Silicon-Based Negative Active Material for Lithium Battery Conductivity
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Solution Overview
Problem
Lithium secondary batteries with non-carbonaceous negative active materials face challenges in electrical conductivity and lifetime characteristics due to poor conductivity and large volume changes during charging and discharging, leading to reduced capacity retention rates and charge/discharge efficiencies.
Innovation Solution
A negative active material comprising a silicon-based core with randomly disposed island-type metal nitride and nanostructures, such as nanowires or carbon-based nanostructures, is developed, where the metal nitride is separated into two phases and the nanostructures are grown directly on the core or nitride, enhancing electrical conductivity and suppressing volume expansions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If non-carbonaceous negative active materials (such as silicon-based materials) are used to achieve high capacity, then the energy density is improved, but the electrical conductivity deteriorates
Solution Approach 1:
The patent uses composite materials by combining silicon-based core particles with metal nitride particles and carbon-based nanostructures. The silicon-based core provides high capacity, the metal nitride particles improve electrical conductivity, and the carbon-based nanostructures form conductive networks, creating a composite material that simultaneously achieves high capacity and good electrical conductivity.
Solution Approach 2:
The patent applies local quality by creating a heterogeneous structure where different components serve different functions: the silicon-based core provides high capacity in the interior, while metal nitride particles and carbon-based nanostructures are distributed on the surface to provide localized electrical conductivity enhancement where it is most needed for charge transfer.
2Quantity of substance
If non-carbonaceous negative active materials are used to achieve high capacity, then the energy density is improved, but the lifetime characteristics deteriorate
Solution Approach 1:
The patent applies beforehand cushioning by pre-forming a protective structure consisting of metal nitride particles and carbon-based nanostructures on the surface of silicon-based core particles before battery assembly. This protective structure cushions the silicon core against volume expansion stress during cycling, preventing particle disintegration and maintaining structural integrity over extended cycles, thereby improving lifetime characteristics.
3Quantity of substance
If silicon-based materials are used to achieve high capacity, then the energy density is improved, but the volume changes during charging and discharging increase
Solution Approach 1:
The patent uses a flexible shell approach by forming a composite structure where carbon-based nanostructures and metal nitride particles create a flexible protective layer around the silicon-based core. This shell structure can elastically expand and contract during lithium insertion/extraction, accommodating the volume changes of the silicon core without causing structural failure or particle disintegration.
Solution Approach 2:
The patent applies segmentation by dividing the negative active material into discrete components: silicon-based core particles, metal nitride particles, and carbon-based nanostructures. This segmented structure allows each component to independently handle volume changes, with the silicon cores expanding/contracting while the surrounding metal nitride and carbon structures provide structural support and maintain electrical connectivity throughout the cycling process.
4Quantity of substance
If silicon-based materials are used to achieve high capacity, then the energy density is improved, but the charge/discharge efficiencies deteriorate
Solution Approach 1:
The patent uses metal nitride particles as intermediaries between the silicon-based core and the electrolyte. These metal nitride particles facilitate charge transfer by providing conductive pathways that mediate the electrochemical reactions, improving charge/discharge efficiencies while allowing the silicon-based core to maintain its high capacity function.
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 proposed negative active material improves the electrical conductivity and lifetime characteristics of lithium batteries by reducing volume expansions and maintaining high capacity retention rates, as demonstrated by increased charge/discharge efficiencies and prolonged cycle life.
Implementation Method 1
the silicon-based core and the metal nitride are formed by separating one compound into two phases by phase inversion
Implementation Method 2
heat-treating a silicon-containing intermetallic compound under a nitrogen-containing gas atmosphere to prepare a silicon-based core on a surface of which particles of metal nitride are randomly formed
Implementation Method 3
heat-treating the silicon-based core on the surface of which the particles of metal nitride are randomly formed to prepare a complex in which nanostructures are formed on at least one of the silicon-based core or the metal nitride
Data Source
AI summary
Negative active materials, lithium batteries including the negative active materials, and methods of preparing the negative active materials. The negative active material includes a complex including: a silicon-based core; particles of metal nitride randomly disposed on the silicon-based core, and nanostructures disposed on at least one of the silicon-based core or the metal nitride. The negative active material may improve the electrical conductivity of a negative electrode. Accordingly, a lithium battery including the negative electrode may have improved lifetime characteristics.