All-solid-state lithium ion battery anode with controlled solid electrolyte density

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Solution Overview

Problem

All-solid-state lithium ion secondary batteries using alloy-based active materials exhibit low capacity retention rates due to uneven distribution of electroconductive materials and electron conducting path blockage caused by volume changes during charge-discharge cycles.

Innovation Solution

Incorporating a LiX—Li2S—P2S5-based solid electrolyte with a bulk density of 0.3 g/cm3 to 0.6 g/cm3, combined with an anode active material like silicon or its alloys, and an electroconductive material such as carbon nanotubes, to maintain ion and electron conductivity while preventing aggregation and ensuring even distribution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If alloy-based active material is used in anode, then theoretical capacity per volume is improved, but capacity retention rate deteriorates during charge-discharge cycles

Engineering Contradiction:

Improvetheoretical capacity per volumeVSAvoidcapacity retention rate

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent controls the bulk density of the solid electrolyte within a specific range (0.3-0.6 g/cm³) to optimize both capacity and cycle characteristics. This parameter control ensures proper distribution and contact between solid electrolyte particles and electroconductive materials, resolving the contradiction between high capacity and good retention

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The anode uses a composite structure combining alloy-based active material particles with solid electrolyte particles and electroconductive materials. This composite approach maintains the high theoretical capacity of alloy materials while the solid electrolyte and electroconductive network prevent capacity fading during cycling

Inventive Principle:

Principle #40Composite materials

2Productivity

If solid electrolyte bulk density is increased, then manufacturing efficiency is improved, but ion conductivity and electroconductive material distribution deteriorate

Engineering Contradiction:

Improvemanufacturing efficiencyVSAvoidion conductivity

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent identifies and controls the bulk density parameter of solid electrolyte within the optimal range of 0.3-0.6 g/cm³. This parameter optimization balances manufacturing efficiency with maintaining adequate ion conductivity and proper distribution of electroconductive materials throughout the anode structure

Inventive Principle:

Principle #35Parameter changes

3Quantity of substance

If alloy-based active material is used, then capacity per volume is improved, but electron conducting path is blocked due to volume changes

Engineering Contradiction:

Improvecapacity per volumeVSAvoidelectron conducting path continuity

Core Design Contradiction:

Quantity of substanceVSDevice complexity

Solution Approach 1:

The patent introduces electroconductive materials as intermediaries between alloy-based active material particles. These electroconductive materials form a continuous network that maintains electron conduction even when alloy particles undergo volume changes during lithium insertion and extraction, preventing blocking of electron conducting paths

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

This configuration enhances capacity retention rates and maintains excellent cycle characteristics by ensuring balanced ion and electron conducting paths, even with alloy-based active materials.

Implementation Method 1

the solid electrolyte is a LiX—Li2S—P2S5-based solid electrolyte... bulk density of the solid electrolyte is 0.3 g/cm3 or more and 0.6 g/cm3 or less

Methodology Applied

Scientific EffectIonic conduction: Conduction (electrical)

Implementation Method 2

anode comprises an anode active material, an electroconductive material and a solid electrolyte... the electroconductive material may be at least one carbonaceous material selected from the group consisting of carbon black, carbon nanotube and carbon nanofiber

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 3

an active material (an alloy-based active material) containing a metal such as Si, the metal being able to form an alloy with Li... volume changes during charge-discharge cycles

Methodology Applied

Scientific EffectAlloying reaction:

Data Source

PatentUS11387485B2All-solid-state lithium ion secondary battery

Publication Date: 2022.07.12 TOYOTA JIDOSHA KK

AI summary

Disclosed is an all-solid-state lithium ion secondary battery being excellent in cycle characteristics. The all-solid-state lithium ion secondary battery may be an all-solid-state lithium ion secondary battery, wherein an anode comprises an anode active material, an electroconductive material and a solid electrolyte; wherein the anode active material comprises at least one active material selected from the group consisting of a metal that is able to form an alloy with Li, an oxide of the metal, and an alloy of the metal and Li; and wherein a bulk density of the solid electrolyte is 0.3 g/cm3 or more and 0.6 g/cm3 or less.