Lithium Battery Electrolyte Additive for Low-Temperature Resistance
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Solution Overview
Problem
Lithium-ion secondary batteries face challenges in maintaining low-temperature performance due to increased internal resistance and decreased power output, especially in electric vehicles and hybrid electric vehicles, where conventional electrolytes like LiPF6 suffer from reduced dissociation at low temperatures and high production costs of alternative solvents.
Innovation Solution
A lithium salt-containing non-aqueous electrolyte with a specific salt structure, such as (C4H9)4NB(C4H9)4, is added to the electrolyte, enhancing lithium ion-electrode reactivity and reducing electrode-interface resistance by forming a charge double layer at the cathode-anode interface, using lithium manganese metal oxide and non-graphitic carbon materials, which improves low-temperature properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiPF6 is used as the lithium salt in the non-aqueous electrolyte, then the battery exhibits stable properties at room temperature and high temperature, but the dissociation degree between Li ions and PF6 anions decreases at low temperature, resulting in increased internal resistance and decreased power output
Solution Approach 1:
A bulky salt compound (Formula I) is introduced as an intermediary substance in the electrolyte. This compound forms a charge double layer at the cathode-anode interface, which mediates the interaction between lithium ions and electrodes at low temperatures, reducing interface resistance and improving power output without compromising overall battery stability
Solution Approach 2:
The invention changes the chemical composition parameters of the electrolyte by adding a specific bulky salt compound (Formula I) with unique molecular structure characteristics. This parameter change enables the formation of a charge double layer that specifically improves low-temperature ionic conductivity and electrode interface reactivity
2Ease of operation
If a low-boiling organic solvent is used to reduce electrolyte viscosity, then low-temperature performance is improved, but the production cost increases
Solution Approach 1:
The invention uses a bulky salt compound (Formula I) that can be added in small amounts (0.1-20% by weight) to achieve significant low-temperature performance improvement. This approach is more cost-effective than using large amounts of low-boiling organic solvents, as the bulky salt provides sustained benefit through charge double layer formation without requiring high concentrations
3Temperature
If PC is used in the electrolyte to reduce freezing point, then low-temperature performance is improved, but it reacts sharply with graphitized carbon anode during charging, making it difficult to use large amounts
Solution Approach 1:
The bulky salt compound (Formula I) acts as an intermediary that protects the anode interface from direct reaction with PC. By forming a charge double layer, it mediates the interaction between PC and the graphitized carbon anode, preventing sharp reactions during charging while allowing PC to contribute to low-temperature performance
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
This configuration results in a more than 40% decrease in internal battery resistance and a 40% increase in power output at low temperatures, making the battery suitable for severe conditions like those encountered in electric vehicles and hybrid electric vehicles.
Implementation Method 1
the non-aqueous electrolyte serves as a medium through which lithium ions migrate between the anode and cathode
Implementation Method 2
via the formation of a charge double layer at the cathode-anode interface upon charging/discharging of the battery at a low temperature
Data Source
AI summary
Provided is a lithium secondary battery which uses a lithium manganese metal oxide as a cathode active material and a non-graphitic carbon material as an anode active material, and based on the total weight of the electrolyte, contains 0.1 to 20% by weight of a salt represented by Formula I in a lithium salt-containing non-aqueous electrolyte:R4X+YZn− (I)wherein R, X, Y, Z and n are as defined in the specification.The lithium secondary battery of the present invention can improve low-temperature properties of the battery by increasing the lithium ion-electrode reactivity and decreasing the electrode-interface resistance, via the formation of a charge double layer at the cathode-anode interface upon charging/discharging of the battery at a low temperature, and therefore can be preferably used in medium/large battery systems such as power sources for electric vehicles (EVs) and hybrid electric vehicles (HEVs) requiring operation under severe conditions.