Today, lithium-ion batteries (LiBs) are widely used in various applications, offering high power, energy density and long cycle life. However, at sub-zero temperatures, their available energy, power and charging capability is limited. In order to address these issues, batteries can be pre-heated from low ambient temperatures to a higher temperature before operation. External heating methods, such as air, liquid or resistance heating, have already been commercialized, but their heating performance is limited by low heat transfer coefficients and high heat losses, resulting in prolonged heating duration, high energy consumption and low temperature uniformity. Here, we propose a novel internal pre-heating method, using integrated heating wires in a battery electrode (AIM electrode), to pre-heat lithium-ion cells in a fast, low-energy and highly uniform way.

A novel internal heating method for low-temperature operation of lithium-ion cells is presented. The proposed heating method incorporates innovative anode electrodes with integrated resistance wires as heating element integrated in the graphite film. Taking advantage of local heating, the generated heat is transferred directly to the anode active material in a uniform manner, offering fast and low-energy heating. Pouch cells, assembled using such anode electrodes and LFP cathodes, were operated at low ambient temperatures, from 0 oC to -40 oC, providing fast heating and improvement over the electrochemical performance compared to standard cells. The cells demonstrated stability and high values in their capacity with high coulombic efficiency during C/2 Charge – C/3 Discharge at an ambient temperature of 0 oC, persisting after 30 cycles. In comparison, standard cells cycled at the same temperature showed significantly lower capacities with low coulombic efficiency, and high irreversible capacity loss after only 20 cycles.

The proposed design is a promising heating method for LiBs operating at low temperature conditions. In EV applications, the input power that is required for heating the battery pack could be supplied by the grid during charging, and by regenerative breaking during driving(discharging), keeping the cell temperatures inside a selected temperature range significantly higher than ambient temperatures, restoring the energy and power of the battery and prolonging its cycle life. Moreover, the proposed design could be suitable for high-energy cells with high mass loadings. Optimizing the thermal insulation of the cell packaging/casing, and selecting the appropriate heating parameters, such as input current and operating temperature window, can further increase the heating effectiveness of the proposed design, in terms of required input power and heating duration.