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Aqueous rechargeable batteries are promising candidates for safe and large-scale energy storage systems, but their electrochemical performances are limited by anode degradation. Herein, poly(2,5-di...

Lithium metal anode has attracted soaring attention for high energy batteries. However, uncontrollable growth of dendritic Li and high chemical reactivity with electrolyte incur serious safety issues, hindering its practical applications. Carbon materials and their composites with controllable structures and properties, have been explored to address these issues and show great potential for lithium anode protection as stable scaffolds or Li storage reservoirs. However, the study of heterogeneous nucleation and growth of Li on carbon surfaces, especially on the basal plane of graphite layers, which is the dominating surface for graphene, carbon nanotube, and many other advanced carbon materials, remains empty, attributing to the lack of a perfect (planar and clean) deposition substrate. Herein, we adopt a single-layer graphene grown on Cu foil as an ideal Li plating substrate to reveal the fundamental behavior of Li metal nucleation and growth on carbon surface for the first time. We demonstrate that single-layer graphene on Cu foil, with nearly perfect structure, has a higher energy barrier for Li nucleation than Cu. Thus, it is more likely to form isolated and thicker dendrite layer on the carbon basal plane, and continuous dendrite was formed easily from Li nuclei even at a low Li deposited capacity of 30 µA h cm−2. Thereby, carbon materials with basal plane-dominated structures are proved lithiophobic and not suitable for the matrix of Li-metal anode. Our approach could lead to the realization of fundamental understanding of Li metal heterogeneous nucleation and growth on carbon surface with various electronic properties.

Garnet-like Li7La3Zr2O12 electrolytes with Nb doping are synthesized by self-consolidation method. Different from conventional methods such as cold or hot isostatic pressing, not any pressing assistance is employed throughout the preparation process. Although the preparation process is dramatically simplified, both density and ionic conductivity of the obtained samples are enhanced. Nb-doped content plays a key role in the sintering of the packed precursor powders and in the structure stabilization of the obtained bulk samples. The optimized 0.60 mol Nb-doped sample with relative density of 94%, fine particle boundaries, and solitary cubic structure possesses the maximum total ionic conductivity of 5.22 × 10−4 S cm−1 at 30 °C, which is comparable to the highest reported value of the samples prepared by conventional pressing methods. This work verifies that self-consolidation strategy is effective, reliable, and productive for the preparation of cubic Li7La3Zr2O12 electrolyte, which would significantly facilitate the development of ceramic electrolyte membrane technology.

Garnet-type Li 5 La 3 Ta 2 O 12 (LLTaO) solid electrolyte is a potential candidate component for future all-solid-state batteries due to its extraordinary stability against the reaction with molten lithium. In contrast with traditional cold isostatic pressing (CIP) method, which generally pursues ultra-high pressure, this paper tries to enhance the density and ionic conductivity of LLTaO by self-consolidation strategy without the assistance of any pressing operations. A LLTaO bulk with a relative density of 95% is obtained. SEM images reveal that the bulk sample is assembled by large dense particles in size of tens of microns indicating that the interstitial space among the particles has been dramatically minimized. Accordingly, the total ionic conductivity and the bulk ionic conductivity at 30 °C are promoted up about one order of magnitude higher to 2.63 × 10 −5 S cm −1 and 1.41 × 10 −4 S cm −1 , respectively. Moreover, the lithium ionic migration network in the crystalline unit cell of LLTaO is first explored from its assembled way. A hexagon-like basic unit with tetrahedral Li1 joint sites and Li1- - Li1 edges is identified. The tetrahedral Li1 sites act as crucial junctions for the transportation of lithium ions. This work would significantly stimulate the development of LLTaO electrolyte membrane technology.

For the preparation of high-density ceramic electrolytes, researchers prefer cold or hot isostatic pressing method, which is not cost effective because of the ultra-high pressure and poor productivity. In this paper, we present a novel “self-consolidation” method to prepare dense cubic Al-doped Li7La3Zr2O12 (LLZO) without the assist of pressing. The relative density of LLZO bulk sample is about 93–96%, and the 0.10 mol Al-doped sample with the purest cubic structure possesses the highest total ionic conductivity of 1.41 × 10−4 S cm−1 at 30 °C, which is comparable to the conductivities of the samples prepared by traditional high-pressure methods. Furthermore, a LLZO crystal unit cell model is constructed and the self-consolidation mechanism for LLZO from crystal unit cell to bulk is explored. The surface tension of the molten Li compounds acts as the intrinsic power for the self-consolidation. This work demonstrates a facile, productive and reliable route for the preparation of dense cubic LLZO, and provides an important insight into the microscopic consolidation mechanism of ceramic electrolytes. Keywords: Lithium ion battery, Li7La3Zr2O12 solid state electrolyte, Ionic conductivity, Cubic structure

Improving the cycling performance without sacrificing its capacity is challenging for high-voltage LiNi0.5Mn1.5O4 cathode due to the trade-off nature among the key properties. A self-polymerization process of dopamine was utilized to grow polydopamine (PDA)-nano titanium dioxide assembly. PDA@TiO2 composite was demonstrated to be integrated with the particles of high-voltage spinel LiNi0.5Mn1.5O4 cathodes via wet chemical method. PDA@TiO2 decorated LNMO improved the long-term cycling performance and rate capability by suppressing detrimental side reactions in balancing the interfacial stability and Li+ diffusion kinetics of LNMO and consequently providing efficient conductive pathways. As a result, 2% PDA@TiO2 modified LNMO cathode exhibited the high reversible capacity of 117 mAh g−1 after 1000 cycles with good capacity retention of 90.7% at 1 C, and superior rate capability (78.5 mAh g−1 at 5 C) at room temperature. Remarkably, a significant improvement in cycling stability at an elevated temperature (50 °C) was obtained for the PDA@TiO2-LNMO composite, giving a capacity retention of 93% after 100 cycles at 1 C. The mechanism of performance improvement could be attributed to the maintenance of the structural stability of LNMO cathode materials and the enhanced kinetics of the remarkable lithium-ion diffusion through the protective effect of PDA@TiO2 decorating.

Aqueous lithium ion batteries (ALIBs) receive increasing attention due to their intrinsic non-flammable nature. However, their practical application, has been limited by the poor comprehensive properties of aqueous electrolytes, which severely restricts the cycle life and cost of ALIBs. In this study, the concentration and components of aqueous electrolytes were optimized to balance the battery performance and cost of ALIBs. The wide electrochemical stability window of around 2 V is achieved for just 9 ~15 m LiTFSI solutions other than the counterparts of widely used LiNO3 solutions, attributed to most water molecules in crystalline hydrates. A great improvement in the performance of LiMn2O4 electrodes is carried out. The optimal LiTFSI solution of 15 m allows LiMn2O4 to be long cycled at 1C with a discharge capacity of 111mAh∙g−1 and a high capacity retention of 88% after 1400 cycles. At the high C-rate of 5 C, a discharge capacity of 91 mAh∙g−1 and a capacity retention rate of as high as 92% after 3000 cycles are achieved. In highly concentrated LiTFSI solutions beyond 15 m, a decay in the performance of LiMn2O4 electrodes is found, especially the rate capability, attributed to the rather low ion conductivity.

The spherical LiTi(PO4)3/C composites were prepared through spray drying method followed high-temperature calcination and used as anodes for aqueous lithium ion batteries. The effect of different organic carbon source based on different coating mechanisms and carbon content on the electrochemical properties of LiTi(PO4)3/C composite anodes were investigated. Results show that the amount of carbon coating is too low to prevent water from eroding. In contrast, if the amount of carbon coating is too high, the resistance of lithium ion diffusion will be high; the optimal carbon coating amount of LiTi2(PO4)3/C electrodes is 13%. The uniformity of carbon coating and the thickness of coating layer are the two main factors affecting the performance of coated electrodes. The coating mechanism has critical influence on the uniformity of carbon coating. The most uniform carbon coating was obtained by using polydopamine as the carbon source, followed by using the organic macromolecule, glucose as the carbon source. Polyacrylonitrile containing both carbon and nitrogen exhibits no special effect of nitrogen doping. (The two main factors affecting the performance of the carbon coated electrode are the uniformity and the thickness of the carbon layer.) The best performance is achieved by LiTi2(PO4)3/C anodes with the carbon amount of 13% prepared by using polydopamine as the carbon source. But, from a viewpoint of mass production and scale-up, it is more suitable to use low-cost and water-soluble glucose as carbon source.

The electrochemical stability of LiFePO4 in a Li+-containing aqueous electrolyte solution is critically dependent on the pH value of the aqueous solution. It shows a considerable decay in capacity of LiFePO4 upon cycling when the pH value is increased to 11. The mechanism responsible for the capacity fading is extensively investigated by means of cyclic voltammogram, ac impedance, charge/discharge, ex situ X-ray diffraction, and chemical analysis. LiFePO4 is relatively electrochemically stable in LiNO3 aqueous solution with pH=7. But the electrochemical performance of LiFePO4 in aqueous electrolyte is inferior to that in organic electrolyte. It is attributed to the loss of Li and the Fe, P dissolution during prolonged charge-discharge in aqueous medium. A precipitate is formed on the surface of LiFePO4 electrodes. It results in the change of crystalline structure, a large electrode polarization, and capacity fading.

A nanoporous glassy carbon (NPGC) used as a new electrochemical capacitor material has been developed and prepared from a novolac phenolic resin. This new porous carbon has a high specific capacity due to its large surface area and a high power density due to its nice bulk conductivity and nanoporous structure. In this paper, main factors that influence the pore structure and electrochemical performance of NPGCs were systematically investigated. The results showed that the porosity of carbonized resin increased with curing temperature up to 225 °C at which the resin can be cross-linked fully, facilitating activation agent molecules to diffuse inward. It was also found that high carbonization temperature helped crystallization of carbonized products, but the shrinkage of carbon skeleton made the extent of activation decrease. Meantime, increasing activation temperature may accelerate reaction rate and prolonging activation time may increase the extent of activation. However, too high activation temperature and too long activation time can make the carbon matrix cracked and distorted. Therefore, a maximum capacity of 203 F g−1 and a conductivity of about 10 S cm−1 was obtained for the NPGC sample prepared under suitable conditions, resulting in high power densities (6.5 kW kg−1 carbon).

An uninterruptible flow power system (UFPS) is proposed, which is comprised of a positive electrode for catalyzing the organic electro-oxidation, a communal negative electrode, and an air electrode for catalyzing the oxygen reduction and flow electrolytes. During electrolysis of the electro-synthesis reactor, the electrical capacity passed through the communal negative electrode is extracted by the zinc-air cell in order to deliver energy. Under the operation condition of successive organic electro-synthesis, this electrochemical system can be applied as an uninterrupted power source. Thus, the UFPS can be used for the organic electro-synthesis and discharge as power supply simultaneously or asynchronously. This paper demonstrates that the uninterruptible flow power system is feasible by utilizing the equilibrium of zinc deposition/dissolution on a perforated nickel-plated steel electrode with a propanol-oxidation electrode and an air electrode. Such combined electrochemical systems are capable of uninterrupted and stable operation with an energy efficiency of around 66%.

Monolithic porous carbon (MPC) was synthesized by a templating method using Na2CO3 as template, novolac-type phenolic resin as carbon precursor and hexamethylenetetramine as hardening agent. The template, carbon precursor and hardening agent were mechanically mixed in a grinding machine, hardened at 150 °C, crushed into fine particles, compacted into a disc, carbonized at 800 °C and finally washed with deionized water to form MPC. MPC–Ni(OH)2 electrodes were prepared by loading Ni(OH)2 into the MPC by cathodic deposition. The MPC is hierarchically porous, has an electric conductivity of 20.40 S cm−1 and a specific surface area of 576 m2 g−1. Charge-discharge characterization of the MPC–Ni(OH)2 electrodes shows that the specific capacities based on active material and the whole electrode are 230 mAh g−1 and 131 mAh g−1, respectively. This suggests that the MPC is a promising lightweight matrix to host nickel hydroxide to achieve a high specific energy in nickel-based alkaline batteries. [New Carbon Materials 2013, 28(2): 115–120]