Lithium-Ion Battery Electrolyte Composition for -40°C Discharge
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Solution Overview
Problem
Lithium ion batteries face challenges in maintaining high discharge capacity and energy density at temperatures below freezing, with existing batteries experiencing significant capacity decrease when discharged at temperatures lower than 0°C.
Innovation Solution
A lithium ion battery design incorporating a positive electrode with lithium cobalt oxide (LixCoO2) and a negative electrode made of non-graphitizing carbon, using an electrolyte solution with a specific volume ratio of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate, which maintains discharge capacity and energy density even at -40°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional lithium ion batteries are used, then they can operate at room temperature, but discharge capacity decreases significantly at temperatures below freezing
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by using a specific mixture of cyclic carbonate (15-30 vol%), chain carbonate (70-85 vol%), and cyclic carboxylate (5-20 vol%). This parameter optimization allows the electrolyte to maintain appropriate viscosity and ionic conductivity at low temperatures, enabling the battery to retain discharge capacity even below freezing temperatures.
Solution Approach 2:
The patent employs a composite electrolyte system combining three different types of solvents (cyclic carbonate, chain carbonate, and cyclic carboxylate) with complementary properties. The cyclic carbonate provides high dielectric constant for lithium salt dissolution, the chain carbonate provides low viscosity for ion mobility, and the cyclic carboxylate forms stable SEI films. This composite approach synergistically improves low-temperature discharge performance.
2Adaptability or versatility
If discharge is performed at temperatures below freezing, then the battery can operate in cold environments, but discharge energy density decreases
Solution Approach 1:
The patent optimizes the electrolyte composition parameters to balance low-temperature fluidity and energy storage capacity. The specific volume ratios of cyclic carbonate (15-30%), chain carbonate (70-85%), and cyclic carboxylate (5-20%) are tuned to maintain adequate ionic conductivity for cold environment operation while preserving sufficient lithium ion capacity for energy density.
Solution Approach 2:
The patent uses non-aqueous solvents that replicate the beneficial properties of aqueous electrolytes (high ionic conductivity and stability) without the freezing point limitation. The cyclic carboxylate component specifically mimics the low-temperature performance of certain aqueous systems while maintaining the non-aqueous advantages of higher operating voltage and energy density.
3Reliability
If the electrolyte composition is optimized for low temperature, then discharge capacity improves at cold temperatures, but the battery design complexity increases
Solution Approach 1:
The patent establishes specific parameter ranges for electrolyte composition (cyclic carbonate: 15-30 vol%, chain carbonate: 70-85 vol%, cyclic carboxylate: 5-20 vol%) that balance low-temperature performance with manufacturing feasibility. These quantified parameters provide clear formulation guidelines that simplify the complex task of electrolyte optimization while achieving reliable low-temperature discharge capacity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The battery achieves high discharge capacity and energy density retention at extremely low temperatures, with discharge capacity at -40°C being at least 40% of that at 25°C, ensuring reliable performance in cold environments.
Implementation Method 1
an electrolyte solution with a specific volume ratio of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate
Implementation Method 2
a positive electrode containing a positive electrode active material... lithium cobalt oxide (LixCoO2)
Implementation Method 3
In X-ray diffraction (XRD) analysis with CuKα1 radiation, the carbon material has peaks at 2θ of greater than or equal to 20° and less than or equal to 24°
Data Source
AI summary
A lithium ion battery having excellent discharge characteristics even at a temperature below freezing is provided. The lithium ion battery includes a positive electrode containing a positive electrode active material, an electrolyte solution, and a negative electrode containing a negative electrode active material that is a carbon material; the carbon material has peaks at 2θ of greater than or equal to 20° and less than or equal to 24°, 2θ of greater than or equal to 42° and less than or equal to 46.5°, and 2θ of greater than or equal to 78° and less than or equal to 82° in X-ray diffraction (XRD) analysis; and a value of the discharge capacity obtained by subjecting the lithium ion battery to constant current and constant voltage charging (0.1 C, 4.5 V, and a termination current of 0.01 C) at 25° C. and then discharging at −40° C. is higher than or equal to 40% of a value of the discharge capacity in discharging at 25° C.