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Tanisha Gupta
Jan 28, 20214 min read

Flexible Batteries: State of the Art


Flexible batteries are an active area of research because they enable electronic products to be more bendable, adaptable, and comfortable. They further enable the development of the Internet of things (IoT), roll-up displays, implantable medical robots, wearable electronics. Most of the well‐performing Li‐ion batteries with rigid features cannot be directly used in flexible devices that experience demanding operating conditions, such as flexing, stretching, bending, twisting, and folding. Accordingly, flexibility‐oriented material and system designs call for exploring a range of carbon, metal and polymer materials with soft features, as well as novel manufacturing methods to fabricate fuel cells.


Developments and Trends


The battery market has bounced back recently with batteries becoming ultra-thin, flexible, rollable, stretchable, etc., and manufacturers offering large batteries focused on large-sized electric vehicle, residential and grid applications.


These new batteries possess :

  • Footprints (micro-batteries or large-area batteries)

  • Thickness (thin-film or bulky batteries)

  • Mechanical properties (flexibility, bendability, rollability, stretchability, foldability, etc.)

  • Manufacturing methods (e.g. printing, coating, etc.)

  • Technologies (e.g. solid-state batteries, lithium-polymer batteries, carbon-zinc batteries, etc.)

Flexible batteries are progressively used in the medical devices industry where manufacturers are designing and offering flexible batteries to power temperature sensors, pacemakers, and smart patches. Implantable medical devices, such as neural stimulators, pacemakers, and defibrillators, require batteries that can deliver steady, reliable power for a long duration of time and thus flexible batteries meet such requirements.

Thin-film batteries are also widely used in smart packaging, smart cards and wearable devices. These batteries offer higher average output voltage and have lower chances of electrolyte leakages than bulky solid-state batteries. The increased demand for miniaturized products used in these applications has led to a rise in the adoption of thin-film lithium-ion flexible batteries, thus leading to noteworthy growth.


Top 10 Players

The above chart shows the total number of flexible battery patents assigned to top market players. With 358 patents, LG Chemicals is the top player in the flexible battery industry. Samsung SDI follows closely behind with 323 patents. Players like Panasonic, Semiconductor Energy Laboratory, Sanyo Electric are at equal footing in this space.


Top 10 Countries

The above chart shows the top 10 patent jurisdictions with China leading the race with 13299 patents in the flexible battery domain followed by the US with 2295 patents. Assignees in these countries have benefitted from an advancement in the digital economy, the focus on flexible electronics, and the growing emphasis on the use of portable electronics along with IoT. Besides these, Korea and Japan are almost on the same level with 1845 and 1802 patents respectively.


Advantages

  • Battery cost cutting: Materials cost and fabrication cost constitute a large portion of the whole battery costs. The fabrication of flexible batteries is not mature enough to be scaled up. Optimization of electrochemical and mechanical properties of polymer electrolytes and assembly technologies in the cathode–electrolyte–anode structures raise the battery cost. Technological maturity and material development can reduce battery costs and in turn stimulate massive production.

  • Better attributes: Thick and dense electrodes inevitably cause crack and resistance build‐up under dynamic shape changes, which contribute to cell performance decay or cell death. Flexible batteries with more than 1000 cycles have been reported by companies. However, most cases do not mention energy density and power densities. Lightweight and soft materials and innovative cell structures that cut down inactive materials portion, release flexing‐induced strain, and keep battery integration could afford solutions for this issue.

  • Better components’ harmony: Flexible batteries work under electrochemical environment and mechanical force, which require compatible battery components, electrochemically, and mechanically. For electrochemical compatibility, the electrolytes need to withstand oxidation and reduction in cathodes and anodes simultaneously. Therefore, electrolytes that possess a wide electrochemical window and stable interface‐film‐forming capability are regarded as key properties to keep the battery working well.

Developed countries all over the world are making great efforts in the field of flexible energy storage where China also stands at the spearhead of the world. With some breakthrough technological advances in recent years, flexible electronics is one of the important development areas of electronic products in the future.


Future Perspectives


The flexible battery market is estimated to grow from USD 98 million in 2020 to USD 296 million by 2025 with a CAGR of 24.7%. The growth of this market is likely to be driven by the rising number of R&D activities for developing flexible batteries for wearable devices, increasing use of thin and flexible batteries in flexible electronic devices, ongoing miniaturization of electronic devices, surging demand for flexible batteries in IoT applications, and increasing use of flexible batteries in medical devices.


Wearable technology and electronic textiles are a major growth area for thin film and flexible batteries. Conventional secondary batteries may meet the energy requirements of wearable devices, but they struggle to achieve flexibility, thinness and lightweight. High-energy thin-film batteries have the highest potential here followed by printed rechargeable zinc batteries. The healthcare sector is also a promising target market. Skin patches using printed batteries are already a commercial reality. Connected device applications are another important trend especially combining special form factors and harsh temperature requirements. The success of flexible batteries in smart energy devices requires a rational design of battery components and structures and cooperative efforts among scientists and engineers in related fields.


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