Lithium Boron Coating for Cathode Material High-Temperature Stability
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Solution Overview
Problem
Lithium secondary battery positive electrode active materials face limitations in high-temperature life characteristics and resistance increase, necessitating an improvement in their thermal stability and reactivity.
Innovation Solution
A lithium boron compound coating layer is applied to the surface of the positive electrode active material, with a specific peak intensity ratio in the ToF-SIMS spectrum, achieved through a two-step firing process where the B source is introduced separately in each step, forming a surface protective layer that enhances the material's high-temperature life and resistance characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a lithium source is mixed with a precursor and fired at high temperature followed by low temperature firing with H3BO3 to coat the surface, then the positive electrode active material is formed, but the high-temperature life characteristics and resistance increase are not improved sufficiently
Solution Approach 1:
The patent applies preliminary action by introducing the B source during the high-temperature firing step (first firing step) rather than only after firing. This preliminary introduction of B allows it to incorporate into the crystal structure and form a protective layer before the material is fully synthesized, thereby improving high-temperature life characteristics and reducing resistance increase more effectively than post-firing coating alone
Solution Approach 2:
The patent changes the parameter of B source introduction timing from post-firing only to during high-temperature firing. By adjusting the process parameter of when B is introduced (during vs. after firing), the patent achieves better high-temperature stability and resistance characteristics, as the B incorporated during firing becomes part of the crystal structure rather than just a surface coating
2Reliability
If the B source is introduced only after firing to coat the surface, then the coating process is simple, but the high-temperature life and resistance characteristics are not improved
Solution Approach 1:
The patent merges the B source introduction step with the high-temperature firing step by introducing B during the first firing step. This combining of operations allows the B to be incorporated into the crystal structure during the main synthesis process, achieving both crystal structure modification and surface protection in one integrated step, thereby improving resistance characteristics without significantly increasing process 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 method improves the high-temperature life, resistance increase, and low-temperature output characteristics of the positive electrode active material by controlling the B coating/doping time point during the firing process, reducing surface deterioration and increasing the material's stability and reactivity.
Implementation Method 1
a first firing step of mixing a lithium source with a precursor and heat treating the resultant mixture; a second firing step of mixing the fired product obtained from the first firing step with a first B source and heat treating the resultant mixture to form a surface protective layer
Implementation Method 2
the coating layer shows a peak intensity ratio of two optional peaks in the spectrum of Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS)
Data Source
AI summary
A positive electrode active material for a lithium secondary battery having improved high-temperature life and an increase in resistance, and a method for preparing the same are disclosed herein. In some embodiments, a positive electrode active material includes a powder of a positive electrode active material and a lithium boron compound coating layer on the surface of the powder, wherein the lithium boron compound coating layer has a peak intensity ratio of two peaks in the spectrum of Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) that is equal to the peak intensity ratio of the corresponding peaks of LiBO2 within a range of ±50%.