Cylindrical Battery Electrode Assembly Alignment for Lithium Plating
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Solution Overview
Problem
Large cylindrical batteries experience performance deterioration and safety hazards due to lithium deposition in local poor fluid caused by uneven stress on the electrode assembly, particularly when the number of terminal sheet turns exceeds 40, leading to electrolyte squeeze-out and radial swelling.
Innovation Solution
The secondary battery design includes a casing with a defined first axis and a wound electrode assembly with a second axis located within a cylindrical region of φ0.6 mm diameter, using a finishing adhesive with a safety slit and insulating layers to enhance coaxiality and prevent electrolyte squeeze-out, thereby reducing lithium deposition and improving safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of turns of terminal sheets is increased to increase battery capacity, then the battery capacity is improved, but the radial swelling of the electrode assembly increases causing electrolyte to be squeezed out
Solution Approach 1:
The patent applies a radial expansion buffer between the electrode assembly and the steel casing. This buffer acts as a flexible layer that absorbs radial swelling of the electrode assembly during charge-discharge cycles, preventing the electrode assembly from directly contacting and squeezing out electrolyte through the casing wall, thus maintaining electrolyte retention while allowing high number of terminal sheet turns for increased capacity
2Stability of the object's composition
If the electrode assembly is constrained by the steel casing to maintain structural stability, then the structural stability is improved, but the radial swelling causes uneven stress leading to lithium deposition
Solution Approach 1:
The radial expansion buffer serves as a flexible intermediary layer between the rigid steel casing and the swelling electrode assembly. This buffer layer distributes the radial swelling forces uniformly, preventing localized stress concentration that would otherwise cause electrolyte squeeze-out and subsequent lithium deposition, while still maintaining overall structural stability through the casing
Solution Approach 2:
The radial expansion buffer acts as an intermediary element between the electrode assembly and the steel casing. It mediates the interaction by absorbing expansion forces and preventing direct contact between the swelling electrode assembly and the rigid casing, thereby eliminating the mechanism that leads to harmful lithium deposition while preserving structural integrity
Data Source
AI summary
A secondary battery, a battery module, and an electronic apparatus are provided. The secondary battery includes a casing and a terminal assembly. The casing includes an end wall and a side wall surrounding the end wall, and an axis of the casing is a first axis. The electrode assembly accommodated in the casing includes a positive terminal sheet, a negative terminal sheet, and a separator stacked and wound to form a wound structure. A number of turns of the negative terminal sheet is greater than 40 turns, and an axis of the wound structure is a second axis. When a state of charge (SOC) of the secondary battery is less than 5%, the second axis is located in a cylindrical region with the first axis as the axis and a diameter d1 of φ0.6 mm.