6 research outputs found
Where is the lithium? Quantitative determination of the lithium distribution in lithium ion battery cells: Investigations on the influence of the temperature, the C-rate and the cell type
With lithium being the capacity determining species in lithium-ion battery (LIB) cells, the local quantification is of enormous importance for understanding of the cell performance. The investigation of the lithium distribution in LIB full cells is performed with two different cell types, T-cells of the SwagelokĀ® type and pouch bag cells with lithium nickel cobalt manganese oxide and mesocarbon microbead graphite as the active materials as well as a lithium hexafluorophosphate based organic carbonate solvent electrolyte. The lithium content of/at the individual components of the cells is analyzed for different states of charge (SOCs) by inductively coupled plasma-optical emission spectrometry (ICP-OES) and the lithium distribution as well as the loss of active lithium within the cells is calculated after cycling. With increasing the SOC, the lithium contents decrease in the cathodes and simultaneously increase in the anodes. The temperature increase shows a clear shift of the lithium content in the direction of the anode for the T-cells. The comparison of the C-rate influence shows that the lower the C-rate, the more the lithium content on the electrodes is shifted into the direction of the anode
Ion Chromatography with Post-column Reaction and Serial Conductivity and Spectrophotometric Detection Method Development for Quantification of Transition Metal Dissolution in Lithium Ion Battery Electrolytes
We present a method for the separation and determination of transition metals in electrolytes based on ion chromatography (IC) with post-column reaction (PCR) and serial conductivity and spectrophotometric detection. Three IC columns [Metrosep C4ā250/4.0 (column A), Metrosep C6ā250/4.0 (column B), and Nucleosil 100-5SAā250/4.6 (column C)] with different capacities, and stationary phases were used and compared with each other for method development. All spectrophotometric measurements were carried out with 4-(2-pyridylazo)resorcinol (PAR) as PCR reagent at a wavelength of 500 nm. To characterize the precision of the separation, the selectivity for the analysis of transition metals (nickel, cobalt, copper, and manganese) in the presence of large amounts of lithium and the resolution of the peaks were determined and compared with one another. Furthermore, the limits of detection (LOD) and quantification (LOQ) were determined for the transition metals. The LODs and LOQs determined by column C were as follows: cobalt (LOD/LOQ): 9.4 Āµg Lā1/31.3 Āµg Lā1, manganese (LOD/LOQ): 7.0 Āµg Lā1/23.5 Āµg Lā1, and nickel (LOD/LOQ): 6.3 Āµg Lā1/21.1 Āµg Lā1. Finally, the concentration of transition metal dissolution of the cathode material Li1Ni1/3Co1/3Mn1/3O2 (NCM) was investigated for different charge cut-off voltages by the developed IC method
Performance tuning of lithium ion battery cells with area-oversized graphite based negative electrodes
The accuracy for positional alignment of the positive electrode vs. the negative electrode is of great importance for the quality of assembly of lithium ion cells. Area-oversized negative electrodes increase the tolerance for electrode alignment. In this study, the impact of area-oversizing of the negative electrode on the specific capacity losses during charge/discharge cycling is systematically investigated by using electrochemical and analytical methodologies. It is shown, that with a higher degree of area-oversizing more active lithium is kinetically trapped in the outer negative electrode areas (āoverhangā), causing performance-deteriorating losses in usable specific capacity. Nevertheless, most of this ālostā specific capacity is of reversible nature as the trapped active lithium can be electrochemically recovered, which is analytically proven by inductively coupled plasma-optical emission spectrometry (ICP-OES) and laser ablation-inductive coupled plasma-mass spectrometry (LA-ICP-MS). Given this relation, a periodic application of a short constant voltage step after discharge results in a significant performance increase. In contrast, holding the cell in the charged state is detrimental for cells with area oversized negative electrodes as the amount of reversible and irreversible trapped active lithium increases. Based on the obtained insights, the influence of variations of the electrochemical conditions on charge/discharge cycling performance is discussed
P2 ā Type Na0.67Mn0.8Cu0.1Mg0.1O2 as a new cathode material for sodium-ion batteries: Insights of the synergetic effects of multi-metal substitution and electrolyte optimization
A P2-type Na0.67Mn0.8Cu0.1Mg0.1O2 has been synthesized as a cathode material for sodium ion batteries. By utilizing the synergetic effects of Cu and Mg substitution, the prepared material delivers a discharge capacity of 84āÆmAh gā1 at 180āÆmAāÆgā1, with a superior capacity retention of 93% after 500 cycles. The Mn, Cu and Mg ions are located in the transition metal sites, and a good structural reversibility during the charge and discharge process has been confirmed. In addition, the electrolyte additive fluoroethylene carbonate is shown to be effective for the formation of passivation layer at the electrode/electrolyte interface and improve the long-term cycling performance of the Na0.67Mn0.8Cu0.1Mg0.1O2 cathode material using a 1āÆM NaPF6 in ethylene carbonate and dimethyl carbonate electrolyte
P2 ā Type Na0.67Mn0.8Cu0.1Mg0.1O2 as a new cathode material for sodium-ion batteries: Insights of the synergetic effects of multi-metal substitution and electrolyte optimization
A P2-type Na0.67Mn0.8Cu0.1Mg0.1O2 has been synthesized as a cathode material for sodium ion batteries. By utilizing the synergetic effects of Cu and Mg substitution, the prepared material delivers a discharge capacity of 84āÆmAh gā1 at 180āÆmAāÆgā1, with a superior capacity retention of 93% after 500 cycles. The Mn, Cu and Mg ions are located in the transition metal sites, and a good structural reversibility during the charge and discharge process has been confirmed. In addition, the electrolyte additive fluoroethylene carbonate is shown to be effective for the formation of passivation layer at the electrode/electrolyte interface and improve the long-term cycling performance of the Na0.67Mn0.8Cu0.1Mg0.1O2 cathode material using a 1āÆM NaPF6 in ethylene carbonate and dimethyl carbonate electrolyte