Electrolytes
for NMC||SiC
cells
NMC||Silicon Graphite (SiC) cells are high-energy cells combining high-voltage cathode materials with high-capacity anodes. Silicon is currently considered one of the most promising negative electrode materials for increasing the energy density of LIBs, as it has a higher volumetric and gravimetric capacity than graphite, while also being inexpensive and abundant. Various types of Si-based cells have been developed, including pure silicon, nanostructured silicon, silicon suboxides, or Si/graphite composites with varying Si contents. Achieving a long cycle life is a major challenge for cells with high a Si content, as Si experiences enormous volume changes during lithiation / delithiation, resulting in accelerated capacity degradation.
Challenges
Nickel manganese cobalt oxide (NMC) is one of the most commonly used cathode materials in LIBs owing to its advantageous properties such as high energy and power. NMC cathodes are produced and used with different transition-metal ratios, such as NMC-111, NMC-622 or NMC-811. By varying the Ni content, the resulting capacity of the material can be tailored to fit specific application requirements.
High-energy cells with Si anodes and high-nickel NMC cathodes have specific electrolyte requirements. To achieve a long cycle life, the formation of highly efficient interphases on both electrodes is required. On the one hand, the SEI must withstand the expansion and shrinkage of Si to reduce irreversible lithium and electrolyte consumption. On the other hand, oxidative electrolyte decomposition and transition metal dissolution at the positive electrode must be minimized.
The Solution
Formation: 3 cycles 0.1C CCCV charge / 0.1C CC discharge
Cycling rate: 1C CCCV charge / 1C CC discharge
Temperature: 45 °C
Voltage range: 4.2 – 2.8 V
