LMFP Cathode Electrolyte Composition for Cycle Life and Conductivity
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Solution Overview
Problem
Current lithium iron phosphate batteries have reached the limit of energy density, and lithium iron manganese phosphate batteries suffer from poor conductivity and cycle life issues due to manganese ion dissolution and SEI film degradation.
Innovation Solution
A lithium-ion battery design that includes a positive electrode sheet with lithium manganese iron phosphate and a specific non-aqueous electrolyte composition, featuring ethylene carbonate, positive electrode film-forming additives like 1,3-propane sultone, and negative electrode film-forming additives like vinylene carbonate, to enhance conductivity and cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If lithium iron manganese phosphate is used to increase energy density, then the energy density of the battery is improved, but the conductivity of the positive electrode active material deteriorates
Solution Approach 1:
The patent introduces a specific electrolyte composition containing ethylene carbonate (15-30 wt%), 1,3-propane sultone (0.01-5 wt%), and vinylene carbonate (0.1-10 wt%) as an intermediary medium. This electrolyte system mediates between the low-conductivity lithium iron manganese phosphate positive electrode and the battery circuit, improving overall conductivity while maintaining the high energy density benefits of the manganese-containing cathode material.
Solution Approach 2:
The patent modifies the electrolyte parameters by specifying precise composition ratios and concentrations. The ethylene carbonate content is controlled at 15-30 wt%, 1,3-propane sultone at 0.01-5 wt%, and vinylene carbonate at 0.1-10 wt%. These parameter changes optimize the electrolyte's conductivity and film-forming properties, compensating for the poor conductivity of lithium iron manganese phosphate while preserving its high energy density characteristics.
2Use of energy by moving object
If lithium iron manganese phosphate is used to increase energy density, then the energy density of the battery is improved, but the cycle life of the battery deteriorates
Solution Approach 1:
The patent applies preliminary action by using 1,3-propane sultone and vinylene carbonate as film-forming additives that pre-establish protective interfaces before manganese dissolution can occur. These additives form stable CEI and SEI films during initial cycles, creating a protective barrier that prevents subsequent manganese ion dissolution and SEI destruction, thereby extending cycle life while maintaining the high energy density of lithium iron manganese phosphate.
Solution Approach 2:
The patent converts the harmful effect of manganese ion dissolution into a beneficial outcome. By introducing vinylene carbonate as a negative electrode film-forming additive, the patent creates a robust SEI film that, when damaged by manganese dissolution, can self-repair and maintain stability. This transforms the previously harmful manganese dissolution into a manageable process that ultimately strengthens the battery's cycle performance.
3Reliability
If the SEI film is destructed by manganese ion dissolution, then the conductivity of the negative electrode is temporarily improved, but the cycle performance deteriorates
Solution Approach 1:
The patent implements self-service through the use of vinylene carbonate as a self-repairing SEI film-forming additive. When the SEI film is damaged by manganese ion dissolution, vinylene carbonate continuously replenishes and repairs the film during subsequent cycles. This self-service mechanism maintains both the conductivity benefits of a porous SEI structure and the cycle performance benefits of a stable, protective interface.
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 proposed battery design improves the conductivity and stability of the electrolyte, enhances the cycle performance by forming dense CEI and SEI films, and extends the cycle life of lithium iron manganese phosphate batteries.
Implementation Method 1
A dense CEI film may be generated on the surface of the positive electrode to reduce the oxidative decomposition of the electrolyte
Implementation Method 2
A dense SEI film may be generated on the negative electrode, and the SEI film may be repaired continuously during the cycle
Implementation Method 3
improve the conductivity of the electrolyte
Data Source
Figure 1
AI summary
Disclosed are a lithium-ion battery and an application thereof. The lithium-ion battery includes: a positive electrode sheet (10), the double-sided density of the positive electrode sheet (10) is greater than or equal to 35 mg/cm2, and the positive electrode sheet (10) includes a positive electrode active material including lithium iron manganese phosphate; a negative electrode sheet (20); a separator (30) located between the positive electrode sheet (10) and the negative electrode sheet (20); and an electrolyte (40) filled among the positive electrode sheet (10), the negative electrode sheet (20) and the separator (30). The electrolyte (40) 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.