Study On Preparation And Properties Of Novel Cathode Materials For Lithium-ion Batteries

The cathode materials are the key to lithium ion batteries,but there are still many problems that affect the performance of cathode materials(whether organic active molecules or ternary).The organic active materials with poor conductivity are easy to dissolve in electrolyte,and the low synthesis rate and poor thermal stability of ternary materials restrict the development of high capacity and long life of the battery.The introduction of carbon-based materials with high conductivity and high specific surface area is excepted to solve these problems.Based on them all,the contents of the thesis are as follows:1.Anthraquinone@carbonized MOFs cathode materialsThe structure stability and storage performance of anthraquinone(AQ)is highly improved through rational strategy by confining AQ into ZIF-8-derived nitrogen-doped carbon scaffold(N-ZIF-8).AQ is effectively encapsulated and trapped within the microporous structure,which restrains the dissolution process.A specific capacity of 241 mAh-g-1 has been achieved by using AQ@N-ZIF-8 electrode at 0.1 C and a capacity of 213 mAh·g-1 has been retained after 300 cycles.The excellent electrochemical performance was attributed to AQ's high load and the inhibition of nano-porous carbon on solubility.2.Polyanthraquinone sulfide@carbonized MOFs cathode materialsPolyanthraquinone sulfide@multiporous carbon(PAQS@3D-C)material was obtained by in-situ polymerization of 1,5-dichloroanthraquinone(DCAQ)in 3D multi-pore carbon(3D-C).The active molecules were firmly limited in the carbon materials by polymerization and carbon-based loading,which effectively solve the problem of solubility and the low conductivity.The organic cathode for LIBs shows a higher reversible specific capacity of 219 mAh·g-1 at 0.2 C and greatly improved cycle life with low-capacity fading speed of?0.015%per cycle.Specifically,PAQS@3D-C shows a remarkable high-rate capacity of 112 mAh·g-1 even at 20 C.3.Indanthrone@carbonized indanthrone cathode materialsMolecular design is used to improve the stability of the organic molecule,and to construct carbonyl molecule with a larger conjugated skeleton.The composites(IDT@IDT-1000)can be prepared by stacking the large-skeleton indanthrone(IDT)with the graphene-like sheet obtained by carbonizing itself(IDT-1000).The layer-by-layer assembly is realized through ?-? effect,which improves the structural stability and regulates the distribution state of electron cloud.The specific capacity up to 238 mAh·g-1 was realized at 0.2 C,and the capacity was>210 mAh·g-1 after 1000 cycles.The capacity decay rate is?0.014%per cycle.There is also a slight increase of voltage platform.The strategy of expanding the conjugated framework effectively fulfills the requirements of long cycling life.4.High-nickel ternary@graphene cathode materialsHigh-quality few layer graphene(HFLG)was added to prepare high-nickel ternary@graphene material in high-temperature solid phase reaction,which improved the synthesis rate and structural stability of the materials.It can be seen from the particle size distribution analysis that the high-nickel ternary composites prepared by adding graphene were denser.According to the battery test,the addition of graphene can slightly improve the capacity and cycling stability of the electrode.