Si-Sn-Al Ternary Alloy Negative Electrode for Li-Ion Batteries
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Solution Overview
Problem
Lithium ion secondary batteries using amorphous Si alloy negative electrodes face challenges in achieving a balance between high cycle durability and initial capacity, with conventional materials experiencing significant volumetric changes that reduce cycle life and capacity retention.
Innovation Solution
A negative electrode using a ternary Si alloy with specific compositions (Si x Sn y M z A a) and a current collector with predetermined elastic elongation, where M is Al, V, or C, to suppress amorphous-crystal phase transitions and accommodate volumetric changes during charge and discharge, ensuring high capacity and cycle durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Si material is used for negative electrode to achieve high energy density, then capacity is improved, but volumetric expansion causes reduction in cycle life
Solution Approach 1:
The patent applies composite materials by combining Si with Sn and Al to form a ternary alloy system. This composite structure allows the electrode to achieve high capacity from Si while Sn and Al components help accommodate volumetric expansion during lithium insertion/extraction, thereby maintaining cycle life. The composite material approach resolves the contradiction by integrating multiple elements with complementary functions.
Solution Approach 2:
The patent changes the compositional parameters by defining specific ranges for Si (31-50 mass%), Sn (0.1-15 mass%), and Al (15-68 mass%). By optimizing these parameter ranges, the electrode achieves a balance between high capacity (from Si) and good cycle life (from the synergistic effect of Sn and Al in managing volumetric changes).
2Reliability
If amorphous Si alloy is used to suppress phase transition, then cycle durability is improved, but initial capacity retention is insufficient
Solution Approach 1:
The ternary Si-Sn-Al alloy composite maintains an amorphous structure that suppresses harmful phase transitions during cycling, improving cycle durability. Simultaneously, the specific composition ratios (particularly optimizing Si content to 31-50 mass%) ensure sufficient initial capacity by balancing the capacity-contributing Si with the structure-stabilizing Sn and Al components.
Solution Approach 2:
The patent optimizes the compositional parameters within specific ranges to achieve both amorphous structure stability (for cycle durability) and high capacity (from sufficient Si content). The parameter optimization ensures that the amorphous phase is maintained while preventing excessive Si content that would cause expansion issues.
3Quantity of substance
If high Si content is used to increase capacity, then energy density is improved, but volumetric change increases causing plastic deformation
Solution Approach 1:
The patent uses composite materials by combining Si with Sn and Al in a ternary system. The Sn and Al components act as structural stabilizers that accommodate the volumetric changes associated with high Si content, preventing plastic deformation while maintaining high capacity. The composite structure distributes stress more evenly throughout the electrode.
Solution Approach 2:
The patent defines Si content within the range of 31-50 mass% rather than using maximum Si content. This parameter optimization ensures high capacity while limiting excessive volumetric change. The simultaneous presence of Sn (0.1-15 mass%) and Al (15-68 mass%) further modulates the structural stability parameter.
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 solution enables a lithium ion secondary battery with improved cycle life and initial capacity retention, as the ternary Si alloy and elastic current collector prevent plastic deformation and maintain even electrode distances, enhancing discharge capacity and durability.
Implementation Method 1
a battery using a material alloyed with Li for a negative electrode has higher energy density than the conventional battery using the carbon/graphite-based negative electrode material
Implementation Method 2
a current collector with predetermined elastic elongation, where M is Al, V, or C, to suppress amorphous-crystal phase transitions and accommodate volumetric changes during charge and discharge
Data Source
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AI summary
[TECHNICAL PROBLEM] There is provided a negative electrode for an electric device such as a Li ion secondary battery capable of exhibiting well-balanced characteristics of a high cycle property and a high initial capacity. [SOLUTION TO PROBLEM] The negative electrode for an electric device includes a current collector and an electrode layer containing a negative electrode active material, a conductive auxiliary agent and a binder and formed on a surface of the current collector, wherein the negative electrode active material contains an alloy represented by the following formula (1): SixSnyMzAa (in the formula (1), M is at least one metal selected from the group consisting of Al, V, C and a combination thereof, A is inevitable impurities, and x, y, z and a represent mass percent values and satisfy the conditions of 0<x<100, 0<y<100, 0<z<100, 0≤a<0.5, and x+y+z+a=100), and elastic elongation of the current collector is 1.30% or greater.