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Using first-principles calculations, we have systematically investigated the adsorption and diffusion behavior of Li in MoO 3 bulk, on MoO 3 (010) surface and in MoO 3 /graphene composite. Our results indicate that, in case of MoO 3 bulk, Li diffusion barriers in the interlayer and intralayer spaces are 0.55 eV and 0.58 eV respectively, which are too high to warrant fast Lithium-ion charge/discharge processes. While on MoO 3 (010) surface, Li exhibits a diffusion barrier as low as 0.07 eV which guarantees an extremely fast Li diffusion rate during charge/discharge cycling. However, in MoO 3 /graphene monolayer, Li diffusion barrier is at the same level as that on MoO 3 (010) surface, which also ensures a very rapid Li charge/discharge rate. The rapid Li charge/discharge rate in this system originates from the removal of the upper dangling O1 atoms which hinder the Li diffusion on the lower MoO 3 layer. Besides this, due to the interaction between Li and graphene, the Li average binding energy increases to 0.14 eV compared to its value on MoO 3 (010) surface which contributes to a higher voltage. Additionally, the increased ratio of surface area provides more space for Li storage and the capacity of MoO 3 /graphene composite increases up to 279.2 mAhg −1 . The last but not the least, due to the high conductivity of graphene, the conductivity of MoO 3 /graphene composite enhances greatly which is beneficial for electrode materials. In the light of present results, MoO 3 /graphene composite exhibits higher voltage, good conductivity, large Li capacity and very rapid Li charge/discharge rate, which prove it as a promising cathode material for high-performance lithium-ion batteries (LIBs). [ABSTRACT FROM AUTHOR]

[Display omitted] • (1 1 0) orientation is favored for energy minimization of LiCoO 2 thin film. • LCO(1 1 0)/LiPON/Li shows a discharge capacity of 47 μAh cm−2 μm−1 (about 101 mAh g−1) on 10C-rate. • Oxygen reactive sputtering promotes the transformation from LiCoO 2 (1 1 0) texture to (0 0 3) texture. • LiCoO 2 (1 1 0) texture has the lowest interface and bulk resistance for Li+ transfer. The solid-solid interfaces have crucial, but still poorly understood, roles in the performance of thin-film lithium batteries (TFBs). The modulating of crystalline preferred growth orientation is an effective method to build rapid ionic diffusion channel with lower interfacial barrier. This work develops and reveals the interfacial electrochemical behaviors of textured cathode/solid electrolyte in TFBs by controlling preferred growth orientation of LiCoO 2 (LCO) thin-film. The LCO(0 0 3) texture is transformed from the (4 4 0) plane of Co 3 O 4 precursor with the lowest surface energy after annealing. Remarkably, oxygen reactive sputtering will promote the formation of LCO grains instead of Co 3 O 4 species, resulting in the growth of LCO along (1 1 0) facet with the lowest volume strain-energy after annealing. TFBs (LCO/LiPON/Li) configuration with LCO(1 1 0) texture exhibit enhanced electrochemical performance with the capacity of about 101 mAh g−1 about twice than that of (0 0 3) texture on 10C-rates, owing to the lower interface and bulk resistance. These results indicate that the method of controlling the lattice orientation not only minimize the lithium-ion diffusion pathways in the film textures, but also is beneficial to the interface between LCO and LiPON electrolyte to establish high performance solid-state batteries. [ABSTRACT FROM AUTHOR]

Lithium cobalt oxide (LiCoO 2 ) is considered as one of the promising building blocks that can be used to fabricate all-solid-state thin film batteries (TFBs) because of its easy accessibility, high working voltage, and high energy density. However, the slow interfacial dynamics between LiCoO 2 and LiPON in these TFBs results in undesirable side reactions and severe degradation of cycling and rate performance. Herein, amorphous vanadium pentoxide (V 2 O 5 ) film was employed as the interfacial layer of a cathode-electrolyte solid-solid interface to fabricate all-solid-state TFBs using a magnetron sputtering method. The V 2 O 5 thin film layer assisted in the construction of an ion transport network at the cathode/electrolyte interface, thus reducing the electrochemical redox polarization potential. The V 2 O 5 interfacial layer also effectively suppressed the side reactions between LiCoO 2 and LiPON. In addition, the interfacial resistance of TFBs was significantly decreased by optimizing the thickness of the interfacial modification layer. Compared to TFBs without the V 2 O 5 layer, TFBs based on LiCoO 2 /V 2 O 5 /LiPON/Li with a 5 nm thin V 2 O 5 interface modification layer exhibited a much smaller charge transfer impedance ( R ct ) value, significantly improved discharge specific capacity, and superior cycling and rate performance. The discharge capacity remained at 75.6% of its initial value after 1000 cycles at a current density of 100 μA cm -2 . This was mainly attributed to the enhanced lithium ion transport kinetics and the suppression of severe side reactions at the cathode-electrolyte interface in TFBs based on LiCoO 2 /V 2 O 5 /LiPON/Li with a 5 nm V 2 O 5 thin layer., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Potassium-ion batteries (PIBs), as one of the alternatives to lithium-ion batteries (LIBs), have attracted considerable attention on account of the affluence and low-cost of potassium. Moreover, CoC₂O₄ and graphene oxide (GO) have been used very well in lithium-ion batteries. Hence, the hybrid CoC₂O₄/GO was investigated as a new anode material for PIBs. The hybrid CoC₂O₄/GO was synthesized by a facile and cheap method combined with supersonic dispersion. Electrochemical measurements reveal that the hybrid CoC₂O₄/GO delivered an excellent cycling stability of 166 mAh g -1 at 50 mA g -1 and a superior rate capability even at 1 A g -1 . These results demonstrate although the cycle ability was insufficient for practical applications, transition-metal oxalates composites can still bring new hope to the development of PIBs.

The critical challenges for fluoride conversion cathodes lie in the absence of built-in Li source, poor capacity retention, and rate performance. For lithiated fluorides, the reason to limit their competitiveness is rooted in the facile coarsing of insulating LiF (as built-in Li source) and its insufficient splitting kinetics during charging. Previous efforts on blending LiF nanodomains with reductive metal, metal oxide, or fluoride by ball-milling method still face the problems of large overpotential and low current density. Herein we propose a strategy of dual-metal (Fe-Cu) driven LiF splitting to activate the conversion reaction of fluoride cathode. This lithiated heterostructure (LiF/Fe/Cu) with compact nanodomain contact enables a substantial charge process with considerable capacity release (300 mAh g -1 ) and low charge overpotential. Its reversible capacity is as high as 375-400 mAh g -1 with high energy efficiency (76%), substantial pseudocapacitance contribution (>50%), and satisfactory capacity retention (at least 200 cycles). The addition of Cu nanodomains greatly catalyzes the kinetics of Fe-Cu-F formation and decomposition compared with the redox process of Fe-F, which lead to the energy and power densities exceeding 1000 Wh kg -1 and 1500 W kg -1 , respectively. These results indicate that LiF-driven cathode is promising as long as its intrinsic conductive network is elegantly designed.