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SnO 2 has been recognized as one of the most potential anodes of lithium-ion batteries due to its high theoretical specific capacity, low cost, simple synthetic method, and environmental friendliness. However, the application of SnO 2 is hindered owing to its huge volume expansion (∼300 %) and poor electronic conductivity. In this work, carbon-coated SnO x containing some SnO anchored on the phosphorus-doped carbon framework (SnO x /C–P@C) has been fabricated via a novel, simple and green precipitation route using phytic acid as the complexing agent, carbon and phosphorus sources, and glucose as the second carbon source. Phosphorus-doped carbon framework in situ forms via calcining phytic acid at a high temperature. Phosphorus doping can further enhance the electronic conductivity of carbon. The carbon framework can provide sufficient buffer space to make the SnO x particles have good dispersion. The carbon layer from glucose can prevent the direct contact between SnO x and the electrolyte to decrease the side reactions and then reinforce the structure of SnO x /C–P@C. The synergistic effect of the double carbon effectively controls the volume expansion, enhances the electronic conductivity and diffusion coefficient of Li+ ions as well as capacitive contribution ratio, and reduces the charge transfer resistance of SnO x /C–P@C. The SnO x /C–P@C-0.5 sample with the carbon content of 25.8 wt% exhibits outstanding electrochemical performance. At 0.1 A g−1, the discharge specific capacity of 776.2 mAh g−1 can be reached after 100 cycles. At 0.5 A g−1, 555.5 mAh g−1 is still delivered after 200 cycles. Moreover, the sample shows good potential practical applications in the LiNi 0.5 Mn 1.5 O 4 //SnO x /C–P@C-0.5 full cell. 687.9, 597.1, 510.1, 434.8 and 595.6 mAh g−1 are retained for the full cell at 0.1, 0.2, 0.5, 1 and 0.1 C, respectively. The full cell cycling for 200 cycles at 0.5 C can still light up the light-emitting diode (LED) bulbs. [Display omitted] • Phytic acid is firstly used as P and C sources to synthesize SnO 2 /C–P@C. • The synthetic route is simple, low cost and environmental friendliness. • The double carbon greatly improves the electrochemical performance of SnO 2 /C–P@C. • SnO 2 /C–P@C holds significantly practical value in full cells. [ABSTRACT FROM AUTHOR]

The vast volume expansion of the Si anode during the charging process leads to rapid cycling performance fading and limits its applications in lithium-ion batteries. In this study, a unique core–double-shell structured porous Si@graphene@glycerin-Al2O3 (p-Si@G@g-Al2O3) composite is successfully prepared by using a porous Si (p-Si) microsphere as the core and graphene(G)/Al2O3 as the double shell layer via an electrostatic self-assembly strategy and a glycerin-involved sol–gel process. The addition of glycerin can reduce the nucleation growth rate of Al(OH)3 during the sol–gel process and enable more uniform deposition of an ultrathin Al2O3 layer on p-Si@G microspheres. Owing to the crucial role of the lithiated Al2O3 (LiAlO2)/G double shell layer in shielding the inner p-Si microsphere from the electrolyte and consolidating the mechanical structure of the p-Si microsphere, the synthesized p-Si@G@g-Al2O3 shows good cycling stability with a high reversible capacity of 1804.5 mA h g−1 at 0.2 A g−1 and excellent rate capacity with a capacity of 439 mA h g−1 at 8 A g−1, superior to those of p-Si@G and p-Si electrodes. Moreover, the electrochemical performance of p-Si@G@g-Al2O3 can also be further improved by ∼10% by only adding 5 wt% of carbon nanotubes (CNTs) in a slurry, due to the good capability of CNTs in building the interconnecting network between p-Si@G@g-Al2O3 microspheres. [ABSTRACT FROM AUTHOR]

To enhance the performance of Li‐ion batteries, hierarchical carbon‐based hollow frameworks embedded with cobalt nanoparticles are prepared by the pyrolysis of core‐shell ZIF‐8@ZIF‐67 polyhedrals prepared via a seed‐mediated growth method. The resultant hollow frameworks are composed of the N‐doped carbon as the inner shells and the porous graphitic carbon embedded with cobalt nanoparticles as the outer shells. Benefiting from the unique hollow architecture with large surface area and good electrical conductivity, the electrode materials exhibit good electrochemical performance with improved specific capacities, high‐rate capability, and good cycling stability for Li‐ion batteries. More importantly, the quantitative kinetic analysis reveals the crucial contributions of N doping and the porous structure of graphitic carbon with cobalt nanoparticles for boosting the performance of carbon‐based materials. The rational design of the unique carbon‐based architecture and the understanding of the underlying mechanism for the charge storage process are crucial to construct advanced carbon‐based materials for high‐performance Li‐ion batteries. [ABSTRACT FROM AUTHOR]

[Display omitted] • Phytic acid is firstly used as P and C sources to synthesize SnP 2 O 7 /C-P@C-N. • N-P co-doped carbon improves the electrical conductivity and generates defects. • SnP 2 O 7 /C-P@C-N exhibits good rate capability and cycling performance. • SnP 2 O 7 /C-P@C-N holds significantly practical value in full cells. N-doped carbon-coated SnP 2 O 7 anodes anchored on P-doped carbon framework (SPO/C-P@C-N) have been successfully synthesized via a novel and environmentally friendly method, using a green raw material of phytic acid as phosphorus and carbon sources, and dimethylimidazole as the second carbon source and nitrogen source. N-doped carbon coating and P-doped carbon framework inhibit the volume shrinkage and expansion, improve the electronic conductivity and diffusion coefficient of Li+ ions as well as capacitive contribution ratio, reduce the charge transfer resistance and the particle size, and then enhance the electrochemical performance of SPO/C-P@C-N. SPO/C-P@C-N-1.2 with the carbon content of 18.5 wt% exhibits excellent electrochemical performance. The discharge specific capacity is 416.6 mAh/g at 0.5 A/g after 200 cycles. 234.3 mAh/g is kept at 2 A/g for the 1000th cycle. In addition, the discharge specific capacity of the LiNi 0.5 Mn 1.5 O 4 //SPO/C-P@C-N-1.2 full cell is 206.6 mAh/g for the 200th cycle at 0.5C in 1.4–4.4 V. The full cell can power green, red, blue, and orange light-emitting diode (LED) bulbs, as well as LED small light strings and heart-shaped circuit boards. It is the first report on SnP 2 O 7 successfully applied to full cells, demonstrating the potential application. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights: • Numerical models are developed for all porous solid oxide fuel cells. • Electrolyte porosity changes are investigated for the solid oxide fuel cells. • Criterion of safe operations are considered in the simulation. • Effects of operating parameters for the solid oxide fuel cells are studied. • A novel design is proposed to improve the performance of solid oxide fuel cells. Abstract Conventional solid oxide fuel cells (SOFCs) could suffer from carbon deposition when fueled with hydrocarbons. For comparison, a new type of SOFC with porous electrolyte can resist carbon deposition because it allows oxygen molecules to transport from the cathode to the anode. As the transport of O 2 to the anode lowers the fuel cell performance and causes the risk of explosion, the rate of O 2 transport must be well controlled to ensure efficient and safe operation. Following our previous model, this paper focuses on electrolyte porosity optimization under various inlet methane mole fractions, inlet oxygen mole fractions and inlet gas flow rates. Furthermore, a new design with a partial porous electrolyte is proposed and numerically evaluated. The new design significantly improves the electrochemical performance compared with all-porous one. A conversion rate >90% from methane to syngas is achieved at the 0.33 inlet CH 4 mole fraction with the new design. The results enhance the understanding of all porous solid oxide fuel cells and the mechanism underlying, inspiring novel designs of solid oxide fuel cells. [ABSTRACT FROM AUTHOR]

In this paper, 2D models for direct carbon solid oxide fuel cells (DC-SOFCs) with in situ catalytic steam-carbon gasification reaction are developed. The simulation results are found to be in good agreement with experimental data. The performance of DC-SOFCs with and without catalyst are compared at different operating potential, anode inlet gas flow rate and operating temperature. It is found that adding suitable catalyst can significantly speed up the in situ steam-carbon gasification reaction and improve the performance of DC-SOFC with H 2 O as gasification agent. The potential of syngas and electricity co-generation from the fuel cell is also evaluated, where the composition of H 2 and CO in syngas can be adjusted by controlling the anode inlet gas flow rate. In addition, the performance DC-SOFCs and the percentage of fuel in the outlet gas are both increased with increasing operating temperature. At a reduced temperature (below 800 °C), good performance of DC-SOFC can still be obtained with in-situ catalytic carbon gasification by steam. The results of this study form a solid foundation to understand the important effect of catalyst and related operating conditions on H 2 O-assisted DC-SOFCs. [ABSTRACT FROM AUTHOR]

This paper established a numerical model for a solid oxide fuel cell (SOFC) button cell, focusing on the effects of finger-like channels on the gas transport process in the anode support. The current densities of channelled button cell and un-channelled button cell are compared at different operating temperature and voltage with H as the fuel. The H transport is discussed in detail, such as the mole fraction distribution of H in the porous layer, the diffusion flux and convective flux of H. It is found that the performance of SOFC can be improved by 2.60 % at 800 °C, 0.5 V, compared with un-channelled SOFC due to the improved gas transport by the finger-like channels. Then, the model is further extended to study 2D-planar SOFC fuelled with syngas. The mole fraction gradients of H, CO, CH and CO are all substantially reduced by the finger-like channels compared to un-channelled planar cell. It is found that the SOFC performance is improved by 5.93 % at 800 °C, 0.5 V, when syngas fuel is used. The present study clearly demonstrated that the use of finger-like channels in the anode support is effective in improving the gas transport and the SOFC performance. The present model can be employed for subsequent optimization of the channel configuration for further performance improvement. [ABSTRACT FROM AUTHOR]

Thermal effects in a H 2 O and CO 2 assisted tubular direct carbon solid oxide fuel cell (DC-SOFC) are numerically investigated. Parametric simulations are further conducted to study the effects of operating potential, the distance between carbon and anode, inlet gas temperature, and anode inlet gas flow rate on the thermal behaviors of the fuel cell. It is found that the fuel cell with H 2 O as gasification agent performs considerably better than the cell with CO 2 as gasification agent in all cases. It is also found that the temperature field of the fuel cell is highly uneven. The breakdown of the heat sources in the fuel cell shows that the H 2 O assisted DC-SOFC has much higher heat generation and consumption than the CO 2 assisted cell. Interestingly, a thermal neutral voltage is observed, at which no heating or cooling of the cell is needed. In addition, the distance between the anode and the carbon layer is required to be as small as possible, which improves the temperature uniformity of the fuel cell. The results of this study demonstrates the importance of thermal effects in DC-SOFCs and form a solid foundation for DC-SOFC thermal management. • Model for the thermal effect in CO 2 and H 2 O assisted DC-SOFC is developed. • The heat generation/consumption are both much higher in H 2 O assisted DC-SOFC. • A thermal neutral voltage is observed. • High anode inlet gas flow rate is not necessary. • A smaller distance between the carbon and the anode is beneficial. [ABSTRACT FROM AUTHOR]

Reversible solid oxide cell (rSOC) can flexibly switch between the electrolysis mode and the fuel cell mode for electrical energy storage and power generation. For practical application, sweeping gas is needed to bring in the reactants and take out the products timely. In this study, we use steam as anode sweeping gas in electrolysis to decrease the overpotential loss and collect pure O 2 , which is then used as the fuel cell cathode oxidant. The real fluctuating power generated from solar photovoltaic is used as the power supply, which allows rSOC to generate H 2 from 6:45 a.m. to 5:45 p.m. and produce electricity in the night. Compared with the conventional strategy, the proposed system can utilize more than 35% electricity in electrolysis, and its efficiency and total H 2 production can be increased by 8% and 50%, respectively. The total power generation and the power density are also increased by 290% and 160%, respectively. Overall, this new strategy results in a doubled round-trip voltage efficiency due to the much-decreased overpotential losses in the electrochemical processes. This study provides a guidance for the optimization of practical rSOC application with dynamic operating conditions. • 2D dynamic models for tubular SOEC and SOFC are developed. • Parametric studies on SOECs are conducted with fluctuating PV power supply. • H 2 O is used as sweeping gas in SOEC and pure O 2 is used as reactant in SOFC. • The production efficiency and rate of H 2 are increased by 8% and 50%, respectively. • Power generation and power density are increased by 2.9 and 1.6 times, respectively. [ABSTRACT FROM AUTHOR]