Composition and function of electrolyte
main content
As the "blood" of the lithium battery, the electrolyte undertakes a dual mission in the cold start scene of the motorcycle: it not only maintains the high-speed migration of lithium ions in the extreme cold of -30℃, but also carries the pulse current of more than 30C at the start moment. Its composition design and performance optimization directly determine the low temperature start-up ability, cycle life and high temperature safety of the battery. This article will analyze the composition of the electrolyte at the molecular level, revealing how it supports the reliable start of the motorcycle in extreme conditions.
1. Lithium salt: carrier of ion migration
Lithium hexafluorophosphorate (LiPF₆), as the mainstream lithium salt, has both advantages and challenges:
High degree of dissociation: the degree of dissociation in carbonate solvent reaches 85%, providing ion conductivity of 6-12mS/cm;
Temperature sensitivity: the degree of dissociation drops sharply to 40% at -20℃, which needs to be optimized with the solvent system;
Thermal stability defects: decomposition above 60℃ produces HF, corrodes the electrode material (adding 1% vinyl carbonate VC can neutralize 90% of HF).
Explore alternatives:
Lithium difluoride sulfonimide (LiFSI) : -30℃ conductivity is 50% higher than LiPF₆, but the cost is 3 times of the latter.
Lithium difluorooxalate borate (LiDFOB) : high temperature gas production reduced by 70%, suitable for closed battery system.
2. Solvent system: the key to temperature adaptation
The demand for all-climate use of motorcycles drives the innovation of solvent systems:
Basic solvent:
Vinyl carbonate (EC) : dielectric constant up to 89.6, promoting the dissociation of lithium salts;
Dimethyl carbonate (DMC) : viscosity of only 0.59cP, improve low temperature fluidity;
Methyl ethyl carbonate (EMC) : freezing point -53℃, broaden the low temperature limit.
Low temperature optimization strategy:
Chain ester doping: add 20% ethyl acetate (EA) to reduce the viscosity from 35cP to 18cP at -40℃;
Eutectic solvent design: EC:EA=1:3, the freezing point is reduced to -78℃, and the ionic conductivity remains 4mS/cm.
3. Additives: Performance enhancing "catalysts"
Additives accounting for 5%-10% of the total electrolyte play a key role in modification:
Film forming agent (VC) :
A dense SEI film was formed on the surface of the graphite negative electrode, and the thickness was controlled at 50-80nm.
The first cycle efficiency of the electrolyte containing VC increased from 75% to 92%;
Flame retardant (trimethyl phosphate TPP) :
The flash point of the electrolyte increased from 36℃ to 125℃ by adding 2%TPP.
The combustion chain reaction was interrupted by free radical trapping mechanism (PO·→POO·).
Multifunctional additive:
0.5% vinyl sulfate (DTD) can simultaneously improve the stability of the cathode CEI film and the thermal stability of lithium salt.
Conclusion
From the basic system of lithium hexafluorophosphate to the intelligent self-healing electrolyte, the "ion highway" of motorcycle starter batteries is undergoing a disruptive upgrade. From the basic system of lithium hexafluorophosphate to the intelligent self-healing electrolyte, the "ion highway" of motorcycle starter batteries is undergoing a disruptive upgrade.
START-STOP LITHIUM battery
Enov start-stop battery is designed to provide excellent performance for high-demand start-stop vaehicles. It adopts the third-generation intelligent lithium platform architecture to achieve technological breakthroughs in core indicators such as cycle life, environmental adaptability and energy density. Compared with the traditional lead-acid battery system, the energy efficiency is increased by 210%, the cycle life is extended by 8-10 times, and the monthly self-discharge rate is controlled within 3%. Enov's unique low-temperature battery technology makes a breakthrough in achieving stable output in the whole climate domain from -30℃ to 65℃, maintaining more than 90% of the effective capacity release under extremely cold conditions (-30℃), and maintaining 90% of the capacity in high temperature environments (65℃).
The start-stop battery series products cover the mainstream voltage platform of 12V/24V/48V, and support flexible configuration of LFP (lithium iron phosphate) and NCM (lithium nickel cobalt manganese oxide) dual-material system. All models adopt modular design to support customization of different model specifications. Enuo engineering and technical team to provide full cycle technical service support, if you need, please contact us.
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