Exploration Of New Rechargeable Chemical Power Source

Although people knew about chemical power sources long time ago, they did not understand the principles of batteries. Batteries were not application until 1800 when Volt Batteries were invented by an Italian Volt. Batteries, varing from lead-acid battery, Ni-Cd battery, nickel-metal hydride battery to lithium ion battery which was born in 1991, have been applied to broad fields in people's lives and are quite significant to the development of society. Meanwhile, in response to the needs of modern society and emerging ecological concerns, it is essential to find new chemical power sources and energy storage systems. This paper aims to explore innovative chemical power sources.Rapid development has been achieved for LIBs since its birth in 1991, due to their advantages of high energy density, high output voltage, little self-discharge and no memory effect. It has been widely used not only in electronic devices, such as mobile phone, lap-top, portable camera, but also in some important fields for the contries' development, such as transportation, military weapons, aerospace and so on. What is more, it is significant to develop electronic vehicles (EVs) to deal with problems caused by energy shortage and pollution. Lithium ion batteries are one of the most promising power sources for EVs. However, the further application of LIBs in EVs has been hindered by its safety and high price. For the commercial LIBs at present, carbon is used for anode and LiCoO₂ for cathode, with great amount of organic electrolyte. The organic electrolyte could cause combustion or even explosion due to improper usage. Such cases happened in Dell and Nokia products, gave rise to - large loss to the companies. And the safety problem would be more serious when adopting LIBs for EVs. Besides, high price of electrolyte and seperating membrane, complex process of organic electrolyte preparation and strict control of moisture, give rise to high price of LIBs.Various kinds of batteries with aqueous electrolyte have been researched since long time ago, such as alkaline manganese batteries, nickel-hydrogen batteries, nickel-cadmium batteries, lead-acid batteries, air batteries, and so on. Although there are still some limits for batteries with aqueous electrolyte, such as narrow electrochemical window, low voltage, they present a lot of advantages compared with organic electrolytes, such as low cost, easy preparation, high conductivity, safety, no restrict of moisture or oxgen, environmental evrionmental friendliness and so on. Efforts were made to develop aqueous reversible lithium ion batteries (ARLB) in previous work. However, there is no systematic and further deep investigation, in terms of electrochemical activities of Li-acitive materials in aqueous electrolyte, differences of their performance between in organic and aqueous electrolytes. Moreover, electrochemical performance of ARLB reported in the previous literatures needs further improvement, especially for its cycle performance.In chapterâ…¢, Several electrode materials were synthesized by solid-state method, such as LiCoO₂, LiMn₂O₄, LiCo_1/3Ni_1/3Mn_1/3O₂, LiFePO₄, LiV₃O₈, and so on. XRD and SEM were used for the characteristic analysis of these materials mentioned above. XRD results reveal that the diffraction peaks are consistent to the previous reports. Cyclic Voltammogram(CV), charge and discharge test system, and EIS were adopted to investigate their electrochemical performance. CVs present that all the materials mentioned can accommodate lithium in aqenous electrolyte. Because of the over-potential effect of the electrode, electrochemical window is wider compared with that of calculated theoretically. The oxygen and hydrogen do not affect insertion and extraction reaction into the electrode materials. By adjusting pH value, the electrochemical window could be adjusted, and more materials could be used in ARLB. Besides, results from ARLB indicate that there is no SEI film formed on the surface of the electrode materials, which is quite different from the phenomenon in organic electrolyte. We suppose that it is the explanation to that the poor cycle performance of ARLB.In chapterâ…£, LiV₃O₈ electrode material was synthesized by the traditional solid-state method. The result of slow scan cyclic voltammetry of LiV₃O₈ in organic electrolyte reveals that there are three redox peaks on the curve, i.e. 2.25 V, 2.21V and 1.72V ( vs. Li), respectively, suggesting that there are three phase transition when lithium ions insert into LiV₃O₈, and only two oxidation peak, 2.36 V and 2.99 V (vs. Li) when lithium ions extract from LiV₃O₈. The results of constant current charge-discharge experiments show that the capacity of LiV₃O₈ is 150 mAh /g. The capacity is lower than that of LiV₃O₈ prepared by other methods reported in literature. However, its charge-discharge reversibility is very good and the coulombic efficiency is almost 100 percent. The as-prepared material has good cycling performance. The capacity did not decay during the first 10 cycles. The cyclic voltammetry experiments of LiV₃O₈ in aqueous solution showed that the behavior of lithium ion insertion/extraction in the LiV₃O₈ is similar with that in organic electrolyte. LiV₃O₈ is suitable for aqueous lithium rechargeable battery anode material because of the redox peaks potential of lithium-ion intercalated/deintercalated into and from LiV₃O₈ in aqueous solution within the electrochemical window of water. AC impedance method was employed to investigated the kinetics of lithium ion insertion in LiV₃O₈ and the kinetic parameters were calculated.In chapterâ…¤, on the basis of the research above, we chose various materials to fabricate batteries with different voltages. The systems we investigated in this chapter are listed as following: LiV₃O₈//LiCoO₂, LiV₃O₈//LiMn₂O₄, LiV₃O₈// LiCo_1/3Ni_1/3Mn_1/3O₂, LiV₃O₈// LiFePO₄. We find that the batteries with LiV₃O₈ as anode materials present excellent cycle performance, which could cycle for 450 times without serious capacity fading. However, the capacities of above cells still decay with long charge/discharge cycle. The reasons were analyzed in this chapter.In chapterâ…¥, We further investigated proper anode materials, and found that some conductive polymer such as polyaniline and polypyrrole, could used not only as cathode materials, but also as anode. For the first time, we proposed a new mechanism of ARLB based on intercalation theory and doping mechanism. The mechanism we proposed is a great innovation in electrochemisty.