Abstract:

A high performance LiMnPO₄/graphene nanocomposite as cathode material for lithium-ion batteries was prepared via surface modification of 3-aminopropyltrimethoxysilane (APS) on LiMnPO₄ nanoparticles and electrostatic self-assembly of positively charged APS-LiMnPO₄ nanoparticles and negatively charged graphene oxide. Successful APS modification on LiMnPO₄ was demonstrated by the existence of 3-aminopropyl and Si-O-C groups in FTIR spectra. LiMnPO₄ nanoparticles (ca. 25 nm) were found uniformly distributed on the surface of graphene sheets. The intimate contact of LiMnPO₄ nanoparticles with graphene conductive network allows achieving fast electron transfer between the active material and charge collector and accommodating volume expansion/contraction of LiMnPO₄ nanoparticles during electric discharge/charge process. The nanocomposite cathode material could deliver an initial capacity of 142.2 mA·h·g^-1 at 0.05 C and maintain 90.5% capacity after 50 cycles, which were significant better than no APS-modified counterpart.

Key words: lithium manganese phosphate, aminopropyltrimethoxysilane modification, nanomaterials, composites, electrochemistry

摘要：

3-氨丙基三甲氧硅烷（APS）改性的磷酸锰锂纳米片与氧化石墨烯通过静电自组装，经喷雾干燥和高温煅烧，得到磷酸锰锂/石墨烯复合材料。APS修饰后的磷酸锰锂带正电荷，并可通过红外光谱中3-氨丙基和Si-O-C官能团的存在证明磷酸锰锂成功被APS修饰，使得其与带负电荷的氧化石墨烯自组装形成磷酸锰锂/石墨烯复合材料。测试结果表明约25 nm的磷酸锰锂纳米颗粒均匀负载在石墨烯表面，石墨烯片层充当导电网络，提高了材料的电子电导率和锂离子扩散速率，缓解了LiMnPO₄在充放电过程中的体积变化。电性能测试发现，该材料的首次放电比容量为142.2 mA·h·g^-1，50个循环后容量保持率达到90.5%，较未经APS修饰的磷酸锰锂/石墨烯材料有大幅提高。

关键词: 磷酸锰锂, 3-氨丙基三甲氧硅烷改性, 纳米材料, 复合材料, 电化学