Boron-Containing Graphite Negative Electrode for Battery Storage Durability

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Solution Overview

Problem

Nonaqueous secondary batteries face challenges with graphite negative electrodes due to side reactions with electrolyte solutions, leading to reduced storage durability and reliability.

Innovation Solution

The use of boron-containing graphite with specific average discharge potentials (0.16 V to 0.2 V) and interlayer distances (3.348 to 3.352 angstroms) as the negative electrode active material, which suppresses side reactions and enhances storage durability by controlling boron content and firing conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If graphite is used as negative electrode active material, then high discharge capacity density is achieved, but side reaction with electrolyte solution occurs leading to reduced storage durability

Engineering Contradiction:

Improvestorage durabilityVSAvoidside reaction with electrolyte solution

Core Design Contradiction:

ReliabilityVSObject-generated harmful factors

Solution Approach 1:

The invention changes the chemical composition parameter by incorporating boron into the graphite structure at specific concentrations (0.01-3 wt%). This compositional modification alters the electrochemical properties of graphite, raising the discharge potential from typical values below 0.1 V to 0.16-0.2 V, thereby reducing the driving force for side reactions with the electrolyte while maintaining lithium insertion/extraction capability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention creates a composite material system by combining boron with graphite to form boron-containing graphite. This composite structure leverages the high capacity properties of graphite while incorporating boron's ability to modulate electrochemical potential and suppress parasitic reactions, achieving synergistic effects that improve storage durability

Inventive Principle:

Principle #40Composite materials

2Reliability

If boron content is increased to suppress side reaction, then storage durability improves, but discharge capacity density may be affected

Engineering Contradiction:

Improvestorage durabilityVSAvoiddischarge capacity density

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

The invention optimizes the boron content parameter within a specific range (0.01-3 wt%, preferably 0.03-0.5 mass%) to achieve the desired balance. This controlled parameter adjustment ensures sufficient boron incorporation to raise discharge potential and suppress side reactions, while preventing excessive boron that would replace carbon atoms and reduce lithium insertion sites, thereby maintaining high discharge capacity

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentEP3404744B1Negative electrode active material and nonaqueous secondary battery

Publication Date: 2022.03.09 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

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AI summary

A negative electrode active material for a nonaqueous secondary battery includes graphite containing boron. The graphite has an average discharge potential of 0.16 V or more and 0.2 V or less, based on Li. A nonaqueous secondary battery includes: a positive electrode including a positive electrode active material capable of occluding and releasing an alkali metal ion; a negative electrode including a negative electrode active material above; and a nonaqueous electrolyte solution.