Battery Positive Electrode Pore Volume Optimization
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Solution Overview
Problem
Non-aqueous electrolyte secondary batteries with lithium composite metal oxide positive electrodes and lithium-titanium composite oxide negative electrodes suffer from insufficient durability during high-rate charge/discharge cycles.
Innovation Solution
Incorporating a positive electrode mixture layer with a first active material having a high pore volume of 100 nm or less pores per mass and a second active material with a lower pore volume, where the first active material constitutes 30 mass % or less of the total, along with a lithium-titanium composite oxide negative electrode, enhances durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a positive electrode containing lithium composite metal oxide with high pore volume is used, then high-rate charge/discharge performance is improved, but durability against high-rate charge/discharge cycles deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the pore volume of the lithium composite metal oxide within the range of 0.03 mL/g to 0.08 mL/g. This optimized parameter range resolves the contradiction by achieving the right balance between high-rate charge/discharge performance (improved by higher pore volume) and cycle durability (maintained by not exceeding the upper pore volume limit). The pore volume is a critical physical parameter that when optimized within this specific range, simultaneously satisfies both high productivity and reliability requirements.
2Speed
If the pore volume of 100 nm or less pores per mass of the positive electrode active material is increased, then charging characteristics at high current rate are improved, but internal resistance increases
Solution Approach 1:
The patent applies parameter changes by optimizing the pore volume of 100 nm or less pores per mass of the positive electrode active material to fall within the specific range of 0.03 mL/g to 0.08 mL/g. This controlled parameter adjustment resolves the contradiction by achieving sufficient pore volume to enhance high current rate charging characteristics while preventing excessive pore volume that would increase internal resistance. The optimal pore volume range allows rapid lithium ion transport without creating excessive resistance.
3Productivity
If the content of the first positive electrode active material with high pore volume is increased, then high-rate charge/discharge characteristics are improved, but crack formation in the positive electrode increases
Solution Approach 1:
The patent applies parameter changes by controlling the content ratio of the first positive electrode active material (with high pore volume) to be within a specific range relative to the total positive electrode active material. This optimized content parameter resolves the contradiction by achieving sufficient high-rate charge/discharge characteristics through adequate presence of the high pore volume material, while preventing excessive content that would lead to increased crack formation and electrode degradation 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
This configuration improves the battery's durability by reducing internal resistance and crack formation in the positive electrode active material, leading to better high-rate charge/discharge performance and extended cycle life.
Implementation Method 1
the first positive electrode active material has a pore volume, of pores each having a pore diameter of 100 nm or less, per mass of 8 mm3/g or more
Data Source
AI summary
The present invention relates to a non-aqueous electrolyte secondary cell comprising: a positive electrode having a positive electrode mixture layer that contains a first positive-electrode active material and a second positive-electrode active material; a negative electrode containing a lithium-titanium composite oxide as a negative-electrode active material; and a non-aqueous electrolyte. The volume per mass of pores in the first positive-electrode active material having a pore diameter of 100 nm or less is four or more times the volume per mass of pores in the second positive-electrode active material having a pore diameter of 100 nm or less. The content of the first positive-electrode active material is 30 mass % or less with respect to the total amount of the first positive-electrode active material and the second positive-electrode active material.