Porous Lithium Oxide Sintered Plate for High-Density Cathodes
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Solution Overview
Problem
Existing lithium secondary batteries with powder-dispersed positive electrodes suffer from low packing density due to the presence of binders, leading to reduced capacity and charge/discharge efficiency.
Innovation Solution
A lithium complex oxide sintered plate with a high porosity of 3 to 40%, a mean pore diameter of 15 μm or less, and an open pore rate of 70% or more is used as the positive electrode, featuring primary grains with a layered rock-salt structure and a mean tilt angle of 0° to 30°, enhancing energy density and rapid charge characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If powder-dispersed positive electrodes are used with binders, then the electrode structure is easier to manufacture, but the packing density of active material decreases and capacity is reduced
Solution Approach 1:
The invention extracts and removes the binder component from the electrode structure, transitioning from a powder-dispersed electrode with binder to a sintered plate electrode without binder. This extraction eliminates the harmful effect of binders occupying volume and not contributing to capacity, thereby achieving high packing density of active material while maintaining ease of manufacture through the sintering process
Solution Approach 2:
The invention employs porous sintered plate structure with controlled porosity (3-30%) to achieve both high packing density and adequate ion transport. The porous structure allows sufficient electrolyte penetration while maximizing the volume fraction of active material, resolving the contradiction between dense packing and manufacturability
2Quantity of substance
If sintered plate structure without binder is used, then packing density and capacity are improved, but grain boundary cracking occurs during charge/discharge cycles
Solution Approach 1:
The invention changes the microstructural parameters of the sintered plate, specifically controlling porosity (3-30%), mean pore diameter (0.1-5 μm), and primary grain diameter (5 μm or less). These parameter changes create a fine-grained porous structure that maintains high packing density while the controlled porosity provides stress relief during expansion/contraction, preventing grain boundary cracking and improving cycle characteristics
Solution Approach 2:
The controlled porous structure acts as a buffer to accommodate volume changes during lithium insertion/extraction, reducing mechanical stress at grain boundaries. The pores serve as stress relief zones that prevent crack propagation, thereby improving reliability without sacrificing the high packing density achieved by binder removal
3Reliability
If high porosity is achieved to prevent cracking, then cycle characteristics are improved, but charge/discharge efficiency may be reduced
Solution Approach 1:
The invention optimizes the porosity parameter within a specific range (3-30%) and controls the pore size distribution (mean diameter 0.1-5 μm) to balance two competing requirements: sufficient porosity to prevent cracking and maintain cycle characteristics, while limiting excessive porosity that would reduce active material density and charge/discharge efficiency. The fine pore size ensures adequate ion transport pathways
4Strength
If primary grain diameter is reduced to prevent cracking, then grain boundary strength is improved, but manufacturing precision requirements increase
Solution Approach 1:
The invention specifies a concrete parameter range for primary grain diameter (5 μm or less) that balances grain boundary strength and manufacturing feasibility. This parameter change creates sufficiently strong grain boundaries to prevent cracking during cycling while remaining achievable through conventional sintering processes, avoiding the need for excessively precise manufacturing that would be required for much finer grains
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 lithium complex oxide sintered plate achieves high energy density and rapid charge characteristics while maintaining satisfactory cycle characteristics, even under high-rate charge/discharge cycles, by effectively restraining grain boundary cracking and bonding interface separation.
Implementation Method 1
the sintered plate has a thickness of 30 μm or more, a porosity of 3 to 30%, and an open pore rate of 70% or more
Data Source
AI summary
Provided is a lithium complex oxide sintered plate for use in a positive electrode of a lithium secondary battery. The lithium complex oxide sintered plate has a structure in which a plurality of primary grains having a layered rock-salt structure are bonded, and has a porosity of 3 to 40%, a mean pore diameter of 15 μm or less, an open porosity of 70% or more, and a thickness of 15 to 200 μm. The plurality of primary grains has a primary grain diameter, i.e., a mean diameter of the primary grains, of 20 μm or less and a mean tilt angle of more than 0° to 30° or less. The mean tilt angle is a mean value of the angles defined by the (003) planes of the primary grains and the plate face of the lithium complex oxide sintered plate.