Thus, practical applications of Li batteries have been limited over the past 50 years.We have gained a substantial amount of information about the nucleation and growth process of Li dendrites and the SEI fi lm over time, [5][6][7][8] and many attempts have been made to inhibit Li dendrites and improve cycling performance. This has led to a revival of Li metal batteries. [9][10][11][12][13] According to previous studies, Li dendrite originates from uneven Li deposition and dissolution. When ionic concentrations at the anode surface becomes zero at Sand's time, cations and anions in the liquid electrolyte show different behaviors, leading to excessive Li + ions at the surface. [ 14,15 ] At this point, lithium nucleates and grows dendritically as a function of current density and interfacial elastic strength. [ 5 ] Initial growth of Li dendrites promotes interfacial contacts between the Li anode, the separator, and the electrolyte, which decreases cell resistance. [ 15 ] However, further growth of Li dendrites may puncture the separator, leading to a short circuit of a cell. It is very important, therefore, to constrain the growth of dendrites in order to eliminate safety hazards associated with the Li anode.From decades of research, it is known that low current density, fl exible SEI fi lm, high Li + transference number (t Li + ), and large shear modulus of electrolytes can suppress the growth of Li dendrite. Many methods have been adopted enabling to increase the surface area of the Li anode to reduce the effective current density, use a single ion conductor (SIC) as an electrolyte to enhance t Li + , form a suitable SEI fi lm, employ quasi-solid or all-solid state electrolytes to promote the shear modulus, and coat the Li anode to avoid direct contact between the anode and the electrolyte. [ 1,3,16 ] Now, it is required to systematically summarize them to gain insights for better and more creative solutions. This review summarizes recent studies about the modifi cation of the electrolyte and the Li anode for Li batteries. Their design concepts and preparation methods are introduced, and the resulting effects on electrochemical performance are discussed in details. Simultaneously, challenges and future perspectives of Li batteries are also outlined. Electrolyte Modifi cationElectrolytes can be divided into three states: liquid, quasi-solid, and all-solid. [ 17 ] Quasi-solid and all-solid state electrolytes have Over the last 40 years, metallic lithium as an anode material has been of great interest owing to its high energy density. However, dendritic lithium growth causes serious safety issues. Awareness and understanding of the Li deposition and stripping processes have grown rapidly especially in recent years, and consequently, there have been many attempts to suppress the Li dendrites. Recent developments that have modifi ed the electrolytes and the Li anode in order to inhibit the growth of Li dendrite and improve cycling performance are summarized. It has been shown that current density, solid-electrolyte in...

In this work, a novel free-standing CuCo 2 S 4 nanosheet cathode (CuCo 2 S 4 @Ni) with high catalytic activity is fabricated for aprotic lithium−oxygen (Li−O 2 ) battery. This deliberately designed oxygen electrode is found to yield lower overpotential (0.82 V), improved specific capacity (9673 mA h g −1 at 100 mA g −1 ), and enhanced cycle life (164 cycles) as compared to the traditional carbonaceous electrode. The improved performance can be ascribed to the superb spinel structure of CuCo 2 S 4 , in which both Cu and Co exhibit more abundant redox properties, improving oxygen reduction reaction and oxygen evolution reaction kinetics effectively and boosting the electrochemical reactions. Furthermore, the welldesigned architecture also plays a critical role in the improved performance. Encouraged by the excellent catalytic activity of this free-standing cathode, large-scale pouch-type Li−O 2 cell based on CuCo 2 S 4 @Ni cathode is fabricated and can work under different bending and twisting conditions. This free-standing electrode provides a new strategy for developing Li−O 2 batteries with excellent performance and flexible wearable devices.

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