Silicon Core Composite Negative Material for Lithium Battery Stability
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Solution Overview
Problem
Silicon-based materials used in lithium secondary batteries undergo significant volume expansion during lithium ion intercalation and deintercalation, leading to mechanical strain, degradation, and reduced electrochemical characteristics such as lifespan.
Innovation Solution
A composite negative active material is developed, comprising a silicon core coated with a water-insoluble polymer composite where anionic components like F−, PO43−, PF6−, BO33−, and BF4− are chemically bonded to a water-soluble polymer, enhancing the material's stability and binding strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based material is used as negative active material to achieve high capacity, then battery capacity is improved, but material stability and lifespan deteriorate due to volume expansion during cycling
Solution Approach 1:
The patent applies composite materials by combining silicon-based material with carbon material to form a composite negative active material. The carbon material forms a coating layer on the silicon-based material, creating a composite structure that maintains the high capacity advantage of silicon while adding the stability and volume tolerance of carbon, thereby resolving the contradiction between capacity and lifespan
Solution Approach 2:
The patent uses a carbon-based coating layer as a flexible shell surrounding the silicon-based material core. This thin film structure allows for volume expansion and contraction during lithium ion intercalation and deintercalation, accommodating the mechanical strain without causing material degradation, thus improving both stability and lifespan while maintaining high capacity
2Quantity of substance
If pure silicon material is used to maximize lithium ion intercalation capacity, then electrochemical capacity is improved, but mechanical strain and degradation increase during cycling
Solution Approach 1:
The patent creates a composite structure where silicon-based material (providing high lithium ion intercalation capacity) is combined with carbon material (providing mechanical strength). The carbon coating layer maintains structural integrity during volume changes, preventing degradation while preserving the high capacity of pure silicon
Solution Approach 2:
The carbon-based coating layer acts as a protective cushion applied beforehand to the silicon-based material. This pre-formed protective layer absorbs and distributes mechanical strain during volume expansion and contraction, preventing direct stress on the silicon material and thereby maintaining both high capacity and structural integrity
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 composite material improves the electrochemical characteristics, including lifespan, by preventing irreversible reactions and maintaining stability during volume changes, thus enhancing the performance of lithium secondary batteries.
Implementation Method 1
the at least one anionic component is chemically bonded to a water-soluble polymer
Implementation Method 2
a coating layer disposed on the core, wherein the coating layer includes a water-insoluble polymer composite
Data Source
AI summary
A composite negative active material, and a negative electrode and a lithium secondary battery that include the composite negative active material, and a method of preparing the composite negative active material are disclosed. The composite negative active material includes: a core including a silicon material and a coating layer disposed on the core, wherein the coating layer includes a water-insoluble polymer composite in which at least one anionic component is chemically bonded to a water-soluble polymer, thereby improving lifespan characteristics of the composite negative active material.