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High-capacity Ni-rich layered oxides are promising cathode materials for secondary lithium-based battery systems. However, their structural instability detrimentally affects the battery performance during cell cycling. Here, we report an Al/Zr co-doped single-crystalline LiNi0.88Co0.09Mn0.03O2 (SNCM) cathode material to circumvent the instability issue. We found that soluble Al ions are adequately incorporated in the SNCM lattice while the less soluble Zr ions are prone to aggregate in the outer SNCM surface layer. The synergistic effect of Al/Zr co-doping in SNCM lattice improve the Li-ion mobility, relief the internal strain, and suppress the Li/Ni cation mixing upon cycling at high cut-off voltage. These features improve the cathode rate capability and structural stabilization during prolonged cell cycling. In particular, the Zr-rich surface enables the formation of stable cathode-electrolyte interphase, which prevent SNCM from unwanted reactions with the non-aqueous fluorinated liquid electrolyte solution and avoid Ni dissolution. To prove the practical application of the Al/Zr co-doped SNCM, we assembled a 10.8 Ah pouch cell (using a 100 μm thick Li metal anode) capable of delivering initial specific energy of 504.5 Wh kg−1 at 0.1 C and 25 °C.

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Potassium-ion batteries (KIBs) have gained significant interest in recent years from the battery research community because potassium is an earth-abundant and redoxactive metal, thus having the potential to replace lithium-ion batteries for sustainable energy storage. However, the current development of KIBs is critically challenged by the lack of competitive electrode materials that can reversibly store large amounts of K + and electrolyte systems that are compatible with the electrode materials. Here, we report that cobalt monochalcogenide (CoSe) nanoparticles confined in N-doped carbon nanotubes (CoSe@NCNTs) can be used as a K + -storing electrode. The CoSe@NCNT composite exhibits a high initial Columbic efficiency (95%), decent capacity (435 mAh g −1 at 0.1 A g −1 ), and stability (282 mAh g −1 2.0 A g −1 after 500 cycles) in a 1 M KPF 6 −DME electrolyte with K as the anode over the voltage range from 0.01 to 3.0 V. A full KIB cell consisting of this anode and a Prussian blue cathode also shows excellent electrochemical performance (228 mAh g −1 at 0.5 A g −1 after 200 cycles). We show that the NCNT shell is effective not only in providing high electronic conductivity for fast charge transfer but also in accommodating the volume changes during cycling. We also provide experimental and theoretical evidence that KPF 6 in the electrolyte plays a catalytic role in promoting the formation of a polymer-like film on the CoSe surface during the initial activation process, and this amorphous film is of critical importance in preventing the dissolution of polyselenide intermediates into the electrolyte, stabilizing the Co 0 /K 2 Se interface, and realizing the reversibility of Co 0 /K 2 Se conversion.

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Despite outstanding theoretical energy density (2600 Wh kg–1) and low cost of lithium–sulfur (Li–S) batteries, their practical application is seriously hindered by inferior cycle performance and low Coulombic efficiency due to the “shuttle effect” of lithium polysulfides (LiPSs). Herein, we proposed a strategy that combines TiO–TiO2 heterostructure materials (H-TiO x , x = 1, 2) and conductive polypyrrole (PPy) to form a multifunctional sulfur host. Initially, the TiO–TiO2 heterostructure can enhance the redox reaction kinetics of sulfur species and improve the conductivity of sulfur cathode together with the PPy coating layer. Moreover, the defect-abundant H-TiO x matrices can trap LiPSs by the formation of Ti–S bond via the Lewis acid–base interaction. Furthermore, the PPy coating can physically hinder the diffusion of LiPSs, as well as chemically adsorb LiPSs by the polar–polar mechanism. Benefiting from the synergistic effect of H-TiO x and PPy layer, the novel cathode delivered high specific capacities at different current rates (1130, 990, 932, 862, and 726 mAh g–1 at 0.1, 0.2, 0.3, 0.5, and 1C, respectively) and an ultralow capacity decay of 0.0406% per cycle after 1000 cycles at 1C. This work can not only indicate effectiveness of employing H-TiO x materials to realize the LiPSs immobilization but also shed light on the feasibility of combining different materials to achieve the multifunctional sulfur hosts for advanced Li–S batteries.