Li-Ion Cathode Composition to Reduce Li Plating at High SOC
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Solution Overview
Problem
Lithium ion batteries with existing mixtures of positive electrode materials face risks of Li-Plating during high-rate charging at high state of charge, low discharge power at low state of charge, and low specific capacity, which affect safety and energy density.
Innovation Solution
A lithium ion battery is developed using a mixture of lithium manganese iron phosphate (LMFP), lithium iron phosphate (LFP), and a ternary material in specific proportions, with controlled initial charging capacity and efficiency parameters to balance charging and discharging characteristics, reducing Li-Plating risk and enhancing power and energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a mixture of LFP and ternary material is used as positive electrode material, then the battery can achieve high energy density, but Li-Plating occurs during high-rate charging at high SOC state reducing safety
Solution Approach 1:
The patent uses a composite positive electrode material system comprising LFP, LMFP, and ternary materials in specific proportions. This composite approach combines the safety benefits of LFP with the high capacity of LMFP and ternary materials, achieving both high energy density and safety by preventing Li-Plating through the synergistic effects of the mixed materials.
Solution Approach 2:
The patent optimizes specific parameters including the mass ratios of different materials (A1, A2, A3), initial charging capacity (M1, M2, M3), and initial efficiency (η1, η2, η3) to satisfy specific mathematical relationships (α and β equations). These parameter adjustments balance the charging and discharging characteristics to prevent Li-Plating while maintaining high energy density.
2Reliability
If a mixture of LMFP and ternary material is used as positive electrode material, then Li-Plating risk is reduced during high-rate charging, but discharge power is low when battery is discharged in low SOC state
Solution Approach 1:
The patent introduces LFP into the composite system to enhance discharge power at low SOC states. LFP's stable olivine structure and high discharge voltage plateau compensate for the lower discharge power of LMFP and ternary materials, while maintaining the safety benefits of reduced Li-Plating risk.
Solution Approach 2:
The patent adjusts the mass ratio parameters (A1, A2, A3) and electrochemical parameters (M1, M2, M3, η1, η2, η3) to optimize the balance between safety and discharge power. The mathematical relationships for α and β ensure that the composite material provides both safety during charging and adequate power during discharging across different SOC states.
3Reliability
If various positive electrode materials are mixed to improve safety and power characteristics, then cycling stability improves, but specific capacity decreases reducing energy density
Solution Approach 1:
The patent uses a three-material composite system (LFP, LMFP, ternary) where each material contributes to cycling stability through its unique structural characteristics. The synergistic combination maintains high specific capacity by selecting materials with complementary properties and optimizing their proportions according to the specified mathematical relationships.
Solution Approach 2:
The patent optimizes the initial charging capacity parameters (M1, M2, M3) and mass ratios (A1, A2, A3) to maximize specific capacity while maintaining cycling stability. The mathematical constraints on α and β ensure that the composite material achieves both long cycle life and high energy density by balancing the contributions of each material.
Data Source
AI summary
A positive electrode plate of a lithium-ion battery includes a positive electrode material layer provided on a positive electrode current collector. A negative electrode plate of the lithium-ion battery includes a graphite negative electrode material layer provided on a negative electrode current collector. The positive electrode material layer includes a positive electrode active material consisting of a lithium manganese iron phosphate material, a lithium iron phosphate material and a ternary material with a mass ratio of A1+A2+A3=1. α=(M4×η4×Y)/[M1×η1×A1+M2×η2×A2+M3×η3×A3)×X], β=[M1×(1−η1)×A1+M2×(1−η2)×A2+M3×(1−η3)×A3]×X/[M4×(1−η4)×Y], 1.03≤α≤1.15, and 0.55≤β≤1.5, where X is the coating amount of the positive electrode active material on the positive electrode plate, and Y is the coating amount of graphite on the negative electrode plate.