Layered-Olivine Positive Electrode Composition for Short-Circuit Heat
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Solution Overview
Problem
Existing non-aqueous electrolyte secondary batteries face challenges in suppressing heat generation during abrupt short circuits, particularly when multiple batteries are connected in parallel, leading to rapid short-circuit current flow and potential chain heating, and the use of layered and olivine compounds with LiFePO4 partially replaced by Mn does not effectively prevent temperature rises during such events.
Innovation Solution
A positive electrode for non-aqueous electrolyte secondary batteries comprising a layered compound and an olivine compound with specific carbon material films, where the second positive electrode active material has a higher tapped density and smaller median diameter than the first, forming a positive electrode mixed material layer with optimized weight and specific surface area ratios to reduce void spaces and enhance thermal stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If layered compound is used as positive electrode active material to achieve high capacitance and high voltage, then energy density is improved, but heat stability deteriorates and thermal runaway risk increases
Solution Approach 1:
The patent applies composite materials by combining layered compound (providing high capacitance and high voltage for energy density) with olivine compound having LiFePO4 partially replaced with Mn (providing heat stability). This composite positive electrode active material layer integrates the advantages of both material types, achieving high energy density while maintaining thermal stability and preventing thermal runaway.
2Productivity
If multiple non-aqueous secondary electrolyte batteries are connected in parallel to increase power output, then productivity is improved, but short-circuit current increases and heat generation worsens
Solution Approach 1:
The patent applies preliminary anti-action by incorporating olivine compound with LiFePO4 partially replaced with Mn into the positive electrode active material before any short circuit occurs. This pre-configured thermal stable material suppresses exothermic reactions and prevents thermal runaway even when abrupt short circuits occur in parallel-connected batteries, countering the heat generation problem before it escalates.
3Reliability
If positive electrode active material occupancy rate is reduced to suppress temperature rise during short circuit, then safety is improved, but energy density deteriorates
Solution Approach 1:
The patent applies parameter changes by modifying the composition parameters of the positive electrode active material - specifically incorporating olivine compound with LiFePO4 partially replaced with Mn at controlled ratios (5-100% by volume fraction). This compositional parameter change enables the material to maintain high energy density while inherently suppressing temperature rise during short circuits through its thermal stable properties, eliminating the need to reduce active material occupancy rate.
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 effectively suppresses heat generation during short circuits by ensuring the second positive electrode active material surrounds the first, reducing exothermic reactions and preventing thermal runaway, thereby enhancing the safety and stability of the battery.
Implementation Method 1
the second positive electrode active material has higher heat stability than the first positive electrode active material
Implementation Method 2
suppresses exothermic reactions between the non-aqueous electrolyte and the first positive electrode active material
Implementation Method 3
a second positive electrode active material that includes a compound represented by general formula (2) and has a carbon material film formed on a surface of the compound
Implementation Method 4
the second positive electrode active material has a tapped density of 0.70 g/cc or more and 1.00 g/cc or less
Data Source
AI summary
Provided is a positive electrode for a non-aqueous electrolyte secondary battery. The positive electrode includes a positive electrode current collector and a positive electrode mixed material layer formed on a surface of the positive electrode current collector. The positive electrode mixed material layer includes: a first positive electrode active material that is a layered compound represented by a following general formula (1), LiaNixCoyM11−x−yO2 (0<a≤1.2, 0<x≤0.9, 0<y≤0.5, 0<x+y<1) (1), a second positive electrode active material having a carbon material film formed on a surface of a phosphate compound that has an olivine structure and is represented by a following general formula (2), LiMnzM2bFe1−z−bPO4 (0<z≤0.9, 0≤b≤0.1, 0<z+b<1) (2), and an electrically conductive agent. A median diameter of the first positive electrode active material is larger than D90 of the second positive electrode active material.