MH2PO2 Coated Positive Electrode for High-Temp Battery Stability
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries, such as lithium secondary batteries, experience degraded charge/discharge efficiency, capacity retention ratio, and discharge capacity retention ratio when continuously charged at high temperatures, particularly due to electrolyte decomposition caused by increased charging voltage.
Innovation Solution
A positive electrode active material layer containing a compound represented by the general formula MH2PO2, where M is a monovalent cation, is used to suppress electrolyte decomposition, improving charge/discharge efficiency and capacity retention by acting as a reducing agent and enhancing surface conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the charging voltage is increased to achieve high capacity, then the battery capacity increases, but the electrolyte is easily decomposed by the positive electrode active material
Solution Approach 1:
A phosphoric acid compound is introduced as an intermediary substance between the positive electrode active material and the electrolyte. This compound forms a protective layer on the electrode surface that mediates the interaction, preventing direct contact and decomposition reactions between the high-voltage electrode material and the electrolyte, thus enabling high capacity operation without electrolyte degradation
Solution Approach 2:
The phosphoric acid compound is applied in advance to the positive electrode active material surface before battery operation. This preliminary treatment creates a protective coating that prevents the harmful decomposition reaction from occurring during subsequent high-voltage charging cycles, countering the potential damage before it can happen
2Speed
If the battery is continuously charged at high temperature, then the charging speed increases, but the charge/discharge efficiency and capacity retention ratio are degraded
Solution Approach 1:
The phosphoric acid compound coating serves as a cushioning protective layer that is applied beforehand to the electrode surface. This layer cushions against the thermal stress and chemical degradation that occur during continuous high-temperature charging, maintaining electrode integrity and preventing capacity loss even under aggressive charging conditions
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 use of MH2PO2 in the positive electrode active material layer prevents electrolyte decomposition, maintaining high charge/discharge efficiency and capacity retention even at high temperatures, reducing gas generation and battery thickness increase.
Implementation Method 1
A positive electrode active material layer containing a compound represented by a general formula (1) MH2PO2, where M is a monovalent cation, is used to suppress electrolyte decomposition, improving charge/discharge efficiency and capacity retention by acting as a reducing agent
Data Source
AI summary
[Object] To provide a positive electrode for a nonaqueous electrolyte secondary battery with which characteristics of the nonaqueous electrolyte secondary battery, such as a charge/discharge efficiency, a capacity retention ratio, and a discharge capacity retention ratio are not easily degraded even in the case where the nonaqueous electrolyte secondary battery is continuously charged at a high temperature.[Solution] A positive electrode 12 of a nonaqueous electrolyte secondary battery 1 includes a positive electrode active material layer 12b. The positive electrode active material layer 12b contains a positive electrode active material and a compound represented by a general formula (1): MH2PO2 (1). In the general formula (1), M represents a monovalent cation.