LFP Battery Electrolyte Composition for High-Temperature Cycling
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Solution Overview
Problem
Lithium secondary batteries using high-loading positive electrodes face reduced electrolyte impregnability and increased resistance due to insufficient porous structure, leading to degraded capacity characteristics, especially under high-temperature conditions.
Innovation Solution
A lithium secondary battery design incorporating lithium iron phosphate as the positive electrode active material, with an electrolyte containing a cyclic lactone compound and lithium nitrate as an additive, controlled within specific ratios, to enhance electrolyte impregnability and form a stable film on the electrode surface, improving charge transfer and suppressing resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a high-loading electrode is used to increase energy density, then the loading amount of active material is increased, but electrolyte impregnability is reduced due to insufficient porous structure
Solution Approach 1:
The patent applies porous materials by constructing a three-dimensional porous conductive network using carbon nanotubes and graphene within the electrode structure. This porous network creates channels that facilitate electrolyte penetration throughout the high-loading electrode, resolving the contradiction between increased loading amount and maintained electrolyte impregnability. The porous structure allows sufficient electrolyte access to active material particles while accommodating high material density.
Solution Approach 2:
The patent employs composite materials by combining lithium iron phosphate active material with a composite conductive network of carbon nanotubes and graphene. This composite structure provides both the high capacity needed for high-loading electrodes and the conductive, porous pathways required for electrolyte impregnability. The synergistic combination of different materials resolves the contradiction between energy density and electrolyte access.
2Quantity of substance
If a high-loading electrode is used to increase energy density, then the loading amount of active material is increased, but battery resistance is increased leading to degraded capacity characteristics
Solution Approach 1:
The three-dimensional porous conductive network reduces battery resistance by providing extensive pathways for electron transport throughout the high-loading electrode. The porous structure of carbon nanotubes and graphene creates a continuous conductive framework that maintains low electrical resistance even as active material loading increases, counteracting the harmful effect of increased resistance.
Solution Approach 2:
The composite conductive network of carbon nanotubes and graphene acts as a highly conductive matrix that reduces overall battery resistance. This composite material system provides superior electrical conductivity compared to traditional conductive additives, enabling high-loading electrodes to maintain low resistance and good capacity characteristics.
3Reliability
If lithium iron phosphate is used instead of high-nickel positive electrode active material, then high-temperature safety is improved, but energy density is reduced
Solution Approach 1:
The patent uses composite materials to compensate for the lower energy density of lithium iron phosphate. By incorporating a high-surface-area three-dimensional porous conductive network of carbon nanotubes and graphene, the electrode structure enables more efficient utilization of active material and improved charge transfer, effectively increasing the practical energy density while maintaining the high-temperature safety benefits of lithium iron phosphate.
Solution Approach 2:
The porous conductive network increases the effective surface area available for electrochemical reactions, allowing more active material to be effectively utilized. This porous structure compensates for the inherently lower theoretical capacity of lithium iron phosphate by improving mass transport and charge transfer efficiency, thereby increasing practical energy density without sacrificing safety.
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 design improves electrolyte impregnability, forming a low-resistance film on the high-loading positive electrode, enhancing charge mobility and cycle capacity retention, particularly at high temperatures.
Implementation Method 1
forming a stable film on the electrode surface
Implementation Method 2
charge transfer, which is a reaction between lithium ions and electrons
Data Source
AI summary
The present disclosure relates to a lithium secondary battery having improved high-temperature cycle characteristics, and particularly, to a lithium secondary battery including a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode includes lithium iron phosphate as a positive electrode active material, and the electrolyte includes a lithium salt; a first organic solvent; a second organic solvent; and an additive, wherein the first organic solvent is a cyclic lactone compound, the second organic solvent is a carbonate-based organic solvent, and the additive is lithium nitrate (LiNO3), and satisfies following Equation 1: 0.0001≤0.02×A×BC×D≤0.050 In Equation 1, A is a total amount (g) of the electrolyte injected into the lithium secondary battery, B is an amount (wt%) of the lithium nitrate (LiNO3) contained in the electrolyte injected, C is a loading amount (g/cm2) of the positive electrode, and D is a total area (cm2) of surfaces of a positive electrode collector.