Lithium Composite Positive Active Material for Battery Overcharge Safety
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Solution Overview
Problem
Conventional nonaqueous electrolyte secondary batteries face issues with maintaining stable electrode performance, cyclic characteristics, and temperature control during overcharging, particularly due to the decomposition of electrolytes and active materials, which can lead to rapid temperature rises and capacity deterioration.
Innovation Solution
A positive active material is developed, expressed by the formula LimMxM′yM″zO2, where M represents elements like Co, Ni, and Mn, M′ includes Al, Cr, V, Fe, and others, and M″ includes Mg, Ca, and B, with specific stoichiometric ratios that enhance structural stability and prevent temperature rises during overcharging, combined with a new battery structure that includes a current cut-off mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If lithium carbonate is included in the positive active material to suppress temperature rise during overcharging, then battery safety is improved, but battery capacity is deteriorated
Solution Approach 1:
The patent changes the chemical composition parameters of the positive active material by incorporating specific metal elements (Al, Cr, V, Fe, Mn, Co, Ni, Cu, Zn, Mo, W) in controlled amounts (0.1-5 wt% each) into the lithium composite oxide structure. This compositional modification allows the material to suppress temperature rise during overcharging while maintaining battery capacity, resolving the contradiction between safety and capacity.
2Temperature
If the battery uses a sealed structure with current cut-off means to prevent overheating, then temperature control is improved, but the battery cannot operate effectively when internal pressure rises below the threshold value
Solution Approach 1:
The positive active material itself provides the temperature suppression function through its compositional characteristics, eliminating the need for external current cut-off means or pressure-based safety mechanisms. The material's inherent properties prevent rapid temperature rise during overcharging, making the battery self-regulating and operationally reliable across all pressure conditions.
3Stability of the object's composition
If additional materials are added to suppress abnormal reactions during overcharging, then battery stability is improved, but device complexity increases
Solution Approach 1:
The patent creates a composite positive active material by combining lithium composite oxide with multiple metal elements (Al, Cr, V, Fe, Mn, Co, Ni, Cu, Zn, Mo, W) in specific proportions. This composite structure provides inherent stability during overcharging through the synergistic effects of different metal elements, achieving battery stability without requiring separate additional stabilizing materials or complex multi-component systems.
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 solution maintains excellent electrode performance, suppresses temperature rises, and ensures high capacity and cyclic stability without the need for additional materials that contribute to charging and discharging reactions, effectively addressing the limitations of conventional batteries.
Implementation Method 1
lithium secondary batteries which are nonaqueous electrolyte secondary batteries utilizing a lithium ion doping and dedoping action
Implementation Method 2
when the electric current of a prescribed quantity of electricity or more is supplied upon charging due to any cause so that the nonaqueous electrolyte battery is overcharged, battery voltage will rise and electrolyte solution or the like will be decomposed to generate gas so that the internal pressure of the battery will rise
Data Source
AI summary
A positive active material including a compound expressed by a general formula LimMxM′yM″zO2 (here, M designates at least one kind of element selected from Co, Ni and Mn, M′ designates at least one kind of element selected from Al, Cr, V, Fe, Cu, Zn, Sn, Ti, Mg, Sr, B, Ga, In, Si and Ge, and M″ designates at least one kind of element selected from Mg, Ca, B and Ga. Further, x is designated by an expression of 0.9≦̸x<1, y is indicated by an expression of 0.001≦̸y≦̸0.5, z is indicated by an expression of 0≦̸z≦̸0.5, and m is indicated by an expression of 0.5≦̸m) and lithium manganese oxide expressed by a general formula LisMn2-tMatO4 (here, the value of s is expressed by 0.9≦̸s, the value of t is located within a range expressed by 0.01≦̸t≦̸0.5, and Ma indicates one or a plurality of elements between Fe, Co, Ni, Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si and Ge) are included, so that both a large capacity and the suppression of the rise of temperature of a battery upon overcharging operation are achieved.