Key features of solid-state thin-film batteries

Solid-state thin-film lithium ion batteries that are produced using thin-film technology can achieve superior characteristics in comparison with traditional Li-ion/Li-po batteries. The exact combination of properties of the thin-film batteries will depend on the specific form-factor of the TFB cells

Key features of solid-state thin-film batteries

Energy density

TFB: 1200 Wh/L

Li-ion/Li-po: 550 Wh/L

The exact combination of this and following properties of the thin-film batteries depends on the specific form-factor of the TFB cells.

Thin-film batteries are produced using thin-film technology, allowing to eliminate the additives and achieve high-crystallinity structure of the battery materials. High crystallinity cathode provides a significant increase in energy density in comparison with pressed powder cathode in Li-ion/Li-po battery cells. In addition, the part of cathode in the whole cell structure is higher for TFB cells (up to 40%). This leads to thin-film battery cells having about double the energy density.

Prismatic pouch cells

Prismatic pouch cells are one of the possible form-factors of TFB. Obvious applications of this TFB form factor are OEMs. OEMs are looking for small volume/high energy density batteries to develop thinner and lighter devices. Energy density is the key to the adoption of this form factor.

Operating temperature

TFB: -40⁰C – +170⁰C

Li-ion/Li-po: 0⁰C – +60⁰C

Lithium-ion and lithium-polymer batteries keep working capacity in a temperature range 0-60⁰C. Special purpose lithium batteries can operate in a temperature up to 125⁰C but have limited lifespan (40-60 charging cycles). Thin-film batteries are able to work in a range from -40⁰C (with some reduction in capacity) to 170⁰C (at a long lifetime). Thin-film batteries are safer than conventional Li-ion or Li-poly batteries, due to using safer materials with high quality structure. Thin-film batteries can be specifically produced to withstand the instantaneous temperature up to +280 ° C, which allows it to be soldered in a reflow process or to be printed by SMD process. In addition, the composition of the TFB cell materials can be changed for specific high-temperature applications.

Chip-cells for IC and SMD

Thin-film batteries can be specifically produced to withstand the instantaneous temperature up to +280 ° C, which allows it to be soldered in a standard reflow process. In the case of existing Li-ion/Li-po batteries, it was necessary to place them in the device only at the final stage of production, often manually. The lack of self-discharge effect allows the battery to be stored for a decade or longer. With the ability to work in a wide temperature range from -40 ° C to +170 ° C, very fast charging, it makes TFBs very suitable to use as a normal SMD component.

Safety

TFB: safe

Li-ion/Li-po: explosive

The key problem of traditional (liquid electrolyte) Li-ion batteries is that the spewing of hot electrolyte vapours from a battery cell at high temperatures and voltages presents an explosion hazard. Li-ion and Li-pol batteries emit gases during operation. While this is usually mitigated by using either low flammability solvents or flame retardant additives, it cannot be eradicated completely. The absence of liquids makes solid-state batteries very safe. Solid-state electrolyte provides low resistive interface without contamination of other layers and undesired localized surface states, which are created by impurities. Parameter of interface structures is crucial as well, since it defines the internal resistance of the battery cell, and limits its efficiency, maximum charge/discharge rate, can cause safety issues.

Special TFB form factor for custom applications

TFB can be made of customized shape for special applications. For example, batteries for wireless headphones. These batteries should have a special shape for, in one hand, to be big enough for having high power rate and, in other hand, to match the form of headphones. These batteries should have long cycle life as well, so these devices will not have to be often replaced or serviced. Thin film lithium ion batteries have the ability to meet all these requirements.

Recharge time

TFB: less than 10 min

Li-ion/Li-po: > 60 min

The charging speed of conventional Li-ion batteries has to be limited to reduce the risks of explosion. This is due to the two factors: liquid or gel electrolyte and the presence of interface structures in the battery cell. Solid-state batteries are safer than conventional Li-ion or Li-poly batteries. Solid-state electrolytes are less reactive than liquid or gel, that are used in Li-ion or Li-poly batteries. The factor the of interface structures is crucial as well, since it defines the internal resistance of the battery cell, and limits its efficiency, maximum charge/discharge rate and can cause safety issues. Solid-state electrolyte provides low resistive interface without contamination of other layers and undesired localized surface states, which are created by impurities.

Bendable ultrathin cells

This TFB form-factor is exceptionally thin of 0.1 mm including the package. It can be bent, flexed and even rolled without damage.

Self-discharge

TFB: 1,5% per year

Li-ion/Li-po: 20,0% per year

The solid-electrolyte interfacial layer formation and other secondary reactions during operation are reduced or even avoided in solid state batteries, which results in very low self-discharge rates and allows for multiyear storage with minimal loss of power. Because all materials in the cell are inorganic, there are no observed side reactions, and self-discharge is negligible.

Number of discharge-charge cycles

TFB: 10 000

Li-ion/Li-po: 600

Solid-state electrolytes (LiPON) have demonstrated excellent stability with only a 5% capacity reduction after 10,000+ charge cycles. Conventional Li-ion batteries offer only 300-1,000 cycles before showing a similar or greater fall in capacity. This means that LiPON batteries could last 40-130 times longer than Li-ion batteries before they need replacing.