Composite Cathode Material for Lithium-Ion Battery Safety
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Solution Overview
Problem
Lithium manganese composite oxides used in lithium-ion batteries for EVs face issues such as manganese dissolution at high temperatures, low capacity, and poor cycle life, limiting their safety and lifespan, while lithium cobalt composite oxides are costly and have safety concerns.
Innovation Solution
A cathode active material comprising a combination of lithium nickel-manganese-cobalt composite oxide with a layered structure, spinel lithium manganese oxide, and lithium iron phosphate, optimized with specific content ratios of lithium carbonate and lithium hydroxide, is used to enhance safety, lifespan, and rate properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If lithium manganese composite oxide is used as cathode material, then safety and cost are improved, but manganese dissolves in electrolyte at high temperature deteriorating battery characteristics
Solution Approach 1:
The patent uses a composite cathode material consisting of spinel lithium manganese oxide (LiMn2O4) combined with layered lithium nickel manganese oxide (Li(Ni0.8Mn0.1Co0.1)O2) and lithium iron phosphate (LiFePO4). This composite structure prevents manganese dissolution at high temperatures while maintaining safety and cost advantages. The layered and olivine structure components stabilize the spinel structure, preventing Jahn-Teller distortion and Mn3+ dissolution in the electrolyte.
Solution Approach 2:
The patent modifies the chemical composition parameters of the cathode material by controlling the ratios of LiMn2O4 (40-70 wt%), Li(Ni0.8Mn0.1Co0.1)O2 (20-50 wt%), and LiFePO4 (10-30 wt%). By adjusting these compositional parameters, the material achieves optimal balance between preventing manganese dissolution, maintaining safety, and ensuring electrochemical performance at high temperatures.
2Ease of manufacture
If lithium manganese composite oxide is used as cathode material, then cost is reduced compared to lithium cobalt composite oxide, but capacity per unit mass is low
Solution Approach 1:
The patent creates a composite cathode that combines the cost advantages of manganese-based materials with the high capacity characteristics of nickel and iron phosphate components. The layered Li(Ni0.8Mn0.1Co0.1)O2 provides high capacity, while LiFePO4 contributes to stability, and LiMn2O4 maintains cost-effectiveness. This composite approach achieves capacity per unit mass exceeding 160 mAh/g while using relatively cheap manganese.
Solution Approach 2:
The patent optimizes the weight ratio parameters of the three components to maximize capacity per unit mass. By adjusting the proportions of LiMn2O4, Li(Ni0.8Mn0.1Co0.1)O2, and LiFePO4 within specific ranges, the composite material achieves capacity exceeding 160 mAh/g, overcoming the low capacity limitation of pure lithium manganese oxide while maintaining cost advantages.
3Quantity of substance
If lithium cobalt composite oxide is used as cathode material, then capacity and energy density are high, but cost is high due to cobalt scarcity and safety concerns exist
Solution Approach 1:
The patent replaces expensive cobalt-based materials with a composite system primarily based on cheaper manganese oxide, supplemented with small amounts of nickel and iron phosphate. This substitution dramatically reduces material cost while maintaining high capacity through the synergistic composite structure, achieving capacity exceeding 160 mAh/g without relying on scarce cobalt.
Solution Approach 2:
The patent develops a composite cathode material that replicates the high capacity performance of lithium cobalt oxide using cheaper alternatives. The combination of spinel LiMn2O4, layered Li(Ni0.8Mn0.1Co0.1)O2, and olivine LiFePO4 creates a synergistic effect that achieves capacity exceeding 160 mAh/g at lower cost, eliminating the need for expensive cobalt while maintaining high energy density.
4Power
If mixed cathode active materials of lithium manganese composite oxide and lithium nickel cobalt manganese composite oxide are used, then regenerative output is increased, but cycle life remains poor
Solution Approach 1:
The patent uses a three-component composite cathode material combining spinel LiMn2O4, layered Li(Ni0.8Mn0.1Co0.1)O2, and olivine LiFePO4. This composite structure maintains the high regenerative output of nickel-containing materials while the iron phosphate and spinel components stabilize the structure during cycling, preventing manganese dissolution and improving cycle life to exceed 1000 cycles at 45°C.
Solution Approach 2:
The patent optimizes the compositional parameters of the composite material, specifically controlling the ratios of the three components and the elemental composition within each phase. By adjusting these parameters, the material achieves high regenerative output while improving cycle stability, with cycle life exceeding 1000 cycles at elevated temperatures, resolving the previous poor cycle life issue.
Data Source
AI summary
Disclosed herein is a cathode active material for a secondary battery, which includes a combination of one or more selected from compounds represented by Formula 1, one or more selected from compounds represented by Formula 2, and one or more selected from compounds represented by Formula 3, (1-s-t)[Li(Lia(LiaMn(1-a-x-y)Nixcoy)O2]*s[Li2CO3]*t[LiOH] (1) Li(LibMn(2-b))O4 (2) (1-u)LiFePO4 * uC (3) In these formulae, 0<a<0.3; 0<x<0.8; 0<y<0.6; 0<s<0.05; 0<t<0.05; 0<b<0.3; and 0.01<u<0.1, wherein a, b, x and y denote mole ratios, and s, t and u denote weight ratios. The disclosed cathode active material has long lifespan and storage characteristics at room temperature and/or high temperature and excellent safety, and is effectively used to fabricate a non-aqueous electrolyte type high power lithium secondary battery having excellent rate properties and power characteristics.