Porous materials have superior electrochemical performance owing to its their structure, which could increase the specific and contact area with the electrode. The spinel Li4Mn5O12has a three-dimensional tunnel structure for a better diffusion path, which has the advantage of lithium ion insertion and extraction in the framework. However, multi-space spherical materials with single morphologies are rarely studied. In this work, waxberry-like and raspberry-like nanospheres for Li4Mn5O12have been fabricated by the wet chemistry and solid-state methods for the first time. The diameter of a single waxberry- and raspberry-like nanosphere is about 1 μm and 600 nm, respectively. The specific capacitance of Li4Mn5O12was 535 mF cm−2and 147.25 F g−1at the scan rate of 2 mV s−1, and the energy density was 110.7 Wh kg−1, remaining at 70% after 5000th charge-discharge cycles. Compared with raspberry-like nanosphere Li4Mn5O12, the waxberry-like nanoporous spinel Li4Mn5O12shows the better electrochemical performance and stability; furthermore, these electrochemical performances have been improved greatly compared to the previous studies. All these results indicate that the waxberry-like nanoporous spinel Li4Mn5O12could provide a potential application in high performance supercapacitors.Keywords:supercapacitors;Li4Mn5O12;waxberry-like nanosphere;high performance
Graphical High energy density : A spinel Li 4 Mn 5 O 12 cathode material with unique nano-/microspheres is prepared by using a low-temperature method. As a cathode for 2 V hybrid Mg−Li batteries, Li 4 Mn 5 O 12 exhibits a reversible specific capacity of 155 mAh g −1 and a long discharge voltage platform exceeding 2.0 V (vs. Mg/Mg 2+ ) coupled with a high energy density of 326 Wh kg −1 at a current density of 0.1 C (1 C=163 mA g −1 ). With the increasing demand for electrical energy storage, a new Mg−Li hybrid battery with Mg anode is regarded as a promising candidate because of low cost, high volumetric capacity, and dendrite-free nature of the Mg anode. Nevertheless, the characteristics of low operation voltage and low energy density for Mg−Li hybrid batteries hinders their widespread application, owing to limited reversible cathodes. To overcome these issues, a highly reversible fast Li + insertion cathode with high voltage is an effective strategy to realize high-energy-density Mg−Li hybrid batteries. Herein, we develop the 2 V high-voltage spinel Li 4 Mn 5 O 12 cathode material with unique nano-/microspheres, using a novel low-temperature method, offering a short Li-diffusion path and sufficient transport channels for electrolyte penetration into the electrode. For the first time, we demonstrate the feasibility of the spinel Li 4 Mn 5 O 12 nano-/microspheres with hierarchical architecture as a cathode for 2 V hybrid Mg−Li batteries. It exhibits a reversible specific capacity of 155 mAh g −1 and a long discharge voltage platform exceeding 2.0 V (vs. Mg / Mg 2+ ) coupled with high energy density of 326 Wh kg −1 at a current density of 0.1 C (1 C=163 mA g −1 ). Our results pave the way of constructing new hybrid Mg−Li batteries with high voltage and high energy density.
Xiangting Yue,Yuan Ha,Honglin Yan,Dongyan Zhang,Qun Zhao,Zhimin Li
The Li-rich cathode Li 1.2 Mn 0.6 Ni 0.2 O 2 (PLR) has garnered much attention as an attractive candidate for lithium-ion batteries due to its low cost, environmental friendliness, and wide voltage window. However, challenges such as rapid capacity degradation and voltage decay resulting from the release of lattice oxygen remain unresolved. Herein, a spinel phase Li 4 Mn 5 O 12 coating was generated on the surface of Li 1.2 Mn 0.6 Ni 0.2 O 2 cathode (SLR) through KMnO 4 surface modification, aiming to enhance the structure stability and conductivity of PLR. The results demonstrate that the Li 4 Mn 5 O 12 coating effectively inhibits the release of lattice oxygen and accelerates the speed of lithiation and delithiation processes of Li 1.2 Mn 0.6 Ni 0.2 O 2 cathode, thereby significantly enhancing cycling stability over a wide temperature range. Particularly notable is SLR cathode, which shows superior capacity retention of 92.5 % at 1.0 C after 200 cycles at room temperature. Meanwhile, the SLR material retains excellent electrochemical properties even at high temperatures (60°C) with a capacity of 192.9 mAh/g after 100 cycles. This study not only elucidates the mechanism of Li 4 Mn 5 O 12 modification on Li 1.2 Mn 0.6 Ni 0.2 O 2 cathode, but also provides an effective strategy to improve the performance of Li-rich cathode materials .
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