Si-Mn Alloy Negative Electrode Active Material for Lithium Batteries
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Solution Overview
Problem
Lithium secondary batteries face challenges in maintaining high capacity and lifespan due to volumetric changes during charging and discharging, which lead to electrode deterioration and reduced cycle characteristics.
Innovation Solution
A negative electrode active material composed of silicon (Si), manganese (Mn), and a combination of metals like iron (Fe), molybdenum (Mo), chromium (Cr), zinc (Zn), titanium (Ti), and nickel (Ni), along with carbon, is developed, where the atomic ratio of Mn to these metals is optimized to suppress volumetric changes, and carbon is incorporated both within and outside the Si-M-carbon structure to enhance capacity retention and lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If silicon is used as negative electrode active material to increase capacity, then energy density is improved, but volumetric change during charging and discharging increases causing electrode deterioration
Solution Approach 1:
The patent uses a composite material system consisting of Si-Mn alloy particles embedded in a carbon matrix. The carbon matrix provides structural stability and accommodates volumetric changes, while the Si-Mn alloy provides high capacity. This composite structure resolves the contradiction by combining the high energy density of silicon with the structural stability of carbon, preventing electrode deterioration during cycling.
Solution Approach 2:
The patent optimizes the atomic ratio of Mn to Component A (other metals) in the Si-Mn alloy to be between 1:9 and 9:1. This parameter optimization controls the volumetric expansion characteristics of the alloy during lithium insertion/extraction. By adjusting this compositional parameter, the patent achieves a balance between maintaining high silicon content for capacity and controlling volumetric changes to prevent electrode deterioration.
2Quantity of substance
If high amount of silicon is used to achieve high capacity, then discharge capacity is improved, but capacity retention after cycling deteriorates
Solution Approach 1:
The carbon matrix acts as a flexible shell that surrounds and protects the Si-Mn alloy particles. This carbon shell accommodates the volumetric expansion and contraction of silicon during charging and discharging cycles, maintaining structural integrity. The flexible carbon matrix prevents particle aggregation and electrode disintegration, thereby improving capacity retention over extended cycling while preserving high discharge capacity from the silicon content.
3Reliability
If conventional negative electrode materials are used to ensure stability, then electrode durability is maintained, but energy density and charge-discharge capacity are limited
Solution Approach 1:
The patent creates a composite material where Si-Mn alloy particles (providing high capacity) are embedded in a carbon matrix (providing durability). This composite structure allows the electrode to achieve both high charge-discharge capacity from the silicon-based alloy and excellent durability from the stable carbon matrix, overcoming the limitations of conventional single-material electrodes that must choose between stability and high capacity.
Data Source
AI summary
A negative electrode active material for a lithium secondary battery including silicon (Si), manganese (Mn), Component A including at least one selected from iron (Fe), molybdenum (Mo), chromium (Cr), zinc (Zn), titanium (Ti), nickel (Ni), vanadium (V), tungsten (W), and yttrium (Y), and Component B including at least one selected from carbon (C), boron (B), oxygen (O), nitrogen (N), phosphorous (P), and sulfur (S), wherein a total amount of Si, Mn, and Component A is about 70 atom % or less, an amount of Component B is 30 atom % or more, and a total amount of Mn and Component A is in a range of about 10 atom % to about 35 atom %.