Solid Battery Negative Electrode Film Strength Optimization

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Solution Overview

Problem

Solid lithium secondary batteries face performance deterioration due to pore formation in the negative electrode from lithium deposition and elution during charge/discharge cycles, which can be exacerbated by the need for high external pressure to prevent damage, complicating the enhancement of battery module specific energy.

Innovation Solution

A solid secondary battery design featuring a negative electrode with a particulate carbon and lithium alloy or compound active material layer, optimized with a film strength of 50-250 megapascals and specific content per unit area, allowing charge/discharge without external pressure, and incorporating a solid electrolyte and positive electrode with a liquid electrolyte to manage lithium deposition and prevent electrode damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If high external pressure is applied by placing the solid lithium-ion secondary battery between end plates in the thickness direction to suppress pore formation and avoid negative electrode damage, then the negative electrode damage is prevented, but the overall specific energy of the battery module is reduced due to the weight of the end plates

Engineering Contradiction:

Improvenegative electrode damage preventionVSAvoidend plate weight

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The invention extracts and eliminates the end plates from the battery structure by developing a negative electrode material with inherently high film strength that can withstand volume changes during charge-discharge cycles without external pressure, thereby removing the harmful weight of end plates while maintaining negative electrode integrity

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention changes the key parameter of film strength of the negative active material layer to a specific range (50-250 MPa) that enables the material to withstand volume expansion and contraction during lithium deposition and elution without requiring external pressure, thus resolving the contradiction between damage prevention and weight reduction

Inventive Principle:

Principle #35Parameter changes

2Quantity of substance

If the content of the negative active material per unit area is increased to improve capacity, then the battery capacity increases, but the film strength decreases making the electrode more susceptible to damage during volume changes

Engineering Contradiction:

Improvenegative active material contentVSAvoidfilm strength

Core Design Contradiction:

Quantity of substanceVSStrength

Solution Approach 1:

The invention identifies and optimizes the film strength parameter to a specific range (50-250 MPa) that represents the optimal balance point where sufficient negative active material content provides high capacity while maintaining adequate film strength to withstand volume changes during charge-discharge cycles

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention uses a composite negative active material layer comprising particulate carbon and lithium alloy or compound materials, where the carbon component provides structural support and maintains film strength while the lithium alloy/compound provides high capacity, achieving both high content and high strength simultaneously

Inventive Principle:

Principle #40Composite materials

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 enables high discharge rate and cycle characteristics while eliminating the need for external pressure, improving the battery's reliability and energy density by suppressing negative electrode damage and maintaining performance across charge/discharge cycles.

Implementation Method 1

a negative active material layer between the negative electrode current collector and the solid electrolyte, the negative active material layer includes a particulate carbon and a negative active material that forms an alloy or a compound with lithium

Methodology Applied

Scientific EffectAlloy formation:

Implementation Method 2

lithium deposited in the negative electrode during charge

Methodology Applied

Scientific EffectLithium deposition: Deposition (physical)

Implementation Method 3

lithium deposited in the negative electrode during charge is eluted as lithium ions during discharge

Methodology Applied

Scientific EffectIon elution:

Implementation Method 4

a solid electrolyte disposed between the positive electrode and the negative electrode

Methodology Applied

Scientific EffectIon conduction: Conduction (electrical)

Data Source

PatentUS20230238510A1Solid secondary battery, solid secondary battery module comprising solid secondary battery, and charging method thereof

Publication Date: 2023.07.27 SAMSUNG ELECTRONICS CO LTD

AI summary

A solid secondary battery includes: a positive electrode; a negative electrode; and a solid electrolyte disposed between the positive electrode and the negative electrode, wherein the negative electrode includes a negative electrode current collector, and a negative active material layer between the negative electrode current collector and the solid electrolyte, the negative active material layer includes a particulate carbon and a negative active material that forms an alloy or a compound with lithium, a content of the negative active material per unit area of the negative active material layer is about 0.01 milligram per square centimeter or to about 1 milligram per square centimeter, and a film strength of the negative active material layer is about 50 megapascals to about 250 megapascals.