Dezhi Chen,Wei Wei,Ruining Wang,Xiu-feng Lang,Yu Tian,Lin Guo
Olivine-structured LiMnPO4 with 3D foldaway-lantern-like hierarchical structures have been prepared via a one-step, template-free, solvothermal approach in ethylene glycol. The foldaway-lantern-like LiMnPO4 microstructures are composed of numerous nanoplates with thickness of about 20 nm. A series of electron microscopy characterization results indicate that the obtained primary LiMnPO4 nanoplates are single crystalline in nature, growing along the [010] direction in the (100) plane. Time-dependent morphology evolution suggests that ethylene glycol plays dual roles in oriented growth and self-assembly of such unique structures. After carbon coating, the as-prepared LiMnPO4 cathode demonstrated a flat potential at 4.1 V versus Li/Li+ with a specific capacity close to 130 mA h g−1 at 0.1 C, along with excellent cycling stability.
Cai Kanghui,Hong Binsheng,Hu Xueling,Li Zhenkun,Su Jing,Lv Xiaoyan,Wen Yanxuan
MnPO 4 ∙H 2 O is an ideal precursor for the preparation of LiMnPO 4 . However, the instability of Mn 3+ in an aqueous solution necessitates the implementation of the existing preparation methods, which are carried out in ethanol and produce toxic gases such as NO and NO 2 . In this work, a radical-oxidation coupled phosphate stabilization strategy is proposed for synthesizing MnPO 4 ∙H 2 O in an aqueous solution. The strategy involves the initial oxidation of Mn 2+ to Mn 3+ by sulfate radicals, which are produced through the thermal activation of Na 2 S 2 O 8 . Subsequently, Mn 3+ is stabilized by H 3 PO 4 , leading to the formation of MnPO 4 ∙H 2 O. By implementing this strategy, the mesoporous MnPO 4 ∙H 2 O precursor can be readily obtained through a reaction at 90 °C for 5 h. Subsequently, the prepared LiMnPO 4 /C inherits the mesoporous structure of the MnPO 4 ∙H 2 O precursor, exhibiting excellent electrochemical performance. Specifically, the mesoporous LiMnPO 4 /C delivers an initial capacity of 115.8 mAh g −1 with a capacity retention of 83.1% after 100 cycles at 10 C. The enhanced performance is mainly attributed to the mesoporous structure, which facilitates electrolyte penetration, reduces interfacial charge transfer impedance, and accelerates Li + diffusion. The environmentally benign and scalable strategy presented here opens a new approach to the synthesis of high-performance LiMnPO 4 /C.
With the hollow-sphere Li 3 PO 4 as precursor, a delicate polyol-assisted hydrothermal method is devised to synthesize high-performance LiMnPO 4 . Orthorhombic shaped, irregular flaky shaped and sphere-like LiMnPO 4 are sequentially prepared by decreasing the water–diethylene glycol (DEG) ratio. The capacity, cycling stability and rate performance of all samples prepared by the new synthesis method are improved significantly. And the C/LiMnPO 4 with irregular flaky shape exhibits a capacity of 154.1 mA h g −1 at C/20, 147.4 mA h g −1 at C/10 and 102.5 mA h g −1 at 2 C, which is the best performance ever reported for LiMnPO 4 active material with similar carbon additives.
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