Si-Anode Battery Separator Structure for Hi-Pot Defect Reduction

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

The use of Si-based anode active materials in lithium secondary batteries leads to increased volume expansion, internal pressure, and local damage to the separator during lamination, resulting in Hi-pot defects and reduced capacity retention rates.

Innovation Solution

A lithium secondary battery with a separator substrate made of polyolefin resin having a specific polydispersity index (PDI) of 2.5 to 4.2, average pore size of 20 to 40 nm, and maximum pore size of 50 nm or less, exhibiting a strain of 25% or less under tensile stress, and a recovery rate of 70% within 200 seconds, along with an organic/inorganic composite coating layer for improved compression resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If Li4SiO4 is used as negative electrode active material, then battery capacity is improved, but charge-discharge rate capability deteriorates due to slow Li-ion diffusion

Engineering Contradiction:

Improvebattery capacityVSAvoidcharge-discharge rate capability

Core Design Contradiction:

Quantity of substanceVSSpeed

Solution Approach 1:

The Li4SiO4 particles are divided into fine particles with a maximum diameter of 10 μm, preferably 1-5 μm. This segmentation increases the surface area and shortens the Li-ion diffusion path length, thereby improving charge-discharge rate capability while maintaining high battery capacity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A coating layer comprising at least one of Li2SiO3 and amorphous SiO2 is formed on the surface of the Li4SiO4 particles. This local modification at the particle surface improves Li-ion diffusion kinetics at the critical interface where Li-ion insertion/extraction occurs, enhancing rate capability without reducing overall capacity.

Inventive Principle:

Principle #3Local quality

2Quantity of substance

If Si-based negative electrode active material is used, then battery capacity is improved, but volume expansion occurs during charging

Engineering Contradiction:

Improvebattery capacityVSAvoidvolume expansion

Core Design Contradiction:

Quantity of substanceVSVolume of moving object

Solution Approach 1:

The invention uses Li4SiO4 as the core active material, which is a composite material combining silicon (providing high capacity) with lithium oxide (providing structural stability). This composite structure allows the material to utilize silicon's high Li-ion storage capacity while the lithium oxide component constrains volume expansion during charging cycles.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention changes the crystal structure parameter by using the olivine structure of Li4SiO4, which has a stable framework that accommodates Li-ion insertion/extraction with minimal volume change. Additionally, the coating layer of Li2SiO3 or amorphous SiO2 further stabilizes the surface structure and prevents excessive volume expansion.

Inventive Principle:

Principle #35Parameter changes

3Strength

If Li4SiO4 particles are sintered at high temperature, then particle strength is improved, but Li4SiO4 crystal structure transforms to harmful phase

Engineering Contradiction:

Improveparticle strengthVSAvoidcrystal structure stability

Core Design Contradiction:

StrengthVSStability of the object's composition

Solution Approach 1:

The sintering temperature is optimized to 900°C or lower, preventing the phase transformation of Li4SiO4 from the olivine structure to the harmful Li3SiO3 phase. This parameter control maintains both particle strength and crystal structure stability simultaneously.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

A coating layer comprising Li2SiO3 or amorphous SiO2 is formed on the Li4SiO4 particles before or during sintering. This coating layer acts as a protective barrier that prevents excessive grain growth and phase transformation at elevated temperatures, allowing sintering to proceed at lower temperatures while maintaining particle strength.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 the separator's compression resistance, reducing Hi-pot defects and improving capacity retention rates while allowing for faster processing speeds.

Implementation Method 1

it has come to light, however, that Li4SiO4 has a low charge-discharge rate capability due to slow diffusion of Li-ions

Methodology Applied

Scientific EffectLi-ion diffusion: Diffusion

Implementation Method 2

a coating layer comprising at least one of Li2SiO3 and amorphous SiO2 is formed on the surface of the Li4SiO4 particles

Methodology Applied

Scientific EffectSurface coating: Deposition (physical)

Implementation Method 3

the Li4SiO4 particles after the sintering step have a maximum diameter of 10 μm or less, preferably 1 μm to 5 μm

Methodology Applied

Scientific EffectSintering: Sintering

Data Source

PatentEP4404366B1Lithium secondary battery comprising si-based negative electrode active material

Publication Date: 2026.04.29 LG ENERGY SOLUTION LTD

Figure 1~2
Figure 3

AI summary

Provided is a lithium secondary battery with reduced Hi-pot defects and improved capacity retention rate. According to one aspect of the present disclosure, there is provided a lithium secondary battery including an anode, a cathode, and a separator interposed between the anode and the cathode, in which the anode includes a Si-based anode active material, the separator includes a separator substrate having a plurality of pores and including a polyolefin resin, the polyolefin resin has a polydispersity index (PDI) of 2.5 to 4.2, an average pore size of 20 to 40 nm, and a maximum pore size of 50 nm or less.