Design And Investigation Of Lithium/Oxygen Batteries With Advanced Performances

As the limit of energy density, conventional lithium-ion batteries (LIBs) could notsatisfy our increasing demands in many fields, such as electric vehicles and electronicproducts. Recently, as the super high specific capability, rechargeable nonaqueouslithium/oxygen batteries (LOBs) have been a new research area. However, before LOBs’further application in our daily life, some challenges are needed to be overcomeurgently, for example, the poor cycling performance, the low rate capability, the lowround-trip efficiency and the safety problem. Here, we put forward several highlyeffective strategies for advanced nonaqueous LOBs.First of all, we designed a novel oxygen electrode by embedding a multi-functionalunit, TBGL (short for the triple-phase boundary guiding layer). In conventional LOBs,the whole porous electrode was flooded by the electrolyte, which vastly inhibits theoxygen effective transport. Obviously, it will lead to the poor electrochemicalperformance of LOBs. In our novel oxygen electrodes, the TBGL is not wetted byelectrolyte, and thus it improves the diffusion of oxygen in porous electrodes. Weshowed that LOBs with TBGL based novel oxygen electrodes can be cycled at a veryhigh current density of3000mA/g for over50cycles.On the basis of novel oxygen electrodes, we then made a further investigation oncarbon and non-carbon based electrode active materials. For LOBs, the active materialplays a very important role as the reaction zone and the storage room for dischargeproduces, and thus the choice and design of active materials becomes a crucial issue. Onone hand, we investigated the influence of carbon materials’ pore structures on LOBs,and then demonstrated the advanced Super P based LOBs; on the other hand, weprepared polypyrrole based LOBs, which have a higher specific capability than carbonbased LOBs. It is worth to mention that the specific capacity of W-PPy based LOBscould exceed10000mAh/g, which is2.3times as Super P based LOBs.In addition, we also investigated the influence of solvents on LOBs and explorednovel DMI based LOBs, which have a very high round-trip efficiency. Early worksdemonstrated the method to improve LOBs’ round-trip efficiency by using catalysts, butmany catalysts would cause side reactions in oxygen reduction reactions (ORRs) andoxygen evolution reactions (OERs). Here, we proposed a new method. By using DMI asthe solvent, we improved the round-trip efficiency of LOBs to77.2%at current density of100mA/g, which is much higher than widely used DMSO based LOBs (66.4%).