Tin Composite Negative Electrode for Lithium Battery Capacity Retention
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Solution Overview
Problem
Lithium batteries using metal alloy negative electrodes face challenges with capacity retention due to volume expansion and electrolyte decomposition, leading to particle disconnection and reduced capacity retention when charged and discharged repeatedly.
Innovation Solution
Incorporating composite negative electrode active material particles of tin (Sn) with conductive metal particles, such as copper, nickel, or iron, forming intermetallic compounds, with an average particle size of at least 10 μm to suppress aggregation and optimize electrolyte decomposition, while maintaining a suitable weight ratio and using a method like mechanical milling to prepare the electrode material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If metal alloyable with lithium (e.g., Si, Sn, Al) is used as negative electrode active material to achieve higher electric capacity than graphite, then the electric capacity increases, but the volume expands and contracts during charging and discharging, isolating active material and accelerating electrolyte decomposition, resulting in low capacity retention
Solution Approach 1:
The patent embeds metal alloy particles (Si, Sn, or Al) inside carbon particles to form composite negative electrode active material particles. The carbon matrix acts as a container that accommodates the volume expansion and contraction of the metal alloy during lithiation and delithiation, preventing particle isolation while maintaining electrical conductivity and structural integrity, thus resolving the contradiction between high capacity and capacity retention
Solution Approach 2:
The patent creates composite negative electrode active material particles consisting of metal alloy particles embedded in carbon particles. This composite structure combines the high capacity advantage of metal alloys with the structural stability and conductivity of carbon, enabling both high electric capacity and excellent capacity retention by synergistically utilizing the properties of both materials
2Reliability
If graphite is used as negative electrode active material, then capacity retention is excellent and volume stability is high, but the theoretical electric capacity is limited to only about 372 mAh/g
Solution Approach 1:
The patent creates composite negative electrode active material particles combining metal alloy particles with carbon particles. This composite structure enables the electrode to achieve electric capacity higher than pure graphite while maintaining excellent capacity retention, as the metal alloy provides high capacity and the carbon matrix provides structural stability
3Stability of the object's composition
If conductive metal particles with small particle size are used to improve mixing homogeneity, then the homogeneity increases, but the specific surface area increases, accelerating electrolyte decomposition reaction
Solution Approach 1:
The patent specifies that conductive metal particles should have an average particle size of at least 10 μm. This parameter change balances the competing requirements: particles large enough to limit specific surface area and reduce electrolyte decomposition, yet small enough to achieve adequate mixing homogeneity in the electrode slurry
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 approach significantly improves capacity retention ratios of lithium batteries by preventing particle disconnection and maintaining high initial capacity over multiple charge-discharge cycles, as demonstrated by the capacity retention ratios in the examples.
Implementation Method 1
The conductive metal particles may form an intermetallic compound with the Sn
Implementation Method 2
an average particle size of the conductive metal particles is at least 10 μm... aggregation of the Sn may be suppressed, even when a lithium battery including the negative electrode is repeatedly charged and discharged
Implementation Method 3
When such a metal is charged and discharged, the volume of the metal expands and contracts, thereby isolating an active material in an electrode
Data Source
AI summary
A negative electrode, a lithium battery employing the negative electrode, and a method of preparing the negative electrode. The negative electrode includes a current collector, and a negative electrode active material layer disposed on the current collector. The negative electrode active material layer includes: composite negative electrode active material particles comprising tin (Sn), and conductive metal particles. The conductive metal particles form an intermetallic compound with the Sn, and an average particle size of the conductive metal particles is at least 10 μm.