its high specific capacity of 1675 mA h g −1 , which is based on the redox reaction that converts sulfur to lithium sulfide (Li 2 S) reversibly via various intermediate lithium polysulfides (Li 2 S n , n = 2-8). [2] This and the abundance of low-cost sulfur makes the LSB one of the more promising future battery technologies. [2b,3] However, commercialization of LSBs has generally been hampered by low sulfur utilization and poor long-term cyclability. This is due to the poor conductivity of the pristine sulfur, large volumetric expansion during the discharge process (80% volumetric expansion from S to Li 2 S), high solubility of the lithium polysulfides and passivation of the reactive surface of the metallic lithium anode. [2d,4] Dissolution of lithium polysulfides triggers capacity loss via the so-called "shuttle effect" during cycling, which lowers the Coulombic efficiency (CE) of the cell. This problem can be addressed, in part, by producing a cathode in which the sulfur is encapsulated. [5] To tackle these issues, novel host materials have been developed for the sulfur cathode to limit the movement of the lithium polysulfides. These include various carbonaceous materials such as mesoporous carbon, [3b,6] porous carbon capsules, [7] graphene, [8] conductive polymers (such as polypyrrole [9] and polyaniline [10] ), and carbon interlayers. [11] While carbonaceous host materials on the cathode all give the desirable properties of low density and high electronic conductivity, the non-polar nature of the carbon surface offers limited attraction to the polar lithium polysulfides. Therefore, while improved electrochemical performance can be achieved with the available carbonaceous materials, the general reliance on physical trapping and/ or weak chemical bonding limits the level of sulfur loading. [8b] Furthermore, modest improvements have been realized through different morphologies of the carbonaceous materials. Hierarchically porous nanostructures interconnected with conductive walls such as microspheres composed of graphene and nanotubes, demonstrated enhanced entrapment of lithium polysulfides. [8c,12] Overall, even the best carbonaceous host materials do not appear likely to meet the ultimate demands of LSB technology.A number of inorganic oxides have attracted research attention as cathode additives due to the prospect of providing Various host materials have been investigated to address the intrinsic drawbacks of lithium sulfur batteries, such as the low electronic conductivity of sulfur and inevitable decay in capacity during cycling. Besides the widely investigated carbonaceous materials, metal oxides have drawn much attention because they form strong chemical bonds with the soluble lithium polysulfides. Here, mesoporous Magnéli Ti 4 O 7 microspheres are prepared via an in situ carbothermal reduction that exhibit interconnected mesopores (20.4 nm), large pore volume (0.39 cm 3 g −1 ), and high surface area (197.2 m 2 g −1 ). When the sulfur cathode is embedded in a matrix of mesoporous Magnéli T...

As an anode material for lithium-ion batteries, titanium dioxide (TiO 2 ) shows good gravimetric performance (336 mAh g −1 for LiTiO 2 ) and excellent cyclability. To address the poor rate behavior, slow lithium-ion (Li + ) diffusion, and high irreversible capacity decay, TiO 2 nanomaterials with tuned phase compositions and morphologies are being investigated. Here, a promising material is prepared that comprises a mesoporous "yolk-shell" spherical morphology in which the core is anatase TiO 2 and the shell is TiO 2 (B). The preparation employs a NaCl-assisted solvothermal process and the electrochemical results indicate that the mesoporous yolk-shell microspheres have high specific reversible capacity at moderate current (330.0 mAh g −1 at C/5), excellent rate performance (181.8 mAh g −1 at 40C), and impressive cyclability (98% capacity retention after 500 cycles). The superior properties are attributed to the TiO 2 (B) nanosheet shell, which provides additional active area to stabilize the pseudocapacity. In addition, the open mesoporous morphology improves diffusion of electrolyte throughout the electrode, thereby contributing directly to greatly improved rate capacity.

To achieve high efficiency lithium ion batteries (LIBs), an effective active material is important. In this regard, monodisperse mesoporous titania beads (MMTBs) featuring well interconnected nanoparticles were synthesised, and their mesoporous properties were tuned to study how these affect the electrochemical performance in LIBs. Two pore diameters of 15 and 25 nm, three bead diameters of 360, 800 and 2100 nm, and various annealing temperatures (from 300 to 650 °C) were investigated. The electrochemical results showed that while the pore size does not significantly influence the electrochemical behaviour, the specific surface area and the nanocrystal size affect the performance. Also, there is an optimum annealing temperature that enhances electron transfer across the titania bead structure. The carbon content employed in the electrode was varied, showing that the bead diameter strongly influences the minimal content of the conductive carbon required to fabricate the electrode. As a general rule, the smaller the bead diameter, the more carbon was required in the electrode. A large energy capacity and high current rate performance were achieved on the MMTBs featuring high surface area, nano-sized anatase crystals and well-sintered connections between the nanocrystals. The high stability of these mesoporous structures was demonstrated by charge/discharge cycling up to 500 cycles. Devices constructed with the MMTBs retained more than 80% of the initial capacity, indicating an excellent performance.

Optimised dehydrated, nitrogen doped Li4Ti5O12 featuring mesoporosity, high crystallinity and 2D nano-sized flakes properties that deliver high electrochemical performance.