Ultra high capacity and super long cycle life zinc air battery
Recently, the end of a decoupling of air electrodes into a hydrophobic discharge electrode and a hydrophilic charging electrode has improved the rate performance and cycle capacity per revolution of zinc air battery.
In addition, an alkali-resistant zinc-free anode is used to inhibit zinc dendrite and inhibit the hydrogen side reaction, and to improve the discharge depth of the zinc anode. Finally, with the optimization and improvement of the cathode and anode, the zinc air battery achieves ultra-high cycle capacity and long cycle life.
Problems with zinc air battery
Traditional two-electrode zinc air battery face two main problems:
The kinetic contradiction of oxygen reduction (ORR) and oxygen evolution (OER) reactions of catalysts in air electrodes and high potential catalysts is prone to oxidation, and long cycle life is often obtained under very low cycle capacity conditions.
There are problems such as zinc dendrites, hydrogen evolution side reactions and zinc corrosion in the zinc anode, and long cycle life is often obtained under very low discharge depth conditions. The low cycle capacity per turn and the depth of discharge of the zinc anode make the energy density of zinc air battery much lower than their theoretical energy density. It is also precisely because of the long cycle life that top 50 lithium ion battery manufacturers begin to develop in this direction.
Therefore, after the synergistic improvement of the cathode and anode of zinc air battery, improving the cycle capacity per revolution of zinc air battery and the discharge depth of zinc air battery is the first task to improve the practicality of zinc air battery.
Design principle of the zinc air battery
According to the different principles of oxygen reduction and oxygen precipitation reaction on the gas-liquid-solid three-phase interface, the principle of zinc air battery is hydrophobic discharge electrode and hydrophilic charging electrode. Among them, monoatom iron with high oxygen reducing activity is used as an oxygen reducing catalyst, and PTFE is used as a viscous agent to construct a hydrophobic discharge electrode.
Using hydrophilic charging electrodes, three-electrode zinc air battery are automatically switched to the corresponding charging electrodes and discharge electrodes through relays during the charging and discharging processes. After working for a long time, the monoatomic iron structure is maintained.
FeNC will be oxidized to form iron oxide after a short period of operation in C-RZABs, resulting in degradation of FeNC performance. The three-electrode structure can select highly active oxygen reduction catalysts and oxygen evolution catalysts, respectively, to achieve the lowest oxygen precipitation and oxygen reduction voltage differences. The final zinc air battery achieves a large cycle capacity and a low charge and discharge voltage difference. Moreover, it has longer cycle life as lithium ion deep cycle battery.
The zinc-free copper foam tinning anode is resistant to alkali corrosion, induces the growth of zinc on the crystal surface and inhibits the side reaction of hydrogen production, thereby improving the discharge depth and charging efficiency of zinc air battery.
Advantages of zinc air battery
In the zinc air battery system, with the increase in cycle capacity and cycle time per revolution, zinc deep discharge is lacking. As well as problems such as zinc dendrites, zinc corrosion and side reactions, the energy density and cycle life of zinc air battery are severely restricted.
Through theoretical calculation, it is found that tin can effectively induce the growth of zinc crystal face and low hydrogen production activity, so electroless tin plating on copper surfaces is used as zinc-free anode, so as to achieve high discharge depth and charging efficiency.
SEM was found to induce zinc deposition of planar structures. The atomic structure of the crystal plane can be clearly seen by spherical electron microscopy, and the various characteristics fully prove that the formation of the crystal plane is effectively induced.
Electrochemical tests have shown that zinc is more resistant to corrosion. After zinc deep discharge, it can be used as a growth substrate for zinc, thus solving the problem of lack of nucleation sites after zinc metal depth. The hydrogen production activity of znic is lower than that of zinc flakes and copper foam, so it can effectively inhibit the side reactions of HER, and Zn induced by Zn can also inhibit the side reactions.
In addition, the microscope can clearly see that there are almost no hydrogen bubbles on the surface and that large particles of zinc metal have formed. A large number of hydrogen bubbles can be found on the surface of copper foam, and there are obvious zinc dendrites and hydrogen bubbles on the surface of zinc sheets. It shows that copper foam and zinc sheets do not have better loading efficiency and inhibit zinc dendrites.
Performance of zinc air battery
Based on the hydrophobic discharge electrode, hydrophilic charging electrode and zinc-free anode, high discharge power and charging rates can be achieved. Stable operation greater than 5250 under current density and discharge capacity per cycle.
Under these conditions, the difference in charge and discharge voltage is small, the cycle capacity per revolution is higher than that of the reported zinc air battery, and the effect of suppressing zinc dendrites is very good. The large circulation of battery capacity can still work stably for more than 1000 hours and has good rate performance. Three-electrode battery modules are used to drive e-bikes, which have high energy density and low cost.
In this paper, a decoupling strategy is proposed to construct discharge electrodes and charging electrodes with optimal gas-liquid-solid three-phase interface. This prevents oxidation of the oxygen reducing catalyst and increases the cycle capacity of the zinc air battery. As a new idea for improving the cycle life and overall cycle capacity of zinc air battery, it has enlightened the interface design and performance improvement of other metal-air batteries.