LFP Cathode Electrolyte Additives for High-Loading Low-Temperature Cells
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Solution Overview
Problem
Lithium iron phosphate-based positive electrode active materials in lithium secondary batteries face challenges with insufficient electrolyte impregnation at high loading amounts, leading to difficulty in capacity expression, increased resistance, and decreased lifetime, particularly at low temperatures.
Innovation Solution
Incorporating a non-aqueous electrolyte with specific additives represented by Formulas 1 to 3 in a specific content, improving the electrolyte impregnation property of the positive electrode with a loading amount of 450 mg/25 cm² to 740 mg/25 cm², enhancing capacity development and resistance characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the loading amount of the positive electrode is increased to achieve higher energy density, then the battery capacity increases, but the electrolyte impregnation property deteriorates leading to increased resistance and decreased lifetime
Solution Approach 1:
The patent introduces specific chemical compounds (Formulas 1-3) as additives to the non-aqueous electrolyte, changing the chemical composition parameters of the electrolyte system. These additives modify the electrolyte's interaction with the high-loading positive electrode, enabling sufficient impregnation even at loading amounts of 450-740 mg/25cm², thus resolving the contradiction between high capacity and good impregnation property
Solution Approach 2:
The compounds represented by Formulas 1 to 3 act as intermediary substances between the electrolyte and the positive electrode. These additives facilitate the impregnation process by modifying the interface properties, allowing the electrolyte to effectively penetrate and wet the high-loading electrode structure, thereby maintaining reliability while achieving high capacity
2Quantity of substance
If the loading amount of the positive electrode is increased to achieve higher energy density, then the battery capacity increases, but the resistance increases leading to decreased output performance
Solution Approach 1:
By adding specific compounds (Formulas 1-3) to the electrolyte, the patent changes the electrolyte's physical and chemical parameters including viscosity, conductivity, and wetting properties. This enables effective electrolyte distribution throughout the high-loading electrode, maintaining low resistance pathways for ion transport even at 450-740 mg/25cm² loading, thus achieving high capacity with low resistance
Solution Approach 2:
The additives in Formulas 1 to 3 serve as intermediary agents that reduce the harmful resistance effect. They modify the electrolyte-electrode interface to facilitate ion transport, acting as a bridge that enables efficient charge transfer across the high-loading electrode structure, thereby suppressing resistance increase while maintaining high capacity
3Quantity of substance
If the loading amount of the positive electrode is increased to achieve higher energy density, then the battery capacity increases, but the lifetime decreases particularly at low temperatures
Solution Approach 1:
The patent modifies the electrolyte composition by incorporating compounds from Formulas 1-3, which change the electrolyte's low-temperature fluidity and chemical stability parameters. This enables the electrolyte to maintain effective impregnation and ion transport capability at low temperatures, preventing the typical lifetime degradation associated with high-loading electrodes, thus achieving both high capacity and long lifetime
Solution Approach 2:
The additives act as protective intermediaries that stabilize the electrolyte-electrode interface, particularly under low-temperature conditions. They prevent harmful side reactions and maintain structural integrity, serving as a buffer that protects the high-loading electrode from degradation, thereby extending battery lifetime while maintaining high capacity even in cold environments
Data Source
AI summary
A lithium secondary battery includes a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte. The positive electrode includes a positive electrode active material. The positive electrode active material includes lithium iron phosphate particles. A loading amount of the positive electrode is about 450 mg/25 cm2 to 740 mg/25 cm2. The non-aqueous electrolyte includes a lithium salt, an organic solvent, and an additive. The additive includes at least one selected from the group consisting of compounds represented by Formulas 1 to 3 below. The additive is included in the non-aqueous electrolyte in an amount of about 0.1 wt % to 3 wt %.wherein R1, R2, R3, R4, n, and m are as defined above.