Search

Abstract Batteries that utilize low‐cost elemental sulfur and light metallic lithium as electrodes have great potential in achieving high energy density. However, building a lithium–sulfur (Li–S) full battery by controlling the electrolyte volume generally produces low practical energy because of the limited electrochemical Li–S redox. Herein, the high energy/high performance of a Li–S full battery with practical sulfur loading and minimum electrolyte volume is reported. A unique hybrid architecture configured with Ni–Co metal alloy (NiCo) and metal oxide (NiCoO2) nanoparticles heterogeneously anchored in carbon nanotube‐embedded self‐standing carbon matrix is fabricated as a host for sulfur. This work demonstrates the considerable improvement that the hybrid structure's high conductivity and satisfactory porosity promote the transport of electrons and lithium ions in Li–S batteries. Through experimental and theoretical validations, the function of NiCo and NiCoO2 nanoparticles as an efficient polysulfide mediator is established. These particles afford polysulfide anchoring and catalytic sites for Li–S redox reaction, thus improving the redox conversion reversibility. Even at high sulfur loading, the nanostructured Ni–Co metal alloy and metal oxide enable to have stable cycling performance under lean electrolyte conditions both in half‐cell and full‐cell batteries using a graphite anode.

Abstract Layered‐type transition metal (TM) oxides are considered as one of the most promising cathodes for K‐ion batteries because of the large theoretical gravimetric capacity by low molar mass. However, they suffer from severe structural change by de/intercalation and diffusion of K+ ions with large ionic size, which results in not only much lower reversible capacity than the theoretical capacity but also poor power capability. Thus, it is important to enhance the structural stability of the layered‐type TM oxides for outstanding electrochemical behaviors under the K‐ion battery system. Herein, it is investigated that the substitution of the appropriate Ti4+ contents enables a highly enlarged reversible capacity of P3‐type KxCrO2 using combined studies of first‐principles calculation and various experiments. Whereas the pristine P3‐type KxCrO2 just exhibits the reversible capacity of ∼120 mAh g−1 in the voltage range of 1.5–4.0 V (vs. K+/K), the ∼0.61 mol K+ corresponding to ∼150 mAh g−1 can be reversible de/intercalated at the structure of P3‐type K0.71[Cr0.75Ti0.25]O2 under the same conditions. Furthermore, even at the high current density of 788 mA g−1, the specific capacity of P3‐type K0.71[Cr0.75Ti0.25]O2 is ∼120 mAh g−1, which is ∼81 times larger than that of the pristine P3‐type KxCrO2. It is believed that this research can provide an effective strategy to improve the electrochemical performances of the cathode materials suffered by severe structural change that occurred during charge/discharge under not only K‐ion battery system but also other rechargeable battery systems.