Carbon-Coated Polymer Negative Electrode for Battery Efficiency

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Solution Overview

Problem

The compensation for irreversible capacity in nonaqueous electrolyte secondary batteries using silicon oxide and graphite in the negative electrode is insufficient.

Innovation Solution

A negative electrode comprising a carbon material with a surface coated by a polymer that does not react with lithium, combined with a metal or metal oxide that forms an alloy with lithium, improves the initial charge-discharge efficiency by facilitating lithium supply.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If a metal material or oxide that forms an alloy with lithium is used as a negative electrode active material, then energy density and output are improved, but irreversible capacity increases due to incomplete lithium extraction during discharge

Engineering Contradiction:

ImproveoutputVSAvoidirreversible capacity

Core Design Contradiction:

PowerVSLoss of energy

Solution Approach 1:

Lithium is supplied to the negative electrode in advance (before actual use) to compensate for the irreversible capacity that will occur during initial charge-discharge cycles. This preliminary lithium supply ensures that sufficient lithium is available for subsequent reversible cycling.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The negative electrode uses a composite structure combining carbon material (graphite) with metal material or oxide that forms an alloy with lithium. The carbon material provides stable lithium insertion/extraction, while the alloy-forming material provides high capacity, together achieving both high output and reduced irreversible capacity loss.

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If lithium is supplied to compensate for irreversible capacity of silicon oxide, then capacity is improved, but the compensation is insufficient in nonaqueous electrolyte secondary batteries

Engineering Contradiction:

Improvelithium supplyVSAvoidcompensation effectiveness

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

A polymer material that does not react with lithium is introduced as an intermediary substance in the nonaqueous electrolyte system. This polymer mediates the lithium supply process, enabling more effective lithium compensation to the silicon oxide while maintaining system stability.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention changes the chemical composition parameters of the electrolyte system by introducing a specific polymer material that does not react with lithium. This parameter change (adding non-reactive polymer) fundamentally alters how lithium is supplied and retained in the system, achieving sufficient compensation effectiveness.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If a polymer material that does not react with lithium is used, then initial charge-discharge efficiency is improved, but device complexity increases

Engineering Contradiction:

Improveinitial charge-discharge efficiencyVSAvoidelectrode structure

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The polymer material that does not react with lithium is applied locally to specific components (carbon material surfaces) rather than throughout the entire electrode. This localized application improves initial charge-discharge efficiency at the critical interface while minimizing overall structural complexity.

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 a carbon material coated with a non-reactive polymer enhances lithium supply to the metal or metal oxide, leading to improved initial charge-discharge efficiency and capacity in nonaqueous electrolyte secondary batteries.

Implementation Method 1

a polymer material that does not react with lithium

Methodology Applied

Scientific EffectChemical inertness:

Implementation Method 2

a metal or metal oxide that forms an alloy with lithium

Methodology Applied

Scientific EffectAlloy formation:

Data Source

PatentUS10056606B2Negative electrode for nonaqueous electrolyte secondary battery and nonaqueous electrolyte secondary battery

Publication Date: 2018.08.21 PANASONIC ENERGY CO LTD

AI summary

It is an object to improve the initial charge-discharge efficiency of a nonaqueous electrolyte secondary battery that uses, as negative electrode active materials, a carbon material and a metal or metal oxide that forms an alloy with lithium. There is provided a nonaqueous electrolyte secondary battery including a positive electrode, a nonaqueous electrolyte, and a negative electrode which includes, as negative electrode active materials, a carbon material and a metal or metal oxide that forms an alloy with lithium and in which at least part of a surface of the carbon material is coated with a polymer material that does not react with lithium. The mass percentage of the polymer material that does not react with lithium relative to the carbon material is preferably 0.5 to 2 mass %.