LABOHR aimed to develop Ultra High-Energy battery systems for automotive applications making use of lithium or novel alloy anodes, innovative O2 cathode operating in the liquid phase and a novel system for harvesting O2 from air, which can be regenerated during their operative life without need of disassembling.
LABOHR had 5 key objectives:
- development of a green and safe electrolyte chemistry based on non-volatile, non-flammable ionic liquids (ILs);
- use of novel nanostructured high capacity anodes in combination with ionic liquid-based electrolytes;
- use of novel 3-D nano-structured O2 cathodes making use of IL-based O2 carriers/electrolytes with the goal to understand and improve the electrode and electrolyte properties and thus their interactions;
- development of an innovative device capable of harvesting dry O2 from air; and
- construction of fully integrated rechargeable lithium-Air cells with optimised electrodes, electrolytes, O2-harvesting system and other ancillaries.
Accordingly, LABOHR aims to overcome the energy limitation for the application of the present Li-ion technology in electric vehicles with the goal to:
- perform frontier research and breakthrough work to position Europe as a leader in the developing field of high energy, environmentally benign and safe batteries and to maintain the leadership in the field of ILs;
- develop appropriate electrolytes and nano-structured electrodes which combination allows to realize ultra-high energy batteries;
- develop a battery system concept as well as prototypes of the key components (cell and O2-harvesting device) to verify the feasibility of automotive systems with: A) specific energy and power higher than 500 Wh/kg and 200 W/kg; B) coulombic efficiency higher than 99% during cycling; C) cycle life of 1,000 cycles with 40% maximum loss of capacity, cycling between 90% and 10% SOC; and D) evaluate their integration in electric cars and renewable energy systems.
Charging towards a Li-air battery solution
Lithium-ion (Li-ion) rechargeable batteries are the standard in today's electric vehicles, but they need a recharge after about 150 km. Li-air batteries could soon change that, and pioneering work has highlighted design considerations.
A Li metal anode instead of graphite and the use of oxygen (O2) from the air as a cathode promises up to 10 times greater energy density. However, O2 reduction following reaction with Li-ions leads to deposition of a solid product within cathode porosities and to cathode clogging. Scientists addressed this issue with a radical approach not yet tried.
EU funding of the LABOHR (Lithium-air batteries with split oxygen harvesting and redox processes) project supported investigations of Li-air battery operation in the flooded (two-phase) configuration with a dual role for the electrolyte, as charge carrier and O2 carrier.
Conventional metal-air batteries, as well as fuel cells, rely on three-phase contact points within the cathode. The contacts ensure electron transport, hydrogen transport and O2 influx. However, in the case of Li-air, this operating configuration changes the porosity and hydrophobicity of the cathode because of the formation of the reduction products at the three-phase contact points.
In ground breaking studies, the team investigated a two-phase contact-point electrode configuration (a flooded configuration). The electrolyte or charge carrier is also used as the O2 carrier to harvest O2 from ambient air through an external O2 harvesting device.
The LABOHR concept employs environmentally benign ionic liquid electrolytes and nano-structured electrodes that harvest dry O2 from the air. Scientists prepared and tested anode and cathode materials, developed the O2 harvesting concept, and prepared and integrated into the electrode systems numerous ionic liquids as well as solid polymer electrolytes. Fundamental studies provided physicochemical parameters for the model of a full Li-air battery pack.
Although the practical implementation of Li-air batteries is not expected for another decade or two, LABOHR has made a major contribution to the development effort. Studies confirmed the importance of using ionic liquid-based electrolyte solutions to address solvent reactivity and volatility issues, and highlighted the problems of operating the Li-air battery in three-phase configuration. The concept of soluble redox ‘shuttle’ also opened a new possible path toward practical Li/O2 battery. In the meantime, the studies of electrolytes and electrode materials are likely to find short-term application in the Li-ion battery field.