Silicon Compound Negative Electrode with Phosphate Salt Coating
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Solution Overview
Problem
Lithium ion secondary batteries using silicon materials face challenges in achieving high battery capacity and stability due to the expansion and contraction of silicon-based negative electrode active materials during charge and discharge, leading to cracks and reduced cycle retention rates, and the modified silicon oxide materials have low water resistance, making industrial production difficult.
Innovation Solution
A negative electrode active material is developed with silicon compound particles coated with an aluminum or ammonium phosphate salt, enhancing water resistance and stability, and a carbon coat layer is optionally included to improve conductivity, thereby stabilizing the slurry and maintaining high battery capacity and cycle retention rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as the main raw material in the negative electrode active material to increase battery capacity, then the theoretical capacity increases significantly (10 times more than graphite), but the negative electrode active material undergoes expansion and contraction during charge and discharge, leading to cracks and deteriorated cycle property
Solution Approach 1:
The patent applies composite materials by combining silicon compound particles with carbon material particles to form a negative electrode active material. The carbon material serves as a matrix that accommodates the expansion and contraction of silicon during charge-discharge cycles, preventing cracks while maintaining high capacity. This composite structure resolves the contradiction between achieving high battery capacity through silicon and maintaining reliable cycle performance.
2Reliability
If silicon compound particles are modified to improve cycle characteristic and first efficiency, then the battery performance improves, but the modified particles have low water resistance, making industrial production difficult
Solution Approach 1:
The patent creates a composite structure where silicon compound particles are embedded in a carbon material matrix. The carbon material provides water resistance and structural stability, allowing the silicon compound to maintain its improved cycle characteristics while the overall composite gains the water resistance needed for industrial production and handling.
3Stability of the object's composition
If a coating type structure is used with carbon material to maintain stability, then the electrode structure is stable, but the battery capacity cannot be significantly increased
Solution Approach 1:
The patent transitions from a coating structure to a composite particle structure where silicon compound particles are integrated within a carbon material matrix. This composite approach maintains the structural stability provided by carbon while incorporating high-capacity silicon compounds, thereby achieving both stability and significantly increased battery capacity.
4Quantity of substance
If an integral type structure is used with silicon directly deposited onto current collector to increase capacity, then the battery capacity increases, but cracks occur readily near the surface during charge and discharge
Solution Approach 1:
The patent uses a composite material structure where silicon compound particles are dispersed within a carbon material matrix rather than depositing silicon directly onto the current collector. The carbon material provides a flexible, crack-resistant matrix that accommodates the volume changes of silicon during charge-discharge, maintaining surface integrity while preserving high capacity.
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 solution provides a stable and high-capacity negative electrode active material for non-aqueous electrolyte secondary batteries, enabling improved industrial production with enhanced cycle characteristics and first efficiency, suitable for various applications including electronic equipment and electric vehicles.
Implementation Method 1
the silicon compound particle is adhered with an aluminum phosphate salt or an ammonium phosphate salt in an outermost surface layer
Implementation Method 2
a carbon coat layer is optionally included to improve conductivity
Implementation Method 3
the negative electrode active material undergoes expansion and contraction during charge and discharge
Data Source
Figure 1~3
AI summary
The present invention relates to a negative electrode active material for a non-aqueous electrolyte secondary battery, wherein the negative electrode active material includes negative electrode active material particles, the negative electrode active material particles include a silicon compound particle which includes a silicon compound including oxygen, the silicon compound particle includes a Li compound, and the silicon compound particle is adhered with a phosphate salt in an outermost surface layer thereof. With this, the negative electrode active material which is high in the capacity and the stability to aqueous slurry as well as excellent in the cycle characteristic and the first efficiency can be provided.