Silicon Oxide-Graphite Electrodes With Electrolyte-Stabilized Cycle Life

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Solution Overview

Problem

Lithium-ion batteries with silicon-based negative electrodes face challenges in achieving long cycle life due to structural changes and large volume expansions associated with lithium intercalation/alloying, leading to irreversible capacity loss and decreased cycling efficiency.

Innovation Solution

A lithium ion cell design incorporating a negative electrode with a blend of silicon oxide-based material and graphite, a nickel-rich lithium nickel cobalt manganese oxide positive electrode, and an electrolyte comprising fluoroethylene carbonate and a combination of dimethyl carbonate, methylethyl carbonate, and diethyl carbonate, which stabilizes the electrode structure and enhances cycling performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If silicon-based negative electrode material is used to increase energy density, then capacity is improved, but structural integrity deteriorates due to large volume expansion

Engineering Contradiction:

Improveenergy densityVSAvoidstructural integrity

Core Design Contradiction:

Quantity of substanceVSStability of the object's composition

Solution Approach 1:

The silicon-based electrode material is divided into nanoscale particles (average diameter 5-50 nm) to segment the volume expansion stress, preventing catastrophic structural failure while maintaining high capacity

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A composite electrode structure is created combining silicon oxide-based material (35-95 wt%) with graphite (5-65 wt%), where graphite provides structural stability and silicon oxide provides high capacity, achieving both energy density and structural integrity

Inventive Principle:

Principle #40Composite materials

2Quantity of substance

If high capacity silicon oxide-based material is used, then energy density is improved, but cycling stability deteriorates due to irreversible capacity loss

Engineering Contradiction:

Improveenergy densityVSAvoidcycling stability

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The electrolyte composition is optimized with specific concentrations (1M-2M lithium salt, 5-30 vol% FEC, 25-95 vol% linear carbonates) to change the electrochemical parameters, forming a stable SEI layer that enables long cycling life (>700 cycles at 1C rate)

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

Different components are assigned specific functions: silicon oxide provides high capacity regions, graphite provides stable cycling regions, and the electrolyte composition is locally optimized to form protective interfaces at the electrode surface

Inventive Principle:

Principle #3Local quality

3Stability of the object's composition

If nanoscale silicon oxide particles are used to reduce volume expansion, then structural stability is improved, but manufacturing complexity increases

Engineering Contradiction:

Improvestructural stabilityVSAvoidmanufacturing complexity

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The particle size parameter is precisely controlled to 5-50 nm range, which is small enough to accommodate volume expansion but large enough to be manufactured using existing nanomaterial synthesis techniques

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

The design achieves extended cycling stability, maintaining over 80% of initial capacity for more than 700 cycles at 1C charge/discharge rates, suitable for electric vehicle applications, by reducing irreversible capacity loss and improving energy density.

Implementation Method 1

electrolyte comprising from about 1M to about 2M lithium salt and non-aqueous solvent, wherein the non-aqueous solvent comprises at least about 5 volume percent fluoroethylene carbonate and at least about 25 volume percent combined amount of dimethyl carbonate, methylethyl carbonate and diethyl carbonate

Methodology Applied

Scientific EffectSolid electrolyte interphase formation:

Implementation Method 2

structural changes and large volume changes can destroy the structural integrity of the electrode, thereby decreasing the cycling efficiency

Methodology Applied

Scientific EffectLithium intercalation:

Implementation Method 3

structural changes and large volume changes can destroy the structural integrity of the electrode, thereby decreasing the cycling efficiency

Methodology Applied

Scientific EffectLithium alloying:

Implementation Method 4

the active material comprises from about 35 wt % to about 95 wt % silicon oxide-based material and from about 5 wt % to about 65 wt % graphite

Methodology Applied

Scientific EffectLithium intercalation:

Data Source

PatentUS11973178B2Lithium ion cells with high performance electrolyte and silicon oxide active materials achieving very long cycle life performance

Publication Date: 2024.04.30 IONBLOX INC

AI summary

Improved negative electrodes can comprise a silicon based active material blended with graphite to provide more stable cycling at high energy densities. In some embodiments, the negative electrodes comprise a blend of polyimide binder mixed with a more elastic polymer binder with a nanoscale carbon conductive additive. Electrolytes have been formulated that provide for extended cycling of cells incorporating a mixture of a silicon-oxide based active material with graphite active material in negative electrodes that can be matched with positive electrodes comprising nickel rich lithium nickel manganese cobalt oxides to cells with unprecedented cycling properties for large capacity cell based on a silicon negative electrode active material.