Actuated Fiber Electrode for Silicon Anode Volume Expansion

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Solution Overview

Problem

Lithium-ion batteries using carbon-based electrodes suffer from low energy density and rapid capacity fade due to the volume expansion of silicon active materials, leading to electrode delamination and increased internal resistance.

Innovation Solution

The electrode design incorporates electrically actuated fibers extending from the current collector into the active material layer, which change dimension under an electric field to maintain conductive pathways and direct electrons vertically, enhancing the electrode's structural integrity and conductivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If silicon is added to active materials to increase theoretical lithium storage capacity, then energy density is improved, but rapid capacity fade and poor cycle life occur due to volume expansion

Engineering Contradiction:

Improvelithium storage capacityVSAvoidcycle life

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The electrode is segmented into multiple functional layers including a buffer layer between the silicon-containing active material and the current collector. This buffer layer absorbs the volume expansion stress, preventing particle cracking and pulverization while maintaining structural integrity throughout charge-discharge cycles

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The electrode uses composite material structure combining silicon-containing active material with carbon-based materials and conductive additives. This composite approach maintains the high lithium storage capacity of silicon while the carbon matrix provides structural stability and prevents rapid capacity fade

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If silicon active materials are used to increase lithium storage capacity, then energy density is improved, but electrode delamination occurs due to volume expansion

Engineering Contradiction:

Improvelithium storage capacityVSAvoidelectrode structural integrity

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

A buffer layer is placed beforehand between the silicon active material and the current collector to cushion the massive volume expansion (up to 300%) upon lithium insertion. This prevents particle cracking and pulverization before they can propagate to the electrode level, thereby preventing delamination and maintaining structural integrity

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The buffer layer acts as a flexible interface that can accommodate the volume changes of silicon during lithiation and delithiation. This flexible structure prevents rigid constraints that would cause cracking and delamination, maintaining electrode stability throughout cycling

Inventive Principle:

Principle #30Flexible shells and thin films

3Reliability

If graphite is used as anode electrode material, then stability and cycle life are improved, but theoretical lithium storage capacity is limited to 372 mAh/g

Engineering Contradiction:

Improvecycle lifeVSAvoidlithium storage capacity

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The invention changes the active material from pure graphite to silicon-containing materials, fundamentally altering the lithium storage mechanism from intercalation (graphite) to alloying (silicon). This parameter change increases theoretical capacity from 372 mAh/g to over 3500 mAh/g while managing the associated volume expansion through buffer layers

Inventive Principle:

Principle #35Parameter changes

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

This design mitigates the rapid capacity fade and internal resistance issues by maintaining conductive pathways throughout the battery's life, improving energy density and durability.

Implementation Method 1

The electrically actuated fibers have an actuated state, in which the electrically actuated fibers change dimension in a linear direction under application of an electric field

Methodology Applied

Scientific EffectElectric field: Electric Field

Implementation Method 2

The electrically actuated fibers configured to direct electrons through the active electrode material in a stacked direction of the electrode

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Data Source

PatentUS10153494B2Electrode having electrically actuated fibers for electron conduction

Publication Date: 2018.12.11 NISSAN MOTOR CO LTD

AI summary

An electrode has a first active material layer between a current collector and a separator. The first active material layer comprises an active electrode material and electrically actuated fibers extending from a surface of the current collector and into the active electrode material. The electrically actuated fibers have an actuated state, in which the electrically actuated fibers change dimension in a linear direction under application of an electric field, the electrically actuated fibers configured to direct electrons through the active electrode material in a stacked direction of the electrode, and an unactuated state, in which the electrically actuated fibers are conductive but remain in an original state.