CO2-Derived SEI Chemistry for Silicon-Anode Lithium Batteries

Solution Overview

Problem

Lithium secondary batteries with silicon-based anode active materials face significant volume changes during charging and discharging, leading to chemical and mechanical stability issues and reduced lifespan due to large capacity demands.

Innovation Solution

A lithium secondary battery design incorporating a solid electrolyte interface (SEI) layer formed with a CO2-derived material on the anode active material layer, using a lithium metal oxide cathode with high nickel content and a silicon-based anode, where the SEI layer has a C—O peak intensity to Li—F peak intensity ratio of 0.38 or more, and a CO2 supply source in the electrolyte solution to enhance stability and capacity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If a silicon-based active material is used as anode active material to obtain high capacity, then the theoretical capacity is improved, but the volume change during charging and discharging increases significantly

Engineering Contradiction:

ImprovecapacityVSAvoidvolume change

Core Design Contradiction:

Quantity of substanceVSVolume of moving object

Solution Approach 1:

The silicon-based active material particles are embedded within a porous carbon matrix structure, creating a nested configuration where silicon particles are contained within the carbon framework. This nesting approach allows the silicon to expand and contract during lithium insertion/extraction while being constrained by the surrounding carbon matrix, thereby maintaining structural integrity and reducing overall volume change of the anode active material layer

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The anode active material layer is constructed as a composite material system combining silicon-based active material with carbon matrix and conductive additives. This composite structure leverages the high capacity of silicon while utilizing the structural stability and electrical conductivity of carbon components to mitigate silicon's volume expansion issues during cycling

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If a silicon-based active material is used as anode active material to obtain high capacity, then the theoretical capacity is improved, but the chemical and mechanical stability deteriorates

Engineering Contradiction:

ImprovecapacityVSAvoidchemical and mechanical stability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The silicon-based active material particles are embedded within a porous carbon matrix structure, creating a nested configuration where silicon particles are contained within the carbon framework. This nesting approach allows the silicon to expand and contract during lithium insertion/extraction while being constrained by the surrounding carbon matrix, thereby maintaining structural integrity and reducing overall volume change of the anode active material layer

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The anode active material layer is constructed as a composite material system combining silicon-based active material with carbon matrix and conductive additives. This composite structure leverages the high capacity of silicon while utilizing the structural stability and electrical conductivity of carbon components to mitigate silicon's volume expansion issues during cycling

Inventive Principle:

Principle #40Composite materials

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 SEI layer improves the lithium secondary battery's capacity and lifespan by stabilizing the anode active material layer, reducing volume expansion and mechanical stress, and maintaining a sufficient CO2-derived material content for prolonged battery performance.

Implementation Method 1

a solid electrolyte interface (SEI) layer formed on the anode active material layer

Methodology Applied

Scientific EffectSolid electrolyte interface (SEI) layer formation:

Implementation Method 2

the SEI layer may include a CO2-derived material

Methodology Applied

Scientific EffectCO2-derived material incorporation:

Implementation Method 3

the silicon-based active material may cause a large volume change (about 300% to 400%) during charging and discharging of the lithium secondary battery, which may deteriorate chemical and mechanical stability

Methodology Applied

Scientific EffectVolume change mitigation:

Implementation Method 4

A ratio of a C—O peak intensity to a Li—F peak intensity is 0.38 or more in an X-ray photoelectron spectroscopy spectrum of the SEI layer

Methodology Applied

Scientific EffectX-ray photoelectron spectroscopy:

Data Source

PatentUS20230369651A1Lithium secondary battery and method of fabricating the same

Publication Date: 2023.11.16 SK ON CO LTD

AI summary

A lithium secondary battery includes an electrolyte solution including a lithium salt, an organic solvent and a CO2 supply source, a cathode including a cathode active material layer that includes a lithium metal oxide particle containing nickel, and an anode including an anode active material layer and a solid electrolyte interface (SEI) layer formed on the anode active material layer. The anode active material layer includes a silicon-based active material. A ratio of a C—O peak intensity to a Li—F peak intensity is 0.38 or more in an X-ray photoelectron spectroscopy spectrum of the SEI layer.