Phosphate Coating Liquid for Thin Cathode Protection Films
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Solution Overview
Problem
Conventional coating liquids for positive electrode active material particles in sulfide-based all solid state batteries result in thick coating films, increasing battery resistance and reducing sulfide solid electrolyte durability due to high coverage ratios.
Innovation Solution
A coating liquid with a phosphoric acid compound composition that satisfies specific abundance ratios of PO4 units, including Q0, Q1, and Q2 units, is used to form a thin and continuous coating film, improving coverage and reducing film thickness, thereby enhancing battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional coating liquid is used to increase coverage ratio, then protection of sulfide solid electrolyte is improved, but coating film thickness increases and battery resistance increases
Solution Approach 1:
The patent changes the chemical composition parameters of the coating liquid by controlling the Q0 unit ratio of phosphoric acid compound to be 0.7 or less. This parameter change enables the formation of a coating film that achieves high coverage ratio (83% or more) while maintaining thin film thickness (28.5 nm or less), thereby resolving the contradiction between electrolyte protection and resistance reduction.
Solution Approach 2:
The patent uses a composite coating liquid containing multiple phosphoric acid compounds with different Q0 unit ratios, or a mixture of phosphoric acid compounds and other protective compounds. This composite approach allows optimization of both coverage and film thickness by combining the benefits of different materials.
2Ease of manufacture
If conventional coating liquid is used, then coating process is simple, but coating film thickness increases leading to higher battery resistance
Solution Approach 1:
The patent maintains the simplicity of the conventional coating process while changing the key parameter of the phosphoric acid compound composition (Q0 unit ratio ≤ 0.7). This allows the same easy coating process to produce a thinner coating film that reduces battery resistance, resolving the contradiction between manufacturing ease and energy loss.
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 achieves a high coverage ratio of 83% or more and a thin coating film thickness of 28.5 nm or less, reducing battery resistance and minimizing sulfide solid electrolyte deterioration.
Implementation Method 1
The coating liquid includes a solute and a solvent. The solute includes a phosphoric acid compound... a coating film having continuity is likely to be formed due to a large abundance ratio of a phosphoric acid compound having a long molecular chain
Data Source
AI summary
The coating liquid includes a solute and a solvent. The solute comprises a phosphoric acid compound. “I0/(I0+I1+I2)” is 0.7 or less. In the 31P-NMR spectrum, I0 indicates the area of the signal from the PO4, Q0 unit, I1 indicates the area of the signal from the PO4, Q1 unit, and I2 indicates the area of the signal from the PO4, Q2 unit.