Non-aqueous Electrolyte Battery Low-Temperature Ion Conductivity
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Solution Overview
Problem
Lithium ion secondary batteries experience performance degradation at low temperatures, requiring improved performance even below freezing points.
Innovation Solution
A non-aqueous electrolyte secondary battery design incorporating a mixture of lithium electrolytes, a titanium-containing oxide negative electrode, and a specific solvent composition with a self-diffusion coefficient of chain carbonates between 1.4 × 10^-10 and 2.0 × 10^-10 m^2/sec at -20°C, along with a thin separator having holes of 10 to 100 µm in diameter, to enhance low-temperature characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional lithium ion batteries are used, then they provide good performance at room temperature, but their performance degrades significantly at low temperatures below freezing point
Solution Approach 1:
The patent applies parameter changes by carefully controlling the concentration ratios of different lithium salts (LiPF6, LiBF4, LiClO4) in the electrolyte solution, and by selecting specific chain carbonates with controlled self-diffusion coefficients. These parameter adjustments optimize ion mobility and electrolyte conductivity at low temperatures, resolving the contradiction between room temperature reliability and low temperature productivity
Solution Approach 2:
The patent uses composite materials by combining multiple lithium salts (LiPF6, LiBF4, LiClO4) in specific ratios within the electrolyte solution, and by using mixed solvent systems containing cyclic carbonates and chain carbonates. This composite approach creates synergistic effects that maintain battery performance across a wide temperature range, addressing both room temperature reliability and low temperature output characteristics
2Reliability
If the electrolyte viscosity is reduced to improve low-temperature ion conductivity, then ion mobility increases, but the electrode reaction resistance may increase
Solution Approach 1:
The patent controls the self-diffusion coefficient of chain carbonates within a specific range (1.0×10^-10 to 2.0×10^-10 m²/sec at -20°C) and adjusts lithium salt concentrations to optimize the balance between electrolyte viscosity and ion conductivity. This parameter optimization ensures adequate ion mobility while maintaining effective electrode reactions at low temperatures
Solution Approach 2:
The patent creates local quality differences by using different types of chain carbonates (dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, propyl methyl carbonate) with different diffusion characteristics in different regions of the electrolyte system, and by controlling the micro-environment at the electrode-electrolyte interface to facilitate both ion transport and electrode reactions
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 improved output characteristics and cycle stability at low temperatures, balancing ion conductivity and electrode reaction resistance, maintaining high performance from low to high temperatures.
Implementation Method 1
A self-diffusion coefficient of the chain carbonate in the non-aqueous electrolyte solution at -20°C is from 1.4 × 10^-10 to 2.0 × 10^-10 m^2/sec
Data Source
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AI summary
A non-aqueous electrolyte secondary battery of an embodiment includes an exterior member, a negative electrode containing a titanium-containing oxide housed in the exterior member, a positive electrode housed in the exterior member, a separator housed in the exterior member and arranged between the positive electrode and the negative electrode, and a non-aqueous electrolyte solution housed in the exterior member. At least one type or more chain carbonates are contained in a solvent of the non-aqueous electrolyte solution. A self-diffusion coefficient of the chain carbonate in -20°C is from 1.4 × 10-10 to 2.0 × 10-10 m2/sec.