Synthesis of Spherical Nano to Micro-Scale Core-Shell Particle Li[(Ni0.8Co0.1Mn0.1)1-x(Ni0.5Mn0.5)x]O2 and Their Applications to Lithium Batteries

Abstract

In Part Ⅰ, The high capacity of Ni-rich Li[Ni1-xMx]O2 (M = Co, Mn) is very attractive, if the structural instability and thermal properties are improved. Li[Ni0.5Mn0.5]O2 has good thermal and structural stabilities but it has a low capacity and rate capability relative to the Ni-rich Li[Ni1-xMx]O2. We synthesized a spherical core-shell structure with a high capacity (from the Li[Ni0.8Co0.1Mn0.1]O2 core) and a good thermal stability (from the Li[Ni0.5Mn0.5]O2 shell). This report is about the micro-scale spherical core-shell structure, i.e., Li[Ni0.8Co0.1Mn0.1]O2 as the core and a Li[Ni0.5Mn0.5]O2 as the shell. A high capacity was delivered from the Li[Ni0.8Co0.1Mn0.1]O2 core and a high thermal stability was achieved by the Li[Ni0.5Mn0.5]O2 shell. The core-shell structured Li[(Ni0.8Co0.1Mn0.1)0.8(Ni0.5Mn0.5)0.2]O2/carbon cell had a superior cyclability and thermal stability relative to the Li[Ni0.8Co0.1Mn0.1]O2 at the 1 C rate for 500 cycles. The core-shell structured Li[(Ni0.8Co0.1Mn0.1)0.8(Ni0.5Mn0.5)0.2]O2as a new positive electrode material is a significant breakthrough in the development of high capacity lithium batteries. In Part Ⅱ, We report on the preparation, characterization, and electrochemical study of spherical nano to microscale core-shell particles fabricated by coprecipitation. On the basis of sphere [Ni0.8Co0.1Mn0.1](OH)2 cores with a diameter of about 10 - 12 μm, [Ni0.5Mn0.5](OH)2piled on the surface of the [Ni0.8Co0.1Mn0.1](OH)2 core as a function of reaction time, forming nano to micro-scale spherical core-shell morphology, [(Ni0.8Co0.1Mn0.1)1-x(Ni0.5Mn0.5)x](OH)2. A simple thermal lithiation to [(Ni0.8Co0.1Mn0.1)1-x(Ni0.5Mn0.5)x](OH)2 gave a well-ordered Li[(Ni0.8Co0.1Mn0.1)1-x (Ni0.5Mn0.5)x]O2, as confirmed by X-ray diffraction study. From scanning electron microscopic observation, it was found that the nano to micro-scale core-shell morphologies have not changed before and after thermal lithiation. An appropriate thickness of the shell in the core-shell particle, Li[(Ni0.8Co0.1Mn0.1)1-x(Ni0.5Mn0.5)x]O2. In Part Ⅲ, The core-shell type cathode material Li[(Ni0.8Co0.1Mn0.1)0.8(Ni0.5Mn0.5)0.2]O2 (CS) for Li-ion battery was synthesized via co-precipitation method. The electrochemical and thermal properties of the core-shell structured Li[(Ni0.8Co0.1Mn0.1)0.8(Ni0.5Mn0.5)0.2]O2 were compared with those of the average composition of core-shell Li[Ni0.74Co0.08Mn0.18]O2 (ACCS) and the mixture of the core Li[Ni0.8Co0.1Mn0.1]O2 and the shell Li[Ni0.5Mn0.5]O2 material (MCS). The CS shows the enhanced electrochemical properties in a high voltage range (4.5 V and 4.6 V) as well as the typical cut-off voltage range (4.3 V). The capacity retentions of CS, core, and ACCS material were 94.2 % (176.9 mAh g-1), 86.6 % (172 mAh g-1), and 88.4 % (169.3 mAh g-1) after 120 cycles, respectively. We report on the preparation, characterization, and electrochemical study of spherical nano to microscale core-shell particles fabricated by coprecipitation. On the basis of sphere [Ni_(0.8)Co_(0.1)Mn_(0.1)](OH)_(2) cores with a diameter of about 10 - 12 μm, [Ni_(0.5)Mn_(0.5)](OH)_(2)piled on the surface of the [Ni_(0.8)Co_(0.1)Mn_(0.1)](OH)_(2) core as a function of reaction time, forming nano to micro-scale spherical core-shell morphology, [Ni_(0.8)Co_(0.1)Mn_(0.1)_(1)-x(Ni_(0.5)Mn_(0.5))x](OH)_(2). A simple thermal lithiation to [Ni_(0.8)Co_(0.1)Mn_(0.1)_(1)-x(Ni_(0.5)Mn_(0.5))x](OH)_(2) gave a well-ordered Li[Ni_(0.8)Co_(0.1)Mn_(0.1)_(1)-x Ni_(0.5)Mn_(0.5)x]O_(2), as confirmed by X-ray diffraction study. From scanning electron microscopic observation, it was found that the nano to micro-scale core-shell morphologies have not changed before and after thermal lithiation. An appropriate thickness of the shell in the core-shell particle, Li[Ni_(0.8)Co_(0.1)Mn_(0.1)_(1)-x Ni_(0.5)Mn_(0.5)x]O_(2).