How does the purity of Lithium Cobalt Oxide cathodes for Li ion batteries effect the rate capability and cycle life?
The impurities (depending on which impurity) in LiCoO2 can decrease the electronic conductivity of the cathode. Thus, the rate capability also decreases. The impurities may dissolve in the electrolyte and deposite on anode side, destroying the SEI (solid electrolyte interface) layer of anode. Thus, the cycle life of the battery can be shortened.
The impurities (depending on which impurity) in LiCoO2 can decrease the electronic conductivity of the cathode. Thus, the rate capability also decreases. The impurities may dissolve in the electrolyte and deposite on anode side, destroying the SEI (solid electrolyte interface) layer of anode. Thus, the cycle life of the battery can be shortened.
Also, if the LiCoO2 is not in pure form or improperly converted, the material does not regain its original phase after a single charge - discharge cycle. The chemistry changes affecting the cycle life by not maintaining the stoichiometry in the electrodes and also affects the rate at which charge - discharge is carried.
Hope this helps you.
with some impurity, the energy density and power density (rate) will be low due to high polarization of the electrodes. In fact cycle life should be less. Impurities such as LiOH, Li2CO3 deteriorate the electrochemical performance above 4.3 V
Impurities.. which can be also termed as sometimes dopants can play a different role depending on not only which metal oxides you used for electrode materials but also which impurities are existed.. for example, n- or p-type semiconductors doped by acceptor- or donor-dopants. Basically, dopant can influence charge carriers concentration of both electron and lithium ion by which conductivities and also (chemical) Li diffusivity can be drastically changed. The change of chemical Li diffusivity ultimately improves or deteriorates especially rate capability of batteries as this rate capability is closely related to materials' kinetic properties. So I think we cannot simplify a role of impurities in transition metal oxides as either positive or negative. If someone wants to know this complicated relations between impurities (including Li+ as extrinsic defects), intrinsic defects and conductivity with Li diffusivity in detail, please refer to Prof. J. Maier's (Max-Planck-Institute, Stuttgart) papers in which some metal oxides (e.g. LiFePO4, TiO2) as Li-storage materials are deeply studied in terms of defect chemistry.
I want to add to the question-
Do the electrochemical performance of LiCoO2 thin films deposited by PLD method, where if the LiCoO2 target has Li2CO3 impurity, will be affected?
- Badges
- Science topic
- Similar topics
- Chemistry
- Electrochemistry