Lithium Ion Conductive Ceramic Coating for Battery Stability
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Solution Overview
Problem
Lithium secondary batteries face challenges with positive active materials that suffer from performance deterioration at high voltages and temperatures, leading to side reactions with electrolytes and reduced cycleability, especially with materials like LiCoO2 which have low stability during high-rate charge and discharge.
Innovation Solution
A positive active material for lithium secondary batteries is developed, comprising a core particle with a compound that reversibly intercalates/deintercalates lithium, coated with a highly ion conductive ceramic compound represented by Li1+x M(I) x M(II) 2-x Si y P 3-y O 12, where M(I) and M(II) are selected from specific elements, and the ceramic compound is attached as discrete particles or a thin layer to prevent direct contact with the electrolyte, enhancing stability and ion transfer efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If composite metal oxide materials (such as LiCoO2, LiMn2O4, LiNiO2) are used as positive active material, then high energy density and rechargeability are achieved, but side reactions with electrolyte occur at high voltages leading to performance deterioration
Solution Approach 1:
A lithium ion conductive ceramic compound layer is introduced as an intermediary between the positive active material and the electrolyte. This intermediate layer prevents direct contact and side reactions between the active material and electrolyte at high voltages, while still allowing lithium ion transport, thus resolving the contradiction between achieving high energy density and maintaining reliability.
Solution Approach 2:
The positive electrode is designed as a composite structure combining the active material (such as LiCoO2) with a lithium ion conductive ceramic compound. This composite material approach allows the system to benefit from the high energy density of the active material while the ceramic compound provides stability and prevents degradation at high voltages.
2Ease of manufacture
If conventional solid-phase reaction method is used to prepare LiNi1-xCoxO2, then material can be synthesized, but the material cannot maintain main characteristics at high voltages due to side reactions with electrolyte
Solution Approach 1:
The lithium ion conductive ceramic compound is applied to the surface of the active material particles before battery assembly and operation. This preliminary coating action protects the active material from electrolyte contact and side reactions before they can occur during battery cycling, ensuring the material maintains its characteristics even at high voltages.
3Device complexity
If positive active material is used without protective coating, then simple structure and ease of manufacture are achieved, but side reactions with electrolyte cause performance deterioration and reduced cycleability
Solution Approach 1:
A thin film of lithium ion conductive ceramic compound is applied to the surface of the active material particles. This thin protective film prevents side reactions with the electrolyte and maintains cycleability, while being thin enough to allow efficient lithium ion transport and not significantly increasing structural complexity.
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 maintains battery characteristics at high voltages, suppresses side reactions, and improves impedance and efficiency, ensuring stable performance even at high temperatures and voltages, while maintaining high discharge capacity and cycle efficiency.
Implementation Method 1
a highly ion conductive ceramic compound attached to a surface of the core as discrete particles or a layer
Implementation Method 2
a compound that reversibly intercalates/deintercalates lithium
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
A positive active material for a lithium secondary battery comprises a core comprising a compound that can reversibly intercalate and deintercalate lithium; and a lithium ion conductive ceramic compound attached to the surface of the core and represented by Chemical Formula 1: [Chemical Formula 1] Li1+xM(I)M(II)2-xSiyP3-yO12, wherein M(I) and M(II) are selected from the group consisting of Al, Zr, Hf, Ti, Ge, Sn, Cr, Nb, Ga, Fe, Sc, In, Y, La, Lu, and Mg, and 0<x≤0.7, 0≤y≤ 1.