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cathode material was prepared by the sol-gel method. The material was coated with the ionic conductor Li 3 VO 4 via direct reaction with NH 4 VO 3 at 350 C. The Li 3 VO 4 coated material had a higher ordered hexagonal layered structure, and less Li + /Ni 2+ cation mixing. The surface of the coated material was composed of Li 3 VO 4 polycrystals, which were impregnated into the bulk of the active material. The surface coating protected the material from contact with CO 2 in the air, thus inhibiting the formation of an Li 2 CO 3 layer. Electrochemical studies showed that the Li 3 VO 4 surface coating improved the activation of Mn 4+ ions, resulting in a high discharge capacity. It also prohibited the growth of a solid electrolyte interface film, and facilitated the charge transfer reactions at the electrode/electrolyte interface, thus improving the rate capability and cycle stability of the material. DSC analysis of the fully charged electrode showed that the temperature of the exothermic peak increased from 205.2 C to 232.8 C, and that the amount of heat that was released was reduced from 807.5 J g À1 to 551.0 J g À1 , highlighting the improved thermal stability of the material after coating with Li 3 VO 4 .

The continuous phase transformation to spinel LiMn 2 O 4 seriously hinders the electrochemical properties of Li-excess layered oxides in lithium ion batteries. Herein, we prepared a heterostructured Li-excess layered cathode material consisting of a Li(Li 0.18 Ni 0.15 Co 0.15 Mn 0.52 )O 2 active material in conjunction with a surface Li 4 M 5 O 12 spinel and a Li 2 O-LiBO 2 -Li 3 BO 3 glass coating layer. The material showed improved electrochemical kinetic properties with respect to its pristine counterpart because the Li 2 O-LiBO 2 -Li 3 BO 3 glass layer not only improved the ionic conductivity of the material but also depressed the side reactions of the electrode with the electrolyte. In addition, the surface Li 4 M 5 O 12 spinel constantly grew inwards the bulk of the material during long term charge-discharge cycling instead of the conventional LiMn 2 O 4 transformation for the pristine Li(Li 0.18 Ni 0.15 Co 0.15 Mn 0.52 )O 2 . As a result, the heterostructured cathode material showed overall improved electrochemicalperformance. An initial discharge capacity of 258.8 mAh g -1 was obtained at the 0.2 C rate with remarkable capacity retention of 92.2 % after 100 cycles. Moreover, the material showed excellent rate capacity delivering a high discharge capacity of 130.4 mAh g -1 and 100.4 mAh g -1 at the 10 C and 20 C rates, respectively. Differential scanning calorimetry showed that the exothermic temperature of the fully charged electrode was elevated to 324.2 o C with little thermal release of 232.5 J g -1 demonstrating good thermal safety of the material.

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The size and conductivity of the electrode materials play a significant role in the kinetics of sodium-ion batteries. Various characterizations reveal that size-controllable VS nanoparticles can be successfully anchored on the surface of graphene sheets (GSs) by a simple cationic-surfactant-assisted hydrothermal method. When used as an electrode material for sodium-ion batteries, these VS @GS nanocomposites show large specific capacity (349.1 mAh g after 100 cycles), excellent long-term stability (84 % capacity retention after 1200 cycles), and high rate capability (188.1 mAh g at 4000 mA g ). A large proportion of the capacity was contributed by capacitive processes. This remarkable electrochemical performance was attributed to synergistic interactions between nanosized VS particles and a highly conductive graphene network, which provided short diffusion pathways for Na ions and large contact areas between the electrolyte and electrode, resulting in considerably improved electrochemical kinetic properties.

MoS2 nanosheets were impregnated into mesoporous TiO2 and encapsulated by a graphene layer resulting in excellent Li ion storage properties.

A hybrid-ion battery was designed using Mg as the anode and TiS2 as the cathode, combined with a Na+/Mg2+ hybrid electrolyte.

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