Lithium Carbonate Coated Cathode for Solid State Battery

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Solution Overview

Problem

The hardening of borate and silicate coating layers in cathode active materials for all-solid lithium batteries leads to decreased contact points and increased reaction resistance between the cathode active material and the solid electrolyte, compromising battery durability.

Innovation Solution

A coated active material with a soft coating layer containing lithium carbonate and Li ion conductive oxides, such as Li4SiO4—Li3BO3 or LiNbO3, is used to inhibit reaction resistance by increasing the contact area between the cathode active material and the solid electrolyte.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If borate and silicate are used for the coating layer to inhibit reaction between cathode active material and solid electrolyte material, then interface resistance is reduced, but the coating layer hardens and decreases contact area between coated active material particles

Engineering Contradiction:

Improveinterface resistanceVSAvoidcontact area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The coating layer is formed as a composite material containing both borate/silicate components (for reaction inhibition and low interface resistance) and carbonate components (for softness and high contact area). This composite structure allows the coating to simultaneously achieve chemical stability at the interface and mechanical softness for particle contact, resolving the contradiction between interface resistance reduction and contact area maintenance.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention changes the physical and chemical parameters of the coating layer by controlling the composition ratio between borate/silicate (electrochemically stable components) and carbonate (soft components). By adjusting these parameters, the coating layer achieves an optimal balance between hardness (for reaction inhibition) and softness (for contact area), directly addressing the technical contradiction.

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If a hard coating layer is formed to prevent reaction between cathode active material and solid electrolyte material, then chemical stability is improved, but reaction resistance increases due to decreased contact points

Engineering Contradiction:

Improvechemical stabilityVSAvoidreaction resistance

Core Design Contradiction:

Stability of the object's compositionVSReliability

Solution Approach 1:

The coating layer uses a composite formulation where borate/silicate provide chemical stability and reaction inhibition, while carbonate components provide softness to maintain contact points. This composite approach allows simultaneous achievement of chemical stability and low reaction resistance, resolving the contradiction between these two properties.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The coating layer exhibits local quality differentiation where different regions or phases within the coating serve different functions: the borate/silicate phase provides chemical stability at the interface with solid electrolyte, while the carbonate phase provides softness for particle-to-particle contact. This local functional differentiation resolves the contradiction between chemical stability and reaction resistance.

Inventive Principle:

Principle #3Local quality

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 use of lithium carbonate in the coating layer softens the coating layer, enhancing the contact area and reducing reaction resistance, thereby improving the performance and durability of lithium solid state batteries.

Implementation Method 1

the inclusion of lithium carbonate in the coating layer allows the coating layer to be softened

Methodology Applied

Scientific EffectSoftening effect of lithium carbonate:

Implementation Method 2

containing an Li ion conductive oxide

Methodology Applied

Scientific EffectIon conduction: Conduction (electrical)

Implementation Method 3

the formation of the reaction inhibition unit having a polyanion structure with high electrochemical stability at the interface between a cathode active material and a solid electrolyte material inhibits interface resistance

Methodology Applied

Scientific EffectReaction inhibition:

Data Source

PatentUS9214674B2Coated active material and lithium solid state battery

Publication Date: 2015.12.15 TOYOTA JIDOSHA KK

AI summary

The problem of the present invention is to provide a coated active material having a soft coating layer and capable of improving a contact area. The present invention solves the above-mentioned problem by providing a coated active material comprising a cathode active material and a coating layer for coating the above-mentioned cathode active material, containing an Li ion conductive oxide, wherein the above-mentioned coating layer further contains lithium carbonate.