In case of anode materials for Li ion battery I have always found a confusion in case of charge-discharge process and lithiation delithiation process. The second problem is clarified by a recent article named "In Situ Quantification and Visualization of Lithium Transport with Neutrons" published in angewandte chemie, Sept 1, 2014 edition. but I am still confused in the first part.
Some of the articles I found in literature says that the first lithiation process is discharge since the voltage is decreased from high OCV to 0 V and the delithiation process is charge. This is correct in electrochemical point of view. But some of articles including yours says that the first lithiation process is charging and the delithiation is discharging. One argument for this is that, since in the half cell we focus basically on one electrode only, therefore, the charging means insertion of lithium and for discharge of Lithium, the working electrode need to be charged with Li firstly.
I am still in great dilemma, which one should I follow
For half cell assembly, we use lithium electrode as a counter/reference. Since Lithium is most electropositive material of ECS therefore, you do not need to apply an extra potential to remove electrons from lithium electrode. As soon as you connect your material electrode and lithium electrode, lithium electrode looses its electrons (via external circuit) and simultaneously Li ions gets removed from Lithium electrode and intercalates (via electrolytic medium) into your material as it is having sufficient electrons to attract Li ions. This process is discharging. But, for half cell we use Lithium containing Spinel compounds which cannot loose electrons/Li ions until or unless you apply an external potential to do so. That is why you need to charge first in full cell assembly and discharge first in half cell assembly so that Li ions could intercalate into your material electrode.
It depends on your definiton of charging. If you are talking about energetics, then charging means a decrease in Potential difference. Thats the first process in a half cell of e.g. carbon against metallic lithium.
if you are focusing on your active material, charging could mean insertion of lithium into the material. This has not to be connected to the potential.
As Xiaolei Sun said, its up to you or your definition.
Charging involves Li moving into the anode and out of the cathode. During cell discharge (use) the reverse is the case. With respect to a Li electrode (half cell) it depends on whether your Li is acting as anode or cathode i.e. the difference in potential between the two electrodes
thanks a lot to everybody for this discussion. I think, it should be necessary to mention the charge discharge direction in experimental part of a manuscript to avoid any confusion.
The component function of the lithium ion batteries is
cathode : Emit lithium ion to anode during charging ,receive lithium ions during discharging
Anode:Receive lithium-ion from anode during charging Emit lithium-ion during discharging
Electrolyte : Pass lithium-ions between cathode and anode
Separator : Prevent short circuit between cathode and anode Pass lithium ions through pores in separator
Lankipalle Rekha Anode: Receive lithium ion from cathode during charging (intercalation of lithium ions occur) while extracalates or remove lithium ion during discharging
Electrolyte source of Lithium ions and medium assisting lithium ion diffusion
(I think its a typing mistake )
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