Silicon Alloy Core with Metal Oxide Shell for Battery Expansion Control
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Solution Overview
Problem
Lithium secondary batteries face challenges with silicon-based negative active materials due to volumetric expansion during charging and discharging, leading to reduced capacity and lifespan characteristics.
Innovation Solution
A negative active material comprising a silicon alloy core coated with a metal oxide shell, where the metal oxide is uniformly dispersed in a particulate form, acting as a protective layer to control expansion and prevent side reactions with the electrolyte, enhancing charge/discharge characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based negative active material is used, then battery capacity is improved, but volumetric expansion occurs during charging and discharging leading to reduced lifespan
Solution Approach 1:
The patent applies the nesting principle by coating silicon alloy particles with a metal oxide shell, creating a core-shell structure where the silicon alloy core is nested within the protective metal oxide shell. This structure allows the silicon core to expand and contract during lithium insertion/extraction while the shell constrains the expansion and prevents particle disintegration, thereby maintaining battery lifespan while preserving high capacity
Solution Approach 2:
The patent uses composite materials by combining silicon alloy with metal oxide to form a composite negative active material. The silicon alloy provides high lithium storage capacity while the metal oxide component provides structural stability and controls volumetric expansion. This composite structure synergistically addresses both the capacity requirement and the lifespan issue
2Productivity
If silicon alloy core is used to increase capacity, then initial efficiency is improved, but side reactions with electrolyte increase reducing overall performance
Solution Approach 1:
The patent applies the intermediary principle by introducing a metal oxide shell as a mediator between the silicon alloy core and the electrolyte. This shell acts as a protective barrier that prevents direct contact between the silicon alloy and electrolyte, thereby eliminating side reactions while still allowing lithium ion transport. The metal oxide shell serves as an intermediate layer that reconciles the need for high initial efficiency with the need to prevent harmful side reactions
Data Source
AI summary
Provided are a negative active material, an anode and a lithium secondary battery including the same, and a method of preparing the negative active material. The negative active material includes a silicon alloy core including silicon, iron, and manganese, and a shell including a metal oxide on the silicon alloy core, the metal oxide including one or more of titanium, zirconium, aluminum, cobalt, or lithium. An amount of the metal oxide may be from greater than 0 wt % to less than about 12 wt % based on a total weight of the negative active material.