Positive Electrode Active Material Precursor for Lithium Secondary Battery
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Solution Overview
Problem
Lithium secondary batteries face challenges in achieving high capacity and high output simultaneously, with existing materials like LiCoO2 being expensive and having limited pulse discharge capacity, while high capacity-type batteries struggle with high current discharge and long-term continuous discharge.
Innovation Solution
A positive electrode active material precursor for lithium secondary batteries is developed, featuring secondary particles composed of primary particles with varying a-axis to c-axis direction length ratios and concentration gradients, which reduce contact resistance and enhance lithium ion insertion, improving capacity and output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If LiCoO2 is used as positive electrode active material, then good electric conductivity and high battery voltage are achieved, but expensive price and limited pulse discharge capacity occur
Solution Approach 1:
The positive electrode active material is divided into primary particles (50-500 nm) that aggregate to form secondary particles (1-20 μm). This segmentation allows the material to achieve both high conductivity through fine primary particles and high capacity through the aggregated secondary particle structure, resolving the contradiction between power and quantity of substance.
Solution Approach 2:
The invention creates a core-shell structure where the surface of secondary particles has a different composition (higher Li content, different metal oxide ratios) compared to the core. This local quality differentiation enables the surface to provide high conductivity and the core to provide high capacity, simultaneously achieving both improving and worsening features.
2Duration of action of moving object
If high capacity-type non-aqueous electrolyte battery is designed, then long term continuous discharge is achieved, but high current discharge capability deteriorates
Solution Approach 1:
The invention creates a dynamic structure where primary particles can be arranged in different orientations within secondary particles. The a-axis direction length to c-axis direction length ratio varies from center to surface, creating a gradient structure that adapts to different discharge rates, enabling both long-term continuous discharge and high current discharge capability.
Solution Approach 2:
The positive electrode active material is designed as a composite of multiple metal oxides (LiCoO2, LiMn2O4, LiNiO2, etc.) with different properties. This composite structure combines the high voltage of LiCoO2 with the high capacity of other materials, achieving both duration and power requirements simultaneously.
3Ease of manufacture
If Mn-based positive electrode active material is used, then easy synthesis and low cost are achieved, but small capacity occurs
Solution Approach 1:
The invention merges Mn-based materials (easy synthesis, low cost) with Co-based and Ni-based materials (high capacity, high voltage) to create a composite positive electrode active material. This combining allows the material to inherit the ease of manufacture from Mn-based materials while achieving high capacity from the composite structure.
Solution Approach 2:
The invention changes the compositional parameters of the positive electrode active material by adjusting the ratios of different metal oxides and controlling the primary particle size (50-500 nm). These parameter changes enable the material to achieve high capacity while maintaining ease of synthesis through established precipitation methods.
Data Source
AI summary
Positive electrode active materials are provided. The positive electrode active materials include a primary particle formed of a plurality of metals including a first metal and a secondary particle formed of at least one of the primary particle. The secondary particle includes a center part, a surface part, a seed region where the primary particle having concentration gradient of the first metal is disposed, and a maintain region where the primary particle having constant concentration of the first metal is disposed, the seed region adjacent to the core part and a maintain region adjacent to the surface part, the length of the seed region in a direction from the center part to the surface part is 1 μm.