Alloy Negative Electrode Active Material with 10 nm Oxide Layer
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Solution Overview
Problem
Graphite-based negative electrode active materials in lithium ion batteries face challenges with capacity deterioration due to significant volume expansion and contraction during charging/discharging, leading to reduced electron conductivity and short battery life.
Innovation Solution
A negative electrode active material comprising a powder material with an alloy phase that undergoes thermoelastic diffusionless transformation, coated with an oxide layer of thickness not exceeding 10 nm, to mitigate strain and enhance discharge capacity and cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If alloy-based negative electrode active materials are used to increase capacity, then discharge capacity per volume is improved, but charge-discharge cycle characteristics deteriorate due to large volume expansion and contraction
Solution Approach 1:
The patent applies parameter changes by controlling the oxide layer thickness to not more than 10 nm. This specific parameter control allows the alloy-based negative electrode active material to achieve high discharge capacity per volume while maintaining good charge-discharge cycle characteristics, resolving the contradiction between capacity and reliability
Solution Approach 2:
The patent uses composite materials by forming an oxide layer on the surface of the alloy-based negative electrode active material. This composite structure (alloy core + oxide shell) enables the material to benefit from both the high capacity of the alloy and the stability provided by the oxide layer, improving cycle characteristics while maintaining high discharge capacity
2Quantity of substance
If alloy-based negative electrode active materials undergo repeated charging and discharging, then battery capacity increases, but cracking occurs in the negative electrode compound leading to rapid capacity decrease
Solution Approach 1:
The patent applies beforehand cushioning by pre-forming an oxide layer on the surface of the alloy-based negative electrode active material before battery assembly. This oxide layer acts as a protective cushion that absorbs and distributes the stress from volume expansion and contraction during charging and discharging, preventing cracking in the negative electrode compound and maintaining structural integrity throughout the battery's operational life
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 significantly improves discharge capacity per volume and charge-discharge cycle characteristics by relaxing strain through thermoelastic diffusionless transformation and controlling the oxide layer thickness, resulting in higher capacity retention and extended battery life.
Implementation Method 1
The powder material contains an alloy phase which undergoes thermoelastic diffusionless transformation when releasing metal ions or occluding metal ions
Implementation Method 2
The oxide layer is formed on the surface of the powder material, and has a thickness of not more than 10 nm. The negative electrode active material can improve the discharge capacity per volume and the charge-discharge cycle characteristics
Data Source
AI summary
Provided is a negative electrode active material that can improve the discharge capacity per volume and charge-discharge cycle characteristics. The negative electrode active material of the present embodiment includes a powder material and an oxide layer. The powder material contains an alloy phase which undergoes thermoelastic diffusionless transformation when releasing metal ions or occluding the metal ions. The oxide layer is formed on the surface of the powder material, and has a thickness of not more than 10 nm.