Secondary Battery Negative Electrode Composite for Cycle Stability
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Solution Overview
Problem
Conventional secondary batteries face issues with capacity deterioration during high-temperature charging and discharging, inadequate understanding of component interactions in lithium ion batteries, and compromised cycle properties due to added phosphate compounds for flame retardancy.
Innovation Solution
A secondary battery design featuring a negative electrode composed of a metal alloy, metal oxide, and carbon material, bound with a specific binder, and an electrolyte liquid containing phosphate esters, phosphonate esters, or bisphosphonate esters, which enhances flame retardancy and cycle performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a silicon oxide or silicate is used as a negative electrode active substance, then high energy density is achieved, but capacity deterioration becomes significantly large at 45°C or higher
Solution Approach 1:
The negative electrode uses a composite structure combining silicon oxide/silicate particles with carbon material particles. The carbon matrix provides structural stability and conductivity while the silicon oxide/silicate provides high capacity, resolving the contradiction between energy density and cycle stability at elevated temperatures.
Solution Approach 2:
The invention applies different materials to different regions of the negative electrode: silicon oxide/silicate in specific proportions (0.1-5 mass%) provides localized high capacity regions, while the carbon material provides a stable matrix throughout, allowing simultaneous achievement of high energy density and reliable cycling.
2Object-affected harmful factors
If phosphate compounds are added to the electrolyte liquid to impart flame retardancy, then safety is improved, but cycle property is lowered
Solution Approach 1:
The invention optimizes the phosphate compound content to a specific range (0.1-5 mass%) and selects specific phosphate ester compounds with particular molecular structures. This parameter optimization maintains adequate flame retardancy while minimizing the detrimental effect on cycle properties.
Solution Approach 2:
The patent applies different phosphate compound types and concentrations to different electrolyte formulations based on the specific battery application requirements, allowing tailored balance between flame retardancy and cycle performance for different use cases.
3Object-affected harmful factors
If the amount of phosphate compound is increased to improve flame retardancy, then safety is enhanced, but cycle property deteriorates further
Solution Approach 1:
The invention establishes an optimal concentration range for phosphate compounds (0.1-5 mass%) and identifies specific compound types that provide adequate flame retardancy at lower concentrations, thereby preserving cycle properties. This avoids the need to increase phosphate content excessively.
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 high-performance secondary battery with improved flame retardancy and cycle properties by stabilizing the negative electrode and optimizing the electrolyte composition.
Implementation Method 1
a metal (a) capable of being alloyed with lithium
Implementation Method 2
a metal oxide (b) capable of occluding and releasing lithium ions
Implementation Method 3
a carbon material (c) capable of occluding and releasing lithium ions
Data Source
AI summary
An objection is to provide a high performance secondary battery having good flame retardancy and cycle properties. The present exemplary embodiment provides a secondary battery comprising an electrode assembly in which a positive electrode and a negative electrode are arranged to face each other, an electrolyte liquid and a package accommodating the electrode assembly and the electrolyte liquid, wherein the negative electrode is formed by binding a negative electrode active substance comprising a metal (a) capable of being alloyed with lithium, a metal oxide (b) capable of occluding and releasing lithium ions and a carbon material (c) capable of occluding and releasing lithium ions, to a negative electrode current collector, with a negative electrode binder, and the electrolyte liquid comprises a supporting salt and an electrolytic solvent, the electrolytic solvent comprising at least one phosphate ester compound selected from phosphite esters, phosphonate esters and bisphosphonate esters.