Lithium Secondary Battery Interface Layer for Fast-Charge Cycle Stability

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Solution Overview

Problem

Lithium secondary batteries experience degradation in discharge capacity when subjected to repeated high-speed charging and discharging due to interfacial failure between the positive electrode and the separator, leading to misalignment and short-circuiting.

Innovation Solution

Incorporating an intermediate layer containing an oxide with Co and Mg between the positive electrode and the separator, which suppresses interfacial failure and maintains discharge capacity by improving the integrity and cycle characteristics of the battery.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If an integrated sintered plate structure is used with a ceramic separator composed of MgO and glass, then the battery structure is simplified and manufacturing is easier, but interfacial failure occurs between the positive electrode and separator during repeated high-speed charging and discharging

Engineering Contradiction:

Improveintegrated sintered plate structureVSAvoidinterfacial stability

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

An intermediate layer containing an oxide with specific Co and Mg ratios is introduced between the positive electrode and the separator. This intermediate layer acts as a mediator that suppresses interfacial failure during repeated high-speed charging and discharging, while maintaining the integrated sintered plate structure's manufacturing advantages.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The separator is constructed as a composite material combining MgO and glass in specific ratios, and the intermediate layer uses a composite oxide composition with controlled Co and Mg ratios. This composite approach enhances interfacial stability without compromising the integrated structure's ease of manufacture.

Inventive Principle:

Principle #40Composite materials

2Stability of the object's composition

If the ceramic separator is made with glass particles having specific orientation at the interface, then the structural integrity is improved, but the complexity of achieving proper orientation increases

Engineering Contradiction:

Improveseparator interface integrityVSAvoidglass particle orientation control

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The intermediate layer serves as a buffer that reduces the need for precise glass particle orientation control. By placing this intermediate layer between the positive electrode and separator, the system achieves stable interface integrity without requiring complex orientation control of glass particles.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If repeated high-speed charging and discharging is performed, then the productivity and power output are improved, but the discharge capacity degrades due to interfacial failure

Engineering Contradiction:

Improvecharging and discharging speedVSAvoiddischarge capacity maintenance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The intermediate layer with specific oxide composition acts as a protective mediator that enables repeated high-speed charging and discharging cycles without causing interfacial failure. This allows the battery to maintain discharge capacity while achieving high productivity through fast charging and discharging operations.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

By controlling the Co and Mg ratios in the intermediate layer's oxide composition, the interface stability is optimized to withstand high-speed charging and discharging conditions. This parameter optimization allows the battery to maintain performance under high productivity demands.

Inventive Principle:

Principle #35Parameter changes

4Reliability

If an intermediate layer with oxide containing Co and Mg is added between the positive electrode and separator, then the interfacial stability and cycle characteristics are improved, but the device complexity and manufacturing steps increase

Engineering Contradiction:

Improvecycle characteristicsVSAvoidnumber of layers

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The intermediate layer is integrated into the sintering process along with the positive electrode and separator, forming an integrated sintered plate structure. This merging approach reduces the need for separate assembly steps, thereby minimizing the increase in manufacturing complexity despite adding the intermediate layer for improved cycle characteristics.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS20230411676A1Lithium secondary battery

Publication Date: 2023.12.21 NGK INSULATORS LTD

AI summary

A lithium secondary battery includes a positive electrode composed of a sintered body containing lithium cobaltate, a negative electrode, and a separator composed of a sintered body containing magnesia interposed between the positive electrode and the negative electrode. The lithium secondary battery further includes an intermediate layer between the positive electrode and the separator, the intermediate layer containing an oxide containing Co and Mg.