Polyimide-Coated Silicon Anode Material for High-Temperature Stability

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Solution Overview

Problem

Silicon-based negative electrode active materials in lithium secondary batteries suffer from volumetric expansion and contraction during charging and discharging, leading to side reactions with the electrolyte, poor high-temperature lifetime and storage performance, and reduced output performance.

Innovation Solution

A negative electrode active material is developed with a silicon-based core coated by a polyimide layer containing a fluorine-containing imide unit, which serves as a solid electrolyte interface layer to prevent side reactions and enhance lithium intercalation/deintercalation, thereby controlling volumetric expansion and improving high-temperature performance and output.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If silicon-based negative electrode active material is used to achieve high capacity and energy density, then capacity increases, but volumetric expansion occurs leading to side reactions with electrolyte and poor lifetime characteristics

Engineering Contradiction:

ImprovecapacityVSAvoidlifetime characteristics

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent applies composite materials by creating a core-shell structure where silicon-based particles are coated with a carbon-containing layer. This composite structure allows the silicon core to provide high capacity while the carbon shell prevents volumetric expansion and side reactions with electrolyte, thus improving lifetime characteristics.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent uses a thin carbon-containing coating layer as a flexible shell around the silicon-based particles. This thin film structure accommodates volumetric changes during charging-discharging cycles while preventing direct contact between silicon and electrolyte, thereby maintaining reliability without sacrificing capacity.

Inventive Principle:

Principle #30Flexible shells and thin films

2Use of energy by moving object

If silicon-based negative electrode active material is used to achieve high energy density, then energy density increases, but side reactions with electrolyte occur leading to poor high-temperature storage characteristics

Engineering Contradiction:

Improveenergy densityVSAvoidhigh-temperature storage characteristics

Core Design Contradiction:

Use of energy by moving objectVSObject-affected harmful factors

Solution Approach 1:

The patent introduces a carbon-containing intermediate layer as a mediator between the silicon-based particles and the electrolyte. This intermediary layer prevents direct interaction between silicon and electrolyte, blocking harmful side reactions while allowing lithium ion transport, thus improving high-temperature storage characteristics without reducing energy density.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Quantity of substance

If silicon-based negative electrode active material is used to achieve high capacity, then capacity increases, but volumetric expansion leads to reduced output performance

Engineering Contradiction:

ImprovecapacityVSAvoidoutput performance

Core Design Contradiction:

Quantity of substanceVSPower

Solution Approach 1:

The patent employs a flexible carbon-containing thin film shell that conforms to the silicon-based particles. This shell structure allows rapid lithium ion diffusion while preventing excessive volumetric expansion, thereby maintaining high output performance alongside high capacity.

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 polyimide coating effectively prevents electrolyte side reactions, enhances high-temperature lifetime and storage performance, and improves output performance by reducing resistance, thus stabilizing the silicon-based core.

Implementation Method 1

the polyimide comprises a fluorine-containing imide unit... the outer coating layer including polyimide including a fluorine-containing imide unit can serve as a solid electrolyte interface layer (SEI layer) on the negative electrode active material to prevent side reactions with an electrolyte

Methodology Applied

Scientific EffectSolid electrolyte interface layer formation:

Implementation Method 2

the volumetric expansion/contraction of the silicon-based core according to charging and discharging can be controlled... the silicon-based negative electrode active material exhibits a large degree of volumetric expansion according to charging and discharging

Methodology Applied

Scientific EffectVolumetric expansion control:

Implementation Method 3

can allow smooth intercalation/deintercalation of lithium into/from the active material due to the high electronegativity of fluorine... can allow smooth intercalation/deintercalation of lithium into/from the active material

Methodology Applied

Scientific EffectLithium intercalation and deintercalation:

Data Source

PatentUS12456726B2Negative electrode active material, and negative electrode and secondary battery including the same

Publication Date: 2025.10.28 LG ENERGY SOLUTION LTD

AI summary

Provided is a negative electrode active material which includes: a silicon-based core; and an outer coating layer formed on the silicon-based core and including polyimide, wherein the polyimide comprises a fluorine-containing imide unit. The outer coating layer may be included in an amount of more than 0 wt % and 4.5 wt % or less in the negative electrode active material.