Study Of Anode Materials For Aqueous Rechargeable Lithium-ion Batteries

Due to use of organic electrolyte, traditional rechargeable lithium-ion batteries have a severe safety problem which is a big handicap for these batteries as the power sources in electronic vehicles. However, aqueous rechargeable lithium-ion battery (ARLB), which uses an aqueous solution as electrolyte, can solve this safety problem. In addition, aqueous rechargeable lithium-ion battery has some advantages, such as environmental friendliness, cheapness and facility getting. It was considered as the most promising chemical power source to be used as the power sources for electric vehicle. Nevertheless, there are a few materials that can be used in aqueous rechargeable lithium-ion battery owing to the low decomposition voltage of water (1.23 V). It has been reported that LiMn₂O₄ material exhibited a good cycling stability in aqueous electrolyte whereas the aqueous rechargeable lithium-ion batteries using the LiMn₂O₄ cathode and the different anodes exhibited different cycling performances. Hence, anode materials affect electrochemical properties of the ARLB to a great extent.In this paper, we introduced the principle of the aqueous lithium ion battery and reviewed the development of the ARLB. The aims of this study are to concentrate on the anode materials for the ARLB. Thermogravimetry (TG) was used to ascertain the preparation processes. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were adopted to analyse the structural characterization. Cyclic voltammograms (CV) and electrochemical impedance spectroscopy (EIS) were used to study the electrochemical properties of the electrode materials.1. A macaroni-like Li_1+xV₃O₈ nanomaterial was directly prepared by sol-gel method. The results indicated that the sample prepared at 500℃exhibited good electrochemical properties in 1.0 mol·L^-1 Li₂SO₄ aqueous solution. It can be found that the sample had the same electrochemical behavior in aqueous electrolyte as in organic electrolyte. The LiMn₂O₄/1.0 M Li₂SO₄/Li_1+xV₃O₈ cell delivered an initial specific capacity of 189, 140, and 101mAh·g-1 (based on the weight of anode active materials) at the rates of 0.1, 0.5, and 1.0 C, respectively, and maintained about 36%, 38%, and 37% of the initial capacity after 100 cycles.2. In this paper, V₂O₅ porous material was synthesized by sol-gel method. it finds that the sample prepared at 400℃displays good electrochemical properties in 1.0 mol·L^-1 Li₂SO₄ aqueous electrolyte. From the CV data, it was known that the electrochemical behaviors of the V₂O₅ in aqueous electrolyte were also similar to those in organic electrolyte. An ARLB, which constructed with LiMn₂O₄ cathode, V₂O₅ anode and a 1 M Li₂SO₄ electrolyte, revealed that the obtained V₂O₅ could deliver a specific capacity of 76.23, 71.16, and 66.79 mAh·g^-1 at the rates of 0.1, 0.2, and 0.5 C, respectively, and delivered the capacitis of 58.82, 47.25, 36.05 mAh·g^-1 after 20 cycles.3. Anode material LiTi₂(PO₄)₃ was synthesized by the sol-gel method. The CV curves illustrated that LiTi₂(PO₄)₃ could be used as the anode material for aqueous rechargeable lithium-ion battery. From the EIS data, it was found that the impedance of the LiTi₂(PO₄)₃ coated with carbon was obvious lower than that without carbon coating. The ARLB using LiMn2O4 cathode, LiTi₂(PO₄)₃ anode, and 1 M Li₂SO₄ electrolyte delivered a capacity of 77.49 mAh·g^-1 at 0.1 C rate, but remained only 39.9% of the initial capacity after 20 cycles. Further study should be done to promote the cycling performance of this sample.