Co–B Nanoflakes as Multifunctional Bridges in ZnCo₂O₄ Micro‐/Nanospheres for Superior Lithium Storage with Boosted Kinetics and Stability

Abstract

and vehicles. [1,2] With the ever-growing demand for the miniaturization of electrochemical energy storage devices, high volumetric lithium storage becomes more and more important. [3,4] Since conventional carbonaceous electrodes have approached the theoretical capacity limits, non-carbon alternatives with higher capacities are urgently required. [5] Transition metal oxides (TMOs) represent one type of promising alternative owing to their high specific capacities based on the conversion reaction mechanism, high abundance as well as high compacted density. [6] However, unlike the intercalation reaction in carbon electrodes, the conversion reaction in TMO anodes causes severe volume fluctuations during charge/discharge processes and thus leads to significant capacity loss. Meanwhile the poor electron conductivity and low Li + diffusivity result in slow reaction kinetics. [7] Taking ternary metal oxide ZnCo 2 O 4 as an example, it delivers a high theoretical capacity of ≈900 mAh g −1 but with a large volume change of ≈100% upon full discharge as well as sluggish lithium storage kinetics. [8,9] To overcome the above hurdles, intensive research has focused on nanoengineering of TMO electrodes, which may offer large free space to cushion the volume expansion and shorten the ion diffusion pathway, therefore enhancing the Transition metal oxides hold great promise as high-energy anodes in nextgeneration lithium-ion batteries. However, owing to the inherent limitations of low electronic/ionic conductivities and dramatic volume change during charge/ discharge, it is still challenging to fabricate practically viable compacted and thick TMO anodes with satisfactory electrochemical performance. Herein, with mesoporous cobalt-boride nanoflakes serving as multifunctional bridges in ZnCo 2 O 4 micro-/nanospheres, a compacted ZnCo 2 O 4 /Co-B hybrid structure is constructed. Co-B nanoflakes not only bridge ZnCo 2 O 4 nanoparticles and function as anchors forZnCo 2 O 4 micro-/nanospheres to suppress the severe volume fluctuation, they also work as effective electron conduction bridges to promote fast electron transportation. More importantly, they serve as Li + transfer bridges to provide significantly boosted Li + diffusivity, evidenced from both experimental kinetics analysis and density functional theory calculations. The mesopores within Co-B nanoflakes help overcome the large Li + diffusion barriers across 2D interfaces. As a result, the ZnCo 2 O 4 /Co-B electrode delivers high gravimetric/ volumetric/areal capacities of 995 mAh g −1 /1450 mAh cm −3 /5.10 mAh cm −2 , respectively, with robust rate capability and long-term cyclability. The distinct interfacial design strategy provides a new direction for designing compacted conversion-type anodes with superior lithium storage kinetics and stability for practical applications. Lithium StorageThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.

Redox Tuning in Crystalline and Electronic Structure of Bimetal–Organic Frameworks Derived Cobalt/Nickel Boride/Sulfide for Boosted Faradaic Capacitance

“…Compared with the contribution curve (Figure S11a, Supporting Information) of Co‐Ni MOF, both diffusion and capacitive contributions of Co‐Ni‐B‐S are increased, which indicates that the electronic tuning by the redox treatment could enhance the ion diffusion abilities and capacitance simultaneously. For a better understanding of the enhanced performance of Co‐Ni‐B‐S, the capacitive‐ and diffusion‐controlled contributions in the samples of Co‐Ni MOF, Co‐Ni‐B, Co‐Ni‐S, and Co‐Ni‐B‐S are also calculated (Figure S11, Supporting Information) . It is evident that the increased scan rates enhance the proportion of capacitive contribution while the diffusion contribution proportion decrease, which is further proved by the irregular growth of CV curves (Figure S12, Supporting Information).…”

“…Moreover, the O 1s XPS profiles of Co‐Ni MOF and Co‐Ni‐B‐S can be deconvoluted into three distinct peaks (Figure f), which can be classified as lattice oxygen (O I , ≈531.1 eV), oxygen vacancies (O II , ≈531.8 eV), and chemisorbed or dissociated oxygen or OH species (O III , ≈533.4 eV) . Compared with the Co‐Ni MOF, the O II peak intensity in the Co‐Ni‐B‐S sample increases significantly, which implies the introduction of oxygen vacancies in the redox process . The loss of oxygen could produce a large number of positive holes and defects, which are beneficial for the electrons transfer.…”

Natural Compounds Gallic Acid Derivatives for Long‐Life Li/Na Organic Batteries

“…The specific capacities of EA and TA LIBs can be comparable with those of metal oxide LIBs after cycling, and the cycling stabilities of EA and TA LIBs are better than those of metal oxide LIBs. [13,[52][53][54] The exceptional electrochemical performance of EA and TA indicates that they are promising anode materials for LIBs.…”

Using nanoconfinement to inhibit the degradation pathways of conversion-metal oxide anodes for highly stable fast-charging Li-ion batteries

“…There have been several approaches in the literature aimed at minimizing the effects of these MO degradation mechanisms. Many authors have created highly tailored architectures including anchored-materials, 44 shelled-materials (e.g. singleshell, [45][46][47][48] yolk-shell, 49,50 multi-shell [51][52][53] ), and hierarchical frameworks.…”

“…singleshell, [45][46][47][48] yolk-shell, 49,50 multi-shell [51][52][53] ), and hierarchical frameworks. [54][55][56] For instance, Deng et al 44 have demonstrated that ZnCo 2 O 4 with cobalt-boride (Co-B) anchors can reduce degradation, volume change and phase segregation. This is accomplished by utilizing Co-B as an intra-particle "glue" that promotes enhanced intra-particle electron conduction and faster Li + diffusion to/from the ZnCo 2 O 4 structure.…”