Investigation and Improvement of the Low Temperature Performance of High-Capacity Silicon Anodes for Lithium-Ion Batteries

The behavior of a lithium-ion battery is highly influenced by its operating temperature. Kinetics of lithium intercalation may improve upon increased temperature or become sluggish when the temperature is lowered. Many physical properties and reactions within the cell during discharge contribute to poorer performance at low temperatures such as increased viscosity and loss of conductivity of the electrolyte, increased impedance across SEI layers, and a propensity to plate lithium on the anode surface. Performance of these batteries starts to show significant deviation from room temperature at about 0°C and below. The demands of future generations of lithium-ion batteries for Martian rovers, satellites and other aerospace applications require retaining high capacity at -60°C and -80°C so temperatures of -20°C to -40°C are chosen initially to investigate next generation electrodes. The effect of various electrolytes on lithium-ion battery performance at low temperatures has been the most widely studied aspect in improving discharge characteristics, and a trend of mixed carbonates with various additives has been established. These additives help improve conductivity of the electrolyte and facilitate more stable SEI growth. Ether based organic solvents have also emerged as promising electrolytes, imparting greater stability and faster kinetics in lithium-ion cells at low temperatures. Focus for improving performance is not just on the electrolyte however, as electrode processing also plays a role in electrochemical behavior. Size of electrode particles, type of binder used and any possible heat treatments to the electrode all impact the cells performance. The most common anode material used in lithium-ion batteries today is graphite, with a theoretical capacity of 372 mAh/g. In an economy shifting more towards renewable energy, not only is higher energy density more pertinent, but higher capacity anode materials are needed to function across lower temperatures as well. Anodes containing silicon, with a capacity of 4200 mAh/g, are the most studied higher capacity anode with the potential to replace graphite. How the silicon electrode is processed is important to achieving high capacity in a lithium-ion cell as volume expansion and loss of particle contact are major issues to mitigate. This is why physical characteristics such as particle size, choice of binder, additive for structural integrity and heat treatment steps are considerations that need careful examination for improved anode performance. Concerning the electrolyte, fluorinated additives are becoming more known to facilitate stable and robust SEI formation, and ethers, instead of carbonates, may offer protection against lithium plating when using lithium metal as anode (3860 mAh/g) or in full cells with relatively low voltage requirements. After initial experimentation with traditional lithium-ion cells at -20°C to examine low temperature behavior and trends, the main chemistry examined was a copper modified silicon electrode paired with lithium metal counter electrode. Various electrode processing methods of the silicon electrode were investigated along with different electrolyte formulations to improve low temperature performance at -20°C, -30°C and -40°C over traditional graphite-based lithium-ion batteries. Several analytical techniques revealed how performance of the silicon electrode at low temperatures is directly related to fabrication methods and how choice of suitable electrolyte can lead to retaining high discharge capacities for long cycle life testing.

Level thesis:degree_level

Doctorate Degree

Year dc:date.issued

2024

Author dc:creator

• Mennel, Jason

Advisor dc:contributor.advisor

• Chidambaram, Dev

Committee members dc:contributor.committeemember

• Carlson, Krista
• Tsoulfanidis, Nicholas
• Vahidi, Ehsan
• Barile, Christopher

• battery
• electrolyte
• high-capacity
• lithium-ion
• low temperature
• silicon

Language dc:language.iso

en_US, English

Repository record dc:identifier.uri

https://scholarwolf.unr.edu/handle/11714/11239

OAI identifier oai:identifier

oai:scholarwolf.unr.edu:11714/11239