Active Material Composite Coating for Si Anode Cycle Stability
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Solution Overview
Problem
Lithium-ion secondary batteries face challenges in improving cycle and rate characteristics due to the use of materials like Si or Si alloy as anode active materials, which cause volume expansion and low conductivity, leading to poor performance in high-power applications such as plug-in hybrid vehicles and power tools.
Innovation Solution
A composition for forming an active material composite comprising metals, metalloids, metal oxides, and conductive materials with a thermally cured layer, using a dispersant and crosslinking agent, which is formed at lower temperatures without carbonization, enhancing conductivity and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Si or Si alloy is used as anode active material to increase capacity, then battery capacity is improved, but volume expansion occurs causing poor cycle characteristics
Solution Approach 1:
A thin film coating layer is formed on the surface of the Si or Si alloy particles. This coating layer acts as a flexible shell that can accommodate volume expansion during lithium insertion/extraction cycles, preventing particle cracking and maintaining structural integrity, thus improving cycle characteristics while preserving high capacity.
Solution Approach 2:
The invention creates a composite material structure where Si or Si alloy particles are combined with a coating material (such as carbon-containing compound or metal oxide). This composite structure maintains the high capacity advantage of Si while the coating material provides structural stability and prevents harmful reactions, resolving the contradiction between capacity and cycle life.
2Reliability
If graphite is mixed to solve volume expansion problem, then cycle characteristics are improved, but uneven distribution during mixing degrades cycle characteristics
Solution Approach 1:
The coating material is applied to the Si particle surfaces before mixing with graphite. This preliminary coating action ensures uniform distribution of the protective layer on each particle, and when mixed with graphite, the coated particles maintain better dispersion and uniformity, avoiding the aggregation problems that occur with direct mixing of uncoated particles.
Solution Approach 2:
Instead of uniformly mixing graphite with uncoated Si particles (which leads to uneven distribution), the invention applies a local coating to each Si particle surface. This creates local quality enhancement where each particle has its own protective shell, ensuring consistent performance regardless of mixing uniformity.
3Reliability
If electrode active material surface is covered with organic compound and carbonized to increase conductivity, then electron conductivity is improved, but high temperature heat treatment is required
Solution Approach 1:
The invention changes the chemical composition parameters of the coating material from pure organic compounds (requiring high temperature carbonization) to materials containing metal elements or metal oxides. This parameter change allows the coating to provide electron conductivity through metallic pathways rather than requiring carbonization, thus achieving good conductivity at lower temperatures.
Solution Approach 2:
The invention substitutes the thermal carbonization process (high temperature heat treatment) with a chemical/metallurgical approach where metal-containing compounds are used as coating materials. These materials provide conductivity through their inherent metallic properties, replacing the need for high-temperature carbonization to create conductive carbon structures.
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 active material composite improves battery performance by providing excellent cycle and rate characteristics, facilitating high-speed charging and discharging, and reducing the risk of overheating and accidents.
Implementation Method 1
the surface of active material particles is covered with a thermally cured layer containing a conductive material
Implementation Method 2
a dispersant, a solvent, and a crosslinking agent
Data Source
AI summary
Provided is a composition for forming an active material composite that gives an active material composite that can be used for an electrode in a lithium ion secondary battery and the like and that can improve battery cycle and rate characteristics. A composition for forming an active material composite comprising at least one active material selected from a metal, a metalloid, a metal alloy, a metal oxide, a metalloid oxide, a metal phosphate, a metal sulfide, and a metal nitride, a conductive material, a dispersant, a solvent, and a crosslinking agent.