In the design of a normal lithium-ion cell the electrodes are composed of active materials on current collectors which are flat sheets of copper for the anode and aluminium for the cathode. These metal sheets are around 4-9 µm thick for copper and 15-25 µm thick for aluminium and have the active materials coated on one or both sides. The thickness of these can vary depending on whether they are for a power or energy cell.
In cell manufacturing these electrodes are continuously coated, dried and calendared in a roll to roll process. Hence, the mechanical and surface properties of the electrode material are very important.
The trend is to thin these down to improve energy density and reduce cost.
Another way to increase energy density is with 3D electrodes. Increasing the surface area and connection to the active materials can improve a number of features of the cell:
- Energy density
- Power density
- Internal resistance
- Lifetime
- Thermal and mechanical behaviour
This improvement can increase the amount of usable active material, reduce the internal resistance and hence increase energy and power. The connection to the active material is also improved, reducing delamination and hence improving lifetime. This mechanical connection is extremely important when using a high percentage of silicon in the anode.
However, these electrodes are still in the development stage and there are a number of areas that are still in the process of being addressed:
- Increased cost
- Extra stages in cell production process
- Electrical connections to the electrodes
This is not a new field and a number of approaches have been [1] and are being developed. Previous generation of rechargeable batteries so called Nickel Metal Hydride are using 3D porous Nickel foams for their cathodes.
However, the approach needs to work with minimal changes to the existing manufacturing lines as the capital investments are huge.
Cost is everything in most applications and the $/kWh number is being driven down. Hence every component and process used to make the cell is under scrutiny.
The cell electrodes need good electrical connections to the positive and negative tabs of the cell. Often these also form strong thermally and electrically conductive pathways. The 3D structure of the electrode could potentially make this welded joint porous and difficult to form.
However, 3D electrodes look like a strong next step in battery cell development as they can be used with the existing chemistry and improve energy and power density (two key cell metrics). Whilst improving the lifetime of a battery 3D electrodes can reduce overall cost of ownership. Therefore, there are a number of companies working in this field.
References:
- Timothy S. Arthur , Daniel J. Bates , Nicolas Cirigliano , Derek C. Johnson , Peter Malati , James M. Mosby , Emilie Perre , Matthew T. Rawls , Amy L. Prieto , and Bruce Dunn, “Three-dimensional electrodes and battery architectures”, MRS BULLETIN, VOLUME 36, JULY 2011
- Minggang Zhang, Hui Mei, Peng Changa and Laifei Cheng, “3D printing of structured electrodes for rechargeable batteries”, Journal of Materials Chemistry A
- Yuan Yue,Hong Liang, “3D Current Collectors for Lithium-Ion Batteries: A Topical Review”, Small Methods, Volume2, Issue8, Special Issue: Lithium‐Ion Batteries and Beyond
- Arailym Nurpeissova, Akylbek Adi, Assylzat Aishova, Aliya Mukanova, Sung-Soo Kim, Zhumabay Bakenov, Synergistic effect of 3D current collector structure and Ni inactive matrix on the electrochemical performances of Sn-based anodes for lithium-ion batteries, Materials Today Energy, Volume 16, 2020
Addionics
Addionics is developing new technology that aims to transform the way we store and deliver energy. The battery architecture is optimised using in-house algorithms and novel fabrication technology. The technology enables cost-effective and scalable manufacture of the electrodes. The smart 3D electrodes can enhance capacity, power, safety, charging time and cost of batteries. Uniquely the technology is compatible for any battery chemistries – whether existing or emerging. The company having closed a major financing round is looking to accelerate the development and scale-up of proprietary technology to create the next generation of batteries to power the future.
- insideevs.com – Addionics Joins Saint-Gobain To Develop A Solid-State Battery
- bloomberg.com – Saint-Gobain Ceramics (Massachusetts, U.S.) and Addionics IL Ltd. (Tel Aviv, Israel) Will Collaborate on Developing High-Power, High-Capacity Solid-State Batteries for Long-Range, Fast-Charging Electric Vehicles
NAWA Technologies
NAWA Technologies are developing new solutions that improve energy conversion, storage, transport and efficiency by using carbon as the material of choice. Their core product is a nanoscale structure that can be applied roll to roll and imparts an anisotropic topology to the carbon electrode material, the first application being in supercapacitor electrodes.
Blackstone Technology
The most promising technologies that the company is currently developing are its proprietary 3D-printing techniques for the production of lithium-ion batteries that use printed battery electrodes and solid-state battery technology.
Prieto Battery
Prieto Battery has designed a battery architecture intended to address the slow diffusion of lithium-ions (Li+) into and between the anode and cathode. With a copper foam substrate to give a 3 dimensional structure.