Short-range Li diffusion vs. long-range ionic conduction in nanocrystalline lithium peroxide Li 2 O 2 —the discharge product in lithium-air batteries (original) (raw)
Related papers
Nucleation and Growth of Lithium Peroxide in the Li−O2 Battery
We study the relationship between Li 2 O 2 morphology and the electrochemical performance of the Li−O 2 battery using a combination of experiment and theory. Experimental Li−O 2 battery discharge curves are accurately captured by a theoretical model in which electrode performance is limited by the nucleation and growth of discrete Li 2 O 2 nanostructures in the cathode. We further show that the characteristic sharp voltage drop widely reported at the end of discharge results from the decrease in electrochemical surface area as Li 2 O 2 covers the cathode surface. Preventing surface nucleation is highlighted as a core strategy for increasing Li−O 2 battery capacity.
Lithium ion mobility in metal oxides: a materials chemistry perspective
Journal of Materials Chemistry, 2003
Metal oxides containing mobile lithium ions are technologically important materials in the context of design and development of electrolytes and electrodes for solid-state lithium batteries. Mobility of lithium in a solid manifests itself in the following measureable ways: ionic conductivity/diffusion, redox insertion/deinsertion and ion exchange. While ionic conductivity and redox insertion/deinsertion determine the practical use of a material as an electrolyte and electrodes, respectively, ion exchange involving lithium in aqueous/molten salt media under mild conditions not only provides a convenient probe for the investigation of lithium mobility in solids, but also enables synthesis of new metastable phases. In this article, we present a chemical (rather than electrochemical) perspective of lithium ion mobility in inorganic oxide materials, in an attempt to bring out the relationships between structure and properties associated with lithium ion mobility. The survey shows that considerable lithium ion mobility occurs both in closepacked (rocksalt and its relatives, spinel, LiNbO 3 , rutile and perovskite) as well as open-framework (e.g. NASICON) oxide structures. LiCoO 2 (a-NaFeO 2), LiMn 2 O 4 (spinel), LiNbO 3 /LiTaO 3 (structure based on HCP array of anions), LiNbWO 6 (trirutile) and (Li,La)TiO 3 (perovskite) are some of the oxide materials (structure type indicated in parentheses) where high lithium mobility has been well established by various experimental studies. An investigation of the factors that control lithium ion conductivity in the (Li,La)TiO 3 perovskite has enabled us to design new perovskite oxides in the Li-Sr-B-B'-O (B~Ti, Zr; B'~Nb, Ta) systems that exhibit high lithium ion mobility/conductivity. Among the framework materials, NASICON (e.g. Na 3 Zr 2 PSi 2 O 12) turns out to be a versatile structure that supports high lithium mobility under ion-exchange, ionic conductivity and redox insertion/deinsertion conditions.
Journal of Materials Chemistry, 2003
Metal oxides containing mobile lithium ions are technologically important materials in the context of design and development of electrolytes and electrodes for solid-state lithium batteries. Mobility of lithium in a solid manifests itself in the following measureable ways: ionic conductivity/diffusion, redox insertion/deinsertion and ion exchange. While ionic conductivity and redox insertion/deinsertion determine the practical use of a material as an electrolyte and electrodes, respectively, ion exchange involving lithium in aqueous/molten salt media under mild conditions not only provides a convenient probe for the investigation of lithium mobility in solids, but also enables synthesis of new metastable phases. In this article, we present a chemical (rather than electrochemical) perspective of lithium ion mobility in inorganic oxide materials, in an attempt to bring out the relationships between structure and properties associated with lithium ion mobility. The survey shows that considerable lithium ion mobility occurs both in closepacked (rocksalt and its relatives, spinel, LiNbO 3 , rutile and perovskite) as well as open-framework (e.g. NASICON) oxide structures. LiCoO 2 (a-NaFeO 2), LiMn 2 O 4 (spinel), LiNbO 3 /LiTaO 3 (structure based on HCP array of anions), LiNbWO 6 (trirutile) and (Li,La)TiO 3 (perovskite) are some of the oxide materials (structure type indicated in parentheses) where high lithium mobility has been well established by various experimental studies. An investigation of the factors that control lithium ion conductivity in the (Li,La)TiO 3 perovskite has enabled us to design new perovskite oxides in the Li-Sr-B-B'-O (B~Ti, Zr; B'~Nb, Ta) systems that exhibit high lithium ion mobility/conductivity. Among the framework materials, NASICON (e.g. Na 3 Zr 2 PSi 2 O 12) turns out to be a versatile structure that supports high lithium mobility under ion-exchange, ionic conductivity and redox insertion/deinsertion conditions.
Synthesis of nanostructured LiCoO2 AS cathode material for lithium-ion batteries
2013
Nanostructured LiCoO2 powders were prepared by Carbon combustion synthesis of oxide method using carbon as starting materials. The thermo-gravimetric analysis was used to identify interaction features in the system LiNO3-Co3O4-Carbon to produce LiCoO2. X-ray diffraction showed that the as-synthesised product were single phase. The crystalline nanoparticles synthesized were nearly spherical, and their average particle diameters ranged from 60 to 200 nm. Cyclic voltammetry and charge-discharge experiments were applied to characterize the electrochemical properties of the powders as cathode materials for lithium-ion batteries. The cyclic voltammogram curves indicated faster diffusion and migration of Li+ cations in the nanostructured LiCoO2 electrode. In the first charge-discharge process, the material showed the capacity of 200 (mAh)/g.
Lithium peroxide crystal clusters as a natural growth feature of discharge products in Li-O2 cells
Beilstein journal of nanotechnology, 2013
The often observed and still unexplained phenomenon of the growth of lithium peroxide crystal clusters during the discharge of Li-O2 cells is likely to happen because of self-assembling Li2O2 platelets that nucleate homogeneously right after the intermediate formation of superoxide ions by a single-electron oxygen reduction reaction (ORR). This feature limits the rechargeability of Li-O2 cells, but at the same time it can be beneficial for both capacity improvement and gain in recharge rate if a proper liquid phase mediator can be found.
Pure and Applied Chemistry, 2000
Results on the local cation ordering in layered lithium-nickel/cobalt oxides and metal-substituted lithium-manganese spinels are presented. It is shown that electron spin resonance of Ni 3+ and Mn 4+ and magnetic susceptibility measurements are powerful tools to monitor the short-range cation ordering in these compounds, which is not accessible by diffraction techniques. Thus, owing to the different strength of the 90°and 180°N i 3+ -O-Ni 3+/2+ exchange interactions, the distribution of Ni 3+ /Ni 2+ between the lithium and nickel layers in Li 1-x Ni 1+x O 2 with 0 < x < 0.4 can be determined. For layered LiNi 1-y Co y O 2 and spinel LiMn 2-x Co x O 4 solid solutions, analysis of the temperature-independent EPR line width in terms of dipole-dipole and exchange interactions has been used to examine the local Ni 3+ /Co 3+ and Mn 4+ /Co 3+ ordering. The results obtained are correlated with the electrochemical intercalation of lithium in these compounds. the effect of the synthesis conditions on the local cation distribution in LiNi/CoO 2 and LiMn 2-x M x O 4 (M = Co, Mg) are presented. Since magnetic properties are sensitive to the cation distribution, magnetic measurements (electron spin resonance and magnetic susceptibility measurements) were used to monitor the short-range cation ordering in these compounds, which is not possible by means of diffraction techniques.
Rate-Dependent Morphology of Li2O2 Growth in Li–O2 Batteries
The Journal of Physical Chemistry Letters, 2013
Compact solid discharge products enable energy storage devices with high gravimetric and volumetric energy densities, but solid deposits on active surfaces can disturb charge transport and induce mechanical stress. In this Letter we develop a nanoscale continuum model for the growth of Li 2 O 2 crystals in lithium-oxygen batteries with organic electrolytes, based on a theory of electrochemical non-equilibrium thermodynamics originally applied to Li-ion batteries. As in the case of lithium insertion in phase-separating LiFePO 4 nanoparticles, the theory predicts a transition from complex to uniform morphologies of Li 2 O 2 with increasing current. Discrete particle growth at low discharge rates becomes suppressed at high rates, resulting in a film of electronically insulating Li 2 O 2 that limits cell performance. We predict that the transition between these surface growth modes occurs at current densities close to the exchange current density of the cathode reaction, consistent with experimental observations.
A TEM study of cycled nano-crystalline HT-LiCoO2 cathodes for rechargeable lithium batteries
Journal of Power Sources, 2004
LiCoO 2 has ␣-NaFeO 2 structure type and it has been reported that layered cation ordering is preserved during repeated insertion and removal of Li +. We have observed, at a nano-particle scale, cation disorder induced in LiCoO 2 after prolonged cycling. LiCoO 2 cathode powders with nano-grain sized of 70-300 nm were synthesized by a mechano-chemical method. Transmission electron microscopy study of LiCoO 2 showed that the initial O 3 crystal structure partially transformed to a cubic spinel phase. This spinel phase formation may be responsible for capacity degradation after prolonged cycling of LiCoO 2-based rechargeable lithium batteries. Cycle life of small size (70 nm) LiCoO 2 powder until 200 cycles is better than that of large size (300 nm) LiCoO 2 powder due to shorter diffusion distance.