Acid-Modified Lithium Phosphate Dispersion in Battery Paste
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Solution Overview
Problem
Conventional nonaqueous electrolyte secondary batteries face performance degradation due to hydrofluoric acid generation, which elutes transition metals from the positive-electrode active material, as the solvent is decomposed at high potentials, and poor dispersion of lithium phosphate in the positive electrode mixture layer hinders effective reaction with hydrofluoric acid.
Innovation Solution
A manufacturing method for nonaqueous electrolyte secondary batteries that involves mixing an acid compound with the positive-electrode active material, conductive material, binder, lithium phosphate, and solvent to achieve good dispersibility of lithium phosphate, forming a protective coating that reacts with hydrofluoric acid and reduces metal elution, using acid compounds like phosphoric acid, pyrophosphoric acid, or metaphosphoric acid to enhance dispersion and prevent solvent decomposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If kneading energy is increased to improve lithium phosphate dispersibility, then dispersibility of lithium phosphate is improved, but the positive-electrode active material is broken
Solution Approach 1:
An acid compound (phosphoric acid, pyrophosphoric acid, or metaphosphoric acid) is introduced as an intermediary substance to facilitate the dispersion of lithium phosphate particles without requiring excessive mechanical energy. The acid compound acts as a dispersing agent that chemically interacts with lithium phosphate to prevent aggregation, thereby achieving good dispersibility while maintaining the integrity of the positive-electrode active material particles.
2Ease of manufacture
If lithium phosphate is not uniformly dispersed, then manufacturing is easier, but hydrofluoric acid cannot be effectively reacted with, leading to metal elution
Solution Approach 1:
The acid compound is added during the mixing stage to preliminarily ensure uniform dispersion of lithium phosphate throughout the positive electrode mixture paste. This preliminary action of achieving uniform dispersion during manufacturing prevents the formation of aggregated lithium phosphate regions, ensuring that lithium phosphate is uniformly distributed to effectively react with hydrofluoric acid during battery operation, thereby preventing metal elution.
3Device complexity
If conventional mixing is used, then device complexity is low, but lithium phosphate aggregates and dispersibility decreases
Solution Approach 1:
The invention changes the chemical parameters of the mixing system by introducing an acid compound with specific chemical properties (phosphoric acid, pyrophosphoric acid, or metaphosphoric acid). This parameter change transforms the physical-chemical environment during mixing, enabling lithium phosphate to disperse uniformly without requiring complex mixing equipment or processes. The acid compound modifies the interaction between lithium phosphate particles and the surrounding medium, achieving good dispersion with conventional mixing approaches.
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 achieves a high dispersion degree of lithium phosphate in the positive electrode mixture layer, effectively reducing hydrofluoric acid generation and metal elution, forming a protective coating that stabilizes the battery performance even at high voltage operations.
Implementation Method 1
lithium phosphate (Li3PO4), so that hydrofluoric acid generated as described above is reacted with lithium phosphate (Li3PO4) so that the hydrofluoric acid is reduced
Implementation Method 2
at least part of lithium phosphate can be dissolved in the positive electrode mixture paste by the acid compound
Implementation Method 3
manufacturing a positive electrode including a positive electrode mixture layer on a surface of a current collector member, by applying the positive electrode mixture paste to the surface of the current collector member and drying the positive electrode mixture paste
Implementation Method 4
when a potential of the positive-electrode active material (equivalent to a potential of a positive electrode) reaches 4.35 V or more by performing initial charge or the like, a solvent in a nonaqueous electrolyte is decomposed by oxidation on a surface of the positive-electrode active material, so that hydrogen ions generated hereby are reacted with fluorine ions in the nonaqueous electrolyte, which might generate hydrofluoric acid (HF)
Data Source
AI summary
In a positive electrode mixture paste manufacturing step, a positive electrode mixture paste is manufactured by further mixing an acid compound, in addition to a positive-electrode active material, a conductive material, a binder, lithium phosphate, and a solvent.