摘要
锂离子电池在电子产品市场起着重要作用,而应用于可持续交通领域的高能量密度和功率密度的锂离子电池仍然得到广泛的研究。为了将锂离子电池的能量密度提高至200 W·h/kg以上,以尖晶石LiNi_(0.5)Mn_(1.5)O_4(LNMO)作为正极材料,石墨作为负极材料的电池是最有希望的方案之一。这种电池具有很多优点,即工作电压高(约4.7 V vs.Li/Li^+)、可用比容量高(约135 mA·h/g)、倍率性能优异、成本相对较低。本文比较了两种空间群的LNMO(无序的Fd-3m和有序的P4~332)在原子尺度的结构差异以及相应的电化学性能差异,并阐述了二者之间的关系。详细报道了LNMO在首周充放电过程(3.5~4.9 V)中局部原子结构(特别是表面区域)。此外,综述了LNMO的合成方法以及对其包覆和掺杂的效果。除了传统的包覆和掺杂,我们报道了用纳米尺寸的TiO_2对LNMO进行表面修饰,结果表明LNMO的表面被TiO_2颗粒覆盖,并且Ti离子掺杂进入到LNMO表面几纳米的区域。此外报道了表面修饰对LNMO在25℃和55℃条件下的电化学循环性能的影响。
Lithium-ion batteries, which have played important role in the extraordinary expansion of the electronic products market, are still under intensive study for applications in sustainable transportation and energy storages. To obtain lithium ion batteries with specific energy 〉 200 W.h/kg at cell-level, LiNi05Mn1.5O4 (LNMO) is one of the most promising candidates for the cathode. It has many advantages, e.g. high operating voltage [ca. 4.7 V (vs. Li/Li&+)], reasonable practical capacity (ca. 135 mA.h/g), excellent rate capability, relatively low cost. In this paper, the structural differences of LNMO with two space groups (disordered Fd-3m and ordered P4332) and its associated electrochemical performances are presented. The atomic-level structure, especially in the surface region, of LNMO during the first charge/discharge cycle (3.5-4.9V) is reported in detail. The preparation and modification of LNMO, e.g. synthesis methods, effects of coating and doping are then reviewed. We also propose surface modification of LNMO, which is different from conventional coating and doping. Surface modified LNMO with TiO2 shows that the surface is covered by oxide particles and the few nanometer surface structure is also doped with Ti ions. The influence of surface modification on the electrochemical cycling performance of LNMO at25 ℃ and 55 ℃ is reported.
出处
《储能科学与技术》
CAS
CSCD
2017年第5期841-854,共14页
Energy Storage Science and Technology
基金
中科院战略先导专项(XDA01020304)
科技部纳米重大科学研究计划项目(2013CB934002)