Oriented LiCoO2 Sintered Cathode for High-Temperature Durability
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Solution Overview
Problem
Lithium secondary batteries with non-oriented LiCoO2 sintered plates thicker than 50 μm experience resistance increase and performance deterioration when operated or stored at high temperatures, necessitating improved high-temperature durability.
Innovation Solution
A lithium secondary battery design featuring a lithium complex oxide sintered plate with a thickness of 50 μm or more, where the (003) planes of primary grains are oriented at an angle of over 0° and 30° or less, and a part of Co is substituted with elements like Mg, Ni, Al, Ti, or Mn, enhancing high-temperature durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the thickness of LiCoO2 sintered plate is increased to improve energy density, then the capacity increases, but resistance increases and performance deteriorates at high temperatures
Solution Approach 1:
The patent applies parameter changes by controlling the thickness of the LiCoO2 sintered plate to be 50 μm or more, while simultaneously controlling the porosity to be 30% or more and the mean pore size to be 0.03 μm or more. These parameter adjustments allow the plate to maintain high capacity while improving high-temperature durability through enhanced ion transport and stress distribution.
Solution Approach 2:
The patent utilizes porous materials by ensuring the LiCoO2 sintered plate has a porosity of 30% or more with a mean pore size of 0.03 μm or more. This porous structure improves high-temperature durability by facilitating ion transport and reducing internal stress during charge/discharge cycles, while still maintaining the required capacity through sufficient thickness.
2Ease of manufacture
If powder-dispersed positive electrodes are used to simplify manufacturing, then ease of manufacture improves, but packing density of active material decreases due to binder content
Solution Approach 1:
The patent applies the taking out principle by extracting the binder component from the positive electrode structure. Instead of using powder-dispersed electrodes that require binders, the patent employs a sintered plate structure where LiCoO2 particles are directly sintered together, eliminating the need for binder materials and thereby increasing the packing density of active material.
Solution Approach 2:
The patent merges the functions of multiple components into a single integrated sintered plate structure. The LiCoO2 particles are sintered directly to form a self-supporting plate that serves as both the active material layer and the structural framework, eliminating the need for separate binder and current collector layers.
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 battery exhibits improved resistance and performance stability at high temperatures, with reduced risk of deterioration, attributed to uniform ion and electron movement and stress dispersion during charge/discharge cycles.
Implementation Method 1
the (003) planes of primary grains are oriented at an angle of over 0° and 30° or less
Implementation Method 2
a part of Co is substituted with elements like Mg, Ni, Al, Ti, or Mn
Implementation Method 3
uniform ion and electron movement
Data Source
AI summary
Provided is a lithium secondary battery including: a positive electrode plate that is a lithium complex oxide sintered plate with a thickness of 50 μm or more; a negative electrode plate; a separator interposed therebetween; and an electrolytic solution. The sintered plate has a structure in which primary grains having a layered rock-salt structure are bound to each other, the lithium complex oxide has a composition represented by Lix(Co1-yMy)O2±δ, wherein 1.0≤x≤1.1, 0<y≤0.8, and 0≤δ<1 are satisfied, and M is at least one selected from Mg, Ni, Al, Ti, and Mn, and the primary grains have a mean tilt angle of over 0° and 30° or less. The mean tilt angle is a mean value of angles defined by (003) planes of the primary grains and the plate face of the sintered plate.