Positive Electrode Surface Chemistry for Battery Capacity Retention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing nonaqueous electrolyte energy storage devices face challenges in maintaining high initial discharge capacity and capacity retention ratio after charge-discharge cycles, with techniques like surface coating with aluminum compounds or lithium difluorophosphate addition not providing sufficient improvements.
Innovation Solution
A nonaqueous electrolyte energy storage device with a positive electrode containing a composite of phosphorus and aluminum, where the P2p peak position is at 134.7 eV or less and the Al2p/P2p peak height ratio is between 0.1 and 0.5, formed using an oxo acid of phosphorus or its salt and an aluminum coupling agent, which creates a protective film inhibiting active material elution and enhancing adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If surface coating with aluminum compound is applied, then adhesion is improved, but capacity retention ratio is insufficient
Solution Approach 1:
The patent applies composite materials by combining aluminum compound and phosphorus compound in the surface film of the positive electrode. This composite structure allows the aluminum compound to provide adhesion while the phosphorus compound contributes to capacity retention, resolving the contradiction between adhesion strength and capacity retention ratio that cannot be achieved with aluminum compound alone.
Solution Approach 2:
The patent changes the chemical composition parameters of the surface film by incorporating phosphorus compounds with specific P2p peak positions (133.8-134.7 eV) and controlling the Al2p/P2p peak height ratio (0.05-0.5). This parameter optimization enables the surface film to simultaneously achieve good adhesion and high capacity retention ratio.
2Reliability
If lithium difluorophosphate is added to positive electrode, then capacity retention is improved, but initial discharge capacity is reduced
Solution Approach 1:
The patent optimizes the concentration and chemical state parameters of phosphorus compounds in the surface film by controlling the P2p peak position (133.8-134.7 eV) and Al2p/P2p peak height ratio (0.05-0.5). This precise parameter control allows the phosphorus compound to improve capacity retention without significantly reducing initial discharge capacity, unlike conventional lithium difluorophosphate addition.
Solution Approach 2:
The patent applies local quality by concentrating the phosphorus compound specifically in the surface film of the positive electrode rather than uniformly throughout the electrode. This localized placement ensures that the phosphorus compound provides capacity retention benefits at the electrode-electrolyte interface without interfering with the bulk electrode's discharge capacity.
3Reliability
If phosphonic acid is added to positive composite paste, then capacity retention is improved, but initial discharge capacity is reduced
Solution Approach 1:
The patent changes the chemical form and concentration parameters of phosphorus compounds by using compounds with specific P2p peak positions (133.8-134.7 eV) and controlling the Al2p/P2p peak height ratio (0.05-0.5). This parameter optimization allows achieving capacity retention improvement with minimal impact on initial discharge capacity, unlike conventional phosphonic acid addition.
Solution Approach 2:
The patent combines phosphorus compounds with aluminum compounds in the surface film to create a composite structure where the phosphorus compound improves capacity retention while the aluminum compound maintains good adhesion and minimizes impact on initial discharge capacity, resolving the contradiction present when using phosphonic acid alone.
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 results in a device with increased initial discharge capacity and high capacity retention ratio, along with improved adhesion of the positive composite, effectively addressing the limitations of previous methods.
Implementation Method 1
an oxo acid of phosphorus or an oxo acid salt of fluorinated phosphorus and an aluminum coupling agent are mixed with each other, thereby a nonaqueous electrolyte energy storage device having a large initial discharge capacity and a high capacity retention ratio can be provided
Data Source
Figure 1~2
AI summary
Provided are a nonaqueous electrolyte energy storage device having a large initial discharge capacity and a high capacity retention ratio after a charge-discharge cycle, and a method for producing the nonaqueous electrolyte energy storage device. One aspect of the present invention is a nonaqueous electrolyte energy storage device including a positive electrode containing a positive composite, the positive composite containing a positive active material, a phosphorus atom and an aluminum atom, in which in a spectrum of the positive composite as measured by X-ray photoelectron spectroscopy, a peak position of P2p is at 134.7 eV or less, and a peak height ratio of Al2p to P2p (Al2p/P2p) is 0.1 or more.