LiFePO4 Battery Electrolyte for High-Temperature Stability
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Solution Overview
Problem
Nonaqueous-electrolyte batteries using LiFePO4 as a positive-electrode active material face challenges with low electronic conductivity, high-rate discharge characteristics, and metal dissolution at high temperatures, leading to reduced capacity and output, especially in high-temperature environments.
Innovation Solution
Incorporating a chain ether and specific compounds into the electrolytic solution to improve ionic conductivity and form protective coatings on electrodes, enhancing the battery's high-rate discharge capacity, thermal stability, and cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LiFePO4 is used as a positive-electrode active material, then thermal stability and cycle characteristics are improved, but electronic conductivity and high-rate discharge characteristics deteriorate
Solution Approach 1:
The patent changes the chemical composition parameters of the electrolyte by introducing a specific chain ether compound with low viscosity and high dielectric constant. This parameter change in the electrolyte system compensates for the low electronic conductivity of LiFePO4, enabling improved high-rate discharge characteristics while maintaining the thermal stability benefits of LiFePO4.
Solution Approach 2:
The patent creates a composite electrolyte system combining traditional carbonate solvents (EC, DM, DEC) with a specific chain ether compound. This composite electrolyte formulation synergistically combines the high dielectric constant of carbonates with the low viscosity and high ionic conductivity of the chain ether, resolving the contradiction between thermal stability and high-rate discharge performance.
2Reliability
If LiFePO4 is used as a positive-electrode active material, then battery safety is improved, but capacity and output decrease due to metal dissolution at high temperatures
Solution Approach 1:
The patent employs a preliminary action by using the chain ether compound to form a stable protective interface on the electrode surface before metal dissolution can occur. This preliminary protective layer prevents iron dissolution during high-temperature operation, thereby preserving both battery safety and capacity over extended cycles.
Solution Approach 2:
The chain ether compound acts as an intermediary substance between the LiFePO4 positive electrode and the electrolyte. It mediates the interaction by forming a stable interfacial layer that prevents direct contact between the electrolyte and electrode, thereby preventing metal dissolution while maintaining ionic conductivity for capacity retention.
3Ease of manufacture
If conventional electrolyte solvents are used, then manufacturing simplicity is maintained, but high-temperature storability and cycle characteristics deteriorate
Solution Approach 1:
The patent modifies the electrolyte composition parameters by incorporating a specific chain ether compound with distinctive molecular structure (ether oxygen atoms in chain configuration). This parameter change in the electrolyte formulation significantly improves high-temperature storability and cycle characteristics while maintaining manufacturing simplicity through straightforward mixing processes.
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 solution results in improved high-rate discharge capacity, high-temperature storability, and cycle characteristics, maintaining initial output performance and capacity retention after durability tests.
Implementation Method 1
Incorporating a chain ether and specific compounds into the electrolytic solution to improve ionic conductivity and form protective coatings on electrodes
Implementation Method 2
Incorporating a chain ether and specific compounds into the electrolytic solution to improve ionic conductivity
Data Source
AI summary
The invention is to provide nonaqueous-electrolyte batteries which have a high initial output at ordinary temperature and -30°C, attain a high discharge capacity even during high-rate discharge, and have a high capacity retention after a durability test such as a high-temperature storage test or cycle test, and which, even after the durability test, have the excellent initial output performance and high-rate discharge capacity. The invention relates to a nonaqueous-electrolyte battery which comprises a current collector, a positive electrode containing a lithium-containing phosphoric acid compound represented by LixMPO4 (wherein M is at least one element selected from the group consisting of Group-2 to Group-12 metals of the periodic table, and x satisfies 0<x≤1.2) as a positive-electrode active material, a negative electrode containing a negative-electrode active material capable of occluding and releasing lithium ions, and a nonaqueous electrolytic solution, wherein the nonaqueous electrolytic solution contains (1) a chain ether and (2) a cyclic carbonate having an unsaturated bond.