For thin-film battery systems, surface coatings are a simple and effective method. Introducing coating materials onto the surface of Ni-rich layered oxides avoids direct contact with the electrolyte, thus minimizing the parasitic reactions. It also sets a kinetic barrier to O 2 evolution.
Here, the authors predict that stacked thin-film batteries with 0.15-2 µm thin cathodes can achieve a tenfold increase in specific power to over 10 kW kg−1 and demonstrate the design concept in two monolithically stacked thin-film cells.
They also should have a relatively smooth surface. Each component of the thin-film batteries, current collector, cathode, anode, and electrolyte is deposited from the vapor phase. A final protective film is needed to prevent the Li-metal from reacting with air when the batteries are exposed to the environment.
The specific power of Li-ion batteries is restricted to a few thousand W kg −1 due to the required cathode thickness of a few tens of micrometers. We present a design of monolithically-stacked thin-film cells that has the potential to increase the power ten-fold.
Such an anode-free thin-film cell has already been achieved using Lipon as the solid electrolyte with critical current densities of up to 5 mA cm −2 31, which can be further increased up to 8 mA cm −2 with thin carbon interlayers that are only a few tens of nanometers thick 32. Fig. 3: Potential of stacked thin-film batteries.
Sator reported the first thin film cell in 1952 ; it featured a lead chloride electrolyte deposited by vacuum evaporation. Then, the first Li-ion thin film batteries (AgI||LiI||Li) were reported in 1969 . Over the next 20 years, the primary focus of research was on enhancing the performance of SSEs and electrode materials.