Silicon-Compound Battery Charging Stages for Fast Charge Cycle Stability

Solution Overview

Problem

Non-aqueous electrolyte secondary batteries with silicon compounds as negative electrode active materials face challenges in maintaining favorable cycle characteristics when charging, as increased current leads to material cracking and reduced charging efficiency, while low currents result in prolonged charging times.

Innovation Solution

A charging method involving a first constant current step and a large current charging step, with specific capacity ratios and current values, is implemented to efficiently charge the battery while minimizing cycle deterioration, using a charge control device to manage the charging process based on battery state and capacity ratios.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the charging current is increased to reduce charging time, then charging efficiency is improved, but cracking of the silicon compound occurs and cycle characteristics deteriorate

Engineering Contradiction:

Improvecharging efficiencyVSAvoidcycle characteristics

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The charging process is divided into multiple stages: a first charging step with a first constant current value, a second charging step with a second constant current value, and a large current charging step with a third constant current value. This segmentation allows the battery to be charged at different current rates at different states of charge, preventing silicon compound cracking while maintaining high charging efficiency

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The charging current is dynamically adjusted based on the battery's state of charge and the capacity ratio x of the silicon compound. The charging method transitions from lower current values when the silicon compound capacity ratio is higher to higher current values when the ratio is lower, optimizing both battery longevity and charging speed

Inventive Principle:

Principle #15Dynamics

2Reliability

If the charging current is reduced to prevent silicon compound cracking, then cycle characteristics are maintained, but charging time increases

Engineering Contradiction:

Improvecycle characteristicsVSAvoidcharging time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The charging process is divided into multiple stages: a first charging step with a first constant current value, a second charging step with a second constant current value, and a large current charging step with a third constant current value. This segmentation allows the battery to be charged at different current rates at different states of charge, preventing silicon compound cracking while maintaining high charging efficiency

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The charging current is dynamically adjusted based on the battery's state of charge and the capacity ratio x of the silicon compound. The charging method transitions from lower current values when the silicon compound capacity ratio is higher to higher current values when the ratio is lower, optimizing both battery longevity and charging speed

Inventive Principle:

Principle #15Dynamics

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 method enables high-efficiency charging in a short time while maintaining favorable cycle characteristics by optimizing the charging conditions for the silicon compound's capacity change region, reducing material cracking and enhancing lithium ion occlusion.

Implementation Method 1

a silicon compound such as silicon oxide represented by SiOx can occlude more lithium ions per unit volume than a carbon material such as graphite

Methodology Applied

Scientific EffectIon occlusion: Absorption (physical)

Data Source

PatentUS11811255B2Charging method of non-aqueous electrolyte secondary battery, and charging system of non-aqueous electrolyte secondary battery

Publication Date: 2023.11.07 PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO LTD

AI summary

A charging method of a non-aqueous electrolyte secondary battery involves a first charging step in which, defining x as the ratio of the capacity of a silicon compound to the rated capacity Q(0.1≤x≤0.5), a battery capacity Q1st that satisfies the expression below is charged at a first fixed current value; and a high current charging step in which, after completion of the first charging step, charging is performed at a fixed current value higher than the first fixed current value.0.38x+0.063−α≤Q1st/Q≤0.38x+0.063+α Expression: