Lithium-Ion Battery Electrolyte for SEI Stability and Cycle Life
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Lithium iron manganese phosphate batteries suffer from poor conductivity and cycle performance due to the dissolution of manganese ions, which leads to degradation of the solid electrolyte interphase (SEI) and increased resistance, limiting their cycle life.
Innovation Solution
A lithium-ion battery design incorporating a positive electrode sheet with lithium manganese iron phosphate, a non-aqueous electrolyte containing ethylene carbonate, and negative electrode film-forming additives like vinylene carbonate, which enhances electrolyte conductivity and stability, forming dense films to mitigate SEI degradation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium iron manganese phosphate is used to increase energy density, then the energy density is improved, but the conductivity becomes poor and cycle performance deteriorates
Solution Approach 1:
The patent introduces a dual electrolyte system comprising a first electrolyte and a second electrolyte as intermediaries to mediate between the lithium iron manganese phosphate positive electrode and the negative electrode. The first electrolyte contains lithium salts and additives that form protective films on the positive electrode, while the second electrolyte contains additives that form protective films on the negative electrode, thereby reducing the harmful effects of manganese ion dissolution and improving cycle performance.
Solution Approach 2:
The patent uses composite electrolyte materials combining multiple components: the first electrolyte contains lithium salts (LiPF6, LiBF4) and film-forming additives (vinylene carbonate, fluoroethylene carbonate), while the second electrolyte contains different lithium salts and additives (lithium hydroxide, lithium fluoride, lithium oxalate). This composite electrolyte system provides both high conductivity for energy density and protective functions for cycle performance.
2Quantity of substance
If lithium iron manganese phosphate is used to increase energy density, then the energy density is improved, but the conductivity becomes poor
Solution Approach 1:
The patent optimizes the composition parameters of the electrolyte by selecting specific lithium salts (LiPF6, LiBF4) and film-forming additives (vinylene carbonate at 5-20 wt%, fluoroethylene carbonate at 5-20 wt%) in the first electrolyte, and lithium hydroxide (5-20 wt%), lithium fluoride (5-20 wt%), and lithium oxalate (5-20 wt%) in the second electrolyte. These parameter changes enhance the conductivity of the electrolyte system while maintaining the high energy density provided by lithium iron manganese phosphate.
3Duration of action of moving object
If manganese ions dissolve during cycling, then the solid electrolyte interphase is destructed, but this causes increased consumption of active lithium and increased resistance
Solution Approach 1:
The patent applies preliminary anti-action by introducing film-forming additives (vinylene carbonate, fluoroethylene carbonate in the first electrolyte; lithium hydroxide, lithium fluoride, lithium oxalate in the second electrolyte) that proactively form protective films on the electrode surfaces before manganese ion dissolution can occur. These pre-formed protective films prevent manganese ions from dissolving and destroying the solid electrolyte interphase, thereby reducing active lithium consumption and resistance increase during cycling.
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 improves the conductivity and cycle performance of lithium-ion batteries, extends their cycle life by maintaining electrolyte stability and preventing SEI damage from manganese ion dissolution, and enhances high-temperature performance.
Implementation Method 1
the solid electrolyte interphase (SEI) is destructed, which causes the increase of consumption of active lithium in the battery and increase of the resistance of the negative electrode SEI film
Implementation Method 2
the conductivity of lithium iron manganese phosphate is poor. In lithium-ion batteries, the dynamics performance of battery is poor
Data Source
AI summary
Disclosed are a lithium-ion battery and an application thereof. The lithium-ion battery includes: a positive electrode sheet, the double-sided density of the positive electrode sheet is greater than or equal to 35 mg/cm2, and the positive electrode sheet includes a positive electrode active material including lithium iron manganese phosphate; a negative electrode sheet; a separator located between the positive electrode sheet and the negative electrode sheet; and an electrolyte filled between the positive electrode sheet, the negative electrode sheet and the separator. The electrolyte includes a non-aqueous solvent, the non-aqueous solvent includes ethylene carbonate, and the mass fraction of the ethylene carbonate in the non-aqueous solvent is 10 wt %˜35 wt %. Through the lithium-ion battery and its application provided by the present disclosure, the cycle performance and performance of the lithium-ion battery at high temperatures may be improved.