Nonaqueous Battery Electrode Design for Low-Temperature Charging
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Solution Overview
Problem
Nonaqueous electrolyte batteries face challenges in maintaining high performance and cycle life under low temperature environments, particularly at temperatures below −20° C., due to issues with lithium deposition and solvent decomposition during rapid charging, as well as over-discharge of the positive electrode.
Innovation Solution
The battery design incorporates a positive electrode with a metal compound containing lithium and metals like cobalt, nickel, manganese, or vanadium, paired with a negative electrode active material having a Li ion insertion potential above 0.4 V, along with specific surface area and thickness ratios between the electrodes to optimize charge-discharge cycle characteristics, and uses a high-viscous electrolyte to enhance impedance and prevent over-discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If rapid charging is performed under low temperature conditions, then charging speed is improved, but lithium deposition and solvent decomposition occur
Solution Approach 1:
The patent changes the physical and chemical parameters of the electrolyte by using a mixed solvent system comprising cyclic carbonate and chain carbonate in specific proportions (cyclic carbonate 20-80 vol%, chain carbonate 20-80 vol%). This parameter adjustment optimizes the electrolyte's viscosity and impedance characteristics, enabling rapid charging at low temperatures while preventing lithium deposition and solvent decomposition.
Solution Approach 2:
The patent employs a composite electrolyte system combining multiple solvent types (cyclic carbonate and chain carbonate) with complementary properties. The cyclic carbonate provides high dielectric constant and lithium salt dissolution capability, while the chain carbonate provides low viscosity and high ionic conductivity, creating a synergistic effect that resolves the contradiction between fast charging and cycle stability.
2Power
If high output performance is achieved under low temperatures, then power delivery is improved, but over-discharge of positive electrode occurs
Solution Approach 1:
The patent adjusts the electrolyte composition parameters to achieve optimal balance between power delivery and electrode stability. By controlling the ratio of cyclic to chain carbonate within 20-80 vol%, the electrolyte maintains appropriate viscosity and impedance characteristics that enable high power output while preventing positive electrode over-discharge.
Solution Approach 2:
The electrolyte acts as an intermediary medium that facilitates lithium ion transport between electrodes while regulating the charge-discharge process. The mixed solvent system mediates between the conflicting requirements of high power output and electrode composition stability, enabling efficient ion transport without causing over-discharge.
3Reliability
If electrolyte viscosity is increased to enhance impedance control, then over-discharge prevention is improved, but ion transport efficiency decreases
Solution Approach 1:
The patent optimizes the electrolyte viscosity parameter by selecting specific solvent combinations and proportions. The mixed solvent system achieves optimal viscosity that balances impedance control for over-discharge prevention with sufficient ionic conductivity for efficient lithium ion transport.
Solution Approach 2:
The composite electrolyte system combines cyclic carbonate (higher viscosity, better impedance control) with chain carbonate (lower viscosity, better ionic conductivity). This material composition creates a synergistic effect where the combined properties exceed the sum of individual components, simultaneously achieving over-discharge prevention and efficient ion transport.
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 effectively suppresses lithium deposition and solvent decomposition, improving high-output performance and cycle life under low temperatures, while maintaining energy density and preventing over-charging, thus enhancing the battery's charge-discharge cycle characteristics.
Implementation Method 1
a negative electrode comprising a negative electrode layer containing a negative electrode active material having a Li ion insertion potential not lower than 0.4 V (vs. Li/Li+)
Implementation Method 2
a nonaqueous electrolyte
Data Source
AI summary
A nonaqueous electrolyte battery includes a positive electrode and a negative electrode. The positive electrode comprises a positive electrode layer containing a metal compound. The metal compound contains lithium and at least one kind of metal selected from the group consisting of cobalt, nickel, manganese, iron and vanadium. The negative electrode comprises a negative electrode layer containing a negative electrode active material having a Li ion insertion potential not lower than 0.4 V (vs. Li/Li+). The positive electrode layer and the negative electrode layer satisfy formulas (1) to (3) given below:0.5m2/g≦Sn≦50m2/g (1)5≦(Sn/Sp)≦100 (2)0.5≦(Lp/Ln)<1 (3).