Lithium Transition Metal Silicate Coated Cathode for Battery Safety
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Solution Overview
Problem
Current positive active materials for secondary lithium batteries, such as LiCoO2 and LiNixCoyM1-x-yO2, face issues with safety performance, cycling stability, and thermal stability due to cobalt toxicity, high cost, and limitations in lithium ion conductivity, leading to potential safety accidents and reduced battery performance.
Innovation Solution
A positive active material comprising a core of lithium transition metal oxide (LixMyN1-yO2-αAβ) coated with a lithium transition metal silicate (x′Li2O.y′N′Oa.SiO2-λBζ) layer, which enhances lithium ion conductivity, structural stability, and inhibits oxygen evolution and electrolyte decomposition, thereby improving safety and cycling performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If LiCoO2 is used as positive active material, then simple synthesis process and mature application technology are achieved, but high price, toxicity, and poor safety performance occur
Solution Approach 1:
A coating layer comprising Li2SiO3 and SiO2 is introduced as an intermediary between the LiCoO2 core and the external environment. This coating layer acts as a protective barrier that prevents direct contact between the electrolyte and the LiCoO2 surface, thereby improving safety performance while maintaining the simple synthesis process of the core material.
Solution Approach 2:
The positive active material is designed as a composite structure with a LiCoO2 core and a dual-component coating layer (Li2SiO3 and SiO2). This composite structure combines the advantages of the core material (mature technology, simple synthesis) with the protective benefits of the coating layer (improved safety, enhanced stability).
2Quantity of substance
If LiNixCoyM1-x-yO2 is used as positive active material, then low price, high energy density and desirable safety performance are achieved, but cell swelling at high cut-off voltage and particle pulverizing occur
Solution Approach 1:
The coating layer of Li2SiO3 and SiO2 serves as an intermediary protective layer that prevents direct interaction between the Ni-based oxide core and the electrolyte. This intermediary layer stabilizes the surface structure during cycling, preventing particle pulverizing and maintaining structural integrity even at high cut-off voltages.
Solution Approach 2:
The coating layer is applied specifically on the surface of the Ni-based oxide particles, creating a localized protective zone. This local modification preserves the high energy density properties of the Ni-based core while adding surface stability to prevent structural degradation during cycling.
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 coated lithium transition metal oxide exhibits improved capacity retention, cycling performance, safety, and thermal stability, with a wider operating voltage range and reduced risk of thermal runaway, resulting in a more stable and efficient secondary lithium battery.
Implementation Method 1
the coating layer of lithium transition metal silicate...enhances lithium ion conductivity
Implementation Method 2
the coating layer of lithium transition metal silicate...structural stability, and inhibits oxygen evolution
Data Source
AI summary
The present invention provides a positive active material for use in a secondary lithium battery, a method for preparing the positive active material and a secondary lithium battery containing the positive active material. The positive active material includes a core of lithium transition metal oxide represented by Formula LixMyN1-yO2-αAβ and a coating layer of lithium transition metal silicate represented by Formula x′Li2O.y′N′Oa.SiO2-λBζwhich in-situ formed on the core, wherein 0.8≤x≤1.3, 0.6≤y≤1.0, 0.01≤x′≤2.1, 0.2≤y′≤1.5, 0.1≤a≤3.0, 0≤α≤0.2, 0≤β≤0.4, 0≤λ≤0.5, 0≤ζ≤0.5. The positive active material according to the present invention has high capacity, desirable cycling performance and safety performance, as well as desirable thermal stability.