Lithium state diagram as a description of lithium deposit morphology

Lithium cycling behaviour on stainless steel has been investigated in several LiPF6 and LiClO4 organic electrolyte solutions. Complex dependence of cycling efficiency from a plated charge is found. In most LiPF6 electrolyte solutions, cycling efficiency increases slightly with the amount of plated lithium at the lower end range of plated capacity. The critical point of the plated charge has been found for each electrolyte solution over which the cycling efficiency decreases and depends strongly on the plated charge. A 1 M LiClO4/ethylene carbonate electrolyte solution displays quite different behaviour. New parameters are established for the characterization of lithium cycleability. On the basis of this research, using new parameters, a diagram of the lithium state on the amount of plated lithium is proposed for a description of the lithium deposit morphology. This diagram consists of regions of electrochemically active lithium, corrosion and encapsulation losses. Encapsulation losses can consist of (i) a loss of simple shape dendrites, and (ii) a loss of dendrite overstructure. The diagram shows a sub-region of active lithium in the region of electrochemically active lithium instead of a region of dendrite overstructure losses in the case of formation of the electron-conductive SEI.