Lithium-Ion Battery Electrolyte Balance for Fast Charging Cycle Life
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Solution Overview
Problem
Lithium-ion secondary batteries face challenges in maintaining good dynamic performance and cycle life due to damage to the solid electrolyte interface membrane during high-rate charging and discharging, which is exacerbated by inadequate electrolyte mass and intrinsic electrolyte parameters.
Innovation Solution
A lithium-ion secondary battery design that optimizes the mass and density of the electrolyte, concentration of lithium salt, and structural parameters of the electrode materials to achieve a balanced relationship of 2.13≤(m×C)/(ρ×Cap)≤3.0, ensuring sufficient electrolyte for SEI membrane repair while preventing excessive pressure and heat generation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If large-rate charging and discharging is performed to improve dynamic performance, then charging speed increases, but the SEI membrane is damaged and cycle life decreases
Solution Approach 1:
The patent applies preliminary action by pre-coating the negative active material surface with an Al element-containing compound before battery assembly. This pre-formed protective layer acts as a stable SEI membrane that prevents damage during high-rate charging, eliminating the need for continuous repair and thus preserving cycle life while maintaining fast charging capability
Solution Approach 2:
The patent changes the chemical composition parameter of the SEI membrane by introducing Al element-containing compounds (such as Al2O3, Al(OH)3, or Al salts) to form a more stable and damage-resistant membrane. This parameter change in the SEI membrane composition enables the battery to withstand large-rate charging without severe membrane degradation
2Reliability
If electrolyte mass is increased to support SEI membrane repair, then cycle life improves, but battery volume and pressure increase
Solution Approach 1:
By pre-forming a stable Al-containing protective layer on the negative electrode surface before battery assembly, the patent eliminates the need for continuous electrolyte consumption for SEI membrane repair during cycling. This preliminary protective action allows the battery to maintain long cycle life with minimal electrolyte mass, thus avoiding volume and pressure increases
Solution Approach 2:
The patent extracts the repair function from the bulk electrolyte by concentrating the protective Al element-containing compound directly on the negative active material surface. This localization of the protective function reduces the overall electrolyte mass required in the battery while maintaining cycle life
Data Source
AI summary
The present invention provides a lithium-ion secondary battery, which comprises a positive electrode plate, a negative electrode plate, a separator and an electrolyte. The lithium-ion secondary battery satisfies a relationship: 1.5≤(m×C)/(p×Cap)≤6.5. In the present invention, by comprehensively considering the rated capacity of the battery, the mass of the electrolyte and the intrinsic parameters of the electrolyte and reasonably quantifying the relationship thereof, the lithium-ion secondary battery can have good dynamics performance and longer cycle life at the same time.