Xiaobing Lou

Mesoporous nanostructured Co3O4 derived from MOF template: a high-performance anode material for lithium-ion batteries

Mesoporous nanostructured Co3O4 was prepared by the direct pyrolysis of a Co-based metal organic framework (MOF) template at a relatively low temperature rather than a high temperature. When tested as an anode material for lithium-ion batteries (LIBs), this porous Co3O4 exhibited a greatly enhanced performance of lithium storage. The capacity of the porous Co3O4 retained 913 mA h g−1 after 60 cycles at a current rate of 200 mA g−1. Excellent rate capability was also achieved. We also found out that the Co3O4 prepared from the MOF template at a relatively low temperature has better electrochemical performance than that prepared at high temperature.

High Anodic Performance of Co 1,3,5-Benzenetricarboxylate Coordination Polymers for Li-Ion Battery

We report the designed synthesis of Co 1,3,5-benzenetricarboxylate coordination polymers (CPs) via a straightforward hydrothermal method, in which three kinds of reaction solvents are selected to form CPs with various morphologies and dimensions. When tested as anode materials in Li-ion battery, the cycling stabilities of the three CoBTC CPs at a current density of 100 mA g(-1) have not evident difference; however, the reversible capacities are widely divergent when the current density is increased to 2 A g(-1). The optimized product CoBTC-EtOH maintains a reversible capacity of 473 mAh g(-1) at a rate of 2 A g(-1) after 500 galvanostatic charging/discharging cycles while retaining a nearly 100% Coulombic efficiency. The hollow microspherical morphology, accessible specific area, and the absence of coordination solvent of CoBTC-EtOH might be responsible for such difference. Furthermore, the ex situ soft X-ray absorption spectroscopy studies of CoBTC-EtOH under different states-of-charge suggest that the Co ions remain in the Co(2+) state during the charging/discharging process. Therefore, Li ions are inserted to the organic moiety (including the carboxylate groups and the benzene ring) of CoBTC without the direct engagement of Co ions during electrochemical cycling.

The organic-moiety-dominated Li+ intercalation/deintercalation mechanism of a cobalt-based metal–organic framework

Metal–organic frameworks (MOFs) have advanced many application fields due to their intriguing structure. However, the application of MOFs in lithium-ion batteries (LIBs) is severely hindered by the lack of a detailed insight into the delithiation and lithiation behaviors of MOFs. This study employs soft X-ray spectroscopy and high-resolution solid-state NMR techniques to study the electrochemical process of a seashell-like Co-based MOF. These experiments demonstrate that Li-ions are intercalated to the carboxyl groups and benzene rings of this MOF during cycling, accompanied by the distortion of CoO6 octahedral sites. Furthermore, the Co-MOF employing this organic-moiety-dominated intercalation/deintercalation mechanism exhibits high initial coulombic efficiency (80.4%) and unprecedented long-term cyclic stability (1021 mA h g−1 at 100 mA g−1 after 200 cycles; 601 mA h g−1 at 500 mA g−1 after 700 cycles; 435 mA h g−1 at 1 A g−1 after 1000 cycles) when evaluated as the anode material in LIBs. To our knowledge, this is the longest cycle life ever reported for a MOF-based lithium ion battery anode.

Hierarchical CuO octahedra inherited from copper metal–organic frameworks: high-rate and high-capacity lithium-ion storage materials stimulated by pseudocapacitance

The controllable synthesis and tailoring of the structure of metal oxide electrodes to achieve high rate capability and stability still remain formidable challenges. In this paper, a room-temperature solid–solid transformation route was introduced for the fabrication of a hierarchically structured porous CuO octahedron (HPCO) electrode by treating a copper metal–organic framework template, namely, Cu-BTC, with an alkaline solution. The HPCOs substantially inherited the morphology and size of the precursor Cu-BTC and were constructed by the assembly of many ultrathin nanosheets with average lateral sizes of ca. 250 nm. When acting as a host for the storage of Li+ ions, the as-fabricated HPCO electrode exhibited unprecedented performance that benefited from its advantageous structural features, with an ultrahigh capacity of 1201 mA h g−1 and superb high-rate performance with excellent cycling stability (1062, 615, and 423 mA h g−1 at 0.5, 2, and 5 A g−1, after 200, 400, and 400 repeated cycles, respectively). It is noteworthy that a surface redox pseudocapacitive effect contributed significantly to the high capacity and high rate of Li-ion storage of the HPCO electrode. This encouraging result may accelerate the further development of LIBs by a smart strategy for the micro/nanoengineering of metal oxide-based electrode materials.

Reversible lithium storage in manganese and cobalt 1,2,4,5-benzenetetracarboxylate metal–organic framework with high capacity

Metal–organic frameworks (MOFs), are explosively developed as electrode materials for lithium-ion batteries. Mn-BTC MOF possessed low cycling stability. We therefore attempted to improve the electrochemical properties by doping cobalt into the Mn-BTC. Cobalt doped MnCo-BTC MOF greatly improved the cycling stability compared with Mn-BTC. A high capacity of 901 mA h g−1 could be obtained for MnCo-BTC at a rate of 100 mA g−1 after 150 cycles. Even at a high rate of 500 mA g−1, its capacity can still reach 445.3 mA h g−1 after 100 cycles.

A thermally activated manganese 1,4-benzenedicarboxylate metal organic framework with high anodic capability for Li-ion batteries

Metal organic frameworks (MOFs) with considerable structural versatility are considered to be potential materials for energy storage. In this work, a Mn-1,4-benzenedicarboxylate (Mn-1,4-BDC) MOF was synthesized by reaction of 1,4-benzenedicarboxylic acid (1,4-BDC) with manganese(II) chloride (MnCl2) using a solvothermal method. When applied as an anode for lithium-ion batteries, the activated Mn-1,4-BDC@200 electrode delivered a high reversible lithium storage capacity of 974 mA h g−1 after 100 cycles at a current density of 100 mA g−1, exhibiting one of the best lithium storage properties among the reported metal organic frameworks (MOFs), also known as coordination polymer (CP) anodes. The excellent electrochemical performance of the Mn-1,4-BDC electrode is also comparable with those reported for Mn2O3 and Mn3O4 nanostructures calcined from Mn-based MOF templates.

Highly reversible lithium storage in cobalt 2,5-dioxido-1,4-benzenedicarboxylate metal-organic frameworks boosted by pseudocapacitance

Exploiting novel metal-organic frameworks (MOFs) as electrode materials with superior rate capabilities and understanding their electrochemical behaviour in detail are crucial for boosting the application of MOFs in the field of energy storage. Herein, we prepared Co2(DOBDC) (DOBDC=2,5-dioxido-1,4-benzenedicarboxylate) via a hydrothermal method and explored its electrochemical performance as an anode material for lithium-ion batteries. The as-prepared Co2(DOBDC) MOF exhibits a reversible capacity of 526.1mAhg-1 after 200 charge/discharge cycles at a current density of 500mAg-1 and also demonstrates an impressive rate capability, with a high capacity of 408.2mAhg-1 at a high current density of 2Ag-1. Furthermore, synchrotron-based soft X-ray absorption spectroscopy (sXAS) and electron paramagnetic resonance (EPR) spectroscopy have been applied to investigate the spin state of cobalt in the electrodes at different states of charge. Our results suggest that localized electrons in high-spin (S=3/2) Co2+ in pristine Co2(DOBDC) are gradually delocalized after discharging. It was also found that the high rate capability of Co2(DOBDC) is mainly ascribed to an ultrafast ion intercalation pseudocapacitance process, which results from its unique microporous architecture and adequate specific surface that offers sufficient electrode/electrolyte contact and benefits fast Li+ ion diffusion.

Controlled synthesis of CoxMn3−xO4 nanoparticles with a tunable composition and size for high performance lithium-ion batteries

We present a new and simple strategy to synthesize uniform CoxMn3−xO4 nanoparticles with a tunable composition and size. A series of Co and Mn mixed-metal coordination polymer precursors with a precise metal ratio were firstly built solvothermally by merely adjusting the molar ratio of Co and Mn. After subsequent annealing treatment, a pure CoxMn3−xO4 phase was obtained. The particle sizes of the CoxMn3−xO4 products were easily fine-tuned by varying the decomposition temperature. Particularly, the electrochemical properties of the MnCo2O4 nanomaterials for lithium-ion batteries (LIBs) were investigated as a case study. Our experimental results suggested that an optimum size guarantees maximum capacity maintenance.

Capacity control of ferric coordination polymers by zinc nitrate for lithium-ion batteries

Ferric coordination polymers were synthesized via a hydrothermal process. With the addition of zinc nitrate, the as-prepared Fe(Zn)–BDC@300 shows rod-like morphology and exhibits superior electrochemical performance as an anode material for lithium-ion batteries. It shows a reversible capacity of 863.4 mA h g−1 at 0.1 A g−1 after 120 cycles.

Facile synthesis of the Basolite F300-like nanoscale Fe-BTC framework and its lithium storage properties

The Fe-BTC material commercialized as Basolite F300 is one of the most studied MOFs due to its unique features and wide range of industrial applications. In this article, Basolite F300-like Fe-BTC MOF materials were prepared directly with the protonated carboxylated ligand, circumventing the use of an alkaline solution as in previous work, by selecting an appropriate iron source. Results from the detailed characterization indicate that the obtained Fe-BTC was very similar to the commercial counterpart and the one prepared under the alkaline conditions in terms of many physicochemical properties. Besides, the Fe-BTC reported herein was scaled down to the nano-regime to afford nanoscale metal–organic frameworks (nMOFs), which is advantageous for its potential applications. More importantly, the current interest in MOFs in the area of rechargeable batteries has driven us to investigate its electrochemical performance with respect to lithium storage. It was shown that the nanoscale Fe-BTC MOF exhibits an outstanding electrochemical performance with a high reversible capacity up to 1021 mA h g−1 after 100 cycles at a current density of 100 mA g−1 and capacities up to 436 and 408 mA h g−1 after 400 cycles at a higher current density of 500 and 1000 mA g−1, respectively. Our results on the Fe-BTC MOF highlight the potential for high power Li-ion batteries (LIBs) applications.