As is well known, the key point to fabricate hierarchical material is control of the precursor. To address above-mentioned problem, in this work, the NiвЂ“Mn carbonate precursor was initially synthesized via a homogenous precipitation-hydrothermal method using urea as a precipitant reservoir, and LiNi 0.5Mn 1.5O 4 cathode material with hollow hierarchical structure was achieved by high-temperature calcination process with lithium source. In the above literatures, most of MnCO 3 or Ni 0.25Mn 0.75CO 3 has been synthesized by direct precipitation method between NH 4HCO 3/Na 2CO 3 precipitant and Mn/Ni salt solution, which may lead to the inhomogeneous particle size distribution of as-prepared carbonate precursor and corresponding LiNi 0.5Mn 1.5O 4 product. 19вЂ“21) as self-template and Mn/Ni source.

5,10,12вЂ“16ДЄt present, the LiNi 0.5Mn 1.5O 4 cathode material with hollow hierarchical structure has been generally synthesized by high-temperature calcination using MnCO 3, 11,15,17 manganese oxides converted from MnCO 3, 5,10,18 or Ni 0.25Mn 0.75CO 3 ( ref.

On the other hand, the hollow interior can improve the structural integrity by alleviating the mechanical strain induced by volume change during the repeated Li + ion insertion/extraction processes, which can promote the cycling stability. 10,11 On the one hand, this kind of structure can provide a shorter path for Li + ion diffusion and meanwhile have larger electrode/electrolyte contact area for Li + flux across the interface, resulting in better rate capability. 8,9 Recently, the cathodes with hierarchical hollow structure have attracted considerable interests for the co-improvement of rate capability and cycle performance. Unfortunately, low thermodynamic stability of nanoparticles results in electrochemical agglomeration and raises the risk of side reaction with electrolyte, thus leading to inferior cycling stability.

The nanosized materials generally show improved rate performance by shorter Li + ion diffusion channel and larger surface area. To date, there are three main approaches to solve the above problem, such as surface modification, cation doping and particle size reduction to nanoscale level. 5 However, simultaneously achieving satisfactory cyclability and rate performance for LiNi 0.5Mn 1.5O 4 remains challenging due to complex performance-influencing factors and electrolyte/structure instability under high potential. 3,4 In addition, the inherently fast Li + ion diffusion within its 3D spinel structure leads to good rate capability and cycling stability. Li/Li +) and high energy density (650 W h kg в€’1). Among all cathode materials, LiNi 0.5Mn 1.5O 4 spinel has been regarded as one of the most promising cathodes for LIB, owing to high working voltage (4.7 V vs. One practical and cost-effective way to improve the energy density of cathode material is elevating the working voltage. 1,2 The energy density of LIB is generally limited by the cathode material. Introduction Lithium ion batteries (LIBs) are being intensively pursued for high-power and high-energy applications such as electric vehicles (EVs) and hybrid electric vehicles (HEVs). The excellent electrochemical performance can be mainly attributed to morphological characteristics, that is, smaller particle size with homogeneous distribution, in spite of lower Mn 3+ content. The LiNi 0.5Mn 1.5O 4 sample obtained from the carbonate precursor hydrothermally synthesized at a reactant concentration of 0.3 mol L в€’1 exhibits the optimal overall electrochemical properties, with capacity retention rate of 96.8% after 100 cycles at 1C rate and 10C discharge capacity of 124.9 mA h g в€’1, accounting for 99.9% of that at 0.2C rate. SEM observation shows that the particle morphology and size of carbonate precursor can be tailored by changing reactant concentration. The results show that all samples belong to a cubic spinel structure with mainly Fd3 m space group, and the Mn 3+ content and impurity content initially decrease and then increase slightly with the reactant concentration increasing. The as-prepared samples were characterized by XRD, FT-IR, SEM, CV, EIS, GITT and constant-current charge/discharge tests. The effect of reactant concentration on the structure, morphology and electrochemical properties of the carbonate precursor and corresponding LiNi 0.5Mn 1.5O 4 product has been intensively investigated. A hollow hierarchical LiNi 0.5Mn 1.5O 4 cathode material has been synthesized via a urea-assisted hydrothermal method followed by a high-temperature calcination process.

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