Negative-Pressure Formation for Li-Mn-Fe-Phosphate Cells
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Solution Overview
Problem
The current formation process for lithium iron manganese phosphate batteries is limited, leading to issues such as brown spots and inadequate energy storage performance, due to the higher voltage platform and specific gas generation during the formation process, which is not fully addressed by the lithium iron phosphate system's formation methods.
Innovation Solution
A negative pressure formation method involving a three-stage constant-current charging process, vacuumizing the semi-finished battery cells, and controlling the state of charge and charging current to discharge gases and prevent brown spots, including specific steps and conditions like vacuum degree, temperature, and electrolyte composition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the formation process of lithium iron phosphate system is directly adopted for lithium iron manganese phosphate batteries, then the manufacturing process is simple, but the gas generated during formation cannot be discharged promptly and brown spot problems occur
Solution Approach 1:
The patent applies vacuum negative pressure environment during the formation process to create an inert atmosphere that facilitates gas discharge. By maintaining negative pressure (vacuum state) in the formation chamber, gases generated during electrolyte decomposition and SEI film formation are continuously evacuated, preventing gas accumulation and brown spot defects on electrode surfaces.
2Quantity of substance
If higher voltage platform (3.6V) is used for lithium iron manganese phosphate, then energy density is improved, but the formation process produces more gas and interface brown spot problems
Solution Approach 1:
The patent changes the formation process parameters by implementing multi-stage constant current charging with specific current limits (0.05C, 0.1C, 0.2C) and state of charge thresholds (10%, 20%, 30%). This parameter optimization controls the electrochemical reactions during formation, reducing excessive gas generation from high voltage while maintaining energy density benefits. The staged approach allows gradual SEI film formation and electrolyte stabilization.
3Device complexity
If conventional formation charging is used, then the process is simple, but the SEI film stability and battery performance are insufficient
Solution Approach 1:
The patent segments the formation charging process into three distinct constant current stages with different current rates and state of charge targets. This segmentation allows controlled SEI film formation at lower currents initially, then progressively increases current as the film stabilizes. The staged approach improves SEI film quality and battery performance while maintaining reasonable process complexity through automated control.
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
This method improves the stability and density of the SEI film, reduces internal resistance, and enhances the cycling and storage performance of lithium iron manganese phosphate batteries, addressing the limitations of existing formation processes.
Implementation Method 1
performing a vacuumizing process, a resting process and a charging process for a semi-finished battery cell
Data Source
AI summary
Provided in the present application is a negative pressure formation method for lithium iron manganese phosphate batteries and batteries applying the same. The method includes following steps: performing a vacuumizing process, a resting process and a charging process for a semi-finished battery cell to obtain a post-formation battery cell; the charging process is a three-stage constant-current charging process, wherein in the three-stage constant-current charging process, a charging current I, and a state of charge S are required to satisfy following relations: in a first stage constant-current charging process, I1≤0.1 C, state of charge: 5%≤S1≤15%; in a second stage constant-current charging process, 0.05 C≤I2≤0.15 C, state of charge: 15%≤S2≤25%; and in a third stage constant-current charging process, 0.15 C≤I3≤0.25 C, state of charge: 35%≤S3≤45%.