Silicon Anode Current Collector Surface Roughness for Battery Cycle Life

Solution Overview

Problem

Lithium ion secondary batteries face challenges in achieving high capacity and cycle characteristics due to the expansion and shrinkage of silicon-based anode active material layers during charge and discharge, leading to reduced charge and discharge efficiency and cycle life.

Innovation Solution

A battery design with an anode current collector having a surface roughness of 0.2 μm or more, alloyed with the anode active material layer, and an oxygen content of 3 atomic % or more, or with alternating layers of different oxygen content, to prevent expansion and shrinkage, and optimize the maximum utilization ratio of the anode between 35% to 85%, thereby improving charge and discharge efficiency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If silicon is used for the anode active material layer to increase battery capacity, then the battery capacity is improved, but the charge and discharge efficiency is lowered due to expansion and shrinkage of silicon

Engineering Contradiction:

Improvebattery capacityVSAvoidcharge and discharge efficiency

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

A silicon oxide coating layer is formed on the surface of the silicon anode active material layer. This coating layer acts as a protective shell that accommodates the expansion and shrinkage of silicon during charge and discharge cycles, preventing pulverization and maintaining structural integrity while allowing lithium ion transport.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The anode is designed as a composite structure combining silicon with a metal alloy layer containing aluminum and silicon. This composite structure leverages the high capacity of silicon while the metal alloy provides structural stability and prevents excessive expansion, resolving the contradiction between capacity and efficiency.

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If the anode active material layer is made thicker to increase capacity, then the battery capacity is improved, but the cycle characteristics deteriorate due to pulverization from expansion and shrinkage

Engineering Contradiction:

Improvebattery capacityVSAvoidcycle characteristics

Core Design Contradiction:

Quantity of substanceVSDuration of action of stationary object

Solution Approach 1:

A silicon oxide coating layer is formed on the surface of the silicon anode active material layer. This coating layer acts as a protective shell that accommodates the expansion and shrinkage of silicon during charge and discharge cycles, preventing pulverization and maintaining structural integrity while allowing lithium ion transport.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The silicon oxide coating layer is formed in advance on the silicon surface before the anode is assembled. This pre-formed coating provides cushioning and protection against the mechanical stress of expansion and shrinkage that will occur during subsequent charge and discharge cycles, preventing pulverization and maintaining cycle characteristics.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

3Quantity of substance

If the maximum utilization ratio of the anode is increased to improve capacity, then the battery capacity is improved, but side reactions increase and coating quality deteriorates

Engineering Contradiction:

Improvebattery capacityVSAvoidside reactions

Core Design Contradiction:

Quantity of substanceVSObject-generated harmful factors

Solution Approach 1:

A silicon oxide coating layer is formed on the surface of the silicon anode active material layer. This coating layer acts as a protective shell that accommodates the expansion and shrinkage of silicon during charge and discharge cycles, preventing pulverization and maintaining structural integrity while allowing lithium ion transport.

Inventive Principle:

Principle #30Flexible shells and thin films

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

The solution enhances charge and discharge efficiency and cycle characteristics by preventing the anode active material layer from being expanded and shrunk, reducing side reactions, and forming a high-quality coating, while maintaining a balance between capacity and utilization ratio.

Implementation Method 1

The anode active material layer is alloyed with the anode current collector at least in part of the interface with the anode current collector

Methodology Applied

Scientific EffectAlloying:

Implementation Method 2

silicon or the like is largely expanded and shrunk due to charge and discharge

Methodology Applied

Scientific EffectExpansion and shrinkage: Thermal Expansion

Implementation Method 3

when the oxygen (O) content in the anode active material layer is 3 atomic % or more, or when at least one or more second layers with the oxygen content larger than that of the first layer are sandwiched between the first layers, the charge and discharge efficiency can be more improved

Methodology Applied

Scientific EffectOxygen content effect:

Data Source

PatentUS7682742B2Battery

Publication Date: 2010.03.23 MURATA MFG CO LTD

AI summary

A battery capable of improving cycle characteristics is provided. An anode contains Si as an element. Where the Li insertion amount per unit area when the anode is fully charged is A, the Li amount capable of being electronically inserted per unit area of the anode is B, and the maximum utilization ratio C % is (A/B)×100, the maximum utilization ratio C % is in the range from 35% to 85%. The surface roughness Ra value of the anode current collector is 0.2 μm or more.