Abstract
The electrolyte is one of the three essential constituents of a Lithium-Ion battery (LiB) in addition to the anode and cathode. During increasingly high power and high current charging and discharging, the requirement for the electrolyte becomes more strict. Solid State Electrolyte (SSE) sees its niche for high power applications due to its ability to suppress concentration polarization and otherwise stable properties also related to safety. During high power and high current cycling, heat management becomes more important and thermal conductivity measurements are needed. In this work, thermal conductivity was measured for three types of solid state electrolytes: Li 7 La 3 Zr 2 O 12 (LLZO), Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 (LAGP), and Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP) at different compaction pressures. LAGP and LATP were measured after sintering, and LLZO was measured before and after sintering the sample material. Thermal conductivity for the sintered electrolytes was measured to 0.470 ± 0.009 WK − 1 m − 1 , 0.5 ± 0.2 WK − 1 m − 1 and 0.49 ± 0.02 WK − 1 m − 1 for LLZO, LAGP, and LATP respectively. Before sintering, LLZO showed a thermal conductivity of 0.22 ± 0.02 WK − 1 m − 1 . An analytical temperature distribution model for a battery stack of 24 cells shows temperature differences between battery center and edge of 1–2 K for standard liquid electrolytes and 7–9 K for solid state electrolytes, both at the same C-rate of four.
Highlights
Society has seen a major introduction of the lithium-ion battery into the transport sector as of recently, being an attractive and efficient way to store electrical energy in hybrid and electric vehicles.larger transportation vehicles are increasingly equipped with hybrid systems and batteries, creating an ever-increasing need for more specific power and energy, high power opportunity charging, better performance, and longer lifetime [1]
The drive for a solid state electrolyte (SSE) in lithium-ion batteries is mainly motivated by two things; one is to keep performance at high load conditions while simultaneously increasing specific energy and specific power of the battery, and the other is to lower the risk of dangerous fires by removing the liquid and volatile liquid electrolyte [5,6]
Measurements were taken at 3–5 bar compaction pressure only, as Li-ion batteries are not usually compressed beyond that
Summary
Society has seen a major introduction of the lithium-ion battery into the transport sector as of recently, being an attractive and efficient way to store electrical energy in hybrid and electric vehicles. At any given C-rate, a battery can be modified to have lower current density, by lowering the electrode thickness This in turn leads to lower specific energy and specific power (larger weight fraction of electrolyte separator, current collectors, etc.). This means that, to simultaneously have high specific energy and power, current density must increase. A similar evolution took place in the fuel cell sector, where early alkaline fuel cells used a liquid electrolyte that was subject to concentration polarization at higher currents [3] This problem was overcome when solid proton conducting membranes were developed [4]. The drive for a solid state electrolyte (SSE) in lithium-ion batteries is mainly motivated by two things; one is to keep performance at high load conditions while simultaneously increasing specific energy and specific power of the battery, and the other is to lower the risk of dangerous fires by removing the liquid and volatile liquid electrolyte [5,6]
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