Preparation And Electrochemical Performances Of Cathode Materials For Aqueous Rechargeable Lithium-ion Battery

In recent years,scientists have studied the electrochemical properties of different types of lithium-ion intercalated compounds in aqueous electrolytes and improved their electrochemical performance in aqueous electrolytes by new methods of synthesis and modification.Preparation of positive and negative electrode materials that were suitable for use in aqueous electrolytes and having excellent cycle stability is of great importance for the successful preparation of green,environmentally friendly and water-based lithium-ion batteries with excellent electrochemical properties.Because LiMn₂O₄ is low cost,low toxicity and environmentally friendly,its more suitable as a ARLBs cathode material.Therefore,the LiMn₂O₄ nanoparticles and porous spherical particles prepared in this paper were used to study the electrochemical performance of the LiMn₂O₄ in the ARLBs.The methods used to improve the cycle stability of the materials were CNTs doping and using hydrogel electrolytes.The related synthesis mechanism and optimal synthesis process were also studied.The reaction mechanism were studied by studying the influence of the reaction time and the amount of reaction raw materials on the crystal structure and electrochemical properties of LiMn₂O₄.The results show that the LiMn₂O₄ nanoparticles with uniform particle size and high crystallinity can be synthesized when the mole ratio of KMnO4/ascorbic acid is 4.5:1 and the molar ratio of KMnO4/LiOH is 1:1.3.The LiMn₂O₄ synthesized under the optimal conditions can obtained a discharge capacity of 120 mAh/g at 0.5 C in the aqueous electrolyte,and the high discharge specific capacity of 88.6 mAh/g can be obtained even at 10 C.Based on the synthesis of nanocrystalline spinel Li Mn₂O₄ by hydrothermal method,a series of LiMn₂O₄/CNTs composites with high crystallinity were synthesized by adding CNTs with excellent conductivity and stability in the synthesis process.The physical properties,electrochemical properties and kinetic properties of LiMn₂O₄/CNTs composites synthesized under different reducing agents were studied.The effects of reducing agent and CNTs on their physical and electrochemical properties were analyzed in detail.LiMn₂O₄/CNTs composites synthesized under optimal conditions can obtain a specificcapacity of 126.1 mAh/g at 1.0 C in aqueous electrolyte.Even at 20 C,a high discharge specific capacity of 100.3 mAh/g can be obtained.As the addition of high conductivity CNTs not only makes the rate performance greatly improved,the long cycle stability of the composite material has also been greatly improved,at 5.0 C rate after 600 cycles the material can still maintain 82% of the initial capacity.In addition,the application of porous spherical Li Mn₂O₄ particles in ARLBs was also studied.And the PAAM-based hydrogel electrolyte was prepared and applied to the aqueous rechargeable lithium battery,which greatly improved the cycling stability of the porous spherical LiMn₂O₄ particles.At the rate of 5.0 C,can still maintain 80% of the initial capacity after 1800 cycles.