Research On Anode And Electrolyte Regulation Strategy And Its Application In High Performance Metal Air Battery

With the exploitation and consumption of fossil fuels,increasing environmental pollution and resource depletion are unavoidable problems.In order to balance the continuous supply of energy with the quality of the resource environment,we need to explore new forms of green and sustainable energy.Due to the"unlimited supply"of air,many researchers pay attention to metal-air batteries,and lithium-air battery and Zinc-air battery are the two most popular metal-air batteries.Although Li-air batteries have an excellent theoretical energy density(11,400 Wh kg^-1),they are likely to pose potential risks when applied.For example,when the Li metal anode is in contact with the electrolyte,this will lead to the uneven distribution of Li dendrites,which will directly affect the cycle stability of the battery.There are plenty of ways to improve,but Li-air batteries are a long way from commercialisation.While Zn-air batteries have been commercialized due to its obvious advantages of low cost,strong popularity and high safety,corrosion and leakage of strong alkaline electrolytes can not be ruled out during use,therefore,the design of other types of electrolytes is particularly important.Therefore,in order to solve the problems mentioned above effectively,this paper focuses on two aspects of polymer modification and electrolyte design,By inducing the uniform deposition of metals,the efficient utilization of metal electrode can be realized.And its application in Li-air batteries and Zn-air batteries was explored.The main research results are as follows:（1）During the cycling process of Li-air batteries,the uneven nucleation of the Li anode surface often occurs due to the uneven Li⁺flux.The instability of solid electrolyte interphase（SEI）,the irregular growth of dendrite and the poor cycling stability are caused.Therefore,in this study,a functional modified layer was constructed on the Li anode surface to achieve efficient cycle stability of the battery.First,an alloy layer（Li Zn）was constructed on the surface of Li anode by the displacement reaction of Li and Zn I₂ solution,the reaction product（Li I）was further polymerized withα-ethyl cyanoacrylate to form an iodine-modified polymer protective film（IPA）.The combination of uniform and dense Li Zn alloy and IPA polymer with high mechanical strength can not only restrain the formation of dendrite,but also reduce the side reaction induced by electrolyte or other harmful substances,the interface impedance,the local current density and the decomposition potential of the products can also be reduced.Therefore,the cycle stability of IPA-Li based symmetric batteries and Li-air batteries is greatly improved.The results show that the Li-air battery with the IPA-Li anode can achieve an ultra-long cycle life（120 cycles）at low voltage polarization（1.6 V）at a current density of 500 m A g^-1.（2）It is found that the solid electrolytes can avoid the inherent limitations of liquid electrolytes,such as volatilization,leakage,flammability,and inability to self-supporting.Therefore,many solid-state electrolytes research strategies emerge as the times require.However,due to the existence of a solid-solid transport interface between Li anode and solid electrolyte,there are problems such as high interfacial impedance,small active area,and poor wettability.Li1.5Al0.5Ge1.5（PO4）3（LAGP）is a common solid-state electrolyte material,which contains Ge⁴⁺,is prone to direct parasitic reactions with Li metals,seriously affecting the performance of batteries.Therefore,we introduce polymer buffer layer to alleviate the contradiction between solid electrolyte and electrode materials.In this study,the composite electrolyte（P-PEGMA@LAGP）was prepared by in-situ polymerization of poly（ethylene glycol）methyl ether methacrylate（PEGMA）on the anode side of solid electrolyte（LAGP）.P-PEGMA with high interfacial compatibility can reduce the interfacial impedance and reactivity of Li/LAGP,thereby inhibiting the irregular growth of Li dendrites.The results showed that the polymer-inorganic composite electrolyte also reduced the polarization of the battery and enhanced the cycling stability of the Li-air battery.The Li-air battery with the P-PEGMA@LAGP composite electrolyte greatly improved the cycle stability（80 cycles）at a capacity of 500 m Ah g^-1,which was superior to that of the pure LAGP electrolyte（12 cycles）.（3）The traditional alkaline electrolyte has a strong corrosive effect on the Zn anode,although the modification strategy of the Zn anode has been widely studied.However,the development of Zn-air battery still can not avoid the side reaction between anode and electrolyte,the irregular growth of Zn dendrite and the hydrogen evolution reaction of proton（H⁺）.Moreover,most of the current Zn-air battery of commercialisation is one-off and can not be recycled.In order to solve the corrosion problem of the Zn-air battery components,we have abandoned the alkaline electrolyte and designed and regulated the aprotic electrolyte.By comparing the effects of a series of electrolytes on the discharge product（Zn O）,we designed a class of organic zinc salt/aprotic solvent combined electrolytes,and focused on exploring the impact and application of Zn（OTF）₂/DMSO electrolytes on Zn-air batteries.The results showed that the redox of 4e^-between Zn and O₂ occurred at the interface between the Zn-air battery positive electrodes.The high Lewis basic DMSO broke the electrostatic potential energy of Zn O surface and promoted the fracture of Zn-O bond,the formation/decomposition of insulating discharge products（Zn O）at the cathode instead of at the anode is realized,thus eliminating the generation of by-products such as Zn（OH）₄^2-and Zn（OH）₂.This greatly improves the long-term cycling stability of the rechargeable Zn-air battery.Under the condition of 0.1 m A cm^-2,Zn symmetric cells and Zn-air batteries with Zn（OTF）₂/DMSO electrolyte showed long-term cycle stability of 1350 h（voltage polarization～30 m V）and 1000 h（overpotential～1.1 V）,respectively,achieving an ultra-long discharge capacity of 8 m Ah,and a capacity retention rate of 99.3% after 72 hours of storage.