Aqueous Lithium/Air Rechargeable Batteries

Abstract

Several key issues of aqueous lithium/air rechargeable batteries that consists of a water-stable lithium electrode, an aqueous electrolyte, and a bifunctional air electrode are reviewed. Based on research and discussion of these issues, the challenges and prospects for high energy density aqueous lithium/air rechargeable batteries are described. From a broader perspective, lithium/air rechargeable batteries that employ aprotic electrolytes are also briefly introduced for comparison. Ç IntroductionDuring the past few years, lithium/air rechargeable batteries have received significant attention, due to their potential for development as a high energy density battery for electric vehicles (EVs). The number of research papers on lithium/air batteries has increased year by year. The sharp increase in interest is motivated by the high theoretical energy density of lithium/air batteries (11140 W h kg ¹1 , excluding oxygen), which is comparable with that of 13000 W h kg ¹1 for gasoline 1 and such an energy density would be applicable for EV batteries with an acceptable driving range. There is high expectation for high energy density lithium/air batteries to serve as power sources to drive pure EVs, which would contribute to a reduction in global greenhouse gas emissions and address the crisis of fossil energy source exhaustion.Two types of lithium/air batteries have been studied, nonaqueous and aqueous electrolyte systems. Two possible cell reactions for the nonaqueous electrolyte system areand 2Li þ 1=2O 2 ) Li 2 O ð2Þ The reversible cell voltages for reactions (1) and (2) are 2.959 and 2.913 V, respectively. It has been demonstrated that reaction (1) is reversible, whereas reaction (2) is irreversible. 2The energy density of 3456 W h kg ¹1 (including oxygen) is calculated using reaction (1). In an aqueous electrolyte, water molecules are involved in the reaction according to the following reaction:The reversible cell voltage for reaction (3) is 3.84 V in a neutral solution, and the energy density (including oxygen) is 2450 W h kg ¹1. The energy density of the aqueous system is approximately 30% lower than that of the nonaqueous system (including oxygen).It is well known that lithium reacts vigorously with water to produce LiOH and hydrogen gas. Therefore, to avoid this parasitic reaction, most research on lithium/air batteries have focused on using aprotic organic solvents as electrolytes. In the case of using aprotic electrolytes, Bruce and colleagues have given a preliminary demonstration using gravimetric analysis and in situ mass spectrometry that Li 2 O 2 formed upon discharge was decomposed to Li and O 2 during a charge cycle, both with and without a catalyst.2 However, there are some severe problems that must still be addressed, such as lithium corrosion by water and CO 2 ingression when operated in air (poor lifetime), precipitation of Li oxides on the porous cathode (low capacity), and high polarization resistance of the air electrode (low energy conversion efficiency). These problems could be removed...

Hybrid and Aqueous Lithium‐Air Batteries

“…[ 5a , 8 ] In our experiments, we occasionally observed a change in the color of LTAP when lithium dendrites touched the solid electrolyte after long-term cycling, similar to the reduction of Ti 4+ observed in Li 0.33 La 0.57 TiO 3 . [ 56 ] The LTAP is not stable in strong acids or bases, [ 57 ] necessitating the use of a catholyte with a mild pH value as discussed in the catholyte section later.…”

Comment on “Cycling Li-O 2 batteries via LiOH formation and decomposition”

“…This reaction is well known as the charge reaction of aqueous lithium-air batteries (4,5). The potential of this reaction is widely agreed to be 3.84 V (versus Li + /Li) in neutral solutions or 3.42 V when pH = 12, much higher than 3.0 V in Liu et al's paper.…”

Aqueous Lithium-Air Batteries

“…Therefore, higher lithium-ion conductivity solid electrolytes with excellent mechanical properties should be developed to realize a high power density aqueous lithium-air battery. The conductivity target at the operation temperature is 10 −3 S cm −1 [32]; the IR drops for 0.15 and 0.075 mm thick electrolytes is 0.75 and 0.375 V at 5 mA cm −2 , respectively. Many conductivity data for the Li 1+x A x Ge y Ti 2−y (PO 4 ) 3 system have been reported in the last 25 years.…”

“…The lithium-ion conductivity and salt diffusion coefficient of PEO 18 LiTFSI were significantly enhanced by the addition of TEGDME. The lithium-ion conductivity for PEO 18 [32]. The lithium dendrite formation was examined using the Li/PEO 18 LiTFSI-2.0 TEGDME/O-LATP/saturated LiCl aqueous solution/Pt, air cell at 60°C and a constant current density of 1.0 mA cm −2 , where the thickness of the composite polymer electrolyte was 100 μm, and platinum with platinum black was used as the air and reference electrodes.…”