Silicon Anode Doping Gradient for Longer Battery Cycle Life
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Solution Overview
Problem
Silicon-based negative electrode active materials in lithium secondary batteries face challenges with low initial efficiency and short service life due to large volume expansion and irreversible capacity, and existing doping methods either decrease discharge capacity or require uniform distribution of doping elements.
Innovation Solution
A negative electrode active material with a silicon-based composite where boron or phosphorus is distributed in an increasing concentration gradient from the center to the surface, prepared by mixing metal silicon with a doping source and heat-treating the mixture, allowing for improved lithium ion diffusion and reduced capacity loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If silicon particles are doped with doping element to improve cycle performance, then service life is improved, but discharge capacity is decreased
Solution Approach 1:
The doping element is distributed non-uniformly within the silicon particles, with higher concentration at the surface and lower concentration at the center. This local quality variation allows the surface to provide structural stability and cycle performance while the core silicon maintains high discharge capacity, thus resolving the contradiction between service life and discharge capacity.
2Ease of manufacture
If doping element is uniformly distributed in silicon particles, then manufacturing is simplified, but discharge capacity is decreased due to excessive doping
Solution Approach 1:
Instead of uniform distribution, the doping element is concentrated at the surface region of silicon particles. This can be achieved through surface treatment or controlled doping processes that target the surface, providing both manufacturing feasibility and preserved discharge capacity by limiting doping to where it is most needed for structural stability.
3Duration of action of stationary object
If total content of doping element is increased to improve cycle performance, then service life is improved, but discharge capacity is decreased
Solution Approach 1:
The doping element is strategically concentrated at the surface of silicon particles rather than being uniformly distributed throughout. This localized doping approach provides sufficient structural reinforcement for improved cycle performance while minimizing the total amount of doping element required, thereby preserving discharge capacity.
Solution Approach 2:
The silicon particles form a composite structure with the doping element, where the doping element acts as a surface layer or shell. This composite structure provides the benefits of structural stability and cycle performance enhancement while maintaining the high capacity characteristics of the core silicon material.
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
This approach enhances the initial efficiency, resistance performance, and service life of the battery while minimizing capacity loss by maximizing lithium ion diffusion on the surface without increasing the doping amount, facilitating mass production and maintaining high discharge capacity.
Implementation Method 1
heat-treating the resulting mixture at a temperature equal to or higher than the boiling point of the doping source
Implementation Method 2
the doping element is uniformly distributed in the silicon particles
Data Source
AI summary
A negative electrode active material, a negative electrode including the negative electrode active material, a secondary battery including the negative electrode, and a method for preparing the negative electrode active material are provided. The negative electrode active material includes a silicon-based composite which comprises silicon-based particles and one or more elements selected from the group consisting of B and P and distributed in the silicon-based particles, the silicon-based particles comprising Si in an amount of 95 parts by weight or more based on 100 parts by weight of the silicon-based particles, and the one or more elements having an increasing concentration gradient from a center to a surface of the silicon-based composite.