Nonaqueous Electrolyte Battery Low-Temperature Capacity
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries face challenges in maintaining sufficient discharging capacity at low temperatures due to increased viscosity of the electrolytic solution, which hinders electric charge migration, especially in environments below -30°C to -40°C.
Innovation Solution
Optimizing the composition of the electrolytic solution by using a mixed solvent of cyclic carbonate and chain ether solvents, such as propylene carbonate, ethylene carbonate, and dimethoxy ethane, and incorporating supporting salts like lithium bis(fluorosulfonyl)imide, along with using negative electrode active materials like SiOX with a carbon-coated surface or Li—Al alloy, to improve low-temperature characteristics without compromising high-temperature performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If conventional electrolytic solution composition is used, then high energy density is achieved, but viscosity increases at low temperatures causing insufficient discharging capacity
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolytic solution by introducing specific cyclic carbonate esters ( formulas 1 and 2) with optimized molecular structures. This parameter change allows the solution to maintain low viscosity at low temperatures while preserving high energy density, resolving the contradiction between temperature performance and energy capacity
Solution Approach 2:
The patent uses a composite electrolytic solution system combining multiple components: cyclic carbonate esters (formulas 1 and 2), chain carbonic acid esters, and supporting salts. This composite approach creates synergistic effects where the cyclic carbonate esters provide low-temperature fluidity while the chain carbonic acid esters contribute to energy density, achieving both requirements simultaneously
2Speed
If electrolytic solution viscosity is reduced for low-temperature operation, then ion migration improves, but energy density may be compromised
Solution Approach 1:
The patent optimizes the molecular structure parameters of the cyclic carbonate esters (formulas 1 and 2) to achieve the right balance. The specific structural parameters (R1-R6 groups) are tuned to reduce viscosity and enhance ion mobility while maintaining sufficient energy storage capacity, resolving the speed-density trade-off
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 optimized composition and materials ensure improved discharging characteristics and retention of sufficient capacity across a broad temperature range, including low temperatures, by preventing viscosity increases and enhancing electrical conductivity and ion solvation.
Implementation Method 1
an electrolytic solution which contains a cyclic carbonate solvent represented by general formula (1) and a chain ether solvent represented by general formula (2)
Implementation Method 2
the viscosity of the electrolytic solution increases under a low-temperature environment of −30° C. to −40° C., and migration of electric charges is hindered
Data Source
AI summary
A nonaqueous electrolyte secondary battery is provided, including: a positive electrode (10) that includes a lithium-manganese oxide as a positive electrode active material; a negative electrode (20) that includes SiOX (0≤X<2) in which at least a part of a surface is covered with carbon, or a Li—Al alloy as the negative electrode active material; and an electrolytic solution (50) that contains propylene carbonate (PC), ethylene carbonate (EC), and dimethoxy ethane (DME) as an organic solvent in a range of {PC:EC:DME}={0.5 to 1.5:0.5 to 1.5:1 to 3} in terms of a volume ratio, and at least one of lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethane sulfonyl) imide (LiTFSI) as a supporting salt in a total amount of 0.6 to 1.4 (mol/L).