Wound Secondary Battery Wrinkle Control for Low-Resistance Cycling
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Solution Overview
Problem
Niobium-titanium composite oxide materials used in secondary batteries experience significant volume expansion and contraction during charge and discharge cycles, leading to electrode deformation and performance issues due to the insertion and extraction of lithium ions, which causes wrinkles and increases resistance.
Innovation Solution
Control the degree of wrinkle formation in the wound electrode group by adjusting the proportion of void areas within the electrode group to a range of 2.0% to 20.0%, using X-ray CT to evaluate and quantify wrinkle formation, and apply restraint to the electrode group during initial charge to manage expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If niobium-titanium composite oxide material is used as electrode material, then charge-discharge capacity is improved, but volume expansion and contraction occurs during charge-discharge cycles
Solution Approach 1:
The patent applies parameter changes by controlling the grain size of the niobium-titanium composite oxide to a specific range (0.5-5 μm) and adjusting the Li content (x value in Li_xTi_1-yM1_yNb_2-zM2_zO_7+δ) to optimize the balance between charge-discharge capacity and volume stability during cycling
Solution Approach 2:
The patent uses composite materials by combining niobium-titanium composite oxide with specific dopant elements (M1 from Zr/Si/Sn and M2 from V/Ta/Bi) to create a composite oxide structure that maintains high capacity while reducing volume expansion and contraction during charge-discharge cycles
2Power
If rapid charge-discharge cycles are performed, then power performance is improved, but electrode deformation increases due to volume changes
Solution Approach 1:
The patent controls the grain size parameter within 0.5-5 μm to optimize the balance between rapid charge-discharge performance and structural integrity, allowing sufficient lithium ion diffusion pathways while maintaining electrode structural stability during high-rate cycling
3Quantity of substance
If electrode material density is increased, then energy density is improved, but wrinkle formation and resistance increase during cycling
Solution Approach 1:
The patent optimizes the Li content parameter (x value) in the composite oxide formula to achieve the right balance between energy density and electrode stability, preventing excessive film formation and resistance increase while maintaining high capacity
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 approach enhances the life characteristics and reduces resistance in secondary batteries by allowing controlled gas diffusion and maintaining optimal electrode spacing, preventing excessive film formation and damage.
Implementation Method 1
the niobium-titanium composite oxide material causes volume expansion and contraction during rapid charge and charge-and-discharge cycles. This is because the skeleton of the crystal structure changes significantly due to the insertion/extraction of lithium ions to/from the crystal structure.
Implementation Method 2
using X-ray CT to evaluate and quantify wrinkle formation
Data Source
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AI summary
According to one approach, a secondary battery (100) is provided. The secondary battery (100) includes a wound electrode group (2) including a positive electrode (5), a negative electrode (6) containing a negative electrode active material, and a separator (7), and a container member (1) accommodating the wound electrode group (2). The negative electrode active material contains a niobium-titanium composite oxide. A proportion (Rblack) determined by the X-ray CT for the wound electrode group is within the range of more than 2.0% and 20.0% or less.