Multilayer Silicon Oxide Negative Electrode for Battery Cycle Life

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Solution Overview

Problem

Silicon-based negative electrodes in nonaqueous electrolyte secondary batteries experience significant capacity retention rate degradation during rapid charge-discharge cycles due to volume changes, which affects their cycle life.

Innovation Solution

A negative electrode configuration with a multilayer structure, where the second layer contains a higher amount of alkali earth metal silicon oxide than the first layer, unevenly distributed to prevent surface reaction concentration, and a carbon material is included to enhance cycle life and capacity retention.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If a Si-based negative electrode active material is used to increase capacity, then the theoretical capacity is improved, but the capacity retention rate decreases due to large expansion and contraction during charge-discharge cycles

Engineering Contradiction:

ImprovecapacityVSAvoidcapacity retention rate

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The negative electrode active material layer is divided into multiple layers with different compositions. The first layer contains silicon oxide with alkali earth metal at a ratio of 5:45 to 15:85 (silicon oxide:carbon), while the second layer contains silicon oxide with alkali earth metal at a ratio of 20:80 to 40:60. This segmentation allows different regions to perform different functions - the first layer provides structural stability during volume changes, while the second layer ensures sufficient capacity, thereby resolving the contradiction between high capacity and good capacity retention rate.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the negative electrode active material layer are given different local compositions optimized for their specific functions. The first layer (closer to the current collector) has higher carbon content for structural stability during expansion/contraction, while the second layer (closer to the electrolyte interface) has higher silicon oxide content for active lithium insertion/extraction. This local quality differentiation allows simultaneous achievement of high capacity and good cycle stability.

Inventive Principle:

Principle #3Local quality

2Duration of action of stationary object

If a silicon composite oxide with MgSiO3 crystal and carbon coating is used to improve cycle life, then the capacity retention rate is improved, but the capacity retention rate greatly reduces when rapid charge-discharge cycle is performed

Engineering Contradiction:

Improvecycle lifeVSAvoidcapacity retention rate after rapid charge-discharge cycle

Core Design Contradiction:

Duration of action of stationary objectVSReliability

Solution Approach 1:

The invention changes the compositional parameters of the negative electrode active material layer by creating a two-layer structure with specific silicon oxide to carbon ratios in each layer. The first layer uses a ratio of 5:45 to 15:85 and the second layer uses 20:80 to 40:60, which optimizes both structural stability for cycle life and lithium ion conductivity for rapid charge-discharge performance, resolving the contradiction between cycle life and rapid charge-discharge capacity retention.

Inventive Principle:

Principle #35Parameter changes

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 configuration improves both the cycle life and capacity retention rate of the secondary battery during rapid charge-discharge cycles by ensuring efficient lithium ion dispersion and distribution, maintaining high performance over multiple cycles.

Implementation Method 1

an amount of the alkali earth metal in the second layer calculated based on energy dispersive X-ray spectroscopy using a scanning electron microscope image is higher than an amount of the alkali earth metal in the first layer

Methodology Applied

Scientific EffectEnergy dispersive X-ray spectroscopy:

Implementation Method 2

Si-based negative electrode active material described above has a high theoretical capacity, but has a large expansion and contraction (volume change) of the negative electrode active material with a charge-discharge cycle

Methodology Applied

Scientific EffectVolume change:

Data Source

PatentUS20220393148A1Negative electrode and nonaqueous electrolyte secondary battery including the same

Publication Date: 2022.12.08 PRIME PLANET ENERGY & SOLUTIONS INC

AI summary

The negative electrode disclosed herein includes: a negative electrode current collector; and a negative electrode active material layer formed on the surface of the negative electrode current collector. The negative electrode active material layer contains silicon oxide containing at least one alkali earth metal. The negative electrode active material layer includes at least a first layer and a second layer. The first layer is disposed between the second layer and the negative electrode current collector. The amount of the alkali earth metal in the second layer calculated based on energy dispersive X-ray spectroscopy using a scanning electron microscope image is higher than the amount of the alkali earth metal in the first layer.