High-Variation Battery Technology
High-voltage batteries absorb energy much faster than lower-voltage systems and are increasingly being used in off highway vehicles, construction equipment and power storage applications. High voltage architectures can also better manage efficiency transfers and losses.
In addition, they offer excellent scalability, meaning their capacity can be easily adjusted by adding or subtracting battery modules.
High-Voltage Applications
As the world continues to shift toward electrification, high voltage battery technology is enabling new applications and high-voltage-battery propelling industries forward. From electric vehicles to renewable energy storage systems, these batteries power crucial components that require higher levels of energy density and output.
Higher voltage systems provide many advantages, including smaller battery size and weight, faster charging, greater efficiency, and better performance in extreme temperatures. Additionally, higher voltage batteries allow for fewer cells, reducing overall costs.
The automotive industry is leveraging high voltage battery systems to reduce cost and improve performance in their products. Most electric vehicle (EV) systems operate at 400 volts, with larger EVs being designed to use 800 volts. A higher voltage system allows for a smaller battery, faster charging, and a longer driving range.
Construction equipment like telehandlers and boom lifts are also converting to a high voltage system. The move to Li-ion batteries with a higher voltage architecture will improve efficiency, transfer/gain more current at the same time, and allow these machines to charge much faster.
High voltage batteries are also essential for storing renewable energy from solar panels and other sources. By storing surplus energy, these batteries can help balance peak demand and ensure a sustainable power supply.
High-Voltage Materials
The high voltage of HV batteries allows for increased power output and longer battery life. Additionally, it reduces energy losses in transmission by allowing electricity to be conducted over shorter distances.
Increasing the operating voltage of a battery also increases its energy density, since more power can be released from a given amount of working voltage. However, a higher voltage also requires more rigorous safety measures and specialized equipment to ensure that the battery operates safely.
This includes ensuring that the materials used in the battery are electrically insulating, such as plastics and polypropylene. A high-quality insulator is essential for keeping the battery cells isolated from each other, and reducing the risk of short circuits or ruptured cells. Additionally, it is important to understand the risks associated with high voltage systems, such as the possibility of sparks and arcing that could cause personal injury or fires.
Traditional carbonate electrolytes are prone to severe oxidation decomposition at high working voltages due to the poor LUMO-HOMO interaction and carbonate-graphite interlayer polarization, which triggers inhomogeneous charge distribution and promotes dendrite growth4. In contrast, HGPE has a good oxidation window (Ea2) of about 5 V owing to the fluorination of the electrolyte solvent and a robust CEI formed by insertion/extraction of LiF molecules. The high mechanical strength of HGPE, with a shear modulus up to 2768 MPa, further enhances the SEI layer’s robustness and blocks Li dendrite growth (Supplementary Fig. 26).
High-Voltage Electrolytes
Several carbonate and non-carbonate electrolyte formulations have been developed for high-voltage lithium metal batteries. However, they have Off-grid home solar indoor energy storage system limited Coulombic efficiency and poor cycle life due to solvent decomposition at higher upper cutoff voltage. To improve these problems, a variety of additives has been employed to promote the key interfacial chemistries at the cathode and electrolyte interface. These additives include SEI/CEI forming enhancer, HF scavenger, transition metal ion complexing agent, and salt stabilizer (Fig. 8).
Unfortunately, adding electron-withdrawing groups to the carbonate and ether solvents increases the oxidation potential and reduces their boiling points, which limits cell energy/power density and operation safety. In addition, increasing the reduction potential of these solvents raises organic components in the SEI, which further decreases cycling CE and cycle life of uSi anodes.
Fluorinated solvents such as ethylene carbonate-dimethyl carbonate (EC-DMC) and 1,2-dimethoxyethane-tetrahydrofuran (DME-THF) have excellent compatibility with Li and exhibit low vapor pressure. They also have lower reactivity with Si than traditional carbonate solvents. Moreover, they can be mixed with ethylene glycol (EG) and tetraethylene tricarbonate (TTE) to provide a safe and reliable high-voltage electrolyte for NCA cathodes. The chemical structure of these electrolytes enables them to suppress the reduction of C-S bonds in uSi electrodes and prevent the formation of a polymer layer at the cathode/electrolyte interface. The EC-TTE and EG-FST electrolytes can support a wide range of lithography processes for uSi anodes. EELS analysis of the outer and inner layers of SEI formed in these electrolytes reveals that the EE-SEI has a strong C-H/C-C peak at 286.5 eV, while the FST-SEI has a thinner and less intense C-O/C=O peak.
High-Voltage Cathode Materials
The pursuit of high-energy-density lithium-ion batteries (LIBs) for EV applications has stimulated the development of next-generation cathode materials. These new cathodes feature high specific capacity and high operating voltage, but they still suffer from serious problems in the practical application process such as oxygen release, irreversible structural degradation, capacity fading, voltage decay, and poor cycling stability.
These problems mainly result from the decomposition of electrolytes under high voltage, which can lead to violent side reactions in the cathode material and limit the transport of Li+ during charging and discharging. This is a challenge that needs to be solved by utilizing appropriate additives.
The most promising additives can achieve their function by interacting with the cathode surface and preventing the formation of an SEI layer. They can also provide a barrier to prevent the migration of oxygen and other substances into the battery interior, which can affect the performance of the battery.
The most commonly used non-aqueous solvents for LIBs are ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate. These solvents have a low vapor pressure and are resistant to reduction, but they are susceptible to oxidation at voltages higher than the cutoff voltage. This can cause cation mixing, severe cracks, phase transformation, O loss, and the formation of a rock salt phase in the cathode material, resulting in significant capacity attenuation.