ABSTRACT
Downsizing well-established materials to the nanoscale is a key route to novel functionalities, in particular if different functionalities are merged in hybrid nanomaterials. Hybrid carbon-based hierarchical nanostructures are particularly promising for electrochemical energy storage since they combine benefits of nanosize effects, enhanced electrical conductivity and integrity of bulk materials. We show that endohedral multiwalled carbon nanotubes (CNT) encapsulating high-capacity (here: conversion and alloying) electrode materials have a high potential for use in anode materials for lithium-ion batteries (LIB). There are two essential characteristics of filled CNT relevant for application in electrochemical energy storage: (1) rigid hollow cavities of the CNT provide upper limits for nanoparticles in their inner cavities which are both separated from the fillings of other CNT and protected against degradation. In particular, the CNT shells resist strong volume changes of encapsulates in response to electrochemical cycling, which in conventional conversion and alloying materials hinders application in energy storage devices. (2) Carbon mantles ensure electrical contact to the active material as they are unaffected by potential cracks of the encapsulate and form a stable conductive network in the electrode compound. Our studies confirm that encapsulates are electrochemically active and can achieve full theoretical reversible capacity. The results imply that encapsulating nanostructures inside CNT can provide a route to new high-performance nanocomposite anode materials for LIB.
Subject(s)
Electrochemical Techniques/methods , Ions/chemistry , Lithium/chemistry , Nanotubes, Carbon/chemistry , Cobalt/chemistry , Electric Conductivity , Electric Power Supplies , Electrodes , Ferric Compounds/chemistry , Manganese Compounds/chemistry , Microscopy, Electron, Scanning , Microscopy, Electron, Transmission , Nanocomposites/chemistry , Nanocomposites/ultrastructure , Nanotubes, Carbon/ultrastructure , Oxides/chemistry , Tin/chemistryABSTRACT
Microwave-assisted hydrothermal synthesis was used to grow LiMnPO4 micro- and nanocrystals from acetate precursors. By appropriate adjustment of the precursor concentration and the pH-value of the reactant, the product composition and purity along with the crystal size can be manipulated, resulting in particle-dimensions from around 10 µm down to a few 100 nm. Prisms and plates with hexagonal basal faces as well as cuboid and rod-like particles were produced. The effects on the crystal morphology as well as on the materials texture and agglomeration tendency are discussed and a comprehensive agglomeration phase diagram is constructed.
