Lithium Ion Battery Interface Bonding via Intermediate Layer

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Solution Overview

Problem

Multilayer lithium ion rechargeable batteries face issues with high internal resistance and poor charging and discharging cycle characteristics due to impurity layers formed at the interface of the electrode and electrolyte layers, leading to energy loss and reduced functionality.

Innovation Solution

Incorporating an intermediate layer formed through reaction or diffusion between the active materials and the solid electrolyte at the interface, with a conductive matrix structure that supports the active material, and using specific materials like lithium silicate and lithium phosphate to enhance bonding and conductivity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If LiCoO2 and LiTi2(PO4)3 are laminated and baked, then the battery structure is formed, but an impurity layer of CoTiO3, Co2TiO4, or LiCoPO4 is produced at the interface, causing high interface resistance and energy loss

Engineering Contradiction:

Improvebattery functionalityVSAvoidinterface resistance

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent introduces an intermediate layer between the positive electrode layer and electrolyte layer that acts as a buffer to prevent direct harmful reactions. This intermediate layer suppresses the formation of high-resistance impurity compounds while maintaining electrochemical activity, thereby reducing interface resistance and energy loss without compromising battery functionality.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent converts the harmful reaction between LiCoO2 and LiTi2(PO4)3 into a beneficial process by controlling the baking conditions and material composition to form an intermediate layer with optimal properties. The reaction that would normally produce harmful impurities is instead harnessed to create a functional interface layer with appropriate resistance and electrochemical activity.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

2Reliability

If specific materials (LiMPO4 and Li1+xMIIIxTiIV2−x(PO4)3) are used to suppress impurity layer formation, then electrochemically active interface is achieved, but manufacturing complexity increases due to material selection constraints

Engineering Contradiction:

Improveinterface electrochemical activityVSAvoidmaterial selection complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent employs parameter changes in the material composition formulas, specifically adjusting the x values in LiMPO4 (0.1≤x≤0.9) and Li1+xMIIIxTiIV2−x(PO4)3 (0≤x≤0.6), to optimize the balance between suppressing impurity formation and maintaining electrochemical activity. This systematic parameter optimization provides a flexible framework that reduces manufacturing complexity compared to fixed material specifications.

Inventive Principle:

Principle #35Parameter changes

3Weight of moving object

If multilayer structure with thin layers (a few μm) is adopted, then size, weight, and thickness are reduced, but interface bonding strength and charging-discharging characteristics deteriorate due to impurity formation

Engineering Contradiction:

Improvebattery weightVSAvoidcharging-discharging cycle characteristics

Core Design Contradiction:

Weight of moving objectVSReliability

Solution Approach 1:

The intermediate layer serves as a protective mediator that enables the use of thin multilayer structures without compromising charging-discharging characteristics. By preventing harmful interface reactions, the intermediate layer ensures that even with reduced layer thickness, the battery maintains good cycle stability and electrochemical performance while achieving weight and size reduction.

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 approach strengthens the interface bonding, reduces internal resistance, and improves charging and discharging cycle characteristics, enabling the production of high-performance lithium ion rechargeable batteries with enhanced ampere-hour capacity and reduced impedance.

Implementation Method 1

an intermediate layer formed from a reaction and/or diffusion between the positive active material and/or the negative active material and the solid electrolyte

Methodology Applied

Scientific EffectDiffusion: Diffusion

Data Source

PatentUS9457512B2Lithium ion rechargeable battery and process for producing the lithium ion rechargeable battery

Publication Date: 2016.10.04 NAMICS CORPORATION

AI summary

Conventional ion rechargeable batteries having an electrode layer on an electrolyte layer suffer from an impurity layer formed at the interface, degrading performance. Conventional batteries with no such impurity layer have a problem of weak interface bonding. In the present invention, in a baking process step after an electrode layer is laminated on an electrolyte layer, materials for an electrode layer and an electrolyte layer are selected such that an intermediate layer formed of a reaction product contributing to charging and discharging reactions is formed at the interface of the electrode layer and the electrolyte layer. In addition, a paste that an active material is mixed with a conductive material at a predetermined mixing ratio is used to form a positive electrode layer and a negative electrode layer. Reductions in electrode resistance and interface resistance and improvement of charging and discharging cycle characteristics are made possible.