As the number of sectors turning to electrification to curb Green House Gas emissions grows, so too do the demands on energy storage systems.
Even though the lithium-ion battery - currently the dominant energy storage device – is well suited to meeting most demands, at times there are applications where a single battery design-architecture cannot simultaneously meet the widely varied requirements. Hence, a fast-charging battery may not deliver the energy density to support a long-range electric vehicle (EV), or if the battery is optimized for energy density it may not provide the short bursts of high energy required to rapidly charge or accelerate a high-performance EV.
Even though Li-ion batteries have the highest energy density of rechargeable batteries available, they typically suffer from low power because of reversible Coulombic reactions occurring at both electrodes, involving charge transfer and ion diffusion in bulk electrode materials. Since both diffusion and charge transfer are slow processes, power delivery as well as the recharge time of Li-ion batteries is kinetically limited. As a result, batteries have a low power density and lose their ability to retain energy throughout their lifetime due to material degradation.
On the other hand, electrochemical double-layer capacitors or ultracapacitors make up, together with pseudocapacitors, a new type of electrochemical capacitor called supercapacitors (referred to as SCs), which store energy through the accumulation of ions on an electrode’s surface. Although these devices have a limited energy storage capacity, they exhibit excellent power density. The main challenge facing the SC is its low energy density, meaning that the amount of energy stored per unit weight is very small, particularly when compared to a Li-ion battery.
Thus SoreDot’s innovative patent describes the management, through an ECU and novel software, of battery systems comprising a main fast-charging lithium-ion battery (FC) configured to deliver energy to the EV, and a supercapacitor-emulating fast-charging lithium-ion battery configured to receive and deliver short term high power to the FC Li-ion battery and/or to the EV.
StoreDot’s innovation outlines a single, internally adjustable modular battery system capable of storing energy and delivering power in a wide range of electrical systems such as photovoltaic systems, solar systems, grid-scale battery energy storage systems, home energy storage systems, power walls, and in particular, EVs.
The inventors have figured out a way to emulate supercapacitors using fast-charging batteries, thereby retaining the intrinsic advantages of fast-charging batteries while overcoming the typical limitations and drawbacks when compared to supercapacitors.
The patent describes batteries comprising a main fast-charging lithium-ion battery (FC), configured to deliver electrical energy to the EV in conjunction with a supercapacitor-emulating fast-charging lithium-ion battery (SCeFC), designed to receive and deliver power to the FC and/or to the EV. The system is configured to operate at high power ratings within a narrow range of state of charge (SoC), using module management software, and a control unit.
Both the FC and the SCeFC have anodes based on the same anode active material, with the control unit configured to manage power delivery to and from the FC and the SCeFC to optimize the operation of the FC.
With the ECU and appropriate software controlling the fast-charging battery to only operate within a partial operation range, the lithiation of the anode active material can be regulated to within 5 percent around the working point when operating at charge/ discharge rates greater than 5C.
What is more, by limiting the modified fast-charging battery to operate over only a partial range, a larger continuous current can be applied because only a small portion of the whole charging or discharging curve is utilized. This increases the cycle-life by two to three orders of magnitude compared to a typical battery operated over its full range, as in each cycle different areas of the battery are operational.
Whilst in EVs the innovation allows for short bursts of power typically found in supercapacitors with the advantages of energy-dense fast-charging LIBs, by emulating large supercapacitors when integrated into the power grid, spikes in energy demand can also be smoothed out. In another example, a modified fast-charging battery and/or device could be configured to emulate small supercapacitors incorporated into consumer electronic devices to ensure an even power supply to the device.
In other use cases, such as wireless sensors, which require many short operation cycles, modified fast-charging batteries may be particularly advantageous with respect to the emulated supercapacitors. As supercapacitors typically have low energy densities and high leakage currents, such applications typically exhaust supercapacitors quickly, while the much larger energy density and low leakage currents characterizing modified fast-charging batteries could extend the operation of devices in such use cases.
Thus, through the use of an ECU and software to control the two operatively different types of battery modules, the functionality of the battery system can be enhanced to better meet the wide-ranging energy storage and delivery applications.