Silicon Negative Electrode Amorphous Surface Layer
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Solution Overview
Problem
Current lithium-ion batteries face challenges in achieving high energy and output densities due to limitations in the negative electrode material, particularly with silicon particles that expand and pulverize during charge and discharge cycles, leading to reduced battery life and internal resistance issues.
Innovation Solution
A method involving the use of silicon particles with an amorphous surface layer and silicon-carbon composites, combined with a conductive composition including carbon, to enhance electronic conductivity and prevent oxidation, is developed. This involves a dry grinding and wet grinding process to create a slurry for the negative electrode, using non-protic solvents and additives like coal-tar pitch to disperse silicon particles effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon particles are used as negative electrode active material to increase capacity, then energy density is improved, but volume expansion and pulverization occur during charge/discharge cycles reducing reliability
Solution Approach 1:
The silicon particles are divided into fine particulates with controlled size distribution (D50: 0.5-5 μm) to reduce overall volume expansion impact and improve structural stability during charge/discharge cycles
Solution Approach 2:
Silicon particles are combined with carbon materials (graphite, amorphous carbon) to form composite negative electrode structures. The carbon matrix provides structural support and conductivity while accommodating silicon volume expansion, preventing pulverization and maintaining reliability
2Duration of action of stationary object
If mechanical grinding is used to reduce silicon particle size to prevent pulverization, then service life is improved, but oxidation occurs during grinding reducing purity
Solution Approach 1:
Mechanical grinding is performed in an inert atmosphere (nitrogen or argon gas) to prevent oxidation of silicon particle surfaces during size reduction, maintaining material purity while achieving desired particle size for improved service life
3Reliability
If graphite is used as negative electrode material to ensure stability, then reliability is improved, but lithium ion intercalation is limited to 1/6 ratio reducing energy density
Solution Approach 1:
Graphite and silicon particles are combined in composite negative electrode structures, merging the high stability and good conductivity of graphite with the high lithium ion capacity of silicon, achieving both reliability and high energy density
4Quantity of substance
If silicon content is increased to achieve high capacity, then energy density is improved, but internal resistance increases reducing output density
Solution Approach 1:
Carbon materials are selectively distributed in the negative electrode structure, particularly at silicon particle surfaces and within the conductive matrix, to provide localized high conductivity pathways that compensate for silicon's lower conductivity and reduce internal resistance
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 results in a negative electrode with improved energy density, output density, and extended charging/discharging life cycle, while also enhancing the electronic conductivity of the battery, thus addressing the limitations of existing materials.
Implementation Method 1
a silicon particle having an amorphous surface layer... to prevent the aforementioned pulverization
Implementation Method 2
Grinding by the wet beads mill has problems of... (3) suppressing ground particles from re-aggregating
Implementation Method 3
attempts have been conducted for extending the service life of the negative electrode of the battery by grinding silicon or silicon alloys into particulates
Data Source
AI summary
The present invention relates to a negative electrode active material for a secondary battery, a conductive composition for a secondary battery, a negative electrode material including the same, a negative electrode structure and secondary battery including the same, and a method for manufacturing the same. The present invention includes: a silicon particle; and an amorphous surface layer formed on the surface of the silicon particle. According to the present invention, the negative electrode structure is formed of a composite of a silicon particle and carbon or lithium ion, the oxygen contents of the solid electrolyte and silicon particles are low, and thus aggregation of silicon particles is inhibited. Therefore, in the event of using the negative electrode structure in a negative electrode, a power storage device such as a lithium secondary battery may have high energy density, high output density, and a longer charging/discharging life cycle.