Crystalline Solid Electrolyte Internal Resistance Reduction

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Solution Overview

Problem

Bulk-type all-solid-state batteries face high internal resistance issues due to grain-boundary resistance, electrode interface resistance, and bulk resistance, which hinder efficient energy storage and utilization, particularly in environmental power generation applications.

Innovation Solution

A crystalline solid electrolyte composed of Li3PO4, Li4SiO4, and Li3BO3 with a Li3PO4 content less than or equal to 75 mole% is developed, optimized using an Ising model equation and digital annealer, to reduce internal resistance by controlling the crystallization temperature and maintaining the electrode material's integrity during heat treatment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a bulk-type all-solid-state battery is constructed using conventional solid electrolyte materials and sintering methods, then the battery structure is formed, but the internal resistance increases due to grain-boundary resistance, electrode interface resistance, and bulk resistance

Engineering Contradiction:

Improvebattery performanceVSAvoidinternal resistance

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The invention changes the chemical composition parameters of the solid electrolyte by using a specific molar ratio range of Li3PO4 (30-75 mol%), Li4SiO4 (10-50 mol%), and Li3BO3 (10-50 mol%). This compositional parameter change optimizes the balance between grain-boundary resistance and bulk resistance, achieving lower overall internal resistance while maintaining structural stability during sintering.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention creates a composite solid electrolyte material by combining three different lithium compounds (Li3PO4, Li4SiO4, and Li3BO3) in specific proportions. This composite approach leverages the complementary properties of each component: Li3PO4 provides good ionic conductivity, Li4SiO4 reduces grain-boundary resistance, and Li3BO3 enhances structural stability, resulting in a synergistic effect that reduces overall internal resistance.

Inventive Principle:

Principle #40Composite materials

2Reliability

If the Li3PO4 content is increased to improve ion conductivity, then the ion conductivity increases, but the crystallization temperature increases causing decomposition of electrode material

Engineering Contradiction:

Improveion conductivityVSAvoidcrystallization temperature

Core Design Contradiction:

ReliabilityVSTemperature

Solution Approach 1:

The invention optimizes the Li3PO4 content parameter within a specific range (30-75 mol%) rather than maximizing it. This parameter optimization achieves sufficient ion conductivity while preventing excessive crystallization temperature rise. The balanced composition ensures that the crystallization temperature remains below the decomposition temperature of electrode materials like LiCoO2 and graphite.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention creates local compositional optimization by distributing different lithium compounds throughout the solid electrolyte matrix. The specific ratio of Li3PO4, Li4SiO4, and Li3BO3 creates localized regions with different properties that collectively achieve both good ion conductivity and controlled crystallization temperature, preventing hot spots that would cause electrode decomposition.

Inventive Principle:

Principle #3Local quality

3Object-affected harmful factors

If Li3PO4, Li4SiO4, and Li3BO3 are mixed and crystallized to produce the solid electrolyte, then the internal resistance decreases, but the manufacturing process complexity increases

Engineering Contradiction:

Improveinternal resistanceVSAvoidmanufacturing process

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The invention merges multiple functional requirements into a single solid electrolyte composition formula. By combining Li3PO4, Li4SiO4, and Li3BO3 in specific ratios, the material simultaneously achieves low grain-boundary resistance, low bulk resistance, and controlled crystallization temperature, eliminating the need for separate processing steps to address each issue independently.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The invention simplifies manufacturing by establishing specific parameter ranges for the starting materials that guide the crystallization process. By specifying the molar ratio ranges of the three lithium compounds, the process automatically self-optimizes during sintering to produce the desired low-resistance electrolyte without requiring complex real-time monitoring or adjustment procedures.

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

The crystalline solid electrolyte effectively decreases internal resistance and exhibits good ion conductivity and reduction-resistant properties, enabling efficient energy storage and utilization in all-solid-state batteries without decomposing the electrode material.

Implementation Method 1

crystallizing the Li3PO4, the Li4SiO4, and the Li3BO3 that have been mixed with each other

Methodology Applied

Scientific EffectCrystallization: Crystallisation

Data Source

PatentEP3890091B1Crystalline solid electrolyte and method of producing the same

Publication Date: 2023.06.28 FUJITSU LTD

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AI summary

A crystalline solid electrolyte includes: Li3PO4, Li4SiO4, and Li3BO3 and content of the Li3PO4 is less than or equal to 75 mole%.