SiOx Anode Core-Shell Composite for Initial Efficiency and Cycle Life
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Solution Overview
Problem
Lithium secondary batteries face challenges with low initial coulombic efficiency and capacity due to the formation of an irreversible phase and large volume expansion in silicon-based materials, which affects battery life and stability.
Innovation Solution
A negative electrode active material is developed using a core-shell composite structure comprising silicon oxide and metal silicate with a metal-substituted organic compound shell, which effectively removes residual metal compounds and suppresses volume expansion, improving initial efficiency and capacity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based materials are used to increase capacity, then battery capacity is improved, but initial coulombic efficiency decreases due to irreversible phase formation
Solution Approach 1:
The patent applies preliminary action by pre-coating the silicon-based active material with a carbon layer before battery assembly. This carbon coating is applied in advance to prevent irreversible phase formation during initial charging cycles, thereby improving initial coulombic efficiency while maintaining high capacity. The coating is formed through controlled carbonization of organic compounds on the silicon surface prior to battery operation.
Solution Approach 2:
The patent uses composite materials by creating a core-shell structure where silicon-based active material forms the core and a carbon-containing compound forms the shell. This composite structure combines the high capacity advantage of silicon with the stability and conductivity benefits of carbon, resolving the contradiction between capacity and initial efficiency.
2Quantity of substance
If silicon-based materials are used to increase capacity, then battery capacity is improved, but volume expansion occurs affecting battery life
Solution Approach 1:
The patent employs flexible shells by using a carbon-containing compound coating that can accommodate volume expansion of the silicon core during lithiation. This thin film shell acts as a buffer that absorbs expansion stress, preventing particle cracking and maintaining structural integrity over multiple cycles, thereby extending battery life while preserving high capacity.
Solution Approach 2:
The patent applies beforehand cushioning by pre-forming a compliant carbon-containing compound layer on the silicon particles before they undergo volume expansion. This layer serves as a cushion that absorbs expansion forces during subsequent charging cycles, preventing mechanical degradation and extending battery operational life.
3Reliability
If metal compounds are added to improve performance, then battery characteristics are improved, but residual metal compounds increase slurry pH causing side reactions
Solution Approach 1:
The patent uses an intermediary approach by introducing a carbon-containing compound as a mediating layer between the metal compounds and the electrolyte environment. This intermediate coating controls the interaction between metal compounds and slurry, preventing excessive pH increase and side reactions while still allowing the metal compounds to provide their performance benefits.
Solution Approach 2:
The patent converts the harmful effect of residual metal compounds into a benefit by using controlled carbonization to transform them into stable carbon-containing compounds. The metal compounds that would otherwise cause pH increase and side reactions are converted into stable structures that provide both the desired performance enhancement and reduced chemical reactivity.
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 core-shell composite structure enhances battery stability and life characteristics by reducing slurry pH issues and side reactions, leading to improved initial efficiency and capacity retention during charge and discharge cycles.
Implementation Method 1
a composite production process of mixing the metal-doped silicon compound with an organic compound and performing a heat treatment to prepare a composite
Implementation Method 2
a pretreatment process of mixing a silicon compound and an alkali metal or alkaline earth metal precursor and performing a heat treatment to dope a metal into the silicon compound
Implementation Method 3
performing a heat treatment to prepare a composite
Implementation Method 4
the core-shell composite structure comprising silicon oxide and metal silicate with a metal-substituted organic compound shell, which effectively removes residual metal compounds and suppresses volume expansion
Data Source
AI summary
Provided is a negative electrode active material for a secondary battery including a core-shell composite including: a core including a silicon oxide (SiOx, 0<x≤2) and a metal silicate in at least a part of the silicon oxide; and a shell including a metal-substituted organic compound, wherein the metal of the metal silicate and the substituted metal of the organic compound are independent of each other, wherein each of the metal of the metal silicate and the substituted metal of the organic compound includes an alkali metal or an alkaline earth metal.