNTs) and reduction of graphene oxide(RGO) to promote the electrically conductive ability and prevent their dissolving in the organic electrolyte. The rate performance and capacity of the composites were enhanced by this methodology. The main research results obtained and conclusions are as following:(1) Anti-solvent is used to synthesize pure nano-sized LiTPA materials. The pure nano-sized LiTPA materials(size: 200-400 nm) were synthesized with LiOH·H2O and HTPA as raw materials, drying by the vacuum oven in room temperature after spraying method. The synthetic methods were based on the theory of crystal growth. The first discharge specific capacity for this material is 410 m Ah/g at the current rate of 0.05 C, which was much higher than that of micron-sized materials created by the common acid-base neutralization reaction.(2) The effect of particle size on the electrochemical properties of LiTPA materials. LiTPA materials with the different particle sizes were synthesized by adjusting the parameters, resulting in different electrochemical properties. The first discharge specific capacity and the rate performance were improved significantly with the decreasing of the particles size. The smaller particles have larger specific surface area, where the charge-discharge cycle stability deteriorates with the increased solubility in the organic electrolyte.(3) Preparation of LiTPA complex with carbon nanotubes(CNTs). The initial discharge capacity of LiTPA composite with CNTs reach 238 mAh/g(CNTs mass included) in the current rate of 0.05 C. The specific capacity of the first discharge and the rate performance have been improved significantly, compared with that of the pure phase micro-sized LiTPA. But the cyclic performance was not greatly improved since the solution of the active material in the organic electrolyte was not obviously prohibited.(4) LiTPA composite with the reduced graphene oxide(RGO). The specific capacity of the initial discharge process reached 365.6mAh/g(including the mass of RGO) in the current rate of 0.2 C. Furthermore, in the 0.2C rate, the capacity retention rate is 66.4% from the second cycle to the fiftieth cycle, indicating the cycle performance has been improved significantly with respect to that of the pure phase LiTPA. |
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