Prismatic Battery Container Dimensional Optimization
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Solution Overview
Problem
Lithium-ion batteries with negative electrodes experiencing significant volume change during charge and discharge face challenges such as lithium dendrite formation, self-discharge, and micro-short circuits due to electrode misalignment, which affect their life performance and energy density.
Innovation Solution
A secondary battery design featuring a flat wound structure with a titanium-containing oxide negative electrode and a prismatic container, where the electrode group is housed in a container with specific thickness relationships to restrain the electrodes and prevent misalignment, thereby maintaining high energy density and preventing short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the container member is designed with larger dimensions to accommodate electrode volume expansion, then the electrode group can be housed without misalignment, but the energy density decreases due to increased container size
Solution Approach 1:
The container member is designed with predetermined dimensions that anticipate and accommodate the volume expansion of the electrode group during charging. By pre-calculating the expansion magnitude and designing the container with appropriate clearance beforehand, the electrode maintains proper alignment throughout charge-discharge cycles without requiring excessive container size that would reduce energy density.
Solution Approach 2:
The invention optimizes the dimensional parameters of the container member, specifically setting the thickness TPC and wall thickness T1 to satisfy the relationship 1.00 < TPC/(T1×2) ≤ 1.05. This parameter optimization allows the container to provide sufficient restraint and alignment stability while minimizing the container's overall size to maintain high energy density.
2Reliability
If the container member thickness is increased to prevent electrode misalignment and contact, then self-discharge and micro-short circuits are prevented, but the energy density decreases due to thicker container walls
Solution Approach 1:
The invention establishes an optimized parameter relationship where the container thickness TPC and wall thickness T1 satisfy 1.00 < TPC/(T1×2) ≤ 1.05. This mathematical relationship determines the minimum necessary wall thickness to prevent electrode misalignment and contact while minimizing the container's overall thickness to maintain high energy density.
Solution Approach 2:
The container member is designed with just sufficient thickness to provide the necessary restraint and prevention of electrode contact, rather than excessive thickness. This partial action approach ensures adequate protection against self-discharge and micro-short circuits while avoiding the energy density penalty that would result from over-engineering the container wall thickness.
3Quantity of substance
If the container member is designed with smaller dimensions to maintain high energy density, then energy density is improved, but the electrode group may experience misalignment and contact between electrodes
Solution Approach 1:
The invention determines the optimal container dimensions by establishing the parameter relationship 1.00 < TPC/(T1×2) ≤ 1.05, where TPC is the container thickness and T1 is the wall thickness. This optimized parameter set allows the container to be as thin as possible for high energy density while still providing sufficient structural support to prevent electrode misalignment and contact.
Solution Approach 2:
The container member is pre-designed with dimensions that account for the electrode group's volume changes during operation. By calculating the expected expansion and contraction magnitudes beforehand, the container dimensions are set to provide just enough clearance and restraint to maintain alignment stability without requiring excessive thickness that would reduce energy density.
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
According to one approach, provided is a secondary battery (100) including an electrode group (2) having a flat wound structure and a container member (1) that includes a prismatic container. The electrode group (2) includes a positive electrode (5) and a negative electrode (6) including a titanium-containing oxide. The wound structure is configured with a stack including the positive electrode (5) and the negative electrode (6) being wound. The container member (1) houses the electrode group (2) and has a pair of principal walls (30) along a principal surface (21) of the electrode group (2) . A thickness TPC of the prismatic container housing the electrode group (2) in a direction intersecting with the principal walls (30), a wall thickness T1 of the prismatic container, and a thickness TEG of the electrode group (2) in a state outside the prismatic container satisfy a relationship of 1 × (TPC - T1 × 2) < TEG ≤ 1.05 × (TPC - T1 × 2) .