3) Cost
To attain a practical energy density (> 350 W h
kg-1), the cathode capacity should be above 3–4 mA h
cm-2 and a thin Li anode (N/P ratio < 2) is
a prerequisite.[4,64] To meet these criteria, a Li
metal anode of 15–20 µm should be employed. In general, the calendaring
process to produce ultrathin Li foil significantly increases production
costs (Li <20 μm – $13 m-2, Li 20 – 50 μm
– $9.6 m-2, Li >50 μm – $8
m-2).[61] Figure 1C represents
the stack cost per energy estimation of the cells. Interestingly, LMBs
with thinner Li anodes (2 mA h cm-2) are more
expensive than those with thicker Li anodes (4 mA h
cm-2), although less Li is utilized because of the
high cost of the Li calendaring process. Meanwhile, it is possible to
dramatically reduce the production cost while increasing the energy
density, as AFLMBs do not require excess Li. In addition to excluding
the price of the Li processing process, less labor is required, and the
convenience of the process is increased because highly reactive Li metal
is excluded from all manufacturing processes. Furthermore, there is no
need to make new investments in manufacturing facilities because of its
compatibility with the LIBs fabrication
process.[61,65]