Secondary Battery Positive Electrode Phosphorus Mediator
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Solution Overview
Problem
Lithium-ion secondary batteries with ternary positive active materials have poor safety performance, which is a concern for applications in electric vehicles and electronic products, as they require higher safety standards, especially under varying conditions that affect user safety.
Innovation Solution
A secondary battery design incorporating a positive electrode material layer with specific compounds and elements, such as phosphorus and manganese or aluminum, where the mass content ratio and surface density are optimized to enhance structural stability and thermal shock resistance, reducing side reactions and improving safety performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If ternary positive active materials are used to achieve high energy density, then discharge capacity and energy density are improved, but safety performance deteriorates
Solution Approach 1:
A compound containing phosphorus and at least one of Mn or Al is introduced as an intermediary substance in the positive electrode material layer. This compound acts as a mediator between the ternary positive active material and the electrolyte, forming a protective interface that prevents direct harmful interactions while allowing ionic transport, thus improving safety without compromising energy density
Solution Approach 2:
The positive electrode material layer is designed as a composite structure containing ternary positive active material, conductive carbon, binder, and the phosphorus-containing compound. This composite approach combines the high energy density benefits of ternary materials with the safety and stability contributions of the phosphorus-containing additive, achieving both high discharge capacity and improved safety performance
2Temperature
If the content of phosphorus-containing compound is increased to improve safety, then thermal stability is improved, but discharge capacity may deteriorate
Solution Approach 1:
The invention optimizes the content parameter of the phosphorus-containing compound within a specific range (0.1-5 wt% of positive electrode active material). By precisely controlling this parameter, the patent achieves the optimal balance where sufficient phosphorus content provides thermal stability and safety, while avoiding excessive amounts that would dilute the active material and reduce discharge capacity
Solution Approach 2:
The patent applies partial action by using a small but sufficient amount of phosphorus-containing compound (0.1-5 wt%) rather than large quantities. This partial addition is enough to form a protective interface and improve thermal stability, while minimizing the impact on discharge capacity by leaving the majority of the electrode material as active ternary material
Data Source
AI summary
Provided is a secondary battery, comprising a positive electrode, the positive electrode comprises a positive electrode material layer, and the positive electrode material layer comprises a positive electrode active material and a compound represented by structural formula I:the positive electrode active material includes one or more of the compounds represented by Li1+xNiaCobM′1−a−bO2−yAy and Li1+zMncL2−cO4−dBd;the positive electrode material layer meets the following requirements:0.05≤p·u/v≤15wherein, u is the percentage mass content of element phosphorus in the positive electrode material layer, and the unit is wt %;v is the percentage mass content of element M in the positive electrode material layer, element M is selected from one or two of Mn and Al, and the unit is wt %;p is the surface density of one single surface of the positive electrode material layer, and the unit is mg/cm2.