| Lithium-ion batteries（LIBs）has been widely used in electric vehicles and portable electronic products.As an important member of lithium-free cathode materials,VOSO4 has both two-dimensional layered ion diffusion channels and the multivalent characteristics of vanadium-based materials,and has good electrochemical activity.However,the current research on VOSO4’s lithium storage performance is restricted due to the harsher preparation conditions and strong humidity sensitivity.In this thesis,V2O5 was used as the vanadium source to carry out the preparation of VOSO4 micro-nano cathode materials and the study of performance.The specific research contents are as follows:A versatile oxalic acid to synthesize carbon-coatedβ-VOSO4（β-VOSO4@C）in one-step,and the carbon coating layer can directly block moisture in the air.The effect of oxalic acid content on the microstructure and electrochemical performance of VOSO4 was systematically studied.The research results show that VOSO4（VOSO@C-2）with a mass ratio of oxalic acid to vanadium pentoxide of 1.3 has the best performance.The thickness of carbon layer is about5 nm,which can effectively reduce electrode polarization and improve electronic conductivity.In addition,VOSO@C-2 has a maximum initial discharge specific capacity of 163.7 m Ah·g-1at 0.05 C,and the capacity retention rate after 110 cycles at 0.1 C is 70%,and the coulombic efficiency remains at about 100%.The material preparation process and battery test parameters are further studied.（1）Treat the samples at 260,280,320,360,400,450,500 and 550°C series annealing temperatures.When the annealing temperature is 500 and 550℃,some V2O5 appears in the sample,and its corresponding discharge specific capacity is as high as 120.5 and 146.8 m Ah·g-1.In addition,the samples annealed at 280°C have good electrochemical activity.（2）Study the effect of conductive carbon addition on battery performance during electrode preparation.The results show that with the increase of the amount,the phase structure of the sample becomes uniform,the microscopic morphology of the electrode surface shows a trend of densification,and the distribution of EDS elements is uniform.The corresponding charge-discharge specific capacity showed a trend of first increase and then decrease.The first discharge specific capacity of the sample with 20%conductive additive was as high as 148.3 m Ah·g-1,which reached 90.2%of the theoretical specific capacity.（3）Explore the impact of test temperature on the charge and discharge performance of VOSO4@C cathode material lithium-ion batteries.As the test temperature increases,the electrochemical performance gradually increases.The first discharge specific capacity at 30℃is as high as 145.8 m Ah·g-1,and when the test rate is 1 C,the discharge specific capacity is increased by nearly 104.5 and 138.3%compared to 20 and 10℃,respectively.The composite modification of 5%carbon nanotube（CNT）or graphene oxide（GO）on the vanadyl sulfate material was studied.Five composite samples of VOSO4@C,CNT-VOSO4@C,GO-VOSO4@C,VOSO4@C-CNT and VOSO4@C-GO were prepared,and the corresponding first discharge specific capacities were 128.7,151.6,109.8,135.7 and 135.7.141.8 m Ah·g-1.Among them,the particles corresponding to the precursor composite modified samples are significantly reduced.CNT-VOSO4@C has the best electrochemical performance,and the discharge capacity almost no degradation after 30 cycles at a high rate of 1 C.In addition,the samples of VOSO4@C-CNT and VOSO4@C-GO composite materials also show good electrochemical performance,and the corresponding first discharge specific capacities are135.7 and 141.8 m Ah·g-1 at a current density of 0.05 C. |
PDF Full Text Request