Phosphate Cathode Electrolyte for Dense Electrodes and Ion Transport
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Solution Overview
Problem
Secondary batteries face challenges in achieving high energy density while maintaining good kinetic performance, as increasing coating weight and compacted density of the positive electrode film layer leads to poor ion migration and capacity retention issues.
Innovation Solution
A secondary battery design incorporating an olivine-structured lithium-containing phosphate positive electrode and an organic solvent with specific properties, along with an additive, to optimize electrolyte infiltration and ion migration, ensuring high capacity retention and low volume swelling ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If coating weight and compacted density of the positive electrode film layer are increased to improve energy density, then energy density is improved, but ion migration path becomes longer and diffusion rate becomes slower, causing poor kinetic performance
Solution Approach 1:
The patent employs porous positive electrode plates with controlled porosity (20-40%) to maintain short ion migration paths while achieving high coating weights. The porous structure allows electrolyte penetration and facilitates ion diffusion throughout the electrode, resolving the contradiction between high energy density and fast ion transport.
Solution Approach 2:
The patent changes the physical and chemical parameters of the electrolyte, specifically using a fluorinated cyclic carbonate solvent (Compound 1-1) with specific molecular structure and properties. This parameter change enables the electrolyte to effectively penetrate dense electrode structures and maintain high ionic conductivity, achieving both high energy density and good kinetic performance.
2Quantity of substance
If coating weight and compacted density of the positive electrode film layer are increased to improve energy density, then energy density is improved, but capacity retention becomes poorer
Solution Approach 1:
The porous electrode structure with 20-40% porosity ensures uniform electrolyte distribution and effective lithium ion transport throughout the electrode volume, maintaining structural integrity during cycling and achieving capacity retention rates of 80% or more after 500 cycles at high energy density.
Solution Approach 2:
The patent uses composite materials including fluorinated cyclic carbonate (Compound 1-1) combined with chain carbonates in the electrolyte formulation. This composite electrolyte system provides both high ionic conductivity for fast ion transport and stable SEI formation for long-term capacity retention, enabling simultaneous achievement of high energy density and excellent cycling stability.
3Quantity of substance
If conventional electrolytes are used with high coating weight electrodes, then energy density is improved, but kinetic performance deteriorates
Solution Approach 1:
The patent fundamentally changes the electrolyte parameters by introducing fluorinated cyclic carbonate (Compound 1-1) with specific molecular characteristics including fluorine substitution. This parameter change reduces electrolyte viscosity, increases ionic conductivity, and enhances wetting properties, enabling fast ion migration even through high-density electrodes with improved energy density.
Solution Approach 2:
The combination of porous electrode structure (20-40% porosity) with the specialized fluorinated electrolyte creates an optimized ion transport pathway. The porous structure provides physical channels while the fluorinated electrolyte provides high ionic conductivity, together achieving fast ion migration speeds despite high coating weights and energy density.
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 enhances kinetic performance, capacity retention, and reduces volume swelling, maintaining high energy density by optimizing electrolyte composition and electrode structure.
Implementation Method 1
the electrolyte inside the battery can well infiltrate the positive electrode plate and a negative electrode plate
Implementation Method 2
the first solvent improves kinetic performance of the battery to the maximum extent and irreversible consumption of active ions inside the battery can also be controlled
Data Source
AI summary
A secondary battery and a battery module, a battery pack, and an electric apparatus containing the secondary battery are provided. The secondary battery includes a positive electrode plate and an electrolyte. The positive electrode plate includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, and the positive electrode film layer includes one or more of olivine-structured lithium-containing phosphate and its modified compound. The electrolyte includes an organic solvent, and the organic solvent includes a first solvent represented by Formula 1. R11 and R12 in Formula 1 each are independently one of C1-C4 alkyl and C1-C4 haloalkyl. The secondary battery satisfies: mass of first solvent/rated capacity of secondary battery is ≥0.7 g/Ah; and mass of electrolyte/rated capacity of secondary battery is ≤3.5 g/Ah.