Winding Electrode Assembly Width Layout for Lithium Plating Risk

Solution Overview

Problem

Lithium ion batteries face issues with lithium plating, leading to reduced cycle performance and safety risks due to lithium dendrite formation, particularly at the winding start and tail ends of the electrode assembly, where the negative active material layer exceeds the positive active material layer in the winding axial direction, not meeting design requirements.

Innovation Solution

A winding type electrode assembly design where the negative active material layer's maximum width difference at the head or tail exceeds the positive active material layer's width difference, ensuring a larger width difference between the negative active material layer and the positive active material layer at specific sections to prevent lithium plating, with the negative active material layer's width increased at the head or tail to match or exceed the positive active material layer's width, thereby reducing the risk of lithium plating.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the negative active material layer width is increased at the head or tail to exceed the positive active material layer, then the risk of lithium plating is reduced, but the manufacturing precision requirement increases due to the complex width difference control

Engineering Contradiction:

Improvelithium plating riskVSAvoidwidth difference control precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent applies local quality by creating different width relationships between positive and negative active material layers at different locations along the winding axial direction. Specifically, at the head or tail sections, the negative active material layer width is designed to exceed the positive active material layer width, while in the middle section, the width relationship may differ. This localized variation in dimensional relationships prevents lithium plating at critical end sections without requiring uniform dimensional control throughout the entire electrode assembly, thus reducing the overall manufacturing precision burden.

Inventive Principle:

Principle #3Local quality

2Reliability

If the negative active material layer exceeds the positive active material layer at the winding end portions, then lithium plating is prevented, but the device complexity increases due to the non-uniform width distribution

Engineering Contradiction:

Improvelithium plating preventionVSAvoidelectrode assembly structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent segments the electrode assembly into distinct sections along the winding axial direction: head sections, middle sections, and tail sections. Each section has different width relationship characteristics between the positive and negative active material layers. By segmenting the structure, the patent can apply different design strategies to different sections - specifically ensuring that at the head and tail sections where lithium plating is most likely to occur, the negative active material layer exceeds the positive active material layer width, while the middle section can have different dimensional relationships.

Inventive Principle:

Principle #1Segmentation

3Reliability

If the width difference H1-L1 is made larger than H2-L2, then the design requirement for preventing lithium plating is met, but the energy density may be reduced due to excessive material usage

Engineering Contradiction:

Improvelithium plating preventionVSAvoidenergy density

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The patent applies local quality by creating different width relationships between positive and negative active material layers at different locations along the winding axial direction. Specifically, at the head or tail sections, the negative active material layer width is designed to exceed the positive active material layer width, while in the middle section, the width relationship may differ. This localized variation in dimensional relationships prevents lithium plating at critical end sections without requiring uniform dimensional control throughout the entire electrode assembly, thus reducing the overall manufacturing precision burden.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS11862768B2Winding type electrode assembly, battery cell, battery and power consumption device

Publication Date: 2024.01.02 CONTEMPORARY AMPEREX TECHNOLOGY (HONG KONG) LIMITED

AI summary

The embodiments of the present application provide a winding type electrode assembly including a positive electrode plate and a negative electrode plate; the positive electrode plate includes a first positive winding end portion and a positive winding middle section; the negative electrode plate includes a first portion and a second portion; and an active material layer of the negative electrode plate exceeds an active material layer of the positive electrode plate, and a difference between a maximum width of a negative active material layer of the first portion and a minimum width of a positive active material layer of the first positive winding end portion is larger than a difference between a maximum width of a negative active material layer of the second portion and a minimum width of a positive active material layer of the positive winding middle section.