Composite Positive Electrode Material for Low-Temperature Li-Ion Batteries
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Solution Overview
Problem
Lithium iron phosphate materials exhibit low conductivity, low rate performance, and undesirable low-temperature performance, especially below −30°C, while ternary positive electrode materials have low safety performance and high production costs.
Innovation Solution
A positive electrode material comprising a phosphate-based and ternary positive electrode material with controlled elemental ratios, including a core-shell structure and specific doping elements, to enhance low-temperature power and capacity retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If lithium iron phosphate material is used as positive electrode material, then cost is reduced and cycle life is extended, but conductivity is lowered and low-temperature performance deteriorates
Solution Approach 1:
The patent uses a composite material system consisting of lithium iron phosphate base material combined with doped elements (Ni, Co, Mn) and surface coating layers. This composite structure allows the base material to provide cost advantages and cycle stability while the dopants and coatings compensate for conductivity losses and improve low-temperature performance.
Solution Approach 2:
The patent applies local quality modification through selective doping of specific elements at different sites within the lithium iron phosphate crystal structure and applying surface coatings only where needed. This localized modification optimizes conductivity and low-temperature performance without compromising the overall cost-effectiveness and structural stability of the bulk material.
2Quantity of substance
If ternary positive electrode material is used, then energy density is increased, but safety performance deteriorates and production cost increases
Solution Approach 1:
The patent modifies the chemical composition parameters of the ternary material by controlling the ratios of Ni, Co, and Mn elements, and by applying surface coatings. This parameter optimization reduces the harmful effects of high-energy-density ternary materials on safety while maintaining their energy density advantages.
3Speed
If Co percentage in positive electrode material is increased, then rate performance is improved, but low-temperature power deteriorates and material cost increases
Solution Approach 1:
The patent optimizes the Co content parameter within a specific range (0.035-0.065 mass ratio) rather than maximizing it. This parameter optimization achieves a balance where sufficient Co provides adequate rate performance while limiting excessive Co that would harm low-temperature power and increase costs.
Solution Approach 2:
The patent creates a composite positive electrode material combining lithium iron phosphate with controlled amounts of ternary material containing Co, Ni, and Mn. This composite approach allows the lithium iron phosphate to provide structural stability and cost benefits while the controlled ternary component enhances rate performance without excessive Co content.
Data Source
AI summary
A positive electrode material includes a phosphate-based positive electrode material and a ternary positive electrode material, and the positive electrode material satisfies the following relational expression 1:0.032<w(Co)/(w(Ni)+w(Mn)+w(A))≤0.075,relational expression 1where A represents a doping element in the phosphate-based positive electrode material, w(Co) represents a mass percentage of Co in the positive electrode material, w(Ni) represents a mass percentage of Ni in the positive electrode material, w(Mn) represents a mass percentage of Mn in the positive electrode material, and w(A) represents a mass percentage of A in the positive electrode material.